阅读说明：本技术 一种羟甲基化三聚氰胺甲醛树脂及其制备方法及应用 (Hydroxymethylated melamine formaldehyde resin and preparation method and application thereof ) 是由 陈明军 刘幸雅 汪婷 叶桃萍 黄保桃 肖瑶 于 2019-10-12 设计创作，主要内容包括：本发明涉及精细化工和阻燃材料技术领域,具体涉及一种羟甲基化三聚氰胺甲醛树脂粉的制备方法及应用。本发明提供一种羟甲基化三聚氰胺甲醛树脂的制备方法,所述制备方法包括如下步骤：(1)先将三聚氰胺和甲醛溶液加入反应容器中,再加入蒸馏水使体系的固含量保持在10～50％；然后控制反应温度为40℃～95℃,搅拌反应0.5～6h；(2)反应结束后,将盛装反应溶液的反应容器通过冷冻将反应溶液转变为固体反应物；(3)最后将所得固体反应物通过干燥得到羟甲基化三聚氰胺甲醛树脂粉。本发明提供一种羟甲基化三聚氰胺甲醛树脂的制备方法,利用该方法制得的羟甲基化三聚氰胺甲醛树脂具有高羟基含量和高产率的特点。(The invention relates to the technical field of fine chemical engineering and flame-retardant materials, in particular to a preparation method and application of hydroxymethylated melamine formaldehyde resin powder. The invention provides a preparation method of hydroxymethylated melamine formaldehyde resin, which comprises the following steps: (1) firstly, adding melamine and formaldehyde solution into a reaction container, and then adding distilled water to keep the solid content of the system at 10-50%; then controlling the reaction temperature to be 40-95 ℃, and stirring for reaction for 0.5-6 h; (2) after the reaction is finished, the reaction vessel containing the reaction solution is frozen to convert the reaction solution into a solid reactant; (3) and finally, drying the obtained solid reactant to obtain hydroxymethylated melamine formaldehyde resin powder. The invention provides a preparation method of hydroxymethylated melamine-formaldehyde resin, and the hydroxymethylated melamine-formaldehyde resin prepared by the method has the characteristics of high hydroxyl content and high yield.)

1. A preparation method of hydroxymethylated melamine formaldehyde resin is characterized by comprising the following steps:

(1) firstly, adding melamine and formaldehyde solution into a reaction container, and then adding distilled water to keep the solid content of the system at 10-50%; then controlling the reaction temperature to be 40-95 ℃, and stirring for reaction for 0.5-6 h; wherein the mol ratio of melamine to formaldehyde is 1: 2-1: 7; the pH value of a reaction system in the whole reaction process is 8-11;

(2) after the reaction is finished, the reaction vessel containing the reaction solution is frozen to convert the reaction solution into a solid reactant;

(3) and finally, drying the obtained solid reactant to obtain the hydroxymethylated melamine-formaldehyde resin.

2. The method for preparing a hydroxymethylated melamine-formaldehyde resin according to claim 1, wherein in the step (2), the freezing is performed by placing in a quick-freezing refrigerator or in liquid nitrogen.

3. The method for preparing hydroxymethylated melamine-formaldehyde resin according to claim 1 or 2, wherein in the step (1), an alkaline solution is used to regulate the pH value of the reaction system to 8-11; preferably 8 to 9.

4. The method for producing a hydroxymethylated melamine-formaldehyde resin according to any one of claims 1 to 3, wherein in the step (1), the concentration of the formaldehyde solution is 37 wt%.

5. The method for preparing a hydroxymethylated melamine-formaldehyde resin according to any one of claims 1 to 4, wherein in the step (1), the molar ratio of melamine to formaldehyde is 1: 3; or:

in the step (1), the solid content of the system is 20 percent; or:

in the step (1), the reaction temperature is 75-85 ℃; or:

in the step (1), the reaction time is 1-3 h.

6. The method for preparing a hydroxymethylated melamine-formaldehyde resin according to any one of claims 1 to 5, wherein in the step (3), the drying is performed by freeze drying or supercritical drying.

7. The method of claim 6, wherein the temperature of the freeze-drying is from-60 ℃ to-80 ℃.

8. A methylolated melamine-formaldehyde resin, characterized in that it is prepared by the process according to any one of claims 1 to 7.

9. Hydroxymethylated melamine formaldehyde resin according to claim 8, characterized in that it is solid.

10. The hydroxymethylated melamine-formaldehyde resin can be directly blended with other high polymer materials to prepare corresponding composite materials, and is characterized in that the hydroxymethylated melamine-formaldehyde resin is prepared by the preparation method of any one of claims 1 to 7; or a methylolated melamine formaldehyde resin according to claim 8 or 9.

Technical Field

The invention relates to the technical field of fine chemical engineering and flame-retardant materials, in particular to a preparation method and application of hydroxymethylated melamine formaldehyde resin powder.

Background

By controlling the reaction conditions of melamine and formaldehyde, methylolamine resin, methyl ether amine resin and methylene amine resin can be obtained respectively. The methylol amine resin has better water solubility, is easy to self-crosslink and solidify, is often used as a finishing agent of fabrics and paper, and endows the fabrics and the paper with waterproof, shrink-proof and crease-resistant functions. At present, the method of crystallization, centrifugal separation, evaporation drying, etc. is commonly used in industry to remove the water in the solution of methylolated melamine formaldehyde resin (abbreviated as methylol amine resin) so as to prepare the powder thereof, such as chinese patents "201010561762.0", "201010122554.0", "2016104656216" and "201810320523.2". However, the reported preparation methods have the following disadvantages: (1) in the preparation process, the hydroxymethylation melamine formaldehyde resin is easy to crosslink and solidify due to the unavoidable temperature rise and pH value reduction, so that the content of hydroxymethyl in the methylol amine resin is reduced. (2) Since the methylolamine resin solution contains a large number of hydrogen bonds, it is difficult to separate the entire methylolamine resin in the above manner, and thus the yield is low. The Chinese patent '201010122554.0' mentions that the yield is only 30%.

In addition, methylolamine resins are widely used to prepare melamine copolymer resins, melamine foams, and surface treatment agents by utilizing the property that they are susceptible to polycondensation and crosslinking reactions to form methyl ether amine resins and methylene amine resins. However, the application of methylol amine resin directly used for preparing polymer composite material to enhance the mechanical property and char-forming property of the material has not been reported yet.

Disclosure of Invention

Aiming at the defects, the invention provides a preparation method of hydroxymethylated melamine formaldehyde resin, the hydroxymethylated melamine formaldehyde resin prepared by the method has the characteristics of high hydroxyl content and high yield, and the obtained product has good carbon forming property because of high hydroxyl content and good compatibility with polyether and polyester type high polymer materials, the hydroxymethyl group in the molecule can be dehydrated to form carbon, and can be used as a carbon forming agent of an expansion flame-retardant material, and the molecule contains rigid triazine ring to enhance the tensile strength of the thermoplastic material. The polymer composite material can be directly compounded with other polymer materials to prepare the polymer composite material.

The technical scheme of the invention is as follows:

the first technical problem to be solved by the invention is to provide a preparation method of hydroxymethylated melamine formaldehyde resin, which comprises the following steps:

(1) firstly, adding melamine and formaldehyde solution into a reaction container, and then adding distilled water to keep the solid content of the system at 10-50%; then controlling the reaction temperature to be 40-95 ℃, and stirring for reaction for 0.5-6 h; wherein the mol ratio of melamine to formaldehyde is 1: 2-1: 7; the pH value of a reaction system in the whole reaction process is 8-11;

(2) after the reaction is finished, the reaction vessel containing the reaction solution is frozen to convert the reaction solution into a solid reactant;

(3) and finally, drying the obtained solid reactant to obtain hydroxymethylated melamine formaldehyde resin powder.

Further, in the step (2), the freezing mode of placing the frozen food in a quick-freezing refrigerator or liquid nitrogen is adopted.

Further, in the step (1), regulating the pH value of the reaction system to 8-11 by using an alkali solution; preferably 8 to 9. The alkali in the alkali solution is selected from sodium hydroxide or sodium carbonate.

Further, in the step (1), the concentration of the formaldehyde solution is 37 wt%.

Preferably, in the step (1), the molar ratio of melamine to formaldehyde is 1: 3.

preferably, in step (1), the solids content of the system is 20%.

Preferably, in the step (1), the reaction temperature is 75-85 ℃.

Preferably, in the step (1), the reaction time is 1-3 h.

Further, in the step (3), the drying is performed by freeze drying or supercritical drying.

Further, the temperature of the freeze drying is-60 ℃ to-80 ℃.

The second technical problem to be solved by the invention is to provide a hydroxymethylated melamine-formaldehyde resin, which is prepared by the preparation method.

Further, the methylolated melamine formaldehyde resin is a solid.

The third technical problem to be solved by the present invention is to point out: the hydroxymethylated melamine formaldehyde resin can be directly blended with other high polymer materials to prepare corresponding composite materials. For example, the methylolated melamine formaldehyde resin powder is used for enhancing the mechanical property and char formation of various high polymer materials such as polyurethane, epoxy resin, polypropylene and the like, and inhibiting the molten drop of the high polymer materials, thereby providing a new way for the use of the methylolated melamine formaldehyde resin powder.

The invention has the beneficial effects that:

(1) by adopting the method, more stable hydroxymethylated melamine formaldehyde resin powder can be prepared, and the content and yield of hydroxymethyl are higher; the prepared hydroxymethylated melamine formaldehyde resin powder can be completely dissolved in water again, and is sealed and stored for 30-60 days at room temperature after centrifugal test (3000r/min, 15min), and is still clear and transparent and does not settle.

(2) The hydroxymethylated melamine formaldehyde resin powder prepared by the invention is applied to high polymer materials such as polyurethane, epoxy resin, polypropylene and the like, and has the effects of improving char formation, inhibiting molten drops and enhancing mechanical properties; in addition, the flame retardant can be used as a char forming agent and is compounded with ammonium polyphosphate, melamine polyphosphate and other flame retardants to form an intumescent flame retardant so as to improve the flame retardant property of epoxy resin and polypropylene.

(3) The invention has simple process, low cost, environmental protection and easy popularization.

Description of the drawings:

FIG. 1 shows the molar ratio (MOL)1 in example 1: reaction for 1.5h in D of methylolated melamine resin₂The hydrogen spectrum of O; as can be seen from fig. 1:¹H NMR(300MHz，H₂O，δ/ppm)δ_-OH:4.7ppm，δ_-CH2-:3.2ppm，δ_-NH-:5.3ppm,δ_HCHO:8.0ppm。

FIG. 2 shows the MOL ratio of 1: reaction for 1.5h in D of methylolated melamine resin₂A carbon spectrum of O; as can be seen from fig. 2:¹³C NMR(300MHz,H₂O,δ/ppm)δ_N＝C＝N:163ppm，δ_-CH2OH:65ppm，δ_-CH2-O-CH2-:83ppm,δ_-NH-C-NH-:71ppm。

FIG. 3 shows the MOL ratio of 1: 3 infrared picture of methylolated melamine resin reacted for 1.5 h; as can be seen from fig. 3: 3360cm^-1Stretching vibration of N-H; 2960cm^-1Stretching vibration of-CH 2-; 1560-1390 cm^-1C is equal to N and the vibration is flexible; 990cm^-1Stretching vibration absorbed for O-H characteristics; and in 3600-2800 cm^-1A stretching vibration with a broad peak of O-H occurs.

FIG. 4 shows the MOL ratio of 1: 3 reaction time of the methylolated melamine resin and the melamine resin for 1.5h, and a thermogravimetry TG picture; as can be seen from fig. 4: the initial decomposition temperatures of the methylolated melamine resin and the melamine are 148 ℃ and 251 ℃ respectively, and the final carbon residue is 19.5 percent and 0.2 percent.

According to the nuclear magnetic infrared data, the following results are obtained: the resulting melamine resin powder is a methylolated melamine resin. From the TG data: compared with melamine, the obtained hydroxymethylated melamine resin has lower initial thermal decomposition and higher residual carbon content, which shows that the hydroxymethylated melamine resin can be better matched with a material with lower initial decomposition temperature as a char forming agent.

Detailed Description

The first technical problem to be solved by the invention is to provide a method for preparing hydroxymethylated melamine formaldehyde resin powder with high hydroxymethyl content and high yield, wherein the preparation process comprises the following steps:

(1) firstly, mixing melamine and 37% formaldehyde solution according to a molar ratio of 1: 2-1: 7, adding the mixture into a reaction bottle, and adding distilled water to keep the theoretical solid content of the mixture at 10-50%; then, the reaction temperature is controlled to be 40-95 ℃, and the stirring reaction is carried out for 0.5-6 h. The pH value of a system needs to be regulated to 8-11 by using an alkali solution in the whole reaction process;

(2) after the reaction is finished, the reaction solution is contained and placed in a quick-freezing refrigerator or liquid nitrogen, and is frozen into solid ice blocks;

(3) then, the solid ice blocks are subjected to freeze drying or supercritical drying; the hydroxymethylated melamine formaldehyde resin powder with the yield of more than 95 percent is obtained.

The following examples are given to further illustrate the embodiments of the present invention and are not intended to limit the scope of the present invention.