WO2018120741A1

WO2018120741A1 - Barrier material, polyurethane adhesive containing same, skin and aircraft

Info

Publication number: WO2018120741A1
Application number: PCT/CN2017/092061
Authority: WO
Inventors: 刘若鹏; 栾琳; 许永伦
Original assignee: 深圳光启空间技术有限公司
Priority date: 2016-12-29
Filing date: 2017-07-06
Publication date: 2018-07-05
Also published as: CN108250647B; CN108250647A

Abstract

A barrier material, a polyurethane adhesive containing same, a skin and an aircraft. The barrier material comprises a povidone and an ethylene/vinyl alcohol copolymer coupled with a coupling agent. After coupling the povidone and the ethylene/vinyl alcohol copolymer with the coupling agent, the povidone will enclose the ethylene/vinyl alcohol copolymer, thus reducing the water absorbability of the ethylene/vinyl alcohol. Meanwhile, the effects of mixing the ethylene/vinyl alcohol copolymer with the adhesive are increased by using povidone, and therefore the barrier material maintains better barrier properties and has low water absorbability. When applying the barrier material into an adhesive, the adhesive will have better adhesive effects. Therefore, when applying the adhesive comprising the barrier material to an envelope material, a barrier layer can be replaced and the weight of a corresponding aircraft can be lightened, thus increasing flight performance of the aircraft.

Description

Barrier material, polyurethane adhesive with the same, skin and aircraft

[0001] The present invention relates to the field of capsule materials, and in particular to a barrier material, a polyurethane adhesive having the same, a skin and an aircraft.

Background technique

[0002] At this stage, in the manufacture of capsule materials, barrier properties are often provided by a layer of PET film or other barrier film.

technical problem

[0003] This means that an additional layer of barrier layer is required, and the addition of the barrier layer necessarily increases the weight of the boat, resulting in a decrease in the performance of the airship.

Problem solution

Technical solution

[0004] The main object of the present invention is to provide a barrier material, a polyurethane adhesive having the same, a skin and an aircraft, to solve the problem that the balloon material in the prior art causes an increase in weight due to the need to separately provide a barrier layer. .

In order to achieve the above object, according to an aspect of the invention, there is provided a barrier material comprising povidone and an ethylene/vinyl alcohol copolymer coupled by a coupling agent.

Further, the above coupling agent is a silane coupling agent.

Further, the weight ratio of the above coupling agent to the ethylene/vinyl alcohol copolymer is 1:5 to 1:2.

Further, the weight ratio of the coupling agent to povidone is 1:5 to 1:2.

Further, the povidone is a linear homopolymer of povidone, and preferably, the povidone has a K value of 10 to 100.

Further, the vinyl content in the above ethylene/vinyl alcohol copolymer ranges from 20 to 45%.

[0011] According to another aspect of the present invention, there is provided a polyurethane adhesive comprising a main component and a curing agent component, the main component comprising a solution of any of the above barrier materials, the solvent of the solution being Polar solvent.

[0012] Further, the above barrier material has a weight percentage of 2 to 10% in the main component.

[0013] Further, the polar solvent is methyl ethyl ketone, methanol, DMSO, DMF, tetrahydrofuran or chloroform. [0014] Further, the weight ratio of the barrier material to the polar solvent is 2:8 to 3:7.

[0015] According to another aspect of the present invention, there is provided a skin comprising an adhesive layer, a bearing layer, a weather resistant layer, and the adhesive layer is prepared using any of the above adhesives, and the adhesive layer is used as The barrier layer of the skin.

[0016] According to another aspect of the present invention, there is provided an aircraft comprising a skin, the skin being the skin of the invention described above.

Beneficial effect

[0017] Applying the technical solution of the present invention, after coupling the povidone and the ethylene/vinyl alcohol copolymer with a coupling agent, the povidone forms a coating effect on the ethylene/vinyl alcohol copolymer, and the ethylene/vinyl alcohol is lowered. The ability to absorb water, the use of povidone enhances the mixing effect of ethylene/vinyl alcohol copolymer and adhesive, which makes the barrier material maintain better barrier properties and has low water absorption. The bismuth in the adhesive makes the adhesive have a better adhesive effect. Therefore, the application of the adhesive containing the barrier material of the present application to the capsule material can replace the barrier layer, thereby reducing the weight of the corresponding aircraft and improving the flight performance of the aircraft.

Embodiments of the invention

[0018] It should be noted that, in the case of no conflict, the features in the embodiments and the embodiments in the present application may be combined with each other. The invention will be described in detail below with reference to the embodiments.

[0019] As analyzed by the background art of the present application, a barrier layer is generally provided in the prior art capsule material to achieve gas barrier, but the barrier layer is disposed to cause the weight of the aircraft utilizing the capsule material. In order to solve this problem, the present invention provides a barrier material, a polyurethane adhesive having the same, a skin and an aircraft.

In order to solve the above problems, the inventors of the present application desire to apply a material having barrier properties to a capsule material as an adhesive to form a bonding layer, and the bonding layer is used to achieve the effect of bonding and gas combination. The inventors studied the gas barrier properties of various barrier materials in the prior art, and preferred an ethylene/vinyl alcohol copolymer, but in the application of the adhesive to the adhesive of the capsule material, it was found to be extremely difficult to directly Used in adhesives. In order to further solve the problem, the inventors attempted to modify the ethylene/vinyl alcohol copolymer without affecting the original gas barrier effect, and found that the povidone-to-ethylene/vinyl alcohol copolymer was used. After the package modification, the adhesive can be directly applied. After studying the relationship between the two, the inventors used a coupling agent to couple the povidone and the ethylene/vinyl alcohol copolymer, and the ethylene/vinyl alcohol copolymer can maintain the original properties and is applied to the glue. Adhesives in the adhesive can enhance the bonding effect.

Based on this, in an exemplary embodiment of the present application, a barrier material is provided comprising a povidone coupled with a coupling agent and an ethylene/vinyl alcohol copolymer.

[0022] After coupling the povidone and the ethylene/vinyl alcohol copolymer with a coupling agent, the povidone forms a coating effect on the ethylene/vinyl alcohol copolymer, thereby reducing the absorption capacity of ethylene/vinyl alcohol for water,吋 The use of povidone enhances the mixing effect of ethylene/vinyl alcohol copolymer and adhesive, which in turn makes the barrier material maintain good barrier properties and has low water absorption, which makes it sticky in the application to adhesives. The agent has a better adhesive effect. Therefore, the application of the adhesive containing the barrier material of the present application to the capsule material can replace the barrier layer, thereby reducing the weight of the corresponding aircraft and improving the flight performance of the aircraft.

[0023] The above-mentioned barrier material is mainly prepared by coupling povidone and ethylene/vinyl alcohol copolymer. The preparation method can be prepared by referring to the prior art, preferably by the following method:

[0024] In a three-necked flask, PVP (povidone) and distilled water were added, and the mixture was heated to 60 to 70 ° C, and EVOH (ethylene-vinyl alcohol copolymer) to which a coupling agent was added was added dropwise, and refluxed for about 1 hour. The aqueous solution is led to an open bottle and dried in an environment of 30 to 40 ° C to obtain a powder or granular material as a barrier material. PVP is a package for EVOH, EVOH is a high-efficiency barrier component, water is the carrier, and the coupling agent is a bridging agent.

, heating back is the means.

[0025] The main function of the above coupling agent is mainly to couple the ethylene/vinyl alcohol copolymer having gas barrier properties with the cohesive povidone, and the hydrophilic end thereof is connected with the ethylene/vinyl alcohol copolymer. The oleophilic terminal is linked to the povidone, and in order to avoid the influence of the coupling agent on the gas barrier property, the coupling agent is preferably a silane coupling agent, and preferably the terminal group includes a methyl group, a vinyl group, an epoxy group, and an acryloyl group. An oxy or isocyanate based silane coupling agent.

Further, it is preferred that the weight ratio of the above coupling agent to the ethylene/vinyl alcohol copolymer is 1:5 to 1:2 to achieve coupling of as much as possible of the bare hydroxyl group of the ethylene/vinyl alcohol copolymer.

[0027] In order to enable the povidone to function as a coating of the ethylene/vinyl alcohol copolymer, the weight ratio of the coupling agent to the povidone is preferably 1:5 to 1:2.

[0028] The inventors of the present application unexpectedly found in the experiment that when the linear homopolymer of povidone is used, the effect is more obvious, and further, when the K value of povidone is 10 to 100 Å, the barrier material is applied to the polyurethane. In the adhesive, The improvement of the polyurethane adhesive is more suitable, and the resulting bonding effect is better.

[0029] In order to reduce the water absorption of the ethylene/ethylene copolymer as much as possible, it is preferred that the ethylene/vinyl alcohol copolymer has a vinyl content ranging from 20 to 45%.

[0030] In another exemplary embodiment of the present application, the above polyurethane adhesive comprises a main component and a curing agent component, and the main component comprises a solution of any one of the above barrier materials, The solvent of the solution is an organic solvent. The barrier material of the present application is applied to a polyurethane adhesive, and the ethylene/vinyl alcohol copolymer in the barrier material is used to make the polyurethane adhesive have good gas barrier properties, and is enhanced by the action of a coupling agent and povidone. The bonding effect of the polyurethane adhesive. The polar solvent can improve the mixing effect of the barrier material and the original components of the main component.

[0031] The above-mentioned main component is a mixture of the barrier material of the present application and the main component of the conventional polyurethane adhesive of the prior art, that is, the main agent of the conventional polyurethane adhesive in the prior art. The components are not particularly required. In addition, the curing agent component is also selected from the prior art and will not be described herein.

[0032] According to the requirements of the conventional conventional flying device for gas barrier properties, it is preferred that the above-mentioned barrier material has a weight percentage of 2 to 10% in the main component.

Further, it is preferred that the polar solvent be a more polar solvent such as methyl ethyl ketone, methanol, DMSO, DMF, tetrahydrofuran or chloroform.

The viscosity of the main component is adjusted by using the above polar solvent. In order to control the viscosity, the weight ratio of the above barrier material to the polar solvent is preferably 2:8 to 3:7.

[0035] The above polyurethane adhesive is mainly formed by mixing the existing main component of the polyurethane adhesive with the barrier material, preferably by the following method:

[0036] The barrier material is added to a polar solvent to prepare a mixed solution; the mixed solution is added to the original main component of the polyurethane adhesive to form an initial mixture. The initial mixture is placed in an ultrasonic device for heating and shaking, and the temperature is set at 30 to 35 ° C. The oscillating dispersion is about half a mile, and the main component is obtained by discharging.

[0037] In another exemplary embodiment of the present application, a skin is provided, including a bonding layer, a bearing layer, a weathering layer, and the bonding layer is prepared by using any one of the above adhesives, and The tie layer acts as a barrier to the skin. The adhesive layer prepared by using the adhesive of the present application has a gas barrier effect, so that it can be used as a barrier layer, thereby avoiding the problem of an increase in the weight of the skin caused by separately providing the barrier layer.

[0038] In still another exemplary embodiment of the present application, an aircraft is provided, including a skin, the skin being The above mentioned skin. Since the skin of the present application does not need to be provided with a separate barrier layer, the weight of the skin with the barrier layer is lighter, thereby improving the flight performance of the aircraft.

[0039] Advantageous effects of the present application will be further described below in conjunction with the examples and comparative examples.

Embodiment 1

[0041] In a three-necked flask, 45 g of PVP K30 and 210 g were added.

Distilled water, heated to 65 ° C, 45 g of EVOH added with 15 g of KH550 coupling agent was added dropwise, and the reaction was refluxed for 1 hour, and then taken out and placed in an oven at 40 ° C for 12 hours to obtain a barrier material. Then, it was formulated into a methyl ethyl ketone solution with a barrier content of 20%, and 15 g of methyl ethyl ketone solution was added to 100 g of Henkel Liofol UR2880 polyurethane adhesive main agent to form a mixed system with Henkel LA.

5001 curing agent is mixed, the mixing ratio is 5:1, the mixed system is heated to 30 °C in ultrasonic wave, the vibration is dispersed for half a small 吋, and the packaging is discharged. After testing, it is coated on 3F-S8C85TPU film, and the penetration rate of 20~30g/m2 can reach 500mL/(m2x24hxatm;).

Embodiment 2

[0043] In a three-necked flask, 30 g of PVP K30, 15 g of PVP K60 and 210 g of distilled water were added and heated to 70. C, 45 g of EVOH added with 15 g of KH550 coupling agent was added dropwise, and the reaction was refluxed for 1 hour, and then taken out and placed in an oven at 40 ° C for 12 hours to obtain a barrier material. Then formulated into a 20% butanone solution with a barrier material content, 20 g of methyl ethyl ketone solution was added to 100 g of Henkel Liofol UR2880 polyurethane adhesive main agent to form a mixed system, mixed with Henkel LA 5001 curing agent, the mixing ratio was 5:1, The mixed system was heated to 30 ° C in ultrasonic waves, oscillated and dispersed for half a small amount, and discharged. After testing, it is coated on the 3F-S8C85TPU film, and the 20~25g/m2 sizing amount can reach the bleed rate of 600mL/(m2x24hxatm).

Embodiment 3

[0045] In a three-necked flask, 20 g of PVP K30, 35 g of PVP K60 and 210 g of distilled water were added and heated to 70. C, 45 g of EVOH added with 10 g of KH550 and 5 g of KH570 coupling agent was added dropwise, and the reaction was refluxed for 1 hour, and then taken out and placed in an oven at 40 ° C for 24 hours to obtain a barrier material. Then, it is formulated into a 30% butanone solution as a barrier material, and 20 g of a butanone solution is added to 100 g of Henkel Liofol UR2880 polyurethane adhesive main agent to form a mixed system, which is mixed with Henkel LA 5001 curing agent at a mixing ratio of 5:1. Heated to 30 ° C in the ultrasonic wave, oscillated and dispersed half a small 吋, discharge packaging. After testing, it is coated on 3F-S8C85TPU film, and the 20~25g/m2 sizing amount can reach the turbidity rate of 400mL/(m2x24hxatm). Example 4

[0047] In a three-necked flask, 40 g of PVP K30 and 210 g were added.

Distilled water, heated to 65 ° C, 50 g of EVOH added with 10 g of KH550 coupling agent was added dropwise, and the reaction was refluxed for 1 hour, and then taken out and placed in an oven at 40 ° C for 12 hours to obtain a barrier material. Then, a methyl ethyl ketone solution having a barrier content of 20% was prepared, and 15 g of the methyl ketone solution was added to 100 g of Henkel Liofol UR2880 polyurethane adhesive main agent to form a mixed system with Henkel LA.

5001 curing agent is mixed, the mixing ratio is 5:1, the mixed system is heated to 30 °C in ultrasonic wave, the vibration is dispersed for half a small 吋, and the packaging is discharged. After testing, it is coated on 3F-S8C85TPU film, and the turbidity of 20~30g/m2 can reach 氦 484 484mL/(m2x24hxatm).

Embodiment 5

[0049] In a three-necked flask, 50 g of PVP K30 and 210 g were added.

Distilled water, heated to 65 ° C, 40 g of EVOH added with 10 g of KH550 coupling agent was added dropwise, and refluxed for 1 hour, taken out and placed in an oven at 40 ° C, and dried for 12 hours to obtain a barrier material. Then, a methyl ethyl ketone solution having a barrier content of 20% was prepared, and 15 g of the methyl ketone solution was added to 100 g of Henkel Liofol UR2880 polyurethane adhesive main agent to form a mixed system with Henkel LA.

5001 curing agent is mixed, the mixing ratio is 5:1, the mixed system is heated to 30 °C in ultrasonic wave, the vibration is dispersed for half a small 吋, and the packaging is discharged. After testing, it is coated on 3F-S8C85TPU film, and the turbidity of 20~30g/m2 can reach 氦 481 mL/(m2x24hxatm).

Example 6

[0051] In a three-necked flask, 40 g of PVP K30 and 210 g were added.

Distilled water, heated to 65 ° C, 40 g of EVOH added with 20 g of KH550 coupling agent was added dropwise, and refluxed for 1 hour, taken out and placed in an oven at 40 ° C, and dried for 12 hours to obtain a barrier material. Then, a methyl ethyl ketone solution having a barrier content of 20% was prepared, and 15 g of the methyl ketone solution was added to 100 g of Henkel Liofol UR2880 polyurethane adhesive main agent to form a mixed system with Henkel LA.

5001 curing agent is mixed, the mixing ratio is 5:1, the mixed system is heated to 30 °C in ultrasonic wave, the vibration is dispersed for half a small 吋, and the packaging is discharged. After testing, it is coated on 3F-S8C85TPU film, and the turbidity of 20~30g/m2 can reach 507mL/(m2x24hxatm).

Example 7 [0053] In a three-necked flask, 55 g of PVP K30 and 210 g were added.

Distilled water, heated to 65 ° C, 35 g of EVOH added with 10 g of KH550 coupling agent was added dropwise, and the reaction was refluxed for 1 hour, and then taken out and placed in an oven at 40 ° C for 12 hours to obtain a barrier material. Then, it was formulated into a methyl ethyl ketone solution with a barrier content of 20%, and 15 g of a methyl ethyl ketone solution was added to a 100 g Henkel Liofol UR2880 polyurethane adhesive base to form a mixed system with Henkel LA.

5001 curing agent is mixed, the mixing ratio is 5:1, the mixed system is heated to 30 °C in ultrasonic wave, the vibration is dispersed for half a small 吋, and the packaging is discharged. After testing, it is coated on 3F-S8C85TPU film, and the turbidity of 469mL/(m2x24hxato) can be achieved by 20~30g/m2.

Example 8

[0055] In a three-necked flask, 35 g of PVP K30 and 210 g were added.

Distilled water, heated to 65 ° C, 55 _{g of} EVOH added with 10 _{g of} KH550 coupling agent was added dropwise, refluxed for 1 hour, taken out and placed in an oven at 40 ° C, and dried for 12 hours to obtain a barrier material. Then formulated into a methyl ethyl ketone solution with a 20% barrier content, and 15 g of a butanone solution was added to 100 g of Henkel Liofol UR2880 polyurethane adhesive base to form a mixed system with Henkel LA.

The 5001 curing agent was mixed at a mixing ratio of 5:1. The mixed system was heated to 30 ° C in ultrasonic waves, shaken for half an hour, and discharged. After testing, it was coated on 3F-S8C85TPU film, and the turbidity of 20~30g/m2 was 473mL/(m2x24hxatm).

Example 9

[0057] In a three-necked flask, 45 g of PVP K30 and 210 g were added.

Distilled water, heated to 65. C, 45 g of EVOH added with 15 g of KH550 coupling agent was added dropwise, and the reaction was refluxed for 1 hour, and then taken out and placed in an oven at 40 ° C for 12 hours to obtain a barrier material. Then, a methyl ethyl ketone solution having a barrier content of 20% was prepared, and 10 g of a methyl ketone solution was added to a 100 g Henkel Liofol UR2880 polyurethane adhesive base to form a mixed system with Henkel LA.

The 5001 curing agent is mixed at a mixing ratio of 5:1. The mixed system is heated to 30 ° C in ultrasonic waves, shaken for half an hour, and discharged. After testing, it was coated on 3F-S8C85TPU film, and the turbidity of 20~30g/m2 was 492mL/(m2x24hxatm).

Embodiment 10

[0059] In a three-necked flask, 45 g of PVP K30 and 210 g were added Distilled water, heated to 65 ° C, 45 g of EVOH added with 15 g of KH550 coupling agent was added dropwise, refluxed for 1 hour, taken out and placed in an oven at 40 ° C, and dried for 12 hours to obtain a barrier material. Then formulated into a methyl ethyl ketone solution with a barrier content of 20%, and 50 g of a butanone solution was added to 100 g of Henkel Liofol UR2880 polyurethane adhesive base to form a mixed system with Henkel LA.

5001 curing agent is mixed, the mixing ratio is 5:1, the mixed system is heated to 30 °C in ultrasonic wave, the vibration is dispersed for half a small 吋, and the packaging is discharged. After testing, it was coated on 3F-S8C85TPU film, and the turbidity of 510mL/(m2x24hxatm;) was achieved by 20~30g/m2.

Example 11

[0061] In a three-necked flask, 45 g of PVP K30 and 210 g were added.

Distilled water, heated to 65 ° C, 45 g of EVOH added with 15 g of KH550 coupling agent was added dropwise, and the reaction was refluxed for 1 hour, and then taken out and placed in an oven at 40 ° C for 12 hours to obtain a barrier material. Then, a methanol solution having a barrier content of 20% was prepared, and 15 g of a methanol solution was added to 100 g of Henkel Liofol UR2880 polyurethane adhesive main agent to form a mixed system with Henkel LA.

5001 curing agent is mixed, the mixing ratio is 5:1, the mixed system is heated to 30 °C in ultrasonic wave, the vibration is dispersed for half a small 吋, and the packaging is discharged. After testing, it is coated on 3F-S8C85TPU film, and the turbidity of 20~30g/m2 can reach 203mL/(m2x24hxatm;).

Example 12

[0063] In a three-necked flask, 45 g of PVP K10 and 210 g were added.

5001 curing agent is mixed, the mixing ratio is 5:1, the mixed system is heated to 30 °C in ultrasonic wave, the vibration is dispersed for half a small 吋, and the packaging is discharged. After testing, it is coated on 3F-S8C85TPU film, and the turbidity of 20~30g/m2 can reach the penetration rate of 51 lm!J (m2x24hxatm;).

Example 13

[0065] In a three-necked flask, 45 g of PVP K100 and 210 g were added.

Distilled water, heated to 65 ° C, 45 g of EVOH (with vinyl content) added with 15 g of KH550 coupling agent Between 30~45%), the reaction was refluxed for 1 hour, then taken out and placed in an oven at 40 °C, and dried for 12 hours to obtain a barrier material. Then formulated into a butanone solution with a barrier content of 20%, 15 g of methyl ethyl ketone solution was added to 100 g of Henkel Liofol UR2880 polyurethane adhesive main agent to form a mixed system, mixed with Henkel LA 5001 curing agent, the mixing ratio was 5:1, The mixed system was heated to 30 ° C in ultrasonic waves, oscillated and dispersed for half a small amount, and discharged. After testing, it is coated on the 3F-S8C85TPU film, and the turbidity of 20~30g/m2 can reach the osmotic rate of 509mL/(m2x24hxatm;).

The composition of the EVOH used in each of the examples is shown in the following table.

Comparative Example 1

[0068] The polyurethane adhesive formed by the Henkel Liofol UR2880 polyurethane adhesive main agent and the Henkel LA 5001 curing agent is coated on the 3F-S8C85TPU film, and the 20-30 g/m2 sizing amount can reach the bleed rate of 2358 mL/( M2x24hxatm)=

[0069] According to the comparison of the respective examples and Comparative Example 1, it can be seen that the effect of the polyurethane adhesive of the present application is significantly better than that of the comparative example.

[0070] From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects: [0071] Convergence after coupling of povidone and ethylene/vinyl alcohol copolymer using a coupling agent The ketone forms a coating effect on the ethylene/vinyl alcohol copolymer, which reduces the water absorption capacity of the ethylene/vinyl alcohol, and the use of povidone enhances the mixing effect of the ethylene/vinyl alcohol copolymer and the adhesive, thereby making the barrier The material maintains good barrier properties and has low water absorption, and it is applied to the adhesive to make the adhesive have a better adhesive effect. Therefore, the application of the adhesive containing the barrier material of the present application to the capsule material can replace the barrier layer, thereby reducing the weight of the corresponding aircraft and improving the flight performance of the aircraft.

The above description is only the preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes can be made to the present invention. Within the spirit and principles of the present invention Any modifications, equivalent substitutions, improvements, etc., shall be included in the scope of protection of the present invention _;

Claims

Claim

[Claim 1] A barrier material comprising povidone and an ethylene/vinyl alcohol copolymer coupled by a coupling agent.

[Claim 2] The barrier material according to claim 1, wherein the coupling agent is a silane coupling agent.

[Claim 3] The barrier material according to claim 1, wherein a weight ratio of the coupling agent to the ethylene/vinyl alcohol copolymer is 1:5 to 1:2.

[Claim 4] The barrier material according to claim 1, wherein a weight ratio of the coupling agent to the povidone is 1:5 to 1:2.

[Claim 5] The barrier material according to claim 1, wherein the povidone is a linear homopolymer of povidone, and preferably the povidone has a K value of 10 to 100.

[Claim 6] The barrier material according to claim 1, wherein the ethylene/vinyl alcohol copolymer has a vinyl content of 20 to 45 < 3⁄4.

[Claim 7] A polyurethane adhesive comprising a main component and a curing agent component, wherein the main component comprises a solution of the barrier material according to any one of claims 1 to 6. The solvent of the solution is a polar solvent.

[Claim 8] The polyurethane adhesive according to claim 7, wherein the barrier material has a weight percentage of 2 to 10% in the main component.

[Claim 9] The polyurethane adhesive according to claim 7, wherein the polar solvent is butanone, methanol, DMSO, DMF, tetrahydrofuran or chloroform.

[Claim 10] The polyurethane adhesive according to claim 9, wherein a weight ratio of the barrier material to the polar solvent is 2:8 to 3:7.

[Claim 11] A skin comprising a bonding layer, a bearing layer, and a weathering layer, wherein the bonding layer is prepared by using the adhesive according to any one of claims 7 to 10. And the bonding layer acts as a barrier layer for the skin.

[Claim 12] An aircraft comprising a skin, wherein the skin is according to claim 11.