A one-component solvent-free polyurethane adhesive with high oxygen barrier and preparation method thereof

Abstract

The present invention relates to a high oxygen barrier single-component solvent-free polyurethane adhesive and a preparation method thereof. The raw materials include a polyol component, an isocyanate and a catalyst. The polyol component includes polybutadiene diol, polyether polyol, castor oil and fluorinated polyol. The mass ratio of polybutadiene diol, polyether polyol, castor oil and fluorinated polyol is 55-80:3-7:2-5:0.5-3. The single-component solvent-free polyurethane adhesive of the present invention uses polybutadiene diol as the main raw material of the polyol component in its specific formula, utilizes the lower free volume of the polybutadiene diol molecular chain, reduces the passage of oxygen and moisture, improves the barrier property of the polyurethane adhesive, and simultaneously cooperates with the use of fluorinated polyol to effectively increase the adhesion of the polyurethane adhesive on the surface of the substrate, so that the polyurethane adhesive of the present invention has a lower oxygen permeability and also has a higher peel strength.

Description

Technical Field

[0001] The invention belongs to the technical field of adhesives, and in particular relates to a single-component solvent-free polyurethane adhesive with high oxygen barrier and a preparation method thereof. Background Art

[0002] As people's living standards improve, some fresh products such as vegetables, fruits, and cold meat have introduced portable packaging, and these foods have higher and higher requirements for packaging. Early packaging used single-layer plastic films, such as PE and PP. However, these films have a high oxygen permeability. During transportation and storage, the food in the packaging bag is easily contaminated by oxygen, which shortens the shelf life and easily causes food safety problems.

[0003] In order to prevent food from being affected by oxygen and deteriorating, thereby increasing the shelf life of food, product packaging with low oxygen permeability is becoming more and more popular. At present, color printing factories have developed barrier structures with different structures by compounding films with high barrier materials to form an interlayer structure of "film / / high barrier layer / / film", such as PET / / VMPET / / PE, PET / / Al / / PE, PET / / VMPET / / CPP, PET / / Al / / PA / / RCPP, etc. This type of structure can achieve multiple functions of packaging materials, such as low oxygen permeability, high water vapor barrier, wear resistance, and beautiful appearance. However, the middle barrier layer uses metal aluminum, usually VMPET (aluminum-coated PET film) or Al, which has a high cost of use. In addition, due to the poor deformation ability of aluminum foil, the barrier performance of the packaging bag will be greatly reduced when the packaging bag is subjected to external forces such as bending and stretching during transportation and storage. However, the barrier properties of the conventional polyurethane adhesive used to bond adjacent layers in the above structure are poor, and cannot make up for the problem of reduced barrier properties due to the deformation ability of the aluminum foil, and it is even more impossible to omit the use of the intermediate barrier layer. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a single-component solvent-free polyurethane adhesive with high oxygen barrier and a preparation method thereof. The solvent-free polyurethane adhesive can provide a high oxygen barrier effect for a film with a high oxygen permeability, and can compensate to a certain extent for the problem of reduced barrier performance caused by the deformation ability of aluminum foil.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A high oxygen-barrier one-component solvent-free polyurethane adhesive, whose raw materials include a polyol component, an isocyanate and a catalyst, wherein the polyol component includes polybutadiene diol, polyether polyol, castor oil and fluorinated polyol, and the mass ratio of the polybutadiene diol, polyether polyol, castor oil and fluorinated polyol is 55-80:3-7:2-5:0.5-3.

[0007] According to some implementation aspects of the present invention, the polybutadiene diol is at least one of a hydroxyl-terminated polyolefin resin and a hydrogenated hydroxyl-terminated polyolefin resin.

[0008] Furthermore, the number average molecular weight of the polybutadiene diol is 1300-4000.

[0009] Furthermore, the polybutadiene diol is at least one selected from Krasol LBH-2000, Krasol LBH-P3000, and Krasol HLBH-P2000.

[0010] Preferably, the polybutadiene diol is a hydroxyl-terminated polyolefin resin.

[0011] According to some implementation aspects of the present invention, the fluorinated polyol is one or a combination of hexafluoropentanediol, octafluoro-1,6-hexanediol, and 2-fluoro-1,4-benzenediol.

[0012] According to some implementation aspects of the present invention, the polyether polyol is at least one of polyoxypropylene triol and polyoxypropylene-ethylene oxide triol.

[0013] According to some implementation aspects of the present invention, the number average molecular weight of the polyether polyol is 500 to 3500. Specifically, the polyether polyol is selected from MN-1000, MN-500, F3128 (Wanhua Chemical), etc.

[0014] According to some embodiments of the present invention, the isocyanate is at least one of toluene diisocyanate, diphenylmethane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and 1,5-naphthalene diisocyanate.

[0015] According to some implementation aspects of the present invention, the raw materials of the one-component solvent-free polyurethane adhesive include, by weight:

[0016]

[0017] Preferably, the raw materials of the one-component solvent-free polyurethane adhesive include, by weight:

[0018]

[0019] Furthermore, the catalyst is at least one of dibutyltin dilaurate, stannous octoate, zinc isooctanoate, bismuth isooctanoate, bismuth carboxylate, dimorpholine diethyl ether, and dimorpholine triethyl ether.

[0020] The second technical scheme adopted by the present invention is: a method for preparing the above-mentioned high oxygen barrier one-component solvent-free polyurethane adhesive, comprising dehydrating polybutadiene diol, polyether polyol, castor oil, fluorinated polyol and catalyst at 90-130°C to a moisture content of less than 0.03%, then cooling to 50-90°C, adding isocyanate to react so that the NCO% is 2-5%, and then vacuuming at 90-105°C to remove bubbles to obtain the one-component solvent-free polyurethane adhesive.

[0021] The high oxygen barrier single-component solvent-free polyurethane adhesive described above is suitable for various plastic-plastic composites, such as PET / / PE, PET / / PA / / PE, PET / / CPP, and can improve their barrier properties to oxygen; it is also suitable for aluminum-plastic composites, such as PET / / VMPET / / PE, PET / / Al / / PE, PET / / VMPET / / CPP, etc.

[0022] When the high oxygen barrier single-component solvent-free polyurethane adhesive described above is used for compounding PET and PE or CPP, it can replace part of the traditional PET / / PA / / PE or PET / / VMPET / / CPP structure and be used in packaging bags for some products, such as tea and biscuit products, and can also extend the shelf life of some conventional fast-moving consumer goods (such as fresh products).

[0023] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0024] The one-component solvent-free polyurethane adhesive of the present invention adopts polybutadiene diol as the main raw material of the polyol component in its specific formula, and utilizes the lower free volume of the polybutadiene diol molecular chain to reduce the passage of oxygen and moisture, thereby improving the barrier property of the polyurethane adhesive. At the same time, the use of fluorinated polyols is combined to effectively increase the adhesion of the polyurethane adhesive on the surface of the substrate, so that the polyurethane adhesive of the present invention has a lower oxygen permeability and also has a higher peel strength.

[0025] The polyurethane adhesive of the invention is solvent-free and environmentally friendly. DETAILED DESCRIPTION

[0026] The specific implementation of the present invention is further described in detail below in conjunction with specific embodiments, but the implementation and protection scope of the present invention are not limited thereto.

[0027] Example 1

[0028] The preparation method of the one-component solvent-free polyurethane adhesive with high oxygen barrier provided in this embodiment comprises the following steps:

[0029] 1) 73 parts by weight of Krasol LBH-2000 (molecular weight 2000), 5 parts by weight of MN 1000 (molecular weight 2000), 3.5 parts by weight of castor oil, 1.5 parts by weight of hexafluoropentanediol and 0.02 parts by weight of dibutyltin dilaurate were weighed and put into a reaction device, the temperature was raised to 110° C., stirring was started and vacuum was applied to reduce the water content of the mixture in the reaction device to below 0.03%;

[0030] 2) lowering the temperature to 70° C., adding 17 parts by weight of hexamethylene diisocyanate, and controlling the reaction temperature at 70° C., reacting for 2.5 hours, so that the NCO content is between 2% and 5% and tends to be stable;

[0031] 3) Maintaining the temperature at 100° C. and evacuating the system until there are no bubbles in the system, discharging the material, and packaging the material to obtain a one-component solvent-free polyurethane adhesive.

[0032] The prepared polyurethane adhesive was used to composite PET / / PA / / CPP structure through solvent-free composite equipment. The composite parameters were: composite temperature 80°C, composite speed 100m / min, and adhesive amount 1.8g / m 2 After the lamination is completed, it is placed in the aging room for complete aging. The prepared film is tested for peel strength and oxygen permeability. The peel strength of the PET / / PA layer is 3.2N / 15mm, the peel strength of the PA / / CPP layer is 5.3N / 15mm, and the oxygen permeability is 22cm 3 / (m 2 .24 h.0.1Mpa).

[0033] Comparative Example 1

[0034] The one-component solvent-free polyurethane adhesive provided in this comparative example is different from that in Example 1 in that 1.5 parts by weight of pentanediol is used instead of 1.5 parts by weight of hexafluoropentanediol.

[0035] Referring to the test method of Example 1, the peel strength of the PET / / PA layer is 2.7N / 15mm, the peel strength of the PA / / CPP layer is 4.5N / 15mm, and the oxygen permeability is 23cm 3 / (m 2 .24 h.0.1Mpa).

[0036] Comparative Example 2

[0037] The one-component solvent-free polyurethane adhesive provided in this comparative example is different from that in Example 1 in that 40 parts by weight of Krasol LBH-2000 and 33 parts of polyoxypropylene glycol PPG-2000 (molecular weight 2000) are used instead of 73 parts by weight of Krasol LBH-2000 in Example 1.

[0038] Referring to the test method of Example 1, the peel strength of the PET / / PA layer is 3.1N / 15mm, the peel strength of the PA / / CPP layer is 4.9N / 15mm, and the oxygen permeability is 33cm 3 / (m 2 .24 h.0.1Mpa).

[0039] Note: In the above tests, the peel strength test refers to GB / T 8808-1988, adopts T peeling, the sample width is (15±0.1) mm, and the peeling speed is 300 mm / min. The oxygen permeability test refers to GB / T1038-2000 "Plastic Film and Sheeting Gas Permeability Test Method Pressure Difference Method".

[0040] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

[0041] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

Claims

1. A one-component solvent-free polyurethane adhesive with high oxygen barrier, the raw materials of which include a polyol component, an isocyanate and a catalyst, characterized in that: The polyol component consists of polybutadiene diol, polyether polyol, castor oil and fluorinated polyol, and the mass ratio of the polybutadiene diol, polyether polyol, castor oil and fluorinated polyol is 55-80:3-7:2-5:0.5-3; the NCO% of the single-component solvent-free polyurethane adhesive is 2%-5%.

2. The one-component solvent-free polyurethane adhesive with high oxygen barrier according to claim 1, characterized in that: The polybutadiene diol is at least one of a hydroxyl-terminated polybutadiene resin and a hydrogenated hydroxyl-terminated polybutadiene resin.

3. The one-component solvent-free polyurethane adhesive with high oxygen barrier according to claim 1 or 2, characterized in that: The number average molecular weight of the polybutadiene diol is 1300-4000.

4. The one-component solvent-free polyurethane adhesive with high oxygen barrier according to claim 1 or 2, characterized in that: The polybutadiene diol is at least one selected from Krasol LBH-2000, Krasol LBH-P3000, and Krasol HLBH-P2000.

5. The one-component solvent-free polyurethane adhesive with high oxygen barrier according to claim 1, characterized in that: The fluorinated polyol is one or a combination of hexafluoropentanediol, octafluoro-1,6-hexanediol, and 2-fluoro-1,4-benzenediol.

6. The one-component solvent-free polyurethane adhesive with high oxygen barrier according to claim 1, characterized in that: The polyether polyol is at least one of polyoxypropylene triol and polyoxypropylene-ethylene oxide triol.

7. The one-component solvent-free polyurethane adhesive with high oxygen barrier according to claim 1, characterized in that: The number average molecular weight of the polyether polyol is 500 to 3500; and / or the isocyanate is at least one of toluene diisocyanate, diphenylmethane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and 1,5-naphthalene diisocyanate.

8. The one-component solvent-free polyurethane adhesive with high oxygen barrier according to claim 1, characterized in that: The raw materials of the one-component solvent-free polyurethane adhesive include, by weight:

9. The one-component solvent-free polyurethane adhesive with high oxygen barrier according to claim 8, characterized in that: The raw materials of the one-component solvent-free polyurethane adhesive include, by weight:

10. A method for preparing a one-component solvent-free polyurethane adhesive with high oxygen barrier according to any one of claims 1 to 9, characterized in that: The preparation method comprises dehydrating polybutadiene diol, polyether polyol, castor oil, fluorinated polyol and a catalyst at 90-130° C. to a moisture content of less than 0.03%, then cooling to 50-90° C., adding isocyanate to react so that the NCO% is 2%-5%, and then vacuuming at 90-105° C. to remove bubbles, thereby obtaining the one-component solvent-free polyurethane adhesive.

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