CN114015107B

CN114015107B - Flame-retardant melamine foam with high compressive strength and preparation method thereof

Info

Publication number: CN114015107B
Application number: CN202111215578.5A
Authority: CN
Inventors: 靳焘; 严超; 陈玉放; 张文鸽; 曹立久; 朱子凡
Original assignee: Guangzhou Chemical Co Ltd of CAS
Current assignee: Guangzhou Chemical Co Ltd of CAS
Priority date: 2021-10-19
Filing date: 2021-10-19
Publication date: 2022-12-27
Anticipated expiration: 2041-10-19
Also published as: CN114015107A

Abstract

The invention belongs to the field of material chemistry, and relates to a flame-retardant melamine foam with high compressive strength and a preparation method thereof. The preparation method comprises the steps of dissolving melamine in a formaldehyde solution, adding allyl glycidyl ether for modification to obtain modified melamine resin, and adding azodiisobutyronitrile for polymerization of the mixture to obtain the melamine resin. The content of formaldehyde in a system is reduced by using the modifier allyl glycidyl ether, the compressive strength of a foam obtained from the melamine resin is improved, and the application scene of the melamine resin is expanded.

Description

Flame-retardant melamine foam with high compressive strength and preparation method thereof

Technical Field

The invention belongs to the field of high polymer material chemistry, and particularly relates to a flame-retardant melamine foam with high compressive strength and a preparation method thereof.

Background

Justus von Liebig successfully synthesized melamine (2, 4, 6-triamino-1, 3, 5-triazine) in 1834. Melamine has become a very important chemical raw material in about 1934, mainly because melamine resin (MF) made of melamine has been widely used in life and industry. However, melamine resins and products thereof are generally accompanied by Volatile Organic Compounds (VOC) such as formaldehyde, which was listed as a suspected carcinogen in 2004 by united nations. The melamine resin is a traditional amino resin, has the advantages of self-extinguishing property, arc resistance and the like, and the application of the melamine formaldehyde resin in daily life mainly focuses on the aspects of molding compounds, coatings, material processing, coatings, finishing agents and the like. Meanwhile, with the continuous expansion of the market scale of melamine resin and derivatives thereof, the requirements on products are higher and higher.

In the early 90 s of the 20 th century, the preparation of methyl melamine, which is an outer ring N alkylated melamine derivative, was first reported, and researchers later reported the study of the physicochemical properties of methyl melamine and a typical reaction system thereof. Although the methyl melamine has high solubility in organic solvents,the reactivity of the exocyclic nitrogen is strong, but due to the high cost of the raw materials for synthesizing the methyl melamine, strict requirements on synthesis conditions and the like, the methyl melamine is difficult to be industrially produced so as to meet the requirements of industry development. Meanwhile, modification studies in the synthetic route of melamine resin are also very numerous, such as the introduction of polyethylene glycol, urea resin, acrylamide, organic silicon and other modifications to prepare modified melamine resin. The modified melamine resin has the defects of short resin storage time, foaming auxiliary agent required for foaming, low compressive mechanical strength of foam and the like, so that the long-distance transportation of the resin and the practical application of the foam are limited to a greater extent. For example, in patent publication No. CN104250386A, where example 6 corresponds to a melamine resin having a viscosity of 65000 mpa-s, the rigid foam prepared from the resin has the following performance test results: the solid content of the resin is 87.5 percent, and the density is 60g/cm ³ The heat conductivity coefficient is 0.030 w/m.k, the volume water absorption rate is 4.2 percent, the limiting oxygen index is 35.06 percent, and the compression resistance is only 0.275MPa. The melamine foam plastic is used as a material with non-toxic, flame-retardant and low heat-conducting property, and can possibly replace the traditional heat-insulating material. The melamine foam has excellent flame retardant property, the harmful gas emitted during combustion is far lower than the national standard, and the problem of fire prevention and control of high-rise buildings can be solved. The good sound absorption capacity and fire-proof property of the melamine foam plastic make the melamine foam plastic have great potential application value in the field of building materials. Since the properties of melamine resin directly affect the properties of melamine foam, the research on the synthesis of melamine resin is very important.

Disclosure of Invention

Aiming at the problems of high cost of synthetic raw materials, poor resin stability, low mechanical strength of melamine foam and the like of the traditional melamine resin, the invention aims to provide a flame-retardant melamine foam with high compressive strength and a preparation method thereof.

Based on the previous research, the research finds that the allyl glycidyl ether is used for modifying the melamine formaldehyde resin on the basis of the original preparation of the melamine resin, and the obtained modified melamine resin and foams thereof have outstanding pressure resistance, thereby solving the problems of high cost of synthetic raw materials, poor resin stability, low mechanical strength of melamine foams and the like of the traditional melamine resin.

The purpose of the invention is realized by the following technical scheme:

a preparation method of a flame-retardant melamine foam with high compressive strength comprises the following steps: dissolving melamine in a formaldehyde solution, adding an alkaline solution into the system to adjust the pH value of the system, adding allyl glycidyl ether to perform a modification reaction to obtain modified melamine-formaldehyde resin, and adding Azobisisobutyronitrile (AIBN) into the system to perform a polymerization reaction to obtain melamine-formaldehyde resin; and foaming the melamine formaldehyde resin, and cooling to obtain the melamine foam.

Further, the formaldehyde solution is 35-40% of formaldehyde aqueous solution, and the mass ratio of melamine to formaldehyde is 0.5-3.

Further, the mass ratio of melamine to formaldehyde is 1 to 2.

Further, the alkaline solution is any one of a solution of sodium hydroxide, ammonia water, or ethylenediamine.

The concentration of the alkali solution is 0.5-2mol/L, and the pH value of the system is adjusted to 8-10.5.

Further, the alkali solution is 1mol/L sodium hydroxide solution, and the pH value of the system is adjusted to 9.5.

Further, the temperature of the formaldehyde solution is 40-60 ℃, and the temperature of the modification reaction is 70-100 ℃.

Furthermore, the temperature of the formaldehyde solution is 60 ℃, and the temperature of the modification reaction is 85 ℃.

Further, the mass ratio of melamine to allyl glycidyl ether is 0.5 to 3.

Further, the mass ratio of melamine to allyl glycidyl ether is 1 to 2.

Further, the modification reaction time is 2-4.5h.

Further, the modification reaction time was 2.5 hours.

Furthermore, the Azodiisobutyronitrile (AIBN) accounts for 0.01-1% of the mass of the melamine, and the polymerization reaction is carried out for 2-4h at 70-100 ℃.

Furthermore, the Azodiisobutyronitrile (AIBN) accounts for 0.15-0.4% of the mass of the melamine, and the polymerization reaction is carried out for 2.5 hours at the temperature of 80 ℃.

The foam is a flame-retardant melamine foam with high compressive strength.

Further, the foaming is carried out for 1-5h at the temperature of 50-130 ℃.

The heating rate of the foaming is 20 ℃/2-4 h;

and (3) testing the compressive mechanical strength of the melamine foam body on an all-round stretching machine, and testing the limit oxygen index.

And obtaining the optimal preparation conditions, compressive mechanical strength and limiting oxygen index of the foam according to the transformation rule of the test data.

Furthermore, the compressive mechanical strength of the melamine foam is 3.6-6.2MPa, and the limiting oxygen index is 31% -39.2%.

Furthermore, the compressive property of the melamine foam is 6.01MPa, and the limiting oxygen index is 39.06%.

Compared with the prior art, the invention has the following advantages and beneficial effects:

(1) The preparation method is simple, and the added raw materials are few, so that the cost is low.

(2) The melamine foam body has good flame retardant property and compressive mechanical property, the melamine and formaldehyde carry out hydroxymethylation condensation reaction at high temperature, meanwhile, double bonds are introduced outside a ring by ring opening reaction between the melamine and allyl glycidyl ether, addition polymerization reaction can be carried out at high temperature, and the melamine foam body with high compressive mechanical property is prepared under the action.

Detailed Description

The present invention will be described in further detail with reference to examples, but the embodiments of the present invention are not limited thereto. The raw materials related to the invention can be directly purchased from the market. For process parameters not specifically noted, reference may be made to conventional techniques.

Example 1

(1) Preparation of melamine formaldehyde resin: when the temperature of the system is 60 ℃, dissolving 20g of melamine in 50.00ml of formaldehyde solution (35% -40%), adding 1mol/L of sodium hydroxide solution into the system to adjust the pH value of the system to 8.5, then heating to 85 ℃, beginning to dropwise add 25.00ml of allyl glycidyl ether for modification reaction, and obtaining modified melamine formaldehyde resin after 2.5 hours of reaction; 0.050g of Azobisisobutyronitrile (AIBN) was added to the system and reacted at 85 ℃ for 2.0 hours to obtain a melamine formaldehyde resin.

(2) Preparation of melamine foam: weighing 20g of melamine formaldehyde resin, placing the melamine formaldehyde resin into a mold, and placing the mold into a vacuum oven for foaming, wherein the programmed heating range of the oven is 50-130 ℃, and the heating rate is 20 ℃/4h. After the temperature programming of the oven is finished, the highest temperature of 130 ℃ is kept for foaming for 4h, and then the foam is subjected to demoulding after the oven is cooled to the normal temperature.

(3) And (3) characterizing the obtained resin and foam by using a viscosity tester, a universal stretcher, a limiting oxygen index tester and a thermal conductivity coefficient instrument.

Examples 2 to 6

Examples 2-6 the different features of the preparation of melamine formaldehyde resin and the preparation of melamine foam from example 1 are listed in table 1 below.

TABLE 1 different characteristics of examples 2-6 from example 1

The melamine formaldehyde resins and melamine foams obtained in examples 1 to 6 were tested, each according to the national standard, and the resin viscosity and the resin solids content were tested according to the experimental method of GB/T11175-2002 for synthetic resin emulsions; density was tested according to GB/T6343-2009; the heat conductivity coefficient is tested according to the steady-state thermal resistance of the heat-insulating material GB/T10294-2008; the compression resistance is tested according to a GB/T15048-1994 hard foam creep test method; the volume water absorption rate is tested according to the water absorption rate of GB/T8810-2005 rigid foam; the limit oxygen index is tested according to the oxygen index method of the GB/T2406-1993 plastic combustion performance test method. The test results are shown in table 2 below:

TABLE 2 Melamine Formaldehyde resin and Melamine foam test results

As can be seen from Table 2, the compressive property of the melamine foam can reach 6.01MPa, and the limiting oxygen index can reach 39.06 percent.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims

1. The preparation method of the flame-retardant melamine foam with high compressive strength is characterized by comprising the following steps: dissolving melamine in a formaldehyde solution, adding an alkaline solution into the system to adjust the pH value of the system, adding allyl glycidyl ether to carry out modification reaction to obtain modified melamine-formaldehyde resin, and then adding azodiisobutyronitrile into the system to carry out polymerization reaction to obtain melamine-formaldehyde resin; and foaming the melamine formaldehyde resin, and cooling to obtain the melamine foam.

2. The process according to claim 1, characterized in that the mass ratio of melamine to formaldehyde is between 0.5 and 3; the mass ratio of the melamine to the allyl glycidyl ether is 0.5-3; the azodiisobutyronitrile accounts for 0.01-1% of the mass of the melamine.

3. A process according to claim 1 or 2, characterized in that the mass ratio of melamine to formaldehyde is between 1 and 2; the mass ratio of the melamine to the allyl glycidyl ether is 1-2; the azodiisobutyronitrile accounts for 0.15-0.4% of the mass of the melamine.

4. The method of claim 3, wherein the pH of the system is adjusted to 8-10.5; the temperature of the formaldehyde solution is 40-60 ℃; the temperature of the modification reaction is 70-100 ℃, and the reaction time is 2-4.5h; the polymerization reaction is carried out for 2-4h at 70-100 ℃.

5. A process according to claim 4, characterized in that the melamine formaldehyde resin has a solids content of 50-75%.

6. The method according to claim 5, wherein the foaming is performed by holding at 50 ℃ to 130 ℃ for 1 to 5 hours.

7. The method according to claim 6, wherein the temperature rise rate of the foaming is 20 ℃/2-4 h; the formaldehyde solution is 35-40% formaldehyde water solution.

8. Melamine foam obtainable by a process according to any one of claims 1 to 7.

9. Melamine foam according to claim 8, characterized in that it has a compression resistance of 3.6-6.2MPa and a limiting oxygen index of 31-39.2%.