JPH0797420A - Production of aminoformaldehyde resin - Google Patents

Abstract

PURPOSE:To produce easily an aminoformaldehyde resin of desired quality with improved safety of reaction operation by stopping the reaction of melamine, urea or guanamine with formaldehyde when the near-infrared absorbance of the reaction solution reaches the set. CONSTITUTION:The title production process comprises feeding a compound selected from among melamine, urea and guanamine, formaldehyde and an alcohol to a reactor, while performing the reaction, continuously or intermittently measuring the near-infrared absorbance of the reaction solution, and stopping the reaction when the measured value reaches the set. A desirable method of measuring the near-infrared absorbance of the reaction solution uses a system composed of an infrared irradiation and reception section provided in the reactor and a near-infrared spectrocope connected to the irradiation and reception section through an optical fiber, because the progress of the reaction of the reaction solution can be grasped simultaneously with the measurement and a continuous measurement is possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention makes it possible to quickly grasp the progress of a reaction by using a near-infrared spectrophotometer, and to automatically control the reaction conditions based on those data. The present invention relates to an extremely effective method for producing an aminoformaldehyde resin, which can obtain a target product having a constant quality by carrying out.

[0002]

2. Description of the Related Art Conventionally, aminoformaldehyde obtained by reacting a compound selected from melamine, urea and guanamine with formaldehyde to form a methylol compound, and then subjecting the compound to condensation under acidic conditions and alkyl etherification with an alcohol. Resins are widely used as cross-linking agents in baking paints. When these aminoformaldehyde resins are manufactured, the reaction is usually carried out while controlling the temperature and reaction time, but the reaction molar ratio is fluctuated due to fluctuations in the purity of the charged raw materials and measurement errors. However, it was extremely difficult to obtain a target product of stable quality under certain reaction conditions. Therefore, in the above reaction, the reaction solution was collected from the reactor at intervals of 30 to 60 minutes during the reaction, and the viscosity of the reaction product and the dilution value with respect to the solvent were manually analyzed to grasp the progress of the reaction. Based on the above, a method of controlling the reaction temperature, the reaction time and the pH has been carried out.

[0003]

However, in the above-mentioned manual analysis method, it takes 20 to 30 minutes to obtain the measurement result and there is a measurement error, and the reaction is accurately completed at the desired viscosity and solvent dilution value. It was extremely difficult to do. As a cross-linking agent for paints, the above viscosity and solvent dilution value are very important factors affecting the performance of the product, and the problem that the desired viscosity or solvent dilution value cannot be easily obtained is extremely problematic. It was serious.

Further, according to the above-mentioned manual analysis method, when the reaction solution is sampled from a high temperature reactor, formaldehyde gas and alcohol having a strong irritating odor scatter, which is not only a work environment problem but also the composition of the reaction solution. Since it changes, it also causes an analysis error.

The problem to be solved by the present invention is to produce an aminoformaldehyde resin which can easily and safely obtain a desired product having a desired solvent dilution value or viscosity for obtaining a desired quality. To provide the law.

[0006]

Means for Solving the Problems As a result of intensive studies, the inventors of the present invention have measured the near-infrared absorbance in a reaction solution using a near-infrared spectrophotometer, and based on the measured value, show the reaction progress state. The present invention has been completed by discovering that the above problems can be solved by immediately grasping and controlling the temperature and reaction time of the reactor.

That is, according to the present invention, the compound (A) selected from melamine, urea or guanamine, formaldehyde (B) and alcohols (C) are supplied to the reactor to allow the reaction to proceed while the near infrared rays in the reaction solution are added. Measure the absorbance,
The present invention relates to a method for producing an aminoformaldehyde resin, which comprises terminating the reaction when the measured value reaches a preset value.

In the method for producing an aminoformaldehyde resin of the present invention, specifically, in the reaction comprising the above (A) to (C), the value of near infrared absorption corresponding to the desired solvent dilution value or viscosity value is determined. Calculate in advance, and use the near-infrared spectrophotometer at the time of actual reaction to measure the near-infrared absorbance in the reaction solution continuously or intermittently to obtain the near-infrared absorbance corresponding to the target solvent dilution value. A method of terminating the reaction when it reaches is mentioned. More specifically, the compound (A) selected from melamine, urea, and guanamine is reacted with formaldehyde (B) and alcohols (C) to change the absorbance of near-infrared light in a specific wavelength region as the reaction progresses. Tracking, and at the same time, regression analysis of both the viscosity or solvent dilution value data of the reaction product corresponding to each of the above absorbance values, absorbance- (solvent dilution value or viscosity)
A calibration curve is created on a biaxial coordinate with the axis as an axis, and an arithmetic expression is created. Then, based on this calculation formula, calculate the near infrared absorbance corresponding to the desired solvent dilution value or viscosity,
Examples include a method of measuring near-infrared absorbance in a reaction solution continuously or intermittently and terminating the reaction when the desired absorbance is reached. In this case, it is preferable that the same reaction as described above be carried out in advance, a calibration curve be prepared, and an arithmetic expression be obtained in advance. (Hereinafter, the reaction performed to obtain this calculation formula is referred to as the "preliminary reaction".)

When the preliminary reaction is carried out and the calculation formula is obtained in advance, the measurement of the same sample may be performed several times in the preparation of the calibration curve by regression analysis to obtain a more accurate calibration curve. preferable.

Further, when a computer is used to obtain the above arithmetic expression or when the near infrared spectrophotometer has a built-in analytical arithmetic function, the above-mentioned calibration curve is prepared using the function and the arithmetic operation is performed. The viscosity in the reaction liquid or the solvent dilution value may be calculated by a formula.

The near infrared absorption wavelength range used for measurement is not particularly limited, and is usually 750 to 2,100.
in the wavelength range of 1,150 to 1,250 nm, where the absorption is seen in the aminoformaldehyde resin, 1,320
~ 1,450 nm, 1,450-1,500 nm, 1,
500-1,600nm, 1,650-1,740n
m, 1,750-1,850 nm, 1,860-1,9
The wavelength region in which the time-dependent change in absorbance occurs can be selected from 80 nm and 2,000 to 2,100 nm. Among them, the amino group in the compound (A) or the aminoformaldehyde resin obtained in the present invention can be selected. It is preferable to measure the absorption wavelength region due to the methylol group in the methylol compound which is a reaction intermediate, specifically, in the case of the amino group, 1,450 to 1,500 nm, and the methylol group in the methylol compound is measured. In case of 1,500-1,6
A region of 00 nm can be mentioned.

Here, the above-mentioned solvent dilution value means a certain amount (g) of a reaction solution, a predetermined solvent at a predetermined temperature (25 ° C.), and a solvent amount (ml) when a turbidity is observed in the solution. Is read and the value is expressed as the amount of solvent per unit weight of the reaction solution.

The compound (A) selected from melamine, urea and guanamine used in the present invention is a compound having two or more, preferably 2 to 5, amino groups per molecule, and examples thereof include acetoguanamine and benzoguanamine. , Phenylacetoguanamine, phthaloguanamine, C
Examples include guanamine compounds such as TU guanamine, urea, and melamine. These may be used alone or in combination of two or more.

The formaldehyde (B) is not particularly limited, but examples thereof include formalin and paraformaldehyde. These may be used alone or in combination of two or more.

The alcohol (C) used in the present invention is an essential component for alkylating a methylol compound obtained by reacting a compound (A) selected from melamine, urea and guanamine with formaldehyde (B). , Its structure is not particularly limited,
Any monoalkyl alcohol represented by the general formula CnH (2n + 1) OH can be used. The value of n is not particularly limited, but it is usually an integer of 1 to 8, and when a low molecular weight alcohol (C) of n = 1 to 3 is used, a more hydrophilic aminoformaldehyde resin is obtained, When a high molecular weight alcohol (C) having n = 4 to 8 is used, the lipophilicity becomes high and the aminoformaldehyde resin has good compatibility with oil-modified alkyd, oil-free alkyd, acrylic resin and the like. Examples of such alcohols (C) include methanol, ethanol, n-propanol, is
o-propanol; n-butanol, iso-butanol, sec-butanol, tert-butanol, n-
Amyl alcohol, tert-amyl alcohol, n-
Hexyl alcohol, sec-hexyl alcohol, 2
-Methylpentanol, sec-hexyl alcohol,
2-ethylbutyl alcohol, sec-heptyl alcohol, n-octyl alcohol, 2-ethylhexyl alcohol, sec-octyl alcohol, cyclohexanol and the like can be mentioned. These alcohols (C)
May be used alone or in combination of two or more, and may be used in excess as a reaction solvent.

The charging ratio of the compound (A) selected from melamine, urea and guanamine, the aldehyde (B) and the alcohols (C) can be appropriately selected according to the molecular weight or properties of the target aminoformaldehyde resin, and is particularly limited. However, usually 1 to 12 moles of the component (A) and 2 moles of the component (C) are used per 1 mole of the component (A).
~ 20 moles.

Further, in the present invention, methylene crosslinking of the compound (A) can be further promoted by using water (D) together. The amount of water (D) to be used is not particularly limited and can be selected and used according to the desired molecular weight and the like. However, the larger the amount of water in the reaction system, the greater the amount of alcohol (C) It is preferable to carry out the reaction while adjusting the water content in the reaction system, because the reactivity becomes dull and the alkylation tends to be difficult.

The method of reacting the compound (A) selected from melamine, urea and guanamine with the aldehyde (B) and the alcohols (C) may be a known method, for example, formaldehyde (B) is previously reacted with alcohols. (C) or further dissolved in water (D) and then compound (A) consisting of melamine, urea and guanamine
Alternatively, when formaldehyde (B) is solid, (A) to (C) or further (D) may be mixed at the same time.

Further, as a specific method, a reactor equipped with an ordinary stirring device, heating / cooling device, condenser, and separator is used in accordance with the above-mentioned mixing ratio (A).
After charging (C) or (A) to (D) and carrying out a methylolation reaction in a temperature range of 70 to 120 ° C. under alkaline conditions, an alkyl etherification reaction and a condensation reaction are promoted under acidic conditions as a target. The reaction can be carried out up to the desired viscosity or solvent dilution value. Do you use it as a product as it is,
Furthermore, the unreacted aldehyde and alcohol may be removed by distillation under reduced pressure, and then diluted with a necessary solvent to a desired solid content, and then used.

The reaction is allowed to proceed in this way, and the near-infrared absorbance is measured continuously or intermittently. Then, when the absorbance reaches the target value of the viscosity or the solvent dilution value, the reaction is cooled. Can be terminated.

In the aminoformaldehyde resin thus obtained, the molecular weight thereof varies depending on the use of the alkyd resin cross-linking agent or the molding resin and is not particularly limited. For example, the alkyd resin cross-linking agent or the like may be used. When used as a cross-linking agent for baking type paints, the number average molecular weight is 200 to 10,000, preferably 300 to
The range is 7,000. In the present invention, an extremely accurate solvent dilution value can be obtained, which is particularly useful as the above-mentioned baking type paint.

The method of measuring the near-infrared absorbance in the reaction solution is not particularly limited, and for example, the reaction solution is sampled directly from the reactor or a resin circulation line is provided in the reactor to prepare the reaction solution. A method of sampling and measuring with a near-infrared spectrophotometer, or a site for irradiating and receiving near-infrared light in a reactor or a resin circulation line, and the site and the near-infrared spectrometer are optical fibers There is a method using a system connected via a cable. Among these, in particular, the reaction progress state in the reaction solution can be grasped at the same time as the measurement, and the near-infrared light irradiation and light receiving parts are arranged in the reactor from the point of being capable of continuous measurement, and, A method using a system in which the site and the near infrared spectrophotometer are connected via an optical fiber cable is preferable.

The near-infrared light irradiating and light-receiving part is one that irradiates the reaction solution with near-infrared light and receives light transmitted through the reaction solution to collect a near-infrared spectrum, or
It shows the one that can irradiate the reaction solution with near-infrared light and receive the reflected light to collect the near-infrared spectrum.It is not particularly limited, but the irradiation part and the light-receiving part are integrated. It is preferable to use a so-called probe that allows near-infrared light to pass through the reaction solution.

The optical fiber cable is not particularly limited as long as it is made of a material that can transmit near infrared light and does not absorb near infrared light in the near infrared wavelength range. It is preferable to use an optical fiber made of quartz as a medium, the outer periphery of the fiber is protected and coated with a fluororesin or an imide resin, and further reinforced with silicon rubber, carbon fiber, metal wire mesh, etc. Usually 0.3 ~ 0.6mm due to flexibility
Is. In addition, a bundle of 50 to 200 of the optical fibers may be used as a cable.

When the measurement is performed using a probe, the location of the probe is not particularly limited as long as the probe is immersed in the reaction solution and the reaction solution is flowing. As the near-infrared spectrophotometer used in the present invention, any commercially available one can be used, but preferably in the measurement wavelength range of 750 to 2,100 nm, the photometric noise absorbance value is 0.00002 or less and the wavelength accuracy is 0.5 nm. It is suitable to continuously measure the spectrum with the above method, or to measure the absorbance or the transmittance by selecting the measurement wavelength from 750 to 2,500 nm using 6 to 19 fixed filters.
Further, it is preferable that the viscosity value or the solvent dilution value can be analytically calculated by regression analysis from the above-mentioned absorbance values.

Measurement of absorbance by a near infrared spectrophotometer
The interval of the measurement time is not particularly limited, and 3
The measurement can be performed within an interval of 0 minutes or continuously, but it is more preferably within 15 minutes or continuously. With this interval, the reaction situation compared to the manual analysis method,
It is possible to quickly find out, the feedback control to the reactor becomes quick, and a product with more stable quality can be effectively obtained.

In the present invention, it is preferable that the near infrared spectrophotometer is further connected to a reaction control computer to automatically control the reaction from the viewpoint of product stabilization or production efficiency.

Here, the reaction control computer means temperature control by so-called feedback control based on calculated values (viscosity, solvent dilution value) calculated by putting the absorbance indicated by the near infrared spectrophotometer into a predetermined arithmetic expression. Control or p
The sequence is controlled so that the reaction can be controlled by adding an H adjuster and the sequence can be stopped by moving to the cooling step when the viscosity or the solvent dilution value reaches a target value. Further, the reaction control computer is further connected to the process control device and transmits an operation signal online to automatically control.

As such a control computer,
For example, "CENTUM", "CENTUM μ-X" manufactured by Yokogawa Electric Corporation
In addition to dedicated models such as "L" and "TDCS-3000LCN" manufactured by Yamatake Honeywell Co., any known computer can be used.

[0030]

The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples. The near-infrared wavelength used in the examples is an example, and the measurement wavelength shifts to the long wavelength side or the short wavelength side depending on the reaction content and conditions.

Example 1 As shown in FIG. 1, a stirring device, a condenser, a separator,
A 1000 liter reactor equipped with a heating / cooling device, a vacuum device, a temperature sensor, and a probe is connected to a near-infrared spectrophotometer and a reaction control computer to assemble the reactor,
481 parts (6.5 mol) of iso-butanol, 126 parts (1 mol) of melamine, and 187.3 parts (5 mol) of 80% paraformaldehyde were charged, the temperature was raised to 80 ° C, and the methylolation reaction was carried out for 30 minutes under alkaline conditions. Under post-acidic conditions, the alkyl etherification reaction and condensation reaction are allowed to proceed while heating and refluxing dehydration, and the reaction progress in the reactor is measured by measuring the absorbance value at 1478 nm using a near infrared spectrophotometer. did. The n-hexane dilution value shows 4.00 based on the value calculated from the relationship between the reaction progress rate and the absorbance value measured by the n-hexane dilution value, calculated at 5 minute intervals by the following calculation formula. At that point, the reaction was automatically terminated by cooling. When the n-hexane dilution value (ml / g resin, 25 ° C.) of the obtained reaction product solution was measured, it was 4.00.

Y1 = 517X1 ² -584X1 +165 However, the absorbance of Y1: n-hexane dilution value X1: 1478 nm was measured. Then, the solvent was distilled off under reduced pressure to remove xylene / i.
It was diluted with a mixed solvent of so-butanol = 30/70 (weight ratio). The obtained resin had a solid content of 59.3% and a viscosity (Gardner, 25 ° C.) S-T. Further, the number average molecular weight of the solid content was 950 in terms of the value converted from the polystyrene standard substance by GPC.

Example 2 A reaction apparatus was assembled in the same manner as in Example 1, and 518 parts (7.0 mol) of n-butanol, 225 parts (6 mol) of 80% paraformaldehyde were added to the reactor, and 72 parts of water.
(4 mol), 126 parts (1 mol) of melamine were charged, mixed with stirring, heated to 95 ° C. to cause a methylolation reaction, and then allowed to proceed under acidic conditions with heating and reflux dehydration to allow the reaction to proceed. The reaction progress was performed by measuring the absorbance value at 1476 nm using a near infrared spectrophotometer. It was measured and calculated at 5-minute intervals by the following calculation formula previously obtained from the relationship between the n-hexane dilution value and the absorbance value, and when the n-hexane dilution value showed 6.80, 10% hydroxylation was automatically performed. Charge the sodium aqueous solution,
The pH was brought to 7.0 and then cooled to terminate the reaction. When the n-hexane dilution value (ml / g resin, 25 ° C.) of the obtained reaction product solution was measured, it was 6.80.

Y2 = 1739X2 ² −1754X2 + 446 However, the dilution value of Y2: n-hexane X2: the absorbance at 1476 nm, the solvent was removed by vacuum distillation, and then diluted with xylene. The obtained resin has a solid content of 60.2% and a viscosity of F-
It was G. Further, the number average molecular weight of the solid content was 1400 in terms of the value converted from the polystyrene standard substance by GPC.

Example 3 A reaction apparatus was assembled in the same manner as in Example 1, and 444 parts (6.0 mol) of iso-butanol, 97.5 parts (2.6 mol) of 80% paraformaldehyde were added to the reactor.
79.2 parts of water (4.4 mol) and 245 parts of benzoguanamine (1 mol) were charged, mixed with stirring, heated to 95 ° C. to cause a methylolation reaction, then the reaction was allowed to proceed under acidic conditions, and the absorbance value at 1484 nm was measured. While reacting. The reaction was terminated by automatically cooling when the methanol dilution value showed 0.60, which was measured and calculated at 10-minute intervals by the following arithmetic expression previously obtained from the relationship between the methanol dilution value and the absorbance value. The methanol dilution value (ml / g resin, 25 ° C.) of the obtained reaction product solution was measured and found to be 0.60.

Y3 = 18.712 X3-9.644 However, Y3: Methanol dilution value X3: Absorbance at 1484 nm, then remove the solvent by distillation under reduced pressure and mix solvent 100 / butyl cellosolve = 80/20 (weight ratio). Diluted with solvent. The resin thus obtained had a solid content of 66.5% and a viscosity of V-W, and the number average molecular weight of the solid content was 980 in terms of the value converted from a polystyrene standard substance by GPC.

Example 4 A reactor was assembled in the same manner as in Example 1, and 148 parts (2.0 mol) of n-butanol, 112.5 parts (3 mol) of 80% paraformaldehyde were added to the reactor, and 18 parts of water.
(0.9 mol) and 60 parts (1.0 mol) of urea were charged, mixed by stirring, and reacted under alkaline conditions at 95 ° C for 1 hour, and then pH was adjusted to 3.
Under acidic conditions of 5, the alkyl etherification reaction and the condensation reaction were allowed to proceed while heating and refluxing dehydration, and the reaction was performed while measuring the absorbance value at 1570 nm using a near infrared spectrophotometer. Measured and calculated at an interval of 20 minutes by the following arithmetic expression previously obtained from the relationship between the measured value of n-hexane dilution value and the absorbance value.
-When the hexane dilution value showed 2.90, the reaction was terminated by automatically cooling. When the n-hexane dilution value (ml / g resin, 25 ° C.) of the obtained reaction product solution was measured, it was 2.90.
Met.

Y4 = -7.359 X4 + 7.567 However, Y4: n-hexane dilution value X4: Absorbance at 1570 nm After that, the solvent was removed by vacuum distillation to obtain xylol / n-butanol = 60/40 (weight ratio). It diluted with the mixed solvent of. The obtained resin had a solid content of 60.4% and a viscosity R. Further, the number average molecular weight of the solid content was 1060 in terms of the value converted from the polystyrene standard substance by GPC.

Comparative Example 1 A reaction apparatus was assembled in the same manner as in Example 1, the reaction was allowed to proceed in the same reaction operation, and the resin in the reactor was sampled at intervals of 30 minutes to obtain n-hexane which is a known manual analysis method. Dilution value measurement (ml / g resin, 25 ° C) is performed, sampling time is plotted on the horizontal axis and n-hexane dilution value is plotted on the vertical axis, and the measured values are plotted to grasp the reaction speed from the curve of the graph. The time to complete the reflux dehydration was estimated aiming at a hexane dilution value (ml / g resin, 25 ° C.) of 4.00. Then, the reaction was terminated by cooling, and the n-hexane dilution value of the obtained reaction product solution was measured and found to be 4.30.

After that, the solvent was removed by distillation under reduced pressure and diluted with a mixed solvent of xylene / iso-butanol = 30/70 (weight ratio). The resin obtained has a solid content of 6
0.1%, viscosity (Gardner, 25 ° C) S-T. Moreover, the number average molecular weight of the solid content was 1180 in terms of the value converted from the polystyrene standard substance by GPC.

[0041]

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to easily obtain an intended product having a desired quality, particularly a desired solvent dilution value and viscosity, and to provide an aminoformaldehyde resin which is remarkably excellent in safety in reaction operation. A manufacturing method can be provided.

[Brief description of drawings]

FIG. 1 is a process drawing of the apparatus used in Example 1.

[Explanation of symbols]

1: raw material tank, 2: agitator, 3: reaction tank, 4: jacket, 5: condenser, 6: separator, 7: cooling water inlet, 8: temperature sensor, 9: probe, 10: optical fiber cable, 11: near red External spectrophotometer, 12: DCS,
13: steam inlet, 14: vacuum device, 15: numerical operation device

Claims (6)

[Claims] 1. A near infrared absorptivity in a reaction solution is continuously fed while a compound (A) selected from melamine, urea and guanamine, formaldehyde (B) and alcohols (C) are fed to a reactor to proceed the reaction. A method for producing an aminoformaldehyde resin, characterized in that the reaction is terminated when the measured value reaches a preset value. 2. The method according to claim 1, wherein the aminoformaldehyde resin has a number average molecular weight of 200 to 10,000. 3. The method according to claim 1 or 2, which further comprises using water (D) together. 4. A system in which near-infrared irradiation and light-receiving parts are arranged in the reactor, and the parts and the near-infrared spectrometer are connected via an optical fiber cable The method according to claim 1, 2 or 3, wherein infrared absorption is measured. 5. A reactor for irradiating and receiving near-infrared light is provided in the reactor, and the region and the near-infrared spectrophotometer are connected through an optical fiber cable, and the near-infrared light is further provided. 5. The spectrophotometer measures the absorbance in the reaction solution using a system connected to a reaction control computer, and the reaction is automatically terminated when the measured value reaches a preset value. Manufacturing method. 6. The method according to claim 4, wherein the absorbance of near infrared rays having a wavelength range of 1400 to 1600 nm is measured.