阅读说明：本技术 一种低甲醛硬挺剂的制备方法 (Preparation method of low-formaldehyde stiffening agent ) 是由 何文栋 杨小波 缪宇龙 张德明 司马聪 陈萍萍 于 2020-06-30 设计创作，主要内容包括：本发明公开了一种低甲醛硬挺剂的制备方法。现有的硬挺剂主要以三聚氰胺、甲醛和尿素缩聚而成,原料中过量甲醛的使用,使得硬挺剂产品中游离甲醛含量较高,对人体和环境有较大的影响。本发明以尿素、甲醛、三聚氰胺、有机胺和甲醇为原料,通过双釜工艺制备出高醚化度三聚氰胺-尿素-甲醛树脂,提高了甲醛参与反应的转化率,并且通过气体气提工艺将成品中大部分游离甲醛去除,所制备的硬挺剂游离甲醛≤0.2％,更加符合用户对环保的要求。(The invention discloses a preparation method of a low-formaldehyde stiffening agent. The existing stiffening agent is mainly formed by condensation polymerization of melamine, formaldehyde and urea, and excessive formaldehyde is used in the raw materials, so that the content of free formaldehyde in the stiffening agent product is higher, and the stiffening agent product has larger influence on human bodies and the environment. The melamine-urea-formaldehyde resin with high etherification degree is prepared by taking urea, formaldehyde, melamine, organic amine and methanol as raw materials through a double-kettle process, the conversion rate of the formaldehyde participating in the reaction is improved, most of free formaldehyde in a finished product is removed through a gas stripping process, and the prepared stiffening agent free formaldehyde is less than or equal to 0.2 percent and meets the requirement of a user on environmental protection better.)

1. A preparation method of a low-formaldehyde stiffening agent is characterized by comprising the following steps:

1) putting low-carbon alcohol into a reaction kettle A, and adding a proper amount of acid to adjust the pH value of the solution in the reaction kettle A to 4.0-6.0; heating to 60-62 ℃, and keeping the solution in the reaction kettle A in a boiling reflux state for later use;

2) adding low-carbon alcohol into the reaction kettle B, stirring, adding urea, melamine, organic amine and formaldehyde, adjusting the pH value of the reaction system to 7.5-9.5 by using alkali, heating to 78-82 ℃, and preserving heat for 60-90 minutes; the mol ratio of melamine to urea is 1-3: 1; the mol ratio of the lower alcohol to the formaldehyde is 1-3: 1; the dosage of the organic amine is 2-8% of the mass of the formaldehyde;

3) pumping the materials in the reaction kettle B in the step 2) into the reaction kettle A in the step 1), mixing and reacting the materials in the kettle for 20-60 minutes after the materials are added, and adjusting the pH value to 7.0-9.0 by using alkali when the polycondensation end point appears;

4) cooling the material in the reaction kettle A to below 60 ℃, transferring the material to a distillation kettle by a pump, removing redundant water, formaldehyde and low-carbon alcohol in the system by reduced pressure distillation, distilling the solid content of the product to 70-80 percent, and transferring the product to a gas stripping tower, wherein the free formaldehyde content is 0.6-1.0 percent;

5) gas enters from the bottom of the stripping tower after being preheated, the finished product of the stiffening agent in the stripping tower is input from the top of the tower, the feeding amount of the stiffening agent is kept at 600-1200 kg/h, and the feeding amount of the gas is kept at 400-1000m³In the reaction, the free formaldehyde in the stiffening agent is continuously discharged from the top of the tower along with the gas through the gas-liquid separation function in the stripper, and the finished stiffening agent is continuously discharged from the bottom of the tower;

6) and stopping the reaction when the free formaldehyde is less than or equal to 0.2 percent.

2. The method of claim 1, wherein the base used for adjusting the pH is one or a mixture of two or more of liquid alkali, potassium hydroxide and ammonia water.

3. The method according to claim 1, wherein the organic amine is one or a mixture of two or more of triethylamine, triethanolamine, ethylenediamine, ethanolamine and diethanolamide.

4. The method according to claim 1, wherein the acid for adjusting the pH is one or a mixture of two or more of hydrochloric acid, sulfuric acid, nitric acid, citric acid and formic acid.

5. The method of claim 1, wherein the lower alcohol is selected from one or more of methanol, ethanol, isopropanol, and isobutanol.

6. The method of claim 1, wherein the stripping gas is selected from the group consisting of nitrogen and air.

7. The method according to claim 1, wherein the formaldehyde is 44% by mass of an aqueous formaldehyde solution.

Technical Field

The invention relates to the field of printing and dyeing auxiliaries, in particular to a preparation method of a low-formaldehyde stiffening agent.

Background

Formaldehyde is an irritant gas, toxic and dangerous to cause cancer, and thus, various countries have severe restrictions on formaldehyde on textiles. The melamine-urea-formaldehyde resin is a common stiffening agent with high cost performance, and excessive formaldehyde can be used in the preparation of the stiffening agent, so that the stiffening agent product has higher free formaldehyde, and the free formaldehyde of general products is more than or equal to 1%. Particularly in summer, methanol in the product is mixed with free formaldehyde and volatilizes into the air, thereby seriously harming the physical and mental health of producers and users and also reducing the quality of the product.

The reaction process for preparing the stiffening agent comprises two processes of hydroxymethylation reaction and etherification reaction of condensation polymerization of melamine, urea and formaldehyde. The existing preparation process of the stiffening agent mainly adopts a single-kettle process, wherein an etherifying agent is added into a hydroxymethylated polycondensate, the etherifying agent is added into the hydroxymethylated polycondensate for a long time, and the etherifying degree is low due to the shortage of the etherifying agent at the periphery of the hydroxymethylated polycondensate in the early stage of etherification, a large amount of hydroxymethylated compounds exist in resin, and the hydroxymethylated compounds are easy to remove formaldehyde again, so that a large amount of free formaldehyde exists in the stiffening agent, and the free formaldehyde of the common single-kettle process is more than 1 percent.

The existing method for preparing the low-formaldehyde stiffening agent mainly comprises two modes of improving the alcohol-water ratio in synthesis and adding an aldehyde capturing agent after reaction. The main principle of the method is that methanol is removed through a concentration process, and the methanol removal can take away residual formaldehyde, so that the content of the free formaldehyde in the stiffening agent is reduced. The principle of adding the aldehyde capturing agent is that the aldehyde capturing agent reacts with free formaldehyde to reduce the free formaldehyde in the product, and the addition of the aldehyde capturing agent can damage the original structure of the resin, so that the stiffness is reduced, and the hand feeling is influenced. The reaction of the aldehyde trap with formaldehyde produces unstable methylol compounds which readily crosslink, resulting in a stiffening product with a shorter shelf life. None of these methods is a scientifically efficient way to prepare low formaldehyde stiffeners.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides the preparation method of the low-formaldehyde stiffening agent, so that the prepared stiffening agent has higher etherification degree, more stable product and higher stiffness, and the free formaldehyde is less than or equal to 0.2 percent, thereby reducing the harm to users and being more suitable for stiffening processing.

Therefore, the invention adopts the following technical scheme: a preparation method of a low-formaldehyde stiffening agent comprises the following steps:

1) putting low-carbon alcohol into a reaction kettle A, and adding a proper amount of acid to adjust the pH value of the solution in the reaction kettle A to 4.0-6.0; heating to 60-62 ℃, and keeping the solution in the reaction kettle A in a boiling reflux state for later use;

2) adding low-carbon alcohol into the reaction kettle B, stirring, adding urea, melamine, organic amine and formaldehyde, adjusting the pH value of the reaction system to 7.5-9.5 by using alkali, heating to 78-82 ℃, and preserving heat for 60-90 minutes; the mol ratio of melamine to urea is 1-3: 1; the mol ratio of the lower alcohol to the formaldehyde is 1-3: 1; the dosage of the organic amine is 2-8% of the mass of the formaldehyde;

3) pumping the materials in the reaction kettle B in the step 2) into the reaction kettle A in the step 1), mixing and reacting the materials in the kettle for 20-60 minutes after the materials are added, and adjusting the pH value to 7.0-9.0 by using alkali when the polycondensation end point appears;

4) cooling the material in the reaction kettle A to below 60 ℃, transferring the material to a distillation kettle by a pump, removing redundant water, formaldehyde and low-carbon alcohol in the system by reduced pressure distillation, distilling the solid content of the product to 70-80 percent, and transferring the product to a gas stripping tower, wherein the free formaldehyde content is 0.6-1.0 percent;

5) gas (es)The preheated material enters from the bottom of the stripping tower, the finished product of the stiffening agent in the stripping tower is input from the top of the tower, the feeding amount of the stiffening agent is kept at 600-charge 1200 kg/h, and the feeding amount of the gas is kept at 400-charge 1000m³In the reaction, the free formaldehyde in the stiffening agent is continuously discharged from the top of the tower along with the gas through the gas-liquid separation function in the stripper, and the finished stiffening agent is continuously discharged from the bottom of the tower;

6) and stopping the reaction when the free formaldehyde is less than or equal to 0.2 percent.

Preferably, the alkali for adjusting the pH value is one or a mixture of more than two of liquid alkali, potassium hydroxide and ammonia water.

Preferably, the organic amine is one or a mixture of two or more of triethylamine, triethanolamine, ethylenediamine, ethanolamine and diethanolamide.

Preferably, the acid for adjusting the pH is one or a mixture of two or more of hydrochloric acid, sulfuric acid, nitric acid, citric acid, and formic acid.

Preferably, the lower alcohol is one or a mixture of two or more of methanol, ethanol, isopropanol and isobutanol.

Preferably, the stripping gas is selected from nitrogen and air or their mixture.

Preferably, the formaldehyde used is a 44% by mass aqueous formaldehyde solution.

Compared with the prior art, the invention has the following beneficial effects: in the reaction synthesis, the etherification degree of the stiffening agent is improved by adopting a double-kettle process, and the methylol compound in the initial reaction stage can be fully etherified by adopting a process of adding the methylol into the etherifying agent, so that the possibility of converting the methylol into free formaldehyde is reduced. Compared with the single kettle process, the double kettle process can reduce the free formaldehyde in the resin from 1.0-2.0% to 0.6-1.0%. Most of free formaldehyde in the stiffening agent is removed by using a gas stripping process, and the free formaldehyde of the product can be less than or equal to 0.2%; the stiffness of the stiffening agent and the stability of the product can be unchanged, and the prepared stiffening agent is lower in formaldehyde, more friendly and more environment-friendly.

Detailed Description

The present invention will be further illustrated by the following examples