CN115505091A - Preparation method of flame-retardant polyurethane foam - Google Patents

Abstract

The invention discloses a preparation method of flame-retardant polyurethane foam, which comprises the following specific steps: mixing paraformaldehyde and glycerol, adjusting the pH value, adding melamine, and reacting to obtain an intermediate; reacting the intermediate, cooling to 35-40 ℃, and discharging to obtain glycerol modified melamine formaldehyde resin; preparing a component A; adding the polymethylene polyphenyl polyisocyanate as the component B into the component A, and stirring at the speed of 800r/min for 1min; pouring into a mould, and freely foaming at room temperature; and curing the foam at room temperature for 24 hours, then demolding, and curing for 7 days to obtain the flame-retardant polyurethane foam. The invention provides a preparation method of a novel glycerol modified melamine-formaldehyde resin, which has the characteristics of low free formaldehyde content, high solid content and long storage time.

Description

A kind of preparation method of flame retardant polyurethane foam

technical field

The invention relates to the field of preparation of melamine formaldehyde resin, which can be applied to the fields of leather, papermaking, automobile household appliances and wood adhesives, and can also be used as a reactive flame retardant to prepare flame-retardant polyurethane materials, and more specifically relates to a flame retardant Preparation method of combustible polyurethane foam.

Background technique

Melamine formaldehyde resin is self-extinguishing, good mechanical properties and arc resistance. Melamine formaldehyde resin has played a huge role in many aspects: in the leather industry, it can be used as pre-tanning, retanning and filling resin; Used as a water-based paint crosslinking agent; in the molding compound industry of household appliances, automobiles and other industries, it can be widely used in electrical parts, tableware and daily necessities due to its good flame retardancy, high temperature resistance and pollution resistance. ;In addition, it can also be used as a dispersant for ceramics and cement, an adhesive for wood, a finishing agent for textile printing and dyeing, and a flocculant for wastewater treatment.

Usually, melamine-formaldehyde resin is very easy to solidify, forming blocky solids with high hardness and high brittleness, and formaldehyde, one of the raw materials, mostly uses 37% formaldehyde aqueous solution as a reactant, which limits the application in some fields that require high water content . For example, melamine itself is rich in nitrogen and can be added to polyurethane foam as a flame retardant to enhance its flame retardancy and expand its application in areas such as building exterior walls, pipe insulation, and furniture cushions. However, water acts as a foaming agent during the formation of foam, which greatly affects the cell structure of the foam and reduces the mechanical and thermal insulation properties of the foam. Therefore, common melamine formaldehyde resin cannot be used in polyurethane foam because of its high water content, and the development of melamine formaldehyde resin in anhydrous system can expand its application in the field of polyurethane foam.

As mentioned above, a glycerol-modified melamine-formaldehyde resin with low free formaldehyde content, high solid content, and long storage time has not yet been developed. This method has great innovation and can expand the application field of melamine-formaldehyde resin. Development of melamine formaldehyde resin.

Contents of the invention

In view of this, the invention provides a preparation method of flame-retardant polyurethane foam.

A preparation method of flame-retardant polyurethane foam, the specific steps are as follows:

S1, mixing paraformaldehyde and glycerol, adjusting the pH value of the depolymerized solution through sodium hydroxide, adding melamine, and reacting at a temperature of 70-90°C for 80-120min to obtain an intermediate;

S2, the intermediate is reacted at 50-70°C for 20-40min, cooled to 35-40°C and discharged to obtain a glycerol-modified melamine formaldehyde resin;

S3, add polyol, glycerol modified melamine formaldehyde resin, deionized water, A-33 catalyst, T-9 catalyst, L-580 foam stabilizer into a plastic bowl, stir at room temperature at a rate of 800r/min 2min, mix evenly to obtain component A;

S4, adding 160 parts of polymethylene polyphenyl polyisocyanates of component B to component A, stirring for 1min at a speed of 800r/min;

S5, pour the mixture obtained in step S4 into a mold, and freely foam at room temperature;

S6, release the foam after aging for 24h at room temperature, and continue curing at room temperature for 7 days to obtain a flame-retardant polyurethane foam.

Preferably, the above-mentioned solvent and modifying agent are glycerol, and glycerol is substituted for the aqueous solution to depolymerize and dissolve paraformaldehyde, and simultaneously glycerin can also be used as a modifying agent for melamine.

The beneficial effect of adopting the above-mentioned further technical scheme: instead of the aqueous solution system, glycerol can be used as solvent and modifying agent simultaneously, which can make the reaction still proceed in the same phase under anhydrous conditions.

Preferably, in the step S2, anhydrous glycerol modified melamine formaldehyde resin can replace polyols with equal quality and participate in the synthetic process of flame-retardant polyurethane foam.

The beneficial effect of adopting the above-mentioned further technical scheme: reduce the consumption of polyhydric alcohol, strengthen the mechanical property of foam.

Preferably, in the step S1, melamine: paraformaldehyde: the molar ratio of glycerol is 1:2-5:2-4.

The beneficial effects of adopting the above-mentioned further technical scheme: make the solvent phase state uniform, the molar ratio of each component is appropriate, the degree of crosslinking of formaldehyde resin is appropriate, and the molecular weight is appropriate.

Preferably, in the step S1, sodium hydroxide adjusts the pH value to 8-11, and the whole reaction is carried out under alkaline conditions.

The beneficial effects of adopting the above-mentioned further technical scheme: the present invention is carried out in an alkaline environment, while ensuring the crosslinking density of the resin, it greatly increases the storage stability of the resin, and at room temperature, it can be sealed and preserved for more than 300 days. Improve the degree of cross-linking of the resin to form a uniform and stable resin solution.

Preferably, in the step S3, the raw materials of component A are: 35-85 parts of polyol, 15-65 parts of glycerol modified melamine formaldehyde resin, 1 part of deionized water, A-33 0.4 parts of catalyst, 0.6 parts of T-9 catalyst, 2 parts of L-580 foam stabilizer.

Preferably, in the step S5, the size of the mold is 200mm×200mm×200mm.

Beneficial effects of the present invention: the present invention provides a kind of preparation method of novel glycerol modified melamine formaldehyde resin, and this melamine formaldehyde resin has the characteristics of low free formaldehyde content, high solid content and long storage time.

The present invention depolymerizes and dissolves paraformaldehyde and melamine under the condition that glycerol is used as a solvent and a modifying agent, and the melamine-formaldehyde resin generated maintains a liquid state and has the characteristics of high viscosity and anhydrous.

The invention provides a preparation method of flame-retardant polyurethane foam, which can replace polyol with glycerin-modified melamine formaldehyde resin and other qualities to participate in the reaction, reduce the consumption of polyol, and enhance the mechanical properties of the foam.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only It is an embodiment of the present invention, and those skilled in the art can also obtain other drawings according to the provided drawings without creative work.

Fig. 1 is the infrared spectrogram of the glycerol modified melamine formaldehyde resin that the embodiment of the present invention 4 provides;

Fig. 2 is the glycerol modified melamine formaldehyde resin ¹ H-NMR spectrogram that the embodiment of the present invention 4 provides;

Fig. 3 is the foam picture of different glycerol modified melamine formaldehyde resin additions, wherein, Fig. a is 0%, Fig. b is 15%, Fig. c is 20%, Fig. d is 25%, Fig. e is 30%, 35% for picture f, 40% for picture g, 45% for picture h, 50% for picture i, 55% for picture j, 60% for picture k, and 65% for picture l.

detailed description

The technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Example 1

Embodiment 1 of the present invention discloses the preparation of melamine-formaldehyde resin, and concrete steps are as follows: in the 500ml three-neck flask that agitator, thermometer, condensing tube are housed, add 368.4g glycerol, 150.2g paraformaldehyde, mechanically stir at most POM is depolymerized and dissolved, and sodium hydroxide is used to adjust the pH value to 8-11 to form a uniform mixed solution, then add 126.1g of melamine, raise the temperature to 90°C, adjust the solution to alkaline, react for 120min and then quickly cool down to 70°C, After continuing to react for 40 minutes, cool to 35-40°C and discharge to obtain glycerol-modified melamine formaldehyde resin.

Example 2

Embodiment 2 of the present invention discloses the preparation of melamine-formaldehyde resin, and concrete steps are as follows: in the 500ml three-neck flask that agitator, thermometer, condensing tube are housed, add 276.3g glycerin, 105.1g paraformaldehyde, mechanically stir at most POM is depolymerized and dissolved, and sodium hydroxide is used to adjust the pH value to 8-11 to form a uniform mixed solution, then add 126.1g of melamine, raise the temperature to 85°C, adjust the solution to be alkaline, react for 100min and quickly cool down to 65°C, After continuing to react for 30 minutes, cool to 35-40°C and discharge to obtain glycerol-modified melamine formaldehyde resin.

Example 3

Embodiment 3 of the present invention discloses the preparation of melamine-formaldehyde resin, and concrete steps are as follows: in the 500ml three-necked flask that stirrer, thermometer, condensation tube are housed, add 184.2g glycerin, 60.0g paraformaldehyde, mechanically stir at most POM is depolymerized and dissolved, and sodium hydroxide is used to adjust the pH value to 8-11 to form a uniform mixed solution, then add 126.1g of melamine, raise the temperature to 70°C, adjust the solution to be alkaline, react for 80 minutes and quickly cool down to 50°C, After continuing to react for 20 minutes, cool to 35-40°C and discharge to obtain glycerol-modified melamine formaldehyde resin.

Example 4

Embodiment 4 of the present invention discloses the preparation of flame-retardant polyurethane foam, and the specific steps are as follows:

The proportion of each component is as follows:

Component A: 35-85 parts of polyol; 15-65 parts of glycerin modified melamine formaldehyde resin; 1 part of deionized water; 0.4 part of A-33 catalyst; 0.6 part of T-9 catalyst; L-580 foam stabilizer 2 servings.

Component B: 160 parts of polymethylene polyphenyl polyisocyanate.

The preparation method of flame-retardant polyurethane foam is as follows:

(1) Add polyol, glycerol modified melamine formaldehyde resin, deionized water, A-33 catalyst, T-9 catalyst, L-580 foam stabilizer into a plastic bowl, at room temperature at a rate of 800r/min Stir for 2 minutes, mix evenly to obtain component A;

(2) Add 160 parts of polymethylene polyphenyl polyisocyanate in component B to component A, and stir for 1min at a speed of 800r/min;

(3) Pour the homogeneous mixture of component A and component B into a mold whose size is 200mm×200mm×200mm, and foam freely at room temperature;

(4) Demoulding the foam after aging for 24 hours at room temperature, and continuing to solidify at room temperature for 7 days to obtain a flame-retardant polyurethane foam.

Figure 1 and Figure 2 are the infrared characteristic spectrum and ¹ H-NMR spectrum of glycerol modified melamine formaldehyde resin, showing some characteristic peaks: 1560cm ^-1 , 1514cm ^-1 , 817cm ^-1 belong to the triazine ring structure Characteristic peaks. Among them, 1514cm ^-1 and 817cm ^-1 are the absorption peaks caused by the in-plane and out-of-plane stretching vibrations of the triazine ring. 2950 is assigned to the stretching vibration of -CH ₂ . The absorption peak at ¹³⁶⁷ cm was assigned to the bending vibrations of -CH and -CN. 1035cm ^-1 is attributed to the stretching vibration of COC, 3348cm ^-1 is attributed to the stretching vibration of -OH; in the H NMR spectrum, the hydrogen atom peak of melamine is mainly between δ4.6-4.7, and the hydrogen of -NH ₂ is at δ3.5 Atomic peaks, infrared characteristic spectra and ¹ H-NMR spectra indicated that melamine and glycerol successfully participated in the reaction after methylolation to form methylene bridges and ether bond structures. Figure 3 is a picture of the foam with different additions of glycerol-modified melamine formaldehyde resin. It can be seen that when the modified resin is not added, the foam expansion is small, the cells are large, and cracking occurs, which cannot meet the normal conditions of the foam. Requirements for use; as the proportion of modified resin increases from 0% to 65%, the expansion degree of the foam increases gradually, the overall volume increases significantly, the cells are more uniform and dense, and the cracking property of the foam is well improved. The addition of glycerol-modified melamine formaldehyde resin enhances the overall strength and density of the foam, and the uniform and dense cells also enhance the heat insulation performance of the foam, thus greatly improving the performance of polyurethane foam and meeting higher requirements and standard polyurethane foam use conditions.

The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (5)

1. The preparation method of the flame-retardant polyurethane foam is characterized by comprising the following specific steps of:

s1, mixing paraformaldehyde and glycerol, adjusting the pH value of a depolymerized solution by using sodium hydroxide, adding melamine, and reacting for 80-120min at the temperature of 70-90 ℃ to obtain an intermediate;

s2, reacting the intermediate at 50-70 ℃ for 20-40min, cooling to 35-40 ℃, and discharging to obtain glycerol modified melamine formaldehyde resin;

s3, adding the polyol, the glycerol modified melamine formaldehyde resin, the deionized water, the A-33 catalyst, the T-9 catalyst and the L-580 foam stabilizer into a plastic bowl, stirring for 2min at the speed of 800r/min at room temperature, and uniformly mixing to obtain a component A;

s4, adding 160 parts of polymethylene polyphenyl polyisocyanate of the component B into the component A, and stirring for 1min at the speed of 800 r/min;

s5, pouring the mixture obtained in the step S4 into a mold, and freely foaming at room temperature;

s6, curing the foam at room temperature for 24 hours, demolding, and continuously curing at room temperature for 7 days to obtain the flame-retardant polyurethane foam.

2. The method of claim 1, wherein in step S1, the ratio of melamine: paraformaldehyde: the molar ratio of glycerol is 1.

3. The method of claim 1, wherein the pH of the reaction mixture is adjusted to 8-11 in step S1, and the reaction is carried out under alkaline conditions.

4. The method for preparing flame retardant polyurethane foam according to claim 1, wherein in the step S3, the raw materials of the component A comprise, by weight: 35-85 parts of polyol, 15-65 parts of glycerol modified melamine formaldehyde resin, 1 part of deionized water, 0.4 part of A-33 catalyst, 0.6 part of T-9 catalyst and 2 parts of L-580 foam stabilizer.

5. The method of claim 1, wherein in step S5, the mold has a dimension of 200mm x 200mm.

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