CN115895562A - Salt-fog-resistant single-component polyurethane hot melt adhesive and preparation method thereof - Google Patents

Abstract

The invention belongs to the technical field of polyurethane hot melt adhesives, and relates to a single-component salt spray resistant polyurethane hot melt adhesive and a preparation method thereof, wherein the preparation raw materials comprise the following components in parts by weight: 30-40 parts of polycarbonate dihydric alcohol, 10-20 parts of polyethylene terephthalate, 3-8 parts of 1, 6-hexanediol, 8-15 parts of non-crystalline liquid saturated polyester, 15-20 parts of acrylic resin, 0.05-0.15 part of antioxidant, 0.05-0.15 part of flatting agent, 0.02-0.04 part of water remover, 18-23 parts of diisocyanate, 0.3-0.6 part of coupling agent and 0.03-0.06 part of catalyst. The hot melt adhesive prepared by the invention has the functions of salt spray resistance, creep resistance, high temperature and humidity resistance, high and low temperature resistance, artificial sebum resistance and the like, and is particularly suitable for the structural bonding of intelligent watches, mobile phone middle frames and rear covers and the structural bonding assembly of intelligent wearable products.

Description

Salt-fog-resistant single-component polyurethane hot melt adhesive and preparation method thereof

Technical Field

The invention belongs to the technical field of polyurethane hot melt adhesives, and relates to a single-component polyurethane hot melt adhesive and a preparation method thereof.

Background

The rapid development of electronic products, a large number of smart phones, notebook computers, tablet computers, wearable electronic products and other consumer electronic product accessories, and the like. At present, polyurethane hot melt adhesive is used more, and the hot melt adhesive is a novel halogen-free solvent-free advanced structure adhesive. The product is a reactive hot melt adhesive based on polyurethane. The adhesive has certain pressure sensitivity and can provide higher initial strength when contacting the bonded parts. The glue has longer open time, so the glue is suitable for automatic or manual assembly production. However, as the demand of various electronic products increases and the global climate difference increases, the weather resistance of the products is more and more required by electronic manufacturers to reduce the cost from the original idle running to marine transportation.

Therefore, it is urgent to develop a new single-component polyurethane hot melt adhesive with good adhesion, salt spray resistance, creep resistance, high temperature and humidity resistance, high and low temperature resistance, and artificial sebum resistance.

Disclosure of Invention

The invention solves one technical problem of providing the salt mist resistant single-component polyurethane hot melt adhesive which has high bonding strength, short curing time, salt mist resistance, creep resistance, high temperature and high humidity resistance, high and low temperature resistance, artificial sebum resistance and other excellent aging resistance, and is very suitable for bonding application of various electronic products in different climates. The invention solves another technical problem of providing a preparation method of the salt-fog-resistant single-component polyurethane hot melt adhesive.

The invention solves the problems through the following technical scheme:

the salt spray resistant single-component polyurethane hot melt adhesive is prepared from the following raw materials in parts by weight:

30-40 parts of polycarbonate dihydric alcohol, 10-20 parts of polyethylene glycol terephthalate, 3-8 parts of 1, 6-hexanediol phthalic anhydride polyester polyol, 8-15 parts of non-crystalline liquid saturated polyester, 15-20 parts of acrylic resin, 0.05-0.15 part of antioxidant, 0.05-0.15 part of flatting agent, 0.02-0.04 part of water removing agent, 18-23 parts of diisocyanate, 0.3-0.6 part of coupling agent and 0.03-0.06 part of catalyst.

Further, the polycarbonate diol has a molecular weight of 1000 to 2000, preferably about 1000, and has a repeating unit shown as follows:

。

the polycarbonate diols mentioned above can be prepared on the basis of the transesterification of 1, 6-hexanediol with dimethyl carbonate.

Furthermore, the polyethylene terephthalate can be prepared by performing ester exchange on dimethyl terephthalate and ethylene glycol or by esterifying terephthalic acid and ethylene glycol to synthesize dihydroxyethyl terephthalate and then performing polycondensation, belongs to crystalline saturated polyester, and has the molecular weight of 2000-3500.

Further, the 1, 6-hexanediol phthalic anhydride polyester polyol is commercially available as Spiracetam PH-56, and has a molecular weight of 1000 to 2000. Preferably having a molecular weight of about 1000, and obtainable on the basis of 1, 6-hexanediol and phthalic anhydride.

Further, the amorphous liquid saturated polyester is a linear copolymer with a poly-terminal hydroxyl functional group, and the molecular weight of the copolymer is 2000-3500.

Further, the molecular weight of the acrylic resin is 8000-28000.

Further, the antioxidant may be at least one of 3, 5-di-tert-butyl-4-hydroxyhydrocinnamate antioxidant and phenolic antioxidant; preferably 3, 5-di-tert-butyl-4-hydroxyhydrocinnamate antioxidant.

Further, the leveling agent is an acrylate copolymer.

Further, the water removing agent is isocyanate with a single functional group.

Further, the diisocyanate may be at least one of toluene diisocyanate or diphenylmethane diisocyanate; toluene diisocyanate is preferred.

Further, the coupling agent can be at least one or two of gamma- (2, 3-epoxypropoxy) propyl trimethoxy silane, gamma- (methacryloxy) propyl trimethoxy silane, mercaptopropyl trimethoxy silane, 3-isocyanatopropyl trimethoxy silane and gamma-aminopropyl triethoxy silane; gamma- (2, 3-glycidoxy) propyltrimethoxysilane is preferred.

Further, the catalyst can be at least one of dimorpholinyl diethyl ether or dibutyltin dilaurate and an organic bismuth-based catalyst; preferably dimorpholinodiethyl ether.

The invention also provides a preparation method of the salt mist resistant single-component polyurethane hot melt adhesive, which comprises the following steps:

step 1: weighing raw materials by weight, wherein 30-40 parts of polycarbonate dihydric alcohol, 10-20 parts of polyethylene glycol terephthalate, 3-8 parts of 1, 6-hexanediol phthalic anhydride polyester polyol, 8-15 parts of non-crystalline liquid saturated polyester, 15-20 parts of acrylic resin, 0.05-0.15 part of antioxidant, 0.05-0.15 part of flatting agent, 0.02-0.04 part of water removing agent, 18-23 parts of diisocyanate, 0.3-0.6 part of coupling agent and 0.03-0.06 part of catalyst.

Step 2: heating polycarbonate dihydric alcohol, polyethylene glycol terephthalate, 1, 6-hexanediol phthalic anhydride polyester polyol, noncrystalline liquid saturated polyester, acrylic resin, an antioxidant and a flatting agent to 120-130 ℃, dehydrating under the vacuum condition of less than or equal to-0.1 MPa until the moisture content is less than 400ppm, and cooling to 85-95 ℃;

and 3, step 3: adding a water removing agent and diisocyanate under the protection of nitrogen, stirring for 5-15min, heating to 95-105 ℃, and reacting for 1-2h;

and 4, step 4: and adding a coupling agent and a catalyst, stirring for 10-30min, discharging, and sealing and packaging to obtain the salt mist resistant single-component polyurethane hot melt adhesive.

The invention has the beneficial effects that: the salt mist resistant single-component polyurethane hot melt adhesive prepared by the invention has moderate viscosity, short opening time and smooth adhesive discharging, is suitable for various adhesive dispensing and spraying processes, and has good bonding effect on various plastics, ink glass, metals and the like. Meanwhile, compared with the traditional polyurethane hot melt adhesive, the polyurethane hot melt adhesive product has great breakthrough in the performances of salt mist resistance, creep resistance, high temperature and humidity resistance, high and low temperature resistance, artificial sebum resistance and the like, can meet the long-term use of various electronic products in different climates, and is particularly suitable for the structural bonding and assembly of intelligent watches, cell phone middle frames and rear covers and intelligent wearable products.

Detailed Description

The technical solutions of the present invention will be further described in detail with reference to specific examples and comparative examples, it is obvious that the described examples are only a part of the examples of the present invention, and all other examples obtained by those skilled in the art without making any inventive step belong to the protection scope of the present invention. The reagents involved in the present invention can be obtained from ordinary commercial sources unless otherwise specified.

The salt-fog-resistant single-component polyurethane hot melt adhesive disclosed by the invention is prepared from the following raw materials in parts by weight:

30-40 parts of polycarbonate dihydric alcohol, 10-20 parts of polyethylene glycol terephthalate, 3-8 parts of 1, 6-hexanediol phthalic anhydride polyester polyol, 8-15 parts of non-crystalline liquid saturated polyester, 15-20 parts of acrylic resin, 0.05-0.15 part of antioxidant, 0.05-0.15 part of flatting agent, 0.02-0.04 part of water removing agent, 18-23 parts of diisocyanate, 0.3-0.6 part of coupling agent and 0.03-0.06 part of catalyst.

In a preferred embodiment of the present invention, the polycarbonate diol is a polycarbonate diol having a molecular weight of 1000 to 2000, which is prepared by transesterification of 1, 6-hexanediol with dimethyl carbonate, and has a repeating unit as shown below:

。

in a preferred embodiment of the invention, the polyethylene terephthalate has a molecular weight of 2000 to 3500, is prepared by transesterification of dimethyl terephthalate with ethylene glycol or by esterification of terephthalic acid with ethylene glycol, followed by polycondensation to synthesize dihydroxyethyl terephthalate, and has the following repeating units:

。

in a preferred embodiment of the present invention, the 1, 6-hexanediol phthalic anhydride polyester polyol is Spiran, commercially available at pH-56.

In a preferred embodiment of the present invention, the amorphous liquid saturated polyester is a linear copolymer of poly-terminal hydroxyl functional groups with molecular weight of 2000-3500, and any amorphous liquid saturated polyester with molecular weight of 2000-3500 in the art can be used without affecting the effect of the product of the present invention.

In a preferred embodiment of the present invention, the acrylic resin has a molecular weight of 8000 to 28000.

In a preferred embodiment of the present invention, the antioxidant is a 3, 5-di-tert-butyl-4-hydroxyhydrocinnamate antioxidant.

In a preferred embodiment of the invention, the levelling agent is an acrylate copolymer.

In a preferred embodiment of the invention, the water scavenger is a monofunctional isocyanate.

In a preferred embodiment of the present invention, the diisocyanate is toluene diisocyanate.

In a preferred embodiment of the invention, the coupling agent is gamma- (2, 3-glycidoxy) propyltrimethoxysilane.

The salt spray resistant single-component polyurethane hot melt adhesive disclosed by the invention has the following formula of examples 1-3 and comparative examples 1-3:

specifically, the preparation steps of examples 1 to 3 and comparative examples 1 to 3 are as follows:

example 1:

step 1: weighing the raw materials by weight, wherein the raw materials comprise 25 parts of polycarbonate diol, 10 parts of polyether polyol, 15 parts of polyethylene terephthalate, 5 parts of Spilan PH-56, 10 parts of non-crystalline liquid saturated polyester, 15 parts of acrylic resin, 0.12 part of 3, 5-di-tert-butyl-4-hydroxy hydrocinnamate antioxidant, 0.1 part of acrylate copolymer, 0.03 part of monofunctional group isocyanate, 19.1 parts of toluene diisocyanate, 0.6 part of gamma- (2, 3-epoxypropoxy) propyltrimethoxysilane and 0.05 part of dimorpholinyl diethyl ether;

step 2: heating to 125 +/-5 ℃ by using a four-neck flask, putting polycarbonate dihydric alcohol, polyether glycol, polyethylene terephthalate, 1, 6-hexanediol phthalic anhydride polyester polyol, non-crystalline liquid saturated polyester, 3, 5-di-tert-butyl-4-hydroxy hydrocinnamate antioxidant and acrylate copolymer into the four-neck flask, and starting stirring. Vacuumizing to-0.1 MPa, dehydrating at 125 +/-5 ℃ for 2h, then breaking the vacuum by nitrogen, sampling to test the moisture content, wherein the moisture content is less than 400ppm, and cooling to 90 ℃;

and step 3: adding isocyanate with single functional group and toluene diisocyanate under the protection of nitrogen, vacuumizing and stirring for 10min, and heating to 100 ℃. Stirring for 1.5h and then feeding in the next step.

And 4, step 4: adding gamma- (2, 3-epoxypropoxy) propyl trimethoxy silane and dimorpholinyl diethyl ether, stirring for 20min, discharging, and sealing and packaging.

Example 2

Step 1: weighing raw materials by weight, wherein 30 parts of polycarbonate diol, 5 parts of polyether polyol, 15 parts of polyethylene terephthalate, 5 parts of Steilan PH-56, 10 parts of non-crystalline liquid saturated polyester, 15 parts of acrylic resin, 0.12 part of 3, 5-di-tert-butyl-4-hydroxy hydrocinnamate antioxidant, 0.1 part of acrylate copolymer, 0.03 part of monofunctional isocyanate, 19.1 parts of toluene diisocyanate, 0.6 part of gamma- (2, 3-epoxypropoxy) propyltrimethoxysilane and 0.05 part of dimorpholinyl diethyl ether;

step 2: heating to 125 +/-5 ℃ by using a four-neck flask, and putting the polycarbonate diol, the polyether polyol, the polyethylene terephthalate, the 1, 6-hexanediol phthalic anhydride polyester polyol, the amorphous liquid saturated polyester, the acrylic resin, the 3, 5-di-tert-butyl-4-hydroxy hydrocinnamate antioxidant and the acrylate copolymer into the four-neck flask for stirring. Vacuumizing to-0.1 MPa, dehydrating at 125 +/-5 ℃ for 2h, then breaking the vacuum by nitrogen, sampling to test the moisture content, wherein the moisture content is less than 400ppm, and cooling to 90 ℃;

and step 3: adding isocyanate with a monofunctional group and toluene diisocyanate under the protection of nitrogen, vacuumizing, stirring for 10min, and heating to 100 ℃. Stirring for 1.5h and then feeding in the next step.

And 4, step 4: adding gamma- (2, 3-epoxypropoxy) propyl trimethoxy silane and dimorpholinyl diethyl ether, stirring for 20min, discharging, and sealing and packaging.

Example 3

Step 1: weighing raw materials by weight, wherein 35 parts of polycarbonate diol, 15 parts of polyethylene glycol terephthalate, 5 parts of Spiran PH-56, 10 parts of non-crystalline liquid saturated polyester, 15 parts of acrylic resin, 0.12 part of 3, 5-di-tert-butyl-4-hydroxyhydrocinnamate antioxidant, 0.1 part of acrylate copolymer, 0.03 part of monofunctional group isocyanate, 19.1 parts of toluene diisocyanate, 0.6 part of gamma- (2, 3-epoxypropoxy) propyltrimethoxysilane and 0.05 part of dimorpholinyl diethyl ether;

step 2: heating to 125 +/-5 ℃ by using a four-neck flask, and putting the polycarbonate dihydric alcohol, the polyethylene terephthalate, the 1, 6-hexanediol phthalic anhydride polyester polyol, the non-crystalline liquid saturated polyester, the acrylic resin, the 3, 5-di-tert-butyl-4-hydroxy hydrocinnamate antioxidant and the acrylate copolymer into the four-neck flask for stirring. Vacuumizing to-0.1 MPa, dehydrating at 125 +/-5 ℃ for 2h, then breaking the vacuum by nitrogen, sampling to test the moisture content, wherein the moisture content is less than 400ppm, and cooling to 90 ℃;

and step 3: adding isocyanate with a single functional group and toluene diisocyanate under the protection of nitrogen, vacuumizing, stirring for 10min, heating to 100 ℃, stirring for 1.5h, and then carrying out the next feeding.

And 4, step 4: adding gamma- (2, 3-epoxypropoxy) propyl trimethoxy silane and dimorpholinyl diethyl ether, stirring for 20min, discharging, and sealing and packaging.

Comparative example 1

Step 1: weighing raw materials by weight, wherein the raw materials comprise 25 parts of polycarbonate diol, 10 parts of polyether polyol, 15 parts of polyethylene terephthalate, 5 parts of Spiracetam PH-56, 10 parts of amorphous liquid saturated polyester, 15 parts of acrylic resin, 0.12 part of 3, 5-di-tert-butyl-4-hydroxyhydrocinnamate, 0.1 part of acrylate copolymer, 0.03 part of monofunctional isocyanate, 19.1 parts of toluene diisocyanate, 0.6 part of 3-isocyanatopropyl trimethoxy silane and 0.05 part of dimorpholinyl diethyl ether;

step 2: heating to 125 +/-5 ℃ by using a four-neck flask, and putting the polycarbonate dihydric alcohol, the polyether polyol, the polyethylene terephthalate, the 1, 6-hexanediol phthalic anhydride polyester polyol, the non-crystalline liquid saturated polyester, 15 parts of acrylic resin, the 3, 5-di-tert-butyl-4-hydroxy hydrocinnamate antioxidant and the acrylate copolymer into the four-neck flask for stirring. Vacuumizing to-0.1 MPa, dehydrating at 125 +/-5 ℃ for 2h, then breaking the vacuum by nitrogen, sampling to test the moisture content, wherein the moisture content is less than 400ppm, and cooling to 90 ℃;

and step 3: adding isocyanate with a single functional group and toluene diisocyanate under the protection of nitrogen, vacuumizing, stirring for 10min, heating to 100 ℃, stirring for 1.5h, and then feeding in the next step.

And 4, step 4: adding 3-isocyanatopropyl trimethoxy silane and dimorpholinyl diethyl ether, stirring for 20min, discharging, and sealing and packaging.

Comparative example 2:

step 1: weighing raw materials by weight, wherein the raw materials comprise 30 parts of polycarbonate diol, 5 parts of polyether polyol, 15 parts of polyethylene terephthalate, 5 parts of Spilan PH-56, 10 parts of non-crystalline liquid saturated polyester, 15 parts of acrylic resin, 0.12 part of 3, 5-di-tert-butyl-4-hydroxy hydrocinnamate antioxidant, 0.1 part of acrylate copolymer, 0.03 part of monofunctional group isocyanate, 19.1 parts of toluene diisocyanate, 0.6 part of 3-isocyanatopropyl trimethoxy silane and 0.05 part of dimorpholinyl diethyl ether;

and 2, step: heating to 125 +/-5 ℃ by using a four-neck flask, and putting the polycarbonate dihydric alcohol, the polyether polyol, the polyethylene terephthalate, the 1, 6-hexanediol phthalic anhydride polyester polyol, the non-crystalline liquid saturated polyester, 15 parts of acrylic resin, the 3, 5-di-tert-butyl-4-hydroxy hydrocinnamate antioxidant and the acrylate copolymer into the four-neck flask for stirring. Vacuumizing to-0.1 MPa, dehydrating at 125 +/-5 ℃ for 2h, then breaking the vacuum by nitrogen, sampling to test the moisture content, wherein the moisture content is less than 400ppm, and cooling to 90 ℃;

and step 3: adding isocyanate with a single functional group and toluene diisocyanate under the protection of nitrogen, vacuumizing, stirring for 10min, heating to 100 ℃, stirring for 1.5h, and then feeding in the next step.

And 4, step 4: adding 3-isocyanatopropyl trimethoxy silane and dimorpholinyl diethyl ether, stirring for 20min, discharging, and sealing and packaging.

Comparative example 3:

step 1: weighing raw materials by weight, wherein 35 parts of polycarbonate diol, 15 parts of polyethylene glycol terephthalate, 5 parts of Spiran PH-56, 10 parts of non-crystalline liquid saturated polyester, 15 parts of acrylic resin, 0.12 part of 3, 5-di-tert-butyl-4-hydroxyhydrocinnamate antioxidant, 0.1 part of acrylate copolymer, 0.03 part of monofunctional group isocyanate, 19.1 parts of toluene diisocyanate, 0.6 part of 3-isocyanatopropyltrimethoxysilane and 0.05 part of dimorpholinyl diethyl ether;

step 2: heating to 125 +/-5 ℃ by using a four-neck flask, and putting the polyether polyol, the acrylic resin, the polyethylene terephthalate, the 1, 6-hexanediol phthalic anhydride polyester polyol, the non-crystalline liquid saturated polyester, the 3, 5-di-tert-butyl-4-hydroxy hydrocinnamate antioxidant and the acrylate copolymer into the four-neck flask for stirring. Vacuumizing to-0.1 MPa, dehydrating at 125 +/-5 ℃ for 2h, then breaking the vacuum by nitrogen, sampling to test the moisture, wherein the moisture is less than 400ppm, and cooling to 90 ℃;

and 3, step 3: adding isocyanate with a single functional group and toluene diisocyanate under the protection of nitrogen, vacuumizing, stirring for 10min, heating to 100 ℃, stirring for 1.5h, and then feeding in the next step.

And 4, step 4: adding isocyanate propyl trimethoxy silane and dimorpholinyl diethyl ether, stirring for 20min, discharging, and sealing and packaging.

In order to show that the salt mist resistant single-component polyurethane hot melt adhesive prepared by the application has the technical effects of salt mist resistance, creep resistance, high temperature and humidity resistance, high and low temperature resistance and sweat resistance, the performance of the polyurethane hot melt adhesive prepared in the examples 1-3 and the comparative examples 1-3 is detected.

Dispensing and sample preparation are completed under the condition of room temperature, after room temperature curing is completed for 24 hours, the sample assembly is pushed out at the same speed, and the push-out strength of the sample on the plate after various aging is evaluated.

The test criteria were as follows:

the salt spray resistance test method comprises the following steps: GB/T2423.17; the 90 ℃ creep resistance test method comprises the following steps: GB7750-1987, the high temperature and high humidity resistance test method is: GB/T2423.3-2006, the high and low temperature resistance test method is as follows: GB/T2423.4-2008, the test method for artificial sebum resistance is ASTMD4265-14.

The test results are shown in the following table:

item	Example 1	Example 2	Example 3	Comparative example 1	Comparative example 2	Comparative example 3
							RT24H jacking force/MPa	6.42	7.15	8.19	6.24	6.88	8.02
Salt spray resistant 24H rear jacking force/MPa	4.74	6.29	9.38	Fall off	5.22	6.18
							Creep resistance at 90 ℃ H	≥72H	≥72H	≥72H	≥72H	≥72H	≥72H
High temperature and humidity resistance of 55 ℃ and 95 percent, and 72H rear jacking force/MPa	7.61	8.26	10.62	6.79	7.06	10.47
							High and low temperature resistance of-40 to 80 ℃/hour circulation, 72H rear jacking force/MPa	7.46	8.65	11.75	6.82	7.39	11.26
Resisting artificial sebum 24H back jacking force/MPa	4.53	6.82	9.92	3.12	5.74	7.97

The difference between example 1 and comparative example 1 of the present application is: example 1 used was gamma- (2, 3-glycidoxy) propyltrimethoxysilane, comparative example 1 used was isocyanatopropyltrimethoxysilane; the difference between example 2 and comparative example 2 is: example 2 used was gamma- (2, 3-glycidoxy) propyltrimethoxysilane, comparative example 2 used was isocyanatopropyltrimethoxysilane; the difference between example 3 and comparative example 3 is: example 3 used was gamma- (2, 3-glycidoxy) propyltrimethoxysilane, comparative example 3 used was isocyanatopropyltrimethoxysilane; it can be seen from the data in the table that the examples are superior to the comparative examples in both salt spray resistance and artificial fat skin resistance. From the above analysis, it can be seen that the wetting effect and chemical resistance effect are significantly improved by using the gamma- (2, 3-glycidoxy) propyl trimethoxy silane coupling agent instead of the isocyanatopropyl trimethoxy silane coupling agent.

Comparative examples 1 to 3: example 1 contained 25 parts of polycarbonate diol and 10 parts of polyether polyol, example 2 contained 30 parts of polycarbonate diol and 5 parts of polyether polyol, and example 3 contained only 35 parts of polycarbonate diol. The data in the table show that the addition of polycarbonate diol is beneficial to chemical resistance effect, and the bonding strength is also obviously improved. The hot melt adhesive prepared from the polycarbonate polyol has better hydrolysis resistance, heat resistance, oxidation resistance, friction resistance and chemical resistance.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims (10)

1. The salt mist resistant single-component polyurethane hot melt adhesive is characterized by comprising the following preparation raw materials in parts by weight: 30-40 parts of polycarbonate dihydric alcohol, 10-20 parts of polyethylene glycol terephthalate, 3-8 parts of 1, 6-hexanediol phthalic anhydride polyester polyol, 8-15 parts of non-crystalline liquid saturated polyester, 15-20 parts of acrylic resin, 0.05-0.15 part of antioxidant, 0.05-0.15 part of flatting agent, 0.02-0.04 part of water removing agent, 18-23 parts of diisocyanate, 0.3-0.6 part of coupling agent and 0.03-0.06 part of catalyst.

2. The salt spray resistant one-component polyurethane hot melt adhesive as claimed in claim 1, wherein the polycarbonate diol has a molecular weight of 1000-2000 and has repeating units as shown in the following formula:

。

3. the salt fog resistant one-component polyurethane hot melt adhesive of claim 1, wherein the 1, 6-hexanediol phthalic anhydride polyester polyol is PH-56.

4. The salt fog resistant one-component polyurethane hot melt adhesive of claim 1, wherein the molecular weight of the polyethylene terephthalate is 2000-3500; the molecular weight of the acrylic resin is 8000-28000; the amorphous liquid saturated polyester is a linear copolymer of poly-terminal hydroxyl functional groups with the molecular weight of 2000-3500.

5. The salt spray resistant one-component polyurethane hot melt adhesive as claimed in claim 1, wherein the antioxidant is at least one of 3, 5-di-tert-butyl-4-hydroxyhydrocinnamate antioxidant and phenolic antioxidant.

6. The salt spray resistant one-component polyurethane hot melt adhesive as claimed in claim 1, wherein the leveling agent is an acrylate copolymer; the water removing agent is isocyanate containing a monofunctional group.

7. The salt fog resistant one-component polyurethane hot melt adhesive as claimed in claim 1, wherein the diisocyanate is at least one of toluene diisocyanate or diphenylmethane diisocyanate.

8. The salt spray resistant one-component polyurethane hot melt adhesive as claimed in claim 1, wherein the coupling agent comprises at least one of γ - (2, 3-epoxypropoxy) propyltrimethoxysilane, γ - (methacryloyloxy) propyltrimethoxysilane, mercaptopropyltrimethoxysilane, 3-isocyanatopropyltrimethoxysilane, and γ -aminopropyltriethoxysilane.

9. The salt mist resistant single-component polyurethane hot melt adhesive as claimed in claim 1, wherein the catalyst comprises at least one of dimorpholinyl diethyl ether, dibutyltin dilaurate and organic bismuth based catalysts.

10. The preparation method of the salt spray resistant one-component polyurethane hot melt adhesive as claimed in any one of claims 1 to 9, characterized by comprising the following steps:

step 1: weighing the components according to claim 1 to prepare raw materials;

and 2, step: heating polycarbonate dihydric alcohol, polyethylene terephthalate, 1, 6-hexanediol phthalic anhydride polyester polyol, amorphous liquid saturated polyester, acrylic resin, an antioxidant and a flatting agent to 120-130 ℃, dehydrating under the vacuum condition of less than or equal to-0.1 MPa until the moisture content is less than 400ppm, and cooling to 85-95 ℃;

and step 3: adding a water removing agent and diisocyanate under the protection of nitrogen, stirring for 5-15min, heating to 95-105 ℃, and reacting for 1-2h;

and 4, step 4: and adding a coupling agent and a catalyst, stirring for 10-30min, discharging, and sealing and packaging to obtain the salt mist resistant single-component polyurethane hot melt adhesive.