Preparation method of carbodiimide cross-linking agent

Abstract

The invention relates to a preparation method of a carbodiimide cross-linking agent. The preparation method comprises the following steps: under the protection of nitrogen, putting diisocyanate into a 500mL four-mouth flask, and stirring; the temperature is raised to 180-230 DEG C, an initiator and a catalyst are added, the initiator is triisopropyl phosphite, the catalyst is triphenyl bismuth, and the content of isocyanate is measured after reaction; and when the content of the isocyanate is reduced to be less than 10%, cooling, and discharging while hot to obtain a polycondensation product polycarbodiimide. Compared with the prior art, the preparation method has the advantages that diisocyanate is taken as a reaction raw material, the specific initiator and the catalyst are added, so that the reaction can be carried out more quickly, the polymerization effect is better, the synthesis operation is simple, and the obtained product has the characteristics of low toxicity, water solubility, quick age hardening, enough retention time and the like; the polycarbodiimide provides an effective way for the development of a high-performance water-soluble coating agent.

Description

Technical Field

[0001] The invention relates to the technical field of polymer material synthesis, and in particular to a method for preparing a carbodiimide cross-linking agent. Background Art

[0002] Polycarbodiimide crosslinker is a crosslinker that has developed rapidly in recent years. It can be used for room temperature crosslinking in leather finishing agents. It mainly reacts with the carboxylic acid groups in the finishing agent. Since it can self-emulsify in water, it can be used for crosslinking of water-dispersible coatings. The crosslinked coatings have good solvent resistance, water resistance and antifouling properties, excellent wear resistance and light resistance, and high hardness.

[0003] At present, there are few studies on the synthesis of this crosslinking agent in China, and the research trend abroad has shifted to water-based polycarbodiimide crosslinking agents. Water-based cationic polycarbodiimide crosslinking agents have been synthesized, but due to the high selectivity and limitations of the carbodiimide group reaction, its application range is limited. At present, most leather finishing agents are anionic or non-ionic, and anionic and non-ionic polycarbodiimide crosslinking agent products have a wider range of applications, but the synthesis operation of anionic and non-ionic polycarbodiimide crosslinking agent products is currently more complicated and the reaction is slower. Therefore, it is necessary to study the preparation method of this type of carbodiimide crosslinking agent. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing a carbodiimide crosslinking agent, which can solve the problems in the prior art that the application scope of aqueous cationic polycarbodiimide crosslinking agents is limited, the synthesis operation of anionic and nonionic polycarbodiimide crosslinking agents is complicated, and the reaction is slow.

[0005] In order to solve the above technical problems, the technical solution of the present invention is: comprising the following steps: S1. Under nitrogen protection, diisocyanate was placed in a 500 mL four-necked flask and stirred; S2, heating to 180-230°C, adding initiator and catalyst, the initiator is triisopropyl phosphite, the catalyst is triphenyl bismuth, and after the reaction, the isocyanate content is measured. The synthesis process is: , wherein the R group can represent any organic functional group; S3. When the isocyanate content drops below 10%, the temperature is lowered and the material is discharged while hot to obtain the polycondensation product polycarbodiimide.

[0006] Furthermore, the R group is tetramethylcyclohexane or hexamethylene; and the diisocyanate is hexamethylene diisocyanate or tetramethylcyclohexane diisocyanate.

[0007] Furthermore, the mass ratio of the diisocyanate to the initiator and the catalyst is 100:1:0.5.

[0008] Furthermore, in step S2, the reaction is carried out for 3 to 5 hours.

[0009] Furthermore, in step S3, the temperature is lowered to 50-60°C.

[0010] The advantages of the present invention are as follows: the present invention uses diisocyanate as a reaction raw material, and by adding a specific initiator and a catalyst, it is conducive to faster reaction, faster reaction, better polymerization effect, simple synthesis operation, and the obtained product has the characteristics of low toxicity, water solubility, rapid aging hardening, sufficient retention time, etc., so that polycarbodiimide provides an effective way to develop high-performance water-soluble finishing agents. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 The infrared spectrum of the polycondensation product polycarbodiimide of the present invention is shown in FIG. DETAILED DESCRIPTION

[0012] In order to make the purpose, technical solution and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. The following embodiments can enable technicians in this field to understand the present invention more comprehensively, but the present invention is not limited to the scope of the embodiments.

[0013] This specific implementation adopts the following technical solution: comprising the following steps: S1. Under nitrogen protection, diisocyanate was placed in a 500 mL four-necked flask and stirred; S2, heating to 180-230°C, adding initiator and catalyst, the initiator is triisopropyl phosphite, the catalyst is triphenyl bismuth, and the isocyanate content is measured after reacting for 3-5 hours, the mass ratio of diisocyanate to initiator and catalyst is 100:1:0.5; The synthesis process is: , wherein the R group can represent any organic functional group, preferably, the R group is tetramethylcyclohexane or hexamethylene; the diisocyanate is hexamethylene diisocyanate or tetramethylcyclohexane diisocyanate; S3. When the isocyanate content drops below 10%, the temperature is lowered to 50-60°C and the material is discharged while hot to obtain the polycondensation product polycarbodiimide.

[0014] Under nitrogen protection, 100g of hexamethylene diisocyanate was placed in a 500mL four-necked flask and stirred, the temperature was raised to 180-230°C, 1g of initiator and 0.5g of catalyst were added, the initiator was triisopropyl phosphite, and the catalyst was triphenyl bismuth, and the isocyanate content was measured after reacting for 3-5 hours; when the isocyanate content dropped below 10%, the temperature was lowered to 50-60°C, and the material was discharged while hot to obtain a condensation product, polycarbodiimide, with a solid content of 99.0%, a viscosity of 238cp (25°C), and a pH of about 9.8.

[0015] Under nitrogen protection, 100g of tetramethylcyclohexane diisocyanate was placed in a 500mL four-necked flask and stirred, the temperature was raised to 180-230°C, 1g of initiator and 0.5g of catalyst were added, the initiator was triisopropyl phosphite, and the catalyst was triphenylbismuth. The isocyanate content was measured after 3-5 hours of reaction; when the isocyanate content dropped below 10%, the temperature was lowered to 50-60°C, and the material was discharged while hot to obtain a condensation product, polycarbodiimide, with a solid content of 99.3%, a viscosity of 225cp (25°C), and a pH of about 10.2.

[0016] The infrared spectra of the polycarbodiimide obtained in Example 1 and Example 2 are as follows: Figure 1 shown.

[0017] It can be seen from Examples 1 and 2 that by using diisocyanate as a reaction raw material and adding a specific initiator triisopropyl phosphite and a catalyst triphenylbismuth, the reaction proceeds faster, the polymerization effect is better, and the synthesis operation is simple. The obtained product has the characteristics of low toxicity, water solubility, rapid aging hardening, sufficient retention time, etc.

[0018] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for preparing a carbodiimide crosslinking agent, characterized in that: The following steps are involved: S1. Under nitrogen protection, diisocyanate was placed in a 500 mL four-necked flask and stirred; S2, heating to 180-230°C, adding initiator and catalyst, the initiator is triisopropyl phosphite, the catalyst is triphenyl bismuth, and after the reaction, the isocyanate content is measured. The synthesis process is: , wherein the R group can represent any organic functional group; S3. When the isocyanate content drops below 10%, the temperature is lowered and the material is discharged while hot to obtain the polycondensation product polycarbodiimide.

2. The method for preparing a carbodiimide crosslinking agent according to claim 1, characterized in that: The R group is tetramethylcyclohexane or hexamethylene; the diisocyanate is hexamethylene diisocyanate or tetramethylcyclohexane diisocyanate.

3. The method for preparing a carbodiimide crosslinking agent according to claim 1, characterized in that: The mass ratio of the diisocyanate to the initiator and the catalyst is 100:1:0.

5.

4. The method for preparing a carbodiimide crosslinking agent according to claim 1, characterized in that: In the step S2, the reaction is carried out for 3 to 5 hours.

5. The method for preparing a carbodiimide crosslinking agent according to claim 1, characterized in that: In step S3, the temperature is lowered to 50-60°C.

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