Thermosetting resin with high tensile strength and high elongation at break as well as preparation method and application of thermosetting resin

Abstract

The invention discloses thermosetting resin with high tensile strength and high elongation at break as well as a preparation method and application thereof, and relates to the technical field of organic polymer resin materials, the tensile strength range of the thermosetting resin prepared by the method is 39.5-50 MPa, the elongation at break reaches 300% or above, the thermosetting resin has excellent tensile strength and elongation at break, and the thermosetting resin has excellent mechanical properties and excellent mechanical properties. Compared with the existing modified epoxy resin and modified polyurethane resin, the thermosetting resin disclosed by the invention has the advantages that the compatibility of the two performances and the single performance level are obviously improved, the thermosetting resin has a relatively wide process window and construction manufacturability, and the thermosetting resin is applied to preparation of a surface protective coating material.

Description

Technical Field

[0001] The present invention relates to the technical field of organic polymer resin materials, and in particular to a thermosetting resin with high tensile strength and high elongation at break, a preparation method and applications thereof. Background Art

[0002] Stringent requirements on comprehensive mechanical properties are imposed on surface protection, modification, and functional coating materials for equipment, facilities, parts, components, tools, and equipment that generate continuous vibration, vibration deformation, and face the coupling effects of multiple factors such as airflow scouring. In order to maximize the service life of surface protective coating materials and reduce repair and maintenance costs, the coating materials in this coupling environment must have excellent mechanical strength and flexibility. On the one hand, excellent mechanical strength reduces damage caused by vibration and loss caused by airflow scouring. On the other hand, excellent flexibility can adapt to continuous vibration and deformation caused by vibration, and avoid surface coating cracking caused by structural deformation. In protective coating materials, the key component that determines their comprehensive mechanical properties is the resin material. Currently, the commonly used resin systems in surface protective coatings include epoxy resins, polyurethane resins, acrylic resins, etc. In order to achieve excellent mechanical properties and weather resistance, the resins in the above application scenarios are mostly thermosetting resins.

[0003] For applications facing continuous vibration, vibration deformation, and the coupling of multiple factors such as air scouring, resin materials need to have both excellent mechanical strength and flexibility. Specifically, they need to have high tensile strength, high bonding strength, and excellent elongation at break. In epoxy resin and polyurethane resin materials, tensile strength and elongation at break usually have a conjugated relationship, making it difficult to achieve the effect of combining the above two properties. For example, in epoxy resin, tensile strength and bonding strength can be enhanced by increasing the crosslinking density, but its elongation at break is low, and the resin is brittle after curing and prone to cracking in a vibrating environment. In polyurethane resin, high elongation at break can be achieved by using soft segment monomers, chain extenders, and isocyanate prepolymer designs, but its strength is low. After curing, the resin is prone to peeling and falling off under the influence of vibration and air scouring coupling factors.

[0004] Based on this, researchers have carried out modification work on epoxy resins and polyurethane resins to improve the elongation at break of epoxy resins and the tensile strength and bonding strength of polyurethane resins. Preliminary research has found that adding toughening resins to epoxy resins can effectively increase the elongation at break of the cured resin, but this has an adverse effect on its mechanical strength, curing time, and curing temperature. Increasing the content of soft and hard segment monomers in polyurethane resins and introducing initiators to increase crosslinking density can effectively improve the tensile strength and bonding strength of the cured resin, but its original elongation at break will show a significant attenuation, and the resin's working life will be shortened and its storage stability will decrease. Summary of the Invention

[0005] The purpose of the present invention is to solve the above technical problems and provide a thermosetting resin with high tensile strength and high elongation at break, as well as a preparation method and application thereof.

[0006] The present invention is achieved through the following technical solutions: A method for preparing a thermosetting resin having both high tensile strength and high elongation at break, characterized by comprising the following steps: S1, taking raw materials at a molar ratio of soft segment monomer to hard segment monomer of 2.2-1.8:1.0, mixing and obtaining a mixed resin, wherein the soft segment monomer includes a diol resin and a polyol resin; S2, adding toughening resin according to 20-30% of the total mass of the mixed resin to obtain the main resin; S3. Add initiator at 1.2-2.6% of the total mass of the main resin and blend; S4. Take any two isocyanate curing agents and compound them as a curing agent system; S5. Compounding the main resin containing the initiator in step S3 and the curing agent system in step S4 according to an isocyanate index R of 1.0 to 1.1.

[0007] Furthermore, in step S1, the mass ratio of the diol resin to the polyol resin is 4.69-4.71:1.

[0008] Furthermore, the diol resin includes PTMG2000, PTMG1000, PTMG650 and similar diol resins having a hydroxyl value of 50-180 mg▪KOH / g, and a water content of less than 0.35%; The polyol resin includes PCL305, PCL3087, PCL410 and similar polyol resins with a hydroxyl value of 200-320 mg ▪KOH / g, and a water content of less than 0.35%; The hard segment monomers include IPDI, TDI, a mixture of TDI and MDI, HDI and an isocyanate hard segment monomer with an NCO content of 35-55%, and a water content of less than 0.05%.

[0009] Furthermore, in step S2, the toughening resin includes a diol toughening resin or a polyol toughening resin, with a hydroxyl value ranging from 30 to 42 mg ▪KOH / g and a solid content ranging from 62 to 83%.

[0010] Furthermore, in step S3, the initiator is selected from any two of an organometallic tin initiator or a non-tin organometallic initiator. The organometallic tin initiator includes tin naphthenate and stannous octoate; the non-tin organometallic initiator includes lead naphthenate and bismuth naphthenate.

[0011] Furthermore, the mass ratio of the two initiators is 1:1.

[0012] Furthermore, in step S4, the mass ratio of the two isocyanate curing agents is 9-3:1.

[0013] Furthermore, the isocyanate curing agent includes a mixed trimer of TDI and HDI, an IPDI adduct, HB-75MX, and HT-100, with an NCO content ranging from 15 to 32% and a water content less than 0.0035.

[0014] The thermosetting resin is prepared by the above-mentioned preparation method.

[0015] Furthermore, the thermosetting resin meets the following performance indicators: Tensile strength: 39.5~50MPa; Elongation at break: ≥300%; Bonding strength: ≥17MPa.

[0016] The application of thermosetting resin in the preparation of surface protective coating material, wherein the thermosetting resin is a thermosetting resin prepared by the above-mentioned preparation method.

[0017] Furthermore, the main resin containing the initiator is evenly mixed with the curing agent system components, a diluent is added to adjust the viscosity to 21~27s, a resin coating is prepared by a spraying process, and the coating is obtained by heating and curing. The diluent includes one or more of xylene, propylene glycol methyl ether acetate, and nitro diluent.

[0018] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. In the present invention, a composite formula design is used to achieve a multi-stage improvement in the tensile strength and flexibility of the cured resin, as follows: By combining diols and polyols to form a composite soft segment monomer, the tensile strength of the cured resin can be effectively improved; by adding specific hard segment monomers, the tensile strength and elongation at break of the cured resin can be taken into account; by introducing diol / polyol toughening resin, the tensile strength of the cured resin can be maintained while its elongation at break is significantly improved; finally, by using a specific initiator, the side reactions in the polymerization process of the main resin are reduced, the polymerization reaction time of the main resin is shortened, and the active hydroxyl content is kept relatively stable, thereby reducing the adverse effects on the mechanical properties of the cured resin.

[0019] In the curing agent system, a compound curing agent is preferably used to maintain the tensile strength of the cured resin while further improving its elongation at break and achieving high bonding strength characteristics of the cured resin.

[0020] Second, the thermosetting resin prepared using this method exhibits excellent tensile strength and elongation at break. Compared to existing modified epoxy resins and modified polyurethane resins, this thermosetting resin achieves significant improvements in both compatibility and individual performance. The tensile strength of this thermosetting resin ranges from 39.5 to 50 MPa, while its elongation at break exceeds 300%.

[0021] 3. In the present invention, from the perspective of coating resin application, after the main resin is mixed with the curing agent system, the resin operation period can reach 3.5 hours or more, with a wide process window and construction processability, and the bonding strength of the cured resin reaches more than 17MPa.

[0022] 4. The present invention further proposes preferred composite soft segment monomers, hard segment monomers, toughening resins, composite initiators and composite curing agents to ensure that a thermosetting resin product with stable performance can be prepared.

[0023] 5. In the present invention, the thermosetting resin obtained by the preparation method has excellent tensile strength and elongation at break, which are significantly improved compared with the existing modified epoxy resin and modified polyurethane resin. It solves the problem that the tensile strength and elongation at break of commonly used resins in surface protective coatings are difficult to take into account and the mechanical properties cannot meet the application requirements of multiple factors such as vibration and erosion. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a picture of the thermosetting resin sample obtained in Example 1.

[0025] Figure 2 This is a picture of the resin coating sample after the thermosetting resin in spraying Example 1 is cured.

[0026] Figure 3 This is a graph of the cured coating specimen in the tensile strength-elongation at break test.

[0027] Figure 4 This is a picture of the specimen for the pull-off adhesion test (top view).

[0028] Figure 5 This is a picture of the specimen for the pull-off adhesion test (front view). DETAILED DESCRIPTION

[0029] The present invention will be further described in detail below with reference to examples and comparative examples, but the embodiments of the present invention are not limited thereto.

[0030] The raw material information involved in the following examples and comparative examples is as follows: 1. No. 1 diol resin PTMG2000, industrial grade; 2. No. 2 diol resin PTMG1000, industrial grade; 3. No. 3 diol resin PTMG650, industrial grade; 4. No. 1 polyol resin PCL305, industrial grade; 5. No. 2 polyol resin PCL3087, industrial grade; 6. No. ③ polyol resin PCL410, industrial grade; 7. No. ① hard segment monomer IPDI, industrial grade; 8. No. ② hard segment monomer TDI, industrial grade; 9. No. ③ hard segment monomers TDI and MDI, industrial grade; 10. No. ④ hard segment monomer HDI, industrial grade; 11. No. 1 isocyanate curing agent TDI and HDI mixed trimer, industrial grade; 12. No. 2 isocyanate curing agent IPDI adduct, industrial grade; 13. No. 3 isocyanate curing agent HB-75MX, industrial grade; 14. No. 4 isocyanate curing agent HT-100, industrial grade; 15. No. 1 Tin cyclohexane acid organic metal tin initiator, reagent grade; 16. No. 2 Stannous octoate organometallic tin initiator, reagent grade; 17. Lead naphthenate organometallic initiator No. ③, industrial grade; 18. Bismuth cyclohexane acid organometallic initiator No. ④, industrial grade; 19. Type a diol toughened resin, industrial grade; 20. Type b diol toughened resin, industrial grade; 21. C-type polyol toughening resin, industrial grade; 22. Xylene, propylene glycol methyl ether acetate, nitro compound diluent, industrial grade.

[0031] Example 1 This embodiment provides a method for preparing a thermosetting coating resin having both high tensile strength and high elongation at break, which relates to the technical field of organic polymer resin materials and specifically includes the following steps: Step 1: Weigh 840 g of diol resin No. 2 PTMG1000, 179 g of polyol resin No. 2 PCL3087, and 87.1 g of hard segment monomer No. 1 IPDI and mix them to obtain mixed resin 1, wherein diol resin No. 2 PTMG1000 and polyol resin No. 2 PCL3087 are soft segment monomers, and hard segment monomer No. 1 IPDI is a hard segment monomer. The soft segment: hard segment (molar ratio) in mixed resin 1 is 2.1:1.0, and the hydroxyl value is 52.5 mg▪ KOH / g.

[0032] Step 2: Weigh the toughening resin type a diol resin and the mixed resin 1 to compound to obtain the main resin A, the mass ratio of the two is 3:10, wherein the hydroxyl value of the type a diol resin is 39.6 mg▪KOH / g and the solid content is 64.2%.

[0033] Step 3: Blend the organometallic initiators ③ and ④ at a mass ratio of 1:1, and blend the composite organometallic initiator with the main resin at a mass ratio of 1:50.

[0034] Step 4: Weigh isocyanate curing agent No. ② and isocyanate curing agent No. ④ HT-100 for compounding, with the mass ratio of the two being 85:15.

[0035] Step 5: Mix the initiator-containing main resin A prepared in step 3 and the composite isocyanate curing agent prepared in step 4 to obtain a thermosetting resin. The composite isocyanate curing agent is added according to an isocyanate index R=1.1.

[0036] After uniformly mixing the above components, xylene, propylene glycol methyl ether acetate, and a nitro compound diluent were added to adjust the viscosity. A resin coating was prepared using a spraying process and cured at 50°C for 72 hours to obtain a cured coating sample. The coating was then sampled and tested for tensile strength, elongation at break, and other parameters.

[0037] Example 2 Compared with Example 1, this embodiment differs in that: Step 4: Weigh isocyanate curing agent No. ② and isocyanate curing agent No. ④ HT-100 for compounding, with the mass ratio of the two being 90:10.

[0038] The remaining steps are the same as those in Example 1.

[0039] Example 3 Compared with Example 1, this embodiment differs in that: Step 4: Weigh isocyanate curing agent No. ② and isocyanate curing agent No. ④ HT-100 for compounding, with the mass ratio of the two being 80:20.

[0040] The remaining steps are the same as those in Example 1.

[0041] Example 4 Compared with Example 1, this embodiment differs in that: Step 4: Weigh isocyanate curing agent No. ② and isocyanate curing agent No. ④ HT-100 for compounding, with the mass ratio of the two being 75:25.

[0042] The remaining steps are the same as those in Example 1.

[0043] Comparative Example 1 Compared with Example 1, this comparative example has the following differences: Step 4: Use isocyanate single curing agent No. 1.

[0044] The remaining steps are the same as those in Example 1.

[0045] Comparative Example 2 Compared with Example 1, this comparative example has the following differences: Step 4: Use isocyanate single curing agent No. ②.

[0046] The remaining steps are the same as those in Example 1.

[0047] Comparative Example 3 Compared with Example 1, this comparative example has the following differences: Step 4: Use isocyanate single curing agent No. 3 HB-75MX.

[0048] The remaining steps are the same as those in Example 1.

[0049] Comparative Example 4 Compared with Example 1, this comparative example has the following differences: Step 4: Use No. ④ isocyanate single curing agent HT-100.

[0050] The remaining steps are the same as those in Example 1.

[0051] Comparative Example 5 Compared with Example 1, this comparative example has the following differences: Step 2: Weigh toughening resin type B diol resin and mixed resin 1 to obtain main resin B, with a mass ratio of 3:10. Among them, the hydroxyl value of type B diol resin is 30.2 mg▪KOH / g, and the solid content is 82.5%.

[0052] Step 4: Use isocyanate single curing agent No. ②.

[0053] The remaining steps are the same as those in Example 1.

[0054] Comparative Example 6 Compared with Example 1, this comparative example has the following differences: Step 2: Weigh the toughening resin C type polyol resin and the mixed resin 1 to compound to obtain the main resin C, the mass ratio of the two is 3:10, wherein the hydroxyl value of the C type polyol resin is 41.8 mg▪KOH / g and the solid content is 65.4%.

[0055] Step 4: Use isocyanate single curing agent No. ②.

[0056] The remaining steps are the same as those in Example 1.

[0057] Comparative Example 7 Compared with Example 1, this comparative example has the following differences: Step 2: No toughening resin is added to the mixed resin 1.

[0058] Step 4: Use isocyanate single curing agent No. ②.

[0059] The remaining steps are the same as those in Example 1.

[0060] Comparative Example 8 The preparation method of the thermosetting coating resin in this comparative example specifically comprises the following steps: Step 1: Weigh 880g of diol resin No. 2 PTMG1000, 187g of polyol resin No. 2 PCL3087, and 87.1g of hard segment monomer No. 1 IPDI and mix them to obtain mixed resin 2, wherein diol resin No. 2 PTMG1000 and polyol resin No. 2 PCL3087 are soft segment monomers, and hard segment monomer No. 1 IPDI is a hard segment monomer. The soft segment: hard segment (molar ratio) in mixed resin 2 is 2.2:1.0, and the hydroxyl value is 53.9mg▪KOH / g.

[0061] Step 2: Blend the organometallic initiators ③ and ④ at a mass ratio of 1:1, and mix the composite initiator with the mixed resin at a mass ratio of 1:50.

[0062] Step 3: Use isocyanate single curing agent No. ②.

[0063] Step 4: Mix the prepared mixed resin 2 containing the initiator and the isocyanate curing agent, wherein the isocyanate curing agent is added according to the isocyanate index R=1.1.

[0064] After the above components are mixed evenly, xylene, propylene glycol methyl ether acetate, and nitro composite diluent are added to adjust the viscosity. The resin coating is prepared by spraying process, and the cured coating sample is obtained by curing at 50°C for 72 hours. Sample preparation and testing of items such as tensile strength and elongation at break are carried out.

[0065] Comparative Example 9 Compared with Comparative Example 8, this comparative example has the following differences: Step 1: Weigh 800 g of diol resin No. 2 PTMG1000, 170 g of polyol resin No. 2 PCL3087, and 87.1 g of hard segment monomer No. 1 IPDI and mix them to obtain mixed resin 3, wherein diol resin No. 2 PTMG1000 and polyol resin No. 2 PCL3087 are soft segment monomers, and hard segment monomer No. 1 IPDI is a hard segment monomer. The soft segment: hard segment (molar ratio) in mixed resin 3 is 2.0:1.0, and the hydroxyl value is 49.8 mg KOH / g.

[0066] Step 2: Blend the organometallic initiators ③ and ④ at a mass ratio of 1:1, and mix the composite initiator with the mixed resin at a mass ratio of 1:50.

[0067] Step 4: Mix the prepared mixed resin 3 containing the initiator and the isocyanate curing agent, wherein the isocyanate curing agent is added according to the isocyanate index R=1.1.

[0068] The remaining steps are the same as those in Comparative Example 8.

[0069] Comparative Example 10 Compared with Comparative Example 8, this comparative example has the following differences: Step 1: Weigh 760 g of diol resin No. 2 PTMG1000, 162 g of polyol resin No. 2 PCL3087, and 87.1 g of hard segment monomer No. 1 IPDI and mix them to obtain mixed resin 4, wherein diol resin No. 2 PTMG1000 and polyol resin No. 2 PCL3087 are soft segment monomers, and hard segment monomer No. 1 IPDI is a hard segment monomer. The soft segment: hard segment (molar ratio) in mixed resin 4 is 1.9:1.0, and the hydroxyl value is 44.1 mg▪ KOH / g.

[0070] Step 2: Blend the organometallic initiators ③ and ④ at a mass ratio of 1:1, and mix the composite initiator with the mixed resin at a mass ratio of 1:50.

[0071] Step 4: Mix the prepared mixed resin 4 containing the initiator and the isocyanate curing agent, wherein the isocyanate curing agent is added according to the isocyanate index R=1.1.

[0072] The remaining steps are the same as those in Comparative Example 8.

[0073] Comparative Example 11 Compared with Comparative Example 8, this comparative example has the following differences: Step 1: Weigh 720 g of diol resin No. 2 PTMG1000, 153 g of polyol resin No. 2 PCL3087, and 87.1 g of hard segment monomer No. 1 IPDI and mix them to obtain mixed resin 5, wherein diol resin No. 2 PTMG1000 and polyol resin No. 2 PCL3087 are soft segment monomers, and hard segment monomer No. 1 IPDI is a hard segment monomer. The soft segment: hard segment (molar ratio) in mixed resin 5 is 1.8:1.0, and the hydroxyl value is 43.6 mg KOH / g.

[0074] Step 2: Blend the organometallic initiators ③ and ④ at a mass ratio of 1:1, and mix the composite initiator with the mixed resin at a mass ratio of 1:50.

[0075] Step 4: Mix the prepared mixed resin 5 containing the initiator and the isocyanate curing agent, wherein the isocyanate curing agent is added according to the isocyanate index R=1.1.

[0076] The remaining steps are the same as those in Comparative Example 8.

[0077] Comparative Example 12 The preparation method of the thermosetting resin in this comparative example comprises the following steps: Step 1: Weigh a certain amount of diol resin No. ② PTMG1000 and hard segment monomer No. ① IPDI and mix them to obtain mixed resin 6, wherein diol resin No. ② PTMG1000 is a soft segment monomer, hard segment monomer No. ① IPDI is a hard segment monomer, and the molar ratio of active groups in mixed resin 6 is OH:NCO=2:1.

[0078] Step 2: Use organometallic tin single initiator No. ①, and the mass ratio of initiator to mixed resin 6 is 1:50.

[0079] Step 3: Use isocyanate single curing agent No. ②.

[0080] Step 4: Mix the prepared mixed resin 6 containing the initiator and the isocyanate curing agent, wherein the isocyanate curing agent is added according to the isocyanate index R=1.1.

[0081] The above components were mixed evenly, and xylene, propylene glycol methyl ether acetate, and nitro composite diluent were added to adjust the viscosity. The resin coating was prepared by spraying process, and cured at 50°C for 72h to obtain a cured coating sample. Sample preparation and testing of tensile strength, elongation at break, etc. were carried out.

[0082] Comparative Example 13 Compared with Comparative Example 12, this comparative example has the following differences: Step 2: Use organometallic tin single initiator No. ②, and the mass ratio of initiator to mixed resin 6 is 1:50.

[0083] The remaining steps are the same as those in Comparative Example 12.

[0084] Comparative Example 14 Compared with Comparative Example 12, this comparative example has the following differences: Step 2: Use organometallic single initiator No. ③, and the mass ratio of initiator to mixed resin 6 is 1:50.

[0085] The remaining steps are the same as those in Comparative Example 12.

[0086] Comparative Example 15 Compared with Comparative Example 12, this comparative example has the following differences: Step 2: Use organometallic composite initiators No. ③ and No. ④, and the mass ratio of the composite initiator to the mixed resin 6 is 1:50.

[0087] The remaining steps are the same as those in Comparative Example 12.

[0088] Comparative Example 16 This comparative example provides a method for preparing a thermosetting resin, comprising the following steps: Step 1: Weigh a certain amount of diol resin No. ② PTMG1000 and hard segment monomer No. ① IPDI and mix them to obtain mixed resin 6, wherein diol resin No. ② PTMG1000 is a soft segment monomer, hard segment monomer No. ① IPDI is a hard segment monomer, and the molar ratio of active groups in mixed resin 6 is OH:NCO=2:1.

[0089] Step 2: Use isocyanate single curing agent No. ②.

[0090] Step 3: Evenly mix the above mixed resin 6 and isocyanate single curing agent No. ②, and add the isocyanate curing agent according to the isocyanate index R=1.1.

[0091] The above components were mixed evenly, and xylene, propylene glycol methyl ether acetate, and nitro composite diluent were added to adjust the viscosity. The resin coating was prepared by spraying process, and cured at 50°C for 72h to obtain a cured coating sample. Sample preparation and testing of tensile strength, elongation at break, etc. were carried out.

[0092] Comparative Example 17 Compared with Comparative Example 16, this comparative example has the following differences: Step 1: Weigh a certain amount of diol resin No. ② PTMG1000 and hard segment monomer No. ② TDI and mix them to obtain mixed resin 7, wherein diol resin No. ② PTMG1000 is a soft segment monomer, and hard segment monomer No. ② TDI is a hard segment monomer. The molar ratio of active groups in mixed resin 7 is OH:NCO=2:1.

[0093] Step 3: Evenly mix the above mixed resin 7 and isocyanate single curing agent No. ②, and add the isocyanate curing agent according to the isocyanate index R=1.1.

[0094] The remaining steps are the same as those in Comparative Example 16.

[0095] Comparative Example 18 Compared with Comparative Example 16, this comparative example has the following differences: Step 1: Weigh a certain amount of diol resin No. ② PTMG1000 and hard segment monomer No. ③ and mix them to obtain mixed resin 8, wherein diol resin No. ② PTMG1000 is a soft segment monomer, and the molar ratio of active groups in mixed resin 8 is OH:NCO=2:1.

[0096] Step 3: Evenly mix the above mixed resin 8 and isocyanate single curing agent No. ②, and add the isocyanate curing agent according to the isocyanate index R=1.1.

[0097] The remaining steps are the same as those in Comparative Example 16.

[0098] Comparative Example 19 Compared with Comparative Example 16, this comparative example has the following differences: Step 1: Weigh a certain amount of diol resin No. ② PTMG1000 and hard segment monomer No. ④ and mix them to obtain mixed resin 9, wherein diol resin No. ② PTMG1000 is a soft segment monomer, and the molar ratio of active groups in mixed resin 9 is OH:NCO=2:1.

[0099] Step 3: Evenly mix the above mixed resin 9 and isocyanate single curing agent No. ②, and add the isocyanate curing agent according to the isocyanate index R=1.1.

[0100] The remaining steps are the same as those in Comparative Example 16.

[0101] Comparative Example 20 This comparative example provides a method for preparing a thermosetting resin, comprising the following steps: Step 1: Weigh a certain amount of No. 1 diol resin PTMG2000 and No. 1 hard segment monomer IPDI and mix them to obtain a mixed resin 10, wherein No. 1 diol resin PTMG2000 is a soft segment monomer, and the molar ratio of active groups in the mixed resin 10 is OH:NCO=2:1.

[0102] Step 2: Use isocyanate single curing agent No. ②.

[0103] Step 3: Evenly mix the above mixed resin 10 and isocyanate single curing agent No. ②, and add the isocyanate curing agent according to the isocyanate index R=1.1.

[0104] The above components were mixed evenly, and xylene, propylene glycol methyl ether acetate, and nitro composite diluent were added to adjust the viscosity. The resin coating was prepared by spraying process, and cured at 50°C for 72h to obtain a cured coating sample. Sample preparation and testing of tensile strength, elongation at break, etc. were carried out.

[0105] Comparative Example 21 Compared with Comparative Example 20, this comparative example has the following differences: Step 1: Weigh a certain amount of No. ③ diol resin PTMG650 and No. ① hard segment monomer IPDI and mix them to obtain a mixed resin 11, wherein No. ③ diol resin PTMG650 is a soft segment monomer, and the molar ratio of active groups in the mixed resin 11 is OH:NCO=2:1.

[0106] Step 3: Evenly mix the above mixed resin 11 and isocyanate single curing agent No. ②, and add the isocyanate curing agent according to the isocyanate index R=1.1.

[0107] The remaining steps are the same as those in Comparative Example 20.

[0108] Comparative Example 22 Compared with Comparative Example 20, this comparative example has the following differences: Step 1: Weigh a certain amount of polyol resin No. 1 PCL305 and hard segment monomer No. 1 IPDI and mix them to obtain a mixed resin 12, wherein polyol resin No. 1 PCL305 is a soft segment monomer, and the molar ratio of active groups in the mixed resin 12 is OH:NCO=2:1.

[0109] Step 3: Evenly mix the above mixed resin 12 and isocyanate single curing agent No. ②, and add the isocyanate curing agent according to the isocyanate index R=1.1.

[0110] The remaining steps are the same as those in Comparative Example 20.

[0111] Comparative Example 23 Compared with Comparative Example 20, this comparative example has the following differences: Step 1: Weigh a certain amount of polyol resin No. ② PCL3087 and hard segment monomer No. ① IPDI and mix them to obtain a mixed resin 13, wherein polyol resin No. ② PCL3087 is a soft segment monomer, and the molar ratio of active groups in the mixed resin 13 is OH:NCO=2:1.

[0112] Step 3: Evenly mix the above mixed resin 13 and isocyanate single curing agent No. ②, and add the isocyanate curing agent according to the isocyanate index R=1.1.

[0113] The remaining steps are the same as those in Comparative Example 20.

[0114] Comparative Example 24 Compared with Comparative Example 20, this comparative example has the following differences: Step 1: Weigh a certain amount of polyol resin No. ③ PCL410 and hard segment monomer No. ① IPDI and mix them to obtain a mixed resin 14, wherein the polyol resin No. ③ PCL410 is a soft segment monomer, and the molar ratio of active groups in the mixed resin 14 is OH:NCO=2:1.

[0115] Step 3: Evenly mix the above mixed resin 14 and isocyanate single curing agent No. ②, and add the isocyanate curing agent according to the isocyanate index R=1.1.

[0116] The remaining steps are the same as those in Comparative Example 20.

[0117] Performance Testing The difference between Examples 1 to 4 lies in the different mass ratios of curing agent ② and curing agent ④ in the composite curing agent system. The operation period of the resins prepared in Examples 1 to 4 and the tensile strength, elongation at break, and pull-off adhesion test results of the resin coatings after spray curing are shown in Table 1.

[0118] The sample of the thermosetting resin obtained in Example 1 is shown in FIG. Figure 1 The resin coating sample after curing of the thermosetting resin in spraying Example 1 is shown in FIG. Figure 2 Tensile Strength - Elongation at Break Test for Resin Coating Samples Figure 3 Pull-off adhesion test specimens Figure 4 or Figure 5 .

[0119] Among them, the tensile strength and elongation at break are tested according to GB / T 528, and the adhesion by pull-off method is tested according to GB / T5210.

[0120] Table 1 Table 1 shows that the resin coatings formed by curing the thermosetting resins in Examples 1-4 all exhibited tensile strengths greater than or equal to 39.5 MPa, sometimes reaching as high as 46.9 MPa. Furthermore, their elongation at break reached 301.2%, sometimes reaching as high as 364.8%. Their pull-off adhesion reached 17.1 MPa or higher, sometimes reaching as high as 22.5 MPa. Examples 1-4 show that within a curing agent ②:curing agent ④ mass ratio range of 9 to 3:1, as the curing agent ② content in the composite curing agent decreases, the tensile strength of the cured resin coatings gradually decreases, the elongation at break gradually increases, and the pull-off adhesion strengthens.

[0121] Comparative Examples 1-4 differ from Example 1 in their curing agent systems. The curing agent systems in Comparative Examples 1-4 all utilize a single curing agent. The basic physical and chemical properties of isocyanate curing agent No. 1, No. 2, No. 3, No. HB-75MX, and No. 4, No. HT-100, used in Comparative Examples 1-4, are shown in Table 2.

[0122] The tensile strength, elongation at break and adhesion test results of the cured resin coating obtained based on the technical solutions of Comparative Examples 1 to 4 are shown in Table 3.

[0123] Table 2 Table 3 Tables 2 and 3 show that curing agent ① has a high NCO content and highly active reactive groups. After mixing with the prepared resin, the working period is only 0.5 hours. After curing, the crosslink density is high, and the tensile strength of the test piece reaches 64.2 MPa. Curing agents ② and ③ have similar pot lives. Curing agent ② imparts superior flexibility to the resin coating, while curing agent ③ exhibits relatively higher tensile strength. Curing agent ④ is a polymeric compound containing flexible segments, which contributes to the differences in the macroscopic mechanical properties of the cured systems.

[0124] The cured resin coatings prepared using the resin in Comparative Example 1 exhibited pull-off adhesion of 15.6 MPa, 16.2 MPa, 18.4 MPa, and 29.5 MPa, respectively. Compared to the composite curing agent systems of Examples 1-4, the resin coatings obtained using the resins in Comparative Examples 1-4 exhibited poorer balance between tensile strength and elongation at break.

[0125] Comparative Examples 5-7 differ from Example 1 in that they employ different toughening resins and curing agent systems. Comparative Examples 5-7 differ from Comparative Example 2 in that they employ different toughening resins. The basic physical and chemical properties of the toughening resins used in Comparative Examples 2 and 5-7, namely, type a diol resin, type b diol resin, and type c polyol resin, are shown in Table 4.

[0126] The test results of tensile strength and elongation at break of the cured resin coatings obtained based on Comparative Examples 2 and 5 to 7 are shown in Table 5.

[0127] Table 4 Table 5 It can be seen from Tables 4 and 5 that compared with Comparative Example 7 in which no toughening resin is added, Comparative Example 2 is compounded with type a diol resin, and the optimized resin system can maintain stable tensile strength and the elongation at break is increased by about 90%; Comparative Example 5 is compounded with type b diol resin, and the tensile strength of the optimized resin system decreases, and the elongation at break increases by 2.6 times; Comparative Example 6 is compounded with type c polyol resin, and the tensile strength of the optimized resin system remains relatively stable, and the elongation at break is increased by about 40%.

[0128] According to the analysis of the above test results, it can be seen that the technical solution of compounding type a diol resin with mixed resin 1 has significant advantages in taking into account both the tensile strength and elongation at break of the resin coating.

[0129] Comparative Examples 7 to 15 differ in the amounts of diol resin PTMG1000 (No. 2) and polyol resin PCL3087 (No. 2) used in the mixed resins, as well as in the molar ratio of the soft segment to the hard segment. The specific technical solutions are shown in Table 6. Adjusting the soft / hard segment ratio changes the degree of polymerization of the synthetic resin, and consequently, the content of active hydroxyl groups in the structure. Curing systems were prepared using curing agent ② and the above-mentioned polymerized resins. After reaction according to the curing procedure, cured resin coatings were obtained. The mechanical properties of the cured samples were tested, and the test results are shown in Table 7.

[0130] Table 6 Table 7 From the results in Tables 6 and 7, it can be seen that the change in the ratio of soft segment to hard segment leads to differences in the degree of polymerization and active hydroxyl content of the synthetic resin, which affects the mechanical properties of the cured system.

[0131] Comparative data shows that as the proportion of soft segment monomer decreases, the reactive group molar ratio (—OH):(NCO—) decreases, the degree of polymerization increases, and the reactive hydroxyl content of the final polymer decreases, correspondingly reducing the tensile strength of the cured sample. Elongation at break, influenced by multiple factors including soft segment structure, polymer chain length, and crosslink density, exhibits an irregular macroscopic trend.

[0132] Comparative Examples 12-15 differ in the initiators used. These examples employ organometallic tin initiator No. 1, organometallic tin initiator No. 2, organometallic initiator No. 3 (containing neither tin nor zinc), and organometallic composite initiators No. 3 / 4 (containing neither tin nor zinc), respectively. Comparative Example 16 uses no initiator. The effects of initiator type on the polymerized resin were investigated. Table 8 shows the regulation of the hydroxyl value of the polymerized resin by initiator type.

[0133] Table 8 Table 8 shows that under the same reaction conditions, initiator No. 1 significantly initiates the polymerization reaction, shortening the reaction time from 4.5 hours for the blank sample to 1 hour. The hydroxyl value of the post-reaction resin is relatively low. This is due to the significant polymerization degree and side reactions under the action of initiator No. 1, which results in a significant increase in the molecular weight of the synthesized resin and a decrease in the active hydroxyl content. Initiator No. 3 specifically promotes the polymerization process, effectively improving initiation efficiency and shortening the polymerization time. It also exhibits fewer side reactions and has a minimal impact on the active hydroxyl content of the polymer. A combination of initiators No. 3 and No. 4 can further shorten the polymerization time.

[0134] Comparative Examples 12 to 16 all used curing agent No. ② to prepare a curing system. After the reaction was carried out according to the curing procedure, a cured resin coating was obtained. The mechanical properties of the cured samples were examined, and the comparative results are shown in Table 9.

[0135] Table 9 As shown in Table 9, the reduced active group content in the polymer results in a reduced degree of crosslinking during curing, which manifests itself macroscopically as a decrease in mechanical properties. Using initiator ③ and a combination of initiators ③ / ④ minimizes side reactions during the polymerization initiation process, shortens polymerization time, maintains a relatively stable active hydroxyl group content, and results in minimal changes in mechanical properties.

[0136] Comparative Examples 16 to 19 differ in the hard segment monomers used in the mixed resins. The hard segment monomers used in the mixed resins in these comparative examples are, respectively, hard segment monomer No. 1 IPDI, hard segment monomer No. 2 TDI, hard segment monomer No. 3, and hard segment monomer No. 4. The basic physical and chemical properties of each hard segment monomer are shown in Table 10. The reaction times and hydroxyl values ​​of the synthetic resins in these comparative examples were examined, as shown in Table 11.

[0137] Table 10 Table 11 Tables 10 and 11 show that under the same reaction conditions, hard segment monomer TDI (No. 2) exhibits greater polymerization activity and requires a shorter polymerization time. The effect of different hard segment monomers on resin polymerization time follows a pattern of "hard segment monomer No. 2 < hard segment monomer No. 4 < hard segment monomer No. 3 < hard segment monomer No. 1 IPDI." The hydroxyl values ​​of the four synthetic resins are similar. This is because the hard segment monomers have relatively small molecular weights and constitute a small proportion of the polymerized resin, resulting in relatively little impact of hard segment monomer type on the hydroxyl value of the polymerized resin.

[0138] Comparative Examples 16-19 all used curing agent No. ② to prepare a curing system. After the reaction was carried out according to the curing procedure, a cured resin coating was obtained. The mechanical properties of the cured samples were examined, and the comparative results are shown in Table 12.

[0139] Table 12 Table 12 shows that under the same curing system conditions, the resin prepared with hard segment monomer TDI (No. ②) achieved a tensile strength of 22.4 MPa and an elongation at break of 94.5% after curing. The polymer resin prepared with hard segment monomer ③ exhibited excellent flexibility, with an elongation at break of 258.2%. The resin prepared with hard segment monomer IPDI (No. 1) exhibited relatively balanced mechanical properties after curing.

[0140] The difference between Comparative Documents 20-24 lies in the different soft segment monomers in the mixed resins. The soft segment monomers used in Comparative Documents 20-24 are, respectively, diol resin No. 1 PTMG2000, diol resin No. 2 PTMG1000, diol resin No. 3 PTMG650, polyol resin No. 1 PCL305, polyol resin No. 2 PCL3087, and polyol resin No. 3 PCL410. The basic physical and chemical properties of these six soft segment monomers are shown in Table 13. The above comparative examples all use hard segment monomer No. 1 IPDI, and examine the polymerization time and hydroxyl value of the synthetic resin, as shown in Table 14.

[0141] Table 13 Table 14 Tables 13 and 14 show that under the same reaction conditions, diol resin No. 1, PTMG2000, exhibits weaker polymerization activity, requires longer reaction times, and produces a higher molecular weight and lower hydroxyl value. As the molecular weight of the soft segment monomer decreases, polymerization activity increases and the required polymerization time decreases. Polyol resin No. 1, PCL305, exhibits a lower molecular weight and higher functionality as the soft segment monomer, resulting in a shorter reaction time and a higher hydroxyl value.

[0142] For Comparative Examples 16, 20-14, curing agent No. ② was selected and mixed with the above-mentioned polymer resin to form a curing system. After reaction according to the curing procedure, cured test pieces were obtained. The mechanical properties of the cured samples were examined, and the results are shown in Table 15.

[0143] Table 15 Table 15 shows that, under the same curing agent conditions, diol-based soft-segment resins exhibit excellent flexibility after curing. A higher molecular weight in the soft-segment monomers leads to higher elongation at break in the corresponding synthetic resin-cured samples, but this also results in a lower degree of crosslinking and a consequent decrease in tensile strength. Polyol-based soft-segment resins, which react with the curing agent to form a high-density crosslinked network, exhibit tensile strengths exceeding 50 MPa, but exhibit poor flexibility and lower elongation at break.

[0144] In this proposal, by designing Comparative Examples 1 to 24, we further clarify the influence of the composite soft segment monomer, hard segment monomer, toughening resin, composite initiator, and composite curing agent on the hydroxyl value of the main resin, polymerization time, curing resin operation period, tensile strength, and elongation at break. Based on this, the raw materials used in the preparation method disclosed herein can be rationally selected and the raw material ratios adjusted according to the desired thermosetting resin properties to obtain the desired thermosetting resin product.

[0145] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for preparing a thermosetting resin having both high tensile strength and high elongation at break, characterized in that: The steps include: S1, taking raw materials at a molar ratio of soft segment monomer to hard segment monomer of 2.2-1.8:1.0, mixing and obtaining a mixed resin, wherein the soft segment monomer includes a diol resin and a polyol resin; S2, adding toughening resin according to 20-30% of the total mass of the mixed resin to obtain the main resin; S3. Add initiator at 1.2-2.6% of the total mass of the main resin and blend; S4. Take any two isocyanate curing agents and compound them as a curing agent system; S5. Compounding the main resin containing the initiator in step S3 and the curing agent system in step S4 according to an isocyanate index R of 1.0 to 1.

1.

2. The method for preparing a thermosetting resin having both high tensile strength and high elongation at break according to claim 1, wherein: In step S1, the mass ratio of the diol resin to the polyol resin is 4.69-4.71:

1.

3. The method for preparing a thermosetting resin having both high tensile strength and high elongation at break according to claim 2, wherein: The diol resin includes PTMG2000, PTMG1000, PTMG650 and similar diol resins with a hydroxyl value of 50-180 mg ▪KOH / g, and a water content of less than 0.35%; The polyol resin includes PCL305, PCL3087, PCL410 and similar polyol resins with a hydroxyl value of 200-320 mg ▪KOH / g, and a water content of less than 0.35%; The hard segment monomers include IPDI, TDI, a mixture of TDI and MDI, HDI and an isocyanate hard segment monomer with an NCO content of 35-55%, and a water content of less than 0.05%.

4. The method for preparing a thermosetting resin having both high tensile strength and high elongation at break according to claim 1, wherein: In step S2, the toughening resin includes a diol toughening resin or a polyol toughening resin, with a hydroxyl value ranging from 30 to 42 mg ▪KOH / g and a solid content ranging from 62 to 83%.

5. The method for preparing a thermosetting resin having both high tensile strength and high elongation at break according to claim 1, wherein: In step S3, the initiator is selected from any two of an organometallic tin initiator or a non-tin organometallic initiator. The organometallic tin initiator includes tin naphthenate and stannous octoate; the non-tin organometallic initiator includes lead naphthenate and bismuth naphthenate.

6. The method for preparing a thermosetting resin having both high tensile strength and high elongation at break according to claim 5, wherein: The mass ratio of the two initiators is 1:

1.

7. The method for preparing a thermosetting resin having both high tensile strength and high elongation at break according to claim 1, wherein: In step S4, the mass ratio of the two isocyanate curing agents is 9-3:

1.

8. The method for preparing a thermosetting resin having both high tensile strength and high elongation at break according to claim 7, wherein: The isocyanate curing agent includes a mixed trimer of TDI and HDI, an IPDI adduct, HB-75MX, and HT-100, with an NCO content ranging from 15 to 32% and a water content of less than 0.0035.

9. Thermosetting resin prepared by the preparation method according to any one of claims 1 to 8.

10. The thermosetting resin according to claim 9, characterized in that Thermosetting resins meet the following performance indicators: Tensile strength: 39.5~50MPa; Elongation at break: ≥300%; Bonding strength: ≥17MPa.

11. Use of a thermosetting resin in the preparation of a surface protective coating material, characterized in that: The thermosetting resin is a thermosetting resin prepared by the preparation method according to any one of claims 1 to 8.

12. The use according to claim 11, characterized in that: The main resin containing the initiator is mixed evenly with the curing agent system components, and a diluent is added to adjust the viscosity to 21~27s. The resin coating is prepared by spraying, and the coating is cured by heating. The diluent includes one or more of xylene, propylene glycol methyl ether acetate, and nitro diluent.

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