A polyurethane composition with delayed curing and its preparation method

Abstract

A polyurethane composition with delayed curing is prepared from raw materials including the following components: 10 parts by weight of a blocked polyurethane prepolymer; 10 - 15 parts by weight of bisphenol A epoxy resin; 15 - 25 parts by weight of a core - shell rubber toughening agent; 20 - 25 parts by weight of a liquid nitrile rubber - modified epoxy resin; 2 - 6 parts by weight of an active diluent; 1 - 3 parts by weight of a water absorbent; 4 - 5 parts by weight of a thixotropic agent; 15 - 25 parts by weight of an inorganic filler; 1 - 5 parts by weight of a latent curing agent; 0.1 - 0.15 parts by weight of a curing accelerator. The blocked polyurethane prepolymer is prepared by a three - stage reaction of polyisocyanate using a zinc - containing complex as a catalyst. This polyurethane composition with delayed curing uses a zinc - containing complex catalyst. By compounding with an alcohol amine, the catalytic efficiency of the zinc - containing complex catalyst is equivalent to that of a traditional organic catalyst. At the same time, the preparation process involves three - stage reactions of polyisocyanate, ensuring that the blocked isocyanate groups can be stably preserved and the isocyanate has high activity during curing.

Description

Technical Field

[0001] The present invention relates to the technical field of polyurethane compositions, and more particularly, to a polyurethane composition with delayed curing and a preparation method thereof. Background Art

[0002] Polyurethanes are industrially produced by the reaction of polyisocyanates with polyols or polyamine compounds. The reaction between isocyanates and polyols or polyamines, commonly known as the gel reaction, results in the growth of polymer chains, leading to the formation of polymers with high molecular weights. There are three general types of catalysts used in the production of polyurethanes: tertiary amines (mono-tertiary amines and poly-tertiary amines), organometallic compounds (mainly organotin, mercury, and lead compounds), and carboxylates of tin, bismuth, etc. Organotin catalysts mainly facilitate the gelling reaction, increase the number of closed cells, and contribute to the compactness of the polyurethane composition. Amine catalysts exhibit a more variable foaming / gelling balance. Tertiary amines can also effectively act as catalysts for polymer chain growth and can be used in combination with organotin catalysts. CN202210291227.0 discloses a method for preparing a polyurethane adhesive composition using a contact product of a tertiary amine and a carboxylic acid as a catalyst. CN201880067844.4 describes a method for obtaining a zinc ketimine complex by reacting a zinc compound with certain ketimines for catalyzing the reaction of isocyanates and alcohols to produce a polyurethane composition. CN201280060952.1 relates to the use of a zinc (II) complex compound with the chemical formula Zn(L)x(Y)2-x for the catalytic polymerization of a two-component polyurethane composition. CN201880013881.7 describes a bicyclic tertiary amine compound suitable as a catalyst for the production of polyurethanes.

[0003] Polyurethane catalysts are generally organic compounds containing metal elements, such as organic compounds of lead, mercury, tin, etc., which all have high biological toxicity. With the continuous improvement of environmental protection requirements at home and abroad, these highly toxic catalysts are gradually restricted or prohibited from use in many polyurethane products; while zinc and bismuth series organometallic catalysts and organic compounds such as tertiary amines, as low-toxic, safe, and environmentally friendly polyurethane catalysts, have gradually been applied; however, the catalytic activity of using these catalysts alone is relatively low, and during the polyurethane polymerization process, not only is the catalytic efficiency significantly lower than that of lead, mercury, and tin series organic compounds, but it also reduces the comprehensive performance of polyurethanes. Therefore, their use and development in polyurethane synthesis are restricted. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide a polyurethane composition with delayed curing and a preparation method thereof. The polyurethane composition with delayed curing provided by the present invention adopts an environment-friendly zinc complex catalyst, avoiding the use of highly toxic catalysts. Meanwhile, by compounding with alkanolamines, the catalytic efficiency of the zinc complex catalyst is comparable to that of lead, mercury, and tin organic catalysts. At the same time, the preparation process of the polyurethane adduct involves the reactions in three stages of polyisocyanate, ensuring that the blocked isocyanate groups can be stably stored and the isocyanate has high activity during curing.

[0005] The present invention provides a polyurethane composition with delayed curing, which is prepared from raw materials including the following components:

[0006] 10 parts by weight of blocked polyurethane prepolymer;

[0007] 10 - 15 parts by weight of bisphenol A epoxy resin;

[0008] 15 - 25 parts by weight of core - shell rubber toughening agent;

[0009] 20 - 25 parts by weight of liquid nitrile rubber - modified epoxy resin;

[0010] 2 - 6 parts by weight of reactive diluent;

[0011] 1 - 3 parts by weight of water absorbent;

[0012] 4 - 5 parts by weight of thixotropic agent;

[0013] 15 - 25 parts by weight of inorganic filler;

[0014] 1 - 5 parts by weight of latent curing agent;

[0015] 0.1 - 0.15 parts by weight of curing accelerator;

[0016] The blocked polyurethane prepolymer uses a zinc complex as a catalyst and is prepared through the three - stage reaction of polyisocyanate.

[0017] Preferably, the zinc complex is obtained by physically mixing an organozinc compound and an alkanolamine compound in an organic solvent.

[0018] Preferably, the organozinc compound is selected from one or more of zinc 2 - ethylhexanoate, zinc neodecanoate, and zinc naphthenate;

[0019] The alkanolamine compound is selected from one or more of triethanolamine, diethanolamine, and triisopropanolamine;

[0020] The mass ratio of the organozinc compound to the alkanolamine compound is 1:(0.5 - 1.5).

[0021] Preferably, the process of using a zinc-containing complex as a catalyst and undergoing a three-stage reaction of polyisocyanate is as follows:

[0022] Add polyether polyol to the reactor. Under stirring, heat up to 105°C - 110°C, evacuate to remove water, keep warm for 0.5 h - 1.5 h, and then cool down to 30°C - 40°C; add the zinc-containing complex and the first solvent to the reactor, stir for 5 min - 15 min, and add isophorone diisocyanate to the reactor under stirring. Heat up to 80°C - 90°C for the first-stage reaction for 1 h - 1.5 h, and cool down to room temperature; add a mixed solution of trimethylolpropane, 1,3-butanediol, and the second solvent to the reactor. Under stirring, heat up to 75°C - 85°C for the second-stage reaction for 40 min - 60 min, and cool down to room temperature; add a mixed solution of polymethylene polyphenyl isocyanate and the third solvent to the reactor. Under stirring, heat up to 60°C - 70°C for the third-stage reaction for 40 min - 60 min, and cool down to room temperature to obtain a polyurethane prepolymer; add a mixed solution of methyl ethyl ketoxime and the fourth solvent to the reactor. Under stirring, heat up to 70°C - 80°C for the capping reaction for 1 h - 3 h, and cool down to room temperature to obtain a capped polyurethane prepolymer.

[0023] Preferably, the mass ratio of the polyether polyol, zinc-containing complex, first solvent, isophorone diisocyanate, trimethylolpropane, 1,3-butanediol, second solvent, polymethylene polyphenyl isocyanate, third solvent, methyl ethyl ketoxime, and fourth solvent is 100:(0.01 - 0.05):(1 - 3):(20 - 25):(0.1 - 0.5):(0.5 - 1):(1 - 3):(2 - 6):(4 - 6):(5 - 10):(4 - 6).

[0024] Preferably, the bisphenol A epoxy resin is selected from one or more of Yueyang Petrochemical CYD-128, South Asia NPEL-128, and South Asia NPEF-127.

[0025] Preferably, the core-shell rubber toughening agent is a liquid rubber toughening agent with a core-shell structure, where the core material is a copolymer of diene and monoolefin, and the shell material is a homopolymer or copolymer of epoxy-functionalized alkyl methacrylate; the average particle size of the liquid rubber toughening agent with a core-shell structure is less than 400 nm.

[0026] Preferably, the liquid nitrile rubber-modified epoxy resin is a high-viscosity adduct of bisphenol A diglycidyl ether and butadiene-acrylonitrile elastomer;

[0027] The active diluent is a monofunctional aliphatic glycidyl ether and / or a bifunctional aliphatic glycidyl ether;

[0028] The water absorbent is 4A molecular sieve;

[0029] The thixotropic agent is fumed silica;

[0030] The inorganic filler is silica powder;

[0031] The latent curing agent is Dyhard 100S dicyandiamide curing agent;

[0032] The curing accelerator is Dyhard UR700 urea accelerator.

[0033] The present invention also provides a preparation method of the delayed-curing polyurethane composition according to the above technical solution, comprising the following steps:

[0034] a) Adding bisphenol A epoxy resin, core-shell rubber toughener, liquid nitrile rubber-modified epoxy resin, reactive diluent, water absorbent, thixotropic agent and inorganic filler to the blocked polyurethane prepolymer, placing the mixed material in a dynamic mixer, carrying out the first mixing and stirring, and after vacuum degassing, obtaining a preliminary mixture of the polyurethane composition;

[0035] b) Adding the latent curing agent and the curing accelerator to the above preliminary mixture of the polyurethane composition, carrying out the second mixing and stirring, and after vacuum degassing, obtaining the delayed-curing polyurethane composition.

[0036] Preferably, in step a), the temperature of the first mixing and stirring is 30°C to 40°C, the revolution speed is 10 Hz to 20 Hz, and the rotation speed is 25 Hz to 35 Hz;

[0037] In step b), the temperature of the second mixing and stirring is 30°C to 40°C, the revolution speed is 10 Hz to 20 Hz, and the rotation speed is 5 Hz to 15 Hz.

[0038] The present invention provides a polyurethane composition with delayed curing, which is prepared from raw materials including the following components: 10 parts by weight of a blocked polyurethane prepolymer; 10 - 15 parts by weight of bisphenol A epoxy resin; 15 - 25 parts by weight of a core - shell rubber toughening agent; 20 - 25 parts by weight of a liquid nitrile rubber - modified epoxy resin; 2 - 6 parts by weight of an active diluent; 1 - 3 parts by weight of a water absorbent; 4 - 5 parts by weight of a thixotropic agent; 15 - 25 parts by weight of an inorganic filler; 1 - 5 parts by weight of a latent curing agent; 0.1 - 0.15 parts by weight of a curing accelerator; the blocked polyurethane prepolymer is prepared by a three - stage reaction of polyisocyanate using a zinc - containing complex as a catalyst. Compared with the prior art, the polyurethane composition with delayed curing provided by the present invention adopts specific components with specific contents to achieve good overall interaction. In particular, an environment - friendly zinc - containing complex catalyst is used to avoid the use of highly toxic catalysts. At the same time, by compounding with an alcohol amine, the catalytic efficiency of the zinc - containing complex catalyst is equivalent to that of lead, mercury, and tin - based organic catalysts. Moreover, the preparation process of the polyurethane adduct involves three - stage reactions of polyisocyanate, ensuring that the blocked isocyanate groups can be stably stored and the isocyanate has high activity during curing.

[0039] In addition, the preparation method provided by the present invention has a simple process, mild and easy - to - control conditions, easily available raw materials and low cost, and has broad industrial application prospects. Detailed Embodiments

[0040] Next, in combination with the embodiments of the present invention, the technical solutions of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the protection scope of the present invention.

[0041] The present invention provides a polyurethane composition with delayed curing, which is prepared from raw materials including the following components:

[0042] 10 parts by weight of a blocked polyurethane prepolymer;

[0043] 10 - 15 parts by weight of bisphenol A epoxy resin;

[0044] 15 - 25 parts by weight of a core - shell rubber toughening agent;

[0045] 20 - 25 parts by weight of a liquid nitrile rubber - modified epoxy resin;

[0046] 2 - 6 parts by weight of an active diluent;

[0047] 1 - 3 parts by weight of a water absorbent;

[0048] 4 - 5 parts by weight of a thixotropic agent;

[0049] 15 - 25 parts by weight of inorganic filler;

[0050] 1 - 5 parts by weight of latent curing agent;

[0051] 0.1 - 0.15 parts by weight of curing accelerator;

[0052] The blocked polyurethane prepolymer uses a zinc - containing complex as a catalyst and is prepared by a three - stage reaction of polyisocyanate.

[0053] In the present invention, the delay - curing polyurethane composition is prepared from raw materials including a blocked polyurethane prepolymer, bisphenol A epoxy resin, core - shell rubber toughening agent, liquid nitrile rubber - modified epoxy resin, active diluent, water absorbent, thixotropic agent, inorganic filler, latent curing agent, and curing accelerator, and is preferably prepared from a blocked polyurethane prepolymer, bisphenol A epoxy resin, core - shell rubber toughening agent, liquid nitrile rubber - modified epoxy resin, active diluent, water absorbent, thixotropic agent, inorganic filler, latent curing agent, and curing accelerator.

[0054] In the present invention, the delay - curing polyurethane composition is prepared from raw materials comprising the following components:

[0055] 10 parts by weight of blocked polyurethane prepolymer;

[0056] 10 - 15 parts by weight of bisphenol A epoxy resin;

[0057] 15 - 25 parts by weight of core - shell rubber toughening agent;

[0058] 20 - 25 parts by weight of liquid nitrile rubber - modified epoxy resin;

[0059] 2 - 6 parts by weight of active diluent;

[0060] 1 - 3 parts by weight of water absorbent;

[0061] 4 - 5 parts by weight of thixotropic agent;

[0062] 15 - 25 parts by weight of inorganic filler;

[0063] 1 - 5 parts by weight of latent curing agent;

[0064] 0.1 - 0.15 parts by weight of curing accelerator;

[0065] Preferably prepared from raw materials comprising the following components:

[0066] 10 parts by weight of blocked polyurethane prepolymer;

[0067] 11 - 13 parts by weight of bisphenol A epoxy resin;

[0068] 20 - 22 parts by weight of core - shell rubber toughener;

[0069] 23 - 24 parts by weight of liquid nitrile rubber - modified epoxy resin;

[0070] 3 - 5 parts by weight of reactive diluent;

[0071] 1.5 - 2 parts by weight of water absorbent;

[0072] 4.5 parts by weight of thixotropic agent;

[0073] 19 - 21 parts by weight of inorganic filler;

[0074] 2 - 4 parts by weight of latent curing agent;

[0075] 0.11 - 0.13 parts by weight of curing accelerator.

[0076] In the present invention, the blocked polyurethane prepolymer is prepared by a three - stage reaction of polyisocyanate using a zinc - containing complex as a catalyst.

[0077] In the present invention, the zinc - containing complex is preferably obtained by physically mixing an organic zinc compound and an alkanolamine compound in an organic solvent.

[0078] In the present invention, the organic zinc compound is preferably selected from one or more of zinc 2 - ethylhexanoate, zinc neodecanoate, and zinc naphthenate, and more preferably zinc 2 - ethylhexanoate. There is no special limitation on the source of the organic zinc compound in the present invention, and commercially available products well - known to those skilled in the art can be used.

[0079] In the present invention, the alkanolamine compound is preferably selected from one or more of triethanolamine, diethanolamine, and triisopropanolamine, and more preferably triethanolamine. There is no special limitation on the source of the alkanolamine compound in the present invention, and commercially available products well - known to those skilled in the art can be used.

[0080] In the present invention, the mass ratio of the organic zinc compound to the alkanolamine compound is preferably 1:(0.5 - 1.5), and more preferably 1:1.

[0081] In the present invention, the organic solvent is preferably ethyl acetate; commercially available products well - known to those skilled in the art can be used.

[0082] In the present invention, the dosage ratio of the organic solvent to the organic zinc compound is preferably 5 mL - 15 mL of organic solvent added per 1 g of organic zinc compound, and more preferably 10 mL.

[0083] In the present invention, the process of physical mixing is preferably specifically:

[0084] Place the alkanolamine compound and the organozinc compound in an organic solvent, seal it, shake it at room temperature for 15 min to 25 min, and then let it stand for use to obtain a zinc-containing complex catalyst.

[0085] In the present invention, the process of using the zinc-containing complex as a catalyst for the three-stage reaction of polyisocyanate is preferably specifically as follows:

[0086] Add polyether polyol to the reactor, under stirring, heat up to 105 °C to 110 °C, evacuate to remove water, keep warm for 0.5 h to 1.5 h, and then cool down to 30 °C to 40 °C; add the zinc-containing complex and the first solvent to the reactor, stir for 5 min to 15 min, and add isophorone diisocyanate to the reactor under stirring, heat up to 80 °C to 90 °C for the first-stage reaction for 1 h to 1.5 h, and cool down to room temperature; add a mixed solution of trimethylolpropane, 1,3-butanediol and the second solvent to the reactor, under stirring, heat up to 75 °C to 85 °C for the second-stage reaction for 40 min to 60 min, and cool down to room temperature; add a mixed solution of polymethylene polyphenyl isocyanate and the third solvent to the reactor, under stirring, heat up to 60 °C to 70 °C for the third-stage reaction for 40 min to 60 min, and cool down to room temperature to obtain a polyurethane prepolymer; add a mixed solution of butanone oxime and the fourth solvent to the reactor, under stirring, heat up to 70 °C to 80 °C for the capping reaction for 1 h to 3 h, and cool down to room temperature to obtain a capped polyurethane prepolymer.

[0087] More preferably:

[0088] Add polyether polyol to a 500 ml glass reactor, under stirring, heat up to 108 °C, evacuate to remove water, keep warm for 1 h, and then cool down to 35 °C; add the zinc-containing complex and the first solvent to the reactor, stir for 10 min, and add isophorone diisocyanate to the reactor under stirring, heat up to 85 °C for the first-stage reaction for 1.2 h, and cool down to room temperature; add a mixed solution of trimethylolpropane, 1,3-butanediol and the second solvent to the reactor, under stirring, heat up to 80 °C for the second-stage reaction for 50 min, and cool down to room temperature; add a mixed solution of polymethylene polyphenyl isocyanate and the third solvent to the reactor, under stirring, heat up to 65 °C for the third-stage reaction for 50 min, and cool down to room temperature to obtain a polyurethane prepolymer; add a mixed solution of butanone oxime and the fourth solvent to the reactor, under stirring, heat up to 75 °C for the capping reaction for 2 h, and cool down to room temperature to obtain a capped polyurethane prepolymer.

[0089] In the present invention, the polyether polyol is preferably a polyether polyol with a molecular weight of 2000D (DL-2000D); the zinc-containing complex is the zinc-containing complex catalyst described in the above technical solution; the first solvent is preferably ethyl acetate; the second solvent is preferably ethyl acetate; the third solvent is preferably ethyl acetate; the fourth solvent is preferably ethyl acetate.

[0090] In the present invention, the mass ratio of the polyether polyol, zinc-containing complex, first solvent, isophorone diisocyanate, trimethylolpropane, 1,3-butanediol, second solvent, polymethylene polyphenylene polyisocyanate, third solvent, methyl ethyl ketoxime, and fourth solvent is preferably 100:(0.01 - 0.05):(1 - 3):(20 - 25):(0.1 - 0.5):(0.5 - 1):(1 - 3):(2 - 6):(4 - 6):(5 - 10):(4 - 6), more preferably 100:(0.02 - 0.025):2:(23 - 24):(0.2 - 0.4):(0.6 - 0.7):2:(3 - 3.5):5:(7.5 - 8):5.

[0091] The present invention uses the above-mentioned environmentally friendly zinc complex catalyst and multi-stage polymerization process to prepare a delayed-curing polyurethane composition, which specifically includes: (1) physically mixing an organozinc compound and an alkanolamine compound in an organic solvent at room temperature to obtain a zinc-containing complex; (2) using the aforementioned zinc-containing complex as a catalyst to prepare a blocked polyurethane prepolymer through a three-stage reaction of polyisocyanate; (3) using the aforementioned blocked polyurethane prepolymer as one of the components to prepare a delayed-curing polyurethane composition. The catalyst in the present invention is an alkanolamine and an organozinc complex, and the alkanolamine and the organozinc complex have the characteristics of low toxicity, safety, and environmental friendliness, and are suitable for the production of polyurethane compositions.

[0092] In the present invention, the bisphenol A epoxy resin is preferably selected from one or more of Yueyang Petrochemical CYD-128, South Asia NPEL-128, and South Asia NPEF-127, more preferably Yueyang Petrochemical CYD-128. The present invention has no special restrictions on the source of the bisphenol A epoxy resin, and commercially available products well-known to those skilled in the art can be used.

[0093] In the present invention, the core-shell rubber toughening agent is preferably a liquid rubber toughening agent with a core-shell structure, wherein the core material is a copolymer of a diene and a monoolefin, and the shell material is a homopolymer or copolymer of an epoxy-functionalized alkyl methacrylate; the average particle size of the liquid rubber toughening agent with a core-shell structure is preferably less than 400nm. The present invention has no special restrictions on the source of the core-shell rubber toughening agent, and commercially available products well-known to those skilled in the art can be used.

[0094] In the present invention, the liquid nitrile rubber modified epoxy resin is preferably a high-viscosity adduct of diglycidyl ether of bisphenol A and butadiene-acrylonitrile elastomer; the active diluent is preferably a monofunctional aliphatic glycidyl ether and / or a difunctional aliphatic glycidyl ether, more preferably a difunctional aliphatic glycidyl ether; the water absorbent is preferably 4A molecular sieve; the thixotropic agent is preferably fumed silica; the inorganic filler is preferably silica powder; the latent curing agent is preferably Dyhard 100S dicyandiamide curing agent; the curing accelerator is preferably Dyhard UR700 urea accelerator. The present invention has no special restrictions on the sources of the above-mentioned liquid nitrile rubber modified epoxy resin, active diluent, water absorbent, thixotropic agent, inorganic filler, latent curing agent and curing accelerator, and commercially available products well-known to those skilled in the art can be used.

[0095] In the present invention, the mesh number of the silica powder is preferably 500 mesh to 1500 mesh, more preferably 700 mesh to 900 mesh.

[0096] The delayed-curing polyurethane composition provided by the present invention adopts specific components in specific contents to achieve good overall interaction. In particular, an environmentally friendly zinc complex catalyst is used to avoid the use of highly toxic catalysts. At the same time, by compounding with alkanolamine, the catalytic efficiency of the zinc complex catalyst is equivalent to that of lead, mercury, tin-based organic catalysts. At the same time, the preparation process of the polyurethane adduct involves three-stage reactions of polyisocyanate, which ensures that the blocked isocyanate group can be stably stored and the isocyanate has high activity during curing.

[0097] The present invention also provides a preparation method of the delayed-curing polyurethane composition described in the above technical solution, including the following steps:

[0098] a) Adding bisphenol A type epoxy resin, core-shell rubber toughening agent, liquid nitrile rubber modified epoxy resin, active diluent, water absorbent, thixotropic agent and inorganic filler to the blocked polyurethane prepolymer, placing the mixed material in a dynamic mixer, carrying out the first mixing and stirring, and after vacuum degassing, obtaining a preliminary mixture of the polyurethane composition;

[0099] b) Adding a latent curing agent and a curing accelerator to the above-mentioned preliminary mixture of the polyurethane composition, carrying out the second mixing and stirring, and after vacuum degassing, obtaining the delayed-curing polyurethane composition.

[0100] The present invention first adds bisphenol A type epoxy resin, core-shell rubber toughening agent, liquid nitrile rubber modified epoxy resin, active diluent, water absorbent, thixotropic agent and inorganic filler to the blocked polyurethane prepolymer, places the mixed material in a dynamic mixer, carries out the first mixing and stirring, and after vacuum degassing, obtains a preliminary mixture of the polyurethane composition.

[0101] In the present invention, the capped polyurethane prepolymer, bisphenol A epoxy resin, core-shell rubber toughening agent, liquid nitrile rubber-modified epoxy resin, reactive diluent, water absorbent, thixotropic agent and inorganic filler are the same as those described in the above technical solution, and will not be elaborated herein.

[0102] In the present invention, the temperature of the first mixing and stirring is preferably 30°C to 40°C, the revolution is preferably 10 Hz to 20 Hz, more preferably 15 Hz, and the rotation is preferably 25 Hz to 35 Hz, more preferably 30 Hz.

[0103] In the present invention, the time for vacuum degassing is preferably 8 min to 25 min, more preferably 10 min.

[0104] After that, a latent curing agent and a curing accelerator are added to the above-mentioned polyurethane composition premix in the present invention, and after the second mixing and stirring and vacuum degassing, a polyurethane composition with delayed curing is obtained.

[0105] In the present invention, the temperature of the second mixing and stirring is preferably 30°C to 40°C, the revolution is preferably 10 Hz to 20 Hz, more preferably 15 Hz, and the rotation is preferably 5 Hz to 15 Hz, more preferably 10 Hz.

[0106] In the present invention, the time for vacuum degassing is preferably 8 min to 25 min, more preferably 10 min.

[0107] The preparation method provided by the present invention has a simple process, mild and easy-to-control conditions, easily available raw materials and low cost, and has broad industrial application prospects.

[0108] The present invention provides a polyurethane composition with delayed curing, which is prepared from raw materials including the following components: 10 parts by weight of a blocked polyurethane prepolymer; 10 - 15 parts by weight of bisphenol A epoxy resin; 15 - 25 parts by weight of a core - shell rubber toughening agent; 20 - 25 parts by weight of a liquid nitrile rubber - modified epoxy resin; 2 - 6 parts by weight of an active diluent; 1 - 3 parts by weight of a water absorbent; 4 - 5 parts by weight of a thixotropic agent; 15 - 25 parts by weight of an inorganic filler; 1 - 5 parts by weight of a latent curing agent; 0.1 - 0.15 parts by weight of a curing accelerator; the blocked polyurethane prepolymer is prepared by a three - stage reaction of polyisocyanate using a zinc - containing complex as a catalyst. Compared with the prior art, the polyurethane composition with delayed curing provided by the present invention adopts specific components with specific contents to achieve good overall interaction. In particular, an environment - friendly zinc - containing complex catalyst is used to avoid the use of highly toxic catalysts. At the same time, by compounding with alkanolamine, the catalytic efficiency of the zinc - containing complex catalyst is equivalent to that of lead, mercury, and tin - based organic catalysts. Meanwhile, the preparation process of the polyurethane adduct involves three - stage reactions of polyisocyanate, ensuring that the blocked isocyanate groups can be stably stored and the isocyanate has high activity during curing.

[0109] In addition, the preparation method provided by the present invention has a simple process, mild and easy - to - control conditions, easily available raw materials and low cost, and has broad prospects for industrial application.

[0110] To further illustrate the present invention, the following examples are used for detailed description. All raw materials used in the following examples of the present invention are commercially available products; among them:

[0111] The bisphenol A epoxy resin is CYD - 128 from Yueyang Petrochemical;

[0112] The core - shell rubber toughening agent is a liquid rubber toughening agent with a core - shell structure, where the core material is a copolymer of diene and mono - olefin, and the shell material is a homopolymer of epoxy - functionalized alkyl methacrylate. The average particle size of the liquid rubber toughening agent with a core - shell structure is about 200 nm;

[0113] The liquid nitrile rubber - modified epoxy resin is a high - viscosity adduct of diglycidyl ether of bisphenol A and butadiene - acrylonitrile elastomer, specifically a liquid nitrile rubber with a carboxyl - terminated end group and a number - average molecular weight of 4000 - 11000. At the same time, the acrylonitrile monomer content in the selected raw materials is in the range of 17 wt% - 25 wt%, and the brand is CTBN;

[0114] The active diluent is Anhui Xinyuan XY678 bifunctional epoxy diluent;

[0115] The water absorbent is 4A molecular sieve;

[0116] The thixotropic agent is Evonik R202 fumed silica;

[0117] The inorganic filler is silica powder (800 mesh);

[0118] The latent curing agent is Dyhard 100S dicyandiamide curing agent;

[0119] The curing accelerator is Dyhard UR700 urea accelerator;

[0120] The zinc-containing complex catalyst is obtained according to the following preparation method:

[0121] Take 0.2 g of triethanolamine and 0.2 g of zinc 2-ethylhexanoate and place them in 2 ml of ethyl acetate, seal, shake for 20 minutes at room temperature, and then let stand for use to obtain the zinc-containing complex catalyst;

[0122] The blocked polyurethane prepolymer is obtained according to the following preparation method:

[0123] (1) Add 100 g of polyether polyol (DL-2000D) with a molecular weight of 2000 D to a 500 ml glass reactor, under stirring, heat up to 108 °C, evacuate to dehydrate, keep warm for 1 hour, and then cool down to 35 °C; put 0.021 g of the above zinc-containing complex catalyst and 2 g of ethyl acetate as a solvent into the reactor, stir for 10 minutes, and add 23.1 g of isophorone diisocyanate to the reactor under stirring, heat up to 85 °C and keep warm for reaction, the reaction time is 1.2 hours, and cool down to room temperature; put a mixed solution of 0.3 g of trimethylolpropane, 0.65 g of 1,3-butanediol, and 2 g of ethyl acetate into the reactor, under stirring, heat up to 80 °C and keep warm for reaction, the reaction time is 50 minutes, and cool down to room temperature; put a mixed solution of 3.12 g of polymethylene polyphenyl isocyanate (Wanhua Chemical Pm200) and 5 g of ethyl acetate into the reactor, under stirring, heat up to 65 °C and keep warm for reaction, the reaction time is 50 minutes, and cool down to room temperature to obtain the polyurethane prepolymer; put a mixed solution of 7.8 g of methyl ethyl ketoxime and 5 g of ethyl acetate into the reactor, under stirring, heat up to 75 °C and keep warm for reaction, the reaction time is 2 hours, and cool down to room temperature to obtain the blocked polyurethane prepolymer A;

[0124] (2) Add 100 g of polyether polyol (DL-2000D) with a molecular weight of 2000 D to a 500 ml glass reactor. Under stirring, heat up to 108 °C, evacuate to remove water, keep warm for 1 hour, and then cool down to 35 °C. Put 0.021 g of dibutyltin dilaurate catalyst and 2 g of ethyl acetate as a solvent into the reactor, stir for 10 minutes, and add a mixed solution of 23.1 g of isophorone diisocyanate, 3.12 g of polymethylene polyphenyl isocyanate (Wanhua Chemical Pm200), and 5 g of ethyl acetate to the reactor under stirring. Heat up to 85 °C and keep warm for reaction for 1.2 hours, then cool down to room temperature. Put a mixed solution of 0.3 g of trimethylolpropane, 0.65 g of 1,3-butanediol, and 2 g of ethyl acetate into the reactor, under stirring, heat up to 80 °C and keep warm for reaction for 100 minutes, then cool down to room temperature. Put a mixed solution of 7.8 g of methyl ethyl ketoxime and 5 g of ethyl acetate into the reactor, under stirring, heat up to 75 °C and keep warm for reaction for 2 hours, then cool down to room temperature to obtain the blocked polyurethane prepolymer B;

[0125] (3) Add 100 g of polyether polyol (DL-2000D) with a molecular weight of 2000 D to a 500 ml glass reactor. Under stirring, heat up to 108 °C, evacuate to remove water, keep warm for 1 hour, and then cool down to 35 °C. Put 0.021 g of triphenylbismuth catalyst and 2 g of ethyl acetate as a solvent into the reactor, stir for 10 minutes, and add a mixed solution of 23.1 g of isophorone diisocyanate, 3.12 g of polymethylene polyphenyl isocyanate (Wanhua Chemical Pm200), and 5 g of ethyl acetate to the reactor under stirring. Heat up to 85 °C and keep warm for reaction for 1.2 hours, then cool down to room temperature. Put a mixed solution of 0.3 g of trimethylolpropane, 0.65 g of 1,3-butanediol, and 2 g of ethyl acetate into the reactor, under stirring, heat up to 80 °C and keep warm for reaction for 100 minutes, then cool down to room temperature. Put a mixed solution of 7.8 g of methyl ethyl ketoxime and 5 g of ethyl acetate into the reactor, under stirring, heat up to 75 °C and keep warm for reaction for 2 hours, then cool down to room temperature to obtain the blocked polyurethane prepolymer C.

[0126] The performance test standards adopted in the present invention are as follows:

[0127] Shear strength: GB / T 7124-2008, Determination of tensile shear strength of adhesives (rigid material to rigid material);

[0128] T-peel strength: GB / T 2791-1995, Test method for T-peel strength of adhesives Flexible material to flexible material;

[0129] Impact peel strength: ISO 11343-2003, Adhesives–Determination of dynamic resistance to cleavage of high strength adhesive bonds under impact conditions–Wedge impact method;

[0130] Tensile strength at break and elongation at break of the matrix: GB / T 528-2009, Rubber, vulcanized or thermoplastic–Determination of tensile stress-strain properties.

[0131] Example 1 and Comparative Examples 1-2

[0132] The composition and ratio are shown in Table 1.

[0133] Table 1 Composition and ratio (mass percentage) data of Example 1 and Comparative Examples 1-2

[0134]

[0135]

[0136] The specific preparation method is as follows:

[0137] Example 1: Add bisphenol A epoxy resin, core-shell rubber toughener, liquid nitrile rubber modified epoxy resin, active diluent, water absorbent, thixotropic agent and inorganic filler to the above capped polyurethane prepolymer A. Place the mixed material in a dynamic mixer and mix and stir at 30°C - 40°C, with a revolution speed of 15 Hz and a rotation speed of 30 Hz, and degas under vacuum for 10 minutes to obtain a preliminary mixture of polyurethane composition; then add a latent curing agent and a curing accelerator to the above preliminary mixture of polyurethane composition, and mix and stir at 30°C - 40°C, with a revolution speed of 15 Hz and a rotation speed of 10 Hz, and degas under vacuum for 10 minutes to obtain a polyurethane composition with delayed curing.

[0138] Comparative Example 1: The preparation method of Example 1 is adopted, except that: the above capped polyurethane prepolymer B is used to replace the capped polyurethane prepolymer A; a polyurethane composition is obtained.

[0139] Comparative Example 2: The preparation method of Example 1 is adopted, except that: the above capped polyurethane prepolymer C is used to replace the capped polyurethane prepolymer A; a polyurethane composition is obtained.

[0140] Perform various performance tests on the products of Example 1 and Comparative Examples 1-2, and the results are shown in Table 2.

[0141] Table 2 Various performance data of the products of Example 1 and Comparative Examples 1-2

[0142] Example 1 Comparative Example 1 Comparative Example 2 Shearing strength (MPa, Al - Al) 20.32 19.05 18.69 T - peel strength (N / mm) 10.32 8.11 8.39 Impact peel strength (N / mm) 32.45 30.77 26.19 Tensile strength of the body (MPa) 20.02 18.62 18.11 Elongation at break (%) 6.96 5.24 5.42

[0143] In the above experiments, in Example 1, a zinc-containing complex obtained from an organozinc compound and an alkanolamine compound was used as a catalyst, and a blocked polyurethane prepolymer was prepared by a three-stage reaction of polyisocyanate; in Comparative Examples 1-2, an organotin compound and an organobismuth were used as catalysts respectively, and a blocked polyurethane prepolymer was prepared by a two-stage reaction of polyisocyanate; subsequently, each blocked polyurethane prepolymer was used to prepare a polyurethane composition to evaluate the performance of the novel catalyst.

[0144] From the results, Example 1 was superior to Comparative Examples 1-2 in terms of shear strength, T-peel strength and impact peel strength. At the same time, Example 1 also had relatively the best bulk tensile strength and elongation at break; indicating that the environmentally friendly complex catalyst and the multi-stage preparation method in the present invention have good catalytic effects compared with the traditional metal tin and bismuth catalysts.

[0145] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A polyurethane composition with delayed curing, prepared from raw materials including the following components: 10 parts by weight of blocked polyurethane prepolymer; 10 - 15 parts by weight of bisphenol A epoxy resin; 15 - 25 parts by weight of core - shell rubber toughening agent; 20 - 25 parts by weight of liquid nitrile rubber - modified epoxy resin; 2 - 6 parts by weight of reactive diluent; 1 - 3 parts by weight of water absorbent; 4 - 5 parts by weight of thixotropic agent; 15 - 25 parts by weight of inorganic filler; 1 - 5 parts by weight of latent curing agent; 0.1 - 0.15 parts by weight of curing accelerator; The blocked polyurethane prepolymer is prepared by a three - stage reaction of polyisocyanate using a zinc - containing complex as a catalyst; the zinc - containing complex is obtained by physically mixing an organic zinc compound and an alkanolamine compound in an organic solvent; the organic zinc compound is selected from one or more of zinc 2 - ethylhexanoate, zinc neodecanoate, and zinc naphthenate; the alkanolamine compound is selected from one or more of triethanolamine, diethanolamine, and triisopropanolamine; the mass ratio of the organic zinc compound to the alkanolamine compound is 1:(0.5 - 1.5); The process of using the zinc - containing complex as a catalyst through the three - stage reaction of polyisocyanate is specifically as follows: Add polyether polyol into the reactor, under stirring, heat up to 105°C - 110°C, evacuate to remove water, keep warm for 0.5 h - 1.5 h, and then cool down to 30°C - 40°C; add the zinc - containing complex and the first solvent into the reactor, stir for 5 min - 15 min, and add isophorone diisocyanate into the reactor under stirring, heat up to 80°C - 90°C for the first - stage reaction for 1 h - 1.5 h, and cool down to room temperature; add a mixed solution of trimethylolpropane, 1,3 - butanediol, and the second solvent into the reactor, under stirring, heat up to 75°C - 85°C for the second - stage reaction for 40 min - 60 min, and cool down to room temperature; add a mixed solution of polymethylene polyphenyl isocyanate and the third solvent into the reactor, under stirring, heat up to 60°C - 70°C for the third - stage reaction for 40 min - 60 min, and cool down to room temperature to obtain the polyurethane prepolymer; add a mixed solution of methyl ethyl ketoxime and the fourth solvent into the reactor, under stirring, heat up to 70°C - 80°C for the blocking reaction for 1 h - 3 h, and cool down to room temperature to obtain the blocked polyurethane prepolymer.

2. The delayed-curing polyurethane composition according to claim 1, wherein The mass ratio of the polyether polyol, zinc - containing complex, first solvent, isophorone diisocyanate, trimethylolpropane, 1,3 - butanediol, second solvent, polymethylene polyphenyl isocyanate, third solvent, methyl ethyl ketoxime, and fourth solvent is 100:(0.01 - 0.05):(1 - 3):(20 - 25):(0.1 - 0.5):(0.5 - 1):(1 - 3):(2 - 6):(4 - 6):(5 - 10):(4 - 6).

3. The delay-curing polyurethane composition according to claim 1, characterized in that, The bisphenol A epoxy resin is selected from one or more of Yueyang Petrochemical CYD - 128, South Asia NPEL - 128, and South Asia NPEF - 127.

4. The delayed-curing polyurethane composition according to claim 1, characterized in that, The core-shell rubber toughening agent is a liquid rubber toughening agent with a core-shell structure, wherein the core material is a copolymer of diene and monoolefin, and the shell material is a homopolymer or copolymer of epoxy-functionalized alkyl methacrylate; the average particle size of the liquid rubber toughening agent with a core-shell structure is less than 400 nm.

5. The delay-curing polyurethane composition according to claim 1, characterized in that, The liquid nitrile rubber-modified epoxy resin is a high-viscosity adduct of bisphenol A diglycidyl ether and butadiene-acrylonitrile elastomer; The active diluent is a monofunctional aliphatic glycidyl ether and / or a difunctional aliphatic glycidyl ether; The water absorbent is 4A molecular sieve; The thixotropic agent is fumed silica; The inorganic filler is silica powder; The latent curing agent is Dyhard 100S dicyandiamide curing agent; The curing accelerator is Dyhard UR700 urea accelerator.

6. A method for preparing a delay-curing polyurethane composition according to any one of claims 1 to 5, comprising the following steps: a) Adding bisphenol A type epoxy resin, core-shell rubber toughening agent, liquid nitrile rubber-modified epoxy resin, active diluent, water absorbent, thixotropic agent and inorganic filler to the blocked polyurethane prepolymer, placing the mixed material in a dynamic mixer, performing the first mixing and stirring, and after vacuum degassing, obtaining a preliminary mixture of the polyurethane composition; b) Adding a latent curing agent and a curing accelerator to the preliminary mixture of the polyurethane composition, performing the second mixing and stirring, and after vacuum degassing, obtaining a delay-curing polyurethane composition.

7. The preparation method according to claim 6, characterized in that, In step a), the temperature of the first mixing and stirring is 30 °C to 40 °C, the revolution speed is 10 Hz to 20 Hz, and the rotation speed is 25 Hz to 35 Hz; In step b), the temperature of the second mixing and stirring is 30 °C to 40 °C, the revolution speed is 10 Hz to 20 Hz, and the rotation speed is 5 Hz to 15 Hz.

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