JPWO2016072167A1 - Low free formaldehyde amino resin and process for producing the same - Google Patents

Abstract

To provide a method for producing an amino resin that can effectively lower the content of free formaldehyde and that does not increase the formaldehyde content even during storage, and a low free formaldehyde amino resin obtained by the production method. (1) a step of polycondensation reaction of an amino compound and aldehydes in a solvent to obtain a reaction mixture containing an amino resin, (2) the reaction mixture of the above step is heated to 80 to 150 ° C., and the organic phase A process for producing a low-free formaldehyde amino resin, characterized by comprising a step of refluxing or removing a solvent, and a low-free formaldehyde amino resin obtained by the production method.

Description

  The present invention relates to an amino resin, and more particularly to an amino resin having a reduced free formaldehyde content and a method for producing the same.

  Amino resins such as urea resins, melamine resins, and benzoguanamine resins that are widely used as paint resins, etc., are decomposed products of unreacted components of formaldehyde used as raw materials and by-products generated during amino resin production. It is known that about several percent by mass of free formaldehyde is contained.

  This free formaldehyde is known to have an adverse effect on surface hardness and water resistance when used as a paint, and there is also attention as a causative substance of sick house syndrome in recent years. Reducing as much as possible is an important issue.

  Methods for reducing free formaldehyde in amino resins include, for example, hydrazine derivatives and compounds obtained by intercalating metals into crystalline layered phosphate compounds, or formalin scavengers such as activated alumina in coating compositions. (For example, see Patent Document 1) or a method in which an amino alcohol has a primary amine and a hydroxyl group in the molecule and has 3 to 10 carbon atoms (for example, Patent Document 1). 2).

  However, the introduction of unreacted components into the coating composition as provided in Patent Document 1 may affect the strength of the cured coating film, and further, the storage stability as a coating composition. It is difficult to say that it is a fundamental solution. On the other hand, the method provided in Patent Document 2 certainly has a certain effect in terms of low free formaldehyde as an amino resin, but the reduction effect has not reached the practical level, and the amino No verification has been made as to whether or not the effect can be sustained even during long-term storage of the resin.

JP 2005-298694 A JP 11-335521 A

  In view of the above circumstances, an object of the present invention is to establish an amino resin production method capable of effectively reducing the content of free formaldehyde and to provide a low free formaldehyde amino resin obtained by the production method.

  As a result of intensive studies, the present inventors have heated the reaction mixture containing the amino resin in a temperature range within a specific range after the step of obtaining the amino resin, and refluxing or removing the solvent so that the resin is contained in the resin. The present invention is completed by finding that low-formaldehyde amino resin can be obtained by effectively removing unreacted formaldehyde contained therein and by-products that may decompose during storage to generate formaldehyde. It came to.

That is, the present invention includes (1) a step of polycondensation reaction of an amino compound and an aldehyde in a solvent to obtain a reaction mixture containing an amino resin,
(2) heating the reaction mixture of the above step to 80 to 150 ° C. to reflux or remove the organic phase;
The present invention provides a method for producing a low free formaldehyde amino resin characterized by having a low free formaldehyde amino resin obtained by the production method.

  The amino resin obtained by the production method of the present invention contains very little free formaldehyde in comparison with conventional amino resins. Therefore, it can be suitably used as a coating composition that can meet the recent formaldehyde regulations.

  The amino resin produced in the present invention may be an amino resin formed by polycondensation of an amino compound and an aldehyde, and may be a copolycondensate formed by using two or more kinds of amino compounds in combination. .

  Examples of the amino compound include melamine, urea, benzoguanamine, acetoguanamine, spiroguanamine, cyclohexanecarboguanamine, cyclohexenecarboguanamine, guanamine benzoate, and dicyandiamide. Among these, from the viewpoint of versatility as an amino resin, it is preferable to use melamine, urea, or benzoguanamine.

  The aldehyde may be any one that is polycondensed with an amino compound, and examples thereof include formaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde, etc. From the viewpoint that the effect of the present invention is high and versatility is excellent. It is preferable to use it.

  The amino resin may be a methylolated amino resin obtained by a reaction between an amino compound and an aldehyde, which is etherified with an alcohol. In particular, when using the obtained low-free formaldehyde amino resin as a resin composition for coatings, some or all of the methylol groups in the methylolated amino resin are etherified with alcohol from the viewpoint of the obtained coating film hardness and processability. It is preferable.

  Step (1) in the production method of the present invention is a step of producing a normal amino resin, and is not particularly limited. The amino compound and aldehyde are reacted in a solvent. Here, as a solvent, it is preferable that it contains alcohol, and it is preferable to use especially C1-C8 alcohol.

  In the reaction between the amino compound and the aldehyde, it is preferable to use an acid catalyst for further condensation. The acid catalyst is preferably one that is uniformly dissolved in a solvent, and for example, formic acid, phosphoric acid, phthalic acid, hydrochloric acid, nitric acid, sulfuric acid, and the like can be used.

  The use ratio of the amino compound and aldehyde in the step (1) is from the viewpoint of workability, curability, and physical properties of the coating film, with respect to 1.0 mol of the amino group in the amino compound, the aldehyde in the aldehyde. The group (molar ratio) is preferably in the range of 0.1 to 5.0, particularly preferably in the range of 0.8 to 3.2.

  The timing for charging the acid catalyst into the reaction system is not particularly limited, but from the viewpoint of workability, curability, and physical properties of the coating film, it is preferably charged after the methylolation reaction has progressed to some extent. It is preferable to add the amino compound and the aldehyde after reacting them in a solvent at 80 to 100 ° C. for 0.1 to 3.0 hours.

  The acid catalyst is preferably used in a range of 0.001 to 0.1% by mass with respect to the amino compound from the viewpoint that the reaction proceeds satisfactorily and from the viewpoint of controlling the functional group.

  As the reaction end point of the step (1), for example, it is possible to easily determine by measuring the Gardner viscosity and tolerance and setting it as the target value reaching point.

In the production method of the present invention, the reaction mixture containing the amino resin obtained in the step (1) may be used as it is in the step (2), but it is easy to obtain a lower free formaldehyde amino resin. From the viewpoint, it is preferable to go through a solvent removal step. The method for removing the solvent is not particularly limited, but it is preferably removed under reduced pressure of about ^{40 to} 80 Torr (5.3329 × 10 ^{3 to} 1.0665 × 10 ⁴ Pa).

  The level of solvent removal can be determined by the Gardner viscosity of the reaction mixture, and it is preferable that the solvent removal is completed when it reaches about Z1 to Z6.

  Step (2) in the production method of the present invention is a step of refluxing or removing the solvent from the reaction mixture obtained above at 80 to 150 ° C. At this time, a reduced pressure condition is also possible.

  The reaction mixture after the solvent removal has a high viscosity, and if it is heated as it is, temperature unevenness tends to occur in the mixture. Therefore, it is preferable to perform the step (2) after adding a solvent capable of uniformly dissolving the reaction mixture before heating. The solvent that can be used at this time is preferably a solvent that is refluxed at a temperature of 80 to 150 ° C., for example, toluene, xylene, ethyl acetate, butyl acetate, methyl isobutyl ketone, and the like. It may be used as a mixed solvent.

  The use ratio in the case of using a solvent in the step (2) is not particularly limited, but it is 0 to 200% by mass based on the mass of the reaction mixture in the previous stage of the step (2). It is preferable in terms of reducing free formaldehyde.

  The heating in the step (2) is required to be 80 to 150 ° C. as described above. If it is less than 80 ° C., it is difficult to effectively remove formaldehyde (unreacted component) from the reaction mixture and by-products that can decompose to formaldehyde, and the target low free formaldehyde An amino resin cannot be obtained. On the other hand, when the temperature exceeds 150 ° C., the amino resin is likely to be altered, and the molecular weight distribution of the target amino resin is likely to be affected. The heating temperature in step (2) is more preferably in the range of 80 to 130 ° C.

  The determination of the end point of step (2) can be performed, for example, by measuring free formaldehyde. As a guide, the heating time is about 0.5 to 6.0 hours.

  After the step (2), the amino resin is purified (isolated), but this method is not particularly limited, and the work performed after the synthesis of a normal amino resin can be used as it is. For example, after cooling to room temperature, the catalyst may be adjusted as necessary, and the non-volatile component may be prepared with the target solvent.

  The amino resin obtained through the above steps has a free formaldehyde content of 1% by mass or less, particularly 0.5% by mass or less, as measured by the octylamine method. This value, for example, has a non-volatile content of 60%, does not increase even after storage at 25 ° C. for 12 months, and is characterized by the fact that formaldehyde as a decomposition product does not occur even after long-term storage. .

  The use of the low free formaldehyde amino resin of the present invention is not particularly limited, and can be suitably used in applications in which amino resins are conventionally used. For example, it can be combined with a polyester resin, an alkyd resin, and an acrylic resin to form a composition, and can be used for baking general paint applications.

  EXAMPLES Hereinafter, although an Example is given and this invention is further demonstrated, this invention is not limited to these Examples at all. Unless otherwise indicated, both parts and% are based on mass.

Example 1
A flask having a stir bar, a temperature sensor, and a decanter was charged with 847.4 parts of normal butanol, 329.4 parts of 92% paraform, 142.3 parts of water, and 230.0 parts of melamine, and heated to 93 to 98 ° C. while stirring. After that, the pH was adjusted to 6.0 to 6.2 with formic acid. Subsequently, n-butanol refluxing reaction was performed at 95 to 110 ° C. The reaction was stopped when the normal hexane tolerance was 500% or more and the methanol / water = 9/1 tolerance was 400% or less, and the solvent was removed under reduced pressure. When the Gardner viscosity became Z1, the reduced pressure was broken, 650.0 parts of industrial xylene was added, and the solvent was removed at 120 to 140 ° C. After confirming that the amount of free formaldehyde was 0.1% or less and cooling, the nonvolatile content was adjusted to 58 to 62%. A butylated melamine resin (1) having a free formaldehyde of 0.09%, a non-volatile content of 60.2%, a weight average molecular weight (Mn) of 1,350, and an acid value of 1 or less was obtained.

Example 2
A flask having a stirring bar, a temperature sensor, and a decanter was charged with 90.0 parts of 92% paraform, 976.1 parts of methanol, 81.2 parts of water, 0.56 parts of 25% aqueous sodium hydroxide solution, and 400.0 parts of melamine, and stirred. Then, the reaction was heated to 70-80 ° C. to carry out a methylolation reaction. After 1 hour, 1000.0 parts of methanol was charged and cooled to 40 ° C. or lower. 98% sulfuric acid was added to adjust the pH to 4 or less, and then reacted at 30 to 50 ° C. The reaction was stopped when the 9% NaCL tolerance was 200% or less, and after adjusting the pH to 10.0 to 10.5 with a 25% aqueous sodium hydroxide solution, the solvent was removed under reduced pressure. When the Gardner viscosity became Z6 to Z7, the reduced pressure was broken, 950 parts of industrial xylene was added, and the solvent was removed at 130 to 140 ° C. It was confirmed that the amount of free formaldehyde was 0.5% or less, and after cooling, the nonvolatile content was adjusted to 58 to 62%. The resulting amino resin was a methylated melamine resin (1) having a free formaldehyde of 0.3%, a non-volatile content of 60.1%, a weight average molecular weight (Mn) of 515, and an acid value of 1 or less.

Example 3
A flask having a stir bar, a temperature sensor, and a decanter was charged with 847.4 parts of normal butanol, 329.4 parts of 92% paraform, 142.3 parts of water, and 230.0 parts of melamine, and heated to 93 to 98 ° C. while stirring. After that, the pH was adjusted to 6.0 to 6.2 with formic acid. Subsequently, n-butanol refluxing reaction was performed at 95 to 110 ° C. The reaction was stopped when the normal hexane tolerance was 500% or more and the methanol / water = 9/1 tolerance was 400% or less, and the solvent was removed under reduced pressure. When the Gardner viscosity became Z1, the reduced pressure was broken, 650.0 parts of industrial xylene was added, and the solvent was removed at 60-100 ° C. under reduced pressure of 80-120 Torr. After confirming that the amount of free formaldehyde was 0.6% or less and cooling, the nonvolatile content was adjusted to 58 to 62%. A butylated melamine resin (2) having a free formaldehyde of 0.5%, a non-volatile content of 60.2%, a weight average molecular weight (Mn) of 1,250, and an acid value of 1 or less was obtained.

Example 4
A flask having a stir bar, a temperature sensor, and a decanter was charged with 847.4 parts of normal butanol, 329.4 parts of 92% paraform, 142.3 parts of water, and 230.0 parts of melamine, and heated to 93 to 98 ° C. while stirring. After that, the pH was adjusted to 6.0 to 6.2 with formic acid. Subsequently, n-butanol refluxing reaction was performed at 95 to 110 ° C. The reaction was stopped when the normal hexane tolerance was 500% or more and the methanol / water = 9/1 tolerance was 400% or less, and the solvent was removed under reduced pressure. When the Gardner viscosity became Z1, the reduced pressure was broken, 650.0 parts of industrial xylene was added, and the solvent was removed at 80 to 120 ° C. under a reduced pressure of 250 to 350 Torr. After confirming that the amount of free formaldehyde was 0.2% or less and cooling, the nonvolatile content was adjusted to 58 to 62%. Butylated melamine resin having 0.09% free formaldehyde, 60.2% non-volatile content, 1,230 weight average molecular weight (Mn), 3.0 molecular weight distribution (Mw / Mn), and acid value of 1 or less (3) was obtained.

Comparative Example 1
A flask having a stir bar, a temperature sensor, and a decanter was charged with 847.4 parts of normal butanol, 329.4 parts of 92% paraform, 142.3 parts of water, and 230.0 parts of melamine, and heated to 93 to 98 ° C. while stirring. After that, the pH was adjusted to 6.0 to 6.2 with formic acid. Subsequently, n-butanol refluxing reaction was performed at 95 to 110 ° C. The reaction was stopped when the normal hexane tolerance was 500% or more and the methanol / water = 9/1 tolerance was 400% or less, and the solvent was removed under reduced pressure. When the Gardner viscosity became Z1, the reduced pressure was broken and cooled, and then the non-volatile content was adjusted to 58 to 62% with xylene. The obtained amino resin was a butylated melamine resin (4) having a free formaldehyde of 3.0%, a non-volatile content of 59.8%, a weight average molecular weight (Mn) of 1,200, and an acid value of 1 or less.

Comparative Example 2
A flask having a stirring bar, a temperature sensor, and a decanter was charged with 90.0 parts of 92% paraform, 976.1 parts of methanol, 81.2 parts of water, 0.56 parts of 25% aqueous sodium hydroxide solution, and 400.0 parts of melamine, and stirred. Then, the reaction was heated to 70-80 ° C. to carry out a methylolation reaction. After 1 hour, 1000.0 parts of methanol was charged and cooled to 40 ° C. or lower. 98% sulfuric acid was added to adjust the pH to 4 or less, and then reacted at 30 to 50 ° C. The reaction was stopped when the 9% NaCL tolerance was 200% or less, and after adjusting the pH to 10.0 to 10.5 with a 25% aqueous sodium hydroxide solution, the solvent was removed under reduced pressure. When the Gardner viscosity reached Z6 to Z7, the reduced pressure was broken, and after cooling, the nonvolatile content was adjusted to 58 to 62% with xylene and isobutanol. The obtained amino resin was a methylated melamine resin (2) having a free formaldehyde of 4.6%, a weight average molecular weight (Mw) of 500, and an acid value of 1 or less.

In addition, analysis of amino resin and confirmation of reaction progress are performed by the following methods.
<Normal hexane tolerance>
Collect 5.00 g of sample with a pan balance in a 100 ml Erlenmeyer flask.
Add normal hexane dropwise to the flask contents with a burette and mix well.
Adjust the inside of the flask accurately to 25.0 ° C with a thermometer, place it on the examination object, peep from above, drop it through the liquid layer of the Erlenmeyer flask until it is no longer readable, and measure the amount of solvent dripped. .
Tolerance (%) = Amount of solvent used ml × 20

<Methanol / water = 9/1 tolerance>
Collect 5.00 g of sample with a pan balance in a 100 ml Erlenmeyer flask.
A methanol / water = 9/1 solution is dropped into the flask contents with a burette and mixed well.
Adjust the inside of the flask accurately to 25.0 ° C with a thermometer, place it on the examination object, peep from above, drop it through the liquid layer of the Erlenmeyer flask until it is no longer readable, and measure the amount of solvent dripped. .
Tolerance (%) = Amount of solvent used ml × 20

<9% NaCl tolerance>
Collect 5.00 g of sample with a pan balance in a 100 ml Erlenmeyer flask.
A 9% NaCl aqueous solution is dropped into the flask contents with a burette and mixed well.
Adjust the inside of the flask accurately to 25.0 ° C with a thermometer, place it on the examination object, peep from above, drop it through the liquid layer of the Erlenmeyer flask until it is no longer readable, and measure the amount of solvent dripped. .
Tolerance (%) = Amount of solvent used ml × 20

<Amount of free formaldehyde>
Collect 1.50 g of sample with a pan balance in a 100 ml Erlenmeyer flask.
Add and dissolve 70 ml of mixed solvent (xylene (industrial) / isobutyl alcohol = 1/1 wt) with a 100 ml graduated cylinder.
To this, 10 ml of a 1 mol / L 2-ethylhexylamine mixed solution (2-ethylhexylamine / mixed solvent = 70/430 mL) is added with a whole pipette.
Cap and stir for 1 hour.
Using a potentiometer, PH 7.0 is terminated with a 1 mol / L salicylic acid solution.
A blank test is performed in the same manner.
Free formaldehyde content (%) = ((BT) × F × 3) / S
B: Amount of 1 mol / L salicylic acid solution used in the blank test (ml)
T: Amount of 1 mol / L salicylic acid solution used in this test (ml)
F: titer of 1 mol / L salicylic acid solution S: sampling amount (g)

<Weight average molecular weight (Mn)>
Measuring device: HLC-8120GPC manufactured by Tosoh Corporation
Column: TSK-GUARDCOLUMN H _XL -H manufactured by Tosoh Corporation
+ Tosoh Corporation TSK-GEL G5000H _XL
+ Tosoh Corporation TSK-GEL G4000H _XL
+ Tosoh Corporation TSK-GEL G3000H _XL
+ Tosoh Corporation TSK-GEL G2000H _XL
Detector: RI (differential refractometer)
Data processing: Multi-station GPC-8020 model II manufactured by Tosoh Corporation
Measurement conditions: Column temperature 40 ° C
Solvent tetrahydrofuran
Flow rate 1.0 ml / min Standard: Monodispersed polystyrene (A-500, F-2, F-20, F-80, F-288, A-2500, F-10, F-40, F- manufactured by Tosoh Corporation) 128, F-380) was used to create a calibration curve.
Sample: 0.5% by mass of a tetrahydrofuran solution in terms of resin solid content filtered through a microfilter (100 μl)

<Acid value>
10.0 g of sample is collected in a 100 ml Erlenmeyer flask with an upper pan balance.
Add 30 ml of mixed solvent (toluene / methanol = 7/3 wt) with a 100 ml graduated cylinder and dissolve.
Add 2-4 drops of phenolphthalein indicator.
Titrate with 0.1 mol alcoholic KOH and titrate until discoloration persists for 30 seconds.
Acid value (mgKOH / g) = (V × F × 5.61) / S
V: Amount used of 0.1 mol / L alcoholic KOH (ml)
F: 0.1 mol / L alcoholic KOH titer S: Sampling amount (g)

<Nonvolatile content>
Weigh the mass of the metal petri dish with an upper pan balance.
Collect 1.00 g of sample in a petri dish with an upper pan balance.
Add 5 ml of mixed solvent (toluene / methanol = 7/3 wt) and dissolve.
Dry in a hot air circulating drier adjusted to 107.5 ° C. for 60 minutes.
After drying, place the petri dish in a desiccator, and after weighing it to room temperature, weigh it with a pan balance.
Nonvolatile content (%) = (BC) / (AC) × 100
A: Metal Petri dish + Sample mass before drying (g)
B: Metal Petri dish + Sample mass after drying (g)
C: Mass of metal petri dish (g)

Application example 1
The main agent was prepared according to Table 1, the filler was added, the meat was milled with a bead mill, and the curing agent was added to prepare a coating composition. The viscosity was adjusted to 20 seconds (25 ° C.) with an Iwata cup using xylene / n-butanol / butyl cellosolve = 75/15/10 (mass ratio). Bonded steel plate # 144 dull was used as the base material, and baked at 150 ° C. for 20 minutes after spray coating. (Curing 25 ° C. × 50% RH × 1 day) The coated metal plate obtained as described above was measured for gloss, Erichsen, DuPont impact, pencil hardness, and cross cut test.

Application example 2
A paint was prepared and evaluated for coating in the same manner as in Application Example 1 except that the composition ratio (mixing ratio) was changed as shown in Table 1.

Application example 3
The main agent was prepared according to Table 1, the filler was added, the meat was milled in a bead mill, and the curing agent was added to prepare a coating composition. The viscosity was adjusted to 100 seconds (25 ° C.) with a Ford cup using xylene / n-butanol / butyl cellosolve = 75/15/10 (mass ratio). Bonded steel plate # 144 dull was used as the base material, and baked at 250 ° C. for 40 seconds after bar coater coating. (Curing 25 ° C. × 50% RH × 1 day) The coated metal plate obtained as described above was measured for gloss, Erichsen, DuPont impact, pencil hardness, and cross cut test.

Comparative application examples 1 and 2
A coating material was prepared and evaluated for coating in the same manner as in Application Example 1 except that the composition ratio (mixing ratio) was changed as shown in Table 1.

Comparative application example 3
A coating material was prepared and evaluated for coating in the same manner as in Application Example 3 except that the composition ratio (mixing ratio) was changed as shown in Table 1.

Each evaluation judgment item and its evaluation judgment point are as follows.
(1) Gloss: 60 degree specular reflectance was measured.
(2) Erichsen test: The extrusion length (mm) until extrusion was measured with an Erichsen tester until peeling was measured.
(3) DuPont impact value: Using a DuPont impact tester, with a load of 1.0 kg, with a 1/2 inch notch, drop this weight on the coating film from a predetermined height, The maximum height at which no cracks occur on the coated surface was taken as the measured value (JISK-5460).
(4) Hardness (Epits hardness): The coated surface of the steel sheet was measured according to JIS K-5400 using a high-grade pencil specified in JIS S-6006.
(5) Cross cut test: The coated surface of the steel sheet was measured according to a cross cut test defined in JIS K 5600-5-6.

In addition, each raw material used by the application example is as follows.
* 1 Diluting thinner: xylene / n-butanol / butyl cellosolve = 75/15/10 (mass ratio)
ACRICID A-405: Acrylic resin Nonvolatile content 50% DIC Corporation M-6201-40-IM: Modified polyester resin Nonvolatile content 40% DIC Corporation CR-95: Acid value titanium

Claims (10)

(1) A step of polycondensation reaction of an amino compound and aldehyde in a solvent to obtain a reaction mixture containing an amino resin,
(2) A method for producing a low-free formaldehyde amino resin, comprising the step of heating the reaction mixture of the above step to 80 to 150 ° C. to reflux or desolvate the organic phase.   The method for producing a low free formaldehyde amino resin according to claim 1, wherein the solvent used in the step (1) contains an alcohol.   The method for producing a low-free formaldehyde amino resin according to claim 3, wherein the alcohol is an alcohol having 1 to 8 carbon atoms.   The low free formaldehyde according to any one of claims 1 to 3, which is used as a reaction mixture in the step (2) after removing the solvent used in the step (1) after the step (1). A method for producing an amino resin.   The method for producing a low free formaldehyde amino resin according to any one of claims 1 to 4, wherein in the step (2), the solvent is heated after being mixed with a solvent having a boiling point of 80 ° C or higher.   The method for producing a low free formaldehyde amino resin according to claim 5, wherein the solvent having a boiling point of 80 ° C or higher is xylene.   The method for producing a low-free formaldehyde amino resin according to any one of claims 1 to 6, wherein the amino compound is melamine, urea, or benzoguanamine.   The method for producing a low free formaldehyde amino resin according to any one of claims 1 to 7, wherein the aldehyde is formaldehyde.   A low-free formaldehyde amino resin obtained by the production method according to claim 1.   The low free formaldehyde amino resin according to claim 9, wherein the content of free formaldehyde contained in the resin is less than 1% by mass.