Assistant and preparation method thereof, curing agent and preparation method and application thereof

Abstract

The invention discloses a special performance additive and a preparation method thereof, a bi-component polyurethane curing agent and a preparation method and application thereof, and belongs to the technical field of polyurethane. Aiming at the problems that an existing curing agent is difficult to give consideration to rapid curing, excellent mechanical properties, no pollution and low cost, phosphite ester containing hydroxyl alkoxy groups is designed as a special modification auxiliary agent, and the auxiliary agent has a self-catalysis effect and can efficiently catalyze an addition reaction between isocyanate groups and hydroxyl groups, so that the curing effect of the curing agent is improved. The curing efficiency of the polyurethane is improved. Meanwhile, a hydroxyl group connected with an alkoxy group participates in a cross-linking reaction to form a three-dimensional network structure with a proper cross-linking degree, so that the mechanical property of the polyurethane material is improved. The polyurethane adhesive prepared by mixing the two-component polyurethane curing agent and the polyol has the advantages that the curing time at room temperature is shortened to 40 minutes, the tensile strength reaches 50 MPa, and the polyurethane adhesive can be widely applied to efficient sizing scenes in the fields of furniture, buildings, automobiles and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of polyurethanes, and particularly relates to a special modification assistant and its preparation method, a two-component polyurethane curing agent and its preparation method and use. Background Art

[0002] Polyurethane curing agents are very important for the production of polyurethane adhesives, coatings, casting materials, etc., and are also the core factors determining the performance of the final products. Their types, dosages, reaction activities, and molecular structures directly affect the curing time, crosslinking degree, and mechanical properties of polyurethane materials. Compared with single-component polyurethane curing agents, two-component polyurethane curing agents have more excellent advantages such as curing speed, mechanical properties, storage stability, construction flexibility, and environmental friendliness, so they have become the mainstream choice in industrial applications. With the rapid development of the Chinese economy, the demand for high-quality polyurethane curing agents is also increasing continuously.

[0003] For example, in one solution, a polyisocyanate prepolymer solid is obtained by first carrying out an addition reaction of hydrogenated xylylene diisocyanate and a polyol in an ester solvent, then adding an alkane extractant for heating extraction and purification, and finally dissolving it in an ester solvent to prepare a solvent with a solid content of 65% - 85% to obtain a polyurethane curing agent. The polyurethane curing agent of this invention has a high solid content, a low content of free diisocyanate monomer, a high bonding strength, and a fast curing speed, but due to the dependence on high-temperature curing, a high usage amount of organic solvents, and raw material cost problems, it is not suitable for actual industrial applications.

[0004] In another solution, a polyurethane curing agent is obtained by mixing DESMODUR N 330, phosphite, ethyl acetate, dibutyltin dilaurate, biuret, antioxidant, water scavenger, methyl borate, inhibitor under nitrogen protection and then sampling and filtering. This method uses commercially available phosphite as a functional assistant, enabling them to have a good synergistic effect of compounding with each other, reducing the content of free 1,6 - hexamethylene diisocyanate (HDI) in the polyurethane curing agent, and thus improving the storage stability. However, it has a strong dependence on other assistants such as catalysts, antioxidants, inhibitors, etc., and there are many types of raw materials, resulting in an increase in the comprehensive cost of the curing agent.

[0005] Currently, common polyurethane curing agents often cannot simultaneously meet the requirements of fast curing speed, excellent mechanical properties, pollution-free, and low cost. From the analysis of the catalyst system, the existing technologies mainly include organometallic catalysts, organic amine catalysts, environmentally friendly catalysts, and self-catalytic systems. However, organometallic catalysts have a toxicity risk, organic amine catalysts have a low reaction efficiency, and environmentally friendly catalysts are costly. In contrast, the self-catalytic system achieves efficient curing without an external catalyst through intramolecular catalysis, but it requires precise control of the position and activity of the intramolecular catalytic groups, and the synthesis route is complex. Therefore, the present invention proposes a novel two-component polyurethane curing agent, by designing a phosphite structure containing a hydroxyalkoxy group as a special modification additive, which simplifies the process route while achieving a synergistic improvement in the curing rate and mechanical properties of polyurethane. Summary of the Invention

[0006] In order to solve at least one of the above problems and defects existing in the prior art, embodiments of the present invention provide a special modification additive and a preparation method thereof, a two-component polyurethane curing agent and a preparation method and use thereof.

[0007] According to one aspect of the present invention, there is provided a special modification additive, and the special modification additive has the following structural formula:

[0008]

[0009] Wherein, R1, R2, and R3 respectively represent an alkyl group of C2-C8, including a straight-chain or branched-chain structure, n1 + n2 = 0-2, n1 is 0 or 1, and n2 is 0 or 1.

[0010] In some embodiments, the R1 represents one of the alkyl groups of C2-C4, the R2 represents one of the alkyl groups of C2-C4, and the R3 represents one of the alkyl groups of C2-C4.

[0011] According to another aspect of the present invention, there is provided a preparation method of a special modification additive, including:

[0012] Mix an alcohol source with a triethylamine solution, and then dropwise add phosphorus trichloride under normal pressure and at a temperature of 5-10 °C, and keep warm for 3 h, wherein the alcohol source includes an ortho-diol or a mixture of an ortho-diol and a mono-alcohol;

[0013] Remove the triethylamine hydrochloride precipitate by filtration;

[0014] Heat the filtered mixed solution to 140-145 °C and then evacuate to remove unreacted substances to obtain the special modification additive;

[0015] Wherein, the special modification additive is the special modification additive according to the foregoing embodiments.

[0016] In some embodiments, the molar ratio of the alcohol source to triethylamine is 1:1;

[0017] The molar ratio of the alcohol source to phosphorus trichloride is 3:1.

[0018] In some embodiments, the vicinal diol is R1(OH)2, R2(OH)2 or R3(OH)2, and the monohydric alcohol is R2OH or R3OH;

[0019] The alcohol source comprises a mixture of a vicinal diol and a monohydric alcohol, and the molar ratio of the vicinal diol to the monohydric alcohol is 1-2:1-2.

[0020] In some embodiments, the number of hydroxyl groups in the special modifying agent is controlled by adjusting the molar ratio of the vicinal diol to the monohydric alcohol.

[0021] Furthermore, in the embodiments of the present invention, the molar ratio of the vicinal diol to the monohydric alcohol is preferably 2:1.

[0022] In the embodiments of the present invention, the number of hydroxyl groups (-OH) in the special modifying agent is controlled by adjusting the ratio of the diol to the monohydric alcohol, and a special modifying agent containing hydroxyl groups is prepared. By using the molar ratio of the diol to the monohydric alcohol in the range of 1-3:0-2, a phosphite structure containing hydroxyalkoxy groups is prepared. For example, when the molar ratio of the diol to the monohydric alcohol is controlled to be 2:1 (i.e., n1 + n2 = 1), the special modifying agent structure generated at this time contains two hydroxyl groups, and the two hydroxyl groups further undergo an addition reaction with isocyanate groups (-NCO) to form a three-dimensional network structure with an appropriate degree of crosslinking, and then the polyurethane adhesive exhibits excellent mechanical properties. However, when the proportion of the diol is too high, such as when the molar ratio of the diol to the monohydric alcohol is 2:0 (i.e., n1 + n2 = 2), the special modifying agent will contain three hydroxyl groups, and all three hydroxyl groups will undergo an addition reaction with the isocyanate groups, resulting in too high a degree of crosslinking, and then the peel strength of the polyurethane adhesive becomes poor; when the proportion of the diol is low, such as when the molar ratio of the diol to the monohydric alcohol is 1:2 (i.e., n1 + n2 = 0), the generated phosphite contains only one hydroxyl group, and this hydroxyl group undergoes an addition reaction with the isocyanate to form an isocyanate group-terminated prepolymer, which cannot undergo further crosslinking, resulting in a low degree of crosslinking of the polyurethane material and poor mechanical properties; when there is only monohydric alcohol, there are no hydroxyl groups in the special modifying agent, and thus no addition reaction can occur with the isocyanate groups, which only acts as an additive and can only accelerate the curing rate of the polyurethane, but cannot improve the mechanical properties of the polyurethane material.

[0023] According to another aspect of the present invention, there is provided a method for preparing a two-component polyurethane curing agent, comprising:

[0024] Heat the polyisocyanate to 60 - 90 °C, then add the special modification additive, and react for 1 - 2 h under stirring and heat preservation conditions in a protective atmosphere of nitrogen, and then cool to room temperature to obtain the two-component polyurethane curing agent;

[0025] Wherein, the special modification additive is the special modification additive according to the foregoing embodiments, or is prepared by the preparation method according to the foregoing embodiments.

[0026] In some embodiments, the addition amount of the special modification additive is 0.1 - 1 wt%,

[0027] Wherein, the polyisocyanate is 4,4'-diphenylmethane diisocyanate (MDI), 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4-toluene diisocyanate (TDI), 2,6-tolylene diisocyanate, p-phenylene diisocyanate, 1,5-naphthalene diisocyanate, m-xylylene diisocyanate, 3,3'-dimethyl-4,4'-biphenyl diisocyanate, tetramethyl-m-xylylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, 4,4-diisocyanato dicyclohexylmethane, 2,2'-dicyclohexylmethane diisocyanate, 2,4-dicyclohexylmethane diisocyanate, triisocyanatocyclohexane, tris(isocyanatomethyl)cyclohexane, norbornane dimethylene isocyanate, isophorone diisocyanate, L-lysine diisocyanate, 1,4-butane diisocyanate, 1,5-pentane diisocyanate, 1,5-diisocyanato-2-methylpentane, 1,6-diisocyanato-3-(isocyanatomethyl)hexane, trimethylhexane diisocyanate, nonane triisocyanate, 1,8-diisocyanato-4-(isocyanatomethyl)octane, 1,7-diisocyanato-4-(3-isocyanatopropyl)heptane, undecane-1,6,11-triisocyanate, 1,10-decane diisocyanate, 1-isocyanato-1-methyl-4(3)-isocyanatomethylcyclohexane, and one or more of the biuret bodies and trimers of the above types.

[0028] According to another aspect of the present invention, a two-component polyurethane curing agent is provided. The two-component polyurethane curing agent is prepared by the preparation method according to the foregoing embodiments, and the two-component polyurethane curing agent contains a phosphite group and an isocyanate group.

[0029] In another aspect of the present invention, there is provided a use of a two-component polyurethane curing agent, wherein a polyurethane adhesive is prepared by mixing the two-component polyurethane curing agent with a polyol at room temperature. Herein, the two-component polyurethane curing agent is the two-component polyurethane curing agent described in the foregoing embodiments, or is prepared according to the preparation method described in the foregoing embodiments.

[0030] In some embodiments, the functional group molar ratio of the two-component polyurethane curing agent to the polyol is NCO:OH = 1.03 - 1.1:1;

[0031] The polyol is one or more of a polyether polyol, a polyester polyol, a bio-based polyol, and a polycarbonate polyol.

[0032] In the special modification additives of the embodiments of the present invention, the strong electron-donating effect of the alkoxy group connected to the hydroxyl group stabilizes the lone electron pair on the phosphorus atom through induction and conjugation, significantly enhancing its Lewis basicity, thereby efficiently activating the carbon atom in the isocyanate group and promoting the nucleophilic attack of the hydroxyl group, catalyzing the formation of urethane bonds. At the same time, the hydroxyl group in the hydroxyalkoxy group can participate in the cross-linking reaction to form a three-dimensional network structure with a cross-linking degree, improving the tensile strength of the polyurethane material. In terms of the synthesis process, the hydroxyalkoxy group is introduced into the phosphite backbone through a one-step reaction, simplifying the process route. This system can achieve rapid curing at room temperature, providing an efficient and environmentally friendly solution for the industrial application of polyurethane.

[0033] Furthermore, specific embodiments of the special modification additives described in this patent may include:

[0034]

[0035] As used in this patent, the term "C2-C8 alkyl" (preferably C2-C4 alkyl) refers to a branched or unbranched saturated hydrocarbon group having 2 to 8 carbon atoms, such as hydrocarbon groups and their isomers such as ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, etc.

[0036] As used in this patent, the term "vicinal diol" refers to a straight-chain or branched alkyl group having 2 to 8 carbon atoms, wherein two hydroxyl groups are located on adjacent carbon atoms, such as ethylene glycol, 1,2-propanediol, 1,2-butanediol, 2,3-butanediol, etc. and their isomers (including but not limited to positional isomers and stereoisomers).

[0037] Those skilled in the art can understand that other additives, such as adhesion promoters, leveling agents, antibacterial agents, defoaming agents, etc., can also be added according to process requirements in the application of the two-component polyurethane curing agent of the present invention in the field of polyurethane adhesives, which is a routine operation in this field.

[0038] The two-component polyurethane curing agent of the present invention is prepared by reacting a special modified assistant with isocyanate, and both phosphite groups and isocyanate groups are contained in its system. Among them, the phosphite, as a Lewis base, has a self-catalytic effect and can catalyze the addition reaction of the isocyanate group and the hydroxyl group, significantly improving the reaction efficiency, thereby shortening the curing time of the polyurethane without the need to additionally add a catalyst. Through experimental verification, the curing agent of the present invention can achieve the curing of the polyurethane at room temperature, and the curing time is shortened to 40 min.

[0039] Compared with the prior art, the beneficial effects of the technical solution of the invention are as follows:

[0040] (1) The present invention uses a mixture of vicinal diol and monohydric alcohol and phosphorus trichloride to react in one step to prepare a phosphite containing a hydroxyalkoxy group as a special modified assistant. This preparation method has a simple process, no pollution, and high preparation efficiency;

[0041] (2) The special modified assistant of the present invention has a phosphite structure, and the phosphorus atom in it catalyzes the addition reaction of the isocyanate group and its own hydroxyl group, and the resulting adduct and the remaining polyisocyanate form a two-component polyurethane curing agent;

[0042] (3) The special modified assistant of the present invention contains multiple hydroxyl groups, and the hydroxyl groups can undergo a crosslinking reaction with the polyisocyanate to form a three-dimensional network structure with an appropriate degree of crosslinking, thereby improving the mechanical properties of the polyurethane material;

[0043] (4) The special modified assistant of the present invention is used to prepare a two-component polyurethane curing agent in one step by mixing with the polyisocyanate. This curing agent has a self-catalytic effect during the process of preparing the polyurethane adhesive and does not need to be additionally added with a catalyst, showing prospects in industrial production;

[0044] (5) The two-component polyurethane curing agent provided by the present invention is applied to the field of polyurethane adhesives. For example, when used to prepare a polyurethane adhesive, it shows the characteristics of rapid curing. Under the condition of room temperature, the curing time of the polyurethane adhesive prepared from this curing agent and the polyol is shortened to 40 min, and the tensile strength reaches 50 MPa, which is suitable for high-efficiency sizing scenarios. Description of the Drawings Figure 1 It is a schematic structural diagram of a special modified assistant containing a hydroxyalkoxy group; Figure 2 It is a schematic structural diagram of the special modified assistant synthesized according to the exemplary embodiment. Detailed Embodiments

[0045] The present invention will be further described below through specific embodiments. The embodiments described in the present invention are only for the purpose of explaining the present invention and do not limit the scope of the present invention.

[0046] In the various embodiments and comparative examples of the present invention, the sources of the main raw materials are as follows. Unless otherwise specified, other raw materials and reagents are purchased through common commercial channels:

[0047] MDI-50: 98%, NCO%=33.5 wt%, Aladdin;

[0048] TDI-100: 98%, NCO%=48.2 wt%, McLean;

[0049] Polyether polyol C2020: molecular weight 2000, functionality 2, hydroxyl value 56, Shandong Shanhua Chemical;

[0050] Castor oil: 99.9%, molecular weight 987, hydroxyl functionality 3, Jinan Zhiyuancheng Chemical.

[0051] The main performance of the embodiments of the present invention is tested by the following methods:

[0052] Hydroxyl value: Tested in accordance with GB / T 12008.3-2009 Plastic polyether polyols Part 3: Determination of hydroxyl value;

[0053] Tensile strength and elongation at break: tested in accordance with GB / T1040-2006 standard;

[0054] Surface drying time: Tested in accordance with GB / T 13477.5-2002 standard, at room temperature (25 o C) is the time it takes for the surface to become non-sticky after the two components are evenly mixed and left to stand.

[0055] Examples 1-8 and Comparative Examples 1-3

[0056] Example 1

[0057] The special modification additive, the two-component polyurethane curing agent and the polyurethane adhesive are prepared according to the following preparation method, which specifically includes the following steps:

[0058] (1) Add 124 g ethylene glycol, 46 g ethanol and 303.6 g triethylamine to the reactor, slowly add 137.5 g phosphorus trichloride, and maintain the reaction temperature at 6 o C. After the addition was completed, the reaction was continued with stirring for 3 h. The white precipitate of triethylamine hydrochloride was removed by filtration, and the mixed solution was heated to 142 o C, removing the unreacted product under vacuum conditions to obtain a special modified additive A, di(2-hydroxyethoxy)ethoxy phosphite;

[0059] (2) Preheat 500 g of MDI to 70 oC. Under a nitrogen atmosphere, 0.5 g of special modified additive A was added, and stirring reaction was continued for 1 h. After cooling to room temperature, the two-component polyurethane curing agent A was obtained, and the dosage of the special modified additive A was 0.1 wt%.

[0060] (3) 500.5 g of the two-component polyurethane curing agent A and 3878 g of polyether polyol C2020 were stirred and mixed at room temperature to obtain a polyurethane adhesive, and the molar ratio of the two-component polyurethane curing agent to the polyether polyol by functional groups was NCO:OH = 1.03:1.

[0061] Example 2

[0062] According to the preparation method of Example 1, the special modified additive, the two-component polyurethane curing agent and the polyurethane adhesive were prepared. Compared with Example 1, there were only the following differences:

[0063] In step (2), MDI was replaced with TDI, and the dosage of the special modified additive A was 5 g to obtain the two-component polyurethane curing agent B, and the dosage of the special modified additive A was 1.0 wt%.

[0064] In step (3), 500.5 g of the two-component polyurethane curing agent A was replaced with 505 g of the two-component polyurethane curing agent B, and 3878 g of polyether polyol C2020 was replaced with 1703 g of castor oil to obtain a polyurethane adhesive, and the molar ratio of the two-component polyurethane curing agent to the castor oil by functional groups was NCO:OH = 1.1:1.

[0065] Example 3

[0066] According to the preparation method of Example 1, the special modified additive, the two-component polyurethane curing agent and the polyurethane adhesive were prepared. Compared with Example 1, there were only the following differences:

[0067] In step (2), the dosage of the special modified additive A was 2.5 g to obtain the two-component polyurethane curing agent C, and the dosage of the special modified additive A was 0.5 wt%.

[0068] In step (3), 500.5 g of the two-component polyurethane curing agent A was replaced with 502.5 g of the two-component polyurethane curing agent C, and 3878 g of polyether polyol C2020 was replaced with 1234 g of castor oil to obtain a polyurethane adhesive, and the molar ratio of the two-component polyurethane curing agent to the castor oil by functional groups was NCO:OH = 1.06:1.

[0069] Example 4

[0070] According to the preparation method of Example 1, the special modified additive, the two-component polyurethane curing agent and the polyurethane adhesive were prepared. Compared with Example 1, there were only the following differences:

[0071] In step (2), the amount of special modified additive A is 4 g, MDI is replaced by TDI, and two-component polyurethane curing agent D is prepared, wherein the amount of special modified additive A is 0.8 wt%.

[0072] In step (3), 500.5 g of two-component polyurethane curing agent A is replaced by 496.9 g of two-component polyurethane curing agent D, and the amount of polyether polyol C2020 is 5284 g, and a polyurethane adhesive is prepared, wherein the molar ratio of the functional groups of the two-component polyurethane curing agent to the polyether polyol is NCO:OH = 1.08:1.

[0073] Example 5

[0074] The special modified additive, two-component polyurethane curing agent and polyurethane adhesive are prepared according to the preparation method of Example 1, and compared with Example 1, there are only the following differences:

[0075] In step (1), 46 g of ethanol is replaced by 60 g of propanol to prepare special modified additive B, bis(hydroxyethoxy)-propoxy phosphite;

[0076] In step (2), 0.5 g of special modified additive A is replaced by 2.5 g of special modified additive B to prepare two-component polyurethane curing agent E, wherein the amount of special modified additive B is 0.5 wt%.

[0077] In step (3), 500.5 g of two-component polyurethane curing agent A is replaced by 502.5 g of two-component polyurethane curing agent E, and the amount of polyether polyol C2020 is 3740 g, and a polyurethane adhesive is prepared, wherein the molar ratio of the functional groups of the two-component polyurethane curing agent to the polyether polyol is NCO:OH = 1.06:1.

[0078] Example 6

[0079] The special modified additive, two-component polyurethane curing agent and polyurethane adhesive are prepared according to the preparation method of Example 1, and compared with Example 1, there are only the following differences:

[0080] In step (1), 124 g of ethylene glycol is replaced by 152 g of propylene glycol, and 46 g of ethanol is replaced by 60 g of propanol to prepare special modified additive C, bis(2-hydroxypropoxy)-propoxy phosphite;

[0081] In step (2), special modified additive A is replaced by special modified additive C to prepare two-component polyurethane curing agent F, wherein the amount of special modified additive C is 0.1 wt%.

[0082] In step (3), the two-component polyurethane curing agent A is replaced with the two-component polyurethane curing agent F, and the dosage of 3,878 g of polyether polyol C2020 is 3,879 g to prepare a polyurethane adhesive, where the molar ratio of the two-component polyurethane curing agent to the polyether polyol by functional groups is NCO:OH = 1.03:1.

[0083] Example 7

[0084] Prepare the special modified additive, two-component polyurethane curing agent and polyurethane adhesive according to the preparation method of Example 1, and compared with Example 1, there are only the following differences:

[0085] In step (1), 124 g of ethylene glycol is replaced with 152 g of propylene glycol, and 46 g of ethanol is replaced with 60 g of propanol to prepare the special modified additive C;

[0086] In step (2), 0.5 g of the special modified additive A is replaced with 5 g of the special modified additive C, and MDI is replaced with TDI to prepare the two-component polyurethane curing agent G, where the dosage of the special modified additive C is 1.0 wt%;

[0087] In step (3), 500.5 g of the two-component polyurethane curing agent A is replaced with 505 g of the two-component polyurethane curing agent G, and 3,878 g of polyether polyol C2020 is replaced with 1,706 g of castor oil to prepare a polyurethane adhesive, where the molar ratio of the two-component polyurethane curing agent to the castor oil by functional groups is NCO:OH = 1.1:1.

[0088] Example 8

[0089] Prepare the special modified additive, two-component polyurethane curing agent and polyurethane adhesive according to the preparation method of Example 1, and compared with Example 1, there are only the following differences:

[0090] In step (1), 124 g of ethylene glycol is replaced with 152 g of propylene glycol to prepare the special modified additive D, bis(2-hydroxypropoxy)ethyl phosphite;

[0091] In step (2), 0.5 g of the special modified additive A is replaced with 4 g of the special modified additive D, and MDI is replaced with TDI to prepare the two-component polyurethane curing agent H, where the dosage of the special modified additive D is 0.8 wt%;

[0092] In step (3), 500.5 g of the two-component polyurethane curing agent A is replaced with 504 g of the two-component polyurethane curing agent H, and 3,878 g of polyether polyol C2020 is replaced with 1,769 g of castor oil to prepare a polyurethane adhesive, where the molar ratio of the two-component polyurethane curing agent to the castor oil by functional groups is NCO:OH = 1.06:1.

[0093] Comparative Example 1

[0094] 500 g of MDI and 3883 g of polyether polyol C2020 were stirred and mixed at room temperature to obtain a polyurethane adhesive.

[0095] Comparative Example 2

[0096] 500 g of MDI and 1196 g of castor oil were stirred and mixed at room temperature to obtain a polyurethane adhesive.

[0097] Comparative Example 3

[0098] 500 g of TDI and 5421 g of polyether polyol C2020 were stirred and mixed at room temperature to obtain a polyurethane adhesive.

[0099] The obtained polyurethane adhesives were subjected to relevant performance tests, including surface drying time, tensile strength, elongation at break, etc. The test results are shown in Table 1.

[0100] Table 1 Relevant performance test results of polyurethane adhesives in Examples 1 - 8 and Comparative Examples 1 - 3 Product number Skin drying time / min Tensile strength / MPa Elongation at break / % Example 1 60 48 450 Example 2 80 35 390 Example 3 50 43 400 Example 4 80 45 420 Example 5 65 50 410 Example 6 40 46 460 Example 7 60 35 300 Example 8 55 38 380 Comparative example 1 120 35 490 Comparative example 2 100 28 410 Comparative example 3 150 25 420

[0101] According to the performance test results in Table 1, it can be seen that:

[0102] The surface drying time of the polyurethane adhesive prepared by mixing the two - component polyurethane curing agent obtained in the present invention with polyol is short and the tensile strength is high.

[0103] From the above examples, the present invention provides a special modification additive and its preparation method, a two - component polyurethane curing agent and its preparation method and uses. By introducing a phosphite structure, this curing agent promotes the addition reaction between isocyanate groups and hydroxyl groups, shortening the curing time from 150 min to 40 min, significantly improving the curing rate of the polyurethane adhesive, and being applicable to high - efficiency sizing scenarios.

[0104] The present invention can control the number of hydroxyl groups in the special modified additive by adjusting the ratio of diol to monoalcohol, and prepare a special modified additive containing hydroxyl groups. The phosphite structure in the special modified additive plays a key role in the curing efficiency of polyurethane. In the phosphite structure, the phosphorus atom is connected to three alkoxy groups. As strong electron-donating groups, the alkoxy groups can effectively stabilize a pair of lone electron pairs on the phosphorus atom, significantly enhancing its Lewis basicity. As a Lewis base, the phosphite activates the carbon atom in the isocyanate group, making it more electrophilic, and then promoting the nucleophilic attack of the hydroxyl group on the carbon atom to catalyze the formation of urethane products. Moreover, the phosphite is not consumed in the reaction and can be released from the intermediate and participate in the catalytic cycle again to achieve efficient and continuous catalytic action. This additive also participates in the cross-linking reaction with polyisocyanate and has a three-dimensional network structure with appropriate cross-linking degree in the polyurethane adhesive prepared by mixing with polyol, thus showing excellent tensile strength.

[0105] Obviously, the above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A special modified additive, characterized in that, The special modified additive has the following structural formula: ; Wherein, R1, R2, and R3 respectively represent C2-C8 alkyl groups, including straight-chain or branched-chain structures, n1 + n2 = 0-2, n1 is 0 or 1, and n2 is 0 or 1.

2. The special modified additive according to claim 1, wherein R1 represents one of C2-C4 alkyl groups, R2 represents one of C2-C4 alkyl groups, and R3 represents one of C2-C4 alkyl groups.

3. A preparation method of a special modified additive, characterized in that, The preparation method includes: Mix an alcohol source with a triethylamine solution, and then dropwise add phosphorus trichloride under normal pressure and at a temperature of 5-10 °C, and keep the temperature for 3 h, wherein the alcohol source includes vicinal diol or a mixture of vicinal diol and monohydric alcohol; Remove the triethylamine hydrochloride precipitate by filtration; Heat the filtered mixed solution to 140-145 °C and then evacuate to remove unreacted substances to obtain the special modified additive, wherein the special modified additive is the special modified additive according to claim 1 or 2.

4. The preparation method according to claim 3, wherein The molar ratio of the alcohol source to triethylamine is 1:1, The molar ratio of the alcohol source to phosphorus trichloride is 3:

1.

5. The preparation method according to claim 4, wherein The vicinal diol is R1(OH)2, R2(OH)2 or R3(OH)2, and the monohydric alcohol is R2OH or R3OH, The alcohol source includes a mixture of vicinal diol and monohydric alcohol, and the molar ratio of vicinal diol to monohydric alcohol is 1-2:1-2, The number of hydroxyl groups in the special modified additive is controlled by adjusting the molar ratio of vicinal diol to monohydric alcohol.

6. A preparation method of a two-component polyurethane curing agent, characterized in that, The preparation method includes: Heat the polyisocyanate to 60-90 °C, then add the special modified additive, and react for 1-2 h under a nitrogen protection atmosphere with stirring and heat preservation, and then cool to room temperature to obtain the two-component polyurethane curing agent, wherein the special modified additive is the special modified additive according to claim 1 or 2, or is prepared by the preparation method according to any one of claims 3-5.

7. The preparation method according to claim 6, wherein The addition amount of the special modified additive is 0.1-1 wt%, Among them, the polyisocyanate is 4,4'-diphenylmethane diisocyanate (MDI), 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4-toluene diisocyanate (TDI), 2,6-tolylene diisocyanate, p-phenylene diisocyanate, 1,5-naphthalene diisocyanate, m-xylylene diisocyanate, 3,3'-dimethyl-4,4'-biphenyl diisocyanate, tetramethyl-m-xylylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, 4,4-diisocyanate dicyclohexylmethane, 2,2'-dicyclohexylmethane diisocyanate, 2,4-dicyclohexylmethane diisocyanate, triisocyanato cyclohexane, tris(isocyanatomethyl)cyclohexane, norbornane dimethylene isocyanate, isophorone diisocyanate, L-lysine diisocyanate, 1,4-butanediisocyanate, 1,5-pentanediisocyanate, 1,5-diisocyanato-2-methylpentane, 1,6-diisocyanato-3-(isocyanatomethyl)hexane, trimethylhexane diisocyanate, nonane triisocyanate, 1,8-diisocyanato-4-(isocyanatomethyl)octane, 1,7-diisocyanato-4-(3-isocyanatopropyl)heptane, undecane-1,6,11-triisocyanate, 1,10-decanediisocyanate, 1-isocyanato-1-methyl-4(3)-isocyanatomethyl cyclohexane, and one or more of biurets and trimers of the above types.

8. A two-component polyurethane curing agent, characterized in that, The two-component polyurethane curing agent is prepared by the preparation method according to claim 6 or 7, and the two-component polyurethane curing agent contains a phosphite group and an isocyanate group.

9. Use of a two-component polyurethane curing agent, characterized in that, The two-component polyurethane curing agent and a polyol are mixed at room temperature to obtain a polyurethane adhesive, wherein the two-component polyurethane curing agent is the two-component polyurethane curing agent according to claim 8, or is prepared by the preparation method according to claim 6 or 7.

10. The use according to claim 9, wherein, The functional group molar ratio of the two-component polyurethane curing agent to the polyol is NCO:OH = 1.03-1.1:

1. The polyol is one or more of a polyether polyol, a polyester polyol, a bio-based polyol, and a polycarbonate polyol.

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