Amorphous high-initial-adhesion hot-melt polyurethane adhesive and preparation method thereof

Abstract

The invention discloses an amorphous high-initial-adhesion hot-melt polyurethane adhesive and a preparation method thereof, and belongs to the technical field of adhesives. The amorphous high-initial-viscosity hot-melt polyurethane adhesive comprises a component A, a component B, a component C and a component D, the molar ratio of the component A to the component B to the component C to the component D is (30-55): (10-30): (10-20): (15-25), the component A comprises polyester polyol, the component B comprises performance adjusting polyol, the component C comprises an additive, and the component D comprises isocyanate or an isocyanate prepolymer. The amorphous high-initial-adhesion hot-melt polyurethane adhesive not only can avoid the bubbling phenomenon in the curing process, but also has the advantages of environmental protection, low cost and high initial adhesion. The preparation method of the amorphous high-initial-viscosity hot-melt polyurethane adhesive is simple in formula and convenient to operate.

Description

Technical Field

[0001] The present invention relates to an amorphous high-initial-tack hot-melt polyurethane adhesive and a preparation method thereof, belonging to the technical field of adhesives. Background Art

[0002] Polyurethane adhesives are an important part of the rapidly developing polyurethane resins. They have excellent properties and are widely used in many aspects, and are one of the important varieties among the eight major synthetic adhesives.

[0003] Polyurethane adhesives have excellent shear strength and impact resistance characteristics, are suitable for various structural bonding fields, and have excellent flexibility characteristics.

[0004] However, the existing hot-melt polyurethane PUR adhesives use a variety of (5 - 15 kinds) polyester or polyether polyol raw materials, especially in the application fields related to household woodworking. Usually, in a qualified formulation, a tackifying resin and a crystalline polyester need to be used in combination to achieve good initial tack and no obvious bubbling phenomenon during the curing process. Due to the large number of raw materials, the production steps are relatively complex, and the tackifying resin and the highly crystalline polyester are relatively costly. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide an amorphous high-initial-tack hot-melt polyurethane adhesive with low cost and no bubbling phenomenon during the curing process and a preparation method thereof.

[0006] To achieve the aforementioned invention purpose, the technical solutions adopted by the present invention include:

[0007] On the one hand, the present invention discloses an amorphous high-initial-tack hot-melt polyurethane adhesive, which includes component A, component B, component C and component D. The molar percentages of component A, component B, component C and component D are (30 - 55):(10 - 30):(10 - 20):(15 - 25). Component A includes polyester polyol, component B includes property-adjusting polyol, component C includes additives, and component D includes isocyanate or isocyanate prepolymer.

[0008] Furthermore: The polyester polyol includes polyester diol and aromatic dicarboxylic acid chain extender.

[0009] Furthermore: The polyester diol includes phthalic anhydride, diol, antioxidant and catalyst.

[0010] Furthermore: The molar ratio of phthalic anhydride to diol is 1:1 - 1:2.

[0011] Furthermore: The diol includes one or a combination of two of diethylene glycol and ethylene glycol.

[0012] Further, the aromatic dicarboxylic acid chain extender includes terephthalic acid, methyl terephthalate or isophthalic acid.

[0013] Further, the property - regulating polyol includes polyester or polyether polyol.

[0014] Further, the additive includes tackifying resin.

[0015] Further, the content of NCO in the isocyanate prepolymer is 15% - 25%.

[0016] On the other hand, the present invention also discloses a preparation method of an amorphous high - initial - tack hot - melt polyurethane adhesive, which includes the following steps:

[0017] S1. Add polyester diol with a molar percentage of 30 - 55, property - regulating polyol with a molar percentage of 10 - 30, and additive with a molar percentage of 10 - 20 into a reaction kettle;

[0018] S2. Raise the temperature of the reaction kettle to 120 °C and remove water under vacuum for 2 h;

[0019] S3. Lower the temperature of the reaction kettle when the water content in the reaction kettle is 200 ppm;

[0020] S4. When the temperature in the reaction kettle drops to 90 °C, add isocyanate or isocyanate prepolymer with a molar percentage of 15 - 25 to obtain a mixture;

[0021] S5. Raise the temperature of the reaction kettle to 120 °C, react the mixture in the reaction kettle for 2 h, and carry out vacuum defoaming to obtain an amorphous high - initial - tack hot - melt polyurethane adhesive.

[0022] Further, the preparation method of the polyester polyol includes the following steps:

[0023] S10. Prepare polyester diol in a reaction kettle;

[0024] S20. Add an aromatic dicarboxylic acid chain extender to the reaction kettle;

[0025] S30. Raise the temperature of the reaction kettle to 230 - 240 °C and carry out dehydration polymerization.

[0026] Further, the preparation method of the polyester polyol includes the following steps:

[0027] S100. Add phthalic anhydride, diol and antioxidant into a reaction kettle, and raise the temperature of the reaction kettle to 130 °C;

[0028] S200. Raise the temperature of the reaction kettle to 200 °C and stir the materials in the reaction kettle for 2 h;

[0029] S300. Raise the temperature of the reaction kettle to 220 °C and keep it warm for 2 h;

[0030] S400. Vacuum the reaction kettle to 456 - 532 mmHg and keep it under vacuum for 2 h;

[0031] S500. Add a catalyst into the reaction kettle and stir the materials in the reaction kettle for 20 min;

[0032] S600. Vacuum the reaction kettle to make the vacuum degree in the reaction kettle greater than 684 mmHg;

[0033] S700. Let the materials react in the reaction kettle for 7 h.

[0034] Compared with the prior art, the advantages of the present invention include:

[0035] 1) An amorphous high-initial-tack hot-melt polyurethane adhesive provided by the present invention can not only avoid the bubbling phenomenon during the curing process, but also has the advantages of environmental protection, low cost and high initial tack of the product;

[0036] 2) A preparation method of an amorphous high-initial-tack hot-melt polyurethane adhesive provided by the present invention has a simple formula and is easy to operate. Detailed Embodiments

[0037] In view of the deficiencies in the prior art, the inventors of this case have put forward the technical solution of the present invention through long-term research and a large number of practices. The following will further explain and illustrate the technical solution, its implementation process and principle, etc.

[0038] On the one hand, the present invention discloses an amorphous high-initial-tack hot-melt polyurethane adhesive, which includes component A, component B, component C and component D. The molar percentages of component A, component B, component C and component D are (30 - 55):(10 - 30):(10 - 20):(15 - 25). The molar percentages of component A, component B, component C and component D can be 30:30:20:20 or 55:15:17:13 or 40:25:10:25.

[0039] Component A includes polyester polyol. Specifically, the polyester polyol includes polyester diol and aromatic dicarboxylic acid chain extender; more specifically, the polyester diol includes phthalic anhydride, diol, antioxidant and catalyst. The molar ratio of phthalic anhydride to diol is 1:1 - 1:2. More specifically, the diol includes one or a combination of two of diethylene glycol and ethylene glycol.

[0040] The polyester polyol structure contains a polyether soft segment and an amorphous aromatic hard segment, and the hot melt polyurethane adhesive prepared in this way can be used for bonding materials such as textiles, thermal insulation materials, woodworking home panels, soft home furnishings, and motor vehicle compartment sponges and epoxy panels. It not only avoids the initial bonding force that must be formed by using crystalline polyester materials and inhibits the bubbling phenomenon during the curing process of PUR, but also has the advantages of environmental protection and low cost.

[0041] Specifically, the aromatic dibasic acid chain extender includes terephthalic acid, methyl terephthalate or isophthalic acid.

[0042] The B component includes a performance-adjusting polyol. Specifically, the performance-adjusting polyol can be a polyester or polyether polyol with a molecular weight between 2000 and 5500, such as Palonam 1500HNA (MW3000) from the United States, PTMEG 2000 (MW2000) from Hyosung of South Korea, Evonik liquid polyester Dyna℃ol7250 (MW5500), polyether PPG2000 (MW2000), etc.

[0043] The C component includes additives. Specifically, the additives include tackifying resins. The tackifying resins may be ℃-9 resins (such as PF120), terpene phenol modified resins (such as T105, T135), pure monomer resins (such as Clavier W85), and the like.

[0044] The D component includes isocyanate or isocyanate prepolymer, and the isocyanate can be monomeric isocyanate MDI (Wanhua), MDI50 (Wanhua) or liquefied MDI (Wanhua); the isocyanate prepolymer can be a simple prepolymer adduct of monomeric isocyanate and liquid polyester or polyether, and the N°C O content in the isocyanate prepolymer is between 15-25%, and the N°C O content in the isocyanate prepolymer can be 15%, 20% or 25%. In this embodiment, the N°C O content in the isocyanate prepolymer is 20%.

[0045] The present invention also discloses a method for preparing an amorphous high initial viscosity hot melt polyurethane adhesive, comprising the following steps:

[0046] S1, adding 30-55 mole percent of polyester diol, 10-30 mole percent of performance adjusting polyol and 10-20 mole percent of additives into a reactor;

[0047] Specifically, the preparation method of the polyester polyol comprises the following steps:

[0048] S10, preparing polyester diol in a reactor;

[0049] More specifically, the preparation method of the polyester diol comprises the following steps:

[0050] S100, Add phthalic anhydride, diol and antioxidant into the reaction kettle, and raise the temperature of the reaction kettle to 130 °C;

[0051] S200, Raise the temperature of the reaction kettle to 200 °C, and stir the materials in the reaction kettle for 2 h;

[0052] S300, Raise the temperature of the reaction kettle to 220 °C, and keep it warm for 2 h;

[0053] S400, Vacuumize the reaction kettle to 456 - 532 mmHg, and vacuumize for 2 h;

[0054] S500, Add catalyst into the reaction kettle, and stir the materials in the reaction kettle for 20 min;

[0055] S600, Vacuumize the reaction kettle to make the vacuum degree in the reaction kettle greater than 684 mmHg;

[0056] S700, The materials react in the reaction kettle for 7 h to synthesize a low - molecular - weight polyester diol with a molecular weight of 500 - 1000;

[0057] S20, Add an aromatic dicarboxylic acid chain extender into the reaction kettle;

[0058] S30, Raise the temperature of the reaction kettle to 230 - 240 °C, carry out dehydration polymerization, and condense to prepare a viscous semi - solid polyester diol with a molecular weight between 1000 - 3000;

[0059] S2, Raise the temperature of the reaction kettle to 120 °C, and remove water under vacuum for 2 h;

[0060] S3, When the water content in the reaction kettle is 200 ppm, lower the temperature of the reaction kettle;

[0061] S4, When the temperature in the reaction kettle drops to 90 °C, add an isocyanate or isocyanate prepolymer with a molar percentage of 15 - 25 to obtain a mixture;

[0062] S5, Raise the temperature of the reaction kettle to 120 °C, the mixture reacts in the reaction kettle for 2 h, and carry out vacuum defoaming to obtain an amorphous high - initial - tack hot - melt polyurethane adhesive.

[0063] Example 1:

[0064] The preparation method of the polyester polyol includes the following steps:

[0065] S10, Prepare polyester diol in the reaction kettle:

[0066] The number of moles of phthalic anhydride, n, is calculated according to the formula for feeding: nO℃R2℃OO=HOR1[O℃OR2℃OOR1]nOH(n + 1), where the theoretical molecular weight of the polyester is HOR1[O℃OR2℃OOR1]nOH. This step is to design a small molecule diol of phthalic anhydride-diethylene glycol polyester with a molecular weight of 560.

[0067] S100: Add 46.83 parts of phthalic anhydride, 53.06 parts of diethylene glycol, and antioxidant Irganox 1010 to the reaction kettle, initially heat up to 130 °C, and esterification water is discharged at the start of the reaction.

[0068] S200: Set the temperature of the material in the reaction kettle to 200 °C (the reaction time from 130 °C to 200 °C is usually about 5 h). When the temperature reaches 200 °C, stir for 2 h; then set the temperature of the reaction kettle material to 220 °C (the heating reaction time from 200 °C to 220 °C is usually about 2.5 h).

[0069] S300: When the temperature of the material in the reaction kettle rises to 220 °C, keep it at this temperature for 2 h.

[0070] S400: Evacuate to 456 - 532 mmHg (-0.06~-0.07 MPa) at 220 °C. After 2 h, take a sample to test the acid value and hydroxyl value (usually the acid value will drop below 20 mgKOH / g); if the acid value is higher than 20 mgKOH / g, continue to react at 220 °C until the acid value meets the requirements.

[0071] S500: Add n-butyl titanate catalyst to the reaction kettle, stir for 20 min, and then start to evacuate.

[0072] S600: Reach a vacuum degree above 684 mmHg (-0.09 MPa) within 1 h.

[0073] S700: The material continues to react in the reaction kettle at a reaction temperature of 220 °C and a vacuum condition above 684 mmHg (-0.09 MPa) for 7 h. During this period, take a small sample every 4 h to test the acid value and hydroxyl value (take a total of two small samples). After two samplings, change to take a sample every h to test the acid value and hydroxyl value until the acid value < 2.0 mgKOH / g and the hydroxyl value is between 115 + 5 mgKOH / g. When the water output reaches 6.81% of the total feed amount, or the acid value is lower than 2.0, the molecular weight of the polyester diol in the first step is 560 (hydroxyl value 200.3).

[0074] S20: When the first-step reaction is completed, immediately add terephthalic acid or isophthalic acid to the reaction kettle, heat up to 230 - 240 °C, and dehydrate and polymerize until the hydroxyl value drops to the required value.

[0075] Test Example 1. Preparation of polyester polyol with a molecular weight of 1500 (M1500): After the reaction in S10, 86.39 parts by weight of phthalic anhydride - diethylene glycol diol was added to the reaction kettle, and 14.62 parts by weight of terephthalic anhydride TPA was added to the reaction kettle. The reaction was stopped when the hydroxyl value reached 74.8 according to the above S20 steps. At this time, the available polyester polyol with a molecular weight of 1500 was obtained.

[0076] Test Example 2. Preparation of polyester polyol with a molecular weight of 3000 (M3000): After the reaction in S10, 81.22 parts by weight of phthalic anhydride - diethylene glycol diol was added to the reaction kettle, and 18.78 parts by weight of isophthalic acid IPA was added to the reaction kettle. The reaction was stopped when the hydroxyl value reached 37.4 according to the above S20 steps. At this time, the available polyester polyol with a molecular weight of 3000 was obtained.

[0077] Example Two: Preparation method of amorphous high - initial - tack hot - melt polyurethane adhesive, including the following steps:

[0078] S1. Add polyester diol, property - regulating polyol and additive into the reaction kettle;

[0079] S2. Heat the reaction kettle to 120 °C and remove water under vacuum for 2 h;

[0080] S3. When the water content in the reaction kettle is 200 ppm, lower the temperature of the reaction kettle;

[0081] S4. When the temperature in the reaction kettle drops to 90 °C, then add isocyanate or isocyanate prepolymer;

[0082] S5. Raise the temperature of the reaction kettle to 120 °C, react the mixture in the reaction kettle for 2 h, perform vacuum degassing, then measure the viscosity and NCO content. After confirming the end point of the reaction, end the process, and then evaluate the bonding performance.

[0083] Test Example 1 (PUR1):

[0084] Add 40 parts of polyester polyol with a molecular weight of 1500, 20 parts of PTMEG2000 property - regulating polyether and 20 parts of TF120 tackifying resin into the reaction kettle, heat to 120 °C, evacuate and dehydrate for 1 h, then cool to 100 °C, and add 20 parts of monomeric isocyanate MDI. After reacting at 120 °C for 2 h, evacuate for 30 min and discharge to obtain an available PUR product with an NCO content of 3.64%.

[0085] Test Example 2 (PUR2):

[0086] Add 40 parts of polyester polyol with a molecular weight of 3000, 22 parts of PPG2000 performance - regulating polyether, and 25 parts of terpene - phenol T105 tackifying resin into the reaction kettle. Heat up to 120 °C, evacuate to remove water for 1 h, then cool down to 100 °C, and add 13 parts of monomeric isocyanate MDI. React at 120 °C for 2 h, then evacuate for 30 min and discharge to obtain a usable PUR product with an NCO content of 2.32%.

[0087] Test Example 3 (PUR3):

[0088] Add 50 parts of polyester polyol with a molecular weight of 1500, 20 parts of Dyna℃oll7250 performance - regulating polyester, and 10 parts of pure monomer resin W85 tackifying resin into the reaction kettle. Heat up to 120 °C, evacuate to remove water for 1 h, then cool down to 100 °C, and add 20 parts of monomeric isocyanate MDI. React at 120 °C for 2 h, then evacuate for 30 min and discharge to obtain a usable PUR product with an NCO content of 3.60%.

[0089] Test Example 4:

[0090] First, synthesize the isocyanate prepolymer. Add 36 parts of PTMEG2000 into the reaction kettle, evacuate and dry at 100 °C for 1 h, then cool down to 80 °C, and add 64 parts of monomeric isocyanate MDI. Protect with nitrogen, react at 80 °C for 4 h to obtain an MDI simple prepolymer containing 20% NCO for the synthesis of PUR4.

[0091] Synthesize the PUR4 adhesive: Add 55 parts of polyester polyol with a molecular weight of 3000 and 20 parts of American Panolam 1500NHA performance - regulating polyester into the reaction kettle. Heat up to 120 °C, evacuate to remove water for 1 h, then cool down to 100 °C, and add 25 parts of the MDI prepolymer. React at 120 °C for 2 h, then evacuate for 30 min and discharge to obtain a usable PUR product with an NCO content of 2.90%.

[0092] Performance testing and result analysis:

[0093]

[0094] The difference between the present invention and the general polyester polyether polyols used in PUR lies in that: a small molecule polyester diol (such as phthalic anhydride - diethylene glycol, MW560) is prepared using the most readily available and low-cost raw materials in the market. The molecular structure contains hard and soft segments, and the soft segment of diethylene glycol is distributed at both ends of the molecule. This small molecule diol is too reactive to be directly used as the main raw material for the preparation of PUR products. However, when this diol with such a structure is further reacted with an aromatic dicarboxylic acid such as terephthalic acid (the lowest-cost dicarboxylic acid) to prepare a semi-solid polyester diol with a molecular weight of 1500 - 3000, it can be directly used as the main raw material for PUR products, and the dosage in the formula is between 40 - 55%.

[0095] Since the polyester with such a structure is rich in aromatic groups and the hard and soft segments are interspersed, the PUR products made have good initial adhesiveness. Due to the presence of the soft segment in the molecular structure and the appropriate introduction of performance-adjusting diols, the terminal PUR products not only have high initial adhesiveness but also have high and low temperature resistance after curing.

[0096] In the examples of PUR1 - PUR4, regardless of whether there is a tackifying resin or not, their peel forces are all between 18 - 25 N, and this initial adhesive force is sufficient to bond the substrates together. The use of this polyester polyol can make the PUR formula very simple. PUR1 - PUR3 only have 4 raw materials, while PUR4 only has 3 raw materials; this shortens the preparation time and reduces the preparation cost. In particular, the ultra-high initial peel strength is not possessed by general PUR. It can be seen from the experimental examples that there are various choices for the tackifying resin, and the tackifying resin makes the viscosity of the system (PUR1 - PUR3) much lower than that of PUR4 without the tackifying resin under the use condition of 120°C. This PUR product can be used for the bonding of soft materials, thermal insulation materials, textiles, and the bonding of the seats and mattresses of high-speed trains (such as the bonding of epoxy boards and PU sponges, and the bonding strength within 5 - 12 minutes is higher than the strength of the PU sponge itself).

[0097] It should be understood that the above embodiments are only used to illustrate the technical concept and characteristics of the present invention, and the purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. An amorphous high-initial-tack hot melt polyurethane adhesive, characterized in that: including Component A, Component B, Component C and Component D, the molar percentages of Component A, Component B, Component C and Component D being (30 - 55):(10 - 30):(10 - 20):(15 - 25), Component A including polyester polyol, Component B including property - regulating polyol, Component C including additive, and Component D including isocyanate or isocyanate prepolymer.

2. The amorphous high-initial-tack hot-melt polyurethane adhesive according to claim 1, characterized in that: The polyester polyol includes polyester diol and aromatic dicarboxylic acid chain extender.

3. An amorphous high-initial-tack hot-melt polyurethane adhesive according to claim 2, characterized in that: The polyester diol includes phthalic anhydride, diol, antioxidant and catalyst; and / or, the molar ratio of phthalic anhydride to diol is 1:1 - 1:

2. and / or, the diol includes one or a combination of two of diethylene glycol and ethylene glycol.

4. An amorphous high-initial-tack hot-melt polyurethane adhesive according to claim 2, characterized in that: The aromatic dicarboxylic acid chain extender includes terephthalic acid or methyl terephthalate or isophthalic acid.

5. The amorphous high-initial-tack hot-melt polyurethane adhesive according to claim 1, characterized in that: The property - regulating polyol includes polyester or polyether polyol.

6. The amorphous high-initial-tack hot melt polyurethane adhesive according to claim 1, characterized in that: The additive includes tackifying resin.

7. The amorphous high-initial-tack hot-melt polyurethane adhesive according to claim 1, characterized in that: The content of NCO in the isocyanate prepolymer is 15% - 25%.

8. A preparation method of an amorphous high-initial-tack hot melt polyurethane adhesive, characterized in that: including the following steps: S1. Add polyester diol with a molar percentage of 30 - 55, property - regulating polyol with a molar percentage of 10 - 30 and additive with a molar percentage of 10 - 20 into a reaction kettle; S2. Raise the temperature of the reaction kettle to 120°C and remove water under vacuum for 2 h; S3. Lower the temperature of the reaction kettle when the water content in the reaction kettle is 200 ppm; S4. When the temperature in the reaction kettle drops to 90°C, add isocyanate or isocyanate prepolymer with a molar percentage of 15 - 25 to obtain a mixture; S5. Raise the temperature of the reaction kettle to 120°C, and let the mixture react in the reaction kettle for 2 h, then carry out vacuum defoaming to obtain an amorphous high - initial - tack hot - melt polyurethane adhesive.

9. The preparation method of an amorphous high-initial-tack hot melt polyurethane adhesive according to claim 8, wherein: The preparation method of the polyester polyol includes the following steps: S10. Prepare polyester diol in a reaction kettle; S20. Add aromatic dicarboxylic acid chain extender into the reaction kettle; S30. Raise the temperature of the reaction kettle to 230 - 240°C and carry out dehydration polymerization.

10. The preparation method of an amorphous high-initial-tack hot melt polyurethane adhesive according to claim 9, characterized in that: The preparation method of the polyester diol includes the following steps: S100. Add phthalic anhydride, diol and antioxidant into the reaction kettle, and raise the temperature of the reaction kettle to 130°C; S200. Raise the temperature of the reaction kettle to 200°C and stir the materials in the reaction kettle for 2 h; S300. Raise the temperature of the reaction kettle to 220°C and keep it warm for 2 h; S400. Vacuumize the inside of the reaction kettle to 456 - 532 mmHg and carry out vacuum pumping for 2 h; S500. Add catalyst into the reaction kettle and stir the materials in the reaction kettle for 20 min; S600. Vacuumize the inside of the reaction kettle to make the vacuum degree in the reaction kettle greater than 684 mmHg; S700. Let the materials react in the reaction kettle for 7 h.

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