A polyurea acrylate oligomer containing protected groups and its preparation method and application

Abstract

The invention discloses a polyurea acrylate oligomer containing a protected group and a preparation method and application thereof, belonging to the technical field of polymer materials. The invention introduces a protecting group into the polyurea acrylate oligomer, so as to ensure the stability of the resin during synthesis, storage and printing. The photocurable resin prepared by using the polyurea acrylate oligomer containing the protected group has good storage stability, and the viscosity does not change substantially after being placed for one month.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to a polyurea acrylate oligomer containing a protected group and a preparation method and application thereof. Background Art

[0002] Photocuring is usually a process that uses visible or ultraviolet light as a light source to quickly gel a liquid photocurable resin into a cross-linked material through free radical or cationic polymerization. It has outstanding characteristics such as high efficiency, wide adaptability, and good environmental performance. This has also made photocuring technology widely concerned and applied in the fields of coatings, inks, adhesives, photoresists, and 3D printing. From the perspective of chemical composition, photocurable resins mainly include several components such as oligomers, reactive diluents, photoinitiators, and light absorbers. Among them, oligomers are the main factor determining the performance of photocurable resin materials. Oligomers mainly include polyester acrylates, polyurethane / polyurea acrylates, epoxy acrylates, etc. According to the curing method, it can be divided into two forms: direct photocuring and photocuring plus post-treatment. Generally, the cross-linking density of the polymer network obtained by direct photocuring is high, and the mechanical properties of the material are poor, which is specifically manifested as brittleness and poor toughness. The post-treatment process after photocuring can adjust the network structure of the polymer, thereby improving the mechanical properties of the material. The Chinese patent application 202110870234.1 discloses a series of polyurethane acrylate polymers. After photocuring, the large hindered urea bonds will dissociate when heated, and the exposed isocyanate groups will react with water, urea bonds or characteristic functional groups containing active hydrogen on the side chains, causing the molecular structure, cross-linking density and other network structure characteristics of the material to change, ultimately changing the mechanical properties of the material and greatly improving its toughness.

[0003] The photosensitive resin disclosed in the above patent changes the material properties by triggering the change of network structure through heating. During the synthesis, storage and printing process of the photosensitive resin, due to the change of external ambient temperature, the hindered urea bond with large steric hindrance will dissociate and react with the active hydrogen exposed to the outside. The resin is prone to gelation / cross-linking, which brings about the problem of resin stability. This will cause great losses and product unreliability for large-scale industrial applications. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a polyurea acrylate oligomer containing a protected group and a preparation method and application thereof. The present invention introduces a protecting group in the process of synthesizing the polyurea acrylate oligomer, which can ensure that it does not participate in the reaction during the synthesis process, facilitate the introduction of some highly active active hydrogen groups (such as amino groups, hydroxyl groups, etc.), and ensure the storage stability of the resin after synthesis; and after light curing, the protected group can be deprotected by external stimulation, exposing active hydrogen, thereby attacking the large sterically hindered urea bond in the main chain, so that the network cross-linking structure and the thermodynamic properties of the material are essentially changed.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] One of the technical solutions of the present invention:

[0007] A polyurea acrylate oligomer containing a protected group, the structural formula of which is as follows:

[0008]

[0009] Wherein, X1 is hydrogen or methyl;

[0010] X2 is tert-butyl, isopropyl, piperidine or pyrazole;

[0011] X3 is a protected group on the side chain, which can dissociate to generate a characteristic group containing active hydrogen (including hydroxyl, amino, carboxyl, etc.) under heating, light, humidity change or acid-base change, wherein the hydroxyl group can be protected by forming ketal or acetal, the amino group can be protected by forming tert-butyl carbamate or imine, and the carboxyl group can be protected by forming tert-butyl ester or o-nitrobenzene; X3 includes

[0012] In the present invention, a protected characteristic group X3 is introduced into the side chain of the polyurea acrylate oligomer, and the protected characteristic group X3 can dissociate to generate characteristic groups containing active hydrogen such as hydroxyl, amino, carboxyl, and thiol. The dissociation of active hydrogen can be controlled by different conditions, thereby better ensuring the stability of the resin during synthesis, storage, and printing. In short, the present invention protects active hydrogen and then releases it on demand by applying certain external stimuli as needed, thereby improving the thermodynamic properties of the photocurable printing material, while ensuring high selectivity in the resin synthesis process and storage stability, further expanding the application scope of photocuring technology.

[0013] It should be noted that in the above structural formula It does not represent a carbon chain, and its specific structure depends on different monomer raw materials, that is, it represents a polyurethane prepolymer formed by a diol containing X3 functional monomer, a common diol and isocyanate.

[0014] Preferably, the polyurea acrylate oligomer containing a protected group comprises the following structure: in

[0015] in

[0016] in

[0017] in

[0018] The second technical solution of the present invention:

[0019] The present invention also provides a method for preparing the polyurea acrylate oligomer containing protected groups, comprising the following steps:

[0020] The diisocyanate, the diol containing the X3 functional monomer and the common diol are mixed, and reacted at room temperature to 80°C for 1 to 6 hours to generate a polyurethane prepolymer. The NCO value of the system is confirmed by the di-n-butylamine method to determine the reaction end point. The diol is mainly used to adjust the molecular weight and molecular structure of the polyurethane prepolymer obtained in the first step (the wavy part of the obtained product is the polyurethane prepolymer formed by the diol containing the X3 functional monomer, the common diol and the isocyanate). The reaction route is as follows:

[0021]

[0022] The polyurethane prepolymer is mixed with a hindered amine acrylate Mix and react at 50-100° C. for 1-6 hours to generate the polyurea acrylate oligomer containing protected groups. The reaction route is as follows:

[0023]

[0024] The diol containing X3 functional monomer includes N-(2,3-dihydroxypropyl) carbamic acid tert-butyl ester N-(2,3-Dihydroxypropyl)isobutyraldimine Ethyl 1,1-dimethyl-3-[(2,3-dihydroxypropyl)thio]propionate (+)-2,3-O-isopropylidene-L-threitol and 3-[(2,3-dihydroxypropyl)thio]-2-nitrophenyl ethyl ester One of them.

[0025] Preferably, the molar ratio of the diol containing the X3 functional monomer to the ordinary diol is 1:(0-10), and the molar number of the diol is not 0;

[0026] The molar ratio of the diisocyanate to the diol containing the X3 functional monomer and the total active hydrogen in the common diol is (1.1-10):1.

[0027] Preferably, the diisocyanate includes one of hexamethylene diisocyanate, toluene diisocyanate, p-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, isophorone diisocyanate and 1,5-naphthalene diisocyanate;

[0028] The common diol includes one of polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polycaprolactone glycol and polyethylene adipate glycol;

[0029] The hindered amine acrylate includes one of tert-butylaminoethyl methacrylate, tert-butylaminoethyl acrylate, isopropylaminoethyl methacrylate, isopropylaminoethyl acrylate, piperidineaminoethyl acrylate or piperidineaminoethyl methacrylate.

[0030] The third technical solution of the present invention:

[0031] The present invention also provides a photocurable resin prepared from the polyurea acrylate oligomer containing protected groups. The photocurable resin prepared by the present invention can be used as a 3D printing material.

[0032] The fourth technical solution of the present invention:

[0033] The present invention also provides a method for preparing the photocurable resin, comprising mixing the polyurea acrylate oligomer containing protected groups with a reactive diluent, adding a photoinitiator and an inhibitor to obtain a mixture, photocuring the mixture to remove the protective groups, and then treating the mixture at 50 to 140° C. for 1 to 10 hours to obtain the photocurable resin.

[0034] Preferably, the method for removing the protecting group includes heating, light, humidity change or acid-base change. Different protecting groups have different removal methods, and the reaction scheme is as follows:

[0035]

[0036] The tert-butyl carbamate group needs acidic conditions to remove the isobutylene group to obtain the amino group; the imine group needs certain humidity conditions to remove the aldehyde group to obtain the amino group; the ketal structure needs to be heated under acidic conditions and the presence of water to remove acetone to obtain the hydroxyl group; the tert-butyl ester group can remove the isobutylene group under acidic and heated conditions to obtain the carboxyl group; the o-nitrophenyl ester group can remove nitrobenzaldehyde under ultraviolet light to obtain the carboxyl group.

[0037] Preferably, the weight ratio of the reactive diluent to the polyurea acrylate oligomer containing protected groups is (0.05-0.5):1, more preferably (0.2-0.4):1;

[0038] The weight ratio of the photoinitiator to the polyurea acrylate oligomer containing protected groups is (0.01-0.05):1, more preferably 0.01:1;

[0039] The weight ratio of the polymerization inhibitor to the polyurea acrylate oligomer containing protected groups is (0.0005-0.002):1, and more preferably 0.002:1.

[0040] Reactive diluents can be used to adjust the viscosity of the resin system and the mechanical properties of the sample after curing, and photoinitiators and inhibitors can adjust the kinetics of the photopolymerization reaction.

[0041] The reactive diluent is a low-viscosity monofunctional or multifunctional acrylate or methacrylate compound, for example, the reactive diluent is tetrahydrofuranyl acrylate, isobornyl acrylate, 2-phenoxyethyl acrylate or isooctyl acrylate.

[0042] In the present invention, there is no particular limitation on the types of the photoinitiator and the polymerization inhibitor, and any common photoinitiator and polymerization inhibitor in the art may be used, such as the photoinitiator 819 and the polymerization inhibitor p-hydroxyanisole.

[0043] The light source used should match the photoinitiator and can be an ultraviolet or visible light source.

[0044] The polyurea acrylate oligomer containing protected groups forms a cross-linked network after photoinitiated polymerization, and then is treated under certain conditions (heating, illumination, humidity change or acid-base change) to remove the protecting groups, exposing active hydrogen groups, and then placed under certain temperature conditions, the hindered urea bonds in the network will dissociate, react with the active hydrogen groups on the side chains, and obtain a new polymer network. On the one hand, the introduction of protecting groups can ensure the stability of the resin during synthesis, use and storage; on the other hand, active hydrogen groups can be obtained through subsequent deprotection, reacting with the hindered urea bonds in the network to form a cross-linked network of polyacrylate-polyurethane, so that the mechanical properties of the sample are significantly changed compared to before the heating, illumination, humidity change or acid-base change treatment, and the toughness is improved.

[0045] The fifth technical solution of the present invention:

[0046] The present invention also provides application of the polyurea acrylate oligomer containing protected groups in preparing photocurable resin.

[0047] The photocurable resin prepared by using the polyurea acrylate oligomer containing protected groups of the present invention has good storage stability, and the viscosity does not change substantially after being placed for one month.

[0048] Compared with the prior art, the present invention has the following advantages and technical effects:

[0049] 1. The present invention introduces a protective group into the polyurea acrylate oligomer, which can ensure the stability of the resin during synthesis, storage and printing;

[0050] 2. The protecting groups in the polyurea acrylate oligomer of the present invention can be deprotected under certain conditions (heating, light, humidity changes or acid-base changes), and react with the dynamic bonds in the network to regulate and improve the performance of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0052] Figure 1 The viscosity change results of the polyurea acrylate oligomer containing protected groups in Example 1 at different times;

[0053] Figure 2 The viscosity change results of the polyurea acrylate oligomer containing protected groups at different times in Example 2;

[0054] Figure 3The viscosity change results of the polyurea acrylate oligomer containing protected groups at different times in Example 3;

[0055] Figure 4 The viscosity change results of the polyurea acrylate oligomer containing protected groups at different times in Example 4;

[0056] Figure 5 The viscosity change results of the polyurea acrylate oligomer without protected groups in Comparative Example 1 at different times. DETAILED DESCRIPTION

[0057] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0058] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0059] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0060] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0061] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0062] All raw materials used in the embodiments of the present invention are purchased from the market. As an example, all raw materials used in the present invention are purchased from Aladdin, wherein the CAS number of polyethylene adipate glycol is: 24938-37-2.

[0063] The technical solution of the present invention is further illustrated by the following embodiments.

[0064] Example 1

[0065] 1) Add 0.5 mol of polytetramethylene glycol (PTMEG, M w =1000) and 1 mol of p-toluene diisocyanate (TDI, M w =174), and 0.3 mol of tert-butyl N-(2,3-dihydroxypropyl)carbamate, the temperature was controlled at 50°C, the reaction was carried out for 4 hours, and the NCO value of the system was confirmed by the di-n-butylamine method to determine the reaction endpoint, thereby obtaining a polyurethane prepolymer;

[0066] 2) Continue to add 0.4 mol of isopropylaminoethyl methacrylate to the reactor through the constant pressure funnel, control the temperature at 80°C during the addition, keep the temperature and continue the reaction for 4 hours after the addition is completed, and determine the end point of the reaction by confirming the NCO value of the system by the di-n-butylamine method to obtain a polyurea acrylate oligomer containing a protected group ( in ).

[0067] Take 10g of the above-mentioned polyurea acrylate oligomer containing protected groups, add 3g of reactive diluent tetrahydrofuran acrylate, add 0.1g of photoinitiator 819, 0.02g of inhibitor p-hydroxyanisole, obtain a liquid light-cured resin precursor, the light source is a high-pressure mercury lamp, cast a sample bar that meets the ASTM D412 standard in a transparent mold, and test the uniaxial tensile performance; soak the sample bar in a hydrochloric acid solution for 10 hours to remove the protecting group, then place it in a 120°C baking oven and process for 6 hours to test the uniaxial tensile performance. The elongation at break of the sample bar that meets the ASTM D412 standard before processing (i.e. the material directly cast) is 100%, and the breaking strength is 3MPa; the elongation at break of the sample bar that meets the ASTM D412 standard after processing (i.e. the material after removing the protecting group) is 600%, and the breaking strength is 30MPa.

[0068] The viscosity change of the liquid photocurable resin precursor placed at 50°C for different time periods was measured by a viscometer. Figure 1 As shown, the viscosity does not change substantially after one month of storage.

[0069] Example 2

[0070] 1) Add 0.5 mol of polypropylene glycol (PPG, M w =600) and 1 mol of hexamethylene diisocyanate (HDI, M w=168), and 0.25 mol of N-(2,3-dihydroxypropyl)isobutyraldimine, the temperature is controlled at 50°C, the NCO value of the system is confirmed by the di-n-butylamine method to determine the reaction endpoint, and a polyurethane prepolymer is obtained;

[0071] 2) Continue to add 0.5 mol of isopropylaminoethyl acrylate to the reactor through the constant pressure funnel, control the temperature at 50°C during the addition, keep the temperature after the addition is completed and continue the reaction, and determine the end point of the reaction by confirming the NCO value of the system by the di-n-butylamine method to obtain a polyurea acrylate oligomer containing a protected group ( in ).

[0072] Take 10g of the above-mentioned polyurea acrylate oligomer containing protected groups, add 2g of active diluent isobornyl acrylate, 0.1g of photoinitiator 819, and 0.02g of inhibitor p-hydroxyanisole to obtain a liquid light-curable resin precursor. The light source is a high-pressure mercury lamp. A sample bar that meets the ASTM D412 standard is cast in a transparent mold to test the unidirectional tensile performance. The above-mentioned sample bar is treated at a constant temperature and humidity with an air humidity of more than 50% for 24 hours, and then placed in a 70°C oven for 6 hours to test the unidirectional tensile performance. The elongation at break before treatment is 200%, and the breaking strength is 12MPa; the elongation at break after treatment is 500%, and the breaking strength is 40MPa.

[0073] The viscosity change of the liquid photocurable resin precursor placed at 50°C for different time periods was measured by a viscometer. Figure 2 As shown, the viscosity does not change substantially after one month of storage.

[0074] Example 3

[0075] 1) Add 0.5 mol of polycaprolactone diol (PCL, M w =1500) and 1 mol of hexamethylene diisocyanate (HDI, M w =168), and 0.25 mol of (+)-2,3-O-isopropylidene-L-threitol, the temperature is controlled at 50°C, the NCO value of the system is confirmed by the di-n-butylamine method to determine the reaction endpoint, and a polyurethane prepolymer is obtained;

[0076] 2) Continue to add 0.5 mol of tert-butylaminoethyl methacrylate to the reactor through the constant pressure funnel, control the temperature at 50°C during the addition, keep the temperature to continue the reaction after the addition is completed, and determine the end point of the reaction by confirming the NCO value of the system by the di-n-butylamine method to obtain a polyurea acrylate oligomer containing a protected group ( in ).

[0077] Take 10g of the above-mentioned polyurea acrylate oligomer containing protected groups, add 2g of active diluent 2-phenoxyethyl acrylate, 0.1g of photoinitiator 819, and 0.02g of inhibitor p-hydroxyanisole to obtain a liquid light-curable resin precursor. The light source is a high-pressure mercury lamp. A sample bar that meets the ASTM D412 standard is cast in a transparent mold to test the unidirectional tensile performance. The above-mentioned sample bar is immersed in a weakly acidic solution, and then placed in a constant temperature and humidity with an air humidity of more than 50% and a temperature of 60°C for 1 hour, and then transferred to an oven at 80°C for 6 hours to test the unidirectional tensile performance. The elongation at break before treatment is 350%, and the breaking strength is 8MPa; the elongation at break after treatment is 1000%, and the breaking strength is 40MPa.

[0078] The viscosity change of the liquid photocurable resin precursor placed at 50°C for different time periods was measured by a viscometer. Figure 3 As shown, the viscosity does not change substantially after one month of storage.

[0079] Example 4

[0080] 1) Add 0.5 mol of polyethylene glycol (PEG, M w =2,000) and 1 mol of isophorone diisocyanate (IPDI, M w =222), and 0.25 mol of 3-[(2,3-dihydroxypropyl)thio] o-nitrophenyl ethyl ester, the temperature was controlled at 50° C., the NCO value of the system was confirmed by the di-n-butylamine method to determine the reaction endpoint, and a polyurethane prepolymer was obtained;

[0081] 2) Continue to add 0.5 mol of isopropylaminoethyl acrylate to the reactor through the constant pressure funnel, control the temperature at 50°C during the addition, keep the temperature after the addition is completed and continue the reaction, and determine the end point of the reaction by confirming the NCO value of the system by the di-n-butylamine method to obtain a polyurea acrylate oligomer containing a protected group ( in ).

[0082] Take 10g of the above-mentioned polyurea acrylate oligomer containing protected groups, add 4g of active diluent isooctyl acrylate, 0.1g of photoinitiator 819, and 0.02g of inhibitor p-hydroxyanisole to obtain a liquid light-curable resin precursor. The light source is a high-pressure mercury lamp. A sample bar that meets the ASTM D412 standard is cast in a transparent mold to test the unidirectional tensile performance. The above-mentioned sample bar is treated with light for 0.5 hours in the UV curing phase, and then placed in a 100°C oven for 6 hours to test the unidirectional tensile performance. The elongation at break before treatment is 100%, and the breaking strength is 4MPa; the elongation at break after treatment is 600%, and the breaking strength is 30MPa.

[0083] The viscosity change of the liquid photocurable resin precursor placed at 50°C for different time periods was measured by a viscometer. Figure 4 As shown, the viscosity does not change substantially after one month of storage.

[0084] Comparative Example 1 (no protecting group)

[0085] 1) Add 0.5 mol of polyethylene glycol (PEG, M w =2,000) and 1 mol of isophorone diisocyanate (IPDI, M w =222), and 0.25 mol of 3-[(2,3-dihydroxypropyl)thio]propionic acid, the temperature is controlled to 50° C., and the reaction is completed by titration to obtain a polyurethane prepolymer;

[0086] 2) Continue to add 0.5 mol of isopropylaminoethyl acrylate to the reactor through the constant pressure funnel, control the temperature at 50°C during the addition, keep the temperature to continue the reaction after the addition is completed, and determine the end point of the reaction by confirming the NCO value of the system by the di-n-butylamine method to obtain a polyurea acrylate oligomer containing carboxyl groups (unprotected)

[0087] Take 10 g of the above-mentioned polyurea acrylate oligomer containing carboxyl groups, add 4 g of active diluent isooctyl acrylate, 0.1 g of photoinitiator 819, and 0.02 g of inhibitor p-hydroxyanisole to obtain a liquid photocurable resin precursor.

[0088] The viscosity change of the liquid photocurable resin precursor placed at 50°C for different time periods was measured by a viscometer. Figure 5 As shown, the viscosity changes significantly after one day of storage, and the resin begins to gel after five days (the viscosity cannot be measured).

[0089] It can be seen from Example 4 and Comparative Example 1 that the present invention greatly improves the storage stability of the resin by introducing a protecting group.

[0090] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A polyurea acrylate oligomer containing a protected group, characterized in that: Includes the following structures: in or in 2. A method for preparing a polyurea acrylate oligomer containing a protected group according to claim 1, characterized in that: The following steps are involved: The diisocyanate, the diol containing the X3 functional monomer and the common diol are mixed and reacted at room temperature to 80° C. for 1 to 6 hours to generate a polyurethane prepolymer; The polyurethane prepolymer is mixed with the hindered amine acrylate, and reacted at 50 to 100° C. for 1 to 6 hours to generate the polyurea acrylate oligomer containing the protected group; The diol containing the X3 functional monomer includes N-(2,3-dihydroxypropyl)isobutyraldimine or (+)-2,3-O-isopropylidene-L-threitol.

3. The method for preparing a polyurea acrylate oligomer containing a protected group according to claim 2, characterized in that: The molar ratio of the diol containing the X3 functional monomer to the common diol is 1:(0-10), and the molar number of the common diol is not 0; The molar ratio of the diisocyanate to the diol containing the X3 functional monomer and the total active hydrogen in the common diol is (1.1-10):

1.

4. A photocurable resin, characterized in that: The method is prepared from the polyurea acrylate oligomer containing protected groups as claimed in claim 1.

5. A method for preparing the photocurable resin according to claim 4, characterized in that: The polyurea acrylate oligomer containing protected groups is mixed with a reactive diluent, and then a photoinitiator and an inhibitor are added to obtain a mixture, the mixture is photocured to remove the protective groups, and then treated at 50 to 140° C. for 1 to 10 hours to obtain the photocurable resin.

6. The method for preparing a photocurable resin according to claim 5, characterized in that: The weight ratio of the reactive diluent to the polyurea acrylate oligomer containing protected groups is (0.05-0.5):1; The weight ratio of the photoinitiator to the polyurea acrylate oligomer containing protected groups is (0.01-0.05):1; The weight ratio of the polymerization inhibitor to the polyurea acrylate oligomer containing protected groups is (0.0005-0.002):

1.

7. Use of the polyurea acrylate oligomer containing protected groups as claimed in claim 1 in the preparation of photocurable resins.

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