Cardanol-based epoxy resin modifier as well as preparation method and application thereof

Abstract

The invention discloses a cardanol-based epoxy resin modifier as well as a preparation method and application thereof, cardanol is taken as a raw material, a cardanol cyclization dimer is obtained through synthesis, and then the cardanol-based epoxy resin modifier is generated through reaction of the cardanol cyclization dimer and epichlorohydrin. The preparation method disclosed by the invention is high in practicability, the structural formula of the prepared cardanol-based epoxy resin modifier contains a flexible long carbon chain structure and also contains rigid benzene rings and cyclohexyl, the rigidity and the flexibility of the structure are considered, the flexibility and the impact resistance of an epoxy resin coating paint film can be effectively improved, and the practicability is high.

Description

Technical Field

[0001] The present invention relates to the technical field of coating preparation, and in particular to a cardanol-based epoxy resin modifier and a preparation method and application thereof. Background Art

[0002] Bisphenol A epoxy resin E51 has excellent physical and mechanical properties, electrical insulation properties, and excellent bonding properties with various materials, especially its excellent process flexibility, which is not available in other thermosetting plastics. Therefore, bisphenol A epoxy resin E51 is made into coatings, composite materials, casting materials, adhesives, molding materials and injection molding materials, etc., and is widely used in various fields of the national economy.

[0003] However, the coating made of bisphenol A epoxy resin has low toughness and the paint film is very brittle, which affects the use effect. Summary of the invention

[0004] The present invention can solve the problem of brittle paint film of existing coatings made of bisphenol A epoxy resin by providing a cardanol-based epoxy resin modifier and a preparation method and application thereof.

[0005] In order to solve the above technical problems, the present invention provides a cardanol-based epoxy resin modifier, which at least includes a compound of the following structural formula:

[0006]

[0007] Wherein, R is -CH2CH3 or -CH=CH2.

[0008] In order to solve the above technical problems, the present invention also provides a method for preparing a cardanol-based epoxy resin modifier, comprising the following steps:

[0009] (1) Synthesis of cardanol cyclodimer: Add cardanol, a first catalyst and a co-catalyst into a reaction vessel, heat and react under the protection of an inert gas, and after the reaction, purify by distillation to obtain the cardanol cyclodimer, whose structural formula is:

[0010]

[0011] (3) Synthesis of a cardanol-based epoxy resin modifier: Add the cardanol cyclodimer prepared in step (1), epichlorohydrin and a second catalyst into a reaction vessel, heat to carry out a ring-opening etherification reaction, then dropwise add a sodium hydroxide solution with a mass concentration of 10 to 50% to carry out a cyclization reaction. After the reaction is completed, cool, add deionized water, stir and stand to separate, and obtain the cardanol-based epoxy resin modifier.

[0012] In a preferred embodiment of the present invention, in step (1), the first catalyst is activated white clay, and its amount is 1 to 25% by weight of the cardanol.

[0013] In a preferred embodiment of the present invention, in step (1), the co-catalyst includes at least one of CuCl2, FeCl3 or LiCl, and its amount is 0 to 10% by weight of the first catalyst.

[0014] In a preferred embodiment of the present invention, the amount of the co-catalyst is 1-5% by weight of the first catalyst.

[0015] In a preferred embodiment of the present invention, in step (1), the heating reaction conditions are: temperature 200-270° C., time 3-8 h.

[0016] In a preferred embodiment of the present invention, in step (2), the mass ratio of the cardanol cyclodimer to epichlorohydrin is 1:2-3.

[0017] In a preferred embodiment of the present invention, in step (2), the second catalyst comprises at least one of triethylbenzylammonium chloride, triphenylphosphine and tetrabutylammonium bromide, and the amount thereof is 0.5 to 1% of the weight of the cardanol cyclodimer.

[0018] In a preferred embodiment of the present invention, in step (2),

[0019] The conditions of the ring-opening etherification reaction are: temperature 70-100° C., time 3-6 h;

[0020] The conditions of the cyclization reaction are: temperature 70-100° C., sodium hydroxide solution dropwise addition time 3-5 hours, and heat preservation for 0.5-2 hours after the dropwise addition.

[0021] In order to solve the above technical problems, the present invention also provides an application of a cardanol-based epoxy resin modifier, wherein the cardanol-based epoxy resin modifier is mixed with an epoxy resin in a ratio of 95:5 to 50:50.

[0022] The beneficial effects of the present invention are as follows: the present invention provides a cardanol-based epoxy resin modifier and a preparation method and application thereof; the preparation method of the present invention has strong feasibility and low cost; the structural formula of the prepared cardanol-based epoxy resin modifier contains both a flexible long carbon chain structure and a rigid benzene ring and a cyclohexyl group, taking into account both the rigidity and flexibility of the structure, and can effectively improve the flexibility and impact resistance of the epoxy resin coating film, and has strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is an infrared spectrum of the cardanol-based epoxy resin modifier prepared in an embodiment of the present invention;

[0024] Figure 2 Schematic diagram of the test specimen structure showing the tensile strength. DETAILED DESCRIPTION

[0025] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0026] Cardanol is a natural phenolic compound with a saturated or unsaturated long-chain hydrocarbon group. Its chemical structure is shown in the figure below:

[0027]

[0028] The long-chain hydrocarbon groups in the side chain of cardanol include 5% saturated hydrocarbon groups, 49% monoalkenyl groups, 17% diene groups and 29% trialkenyl groups, of which diene and trialkenyl components account for about 46%, which is close to 1:1 with the monoalkenyl components.

[0029] The present invention uses cardanol as a raw material to prepare a cardanol-based epoxy resin modifier, which at least includes a compound of the following structural formula:

[0030]

[0031] Wherein, R is -CH2CH3 or -CH=CH2.

[0032] The structural formula of the cardanol-based epoxy resin modifier contains a long carbon chain with good flexibility, two rigid benzene rings and a rigid cyclohexyl group. It is both rigid and flexible, ensuring the flexibility of the structure while taking into account the rigidity of the structure, and has a beneficial strengthening and toughening effect.

[0033] The preparation method of the above-mentioned cardanol-based epoxy resin modifier specifically comprises the following steps:

[0034] (1) Synthesis of cardanol cyclodimer: A certain amount of cardanol is added to a reaction vessel, and then a first catalyst accounting for 1 to 25% by weight of the cardanol, preferably 5 to 15% by weight, is added, and then a co-catalyst accounting for 0 to 10% by weight of the first catalyst, preferably 1 to 5% by weight, is added. Under the protection of an inert gas such as nitrogen, the mixture is heated to 200 to 270° C., preferably 240 to 250° C., and reacted for 3 to 8 hours. During the above reaction process, the double bonds of the cardanol side chain are first rearranged, and then the cardanol molecules undergo a [4+2] cycloaddition reaction to generate a cyclodimer. After the reaction is completed, molecular distillation separation and purification is performed at 140 to 200° C., preferably 150 to 170° C., to obtain a cardanol cyclodimer with a purity greater than 95%. The reaction process is as follows:

[0035]

[0036] (2) Synthesis of a cardanol-based epoxy resin modifier: The cardanol cyclodimer and epichlorohydrin prepared in step (1) are added to a reaction vessel in a mass ratio of 1:2-3, and then a second catalyst accounting for 0.5-1% of the weight of the cardanol cyclodimer is added, and the mixture is heated to 70-100° C. and kept warm for 3-6 hours to allow the cardanol cyclodimer to undergo ring-opening etherification with epichlorohydrin, and then a sodium hydroxide solution with a mass concentration of 10-50% is added dropwise to catalyze the ring-opening etherification of epichlorohydrin and simultaneously perform cyclodehydrochlorination, and the dropping time is controlled to be 3-5 hours. After the dropping is completed, the heat preservation reaction is continued for 0.5-2 hours to complete the cyclization reaction. After the reaction is completed, the mixture is cooled to 50-60° C., deionized water is added, stirred, and allowed to stand for stratification to obtain the cardanol-based epoxy resin modifier. The reaction process is as follows:

[0037]

[0038] Specifically, the first catalyst is activated clay; the co-catalyst includes at least one of CuCl2, FeCl3 or LiCl.

[0039] The second catalyst includes at least one of triethylbenzylammonium chloride, triphenylphosphine and tetrabutylammonium bromide.

[0040] The above-mentioned cardanol-based epoxy resin modifier is mixed with epoxy resin in a ratio of 95:5 to 50:50, and then the mixture is used in ink, adhesive or coating, which can effectively improve the mechanical strength and toughness of the product.

[0041] The process of the present invention is described in detail below through specific embodiments.

[0042] Example 1

[0043] 300g of cardanol A, 30g of activated clay, and 0.6g of copper chloride are added to a four-necked reaction bottle, stirred for 10 minutes, heated to 200°C, and reacted for 6 hours; after the reaction is completed, it is cooled to 70°C, 200g of anhydrous ethanol is added, stirred for 1 hour, hydrochloric acid is added for neutralization, the insoluble catalyst and salt are filtered out, the filtered material is heated to 80°C, vacuumed to remove ethanol, and discharged. The unreacted cardanol monomer is distilled out at 160°C by molecular distillation to obtain a cardanol dimer with a purity of >95%.

[0044] 150 g of the prepared cardanol dimer, 350 g of epichlorohydrin and 0.75 g of catalyst tetrabutylammonium bromide were added to a reaction bottle, and reacted at 80° C. for 3 hours to complete the ring-opening etherification; then, 50% sodium hydroxide solution was added dropwise at 80° C. for 3 hours, and the reaction was continued for 1 hour after the addition was completed; finally, the mixture was cooled to below 50° C., 100 g of water was added, stirred for 15 minutes, allowed to stand for 1 hour, the water layer was separated, and epichlorohydrin was recovered to obtain cardanol-based epoxy resin modifier P-1, and the epoxy equivalent EEW was measured to be 376.

[0045] Example 2

[0046] Add 300g of cardanol A, 30g of activated clay and 1g of potassium hydroxide into a four-necked reaction bottle, stir for 10 minutes, heat to 260°C, and react for 3 hours; after the reaction, cool to 70°C, add 200g of anhydrous ethanol, stir for 1 hour, add hydrochloric acid to neutralize, filter to remove insoluble catalysts and salts, heat the filtered material to 80°C, vacuum to remove ethanol, and discharge. Through molecular distillation, distill out the unreacted cardanol monomer at 160°C to obtain a cardanol dimer with a purity of >95%.

[0047] 150 g of the prepared cardanol dimer, 350 g of epichlorohydrin and 0.75 g of catalyst triethylbenzylammonium chloride were added to a reaction bottle, and reacted at 80° C. for 6 hours to complete the ring-opening etherification; then, a sodium hydroxide solution with a mass concentration of 50% was added dropwise at 80° C. for 3 hours; after the addition, the reaction was continued for 1 hour; finally, the mixture was cooled to below 50° C., 100 g of water was added, stirred for 15 minutes, allowed to stand for 1 hour, the water layer was separated, and epichlorohydrin was recovered to obtain a cardanol-based epoxy resin modifier P-2, and the epoxy equivalent EEW was measured to be 382.

[0048] Example 3

[0049] Add 300g of cardanol A, 30g of activated clay and 1g of potassium hydroxide into a four-necked reaction bottle, stir for 10 minutes, heat to 260°C, and react for 3 hours; after the reaction, cool to 70°C, add 200g of anhydrous ethanol, stir for 1 hour, add hydrochloric acid to neutralize, filter to remove insoluble catalysts and salts, heat the filtered material to 80°C, vacuum to remove ethanol, and discharge. Through molecular distillation, distill out the unreacted cardanol monomer at 160°C to obtain a cardanol dimer with a purity of >95%.

[0050] 150 g of the prepared cardanol dimer, 350 g of epichlorohydrin and 0.75 g of triphenylphosphine catalyst were reacted at 90° C. for 5 hours to complete the ring-opening etherification; then, a sodium hydroxide solution with a mass concentration of 50% was added dropwise at 90° C. for 3 to 5 hours; the reaction was continued for 1 hour after the addition was completed; finally, the mixture was cooled to below 50° C., 100 g of water was added, stirred for 15 minutes, allowed to stand for 1 hour, the water layer was separated, and epichlorohydrin was recovered to obtain a cardanol-based epoxy resin modifier P-3, and the epoxy equivalent EEW was measured to be 386.

[0051] The infrared spectra of the cardanol-based epoxy resin modifier prepared in Examples 1-3 are shown in the attached figure. Figure 1 shown.

[0052] Depend on Figure 1 It can be clearly seen that 3007cm -1 =C—H stretching vibration peak, indicating the presence of cyclohexene groups; 2919cm -1 and 2856cm -1 It is the stretching vibration peak of —CH3 and —CH2—; 1598cm -1 、1584cm -1 、1492cm -1 , and 1454cm -1 It is the skeleton vibration peak of benzene ring C=C; 1242cm -1 、1159cm -1 1040cm is the stretching vibration peak of phenolic hydroxyl C—O; -1 The C—O—C absorption peak appeared; 910cm -1 It is the characteristic absorption peak of epoxy group, indicating that epoxy group is generated.

[0053] The standard bisphenol A type resin Epon 828 was obtained commercially, and the epoxy equivalent weight (EEW) was 190.

[0054] Application Testing

[0055] The formulations of Application Examples 1-6 and Application Comparative Example 1 are shown in Table 1 below.

[0056] Table 1

[0057]

[0058] The samples of application examples 1-6 and application comparative example 1 were mixed with curing agent PLR738 according to the calculated equivalent and then tested. PLR738, from Changshu Naisu Biomaterial Technology Co., Ltd., has an active hydrogen equivalent of 78.

[0059] 1. Strength test

[0060] 1) Preparation of specimens for tensile strength test

[0061] According to the provisions of Articles 1 and 2 of GB1039, the sample strips are prepared and inspected. After the epoxy resin or sample is mixed with the curing agent PLR738 according to the theoretically calculated ratio, it is poured into the mold, placed in a vacuum box for vacuum degassing, and then baked at 90°C for 30 minutes, and the sample strips are demoulded. Figure 2 The sample dimensions are shown in Table 2 below.

[0062] Table 2

[0063]

[0064] 2) Preparation of bending strength test specimens

[0065] The shape of the sample is as shown in the attached Figure 2 As shown, the sample size is: length L = 80 ± 2 mm width b = 10.0 ± 0.2 mm thickness h = 4.0 ± 0.2 mm

[0066] The specimens were prepared and inspected according to GB / T 9352. The epoxy resin or sample was mixed with the curing agent PLR738 according to the theoretically calculated ratio, poured into the mold, placed in a vacuum box for vacuum degassing, and then baked at 90°C for 30 minutes. The specimens were demoulded to obtain the specimens.

[0067] 3) Test the tensile strength, tensile modulus and elongation according to GB / T 1040 standard; test the flexural strength and flexural modulus according to GB9341 standard.

[0068] The test results are shown in Table 3 below.

[0069] Table 3

[0070]

[0071] It can be seen from the test results in Table 3 that the cardanol epoxy resin modifier prepared by the present invention has excellent elongation and tensile strength; adding 20wt% to the epoxy resin Epon828 can significantly improve the elongation, bending strength and tensile strength of the epoxy resin.

[0072] 2. Make paint film and test mechanical properties

[0073] 1) Preparation of test samples

[0074] According to the general preparation method of coating in GB / T 1727, epoxy resin or sample is mixed with curing agent PLR738 according to the theoretically calculated ratio, and then a proper proportion of solvent is added for dilution. The coating is prepared by air spraying on the polished tinplate. The coating thickness is 20-25um and cured at 23±2℃ for 7 days.

[0075] 2) Test the impact resistance, flexibility, cross-cut adhesion and pencil hardness of the coating according to GB / T 1732, GB / T 1731, GB / T 9286 and GB / T 6739.

[0076] The test results are shown in Table 4 below.

[0077] Table 4

[0078]

[0079] It can be seen from the test results in Table 4 above that the cardanol epoxy resin modifier prepared by the present invention has excellent impact resistance itself. When added in an amount of 20wt% in the epoxy resin, the impact resistance and flexibility of the paint film can be significantly improved.

[0080] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A cardanol-based epoxy resin modifier, characterized in that: A compound comprising at least the following structural formula: Wherein, R is -CH2CH3 or -CH=CH2.

2. A method for preparing the cardanol-based epoxy resin modifier according to claim 1, characterized in that: The steps include: (1) Synthesis of cardanol cyclodimer: Add cardanol, a first catalyst and a co-catalyst into a reaction vessel, heat and react under the protection of an inert gas, and after the reaction, purify by distillation to obtain the cardanol cyclodimer, whose structural formula is: (2) Synthesis of a cardanol-based epoxy resin modifier: Add the cardanol cyclodimer prepared in step (1), epichlorohydrin and a second catalyst into a reaction vessel, heat to carry out a ring-opening etherification reaction, then dropwise add a sodium hydroxide solution with a mass concentration of 10 to 50% to carry out a cyclization reaction. After the reaction is completed, cool, add deionized water, stir and stand to separate, and obtain the cardanol-based epoxy resin modifier.

3. The method for preparing the cardanol-based epoxy resin modifier according to claim 2, wherein: In step (1), the first catalyst is activated white clay, and its usage is 1 to 25% of the weight of the cardanol.

4. The method for preparing the cardanol-based epoxy resin modifier according to claim 3, wherein: In step (1), the co-catalyst includes at least one of CuCl2, FeCl3 or LiCl, and its amount is 0 to 10% by weight of the first catalyst.

5. The method for preparing the cardanol-based epoxy resin modifier according to claim 4, wherein: The amount of the co-catalyst is 1-5% of the weight of the first catalyst.

6. The method for preparing the cardanol-based epoxy resin modifier according to claim 3, wherein: In step (1), the heating reaction conditions are: temperature 200-270° C., time 3-8 h.

7. The method for preparing the cardanol-based epoxy resin modifier according to claim 2, characterized in that: In step (2), the mass ratio of the cardanol cyclodimer to epichlorohydrin is 1:2-3.

8. The method for preparing the cardanol-based epoxy resin modifier according to claim 7, wherein: In step (2), the second catalyst comprises at least one of triethylbenzylammonium chloride, triphenylphosphine and tetrabutylammonium bromide, and its amount is 0.5 to 1% of the weight of the cardanol cyclodimer.

9. The method for preparing the cardanol-based epoxy resin modifier according to claim 2, wherein: In step (2), The conditions of the ring-opening etherification reaction are: temperature 70-100° C., time 3-6 h; The conditions of the cyclization reaction are: temperature 70-100° C., sodium hydroxide solution dropwise addition time 3-5 hours, and heat preservation for 0.5-2 hours after the dropwise addition.

10. An application of the cardanol-based epoxy resin modifier according to claim 1, characterized in that: The cardanol-based epoxy resin modifier and the epoxy resin are mixed in a ratio of 95:5 to 50:50.

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