High-strength DMC bulk material and preparation method thereof

Abstract

The invention relates to the technical field of molding compounds, in particular to a high-strength DMC bulk material and a preparation method thereof. The high-strength DMC bulk material is prepared from the following raw materials in parts by weight: 80 to 120 parts of unsaturated polyester resin, 20 to 28 parts of cross-linking agent, 18 to 22 parts of low shrinkage agent, 1.5 to 3 parts of initiator, 0.3 to 1 part of polymerization inhibitor, 15 to 40 parts of chopped glass fiber, 180 to 250 parts of aluminum hydroxide, 2 to 4 parts of release agent, 5 to 15 parts of defoaming agent, 8 to 15 parts of nano calcium carbonate and 8 to 12 parts of wetting agent. The defoaming agent is an organic silicon defoaming agent containing double bonds; the wetting agent is a mixture of polyvinylpyrrolidone, a silane coupling agent and a small molecule chelating agent; the method has the advantage that the strength of the DMC agglomerate is improved.

Description

Technical Field

[0001] The present application relates to the technical field of molding compounds, and in particular to a high-strength DMC agglomerate and a preparation method thereof. Background Art

[0002] Currently, the most commonly used molding compounds on the market are SMC composites and DMC (BMC) composites. DMC, short for Dough Molding Compound, is a bulk molding compound, often referred to as unsaturated polyester bulk molding compound. It is a semi-dry process for producing glass fiber-reinforced thermoset products. It is primarily made by thoroughly mixing unsaturated resin, chopped glass fibers, fillers, and various additives. DMC bulk molding compounds are increasingly used due to their low water absorption, dimensional stability, excellent flame retardancy, and good arc extinguishing and leakage resistance. However, their strength is insufficient in high-end applications. To improve the strength of DMC materials, current industry practices include adding inorganic fillers and surface treating the fibers with silane coupling agents. However, excessive addition of inorganic fillers can increase the material's brittleness and reduce its overall performance. The silane coupling agent treatment of glass fibers is complex and costly, and the improvement achieved is limited. Therefore, improving the strength of DMC materials remains a significant challenge. Summary of the Invention

[0003] In order to improve the strength of DMC agglomerates, the present application provides a high-strength DMC agglomerate and a preparation method thereof.

[0004] In the first aspect, the present application provides a high-strength DMC pellet, which adopts the following technical solution: A high-strength DMC aggregate comprises the following raw materials in parts by weight: 80-120 parts of unsaturated polyester resin, 20-28 parts of cross-linking agent, 18-22 parts of low shrinkage agent, 1.5-3 parts of initiator, 0.3-1 part of polymerization inhibitor, 15-40 parts of chopped glass fiber, 180-250 parts of aluminum hydroxide, 2-4 parts of release agent, 5-15 parts of defoaming agent, 8-15 parts of nano-calcium carbonate, and 8-12 parts of wetting agent; The defoaming agent is an organosilicon defoaming agent containing double bonds; and the wetting agent is a mixture of polyvinyl pyrrolidone, a silane coupling agent and a small molecule chelating agent.

[0005] By adopting the above technical solution, the present application can remove a large number of bubbles generated in the DMC agglomerate during its production by adding a defoaming agent, so as to achieve the effect of improving the strength of DMC. At the same time, the present application adopts a silicon-containing defoaming agent containing double bonds. On the one hand, the double bonds contained can participate in the cross-linking of the system and improve the cross-linking density of the system; on the other hand, by cross-linking with the system, the DMC agglomerate can be modified, and the silicon-containing flexible chain segments can improve the toughness of the DMC agglomerate. In addition, the modification of the silicon-containing polymer material can improve the compatibility between the DMC system and inorganic fillers, such as glass fiber and nano-calcium carbonate; at the same time, nano-calcium carbonate can also fill the micropores in the system; under the multi-faceted effects, the strength and toughness of the DMC agglomerate can be greatly improved; The purpose of adding a wetting agent is to further enhance the bonding strength between the system and the chopped glass fibers and nano-calcium carbonate, further reducing the generation of microbubbles at the interface between the inorganic filler and the system due to interfacial tension, which can lead to lower strength in the DMC aggregate. The wetting agents include polyvinyl pyrrolidone, 7-octenyltrimethoxysilane, and ethylenediaminetetraacetic acid monoethyl ester. Polyvinyl pyrrolidone can deposit onto the surface of the inorganic filler during mixing and stirring of the system. Its strong film-forming properties allow it to form a film structure on the surface of the inorganic filler, thereby greatly improving the compatibility between the inorganic filler and the system, reducing its interfacial tension, and strengthening the integrity of the DMC aggregate. Furthermore, 7-octenyltrimethoxysilane, as a silane coupling agent, can adsorb onto the surface of the inorganic filler, forming a film with polyvinyl pyrrolidone. The double bonds it contains participate in cross-linking the system, strengthening the bonding strength between the inorganic filler and the system. The added small molecule chelating agent can be adsorbed on the surface of inorganic fillers, such as nano-calcium carbonate, and chelate the calcium ions on its surface, thereby further improving the dispersibility of the nano-calcium carbonate, making it more filling, and also improving its compatibility with the system to a certain extent; through the synergistic effect of the ester bond of polyvinyl pyrrolidone, 7-octenyltrimethoxysilane and ethylenediaminetetraacetic acid monoethyl ester, the strength and toughness of the DMC resin are further improved.

[0006] Preferably, the defoaming agent is a polysiloxane-polyacrylate copolymer.

[0007] By adopting the above technical solution, the polysiloxane-polyacrylate copolymer, on the one hand, the double bonds contained in the polyacrylate chain segment can participate in the cross-linking of the system and increase the cross-linking density of the system; on the other hand, the DMC agglomerate can be modified by cross-linking with the system, and the silicon-containing flexible chain segment can improve the toughness of the DMC agglomerate. In addition, the modification of the silicon-containing polymer material can improve the compatibility between the DMC system and inorganic fillers, such as glass fiber and nano-calcium carbonate. Under the action of multiple aspects, the strength and toughness of the DMC agglomerate can be greatly improved.

[0008] Preferably, the mass ratio of the polyvinyl pyrrolidone, the silane coupling agent and the small molecule chelating agent is 10:(2-4):(0.5-1.5).

[0009] By adopting the above technical solution, at this ratio, the synergistic effect of polyvinyl pyrrolidone, silane coupling agent and small molecule chelating agent is better exerted.

[0010] Preferably, the silane coupling agent is a double-bond silane coupling agent.

[0011] By adopting the above technical solution, the double bond silane coupling agent can be adsorbed on the surface of the inorganic filler as a silane coupling agent, forming a film together with polyvinyl pyrrolidone. At the same time, the double bonds it contains participate in the cross-linking of the system, thereby strengthening the bonding force between the inorganic filler and the system.

[0012] Preferably, the double bond silane coupling agent is one or more of vinyl triethoxysilane, γ-methacryloxypropyl trimethoxysilane, vinyl tributylon oxime silane, 7-octenyl trimethoxysilane, vinyl triisopropoxysilane and acryloxymethyl trimethoxysilane.

[0013] By adopting the above technical solutions, the technical solutions of the present application are extremely inclusive and can achieve good compounding effects on general vinyl silane coupling agents. In theory, all of them can be realized. Although they are not explored one by one in the examples of the present application, they are all within the scope of protection of the present application.

[0014] Preferably, the polyvinyl pyrrolidone is of model K17-K30.

[0015] By adopting the above technical solution, the present application explored the molecular weight of polyvinyl pyrrolidone and found that PVP K25 was the optimal molecular weight. It is speculated that this is because a lower molecular weight affects its film formation on the surface of the inorganic filler, while a higher molecular weight affects its deposition on the surface of the inorganic filler. When the molecular weight is high, its viscosity is also higher, making it easier to act in the system.

[0016] Preferably, the small molecule chelating agent is ethylenediaminetetraacetic acid monoethyl ester.

[0017] By adopting the above technical solution, ethylenediaminetetraacetic acid monoethyl ester has higher selectivity for calcium ions and can better chelate with calcium ions on the surface of nano-calcium carbonate.

[0018] In a second aspect, the present application provides a method for preparing a high-strength DMC agglomerate, which adopts the following technical solution: A method for preparing a high-strength DMC agglomerate comprises the following steps: S1, stirring and kneading unsaturated polyester resin, crosslinking agent, polystyrene low shrinkage agent, tert-butyl benzoyl peroxide, p-benzoquinone, zinc stearate, defoaming agent and wetting agent to prepare a resin paste; S2. Then, chopped glass fiber, aluminum hydroxide and nano-calcium carbonate are added to the resin paste, and stirring is continued. Then, the resin paste is sealed and aged. The temperature is maintained in the range of 30-45° C. during the aging process to obtain a bulk molding compound. S3. The bulk molding compound is compression molded at a compression molding temperature of 155-175°C, a molding pressure of 4-7 MPa, and a mold closing speed of 20-30 mm / min. After holding the pressure for 250-400 seconds, the compound is naturally cooled to obtain a high-strength DMC bulk material.

[0019] By adopting the above technical solution, the various raw materials of the DMC agglomerate are distributed, stirred and mixed, so that the inorganic filler and the system can be fully wetted and dispersed, thereby making the production qualification rate of the prepared DMC agglomerate higher, the performance of the prepared DMC agglomerate uniform, and the quality can be guaranteed.

[0020] In summary, this application includes at least one of the following beneficial technical effects: 1. This application can remove a large number of bubbles generated in the DMC agglomerate during its production process by adding a defoaming agent, thereby achieving the effect of improving the strength of DMC. At the same time, this application uses a silicon-containing defoaming agent containing double bonds. On the one hand, the double bonds contained can participate in the cross-linking of the system and improve the cross-linking density of the system; on the other hand, by cross-linking with the system, the DMC agglomerate can be modified, and the silicon-containing flexible chain segments can improve the toughness of the DMC agglomerate. In addition, the modification of the silicon-containing polymer material can improve the compatibility between the DMC system and inorganic fillers, such as glass fiber and nano-calcium carbonate; at the same time, nano-calcium carbonate can also fill the micropores in the system; under the multi-faceted effects, the strength and toughness of the DMC agglomerate can be greatly improved; The polyvinyl pyrrolidone in the wetting agent can form a film structure on the surface of the inorganic filler, thereby greatly improving the compatibility between the inorganic filler and the system, reducing its interfacial tension, and making the DMC aggregate more integrated. At the same time, 7-octenyltrimethoxysilane can not only assist in film formation, but also participate in the cross-linking of the system through its double bonds, thereby strengthening the binding force between the inorganic filler and the system. The added small molecule chelating agent can adsorb on the surface of inorganic fillers, such as nano-calcium carbonate, and chelate the calcium ions on its surface, thereby further improving the dispersibility of the nano-calcium carbonate and enhancing its filling capacity. The synergistic effect of polyvinyl pyrrolidone, 7-octenyltrimethoxysilane and ethylenediaminetetraacetic acid monoethyl ester ester bond further enhances the strength and toughness of the DMC resin.

[0021] 2. The DMC agglomerates prepared in this application have excellent strength and toughness, which are more conducive to applications in high-end fields; among them, their tensile strength is 107MPa and above, and can reach up to 123MPa; their flexural strength is between 136-148MPa; at the same time, their notched impact strength is 62kJ / m 2 and above, up to 69kJ / m 2 . DETAILED DESCRIPTION

[0022] The following is a further detailed description of this application in conjunction with the specific content.

[0023] raw material The raw materials used in the examples of the present application are all common commercially available products, among which the unsaturated polyester resin is an o-phthalic unsaturated resin purchased from Jinling Petrochemical, with the product model being JLC-800; the manufacturer of the polysiloxane-polyacrylate copolymer is BYK Chemical, with the model being BYK-037; polydimethylsiloxane is purchased from Shandong Guiyu Intelligent Equipment Co., Ltd., with the model being GY-201; the polystyrene low shrinkage agent is purchased from Kingfa Technology, with the product model being GF-PS-800, and the molecular weight range being 60,000-80,000; and zinc stearate is purchased from Hebei Kuojun Chemical Technology Co., Ltd., which is a general-purpose product. Example

[0024] Example 1 A high-strength DMC agglomerate, the raw materials and the amounts of the raw materials are shown in Table 1, and the preparation method is as follows: S1. Stir and knead unsaturated polyester resin, crosslinking agent, polystyrene low shrinkage agent, tert-butyl benzoyl peroxide, p-benzoquinone, zinc stearate, defoaming agent and wetting agent at a stirring speed of 800 r / min and a stirring temperature maintained below 40° C. for 30 min to obtain a resin paste; The wetting agent is a mixture of polyvinyl pyrrolidone, 7-octenyltrimethoxysilane and ethylenediaminetetraacetic acid monoethyl ester in a mass ratio of 10:3:1; the crosslinking agent is styrene; the defoaming agent is polysiloxane-polyacrylate copolymer; the model of polyvinyl pyrrolidone is PVP K25; S2. Then, chopped glass fiber, aluminum hydroxide and nano-calcium carbonate are added to the resin paste, and the temperature is continued to be maintained below 40° C., and stirred at a speed of 800 r / min for 30 minutes. Then, it is sealed and aged for 48 hours. During the aging process, the temperature is maintained in the range of 30-45° C. to obtain a bulk molding compound; Among them, the average particle size of aluminum hydroxide is 8μm; the average length of chopped glass fiber is 15mm and the diameter is 20μm; the average particle size of nano calcium carbonate is 100μm; S3. Fill the bulk molding compound into the mold, and then press the mold on a hot press at a molding temperature of 160°C, a molding pressure of 5 MPa, and a mold closing speed of 25 mm / min. After holding the pressure for 300 seconds, naturally cool for 24 hours to obtain a high-strength DMC bulk material.

[0025] Table 1 Raw materials and amounts of raw materials used in Example 1 (kg) Unsaturated polyester resin 100 crosslinking agent 24 Polystyrene low shrinkage agent 20 tert-Butyl Benzoyl Peroxide 2.6 p-Benzoquinone 0.6 Chopped glass fiber 30 aluminum hydroxide 220 Zinc stearate 2.5 defoaming agent 10 Nano calcium carbonate 12 Wetting agent 10 Example 2 A high-strength DMC aggregate is different from Example 1 in that its defoaming agent is polydimethylsiloxane with a viscosity of 500 cst, and the remaining steps are the same as Example 1.

[0026] Example 3 A high-strength DMC agglomerate is different from Example 1 in that ethylenediaminetetraacetic acid monoethyl ester is not added to the wetting agent, and the remaining steps are the same as Example 1.

[0027] Example 4 A high-strength DMC aggregate is different from Example 1 in that the model of polyvinyl pyrrolidone added to the wetting agent is PVP K17, and the remaining steps are the same as Example 1.

[0028] Example 5 A high-strength DMC aggregate is different from Example 1 in that the model of polyvinyl pyrrolidone added to the wetting agent is PVP K30, and the remaining steps are the same as Example 1.

[0029] Example 6 A high-strength DMC aggregate is different from Example 1 in that 7-octenyltrimethoxysilane is replaced with methyltriethoxysilane of equal mass in the wetting agent, and the remaining steps are the same as those in Example 1.

[0030] Comparative Example Comparative Example 1 A high-strength DMC aggregate is different from Example 1 in that no defoaming agent is added to the raw materials, and the remaining steps are the same as Example 1.

[0031] Comparative Example 2 A high-strength DMC agglomerate is different from Example 1 in that no wetting agent is added to the raw materials, and the remaining steps are the same as Example 1.

[0032] Comparative Example 3 A high-strength DMC aggregate is different from Example 1 in that polyvinyl pyrrolidone is not added to the wetting agent, and the remaining steps are the same as Example 1.

[0033] Performance testing Detection method / test method High-strength DMC agglomerates were prepared according to the preparation methods of Examples 1-6 and Comparative Examples 1-4, and then tested according to the following test methods. The test results are shown in Table 2.

[0034] Tensile strength: tested according to the test method in GB / T1447-2005 "Test method for tensile properties of fiber reinforced plastics"; Impact toughness: tested according to the test method in GB / T1451-2005 "Test method for simply supported beam impact toughness of fiber reinforced plastics"; Bending strength: Test according to the test method in GB / T1449-2005 "Test method for bending properties of fiber reinforced plastics".

[0035] Table 2 Test results of Examples 1-6 and Comparative Examples 1-4 It can be seen from the test data of Examples 1-6 and Comparative Examples 1-3, as well as Table 2, that the DMC agglomerates prepared in this application have excellent strength and toughness, and are more conducive to applications in high-end fields; among them, their tensile strength is 107 MPa and above, and can reach up to 123 MPa; their flexural strength is between 136-148 MPa; and their notched impact strength is 62 kJ / m 2 and above, up to 69kJ / m 2 .

[0036] This application, by adding a defoaming agent, can remove a large number of bubbles generated during the production of DMC agglomerates, thereby achieving the effect of improving the strength of DMC. At the same time, this application uses a silicon-containing defoaming agent containing double bonds, such as the polysiloxane-polyacrylate copolymer in Example 1. On the one hand, the double bonds contained can participate in the cross-linking of the system and increase the cross-linking density of the system; on the other hand, by cross-linking with the system, the DMC agglomerate can be modified, and the silicon-containing flexible chain segments can improve the toughness of the DMC agglomerate, and the modification of the silicon-containing polymer material can improve the compatibility between the DMC system and inorganic fillers, such as glass fiber and nano-calcium carbonate; at the same time, nano-calcium carbonate can also fill the micropores in the system; under the multi-faceted effects, the strength and toughness of the DMC agglomerate can be greatly improved. This conclusion can be verified by the test data of Example 1-1 and Comparative Example 1.

[0037] On this basis, in combination with Example 1, Example 3, Example 6, and the test data of Comparative Examples 2-3, it can be seen that the present application is by adding a wetting agent, the purpose is to further improve the bonding force between the system and the chopped glass fiber and nano-calcium carbonate, further reduce the inorganic filler and the system due to the interfacial tension and cause the interface to produce tiny bubbles, resulting in a situation where the strength of the DMC group material is relatively low. Wherein, the wetting agent includes polyvinyl pyrrolidone, 7-octenyl trimethoxy silane and ethylenediamine tetraacetic acid monoethyl ester, and polyvinyl pyrrolidone can be deposited on the surface of the inorganic filler when the system is mixed and stirred, and the film-forming property of polyvinyl pyrrolidone is relatively strong, which can form a film structure on the surface of the inorganic filler, thereby greatly improving the compatibility between the inorganic filler and the system, reducing its interfacial tension, and making the integrity of the DMC group material stronger. At the same time, 7-octenyl trimethoxy silane can be adsorbed on the surface of the inorganic filler as a silane coupling agent, and forms a film together with polyvinyl pyrrolidone, while the double bond it contains participates in the cross-linking of the system, so that the bonding force of the inorganic filler and the system is strengthened. The added monoethyl ethylenediaminetetraacetic acid is used as a small molecule chelating agent, which can be adsorbed on the surface of inorganic fillers, mainly the surface of nano-calcium carbonate, and chelate the calcium ions on its surface, thereby further improving the dispersibility of nano-calcium carbonate, making it more filling, and also improving its compatibility with the system to a certain extent.

[0038] The test data of Examples 1 and 4-5 show that the present application further explores the molecular weight of polyvinyl pyrrolidone, and its model is PVP K25, which is the optimal molecular weight. It is speculated that this is because the lower molecular weight affects its film formation on the surface of the inorganic filler, while the higher molecular weight affects its deposition on the surface of the inorganic filler. When the molecular weight is high, its viscosity is also higher, making it easier to act in the system.

[0039] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art may make non-creative modifications to this embodiment as needed. However, as long as such modifications are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A high-strength DMC agglomerate, characterized by: The invention comprises the following raw materials in parts by weight: 80-120 parts of unsaturated polyester resin, 20-28 parts of cross-linking agent, 18-22 parts of low shrinkage agent, 1.5-3 parts of initiator, 0.3-1 parts of polymerization inhibitor, 15-40 parts of chopped glass fiber, 180-250 parts of aluminum hydroxide, 2-4 parts of release agent, 5-15 parts of defoaming agent, 8-15 parts of nano calcium carbonate and 8-12 parts of wetting agent; The defoaming agent is an organosilicon defoaming agent containing double bonds; and the wetting agent is a mixture of polyvinyl pyrrolidone, a silane coupling agent and a small molecule chelating agent.

2. The high-strength DMC agglomerate according to claim 1, characterized in that: The defoaming agent is a polysiloxane-polyacrylate copolymer.

3. The high-strength DMC agglomerate according to claim 1, characterized in that: The mass ratio of the polyvinyl pyrrolidone, the silane coupling agent and the small molecule chelating agent is 10: (2-4): (0.5-1.5).

4. The high-strength DMC agglomerate according to claim 3, characterized in that: The silane coupling agent is a double-bond silane coupling agent.

5. The high-strength DMC agglomerate according to claim 4, characterized in that: The double bond silane coupling agent is one or more of vinyl triethoxysilane, γ-methacryloxypropyl trimethoxysilane, vinyl tributylon oxime silane, 7-octenyl trimethoxysilane, vinyl triisopropoxysilane and acryloxymethyl trimethoxysilane.

6. The high-strength DMC agglomerate according to claim 4, characterized in that: The model of the polyvinyl pyrrolidone is K17-K30.

7. The high-strength DMC agglomerate according to claim 4, characterized in that: The small molecule chelating agent is ethylenediaminetetraacetic acid monoethyl ester.

8. A method for preparing the high-strength DMC agglomerate according to any one of claims 1 to 7, characterized in that: It includes the following steps: S1, stirring and kneading unsaturated polyester resin, crosslinking agent, polystyrene low shrinkage agent, tert-butyl benzoyl peroxide, p-benzoquinone, zinc stearate, defoaming agent and wetting agent to prepare a resin paste; S2. Then, chopped glass fiber, aluminum hydroxide and nano-calcium carbonate are added to the resin paste, and stirring is continued. Then, the resin paste is sealed and aged. The temperature is maintained in the range of 30-45° C. during the aging process to obtain a bulk molding compound. S3. The bulk molding compound is compression molded at a compression molding temperature of 155-175°C, a molding pressure of 4-7 MPa, and a mold closing speed of 20-30 mm / min. After holding the pressure for 250-400 seconds, the compound is naturally cooled to obtain a high-strength DMC bulk material.

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