EP1899424A1

EP1899424A1 - Method for production of polyester resins containing nanodisperse nanoscale additives as binder for powder paints

Info

Publication number: EP1899424A1
Application number: EP06741046A
Authority: EP
Inventors: Dieter Holzinger; Thomas Schmidt
Original assignee: Tiger Coatings GmbH and Co KG
Current assignee: Tiger Coatings GmbH and Co KG
Priority date: 2005-06-28
Filing date: 2006-06-19
Publication date: 2008-03-19
Also published as: WO2007000002A1; AT501471B1; US20090176933A1; AT501471A4; CN101203576A

Abstract

The invention relates to a method for production of polyester resins containing nanodisperse nanoscale additives as binder for powder paints, whereby firstly at least one precursor compound for nanoscale solid particles to be formed is added to the reaction starting materials during the resin synthesis and distributed in the reaction starting materials. The precursor compound(s) which may be reacted at a temperature between 30° and 260° C, preferably between 80° and 250° C, are reacted to give the desired nanoscale solid particles under the effect of a reaction temperature in the range between 30° and 260° C, preferably between 80° and 250° C, the nanoscale solid particles thus formed being nanodispersedly distributed in the polyester resin.

Description

Process for the preparation of nanoscale additives containing nanodispersed polyester resins as a binder for powder coatings.

The present invention relates to a process for the preparation of nanoscale additives containing nanodispersed polyester resins as a binder for powder coatings.

Powder coatings have found wide application in the coating of materials such as metal, glass, ceramics, etc. due to the high efficiency of the process and the favorable assessment from the perspective of environmental protection.

A variety of different binder systems, pigments, fillers and additives have in the past developed powder coatings for a wide variety of applications. For example, decorative coatings, corrosion protection systems, heat-resistant coatings, weather-resistant coatings on facades and vehicles as well as diverse functional coatings in glossy to matt, smooth to textured finish have long been the state of the art. It should be noted that among the binder systems used, the polyester resins have a special meaning, which is due to their balanced property profile without particular weaknesses.

Polyester resins as binders for powder coatings have been the state of the art for over 30 years. For example, DE 21 63 962 A1 or DE 26 18 729 A1 describe carboxyl-functional polyester resins in the acid number range 30-100 or 50-100 mg KOH / g resin, which are reacted with polyepoxide compounds such as epoxy resins based on bisphenol A and epichlorohydrin or else triglycidyl isocyanurate can be networked. Similar early examples of hydroxy-functional polyester resins as binders for powder coatings are provided by NL 72 01 656 A. The polyester resins disclosed in the examples have hydroxyl numbers of 124 to 160 mg KOH / g resin, the resins are crosslinked by reaction with blocked polyisocyanates. Recent prior art reveals the trend for polyester resins, which have lower hardness requirements due to lower characteristic values. For example, EP 0 107 888 B1 and EP 0 110 450 B1 disclose polyester resins having an acid number range of 10 to 26 or 10 to 30 mg KOH / g resin.

In addition, qualitative differentiation can be observed. For example, according to EP 0 664 325 B1, a low proportion of isophthalic acid in the resins leads to increased resistance of the powder coatings produced therefrom to physical aging of the films. High proportions of isophthalic acid in turn result in increased weathering stability of the coatings produced therefrom, as disclosed by EP 0 389 926 B1 and DE 43 35 845 C2. This allows polyester as a binder for powder coatings to produce a wide range of different powder coating qualities.

With the increasing availability of nanoscale solids - those with a characteristic particle size <1 .mu.m and preferably of <0.1 .mu.m - which can impart diverse and hitherto unattainable characteristics to the materials containing them owing to highly specific property profiles, it is possible to coat powder coatings with others provide special features that did not exist before, giving them completely new applications. Examples of powder coatings containing nanoparticles provide, for example, EP 1 164 159 A1, EP 1 361 257 A1 and US Pat

WO 02/051922 A2. However, according to the prior art disclosed in these documents, there is no further teaching about the nature and form of the distribution of the nanoparticles in the

Derive powder coating, these disclosures do not even deal with the problem of an irregular and incomplete distribution of nanoparticles in the powder coating.

WO 2005/075548 A2 or AT 413 699 Bl gives a detailed overview of quality features which can be introduced into coatings via different nanoparticles.

Coatings with nanodispersed nanoscale particles, which consist of compounds of the elements silver or copper or equal to the metals in their elemental form, show biocidal activity due to a slight but constant presence of silver or copper ions on their surface. The use of nanodispersed nanoscale oxide particles of the elements silicon, aluminum, zirconium and titanium leads in coatings to increased hardness and scratch resistance. In addition, such titanium dioxide - as well as zinc oxide - also known as UV absorber, moreover, it shows photochemical activity.

According to WO 2005/075548 A2, it has been found that the incorporation of dry nanoparticulate material in powder coating formulations results in a suboptimal distribution of these particles in the powder coating, which is mainly attributable to the fact that dry nanoparticles are generally predominantly agglomerated and scarcely present as primary particles.

Significantly more favorable conditions with respect to the nanoparticulate character are present in the nanoparticles offered in suspension. WO 2005/075548 A2 describes a production process in which such nanoparticles distributed in liquid are added in the synthesis of polyester resins as binders for powder coatings. In this case, the largely nanodisperse distribution of those particles in such suspensions is maintained in the course of the polyester synthesis. The powder coatings prepared using such polyesters show, in view of the specific properties of the nanomaterials used, significantly higher efficiency than powder coatings, in which the corresponding nanomaterials are added as a dry substance to the powder coating components, mixed in dry and homogeneously distributed by extrusion.

Nevertheless, the above method also has certain shortcomings. On the one hand, the restriction applies that the liquids of those suspensions must be compatible with the formulation and synthesis of a polyester resin as a binder for powder coatings. Although this basically applies to water as the continuous phase of such suspensions, it can be quite complicated if large amounts of water, which can thus be introduced into the raw material batch of a polyester resin, have to be distilled off before the actual synthesis reaction. If the respective nanoparticulate solid particles are dispersed in a glycol, qualitative and quantitative limitations are preprogrammed: not all glycols are equally suitable for producing polyester resins as binders for powder coatings, and even for the appropriate ones there will be upper limits imposed by the desired resin formulation are set. Another and not to be underestimated problem are those substances which are added to those suspensions in order to prevent the coalescence of the nanoparticles contained in larger agglomerates and to keep such suspensions stable for as long as possible, generally these additives are based on highly specific know-how of the manufacturers Suspensions, which is not disclosed in product information. However, it has been found that such additives, while effective in stabilizing said suspensions, can be detrimental to resin synthesis or detrimental to the desired resin quality.

Finally, it should be noted that the commercial suspensions of nanoparticulate solids are generally very expensive. Thus, polyester resins, in which such nanoparticles are incorporated, often a very significant cost increase.

There is therefore a need for a process which makes it possible to introduce nanoscale solid nanoparticles dispersed in a polyester resin as a binder for powder coatings, without possibly large amounts of liquid in the

Polyester synthesis must be introduced. Furthermore, there is a need for a

Process that allows nanoscale solid particles nanodispersed in one

Polyester resin as a binder for powder coatings and bring in suspensions with often undeclared and possibly hinderlichen for the course of resin synthesis and / or detrimental to the desired resin quality additives which

To ensure stability of these suspensions to dispense. Furthermore, there is a need for polyester resins as binders for powder coatings, which contain nanoscale solid particles nanodispersed, without therefore priced in completely different dimensions, as is the case with conventional polyester resins, to penetrate.

Surprisingly, it has been found that nanoscale solid particles in a stable nanodisperse state containing polyester resins can be prepared as a binder for powder coatings, if according to the method according to the invention in the reaction mixture in the course of resin synthesis initially introduced at least one miscible with the reaction mixture precursor of nanoscale solid particles to be formed and is distributed in the reaction mixture and that at a temperature between 30 ° and 260 ° C, preferably between 80 ° and 250 ° C, convertible (s) precursor compound (s) under the action of synthesis temperature in The range between 30 ° and 260 ° C, preferably between 80 ° and 250 ° C is reacted to form the desired nanoscale solid particles, wherein the nanoscale solid particles thus produced are distributed nanodispersed in the polyester resin.

By the term "miscible with the reaction mixture" in connection with a precursor compound is also included that the precursor compound in the reaction mixture may also be soluble.

Further features and advantageous embodiments of the invention are characterized in the subclaims 2 to 14 and can be found in the following description.

These precursors are chemical compounds which contain the chemical element (s) from which the desired nanoscale particulate matter is composed and which, in the raw material mixture for producing the polyester resin, can first be dispersed due to their miscibility / solubility before they under the action of synthesis temperature and optionally also under the action of small amounts of water which were added to the batch or are present anyway as reaction water during a large part of the synthesis time, are reacted to form the desired nanoscale solids. In order for chemical compounds to be suitable as precursor substances for nanodispersed nanosize solid particles distributed in the polyester resin according to the invention, their reaction temperature must be in the range from about 30 ° to 260 ° C., preferably 80 ° to 250 ° C. The nanoscale nature of the solid particles thus produced in polyester resins as a binder for powder coatings was as well as their nanodisperse distribution in these resins occupied by electron microscopic examination of the resins prepared by this process.

The character of the chemical compounds used as precursors depends on the nature of the particles to be produced. In addition to a reaction temperature in the aforementioned range of about 30 ° and 260 ° C, preferably 80 - 250 ⁰ C, the availability plays an essential role. For the preparation of polyester resins as binders for powder coatings containing nanoscale metal particles, such as copper or silver, or nobler metals than those mentioned, eg gold or other noble metals nanodispersed, preferably used as precursors salts of these metals with organic acids, in particular (hydroxy) ) Carboxylic acids. For example, additions of silver citrate, copper citrate, copper oxalate or copper gluconate to the raw material mixtures of the respective polyesters lead to the corresponding resins which contain nanodispersed metal in the form of nanoscale particles. Electron microscopy revealed that the particles generated during resin synthesis are indeed nanoscale particles nanodispersed in the resin matrix. The advantage of using the corresponding metal carboxylates lies in the fact that their acid residues have a strong analogy to the (hydroxy) carboxylic acids used in the synthesis of the corresponding polyesters.

If organic salts are not commercially available, as in the case of gold, it is also possible to use inorganic substances such as tetrachloroauric (IH) acid.

For the production of polyester resins as binders for powder coatings which are to contain nanoscale oxidic particles of the elements silicon, titanium, zirconium, aluminum, vanadium and / or tin, it can also be assumed that the salts of organic acids, if they are available, as in the case of Tin of tin oxalate. Otherwise, it is advantageous to start from the alkoxylates of the relevant elements. In some of these elements, it is advantageous or necessary to commercially available precursors by complex formation - for example, addition of (hydroxy) carboxylic acids, such as citric acid, and / or diketones, including their derivatives, e.g. Acetylacetone - limit their sensitivity to hydrolysis so that a homogeneous distribution of the precursor substance in the resin mixture is possible, before it comes to the formation of the respective nanoparticles by the action of elevated temperature and optionally moisture. Of course, it is within the scope of the invention also possible to use combinations of complexing agents.

The alkoxylates are characterized by the general formula R _n X (OR ') _mn , where: X = Si, Ti (IV), Zr (IV), Al, Va (III), Va (V)

R = non-hydrolyzable substituent, optionally with one or more functional group (s), such as epoxy,

Hydroxyl, carboxyl provide m = 5 for Va (V); = 4 for Si, Ti (IV) ₅ Zr; = 3 for Al, Va (TS) n = [0 <n <(m-2)] R '= alkyl

Alkyl may preferably be methyl, ethyl, propyl, i-propyl, n-butyl, i-butyl, tert. Be butyl.

In this way, oxides and / or oxyhydrates of said elements can be prepared in the form of nanoscale particles which are optionally (n> 0) surface-modified by organic substituents. Of course, it is possible to use more than one precursor in the context of the resin synthesis in the context of the present invention.

In the case of the nanoparticulate oxide nanoparticles distributed according to the invention in the course of the polyester synthesis, it was also possible to detect the particle fineness and its distribution in the resin by electron microscopy.

The invention will be explained in more detail below by the following examples. They should help to explain the essence of the subject of the invention in more detail, without restricting it in any way.

Example 1:

In accordance with DE 21 63 962 A1, in a 1-1 reaction vessel equipped with stirrer, temperature sensor, partial reflux column, distillation bridge and inert gas inlet (nitrogen), 241.08 g of 2,2-dimethylpropanediol 1.3, 18.63 g Ethyl englykol and 10 g of silver citrate and liquefied with the addition of 10 g of water and heating to a maximum of 100 ⁰ C under a nitrogen atmosphere. With stirring 361.35 g of terephthalic acid and 32.88 g of adipic acid and 0.1%, based on the total amount of the finished resin, Sn-containing catalyst is added and the melt temperature gradually increased to 240 ° C, starting from about 150 ° C a dark color of the Haxz approach occurs. The reaction is continued at this temperature until no distillate is produced. The mixture is then further esterified under reduced pressure, about 400 mbar, until the acid number of the hydroxy-functional polyester resin is ~7 mg KOH / g polyester resin.

Subsequently, the temperature in the reaction vessel is lowered to 195 ° C and there are added 76.85 g of trimellitic anhydride. After stirring for one and a half hours at about 195 ° C, the resin is poured into a metal cup. The cooled resin of Example 1 has the following characteristics: acid number 70.8 mg KOH / g polyester, hydroxyl number 10.3 mg KOH / g polyester.

A subsequent examination of the polyester by means of a transmission electron microscope shows the presence of individual spherical (silver) particles, of which 90% of their number has a size of 58 +/- 28 μm.

Example 2:

In an analogous manner as in Example 1, the same materials are used in the same amount, but instead of the 10 g of silver citrate 17.48 g of copper citrate are used. Starting with about 200 ⁰ C, a color change of the resin starting material is observable, which goes from blue to muddy green and brown to reddish. The esterification is continued first under atmospheric pressure and then under reduced pressure (~ 400 mbar) until the acid number of the hydroxy-functional polyester resin is ~ 8 mg KOH / g polyester resin.

This hydroxylated polyester resin is then reacted according to Example 1 with trimellitic anhydride and ultimately has the following characteristics: acid value 75.0 mg KOH / g polyester, hydroxyl number 6.6 mg KOH / g polyester.

Subsequent examination of the polyester by means of a transmission electron microscope shows the presence of individual spherical (copper) particles, 90% of which have a size of 31 +/- 8 nm. Example 3:

In an analogous manner as in Example 1, the same materials are used in the same amount, but 16.42 g of copper oxalate are used instead of the 10 g of silver citrate. Starting at approx. 237 ° C, a change in color of the resin mixture is observed, which leads from blue to dirty green and brown to red-black. The esterification is continued under normal pressure and then under reduced pressure (~ 400 mbar) until the acid number of the hydroxy-functional polyester resin ~ 4 mg KOH / g polyester resin.

This hydroxylated polyester resin is then reacted according to Example 1 with trimellitic anhydride and ultimately has the following characteristics: acid value 69.6 mg KOH / g polyester, hydroxyl value 11.4 mg KOH / g polyester.

Example 4: In an analogous manner as in Example 1, the same materials are used in the same amount, but instead of the 10 g of silver citrate 24.09 g of copper gluconate are used. Starting at about 140 ° C, a change in color of the resin mixture is observed, which leads from green-blue to colorless. From about 180 ° C, the approach turns dark and ultimately reddish black. The esterification is initially carried out under atmospheric pressure and then under reduced pressure (~ 400 mbar) until the acid number of the hydroxy-functional polyester resin ~ 9 mg KOH / g polyester resin.

This hydroxylated polyester resin is then reacted according to Example 1 with trimellitic anhydride and ultimately has the following characteristics: acid value 75.5 mg KOH / g polyester, hydroxyl value 3.5 mg KOH / g polyester.

Example 5: In an analogous manner as in Example 1, the same materials are used in the same amount, but instead of 10 g of silver citrate and water 24.60 g of a 0.0106 molar aqueous solution of tetrachloroauric (III) acid (Fa Merck). Commencing at about 110 ⁰ C, a color change of the resin starting material is observable, which goes from yellow to reddish. The esterification is initially under Normal pressure and then under reduced pressure (~ 400 mbar) continued until the acid number of the hydroxy-functional polyester resin is ~ 7 mg KOH / g polyester resin.

This hydroxylated polyester resin is then reacted according to Example 1 with trimellitic anhydride and ultimately has the following characteristics: Acid value 73.1 mg KOH / g polyester, hydroxyl number 11.3 mg KOH / g polyester.

Example 6: In an analogous manner as in Example 1, the same materials are used in the same amount, but 11.35 g of tin oxalate are used instead of 10 g of silver citrate. Commencing at about 170 ⁰ C a slight foaming of the resin starting material is observable, which was caused by the collapse of the tin oxalate. The esterification is continued under normal pressure and then under reduced pressure (~ 400 mbar) until the acid number of the hydroxy-functional polyester resin ~ 8 mg KOH / g polyester resin.

This hydroxylated polyester resin is then reacted according to Example 1 with trimellitic anhydride and ultimately has the following characteristics: acid value 73.0 mg KOH / g polyester, hydroxyl value 5.7 mg KOH / g polyester.

Subsequent examination of the polyester by means of a transmission electron microscope reveals the presence of individual spherical (tin oxide) particles, 90% of which have a size of 12 +/- 2 nm.

Example 7:

In a 1-1 reaction vessel equipped with stirrer, temperature sensor, partial reflux column, distillation bridge and inert gas (nitrogen) 241.08 g of 2,2-dimethylpropanediol 1.3 and 18.63 g of ethylene glycol are introduced and with the addition of 20 g of water and heating to a maximum of 8O ⁰ C liquefied under a nitrogen atmosphere. 361.35 g of terephthalic acid, 32.88 g of adipic acid, 0.1%, based on the total amount of the finished resin, Sn-containing catalyst and 11.20 g of tetraethoxysilane are added in succession in such a way that the addition of tetraethoxysilane at a temperature of ~ 60 ⁰ C takes place. The melt temperature is now gradually to 240 ⁰ C. elevated. The reaction is continued at this temperature until no distillate is produced. The mixture is then further esterified under reduced pressure, about 400 mbar, until the acid number of the hydroxyfunctional polyester resin is ~7 mg KOH / g polyester resin.

This hydroxylated polyester resin is then reacted according to Example 1 with Tiimellitsäureanhydrid and ultimately has the following characteristics: acid number 72.0 mg KOH / g polyester, hydroxyl number 11.2 mg KOH / g polyester.

A subsequent examination of the polyester by means of a transmission electron microscope shows the presence of individual spherical (silicon dioxide) particles, 90% of which have a size of 7 +/- 3 nm.

Example 8: In an Erlenmeyer flask 25.62 g of citric acid are dissolved in 136.71 ml of water at room temperature. Then 19.85 g of titanium acetylacetonate and 0.96 g of 3- (triethoxysilyl) propylsuccinic anhydride are added and stirred for 30 minutes. The resulting solution is hereinafter referred to as "solution 1".

In a 1-1 reaction vessel equipped with stirrer, temperature sensor, partial reflux column, distillation bridge and inert gas (nitrogen) are 194.01 g of 2,2-dimethylpropanediol 1.3, 7.80 g of 1,5-pentanediol and 20.31 submitted g hydroxypivalate and with the addition of "solution 1" and heating liquefied to a maximum of 80 ⁰ C under nitrogen atmosphere. While stirring, then successively 230.76 g of terephthalic acid, and 0.1%, based on the total amount of the finished resin Sn- containing catalyst was added. The mass temperature is then gradually increased to 240 ⁰ C. The reaction is continued at this temperature until no more distillate is produced. After cooling to 220 ⁰ C successively 81.34 g of isophthalic acid and 12.00 g of adipic acid are added after the addition, the temperature is increased again to 240 ⁰ C. The reaction is continued at this temperature until no more distillate arises nd is further esterified under reduced pressure, about 200 mbar, until the acid value of the carboxy-functional polyester resin is 45.6 mg KOH / g polyester resin. (Hydroxyl number 2.8 mg KOH / g polyester) Subsequent examination of the polyester by means of a transmission electron microscope shows the presence of individual spherical (titanium oxide) particles, 90% of which have a size of 30 +/- 10 nm.

Example 9:

In an Erlenmeyer flask, 22.20 g of oxalic acid dihydrate are dissolved in 140.00 ml of water at room temperature. Subsequently, 7.52 g of acetylacetone and 25.00 g of zirconium n-butoxide are added and stirred for 90 minutes. The resulting solution is hereinafter referred to as "solution 2".

In a 2-1 reaction vessel equipped with stirrer, temperature sensor, partial reflux column, distillation bridge and inert gas (nitrogen) 446.16 g of 2,2-dimethylpropanediol 1.3, 10.4 g of 1,5-pentanediol, 37.3 g of ethylene glycol and 40.62 g of hydroxypivalic acid neopentyl glycol ester and liquefied under the addition of "solution 2" and heating to a maximum of 80 ° C. under nitrogen atmosphere, then 637.8 g of terephthalic acid are added successively with stirring, and 0.1%, based on the total amount The melt temperature is then gradually increased to 240 ° C. The reaction is continued at this temperature until no more distillate is formed, followed by further esterification under reduced pressure, about 400 mbar, until the acid number of the hydroxy-functional polyester resin is ~7 mg KOH / g polyester resin.

Then, as described in Example 1, added 153.7 g of trimellitic anhydride and stirred at 195 ° C for 75 minutes. The resulting resin had the following characteristics: acid value 71.9 mg KOH / g polyester, hydroxyl number 12.2 mg KOH / g polyester.

A subsequent examination of the polyester by means of a transmission electron microscope shows the presence of individual spherical (zirconium oxide) particles, which to 90% of their number have a size of 8 +/- 4 nm.

Claims

claims:

1. A process for the preparation of nano-scale additives nanodisperse distributed polyester resins as a binder for powder coatings, characterized in that in the reaction mixture in the course of the synthesis of resin first at least one miscible with the reaction mixture precursor of nanoscale solid particles to be formed is introduced and distributed in the reaction mixture and that the at a temperature between 30 ° and 260 ° C, preferably between 80 ° and 250 ° C, convertible (s) precursor compound (s) under the action of synthesis temperature in the range between 30 ° and 260 ° C, preferably between 80 ° and 250 ° C. , is reacted to form the desired nanoscale solid particles, the nanoscale solid particles thus produced being distributed nanodispersed in the polyester resin.

2. The method according to claim 1, characterized in that the precursor compound (s) are introduced in the initial phase of the resin synthesis.

3. The method according to claim 1 or 2, characterized in that the reaction of the precursor compound (s) is carried out under the action of water added to the reaction mixture or in the presence of existing during the synthesis time of the reaction water.

4. The method according to any one of claims 1 to 3, characterized in that as

Precursor compounds organic or inorganic metal or semimetal compounds are used.

5. The method according to claim 4, characterized in that as precursor compounds copper, silver, titanium, zirconium, aluminum,

Vanadium, tin and / or silicon compounds are used.

6. The method according to claim 4, characterized in that as precursor compounds noble metal compounds, e.g. Gold compounds are used.

7. The method according to any one of claims 4 to 6, characterized in that as

Precursor metal or metal salts of organic acids, in particular (hydroxy) carboxylic acids are used.

8. The method according to claim 7, characterized in that metal or semimetal citrates, oxalates or gluconates are used as precursor compounds.

9. The method according to claim 4 to 6, characterized in that are used as precursor compounds metal or Halbmetallalkoxylate.

10. The method according to claim 9, characterized in that the usable as precursor compounds metal or Halbmetallalkoxylate of the general formula R _n X (OR ') correspond to _mn , wherein

X = Si ₅ Ti (IV) ₅ Zr (IV) ₅ Al ₅ Va (IH) ₅ Va (V) R = non-hydrolyzable substituent, optionally with one or more

Groups, eg, epoxy, hydroxyl, carboxyl provide m = 5 for Va (V); = 4 for Si ₅ Ti (IV), Zr; = 3 for Al, Va (III) n = [0 <n <(m-2)]

R '= alkyl

11. The method according to claim 9 or 10, characterized in that the precursor compounds usable as metal or Halbmetallalkoxylate to limit their hydrolysis one or more complexing agents are added.

12. The method according to claim 11, characterized in that is used as the complexing agent diketones, including their derivatives, such as acetylacetone / are used.

13. The method according to claim 11, characterized in that are used as complexing agent (hydroxy) carboxylic acids.

14. The method according to claim 13, characterized in that the (hydroxy) carboxylic acid is citric acid.