Hyperbranched polyurethane, preparation method thereof and modified epoxy resin

Abstract

The invention discloses hyperbranched polyurethane and a preparation method thereof and modified epoxy resin, and the preparation method of the hyperbranched polyurethane comprises the following steps: mixing dihydric alcohol and diisocyanate, dissolving in a solvent, and stirring for reaction to prepare an isocyanate-terminated linear prepolymer; adding dihydroxy alcohol amine into the linear prepolymer, and reacting to obtain a hyperbranched intermediate; and carrying out self-polymerization on the hyperbranched intermediate, then adding an end-capping reagent, and continuously reacting to obtain the hyperbranched polyurethane. According to the method, hydroxyl in the hyperbranched intermediate and an isocyanate group are subjected to a self-polymerization reaction, and a termination reaction can be performed through an end-capping reagent, so that self-crosslinking of hydrogen bonds and the like in the prior art is effectively avoided, and the performance adjustment of a final product is effectively realized.

Description

Technical Field

[0001] The invention belongs to the technical field of modified epoxy resin development, and relates to a hyperbranched polyurethane and a preparation method thereof, and a modified epoxy resin. Background Art

[0002] Epoxy resin is a high molecular polymer. Due to its excellent mechanical properties, high bonding strength, corrosion resistance, electrical insulation and good processing ability, it has been widely used in many fields such as aerospace, machinery manufacturing, electronics and civil construction. However, due to its unique chemical structure, the cured epoxy resin material has poor toughness and is brittle. It is easy to crack and produce microcracks when impacted, resulting in damage to the material surface and degradation of mechanical properties, which seriously affects the appearance, safety and sustainability of the material used, limiting its application in high-end and precision fields. In addition, the curing temperature required in the production process of traditional epoxy resin is high, the time is long, and the energy consumption is also relatively large. Therefore, a large amount of curing accelerator needs to be added to accelerate the curing reaction, which increases the production cost.

[0003] Hyperbranched polymers (HBPs) are a type of dendrite-like polymer. Due to their special branched molecular structure, there is no entanglement between molecules, and the molecular chains of the hyperbranched structure have strong mobility. When introduced into traditional resin systems (such as epoxy resin curing systems), the branched structure can increase the free volume of the curing system, thereby improving the toughness of the cured product. At the same time, the periphery of the HBPs molecule contains abundant active end groups, which increases the cross-linking density of the resin cured product, thereby ensuring the mechanical strength of the material, while increasing the curing rate of the epoxy resin and saving energy. In addition, the introduction of HBPs can reduce the viscosity of its epoxy complex, improve fluidity, and thus improve its processing properties. However, the synthesis process of most hyperbranched polymers is cumbersome, the internal structure is prone to self-crosslinking, and the performance is not easy to adjust. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a hyperbranched polyurethane and a preparation method thereof and a modified epoxy resin, thereby solving the technical problems in the prior art that the hyperbranched polymer preparation process is complicated, the internal structure is prone to self-crosslinking, and the performance is difficult to adjust, and at the same time solves the technical problems that the existing modified epoxy resin has poor mechanical properties and low curing efficiency.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for preparing a hyperbranched polyurethane comprises the following steps:

[0007] S1: mixing a diol and a diisocyanate and dissolving them in a solvent, stirring and reacting them to obtain an isocyanate-terminated linear prepolymer;

[0008] S2: adding dihydroxy alcohol amine to the linear prepolymer to obtain a hyperbranched intermediate after reaction;

[0009] S3: allowing the hyperbranched intermediate to undergo self-polymerization, then adding a capping agent, and continuing the reaction to obtain a hyperbranched polyurethane.

[0010] Preferably, the diol is at least one of polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polycaprolactone diol, polycarbonate diol and polybutylene terephthalate; and the diisocyanate is at least one of isophorone diisocyanate, toluene diisocyanate, hexamethylene diisocyanate and 4,4-diphenylmethane diisocyanate.

[0011] Preferably, the molar ratio of the diol to the diisocyanate is (1-2):(2-4).

[0012] Preferably, in step S1, the stirring reaction temperature is 60-80° C. and the time is 1-3 h.

[0013] Preferably, the dihydroxy alcoholamine is one of diethanolamine, diisopropanolamine, 4-(4-hydroxybutylamino)-1-butanol and 3,3'-dihydroxydiphenylamine; the reaction temperature of the linear prepolymer and the dihydroxy alcoholamine is 0-5°C, and the reaction time is 0.5-1h.

[0014] Preferably, in step S3, the temperature of the self-polymerization of the hyperbranched intermediate is 60-80° C. and the time is 2-4 hours; and then the reaction time after adding the end-capping agent is 0.5-1 hour.

[0015] A hyperbranched polyurethane is prepared by the method.

[0016] A modified epoxy resin, added with the above-prepared hyperbranched polyurethane; the modified epoxy resin has a bending strength of 175-200MPa and an impact strength of 35-41kJ / m 2 .

[0017] The method for preparing the modified epoxy resin is characterized in that the hyperbranched polyurethane, epoxy resin, curing agent and catalyst prepared in claim 5 are uniformly mixed and then thermally cured to obtain the modified epoxy resin.

[0018] Preferably, in terms of mass fractions, the ratio of the epoxy resin, the hyperbranched polyurethane, the curing agent and the catalyst is (100-200):(2-10):(10-20):(0.3-0.8).

[0019] Compared with the prior art, the present invention has the following beneficial technical effects:

[0020] The invention discloses a method for preparing a hyperbranched polyurethane, which first uses a diol and a diisocyanate to synthesize an isocyanate-terminated linear prepolymer, then adds a dihydroxy alcohol amine, reacts the amine group in the dihydroxy alcohol amine with the isocyanate group in the linear prepolymer, forms an enlarged branched structure, forms a hyperbranched intermediate, then undergoes a self-polymerization reaction of the hyperbranched intermediate, and finally adds a capping agent to obtain a hyperbranched polyurethane (HBPU) to form a spherical network structure. In this process, the hydroxyl group in the hyperbranched intermediate undergoes a self-polymerization reaction with the isocyanate group, and a termination reaction can be performed by the capping agent, thereby effectively avoiding self-crosslinking such as hydrogen bonds in the prior art, and the degree of polymerization is easily adjusted, thereby effectively achieving the adjustment of the performance of the final product. The method utilizes the elongated side chains in the hyperbranched structure to self-polymerize and form a spherical network structure, which can reduce the shrinkage rate of epoxy resin after high-temperature curing. The spherical network has a large free volume, which can greatly improve the spatial volume of the cross-linked network after the epoxy resin is cured, thereby increasing the toughness and impact strength of the epoxy resin material; secondly, the high density and rich active end groups at the ends of the hyperbranched polymer, such as hydroxyl and epoxy groups, can significantly improve the compatibility of HBPU with the epoxy resin matrix, and can improve the curing efficiency of the epoxy resin, accelerate the curing reaction, reduce the curing temperature, and reduce energy consumption. In addition, by utilizing the block structure of the polyurethane soft segment and hard segment, when the epoxy resin is cured, the molecular segments of the two are entangled with each other to form an independent cross-linked network structure, which increases the compatibility with the epoxy resin. When subjected to external force, the stress will be transmitted to each other in the independent cross-linked network structure, significantly improving the impact strength. Secondly, the microphase separation structure of the polyurethane is utilized to further improve the toughness of the epoxy resin.

[0021] Furthermore, the diol is at least one of polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polycaprolactone diol, polycarbonate diol and polybutylene terephthalate; the diisocyanate is at least one of isophorone diisocyanate, toluene diisocyanate, hexamethylene diisocyanate and 4,4-diphenylmethane diisocyanate, so that the diol and diisocyanate can react in any combination to generate a polyurethane prepolymer.

[0022] Furthermore, the molar ratio of the diol to the diisocyanate is (1-2):(2-4), which can make the diisocyanate account for a larger proportion during the prepolymerization reaction and generate an isocyanate-terminated linear prepolymer during the synthesis process.

[0023] Furthermore, in step S1, the stirring reaction temperature is 60-80°C and the time is 1-3 hours, which can make the diol and diisocyanate have a faster reaction rate within the reaction temperature in the prepolymerization stage. Secondly, within the reaction time, the diol and diisocyanate can react completely according to the proportion to generate an isocyanate-terminated linear prepolymer.

[0024] Furthermore, the dihydroxy alcoholamine is one of diethanolamine, diisopropanolamine, 4-(4-hydroxybutylamino)-1-butanol and 3,3'-dihydroxydiphenylamine, which can make the linear prepolymer react with the dihydroxy alcoholamine to generate a hyperbranched intermediate with an isocyanate group at one end and a dihydroxyl group at the other end. The reaction temperature of the linear prepolymer and the dihydroxy alcoholamine is 0-5°C, and the reaction time is 0.5-1h, which can make the terminal isocyanate group of the linear prepolymer react with the terminal amino group of the dihydroxy alcoholamine at this temperature during the reaction, and after the reaction time, the isocyanate group can react completely with the amino group.

[0025] Furthermore, in step S3, the temperature of the hyperbranched intermediate self-polymerization is 60-80°C and the time is 2-4 hours, so that the terminal isocyanate group in the hyperbranched intermediate can react with the terminal hydroxyl group in another branched intermediate to form a hyperbranched structure within the reaction temperature during the reaction. Secondly, after the reaction time, the hyperbranched intermediate can completely react to form a hyperbranched polyurethane; then the reaction time after adding the end-capping agent is 0.5-1 hour, so that the amino group in the end-capping agent can react with the excess isocyanate group in the hyperbranched polyurethane to prevent the hyperbranched polyurethane from further cross-linking reaction.

[0026] The present invention also discloses a modified epoxy resin, which is added with the hyperbranched polyurethane prepared above; the modified epoxy resin has good toughness, impact strength and curing efficiency, and the bending strength of the modified epoxy resin is 175-200MPa and the impact strength is 35-41kJ / m 2 .

[0027] Furthermore, the ratio of the epoxy resin, hyperbranched polyurethane, curing agent and catalyst is (100-200):(2-10):(10-20):(0.3-0.8) in terms of mass fractions, which enables the hyperbranched polyurethane to better modify the epoxy resin and increase the toughness and strength of the epoxy resin composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 is the reaction equation for synthesizing the hyperbranched polyurethane modified epoxy resin in the present invention;

[0030] Figure 2 is the infrared spectrum of hyperbranched polyurethane;

[0031] Figure 3 For hyperbranched polyurethane 1 H-NMR spectra (a) and 13 C-NMR spectrum (b);

[0032] Figure 4 The impact strength comparison results of the unmodified epoxy resin prepared in Comparative Example 1 and the hyperbranched polyurethane modified epoxy resin composite material prepared in Example 1 are shown in FIG.

[0033] Figure 5 The comparative results of the flexural strength of the unmodified epoxy resin prepared in Comparative Example 1 and the hyperbranched polyurethane modified epoxy resin composite material prepared in Example 1;

[0034] Figure 6 The differential scanning calorimetry results of the unmodified epoxy resin prepared in Comparative Example 1 and the hyperbranched polyurethane modified epoxy resin composite material prepared in Example 1;

[0035] Figure 7 The SEM images of the unmodified epoxy resin prepared in Comparative Example 1 and the hyperbranched polyurethane modified epoxy resin composite material prepared in Example 1, wherein a is unmodified and b is modified. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0037] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0038] Herein, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0039] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0040] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0041] like Figure 1 As shown, the present invention discloses a method for preparing a hyperbranched polyurethane, which specifically comprises the following steps:

[0042] 1) Preparation of linear prepolymer

[0043] A total of 27 to 64 parts of diol and diisocyanate are mixed and dissolved in 50 to 100 parts of a solvent in a molar ratio of (1 to 2): (2 to 4), and stirred at 300 to 500 r / min and 60 to 80° C. for 1 to 3 hours to obtain an isocyanate-terminated linear prepolymer.

[0044] The diol is one or a mixture of polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polycaprolactone glycol, polycarbonate glycol and polybutylene terephthalate.

[0045] The diisocyanate is one or more of isophorone diisocyanate, toluene diisocyanate, hexamethylene diisocyanate and 4,4-diphenylmethane diisocyanate.

[0046] The solvent is one or a mixture of methyl ethyl ketone, acetone, ethyl acetate, butyl acetate, toluene, N,N-dimethylformamide, tetrahydrofuran and dioxane.

[0047] 2) Preparation of hyperbranched intermediates

[0048] 12 to 25 parts of dihydroxy alcohol amine are added to an isocyanate-terminated linear prepolymer, and the mixture is stirred at 0 to 5° C. and a rotation speed of 300 to 500 r / min for 0.5 to 1 hour to obtain a hyperbranched intermediate.

[0049] Wherein, the dihydroxy alcohol amine is one of diethanolamine, diisopropanolamine, 4-(4-hydroxybutylamino)-1-butanol and 3,3'-dihydroxydiphenylamine.

[0050] 3) Preparation of hyperbranched polyurethane (HBPU)

[0051] After the hyperbranched intermediate is heated to 60-80°C, it is subjected to a self-polymerization reaction at a rotation speed of 300-500 r / min. After the reaction for 2-4 hours, 0.5-1 part of a capping agent is added and stirred for another 0.5-1 hour. After the reaction is completed, the solvent is removed by rotary evaporation to obtain a hyperbranched polyurethane (HBPU).

[0052] Wherein, the end-capping agent is one of 3-(aminomethyl)oxetane, 3-amino-3-methyloxetane, [3-(aminomethyl)oxetane-3-yl]methanol, 3-(methylamino)oxetane and 3-oxetaneamine, so that after the hyperbranched polyurethane ends the reaction, the end-capping agent reacts with the end of the polymer chain to terminate the polymer chain reaction, thereby avoiding excessive cross-linking of the hyperbranched polyurethane. Secondly, the specific functional groups introduced by the end-capping agent can play a certain role as a catalyst in the curing process of the modified epoxy resin composite material, thereby improving the curing efficiency.

[0053] In addition, the present invention also discloses a hyperbranched polyurethane prepared by the above method, and also discloses a modified epoxy resin prepared based on the above method. The preparation process of the modified epoxy resin is as follows:

[0054] 100-200 parts of epoxy resin and 2-10 parts of HBPU are mixed and stirred evenly, and then 10-20 parts of curing agent and 0.3-0.8 parts of catalyst are added thereto, mixed and stirred evenly at 60-80°C, and gradient curing is performed under the conditions of 120-150°C, 2-3h; 180-200°C, 1-2h; 210-250°C, 0.5-1h, to obtain the modified epoxy resin material. The modified epoxy resin material has a flexural strength of 175-200MPa and an impact strength of 35-41kJ / m 2 The curing temperature is 105-115°C and the curing efficiency is 20%-30%.

[0055] The temperature gradient curing process can reduce the generation of internal stress during curing, reduce the risk of cracking and deformation of the composite material, and the gradient curing can ensure a tighter interface bonding in the composite material, which is conducive to long-term stability.

[0056] Among them, the curing agent is diethylenetriamine, tetrahydropyridine, polyetheramine, linolenic acid diamine, phthalic anhydride, acetic anhydride, maleic anhydride and methyltetrahydrophthalic anhydride, which can react with the epoxy groups in the epoxy resin during the curing process to form a chemical cross-linking structure, thereby enhancing the mechanical strength and chemical resistance of the resin.

[0057] The catalyst is one of dimethylaniline, triethanolamine, piperidine, trimethylammonium chloride, trimethylphenylammonium, tetrabutylammonium bromide and tin divinylhexanoic acid, which can reduce the activation energy of the curing reaction when the epoxy composite material is cured, accelerate the reaction rate of the epoxy resin and the curing agent, thereby shortening the curing time. The catalyst can also improve the reaction efficiency, making the curing process more uniform and thorough, thereby improving the consistency of the final product.

[0058] In addition, the present invention also discloses a method for modifying the hyperbranched polyurethane and epoxy composite material prepared by the above method. After testing, the bending strength of the modified epoxy resin is enhanced by at least 180%, the impact strength is enhanced by at least 240%, and the curing efficiency is improved by at least 20%. It can be seen that the hyperbranched polyurethane modified epoxy resin can significantly increase the toughness and impact strength of the modified epoxy resin, improve the curing efficiency of the modified epoxy resin, and save energy consumption. The bending test of the bending strength of the modified epoxy resin is determined according to the GB / T 9341-2008 standard, and the impact strength test is carried out according to GB / T 2571-1995, using a simply supported beam pendulum impact tester.

[0059] The invention discloses a hyperbranched polyurethane and a preparation method thereof. The preparation method first synthesizes an isocyanate-terminated linear prepolymer, then adds dihydroxy alcohol amine to synthesize a hyperbranched intermediate at low temperature, then raises the temperature to self-polymerize the hyperbranched intermediate for a period of time, and finally adds a capping agent to obtain a hyperbranched polyurethane (HBPU). The shrinkage rate of epoxy resin after high-temperature curing can be reduced by utilizing the elongated side chains and spherical network structure in the hyperbranched structure; at the same time, the spherical network has a very large free volume, which can greatly improve the spatial volume of the cross-linked network after the epoxy resin is cured, thereby increasing the toughness and impact strength of the epoxy resin material; secondly, the high density and abundant active end groups at the ends of the hyperbranched polymer, such as hydroxyl and epoxy groups, can significantly improve the compatibility of HBPU with an epoxy resin matrix, and can improve the curing efficiency of the epoxy resin, accelerate the curing reaction, reduce the curing temperature, and reduce energy consumption. In addition, by utilizing the block structure of the polyurethane soft segment and hard segment, when the epoxy resin is cured, the molecular segments of the two are entangled with each other to form a cross-linked network structure that is independent of each other, which increases the compatibility with the epoxy resin. When subjected to external forces, stresses are transmitted to each other in the cross-linked network structure that is independent of each other, significantly improving the impact strength. Secondly, by utilizing the polyurethane microphase separation structure, the toughness of the epoxy resin is further improved. And the hyperbranched polyurethane has the advantages of mild preparation process conditions, simple and easy control, low cost, and easy to scale up preparation.

[0060] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0061] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0062] Example 1

[0063] A method for preparing a hyperbranched polyurethane comprises the following steps:

[0064] 1) Preparation of linear prepolymer

[0065] A total of 27 parts of polyethylene glycol and isophorone diisocyanate were mixed in a molar ratio of 1:2 and dissolved in 50 parts of acetone, and stirred at 60° C. at a speed of 300 r / min for 3 hours to obtain an isocyanate-terminated linear prepolymer.

[0066] 2) Preparation of hyperbranched intermediate monomers

[0067] 12 parts of diethanolamine were added to the isocyanate-terminated linear prepolymer and stirred at 0°C and 300 r / min for 0.5 h to obtain a hyperbranched intermediate monomer.

[0068] 3) Preparation of hyperbranched polyurethane polyol (HBPU)

[0069] After the hyperbranched intermediate monomer in 2) is heated to 60°C, it is subjected to a self-polymerization reaction at a speed of 300 r / min. After the reaction for 4 hours, 0.5 parts of 3-(aminomethyl)oxetane are added and stirred for another 0.5 hours. After the reaction is completed, acetone is removed by rotary evaporation to obtain a hyperbranched polyurethane polyol (HBPU), i.e., a hyperbranched polyurethane.

[0070] A method for preparing a modified epoxy resin is prepared using the hyperbranched polyurethane prepared in this embodiment, and the specific steps are:

[0071] First, 100 parts of epoxy resin and 2 parts of HBPU are mixed and stirred evenly, and then 10 parts of diethylenetriamine and 0.3 parts of dimethylaniline are added thereto. After mixing and stirring evenly at 60°C, gradient curing is carried out under the conditions of 120°C, 2h; 180°C, 1h; 210°C, 1h to obtain a modified epoxy resin material.

[0072] The mechanical and thermal properties of the modified epoxy resin material were tested. The results showed that compared with the unmodified epoxy resin material, the flexural strength of the modified epoxy resin material was 179.01MPa and the impact strength was 35.23kJ / m 2 The curing temperature is 114°C, among which the bending strength is increased by 185%, the impact strength is increased by 242%, and the curing efficiency is improved by 25%.

[0073] Example 2

[0074] A method for preparing a hyperbranched polyurethane comprises the following steps:

[0075] 1) Preparation of linear prepolymer

[0076] A total of 64 parts of polypropylene glycol and isophorone diisocyanate were mixed in a molar ratio of 2:4 and dissolved in 100 parts of tetrahydrofuran, and stirred at 80° C. at a speed of 500 r / min for 1 hour to obtain an isocyanate-terminated linear prepolymer.

[0077] 2) Preparation of hyperbranched intermediate monomers

[0078] 25 parts of diethanolamine were added to the isocyanate-terminated linear prepolymer and stirred at 5° C. and 500 r / min for 1 hour to obtain a hyperbranched intermediate monomer.

[0079] 3) Preparation of hyperbranched polyurethane polyol (HBPU)

[0080] After the hyperbranched intermediate monomer in 2) is heated to 80°C, it is subjected to a self-polymerization reaction at a speed of 500 r / min. After reacting for 2 hours, 1 part of 3-amino-3-methyloxetane is added and stirred for another 0.5 hour. After the reaction is completed, tetrahydrofuran is removed by rotary evaporation to finally obtain a hyperbranched polyurethane (HBPU).

[0081] A method for preparing a modified epoxy resin is prepared using the hyperbranched polyurethane prepared in this embodiment, and the specific steps are:

[0082] First, 200 parts of epoxy resin and 10 parts of HBPU are mixed and stirred evenly, and then 20 parts of tetrahydropyridine and 0.8 parts of triethanolamine are added thereto. After mixing and stirring evenly at 80°C, gradient curing is carried out under the conditions of 150°C, 3h; 200°C, 1h; 250°C, 0.5h to obtain a modified epoxy resin material.

[0083] The mechanical and thermal properties of the modified epoxy resin material were tested. The results showed that compared with the unmodified epoxy resin material, the flexural strength of the modified epoxy resin material was 176.51MPa and the impact strength was 39.24kJ / m 2 The curing temperature is 109°C, among which the bending strength is increased by 207%, the impact strength is increased by 281%, and the curing efficiency is improved by 28%.

[0084] Example 3

[0085] A method for preparing a hyperbranched polyurethane comprises the following steps:

[0086] 1) Preparation of linear prepolymer

[0087] A total of 30 parts of polytetrahydrofuran diol and toluene diisocyanate were mixed in a molar ratio of 1:2.2 and dissolved in 60 parts of ethyl acetate, and stirred at 65° C. at a speed of 350 r / min for 2 hours to obtain an isocyanate-terminated linear prepolymer.

[0088] 2) Preparation of hyperbranched intermediate monomers

[0089] 15 parts of diisopropanolamine were added to the isocyanate-terminated linear prepolymer and stirred at 2° C. and 350 r / min for 0.5 h to obtain a hyperbranched intermediate monomer.

[0090] 3) Preparation of hyperbranched polyurethane polyol (HBPU)

[0091] After the hyperbranched intermediate monomer in 2) is heated to 65°C, it is subjected to self-polymerization at a speed of 350 r / min. After reacting for 3 hours, 0.5 parts of [3-(aminomethyl)oxetan-3-yl]methanol are added and stirred for another 0.5 hours. After the reaction is completed, ethyl acetate is removed by rotary evaporation to obtain a hyperbranched polyurethane (HBPU).

[0092] A method for preparing a modified epoxy resin is prepared using the hyperbranched polyurethane prepared in this embodiment, and the specific steps are:

[0093] First, 150 parts of epoxy resin and 6 parts of HBPU are mixed and stirred evenly, and then 15 parts of polyetheramine and 0.5 parts of trimethylammonium chloride are added thereto. After mixing and stirring evenly at 70°C, gradient curing is carried out under the conditions of 130°C, 2.5h; 180°C, 1.5h; 220°C, 0.5h to obtain a modified epoxy resin material.

[0094] The mechanical and thermal properties of the modified epoxy resin material were tested. The results showed that compared with the unmodified epoxy resin material, the flexural strength of the modified epoxy resin material was 182.78MPa and the impact strength was 38.42kJ / m 2 The curing temperature is 111°C, among which the bending strength is increased by 191%, the impact strength is increased by 273%, and the curing efficiency is improved by 27%.

[0095] Example 4

[0096] A method for preparing a hyperbranched polyurethane comprises the following steps:

[0097] 1) Preparation of linear prepolymer

[0098] A total of 35 parts of polycaprolactone diol and hexamethylene diisocyanate were mixed in a molar ratio of 1.2:2.4 and dissolved in 70 parts of butyl acetate, and stirred at 70° C. at a speed of 400 r / min for 2 hours to obtain an isocyanate-terminated linear prepolymer.

[0099] 2) Preparation of hyperbranched intermediate monomers

[0100] 17 parts of 4-(4-hydroxybutylamino)-1-butanol were added to the isocyanate-terminated linear prepolymer and stirred at 3° C. and 400 r / min for 0.5 h to obtain a hyperbranched intermediate monomer.

[0101] 3) Preparation of hyperbranched polyurethane polyol (HBPU)

[0102] After the hyperbranched intermediate monomer in 2) is heated to 70°C, it is subjected to a self-polymerization reaction at a rotation speed of 4 r / min. After the reaction for 2.5 hours, 0.6 parts of 3-(methylamino)oxetane are added and stirred for another hour. After the reaction is completed, butyl acetate is removed by rotary evaporation to obtain a hyperbranched polyurethane (HBPU).

[0103] A method for preparing a modified epoxy resin is prepared using the hyperbranched polyurethane prepared in this embodiment, and the specific steps are:

[0104] First, 180 parts of epoxy resin and 8 parts of HBPU are mixed and stirred evenly, and then 16 parts of linolenic acid diamine and 0.6 parts of trimethylphenylammonium are added thereto. After mixing and stirring evenly at 70°C, gradient curing is carried out under the conditions of 13°C, 2h; 200°C, 1h; 230°C, 0.5h to obtain a modified epoxy resin material.

[0105] The mechanical and thermal properties of the modified epoxy resin material were tested. The results showed that compared with the unmodified epoxy resin material, the flexural strength of the modified epoxy resin material was 179.55MPa and the impact strength was 38.93kJ / m 2 The curing temperature is 106°C, among which the bending strength is increased by 186%, the impact strength is increased by 278%, and the curing efficiency is improved by 30%.

[0106] Example 5

[0107] A method for preparing a hyperbranched polyurethane comprises the following steps:

[0108] 1) Preparation of linear prepolymer

[0109] A total of 46 parts of polycarbonate diol and 4,4-diphenylmethane diisocyanate were mixed in a molar ratio of 1.5:3.1 and dissolved in 80 parts of N,N-dimethylformamide, and stirred at 400 r / min and 70° C. for 2.5 hours to obtain an isocyanate-terminated linear prepolymer.

[0110] 2) Preparation of hyperbranched intermediate monomers

[0111] 18 parts of 3,3'-dihydroxydiphenylamine were added to the isocyanate-terminated linear prepolymer and stirred at 4°C and 400 r / min for 1 hour to obtain a hyperbranched intermediate monomer.

[0112] 3) Preparation of hyperbranched polyurethane polyol (HBPU)

[0113] After the hyperbranched intermediate monomer in 2) is heated to 75°C, it is subjected to self-polymerization reaction at a speed of 350 r / min. After the reaction for 3 hours, 0.7 parts of 3-oxetaneamine is added and stirred for another 0.5 hours. After the reaction is completed, N,N-dimethylformamide is removed by rotary evaporation, and finally a hyperbranched polyurethane (HBPU) is obtained.

[0114] A method for preparing a modified epoxy resin is prepared using the hyperbranched polyurethane prepared in this embodiment, and the specific steps are:

[0115] First, 160 parts of epoxy resin and 5 parts of HBPU are mixed and stirred evenly, and then 14 parts of linolenic acid diamine and 0.6 parts of trimethylphenylammonium are added thereto. After mixing and stirring evenly at 60°C, gradient curing is carried out under the conditions of 140°C, 2h; 180°C, 1h; 250°C, 0.5h to obtain a modified epoxy resin material.

[0116] The mechanical and thermal properties of the modified epoxy resin material were tested. The results showed that compared with the unmodified epoxy resin material, the flexural strength of the modified epoxy resin material was 183.32MPa and the impact strength was 37.39kJ / m 2 , the curing temperature is 115°C, among which the flexural strength of the modified epoxy resin is enhanced by 192%, the impact strength is enhanced by 263%, and the curing efficiency is improved by 24%.

[0117] Example 6

[0118] A method for preparing a hyperbranched polyurethane comprises the following steps:

[0119] 1) Preparation of linear prepolymer

[0120] A total of 50 parts of polybutylene terephthalate and 4,4-diphenylmethane diisocyanate were mixed in a molar ratio of 1.3:2.6 and dissolved in 65 parts of dioxane, and stirred at 450 r / min and 60° C. for 2 hours to obtain an isocyanate-terminated linear prepolymer.

[0121] 2) Preparation of hyperbranched intermediate monomers

[0122] 20 parts of diisopropanolamine were added to the isocyanate-terminated linear prepolymer and stirred at 2° C. and 300 r / min for 1 hour to obtain a hyperbranched intermediate monomer.

[0123] 3) Preparation of hyperbranched polyurethane polyol (HBPU)

[0124] After the hyperbranched intermediate monomer in 2) is heated to 70°C, it is subjected to self-polymerization reaction at a speed of 400 r / min. After the reaction for 3 hours, 0.8 parts of [3-(aminomethyl)oxetan-3-yl]methanol is added and stirred for another 0.5 hours. After the reaction is completed, dioxane is removed by rotary evaporation to finally obtain a hyperbranched polyurethane (HBPU).

[0125] A method for preparing a modified epoxy resin is prepared using the hyperbranched polyurethane prepared in this embodiment, and the specific steps are:

[0126] First, 150 parts of epoxy resin and 5 parts of HBPU are mixed and stirred evenly, and then 16 parts of phthalic anhydride and 0.5 parts of tin divinyl hexanoic acid are added thereto. After mixing and stirring evenly at 70°C, gradient curing is carried out under the conditions of 130°C, 2.5h; 180°C, 1h; 240°C, 0.5h to obtain the modified epoxy resin material.

[0127] The mechanical and thermal properties of the modified epoxy resin material were tested. The results showed that compared with the unmodified epoxy resin material, the flexural strength of the modified epoxy resin material was 183.95MPa and the impact strength was 40.79kJ / m 2 The curing temperature is 108°C, among which the flexural strength of the modified epoxy resin is increased by 193%, the impact strength is increased by 296%, and the curing efficiency is improved by 29%.

[0128] Example 7

[0129] A method for preparing a hyperbranched polyurethane comprises the following steps:

[0130] 1) Preparation of linear prepolymer

[0131] A total of 60 parts of polytetrahydrofuran diol and isophorone diisocyanate were mixed and dissolved in 85 parts of acetone at a molar ratio of 1.6:3.3, and stirred at 60° C. at a speed of 300 r / min for 1.5 hours to obtain an isocyanate-terminated linear prepolymer.

[0132] 2) Preparation of hyperbranched intermediate monomers

[0133] 19 parts of diethanolamine were added to the isocyanate-terminated linear prepolymer and stirred at 4° C. and 300 r / min for 1 hour to obtain a hyperbranched intermediate monomer.

[0134] 3) Preparation of hyperbranched polyurethane polyol (HBPU)

[0135] After the hyperbranched intermediate monomer in 2) is heated to 70°C, it is subjected to self-polymerization reaction at a rotation speed of 300 r / min. After reacting for 2 hours, 1 part of 3-amino-3-methyloxetane is added and stirred for another hour. After the reaction is completed, acetone is removed by rotary evaporation to finally obtain a hyperbranched polyurethane (HBPU).

[0136] A method for preparing a modified epoxy resin is prepared using the hyperbranched polyurethane prepared in this embodiment, and the specific steps are:

[0137] First, 120 parts of epoxy resin and 4 parts of HBPU are mixed and stirred evenly, and then 12 parts of methyltetrahydrophthalic anhydride and 1.5 parts of tetrabutylammonium bromide are added thereto. After mixing and stirring evenly at 65°C, gradient curing is carried out under the conditions of 140°C, 2h; 200°C, 1h; 210°C, 0.5h to obtain a modified epoxy resin material.

[0138] The mechanical and thermal properties of the modified epoxy resin material were tested. The results showed that compared with the unmodified epoxy resin material, the flexural strength of the modified epoxy resin material was 186.46MPa and the impact strength was 39.04kJ / m 2 The curing temperature is 112°C, among which the flexural strength of the modified epoxy resin is enhanced by 197%, the impact strength is enhanced by 279%, and the curing efficiency is improved by 26%.

[0139] Example 8

[0140] A method for preparing a hyperbranched polyurethane comprises the following steps:

[0141] 1) Preparation of linear prepolymer

[0142] A total of 62 parts of polytetrahydrofuran diol and hexamethylene diisocyanate were mixed and dissolved in 75 parts of N,N-dimethylformamide at a molar ratio of 1.7:3.4, and stirred at 70° C. at a speed of 400 r / min for 1 hour to obtain an isocyanate-terminated linear prepolymer.

[0143] 2) Preparation of hyperbranched intermediate monomers

[0144] 21 parts of 4-(4-hydroxybutylamino)-1-butanol were added to the isocyanate-terminated linear prepolymer and stirred at 2° C. and 400 r / min for 0.5 h to obtain a hyperbranched intermediate monomer.

[0145] 3) Preparation of hyperbranched polyurethane polyol (HBPU)

[0146] After the hyperbranched intermediate monomer in 2) is heated to 65°C, it is subjected to self-polymerization reaction at a speed of 350 r / min. After the reaction for 3 hours, 0.8 parts of 3-(aminomethyl)oxetane is added and stirred for another hour. After the reaction is completed, N,N-dimethylformamide is removed by rotary evaporation, and finally a hyperbranched polyurethane (HBPU) is obtained.

[0147] A method for preparing a modified epoxy resin is prepared using the hyperbranched polyurethane prepared in this embodiment, and the specific steps are:

[0148] First, 180 parts of epoxy resin and 9 parts of HBPU are mixed and stirred evenly, and then 14 parts of methyltetrahydrophthalic anhydride and 0.8 parts of tetrabutylammonium bromide are added thereto. After mixing and stirring evenly at 70°C, gradient curing is carried out under the conditions of 150°C, 1.5h; 220°C, 1h; 250°C, 0.5h to obtain a modified epoxy resin material.

[0149] The mechanical and thermal properties of the modified epoxy resin material were tested. The results showed that compared with the unmodified epoxy resin material, the flexural strength of the modified epoxy resin material was 188.97MPa and the impact strength was 40.17kJ / m 2 The curing temperature is 109°C, among which the flexural strength of the modified epoxy resin is enhanced by 201%, the impact strength is enhanced by 290%, and the curing efficiency is improved by 28%.

[0150] Comparative Example 1

[0151] The difference between this comparative example and Example 1 is that when preparing the epoxy resin material, HBPU is not added, and an unmodified epoxy resin material is obtained.

[0152] Figure 2 This is the infrared spectrum of hyperbranched polyurethane. It can be seen from the figure that 3340cm -1NH or OH stretching vibration peak; 1730cm -1 is the stretching vibration peak of the carbonyl (C=O) in the urethane group, 1530 cm -1 It is the bending vibration peak of the amino group (NH) in the urethane group; 1637cm -1 The stretching vibration peak of the carbonyl group (C=O) in the urea group is at 2270 cm -1 There is no characteristic absorption peak of isocyanate (NCO) group nearby, indicating that NCO is completely reacted. The urea group is the branching point of HBPU, which indicates that the polyurethane has been successfully synthesized and has a hyperbranched structure.

[0153] Figure 3 The NMR spectrum of hyperbranched polyurethane is shown in Figure 1. In the hydrogen spectrum (a), the NMR peaks are assigned as follows: δ = 0.83-1.34 ppm is the characteristic peak of protons on -CH2CH2CH2CH2-, δ = 3.42 ppm is the characteristic peak of protons on -COONH-, and δ = 1.58-1.76 ppm is the characteristic peak of protons on -CH2CH2OH. 13 As shown in the C-NMR spectrum (b), the attribution of its nuclear magnetic resonance peaks is as follows: δ = 26.83 ppm is the characteristic peak of carbon in -CH2CH2CH2CH2-, δ = 70.25 ppm is the characteristic peak of carbon in -COONH-, and δ = 34.28~36.53 ppm is the characteristic peak of carbon in -CH2CH2OH, which indicates that the polyurethane has been successfully synthesized and has a hyperbranched structure.

[0154] Figure 4 The impact strength comparison results of the unmodified epoxy resin prepared in comparative example 1 and the hyperbranched polyurethane modified epoxy resin composite material prepared in example 1 are shown in the figure. It can be seen from the figure that the impact strength of the epoxy resin composite material modified by hyperbranched polyurethane is greatly improved compared with the pure epoxy resin system without adding HBPU. This shows that HBPU can increase the toughness of EP after curing. The main reason is that during the curing process, HBPU increases the freedom of the macromolecular chain in the three-dimensional network, thereby accelerating the movement between molecules. The internal soft segment causes the spline to deform to a certain extent during the impact process, absorbs part of the impact energy, and enhances the impact performance of the HBPU / EP epoxy composite material.

[0155] Figure 5The comparative results of the bending strength of the unmodified epoxy resin prepared in comparative example 1 and the hyperbranched polyurethane modified epoxy resin composite material prepared in Example 1 show that the bending strength of the epoxy resin composite material modified by the hyperbranched polyurethane is greatly improved compared with the pure epoxy resin system without adding HBPU. This shows that HBPU can increase the mechanical properties of the cured EP. After the hyperbranched polyurethane is introduced into the epoxy resin, the spline can better tolerate the additional load during the bending deformation process, making it more stable and durable when bearing heavy loads, thereby reducing the risk of fracture.

[0156] Figure 6 The differential scanning calorimetry (DSC) results of the unmodified epoxy resin prepared in Comparative Example 1 and the hyperbranched polyurethane modified epoxy resin composite material prepared in Example 1 show that, compared with the curing temperature of the pure epoxy resin system, the curing temperature of the modified HBPU / EP epoxy composite material is significantly reduced, indicating that the hydroxyl group (-OH) in HBPU can promote curing or reduce the curing temperature to accelerate the curing rate.

[0157] Figure 7 This is a SEM image of the unmodified epoxy resin prepared in Comparative Example 1 and the hyperbranched polyurethane modified epoxy resin composite material prepared in Example 1. As can be seen from the figure, the fracture morphology of the HBPU / EP epoxy composite impact specimen was observed by SEM. Figure 7 (a) is the cross-sectional morphology of the epoxy system without HBPU added. Its surface is smooth and flat, showing obvious brittle fracture characteristics. This is because the cross-linking density of the epoxy resin is large after curing. This high-density cross-linking structure leads to enhanced intermolecular interactions, making the movement between molecular segments very difficult. Since the movement of the segments is restricted, the ability to transmit and disperse fractures through segment movement is weak. Therefore, when impact force acts on this resin material, the segments cannot be effectively dispersed and broken. It will show greater brittleness and be more prone to brittle fracture. With the addition of HBPU, the fracture of the epoxy composite sample shows more rough, fibrous and irregular holes, with obvious toughness fracture characteristics ( Figure 7 (b)). This is because the addition of HBPU reduces the cross-linking density of epoxy resin, making the epoxy resin more flexible.

[0158] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing a hyperbranched polyurethane, characterized in that: The following steps are involved: S1: mixing a diol and a diisocyanate and dissolving them in a solvent, stirring and reacting them to obtain an isocyanate-terminated linear prepolymer; S2: adding dihydroxy alcohol amine to the linear prepolymer to obtain a hyperbranched intermediate after reaction; S3: allowing the hyperbranched intermediate to undergo self-polymerization, then adding a capping agent, and continuing the reaction to obtain a hyperbranched polyurethane.

2. The method for preparing a hyperbranched polyurethane according to claim 1, wherein The diol is at least one of polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polycaprolactone glycol, polycarbonate glycol and polybutylene terephthalate; the diisocyanate is at least one of isophorone diisocyanate, toluene diisocyanate, hexamethylene diisocyanate and 4,4-diphenylmethane diisocyanate.

3. The method for preparing a hyperbranched polyurethane according to claim 1, characterized in that: The molar ratio of the diol to the diisocyanate is (1-2):(2-4).

4. The method for preparing a hyperbranched polyurethane according to claim 1, characterized in that: In step S1, the stirring reaction temperature is 60-80° C. and the time is 1-3 hours.

5. The method for preparing a hyperbranched polyurethane according to claim 1, characterized in that: The dihydroxy alcohol amine is one of diethanolamine, diisopropanolamine, 4-(4-hydroxybutylamino)-1-butanol and 3,3'-dihydroxydiphenylamine; the reaction temperature of the linear prepolymer and the dihydroxy alcohol amine is 0-5°C, and the reaction time is 0.5-1h.

6. The method for preparing a hyperbranched polyurethane according to claim 1, characterized in that: In step S3, the temperature of the self-polymerization of the hyperbranched intermediate is 60-80° C. and the time is 2-4 hours; and then the reaction time after adding the end-capping agent is 0.5-1 hour.

7. A hyperbranched polyurethane, characterized in that It is prepared by the method according to any one of claims 1 to 6.

8. A modified epoxy resin, characterized in that A hyperbranched polyurethane prepared in claim 7 is added; the bending strength of the modified epoxy resin is 175-200MPa, and the impact strength is 35-41kJ / m 2 .

9. The method for preparing a modified epoxy resin as claimed in claim 8, characterized in that: The modified epoxy resin is obtained by uniformly mixing a hyperbranched polyurethane prepared in claim 5, an epoxy resin, a curing agent and a catalyst, and then heat curing the mixture.

10. The method for preparing a modified epoxy resin according to claim 9, characterized in that: Calculated by weight, the ratio of the epoxy resin, hyperbranched polyurethane, curing agent and catalyst is (100-200):(2-10):(10-20):(0.3-0.8).

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