A low-viscosity thermally conductive hot melt adhesive and preparation method thereof

Abstract

The present application discloses a low-viscosity heat-conductive hot melt adhesive and a preparation method thereof, and relates to the field of hot melt adhesives. Among them, the low-viscosity heat-conductive hot melt adhesive includes 45-55 parts by weight of polymerized diols, 8-12 parts by weight of hydroxyl-terminated silicone oils, 2-2.5 parts by weight of maleic anhydride grafted wax powder, 15-20 parts by weight of diisocyanates, 0.5-0.7 parts by weight of chain extenders, 0.01-0.02 parts by weight of catalysts, 0.03-0.05 parts by weight of antioxidants, and 4.5-5.5 parts by weight of aminosilane coupling agents. The low-viscosity heat-conductive hot melt adhesive of the present application takes into account the advantages of low viscosity, good coating dispersibility, high bonding strength, and high thermal conductivity efficiency.

Description

Technical Field

[0001] The present application relates to the field of hot melt adhesives, and in particular to a low-viscosity thermally conductive hot melt adhesive and a preparation method thereof. Background Art

[0002] At present, in order to improve the thermal conductivity of traditional hot melt adhesives, thermal conductive fillers are usually added to the hot melt adhesive system to improve its thermal properties. These thermal conductive fillers mainly include metal powders such as nano-alumina, nano-magnesium oxide, etc. However, directly mixing in a high amount of thermal conductive particles often leads to excessive viscosity of the final product, which not only makes it difficult for the thermal conductive filler to be evenly dispersed in the hot melt adhesive matrix, but also affects the efficiency and quality of the coating operation, resulting in the hot melt adhesive's bonding strength and thermal conductivity efficiency failing to meet expectations. Summary of the invention

[0003] In order to improve the problems of low viscosity thermally conductive hot melt adhesive in the related art, such as high viscosity and poor coating uniformity, resulting in poor bonding strength and thermal conductivity efficiency, the present application provides a low viscosity thermally conductive hot melt adhesive and a preparation method thereof.

[0004] In the first aspect, the present application provides a low-viscosity thermally conductive hot melt adhesive using the following technical solution:

[0005] A low-viscosity thermally conductive hot melt adhesive comprises 45-55 parts by weight of polymerized diol, 8-12 parts by weight of hydroxyl-terminated silicone oil, 2-2.5 parts by weight of maleic anhydride grafted wax powder, 15-20 parts by weight of diisocyanate, 0.5-0.7 parts by weight of chain extender, 0.01-0.02 parts by weight of catalyst, 0.03-0.05 parts by weight of antioxidant and 4.5-5.5 parts by weight of aminosilane coupling agent modified thermally conductive filler.

[0006] In the present application, the thermally conductive filler is added in the form of a thermally conductive filler modified by an aminosilane coupling agent. In order to improve the problems of increased viscosity and poor dispersibility of the hot melt adhesive caused by the addition of the thermally conductive filler modified by the aminosilane coupling agent, hydroxyl-terminated silicone oil and maleic anhydride grafted wax powder are added to the polymerized diol. The introduction of hydroxyl-terminated silicone oil and maleic anhydride grafted wax powder can reduce the viscosity of the thermally conductive hot melt adhesive, improve the wettability and permeability of the thermally conductive hot melt adhesive to the substrate, and improve the dispersibility of the thermally conductive filler modified by the aminosilane coupling agent, thereby improving the bonding strength of the thermally conductive hot melt adhesive to the substrate and the thermal conductivity of the thermally conductive hot melt adhesive.

[0007] In some specific embodiments, the hydroxyl-terminated silicone oil is hydroxyl-terminated trifluoropropylmethylsiloxane.

[0008] In the present application, the hydroxyl-terminated silicone oil is preferably hydroxyl-terminated trifluoropropyl methylsiloxane. Compared with hydroxyl-terminated polydimethylsiloxane, hydroxyl-terminated trifluoropropyl methylsiloxane can further improve the wetting ability of the thermally conductive hot melt adhesive to the substrate, enhance the bonding effect, and at the same time, improve the moisture and heat resistance of the low-viscosity thermally conductive hot melt adhesive.

[0009] In some specific embodiments, the viscosity of the hydroxyl-terminated trifluoropropylmethylsiloxane at 25° C. is 420-560 mm 2 / s.

[0010] In the present application, the hydroxyl-terminated trifluoropropyl methylsiloxane preferably has a viscosity of 420-560 mm 2 / s hydroxyl-terminated trifluoropropyl methylsiloxane, the thermal conductive hot melt adhesive has good heat and moisture resistance and hygroscopicity, which is helpful to prevent the problem of slow curing speed of the thermal conductive hot melt adhesive.

[0011] In some specific embodiments, the polymeric diol includes polyether diol and styrene-grafted polyether diol, and the weight ratio of the polyether diol to the styrene-grafted polyether diol is (3-4):1.

[0012] In the present application, the polymeric diol is preferably a composition of polyether diol and styrene-grafted polyether diol in a weight ratio of (3-4):1, which can further improve the bonding strength and moisture and heat resistance while maintaining good thermal conductivity, while not affecting the rapid curing of the thermally conductive hot melt adhesive.

[0013] In some specific embodiments, the molecular weight of the polyether diol is 1000-2000.

[0014] In some specific embodiments, in the styrene-grafted polyether diol, the grafting rate of styrene is 1-1.5%.

[0015] In the present application, the grafting rate of styrene in the styrene-grafted polyether diol is controlled to be 1-1.5%, which is beneficial to reducing the effect of the addition of the styrene-grafted polyether diol on the curing speed of the thermally conductive hot melt adhesive.

[0016] In some specific embodiments, the maleic anhydride grafted wax powder is at least one of maleic anhydride grafted polyethylene wax and maleic anhydride grafted polypropylene wax.

[0017] In some specific embodiments, the aminosilane coupling agent modified filler is at least one of aminosilane coupling agent modified magnesium oxide, aminosilane coupling agent modified aluminum oxide, and aminosilane coupling agent modified zinc oxide.

[0018] In some specific embodiments, the diisocyanate is at least one of isophorone diisocyanate, hexamethylene diisocyanate, and diphenylmethane diisocyanate; the chain extender is at least one of ethylene glycol, 1,3-propylene glycol, and 1,4-butanediol; the catalyst is at least one of dibutyltin dilaurate, 2,2-dimorpholinyl diethyl ether, and stannous octoate; and the antioxidant is at least one of antioxidant 1010 and antioxidant 1076.

[0019] In a second aspect, the present application provides a method for preparing a low-viscosity thermally conductive hot melt adhesive using the following technical solution: A method for preparing a low-viscosity thermally conductive hot melt adhesive, comprising the following steps:

[0020] After mixing the polymerized diol, hydroxyl-terminated silicone oil, maleic anhydride grafted wax powder and antioxidant, the temperature is raised to 100-110°C, and the vacuum degree is maintained at -0.04 to -0.05 MPa for dehydration. Then, diisocyanate is added, the temperature is raised to 80-90°C, and the vacuum degree is maintained at -0.04 to -0.05 MPa. After reacting for 4-4.5 hours, aminosilane coupling agent is added to modify the thermal conductive filler, chain extender and catalyst, and the reaction is continued at 80-90°C for 1-1.5 hours before discharging the material to obtain a low-viscosity thermally conductive hot melt adhesive.

[0021] In the present application, the thermally conductive hot melt adhesive is prepared by the above method, and a hot melt adhesive with low viscosity, good thermal conductivity, high bonding strength to the substrate and good low-temperature toughness can be obtained.

[0022] In summary, this application at least includes the following beneficial technical effects:

[0023] (1) The present application adds hydroxyl-terminated silicone oil and maleic anhydride grafted wax powder on the basis of polymerized diol. The introduction of hydroxyl-terminated silicone oil and maleic anhydride grafted wax powder can reduce the viscosity of the thermally conductive hot melt adhesive, improve the wettability and permeability of the thermally conductive hot melt adhesive to the substrate, and improve the dispersibility of the aminosilane coupling agent modified thermally conductive filler, thereby improving the bonding strength of the thermally conductive hot melt adhesive to the substrate and the thermal conductivity of the thermally conductive hot melt adhesive.

[0024] (2) The hydroxyl-terminated silicone oil is preferably hydroxyl-terminated trifluoropropyl methylsiloxane. Compared with hydroxyl-terminated polydimethylsiloxane, hydroxyl-terminated trifluoropropyl methylsiloxane can further improve the wetting ability of the thermally conductive hot melt adhesive to the substrate, enhance the bonding effect, and at the same time, improve the moisture and heat resistance of the low-viscosity thermally conductive hot melt adhesive.

[0025] (3) The preferred viscosity of hydroxyl-terminated trifluoropropyl methylsiloxane is 420-560 mm 2 / s hydroxyl-terminated trifluoropropyl methylsiloxane, the thermal conductive hot melt adhesive has good heat and moisture resistance and hygroscopicity, which is helpful to prevent the problem of slow curing speed of the thermal conductive hot melt adhesive. DETAILED DESCRIPTION

[0026] The present application is further described below through specific examples and comparative examples. However, it should be noted that the specific material ratios, process conditions and results described in the embodiments of the present invention are only used to illustrate the present invention and cannot be used to limit the scope of protection of the present invention.

[0027] Example

[0028] [Example 1]

[0029] A low-viscosity thermally conductive hot melt adhesive comprising the following raw materials:

[0030] Polymer diol: 45 kg. In this embodiment, the polymer diol is polytetramethylene glycol with a molecular weight of 2000 produced by BASF-Mitsubishi.

[0031] Hydroxyl-terminated silicone oil: 8 kg. In this embodiment, the hydroxy-terminated silicone oil is specifically hydroxy-terminated polydimethylsiloxane, and the viscosity of hydroxy-terminated polydimethylsiloxane at 25° C. is 420 mm 2 / s;

[0032] Maleic anhydride grafted wax powder: 2 kg. In this embodiment, the maleic anhydride grafted wax powder is specifically Mitsui Chemicals maleic anhydride grafted polyethylene wax HI-WAX 1105A;

[0033] Diisocyanate: 15 kg. In this embodiment, the diisocyanate is specifically isophorone diisocyanate;

[0034] Chain extender: 0.5 kg. In this embodiment, the chain extender is 1,3-propylene glycol;

[0035] Catalyst: 0.01 kg. In this embodiment, the catalyst is dibutyltin dilaurate;

[0036] Antioxidant: 0.03 kg. In this embodiment, the antioxidant is specifically antioxidant 1010;

[0037] Aminosilane coupling agent modified thermal conductive filler: 4.5 kg. In this embodiment, the aminosilane coupling agent modified thermal conductive filler specifically adopts aminosilane coupling agent modified zinc oxide, wherein the preparation method of aminosilane coupling agent modified zinc oxide is as follows:

[0038] 1 kg of silane coupling agent KH550 and 4 kg of nano zinc oxide were added to 10 kg of ethanol solution, and then the temperature was raised to 60° C., stirred and refluxed for reaction for 2 hours, followed by centrifugal separation, washing and drying to obtain aminosilane coupling agent modified zinc oxide.

[0039] In addition, in this embodiment, the preparation method of the low-viscosity thermally conductive hot melt adhesive includes the following steps:

[0040] After mixing the polymerized diol, hydroxyl-terminated silicone oil, maleic anhydride grafted wax powder and antioxidant, the temperature is raised to 100°C, and the vacuum degree is maintained at -0.05MPa for dehydration. Then, diisocyanate is added, the temperature is raised to 80°C, and the vacuum degree is maintained at -0.05MPa. After reacting for 4.5 hours, the vacuuming is stopped, and aminosilane coupling agent-modified thermal conductive filler, chain extender and catalyst are added. The reaction is continued at 80°C for 1.5 hours before discharging the material to obtain a low-viscosity thermally conductive hot melt adhesive.

[0041] [Example 2]

[0042] A low-viscosity thermally conductive hot melt adhesive comprising the following raw materials:

[0043] Polymer diol: 55 kg. In this embodiment, the polymer diol is polytetramethylene glycol with a molecular weight of 2000 produced by BASF-Mitsubishi.

[0044] Hydroxyl-terminated silicone oil: 12 kg. In this embodiment, the hydroxy-terminated silicone oil is specifically hydroxy-terminated polydimethylsiloxane, and the viscosity of hydroxy-terminated polydimethylsiloxane at 25° C. is 420 mm 2 / s;

[0045] Maleic anhydride grafted wax powder: 2.5 kg. In this embodiment, the maleic anhydride grafted wax powder is specifically Mitsui Chemicals maleic anhydride grafted polyethylene wax HI-WAX 1105A;

[0046] Diisocyanate: 20 kg. In this embodiment, the diisocyanate is specifically diphenylmethane diisocyanate;

[0047] Chain extender: 0.7 kg. In this embodiment, the chain extender is specifically 1,4-butanediol;

[0048] Catalyst: 0.02 kg. In this embodiment, the catalyst is dibutyltin dilaurate;

[0049] Antioxidant: 0.05 kg. In this embodiment, the antioxidant is specifically antioxidant 1076;

[0050] Aminosilane coupling agent modified thermal conductive filler: 5.5 kg. In this embodiment, the aminosilane coupling agent modified thermal conductive filler specifically adopts aminosilane coupling agent modified zinc oxide, wherein the preparation method of aminosilane coupling agent modified zinc oxide is as follows:

[0051] 1 kg of silane coupling agent KH550 and 4 kg of nano zinc oxide were added to 10 kg of ethanol solution, and then the temperature was raised to 60° C., stirred and refluxed for reaction for 2 hours, followed by centrifugal separation, washing and drying to obtain aminosilane coupling agent modified zinc oxide.

[0052] In addition, in this embodiment, the preparation method of the low-viscosity thermally conductive hot melt adhesive includes the following steps:

[0053] After mixing the polymerized diol, hydroxyl-terminated silicone oil, maleic anhydride grafted wax powder and antioxidant, the temperature is raised to 110°C, and the vacuum degree is maintained at -0.04MPa for dehydration. Then, diisocyanate is added, the temperature is raised to 90°C, and the vacuum degree is maintained at -0.04MPa. After reacting for 4 hours, the vacuuming is stopped, and aminosilane coupling agent is added to modify the thermal conductive filler, chain extender and catalyst. The reaction is continued at 90°C for 1 hour before discharging the material to obtain a low-viscosity thermally conductive hot melt adhesive.

[0054] [Example 3]

[0055] A low-viscosity heat-conductive hot melt adhesive, which is different from [Example 1] in that the hydroxyl-terminated silicone oil is different. In this embodiment, the hydroxyl-terminated silicone oil specifically uses hydroxyl-terminated trifluoropropyl methylsiloxane, and the viscosity of hydroxyl-terminated trifluoropropyl methylsiloxane at 25°C is 420 mm 2 / s.

[0056] [Example 4]

[0057] A low-viscosity heat-conductive hot melt adhesive, which differs from [Example 1] in that the hydroxyl-terminated silicone oil is different. In this embodiment, the hydroxyl-terminated silicone oil specifically uses hydroxyl-terminated trifluoropropyl methylsiloxane, and the viscosity of hydroxyl-terminated trifluoropropyl methylsiloxane at 25°C is 560 mm 2 / s.

[0058] [Example 5]

[0059] A low-viscosity heat-conductive hot melt adhesive, which is different from [Example 1] in that the hydroxyl-terminated silicone oil is different. In this embodiment, the hydroxyl-terminated silicone oil specifically adopts hydroxyl-terminated trifluoropropyl methylsiloxane, and the viscosity of hydroxyl-terminated trifluoropropyl methylsiloxane at 25°C is 880 mm 2 / s.

[0060] [Example 6]

[0061] A low-viscosity thermally conductive hot melt adhesive, which differs from [Example 3] in that the polymerized diol is different.

[0062] In this embodiment, the polymeric diol includes polytetramethylene glycol (BASF Mitsubishi, molecular weight 2000) and styrene grafted polypropylene glycol, and the weight ratio of polytetramethylene glycol to styrene grafted polypropylene glycol is 3: 1. Among them, the grafting rate of styrene in the styrene grafted polypropylene glycol is 1.2%, and the viscosity of the styrene grafted polypropylene glycol is 850 mPa.s.

[0063] [Example 7]

[0064] A low-viscosity thermally conductive hot melt adhesive, which differs from [Example 6] in that the weight ratio of polytetramethylene ether glycol (BASF-Mitsubishi, molecular weight 2000) to styrene-grafted polypropylene glycol is 1:3.

[0065] [Example 8]

[0066] A low-viscosity thermally conductive hot melt adhesive, which differs from [Example 6] in that the grafting rate of styrene in the styrene-grafted polypropylene glycol is 3.8%, and the viscosity of the styrene-grafted polypropylene glycol is 1360 mPa.s.

[0067] Comparative Example

[0068] [Comparative Example 1]

[0069] A heat-conductive hot melt adhesive, which differs from [Example 1] in that:

[0070] In this comparative example, the hydroxyl-terminated polydimethylsiloxane is replaced by an equal amount of polytetramethylene glycol.

[0071] [Comparative Example 2]

[0072] A heat-conductive hot melt adhesive, which differs from [Example 1] in that:

[0073] In this comparative example, the maleic anhydride grafted polyethylene wax is replaced by an equal amount of polytetramethylene glycol.

[0074] Performance testing

[0075] Test 1: Viscosity test: After the thermally conductive hot melt adhesives in the embodiments and comparative examples were melted in an oven at 100° C., the viscosity of the thermally conductive hot melt adhesives was tested using a rotary viscometer. The viscosity was 4000-5000 mPa.s to meet the requirements.

[0076] Experiment 2, thermal conductivity test: The hot melt adhesives in the embodiments and comparative examples were made into hot melt adhesive sheets, and then the thermal conductivity of different hot melt adhesive sheets was tested according to ISO 22007-2.

[0077] Test 3, tensile shear strength test: After the thermally conductive hot melt adhesive in each embodiment and comparative example is melted, it is coated between two PP substrates, the bonding surface length is 1.25 cm, the adhesive layer thickness is 0.2 mm, and after standing for 48 hours in an environment with a temperature of 25°C and a humidity of 80%, a sample to be tested is obtained. The tensile shear strength test is performed on the sample to be tested in accordance with GB / T 7124-2008, wherein the higher the tensile shear strength, the higher the bonding strength of the thermally conductive hot melt adhesive to the substrate.

[0078] Test 4: Moisture and heat resistance test: The test sample prepared in Test 3 was placed in an environment with a temperature of 85°C and a humidity of 85% for 1500 hours. After being taken out and cooled to room temperature, the shear strength of the sample was tested in accordance with GB / T 7124-2008.

[0079] Test 5: Open time test: Test according to ASTM D 4497-1994.

[0080] Table 1

[0081]

[0082] According to Example 1 and Comparative Examples 1-2 and the test results in Table 1, it can be seen that after the hydroxyl-terminated polydimethylsiloxane or maleic anhydride grafted polyethylene wax is replaced by polytetramethylene ether glycol, the viscosity of the thermally conductive hot melt adhesive increases significantly, the thermal conductivity decreases, and the bonding strength to the substrate also decreases. The reason is that after the viscosity of the thermally conductive hot melt adhesive increases, the dispersibility of the aminosilane coupling agent modified thermally conductive filler is affected, and the formation of a complete thermal conductive network is affected, resulting in a decrease in thermal conductivity. In addition, after the viscosity increases, the uniform coating of the hot melt adhesive is affected, resulting in a decrease in the bonding strength of the hot melt adhesive to the substrate.

[0083] According to the test results in Example 1 and Example 3-4 combined with Table 1, it can be seen that the hydroxyl-terminated silicone oil using hydroxyl-terminated trifluoropropyl methylsiloxane can improve the bonding strength of the thermally conductive hot melt adhesive to the substrate. However, the preferred viscosity range of hydroxyl-terminated trifluoropropyl methylsiloxane is 420-560 mm 2 / s range. The reason is that when the viscosity of the hydroxyl-terminated trifluoropropyl methylsiloxane is too large, the moisture absorption rate of the thermally conductive hot melt adhesive is affected, resulting in a slow curing speed.

[0084] According to Example 3 and Examples 6-8 and combined with the test results in Table 1, it can be seen that the composition in which the weight ratio of the polymeric diol is preferably polyether diol and styrene-grafted polypropylene glycol is in the range of (3-4):1 can further improve the bonding strength and moisture and heat resistance while maintaining good thermal conductivity, while not affecting the rapid curing of the thermally conductive hot melt adhesive.

[0085] This specific implementation manner is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the specific implementation manner as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A low-viscosity thermally conductive hot melt adhesive, characterized in that: The invention comprises 45-55 parts by weight of polymeric diol, 8-12 parts by weight of hydroxyl-terminated silicone oil, 2-2.5 parts by weight of maleic anhydride grafted wax powder, 15-20 parts by weight of diisocyanate, 0.5-0.7 parts by weight of chain extender, 0.01-0.02 parts by weight of catalyst, 0.03-0.05 parts by weight of antioxidant and 4.5-5.5 parts by weight of aminosilane coupling agent modified thermal conductive filler; The hydroxyl-terminated silicone oil is hydroxyl-terminated trifluoropropyl methylsiloxane, and the viscosity of the hydroxyl-terminated trifluoropropyl methylsiloxane at 25° C. is 420-560 mm 2 / s.

2. The low-viscosity thermally conductive hot melt adhesive according to claim 1, characterized in that: The polymeric diol includes polyether diol and styrene-grafted polyether diol, and the weight ratio of the polyether diol to the styrene-grafted polyether diol is (3-4):

1.

3. The low-viscosity thermally conductive hot melt adhesive according to claim 2, characterized in that: The molecular weight of the polyether diol is 1000-2000.

4. The low-viscosity thermally conductive hot melt adhesive according to claim 2, characterized in that: In the styrene-grafted polyether diol, the grafting rate of styrene is 1-1.5%.

5. The low-viscosity thermally conductive hot melt adhesive according to claim 1, characterized in that: The maleic anhydride grafted wax powder is at least one of maleic anhydride grafted polyethylene wax and maleic anhydride grafted polypropylene wax.

6. The low-viscosity thermally conductive hot melt adhesive according to claim 1, characterized in that: The aminosilane coupling agent modified thermal conductive filler is at least one of aminosilane coupling agent modified magnesium oxide, aminosilane coupling agent modified aluminum oxide, and aminosilane coupling agent modified zinc oxide.

7. The low-viscosity thermally conductive hot melt adhesive according to claim 1, characterized in that: The diisocyanate is at least one of isophorone diisocyanate, hexamethylene diisocyanate, and diphenylmethane diisocyanate; the chain extender is at least one of ethylene glycol, 1,3-propylene glycol, and 1,4-butanediol; the catalyst is at least one of dibutyltin dilaurate, 2,2-dimorpholinyl diethyl ether, and stannous octoate; and the antioxidant is at least one of antioxidant 1010 and antioxidant 1076.

8. A method for preparing a low-viscosity thermally conductive hot melt adhesive according to any one of claims 1 to 7, characterized in that: The following steps are involved: After mixing the polymerized diol, hydroxyl-terminated silicone oil, maleic anhydride grafted wax powder and antioxidant, the temperature is raised to 100-110°C, and the vacuum degree is maintained at -0.04~-0.05MPa for dehydration. Then, diisocyanate is added, the temperature is raised to 80-90°C, and the vacuum degree is maintained at -0.04~-0.05MPa. After reacting for 4-4.5h, aminosilane coupling agent is added to modify the thermal conductive filler, chain extender and catalyst, and the reaction is continued at 80-90°C for 1-1.5h before discharging to obtain a low-viscosity thermally conductive hot melt adhesive.

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