Preparation method of bio-based reversible cross-linked polyurethane hot melt adhesive

Abstract

The invention provides a preparation method of a bio-based reversible cross-linked polyurethane hot melt adhesive. The method comprises the following steps: firstly, carrying out polymerization reaction on bio-based polyol PO3G (poly trimethylene ether glycol) and isophorone diisocyanate which are used as raw materials to prepare an isocyanate-terminated bio-based prepolymer; then, diethyl toluenediamine and isophthaloyl hydrazine are adopted as a mixed chain extender for a chain extension reaction, and after drying treatment, the bio-based polyurethane hot melt adhesive is obtained. The bio-based hot-melt adhesive prepared by the invention is suitable for hot-melt sealants in the field of electronic devices. The adhesive shows good bonding performance to a stainless steel base material, the tensile shear strength reaches 0.45-0.5 MPa, the adhesive has excellent reversible disassembly characteristic, and convenient separation of a bonding interface can be achieved by heating at 100 DEG C for 10 minutes.

Description

Technical Field

[0001] This invention relates to a recyclable and environmentally friendly adhesive, specifically, to a bio-based polyurethane hot melt adhesive and its preparation method that achieves thermally reversible crosslinking based on bio-based polyol soft segments and multi-level hydrogen bonding. Technical Background

[0002] Hot melt adhesives, as solvent-free and environmentally friendly adhesive materials, are widely used in packaging, textiles, electronics, and automotive industries. Polyurethane hot melt adhesives have attracted much attention due to their excellent bonding properties, good flexibility, and weather resistance. From a molecular structure perspective, polyurethane hot melt adhesives also possess the characteristics of block copolymerization composed of soft and hard segments. Their microscopic phase separation structure and tunable molecular design provide a foundation for performance optimization. Under the global trend of environmental protection and sustainable development, using bio-based raw materials (such as bio-based polyols) to replace petroleum-based raw materials in the synthesis of polyurethane hot melt adhesives not only meets the needs of green and low-carbon development but also provides new ideas for expanding their application areas.

[0003] However, bio-based polyurethane hot melt adhesives still face key bottlenecks in practical applications. On the one hand, their mechanical properties and adhesive strength are generally lower than those of petroleum-based products, making it difficult to meet the needs of high-strength applications. On the other hand, the impact of thermal reversibility and structural stability on adhesive performance during repeated melting and processing has not been fully addressed. It is worth noting that how to achieve a synergistic improvement in adhesive strength while maintaining good flowability and reversible adhesive performance has become a key research focus in this field. Chinese invention patent CN120310511B discloses a bio-based polyurethane hot melt adhesive and its preparation method, which reportedly possesses high hydrolysis resistance, high initial tack, and high bond strength. Chinese invention patent CN115926722B discloses a method for preparing a recyclable bio-based thermosetting polyurethane hot melt adhesive, which reportedly features low melt viscosity, high peel strength, and recyclability.

[0004] The present invention aims to construct a bio-based polyurethane hot melt adhesive that combines thermal reversibility, high peel strength and recyclability by introducing bio-based soft segments and synergistically enhancing the role of disordered hydrogen bonds in hard segments. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a bio-based polyurethane hot melt adhesive. The hot melt adhesive prepared by this method has excellent bonding strength, thermal reversibility and recyclability, thereby achieving green sustainability throughout the entire product life cycle.

[0006] To achieve the above objectives, the present invention provides a bio-based polyurethane hot melt adhesive. This adhesive uses bio-based polyols as soft segments and, through multi-level hydrogen bonding, achieves both excellent adhesive strength and good thermal recyclability.

[0007] The present invention provides a method for preparing a bio-based reversible crosslinked polyurethane hot melt adhesive, comprising the following steps:

[0008] (1) Mix 1-3 mmol of bio-based polyol PO3G (polytrimethylene ether glycol), 2-6 mmol of isophorone diisocyanate and 10-15 mg of dibutyltin dilaurate, and react under N2 protection at 60-75 °C for 1-2 h to obtain isocyanate-terminated bio-based prepolymer;

[0009] (2) Dissolve 0.5-1.5 mmol of chain extender monomer diethyltoluenediamine and 0.5-1.5 mmol of hydrazide monomer isophthalic hydrazide in 5-15 mL of NN-dimethylacetamide, and add dropwise to the bio-based prepolymer prepared in (1) above and continue the chain extension reaction for 12-24 h. Dry to obtain bio-based polyurethane hot melt adhesive; the number average molecular weight of the above bio-based polyol PO3G is 1000 or 2000 g / mol; the molar ratio of PO3G, isophorone diisocyanate, diethyltoluenediamine and isophthalic hydrazide is 2:4:1:1;

[0010] (3) The application of the bio-based reversible crosslinked polyurethane hot melt adhesive prepared in (2) above as a hot melt sealant in the field of electronic devices is characterized in that the tensile shear strength of the hot melt adhesive on the stainless steel substrate is 0.45-0.5 MPa, and the bonding interface can be separated after heating at 100 °C for 10 minutes; the experimental method is relatively simple, has good biocompatibility, and can be used for large-scale production.

[0011] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0012] (1) Using bio-based polyol PO3G as the main raw material, it has good biocompatibility and renewability, which meets the requirements of green chemistry and sustainable development.

[0013] (2) The preparation process is simple to operate, consisting of two steps: prepolymerization and chain extension. It is easy to control and implement, and is suitable for industrial production. Attached Figure Description

[0014] Figure 1 This is an image of the bio-based reversible crosslinked polyurethane hot melt adhesive obtained in Example 1.

[0015] Figure 2The tensile shear strength of the stainless steel lap joint specimen bonded with the bio-based reversible crosslinked polyurethane hot melt adhesive obtained in Example 2.

[0016] Figure 3 This is a photograph showing the load-bearing capacity of a stainless steel lap joint specimen bonded with the bio-based reversible crosslinked polyurethane hot melt adhesive obtained in Example 3. Detailed Implementation

[0017] The following embodiments illustrate the present invention in detail, but the present invention is not limited to these embodiments.

[0018] Unless otherwise specified, all raw materials and reagents used in the following implementation examples are commercially available.

[0019] Example 1

[0020] The specific preparation method is as follows: (1) Mix 1 mmol of bio-based polyol PO3G, 2 mmol of isophorone diisocyanate and 10 mg of dibutyltin dilaurate, and react at 60 °C for 1.5 h under N2 protection to obtain isocyanate-terminated bio-based prepolymer;

[0021] (2) Dissolve 0.5 mmol diethyltoluene diamine and 0.5 mmol isophthalohydrazide in 5 mL NN-dimethylacetamide, and add them dropwise to the bio-based prepolymer prepared in (1) above and continue the chain extension reaction for 12 h. Dry to obtain bio-based polyurethane hot melt adhesive.

[0022] (3) The bio-based hot melt adhesive prepared in (2) above has a tensile shear strength of 0.5 MPa on stainless steel substrate, and the bonding interface can be separated after heating at 100 °C for 10 minutes.

[0023] Example 2

[0024] The specific preparation method is as follows: (1) 2 mmol of bio-based polyol PO3G, 4 mmol of isophorone diisocyanate and 12 mg of dibutyltin dilaurate are mixed and reacted at 70 °C for 2 h under N2 protection to obtain isocyanate-terminated bio-based prepolymer;

[0025] (2) Dissolve 1 mmol diethyltoluenediamine and 1 mmol isophthalohydrazide in 10 mL NN-dimethylacetamide, and add them dropwise to the bio-based prepolymer prepared in (1) above and continue the chain extension reaction for 18 h. Dry to obtain bio-based polyurethane hot melt adhesive.

[0026] (3) The bio-based hot melt adhesive prepared in (2) above has a tensile shear strength of 0.48 MPa on stainless steel substrate, and the bonding interface can be separated after heating at 100 °C for 10 minutes.

[0027] Example 3

[0028] The specific preparation method is as follows: (1) Mix 3 mmol of bio-based polyol PO3G, 6 mmol of isophorone diisocyanate and 15 mg of dibutyltin dilaurate, and react at 75 °C for 1 h under N2 protection to obtain isocyanate-terminated bio-based prepolymer.

[0029] (2) Dissolve 1.5 mmol diethyltoluene diamine and 1.5 mmol isophthalohydrazide in 15 mL NN-dimethylacetamide, and add them dropwise to the bio-based prepolymer prepared in (1) above and continue the chain extension reaction for 24 h. Dry to obtain bio-based polyurethane hot melt adhesive.

[0030] (3) The bio-based hot melt adhesive prepared in (2) above has a tensile shear strength of 0.45 MPa on stainless steel substrate, and the bonding interface can be separated after heating at 100 °C for 10 minutes.

Claims

1. A method for preparing a bio-based reversible crosslinked polyurethane hot melt adhesive, characterized in that, Includes the following steps: ① Mix 1-3 mmol of bio-based polyol PO3G (polytrimethylene ether glycol), 2-6 mmol of isophorone diisocyanate, and 10-15 mg of dibutyltin dilaurate, and react under N2 protection at 60-75 °C for 1-2 h to obtain an isocyanate-terminated bio-based prepolymer; ② Dissolve 0.5-1.5 mmol of chain extender monomer diethyltoluene diamine and 0.5-1.5 mmol of hydrazide monomer isophthalohydrazide in 5-15 mL of NN-dimethylacetamide, and add dropwise to the bio-based prepolymer prepared in ① above, and continue the chain extension reaction for 12-24 h, and dry to obtain a bio-based polyurethane hot melt adhesive; the number average molecular weight of the above bio-based polyol PO3G is 1000 or 2000 g / mol; the molar ratio of PO3G, isophorone diisocyanate, diethyltoluene diamine, and isophthalohydrazide is 2:4:1:

1.

2. The application of a bio-based reversible crosslinked polyurethane hot melt adhesive obtained by the preparation method of claim 1 as a hot melt sealant in the field of electronic devices, characterized in that, The hot melt adhesive has a tensile shear strength of 0.45-0.5 MPa on a stainless steel substrate, and the bonding interface can be separated by heating at 100 °C for 10 minutes.

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