Preparation method of high-toughness melamine resin

Abstract

The invention relates to a preparation method of high-toughness melamine resin, and belongs to the technical field of melamine resin preparation. In the preparation method of the high-toughness melamine resin, the modifier is adopted to change crosslinking sites in the melamine resin and reduce the crosslinking density, and meanwhile, the modified white carbon black is added, so that the reduction of rigidity and wear resistance caused by the reduction of the crosslinking density can be effectively avoided. The melamine resin obtained by the preparation method disclosed by the invention has relatively good mechanical properties and relatively good wear resistance, and the toughness is remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of melamine resin preparation, and relates to a method for preparing high-toughness melamine resin. Background Art

[0002] Melamine resin is the abbreviation of melamine formaldehyde resin. It is a high molecular compound connected by methylene or ether bonds formed by carboxymethylation and polycondensation of melamine and formaldehyde. The resin has a wide range of uses. However, melamine resin liquid has some disadvantages, the most prominent of which is that it is brittle and easy to crack after curing, which greatly limits the scope of use of the product.

[0003] The curing of melamine resin is a cross-linking reaction. The two ends of the methylene or dimethylene ether bond in the resin have triazine ring structures. These triazine ring structures will be intertwined during the cross-linking process, resulting in great hardness and brittleness of the cured resin. In addition, some hydroxymethyl groups that do not participate in the cross-linking reaction will remain in the resin during the curing process. These hydroxymethyl groups will react with water in the atmosphere, making the resin hygroscopic to a certain extent. When the natural environment changes, the resin will undergo a cycle of moisture absorption and desorption, gradually generating stress, which will cause the cured resin to crack and produce many cracks, seriously affecting its application. Summary of the invention

[0004] The main purpose of the present invention is to provide a method for preparing a high-toughness melamine resin. The melamine resin prepared by the method has better toughness than traditional resins and can effectively avoid cracking and cracking that affect its use.

[0005] The present invention adopts the following technical solutions to achieve the above purpose:

[0006] A method for preparing a high-toughness melamine resin specifically comprises the following steps:

[0007] Step A, add distilled water to the reaction kettle, adjust the pH to 8.0-8.5, add paraformaldehyde and melamine, raise the temperature to 70-80° C. and keep the temperature for 1-1.5 hours to obtain reaction solution I;

[0008] Step B, adding modified white carbon black, phytic acid, and titanate coupling agent to reaction solution I, reacting at 50-60° C. under vacuum for 0.5-1 h to obtain reaction solution II;

[0009] Step C, adding semicarbazide to the reaction solution II, reacting at 50-60° C. for 0.5-1 h, filtering with suction, and drying to obtain high-toughness melamine resin.

[0010] Preferably, in step A of the above preparation method, the usage amounts of the components are: 40-45 parts by weight of paraformaldehyde and 65-75 parts by weight of melamine.

[0011] Preferably, in step B of the above preparation method, the usage amounts of the components are: 15-20 parts by weight of modified silica, 6-8 parts by weight of phytic acid, and 6-10 parts by weight of titanate coupling agent.

[0012] Preferably, in step C of the above preparation method, the amount of semicarbazide used is 8-10 parts by weight.

[0013] The present invention provides a method for preparing the modified white carbon black in step B of the above-mentioned preparation method, which specifically comprises the following steps:

[0014] Sodium cocoyl methyl taurate is heated to liquid state, white carbon black is added and ultrasonic treatment is performed, and then dimethylaminoethyl acrylate and trimellitic anhydride are added, mixed evenly, heated to 80-90°C, concentrated sulfuric acid is added, and the reaction is completed to obtain modified white carbon black;

[0015] Preferably, in the above-mentioned modified silica preparation method, the usage amount of each component is: 10-15 parts by weight of sodium cocoyl methyl taurate, 8-12 parts by weight of silica, 3-5 parts by weight of dimethylaminoethyl acrylate, 3-7 parts by weight of trimellitic anhydride, and 2-3 parts by weight of concentrated sulfuric acid.

[0016] The present invention has the following beneficial effects:

[0017] In the prior art, the flexibility of melamine resin is usually improved by reducing the crosslinking density of melamine resin and extending its flexible chain length, but the reduction of crosslinking density means that the rigid structure of the triazine ring in the resin is dispersed, and the surface rigidity and wear resistance of melamine resin will be affected to varying degrees. This problem is better avoided in the present invention. In the present invention, the use of a modifier to react with the active amino group of melamine resin can reduce the crosslinking sites in melamine resin, convert part of the network crosslinking into linear crosslinking, reduce the crosslinking density of melamine resin, and thus achieve a certain toughening effect; in order to avoid the reduction of the surface rigidity and wear resistance of the resin caused by the reduction of crosslinking density, white carbon black is added in the preparation process, but the surface of white carbon black has a large number of hydroxyl groups, so that its dispersion performance is poor, and the aggregate has the characteristic of tending to condense, resulting in its application performance being affected. In the present invention, its surface modification treatment is performed to increase its dispersibility.

[0018] The toughness of the melamine resin prepared by the method of the present invention is greatly improved compared with that of traditional melamine resin, and it has higher mechanical properties, and its impact strength and tensile strength are significantly improved, which can effectively avoid the cracks caused after curing that affect its performance, and at the same time has good wear resistance. DETAILED DESCRIPTION

[0019] The present invention is further explained below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, various equivalent modifications to the present invention by those skilled in the art all fall within the scope of protection of the claims of this application.

[0020] Example 1

[0021] Preparation of modified silica:

[0022] Heat 10 parts of sodium cocoyl methyl taurate to liquid state, add 8 parts of white carbon black and perform ultrasonic treatment, then add 3 parts of dimethylaminoethyl acrylate and 3 parts of trimellitic anhydride, mix well, heat to 90°C, add 2 parts of concentrated sulfuric acid, and complete the reaction to obtain modified white carbon black;

[0023] Preparation of high toughness melamine resin:

[0024] Step A, add distilled water to the reaction kettle, adjust the pH to 8.0, add 45 parts of paraformaldehyde and 75 parts of melamine, raise the temperature to 80°C and keep it warm for 1.5 hours to obtain reaction solution I;

[0025] Step B, adding 15 parts of modified white carbon black, 6 parts of inositol hexaphosphate, and 6 parts of titanate coupling agent to reaction solution I, reacting at 50° C. under vacuum for 1 hour to obtain reaction solution II;

[0026] Step C, add 8 parts of semicarbazide to the reaction solution II, react at 50°C for 1 hour, filter and dry to obtain high-toughness melamine resin.

[0027] Example 2

[0028] Preparation of modified silica:

[0029] Heat 15 parts of sodium cocoyl methyl taurate to liquid state, add 12 parts of white carbon black and perform ultrasonic treatment, then add 5 parts of dimethylaminoethyl acrylate and 7 parts of trimellitic anhydride, mix well, heat to 80°C, add 3 parts by weight of concentrated sulfuric acid, and complete the reaction to obtain modified white carbon black;

[0030] Preparation of high toughness melamine resin:

[0031] Step A, add distilled water to the reaction kettle, adjust the pH to 8.5, add 40 parts of paraformaldehyde and 65 parts of melamine, raise the temperature to 70°C and keep it warm for 1 hour to obtain reaction solution I;

[0032] Step B, adding 20 parts of modified white carbon black, 8 parts of inositol hexaphosphate, and 10 parts of titanate coupling agent to reaction solution I, reacting at 60° C. under vacuum for 0.5 h to obtain reaction solution II;

[0033] Step C, adding 10 parts by weight of semicarbazide to the reaction solution II, reacting at 60° C. for 0.5 h, filtering with suction, and drying to obtain a high-toughness melamine resin.

[0034] Example 3

[0035] Preparation of modified silica:

[0036] Heat 13 parts of sodium cocoyl methyl taurate to liquid state, add 10 parts of white carbon black and perform ultrasonic treatment, then add 4 parts of dimethylaminoethyl acrylate and 5 parts of trimellitic anhydride, mix well, heat to 90°C, add 2 parts of concentrated sulfuric acid, and complete the reaction to obtain modified white carbon black;

[0037] Preparation of high toughness melamine resin:

[0038] Step A, add distilled water to the reaction kettle, adjust the pH to 8.5, add 42 parts of paraformaldehyde and 70 parts of melamine, raise the temperature to 80° C. and keep the temperature for 1.5 hours to obtain reaction solution I;

[0039] Step B, adding 18 parts of modified white carbon black, 7 parts of inositol hexaphosphate, and 9 parts of titanate coupling agent to reaction solution I, reacting at 60° C. under vacuum for 1 hour to obtain reaction solution II;

[0040] Step C, add 9 parts of semicarbazide to the reaction solution II, react at 60°C for 1 hour, filter and dry to obtain high-toughness melamine resin.

[0041] Comparative Example 1

[0042] Preparation of high toughness melamine resin:

[0043] Step A, add distilled water to the reaction kettle, adjust the pH to 8.5, add 42 parts of paraformaldehyde and 70 parts of melamine, raise the temperature to 80° C. and keep the temperature for 1.5 hours to obtain reaction solution I;

[0044] Step B, adding 7 parts of inositol hexaphosphate and 9 parts of titanate coupling agent to reaction solution I, reacting at 60° C. under vacuum for 1 hour to obtain reaction solution II;

[0045] Step C, add 9 parts of semicarbazide to the reaction solution II, react at 60°C for 1 hour, filter and dry to obtain high-toughness melamine resin.

[0046] Comparative Example 2

[0047] Preparation of high toughness melamine resin:

[0048] Step A, add distilled water to the reaction kettle, adjust the pH to 8.5, add 42 parts of paraformaldehyde and 70 parts of melamine, raise the temperature to 80° C. and keep the temperature for 1.5 hours to obtain reaction solution I;

[0049] Step B, adding 18 parts of white carbon black and 9 parts of titanate coupling agent to reaction solution I, reacting at 60° C. under vacuum for 1 hour to obtain reaction solution II;

[0050] Step C, add 9 parts of semicarbazide to the reaction solution II, react at 60°C for 1 hour, filter and dry to obtain high-toughness melamine resin.

[0051] Comparative Example 3

[0052] Preparation of modified silica:

[0053] Heat 13 parts of sodium cocoyl methyl taurate to a liquid state, add 10 parts of white carbon black and perform ultrasonic treatment to obtain modified white carbon black;

[0054] Preparation of high toughness melamine resin:

[0055] Step A, add distilled water to the reaction kettle, adjust the pH to 8.5, add 42 parts of paraformaldehyde and 70 parts of melamine, raise the temperature to 80° C. and keep the temperature for 1.5 hours to obtain reaction solution I;

[0056] Step B, adding 18 parts of modified white carbon black, 7 parts of inositol hexaphosphate, and 9 parts of titanate coupling agent to reaction solution I, reacting at 60° C. under vacuum for 1 hour to obtain reaction solution II;

[0057] Step C, add 9 parts of semicarbazide to the reaction solution II, react at 60°C for 1 hour, filter and dry to obtain high-toughness melamine resin.

[0058] Melamine resin performance test

[0059] The wear rate, impact strength and tensile strength of the melamine resins prepared according to the methods of Examples 1-3 and Comparative Examples 1-3 were tested, and the toughening amplitude was tested with conventional commercially available melamine resins as a reference.

[0060] As can be seen from the results in Table 1, the mechanical properties of the melamine resin prepared according to the method of the present invention are significantly improved, and its impact strength and tensile strength are relatively high. Compared with the traditional commercially available melamine resin, the toughness is significantly enhanced, and it is wear-resistant, and the overall effect is better than the melamine resin obtained by other preparation methods (such as the melamine resin obtained in Comparative Examples 1 to 3).

[0061] Table 1 Performance indexes of melamine resin

[0062] Resin <![CDATA[Impact strength (KJ / m 2 )]]> Tensile strength(MPa) Toughening range (%) Wear rate (%) Example 1 5.38 58.67 310 0.11 Example 2 5.49 55.24 430 0.15 Example 3 5.13 53.91 390 0.20 Comparative Example 1 3.19 33.25 90 0.43 Comparative Example 2 3.51 39.84 130 0.33 Comparative Example 3 4.02 45.59 150 0.28

Claims

1. A method for preparing a high-toughness melamine resin, characterized in that: The preparation method comprises the following steps: Step A, add distilled water to the reaction kettle, adjust the pH to 8.0-8.5, add paraformaldehyde and melamine, raise the temperature to 70-80° C. and keep the temperature for 1-1.5 hours to obtain reaction solution I; Step B, adding modified white carbon black, phytic acid, and titanate coupling agent to reaction solution I, reacting at 50-60° C. under vacuum for 0.5-1 h to obtain reaction solution II; Step C, adding semicarbazide to the reaction solution II, reacting at 50-60° C. for 0.5-1 h, filtering with suction, and drying to obtain high-toughness melamine resin.

2. The preparation method according to claim 1, characterized in that: In step A of the preparation method, the usage amounts of the components are: 40-45 parts by weight of paraformaldehyde and 65-75 parts by weight of melamine.

3. The preparation method according to claim 1, characterized in that: In step B of the preparation method, the usage amounts of the components are: 15-20 parts by weight of modified white carbon black, 6-8 parts by weight of phytic acid, and 6-10 parts by weight of titanate coupling agent.

4. The preparation method according to claim 1, characterized in that: In step C of the preparation method, the amount of semicarbazide used is 8-10 parts by weight.

5. The preparation method according to claim 1, characterized in that: The preparation method of modified white carbon black in step B of the preparation method is: Heat sodium cocoyl methyl taurate to liquid state, add white carbon black and perform ultrasonic treatment, then add dimethylaminoethyl acrylate and trimellitic anhydride, mix well, heat to 80-90°C, add concentrated sulfuric acid, and complete the reaction to obtain modified white carbon black.

6. The preparation method according to claim 5, characterized in that: In the modified white carbon black preparation method, the usage amount of each component is: 10-15 parts by weight of sodium cocoyl methyl taurate, 8-12 parts by weight of white carbon black, 3-5 parts by weight of dimethylaminoethyl acrylate, 3-7 parts by weight of trimellitic anhydride, and 2-3 parts by weight of concentrated sulfuric acid.