Preparation method and application of melamine rigid foam polyol for opening cells

Abstract

The present invention relates to a preparation method and application of a melamine rigid foam polyol for opening a cell, and mainly solves the problem that the preparation method of the melamine rigid foam polyol in the prior art is complicated and costly, and a cell-opening agent needs to be added when the foam is used for foaming to open the cells of the foam. The present invention provides a melamine rigid foam polyol for opening a cell, and the preparation method thereof comprises the following steps: (1) adding hexamethoxymethyl melamine and diol in a molar ratio of 1:4-6 into a reaction kettle; (2) heating under stirring, and when the material temperature is 100-129°C, adding an acidic regulator to adjust the temperature; The method comprises the following steps: (1) reacting the mixture under normal pressure at a temperature of 100 to 129° C. for 3 to 6 hours, and adding an alkaline regulator to adjust the pH value to 7 to 9; (2) performing vacuum distillation to separate small molecules, wherein the vacuum distillation temperature is 100 to 129° C. and the pressure is ‑0.08 to ‑0.10 MPa, measured by gauge pressure; and (3) performing a water content monitoring operation until the water content by mass is ≤0.5%. The method comprises the following steps: obtaining a melamine rigid foam polyol for open-cell use and applying the melamine rigid foam polyol to the open-cell use, and the melamine rigid foam polyol can be used in industrial applications of polyurethane foam.

Description

Technical Field

[0001] The invention relates to the field of melamine rigid foam polyol, and in particular to a preparation method and application of melamine rigid foam polyol for opening cells. Background Art

[0002] Polyurethane (PU) is the abbreviation of polyurethane, which is formed by the addition polymerization of polyisocyanate and polyhydroxy polymer. It is a polymer compound containing many repeated urethane segments (-NHCOO-) on the polymer main chain. Generally speaking, the cell structure of rigid polyurethane foam is mostly closed-cell type, that is, the cells are not connected to each other and exist independently. The thermal conductivity of rigid polyurethane foam is about 0.018W / (m·K) -1 , and theoretical calculations and experiments have shown that if the closed cells in rigid polyurethane foam are opened to make it into open-cell rigid polyurethane foam, its thermal conductivity under vacuum conditions can be as low as 0.007W / (m·K) -1 , which greatly improves the thermal insulation performance of rigid polyurethane foam. In addition, due to its large specific surface area, open-cell polyurethane rigid foam can also be used in sound absorption, filtration and other fields; with the development of human civilization, noise pollution has become increasingly prominent, and noise is harmful to humans in many ways, affecting people's rest, study and work; therefore, the development of open-cell polyurethane rigid foam can not only optimize and improve the thermal insulation and sound absorption performance of rigid polyurethane foam, but also broaden its application field, which is in line with the development trend of multifunctional materials.

[0003] Open-cell rigid polyurethane foam combines the characteristics of closed-cell rigid polyurethane foam and open-cell soft polyurethane foam. It not only has the excellent mechanical properties of rigid closed-cell foam, but also makes up for the defects of traditional open-cell soft foam materials in application. In the prior art, in the research of open-cell rigid polyurethane foam, most of the polyurethane foam is modified by powder, or a cell-opening agent is added. The phase separation of solid powder added to liquid composite material during the foaming process promotes the opening of foam pores. However, solid powder will seriously wear the gun head of the foaming machine, increasing the cost.

[0004] Chinese patent CN 102295616B discloses an amino resin with a polyhydroxy structure and a preparation method thereof. The preparation method comprises: (1) melamine methylolation reaction; (2) methyl etherification reaction; (3) alkali neutralization; (4) distillation to remove water, methanol and formaldehyde; (5) cooling and filtration; (6) ether exchange reaction; (7) distillation dealcoholization and cooling and filtration to obtain the finished product. The preparation method has many steps, and the reaction conditions are relatively harsh and the energy consumption is high. The polyurethane foam prepared by using the amino resin with a polyhydroxy structure is very brittle, has poor bonding performance and high cost, which limits its application and is not suitable for large-scale industrial production.

[0005] Chinese patent CN 112225862A discloses a polyurethane open-cell rigid foam composition, a preparation method and an application thereof. By adding substances such as a cell-opening agent, polyetheramine and a calcium hydroxide solution, the number of cells is increased to obtain a polyurethane rigid foam with a high open-cell ratio. However, it requires the additional addition of substances such as a cell-opening agent, which increases the material cost. Moreover, the added cell-opening agent is a solid powder. The solid powder remaining in the foaming mixture will seriously wear the gun head of the foaming machine and will also affect the mechanical properties of the foam. Summary of the invention

[0006] One of the technical problems to be solved by the present invention is that the preparation method of melamine rigid foam polyol in the prior art is complicated and costly, and a cell-opening agent needs to be added when used for foaming to make the foam open. A cell-opening melamine rigid foam polyol is provided, which has the advantages of simple preparation steps and low cost, and can make the foam open when used for polyurethane foaming without adding a cell-opening agent.

[0007] The second technical problem to be solved by the present invention is to provide an application corresponding to solving the first technical problem.

[0008] In order to solve one of the above technical problems, the technical solution adopted by the present invention is as follows: a melamine rigid foam polyol for opening cells, the preparation method of which comprises the following steps:

[0009] (1) adding hexamethoxymethyl melamine and diol in a molar ratio of 1:4-6 into a reaction kettle to form material I;

[0010] (2) heating the reaction vessel under stirring conditions, and when the temperature of the material in the reaction vessel is 100 to 129° C., adding an acidic regulator to adjust the pH value of the system to 2 to 6, thereby obtaining material II;

[0011] (3) Material II is reacted under normal pressure, the reaction temperature is 100-129° C., the reaction time is 3-6 hours, and then an alkaline regulator is added to adjust the pH value of the system to 7-9 to obtain material III;

[0012] (4) subjecting material III to vacuum distillation to separate small molecules in the system, wherein the vacuum distillation temperature is 100 to 129° C. and the pressure is -0.08 to -0.10 MPa, measured by gauge pressure, to obtain material IV;

[0013] (5) Monitoring the moisture content of material IV until the mass percentage of moisture content is ≤0.5%, thereby obtaining melamine rigid foam polyol for open-cell use.

[0014] In the above technical solution, preferably, the diol in step (1) is selected from at least one of ethylene glycol and diethylene glycol.

[0015] In the above technical solution, preferably, the acidic regulator in step (2) is selected from at least one of hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, p-toluenesulfonic acid or oxalic acid.

[0016] In the above technical solution, preferably, the pH value in step (2) is 3.5 to 5.5.

[0017] In the above technical solution, preferably, the alkaline regulator in step (3) is selected from at least one of a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution or an alkaline organic amine.

[0018] In the above technical solution, preferably, the pH value in step (3) is 7.5-8.5.

[0019] In the above technical solution, preferably, the small molecule substance in step (4) is a mixture of methanol, water, formaldehyde and diols.

[0020] In order to solve the second technical problem mentioned above, the technical solution adopted by the present invention is: adding the prepared open-cell melamine rigid foam polyol to the formula of polyurethane foam for foaming to prepare a polyurethane rigid foam product.

[0021] The invention provides a melamine rigid foam polyol for opening a cell. The preparation method thereof involves only one chemical reaction, namely, an ether exchange reaction between hexamethoxymethyl melamine and a diol under acidic conditions. At the beginning of the preparation, all the main raw materials are added into a reaction kettle at one time, and the reaction is subsequently controlled by controlling the temperature and pH of the reaction system. The whole preparation process is simple in steps, and the reaction is carried out under normal pressure, low in temperature, mild in conditions, and low in energy consumption. The prepared melamine rigid foam polyol for opening a cell is a series of medium molecular weight compounds with multiple hydroxyl groups and a certain degree of crosslinking, and has good compatibility with other raw materials for polyurethane foaming and is stable in storage. The performance test results of the melamine rigid foam polyol for opening a cell show that the hydroxyl value thereof can be as high as 582.51 mgKOH / g , the acid value is lower than 0.2mgKOH / g, which is beneficial to the improvement of the mechanical properties of the foam in the later stage; the melamine rigid foam polyol is added to the foaming formula for foaming, and we also unexpectedly found that the open-cell foam can be obtained without the need to add an additional pore opening agent. The open-cell rate of the obtained polyurethane rigid foam can be as high as 89.1%, with good open-cell property and cost saving; it avoids the disadvantage that the conventional powdered pore opening agent stays in the foaming mixture and seriously wears the foaming machine gun head; the melamine rigid foam polyol for opening cells of the present invention has the advantages of simple preparation steps, mild conditions and low energy consumption. It can be used for polyurethane foaming without the need to add an additional pore opening agent to make the foam have the advantages of high open-cell rate, no wear on the foaming gun head and low cost. It can be used in vacuum insulation, sound absorption and other fields, and has achieved good technical effects. DETAILED DESCRIPTION

[0022] The following are only preferred implementations of the present invention, and are not intended to limit the scope of protection of the present invention. All technical solutions within the scope of the present invention should fall within the scope of protection of the present invention. For professional and technical personnel in this technical field, minor improvements and modifications to the present invention without departing from the principles of the present invention should also fall within the scope of protection of the present invention.

[0023] [Example 1]

[0024] A melamine rigid foam polyol for opening cells, the preparation method of which comprises the following steps:

[0025] (1) Add 1 mol of hexamethoxymethyl melamine and 4 mol of diethylene glycol into a reaction kettle and stir evenly to obtain material I;

[0026] (2) When the temperature in the autoclave reaches 100° C., p-toluenesulfonic acid is added to material I to adjust the pH value to 3.5 to obtain material II;

[0027] (3) Material II was reacted under normal pressure, the reaction temperature was 100°C, the reaction time was 3 hours, and then triethanolamine was added to adjust the pH value to 8.0 to obtain material III;

[0028] (4) subjecting material III to vacuum distillation to separate small molecular substances in the system, the vacuum distillation temperature is 100° C., the pressure is -0.095 MPa, and the material IV is obtained by gauge pressure;

[0029] (5) The moisture content of material IV is monitored until the mass percentage of moisture is ≤0.5%, thereby obtaining melamine rigid foam polyol S1 for open-cell use. The performance data of S1 are shown in Table 3.

[0030] The prepared open-cell melamine rigid foam polyol S1 was added to the polyurethane foaming formula according to the mass fraction in Table 1. The performance index data of the prepared polyurethane rigid foam are shown in Table 4.

[0031] The raw materials used in Table 1 are as follows:

[0032] 1) AK-8805: silicone oil, manufactured by Meside;

[0033] 2) PC8: N,N-dimethylcyclohexylamine, amine catalyst, manufactured by Evonik;

[0034] 3) HCFC-141b: dichloromonofluoroethane, blowing agent, produced by Zhejiang Sanmei;

[0035] 4) M20S: a mixture of 2,4-diphenylmethane diisocyanate and 4,4-diphenylmethane diisocyanate, produced by Wanhua Chemical;

[0036] 5) NJ-4110: functionality is 4, hydroxyl value is 440 mgKOH / g, manufacturer is Jurong Ningwu New Materials Co., Ltd.

[0037] Table 1 Mass fractions of polyurethane foaming formula in Examples 1 to 6 and Comparative Examples 1 to 2

[0038]

[0039] [Examples 2 to 6]

[0040] Examples 2 to 6 are carried out according to the steps in Example 1, except that the reaction raw materials, raw material ratio, reaction time, reaction temperature, acidic regulator, alkaline regulator, and adjusted pH value are different, as shown in Table 2; the prepared open-cell melamine rigid foam polyol is added to the foaming formula of the polyurethane foam according to the mass fraction in Table 1 for foaming, and the performance index data of the prepared polyurethane rigid foam are shown in Table 4.

[0041] Table 2 Raw material mole number and reaction conditions in the preparation of melamine rigid foam polyol for opening cells in Examples 1 to 6

[0042]

[0043]

[0044] [Comparative Example 1]

[0045] Melamine rigid foam polyol was synthesized by referring to the scheme in Example 1 of the present invention, except that diethylene glycol was replaced by dipropylene glycol, and the other conditions were the same, to obtain melamine rigid foam polyol S, and the performance data of S are shown in Table 3; the prepared melamine rigid foam polyol S was added to the polyurethane foaming formula according to the mass fractions in Table 1, and the performance index data of the prepared polyurethane rigid foam are shown in Table 4.

[0046] [Comparative Example 2]

[0047] The melamine rigid foam polyol in the foaming formula was replaced with conventional polyether NJ-4110, as shown in Table 1. The performance index data of the prepared polyurethane rigid foam are shown in Table 4.

[0048] Table 3 Performance data of melamine rigid foam polyol and polyether in Examples 1 to 6 and Comparative Examples 1 to 2

[0049]

[0050]

[0051] Table 4 Performance data of polyurethane rigid foams prepared in Examples 1 to 6 and Comparative Examples 1 to 2

[0052]

[0053] From the performance data in Table 3, it can be seen that the performance test results of the open-cell melamine rigid foam polyol show that its hydroxyl value can be as high as 582.51 mgKOH / g and its acid value is lower than 0.2 mgKOH / g, which is beneficial to improving the mechanical properties of the later foaming foam.

[0054] It can be seen from the performance data of the foam in Table 4 that, under the condition of similar density, the compression strength of Examples 1 to 6 is high, which is equivalent to that of Comparative Examples 1 to 2, but the open porosity of Examples 1 to 6 is all above 85%, which is much larger than that of Comparative Examples 1 to 2. The polyurethane rigid foam has the advantage of high compression strength and high open porosity.

[0055] In summary, the present invention has the advantages of simple preparation steps, mild conditions, and low energy consumption. It can be used for polyurethane foaming to obtain high-opening-porosity polyurethane rigid foam without adding a cell-opening agent, achieves good technical effects, and can be used in the industrial production of polyurethane foam.

Claims

1. A melamine rigid foam polyol for opening cells, the preparation method of which comprises the following steps: (1) adding hexamethoxymethyl melamine and diol in a molar ratio of 1:4-6 into a reaction kettle to form material I; (2) heating the reaction vessel under stirring conditions, and when the temperature of the material in the reaction vessel is 100 to 129° C., adding an acidic regulator to adjust the pH value of the system to 2 to 6, thereby obtaining material II; (3) Material II is reacted under normal pressure, the reaction temperature is 100-129° C., the reaction time is 3-6 hours, and then an alkaline regulator is added to adjust the pH value of the system to 7-9 to obtain material III; (4) subjecting material III to vacuum distillation to separate small molecules in the system, wherein the vacuum distillation temperature is 100 to 129° C. and the pressure is -0.08 to -0.10 MPa, measured by gauge pressure, to obtain material IV; (5) monitoring the moisture content of material IV until the moisture content by mass is ≤0.5%, thereby obtaining melamine rigid foam polyol for opening cells; Wherein, the diol in step (1) is selected from at least one of ethylene glycol and diethylene glycol.

2. The melamine rigid foam polyol for opening cells according to claim 1, characterized in that The acidic regulator in step (2) is selected from at least one of hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, p-toluenesulfonic acid or oxalic acid in the form of a stock solution or a solution.

3. The melamine rigid foam polyol for opening cells according to claim 1, characterized in that The pH value in the step (2) is 3.5 to 5.

5.

4. The melamine rigid foam polyol for opening cells according to claim 1, characterized in that The alkaline regulator in step (3) is selected from at least one of a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution or an alkaline organic amine.

5. The melamine rigid foam polyol for opening cells according to claim 1, characterized in that The pH value in the step (3) is 7.5 to 8.

5.

6. The melamine rigid foam polyol for opening cells according to claim 1, characterized in that The small molecule substance in step (4) is a mixture of methanol, water, formaldehyde and diols.

7. Use of the open-cell melamine rigid foam polyol according to claim 1 in polyurethane rigid foam.

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