Light / wet dual-curing reaction type polyurethane hot melt adhesive and preparation method thereof

Abstract

The application discloses a kind of light / wet dual-curing reactive polyurethane hot melt adhesive and preparation method thereof.The reactive polyurethane hot melt adhesive is prepared from the following weight parts of raw materials: liquid polyester polyol 20-60 parts, polyether polyol 10-30 parts, dihydroxy diacrylate 0.3-4 parts, polymerization inhibitor 0.002-0.1 parts, isocyanate 10-45 parts, adhesion promoter 0.5-3 parts, hydroxy triacrylate 0.5-6 parts, photoinitiator 1-5 parts, catalyst 0.01-0.2 parts.The light / wet dual-curing PUR prepared by the application has the characteristics of low melt viscosity, high initial bonding strength, long open time, high temperature and humidity resistance, excellent comprehensive performance and the like.

Description

Technical Field

[0001] This invention relates to the field of hot melt adhesive technology, and in particular to a light / wet dual-curing reactive polyurethane hot melt adhesive and its preparation method. Background Technology

[0002] Reactive polyurethane hot melt adhesives (PUR) mainly refer to polyurethane hot melt adhesives that utilize moisture in the air for cross-linking and curing. They combine the characteristics of ordinary hot melt adhesives and reactive adhesives. Compared with ordinary hot melt adhesives, they have a lower application temperature, higher bonding strength after curing, and better heat resistance, chemical resistance, and durability. They can exhibit good adhesion to substrates such as wood, ceramics, fabrics, metals, glass, plastics, and rubber. In recent years, they have seen rapid development in fields such as construction, automobiles, electronics, wood processing, bookbinding, and food packaging.

[0003] The curing of PUR involves two stages. First, after the PUR is melted and applied to the substrate, it cools and solidifies to generate initial bond strength. Then, the -NCO in the system reacts with moisture in the air to achieve the final viscosity strength. However, because moisture penetration into the air is slow after PUR is applied, the initial bond strength is usually very low, and complete curing often takes several days. To improve the initial bond strength of PUR, current methods mainly involve increasing the proportion of solid polyester, high-Tg resin, and high-molecular-weight thermoplastic resin in the system. However, due to the poor hydrolysis resistance of polyester, the high brittleness of high-Tg resin, and the high melt viscosity and lack of reactivity of high-molecular-weight thermoplastic resin, using these methods to improve the initial bond strength often leads to problems such as high melt viscosity, short open time, poor hydrolysis resistance, and unstable bonding performance in PUR products. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to provide a reactive polyurethane hot melt adhesive with high initial bond strength.

[0005] To achieve the above objectives, the present invention includes the following technical solutions.

[0006] A light / wet dual-curing reactive polyurethane hot melt adhesive is prepared from the following raw materials in parts by weight: 20-60 parts liquid polyester polyol, 10-30 parts polyether polyol, 0.3-4 parts dihydroxy diacrylate, 0.002-0.1 parts polymerization inhibitor, 10-45 parts isocyanate, 0.5-3 parts adhesion promoter, 0.5-6 parts hydroxy triacrylate, 1-5 parts photoinitiator, and 0.01-0.2 parts catalyst.

[0007] In some embodiments, the light / wet dual-curing reactive polyurethane hot melt adhesive is prepared from the following raw materials in parts by weight: 30-55 parts liquid polyester polyol, 15-30 parts polyether polyol, 1-3 parts dihydroxy diacrylate, 0.005-0.08 parts polymerization inhibitor, 14-25 parts isocyanate, 1-2.5 parts adhesion promoter, 1-4.5 parts hydroxy triacrylate, 2-4 parts photoinitiator, and 0.05-0.15 parts catalyst.

[0008] In some embodiments, the light / wet dual-curing reactive polyurethane hot melt adhesive is prepared from the following raw materials in parts by weight: 48-52 parts liquid polyester polyol, 18-22 parts polyether polyol, 1.5-2.5 parts dihydroxy diacrylate, 0.008-0.015 parts polymerization inhibitor, 20-24 parts isocyanate, 1.5-2.2 parts adhesion promoter, 3.5-4.5 parts hydroxy triacrylate, 2-4 parts photoinitiator, and 0.05-0.15 parts catalyst.

[0009] In some embodiments, the dihydroxy diacrylate is one or both of pentaerythritol diacrylate and pentaerythritol dimethacrylate.

[0010] In some embodiments, the hydroxytriacrylate is one or both of pentaerythritol triacrylate and pentaerythritol trimethacrylate.

[0011] In some embodiments, the hydroxyl value of the liquid polyester polyol is 10-112 mg KOH / g.

[0012] In some embodiments, the hydroxyl value of the liquid polyester polyol is 18-60 mg KOH / g.

[0013] In some embodiments, the hydroxyl value of the liquid polyester polyol is 18-34 mg KOH / g.

[0014] In some embodiments, the liquid polyester polyol is 7230 and / or 7250.

[0015] In some embodiments, the liquid polyester polyol is in a mass ratio of 3-5:1. 7230 and The combination of 7250.

[0016] In some embodiments, the polyether polyol is polyoxypropylene glycol with a number average molecular weight of 1000-3000.

[0017] In some embodiments, the isocyanate is one or more of 4,4'-diphenylmethane diisocyanate (MDI), carbodiimide-modified MDI, and MDI-50.

[0018] In some embodiments, the adhesion promoter is one or more of 3-isocyanate-propyltriethoxysilane, 3-isocyanate-propyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, and 3-mercaptopropyltriethoxysilane.

[0019] In some embodiments, the polymerization inhibitor is 2,5-di-tert-butylhydroquinone.

[0020] In some embodiments, the catalyst is at least one of dibutyltin dilaurate (DBTDL), triethylenediamine, and dimorpholinodiethyl ether (DMDEE).

[0021] In some embodiments, the photoinitiator is ethyl 2,4,6-trimethylbenzoylphenylphosphonate.

[0022] This invention also provides a method for preparing the above-mentioned light / wet dual-curing reactive polyurethane hot melt adhesive, comprising the following steps:

[0023] (1) The liquid polyester polyol, polyether polyol and polymerization inhibitor are put into the reaction vessel and heated to 110-130°C. The mixture is then vacuum dehydrated for 60-180 minutes under stirring, with a vacuum degree of -0.095 to -0.05 MPa.

[0024] (2) Add the isocyanate and stir the mixture at 110-130°C for 60-180 minutes under inert gas protection;

[0025] (3) Add the dihydroxy diacrylate and stir and react at 110-130°C for 30-60 minutes under inert gas protection;

[0026] (4) Add the hydroxytriacrylate and stir the mixture at 110-130°C for 30-60 minutes under inert gas protection;

[0027] (5) Under light-protected conditions, the adhesive accelerator, catalyst and photoinitiator are added in sequence, and stirred and mixed at 110-130°C for 20-40 minutes under inert gas protection.

[0028] (6) Maintain a constant temperature of 110-130℃, evacuate until no bubbles appear, and then discharge the material.

[0029] In some embodiments, the preparation method of the light / wet dual-curing reactive polyurethane hot melt adhesive includes the following steps:

[0030] (1) The liquid polyester polyol, polyether polyol and polymerization inhibitor are put into the reaction vessel and heated to 115-125°C. The mixture is then vacuum dehydrated for 100-140 minutes with stirring, and the vacuum degree is -0.095 to -0.08 MPa.

[0031] (2) Add the isocyanate and stir the mixture at 115-125°C for 100-140 minutes under inert gas protection;

[0032] (3) Add the dihydroxy diacrylate and stir and react at 115-125°C for 35-45 minutes under inert gas protection;

[0033] (4) Add the hydroxytriacrylate and stir the mixture at 115-125°C for 35-45 minutes under inert gas protection.

[0034] (5) Under light-protected conditions, the adhesive accelerator, catalyst and photoinitiator are added in sequence, and stirred and mixed at 115-125°C for 25-35 minutes under inert gas protection;

[0035] (6) Maintain a constant temperature of 115-125℃, evacuate until no bubbles appear, and then discharge the material.

[0036] The photo / wet dual-curing reactive polyurethane hot melt adhesive (PUR) of this invention, during its preparation process, sequentially adds appropriate amounts of dihydroxy diacrylate as a chain extender and appropriate amounts of hydroxy triacrylate as a capping agent. This allows for the introduction of carbon-carbon double bonds into the side groups and end groups of the polyurethane prepolymer backbone in the photo / wet dual-curing PUR system, respectively. During UV curing, both the polyfunctional side chains and the trifunctional end groups participate in the photocuring reaction, significantly increasing the crosslinking density and thus providing better initial bond strength. Simultaneously, after wet curing, the final bond strength is also better due to the more compact cured crosslinking structure of the system. The addition of [a specific ingredient]... Coupling agents with active isocyanate or mercapto groups are used as adhesion promoters. Mercapto-containing coupling agents can react chemically with -NCO, while isocyanate-containing coupling agents can participate in the wet curing reaction of PUR. Both can be introduced into the cross-linking curing system. At the same time, their attached alkoxy groups form hydrogen bonds or react chemically with the surface of the substrate being bonded, which can improve the adhesion of PUR to the substrate. Because no raw materials such as crystalline polyester polyol, amorphous polyester polyol, or high molecular weight thermoplastic resin are added to the light / wet dual-curing PUR system, the resulting light / wet dual-curing PUR has a longer open time and a lower melt viscosity.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. The present invention describes how the above-mentioned components are reasonably combined in a certain ratio to produce a light / wet dual-cured PUR with characteristics such as low melt viscosity, high initial bond strength, long open time, high temperature and high humidity resistance, and excellent comprehensive performance, which has good market prospects.

[0039] 2. The preparation process of the reactive polyurethane hot melt adhesive of the present invention is simple, easy to operate, and easy to industrialize. Detailed Implementation

[0040] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments are merely illustrative of the present invention and should not be construed as limiting the invention.

[0041] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0042] The terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, apparatus, product, or device that includes a series of steps is not limited to the steps or modules listed, but may optionally include steps not listed, or may optionally include other steps inherent to such process, method, product, or device.

[0043] In this invention, "multiple" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0044] The viscosity mentioned in this invention refers to the viscosity tested at 25°C.

[0045] The following are specific examples.

[0046] The liquid polyester polyol used in the embodiments of this invention was purchased from Evonik. The 7200 series is detailed below:

[0047] 7230, with a hydroxyl value of 27–34 mg KOH / g;

[0048] 7250, with a hydroxyl value of 18-24 mgKOH / g.

[0049] Polyether polyol: Polypropylene glycol (PPG2000) was purchased from Jiangsu Zhongshan Chemical Co., Ltd., Mn=2000, hydroxyl value is 54-58mgKOH / g.

[0050] Pentaerythritol diacrylate and pentaerythritol triacrylate were purchased from Shanghai Mairui Biochemical Technology Co., Ltd.

[0051] The remaining raw material components are all commercially available products.

[0052] The raw materials used in the light / wet dual-curing reactive polyurethane hot melt adhesives of the embodiments and comparative examples of the present invention are shown in Table 1 below.

[0053] Table 1: Distribution ratios (parts by weight) of each group in each embodiment

[0054]

[0055]

[0056] Note: In Comparative Example 5, pentaerythritol triacrylate in Example 3 was replaced by polydipentaerythritol pentaacrylate in an equal amount; in Comparative Example 6, pentaerythritol triacrylate in Example 3 was replaced by hydroxyethyl methacrylate in an equal amount; and in Comparative Example 7, pentaerythritol diacrylate in Example 3 was replaced by trimethylolpropane monoallyl ether in an equal amount.

[0057] The light / wet dual-curing reactive polyurethane hot melt adhesives of Examples 1-3 above were prepared using the following methods, with the only difference being the changes in the types and amounts of raw materials as shown in Table 1:

[0058] (1) Add liquid polyester polyol, polyether polyol and polymerization inhibitor into the reactor, heat to 120°C, and vacuum dehydrate for 120 minutes with stirring. The vacuum degree is -0.09MPa.

[0059] (2) Add isocyanate and stir at 120°C for 120 minutes under N2 protection;

[0060] (3) Add dihydroxydiacrylate and stir at 120°C for 40 minutes under N2 protection;

[0061] (4) Add hydroxytriacrylate and stir at 120°C for 40 minutes under N2 protection;

[0062] (5) Under light-protected conditions, add adhesive accelerator, catalyst and photoinitiator in sequence, and stir and mix at 120°C for 30 minutes under N2 protection;

[0063] (6) Maintain a constant temperature of 120℃, evacuate until no bubbles appear, and then discharge the material.

[0064] The preparation method of the light / wet dual-curing reactive polyurethane hot melt adhesive provided in Comparative Examples 1-4 differs from the above embodiments in that the corresponding steps are omitted when no corresponding components are added; the other steps are the same as in the embodiments.

[0065] The difference between the preparation methods of the light / wet dual-curing reactive polyurethane hot melt adhesives provided in Comparative Examples 5-7 and the above embodiments is that in step (4) of Comparative Example 5, polydipentaerythritol pentaacrylate is used instead of pentaerythritol triacrylate; in step (4) of Comparative Example 6, hydroxyethyl methacrylate is used instead of pentaerythritol triacrylate; and in step (3) of Comparative Example 7, trimethylolpropane monoallyl ether is used instead of pentaerythritol diacrylate. All other steps are the same as in the embodiments.

[0066] Effect test:

[0067] The reactive polyurethane hot melt adhesives prepared in Examples 1-3 and Comparative Examples 1-7 were tested according to HG / T3660-1999 for melt viscosity; HG / T3716-2003 for open time; and GB / T7124-2008 for initial bond strength (tensile shear strength after 5 min of UV irradiation on a polycarbonate (PC) substrate), final bond strength (tensile shear strength after 7 days of UV irradiation on a PC substrate and moisture curing at 25°C / 50%RH), and high-temperature and high-humidity bond strength (tensile shear strength after 7 days of UV irradiation on a PC substrate and moisture curing at 25°C / 50%RH, followed by 7 days of exposure to 85°C / 85%RH) for high-temperature and high-humidity exposure on a PC substrate).

[0068] The test results are shown in Table 2.

[0069] Table 2. Performance test results of reactive polyurethane hot melt adhesives in Examples 1-3 and Comparative Examples 1-7

[0070]

[0071] As can be seen from the performance comparison of Examples 1-3 and Comparative Examples 1-3 in Table 2, the light / wet dual-curing reactive polyurethane hot melt adhesives of Examples 1-3, which simultaneously add pentaerythritol diacrylate and pentaerythritol triacrylate, show a significant improvement in both initial and final bond strength compared to Comparative Examples 1-3. Furthermore, the light / wet dual-curing reactive polyurethane hot melt adhesives of Examples 1-3, which simultaneously add pentaerythritol diacrylate and pentaerythritol triacrylate, exhibit better initial and final bond strengths than those of the light / wet dual-curing reactive polyurethane hot melt adhesives that only add pentaerythritol diacrylate or pentaerythritol triacrylate.

[0072] As can be seen from the performance comparison of Examples 1-3 and Comparative Example 4 in Table 2, Examples 1-3 with added adhesion promoters have significantly improved final bond strength and bond strength after high temperature and high humidity compared with Comparative Example 4 without added adhesion promoters.

[0073] As can be seen from the performance comparison of Examples 1-3 and Comparative Examples 5-7 in Table 2, although the initial bond strength of the polyurethane hot melt adhesive obtained by Comparative Example 5, which replaced the pentaerythritol triacrylate in Example 3 with an equal amount of polydipentaerythritol pentaacrylate, was comparable to that of Example 3, the final bond strength was much lower than that of Example 3. Comparative Example 6, which replaced the pentaerythritol triacrylate in Example 3 with an equal amount of hydroxyethyl methacrylate, and Comparative Example 7, which replaced the pentaerythritol diacrylate in Example 3 with an equal amount of trimethylolpropane monoallyl ether, both had much lower initial bond strength and final bond strength than that of Example 3.

[0074] Therefore, the specific types of chain extenders and end-capping agents have a significant impact on the initial and final bond strength of the resulting polyurethane hot melt adhesive; the addition of specific adhesion promoters has a significant effect on improving the final bond strength and the bond strength after high temperature and humidity. The light / wet dual-curing reactive polyurethane hot melt adhesives prepared by simultaneously adding pentaerythritol diacrylate and pentaerythritol triacrylate, along with adhesion promoters, in Examples 1-3 of this invention exhibit characteristics such as low melt viscosity, high initial bond strength, long open time, resistance to high temperature and humidity, and excellent overall performance. Among them, the reactive polyurethane hot melt adhesive in Example 3 has the most outstanding overall performance.

[0075] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0076] The above-described embodiments are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent.

[0077] The invention is not limited to any particular type of invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept, and these all fall within the scope of protection of this invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A light / wet dual-curing reactive polyurethane hot melt adhesive, characterized in that, It is prepared from the following raw materials in parts by weight: 20-60 parts liquid polyester polyol, 10-30 parts polyether polyol, 0.3-4 parts dihydroxy diacrylate, 0.002-0.1 parts polymerization inhibitor, 10-45 parts isocyanate, 0.5-3 parts adhesion promoter, 0.5-6 parts hydroxy triacrylate, 1-5 parts photoinitiator, and 0.01-0.2 parts catalyst; The adhesion promoter is one or more of 3-isocyanate-propyltriethoxysilane, 3-isocyanate-propyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, and 3-mercaptopropyltriethoxysilane. The preparation method of the light / wet dual-curing reactive polyurethane hot melt adhesive includes the following steps: (1) The liquid polyester polyol, polyether polyol and polymerization inhibitor are put into the reaction vessel and heated to 110-130°C. The mixture is then vacuum dehydrated for 60-180 minutes under stirring, with a vacuum degree of -0.095 to -0.05 MPa. (2) Add the isocyanate and stir the mixture at 110-130°C for 60-180 minutes under inert gas protection; (3) Add the dihydroxy diacrylate and stir and react at 110-130°C for 30-60 minutes under inert gas protection; (4) Add the hydroxytriacrylate and stir the mixture at 110-130°C for 30-60 minutes under inert gas protection; (5) Under light-protected conditions, the adhesive accelerator, catalyst and photoinitiator are added in sequence, and stirred and mixed at 110-130°C for 20-40 minutes under inert gas protection. (6) Maintain a constant temperature of 110-130℃, evacuate until no bubbles appear, and then discharge the material.

2. The light / wet dual-curing reactive polyurethane hot melt adhesive according to claim 1, characterized in that, It is prepared from the following raw materials in parts by weight: 30-55 parts liquid polyester polyol, 15-30 parts polyether polyol, 1-3 parts dihydroxy diacrylate, 0.005-0.08 parts polymerization inhibitor, 14-25 parts isocyanate, 1-2.5 parts adhesion promoter, 1-4.5 parts hydroxy triacrylate, 2-4 parts photoinitiator, and 0.05-0.15 parts catalyst.

3. The light / wet dual-curing reactive polyurethane hot melt adhesive according to claim 2, characterized in that, It is prepared from the following raw materials in parts by weight: 48-52 parts liquid polyester polyol, 18-22 parts polyether polyol, 1.5-2.5 parts dihydroxy diacrylate, 0.008-0.015 parts polymerization inhibitor, 20-24 parts isocyanate, 1.5-2.2 parts adhesion promoter, 3.5-4.5 parts hydroxy triacrylate, 2-4 parts photoinitiator, and 0.05-0.15 parts catalyst.

4. The light / wet dual-curing reactive polyurethane hot melt adhesive according to any one of claims 1-3, characterized in that, The dihydroxy diacrylate is one or both of pentaerythritol diacrylate and pentaerythritol dimethacrylate; and / or, The hydroxytriacrylate is one or both of pentaerythritol triacrylate and pentaerythritol trimethacrylate.

5. The light / wet dual-curing reactive polyurethane hot melt adhesive according to any one of claims 1-3, characterized in that, The hydroxyl value of the liquid polyester polyol is 10-112 mgKOH / g.

6. The light / wet dual-curing reactive polyurethane hot melt adhesive according to claim 5, characterized in that, The hydroxyl value of the liquid polyester polyol is 18-60 mg KOH / g.

7. The light / wet dual-curing reactive polyurethane hot melt adhesive according to claim 6, characterized in that, The hydroxyl value of the liquid polyester polyol is 18-34 mgKOH / g.

8. The light / wet dual-curing reactive polyurethane hot melt adhesive according to claim 5, characterized in that, The liquid polyester polyol is Dynacoll. ® 7230 and / or Dynacoll ® 7250.

9. The light / wet dual-curing reactive polyurethane hot melt adhesive according to claim 8, characterized in that, The liquid polyester polyol is Dynacoll. ® 7230 and Dynacoll ® The combination of 7250, the Dynacoll ® 7230 and Dynacoll ® The mass ratio of 7250 is 3-5:

1.

10. The light / wet dual-curing reactive polyurethane hot melt adhesive according to any one of claims 1-3, characterized in that, The polyether polyol is polyoxypropylene glycol with a number average molecular weight of 1000-3000; and / or, The isocyanate is one or more selected from 4,4'-diphenylmethane diisocyanate, carbodiimide-modified MDI, and MDI-50; and / or, The polymerization inhibitor is 2,5-di-tert-butylhydroquinone; and / or, The catalyst is at least one selected from dibutyltin dilaurate, triethylenediamine, and dimorpholinodiethyl ether; and / or The photoinitiator is ethyl 2,4,6-trimethylbenzoylphenylphosphonate.

11. A method for preparing a light / wet dual-curing reactive polyurethane hot melt adhesive according to any one of claims 1-10, characterized in that, Includes the following steps: (1) The liquid polyester polyol, polyether polyol and polymerization inhibitor are put into the reaction vessel and heated to 110-130°C. The mixture is then vacuum dehydrated for 60-180 minutes under stirring, with a vacuum degree of -0.095 to -0.05 MPa. (2) Add the isocyanate and stir the mixture at 110-130°C for 60-180 minutes under inert gas protection; (3) Add the dihydroxy diacrylate and stir and react at 110-130°C for 30-60 minutes under inert gas protection; (4) Add the hydroxytriacrylate and stir the mixture at 110-130°C for 30-60 minutes under inert gas protection; (5) Under light-protected conditions, the adhesive accelerator, catalyst and photoinitiator are added in sequence, and stirred and mixed at 110-130°C for 20-40 minutes under inert gas protection. (6) Maintain a constant temperature of 110-130℃, evacuate until no bubbles appear, and then discharge the material.

12. The preparation method of the light / wet dual-curing reactive polyurethane hot melt adhesive according to claim 11, characterized in that, Includes the following steps: (1) The liquid polyester polyol, polyether polyol and polymerization inhibitor are put into the reaction vessel and heated to 115-125°C. The mixture is then vacuum dehydrated for 100-140 minutes with stirring, and the vacuum degree is -0.095 to -0.08 MPa. (2) Add the isocyanate and stir the mixture at 115-125°C for 100-140 minutes under inert gas protection; (3) Add the dihydroxy diacrylate and stir and react at 115-125°C for 35-45 minutes under inert gas protection; (4) Add the hydroxytriacrylate and stir the mixture at 115-125°C for 35-45 minutes under inert gas protection. (5) Under light-protected conditions, the adhesive accelerator, catalyst and photoinitiator are added in sequence, and stirred and mixed at 115-125°C for 25-35 minutes under inert gas protection. (6) Maintain a constant temperature of 115-125℃, evacuate until no bubbles appear, and then discharge the material.

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