Reversible cross-linking thermoplastic polyurethane elastomer and preparation method thereof

Abstract

The invention discloses a reversible cross-linking thermoplastic polyurethane elastomer and a preparation method thereof. The reversible cross-linking thermoplastic polyurethane elastomer comprises afuran-containing thermoplastic polyurethane (TPU) component (A) and a bismaleimide component (B); the furan-containing TPU component (A) is prepared from the following raw materials by weight: 25-46 parts by weight of an isocyanate (a1), 32-67 parts by weight of a polymer polyol (a2), 3.5-13 parts by weight of a small molecular dihydric alcohol (a3) and 0.3-4.5 parts by weight of furan (a4) containing two reactive groups for isocyanate radicals; and the bismaleimide component (B) is a mixture of a bismaleimide-containing compound (b1) and TPU (b2). According to the invention, through a reversible Diels-Alder reaction of functional components, the cross-linking effect among molecular chains is increased, the thermoplastic property of TPU is ensured, and the TPU is endowed with an excellentself-repairing ability.

Description

technical field [0001] The invention relates to a thermoplastic polyurethane elastomer and a preparation method thereof, and relates to a thermoplastic polyurethane material with a reversible crosslinking structure. Background technique [0002] The main difference between thermoplastic resin materials and thermosetting resin materials is that most linear polymers of thermoplastic resin materials can flow and deform after heating, and can maintain a certain shape after cooling; thermosetting resin materials have a network cross-linked structure. It cannot be plasticized again, but due to the chemical crosslinking of thermosetting resins, it also has the characteristics of high temperature resistance, high rigidity, and good dimensional stability of products, which are not available in conventional thermoplastic resin materials. In addition, thermoplastic polyurethane elastomer (TPU), as a kind of block linear polymer, has hydrogen bond crosslinking between linear molecules o...

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Problems solved by technology

For example, patent CN201310006811.8 provides a reversible covalently cross-linked thermoplastic polyurethane, which uses a small molecule diol chain extender containing maleimide side groups (dienophiles) to react with isocyanates and long-chain polyols Obtain a prepolymer, then add a cross-linking agent containing at least two furan groups (dienes) to obtain a reversibly cross-linked TPU, however, the reversible chain extender in this patent scheme needs to be prepared in the presence of a large amount of organic solvents , the solvent is difficult to recover later, it is only suitable for a small amount of research in the laboratory, and it is difficult for large-scale industrial production; patent CN201710046449.5 discloses a polyurethane that can be used for 3D printing. Polymerization of diisocyanate and dendritic polymer of imide, but the direct addition of crosslinking agent maleimide-terminated diisocyanate composition in the process of polyurethane synthesis in this patent will cause the molecular weight growth of the reaction system to be limited, and eventually It affects the comprehensive performance and application of materials; similarly, patents CN201710032884.2 and CN201710032790.5 use maleimide-containing polyols, diisocyanates, triisocyanate compositions containing furan groups at the end groups or The 3D printing polyurethane material prepared by trimaleimide-terminated triisocyanate composition and dendritic polymer, due to the existence of maleimide-terminated triisocyanate composition in the polymerization process, is also easy to cause the linearity of the material. The growth of the chain structure is limited, resulting in insufficient elasticity of the material, and at the same time, the structure of the triisocyanate composition leads to an excessively high density of intermolecular cross-linking points, making the material brittle

[0004] Existing research on the reversible crosslinking of polyurethane and thermoplastic polyurethane materials mainly focuses on the modification of macromolecular polyols, chain extenders or isocyanates with dienophiles or dienes and then one-step polymerization reaction. The above-mentioned one-step preparation of reversibly cross-linked TPU will limit the growth of the chain molecular structure of TPU. In addition, it will affect the linear chain structure of TPU, and cause the final material to be significantly less elastic or even brittle. It is difficult to achieve the repeated processing and molding of thermoplastic polyurethane. Requirements, while the temperature resistance of the material is insufficient and ultimately affects its processing and application

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