KR100563771B1 - Method for preparing melamine-formaldehyde resin for paint waste removal - Google Patents

Abstract

The present invention relates to a process for preparing melamine-formaldehyde resins useful as paint waste remover for removing oversprayed paint in wet coating lines.

In order to prepare melamine-formaldehyde resin, which is useful as a paint waste remover, melamine and formaldehyde are mixed to form methyl amine by adding formaldehyde to the amine group (-NH ₂ ) of melamine in the alkali region, After the addition of acid to the condensation reaction of amine and methylolamine (-NHCH ₂ OH) through a partial three-dimensional network structure to increase the molecular weight, consisting of a secondary process, stabilizer input and the third process of adjusting the solid content, A method for preparing a new melamine-formaldehyde resin useful as a paint waste remover.

Paint, Wet Paint, Waste Remover, Melamine-Formaldehyde Resin                  

Description

The preparation method of melamine-formaldehyde resin for detackification of paint wastes}                 

Automotive parts, machinery, industrial products and parts generally undergo a final painting and coating process to achieve commercialization. To this end, the pre-treatment process of washing, washing and drying the coating and the next step is carried out in the so-called spray booth. Although there are many methods of painting, in the process of spraying and spraying organic solvent paints such as epoxy, urethane, enamel, lacquer or liquid paints such as water based paints, a water curtain is applied to the back of the paint to remove the oversprayed paint. ), A method of cleaning air and removing oversprayed paint is commonly used.

The main problem in spraying such paints relates to the stickiness of the paint waste. The over-sprayed paint waste is circulated in the circulating water to collect it, and adheres or adheres to paint spray chambers, pipes, and pumps, causing product defects and process problems. Therefore, many methods have been researched and developed to remove the stickiness before the paint waste is attached to the wall, the pipe, and the like of the spray chamber. Removal methods using bentonite clay, aluminum salt and zinc salt, which have been used in the past, have problems in performance and problems for landfilling and disposal, and deterioration of resin stability in the removal method using melamine-formaldehyde polymer, which is mainly used nowadays. Due to the shortening of the handling period, deterioration of the physical properties are appearing. For example, Korean Patent No. 1996-13929, issued to Calgonsa, recommends an optimal molar ratio of melamine and aldehyde 1: 3 so that the molar ratio of amine group (-NH ₂ ) and aldehyde group (R ₁ -CO-R ₂ ) is 3: Adjusted to 3. In such a polymer, it can be expected to express the best resin performance, but the progress of the polymerization over time causes a problem of increased viscosity, decrease in transparency, and thus fail to produce a high solid content of the product. In addition, Korean Patent Publication No. 2002-42252 attempted to improve the performance of the melamine-formaldehyde polymer by optimizing the reaction process, but did not overcome the above-mentioned problems, and in US Patent 5,073,205 issued by Merck, melamine-form N-methylolacrylamide and methyldiallylamine, not aldehyde, were used to prepare a useful resin as a paint waste remover. However, the amount of the used amount is excessive to show effective performance as a paint waste remover.

Unlike the conventional method, the present invention optimizes the reaction with specific reaction conditions (pH, temperature, molar ratio of aldehyde group / amine group), and excessively exceeds the amine group (-NH ₂ ) and the aldehyde group (R ₁ -CO-R ₂ ). It is an object of the present invention to provide a method for preparing melamine-formaldehyde resin, which is useful as a coating waste remover that can maintain the storage stability of a resin for a long time through the use of additives such as methanol and urea to prevent molecular weight increase due to polymerization.

The present invention is a method for producing a melamine-formaldehyde resin useful as a coating waste remover by polycondensation of melamine and formaldehyde monomer,

  1) Melamine and formaldehyde were added at a molar ratio of aldehyde group / amine group 0.8 to 1.5 and melamine 3 to 10 wt%, respectively, and then adjusted to pH 7.5 to 10.5 using 10% NaOH and methylolation reaction temperature (70 to Gradually increasing the temperature to 90 ° C.) and proceeding with the reaction for 30 to 60 minutes, and adding formaldehyde to melamine to proceed with the methylol reaction.

  2) An acid diluent was added to the reactant, and the reaction was carried out for 30 to 60 minutes at a pH of 1.5 to 2.5 and a reaction temperature of 70 to 90 ° C. Secondary process to proceed to increase molecular weight

  3) It is characterized by consisting of a tertiary process by adding urea, methanol, etc. to block the reactivity of the methylolated amine group to increase the stability, to adjust the solid content to commercialize.

In another aspect, the present invention includes using the melamine-formaldehyde resin prepared by the production method as a coating waste remover.

Such a process for preparing a melamine-formaldehyde resin useful as a coating waste remover of the present invention will be described in detail as follows.

The primary process is the step of reacting formaldehyde with melamine in a pH range of pH 7.5 to 10.5, more preferably pH 8.5 to 9.5, in alkaline conditions to produce methylol amines. The pH adjustment of the initial reactants is important at this stage. That is, it is preferable that the reaction proceeds under alkaline conditions. In the conventional manufacturing method, the raw materials of melamine and formalin are added without adjusting the pH to increase the temperature using an exothermic reaction and to perform the condensation-polymerization reaction using the same. Under these conditions, the condensation reaction proceeds simultaneously with the methylolation reaction of the amine group (-NH ₂ ) and the aldehyde group (R ₁ -CO-R ₂ ) (-NH-C (R ₁ R ₂ ) -OH), resulting in resin stability. It will act as a factor that greatly inhibits.

Methylolation of Amine (Melamine)

Condensation Reaction of Methylol Amine

(Methylene bond)

(ether bonding)

The condensation reaction product of the initially produced methylol amine results in a decrease in resin transparency, an increase in viscosity, and a decrease in product stability due to excessive molecular weight increase as the reaction proceeds. In addition, ether bonds are chemically unstable and easily decompose under acidic conditions, resulting in deterioration of product quality. Therefore, in order to prevent condensation reaction of methylol amine, methylolation reaction is performed in an alkaline region of pH 7.5-10.5, and temperature control is performed to prevent sudden reaction of amine and aldehyde monomer. The reaction should proceed by gradually raising the temperature to ℃.

The molar ratio of aldehyde group / amine group in the first step is preferably 0.8 to 1.5, more preferably 0.9 to 1.3. Lower mole ratios of aldehyde groups / amine groups have a positive effect on product properties due to a decrease in release formalin and a relative increase in effective amine groups participating in the condensation reaction, but at a molar ratio of aldehyde / amine groups of 0.8 or less, it is appropriate for secondary reactions. There is a disadvantage that it is difficult to show the product properties, there is also a problem that the stability is also reduced, such as the occurrence of precipitates in the final product. In addition, when the molar ratio of the aldehyde group / amine group is 1.5 or more, difficulty in controlling the process occurs due to rapid progress of the condensation reaction during the secondary reaction, and if the proper reaction temperature is not controlled, the gelation of the resin product in the reactor or the stability of the final product is rapid. The phenomenon of deterioration occurs.

The secondary process is a step in which the actual resin polymer is produced through the condensation and polymerization of the methylolamine produced in the previous process and the amine remaining unreacted. 10% acid diluent is added to the initial polymer prepared in the first step to adjust the pH to 1.5 to 2.5, and the condensation reaction is performed for 30 to 60 minutes at a reaction temperature of 70 to 90 ° C, preferably 75 to 85 ° C. . In this case, sulfuric acid, hydrochloric acid, formic acid, etc. may be used as the acid diluent, and there is no significant change in the physical properties of the resin according to the acid type. In the secondary process, the actual resin performance and molecular weight increase are achieved. Therefore, if the reaction proceeds for 60 minutes or more at a high temperature of 90 ° C. or higher, excessive stability of the final product or gelation in the reactor may occur due to excessive molecular weight increase. Be careful as it appears. In addition, when the condensation reaction of less than 30 minutes at a temperature of less than 70 ℃ proceeds to the proper resination will not appear the proper performance when such a product is used as a waste removal agent for painting.

The tertiary process is a step of solids adjustment and physical property adjustment for additive addition and commercialization to increase resin stability. The main reason for the decrease in the stability of melamine-formaldehyde resin is that the continuous condensation-polymerization reaction proceeds under acidic conditions. Therefore, when the active reactor (methylol amine) is removed through reaction with amines, alcohols, etc., it is shown that the storage stability of the resin is greatly increased.

-NHCH ₂ OH + CH ₃ OH =>-NHCH ₂ OCH ₃ + H ₂ O

In such a reaction, the active methylol group is blocked due to esterification with other alcohols or by reaction with low molecular weight amines, thereby making it difficult to further increase molecular weight. As an additive for resin stability, storage stability has been shown to increase with increasing use of alcohols, polyhydric alcohols and higher alcohols. However, in order to satisfy the performance of the product as a paint waste remover, the amount of use is appropriately within 30% of the final product. In the application of urea and amines, urea monomers remaining unreacted after the reaction may be precipitated due to a decrease in solubility in the cooling process. It is preferably used within 5% of the final product experimentally.

An important point in the production method of the present invention is a method for producing a melamine-formaldehyde resin having excellent storage stability while having excellent performance as a paint waste remover, and in particular, the resin produced by the present invention reviews the existing manufacturing process. By separating the methylol reaction and the condensation-polymerization reaction, it was confirmed that the product has a uniform polymerization degree, storage stability of the polymer, and shows excellent physical properties as a paint waste remover. According to the addition, it was confirmed that the storage stability of the existing resin can be greatly improved. The storage stability of the resin was confirmed by the change in viscosity and appearance over time, and related experiments were performed to check the physical properties.

Hereinafter, the present invention will be described in more detail based on Examples and evaluated on the basis of Experimental Examples. However, the present invention is not limited by the following examples and experimental examples.

Example 1

89.2 g of 99% melamine and 180.2 g of 35.0% formalin are added to a 2 L reactor and stirred. The pH is adjusted to 9.0 using a 10% NaOH solution, and the temperature is gradually raised to 75 to 80 ° C. for at least 30 minutes using a heating apparatus and maintained for 45 minutes. Next, the pH is adjusted to 2.0 using 10% HCl solution, and 700 g of distilled water is added thereto. It heats up at 80-85 degreeC, hold | maintains for 45 minutes, stops heating, and cools to normal temperature. After adding 455 g of distilled water, the mixture was stirred for 30 minutes and the reaction was terminated.

Example 2

89.2 g of 99% melamine and 180.2 g of 35.0% formalin are added to a 2 L reactor and stirred. The pH is adjusted to 9.0 using a 10% NaOH solution, and the temperature is gradually raised to 75 to 80 ° C. for at least 30 minutes using a heating apparatus and maintained for 45 minutes. Next, the pH is adjusted to 2.0 using 10% HCl solution, and 700 g of distilled water is added thereto. It heats up at 80-85 degreeC, hold | maintains for 45 minutes, stops heating, and cools to normal temperature. 245.0 g of distilled water and 236.1 g of 95% methanol were added, followed by stirring for 30 minutes to complete the reaction.

Example 3

89.2 g of 99% melamine and 180.2 g of 35.0% formalin are added to a 2 L reactor and stirred. The pH is adjusted to 9.0 using a 10% NaOH solution, and the temperature is gradually raised to 75 to 80 ° C. for at least 30 minutes using a heating apparatus and maintained for 45 minutes. Next, the pH is adjusted to 2.0 using 10% HCl solution, and 700 g of distilled water is added thereto. After heating to 80 ~ 85 ℃ for 45 minutes, the heating is stopped and 42.5g of 99% urea is added, stirred for 30 minutes and naturally cooled. After cooling to room temperature, 455 g of distilled water was added thereto, followed by stirring for 30 minutes to terminate the reaction.

Comparative example

Comparative testing of A's paint waste remover within 7 days of commercially available manufacture.

Experimental Example 1

The results of experiments on the physical properties and storage stability of the coating waste remover prepared in Examples 1 to 5 and Comparative Examples (domestic products) are shown in Table 1 below.

Example 1 Example 2 Example 3 Comparative example Solid content1) (%) 10.1 9.9 12.5 8.4 Viscosity 2) (cps) and appearance 3) Early 43 Transparency 41 Transparency 52 Transparency 32 Transparency After 2 weeks at 50 ℃ 53 Transparency 48 Transparency 60 Slightly cloudy 84 Translucent After 4 weeks at 50 ℃ 72 Slightly cloudy 53 Transparency 69 Slightly cloudy Gelation White cloud  1) Determination of weight change after drying at 150 ° C for 30 minutes 2) Measurement at Brookfield Viscometer at 25 ° C 3) Observation of the resin state visually

From the results of Table 1, the melamine-formaldehyde resin prepared by the production method of the present invention can be seen that the storage stability is significantly improved compared to the comparative example, and the storage stability according to the addition of methanol, urea, etc. It was found that it can be improved.

Experimental Example 2

The performance was evaluated by the following method using the coating waste remover obtained in Examples 1 to 3 and Comparative Examples and the results are shown in Table 2.

  1) Put 300g of distilled water into 500mL beaker.

  2) 1.0 g of the prepared melamine-formaldehyde resin was added thereto, followed by stirring for 30 seconds using a magnetic stirrer.

3) After adding 1.5g (500ppm) of 10% Na ₂ CO ₃ aqueous solution and stirred for 30 seconds.

  4) Add 1.0 g of commercial enamel paint of Kumkang Korea Chemical, which is commercially available, and stir for 60 seconds.

  5) Add 1.0 g of a 1.0% diluent of a commercially available cationic polymer flocculant and stir for 60 seconds.

  6) Record the water supply, floc size and wall attachment status and evaluate the results.

Example 1 Example 2 Example 3 Comparative example Water purification Transparency Transparency Slightly cloudy Slightly cloudy Flock size versus versus versus versus Wall Coating Paint none Almost none Almost none Almost none

From the results in Table 2, it can be seen that the paint waste removal effect of the melamine-formaldehyde resin produced by the production method of the present invention shows an equivalent performance or higher than that of the existing product.

The present invention can significantly increase the storage stability compared to existing products in terms of securing the stability of the resin, which was a problem in the conventional manufacturing method, as shown in the results of the experiment after the preparation according to the above embodiment. Since the paint waste removal performance is also improved, it was found that the melamine-formaldehyde resin prepared by the method of the present invention has a useful effect as a paint waste remover.

Claims (3)

Method for producing a melamine-formaldehyde resin for paint waste removal, comprising the following steps in the method for producing a melamine-formaldehyde resin by polycondensation of melamine and formaldehyde monomers   1) The first step of adjusting the pH to 7.5 to 10.5 in the molar ratio of aldehyde group / amine group of 0.8 to 1.5 and melamine 3 to 10% by weight, gradually raising the temperature to 70 to 90 ° C. and proceeding with the methylol reaction for 30 to 60 minutes.   2) Secondary step of adjusting the reaction product to pH 1.5-2.5 and proceeding condensation polymerization reaction at 70-90 ° C. for 30-60 minutes.   3) Tertiary step of increasing storage stability by adding amines such as melamine or urea or alcohols of methanol or ethanol. delete Melamine-formaldehyde resin useful as a paint waste remover, characterized in that prepared by the method of claim 1