阅读说明：本技术 低甲醛型密胺树脂及其应用 (Low-formaldehyde melamine resin and application thereof ) 是由 李少杰 朱益林 施剑峰 赵俊飞 孙江 于 2020-12-11 设计创作，主要内容包括：本发明涉及一种低甲醛型密胺树脂及其应用,主要解决现有技术中存在的密胺树脂中游离甲醛含量高,用于聚氨酯发泡时得到的聚氨酯泡沫气味大的问题,本发明通过提供一种低甲醛型密胺树脂,其制备方法包括以下步骤：(1)将六羟甲基三聚氰胺、甲醇、多组分醇及聚醚多元醇按摩尔比1：6～9：1～2：0.1～1加入反应容器；(2)加入酸液调节pH值；(3)常压下反应,然后加入碱液调节pH值；(4)加入甲醛捕捉剂,甲醛捕捉剂与(1)中六羟甲基三聚氰胺的摩尔比为0.01～0.1：1；(5)减压蒸馏；(6)水分监测至水分质量百分含量≤0.5％,得到游离甲醛质量百分含量≤0.1％的低甲醛型密胺树脂及其应用的技术方案,较好地解决了该问题,可用于聚氨酯泡沫制品的工业应用中。(The invention relates to a low-formaldehyde melamine resin and application thereof, and mainly solves the problems that in the prior art, the melamine resin has high free formaldehyde content and the polyurethane foam obtained when the melamine resin is used for polyurethane foaming has large odor, and the invention provides the low-formaldehyde melamine resin, and the preparation method comprises the following steps: (1) mixing hexamethylol melamine, methanol, multicomponent alcohol and polyether polyol according to a molar ratio of 1: 6-9: 1-2: 0.1-1 part of the mixture is added into a reaction container; (2) adding acid liquor to adjust the pH value; (3) reacting under normal pressure, and then adding alkali liquor to adjust the pH value; (4) adding a formaldehyde catching agent, wherein the molar ratio of the formaldehyde catching agent to the hexamethylol melamine in the step (1) is 0.01-0.1: 1; (5) carrying out reduced pressure distillation; (6) the water content is monitored until the water content is less than or equal to 0.5 percent by mass, and the low-formaldehyde melamine resin with the free formaldehyde content of less than or equal to 0.1 percent by mass and the application technical scheme thereof are obtained, so that the problem is better solved, and the melamine resin can be used for industrial application of polyurethane foam products.)

1. A low-formaldehyde melamine resin is characterized in that the preparation method comprises the following steps:

(1) mixing hexamethylol melamine, methanol, multicomponent alcohol and polyether polyol according to a molar ratio of 1: 6-9: 1-2: 0.1-1, adding the mixture into a reaction container to form a material I; the polyether polyol is at least one of polyether polyol with a hydroxyl value of 100-300 mgKOH/g, a molecular weight of less than or equal to 2000 and PO end capping;

(2) under the stirring condition, adding acid liquor into the material I when the temperature reaches 30-75 ℃, and adjusting the pH value of the system to 3-5 to obtain a material II;

(3) reacting the material II at normal pressure at the reaction temperature of 80-100 ℃ for 1-4 h, adding alkali liquor, and adjusting the pH value of the system to 7-10 to form a material III;

(4) adding a formaldehyde catching agent into the material III, and uniformly mixing, wherein the molar ratio of the added formaldehyde catching agent to the hexamethylol melamine in the step (1) is 0.01-0.1: 1, obtaining a material IV;

(5) carrying out reduced pressure distillation on the material IV to separate out small molecular substances in the system, wherein the reduced pressure distillation temperature is 30-120 ℃, the pressure is-0.08 to-0.10 MPa, and the material V is obtained by gauge pressure;

(6) and (4) monitoring the moisture of the material V until the mass percentage of the moisture is less than or equal to 0.5 percent, and obtaining the low-formaldehyde melamine resin with the mass percentage of free formaldehyde being less than or equal to 0.1 percent.

2. The melamine resin with low formaldehyde content according to claim 1, wherein the multicomponent alcohol in step (1) is at least one selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol and glycerin.

3. The low formaldehyde melamine resin of claim 1, wherein in step (1) the polyether polyol is at least one member selected from the group consisting of CHE-204 and CHE-210.

4. The melamine resin according to claim 1, wherein said acid solution in step (2) is at least one selected from the group consisting of a stock solution and a solution of hydrogen chloride, hydrogen bromide, hydrogen iodide, nitric acid, phosphoric acid, sulfuric acid, p-toluenesulfonic acid, formic acid, benzoic acid and oxalic acid.

5. The melamine resin with low formaldehyde content according to claim 1, wherein the alkali solution in the step (3) is at least one selected from the group consisting of an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution and an organic amine.

6. The melamine resin with low formaldehyde content according to claim 1, wherein the formaldehyde scavenger in step (4) is at least one selected from the group consisting of urea, hydrazine hydrate and ammonia.

7. The melamine resin with low formaldehyde content according to claim 1, wherein the small molecule substance in the step (5) is a mixture of free formaldehyde, water and methanol.

8. Use of the low-formaldehyde melamine resin of claim 1 in polyurethane foams.

Technical Field

The invention relates to the field of melamine resin, in particular to low-formaldehyde melamine resin and application thereof.

Background

Along with the continuous development of national economy, the application field of melamine resin is continuously expanded, the using amount is continuously increased, and meanwhile, along with the improvement of environmental awareness of people, the influence of free formaldehyde in the melamine resin on human health is more and more concerned. Formaldehyde is a gas, also called ant aldehyde, colorless gas at normal temperature has special smell, and its aqueous solution is formalin which is commonly called as a common preservative. Formaldehyde is the second highest on the priority control list of toxic chemicals in China, and is listed as a first carcinogen by the International agency for research on cancer (IARC) in 2004, and is a carcinogenic and teratogenic substance. Formaldehyde can cause eye lacrimation and stomach dysfunction, and can cause persistent headache, pneumonia, pulmonary edema, loss of appetite and even death in severe cases; chronic respiratory diseases can be caused by long-term exposure to low-dose formaldehyde, nasopharyngeal carcinoma, colon cancer, brain tumor, menstrual disorder and gene mutation of cell nucleus can be caused, and nausea, vomiting, cough, chest distress, asthma, pulmonary edema and even death caused immediately can be caused when the formaldehyde is in higher concentration. At present, the minimum standard of the content of free formaldehyde in melamine resin in China is less than or equal to 2.0 percent, generally 3.0 percent, seriously pollutes the environment and influences the physical and psychological health of human beings, so the problem that how to reduce the content of the free formaldehyde in the melamine resin is necessary to be faced. Although there have been some reports of reducing free formaldehyde in melamine resins, it generally increases the cost and processing steps.

Chinese patent CN106046285A discloses a production method of melamine type series polyols, which is a method for preparing melamine resin by reacting melamine with paraformaldehyde under an alkaline condition to obtain methylol melamine and then etherifying the methylol melamine with a multi-component alcohol mixture under an acidic condition.

According to the technical scheme, on the premise of not increasing cost and working procedures, the content of free formaldehyde can be reduced to be below 1.0% by adjusting the synthesis process, so that the pollution of formaldehyde is reduced, and the basic performance of melamine resin is ensured; when the polyurethane foam is applied to polyurethane foam, the effect of reducing the odor of the polyurethane foam can be achieved.

VDA270-2018 are common odor test criteria, and 6-grade evaluation criteria are adopted for odor evaluation: level 1 indicates no odor, level 2 indicates odor but not disturbing, level 3 indicates significant odor but not disturbing, level 4 indicates disturbing odor, level 5 indicates strong disturbing odor, and level 6 indicates intolerable; and 3-5 people participate in odor evaluation, the evaluation result can be described in a half-grade mode, the average value is taken as the final odor grade result, and the lower the grade is, the smaller the odor is.

Disclosure of Invention

One of the technical problems to be solved by the present invention is to provide a low-formaldehyde melamine resin, which has the advantages of high free formaldehyde content and low odor of polyurethane foam obtained when the melamine resin is used for polyurethane foaming, wherein the melamine resin has the problems of high free formaldehyde content and high odor of polyurethane foam obtained when the melamine resin is used for polyurethane foaming in the prior art.

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

In order to solve one of the above technical problems, the technical scheme adopted by the invention is as follows: a low-formaldehyde melamine resin is characterized in that the preparation method comprises the following steps:

(1) mixing hexamethylol melamine, methanol, multicomponent alcohol and polyether polyol according to a molar ratio of 1: 6-9: 1-2: 0.1-1, adding the mixture into a reaction container to form a material I; the polyether polyol is at least one of polyether polyol with a hydroxyl value of 100-300 mgKOH/g, a molecular weight of less than or equal to 2000 and PO end capping;

(2) under the stirring condition, adding acid liquor into the material I when the temperature reaches 30-75 ℃, adjusting the pH value of the system to 3-5,

obtaining a material II;

(3) reacting the material II at normal pressure at the reaction temperature of 80-100 ℃ for 1-4 h, adding alkali liquor, and adjusting the pH value of the system to 7-10 to form a material III;

(4) adding a formaldehyde catching agent into the material III, and uniformly mixing, wherein the molar ratio of the added formaldehyde catching agent to the hexamethylol melamine in the step (1) is 0.01-0.1: 1, obtaining a material IV;

(5) carrying out reduced pressure distillation on the material IV to separate out small molecular substances in the system, wherein the reduced pressure distillation temperature is 30-120 ℃, the pressure is-0.08 to-0.10 MPa, and the material V is obtained by gauge pressure;

(6) and (4) monitoring the moisture of the material V until the mass percentage of the moisture is less than or equal to 0.5 percent, and obtaining the low-formaldehyde melamine resin with the mass percentage of free formaldehyde being less than or equal to 0.1 percent.

In the above technical solution, preferably, the multicomponent alcohol in step (1) is at least one selected from ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, and glycerin.

In the above technical solution, preferably, the polyether polyol in the step (1) is selected from at least one of CHE-204 or CHE-210.

In the above technical solution, preferably, the acid solution in step (2) is at least one of a stock solution or a solution of hydrogen chloride, hydrogen bromide, hydrogen iodide, nitric acid, phosphoric acid, sulfuric acid, p-toluenesulfonic acid, formic acid, benzoic acid, and oxalic acid.

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

In the above technical solution, preferably, the formaldehyde scavenger in the step (4) is at least one selected from urea, hydrazine hydrate, and ammonia water.

In the above technical solution, preferably, the small molecule substance in step (5) is a mixture of free formaldehyde, water and methanol.

In order to solve the second technical problem, the invention adopts the technical scheme that: adding the prepared low-formaldehyde melamine resin into a formula of polyurethane foam for foaming to prepare a polyurethane foam product.

The invention provides a low-formaldehyde melamine resin, which is prepared by adjusting a synthesis process, wherein free formaldehyde is removed in two steps in the reaction process by adjusting the synthesis process, firstly, the formaldehyde is removed by using polyether polyol under an acidic condition, secondly, the formaldehyde is removed by using a formaldehyde catcher under an alkaline condition, specifically, PO (Poly ether polyol) terminated end is added in a synthesis raw material, hexamethylol melamine firstly undergoes etherification reaction with methanol under the acidic condition to generate hexamethoxy melamine, the hexamethoxy melamine then undergoes ether exchange reaction with polyol and polyether polyol to form a structure with a polyether long chain, and secondary hydroxyl and ortho methyl at the tail end in the PO terminated polyether undergo acetal reaction with the formaldehyde to achieve the purpose of removing the formaldehyde in the reaction process; in addition, after the reaction is finished, formaldehyde catching agents such as urea and the like are added to achieve the aim of continuously removing residual formaldehyde in the system under the alkaline condition; under the condition that basic performance of the finally obtained melamine resin is not changed, the mass percentage content of free formaldehyde can reach below 0.1 percent, and the melamine resin has the advantage of low content of free formaldehyde; when the low-formaldehyde melamine resin is added into a polyurethane foam formula to prepare a polyurethane foam product, the odor grade of the obtained polyurethane foam is reduced from 6.0 to 3.5, and the low-formaldehyde melamine resin has the advantage of low odor and achieves better technical effects.

Detailed Description

The following is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and any technical solutions that fall under the spirit of the present invention should fall within the scope of the present invention, and it should be understood that those skilled in the art should make minor modifications and decorations to the present invention without departing from the principle of the present invention.

The polyether polyols used in examples 1-6 were as follows:

1) CHE-204: a PO capped polyether polyol having a functionality of 2 and a molecular weight of 400;

2) CHE-210: a PO capped polyether polyol with a functionality of 2 and a molecular weight of 1000.

[ example 1 ]

1. The preparation method of the low-formaldehyde melamine resin comprises the following steps:

(1) adding 1mol of hexamethylol melamine, 7.5mol of methanol, 1.5mol of propylene glycol and 0.5mol of polyether polyol CHE-204 into a reaction kettle to form a material I;

(2) under the condition of stirring, when the temperature reaches 65 ℃, adding a methanol solution of p-toluenesulfonic acid with the mass percentage of 31.5% into the material I, and adjusting the pH value of the system to be 3.5 to obtain a material II;

(3) reacting the material II at normal pressure at the reaction temperature of 90 ℃ for 2h, adding triethanolamine, and adjusting the pH value of the system to 8 to form a material III;

(4) adding 0.07mol of urea into the material III, and uniformly mixing to obtain a material IV;

(5) carrying out reduced pressure distillation on the material IV to separate out small molecular substances in the system, wherein the reduced pressure distillation temperature is 90 ℃, the pressure is-0.085 MPa, and the material V is obtained by gauge pressure;

(6) monitoring the moisture of the material V until the moisture mass percentage content is less than or equal to 0.5 percent, and obtaining the low-formaldehyde melamine resin S₁，S₁The performance data of (A) are shown in Table 3.

2. The prepared melamine resin S with low formaldehyde content₁The performance index data of the polyurethane foam prepared by adding the components in the mass parts in the table 1 into the polyurethane foaming formula are shown in the table 4.

The raw materials used in table 1 are as follows:

1) NJ-4110: polyether polyol with a hydroxyl value of 440 +/-30 mgKOH/g, a functionality of 4-4.5 and a viscosity of 3000 +/-500 mPa & s (25 ℃), wherein a manufacturer is full sentence Ningwu;

2) AK-8805: silicone oil, manufacturer is maillard;

3) PC 8: n, N-dimethyl cyclohexylamine and an amine catalyst are created by manufacturers;

4) HCFC-141 b: monofluoro dichloroethane, foaming agent, the manufacturer is Zhejiang Sanmei;

5) MDI-50: the mixture of 2, 4-diphenylmethane diisocyanate and 4, 4-diphenylmethane diisocyanate was manufactured in kaleidoscope chemistry.

TABLE 1 parts by mass of polyurethane foaming formulations in examples 1 to 6 and comparative example 1

[ examples 2 to 6 ]

Examples 2 to 6 were carried out according to the steps of example 1, except that the reaction raw materials, raw material ratios, reaction time, reaction temperature, acid solution, alkali solution, and adjusted pH values were different, as shown in table 2; the prepared low-formaldehyde melamine resin is added into a foaming formula of the polyurethane foam according to the mass parts in the table 1 for foaming, and the performance index data of the prepared polyurethane foam is shown in the table 4.

TABLE 2 EXAMPLES 1 TO 6 raw material moles and reaction conditions in preparation of Low Formaldehyde Melamine resin

[ COMPARATIVE EXAMPLE 1 ]

1. The melamine resin was synthesized according to the method of example 1 in patent CN106046285a, the steps are as follows:

(1) checking whether the equipment is ready, ensuring that the reaction kettle is dried, and a condensed water, heating and vacuumizing system runs normally;

(2) and (2) opening a condensed water and heating system, setting the temperature in the reaction kettle to be 95 ℃, setting the operating pressure of the reaction kettle to be 0.101MPa, putting 630g of melamine, 1200g of paraformaldehyde, 760g of 1, 2-propylene glycol and 1200g of methanol into the reaction kettle by gauge pressure, stirring at the rotating speed of 80rpm, starting heating, adding 27.5g of sodium hydroxide solution with the mass percentage content of 20% when the temperature in the kettle is 65 +/-2 ℃, adjusting the pH value of the system to be 9.5, continuing to heat up to reach the set temperature value, and then keeping the temperature for reaction for 2 hours.

(3) Adding 25g of 35% hydrochloric acid solution in percentage by mass to adjust the pH of the system to 3.5, continuing to perform heat preservation reaction for 1 hour, starting a vacuum pump to perform reduced pressure distillation on the system to separate free micromolecular substances in the system, wherein the operating pressure is-0.080 MPa, and the operating temperature is 30 +/-2 ℃.

(3) Collecting distillate until the mass of the distillate is 1175 +/-5 kg, adjusting the pH of the system to 8.5 by using 20g of 20% sodium hydroxide solution in percentage by mass, continuously reducing the pressure of the system, testing the water content of the product in the kettle in the middle until the mass percentage of the water content is less than or equal to 0.5%, and obtaining the propylene glycol type melamine resin S after the preparation, wherein the performance data of the S is shown in Table 3.

2. The prepared melamine resin S was added in the mass parts shown in table 1 to the foaming formula of the polyurethane foam for foaming, and the performance index data of the obtained polyurethane foam is shown in table 4.

TABLE 3 Performance data of the melamine resins prepared in examples 1 to 6 and comparative example 1

TABLE 4 Performance data for polyurethane foams prepared in examples 1-6 and comparative example 1

As can be seen from the performance data in table 3, the conventional index performance data of the low-formaldehyde melamine resin prepared in the embodiments 1 to 6 of the present application is similar to that of the comparative example 1, but the mass percentage of free formaldehyde is below 0.1%, which is much less than 2.60% in the comparative example 1, and it can be seen that by using the process adjustment scheme of the present invention, the process and cost are not increased for the synthesis process, the operation is simple, and the content of free formaldehyde in the prepared melamine resin is effectively reduced on the premise of not affecting the conventional performance index, and the prepared melamine resin is a low-formaldehyde melamine resin; the prepared melamine resin is applied to a foaming formula of polyurethane foam, the odor grade of the obtained polyurethane foam is effectively reduced under the condition that the conventional physical performance indexes of the oxygen index and the compression strength of the polyurethane foam are basically unchanged, the odor grade of examples 1-6 is smaller than that of comparative example 1, the odor grade of examples 1-6 can be reduced from 6.0 of comparative example 1 to 3.5 of example 4, a good technical effect is achieved, and the melamine resin can be applied to the application of the polyurethane foam.