JPH09235359A - Continuous production of polyester resin for powder coating material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for continuously producing a polyester resin for powder coating materials, capable of continuously producing the polyester resin stable in qualities and used for the powder coating materials, and further capable of producing the polyester resin for the powder coating materials at a low cost. SOLUTION: This method for continuously producing a polyester resin comprising an aromatic dicarboxylic acid and an aliphatic diol as main components and having an intrinsic viscosity of 0.15-0.40 and an acid value of 14-100mgKOH/g comprises continuously adding a slurry containing the aromatic dicarboxylic acid component and the aliphatic diol component in a molar ratio of 1/1 to 1/2.5 to an esterification reactor 2 having polyester low polymers therein, subjecting the mixture to an esterification reaction at a temperature of >=200 deg.C so as to give an esterification reaction degree of >=90%, while removing the by-produced water outside the system, continuously transferring the esterification product into a polycondensation reactor 3, polycondensing the esterification product until to give the polyester having an approximately described intrinsic viscosity, transferring the product into an addition reactor 4, adding an aromatic polybasic carboxylic acid anhydride in an amount of 0.02-0.1 mole per mole of the acid component constituting the polyester and subsequently subjecting the mixture to an addition reaction.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for continuously producing a polyester resin for powder coating.

[0002]

2. Description of the Related Art Compared with solvent-based paints, powder paints have advantages such as low pollution, ready-to-use immediately after painting, and relatively low price. It is used in many fields, including building materials, and in recent years the demand has expanded rapidly. Epoxy resin-based, acrylic resin-based, and polyester resin-based powder coatings are mainly known as powder coatings. Among them, polyester resin-based powder coatings are known as coatings with balanced coating performance. Has been.

Polyester resins for powder coatings have hitherto been produced exclusively in a batch system, because the production of polyester resins is a relatively large variety of products in small quantities.
In other words, when various types of products are produced in a continuous system, it is necessary to change brands frequently, and a large amount of loss occurs until the characteristic values of the changed brands stabilize, resulting in high costs. was there.

However, with the recent increase in consumption, general-purpose brands with a large production volume have also appeared. In the case of such a mass-produced product, it is advantageous in terms of cost if it can be produced by a continuous method, and in the continuous production method, the characteristic values of the polyester resin such as the color tone of the resin and the number of terminal groups that influence the quality of the paint are stabilized. The establishment of technology is required.

[0005]

In view of such a situation, the present invention makes it possible to continuously produce a polyester resin for powder coating material with stable quality, and to reduce the cost of the polyester resin for powder coating material. It is intended to provide a method that can be manufactured in.

[0006]

Means for Solving the Problems The present invention is to solve the above-mentioned problems and comprises an aromatic dicarboxylic acid and an aliphatic diol as main constituent components, and has an intrinsic viscosity of 0.15 to 0.40 and an acid value of
When continuously producing a polyester resin of 14 to 100 mg KOH / g, an aromatic dicarboxylic acid component and an aliphatic diol component having a molar ratio of 1/1 to 1 / 2.5 are placed in an esterification reaction tank containing a polyester low polymer. And the slurry are continuously added, and the esterification reaction is performed at a temperature of 200 ° C or higher while removing the generated water outside the system so that the esterification reaction rate is 90% or higher. To a polycondensation reaction until a polyester having an intrinsic viscosity of almost a predetermined value is obtained, and then fed to an addition reaction tank, and the polyfunctional aromatic carboxylic acid is added to 1 mol of the acid component constituting the polyester. The present invention is directed to a continuous production method of a polyester resin for powder coating, which comprises adding 0.02 to 0.1 mol of an anhydride and carrying out an addition reaction.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

The polyester resin in the present invention is mainly composed of an aromatic dicarboxylic acid component and an aliphatic diol component, and is preferably a resin mainly composed of the following carboxylic acid component and aliphatic diol component.

Carboxylic Acid Component Mainly composed of terephthalic acid (TPA) and isophthalic acid (IPA), and if necessary, other dicarboxylic acids such as phthalic acid (PA), phthalic anhydride, 2,6-naphthalenedicarboxylic acid, etc. To which aliphatic dicarboxylic acids such as aromatic dicarboxylic acid, succinic acid, adipic acid and azelaic acid, and alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid are added

Diol component Ethylene glycol (EG), neopentyl glycol (NPG), 1,4-butanediol, 1,6-hexanediol, 1,3-propylene glycol, 1,4-cyclohexanedimethanol

In the range where the polyester resin is not gelled, trimellitic acid (TMA), trifunctional or more carboxylic acid such as pyromellitic acid, trimethylolpropane, trimethylolethane, 3-methylpentane-1,3,
You may use together trifunctional or more than trifunctional alcohols, such as 5-triol, glycerin, and pentaerythritol. Furthermore, if necessary, para-hydroxybenzoic acid, tartaric acid,
A hydroxycarboxylic acid such as ε-caprolactone can also be used in combination.

Examples of the aromatic polyfunctional carboxylic acid anhydride used in the addition reaction include phthalic anhydride (PAA), trimellitic anhydride (TMAA) and pyromellitic dianhydride.

Polyester resin has an intrinsic viscosity of 0.15 to 0.
40, it is necessary to have a hydroxyl value of 14 to 100 mg KOH / g.

When the intrinsic viscosity of the polyester resin is less than 0.15, the blocking resistance of the composition tends to be poor, or the mechanical strength of the coating film tends to be low. On the contrary, when it exceeds 0.40, the pulverizability, The smoothness of the coating film tends to deteriorate.
Particularly preferred are those having an intrinsic viscosity of 0.20 to 0.35.

The hydroxyl value of the polyester resin is 100 m
If it exceeds gKOH / g, not only the mechanical strength of the coating film tends to decrease, but also a large amount of a curing agent needs to be added, and the cost of the coating material increases, which is not preferable. On the other hand, when the hydroxyl value is less than 14 mgKOH / g, the surface of the coating film is uneven and has large irregularities, which deteriorates the smoothness.

Further, the softening point of the polyester resin is 50 to
It is desirable to select the copolymer composition so that the temperature is 150 ° C. If the softening point is less than 50 ° C, the resin causes blocking during storage, and if it exceeds 150 ° C, it is necessary to raise the kneading temperature during the production of the coating composition, which may cause curing during kneading, which is not preferable. .

Next, the method of the present invention will be described with reference to the drawings. First, the aromatic dicarboxylic acid component and the aliphatic diol component are slurried in the slurry-forming tank 1 shown in FIG. 1 and continuously supplied to the esterification reaction tank 2 in which the polyester low polymer is present.

In the steady operation state, the polyester low polymer is naturally present in the esterification reaction tank 2, but at the start of the operation, the raw materials are charged and the esterification reaction is carried out without extracting the reaction product or it is synthesized separately. It is necessary to shift to continuous operation after charging the polyester low polymer.

The amount of the polyester low polymer present in the esterification reaction tank 2 is suitably 3.5 to 10 times the amount of the slurry supplied per hour in terms of the number of moles of the acid component. If this amount is too small, the esterification reaction will not proceed smoothly, while if it is too large, the color tone of the resulting polyester resin will deteriorate.

The composition of the slurry supplied to the esterification reaction tank 2 must be such that the molar ratio of the aromatic dicarboxylic acid component and the aliphatic diol component is 1/1 to 1 / 2.5. If this ratio is less than 1/1, the esterification reaction will take a long time, and the reaction will not proceed in some cases. On the other hand, when this ratio is larger than 1 / 2.5, the content of ether bonds in the polyester resin becomes too large,
The softening point of the resin is lowered, and the weather resistance of the coating film after being made into a paint is deteriorated.

When the copolymerization component is used in combination with the aromatic dicarboxylic acid component and the aliphatic diol component, the slurry contains the copolymerization component.

In the esterification reaction tank, the esterification reaction is carried out at a temperature of 200 to 270 ° C. under atmospheric pressure while removing the produced water out of the system. The esterification reaction rate is
It is necessary to do it so that it is 90% or more. If the esterification reaction rate is less than 90%, the subsequent polycondensation reaction may take an extremely long time, which is not preferable.

As the esterification reaction tank, one which has been widely adopted in the continuous esterification process of polyethylene terephthalate can be used.

Next, the esterification reaction product (low polymer of polyester) is continuously withdrawn from the esterification reaction tank 2 and fed to the polycondensation reaction tank 3 until polycondensation is obtained until a polyester having a substantially predetermined intrinsic viscosity is obtained. Perform the reaction.

A polycondensation catalyst solution supply pipe is connected to the liquid feed pipe for the esterification reaction product, and the catalyst solution is supplied through the pump 5. As the polycondensation catalyst, antimony trioxide, tetrabutyl titanate,
Dimethyltin maleate, germanium dioxide, etc. are used and are usually supplied as a diol solution. (A polycondensation catalyst may be added during the esterification reaction, and in that case, it may not be necessary to supply the polycondensation catalyst to the polycondensation reaction tank 3.)

In the polycondensation reaction tank 3, the polycondensation reaction is continuously carried out at a temperature of 200 to 300 ° C., preferably 230 to 290 ° C. under a reduced pressure of 30 to 1 hPa. At this time, the degree of pressure reduction, the temperature, the residence time, etc. are adjusted so that the polyester has a substantially predetermined intrinsic viscosity. Since the intrinsic viscosity of the polyester resin is slightly increased by the addition reaction with the aromatic polyfunctional carboxylic acid anhydride that is carried out later, the amount of the intrinsic viscosity of the polyester at this stage is better than the predetermined intrinsic viscosity. May be slightly smaller.

As the polycondensation reaction tank, since the polyester resin for powder coating has a low intrinsic viscosity, a stirring tank type may be used. Usually, one tank is sufficient, but if necessary, 2
It is also possible to divide into three tanks so that the polycondensation reaction proceeds in multiple stages.

Subsequently, the polyester obtained by the polycondensation reaction is fed to the addition reaction tank 4 and mixed with a predetermined amount of the aromatic polyfunctional carboxylic acid anhydride (melt) supplied from the supply pump 6, The addition reaction is carried out continuously at a temperature of 180 to 260 ° C and atmospheric pressure.

The polyester obtained by the polycondensation reaction has an acid value of about 1 to 3 mgKOH / g, and the acid value can be increased by addition reaction of this with an aromatic polyfunctional carboxylic acid anhydride. it can. It is necessary to add the aromatic polyfunctional carboxylic acid anhydride in an amount of 0.02 to 0.1 mol with respect to 1 mol of the acid component constituting the polyester. Within this range, a predetermined acid value (14 to 100 mgKOH / g) Adjust so that the above polyester resin can be obtained. If the amount added is less than this, the acid value does not rise sufficiently, resulting in uneven and large unevenness on the surface of the coating film, resulting in poor smoothness. On the other hand, if the amount added is larger than this, the crosslinking reaction also progresses during the addition reaction, the intrinsic viscosity greatly increases, and in some cases gelation occurs.

The addition reaction tank 4 may be a closed container capable of continuously mixing and reacting the polyester and the aromatic polyfunctional carboxylic acid anhydride, such as a jacketed mixing tank, a tubular reactor or a kneader. A machine or the like can be used.

The polyester resin obtained by the method of the present invention is dry-blended with an epoxy type curing agent, a leveling agent, benzoin, a curing catalyst, a pigment, etc., and then 70 to 150 ° C.
A polyester resin composition for powder coating can be obtained by melt-kneading with, cooling, pulverizing, and then classifying.

[0032]

In the past, polyester resins for powder coatings having a large acid value were generally manufactured by a batch method in which a polyester having a high degree of polymerization was once prepared and then depolymerized with a polyfunctional carboxylic acid. In the present invention, a polyester having a substantially predetermined intrinsic viscosity is continuously produced, and the obtained polyester is subjected to an addition reaction with an aromatic polyfunctional carboxylic acid anhydride. A polyester resin having a high valency can be continuously produced.

[0033]

Next, the present invention will be described in detail with reference to examples and comparative examples. The characteristic values were measured by the following method. (a) Intrinsic viscosity ([η]) It was measured at a temperature of 20 ° C. with a solvent of equal weight mixture of phenol and ethane tetrachloride. (b) Esterification reaction rate (E) The acid value AV and saponification value SN of the esterification reaction product were measured by the following methods, and determined by the following formula. E = [1- (AV / SN)] × 100 AV: The sample was dissolved in dioxane and then titrated with a methanol solution of potassium hydroxide. SN: The sample was saponified with an ethanol solution of potassium hydroxide for 2 hours, and then excess potassium hydroxide was back-titrated with hydrochloric acid to obtain the sample. (c) Acid value Polyester resin (0.5 g) is added to water and dioxane in a weight ratio of 1
It was dissolved in a mixed solution of / 9 and titrated with a potassium hydroxide methanol solution. (d) Composition of resin The polyester resin was decomposed by heating with methanol, and the peak area ratio of each component to a standard sample was determined by gas chromatography. (e) Impact resistance According to JIS K 5400, a ball with a diameter of 1.27 cm and a weight of 1 kg was dropped vertically to determine the height at which the coating film was destroyed. (f) Smoothness The smoothness of the coating film was visually evaluated and evaluated in the following two stages. ◯: No irregularities on the surface ×: Many irregularities on the surface (g) Blocking resistance 10 cm x 3c for a coating composition that passed through a 140 mesh sieve
Fill a mφ test tube to a height of 5 cm and place it in a 40 ° C incubator.
After standing for 2 hours, the state of blocking was visually determined. ◯: No blocking X: Blocking (h) Specular gloss of 60 degrees According to JIS K 5400, it was measured with a gloss meter manufactured by Murakami Color Research Laboratory. (i) Gloss retention The following accelerated weather resistance test was performed to determine the ratio of the 60-degree specular gloss after 300 hours of irradiation to the 60-degree specular gloss before irradiation. Accelerated weathering test: A test piece manufactured by Suga Test Instruments Co., Ltd. according to JIS K 5400, for a test piece that was powder-coated on a zinc phosphate-treated steel plate by electrostatic coating to a film thickness of 50 to 60 μm and baked. Using the Sunshine Weather Meter WEL6XS-HC-B / Ec type, set the black panel temperature to 63 ° C, irradiate the light from the carbon arc lamp, and set one cycle to 120 minutes, of which 18 minutes are fog of water. To spray.

Examples 1 to 5 and Comparative Examples 1 to 7 Slurry of the raw material compounds in the proportions shown in Tables 1 and 2 were prepared in the slurry-forming tank 1, and the slurry was adjusted to 1 by the amount of the acid component.
It was continuously fed to the esterification reaction tank 2 in which the amount of the polyester low polymer shown in Tables 1 and 2 was present at a rate of 00 mol / h. Operating conditions of the esterification reaction tank, pressure 1400 hPa,
The values in Tables 1 and 2 were maintained for the temperature in the system, the average residence time and the retention amount. A polyester low polymer having an esterification reaction rate of 90% or more was continuously withdrawn from the esterification reaction tank 2 and continuously fed to the polycondensation reaction tank 3. At this time, an EG solution of antimony trioxide was added as a polycondensation catalyst into the liquid delivery pipe of the low-polymer polyester so that the amount of antimony trioxide was 3 × 10 ⁻⁴ mol with respect to 1 mol of all acid components. did. The operating conditions of the polycondensation reaction tank were a pressure of 20 hPa, and the system temperature and average residence time were maintained at the values shown in Tables 1 and 2. Polyester was continuously extracted from the polycondensation reaction tank and continuously fed to the addition reaction tank 4. At this time, the aromatic polyfunctional carboxylic acid anhydrides shown in Tables 1 and 2 were added to the polyester liquid delivery pipe in the amounts shown in Tables 1 and 2. The addition reaction tank was maintained under an inert atmosphere, atmospheric pressure, a temperature of 260 ° C., and an average residence time of 1 hour. The polyester resin was continuously extracted from the addition reaction tank to obtain a polyester resin having the characteristic values shown in Tables 1 and 2. (However, in Comparative Examples 6 to 7, the reaction was terminated midway.) 100 parts by weight of the polyester resin obtained by the above method and epi-bis type epoxy resin (diglycidyl polycondensate of bisphenol A and epichlorohydrin) Modified etherification): Ciba Geigy's "Araldite AER6003" is a functional group equivalent to the acid value of the polyester resin, butyl acrylate leveling agent: Basuf's "Acronal 4F" 1 part by weight, benzoin 0.5 part by weight , Undecyl imidazole curing catalyst: Shikoku Kasei Co., Ltd. "Curezol C ₁₁ Z" 0.2 parts by weight, titanium dioxide 50 parts by weight, FM
After dry blending with a 10B Henschel mixer (Mitsui Miike Seisakusho), PR-46 type Co-Kneader (Bus)
Was melt-kneaded at 110 ° C., cooled, pulverized, and separated by a wire mesh of 140 mesh to obtain a powder coating material. The powder coating thus obtained was electrostatically coated on a zinc phosphate-treated steel plate to a film thickness of 50 to 60 μm and baked at 170 ° C. for 20 minutes. The results of evaluation of coating film performance are shown in Tables 1-2. Tables 1-2
In, DEG represents diethylene glycol and DNPG represents dineopentyl glycol.

[0035]

[Table 1]

[0036]

[Table 2]

In the examples of the present invention, it was possible to continuously produce a polyester resin for powder coating of good quality, but in the comparative examples, there were the following problems. In Comparative Example 1, since the intrinsic viscosity of the polyester resin used is high,
The smoothness of the coating film is poor. In Comparative Example 2, since the polyester resin used has a low intrinsic viscosity, the impact resistance is poor. In Comparative Example 3, EG of the slurry supplied to the esterification reaction tank
Since the ratio is large, there are many ether bonds in the polyester resin, resulting in poor weather resistance. In Comparative Example 4, since the polyester resin has a small acid value, the coating film has poor smoothness. In Comparative Example 5, since the polyester resin has a large acid value, the mechanical strength of the coating film is low. In Comparative Example 6, since the proportion of EG in the slurry supplied to the esterification reaction tank was small, the dicarboxylic acid component did not dissolve in the reaction system even after it was allowed to stay in the esterification reaction tank for 20 hours, and thus it could be supplied to the polycondensation step. could not. In Comparative Example 7, since the esterification reaction rate of less than 90% was supplied to the polycondensation reaction tank, the viscosity did not increase even after being retained for 8.6 hours, and the polycondensation reaction could not be supplied to the addition reaction step.

Example 6 Continuous operation was carried out for 10 days under the conditions of Example 2, and the obtained polyester resin was sampled every 12 hours to evaluate the characteristic value of the resin and the coating film performance. The results are shown in Table 3.

Comparative Example 8 A batch type esterification reaction tank was charged with the same raw material compound as in Example 2 and the esterification reaction was carried out at a temperature of 260 ° C. under normal pressure for 7 hours to obtain an esterification reaction rate of 90% or more. A reaction product (polyester low polymer) was obtained. After transferring the obtained esterification reaction product to a batch-type polycondensation reaction tank, an EG solution of antimony trioxide was used as a polycondensation catalyst, and the amount of antimony trioxide was 3 × 10 ⁻⁴ mol based on 1 mol of all acid components. Was added so that the temperature was 260 ° C., the pressure was gradually reduced from atmospheric pressure to 2 hPa or less over 60 minutes, and the polycondensation reaction was carried out for 2.5 hours. Next, 4 mol of trimellitic anhydride was added to the obtained polyester, and the addition reaction was carried out at 260 ° C. for 1 hour under normal pressure. This operation was repeated 20 times to evaluate the characteristic values of the resin and the coating film performance. The results are shown in Table 3.

[0040]

[Table 3]

In Example 6, it was possible to continuously produce a polyester resin for powder coating material with stable quality.
In Comparative Example 8, since the batch method was used, the quality variation was large.

[0042]

According to the present invention, it becomes possible to continuously produce a polyester resin for powder coating material with stable quality, and it is possible to produce a polyester resin for powder coating material at low cost.

[Brief description of drawings]

FIG. 1 is a schematic process drawing showing an example of the method of the present invention.

[Explanation of symbols]

 1 Slurry tank 2 Esterification reaction tank 3 Polycondensation reaction tank 4 Addition reaction tank 6 Aromatic polyfunctional carboxylic acid anhydride supply pump

Claims (1)

[Claims] 1. An aromatic dicarboxylic acid and an aliphatic diol as main constituent components, and an intrinsic viscosity of 0.15 to 0.40 and an acid value of 14
When continuously producing a polyester resin having a concentration of ˜100 mg KOH / g, an aromatic dicarboxylic acid component and an aliphatic diol component having a molar ratio of 1/1 to 1 / 2.5 were placed in an esterification reaction tank containing a polyester low polymer. The slurry is continuously added, and at a temperature of 200 ° C or higher, the produced water is removed to the outside of the system to perform an esterification reaction so that the esterification reaction rate is 90% or more, and then the polycondensation reaction tank is used. Continuous liquid transfer,
After polycondensation reaction until a polyester having an almost predetermined intrinsic viscosity is obtained, the mixture is fed to an addition reaction tank and 0.02 to 0.1 mol of an aromatic polyfunctional carboxylic acid anhydride is added to 1 mol of an acid component constituting the polyester. Then, a continuous process for producing a polyester resin for powder coating is characterized by carrying out an addition reaction.