High-strength gas barrier polyurethane adhesive and preparation method thereof

Abstract

The invention discloses a high-strength gas barrier polyurethane adhesive and a preparation method thereof.The high-strength gas barrier polyurethane adhesive is composed of a main agent component A and a curing agent component B. The main agent component A comprises, by weight, 80-85 parts of a solvent A and 15-20 parts of polyurethane resin; and the curing agent B component comprises the following components in parts by weight: 0.75 to 2.0 parts of lamellar hydrotalcite (LDHs), 2.0 to 6.0 parts of polyisocyanate and 20.0 to 50.0 parts of solvent B. According to the invention, the polyisocyanate modified lamellar LDHs can be uniformly dispersed with a polyurethane matrix, and the prepared polyurethane adhesive has excellent gas barrier property and mechanical property, is used for film material bonding, and has good bonding property.

Description

Technical Field

[0001] This invention belongs to the field of polyurethane adhesive materials, and particularly relates to a high-strength gas barrier polyurethane adhesive and its preparation method. Background Technology

[0002] Polyurethane (PU) is a type of polymer material formed by block copolymerization of flexible soft segments and rigid hard segments. Due to its highly tunable molecular structure, it possesses excellent flexibility, a wide hardness range, good wear resistance, and adhesive properties, making it widely used in military and civilian fields such as food packaging, hot air balloons, civilian airships, airships, and inflatable fenders for ships. Especially as a barrier adhesive, PU can effectively achieve high-strength bonding between various substrates such as polyester (PET), polyvinylidene fluoride (PVF), polyvinylidene fluoride (PVDF), and fabrics, while also providing barrier properties against gases such as air, water vapor, oxygen, and helium. Therefore, it shows broad application prospects in high-end flexible packaging, new energy storage and transportation equipment, and special protective materials.

[0003] However, conventional polyurethane materials have poor gas barrier properties, making it difficult to meet the stringent requirements of low permeability in high-performance barrier applications. To improve their barrier performance, existing technologies generally employ the introduction of two-dimensional layered nanomaterials (such as montmorillonite (MMT), layered double hydroxides (LDHs), graphene and its derivatives, hexagonal boron nitride (h-BN), molybdenum disulfide (MoS2), transition metal carbon / nitrides (MXene), etc.) into the PU matrix. Utilizing the tortuous path effect imparted by their layered structure, the diffusion path of gas molecules is effectively extended at relatively low addition amounts, thereby significantly improving the gas barrier performance of polyurethane-based composite materials.

[0004] CN114853978A and CN116063650A respectively used in-situ polymerization to synthesize Ti3C2T x MXene and flake pearlescent powder are introduced into the PU matrix to prepare a gas barrier membrane material with high weather resistance and good mechanical properties. However, this method has problems such as complex preparation process, poor process stability and difficulty in large-scale production.

[0005] CN113831830A and CN119503850A propose introducing graphene microcapsules or large-size hydrotalcite into polyurethane (PU), but the resulting materials still do not achieve ideal gas barrier properties. Furthermore, CN113337101A discloses a method of introducing ionol into thermoplastic polyurethane (TPU) films. After the ionol reacts with vinyl polysiloxane, it coats the surface of graphene-hydrotalcite, ensuring uniform dispersion, thus preparing a high-barrier TPU film. This successfully improves the material's barrier properties, but the tensile strength of the resulting film is only about 20 MPa, far from meeting the requirements for high-strength applications.

[0006] In summary, while most studies have confirmed the enhancing effect of nanolayered fillers on the barrier properties of polyurethane (PU), achieving high strength, high barrier properties, good compatibility, and simplified processing still faces numerous challenges. In particular, effective solutions are lacking in areas such as polyurethane matrix structure design, nanofiller dispersion, and simplified preparation processes. Therefore, how to synergistically improve the mechanical and barrier properties of materials based on reasonable polyurethane molecular structure design and composite strategies, solve the problems of nanofiller dispersion and compatibility with the polyurethane matrix, and achieve simplified and optimized preparation processes have become urgent technical challenges to overcome in the preparation of high-performance polyurethane adhesives. Summary of the Invention

[0007] To address the aforementioned technical problems, the present invention aims to provide a high-strength gas-barrier polyurethane adhesive and its preparation method.

[0008] To address the aforementioned technical problems, the first aspect of this invention is to provide a high-strength gas-barrier polyurethane adhesive, comprising a main component A and a curing agent component B. Main component A, by weight, comprises: Solvent A 80~85 Polyurethane resin 15~20 Component B of the curing agent comprises, by weight: Layered hydrotalcites (LDHs) 0.75~2.0 Polyisocyanates 2.0~6.0 Solvent B 20.0~50.0.

[0009] Preferably, the polyurethane resin is prepared from polyester polyol, diisocyanate, and a small molecule alcohol chain extender. The polyester polyol is preferably one or more selected from polyethylene adipate diol, polybutylene adipate diol, polyhexyl adipate diol, polybutylene adipate hexylene adipate diol, and polyethylene adipate hexylene adipate polyol; the number average molecular weight of the polyester polyol is 2000-3000. The diisocyanate is preferably one or more selected from diphenylmethane diisocyanate (MDI), 4-4'-dicyclohexylmethane diisocyanate (HMDI), isoflurone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), and phenylenediamine diisocyanate (XDI). The small molecule alcohol chain extender is preferably one or two selected from 1,4-butanediol, 1,6-hexanediol, dipropylene glycol, diethylene glycol, propylene glycol, and neopentyl glycol.

[0010] Preferably, the molar ratio of polyester polyol to small molecule alcohol chain extender in the polyurethane resin is 1:0.35 to 1:4.6.

[0011] Preferably, the polyurethane resin has a hard segment content of 15% to 35% and an R value of 0.95 to 0.98.

[0012] Preferably, solvent A is one of acetone, butanone, ethyl acetate, butyl acetate, toluene, or any mixture thereof.

[0013] Preferably, the average particle size of the layered hydrotalcite is 3-8 μm. The layered hydrotalcite is selected from binary hydrotalcites such as magnesium aluminum hydrotalcite and zinc aluminum hydrotalcite, as well as modified hydrotalcites. The modified hydrotalcite is preferably prepared by intercalation modification with 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid (DBHP) organic anionic antioxidant, 2,4-dimethoxybenzoic acid (2,4-DMBA), and 4,4'-stilbene dicarboxylic acid (SDCA) organic anionic ultraviolet absorber.

[0014] Preferably, the polyisocyanate is a polyisocyanate with a functionality greater than 2, and is preferably one or a mixture of HDI-TMP adducts, HDI trimers, HDI biuret, IPDI trimers, polyphenyl polymethylene diisocyanates, TDI-TMP adducts, and XDI-TMP adducts.

[0015] Preferably, solvent B is one of N,N-dimethylformamide (DMF), ethyl acetate (EA), tetrahydrofuran (THF), or any mixture thereof.

[0016] Preferably, the mass ratio of main component A to curing agent component B is 100 / 22.7 to 100 / 56.

[0017] A second aspect of this invention provides a method for preparing a high-strength gas-barrier polyurethane adhesive, comprising the following steps: (1) Mix polyurethane resin and solvent A evenly to obtain adhesive component A; (2) Add layered hydrotalcite (LDHs), polyisocyanate and solvent B to the reaction apparatus in a metric ratio, reflux the reaction and then grind and disperse to obtain adhesive curing agent component B; (3) Mix the polyurethane adhesive component A and the curing agent component B according to the mass ratio and stir evenly. After curing, the polyurethane adhesive is obtained.

[0018] Preferably, in step (2), the sheet-like LDHs are dried before use; the reaction temperature is preferably 60~80℃, and the reaction time is preferably 4~6h; preferably, they are ground and dispersed in a grinding and dispersing apparatus for 1~2h.

[0019] Compared with the prior art, the polyurethane adhesive provided by the present invention has the following superior effects: the polyisocyanate modified lamellar LDHs can achieve uniform dispersion with the polyurethane matrix, and the prepared polyurethane adhesive has excellent gas barrier properties and mechanical properties, and has good adhesion performance when used for bonding film materials. Detailed Implementation

[0020] Example 1 (1) Preparation of adhesive component A: 15g of polyhexamethylene adipate diol (PEHA2000) / dipropylene glycol (DPG) / diphenylmethane diisocyanate (MDI) polyurethane resin (PEHA / dipropylene glycol molar ratio 1 / 0.68, R value 0.98, hard segment content 20%) was dissolved in a mixed solvent system of 28.33g butyl acetate, 28.33g methyl ethyl ketone, and 28.33g acetone to obtain adhesive component A.

[0021] (2) Preparation of adhesive component B: 0.75g of dried lamellar magnesium aluminum hydrotalcite with an average particle size of 7~8μm and 2g of polymethylene polyisocyanate were added to 20g of DMF. The reaction was carried out in a reaction apparatus at 80℃ under reflux for 4h, and then ground and dispersed in a grinding and dispersing apparatus for 1h to obtain polyurethane adhesive component B.

[0022] (3) Preparation of polyurethane adhesive: Mix A and B at a mass ratio of 100 / 22.7 to prepare an 80 μm adhesive film.

[0023] Example 2

[0024] (1) Preparation of component A of adhesive: 20g of polyurethane resin (PBA / hexanediol molar ratio 1 / 0.35, R value 0.96, hard segment content 15%) in a mixed solvent system of 26.7g toluene, 26.7g butanone, and 26.7g acetone was dissolved to obtain component A of polyurethane adhesive.

[0025] (2) Preparation of adhesive component B: 2g of dried lamellar magnesium aluminum hydrotalcite with an average particle size of 3~4μm, 4g of TDI-TMP adduct, 20g of DMF and 30g of EA were added to the reaction apparatus and refluxed at 80℃ for 6h. Then, the mixture was ground and dispersed in a grinding and dispersing apparatus for 2h to obtain polyurethane adhesive component B.

[0026] (3) Preparation of polyurethane adhesive: Mix A / B at a mass ratio of 100 / 56 to prepare an 80μm adhesive film.

[0027] Example 3

[0028] (1) Preparation of adhesive component A: 20g of polyurethane resin (PBA / BDO molar ratio 1 / 4.6, R value 0.97, hard segment content 35%) in a mixed solvent system of 16g ​​butyl acetate and 64g methyl ethyl ketone (MEK) was dissolved to obtain polyurethane adhesive component A.

[0029] (2) Preparation of component B of adhesive: 1.5g of DBHP intercalated lamellar magnesium aluminum hydrotalcite with an average particle size of 6~7μm and dried, 5g of XDI-TMP adduct were added to 20g of DMF and 20g of THF. The reaction was carried out in a reaction apparatus at 60℃ under reflux for 6h, and then ground and dispersed in a grinding and dispersing apparatus for 2h to obtain component B of polyurethane adhesive.

[0030] (3) Preparation of polyurethane adhesive: Mix A and B at a mass ratio of 100 / 46.5 to prepare an 80μm adhesive film.

[0031] Example 4

[0032] (1) Preparation of adhesive component A: 15g of polyurethane resin (PBHA2000) / 1,4-butanediol (BDO) / dicyclohexylmethane diisocyanate (HMDI) system (PBHA / BDO molar ratio 1 / 0.78, R value 0.95, hard segment content 20%) was dissolved in a mixed solvent system of 28.33g butyl acetate, 28.33g butanone, and 28.33g acetone to obtain adhesive component A.

[0033] (2) Preparation of adhesive component B: 1g of dried lamellar zinc aluminum hydrotalcite with an average particle size of 7~8μm and 6g of HDI trimer were added to 20g of DMF. The reaction was carried out in a reaction apparatus at 80℃ under reflux for 4h, and then ground and dispersed in a grinding and dispersing apparatus for 1~2h to obtain polyurethane adhesive component B.

[0034] (3) Preparation of polyurethane adhesive: Mix A / B at a mass ratio of 100 / 27 to prepare an 80μm adhesive film.

[0035] Comparative Example 1 (1) Preparation of adhesive component A: 20g of polyurethane resin (PBA / hexanediol molar ratio 1 / 0.35, R value 0.96, hard segment content 15%) in a polybutadiene adipate (PBA2000) / butanediol (BDO / diphenylmethane diisocyanate (MDI) system) was dissolved in a mixed solvent system of 26.7g toluene, 26.7g methyl ethyl ketone and 26.7g acetone to obtain polyurethane adhesive component A.

[0036] (2) Preparation of adhesive component B: 2g of dried lamellar magnesium aluminum hydrotalcite with an average particle size of 1~2μm, 4g of TDI-TMP adduct, 20g of DMF and 30g of EA were added to the reaction apparatus and refluxed at 80℃ for 6h. Then, the mixture was ground and dispersed in a grinding and dispersing apparatus for 2h to obtain polyurethane adhesive component B.

[0037] (3) Preparation of polyurethane adhesive: Mix A / B at a mass ratio of 100 / 56 to prepare an 80μm adhesive film.

[0038] Comparative Example 2 (1) Preparation of adhesive component A: 20g of polyurethane resin (PBA / hexanediol molar ratio 1 / 0.35, R value 0.96, hard segment content 15%) in a polybutadiene adipate (PBA2000) / butanediol (BDO / diphenylmethane diisocyanate (MDI) system) was dissolved in a mixed solvent system of 26.7g toluene, 26.7g methyl ethyl ketone and 26.7g acetone to obtain polyurethane adhesive component A.

[0039] (2) Preparation of adhesive component B: 2g of dried lamellar magnesium aluminum hydrotalcite with an average particle size of 3~4μm was added to 20g of DMF and 30g of EA and ground and dispersed in a grinding and dispersing apparatus for 2h to obtain polyurethane adhesive component B.

[0040] (3) Preparation of polyurethane adhesive: Mix A / B at a mass ratio of 100 / 52 to prepare an 80μm adhesive film.

[0041] Comparative Example 3 (1) Preparation of component A of adhesive: 20g of polyurethane resin in polybutylene adipate diol (PBA1000) / butanediol (BDO / isophorone diisocyanate (IPDI) system (PBA1000 / BDO molar ratio / 1 / 1.06, R value 0.97, hard segment content 35%) was dissolved in a mixed solvent system of 16g ​​butyl ester and 64g methyl ethyl ketone to obtain component A of polyurethane adhesive.

[0042] (2) Preparation of adhesive component B: 1.5g of DBHP intercalated lamellar magnesium aluminum hydrotalcite with an average particle size of 6~7μm and dried, 5g of XDI-TMP adduct were added to 20g of DMF and 20g of THF. After reflux reaction at 60℃ for 6h in a reaction apparatus, the mixture was ground and dispersed in a grinding and dispersing apparatus for 2h to obtain polyurethane adhesive component B.

[0043] (3) Preparation of polyurethane adhesive: Mix A and B at a mass ratio of 100 / 46.5 to prepare an 80μm adhesive film.

[0044] Comparative Example 4: (1) Preparation of adhesive component A: 15g of polyurethane resin (PBHA2000) / 1,4-butanediol (BDO) / dicyclohexylmethane diisocyanate (HMDI) system (PBHA / BDO molar ratio 1 / 0.78, R value 0.95, hard segment content 20%) was dissolved in a mixed solvent system of 28.33g butyl acetate, 28.33g butanone, and 28.33g acetone to obtain adhesive component A.

[0045] (2) Preparation of component B of adhesive: 1g of dried lamellar zinc-aluminum hydrotalcite with an average particle size of 7-8μm and 6g of toluene diisocyanate (TDI) were added to 20g of DMF. The mixture was refluxed at 80℃ for 4h in a reaction apparatus. After the reaction was completed, the mixture was washed at least three times with anhydrous DMF to obtain TDI-modified hydrotalcite. After washing and drying, 1g of lamellar zinc-aluminum hydrotalcite was weighed and added to 26g of DMF. The mixture was then ground and dispersed in a grinding and dispersing apparatus for 1-2h to obtain component B of the polyurethane adhesive.

[0046] (3) Preparation of polyurethane adhesive: Mix A and B at a mass ratio of 100 / 27.0 to prepare an 80 μm adhesive film.

[0047] Performance testing methods:

[0048] The thickness, gas barrier properties, tensile strength, and adhesive properties of the polyurethane adhesive films prepared in Examples 1-4 and Comparative Examples 1-4 were tested. Thickness was measured using a film thickness gauge, with 5-8 values ​​taken and the average calculated. Gas barrier properties were tested using the differential pressure method. Samples were cut into circular pieces with a diameter of not less than 100 mm and tested at room temperature according to GB / T 1038 standard to measure the helium permeation. Three samples were tested in each group, and the average value was calculated. The tensile strength of the polyurethane adhesive film was tested at room temperature according to GB / T 1040.3-2006 standard. Peel strength was tested according to GB / T 8808-1988, with five samples tested in each group, and the average value calculated.

[0049] Analysis of the helium permeability, tensile strength, and bonding performance test results of the polyurethane adhesives in the examples and comparative examples revealed that, in the design of polyurethane adhesives, the gas barrier properties and mechanical properties are enhanced by introducing functional filler sheets (LDHs) with gas barrier properties and increasing the crosslinking density of the polyurethane adhesive. The polyurethane adhesive prepared by this invention not only possesses excellent gas barrier properties but can also be used for bonding films, fabrics, and other flexible composite materials.

[0050] Table 1 Performance Tests of Polyurethane Adhesives

[0051] The above description represents the preferred embodiments of the present invention. It should be noted that, for those skilled in the art, various modifications and refinements can be made without departing from the principles of the present invention, and these modifications and refinements should also be considered within the scope of protection of the present invention.

Claims

1. A high-strength gas-barrier polyurethane adhesive, comprising a main component A and a curing agent component B, wherein the main component A comprises, by weight: Solvent A 80~85 Polyurethane resin 15~20 Component B of the curing agent comprises, by weight: Layered hydrotalcites (LDHs) 0.75~2.0 Polyisocyanates 2.0~6.0 Solvent B 20.0~50.

0.

2. The high-strength gas barrier polyurethane adhesive according to claim 1, characterized in that, The polyurethane resin is prepared from polyester polyol, diisocyanate, and small molecule alcohol chain extender.

3. The high-strength gas barrier polyurethane adhesive according to claim 1, characterized in that, The polyester polyol is one or more of polyethylene adipate diol, polybutylene adipate diol, polyhexane adipate diol, polybutylene adipate hexane adipate diol, and polyethylene adipate hexane adipate polyol, and the number average molecular weight of the polyester polyol is preferably 2000-3000.

4. The high-strength gas barrier polyurethane adhesive according to claim 1, characterized in that, The diisocyanate is preferably one or more of diphenylmethane diisocyanate (MDI), 4-4'-dicyclohexylmethane diisocyanate (HMDI), isoflurone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), and phenylmethylene diisocyanate (XDI).

5. The high-strength gas barrier polyurethane adhesive according to claim 1, characterized in that, The preferred small molecule alcohol chain extender is one or two of 1,4-butanediol, 1,6-hexanediol, dipropylene glycol, diethylene glycol, propylene glycol, and neopentyl glycol.

6. The high-strength gas barrier polyurethane adhesive according to claim 1, characterized in that, Preferably, the molar ratio of polyester polyol to small molecule alcohol chain extender in the polyurethane resin is 1:0.35 to 1:4.

6.

7. The high-strength gas barrier polyurethane adhesive according to claim 1, characterized in that, Preferably, the hard segment content of the polyurethane resin is 15% to 35%, and the R value is 0.95 to 0.

98.

8. The high-strength gas barrier polyurethane adhesive according to claim 1, characterized in that, The layered hydrotalcite is selected from binary hydrotalcite or modified hydrotalcite. The binary hydrotalcite is preferably magnesium aluminum hydrotalcite or zinc aluminum hydrotalcite. The modified hydrotalcite is preferably a hydrotalcite prepared by intercalation modification with 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid (DBHP) organic anionic antioxidant, 2,4-dimethoxybenzoic acid (2,4-DMBA) and 4,4'-stilbene dicarboxylic acid (SDCA) organic anionic ultraviolet absorber.

9. The high-strength gas barrier polyurethane adhesive according to claim 1, characterized in that, The polyisocyanate is a polyisocyanate with a functionality greater than 2, preferably one or a mixture of HDI-TMP adducts, HDI trimers, HDI biuret, IPDI trimers, polyphenyl polymethylene diisocyanates, TDI-TMP adducts, and XDI-TMP adducts.

10. A method for preparing the high-strength gas-barrier polyurethane adhesive according to any one of claims 1-9, comprising the following steps: (1) Mix polyurethane resin and solvent A evenly to obtain adhesive component A; (2) Add layered hydrotalcite (LDHs), polyisocyanate and solvent B to the reaction apparatus in a metric ratio, reflux the reaction and then grind and disperse to obtain adhesive curing agent component B; (3) Mix the polyurethane adhesive component A and the curing agent component B according to the mass ratio and stir evenly. After curing, the polyurethane adhesive is obtained.

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