DE2457381C3 - Process for the preparation of a powder paint - Google Patents

Description

The invention relates to a method for the production of powder coating compositions for the production of Schut ™ and decorative surface coatings on a variety of substrates including glass, Metal and other substrates that exceed the hardening temperature of the powder are suitable. In particular, the invention relates to a method for Production of homogeneous, thermosetting powder paints which harden with the formation of coatings, which have excellent outdoor durability, adhesion, impact resistance and color matching.

The inventive method comprises the introduction of a liquid mass, the at least one contains crosslinkable copolymer and an inert solvent, in one for evaporation of the inert Evaporation zone suitable for solvents, transfer of the liquid mass into a separation zone, in which the inert solvent vapor is removed and the non-volatile constituents from the mass in mechanically displaced from it in the molten state. Cooling of the non-volatile components and Pulverization to form a powder. The separation zone is a conical chamber, the other a conical one Has screw or screw, which the melted non-volatile components under Pushes pressure out of the chamber.

Powder coating compositions have been used in recent years for a variety of reasons including those which concern the ecology, health and safety, increasingly desirable. In particular are Powder coating compositions are preferred over liquid paint compositions which use volatile solvents contain, which must be volatilized after use and thus lead to solvents in the Atmosphere and create health and safety hazards and undesirable pollution problems. On the other hand, powder coating compositions are heat curable in a manner such that little, if any, volatile material can adhere to the Environment.

While powder paints have been proposed, those formed from such compositions provide Overlays various problems, most of which are at least partially due to the process that they were made go back. Too before

known methods include ball milling, blending using Z-blades, and extrusion, all of which have certain disadvantages.

Ball milling is the simplest of these three methods. In the manufacture of Powder coatings based on epoxy, for example, all components, e.g. B. granulated epoxy resin, Hardeners or hardeners, pigments and other additives in a ceramic-clad atis-clad Given ball mill. Ceramic grinding media of various types Sizes and shapes are generally used to grind the materials for 10 to 15 hours used to produce a mixture. Although other types of ball grinding are used for manufacturing a similar mixture can be used in a shorter time, this method is very time consuming and not suitable for a continuous process. Such a process also does not provide a good dispersion of pigments and other additives, such as crosslinking agents. Therefore, they harden on this Wisely produced powders with the formation of coatings with exceptionally low gloss and low Opacity. Furthermore, such a method does not allow satisfactory color and shade adjustment.

When mixing using Z-blades, the resin is first mixed in a Z-blade heated to at least its melting point, and when it is melted all other ingredients are with the exception of the hardener added slowly. Generally, the dispersion requires about 6 hours, after which the temperature of the Z-blade mixer is decreased and the hardener is added. Once the hardener is correct is mixed, the melt is cooled, pulverized and classified. Those made by this process Compounds generally produce coatings with inadequate pigment dispersion and gloss requirements for topcoat applications such as automobiles. As in the case of ball milling, it is also difficult to get sufficient color and shade matching with this method. Also must, since that process is a batch process, the mill because of the accumulation of heat-sensitive material should be cleaned thoroughly after each pass.

In the extrusion method, the resin used is mixed with all the other ingredients and put into A heated extruder is introduced where high shear forces are used to mix the viscous melted Components are applied. Although the powders made by this process are generally higher quality than those obtained after processes which include ball milling or mixing stages Application of Z-wings included, the procedure still has several serious ones Disadvantages on. First, cause the high levels necessary to induce mixing Shear forces result in a loss of color matching in the finished powder. Second, depends on such a procedure the thoroughness of the mixing and the speed at which a properly mixed extrudate can be generated depending on the amount of shear force applied to the material, which is another Is a function of the speed at which the extruder screw rotates. To get a quick thorough Mixing of viscous resin and molten

To achieve crosslinking agents, high force requirements arise on the extrusion process, and it is therefore expensive. Third, the process is also expensive because of the relatively high cost of the extrusion equipment. Finally, because of the inherent performance of any given extruder, the process is limited gei. not easy to adapt to changing treatment speeds. Thus, the input in the Extruder be dimensioned in such a process to the capacity of the extruder.

Those described in BE-PS 8 18 969 and 8 18 968 Procedures, many eliminate the difficulties associated with these previous procedures by using them Provide more complete and uniform dispersion of paint additives. The two procedures include the introduction of liquid masses containing at least one crosslinkable copolymer and uniform dispersed pigment contained, in a for evaporation of the solvents contained therein suitable evaporation zone; Forwarding the liquid to a separation zone; Removal of the solvent vapor; Removal of the non-volatile components of the paint in a molten state Reason of gravity; Cool the non-volatile components and pulverize them to form one Powder. The former patent application relates to processes in which either a self-crosslinking Copolymer or a crosslinkable copolymer and a crosslinking agent therefor in the liquid Paint composition are included and directly through evaporation and separation zones before cooling and Pulverization to be treated. Such a method has obvious advantages in all of them Additives including crosslinking agents, if used, uniformly in the molten resin are dispersed. However, such a method has the disadvantage that while the molten material is withdrawn from the separation zone, premature gelation or crosslinking can occur. The procedure the second patent prevents this problem by using liquid compositions, which are crosslinkable copolymers however does not contain crosslinking agents, treated, and then the powder and crosslinking agents are added a temperature above the melting point of the two components are mixed, the resulting molten homogeneous mass is cooled to form a solid and then to form the finished powder is pulverized. While this procedure eliminates premature networking, those are The equipment used and the process are uneconomical because of the number of stages involved.

Thus, it is an object of the invention in a process for the production of powders, in which complete and even dispersion of all paint additives, including where appropriate present crosslinking agent, is carried out in an effective manner and at a minimum of cost, without decomposition of the mass or premature crosslinking occurring.

The above object is achieved according to the invention by a method for producing a powder paint achieved in which:

(A) a liquid mass which is a solution of an inert solvent and a copolymer containing crosslinkable functional groups with a glass transition temperature in the range from 40 to 90 ⁰ C and a numerical average molecular

has a weight of about 1,000 to about 15,000, in an evaporation zone suitable for heating the solution with evaporation of the inert solvent is introduced;

(B) the solution in the evaporation zone to a temperature

(1) above the melting point of the copolymer but below the point at which Decomposition or gelation of the copolymer occurs and

(2) above the temperature at which the inert solvent begins to evaporate,

is heated;

(C) the solution from the evaporation zone is passed into a separation zone and, while the temperature is kept within the separation / .one above the melting point of the copolymer,

(1) the solvent vapor is removed from the separation zone and

(2) remove the non-volatile components while in the molten state removed from the separation zone;

(D) the non-volatile: constituents are cooled to form a solid material and

(Ii) the solid material to form a homogeneous one Powder is pulverized.

The method is characterized in that the non-volatile constituents are mechanically removed from the separation zone driven using a separation zone having a conical chamber, which contains a conical rotating screw and in which the non-volatile material mechanically the rotating screw is driven down and out of the conical chamber.

It is generally useful to include additives such as for example, pigments, flow control agents, antistatic agents, catalysts, plasticizers, and To include crosslinking agents and the like in the liquid mass to be treated. However, it may be desirable the crosslinking agent with the material after volatilization or before the powder is formed mix if there is any risk of premature gelation or crosslinking due to the extreme Conditions of the evaporation and separation zones exist as crosslinking agents are preferably straight-chain aliphatic dicarboxylic acids used. Of course, no crosslinking agent is required, when the copolymer used is self-crosslinking.

Further tasks and associated advantages emerge from the following description in conjunction with the drawings in which

1 is a schematic diagram of an apparatus suitable for carrying out the invention;

F i g. FIG. 2 is an enlarged partial cross-sectional view of the evaporation device of FIG. 1 and

F i g. 3 is an enlarged partial cross-sectional view of the separator of FIG . 1 reproduces

Suitable compositions in the method of the invention

Compositions which can be treated according to the method of the invention are liquids which contain all or almost all of the constituents of the desired powder coating dissolved in an inert solvent. Various known liquid paints including those containing epoxy and polyester copolymers as well as the preferred acrylic copolymers can be used so long as the copolymers have the appropriate glass transition temperatures and molecular weights to form the powders.

An example of a type of liquid paint that does not make a suitable powder paint, when treated in accordance with the invention is that described in US Pat. No. 2,857,354. The paint of Examples 4 and 5 of this patent do not form dry powders when in accordance with the invention be treated while out of the crowds of

ίο Examples 1, 2, 3 and 6 do not melt powders produced when applied to a metal plate to form a smooth film if the plates ^{are baked at 150 to 200 °} C. for 20 minutes. The burned-in coatings

is result in poor adhesion, lack of flexibility and very low gloss.

The copolymers of the liquid compositions suitable for the process have a glass transition temperature (Tg) in the range from 40 to 90 ^° C. and a numerical average molecular weight (M _n ) between about 1000 and about 15,000 have about 8500. A preferred glass transition temperature is between etwa_50 ° C and about 80 ⁰ C, wherein the molecular weight (M _n) is in the range of 3000 to 6500th The most preferred glass transition temperature, however, is 55 to 70 ° C with a molecular weight (M n) in the range of 3,000 to 4,000.
The pigment is preferably dispersed in the copolymer solution, thus facilitating uniform and accurate color and shade matching prior to the formation of the powder. The pigmented liquid can be applied to test panels and compared with Slandard test panels with regard to color and shade matching using methods known to those skilled in the art of color matching liquid paints.

The copolymer solution can also contain a flow regulator. Such flow regulators should have a molecular weight greater than about 100 . Preferably, however, the molecular weight (M _n ) should be above about 1,000, and most preferably between about 6,000 and about 20,000. Further, a crosslinking agent for the copolymer as well as various other additives such as catalysts and antistatic agents can be dispersed or dissolved in the copolymer solution. These materials can optionally be mixed with the uniformly pigmented powder after treatment. However, the quality of the coating obtained from the powders is generally higher if these materials are dispersed prior to treatment. The superior quality is a result of the more thorough and uniform dispersion of the additives.

As indicated above, the preferred liquids for treatment according to the invention contain Acrylic copolymers. These acrylic copolymers can be self-crosslinking or they can be through suitable Crosslinking agents are crosslinked. examples for Copolymers, which in the by the method of Invention treated liquid masses may be included are those according to US Pat. No. 3,730,930 and 37 58 635, BE-PS 7 87 552, US-PS 37 81 379, 37 87 520, 37 58 633. 37 58 634, 37 81 380 and 37 81 379, BE-PS 8 19 619.8 19 624.8 19 625 and 8 19 626. The copolymers of the respective paint compositions specified in these patents contain crosslinkable functional components Groups consisting of epoxy, hydroxyl, amide

and / or carboxyl groups. Furthermore, the respective coating compositions specified in these patents the above-mentioned additives, such as flow regulators, pigments, catalysts, contain antistatic agents, plasticizers and crosslinking agents if necessary, and these can also be incorporated into the treated liquid paints.

As indicated above, the liquid compositions to be treated according to the invention contain all, _zero or almost all of the constituents of the desired final powder paint composition. Thus, the chemistry set forth in the patents cited above applies equally to the liquid compositions of the present invention, the only difference being in the inclusion of the inert solvent in the present invention, which is ultimately removed. For a more complete description of the preferred compositions for treatment in accordance with the present invention, reference is made to the patents identified above.

A particularly suitable liquid paint for the production of powder paints according to the invention consists of a copolymer formed from glycidyl acrylate or glycidyl methacrylate and an ethylenically unsaturated monomer in proportions such that a copolymer with a glass transition temperature in the range from 40 to 90 ⁰ C and a numerical average molecular weight in the range from 2500 to 8500, a crosslinking agent. Pigment and an inert solvent.

Method of handling masses

The liquid mass, which is preferably as stated above at least one crosslinkable functional Group-containing copolymer, a pigment, a flow regulator and a crosslinking agent in Contains an inert solvent dispersed, is in a suitable device for transferring the liquid paint introduced into a powder. As mentioned above, the liquid mass must of course not a networking center! contain. In such cases, where the copolymer is self-crosslinking, of course, a crosslinking agent is not necessary. Even in those In cases where there is a risk of significant crosslinking during treatment, this may be desirable Add crosslinking agent after the volatilization.

The preferred apparatus for performing this function is a modification of a vaporization and separation system disclosed in U.S. Patent No. 3,073,380. While certain portions of this patent publication are discussed in greater detail below, reference is made here to the contents of the patent. It will be understood that this information is included merely as an example of a suitable type of evaporation and separation system for modification in accordance with the teachings of the present disclosure.

Referring to FIG. 1 the liquid mass is introduced into a so-called mixer and moved there while maintaining complete and uniform dispersion of pigment, crosslinking agent and other additives in order to enable a continuous material loading of the rest of the device . From the storage system, the liquid is transferred via line 2 through a positive displacement pump 4 with variable speed into an evaporation zone, which may have a plate evaporator 8, at a speed which is preferably in the range from about 90 to about 230 kg / h, the am most preferred feed rate is about 180 kg / h. When the liquid is pumped from the storage system by the variable speed pump 4, it can be passed through a cleaner or filter, not shown, in order to remove any foreign matter.

While the liquid mass is in the plate evaporator 8, inert solvents and others are volatile Impurities evaporate when the mass between the plates, which form a tortuous passage, passes through. The material travels through the evaporator as a homogeneous mixture of the vapors the volatiles and dispersed particles of molten polymer and additives.

The plate evaporator, the plate arrangement of which is partially shown in cross section in FIG. 2, includes a plurality of plates 10 spaced from one another by gaskets 12. The plates are formed as a compact unit in the frame 14 by pressure devices 16 which press the plates against the seals 12. This arrangement defines a plurality of cavities which alternately form material and heating medium passages. The first plate of a pair forming a material passage has an inlet opening 18 and the second plate has an outlet opening 20. Using the seals 12 , alternating cavities are arranged for the flow of the heating medium, such as superheated steam or the like.

As stated above, alternating passages of the evaporator 8 provide a path for a heating medium, such as superheated water vapor, so that liquid paint passing through the remaining passage can be heated so that the volatile components are evaporated. The heating medium should bring the mass to a temperature (1) above the temperature at which the inert solvent begins to evaporate, (2) above the melting point of the copolymer, but below the point at which decomposition occurs and (3) below the temperature, when gelation occurs, heat. The temperature at which the various compositions can be treated depends on the inert solvents used, the crosslinking agent and the like. In general, the compositions may be treated to about 316 ° C in the present invention above about 6O ⁰ C, particularly at about 60th Preferably, however, the temperature of the evaporation and separation zones is maintained above about 104 ⁰ C, and the temperature is more preferably maintained at about 121-202 ° C.

In operation, the heat evaporator depicted in the drawing is placed in so-called "material" passages wherein one is held between the upstream face of one plate and the downstream face of the following plate Seal the liquid mass and vapor generated from the volatiles from an inlet port at one extreme end of a panel to a vent at the opposite extreme The end of an adjacent downstream plate leads to turbulent flow of the liquid mass

709 684/374

is initiated rapidly by passing through the extremely small cross-sectional area of the passage, when it comes into contact with the relatively large surface area through which the heat passes. Under these conditions the temperature of the material rises rapidly to a point where the steam is produced. Hold abrupt changes in the flow direction and speed of the material the steam at any point in time while the material is within the heating or evaporation zone is in intimate admixture with the molten polymer components. The speed and turbulence allow good heat exchange and cause a high degree of volatilization as well thorough mixing of all non-volatile components. The turbulence also practically prevents completely the deposition of solid materials in a way that would normally result from evaporation of a sensitive material on a hot surface.

The homogeneous mixture of volatiles and molten ingredients migrates in combination from the outlet 22 into a separation zone, which can have a conical separation device 26. The temperature in the more detailed in FIG. 3 reproduced conical ^ separator is above the melting point of the non-volatile components and kept above the evaporation temperature of the solvent.

The separation device 26 is carried by transmission jackets 28 through which a heating medium is transferred Openings 30 for heat transfer fluid is passed, heated. Inside the conical separator 26 a conical screw 32 is arranged, which is attached to the shaft 34, which in turn with no drive means shown is connected. The shaft 34 rotates the conical worm 32 at about 400 to about 700 rpm, preferably at about 500 rpm. The homogeneous mixture from line 24 triu into the conical Separator 26 through material inlet port 36. Due to centrifugal force this will Material moves rapidly outside the screw 32 in contact with the housing wall 38. The material is continuously machined between the screw surface on the outside and the casing wall, continually breaking off any foaming and exposing new surfaces around the Complete steam removal. Non-volatile components of the mixture migrate along the wall forward and are mechanically driven downward against the outlet port 40 by the auger 32. At the same time, the volatiles migrate towards the vapor removal or vacuum port 42.

The area d'.T screw 32 adjacent the inlet port 36 has a large clearance area to handle the large volume of gas and possible foaming. As the material progresses down the screw 32, it takes up less space and gives off fewer volatiles. The end of the screw 32 is a short pump screw 44 in the extruder section housing 46, whereby the non-volatile molten material is extruded before it passes through the opening 40. Even though a vacuum is applied to the separator 26, the molten material is after it the separating device 26 has been conveyed down by the screw 32, under a pressure of about 2.8 to 5 kg / cm ² , preferably 3.9 kg / cm ² , when it migrates into the extrusion zone and passes through the opening 40 . It will be readily apparent that using a separator having such a screw or drive mechanism which mechanically drives the non-volatile material through an orifice, the non-volatile material can be processed more rapidly than if the outlet from the separator was controlled solely by gravity will. Thus, because the molten material does not pool in a substantial puddle waiting for an opportunity to flow to a cooling zone, problems of premature crosslinking or copolymer degradation are substantially alleviated.

Volatile constituents of the mixture introduced into the conical separator 26 are passed through Line 42 removed and condensed in the condenser indicated in FIG. The condensed volatiles migrate through line 48 into a solvent receiver. A reduced pressure between about 10 mm Hg and about 500 mm Hg, preferably between about 20 and about 30 mm Hg, is achieved by means of a Maintain vacuum pump passing through line 48, line 42 and the conical separator 26 Creates a vacuum. Thus, the separation zone is kept under reduced pressure to remove the to support volatile constituents. Since the line 24 to the plate evaporator 8 is in an open state is held, a reduced pressure is also maintained in the plate evaporator 8. This decreased Pressure increases the speed at which the material can be passed through the evaporation zone and also causes more complete evaporation of the volatiles.

After the molten non-volatile material has passed through outlet 40 of conical separator 26, it is fed by variable speed pump 50 through line 52 and is conveyed by spreader rollers 54 onto chilled belt 56 where the molten material is cooled below its melting point and forms a solid sheet material. The material falling from the end of the cooling belt 56 is broken up by the scraper 58 and falls onto the conveyor 60. The conveyor 60 guides the material to the hopper 62, through which it falls into the pulverizer 64. In the pulverizer 64, the material is ground to the proper size for use as a powder paint composition, for example μιη between about 150 and about 37, and the powder is then conveyed by a vacuum to the assembly housing 66. The powder is fed through the sifter 68 for classification according to particle size and is then promoted to weighing station 70.

It should be noted that, as indicated above, it is within the scope of the invention to use other devices which bring about the same stages of evaporation and separation of the various components of the liquid paint. It should also be noted that the following specific examples are illustrative and not limiting.

example 1

A powder paint is prepared in the following way:

Preparation of the resin solution A

100 parts by weight of toluene are placed in a reaction flask equipped with a stirrer, thermometer, water condenser and addition funnel for monomer

and heated to the reflux temperature of about 110 "C. A mixture of 15 parts by weight of glycidyl methacrylate, 45 parts by weight of methyl methacrylate, 40 parts by weight of butyl methacrylate and 3 parts by weight of tert-butyl peroctoate is added dropwise through the monomer addition funnel over a period of about 3 hours added with stirring and while maintaining the reflux temperature. The reflux treatment is then continued for a further 3 hours, after which the monomers practically completely unconverted into polymer are. The resulting resin solution has a Gardner-Holdt bubble viscosity of F to H at about 25 ° C.

Preparation of the pigment grinding base,.

A titanium dioxide pigment grinding base is made, by adding 60 parts by weight of titanium dioxide, 30 parts by weight of resin solution A and 10 parts by weight of toluene sand milled to a Gegman fineness of 7.5 plus.

Preparation of the pigmented solution

A white solution is prepared by mixing 45 parts by weight of the titanium dioxide pigment grinding base with 57 parts by weight of resin solution A, 0.3 parts of polylauryl acrylate (M _n = 10,000) and 3.5 parts by weight of azelaic acid as a crosslinking agent, dissolved in a 20% solution of methanol Stir mixed for 20 min.

This white solution becomes the desired shade of white with traces of the colored pigment grinding base adjusted in color by repeated application on test plates.

Manufacture of the powder _1S

The above solution is placed in a feed tank where it is constantly stirred with a stirrer. The solution is then passed through a feed line with a positive displacement pump of variable speed at a rate of 181 kg / h to a plate heat exchanger ^{heated with superheated steam at 9.8 kg / cm 2} so that a temperature of 171-177 ° C is maintained. The volatile constituents of the solution, which consist of toluene and small amounts of unreacted monomers and impurities, are evaporated in the plate heat exchanger to form a 2-fluid flow from a continuous superheated vapor phase of the volatile components and a discontinuous phase of the non-volatile components of the paint solution. The non-volatile components, including copolymers, flow regulators, pigment and crosslinking agents, are suspended in the vapor phase and are continuously exposed to new heated surfaces, resulting in an increasingly concentrated liquid.

The mixture of volatile and non-volatile components migrates from the plate heat evaporator into a conical separator, which is heated by means of the same superheated steam as above, which flows through jackets around the separator. A reduced pressure of about 30 minutes Hg is maintained in the separator. The separator into which the mixture of volatile and molten non-volatile components is introduced is a conical chamber with a conical screw disposed therein. The conical screw rotates at a speed of 500 rpm and drives the molten non-volatile materials down the conical chamber through an outlet plate at a speed of 59 kg / h. The inlet temperature of the mixture of volatile and non-volatile components is between about 171 "C and about 176 ° C. The wall temperature of the conical separator is maintained at about 180 ⁰ C, and the outlet temperature of the molten non-volatile material is about 130 ⁰ C. Even though a vacuum is applied to the separator, the non-volatile material is conveyed from the separator through the screw at a pressure of about 3.9 kg / cm- '. The volatile constituents of the mixture are condensed in a water-jacketed condenser and collected in a receptacle Polymer is then pumped to solid form onto a chilled belt equipped with a spreader roll for rapid quenching, the solid product is removed from the chilled belt by a doctor blade and placed in a product container from which it is conveyed to a pulverizer for grinding.

Coating of substrates

The pigmented powder paint is sprayed onto electrically primed steel panels using an electrostatic powder spray gun operating at 50kV charging voltage. After Sprühvor gear plate 20 is heated at 175 C ¹ min. The paint provides good outdoor durability, adhesion, impact resistance and excellent color matching. The same paint also gives good adhesion to panels made of glass, brass, zinc, aluminum, copper and bronze.

Example 2

A powder paint is made in the following way:

Preparation of the resin solution A

In one with a stirrer, thermometer. Water cooler and Addition funnel for monomer-equipped reaction flasks add 100 parts by weight of methyl ethyl ketone given, and it is heated to reflux temperature of about 80 ° C. A mixture of 42 parts by weight Methyl methacrylate, 18 parts by weight glycidyl acrylate. 40 parts by weight of butyl methacrylate and 3 parts by weight Tertiary butyl peroctoate is added dropwise through the monomer addition funnel over a period of time of about 3 hours while stirring and refluxing the solvent. The reflux treatment is continued for a further 3 hours, after which the monomers are practically complete dig are converted into the polymer.

Manufacture of the pigment grinding base

A titanium dioxide pigment milling base is prepared by dispersing 60 parts by weight of titanium dioxide, 30 parts by weight of Resin Solution A and 10 parts by weight of methyl ethyl ketone.

A pastel-colored grinding base is prepared by dispersing 10 parts by weight of green chromium oxide with 70 parts of resin solution A and 20 parts of methyl ethyl ketone.

Preparation of pigmented solution

A pastel green solution is made by adding 17.8 Parts by weight of the titanium dioxide diaphragm grinder

mil 69.1 parts by weight of resin solution A. 2.7 parts of grinding base of green chromium oxide and 0.3 parts of polylauryl acrylate (M _n = 10,000) and 3.9 parts by weight of adipic acid as crosslinking agent dissolved in a 2O% solution of methanol with stirring during Mix for 20 hours.

The green solution is applied to test plates and to the desired shade of green with traces Subjected to the color adjustment on the grinding base.

Manufacture of the powder

The above solution is made through a plate evaporator as described in Example 1 at one speed of 181 kg / h. The temperature inside the plate heat evaporator is maintained at about 121 ° C. The mixture of steam and non-volatiles is then placed in a conical separator which is maintained at a reduced pressure of b0 mm Hg. The temperature of the separator is maintained at about 121 ° C and the screw speed is set at 600 rpm. The molten non-volatile material is expelled from the separator, cooled and as in FIG Example 1 powdered.

Coating of substrates

The pigmented powder paint is applied onto electrically primed steel plates using an electrostatic powder spray gun operating at 50 kV. After the spraying process, the Plane heated to 170 ° C for 20 min. The painting delivers good Adhesion, good impact resistance and excellent larbanpas & ung. The same mass of paint also makes good ones Adhesion to glass plates. Brass, zinc, aluminum, copper and bronze.

Example 3

A powder paint is prepared in the following way:

A monomer mixture of the following composition is prepared: glycidyl methacrylate 15% by weight. Butyl acrylate 20% by weight and methyl methacrylate b5% by weight. 4% by weight of a catalyst 2,2'-azobis (2-methylpropionitrile) (AIBN) are dissolved in the monomer mixture. The mixture is slowly added to refluxed toluene (100 parts) which is stirred vigorously under a nitrogen atmosphere. A cooler is provided at the top of the toluene tank to condense the toluene vapors and return them to the tank. The monomer mixture is added through a control valve and the rate of addition is controlled to maintain a reflux temperature with only a small amount of heat supplied from the external heater. After the addition of the monomer? With the mixture, the reflux treatment is maintained by external heat for a further 3 hours. The polymer has a Ci transition temperature of 65 ⁰ C and a molecular weight (M _n ) of 3000.

Preparation of the grinding base

A titanium dioxide pigment grinding base is made, by sand-grinding 60 parts of titanium dioxide, 30 parts of the above resin solution and 10 parts of toluene.

A blue grind base is made by taking 10 hs Grind parts of blue phthalocyanine pigment with 70 parts of the resin solution and 20 parts of toluene will.

Manufacture of pigmented solution

A pastel blue solution is prepared by mixing 17.8 parts by weight of titanium dioxide pigment grinding base with 69.1 parts by weight of the resin solution. 2.7 parts by weight of the blue grinding base and 0.038 parts by weight of triethylenediamine, 0.109 parts by weight of tetraethylammonium chloride, 0.76 parts by weight of polylauryl methacrylate (M _n = 6000) and 3.54 parts by weight of suberic acid are mixed as a crosslinking agent.

Manufacture of the powder

The above solution is passed through a plate evaporator and separator as in Example 1. After the molten non-volatile material comes out of the conical separator through the rotating conical screw has been driven, it is pumped to a cooled belt, to the solid state chilled and then pulverized.

Coating of substrates

The above powder mass is electrostatically sprayed onto various substrates as in Example 1 and cured ^{by heating at 150 ° C. for 15 minutes.} The coating obtained has good adhesion to steel, glass, brass, zinc and aluminum. in the. Copper and bronze. The coatings also give good impact resistance and excellent color matching.

Example 4

A powder paint is prepared as follows: A monomer mixture of the following composition is produced:

Glycidyl methacrylate 15% by weight, methyl methacrylate 45% by weight and butyl methacrylate 40% by weight. 3% by weight of the AIBN catalyst are dissolved in the monomer mixture, which is then slowly added to the refluxing toluene and in the manner indicated in Example 2 to form a copolymer with a glass transition temperature of 53 ° C. and an average molecular weight (M _n ) is treated by 4000.

A titanium dioxide pigment grinding base is made, adding 60 parts by weight of titanium dioxide, 30 parts by weight of the above resin solution and 10 parts by weight Toluene can be sand-milled.

A white solution is prepared by mixing 45 parts by weight of the titanium dioxide pigment milling base with 57 parts by weight of the above resin solution, 0.07 parts by weight of tetrabutylammonium bromide, 0.175 parts by weight of polylauryl acrylate (M _n = 10,000), 0.74 parts of lauric acid and 3.17 parts of azelaic acid. This white solution is applied to test plates and subjected to color matching to the desired shade of white with traces of the colored pigment grinding base.

This paint solution is then treated through the plate heat exchanger as in Example 1, with the exception that the temperature in the evaporation zone is kept at 232 ° C. The coming out of the evaporation zone mixture of volatile and non-volatile components is introduced into the conical separator, whose walls are kept at 232 ⁰ C. A pressure of approximately 120 mm Hg is maintained in the separation chamber. The speed of the conical screw is set at 700 rpm and the molten non-volatile material is discharged through the discharge plate under a pressure of about 4?

kg / cm ² driven.

After exiting the separator, the molten paint is discharged from the separator guided, chilled and pulverized to form a uniformly pigmented powder

The powder paint containing crosslinking agents is electrostatically applied to various substrates applied which are then heated to 175 ° C for 20 minutes. The coating compound provides good adhesion. Impact resistance and color matching. ι ο

Example 5

A powder paint is prepared in the following way:

The same copolymer as prepared in Example 4 is used in the paint of this example. A titanium dioxide pigment milling base is prepared by adding 60 parts of titanium dioxide to 30 parts of the Resin solution and 10 parts of toluene are sand-milled. A yellow base is made by 10 Parts of ferrite yellow pigment are mixed with 70 parts of resin solution and 20 parts of toluene.

A pastel-colored yellow solution is prepared by mixing 17.8 parts by weight of titanium dioxide pigment grinding base with 69.1 parts of the resin solution, 2.7 parts of the yellow grinding base, 0.076 parts of tetrabutylammonium bromide, 0.190 parts of polylauryl acrylate (M _n = 10,000) and 4.58 parts of bisphenol A. are mixed as a crosslinking agent. This solution is applied to various test plates and adapted in terms of color and shade to standard plates.

The color matched solution then becomes a powdered powder according to those given in Example 1 Treatments processed, with the exception that the conical screw in the separator is set at 350 rpm and the pressure in the separator is maintained at 75 mm Hg. The Powder obtained is classified according to particle size and placed on an electrically primed steel plate sprayed using an electrostatic powder spray gun that works at 50kV charging voltage After the spraying process, the plate is heated at 175 ° C. for 20 minutes. The resulting coating on the plate has good adhesion, impact resistance and color matching as well as good resistance to toluene, Gasoline, butanone or methanol.

Example 6

A powder paint is prepared as follows: A monomer mixture of the following composition is produced: glycidyl methacrylate 15% by weight, Methyl methacrylate 50% by weight and styrene 35% by weight. The monomers are according to the method in Example 5 specified process implemented using 3 wt .-% of the catalyst AIBN. The The resulting copolymers have a molecular weight of 4,500 and a glass transition temperature of 90.degree

A titanium dioxide pigment grinding base is made, by sand-milling 60 parts of titanium dioxide, 30 parts of the above resin solution and 10 parts of toluene. A yellow grind base is made by adding 10 parts ferrite yellow with. 30 parts of the resin solution and 20 Parts of toluene are sand-milled.

A pastel colored yellow solution is made by adding 17.8 parts of the titanium dioxide pigment base with 69.1 parts of the resin solution, 2.7 parts of the yellow grinding base, 0.38 parts of tetramethylammonium chloride, 0.76 parts of poly (2-ethylhexyl acrylate) and 14.9 parts by weight of a crosslinking agent with a terminal Carboxyl group are mixed. The crosslinking agent is prepared as follows: 500 g of one Polycondensation product of epichlorohydrin and bisphenol A of the formula

-CH-CH ₂ -

CH,

1 CH

G-CH ₂ -C-CH ₂ OH -O

CH,

CH,

-CH ₂

(Epoxy equivalent 500) is placed in a 500 ml stainless steel beaker with a heating mantle. The epoxy resin is heated to 110 ⁰ C. As the epoxy resin is stirred, 194 grams of azelaic acid are added. A homogeneous mixture is obtained after a reaction time of 30 minutes. The only half-converted resin mixture is poured into an aluminum pan and cooled. The solid mixture is pulverized using a mixer on a sieve passage through a sieve with openings of 150μΐη. The liquid mass including copolymers, catalyst, pigment flow control agent and crosslinking agent is sprayed onto various test panels and subjected to color matching with additional pigment. The paint is then processed into powder form by evaporation and separation devices as described in Example 1.

The powder paint composition prepared as mentioned above is electrostatically applied to various substrates and heated to a temperature of 170 ⁰ C for a period of 30 min. The coatings provide good adhesion, impact resistance and color matching.

Example 7

A powder paint is prepared as follows: The monomers, glycidyl methacrylate 15% by weight, Methyl methacrylate 45% by weight and butyl methacrylate 40% by weight are mixed with one another. 3% by weight of the Catalyst AIBN are dissolved in the monomer mixture. The mixture slowly refluxes located sec-butyl alcohol (100 parts), which is strong is stirred under a nitrogen atmosphere is added. A cooler is at the top of the alcohol vessel added to condense the alcohol vapors and return them to the vessel. The monomer mixture is added through a control valve, and the rate of addition is controlled so that a Maintain reflux temperature with only a small amount of heat supplied from the external heater

will. After the addition of the monomer is complete, reflux is maintained by an external heat source for a further 3 hours. The copolymer formed by such a solution polymerization method has a glass transition temperature of 53 ° C and a molecular weight (M _n ) of 40Ö0.

A titanium dioxide pigment milling base is prepared by sand-milling 60 parts by weight of titanium dioxide, 30 parts of the above resin solution, and 10 parts by weight of sec-butyl alcohol. A pigmented solution is prepared by adding 45 parts by weight of the titanium dioxide pigment grinding base with 57 parts by weight of the resin solution, 0.076 parts of tetrabutylammonium bromide and 0.175 parts of polylauryl acrylate (M _n = 10,000) and 14.9 parts of a phenolic crosslinking agent with a terminal hydroxyl group, as in US Pat 87 520 described, mixed. This solution is treated according to the procedure given in Example 1 except that the temperature within the evaporation and separation zones is maintained at 82 ° C, the vacuum applied to the separation device is maintained at 25 mm Hg and the speed of the conical screw is set at 700 rpm.

The powder paint prepared as above is applied to various substrates and during 20 min heated to a temperature of 175 ° C. The coatings give good adhesion, impact resistance and Color matching.

Example 8

A powder paint is prepared as follows: The monomers, 2-hydroxyethyl methacrylate 10 wt .-%, methacrylic acid 6.7 wt .-%, methyl methacrylate 43.3 wt .-%, butyl methacrylate 40 wt .-%, are formed to form a Mixture mixed, and 4 g of tert-butyl peroxypival as initiator are added. 100 parts by weight of benzene are placed in a 1 liter flask equipped with a dropping funnel, condenser, stirrer, thermometer and nitrogen inlet. The monomer mixture is placed in the dropping tube. The flask is heated to 80 ⁰ C under reflux of the solvent. While maintaining the reaction temperature at 80 "C, the monomer mixture is added dropwise over a period of 2 hours. When the addition is complete, the reaction is continued for a further 2 hours. The contents of the flask are cooled to room temperature.

A titanium dioxide pigment milling base is prepared by adding 60 parts of titanium dioxide, 30 parts of the above Resin solution and 10 parts of benzene are mixed. One Green mill base is made by mixing 10 parts of green phthalocyanine pigment with 70 parts of the Resin solution and 20 parts of benzene are mixed.

A pastel green solution is prepared by mixing 17.8 parts by weight of the titanium dioxide pigment grinding base with 69.1 parts of the resin solution, 2.7 parts of the green. Mill base, 7.7 parts of poly (2-ethylhexyl acrylate) (M _n = 9000) and 0.38 parts of phosphoric acid are mixed. This paint solution is treated according to the procedure given in Example 1 with the exception that the heat in the plate heat exchanger and separator is maintained at 93 ° C, the pressure in the separator is maintained at 15 mm Hg and the speed of the conical screw is 575 IJpM is discontinued.

The pulverized powder obtained by this method is applied to various substrates and by heating to 175 ° C for a period of Hardened for 20 minutes. The upper layers obtained show good results Adhesion, impact resistance and color matching.

Example 9

A powder paint is made as follows: The following mixture of monomers is made: Glycidyl methacrylate 5% by weight, methyl methacrylate 55% by weight and butyl methacrylate 40% by weight. 3 Weight percent of the AIBN catalyst is mixed with the monomers and the entire mixture becomes dissolved in 100 parts of toluene. The response will be after The procedure given in Example 5 is carried out, and the resulting copolymer has a glass transition temperature of 58 ° C and a molecular weight of 4000.

A titanium dioxide pigment grinding base is made, by mixing 60 parts of the resin solution and 10 parts of toluene. A red base will be used prepared by mixing 10 parts of quinine red pigment with 70 parts of the resin solution and 20 parts of toluene will.

A red solution is prepared by mixing 17.8 parts by weight of titanium dioxide pigment grinding base with 69.1 parts of the resin solution, 2.7 parts of the red grinding base, 0.76 parts of tetrabutylammonium bromide and 0.190 parts of polylauryl acrylate (M _n = 10,000) and 3.3 parts of polyazelaic anhydride be mixed. This paint solution is sprayed onto test panels and matched to standard panels in terms of color and shade. After this adjustment, the solution is processed into powder form using the procedure given in Example 1.

After the solid material is pulverized into powder form, it becomes electrostatic on various substrates upset. The coatings give good adhesion, good impact resistance and color and shade matching.

Example 10

A Pitlveranstrichmas.se is made as follows: The following monomers are mixed with one another: 2-hydroxyethyl methacrylate 15 parts, ethyl acrylate 25 parts, methyl methacrylate 60 parts. 4 parts of AIBN are added to this mixture. A 1-1 four-necked flask containing 50 mm of toluene and 50 mm of methyl ethyl ketone is brought to reflux temperature of 85 "C. The monomer mixture is added dropwise over a period of 1/2 hour the reaction mixture, which is kept at 85 ° C, is added. When the addition of monomers is complete 0.5 g of AIBN is added and the reflux treatment is ceased another 1/2 hour to complete the polymerization continued.

A titanium dioxide pigment grinding base is prepared, by mixing 60 parts of titanium dioxide, 30 parts of the above resin solution and 10 parts of toluene.

A white solution is prepared by mixing 45 parts by weight of the titanium dioxide mill base, 57 parts of the above resin solution, 0.28 part of zinc chloride, 0.245 part of polylauryl acrylate (M _n = 5000). This pigmented solution is mixed thoroughly and applied to test plates for color matching. The pigmented solution is then processed into powder according to the procedure given in Example I. The powder is then applied to various substrates by electrostatic spraying.

Example! ti

A powder paint is prepared as follows: There is a monomer mixture of the following composition formed: glycidyl methacrylate 18% by weight, ethyl acrylate 20% by weight, methyl methacrylate 40 Wt% and vinyl chloride 22 wt%. The monomer mixture is according to that given in Example 3 Process using 2 wt .-% of the catalyst AIBN as initiator polymerized.

A titanium dioxide pigment milling base is prepared as in the previous examples but with the above resin solution. A pigmented liquid mass is made by mixing 45 parts of the grinding base with 57 parts of the above resin solution, 0.35 parts of trimethylbenzylammonium chloride, 0.7 parts of poly (2-ethylhexyl acrylate) (M _n = 11,000) and 0.7 parts of Ν, Ν-Dimethylaniline produced. This liquid paint is sprayed onto test panels and adjusted in terms of color and shade by adding small amounts of colored Pign.ent.

This liquid mass is then comminuted into powder form according to the measures given in Example 1. The powder obtained is applied to various substrates and heated at 170 ° C. for 15 minutes.

Example 12

A powder paint is prepared as follows. The following monomer mixture is prepared: methacrylic acid 5% by weight, methyl methacrylate 50 Wt% and butyl melacrylic x 45 wt%. This monomer mixture is after the example in! J specified process polymerized with the addition of 3% AIBN as a catalyst.

Titanium dioxide and blue pigment grind bases are prepared as in the previous examples but using the above resin solution. A pigmented liquid mass is prepared by 17.8 parts of the tilane dioxide grinding base, 69.1 parts of the resin solution, 2.7 parts of the blue grinding base, 0.076 parts of tetrabutylammonium bromide, 0.190 parts of polylaurylacrylai (M _n = 10,000) and 9.9 parts of a Polycondensation products. from epichlorohydrin! Bisphenol A of the formula

H ₁ C CH-CH,

() <> -C- <0-CTI ₁ -C-CH,

V. s j V / ι

CH, OH

CH,

! χ

c \; ο en, (Ii (H,

CH, O

(Epoxy equivalent about 500) (see pages 4 to 66, Handbook of Epoxy Resins). The copolymer obtained in this way has a 7 g value of 53 ° C. and a molecular weight (M _n ) of 4,000. This liquid mass is sprayed onto hot plates and adjusted in terms of color. The liquid is then according to the measures given in Example I with the exception that the temperature in the evaporation and separation zones is kept at 104 ° C, the pressure in the separation zone is kept at 50 mm Hg and the speed of the conical screw at 425 RPM is set, processed into a powder. The powder coating compound obtained for 4 seconds is applied to various substrates and cured by heating to 175 "C for 20 minutes.

Be is picl 13

A powder paint is prepared as follows: The monomers: maleic anhydride 4 parts, styrene 4 parts, glycidyl methacrylate 6 parts, methyl methacrylate 46 parts and butyl methacrylate 40 parts are mixed with 3 parts of tert-butyl peroxypivalal as initiator. 100 parts of benzene are placed in a 1-1 flask fitted with a dropping funnel, condenser. Stirrer, thermometer and nitrogen inlet is provided. The monomer mixture is placed in the dropping funnel and the flask is refluxed to 80 ° C. While the reaction temperature is maintained at 8O ⁰ C, the monomer is added dropwise over a period of 2 hours. After the addition has ended, the reaction is continued for a further 2 hours. The contents of the flask are then cooled to room temperature.

A pigmented solution is prepared from this solution by combining 45 parts of a titanium dioxide grinding base formed from the resin, 57 parts of the resin solution and 0.105 parts of poly (2-ethylhexyl acrylic) (M _n = 9000). This liquid is then made into powder according to the procedure given in Example 1 with the exception that the temperature in the evaporation and separation zones is maintained at 150 ° C. and the speed of the conical screw is set at 350 rpm. The powder formed is applied to various substrates and hardened by heating to 175 "C for 20 minutes.

IÜLTZU Λ sheet /

Claims (8)

Patent claims: 1. Process for the production of a powder paint, at the S (A) a liquid mass which has a solution of an inert solvent and a copolymer containing crosslinkable functional groups with a glass transition temperature in the range from 40 to 90 ⁰ C and a numerical ι ο average molecular weight of about 1000 to about 15,000, in a for For heating the solution with evaporation of the inert solvent, a suitable evaporation zone is introduced, (B) the solution in the evaporation zone to a temperature (1) above the melting point of the copolymer but below the point at decomposition or gelation occurs, (2) above the temperature at which the inert solvent begins to evaporate, is heated, (C) the solution from the evaporation zone is passed into a separation zone and, while the Maintained temperature within the separation zone above the melting point of the copolymer will, (1) the solvent vapor is removed from the separation zone and (2) the non-volatile components while in the molten state, be removed from the separation zone, (D) the non-volatile components are cooled to form a solid material; and (E) the solid material is pulverized to form a homogeneous powder, characterized in that the non-volatile constituents are mechanically removed from the separation zone are driven using a separation zone, which is a conical chamber which contains a conical rotating screw and in which the non-volatile material mechanically the rotating screw is driven down and out of the conical chamber. 2. The method according to claim 1, characterized in that the rotating screw with a Rotates speed between about 300 and about 700 RPM. 3. The method according to claim 1 or 2, characterized in that the rotating screw drives the molten non-volatile material from the separation zone under a pressure of about 2.8 to about 5 kg / cm ^2. 4. The method according to claim 1 to 3, characterized in that the molten non-volatile Material from the separation zone through an orifice plate fitted as a closure in the conical chamber is driven. fio 5. The method according to claim 1 to 4, characterized in that the temperature in the evaporation and separation zones are maintained between about 121 and about 30 ° C. 6. The method according to claim 1 to 5, characterized in that a in the evaporation zone particularly, between about 10 and about 500 mm Hg, reduced pressure is maintained. 7. The method according to claim 1 to 6, characterized in that a liquid mass is used which additionally contains a crosslinking agent and the evaporation and separation zones reduced pressure, with the formation of the solid material by deposition a cooled surface takes place 8. The method according to claim 1 to 7, characterized in that the evaporation zone one Plate heat exchanger has a tortuous path of relatively narrow cross-section along the length of FIG a direction transverse to the flow of the solution through which the solution as it flows Induction of volatilization of the inert solvent is heated, passes through and through which the solution continued after volatilization of the inert solvent as a mixture of inert Solvent and non-volatile components.