Moisture-curable polyurethane hot melt adhesive and preparation method thereof

Abstract

The invention relates to the technical field of hot melt adhesives, and relates to a moisture-curable polyurethane hot melt adhesive and a preparation method thereof, the moisture-curable polyurethane hot melt adhesive comprises the following components by weight: 20 to 60 parts of polyether polyol, 30 to 50 parts of polyester polyol, 0.2 to 0.8 part of an antioxidant, 0.5 to 1.0 part of a leveling agent, 25 to 45 parts of isocyanate, 0.5 to 1.2 parts of a coupling agent, and 0.05 to 0.25 part of an organic amine catalyst; and the isocyanate is m-xylylene dimethyl isocyanate. According to the moisture-curing hot melt adhesive disclosed by the invention, through selection of the polyol and the isocyanate and proper proportion design, the moisture-curing hot melt adhesive not only has excellent bonding strength and flexibility, but also has excellent yellowing resistance, so that the problem that the existing moisture-curing hot melt adhesive cannot simultaneously give consideration to yellowing resistance and adhesion is solved, and the moisture-curing hot melt adhesive is suitable for practical application conditions.

Description

Technical Field

[0001] The invention belongs to the technical field of hot melt adhesives, and in particular relates to a moisture-curing polyurethane hot melt adhesive and a preparation method thereof. Background Art

[0002] With the development of the times, moisture-curing polyurethane hot melt adhesive has become one of the most active new chemical materials in recent years due to its many advantages. It has shown irreplaceable advantages in preparation and use, and has rapidly gained widespread application.

[0003] At present, moisture-curing polyurethane hot melt adhesive is widely used in consumer electronics and wearable products due to its good bonding strength, flexibility, anti-drop performance, and adaptability to a variety of gluing methods, playing the role of bonding, sealing, and protection.

[0004] However, after conventional moisture-curing polyurethane hot melt adhesives absorb light with a wavelength greater than 340nm, the methylene group on diphenylmethane-4,4'-diisocyanate (MDI) is oxidized to form unstable hydroperoxides, which in turn form a chromophore quinone-imide structure, which causes the polyurethane to turn yellow, and then further oxidizes to form a diquinone-imide structure, and finally turns amber; the second mechanism is: after polyurethane absorbs light with a wavelength less than 340nm, Photo-Fries rearrangement occurs to generate aromatic amines, which further degrade and produce yellowing.

[0005] Data show that the moisture-curing hot melt adhesive obtained by polymerization reaction of isocyanates such as hexamethylene diisocyanate (HDI) and 4,4'-dicyclohexylmethane diisocyanate (HMDI) with polyols has excellent yellowing resistance. However, after testing, the moisture-curing polyurethane hot melt adhesive of this system has a slow curing speed and extremely low bonding strength. Therefore, it cannot meet the high bonding strength requirements of consumer electronics and wearable products.

[0006] Therefore, how to provide a moisture-curing polyurethane hot melt adhesive that has the excellent adhesion, flexibility, anti-drop performance of conventional moisture-curing polyurethane hot melt adhesives and is adaptable to a variety of gluing methods, while also being resistant to yellowing and having a more convenient and quick rework method has become a problem to be solved. Summary of the invention

[0007] In view of the deficiencies of the above-mentioned prior art, the present invention provides a moisture-curing polyurethane hot melt adhesive and a preparation method thereof. The specific technical scheme is as follows:

[0008] The first object of the present invention is to provide a moisture-curable polyurethane hot melt adhesive comprising the following components in parts by weight:

[0009] 20-60 parts of polyether polyol, 30-50 parts of polyester polyol, 0.2-0.8 parts of antioxidant, 0.5-1.0 parts of leveling agent, 25-45 parts of isocyanate, 0.5-1.2 parts of coupling agent, 0.05-0.25 parts of organic amine catalyst;

[0010] The polyether polyol is a polyether polyol with a functionality of 2 and a number average molecular weight of 1000-4000; the polyester polyol is a linear polyester polyol with a functionality of 2 and a number average molecular weight of 1000-4000; and the isocyanate is meta-xylylene isocyanate.

[0011] The present invention makes the moisture-curing hot melt adhesive have excellent bonding strength and flexibility as well as excellent yellowing resistance by selecting polyols and isocyanates and designing appropriate ratios. With the same R value (i.e., the proportion of isocyanates in the system), the use of m-phenylenedimethyl isocyanate can further improve the bonding strength and the yellowing value, even if the yellowing resistance value is reduced; compared with MDI and TDI, it has a significant yellowing resistance advantage.

[0012] Furthermore, the polyether polyol is one or more of polyoxypropylene glycol, polyethylene glycol, polytetramethylene ether glycol, and polytrimethylene ether glycol, preferably polytrimethylene ether glycol with a molecular weight of 2000 and a brand of H2000.

[0013] Furthermore, the polyester polyol is one or more of polyethylene adipate diol, polyhexylene adipate diol, polybutylene adipate diol, polyhexylene terephthalate diol, polybutylene terephthalate diol and polypropylene terephthalate diol, preferably polyhexylene adipate diol with a brand number of 7360.

[0014] Furthermore, the antioxidant is antioxidant 1010.

[0015] Furthermore, the leveling agent is FL 3740.

[0016] Furthermore, the coupling agent is KH550.

[0017] Furthermore, the organic amine catalyst is bis(2-morpholinediethyl) ether (DMDEE).

[0018] The second object of the present invention is to provide a method for preparing the moisture-curable polyurethane hot melt adhesive, comprising the following steps:

[0019] 1) Put polyether polyol, polyester polyol, antioxidant and leveling agent into a reaction kettle, stir and mix, heat to 135-140° C., and dehydrate under vacuum -0.10 MPa for 2-3 hours;

[0020] 2) Cooling to 75-90°C, adding isocyanate under stirring, and heating to 110-125°C at the same time, reacting for 60-90 minutes under vacuum degree ≤ 0.10MPa;

[0021] 3) Add coupling agent and stir the reaction for 10-30 min under vacuum degree ≤ 0.10 MPa;

[0022] 4) adding an organic amine catalyst and stirring the reaction for 10-30 minutes under a vacuum degree of ≤0.10 MPa;

[0023] 5) The product is quickly discharged under nitrogen protection and packaged in an aluminum foil bag, and then aged in an oven at 80-85° C. to obtain the product.

[0024] The beneficial effects of the present invention are:

[0025] The present invention adopts the selection of polyols and isocyanates and designs appropriate ratios to make the moisture-curing hot melt adhesive have both excellent bonding strength and flexibility and excellent yellowing resistance, thereby solving the problem that the current moisture-curing hot melt adhesive cannot take into account both yellowing resistance and adhesion at the same time, so as to adapt to actual application conditions. DETAILED DESCRIPTION

[0026] The principles and features of the present invention are described below in conjunction with embodiments. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0027] Embodiment 1:

[0028] A preparation method of a yellowing-resistant moisture-curing polyurethane hot melt adhesive comprises the following steps:

[0029] 1) By weight, 20 parts of polytrimethylene ether glycol H2000, 30 parts of polyhexane adipate glycol 7360, 0.5 parts of antioxidant 1010 and leveling agent were mixed. 0.5 parts of FL 3740 was added into the reaction kettle and stirred and mixed, heated to 140°C, and vacuum dehydrated for 2.5 hours under vacuum condition of -0.10 MPa;

[0030] 2) Cooling to 85°C, stirring in the reactor at a revolution of 35 r / min, high-speed dispersing disk ① at 1000 r / min, high-speed dispersing disk ② at 1100 r / min, adding 32 parts of m-xylylene diisocyanate, and simultaneously heating to 120°C, reacting for 75 min under a vacuum degree of ≤0.10 MPa;

[0031] 3) Add 0.7 parts of coupling agent KH550, and stir the reaction for 20 minutes under the condition of vacuum degree ≤ 0.10 MPa;

[0032] 4) adding 0.2 parts of organic amine catalyst DMDEE, stirring and reacting for 15 minutes under the condition of vacuum degree ≤ 0.10 MPa;

[0033] 5) The product is quickly discharged under nitrogen protection and packaged in an aluminum foil bag, and aged in an oven at 80-85° C. to obtain a product marked as A1.

[0034] Embodiment 2:

[0035] A preparation method of a yellowing-resistant moisture-curing polyurethane hot melt adhesive comprises the following steps:

[0036] 1) By weight, 20 parts of polytrimethylene ether glycol H2000, 30 parts of polyhexane adipate glycol 7360, 0.5 parts of antioxidant 1010 and leveling agent were mixed. 0.5 parts of FL 3740 was added into the reaction kettle and stirred and mixed, heated to 140°C, and vacuum dehydrated for 2.5 hours under vacuum condition of -0.10 MPa;

[0037] 2) Cooling to 85°C, stirring in the reactor at a revolution of 35 r / min, high-speed dispersing disk ① at 1000 r / min, high-speed dispersing disk ② at 1100 r / min, adding 36 parts of m-xylylene diisocyanate, and simultaneously heating to 120°C, reacting for 75 min under a vacuum degree of ≤0.10 MPa;

[0038] 3) Add 0.7 parts of coupling agent KH550, and stir the reaction for 20 minutes under the condition of vacuum degree ≤ 0.10 MPa;

[0039] 4) adding 0.2 parts of organic amine catalyst DMDEE, stirring and reacting for 15 minutes under the condition of vacuum degree ≤ 0.10 MPa;

[0040] 5) The product is quickly discharged under nitrogen protection and packaged in an aluminum foil bag, and aged in an oven at 80-85° C. to obtain a product marked as A2.

[0041] Comparative Example 1:

[0042] A preparation method of a moisture-curable polyurethane hot melt adhesive comprises the following steps:

[0043] 1) By weight, 20 parts of polytrimethylene ether glycol H2000, 30 parts of polyhexamethylene adipate glycol 7360, 0.5 parts of antioxidant 1010 and 0.5 parts of FL 3740 was added into the reaction kettle and stirred and mixed, heated to 140°C, and vacuum dehydrated for 2.5 hours under vacuum condition of -0.10 MPa;

[0044] 2) Cooling to 85°C, stirring in the reactor at a revolution of 35 r / min, high-speed dispersing plate ① at 1000 r / min and high-speed dispersing plate ② at 1100 r / min, adding 45 parts of 4,4'-diphenylmethane diisocyanate, and simultaneously heating to 120°C, reacting for 75 min under a vacuum degree of ≤0.10 MPa;

[0045] 3) Add 0.7 parts of coupling agent KH550, and stir the reaction for 20 minutes under the condition of vacuum degree ≤ 0.10 MPa;

[0046] 4) adding 0.2 parts of organic amine catalyst DMDEE, stirring and reacting for 15 minutes under the condition of vacuum degree ≤ 0.10 MPa;

[0047] 5) The product is quickly discharged under nitrogen protection and packaged in an aluminum foil bag, and aged in an oven at 80-85° C. to obtain a product marked as D1.

[0048] Comparative Example 2:

[0049] A preparation method of a moisture-curable polyurethane hot melt adhesive comprises the following steps:

[0050] 1) By weight, 20 parts of polytrimethylene ether glycol H2000, 30 parts of polyhexane adipate glycol 7360, 0.5 parts of antioxidant 1010, 0.5 parts of FL 3740 was added into a reaction kettle and stirred, heated to 140°C, and vacuum dehydrated for 2.5 hours under vacuum conditions of -0.10 MPa;

[0051] 2) Cool down to 85°C, stir in the reactor at a revolution of 35 r / min, high-speed dispersing disk ① at 1000 r / min, high-speed dispersing disk ② at 1100 r / min, add 37 parts of toluene diisocyanate (TDI), and heat to 120°C at the same time, and react for 75 min under a vacuum degree of ≤0.10 MPa;

[0052] 3) Add 0.7 parts of coupling agent KH550, and stir the reaction for 20 minutes under the condition of vacuum degree ≤ 0.10 MPa;

[0053] 4) Add 0.2 parts of DMDEE catalyst and stir the reaction for 15 minutes under the condition of vacuum degree ≤ 0.10 MPa;

[0054] 5) The product is quickly discharged under nitrogen protection and packaged in an aluminum foil bag, and aged in an oven at 80-85° C. to obtain a product marked as D2.

[0055] Comparative Example 3:

[0056] A preparation method of a moisture-curable polyurethane hot melt adhesive comprises the following steps:

[0057] 1) By weight, 20 parts of polytrimethylene ether glycol H2000, 30 parts of polyhexamethylene adipate glycol 7360, 2.5 parts of antioxidant 1010 and 0.5 parts of FL 3740 was added into the reaction kettle and stirred and mixed, heated to 140°C, and vacuum dehydrated for 2.5 hours under vacuum condition of -0.10 MPa;

[0058] 2) Cooling to 85°C, stirring in the reactor at a revolution of 35 r / min, high-speed dispersing disk ① at 1000 r / min, high-speed dispersing disk ② at 1100 r / min, adding 45 parts of 4,4'-diphenylmethane diisocyanate, and simultaneously raising the temperature to 120°C, reacting for 75 min under a vacuum degree of ≤0.10 MPa;

[0059] 3) Add 0.7 parts of coupling agent KH550, and stir the reaction for 20 minutes under the condition of vacuum degree ≤ 0.10 MPa;

[0060] 4) adding 0.2 parts of organic amine catalyst DMDEE, stirring and reacting for 15 minutes under the condition of vacuum degree ≤ 0.10 MPa;

[0061] 5) The product is quickly discharged under nitrogen protection and packaged in an aluminum foil bag, and aged in an oven at 80-85° C. to obtain a product marked as D3.

[0062] Comparative Example 4:

[0063] A preparation method of a moisture-curable polyurethane hot melt adhesive comprises the following steps:

[0064] 1) By weight, 20 parts of polytrimethylene ether glycol H2000, 30 parts of polyhexane adipate glycol 7360, 0.5 parts of antioxidant 1010, 0.05 parts of ultraviolet light absorber phenyl o-hydroxybenzoate and 0.5 parts of FL 3740 was added into the reaction kettle and stirred and mixed, heated to 140°C, and vacuum dehydrated for 2.5 hours under vacuum condition of -0.10 MPa;

[0065] 2) Cooling to 85°C, stirring in the reactor at a revolution of 35 r / min, high-speed dispersing disk ① at 1000 r / min, high-speed dispersing disk ② at 1100 r / min, adding 45 parts of 4,4'-diphenylmethane diisocyanate, and simultaneously heating to 120°C, reacting for 75 min under a vacuum degree of ≤0.10 MPa;

[0066] 3) Add 0.7 parts of coupling agent KH550, and stir the reaction for 20 minutes under the condition of vacuum degree ≤ 0.10 MPa;

[0067] 4) adding 0.2 parts of organic amine catalyst DMDEE, stirring and reacting for 15 minutes under the condition of vacuum degree ≤ 0.10 MPa;

[0068] 5) The product is quickly discharged under nitrogen protection and packaged in an aluminum foil bag, and aged in an oven at 80-85° C. to obtain a product marked as D4.

[0069] The products of Examples 1-2 and Comparative Examples 1-4 above were tested in the following manner:

[0070] Test 1: Examples A1, A2, and comparative examples D1, D2, D3, and D4 were heated to 110°C, and the tensile strength of PC to PC was measured by dispensing. The bonding samples were made according to the requirements of GB / T7124-2008. After curing for 168 hours at 25°C and 50% humidity, a tensile strength test was performed using a universal tensile testing machine.

[0071] Test 2: Cut the cured samples of Examples A1, A2, and Comparative Examples D1, D2, D3, and D4 to standard size and place them under a 365nm UV lamp with a power of 0.033mw / cm 2 After irradiation for 168 hours, the yellowing degree was tested using a colorimeter.

[0072] The experimental test results are shown in Table 1:

[0073] Table 1 Experimental test results of examples and comparative examples

[0074]

[0075] By comparing the data of Examples A1 and A2, it can be seen that increasing the R value, i.e. the proportion of isocyanate in the system, significantly improves the adhesion, while the DE94 value slightly increases, i.e. the yellowing resistance decreases.

[0076] By comparing the data of Examples A1 and A2 with Comparative Examples D1 and D2, it can be seen that the isocyanate used in the examples has an obvious yellowing resistance advantage compared to MDI and TDI, and the bonding strength is slightly better than the two.

[0077] By comparing the data of comparative example D1 with comparative examples D3 and D4, it can be seen that the increase in the content of the antioxidant and the introduction of the ultraviolet light absorber can slightly reduce the yellowing degree of the system, but there is still a large gap compared with the comparative examples.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A moisture-curing polyurethane hot melt adhesive, characterized in that: The composition comprises the following components in parts by weight: 20-60 parts of polyether polyol, 30-50 parts of polyester polyol, 0.2-0.8 parts of antioxidant, 0.5-1.0 parts of leveling agent, 25-45 parts of isocyanate, 0.5-1.2 parts of coupling agent, 0.05-0.25 parts of organic amine catalyst; The polyether polyol is a polyether polyol with a functionality of 2 and a number average molecular weight of 1000-4000; the polyester polyol is a linear polyester polyol with a functionality of 2 and a number average molecular weight of 1000-4000; and the isocyanate is meta-xylylene isocyanate.

2. The moisture-curable polyurethane hot melt adhesive according to claim 1, characterized in that: The polyether polyol is one or more of polyoxypropylene glycol, polyethylene glycol, polytetramethylene ether glycol, and polytrimethylene ether glycol.

3. The moisture-curable polyurethane hot melt adhesive according to claim 1, characterized in that: The polyester polyol is one or more of polyethylene adipate diol, polyhexylene adipate diol, polybutylene adipate diol, polyhexylene terephthalate diol, polybutylene terephthalate diol and polypropylene terephthalate diol.

4. The moisture-curable polyurethane hot melt adhesive according to claim 1, characterized in that: The antioxidant is antioxidant 1010.

5. The moisture-curable polyurethane hot melt adhesive according to claim 1, characterized in that: The leveling agent is FL3740.

6. The moisture-curable polyurethane hot melt adhesive according to claim 1, characterized in that: The coupling agent is KH550.

7. The moisture-curable polyurethane hot melt adhesive according to claim 1, characterized in that: The organic amine catalyst is bis(2-morpholine diethyl) ether.

8. A moisture-curable polyurethane hot melt adhesive as claimed in claims 1 to 7, characterized in that: The steps include: 1) Put polyether polyol, polyester polyol, antioxidant and leveling agent into a reaction kettle, stir and mix, heat to 135-140° C., and dehydrate under vacuum -0.10 MPa for 2-3 hours; 2) Cooling to 75-90°C, adding isocyanate under stirring, and heating to 110-125°C at the same time, reacting for 60-90 minutes under vacuum degree ≤ 0.10MPa; 3) Add coupling agent and stir the reaction for 10-30 min under vacuum degree ≤ 0.10 MPa; 4) adding an organic amine catalyst and stirring the reaction for 10-30 minutes under a vacuum degree of ≤0.10 MPa; 5) The product is quickly discharged under nitrogen protection and packaged in an aluminum foil bag, and then aged in an oven at 80-85° C. to obtain the product.

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