Polyurethane-modified epoxy resin, and preparation method and application thereof

Abstract

The application provides a polyurethane modified epoxy resin and a preparation method and application thereof. The resin comprises an NCO-terminated polyurethane, an amine curing agent and an epoxy resin, wherein the NCO-terminated polyurethane has a specific structure and is prepared by reacting a dihydric phenol and / or an alcohol with an isocyanate with an NCO functional group of greater than or equal to 2. The application also provides a preparation method and application of the resin. The resin can increase flexibility without reducing the mechanical properties of the epoxy resin, improve the reaction speed and final curing degree of the resin, reduce the use of catalysts and reduce production costs.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a polyurethane-modified epoxy resin, its preparation method, and its application. Background Technology

[0002] Epoxy resin (EP) possesses advantages such as good adhesion, high chemical stability, strong resistance to high and low temperatures, and low curing shrinkage. It is a class of thermosetting resins with excellent overall performance and has been widely used in adhesives, coatings, and other fields since its introduction to the domestic market in the late 1950s. After curing, epoxy resin forms a highly cross-linked network structure, leading to increased internal stress, brittleness, and poor impact resistance. Toughening modification is necessary to improve its overall application performance.

[0003] There are numerous methods for toughening and modifying epoxy resins, but polyurethane (PU)-modified epoxy resin (EP) materials all suffer from incomplete compatibility between PU and EP. The amount of PU added cannot be too high, resulting in unsatisfactory toughening effects. Traditional methods for toughening and modifying epoxy resins with polyurethane mainly fall into two categories: one is to incorporate hydroxyl-terminated polyurethane into the epoxy resin for blending, utilizing the flexibility of the polyurethane molecular chain to toughen the epoxy resin; the other is to utilize the reaction between the isocyanate groups in the polyurethane structure and the hydroxyl groups in the epoxy resin structure to significantly improve the adhesive and mechanical properties of the toughened system. The first method, being a physical blend, has relatively poor compatibility. The second method, utilizing the reaction between hydroxyl groups and NCO, suffers from insufficient reaction due to the low hydroxyl content and significant steric hindrance in the macromolecular epoxy, resulting in incomplete compatibility.

[0004] In summary, the current field of polyurethane-modified toughened epoxy resin still faces the problem of poor compatibility between polyurethane and epoxy resin, which leads to a decrease in the mechanical strength of the toughened resin and urgently needs to be addressed. Summary of the Invention

[0005] To address the above technical problems, one objective of this invention is to provide a polyurethane-modified epoxy resin that can increase flexibility without reducing the mechanical properties of the epoxy resin, while simultaneously improving the resin's reaction rate and final curing degree, reducing the use of catalysts, and lowering production costs.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows:

[0007] A polyurethane-modified epoxy resin, the resin comprising the following components: NCO-terminated polyurethane; an amine curing agent; and an epoxy resin; wherein the NCO-terminated polyurethane has the following structure:

[0008]

[0009] One or more of the following, where n is an integer greater than or equal to 1.

[0010] In this invention, the special structure of bisphenols or alcohols and the isocyanate selected to correspond with amines give -NCO-terminated polyurethanes a structure completely similar to epoxy resins, making them fully compatible with epoxy resins. This allows for improvements in the toughness and impact resistance of epoxy resins without sacrificing their inherent strength. Simultaneously, the NCO-terminated polyurethanes preferentially react with amine curing agents, releasing a large amount of heat, further promoting the reaction between the amine curing agents and epoxy resins. This allows for segmented reaction, segmented exothermic processes, and eventual complete curing without the addition of a catalyst, resulting in a high-performance polymer material.

[0011] In one embodiment of the present invention, the NCO-terminated polyurethane is prepared by reacting a diphenol and / or an alcohol with an isocyanate having ≥2 NCO functional groups; preferably, the diphenol and / or alcohol contains 2,2-diphenylpropane in its structure.

[0012]

[0013] One or more of the following; preferably, the isocyanate is selected from aromatic and / or aliphatic isocyanates, preferably one or more of 4,4'-diisocyanate diphenylmethane MDI, 4,4'-diisocyanate dicyclohexylmethane HMDI, toluene diisocyanate TDI, and isoflurone diisocyanate IPDI; preferably, the molar ratio of the NCO group of the isocyanate to the OH group of the diphenol and / or alcohol is (1.2-2):1.

[0014] In one embodiment of the present invention, the amine curing agent is selected from diamines, preferably the residue structure of the diamine after removing the amino functional group is the same as the residue structure of the isocyanate after removing the NCO functional group.

[0015] In one embodiment of the present invention, the epoxy resin is selected from bisphenol A epoxy resin, preferably one or more of E44, E51, and E54.

[0016] In one embodiment of the present invention, the -NH2 in the amine curing agent and the -NCO in the NCO-terminated polyurethane, and the epoxy resin... The molar ratio is 1:(0.1-0.3):(0.9-0.7).

[0017] Another object of the present invention is to provide a method for preparing polyurethane-modified epoxy resin.

[0018] A method for preparing the above-mentioned polyurethane modified epoxy resin, the method comprising the following steps: reacting a diphenol and / or an alcohol with an isocyanate having ≥2 NCO functional groups, and then mixing it with an epoxy resin to prepare component A, wherein an amine curing agent is used as component B.

[0019] In one embodiment of the present invention, the reaction temperature is 60-120°C and the reaction time is 2-3 hours.

[0020] Another object of the present invention is to provide a use of polyurethane-modified epoxy resin.

[0021] The use of a polyurethane-modified epoxy resin, wherein the resin is the resin described above or the resin prepared by the method described above, and the polyurethane-modified epoxy resin is used in composite materials.

[0022] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows:

[0023] The modified -NCO-terminated polyurethane has a similar structure to epoxy resin and good compatibility, which can improve the toughness and impact resistance of epoxy resin without sacrificing its strength. Detailed Implementation

[0024] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not limit the scope of the invention.

[0025] The isocyanates and amine curing agents with at least two NCO functional groups in the following examples and comparative examples are all products sold by Wanhua Chemical, with a main component content of greater than or equal to 97%, and other raw materials were obtained through commercial channels and are chemically pure.

[0026] The main testing methods of this invention are as follows:

[0027] Glass transition temperature: DSC test, Discovery DSC2500 / 250 / 25, temperature range 25-200℃, heating rate 10℃ / min, two scans.

[0028] Impact strength: GB / T 1843-2008 Determination of impact strength of plastic cantilever beams;

[0029] Tensile strength and elongation at break: GB / T1040.1-2006 Determination of tensile properties of plastics, with a tensile rate of 5 mm / min.

[0030] Example 1

[0031] 1 mol of bisphenol A and 1.2 mol of HMDI were added to a reactor, nitrogen gas was introduced, the temperature was raised to 60°C, and the mixture was stirred for 3 hours. After cooling, the product was discharged to obtain -NCO-terminated polyurethane, which was then mixed with 3.6 mol of E51 to obtain component A.

[0032] HMDA is the component B.

[0033] Mix 2 mol of component B with the above component A until homogeneous, centrifuge at 5000 r / min for 3 min to remove bubbles, pour into a PTFE mold, cure at 80℃ for 2 h, and then remove for performance testing.

[0034] Example 2

[0035] 1 mol of bisphenol A bis(2-hydroxypropyl) ether and 2 mol of IPDI were added to a reactor, nitrogen gas was introduced, the temperature was raised to 100°C, and the mixture was stirred for 2.5 hours. The mixture was then cooled and discharged to obtain -NCO-terminated polyurethane, which was then mixed with 4.7 mol of E51 to obtain component A.

[0036] IPDA is part B.

[0037] Mix 3.35 mol of component B with the above component A until homogeneous, centrifuge at 5000 r / min for 3 min to remove bubbles, pour into a PTFE mold, cure at 80℃ for 2 h, and then remove for performance testing.

[0038] Example 3

[0039] 1 mol of bisphenol A bis(hydroxypropyl) ether and 1.5 mol of MDI were added to a reactor, nitrogen gas was introduced, the temperature was raised to 120°C, and the mixture was stirred for 2 hours. The mixture was then cooled and discharged to obtain -NCO-terminated polyurethane, which was then mixed with 4 mol of E44 to obtain component A.

[0040] MDA is component B.

[0041] Mix 2.5 mol of component B with the above-mentioned component A until homogeneous. Centrifuge at 5000 r / min for 3 min to remove bubbles. Pour the mixture into a PTFE mold and cure at 80℃ for 2 h. Remove the mixture and perform performance testing.

[0042] Example 4

[0043] 1 mol of bisphenol A and 1.2 mol of HMDI were added to a reactor, nitrogen gas was introduced, the temperature was raised to 80°C, and the mixture was stirred for 3 hours. After cooling, the product was discharged to obtain -NCO-terminated polyurethane, which was then mixed with 3.6 mol of E51 to obtain component A.

[0044] IPDA is part B.

[0045] Mix 2 mol of component B with the above component A until homogeneous, centrifuge at 5000 r / min for 3 min to remove bubbles, then pour into a PTFE mold and cure at 100℃ for 2.5 h. Remove and perform performance testing.

[0046] Comparative Example 1

[0047] Compared with Example 1, the difference is that component A of this comparative example is E51 resin, which does not contain -NCO-terminated polyurethane.

[0048] Mix 1 mol HMDA and 2 mol of the above component A evenly, centrifuge at 5000 r / min for 3 min to remove bubbles, pour into a PTFE mold, cure at 80℃ for 2 h, and then take it out for performance testing.

[0049] Comparative Example 2

[0050] Compared with Example 3, the difference is that the -NCO-terminated polyurethane is prepared from a common diol, and a diamine with the same residue structure as the isocyanate residue structure after removing the functional groups is not used.

[0051] 1 mol of ethylene glycol and 1.5 mol of MDI were added to a reactor, nitrogen gas was introduced, the temperature was raised to 120°C, and the mixture was stirred for 2 hours. After cooling, the product was discharged to obtain -NCO-terminated polyurethane, which was then mixed with 4 mol of E44 to obtain component A.

[0052] MDA is component B.

[0053] Mix 2.5 mol of component B with the above component A until homogeneous, centrifuge at 5000 r / min for 3 min to remove bubbles, pour into a PTFE mold, cure at 80℃ for 2 h, and then remove for performance testing.

[0054] The test results are shown in the table below:

[0055]

[0056] It is readily understood that the above embodiments are merely illustrative examples for clear explanation and do not imply that the invention is limited thereto. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A polyurethane-modified epoxy resin, characterized in that, The resin comprises the following components: NCO-terminated polyurethane; Amine curing agent; Epoxy resin; The NCO-terminated polyurethane has the following structure: One or two of them, where n is an integer greater than or equal to 1.

2. The resin according to claim 1, characterized in that, NCO-terminated polyurethane is prepared by reacting a diol with an isocyanate having an NCO functional group of 2. The diol is 、 One or two of them.

3. The resin according to claim 2, characterized in that, The isocyanate is selected from aromatic and / or aliphatic isocyanates; The molar ratio of the NCO group of the isocyanate to the OH group of the diol is (1.2-2):

1.

4. The resin according to claim 3, characterized in that, The isocyanate is selected from one or more of 4,4'-diisocyanate diphenylmethane MDI, 4,4'-diisocyanate dicyclohexylmethane HMDI, toluene diisocyanate TDI, and isoflurone diisocyanate IPDI.

5. The resin according to claim 1 or 2, characterized in that, The amine curing agent is selected from diamines.

6. The resin according to claim 5, characterized in that, The residue structure of the primary amine of the amine curing agent after removing the amino functional group is the same as the residue structure of the isocyanate after removing the NCO functional group.

7. The resin according to claim 1, characterized in that, The epoxy resin is selected from bisphenol A epoxy resin.

8. The resin according to claim 7, characterized in that, The epoxy resin is selected from one or more of E44, E51, and E54.

9. The resin according to claim 1, characterized in that, In amine curing agents, -NH2 and NCO-terminated polyurethanes contain -NCO, and in epoxy resins... The molar ratio is 1:(0.1-0.3):(0.9-0.7).

10. A method for preparing the polyurethane-modified epoxy resin according to any one of claims 1-9, characterized in that, The method includes the following steps: reacting a diol with an isocyanate having an NCO functional group of 2, and then mixing it with an epoxy resin to prepare component A, with an amine curing agent as component B.

11. The method according to claim 10, characterized in that, The reaction temperature is 60-120℃, and the reaction time is 2-3 hours.

12. Use of a polyurethane-modified epoxy resin, wherein the resin is the resin according to any one of claims 1-9, or the resin prepared by the method according to claim 10 or 11, and the polyurethane-modified epoxy resin is used in composite materials.

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