A polyurea-based resin having excellent solvent resistance and a method for producing the same

Abstract

The present application relates to the technical field of paint, especially to the field of IPC C08G18, more particularly to a polyurea resin with excellent solvent resistance and a preparation method thereof. The components include: diisocyanate, aromatic diamine, epoxy monomer, epoxy resin, organic acid, chain extender, solvent and water. When the weight ratio of the epoxy monomer to the epoxy resin is 1:(7-15), the solvent resistance and film hardness of the prepared resin can be improved; when the epoxy resin includes bisphenol A type epoxy resin, the insulation performance of the prepared resin can be further improved, and the prepared resin can be applied in the field of electrophoretic paint; when the molar ratio of the diisocyanate to the aromatic diamine is 1:(2-3), the reaction efficiency can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of coating technology, in particular to the field of IPC C08G18, and more particularly to a polyurea resin with excellent solvent resistance and a preparation method thereof. BACKGROUND

[0002] The polarity of the urea group in the polyurea material is greater than that of the urethane group in the polyurethane material, so the polyether with a long-chain macromolecular structure and the urea group structure with strong polarity form a similar feature to "chelate" in the high molecular structure, and a more stable molecular structure can be obtained, so the overall performance of the polyurea material is better than that of the polyurethane in many aspects, such as temperature insensitivity, no joint in the coating, excellent corrosion resistance, fast drying speed at low temperature, and high temperature resistance (the coating can reach 120℃). However, the adhesion of the polyurea coating to the substrate is not high, the damping performance is poor, and the acid and alkali resistance is poor. The epoxy resin contains hydroxyl groups that can react with isocyanate groups, which can produce certain chemical connections in the network of the high polymer, helping to improve the resistance to strong acid and alkali and the resistance to electrolyte, and the application in the field of electrophoretic paint.

[0003] CN114262422A discloses a polyurea resin and a preparation method and application thereof. The polyurea resin includes components: isocyanate, modifier, chain extender, toughening agent and blocking agent. The application uses isocyanate to react with amine to avoid the generation of tertiary amine. The polyurea resin is used to prepare cathode electrophoretic paint. During the entire curing process, the isocyanate groups not only rapidly react with amine groups, but also can undergo secondary reaction with urea groups on the main chain to generate substituted urea. Therefore, the curing reaction of the paint film at the same baking temperature can be more rapid and complete than that of the conventional amine-modified epoxy / acrylic product. The coating has higher crosslinking density, thereby having good low-temperature curing performance and paint film performance. However, the acid and alkali resistance of the polyurea resin is poor, which limits the application of the polyurea resin to some extent. SUMMARY

[0004] To overcome the deficiencies in the background art, the present application provides a polyurea resin with excellent solvent resistance and a preparation method thereof. The polyurea resin is modified by adding an epoxy monomer. The prepared polyurea resin has excellent acid and alkali resistance, and after electrophoretic film forming, has high paint film hardness.

[0005] To achieve the purpose of the present application, the first aspect of the present application provides a polyurea resin with excellent solvent resistance. The components include: diisocyanate, aromatic diamine, epoxy monomer, epoxy resin, organic acid, chain extender, solvent and water.

[0006] The diisocyanate includes at least one of diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate and dicyclohexyl diisocyanate;

[0007] Preferably, the diisocyanate comprises diphenylmethane diisocyanate, toluene diisocyanate.

[0008] Further preferably, the diisocyanate comprises toluene diisocyanate (CAS: 91-08-7).

[0009] The aromatic diamine comprises one of 4,4'diaminodiphenyl methane, 4,4'diaminodiphenyl ether, 4,4'diaminodiphenyl sulfone, p-xylidine, 4,4'-diaminodiphenyl ether.

[0010] Preferably, the aromatic diamine comprises 4,4'-diaminodiphenyl ether (CAS: 101-80-4).

[0011] Preferably, the molar ratio of the diisocyanate to the aromatic diamine is 1:(2-3).

[0012] Further preferably, the molar ratio of the diisocyanate to the aromatic diamine is 1:2.

[0013] The applicant found that when the weight ratio of the epoxy monomer to the epoxy resin is 1:(7-15), the solvent resistance and the hardness of the prepared resin can be improved, one secondary amine molecule can react with two epoxy groups to introduce the oligomer containing secondary amine into the epoxy resin in the form of polyurea, the epoxy monomer is added in too low an amount, the epoxy resin reacts with the secondary amine molecule, the crosslinking degree is too large, and the system is prone to precipitation, which affects the dispersion performance, thereby leading to a decrease in the solvent resistance, and as the addition amount of the epoxy monomer continues to increase, the dispersion performance gradually improves, but the crosslinking point density is too low, which affects the film hardness of the polyester material to a certain extent, and further research found that when the epoxy resin comprises a bisphenol A type epoxy resin, the insulation performance of the prepared resin can be further improved, the bisphenol A type epoxy resin contains a large number of conjugated double bonds, the conjugated system produces a conjugation effect on the surrounding space, because there is one large π bond on each side of the benzene ring, the two large π bonds form a conjugated system and make the benzene ring symmetric to the axis of the ring plane, so that the dielectric constant is large, and at the same time, the large π bond in the polyurea structure interacts with each other, so that it has excellent insulation performance and can be applied to the field of electrophoretic paint with high requirements for insulation performance.

[0014] The weight ratio of the epoxy monomer to the epoxy resin is 1:(7-15).

[0015] Preferably, the weight ratio of the epoxy monomer to the epoxy resin is 1:(8-12).

[0016] Further preferably, the weight ratio of the epoxy monomer to the epoxy resin is 1:10.6.

[0017] Preferably, the epoxy monomer comprises at least one of propylene oxide and butylene oxide.

[0018] Further preferably, the epoxy monomer comprises propylene oxide.

[0019] The epoxy resin comprises at least one of bisphenol A type epoxy resin and bisphenol F type epoxy resin.

[0020] Preferably, the epoxy equivalent weight of the epoxy resin is 170-210 g / mol.

[0021] Further preferably, the epoxy resin comprises bisphenol A type epoxy resin, and the epoxy equivalent weight is 189 g / mol, which is available from Nantong Xingchen Synthetic Material Co., Ltd., model: E51.

[0022] The organic acid comprises at least one of tartaric acid, lactic acid, glycine, gluconic acid, malic acid, malonic acid, citric acid, maleic acid, and acetic acid.

[0023] Preferably, the organic acid comprises acetic acid.

[0024] The solvent comprises at least one of N-methylpyrrolidone, dimethyl sulfoxide, hexamethylphosphoramide, and dimethylformamide.

[0025] Preferably, the solvent comprises N-methylpyrrolidone.

[0026] The chain extender comprises at least one of amine-based chain extenders and alcohol-based chain extenders.

[0027] Preferably, the chain extender comprises at least one of diethanolamine, ethylenediamine, and N, N-dihydroxy(diisopropyl) aniline.

[0028] Further preferably, the chain extender comprises diethanolamine.

[0029] Preferably, the solid content of the polyurea type resin is 15-30 wt%.

[0030] Further preferably, the solid content of the polyurea type resin is 20-30 wt%.

[0031] The second aspect of the present application provides a preparation method of a polyurea type resin with excellent solvent resistance, comprising the following steps:

[0032] Step 1: Mix part of the solvent with aromatic diamine, heat in a water bath to obtain a mixed solution 1, and drop diisocyanate into the mixed solution 1 to react, to obtain an amine-terminated trimer or polymer;

[0033] Step 2: Mix the remaining solvent with the epoxy resin to obtain a mixed solution 2, and drop the mixed solution 2 into the product obtained in step 1 to obtain a mixed solution 3;

[0034] Step 3: adding epoxy resin into the mixed solution 3, and reacting to obtain an epoxy resin with epoxy group and polyurea structure at the end;

[0035] Step 4: adding chain extender into the product obtained in step 3, and reacting to obtain a main resin;

[0036] Step 5: adding organic acid into the main resin to neutralize;

[0037] Step 6: adding water into the product obtained in step 5, and stirring at high speed to obtain the product.

[0038] Preferably, the temperature of the water bath heating is 10-50℃.

[0039] Further preferably, the temperature of the water bath heating is 20℃.

[0040] Preferably, the dropping time in step 1 is 1.5-2.5h.

[0041] Further preferably, the dropping time in step 1 is 2h.

[0042] Preferably, the dropping time in step 2 is 0.5-1.5h.

[0043] Further preferably, the dropping time in step 2 is 1h.

[0044] Advantageous effects:

[0045] 1. When the weight ratio of the epoxy monomer to the epoxy resin is 1:(7-15), the solvent resistance, electrolyte resistance and film hardness of the prepared resin can be improved.

[0046] 2. When the epoxy resin comprises bisphenol A type epoxy resin, the heat resistance of the prepared resin can be further improved, and the prepared resin can be applied in the field of electrophoretic paint.

[0047] 3. When the molar ratio of the diisocyanate to the aromatic diamine is 1:(2-3), the reaction efficiency can be improved.

[0048] 4. The dropping time in step 1 is 1.5-2.5h, and the stable amine-terminated trimer or polymer can be obtained, and the dispersion of the product in solution can be improved.

[0049] 5. The dropping time in step 2 is 0.5-1.5h, and the conversion rate of the epoxy group can be improved, and the stability of the system can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0050] Figure 1 An emulsion of the polyurea type resin prepared in Example 1.

[0051] Figure 2 An infrared spectrum of the paint film prepared for Example 1. DETAILED DESCRIPTION

[0052] Example 1

[0053] A polyurea type resin having excellent solvent resistance, the components of which are: diisocyanate, aromatic diamine, epoxy monomer, epoxy resin, organic acid, chain extender, solvent, water.

[0054] The diisocyanate is toluene diisocyanate (CAS: 91-08-7).

[0055] The aromatic diamine is 4,4'-diaminodiphenyl ether (CAS: 101-80-4).

[0056] The molar ratio of the diisocyanate to the aromatic diamine is 1:2.

[0057] The diisocyanate is added in an amount of 0.5 mol.

[0058] The epoxy resin is a bisphenol A type epoxy resin, the epoxy equivalent weight of which is 189 g / mol, and is purchased from Nantong Xingchen Synthetic Material Co., Ltd., model number: E51.

[0059] The epoxy monomer is propylene oxide, and the epoxy monomer is added in an amount of 29 g.

[0060] The weight ratio of the epoxy monomer to the epoxy resin is 1:10.6.

[0061] The solvent is N-methylpyrrolidone, and the solvent is added in an amount of 310 g.

[0062] The organic acid is acetic acid.

[0063] The chain extender is diethanolamine, and the diethanolamine is added in an amount of 65 g.

[0064] A method for preparing a polyurea type resin having excellent solvent resistance, the method comprising the following steps:

[0065] Step 1: 300 g of a solvent is mixed with an aromatic diamine, heated in a water bath to obtain a mixed solution 1, and a diisocyanate is added dropwise to the mixed solution 1 to react to obtain a mixture of amine-terminated trimers and polymers;

[0066] Step 2: 10 g of a solvent is mixed with an epoxy resin to obtain a mixed solution 2, and the mixed solution 2 is added dropwise to the product obtained in step 1 to obtain a mixed solution 3;

[0067] Step 3: The temperature is raised to 100°C, an epoxy resin is added to the mixed solution 3 to react to obtain an epoxy resin having an epoxy group as a terminal group and containing a polyurea structure.

[0068] Step 4: The chain extender is added to the product obtained in Step 3, and the reaction is carried out for 3 h, and the temperature is lowered to 60°C to obtain a main resin;

[0069] Step 5: The organic acid is added to the main resin to neutralize it to a pH of 6.5;

[0070] Step 6: 2000 g of water is added to the product obtained in Step 5, and the stirring is carried out at a rate of 2000 rpm for 10 min to obtain a polyurea type resin as shown in Figure 1 , which is in the form of an emulsion.

[0071] The temperature of the water bath heating is 20°C.

[0072] The time for the dropwise addition in Step 1 is 2 h.

[0073] The time for the dropwise addition in Step 2 is 1 h.

[0074] Example 2

[0075] The specific implementation is the same as in Example 1, except that the weight ratio of the epoxy monomer to the epoxy resin in Example 2 is 1:8.

[0076] Example 3

[0077] The specific implementation is the same as in Example 1, except that the time for the dropwise addition in Step 1 in Example 3 is 1.5 h.

[0078] Comparative Example 1

[0079] The specific implementation is the same as in Example 1, except that the weight ratio of the epoxy monomer to the epoxy resin in Comparative Example 1 is 1:7.

[0080] Comparative Example 2

[0081] The specific implementation is the same as in Example 1, except that the weight ratio of the epoxy monomer to the epoxy resin in Comparative Example 2 is 1:14.

[0082] Comparative Example 3

[0083] The specific implementation is the same as in Example 1, except that the time for the dropwise addition in Step 1 in Comparative Example 3 is 0.5 h.

[0084] Performance test method

[0085] The polyurea type resin emulsion prepared from Example 1-3 and Comparative Example 1-3 was diluted to a solid content of 13 wt%, and electrophoretic film forming was performed at a voltage of 120 V and a film thickness of 30 μm. The film was subjected to the following performance tests, and the test data are shown in Table 1. The paint film prepared from Example 1 was subjected to infrared testing, and the test results are shown in Figure 1. Figure 2

[0086] 1) Heat resistance: 150°C, test voltage DC 1000 V, test time 60 s, and insulation resistance value was recorded.

[0087] 2) Hardness test: reference standard GB / T 6739-2006, "Pencil hardness method for film hardness" test.

[0088] 3) Acid / alkali resistance: reference standard GB / T 9274-1998, 5 wt% NaOH aqueous solution and 5 wt% HCl aqueous solution, 1 ml of each was added dropwise to the surface of the paint film, and after 2 h, the film was observed for cracking, peeling, blistering, and the like.

[0089] 4) Electrolyte resistance: 1 ml of electrolyte (purchased from Shanghai Kaijin Chemical Industry Co., Ltd.) was added dropwise to the surface of the paint film, and after 2 h of baking, the film was observed for blistering, wrinkling, discoloration, and the like.

[0090] 5) Adhesion: reference standard GB / T 1730-1993, "Adhesion of paint film to substrate".

[0091] Performance test data

[0092] Table 1

[0093] ​

Claims

1. A polyurea resin with excellent solvent resistance, characterized in that, The components include: diisocyanate, aromatic diamine, epoxy monomer, epoxy resin, organic acid, chain extender, solvent, water; The weight ratio of the epoxy monomer to the epoxy resin is 1: (8-12); The molar ratio of the diisocyanate to the aromatic diamine is 1: (2-3); The epoxy equivalent weight of the epoxy resin is 170-210 g / mol; the solid content of the polyurea type resin is 15-30 wt%; The preparation method of the polyurea type resin comprises the following steps: Step 1: mix part of the solvent with the aromatic diamine, heat in a water bath to obtain a mixed solution 1, drop the diisocyanate into the mixed solution 1 to react, and obtain an amine group terminated trimer or polymer; Step 2: mix the remaining solvent with the epoxy monomer to obtain a mixed solution 2, drop the mixed solution 2 into the product obtained in step 1 to obtain a mixed solution 3; Step 3: add the epoxy resin into the mixed solution 3 to react, and obtain an epoxy resin with an epoxy group as an end group and containing a polyurea structure; Step 4: add the chain extender into the product obtained in step 3 to react, and obtain a main body resin; Step 5: add the organic acid into the main body resin to neutralize; Step 6: add water into the product obtained in step 5, and stir at high speed to obtain the polyurea type resin; The temperature of the water bath heating is 10-50℃; The dropping time in step 1 is 1.5-2.5 h.

2. The polyurea-based resin having excellent solvent resistance according to claim 1, wherein The dropping time in step 2 is 0.5-1.5 h.

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