A melamine formaldehyde molding compound and its preparation method

Abstract

The present application relates to the technical field of molding compound preparation, specifically disclosing a melamine-formaldehyde molding compound and a preparation method thereof. A melamine-formaldehyde molding compound comprises the following components in weight percentage: 40-60% modified melamine-formaldehyde resin; 10-20% inorganic fiber; 20-40% filler; and 1-2% curing agent. The modified melamine-formaldehyde resin is prepared by the following method: mixing 4,4-diphenylmethane diisocyanate with aminopolyethylene glycol hydroxy to obtain a mixture A; mixing cellulose with mixture A, allowing the mixture to react at a temperature of 100°C to obtain a mixture B; cooling the mixture, adding the mixture to anhydrous ethanol, and precipitating the mixture to obtain an aminopolyethylene glycol hydroxy-cellulose graft copolymer; adjusting the pH of the formaldehyde to alkaline, adding melamine and the aminopolyethylene glycol hydroxy-cellulose graft copolymer, heating the mixture to react, and vacuum dehydrating the mixture to obtain the modified melamine-formaldehyde resin.

Description

Technical Field

[0001] The present application relates to the technical field of molding compounds, and more specifically, to a melamine formaldehyde molding compound and a preparation method thereof. Background Art

[0002] Melamine-formaldehyde molding compound is a thermosetting plastic composed of a resin formed by the co-condensation of formaldehyde and melamine, combined with various additives. It offers advantages such as easy molding, low molding shrinkage, high dimensional accuracy, and excellent processing properties. Due to its excellent flame retardancy, electrical leakage resistance, and arc resistance, melamine-formaldehyde molding compound products are widely used in the manufacture of electrical components such as electrical appliance housings, components, coil brackets, and switches.

[0003] However, due to the rigid polymer grid structure of melamine-formaldehyde resin, the resulting melamine-formaldehyde molding compound products have inherent mechanical defects such as insufficient toughness and brittle fracture, which limits their application. Currently, related technologies use polyethylene glycol to modify melamine-formaldehyde molding compounds to enhance their toughness. For example, a polyethylene glycol-modified melamine-methanol molding compound is prepared by subjecting melamine to a hydroxymethylation reaction with a 37wt% formaldehyde aqueous solution at 80-90°C and a pH of 8.0-9.0 to produce polyhydroxy melamine. Polyethylene glycol is then added to the polyhydroxy melamine, and the two react in a weakly alkaline environment, connecting the long polyethylene glycol chains to the triazine rings to form a flexible bis-triazine ring structure compound. This increases the distance between adjacent triazine rings, thereby improving the toughness of the material.

[0004] The test results show that the notched impact resistance of polyethylene glycol modified melamine formaldehyde molding compound is 1.5kJ / m 2 , unnotched impact strength is 5.4kJ / m 2 , with a flexural strength of 73 MPa. However, with the continuous development of technology, the toughness of polyethylene glycol-modified melamine formaldehyde molding compounds can no longer meet people's needs. Therefore, the toughness of melamine formaldehyde molding compounds still needs to be improved. Summary of the Invention

[0005] In order to improve the toughness of melamine-formaldehyde molding compound, the present application provides a melamine-formaldehyde molding compound and a preparation method thereof.

[0006] In a first aspect, the present application provides a melamine formaldehyde molding compound, which adopts the following technical solution:

[0007] A melamine formaldehyde molding compound comprises the following components in percentage by weight:

[0008] Modified melamine formaldehyde resin 40-60%;

[0009] Inorganic fiber 10-20%;

[0010] Filler 20-40%;

[0011] Curing agent 1-2%;

[0012] The modified melamine formaldehyde resin is prepared by the following method:

[0013] S1. 4,4-diphenylmethane diisocyanate and an aminopolyethylene glycol hydroxyl N,N-dimethylformamide solution are mixed to obtain a mixture A;

[0014] S2. The cellulose N,N-dimethylformamide solution was mixed with the mixture A and the mixture was reacted at room temperature to obtain a mixture B;

[0015] S3. After the mixture B was cooled, it was added to anhydrous ethanol and precipitated to obtain an amino polyethylene glycol hydroxyl - cellulose graft copolymer;

[0016] S4. The pH of the formaldehyde was adjusted to alkaline, and melamine and amino polyethylene glycol hydroxyl - cellulose graft copolymer were added, the reaction was heated to obtain a mixture C, and vacuum dehydration was performed to obtain a modified melamine formaldehyde resin;

[0017] The weight ratio of the aminopolyethylene glycol hydroxyl group, cellulose and 4,4-diphenylmethane diisocyanate is 1:(0.3-0.8):(0.5-1.5);

[0018] The weight ratio of the melamine, formaldehyde and amino polyethylene glycol hydroxyl-cellulose graft copolymer is 1:(3-6):(0.2-2).

[0019] By adopting the above technical solution, aminopolyethylene glycol hydroxyl groups are grafted onto the cellulose backbone via hydroxyl groups. By allowing the terminal amino groups of the aminopolyethylene glycol hydroxyl groups to participate in hydroxymethylation, polycondensation, and crosslinking reactions, the aminopolyethylene glycol hydroxyl-cellulose graft copolymer is inserted between two adjacent triazine rings of a melamine-formaldehyde resin, thereby modifying the melamine-formaldehyde resin. The grafting of cellulose effectively improves the toughness of the finished melamine-formaldehyde molding compound. This process allows the cellulose to be chemically modified and attached to the resin bulk, reversing the traditional practice of physically modifying cellulose molding compounds, which limits their toughening effect. This effectively enhances the cellulose modification effect and improves the toughness of the melamine-formaldehyde molding compound. Furthermore, the graft copolymer exhibits superior heat resistance to that of polyethylene glycol, effectively reducing the impact of grafting on the heat resistance of the melamine-formaldehyde molding compound.

[0020] Preferably, the average molecular weight of the aminopolyethylene glycol hydroxyl group is 2000-3500.

[0021] By adopting the above technical solution, cellulose and aminopolyethylene glycol hydroxyl groups are connected to multiple triazine rings through the reaction of amino groups on both sides of the cellulose main chain. The use of aminopolyethylene glycol hydroxyl groups with an average molecular weight of 2000-3500 can effectively increase the distance between two adjacent triazine rings, thereby further increasing the toughness of melamine formaldehyde molding compound products. At the same time, it reduces the impact of excessive polyethylene glycol chain length on other properties of the modified melamine formaldehyde molding compound, thereby improving the comprehensive performance of the modified melamine formaldehyde molding compound.

[0022] Preferably, the solid content of the modified melamine formaldehyde resin is 60-80 wt%.

[0023] By adopting the above technical solution, a modified melamine-formaldehyde resin with a solids content of 60-80wt% achieves the best results in improving the toughness of the molding compound. Furthermore, the modified melamine-formaldehyde molding compound contains less water, effectively improving adhesion between the modified melamine-formaldehyde molding compound and the mold during the molding process and reducing material warping during the molding and drying process, facilitating the molding compound's processing and thus enhancing its workability.

[0024] Preferably, the filler is an inorganic rigid filler, the inorganic rigid filler is spherical nanoparticles, and the particle size of the inorganic rigid filler is 6000-8000 mesh. More preferably, the inorganic rigid filler is one or more of alumina, silica, and calcium carbonate.

[0025] By adopting the above technical solution, the inorganic rigid filler fills the framework formed by cross-linking. When the material is deformed under stress, the inorganic rigid filler can produce a stress concentration effect, causing the surrounding body to yield, thereby absorbing a large amount of deformation work and further playing a toughening effect. Spherical nanoparticles are conducive to the occurrence of yielding, so that when the main body has not reached the yield stress of the body, local yielding occurs, thereby improving the toughness of the material body. In addition, aluminum oxide has high-temperature inertness, porosity, and good dimensional stability, and can reinforce and toughen modified melamine formaldehyde resin. Silicon dioxide can resist ultraviolet rays and improve the material's anti-aging properties, strength and chemical resistance. Calcium carbonate has a low cost and can improve the stability, hardness and rigidity of the material, improve the processing performance of plastics, improve the viscosity during the mixing process, reduce the occurrence of mold sticking, and improve the overall performance of molding materials.

[0026] Preferably, the inorganic rigid filler and the inorganic fiber are both surface-treated with a coupling agent; the coupling agent is one or more of a silane coupling agent, a titanate coupling agent, and an aluminate coupling agent.

[0027] By adopting the above technical solution, the above coupling agent molecules can react with the surface chemical groups of the inorganic material and the modified melamine formaldehyde resin at the same time to form a strong bonding effect or a physical adsorption and entanglement effect, thereby connecting the inorganic material with the modified melamine formaldehyde resin, increasing the affinity and compatibility of the filler and inorganic fiber with the modified melamine formaldehyde resin, and making the filler and inorganic fiber evenly distributed in the organic resin, ensuring that the filler and inorganic fiber can fully play their role, and maximizing the comprehensive performance of the melamine formaldehyde molding compound.

[0028] Preferably, the inorganic fibers have a fiber length of 3-12 mm.

[0029] By adopting the above technical solution, when the inorganic fiber length is less than 3 mm, the toughness of the molded product increases with fiber length, while other properties remain unchanged. When the inorganic fiber length is within the range of 3-12 mm, the toughness of the molded product is optimal, while the strength decreases slightly. As the inorganic fiber length increases, the toughness of the molded product remains unchanged, but the strength decreases significantly.

[0030] Preferably, the curing agent is one or more of dicyandiamide, m-phenoxybenzoic acid, and organic acid anhydride.

[0031] By adopting the above technical solution, all of the aforementioned curing agents are latent curing agents. These latent curing agents have no effect on the molding compound at room temperature, extending its storage life and reducing the waste of molding compound raw materials. During processing, the molding compound is heated to above 120°C, whereupon the curing agent catalyzes crosslinking and curing, facilitating its formation. Dicyandiamide is a high-temperature curing agent that is stable during production and storage. However, a low enough acid value after decomposition can affect the degree of cure and the surface gloss of the finished product. Additives such as m-phenoxybenzoic acid and organic anhydrides can promote cure and improve the surface gloss of the finished product.

[0032] In a second aspect, the present application provides a method for preparing a melamine formaldehyde molding compound, which adopts the following technical solution:

[0033] A method for preparing a melamine formaldehyde molding compound comprises the following steps:

[0034] S1. Mixing the inorganic fiber, filler and curing agent uniformly to obtain a mixture D;

[0035] S2, kneading the modified melamine formaldehyde resin and the mixture D to obtain a mixture E;

[0036] S3, spray drying to obtain melamine formaldehyde molding compound.

[0037] By adopting the above technical solution and kneading the materials, the inorganic fibers, inorganic rigid fillers and curing agent can be fully dispersed in the modified melamine formaldehyde resin, thereby ensuring the dispersion of effective molecules and improving the comprehensive performance of the molding compound.

[0038] In summary, this application has the following beneficial effects:

[0039] 1. Since the present application adopts a method of grafting cellulose with aminopolyethylene glycol hydroxyl groups, the aminopolyethylene glycol hydroxyl groups are connected to the main chain of cellulose, thereby introducing amino groups into the cellulose. Since the amino groups can participate in the hydroxylation and polycondensation reactions during the production of melamine formaldehyde resin, the aminopolyethylene glycol hydroxyl-cellulose copolymer is connected to the melamine formaldehyde resin, and the melamine formaldehyde resin is chemically modified to improve the toughness of the resin itself, thereby improving the toughness of the melamine formaldehyde molding material. At the same time, after the cellulose is grafted with the aminopolyethylene glycol hydroxyl groups, the heat resistance of the aminopolyethylene glycol hydroxyl groups is effectively improved, thereby improving the heat resistance of the modified melamine formaldehyde molding material and improving the comprehensive performance of the material.

[0040] 2. In this application, aminopolyethylene glycol hydroxyl groups with an average molecular mass of 5000-7000 are preferred. Since the aminopolyethylene glycol hydroxyl groups within this molecular mass range have a longer chain length, they can effectively increase the distance between two adjacent triazine rings, further improving the toughness of the material. At the same time, the aminopolyethylene glycol hydroxyl groups within this molecular weight range have little effect on the strength of the material, thereby maximizing the overall performance of the material.

[0041] 3. In the present application, the inorganic rigid filler is preferably spherical nanoparticles with a particle size of 6000-8000 mesh. Ultrafine particles within this particle size range have fewer surface defects and more unpaired atoms, and are more likely to physically or chemically combine with the polymer, thereby enhancing the interfacial bonding between the particles and the matrix and being more conducive to enhancing the toughness of the material. DETAILED DESCRIPTION

[0042] The present application is further described in detail below with reference to the embodiments.

[0043] Preparation Example

[0044] Preparation Example 1

[0045] A modified melamine formaldehyde resin is prepared by the following steps:

[0046] S1. 20kg of amino polyethylene glycol hydroxyl group was mixed with 40kgN,N-dimethylformamide to obtain an amino polyethylene glycol hydroxyl group-containing N,N-dimethylformamide solution, followed by the addition of 10kg4,4-diphenylmethane diisocyanate, stirred and heated to 80 ° C, and the reaction was maintained for 60min to obtain a mixture A;

[0047] S2. Vacuum-dry the cellulose at 100°C and 0.035 MPa for 48 hours to fully remove moisture from the cellulose. 6 kg of the dried cellulose was mixed with 9 kg of N,N-dimethylformamide. The mixture was heated to 100°C with stirring and maintained for 60 minutes to completely dissolve the cellulose, thereby obtaining a cellulose-containing N,N-dimethylformamide solution. The cellulose-containing N,N-dimethylformamide solution was then mixed with Mixture A and reacted at 80°C for 120 minutes to obtain Mixture B.

[0048] S3. The mixture B was cooled to 23 ° C and poured into an excess of anhydrous ethanol to precipitate the mixture to obtain an amino polyethylene glycol hydroxyl-cellulose graft copolymer;

[0049] S4. Use 30wt% sodium hydroxide to adjust the pH value of 162kg, 37wt% formaldehyde aqueous solution to 8.5, add 20kg melamine and 4kg of the prepared aminopolyethylene glycol hydroxyl-cellulose graft copolymer at 90°C, react for 120min to obtain a mixture C, and vacuum dehydrate at 0.035MPa to a solid content of 50% to obtain a modified melamine formaldehyde resin; wherein the molecular weight of the aminopolyethylene glycol hydroxyl is 1000, which is purchased from Shanghai Pengsheng Biotechnology Co., Ltd.

[0050] Preparation Example 2

[0051] A modified melamine formaldehyde resin is different from Preparation Example 1 in that the amount of aminopolyethylene glycol hydroxyl in S1 is 20 kg, the amount of N,N-dimethylformamide is 40 kg, and the amount of 4,4-diphenylmethane diisocyanate is 30 kg; the amount of dried cellulose in S2 is 6 kg, and the amount of N,N-dimethylformamide is 9 kg.

[0052] Preparation Example 3

[0053] A modified melamine formaldehyde resin is different from Preparation Example 1 in that the amount of aminopolyethylene glycol hydroxyl in S1 is 20 kg, the amount of N,N-dimethylformamide is 40 kg, and the amount of 4,4-diphenylmethane diisocyanate is 10 kg; the amount of dried cellulose in S2 is 16 kg, and the amount of N,N-dimethylformamide is 24 kg.

[0054] Preparation Example 4

[0055] A modified melamine formaldehyde resin is different from Preparation Example 1 in that the amount of aminopolyethylene glycol hydroxyl in S1 is 20 kg, the amount of N,N-dimethylformamide is 40 kg, and the amount of 4,4-diphenylmethane diisocyanate is 30 kg; the amount of dried cellulose in S2 is 16 kg, and the amount of N,N-dimethylformamide is 24 kg.

[0056] Preparation Example 5

[0057] A modified melamine formaldehyde resin is different from Preparation Example 1 in that the amount of aminopolyethylene glycol hydroxyl in S1 is 20 kg, the amount of N,N-dimethylformamide is 40 kg, and the amount of 4,4-diphenylmethane diisocyanate is 20 kg; the amount of dried cellulose in S2 is 10 kg, and the amount of N,N-dimethylformamide is 15 kg.

[0058] Preparation Example 6

[0059] A modified melamine formaldehyde resin is different from Preparation Example 5 in that the amount of formaldehyde aqueous solution used in S4 is 162 kg, the amount of melamine used is 20 kg; and the amount of the prepared amino polyethylene glycol hydroxyl-cellulose graft copolymer used is 40 kg.

[0060] Preparation Example 7

[0061] A modified melamine formaldehyde resin is different from Preparation Example 5 in that the amount of formaldehyde aqueous solution used in S4 is 324 kg, the amount of melamine used is 20 kg; and the amount of the prepared amino polyethylene glycol hydroxyl-cellulose graft copolymer used is 4 kg.

[0062] Preparation Example 8

[0063] A modified melamine formaldehyde resin is different from Preparation Example 5 in that the amount of formaldehyde aqueous solution used in S4 is 324 kg, the amount of melamine used is 20 kg; and the amount of the prepared amino polyethylene glycol hydroxyl-cellulose graft copolymer used is 40 kg.

[0064] Preparation Example 9

[0065] A modified melamine formaldehyde resin is different from Preparation Example 5 in that the amount of formaldehyde aqueous solution used in S4 is 216 kg, the amount of melamine used is 20 kg; and the amount of the prepared amino polyethylene glycol hydroxyl-cellulose graft copolymer used is 20 kg.

[0066] Preparation Example 10

[0067] A modified melamine formaldehyde resin is different from that in Preparation Example 9 in that the molecular weight of the amino polyethylene glycol hydroxyl group is 2000.

[0068] Preparation Example 11

[0069] A modified melamine formaldehyde resin is different from that in Preparation Example 9 in that the molecular weight of the amino polyethylene glycol hydroxyl group is 3000.

[0070] Preparation Example 12

[0071] A modified melamine formaldehyde resin is different from Preparation Example 9 in that the molecular weight of the amino polyethylene glycol hydroxyl group is 3500.

[0072] Preparation Example 13

[0073] A modified melamine formaldehyde resin is different from that in Preparation Example 9 in that the molecular weight of the aminopolyethylene glycol hydroxyl group is 4000.

[0074] Preparation Example 14

[0075] A modified melamine formaldehyde resin is prepared, which differs from Preparation Example 11 in that the mixture C is vacuum dehydrated at 0.035 MPa to a solid content of 60 wt %, thereby obtaining the modified melamine formaldehyde resin.

[0076] Preparation Example 15

[0077] A modified melamine formaldehyde resin is prepared, which differs from Preparation Example 11 in that the mixture C is vacuum dehydrated at 0.035 MPa to a solid content of 70 wt %, thereby obtaining the modified melamine formaldehyde resin.

[0078] Preparation Example 16

[0079] A modified melamine formaldehyde resin is prepared, which differs from Preparation Example 11 in that the mixture C is vacuum dehydrated at 0.035 MPa to a solid content of 80 wt %, thereby obtaining the modified melamine formaldehyde resin.

[0080] Preparation Example 17

[0081] A modified melamine formaldehyde resin is prepared, which differs from Preparation Example 11 in that the mixture C is vacuum dehydrated at 0.035 MPa to a solid content of 90 wt %, thereby obtaining the modified melamine formaldehyde resin.

[0082] Example

[0083] Example 1

[0084] A melamine formaldehyde molding compound is prepared by the following steps:

[0085] S1. At 80°C and 2700 rpm, 20 kg of inorganic fiber and 39 kg of filler were mixed uniformly, and dried at 90°C to constant weight. Then, 1 kg of curing agent was added at 80°C and 1200 rpm, and mixed uniformly to obtain a mixture D.

[0086] S2. Kneading mixture D and 40 kg of modified melamine formaldehyde resin at 50° C. for 60 min to obtain mixture E;

[0087] S3, spray drying to obtain powdered melamine formaldehyde molding compound.

[0088] The modified melamine formaldehyde resin is prepared according to Preparation Example 1; the inorganic fiber is ultrafine glass wool with a fiber length of 2 mm; the filler is zinc oxide with a particle size of 5000 mesh; and the curing agent is ammonium chloride.

[0089] Example 2

[0090] A melamine formaldehyde molding compound is different from Example 1 in that the amount of modified melamine formaldehyde resin used is 50 kg, the amount of inorganic fiber used is 15 kg, the amount of filler used is 33.5 kg, and the amount of curing agent used is 1.5 kg.

[0091] Example 3

[0092] A melamine formaldehyde molding compound is different from Example 1 in that the amount of modified melamine formaldehyde resin used is 60 kg, the amount of inorganic fiber used is 10 kg, the amount of filler used is 28 kg, and the amount of curing agent used is 2 kg.

[0093] Example 4-19

[0094] A melamine formaldehyde molding compound, which is different from Example 2 in that the usage of the modified melamine formaldehyde resin is shown in Table 1 below:

[0095]

[0096]

[0097] Table 1

[0098] Example 20

[0099] A melamine formaldehyde molding compound, which is different from Example 18 in that the filler zinc oxide is spherical nanoparticles with a particle size of 6000 mesh.

[0100] Example 21

[0101] A melamine formaldehyde molding compound, which is different from Example 18 in that the filler zinc oxide is spherical nanoparticles with a particle size of 7000 mesh.

[0102] Example 22

[0103] A melamine formaldehyde molding compound, which is different from Example 18 in that the filler zinc oxide is spherical nanoparticles with a particle size of 8000 mesh.

[0104] Example 23

[0105] A melamine formaldehyde molding compound, which is different from Example 18 in that the filler zinc oxide is spherical nanoparticles with a particle size of 9000 mesh.

[0106] Example 24

[0107] A melamine formaldehyde molding compound, which differs from Example 21 in that the filler is aluminum oxide with a particle size of 7000 mesh.

[0108] Example 25

[0109] A melamine formaldehyde molding compound, which differs from Example 21 in that the filler is a mixture of alumina, silica and calcium carbonate with a particle size of 7000 mesh, and the weight ratio of alumina, silica and calcium carbonate is 1:1.5:1.

[0110] Example 26

[0111] A melamine-formaldehyde molding compound differs from Example 25 in that, before step S1, a filler is mixed with a silane coupling agent and stirred for 120 minutes, inorganic fibers are mixed with the silane coupling agent and stirred for 120 minutes, and the filler and inorganic fibers are dried. The silane coupling agent is 3-chloropropylmethyldimethoxysilane, purchased from Nanjing Chengong Silicone, with the designation CG-221.

[0112] Example 27

[0113] A melamine-formaldehyde molding compound, which is different from Example 26 in that the inorganic fibers have a fiber length of 3 mm.

[0114] Example 28

[0115] A melamine-formaldehyde molding compound, which is different from Example 26 in that the inorganic fibers have a fiber length of 10 mm.

[0116] Example 29

[0117] A melamine formaldehyde molding compound, which is different from Example 26 in that the inorganic fibers have a fiber length of 12 mm.

[0118] Example 30

[0119] A melamine-formaldehyde molding compound, which is different from Example 26 in that the inorganic fibers have a fiber length of 15 mm.

[0120] Example 31

[0121] A melamine formaldehyde molding compound, which is different from Example 28 in that the curing agent is dicyandiamide, purchased from Guangzhou Xinxi Chemical, model SH-500.

[0122] Comparative Example

[0123] Comparative Example 1

[0124] A melamine formaldehyde molding compound, which differs from Example 1 in that the modified melamine formaldehyde resin is prepared by the following method:

[0125] 100 kg of 37 wt% formaldehyde was adjusted to pH 8 with 30 wt% sodium hydroxide, then heated to 50°C, 80 kg of melamine and 20 kg of polyethylene glycol were added, and the temperature was raised to 80°C. The mixture was reacted for 120 minutes and vacuum dehydrated at 0.02 MPa for 30 minutes to obtain a modified melamine formaldehyde resin.

[0126] Comparative Example 2

[0127] A melamine formaldehyde molding compound, which differs from Example 1 in that, when preparing the modified melamine formaldehyde resin, the amount of aminopolyethylene glycol hydroxyl in S1 is 20 kg, the amount of N,N-dimethylformamide is 40 kg, and the amount of 4,4-diphenylmethane diisocyanate is 6 kg; the amount of dried cellulose in S2 is 4 kg, and the amount of N,N-dimethylformamide is 6 kg.

[0128] Comparative Example 3

[0129] A melamine formaldehyde molding compound, which differs from Example 1 in that, when preparing the modified melamine formaldehyde resin, the amount of amino polyethylene glycol hydroxyl in S1 is 20 kg, the amount of N,N-dimethylformamide is 40 kg, and the amount of 4,4-diphenylmethane diisocyanate is 40 kg; the amount of dried cellulose in S2 is 20 kg, and the amount of N,N-dimethylformamide is 30 kg.

[0130] Comparative Example 4

[0131] A melamine formaldehyde molding compound, which is different from Example 1 in that when preparing the modified melamine formaldehyde resin, the amount of formaldehyde aqueous solution in S4 is 108 kg, the amount of melamine is 20 kg; the amount of the prepared amino polyethylene glycol hydroxyl-cellulose graft copolymer is 2 kg

[0132] Comparative Example 5

[0133] A melamine formaldehyde molding compound, which differs from Example 1 in that, when preparing the modified melamine formaldehyde resin, the amount of formaldehyde aqueous solution in S4 is 378 kg, the amount of melamine is 20 kg; the amount of the prepared amino polyethylene glycol hydroxyl-cellulose graft copolymer is 60 kg

[0134] Performance testing

[0135] Detection method

[0136] Bending strength: in accordance with GB / T9341-2008 standard;

[0137] Notched impact performance: in accordance with GB / T1043-2008 standard;

[0138] Unnotched impact performance: in accordance with GB / T1043-2008 standard;

[0139] Thermal deformation temperature: in accordance with GB / T1634-2004 standard; maximum bending normal stress 0.46MPa, heating rate: 2℃ / min;

[0140] The test results are detailed in Table 2 below.

[0141]

[0142]

[0143]

[0144] Table 2

[0145] Compared to Comparative Example 1, Examples 1-31 used modified melamine-formaldehyde resin grafted with aminopolyethylene glycol hydroxyl-cellulose to prepare melamine molding compounds. As shown in Table 2 above, the notched impact strength, unnotched impact strength, and flexural strength of the molding compounds prepared in Examples 1-31 were all improved to a certain extent, indicating enhanced toughness. Furthermore, the heat deformation temperature of the melamine-formaldehyde molding compounds prepared in Examples 1-31 was also increased to a certain extent, thereby improving the overall performance of the melamine-formaldehyde molding compounds. Furthermore, compared to Comparative Example 1, the melamine-formaldehyde molding compounds prepared in Comparative Examples 2-5 also exhibited improvements in various properties.

[0146] Examples 1-3 investigated the effects of varying amounts of modified melamine-formaldehyde resin, inorganic fiber, filler, and curing agent on the properties of melamine-formaldehyde molding compounds. As shown in Table 2 above, compared with Example 2, Example 1 increased the amount of inorganic fiber and filler, while Example 3 increased the amount of modified melamine-formaldehyde resin. It was found that the notched impact strength, unnotched impact strength, and flexural strength of the melamine-formaldehyde molding compounds prepared in Examples 1 and 3 all decreased, indicating that the toughness of the melamine-formaldehyde molding compound prepared in Example 2 increased, while heat resistance improved with increasing amounts of modified melamine-formaldehyde molding resin. In other words, the heat resistance of the melamine-formaldehyde molding compounds prepared in Examples 2 and 3 improved, but the improvement in heat resistance in Example 3 was smaller than that in Example 2. In summary, Example 2 exhibited the best overall performance.

[0147] Compared with Comparative Examples 2 and 3, the weight ratios of aminopolyethylene glycol hydroxyl, cellulose, and 4,4-diphenylmethane diisocyanate added in Examples 2 and 4-7 when preparing modified melamine formaldehyde resins are different. Combined with Table 2 above, it can be seen that the notched impact strength, unnotched impact strength, flexural strength, and heat distortion temperature of the melamine formaldehyde molding materials prepared in Examples 2 and 4-7 are improved, indicating that when the weight ratio of aminopolyethylene glycol hydroxyl, cellulose, and 4,4-diphenylmethane diisocyanate is within the range of 1: (0.3-0.8): (0.5-1.5), the grafting effect of cellulose and aminopolyethylene glycol hydroxyl long chains is better, the number of amino groups introduced on both sides of the cellulose main chain is the largest, and the toughness of the melamine formaldehyde molding material is improved. In addition, the heat resistance of the aminopolyethylene glycol hydroxyl-cellulose copolymer is good, which reduces the impact of the modification on the heat resistance of the melamine molding material. Among them, the one prepared in Example 7 is the best.

[0148] Compared to Comparative Examples 4 and 5, Examples 8-11 used different weight ratios of melamine, formaldehyde, and aminopolyethylene glycol hydroxyl-cellulose graft copolymer to prepare modified melamine-formaldehyde resins. As shown in Table 2 above, the melamine-formaldehyde molding compounds produced in Examples 8-11 exhibited improved notched impact strength, unnotched impact strength, flexural strength, and heat distortion temperature, with Example 11 achieving the highest performance.

[0149] Compared to Example 11, Examples 12-15 used different aminopolyethylene glycol hydroxyl molecular weights to prepare modified melamine-formaldehyde resins. As shown in Table 2, increasing the aminopolyethylene glycol hydroxyl molecular weight improves the notched impact strength, unnotched impact strength, and flexural strength of the resulting molding compounds, while decreasing the heat distortion temperature. Taking all of these factors into consideration, the melamine-formaldehyde molding compound prepared in Example 13 exhibits the best overall performance.

[0150] Compared with Example 13, the solid content of the modified melamine formaldehyde resin added in Examples 16-19 is different. Combined with Table 2 above, it can be seen that the comprehensive performance of the melamine formaldehyde molding materials prepared in Examples 16-18 improves with the increase of the solid content value. The performance of Example 19 does not change significantly, but the cost will increase. Considering the above, the melamine formaldehyde molding material prepared in Example 18 is the most preferred.

[0151] Compared with Example 18, the fillers used in Examples 20-23 have different particle sizes, and the fillers used in Examples 24 and 25 have different types. Combined with Table 2 above, it is found that the melamine formaldehyde molding compound prepared in Example 25 has the best toughness improvement effect.

[0152] Compared with Example 25, Example 26 uses a coupling agent to treat the filler and inorganic fiber. Combined with Table 2 above, it can be seen that after the filler and inorganic fiber are treated with a coupling agent, the toughness of the melamine formaldehyde molding compound is further improved.

[0153] Compared to Example 26, Examples 27-30 used inorganic fibers of varying fiber lengths. Combined with Table 2, the toughness of the melamine-formaldehyde molding compounds produced in Examples 27 and 28 was improved, while the toughness of the melamine-formaldehyde molding compounds produced in Examples 29 and 30 was not significantly improved, and the heat deformation temperature of Example 29 was somewhat reduced. In summary, Example 28 exhibited the best performance.

[0154] Compared with Example 27, the curing agent added in Example 30 is different. Combined with Table 2 above, it can be seen that Example 30 has less effect on the toughness and heat deformation temperature of the material.

[0155] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A melamine formaldehyde molding compound, characterized in that: The composition comprises the following components in weight percentage: Modified melamine formaldehyde resin 40-60%; Inorganic fiber 10-20%; Filler 20-40%; Curing agent 1-2%; The modified melamine formaldehyde resin is prepared by the following method: S1. 4,4-diphenylmethane diisocyanate and an aminopolyethylene glycol hydroxyl N,N-dimethylformamide solution are mixed to obtain a mixture A; S2. The cellulose N,N-dimethylformamide solution was mixed with the mixture A and the mixture was reacted at room temperature to obtain a mixture B; S3. After the mixture B was cooled, it was added to anhydrous ethanol and precipitated to obtain an amino polyethylene glycol hydroxyl - cellulose graft copolymer; S4. The pH of the formaldehyde was adjusted to alkaline, and melamine and amino polyethylene glycol hydroxyl - cellulose graft copolymer were added, the reaction was heated to obtain a mixture C, and vacuum dehydration was performed to obtain a modified melamine formaldehyde resin; The weight ratio of the aminopolyethylene glycol hydroxyl group, cellulose and 4,4-diphenylmethane diisocyanate is 1:(0.3-0.8):(0.5-1.5); The weight ratio of the melamine, formaldehyde and amino polyethylene glycol hydroxyl-cellulose graft copolymer is 1:(3-6):(0.2-2).

2. The melamine formaldehyde molding compound according to claim 1, characterized in that: The molecular weight of the amino polyethylene glycol hydroxyl group is 2000-3500.

3. The melamine formaldehyde molding compound according to claim 1, characterized in that: The modified melamine formaldehyde resin has a solid content of 60-80 wt %.

4. The melamine formaldehyde molding compound according to claim 1, characterized in that: The filler is an inorganic rigid filler, the inorganic rigid filler is spherical nanoparticles, and the particle size of the inorganic rigid filler is 6000-8000 meshes.

5. The melamine formaldehyde molding compound according to claim 4, characterized in that: The inorganic rigid filler is one or more of alumina, silica and calcium carbonate.

6. The melamine formaldehyde molding compound according to claim 5, characterized in that: The inorganic rigid filler and the inorganic fiber are both surface-treated with a coupling agent.

7. The melamine formaldehyde molding compound according to claim 6, characterized in that: The coupling agent is one or more of a silane coupling agent, a titanate coupling agent and an aluminate coupling agent.

8. The melamine formaldehyde molding compound according to claim 6, characterized in that: The inorganic fibers have a fiber length of 3-12 mm.

9. The melamine formaldehyde molding compound according to claim 1, characterized in that: The curing agent is one or more of dicyandiamide, m-phenoxybenzoic acid, and organic acid anhydride.

10. The method for preparing a melamine formaldehyde molding compound according to any one of claims 1 to 9, characterized in that: The method comprises the following preparation steps: S1. Mixing the inorganic fiber, filler and curing agent to obtain a mixture D; S2, kneading the modified melamine formaldehyde resin and the mixture D to obtain a mixture E; S3, spray drying to obtain melamine formaldehyde molding compound.

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