Reactive polyurethane hot melt adhesive containing polycarbonate-polyether block polyol and preparation method of reactive polyurethane hot melt adhesive

Abstract

The invention belongs to the technical field of polyurethane adhesives, and particularly relates to a reactive polyurethane hot melt adhesive containing polycarbonate-polyether block polyol and a preparation method of the reactive polyurethane hot melt adhesive. The reactive polyurethane hot melt adhesive is prepared from the following components in parts by weight: 25 to 60 parts of polycarbonate-polyether block polyol, 10 to 25 parts of polycarbonate polyol, 5 to 20 parts of dimer acid modified polyester polyol, 10 to 30 parts of isocyanate, 0.1 to 0.5 part of a catalyst and 0.1 to 0.3 part of an antioxidant. According to the invention, by introducing a polycarbonate-polyether block polyol and isocyanate compound system, the single-component moisture-cured reactive polyurethane hot melt adhesive with balanced flexibility and durability is realized, and the storage stability, the initial viscosity, the final strength, the weather resistance and the reliability can be better balanced; and the adhesive is suitable for high-reliability bonding of wearable equipment, optical display modules and other flexible electronic structural members.

Description

Technical Field

[0001] This invention belongs to the field of polyurethane adhesives technology, specifically relating to a low-modulus, high-durability reactive polyurethane hot melt adhesive containing polycarbonate-polyether block polyols and its preparation method. Background Technology

[0002] Moisture-curing reactive polyurethane hot melt adhesives (PURs) combine the rapid initial tack of thermoplastic hot melt adhesives with the high strength of thermosetting materials after moisture curing. Therefore, they are widely used in electronic structural component packaging, touch displays, headphone cavities, metal-plastic bonding and other fields.

[0003] However, existing technologies have the following prominent problems: 1. The contradiction between flexibility and durability: Polyether-type PUR is soft, but has poor heat and aging resistance; polycarbonate-type PUR has good durability, but has high modulus and is brittle.

[0004] 2. Stress and fatigue failure: In headphones and wearable devices, adhesive layers need to withstand repeated thermal expansion and contraction and mechanical bending. Traditional systems often develop cracks or lose adhesion after cyclic stress.

[0005] 3. High requirements for environmental stability: Sweat, sebum, sunscreen, etc. can cause oxidative degradation of polyether segments, while polyester-type PUR is easily hydrolyzed, leading to long-term performance decline.

[0006] Furthermore, in existing technologies, one-component moisture-curing polyurethane (1K PUR) typically uses a single isocyanate (such as MDI, TDI, IPDI, HDI) to end-cap prepolymers in order to achieve both curing reaction and adhesive properties. However, this single-component system has the following shortcomings: 1. Systems prepared using aromatic isocyanates (such as MDI and TDI) have fast curing speed and strong initial tack, but poor storage stability, high risk of self-crosslinking, and are prone to yellowing and performance degradation under long-term or high-temperature conditions. 2. Although alicyclic or aliphatic isocyanate systems (such as IPDI and HDI) have good stability and color performance, they have slow reaction speed and insufficient initial tack, making it difficult to meet the bonding requirements of rapid prototyping. 3. A single system is unlikely to achieve a good balance between rapid initial bonding and long-term mechanical properties and weather resistance.

[0007] Existing modification strategies (such as using end-capping agents, adding retarders, using polymerization inhibitors, etc.) may improve certain properties, but often sacrifice the integrity of the crosslinked network, reduce the final strength, or increase complexity. Summary of the Invention

[0008] To address the shortcomings of the prior art, this invention provides a low-modulus, high-durability reactive polyurethane hot melt adhesive containing polycarbonate-polyether block polyols and its preparation method. By introducing a polycarbonate-polyether block polyol and isocyanate compound system, a single-component moisture-curing reactive polyurethane hot melt adhesive (PUR) that balances flexibility and durability is achieved can obtain a better balance between storage stability, initial tack, final strength, weather resistance and reliability, and is suitable for highly reliable bonding of wearable devices, optical display modules and other flexible electronic structural components.

[0009] The specific technical solution is as follows: The first objective of this invention is to provide a reactive polyurethane hot melt adhesive containing polycarbonate-polyether block polyol, comprising the following components by weight: 25-60 parts of polycarbonate-polyether block polyol, 10-25 parts of polycarbonate polyol, 5-20 parts of dimer acid modified polyester polyol, 10-30 parts of isocyanate, 0.1-0.5 parts of catalyst, and 0.1-0.3 parts of antioxidant.

[0010] Furthermore, by weight, it also includes 1-5 parts of monofunctional alcohols.

[0011] Furthermore, the isocyanate is a compound system of diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), and hexamethylene diisocyanate (HDI), with a weight ratio of (3-7):(2-4):(1-4) for MDI, IPDI, and HDI.

[0012] Furthermore, the polycarbonate polyol has a molecular weight of 1000-4000 and a hydroxyl value of 30-114 mgKOH / g.

[0013] Furthermore, the dimer acid-modified polyester polyol has a molecular weight of 1000-3000 and a hydroxyl value of 37-114 mgKOH / g.

[0014] Furthermore, the catalyst is selected from one or more of dibutyltin dilaurate (DBTDL), bis(acetylacetone)dibutyltin, or tertiary amine catalysts.

[0015] A second objective of this invention is to provide a method for preparing the above-mentioned reactive polyurethane hot melt adhesive containing polycarbonate-polyether block polyols, comprising the following steps: (1) Dehydration of polyols: Under vacuum conditions, polycarbonate-polyether block polyols, polycarbonate polyols and dimer acid modified polyester polyols are mixed and heated to 90-110℃ for vacuum dehydration to obtain a polyol mixture. (2) Prepolymerization reaction: Cool the polyol mixture obtained in step (1) to 70-90℃, break the vacuum with nitrogen, add isocyanate and catalyst, control the reaction temperature at 100-120℃ and continue the reaction for 60-120 min, and monitor the NCO content; (3) End-capping and degassing: After the reaction reaches the theoretical NCO content of 2.0-4.0%, the temperature is lowered to 70-90℃, and the material is discharged after vacuum degassing for 30 minutes. It is then cooled into blocks or filled and packaged.

[0016] Furthermore, in step (2), when adding isocyanate, MDI is added to carry out the first prepolymerization reaction, and the NCO content is controlled to be 2.0-4.0%.

[0017] Furthermore, in step (2), after adding MDI, IPDI and HDI are added dropwise in sequence.

[0018] MDI is added in the early stages of the reaction to provide highly reactive end-capping; IPDI is added in the middle stages to slow down the reaction rate; and HDI is added at the end stages to form a flexible gradient layer. The three isocyanates are added stepwise during the prepolymer synthesis process, controlling their respective reaction stages, thereby forming a reaction gradient structure with isocyanate end-capping in the prepolymer backbone, achieving crosslink density distribution in different regions, and thus balancing initial tack and durability.

[0019] Furthermore, in step (3), after cooling, a monofunctional alcohol is added, followed by vacuum degassing.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Soft segment block design: Polycarbonate and polyether soft segments are alternately blocked to form a microphase separation structure. The carbonate part provides heat resistance and polar interaction, while the polyether part provides flexibility and low temperature performance. Isocyanate compounding reaction gradient: By compounding MDI (aromatic) with IPDI and HDI (aliphatic), the difference in reactivity is controlled to achieve a gradient distribution of hard segments, so that the colloid has both strength and flexibility; Interface adhesion enhancement: By introducing dimer acid-modified polyester polyol, the adhesion adaptability to polar and non-polar substrates (polycarbonate PC, thermoplastic elastomer TPE, metals, etc.) is improved. The molar ratio of NCO / OH is controlled in the range of 1.6-1.9 to obtain a prepolymer with an end NCO content of 2-4%. The above design achieves structural hierarchy: block-type soft segments form micro-phase domains, effectively dispersing external force strain and improving fatigue resistance; gradient reaction: the MDI / IPDI / HDI compound controls the hard segment formation rate, achieving sustained stress relief during curing; balanced performance: modulus as low as 14-25 MPa, elongation ≥420%, and moisture heat retention ≥80%; strong application adaptability: it has high adhesion to substrates such as PC, TPU (thermoplastic polyurethane elastomer), TPE, aluminum, and stainless steel, making it suitable for bonding wearable devices, headphone modules, and optical displays.

[0021] (2) This invention provides a novel PUR system that achieves a balance between “low modulus and high durability” through block design. By introducing polycarbonate-polyether block polyols into the molecular backbone and using an MDI / IPDI / HDI ternary isocyanate compound system, internal stress is released, resulting in better reliability and forming a network structure with microphase control capability. This allows the colloid to maintain flexibility while also being fatigue-resistant and chemical-resistant, making it suitable for structural bonding of electronic display modules, earphone cavities, or wearable devices.

[0022] (3) The reactive polyurethane hot melt adhesive of the present invention has a Shore A hardness of 40-70A, a modulus of less than 14 MPa, an elongation of ≥420%, a shear strength of ≥2.5 MPa, and retains strength (moist heat retention rate) of ≥80% after aging for 7 days under 80℃ / 85%RH conditions. Detailed Implementation

[0023] The principles and features of the present invention are described below with reference to examples. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention. The parts mentioned in the specific embodiments are parts by weight.

[0024] Example 1 A method for preparing a reactive polyurethane hot melt adhesive containing polycarbonate-polyether block polyols includes the following steps: Under vacuum conditions, 15 parts of polycarbonate polyol (Mn=2000), 35 parts of polycarbonate-polyether block polyol (Mn=2000, polyether content 40%, Huizhou Daya Bay Dazhi Fine Chemical Co., Ltd.), and 10 parts of dimer acid modified polyester polyol (Mn=2000, Cargill Priplast™ XL) were mixed. Mix 101) 0.2 parts of antioxidant 1010, heat to 110℃ and dehydrate under vacuum (-0.098MPa) for 2 hours; then cool to 90℃, break the vacuum with nitrogen, add 25 parts of isocyanate mixture (MDI / IPDI / HDI weight ratio of 5:3:2, where MDI is added for the first prepolymerization reaction, controlling the NCO content to 2.5%, and then IPDI and HDI are added dropwise) and 0.3 parts of catalyst DMDEE, control the reaction temperature at 110℃ and continue the reaction for 120 minutes. After the NCO content reaches 2.5%, cool to 80℃ and continue vacuum degassing for 30 minutes, then bottle.

[0025] Example 2 (Increased proportion of soft segments) A method for preparing a reactive polyurethane hot melt adhesive containing polycarbonate-polyether block polyols includes the following steps: Under vacuum conditions, 10 parts of polycarbonate polyol (Mn=2000), 50 parts of polycarbonate-polyether block polyol (Mn=2000, polyether content 40%, Huizhou Daya Bay Dazhi Fine Chemical Co., Ltd.), and 10 parts of dimer acid modified polyester polyol (Mn=2000, Cargill Priplast™ XL) were mixed. Mix 101) 0.2 parts of antioxidant 1010, heat to 110℃ and dehydrate under vacuum (-0.098MPa) for 2 hours; then cool to 90℃, break the vacuum with nitrogen, add 20 parts of isocyanate mixture (MDI / IPDI / HDI weight ratio of 5:3:2, where MDI is added for the first prepolymerization reaction, controlling the NCO content to 2.5%, and then IPDI and HDI are added dropwise) and 0.3 parts of catalyst DMDEE, control the reaction temperature at 110℃ and continue the reaction for 120 minutes. After the NCO content reaches 2.5%, cool to 80℃ and continue vacuum degassing for 30 minutes, then bottle.

[0026] Example 3 (Increasing HDI ratio to improve flexibility) A method for preparing a reactive polyurethane hot melt adhesive containing polycarbonate-polyether block polyols includes the following steps: Under vacuum conditions, 15 parts of polycarbonate polyol (Mn=2000), 35 parts of polycarbonate-polyether block polyol (Mn=2000, polyether content 40%, Huizhou Daya Bay Dazhi Fine Chemical Co., Ltd.), and 10 parts of dimer acid modified polyester polyol (Mn=2000, Cargill Priplast™ XL) were mixed. Mix 101) 0.2 parts of antioxidant 1010, heat to 110℃ and dehydrate under vacuum (-0.098MPa) for 2 hours; then cool to 90℃, break the vacuum with nitrogen, add 25 parts of isocyanate mixture (MDI / IPDI / HDI weight ratio of 3:3:4, where MDI is added for the first prepolymerization reaction, controlling the NCO content to 2.5%, and then IPDI and HDI are added dropwise) and 0.3 parts of catalyst DMDEE, control the reaction temperature at 110℃ and continue the reaction for 120 minutes. After the NCO content reaches 2.5%, cool to 80℃ and continue vacuum degassing for 30 minutes, then bottle.

[0027] Example 4 (Polycarbonate block polyol with 40% PCD content) A method for preparing a reactive polyurethane hot melt adhesive containing polycarbonate-polyether block polyols includes the following steps: Under vacuum conditions, 15 parts of polycarbonate polyol (Mn=2000), 35 parts of polycarbonate-polyether block polyol (Mn=2000, polyether content 20%, Huizhou Daya Bay Dazhi Fine Chemical Co., Ltd.), and 10 parts of dimer acid modified polyester polyol (Mn=2000, Cargill Priplast™ XL) were mixed. Mix 101) 0.2 parts of antioxidant 1010, heat to 110℃ and dehydrate under vacuum (-0.098MPa) for 2 hours; then cool to 90℃, break the vacuum with nitrogen, add 25 parts of isocyanate mixture (MDI / IPDI / HDI weight ratio of 5:3:2, where MDI is added for the first prepolymerization reaction, controlling the NCO content to 2.5%, and then IPDI and HDI are added dropwise) and 0.3 parts of catalyst DMDEE, control the reaction temperature at 110℃ and continue the reaction for 120 minutes. After the NCO content reaches 2.5%, cool to 80℃ and continue vacuum degassing for 30 minutes, then bottle.

[0028] Example 5 (with addition of monofunctional alcohol) A method for preparing a reactive polyurethane hot melt adhesive containing polycarbonate-polyether block polyols includes the following steps: Under vacuum conditions, 15 parts of polycarbonate polyol (Mn=2000), 35 parts of polycarbonate-polyether block polyol (Mn=2000, polyether content 20%, Huizhou Daya Bay Dazhi Fine Chemical Co., Ltd.), and 10 parts of dimer acid modified polyester polyol (Mn=2000, Cargill Priplast™ XL) were mixed. Mix 101) and 0.2 parts of antioxidant 1010, heat to 110℃ and dehydrate under vacuum (-0.098MPa) for 2 hours; then cool to 90℃, break the vacuum with nitrogen, add 25 parts of isocyanate mixture (MDI / IPDI / HDI weight ratio of 5:3:2, where MDI is added for the first prepolymerization reaction, controlling the NCO content to 2.5%, and then IPDI and HDI are added dropwise) and 0.3 parts of catalyst DMDEE, control the reaction temperature at 110℃ and continue the reaction for 120 minutes. After the NCO content reaches 2.5%, cool to 80℃, add 1 part of monofunctional alcohol (Ito Oil URIC H-31), continue vacuum degassing for 30 minutes, and then bottle.

[0029] Comparative Example 1 (Pure polyether type PUR) A method for preparing a reactive polyurethane hot melt adhesive includes the following steps: Under vacuum conditions, 60 parts of polyether polyol (Mn=2000) and 0.2 parts of antioxidant 1010 were mixed and heated to 110°C for vacuum dehydration (-0.098 MPa) for 2 hours. Then, the temperature was lowered to 90°C, the vacuum was broken with nitrogen, and 25 parts of isocyanate mixture (MDI / IPDI / HDI weight ratio of 5:3:2, where MDI was added for the first prepolymerization reaction, controlling the NCO content to 2.5%, and then IPDI and HDI were added dropwise) and 0.3 parts of catalyst DMDEE were added. The reaction temperature was controlled at 110°C and the reaction was continued for 120 minutes. After the NCO content reached 2.5%, the temperature was lowered to 60°C and vacuum degassing was continued for 30 minutes before packaging.

[0030] Comparative Example 2 (Pure Polycarbonate Type PUR) A method for preparing a reactive polyurethane hot melt adhesive includes the following steps: Under vacuum conditions, 60 parts of polycarbonate polyol (Mn=2000), 10 parts of dimer acid modified polyester polyol (Mn=2000, Cargill Priplast™ XL 101), and 0.2 parts of antioxidant 1010 were mixed and heated to 110°C for vacuum dehydration (-0.098MPa) for 2 hours. Then, the mixture was cooled to 90°C, the vacuum was broken with nitrogen, and 25 parts of isocyanate mixture (MDI / IPDI / HDI weight ratio of 5:3:2, where MDI was added for the first prepolymerization reaction, controlling the NCO content to 2.5%, and then IPDI and HDI were added dropwise) and 0.3 parts of catalyst DMDEE were added. The reaction temperature was controlled at 110°C and the reaction was continued for 120 minutes until the NCO content reached 2.5%. Then, the mixture was cooled to 60°C and vacuum degassing was continued for 30 minutes before packaging.

[0031] test: After the products of each embodiment and comparative example were applied, they were cured in a normal temperature and humidity environment and reached their final strength in 7 days.

[0032] Performance tests were conducted on the products of each embodiment and comparative example, and the experimental data of the performance tests of each embodiment and comparative example are shown in Table 1.

[0033] Table 1 Performance test data of each embodiment and comparative example

[0034] By comparing the performance test data in Table 1, it can be seen that the reactive polyurethane hot melt adhesive of the present invention, after curing, forms an adhesive layer with a Shore A hardness of 40-70A, a modulus of less than 25 MPa, an elongation of ≥420%, a shear strength of ≥2.5 MPa, and retains ≥80% of its strength (wet heat retention rate) after aging for 7 days at 80℃ / 85%RH.

[0035] The block structure system of the present invention is significantly superior to the single polyether (Comparative Example 1) or single polycarbonate (Comparative Example 2) systems in terms of durability and flexibility, achieving a performance balance, and the addition of monofunctional alcohols can control the hardness.

[0036] 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 principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A reactive polyurethane hot melt adhesive containing polycarbonate-polyether block polyols, characterized in that, By weight, it includes the following components: 25-60 parts of polycarbonate-polyether block polyol, 10-25 parts of polycarbonate polyol, 5-20 parts of dimer acid modified polyester polyol, 10-30 parts of isocyanate, 0.1-0.5 parts of catalyst, and 0.1-0.3 parts of antioxidant.

2. The reactive polyurethane hot melt adhesive containing polycarbonate-polyether block polyols according to claim 1, characterized in that, It also includes 1-5 parts by weight of monofunctional alcohols.

3. The reactive polyurethane hot melt adhesive containing polycarbonate-polyether block polyols according to claim 1, characterized in that, The isocyanate is a compound system of diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), and hexamethylene diisocyanate (HDI), with a weight ratio of (3-7):(2-4):(1-4) for MDI, IPDI, and HDI.

4. The reactive polyurethane hot melt adhesive containing polycarbonate-polyether block polyols according to claim 1, characterized in that, The polycarbonate polyol has a molecular weight of 1000-4000 and a hydroxyl value of 30-114 mgKOH / g.

5. The reactive polyurethane hot melt adhesive containing polycarbonate-polyether block polyols according to claim 1, characterized in that, The dimer acid-modified polyester polyol has a molecular weight of 1000-3000 and a hydroxyl value of 37-114 mgKOH / g.

6. The reactive polyurethane hot melt adhesive containing polycarbonate-polyether block polyols according to claim 1, characterized in that, The catalyst is selected from one or more of dibutyltin dilaurate (DBTDL), bis(acetylacetone)dibutyltin, or tertiary amine catalysts.

7. A method for preparing a reactive polyurethane hot melt adhesive containing polycarbonate-polyether block polyols as described in any one of claims 1 to 6, characterized in that, Includes the following steps: (1) Dehydration of polyols: Under vacuum conditions, polycarbonate-polyether block polyols, polycarbonate polyols and dimer acid modified polyester polyols are mixed and heated to 90-110℃ for vacuum dehydration to obtain a polyol mixture. (2) Prepolymerization reaction: Cool the polyol mixture obtained in step (1), break the vacuum with nitrogen, add isocyanate and catalyst, control the reaction temperature and continue the reaction for 60-120 min, and monitor the NCO content; (3) End sealing and degassing: After the reaction reaches the theoretical NCO content of 2.0-4.0%, the temperature is reduced, the material is degassed under vacuum and discharged, cooled into blocks or filled and packaged.

8. The reactive polyurethane hot melt adhesive containing polycarbonate-polyether block polyols according to claim 7, characterized in that, In step (2), when adding isocyanate, MDI is added to carry out the first prepolymerization reaction, and the NCO content is controlled to be 2.0-4.0%.

9. The reactive polyurethane hot melt adhesive containing polycarbonate-polyether block polyols according to claim 8, characterized in that, In step (2), after adding MDI, IPDI and HDI are added dropwise in sequence.

10. The reactive polyurethane hot melt adhesive containing polycarbonate-polyether block polyols according to claim 7, characterized in that, In step (3), after cooling, a monofunctional alcohol is added, followed by vacuum degassing.

Images