Color paste for epoxy prepreg and preparation method thereof

Abstract

The application belongs to the technical field of color paste and specifically relates to a color paste for epoxy prepreg and a preparation method thereof. The color paste for epoxy prepreg comprises the following raw materials in percentage by mass: 10-30% of epoxy resin, 20-50% of inorganic pigment, 3-8% of dispersant, 1-2% of functional additive, and the rest of diluent to 100%. The dispersant comprises polyether phosphate fatty acid ammonium salt, castor oil modified silane and hyperbranched polyester polyamide. The functional additive is a silane copolymer. The color paste for epoxy prepreg has good dispersibility when applied in epoxy prepreg, the color difference of the cured product is small, and the color of the cured product is still uniform and stable after long-term storage at-18 DEG C.

Description

Technical Field

[0001] This invention belongs to the field of color paste technology, specifically relating to a color paste for epoxy prepreg and its preparation method. Background Technology

[0002] Epoxy prepreg is a composite material preform made by uniformly impregnating epoxy resin onto fiber-reinforced materials (such as glass fiber, carbon fiber, etc.) and processing it through specific processes. To improve the appearance and aesthetics of the final product, epoxy prepreg needs to be colored. Directly using pigments as colorants in the epoxy prepreg results in high grinding costs and requires on-site preparation. Pigment paste, on the other hand, is a concentrated paste in which pigments are pre-dispersed and stabilized in a specific carrier. Centralized grinding of the pigments reduces grinding costs and allows for storage and convenient access.

[0003] Color pastes for epoxy prepregs share the same technical requirements as those for conventional coatings and adhesives, namely, good compatibility with the system (epoxy prepregs in this invention) and good dispersibility within the system to avoid uneven color distribution in the product. However, in addition to the above requirements, color pastes for epoxy prepregs differ from those for conventional coatings and adhesives in that epoxy prepregs are also storable products. Due to the instability of epoxy prepregs, they are often immediately stored in cold storage after production and kept at low temperatures (below -18°C) during subsequent transportation and storage. Therefore, the color pastes in epoxy prepregs also need to have good stability under freezing conditions to avoid uneven color depth and severe color difference problems in different areas of epoxy prepreg products stored at -18°C.

[0004] However, there are no reports on color pastes for epoxy prepregs in the prior art. In view of this, the present invention is proposed. Summary of the Invention

[0005] To address the problems mentioned in the background art, the present invention aims to provide a color paste for epoxy prepreg and its preparation method. The color paste for epoxy prepreg provided by the present invention has good dispersibility when applied in epoxy prepreg, small color difference in the cured product, and the color of the cured product remains uniform and stable after long-term storage at -18℃.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] On one hand, the present invention provides a color paste for epoxy prepreg, comprising, by weight percentage, the following raw materials: 10-30% epoxy resin, 20-50% inorganic pigment, 3-8% dispersant, 1-2% functional additives, and diluent to make up the balance to 100%;

[0008] The dispersant includes polyether phosphate fatty acid ammonium salt, castor oil-modified silane, and hyperbranched polyester polyamide;

[0009] The functional additive is a silane copolymer.

[0010] In some preferred embodiments, the epoxy resin is a prepreg-specific epoxy resin, such as Whippar WP-R1312 or Whippar WP-5600W3K.

[0011] In some preferred embodiments, the mass percentage of the epoxy resin may specifically be 10%, 15%, 20%, 25%, or 30%.

[0012] In some preferred embodiments, the inorganic pigment is selected from at least one of carbon black, titanium dioxide, chrome yellow, iron oxide red, iron blue, iron oxide yellow, cobalt blue, chrome green, chrome oxide green, cadmium green, iron oxide brown, chrome orange, cadmium orange manganese violet, and cobalt violet.

[0013] In some preferred embodiments, the mass percentage of the inorganic pigment may specifically be 20%, 25%, 30%, 35%, 40%, 45%, or 50%.

[0014] In some preferred embodiments, the mass ratio of the polyether phosphate fatty acid ammonium salt, castor oil modified silane, and hyperbranched polyester polyamide is 2-3:4-5:2-4.

[0015] Preferably, the mass ratio of the polyether phosphate fatty acid ammonium salt, castor oil-modified silane, and hyperbranched polyester polyamide is 2:5:3.

[0016] In some preferred embodiments, the castor oil-modified silane is castor oil-modified tetramethylcyclotetrasiloxane.

[0017] Preferably, the method for preparing the castor oil modified silane is as follows: tetramethylcyclotetrasiloxane and toluene are mixed, castor oil and chloroplatinic acid are added to react, and the solvent is removed after the reaction is completed to obtain the castor oil modified silane.

[0018] Preferably, the mass ratio of tetramethylcyclotetrasiloxane, toluene, castor oil and chloroplatinic acid is 5-8:30-40:60-80:0.001-0.003.

[0019] More preferably, the method for preparing the castor oil modified silane is as follows: tetramethylcyclotetrasiloxane and toluene are mixed and heated to 60-80°C, castor oil and chloroplatinic acid are added, and the temperature is raised to 80-100°C for 4-6 hours. After the reaction is completed, the solvent is removed to obtain the castor oil modified silane.

[0020] In some preferred embodiments, the mass percentage of the dispersant may specifically be 3%, 4%, 5%, 6%, 7% or 8%.

[0021] In some preferred embodiments, the silane copolymer is Crosile® 1212 from Guangzhou Aikepu New Materials Co., Ltd.

[0022] In some preferred embodiments, the mass percentage of the dispersant may specifically be 1%, 1.2%, 1.5%, 1.6%, 1.8%, or 2%.

[0023] In some preferred embodiments, the diluent is selected from at least one of aliphatic glycidyl ether or polypropylene glycol diglycidyl ether.

[0024] Preferably, the aliphatic glycidyl ether is selected from at least one of C12-C14 long alkyl chain glycidyl ethers.

[0025] On the other hand, the present invention provides a method for preparing the above-mentioned color paste for epoxy prepreg, comprising the following steps:

[0026] S1. Mix the epoxy resin and diluent, and stir until homogeneous to obtain the first mixture;

[0027] S2. Add inorganic pigments, dispersants and functional additives to the first mixture, stir until homogeneous, and obtain the second mixture.

[0028] S3. Grind the second mixture to obtain a color paste for epoxy prepreg.

[0029] Preferably, the fineness of the pigment used in the epoxy prepreg after the grinding process in step S3 is ≤25µm.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] This invention selects specific dispersants and functional additives, including polyether phosphate fatty acid ammonium salt, castor oil-modified silane, and hyperbranched polyester polyamide as dispersants. Through wetting, electrostatic repulsion, and steric hindrance effects, these three agents not only ensure uniform dispersion of inorganic pigments in epoxy prepreg color pastes but also improve the freeze-thaw stability of the inorganic pigments, ensuring that the color difference of the epoxy prepreg remains essentially unchanged after long-term storage at -18°C. Specifically, this invention utilizes the hydrosilylation reaction of castor oil and tetramethylcyclotetrasiloxane to prepare castor oil-modified silane. When the epoxy prepreg color paste undergoes freeze-thaw cycles at -18°C... During the process, micro-stress is generated inside the epoxy prepreg. Polyether phosphate fatty acid ammonium salt, castor oil modified silane, and hyperbranched polyester polyamide can buffer the stress and prevent inorganic pigments from settling, agglomerating, or migrating, thereby avoiding color differences in epoxy prepreg products. Silane copolymers are used as functional additives. They have a multi-arm structure and can form a bridging network between inorganic pigments and fiber reinforcement materials in the epoxy prepreg. This further enables the inorganic pigments to be uniformly dispersed and attached to the fiber reinforcement materials, preventing migration of inorganic pigments after storage, and thus preventing color differences in epoxy prepregs after storage at -18°C. Attached Figure Description

[0032] Figure 1 Here is a photograph of the color paste used in the epoxy prepreg of Example 1;

[0033] Figure 2 Here is a photograph of the color paste used in the epoxy prepreg of Example 2;

[0034] Figure 3 Here is a photograph of the color paste used in the epoxy prepreg of Example 3;

[0035] Figure 4 The image shows a physical sample of the epoxy prepreg pigment obtained when the inorganic pigment is iron oxide yellow.

[0036] Figure 5 This is a physical image of the epoxy prepreg pigment obtained when the inorganic pigment is cobalt blue. Detailed Implementation

[0037] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0038] Unless otherwise specified, the raw materials, reagents or apparatus used in the following examples and comparative examples are available from conventional commercial sources or can be obtained by existing known methods.

[0039] Example 1

[0040] A color paste for epoxy prepreg, comprising the following raw materials by weight percentage: 22% epoxy resin, 35% inorganic pigment, 6% dispersant, 1.5% functional additives, and diluent to make up to 100%;

[0041] The epoxy resin is a prepreg-specific epoxy resin, manufactured by Changzhou Yunuo Composite Materials Technology Co., Ltd., and is Huibai WP-R1312.

[0042] The inorganic pigment is carbon black.

[0043] The dispersant includes polyether phosphate fatty acid ammonium salt, castor oil modified silane, and hyperbranched polyester polyamide.

[0044] The mass ratio of the polyether phosphate fatty acid ammonium salt, castor oil-modified silane, and hyperbranched polyester polyamide is 2:5:3.

[0045] The polyether phosphate fatty acid ammonium salt, Zhuhai Jintuan Chemical Co., Ltd., is KEPERDISP®-603.

[0046] The hyperbranched polyester polyamide is manufactured by Changxing Xiehe Polymer Materials Co., Ltd., SD-2400.

[0047] The castor oil-modified silane is castor oil-modified tetramethylcyclotetrasiloxane, and the preparation method is as follows: 6 parts by mass of tetramethylcyclotetrasiloxane and 36 parts by mass of toluene are mixed, heated to 70°C, 70 parts by mass of castor oil and 0.003 parts by mass of chloroplatinic acid are added, the temperature is raised to 90°C and the reaction is carried out for 5 hours. After the reaction is completed, the solvent is removed to obtain castor oil-modified silane.

[0048] The CAS number for the aforementioned tetramethylcyclotetrasiloxane is 2370-88-9.

[0049] The castor oil mentioned above has a hydroxyl value of 163 mg KOH / g, produced by Fucheng Huanyu Oil Co., Ltd.

[0050] The functional additive is a silane copolymer, Guangzhou Aikepu New Materials Co., Ltd., Crosile® 1212.

[0051] The diluent is polypropylene glycol diglycidyl ether.

[0052] The preparation method of the above-mentioned color paste for epoxy prepreg includes the following steps:

[0053] S1. Mix the epoxy resin and diluent, and stir until homogeneous to obtain the first mixture;

[0054] S2. Add inorganic pigments, dispersants and functional additives to the first mixture, stir until homogeneous, and obtain the second mixture.

[0055] S3. Grind the second mixture to obtain a color paste for epoxy prepreg.

[0056] The fineness of the pigment used in the epoxy prepreg after the grinding process described in step S3 is 25µm.

[0057] The physical diagram of this embodiment is shown below. Figure 1 As shown.

[0058] Example 2

[0059] A color paste for epoxy prepreg differs from Example 1 in that the inorganic pigment is titanium dioxide; otherwise, they are the same.

[0060] The physical diagram of this embodiment is shown below. Figure 2 As shown.

[0061] Example 3

[0062] A color paste for epoxy prepreg differs from Example 1 in that the inorganic pigment is iron oxide red; otherwise, they are the same.

[0063] The physical diagram of this embodiment is shown below. Figure 3 As shown.

[0064] Other inorganic pigments can also be used for the color paste of the above-mentioned epoxy prepreg, which will not be shown in detail here. When the inorganic pigment is iron oxide yellow, its physical image is as follows. Figure 4 As shown, when the inorganic pigment is cobalt blue, its actual image is as follows. Figure 5 As shown.

[0065] Example 4

[0066] A color paste for epoxy prepreg differs from Example 1 in that, by mass percentage, the color paste for epoxy prepreg comprises the following raw materials: 15% epoxy resin, 45% inorganic pigment, 8% dispersant, 2% functional additive, and diluent to make up the balance to 100%; the rest are the same.

[0067] Example 5

[0068] A color paste for epoxy prepreg differs from Example 1 in that, by mass percentage, the color paste for epoxy prepreg comprises the following raw materials: 30% epoxy resin, 30% inorganic pigment, 5% dispersant, 1.2% functional additive, and diluent to make up the balance to 100%; the rest are the same.

[0069] Comparative Example 1

[0070] A color paste for epoxy prepreg differs from Example 1 in that the polyether phosphate fatty acid ammonium salt is replaced with an equal mass of castor oil-modified silane; all other aspects are the same.

[0071] Comparative Example 2

[0072] A color paste for epoxy prepreg differs from Example 1 in that castor oil-modified silane is replaced with an equal mass of hyperbranched polyester polyamide; all other aspects are the same.

[0073] Comparative Example 3

[0074] A color paste for epoxy prepreg differs from Example 1 in that the hyperbranched polyester polyamide is replaced with an equal mass of polyether phosphate fatty acid ammonium salt; all other aspects are the same.

[0075] Comparative Example 4

[0076] A color paste for epoxy prepreg differs from Example 1 in that the polyether phosphate fatty acid ammonium salt is replaced with an equal mass of acidic polymer, KEPERDISP®-600, manufactured by Zhuhai Jintuan Chemical Co., Ltd.; all other aspects are the same.

[0077] Comparative Example 5

[0078] A color paste for epoxy prepreg differs from Example 1 in that the castor oil-modified silane is prepared according to the method of Example 1 of Chinese Invention Patent No. CN114230602B, namely: 10 parts by weight of trimethoxysilane and 46 parts by weight of toluene are mixed, heated to 80°C, 70 parts by weight of castor oil and 0.0030 parts by weight of chloroplatinic acid are added, the temperature is raised to 90°C and reacted for 5 hours. After the reaction is completed, the solvent is removed to obtain the castor oil-modified silane; the rest is the same.

[0079] Comparative Example 6

[0080] A color paste for epoxy prepreg, differing from Example 1 in that hyperbranched polyester polyamide is replaced with an equal mass of block polyurethane, Shanghai Tiger Polymer Technology Co., Ltd., Tech-58683; otherwise, they are the same.

[0081] Comparative Example 7

[0082] A color paste for epoxy prepreg differs from Example 1 in that the mass percentage of the functional additive is 0%; all other aspects are the same.

[0083] Comparative Example 8

[0084] A color paste for epoxy prepreg differs from Example 1 in that the functional additive is an aminosiloxane polymer, Guangzhou Aikepu New Materials Co., Ltd., Crosile® 5203; all other aspects are the same.

[0085] The following performance tests were conducted on the color pastes used in the epoxy prepregs of Examples 1-5 and Comparative Examples 1-8:

[0086] (1) The color paste of epoxy prepregs in Examples 1-5 and Comparative Examples 1-8 was added to epoxy resin Whopper WP-R1312 at a dosage of 3%, and then combined with glass fiber at a ratio of epoxy resin Whopper WP-R1312: glass fiber = 70%: 30% to prepare epoxy prepreg. After curing, the prepreg was marked according to the three-point sampling method. The color difference between each pair of the three sample points was measured with a colorimeter, and the maximum color difference ΔE1 was recorded.

[0087] (2) The color paste of epoxy prepregs in Examples 1-5 and Comparative Examples 1-8 was added to epoxy resin Whopper WP-R1312 at a dosage of 3%, and then combined with glass fiber at a ratio of epoxy resin Whopper WP-R1312: glass fiber = 70%: 30% to prepare epoxy prepreg. The epoxy prepreg was stored at -18℃ for 30 days, then thawed at room temperature for 8 hours, and then cured. After curing, it was marked according to the three-point sampling method. The color difference between each pair of the three sample points was measured with a colorimeter, and the maximum color difference ΔE2 was recorded.

[0088] The test results for color difference ΔE1 and color difference ΔE2 are shown in Table 1 below.

[0089] Table 1. Performance test results of color pastes for epoxy prepregs in Examples 1-5 and Comparative Examples 1-8

[0090]

[0091] As can be seen from Table 1, the color paste prepared by the present invention using specific dispersants and functional additives has good compatibility with epoxy prepregs, and can still be uniformly dispersed in epoxy prepregs after thawing following storage at -18℃, with uniform color distribution and small color difference.

[0092] Comparison of Examples 1 and Comparative Examples 1-3 shows that the ether phosphate fatty acid ammonium salt, castor oil modified silane and hyperbranched polyester polyamide in the dispersant are indispensable. The three have a synergistic effect and can improve the uniform dispersion of the color paste for epoxy prepreg in the epoxy prepreg.

[0093] Comparison of Examples 1 and 4-6 shows that replacing any one of the components of the dispersant, namely, ammonium ether phosphate fatty acid salt, castor oil modified silane, and hyperbranched polyester polyamide, with other dispersants does not produce the same effect as the combination of ammonium ether phosphate fatty acid salt, castor oil modified silane, and hyperbranched polyester polyamide.

[0094] As can be seen from the comparison of Examples 1 and Comparative Examples 7-8, the specific silane copolymer can effectively enable inorganic pigments to be uniformly dispersed and attached to the fiber-reinforced material, avoiding the migration of inorganic pigments after storage, and thus avoiding color difference in epoxy prepreg after storage at -18°C.

[0095] (3) The factory inspection report of the color paste for epoxy prepreg in Example 1 is shown in Table 2 below.

[0096] Table 2 Factory Inspection Report of Colorant for Epoxy Prepreg in Example 1

[0097]

[0098] Note: "JS / III-0214" specifically refers to: adding black pigment to 20g of prepreg-specific epoxy resin, stirring evenly, and then curing it on a white substrate. The detection area is defined as the region within 10mm of the coating boundary, the interface between the reference sample and the test sample coatings. Two points are taken within each detection area, and the color difference ΔE between the reference sample and the test sample coatings is measured using a dual-beam spectrophotometer. The reference sample is a standard black pigment sample; full color refers to 0.4g of black pigment; subtractive color refers to 0.02g of black pigment mixed with 0.4g of white pigment.

[0099] "JS / III-0104" specifically refers to the test performed according to GB / T 1724-2019, Method A, for the determination of the fineness of grinding of paints, varnishes and printing inks.

[0100] "JS / III-0105" specifically refers to the test performed according to GB / T 6750-2007 Determination of density of paints and varnishes - specific gravity bottle method.

[0101] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A color paste for epoxy prepreg, characterized by, The raw materials include the following by mass percentage: epoxy resin 10-30%, inorganic pigment 20-50%, dispersant 3-8%, functional additive 1-2%, and diluent to make up the balance to 100%; The dispersant includes polyether phosphate fatty acid ammonium salt, castor oil modified silane, and hyperbranched polyester polyamide; the mass ratio of the polyether phosphate fatty acid ammonium salt, castor oil modified silane, and hyperbranched polyester polyamide is 2-3:4-5:2-4; The castor oil modified silane is castor oil modified tetramethylcyclotetrasiloxane; The functional additive is a silane copolymer; The silane copolymer is Crosile from Guangzhou Aikopu New Material Co., Ltd. ® 1212.

2. The color paste for epoxy prepreg according to claim 1, characterized by, The inorganic pigment is at least one selected from carbon black, titanium white, chromium yellow, iron oxide red, iron blue, iron oxide yellow, cobalt blue, chromium green, chromium oxide green, cadmium green, iron oxide brown, chromium orange, cadmium orange, manganese violet, and cobalt violet.

3. The color paste for epoxy prepreg according to claim 2, characterized by, The preparation method of the castor oil modified silane is as follows: tetramethylcyclotetrasiloxane and toluene are mixed, castor oil and chloroplatinic acid are added for reaction, and after the reaction is completed, the solvent is removed to obtain the castor oil modified silane.

4. The color paste for epoxy prepreg according to claim 3, characterized by, The mass ratio of the tetramethylcyclotetrasiloxane, toluene, castor oil, and chloroplatinic acid is 5-8:30-40:60-80:0.001-0.

003.

5. The color paste for epoxy prepreg according to claim 4, characterized by, The diluent is at least one selected from aliphatic glycidyl ether or polypropylene glycol diglycidyl ether.

6. A process for the preparation of a colorant paste for epoxy prepreg according to any one of claims 1 to 5, characterized in that, The method includes the following steps: S1, mixing epoxy resin and diluent, stirring uniformly to obtain a first mixture; S2, adding inorganic pigment, dispersant, and functional additive to the first mixture, stirring uniformly to obtain a second mixture; S3, performing grinding treatment on the second mixture to obtain the color paste for epoxy prepreg.

7. The method of preparing a color paste for epoxy prepreg according to claim 6, characterized in that, The fineness of the color paste for epoxy prepreg after the grinding treatment of step S3 is ≤25 µm.

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