DE2534764B2 - PROCESS FOR THE MANUFACTURING OF A HEAT-CURABLE POWDER-FORM COATING COMPOSITION - Google Patents

Description

CH ₂ = CX

has been used in which R3 is hydrogen or the methyl group, X is the grouping -COOH, -COOR ₄ or -CN and R _{4 is} an alkyl group having 1 to 12 carbon atoms or a cyclohexyl group

4. The method according to claim 2, characterized in that monounsaturated as ethylenically Compound b) at least one compound of the formula

Ο "*

C-CH ₁

has been used where Rs is hydrogen or the methyl group and R _{6 is} hydrogen or an alkyl group having 1 to 4 carbon atoms.

5. The method according to claim 1, characterized in that the solvent at a Pressure in the range of 10 to 40 mm Hg away.

6. The method according to claim 1, characterized in that the pigment dispersion is ^{preheated at atmospheric pressure to about 170 0} C to partially remove the solvent and then further heated to 170 to 220 ° C at a pressure below 70 mm Hg to to remove substantially all of the solvent.

The invention relates to a method of manufacture

a thermosetting powdery coating agent based on a hydroxyl group-containing Mixed polymer.

Conventional processes for the production of powdery coating agents by the melt-kneading process using a heatable roll and an extruder have the disadvantages that they are extremely ineffective as compared with the preparation of solution type coating agents, and that their color matching takes a long time and inaccuracies and technical difficulties includes. Indeed, such problems arise in terms of the constant availability of powdered form Coating agents in large quantities.

An object of the invention consists in a novel production method for a powdery Total coating composition from a coating composition of the solution type. The procedure is to be carried out on a large scale be feasible and enable easy and precise color matching within a short period of time Furthermore, the process according to the invention should be a powdery coating medium with a high pigment concentration provide centering and high coverage. Thereby: coating agents produced according to the invention should be practical

solvent-free, excellent blocking test ability (the property in the form of fine Particles free from cohesion during storage) and coating films with result in a flat surface.

The objects of the invention are achieved by the present method

The invention relates to a method for producing a thermosetting powdery Coating agent based on a copolymer containing hydroxyl groups, characterized in that is that one

A) a pigment is dispersed in a solution of a copolymer in an organic solvent with a boiling point of at least 70 and at most 160 ^° C., the copolymer being composed of

a) a compound of the formula

Rl R ₂

CH ₂ C-COOCH ₂ CH
OH

wherein R, hydrogen or the methyl group and R _{2 is} hydrogen, the methyl or ethyl group and

b) an ethylenically monounsaturated compound has been obtained and where the Copolymer contains 0.75 to 2.0 mol of hydroxyl groups per kilogram, then one

B) to remove the solvent, the dispersion is ^{heated to a temperature of 170 to 220 °} C. at a pressure below 70 mm Hg and then it is heated

C) rcischt the mixture of pigment and copolymer in the molten state at a temperature below 140 ⁰ C with an amino resin.

40

The method of the invention has the following advantages:

(1) Because the pigment and the like additives are dispersed in the interpolymer solution, the powdery coating agents such as ordinary solution type coating agents using a Ball mill or sand mill can be produced, which is suitable for large-scale production. the Color matching, which can be done in the same way as solution-type masses, lasts like only a short period of time in the case of coating agents of the solution type. Thus, the method of the invention switches the serious disadvantage of the conventional melt-kneading method for producing powdery ones Coating compounds from the fact that the color matching measures take a long time and an imprecise one Deliver result.

According to the invention, the removal of the solvent is carried out at a high temperature of 170 to 220 ^° C. under a pressure below 70 mm Hg ho and therefore takes an extremely short period of time. Because of the low viscosity of the system, which easily allows thorough stirring, it is possible to use a cylindrical container for solvent removal which has a small surface area relative to its volume. Effective solvent removal and dispersion of pigment and the like additives leads to a noticeably improved overall efficiency compared to the conventional melt-kneading process.

(2) The method of the invention easily gives a powder coating composition having a high pigment concentration (e.g. 120 parts by weight of pigment per 100 Parts by weight of resin [interpolymer plus amino resin]), while it was practically impossible to obtain such A mass to be produced by the conventional melt-kneading method has recently been increasing Need for powder coating agents capable of forming coating films from 30 to 50 microns thick, the thickness of which corresponds to that made from solution-type coatings To meet this need, the powder coating agent must have a high pigment concentration in terms of hiding power exhibit. In this hi-fi point of view, the invention is very advantageous

(3) The complete removal of the solvent achieved on the basis of the process according to the invention provides coating agents with a long shelf life, namely excellent blocking resistance.

These advantages are ensured by the method according to the invention, in which a pigment is dispersed in a mixed polymer solution which does not contain a curing agent (amino resin), then the dispersion is heated to a high temperature of 170 to 220 ° C. under reduced pressure to remove the solvent and the resulting solid mass is mixed in the molten state at a temperature of less than 140 ⁰ C with a hardening agent.

One of the distinctive features of the invention is to remove the solvent at 170 to 220 ^° C. at a pressure below 70 mm Hg. Usually, a copolymer solution having glycidyl groups or the like functional groups is heated to remove the solvent therefrom. In order to avoid the possible reaction between the functional groups, the solution is heated to a maximum of 150 ° C. ⁰ C is heated under reduced pressure, the system becomes noticeably viscous and cannot be stirred thoroughly in the later stage of removing the solvent and thus requires a longer period of time to remove the solvent. If in Gegensau, the solvent at 170 to 220 ⁰ C under a pressure below 70 mm Hg of the invention is shown removed, the system displays a lower viscosity and permits thorough stirring to remove the solvent in a short period of time. In addition, the determination of the molecular weight by gel permeation chromatography and determination of the hydroxyl value and the acid number has shown that, unexpectedly, the resulting copolymer remains free of any reaction between its functional groups. Further, under the conditions of the invention, the amount of the solvent remaining in the obtained coating composition can be easily reduced to not more than 0.5% by weight.

On the other hand, when the solvent is at a temperature not higher than 150 ° C below the Removed reduced pressure, it is utterly

difficult to get the amount of remaining solvent up to reduce a value not higher than 0.8% by weight. Thus, it creates very little difference noticeable improvements in the blocking resistance of the coating agent in the amount of the remaining solvent and the smoothness of the coating made therefrom.

(4) The method of the invention can be carried out in batches. One of the advantages of paragraph wise working system consists in evaporation and separation of the solvent in one operation can be carried out, and evaporation can be effected efficiently and easily. Another The advantage is that the previously prepared pigment-dispersed mixed polymer solution in the from the interpolymerization process obtained hot interpolymer solution can be introduced. That's why The removal of solvent requires less heat and can be done in a shorter time Period to be ended.

A copolymer of hydroxylalkyl acrylate or is suitable as the binder resin according to the invention methacrylate of the above formula and an ethylenically monounsaturated compound.

The amount of hydroxyl groups, the functional groups of the copolymer, is the same as in common solution-type coating agents. The copolymer must have about 0.75 to 2.0 mol of hydroxyl groups included per kilogram of copolymer. A copolymer is also in the process of the invention usable, which as an intramolecular catalyst up to 0.5 mol of carboxyl groups per kilogram of the Interpolymer contains, as is usually the case with solution-type coating agents such a copolymer containing carboxyl groups is made by using acrylic acid or Methacrylic acid available as an ethylenically monounsaturated compound.

The copolymer preferably has a softening point of at least 65 ° C, so that the coating composition produced therefrom has good storage stability at room temperature

However, the copolymer can have a softening point of less than 65 ° C if the Coating agent can be stored under cooling.

In order to enable the good coating agent to retain good flowability and to produce coatings with a smooth surface, the softening point of the copolymer is advantageously up to 130 ^° C.

Examples of the hydroxyalkyl acrylate or methacrylate the formula

R ₁ R ₂

(H ₂ (COOCH ₂ CH

₅₅

OH

wherein Ri is a hydrogen atom or a methyl radical and R2 is a hydrogen atom, a methyl or ethyl radical is, are

2- hydroxyethyl acrylate,

2-hydroxyethyl methacrylate

2- hydroxy propyl acrylate,

2-hydroxypropyl methacrylate

2-hydroxybutyl acrylate and

2-hydroxybutyl methacrylate

ίκ>

65 The hydroxyalkyl acrylate or methacrylate can be used alone or in admixture with one another.

Examples of ethylenically monounsaturated compounds are a) acrylic compounds of the formula

H ₂ C = CX

wherein R _{3 is} a hydrogen atom or a methyl group and X represents the groupings -COOH, -COOR ₄ or —CN, where R »is an alkyl group having 1 to 12 carbon atoms or a cyclohexyl radical, and b) styrene compounds of the formula

C-CH,

wherein R _{5 is} a hydrogen atom or a methyl group and Rb is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Examples of the acrylic compounds are acrylic acid, methacrylic acid and methyl, ethyl, propyl, i-propyl, η-butyl, i-butyl, tert-butyl, sec-butyl, 2-ethylhexyl, n-octyl -, lauryl, cyclohexyl or the like esters of acrylic acid and methacrylic acid and acrylonitrile and methacrylonitrile. Examples of styrene compounds are styrene, α-methyl styrene, vinyl toluene, tert-butyl styrene, etc. The acrylic compounds can be used alone or in admixture with each other. The copolymer can be produced by various polymerization processes, such as, for example, solution polymerization. Bulk polymerization, emulsion polymerization, suspension polymerization and the like methods. Because of the need to prepare a mixed polymer solution and the ease of controlling the polymerization reaction, the solution polymerization method is preferred in attaining the objects of the invention. Suitable solvents for the solution polymerization are those with a boiling point of 70 to 16O ⁰ C, for example benzene, toluene, xylene, ethyl acetate, butyl acetate, amyl acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether, methyl ethyl ketone, methyl butyl ketone, generally methyl isobutyl ketone, etc. preferably Run reflux. The polymerization is carried out in the presence of a radical polymerization initiator widely used for the polymerization of vinyl compounds such as

Benzoyl peroxide, lauroyl peroxide,
tert-butyl hydroperoxide, tert-butyl peroxybenzoate, acetylcyclohexanesulfonyl peroxide,
Isobutyroyl peroxide,
Di- (2-ethylhexyl) peroxydicarboxylate,
Diisopropyl peroxydicarboxylate,
tert-butyl peroxypivalate, decanoyl peroxide,
Azobisisovaleronitrile, azobisisobutyronitrile etc.

According to the invention, a pigment is used in a solution of the copolymer in the first stage dispersed. When the copolymer through

Solution polymerization is obtained, the interpolymer solution is usable as it is or suitably diluted or concentrated. If it is produced by any other polymerization process, the resulting copolymer is dissolved in a solvent to produce a copolymer solution. Solvents which can be used are likewise those which can be used for solution polymerization. The concentration of the mixed polymer solution, although largely variable, is | _O suitably 40 to 70% by weight.

Usable as the pigments are a wide variety of those used in solution-type coating agents and powdered coating agents are used. Depending on the particular color desired, the pigment in an amount of 3 to 150 parts by weight per 100 parts by weight of the combined copolymer and amino resin can be used. Furthermore, mixed polymer solutions, which are different therein dispersed pigments contain, are mixed together in this operation, creating a color match can be easily carried out, as with general solution-type coating agents. Aside from that Pigments, various additives can optionally also be used, such as leveling agents and antistatic agents Agents and the like It is also possible to add the above viscosity control solvent to the dispersion or to add the mixed polymer solution in a suitable manner to adjust the pigment concentration.

In the following second stage, the dispersion is placed in a container which is equipped with a stirrer, a co-current condenser and an evacuation arrangement and is preferably preheated to about 170 ° C. at atmospheric pressure with stirring in order to remove the solvent. The remaining solvent is then removed at a temperature of 170 to 220 ° C. at a pressure below 70 mm Hg. In this operation, the solvent is evaporated and at the same time separated off. The solvent can thus be separated practically completely from the solid constituent in a single operation. Because the present method can be carried out in batches, evacuation can be carried out efficiently and easily. In this operation it is critical to heat the dispersion to a temperature of 170 to 220 ° C. under reduced pressure. This enables the practically complete separation of the solvent from the solid component. At temperatures below 170 ° C. there is incomplete separation of the solvent and the blocking resistance of the coating agent is reduced, whereas temperatures above 220 ° C. ^lead in the same way to lower blocking resistance due to the decomposition of the copolymer. A temperature range 175-210 ⁰ C is particularly preferred The preferred pressure is between 10bis40 mm Hg.

After sufficient removal of the solvent, the solid component for the third stage is brought into a heatable mixer, such as a hot kneader, an extruder or the like, in which it is evenly mixed with an amino resin in the molten state. A catalyst can be added if necessary. The temperature is higher than the necessary for melting of the solid component, but lower than 140 ⁰ C Mixing at temperatures above 140 ⁰ C is disadvantageous in that the copolymer readily reacts with the amino resin, the preferred temperature is in the range of 100 bii 120 ⁰ C. The mixture is then pulverized and then sieved to obtain a powdery coating agent in the form of fine particles which pass through a sieve with a mesh size of 0.1 mm. Examples of the amino resin are alcohol-modified melamine-formaldehyde condensation products, such as hexamethylolmelamine derivatives.

The hexamethylol melamine derivatives include ζ. Β Hexakismethoxymethylmeiamine and etherified products of hexamethylolmelamine, which substitutes CH3O and RO groups for the hydroxyl group in the dei Methylol group of hexamethylolmelamine have the average total number of CH3O and RO groups is 5.5 to 6.0 per melamine core and the average number of RO groups is 0.5 to 3, C. per melamine core, wherein R is a

R "

R'OCHCH _r group

CH ₂ - CH ₂

CH ₂

CH group

CH ₂ - CH ₂

means in which R 'is an alkyl group having 1 to 4 carbon atoms and R "is a hydrogen atom or is a methyl group.

The ratio of copolymer to amino resin is preferably 96/4 to 80/20, based on the Weight. The known acid catalysts to be used when the copolymer and the amino resin mixed together as above include e.g. B. amine salts of paratoluenesulfonic acid, phosphoric acid, Dichloroacetic acid etc.

The invention is described below with reference to Reference Examples and Examples in which parts are by weight.

Reference example 1

Toluene (800 parts) is brought into a 2-1 four-necked flask equipped with a reflux condenser, a stirrer and a dropping funnel, and is heated to 90 to 100 ⁰ C, while Stickstoffgns is introduced into the flask. To the toluene kept at the same temperature, a mixture of 120 parts of 2-hydroxypropyl methacrylate, 40 parts of butyl acrylate, 624 parts of ethyl methacrylate, 16 parts of acrylic acid and 10 parts of benzoyl peroxide is added dropwise over a period of 2 hours, the mixture being introduced into the dropping funnel beforehand . To the resulting mixture, kept at the same temperature, a solution of one part of benzoyl peroxide in 10 parts of toluene in 3 parts is added dropwise at an interval of 1 hour Maintained at 90 to 100 ^° C. for a further 3 hours and then cooled in order to obtain a mixed polymer solution ( hereinafter referred to as “mixed polymer solution”). The copolymer has a softening point of 86 ⁰ C to

709 514/456

and an acid number of 18.5 and contains 1.04 moles of free Hydroxyl groups per kilogram of copolymer.

Reference example 2 Styrene 248 pieces Methyl methacrylate 240 pieces Butyl methacrylate 206 pieces 2-hydroxyethyl methacrylate 78 pieces Methacrylic acid 8 parts Azobisisobutyronitrile 16 parts

.1 °

The above mixture is copolymerized in 800 parts of toluene at a temperature of 100 to HO ⁰ C. In the same manner as in Reference Example 1, a mixture of 30 parts of toluene and 3 parts of azobisdimethylvaleronitrile, which serves as an additional catalyst, is added in three equal parts to the Reaction mixture added. The other reaction procedures and conditions are similar to those of Reference Example 1 to obtain an interpolymer solution (hereinafter referred to as "interpolymer solution-B"). The copolymer obtained has a softening point of lOrC and an acid number of 7.6 and contains 0.922 mol of free hydroxyl groups per kilogram of copolymer.

Reference example 3

Styrene 305 parts

Ethyl acrylate 200 parts

Ethyl methacrylate 135 parts

2-hydroxyethyl methacrylate 160 parts

terL-butyl peroxybenzoate 3 parts

The above mixture is copolymerized in 800 parts Butyiacetat eir.cr at temperature of 110 to 120 ⁰ C using a mixture of 12 parts of tert.-butyl peroxybenzoate and 30 parts Butyiacetat as an additional catalyst. The other reaction procedures and conditions are exactly the same as those of Reference Example 1 to obtain an interpolymer solution (hereinafter referred to as "interpolymer solution-C").

The resulting copolymer has a softening point of 78 ° C. and an acid number of 0.5 and contains 1.54 mol of free hydroxyl groups per kilogram of copolymer.

Reference example 4

Ethyl methacrylate 592 parts

2-hydroxyethyl methacrylate 80 parts

2-hydroxypropyl methacrylate 120 parts

Acrylic acid 8 parts

Benzoyl peroxide 3 parts

55

The above mixture is in 800 parts of toluene at a Temperature from 110 to 120 ° C using a Mixture of 12 parts of azobisisovaleronitrile and 30 parts of toluene copolymerized as an additional catalyst The other reaction procedures and conditions are exactly the same as those of Reference Example 1, to obtain a mixed polymer solution (hereinafter referred to as "mixed polymer solution-D"). That I The resulting copolymer has a softening point of 91 ° C. and an acid number of 7.8 and contains 81 moles of free hydroxyl groups per kilogram of copolymer

Reference example 5

Ethyl methacrylate

Isobutyl acrylate

2-hydroxyethyl methacrylate

Methacrylic acid

tert-dodecyl mercaptan

Benzoyl peroxide

512 parts

100 parts

170 parts

18 parts

12 parts

3 parts

The above mixture is copolymerized in 800 parts of methyl isobutyl ketone at a temperature of 110 to 120 ⁰ C using a mixture of 16 parts of benzoyl peroxide and 30 parts of methyl isobutyl ketone as an additional catalyst. The other reaction procedures and conditions are exactly the same as those of Reference Example 1 to obtain an interpolymer solution (hereinafter referred to as "interpolymer solution-E"). The resulting copolymer has a softening point of 70 ^° C. and an acid number of 18.2 and contains 1.63 mol of free hydroxyl groups per kilogram of copolymer.

Reference example 6

^St y ^ro1 720 pieces

2-hydroxyethyl methacrylate 78 parts

Acrylic acid 16 parts

tert-butyl peroxybenzoate 3 parts

The above mixture is copolymerized as an additional catalyst in 800 parts of toluene at a temperature of 110 to 120 ⁰ C using a mixture of 12 parts of tert-butyl peroxybenzoate and 30 parts toluene. The other reaction procedures and conditions are exactly the same as those of Reference Example 1 to obtain an interpolymer solution (hereinafter referred to as "interpolymer solution-F").

The copolymer obtained has a softening point of 116.degree. C. and an acid number of 183 and contains 0.922 mol of free hydroxyl groups per kilogram of copolymer.

example 1

A 150 g amount of that prepared in Reference Example 1 Mixed polymer solution-A, 300 g titanium dioxide (rutile type), 75 g of toluene and 6 g of polylauryl methacrylate (leveling agent) are placed in a 1 liter ball mill introduced and dispersed for 15 hours to produce a dispersion to which 150 g of the mixed polymer solution-A (hereinafter referred to as the »first additional mixed polymer solution-A« designated) is added. The mixture is dispersed in the same way for another 30 minutes, to make a pigment dispersion

The pigment dispersion (681 g) and 240 g of the mixed polymer solution-A (hereinafter referred to as "second additional Mir-hpolvmerlösung-A") are in a The 1.5 liter container equipped with a direct current cooler, stirrer and thermometer is brought and will be heated with stirring at atmospheric pressure to to evaporate the solvent. The temperature of the Ingredients increases with the outflow of the solvent and when the temperature reaches 170 ° C the system was kept at a reduced pressure of 30 mm Hg for 15 minutes to remove the solvent to remove. The pigment-dispersed solid resin obtained containsO3 wt .-% residual solvent.

980

To 384 g of the solid resin, 20 g of melamine resin in which one of the methoxy groups des Hexakismethoxymethylmelaniins by a

CH ₂ - CH ₂
CH ₂ Vh -O group

CH ₂ - CH ₂

is replaced (hereinafter referred to as "Aminoharz-A"), and the mixture is through a heatable kneader at Kneaded at 110 ° C for 10 minutes. The mass obtained is

Table 1

pulverized and then sieved to obtain a coating agent in the form of fine particles passed through a sieve a mesh size of 0.1 mm, because: coating agent has a weight ratio of pigment / Resin of 100/100 and a weight ratio mixed polymer / amino resin of 9/1.

Examples 2-6 and Comparative Examples 1 and 2

IO pigment-dispersed solid resins in the same manner as in Example 1 except for the conditions listed in the following Table I were prepared.

Obtained mixed pigment polymer dispersion solution and
greed their crowd
Solid resin

ig) (g)

Pigment and its other additives quantity (leveling mitie! *

(8) Solvent Additional Vacuum u. its amount of mixed polymer bedin solution worked

(g) first second

(g) (g) CC, min.)

Remaining solvent and its amount

(Wt .-%)

Resin-2
Resin-3

Harz 4
Resin-5
Resin-6

Resin-7
Resin-8

B 150
C 300

D 300
E 150
F 300

A 150
A 150

Titanium dioxide (Ru til type) 300 Lamp soot 20

Phthalocyanine blue 40

Benzoin 6

fl. epoxy resin 20

Polylauryl acrylate 6 poly-2-ethyl-

hexyl methacrylate

Titanium dioxide benzoin 6 methyl iso-

(Rutile type) 300 polylauryl butyl ketone

300 methacrylate 6

red iron oxide fl. epoxy resin 25 toluene 100 polylauryl

methacrylate 6

Titanium dioxide polylauryl toluene

(Rtitiltyp) 300 methacrylate 6 titanium dioxide polylauryl toluene

(Rutile type) methacrylate 6

Toluene 50 B 150 B 240 180 ° C

10 min. Toluene 50 C 300 C 60 210 ° C

10 min.

Bulylacetai 80 D 300 D 120 190 ° C

0.20 0.15

0.15

10 min.

E. 150 E. 180 190 ° C 0.15 10 min. F. 100 F. 240 190 ° C 0.20 10 min. A. 150 A. 240 150 ° C 0.90 40 min. A. 150 A. 240 240 ° C 0.20 10 min.

Using the above pigment-dispersed solid resins, in the same manner as in Example 1, except The conditions listed in Table II below, prepared seven types of coating agents

Table II Dispersed
Pigment resin
(G) Amino resin Pigment / resin
(Weight
relationship) Mixed poly
merisa t / amino
resin
(Weight
relationship) Resin-2 384
Resin-3 213
Resin-4 203
Resin-5 408
Resin-6 300
Resin-7 384
Resin-8 384 B 20 *)
(A 10
\ Catalyst
(0.2)
A 10
A40
A 60
A 20
A 20 100/100
5/100
10/100
120/100
25/1 CO
100/100
100/100 90/10
95/5
90/10
80/20
80/20
90/10
90/10 Example 2
Example 3
Example 4
Example 5
Example 6
Comp. Ex. 1
Comp. Ex. 2

Comment:

*) Morpholine salt of paratoluenesulfonic acid.

*) Araino resin, produced by substituting one CH3CH-OCH2-CH2-O group for 1 mole of methoxy group of Hexylasmeüioxymethylinelamin.

Comparative example 3

45

Example 8

A 681 g amount of the pigment dispersion prepared in Example 1, 240 g of mixed polymer solution-A and 30 g of amino resin-A are mixed together and placed in a container with a flat bottom to a depth of about 5 cm. The mixture is dried in a vacuum dryer at 30 ^° C. for 25 hours. The dried mass contains 1.8 % by weight of residual solvent. The solid mass is pulverized and then sieved to obtain powdery coating agent which passes through a sieve with a mesh size of 0.1 mm.

Comparative example 4

The same mixture as used in Comparative Example 3 and dried under reduced pressure at 6O ⁰ C. The mixture gels 5 hours after the initiation of vacuum drying. The gel contains 12.5% by weight residual solvent.

Comparative example 5

In exactly the same manner as in Example 1, 1000 g of the interpolymer solution-A was desolventized to obtain a solid resin containing 0.2% by weight of residual solvent. Is the solid resin (180 g), 200 g titanium dioxide (rutile type), 20 g amino resin A and 4 g of polylauryl are mixed by a heated roll at 100 ⁰ C for 30 minutes together to prepare a dispersion, pulverized, which are then passed to obtain a powdery coating agent which passes through a sieve with a mesh size of 0.1 mm. The composition has a pigment / resin weight ratio of 100/100 and a mixed polymer / amino resin weight ratio of 90/10.

Example 7

This is a large-scale example. A 2000 kg amount of the mixed polymer solution-A, 4000 kg of titanium dioxide (rutile type), 60 kg of polylauryl methacrylate and 750 kg of toluene are placed in a 10-kl ball mill and treated for 15 hours to produce a dispersion, which is then 1000 kg of mixed polymer solution-A is added. The mixture is treated further for 30 minutes for dispersion.A 7810 kg portion of the resulting pigment dispersion and 4200 kg of the mixed polymer solution-A are placed in a cylindrical 15-kl container (1 m diameter and 5 m height), and the solvent is removed from the mixture in exactly the same way as in Example 1. The removal of the solvent takes 2 hours. The mass obtained in a yield of about 90% by weight contains 0.2% by weight of residual solvent. A 6894 kg amount of the prepared pigment-dispersed solid resin and 360 kg of amino resin-A are placed in a heatable kneading machine and mixed together for 10 minutes with heating. The mixture is then pulverized and sieved to prepare about 7200 kg of a deformable coating agent represented by Mn Sieve with a mesh size of 0.1 mm passes and has a pigment / resin weight ratio of 100/100 to a copolymer / amino resin weight ratio of 90/10

Toluene (800 T ¹ UIE) is placed in a flask equipped with einerr reflux condenser, a stirrer and a dropping funnel, 2-liter four-necked flask and heated aul 90 to 100 ⁰ C, while nitrogen gas is introduced into the flask. A mixture of 120 parts of 2-hydroxypropyl methacrylate, 40 parts of butyl acrylate, 624 parts of ethyl methacrylate, 16 parts of acrylic acid and 10 parts of benzoyl peroxide is added dropwise to the toluene, which is kept at the same temperature, over a period of 2 hours, the mixture having previously been placed in the dropping funnel . To the mixture kept at the same temperature, a solution of 1 part of benzolyperoxide in 10 parts of toluene is added dropwise in three parts at an interval of 1 hour. The mixture is kept at 90 to 100 ^° C. for a further 3 hours, to which 5664 parts of a pigment dispersion are added at the same temperature, the 1600 parts of the mixed polymer solution-A prepared in reference example 1, 3200 parts of titanium dioxide (rutile type), 800 parts of toluene and 64 parts Contains parts of polylauryl methacrylate.

The resulting mixture is heated with stirring at atmospheric pressure to distill off the solvent. The temperature of the ingredients increases with the outflow of the solvent, and when the temperature reaches 170 ^° C., the system is kept at a reduced pressure of 30 mm Hg for 15 minutes to remove the solvent. The pigment-dispersed solid resin obtained contains 03 parts by weight of residual solvent.

To 384 g of the solid resin are added 20 g of melamine resin in which one of the methoxy groups of Hexakismethoxymethyimelamine by a

40 H ₂ C

H ₂ H ₂
CC

CC
H ₂ H ₂

CH-O group

is replaced and the mixture is ^{kneaded in a heatable kneader at 110 0} C for 10 minutes. The resulting mass is pulverized and then sieved to obtain a coating agent in the form of fine particles which are passed through a sieve of 0.1 mm mesh. The coating agent has a pigment / resin weight ratio of 100/100 and a mixed polymer / amino resin weight ratio of 90/10.

Comparative example 6

This is a larger-scale example. Exactly the same operations as in Example 7 are carried out except that the Vakuumbehand development is carried out at a temperature of up to 150 ⁰ C. The removal of the solvent takes 6 hours, a pigment-dispersed solid resin being obtained in a yield of about 75% by weight which contains 0β % by weight of residual solvent. Resin of 100/100 and a weight ratio mixed polymer / amino resin of 90/10.

980

Comparative example 7

This is an example! on a larger scale. A 6300 kg amount of solid resin (containing 0.2% by weight of residual solvent) prepared by using the same apparatus as in Example 7 and removing the solvent under the same conditions as in Comparative Example 4, 7000 kg of titanium dioxide ( rutile type), 700 kg amino resin a and 105 kg polylauryl by a heated kneading machine at 100 ⁰ C at a rate of 500 kg / hr. in a Buss kneading device model PR-H, one of the largest z. Melt kneader currently available, treated to make a dispersion. The mass obtained is pulverized and then sieved, about 14,000 kg of a powdery coating agent being obtained, which passes through a sieve with a mesh size of 0.1 mm and a weight ratio of pigment / resin of 100/100 and a weight ratio of copolymer / Anunohar / of 90 / 10 has.

There are significant differences between example 7 and comparative example! b regarding the time required to remove the warning tool and the amount of the remaining solution, what the Indicating superiority of the former

Simple calculations show that the production of 1 ton of coating agent takes about 2.5 hours according to Example 7 takes about 2.2 hours according to Comparative Example 7, which does not appear to be essential Indicating difference in productivity between the two. During the dispersion by the ball mill no work required during the process and includes low electrical power consumption, requires the removal of the solvent and the process of pigment dispersion by a melt kneader a lot of work and high electrical power consumption. Manufacturing takes time for these operations of 1 ton of powder coating agent for about 10 minutes according to Example 7, in sharp contrast to about 120 minutes according to comparative example 7. There are therefore wide differences between the two in the preparation of the powder coating agent, the one being superior to the other in productivity.

Steel plates treated with phosphoric acid, which have a thickness of 0.8 mm, are electrostatically coated in the usual manner with the powdered coating compositions of the examples and comparative examples to gradually varying thicknesses and to a cured film thickness of 80 microns. The coated panels are baked for 30 minutes at 18O ⁰ C to prepare test pieces.

The properties of the powder coating agent and the coating films are determined by the following methods determined with the results given in the following table Ilι:

(1) Blocking resistance:

The powder coating agent is subjected to a load of 30 g / cm ² while it is kept at 40 + 0.5 "C for 120 hours and is then observed.
(2) Film gloss:

IISK-5400 6.7

- (J) Erichsen test:

The coated plate is placed in a chamber of constant temperature and humidity for 1 hour and kept at 20 ^° C. and a humidity of 75%. Then the plate is placed on the

υ- Erichsen tester with the coating according to

set outside. A punch with a radius of 10 mm is in contact with certain distances with the rear surface of the plate at the most uniform speed possible of

ι ·. about 0.1 mm / sec. pushed outwards. Of the

The ejected part of the plate is checked with the naked eye for cracks or peeling immediately after ejecting, in order to determine the maximum distance (mm) of the punch stroke which does not cause any change on the coating.
(4) Breakout of the film thickness:

The Bcschichtutigsfilni is unarmed with Eye observes to thou · maximum BcsiliKhiuni-s

- · ■ determine film thickness c / u that is free of Aiis |> ... t / en;

Table III dian / I IK-IlMT Ui. ία id- Ansp'ali l'-ii your Ni value ti ··. I. hi'si.itidii: ih-t I ilii kt-n ill. Ki (W) (well) (Mlklllll dian /) example 92 • 7 Well 150 1 93 > 7 Well 145 2 97 > 7 Well 135 3 95 > 7 Well 140 4th 90 > 7 Well 150 5 93 > 7 Well 150 b 9} > 7 Well 150 7th 93 > 7 Well 150 S. Compare - Example 92 > 7 bad 85 1 89 > 7 bad 90 2 92 > 7 bad 70 3 17th 2.5 Well 70 5 91 > 7 bad 80 b 15th 2.5 KUt 75 7th

According to the solvent kneading process, compositions with a high pigment concentration do not yield any glossy coating surface, as can be seen in Comparative Examples 5 and 7. Comparative examples 1, 2, 3 and 6 show that when the solvent is at low temperatures and excessively high temperatures is removed, the coating agents obtained have poor blocking resistance.

Claims (3)

Patent claims: 1. A process for the preparation of a thermosetting powdery coating agent based on a Copolymer containing hydroxyl groups, characterized in that one A) a pigment in a solution of a copolymer in an organic one. Dispersed solvent with a boiling point of at least 70 and at most 150 ⁰ C, the copolymer from
a) a compound of the formula R, R, CH ₂ - ^ = C-COOCH ₂ CH
OH wherein Ri is hydrogen or the methyl group and R2 is hydrogen, the methyl or ethyl group and
b) an ethylenically monounsaturated compound has been obtained and the copolymer contains 0.75 to 2.0 mol of hydroxyl groups per kilogram, then one B) to remove the solvent, the dispersion is ^{heated to a temperature of 170 to 220 °} C. at a pressure below 70 mm Hg and then it is heated C) the mixture of pigment and copolymer in the molten state at a Temperature below 140 "C with an amino resin mixes. 2. The method according to claim 1, daduich gekennieichnet, that one uses a copolymer in which as an ethylenically monounsaturated compound b) an acrylic compound of the formula H ₂ C CX wherein R _{3 is} hydrogen or the methyl group and X is the grouping -COOH, -COOR ₄ or -NC, where R _{4 is} an alkyl group having 1 to 2 carbon atoms or a cyclohexyl radical and / or a styrene compound of the formula C CH ₂ where R5 is hydrogen or the methyl group and Rf is hydrogen or an alkyl group with 1 to 4 Carbon atoms has been used. 3. The method according to claim 2, characterized in that alb ethylenically monounsaturated Compound b) at least one compound of the formula