Preparation method of high-solid-content aqueous polyurethane for leather

Abstract

The invention relates to the field of synthetic leather material polyurethane, in particular to a preparation method of high-solid-content aqueous polyurethane for leather. The method comprises the process steps of: prepolymerization reaction: reacting polyol, a hydrophilic chain extender and isocyanate monomer; monomer modification: adding polyhydroxy monomer to be modified together with polyurethane prepolymer; salt formation by neutralization: adding a neutralizing agent so that an emulsion forms salt ion groups; and chain extension subsequent to emulsification: dissolving an external emulsifying agent and a sulfonic acid chain extender in water to obtain a solution and adding the solution to the system for performing emulsification. In the invention, the emulsification property of theemulsion is improved by using carboxylic acid type and sulfonic acid type chain extenders, so that polyurethane and water are fully emulsified; simultaneously, due to the employment of the method in which self emulsification and external emulsification are combined, not only the stable emulsion can be synthesized, but also the solid content can be increased; in addition, the use of water as the solvent in emulsification is consistent with the requirement of clean production process; and the finally-synthesized emulsion has good film forming performance, high drying speed, no yellowing, excellent mechanical properties and short process flow, is suitable for the synthesis of leather substrates or surface materials, and can take the place of solvent-type products.

Description

technical field [0001] The invention relates to the field of synthetic leather material polyurethane, in particular to a method for preparing water-based polyurethane with high solid content for leather. Background technique [0002] At present, polyurethane is developing rapidly as a synthetic leather material. Synthetic leather is based on non-woven fabrics made of hollow-core fibers with a lotus-shaped cross-section structure. After a series of finishing treatments such as gravure printing and embossing, it is a synthetic material with a structure similar to natural leather. Most of the synthetic leather products currently on the market are solvent-based polyurethanes. This type of resin is mostly used as toluene, xylene, acetone, butanone (MEK), ethyl acetate, and dimethylformamide (DMF). main solvent. The harm caused by solvents to the human body is manifold. The cost of water-based polyurethane for leather is much lower than that of solvent-based, and it is environm...

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Problems solved by technology

[0003] Chinese patent CN101613455A introduces a production method of water-based polyurethane for high-solid leather by self-emulsification method: after synthesizing a prepolymer with polyethylene glycol butylene glycol adipate diol, polytetrahydrofuran diol and toluene diisocyanate as raw materials , adding a blocking agent before the chain extension of the small molecule diamine, so that the molecular weight is reduced, but the viscosity of the emulsion is still 5000mPa . S / 25℃, the coating performance is poor, and toluene diisocyanate has poor oxidation resistance, and it will turn yellow after being coated on synthetic leather, which will affect the appearance

[0004] Chinese patent CN101328253A adopts the self-emulsification method, adding polyol, isocyanate and chain extender to the synthetic prepolymer at one time, adding sulfonic acid chain extender after cooling down, and then adding water to emulsify and disperse to obtain an emulsion with a solid content of about 50%, which can be used Suitable for leather, but the mechanical properties (tensile strength, elongation at break and modulus, etc.) of the emulsion are poor after film formation, so it is not suitable for leather base or surface materials

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