Polyurethane curing agent and application thereof in preparation of elastomer

Abstract

The invention relates to the field of polyurethane curing agents and polyurethane materials, in particular to a polyurethane curing agent and application thereof in preparation of an elastomer, and solves the problems that peroxide free radicals are accumulated in the polyurethane elastomer, so that the polyurethane elastomer is aged, colored groups are generated under the influence of ultraviolet rays, the color of the elastomer is deepened and discolored and the like. According to the specific scheme, the method comprises the following steps: reacting 2, 6-di-tert-butyl phenol with dimethyl sulfate to obtain 2, 6-di-tert-butyl anisole; 2, 6-di-tert-butyl anisole is subjected to a para-acylation reaction, and a para-acyl compound is generated; carrying out esterification reaction on the basic polyhydroxy curing agent and a para-acyl compound to generate an antioxidant curing agent; the basic polyhydroxy curing agent is one of triethanolamine, trimethylolpropane or pentaerythritol, the polyurethane prepared by the method is not influenced by the dispersing type antioxidant, and the anti-aging capability and the physical and mechanical properties of the elastomer are strong.

Description

Technical Field

[0001] The invention relates to the technical field of polyurethane curing agent and polyurethane material, and in particular to a polyurethane curing agent and application thereof in preparing elastomer. Background Art

[0002] The raw materials for the preparation of polyurethane elastomers are composed of isocyanate, polyol and curing agent. According to the synthesis method, it can be divided into a one-step method, a prepolymer method and a semi-prepolymer method. The mainstream method mostly uses the second prepolymer method. First, diisocyanate and diol are reacted to prepare a linear polyurethane prepolymer with a blocked structure. The blocked structure includes isocyanate blocking and hydroxyl blocking, which is mainly related to the excessive use of diisocyanate or diol. Then, the corresponding small molecule diamine, diol or trimer and other curing agents are used to diffuse and cross-link the blocked prepolymer to finally obtain a polyurethane elastomer, among which isocyanate blocking and the corresponding diamine type curing agent are the most common. The symmetrical short chain structure gives the polyurethane a regular structure, and forms a hard segment in the polyurethane elastomer with the isocyanate blocking, thereby improving the mechanical properties of the polyurethane. The polyurethane elastomer prepared by this method has the best performance, and no large amount of reaction heat is generated. The reaction process is relatively controllable, but the water content in the raw materials is extremely high and the preparation environment is relatively harsh.

[0003] Polyurethane has different characteristics and effects according to the different chemical structures of each component. According to the chemical structure of polyols, there are two major categories: polyester polyols and polyether polyols. Correspondingly, different polyurethanes have different tolerance properties and chemical media. The intermolecular chemical bonds of polyester polyurethane elastomers are very polar, and they have strong tolerance to oil products, but they are not very tolerant to water and are easily affected by water. Water molecules penetrate into polyurethane materials and cause the migration of additives, which leads to the reaction of water and isocyanate to generate unstable carbamic acid, which then decomposes into carbon dioxide. and amines; the presence of ether bonds in polyether polyurethane elastomers makes their water resistance much better than that of polyester polyurethane elastomers, but the carbon atom of the ether bond of polyether polyurethane will excite a hydrogen atom under high temperature environment to form secondary carbon free radicals, and then form peroxide free radicals, thereby accelerating aging, and decomposing some polyurethane molecules under ultraviolet rays to form colored groups, causing the color of the polyurethane elastomer to darken. The usual external antioxidant acts as a dispersed phase in the polyurethane elastomer to play an anti-maintenance role, but its antioxidant ability is related to the dispersion effect and is difficult to control. Summary of the invention

[0004] In order to solve the problems that polyurethane elastomers are easily affected by thermal oxygen environments after meeting the requirements of water resistance, the accumulation of generated peroxide radicals leads to aging of the polyurethane elastomer, the polyurethane elastomer generates colored groups under the influence of ultraviolet rays, the color of the elastomer deepens and changes color, and the dispersion effect is difficult to control, the present invention provides a polyurethane curing agent, and applies it to the preparation of elastomers.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] The polyurethane curing agent comprises the following preparation steps:

[0007] S1, reacting 2,6-di-tert-butylphenol with dimethyl sulfate to obtain 2,6-di-tert-butylanisole;

[0008] S2, performing a para-acylation reaction on 2,6-di-tert-butylanisole to generate a para-acyl compound;

[0009] S3, esterifying the basic polyhydroxy curing agent with the para-acyl compound to generate an antioxidant curing agent;

[0010] The basic polyhydroxy curing agent is one of triethanolamine, trimethylolpropane or pentaerythritol.

[0011] The present application first introduces an acyl group at the para position of 2,6-di-tert-butylphenol to make it easy to undergo an esterification reaction with a curing agent having multiple hydroxyl groups. During the acylation process, since the hydroxyl groups on the phenol have high activity, dimethyl sulfate is used to perform an oxygen-methylation addition on the phenol to protect it, thereby retaining the hindered phenol structure and function of 2,6-di-tert-butylphenol. After the subsequent acylation reaction is completed, the acyl group undergoes an esterification reaction with the hydroxyl groups in the basic polyhydroxy curing agent, and the reaction ratio is controlled to achieve the connection of one acyl group to a basic polyhydroxy curing agent, thereby obtaining a hindered phenol structure in the curing agent, thereby forming an antioxidant curing agent with two or more -OH structures.

[0012] After the acylation reaction, the oxygen methylation between the 2,6-di-tert-butyl groups will be removed, and the hydroxyl groups therebetween will be spatially hindered by the side chains. It has a unique spatial structure and can prevent and trigger the reaction by capturing peroxyl radicals, thereby terminating the chain reaction of free radicals and preventing the polyurethane from being oxidized and discolored in a high temperature and high oxygen environment.

[0013] Furthermore, the mass ratio of the basic polyhydroxy curing agent to the para-acyl compound is 1:1-1.2, the reagent solution of the esterification reaction is N,N-dimethylacetamide, the mass ratio of N,N-dimethylacetamide to the para-acyl compound is 4:1, the temperature of the esterification reaction is 90°C, and the reaction time is 2.5h.

[0014] According to the examples, the best reaction ratio is 1:3-4. This is because a single polyhydroxy curing agent has 3-4 -OH groups. In order to retain the cross-linking effect of the curing agent, the hindered phenol structure is connected only on one of the -OH groups.

[0015] Further, the steps of the acylation reaction are as follows:

[0016] A1. Formation of para-carboxyl group: 2,6-di-tert-butylanisole and a methanol solution of sodium methoxide were mixed at a reaction temperature of 55-65° C., vacuum distilled until no fraction flowed out, and then DMF was added. The amount of DMF was 2-3 times that of 2,6-di-tert-butylanisole. The solvent was continuously vacuum distilled out and the temperature was lowered. Carbon dioxide was introduced into the remaining material and the pressure was increased to 0.5-1.0 MPa. The temperature was raised to 100-110° C. and the reaction time was 24 h to obtain a crude para-carboxyl compound.

[0017] Then, the above materials are dissolved and layered using sulfuric acid and toluene, and then heated for dehydration, cooled and filtered to obtain a para-carboxyl compound;

[0018] A2. Mix the para-carboxyl compound with an acyl chloride reagent to react to obtain a para-acyl chloride compound, mix the para-acyl compound with dichloromethane in a mixing ratio of 100 g:1 L, cool to below zero, mix boron tribromide with dichloromethane in a mixing ratio of 100 g:1 L, add the dichloromethane solution of boron tribromide dropwise to the dichloromethane solution of the para-acyl compound for 2 hours, stir at room temperature for 5 hours, add distilled water for extraction, and obtain a pure para-acyl compound after drying with a desiccant and vacuum drying.

[0019] The present application adopts the synthesis method of Körber-Schmidt reaction to introduce a carboxyl group at the para position of 2,6-di-tert-butylanisole. The method has high conversion efficiency and high product purity. The carboxyl group is introduced by carboxylation reaction under a pressurized environment, and then an acyl chloride reagent is used to react the halogen atom with the hydroxyl group on the carboxyl group to form an acyl halide group. The acyl halide group undergoes an esterification reaction with the hydroxyl group on the hydroxymethyl group in an environment where DMAP and triethylamine are present, thereby connecting the hindered phenol structure and the solidified long chain, and finally obtaining an antioxidant and scale inhibitor.

[0020] Furthermore, the reaction ratio of 2,6-di-tert-butylanisole to sodium methoxide is 1.0:1.1-1.3eq.

[0021] Furthermore, the acyl chloride reagent is one of phosphorus trichloride, phosphorus pentachloride or thionyl chloride, and the mixing ratio of the acyl chloride reagent to the para-carboxyl compound is 1.05:1.00.

[0022] Furthermore, the molar ratio of the reaction between 2,6-di-tert-butylphenol and dimethyl sulfate is 1:1.5-3, the reaction solvent is dichloromethane or toluene, and after the reaction, extraction and stratification are performed, and the organic phase is evaporated to obtain 2,6-di-tert-butylanisole.

[0023] Furthermore, the reaction molar ratio of the boron tribromide to the para-acyl compound is 2-3:3.

[0024] The present application also provides a polyurethane elastomer, which comprises the following components:

[0025] Diol, toluene diisocyanate, antioxidant curing agent;

[0026] The preparation method of the elastomer comprises the following steps: mixing diol and toluene diisocyanate in a ratio of total -NCO to total -OH of 1.1-2:1, heating to 90°C for reaction for 2h, degassing to obtain a polyurethane prepolymer, heating and melting an antioxidant curing agent and adding the agent to the polyurethane prepolymer, wherein the mixing ratio of the antioxidant curing agent to the polyurethane prepolymer is 5-15:100 by weight, mixing evenly, molding, and performing secondary vulcanization to obtain the elastomer.

[0027] In the process of preparing the polyurethane elastomer, the amount of toluene diisocyanate and diol is strictly controlled to obtain a prepolymer with isocyanate end-capping groups, which is then cross-linked and cured with the curing agent having multiple -OH groups of the present application, thereby achieving the removal of peroxide free radicals at the molecular level.

[0028] Furthermore, the diol is one of polytetramethylene glycol, polyester 218 or polycarbonate glycol.

[0029] The polyurethane curing agent can also be used to prepare elastomers.

[0030] The beneficial effects of the present invention are:

[0031] The antioxidant curing agent of the present application adds a hindered phenol structure capable of removing peroxide free radicals to the molecular structure. Based on this, during the curing and cross-linking process of the polyurethane elastomer, each cross-linking node of the curing agent has the ability to remove peroxide free radicals. Therefore, compared with directly adding antioxidant substances to the polyurethane, the present application does not have the problem of poor dispersibility, will not have the problem of low physical and mechanical properties of the polyurethane elastomer due to uneven dispersion of the dispersed phase in the polyurethane, and will not destroy the uniform structure of the polyurethane during the cross-linking process. The polyurethane has extremely strong antioxidant and anti-color change capabilities. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the strength retention rate after aging of the embodiments of the present invention and the comparative example. DETAILED DESCRIPTION

[0033] The following will refer to the attached Figure 1 The embodiments of the present invention are described in detail. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0034] Preparation Example 1

[0035] A preparation method of a polyurethane curing agent specifically comprises the following steps:

[0036] S1, adding 2,6-di-tert-butylphenol and dimethyl sulfate to dichloromethane, reacting the two at a molar ratio of 1:2 for 1 hour, extracting and stratifying with a carbonate solution, and evaporating the organic phase solvent to obtain 2,6-di-tert-butylanisole;

[0037] S2, the 2,6-di-tert-butylanisole obtained in S1 is added to a methanol solution of sodium methoxide, the reaction ratio of 2,6-di-tert-butylanisole to sodium methoxide is 1.0:1.2eq, the reaction temperature is set to 60°C, vacuum distillation is performed until no fraction flows out, and then DMF is added to the remaining solution, the amount of DMF added is 2 times that of 2,6-di-tert-butylanisole, and the DMF solvent is continuously vacuum distilled out, the remaining solution is cooled to room temperature in an ice bath, and then carbon dioxide is introduced into the remaining solution and pressurized to 1.0 MPa, and then the temperature is raised to 105°C, and the reaction time is 24h to obtain a crude para-carboxyl compound, sulfuric acid and toluene solution are mixed in a weight ratio of 1:3, and the crude para-carboxyl compound is added to a mixed solution of sulfuric acid and toluene. After standing and stratification, the phase liquid containing the para-carboxyl compound is heated and dehydrated, and after anhydrous distillation, the temperature is lowered and filtered to obtain the para-carboxyl compound;

[0038] The para-carboxyl compound and phosphorus trichloride are mixed and reacted in a ratio of 1.00:1.05eq to obtain a para-acyl chloride compound, the para-acyl compound is mixed with dichloromethane in a mixing ratio of 100g:1L, and the temperature is lowered to below zero for standby use; boron tribromide is placed in dichloromethane in a mixing ratio of 100g:1L, and the dichloromethane solution of boron tribromide is gradually added dropwise to the dichloromethane solution of the para-acyl compound in a molar ratio of 2.5:3 within 2 hours, the temperature is raised to room temperature and stirred for 4 hours, distilled water is added to extract the para-acyl compound, a desiccant is used to absorb water and vacuum drying is performed to obtain a pure para-acyl compound.

[0039] S3. Place triethanolamine and a para-acyl compound in a ratio of 1:1 in N,N-dimethylacetamide for esterification reaction, the mass ratio of N,N-dimethylacetamide to the para-acyl compound is 4:1, the temperature of the esterification reaction is 90°C, the reaction time is 2.5h, and an antioxidant curing agent is generated.

[0040] Preparation Example 2

[0041] A preparation method of a polyurethane curing agent specifically comprises the following steps:

[0042] S1, adding 2,6-di-tert-butylphenol and dimethyl sulfate to dichloromethane or toluene, reacting the two at a molar ratio of 1:1.5 for 1 hour, extracting and stratifying with a carbonate solution, and evaporating the organic phase solvent to obtain 2,6-di-tert-butylanisole;

[0043] S2, the 2,6-di-tert-butylanisole obtained in S1 is added to a methanol solution of sodium methoxide, the reaction ratio of 2,6-di-tert-butylanisole to sodium methoxide is 1.0:1.1eq, the reaction temperature is set to 55°C, vacuum distillation is performed until no fraction flows out, and then DMF is added to the remaining solution, the amount of DMF added is 3 times that of 2,6-di-tert-butylanisole, and the DMF solvent is continuously vacuum distilled out, the remaining solution is cooled to room temperature in an ice bath, and then carbon dioxide is introduced into the remaining solution and pressurized to 0.5MPa, and then the temperature is raised to 100°C, and the reaction time is 24h to obtain a crude para-carboxyl compound, sulfuric acid and toluene solution are mixed in a weight ratio of 1:3, and the crude para-carboxyl compound is added to a mixed solution of sulfuric acid and toluene. After standing and stratification, the phase liquid containing the para-carboxyl compound is heated and dehydrated, and after anhydrous distillation, the temperature is lowered and filtered to obtain the para-carboxyl compound;

[0044] A para-carboxyl compound and phosphorus pentachloride are mixed and reacted in a ratio of 1.00:1.05eq to obtain a para-acyl chloride compound, and the para-acyl compound is mixed with dichloromethane in a mixing ratio of 100g:1L, and the temperature is lowered to below zero for standby use; boron tribromide is placed in dichloromethane in a mixing ratio of 100g:1L, and the dichloromethane solution of boron tribromide is gradually added dropwise to the dichloromethane solution of the para-acyl compound in a molar ratio of 2:3 within 2 hours, the temperature is raised to room temperature and stirred for 4 hours, distilled water is added to extract the para-acyl compound, a desiccant is used to absorb water and vacuum drying is performed to obtain a pure para-acyl compound.

[0045] S3. Place trimethylolpropane and a para-acyl compound in a ratio of 1:1.1 in N,N-dimethylacetamide for esterification reaction, the mass ratio of N,N-dimethylacetamide to the para-acyl compound is 4:1, the temperature of the esterification reaction is 90°C, the reaction time is 2.5h, and an antioxidant curing agent is generated.

[0046] Preparation Example 3

[0047] A preparation method of a polyurethane curing agent specifically comprises the following steps:

[0048] S1, adding 2,6-di-tert-butylphenol and dimethyl sulfate to dichloromethane or toluene, reacting the two at a molar ratio of 1:3 for 1 hour, extracting and stratifying with a carbonate solution, and evaporating the organic phase solvent to obtain 2,6-di-tert-butylanisole;

[0049] S2, the 2,6-di-tert-butylanisole obtained in S1 is added to a methanol solution of sodium methoxide, the reaction ratio of 2,6-di-tert-butylanisole to sodium methoxide is 1.0:1.3eq, the reaction temperature is set to 65°C, vacuum distillation is performed until no fraction flows out, and then DMF is added to the remaining solution, the amount of DMF added is 3 times that of 2,6-di-tert-butylanisole, and the DMF solvent is continuously vacuum distilled out, the remaining solution is cooled to room temperature in an ice bath, and then carbon dioxide is introduced into the remaining solution and pressurized to 1.0 MPa, and then the temperature is raised to 110°C, and the reaction time is 24h to obtain a crude para-carboxyl compound, sulfuric acid and toluene solution are mixed in a weight ratio of 1:3, and the crude para-carboxyl compound is added to a mixed solution of sulfuric acid and toluene. After standing and stratification, the phase liquid containing the para-carboxyl compound is heated and dehydrated, and after anhydrous distillation, the temperature is lowered and filtered to obtain the para-carboxyl compound;

[0050] The para-carboxyl compound and thionyl chloride are mixed and reacted in a ratio of 1.00:1.05eq to obtain a para-acyl chloride compound, the para-acyl compound is mixed with dichloromethane in a mixing ratio of 100g:1L, and the temperature is lowered to below zero for standby use; boron tribromide is placed in dichloromethane in a mixing ratio of 100g:1L, and the dichloromethane solution of boron tribromide is gradually added dropwise to the dichloromethane solution of the para-acyl compound in a molar ratio of 3:3 within 2 hours, the temperature is raised to room temperature and stirred for 4 hours, distilled water is added to extract the para-acyl compound, a desiccant is used to absorb water and vacuum drying is performed to obtain a pure para-acyl compound.

[0051] S3. Place pentaerythritol and a para-acyl compound in a ratio of 1:1.2 in N,N-dimethylacetamide for esterification reaction, the mass ratio of N,N-dimethylacetamide to the para-acyl compound is 4:1, the temperature of the esterification reaction is 90°C, the reaction time is 2.5h, and an antioxidant curing agent is generated.

[0052] Comparative Preparation Example 1

[0053] The difference between this comparative example and Preparation Example 1 is that the amount of the para-acyl compound used in step S3 is changed, and the specific changes are as follows:

[0054] S3. Place triethanolamine and a para-acyl compound in a ratio of 1:3 in N,N-dimethylacetamide for esterification reaction, the mass ratio of N,N-dimethylacetamide to the para-acyl compound is 4:1, the temperature of the esterification reaction is 90°C, the reaction time is 2.5h, and an antioxidant curing agent is generated.

[0055] Comparative Preparation Example 2

[0056] The difference between this comparative example and Preparation Example 1 is that the amount of the para-acyl compound used in step S3 is changed, and the specific changes are as follows:

[0057] S3. Place triethanolamine and a para-acyl compound in a ratio of 1:0.5 in N,N-dimethylacetamide for esterification reaction, the mass ratio of N,N-dimethylacetamide to the para-acyl compound is 4:1, the temperature of the esterification reaction is 90° C., the reaction time is 2.5 h, and an antioxidant curing agent is generated.

[0058] Comparative Preparation Example 3

[0059] The difference between this comparative preparation example and preparation example 1 is that 2,6-di-tert-butylphenol is not reacted with dimethyl sulfate, and the specific changes are as follows:

[0060] S1. Add 2,6-di-tert-butylphenol to a methanol solution of sodium methoxide, the reaction ratio of 2,6-di-tert-butylphenol to sodium methoxide is 1.0:1.2eq, the reaction temperature is set to 60°C, vacuum distillation is performed until no fraction flows out, and then DMF is added to the remaining solution, the amount of DMF added is 2 times that of 2,6-di-tert-butylphenol, and the DMF solvent is continuously vacuum distilled out, the remaining solution is cooled to room temperature in an ice bath, and then carbon dioxide is introduced into the remaining solution and pressurized to 1.0MPa, and then the temperature is raised to 110°C, and the reaction time is 24h to obtain a crude para-carboxyl compound, sulfuric acid and toluene solution are mixed in a weight ratio of 1:3, and the crude para-carboxyl compound is added to a mixed solution of sulfuric acid and toluene. After standing and stratification, the phase liquid containing the para-carboxyl compound is heated and dehydrated, and after anhydrous distillation, the temperature is lowered and filtered to obtain the para-carboxyl compound;

[0061] The para-carboxyl compound and phosphorus trichloride are mixed and reacted in a ratio of 1.00:1.05eq to obtain a para-acyl chloride compound, the para-acyl compound is mixed with dichloromethane in a mixing ratio of 100g:1L, and the temperature is lowered to below zero for standby use; boron tribromide is placed in dichloromethane in a mixing ratio of 100g:1L, and the dichloromethane solution of boron tribromide is gradually added dropwise to the dichloromethane solution of the para-acyl compound in a molar ratio of 2:3 within 2 hours, the temperature is raised to room temperature and stirred for 4 hours, distilled water is added to extract the para-acyl compound, a desiccant is used to absorb water and vacuum drying is performed to obtain a pure para-acyl compound.

[0062] S3. Place triethanolamine and a para-acyl compound in a ratio of 1:1 in N,N-dimethylacetamide for esterification reaction, the mass ratio of N,N-dimethylacetamide to the para-acyl compound is 4:1, the temperature of the esterification reaction is 90°C, the reaction time is 2.5h, and an antioxidant curing agent is generated.

[0063] Comparative Preparation Example 4

[0064] The difference between this comparative example and Preparation Example 1 is that in the acylation reaction, the reaction of boron tribromide is not carried out. The specific differences are as follows:

[0065] S1, adding 2,6-di-tert-butylphenol and dimethyl sulfate to dichloromethane or toluene, reacting the two at a molar ratio of 1:2 for 1 hour, extracting and stratifying with a carbonate solution, and evaporating the organic phase solvent to obtain 2,6-di-tert-butylanisole;

[0066] S2, the 2,6-di-tert-butylanisole obtained in S1 is added to a methanol solution of sodium methoxide, the reaction ratio of 2,6-di-tert-butylanisole to sodium methoxide is 1.0:1.2eq, the reaction temperature is set to 60°C, vacuum distillation is performed until no fraction flows out, and DMF is added to the remaining solution, the amount of DMF added is 2 times that of 2,6-di-tert-butylanisole, and the DMF solvent is continuously vacuum distilled out, the remaining solution is cooled to room temperature in an ice bath, and then carbon dioxide is introduced into the remaining solution and pressurized to 1.0 MPa, and then the temperature is raised to 110°C, and the reaction time is 24h to obtain a crude para-carboxyl compound, sulfuric acid and toluene solution are mixed in a weight ratio of 1:3, and the crude para-carboxyl compound is added to a mixed solution of sulfuric acid and toluene. After standing and stratification, the phase liquid containing the para-carboxyl compound is heated and dehydrated, and after anhydrous distillation, the temperature is lowered and filtered to obtain the para-carboxyl compound;

[0067] The para-carboxyl compound and phosphorus trichloride are mixed and reacted in a ratio of 1.00:1.05eq to obtain a para-acyl chloride compound, which is added to a toluene solution and stirred, and then distilled water is added for extraction. A desiccant is used to absorb water and vacuum drying is performed to obtain a pure para-acyl compound.

[0068] S3. Place triethanolamine and a para-acyl compound in a ratio of 1:1 in N,N-dimethylacetamide for esterification reaction, the mass ratio of N,N-dimethylacetamide to the para-acyl compound is 4:1, the temperature of the esterification reaction is 90°C, the reaction time is 2.5h, and an antioxidant curing agent is generated.

[0069] Example 1

[0070] This embodiment provides an elastomer using the polyurethane curing agent of the present application, wherein the antioxidant curing agent uses the antioxidant curing agent in Preparation Example 1, and the specific preparation method is as follows:

[0071] Polytetrahydrofuran ether diol and toluene diisocyanate are mixed in a ratio of total -NCO to total -OH of 1.6:1, the temperature is raised to 90°C for reaction for 2 hours, and a polyurethane prepolymer is obtained by degassing. Then, an antioxidant curing agent is heated and melted and added to the polyurethane prepolymer. The mixing ratio of the antioxidant curing agent to the polyurethane prepolymer is 10:100 by weight. The mixture is evenly mixed and molded, and a polyurethane elastomer is obtained by secondary vulcanization.

[0072] Example 2

[0073] This embodiment provides an elastomer using the polyurethane curing agent of the present application, wherein the antioxidant curing agent uses the antioxidant curing agent in Preparation Example 2, and the specific preparation method is as follows:

[0074] Polyester 218 and toluene diisocyanate are mixed in a ratio of total -NCO to total -OH of 2:1, the temperature is raised to 90°C for reaction for 2 hours, and a polyurethane prepolymer is obtained by degassing. The antioxidant curing agent is melted and added to the polyurethane prepolymer at a weight ratio of 15:100. The mixture is evenly mixed and molded, and a polyurethane elastomer is obtained by secondary vulcanization.

[0075] Example 3

[0076] This embodiment provides an elastomer using the polyurethane curing agent of the present application, wherein the antioxidant curing agent uses the antioxidant curing agent in Preparation Example 3, and the specific preparation method is as follows:

[0077] Polycarbonate diol and toluene diisocyanate are mixed in a ratio of total -NCO to total -OH of 1.1:1, the temperature is raised to 90°C for reaction for 2 hours, and a polyurethane prepolymer is obtained by degassing. An antioxidant curing agent is melted and added to the polyurethane prepolymer at a mixing ratio of 5:100 by weight. The mixture is evenly mixed and molded, and a polyurethane elastomer is obtained by secondary vulcanization.

[0078] Comparative Example 1

[0079] The difference between this comparative example and Example 1 is that the antioxidant curing agent in Comparative Preparation Example 1 is used, and the specific preparation method is as follows:

[0080] Polytetrahydrofuran ether diol and toluene diisocyanate are mixed in a ratio of total -NCO to total -OH of 1.6:1, the temperature is raised to 90°C for reaction for 2 hours, and a polyurethane prepolymer is obtained by degassing. Then, an antioxidant curing agent is heated and melted and added to the polyurethane prepolymer. The mixing ratio of the antioxidant curing agent to the polyurethane prepolymer is 10:100 by weight. The mixture is evenly mixed and molded, and a polyurethane elastomer is obtained by secondary vulcanization.

[0081] Comparative Example 2

[0082] The difference between this comparative example and Example 1 is that the antioxidant curing agent in Comparative Preparation Example 2 is used, and the specific preparation method is as follows:

[0083] Polytetrahydrofuran ether diol and toluene diisocyanate are mixed in a ratio of total -NCO to total -OH of 1.6:1, the temperature is raised to 90°C for reaction for 2 hours, and a polyurethane prepolymer is obtained by degassing. Then, an antioxidant curing agent is heated and melted and added to the polyurethane prepolymer. The mixing ratio of the antioxidant curing agent to the polyurethane prepolymer is 10:100 by weight. The mixture is evenly mixed and molded, and a polyurethane elastomer is obtained by secondary vulcanization.

[0084] Comparative Example 3

[0085] The difference between this comparative example and Example 1 is that the antioxidant curing agent in Comparative Preparation Example 3 is used, and the specific preparation method is as follows:

[0086] Polytetrahydrofuran ether diol and toluene diisocyanate are mixed in a ratio of total -NCO to total -OH of 1.6:1, the temperature is raised to 90°C for reaction for 2 hours, and a polyurethane prepolymer is obtained by degassing. Then, an antioxidant curing agent is heated and melted and added to the polyurethane prepolymer. The mixing ratio of the antioxidant curing agent to the polyurethane prepolymer is 10:100 by weight. The mixture is evenly mixed and molded, and a polyurethane elastomer is obtained by secondary vulcanization.

[0087] Comparative Example 4

[0088] The difference between this comparative example and Example 1 is that the antioxidant curing agent in Comparative Preparation Example 4 is used, and the specific preparation method is as follows:

[0089] Polytetrahydrofuran ether diol and toluene diisocyanate are mixed in a ratio of total -NCO to total -OH of 1.6:1, the temperature is raised to 90°C for reaction for 2 hours, and a polyurethane prepolymer is obtained by degassing. Then, an antioxidant curing agent is heated and melted and added to the polyurethane prepolymer. The mixing ratio of the antioxidant curing agent to the polyurethane prepolymer is 10:100 by weight. The mixture is evenly mixed and molded, and a polyurethane elastomer is obtained by secondary vulcanization.

[0090] Comparative Example 5

[0091] The difference between this comparative example and Example 1 is that no antioxidant curing agent is used, but the basic polyhydroxy curing agent in the present application is directly used. The specific preparation method is as follows:

[0092] Polytetramethylene glycol and toluene diisocyanate are mixed in a ratio of total -NCO to total -OH of 1.6:1, heated to 90°C for reaction for 2 hours, and degassed to obtain a polyurethane prepolymer. Trimethylolpropane is heated and melted and added to the polyurethane prepolymer. The mixing ratio of the antioxidant curing agent to the polyurethane prepolymer is 10:100 by weight. The mixture is evenly mixed and molded, and a secondary vulcanization treatment is performed to obtain a polyurethane elastomer.

[0093] Experiments and data

[0094] The polyurethane elastomers prepared in the above examples and comparative examples were subjected to anti-aging tests for physical and mechanical properties and oxidation discoloration ability. The test methods are as follows:

[0095] Anti-aging test: According to GB / T 14274-2003, the strength retention rate of polyurethane elastomer after aging for 5 hours at 120°C and 100% relative humidity was tested.

[0096] Color change degree: Test the yellowing resistance level of polyurethane elastomer under the B method test in accordance with HG / T3689-2001.

[0097] Test data is shown in Table 1 below

[0098]

[0099] The strength retention rate in Table 1 is plotted as a line graph, such as Figure 1 shown.

[0100] analyze

[0101] According to Table 1 and Figure 1 It can be seen that the polyurethane elastomers prepared in Example 1, Example 2 and Example 3 show excellent retention of strength after aging test, can maintain strong physical and mechanical properties under high temperature and high humidity, maintain strong yellowing resistance after ultraviolet irradiation, and have strong resistance to yellowing and discoloration.

[0102] In the preparation process of Comparative Example 1, too much para-acyl compound is used. According to the data obtained in Table 1, the strength retention rate of the polyurethane of Comparative Example 1 decreases significantly after aging, but the yellowing resistance grade decreases slightly, indicating that the use of an appropriate amount of para-acyl compound within an appropriate range will not cause excessive consumption of the hydroxyl groups on the basic polyhydroxy curing agent. Therefore, the amount of the para-acyl compound used cannot exceed 1.2 eq of the polyhydroxy curing agent.

[0103] In the preparation process of Comparative Example 2, a small amount of para-acyl compound is used. According to the data in Table 1, the strength retention rate of the polyurethane elastomer of Comparative Example 2 decreases moderately after aging, and the yellowing resistance registration decreases significantly, indicating that too small a amount of para-acyl compound is used, resulting in insufficient antioxidant performance. Its cross-linking ability is greater than that of Comparative Example 1, and there are more hydroxyl groups. However, after aging, it is still affected by peroxide free radicals and does not reach the physical strength performance of the embodiment.

[0104] In the preparation process of Comparative Example 3, the phenolic hydroxyl group of 2,6-di-tert-butylphenol was not protected. According to the data in Table 1, the polyurethane elastomer of Comparative Example 3 showed a decrease in strength retention rate and yellowing resistance grade, which proves that the hydroxyl group of the hindered phenol structure on phenol did not fully show the ability to absorb peroxyl radicals, so its hydroxyl structure may have been changed, and the synchronous chain aging reaction of peroxyl radicals was not terminated, so the strength retention rate decreased and the yellowing resistance also decreased.

[0105] During the preparation process of Comparative Example 4, the methoxylated phenolic hydroxyl group was not freed from the protecting group. According to Table 1, the strength retention rate of the polyurethane of Comparative Example 4 decreased the most after aging, and the yellowing resistance grade was also the lowest, indicating that the hindered phenol structure that was not freed from the protecting group did not show antioxidant ability and occupied the hydroxyl group of the polyhydroxy curing agent, thereby weakening its own physical and mechanical properties.

[0106] The basic polyhydroxy curing agent used in the preparation of Comparative Example 5 did not undergo an esterification reaction with the para-acyl compound. According to Table 1, the strength retention rate of the polyurethane elastomer decreased significantly after aging treatment, and the yellowing resistance grade also decreased, indicating that the establishment of a hindered phenol structure on the molecular chain of the polyhydroxy curing agent can effectively improve the oxidation resistance of the polyurethane elastomer, and correspondingly improve the mechanical properties of the polyurethane elastomer, and in the yellowing test, it has a strong ability to resist color change.

[0107] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A polyurethane curing agent, characterized in that The method comprises the following preparation steps and the obtained product: S1, reacting 2,6-di-tert-butylphenol with dimethyl sulfate to obtain 2,6-di-tert-butylanisole; S2, performing a para-acylation reaction on 2,6-di-tert-butylanisole to generate a para-acyl compound; S3, esterifying the basic polyhydroxy curing agent with the para-acyl compound to generate an antioxidant curing agent; The basic polyhydroxy curing agent is one of triethanolamine, trimethylolpropane or pentaerythritol.

2. A polyurethane curing agent according to claim 1, characterized in that: The mass ratio of the basic polyhydroxy curing agent to the para-acyl compound is 1:1-1.2, the reagent solution of the esterification reaction is N,N-dimethylacetamide, the mass ratio of N,N-dimethylacetamide to the para-acyl compound is 4:1, the temperature of the esterification reaction is 90°C, and the reaction time is 2.5h.

3. A polyurethane curing agent according to claim 1, characterized in that: The steps of the para-acylation reaction are as follows: A1. Formation of para-carboxyl group: 2,6-di-tert-butylanisole and a methanol solution of sodium methoxide were mixed at a reaction temperature of 55-65° C., vacuum distilled until no fraction flowed out, and then DMF was added. The amount of DMF was 2-3 times that of 2,6-di-tert-butylanisole. The solvent was continuously vacuum distilled out and the temperature was lowered. Carbon dioxide was introduced into the remaining material and the pressure was increased to 0.5-1.0 MPa. The temperature was raised to 100-110° C. and the reaction time was 24 h to obtain a crude para-carboxyl compound. Then, the above materials are dissolved and layered using sulfuric acid and toluene, and then heated for dehydration, cooled and filtered to obtain a para-carboxyl compound; A2. Mix the para-carboxyl compound with an acyl chloride reagent to react to obtain a para-acyl chloride compound, mix the para-acyl compound with dichloromethane in a mixing ratio of 100 g:1 L, cool to below zero, mix boron tribromide with dichloromethane in a mixing ratio of 100 g:1 L, add the dichloromethane solution of boron tribromide dropwise to the dichloromethane solution of the para-acyl compound for 2 hours, stir at room temperature for 5 hours, add distilled water for extraction, treat with a desiccant and vacuum dry to obtain a pure para-acyl compound.

4. A polyurethane curing agent according to claim 3, characterized in that: The reaction ratio of the 2,6-di-tert-butylanisole to sodium methoxide is 1.0:1.1-1.3eq.

5. A polyurethane curing agent according to claim 3, characterized in that: The acyl chloride reagent is one of phosphorus trichloride, phosphorus pentachloride or thionyl chloride, and the mixing ratio of the acyl chloride reagent to the para-carboxyl compound is 1.05:1.

00.

6. A polyurethane curing agent according to claim 1, characterized in that: The molar ratio of the reaction of 2,6-di-tert-butylphenol and dimethyl sulfate is 1:1.5-3, the reaction solvent is dichloromethane or toluene, and after the reaction, extraction and stratification are performed, and the organic phase is evaporated to obtain 2,6-di-tert-butylanisole.

7. A polyurethane curing agent according to claim 3, characterized in that: The reaction molar ratio of the boron tribromide to the para-acyl compound is 2-3:

3.

8. An elastomer comprising the polyurethane curing agent according to any one of claims 1 to 7, characterized in that: The elastomer comprises the following components: Diol, toluene diisocyanate, antioxidant curing agent; The preparation method of the elastomer comprises the following steps: mixing diol and toluene diisocyanate in a ratio of total -NCO to total -OH of 1.1-2:1, heating to 90°C for reaction for 2h, degassing to obtain a polyurethane prepolymer, heating and melting an antioxidant curing agent and adding the agent to the polyurethane prepolymer, wherein the mixing ratio of the antioxidant curing agent to the polyurethane prepolymer is 5-15:100 by weight, mixing evenly, molding, and performing secondary vulcanization to obtain the elastomer.

9. The elastic body according to claim 8, characterized in that The diol is one of polytetramethylene glycol, polyester 218 or polycarbonate glycol.

10. Use of the polyurethane curing agent according to any one of claims 1 to 7 in the preparation of elastomers.

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