WO2002094947A1

WO2002094947A1 - Spherical lacquer additives, the production and utilization thereof

Info

Publication number: WO2002094947A1
Application number: PCT/EP2002/005202
Authority: WO
Inventors: Gerhard Wollmann; Harald Frommelius; Wolfgang Gress
Original assignee: Cognis Deutschland Gmbh & Co. Kg
Priority date: 2001-05-22
Filing date: 2002-05-11
Publication date: 2002-11-28
Also published as: DE10124916A1

Abstract

The invention relates to lacquer additives converted into droplets having a narrow particle size distribution, which are obtained by liquefying a solid preparation containing one or more dispersing agents and one or more consistency agents, droplets are produced by vibration from said molten material with the aid of a nozzle or a casting plate and the droplets are then hardened with the aid of a cooling agent.

Description

"Spherical paint additives, their manufacture and use"

Field of the Invention

The invention relates to spherical paint additives based on polyalkyl acrylates and waxy consistency agents, their preparation and their use for the production of powder coatings.

State of the art

Flow additives and mixtures with carriers are used as additives in the production of powder coatings.

Product groups of powder coatings are e.g. Clear varnishes or pigmented varnishes that are used to paint e.g. Refrigerators, radiators, office furniture, bicycles or auto parts are used. The powder coatings are based, for. B. on

• epoxy resins, hardened with amide hardeners;

• Combinations of carboxyl-containing polyesters with epoxy resins;

• Combinations of polyesters or polyacrylates with blocked isocyanates or alternatives.

The components are usually premixed and then extruded at about 90-130 ° C. All components, i.e. resins, pigments and additives, must be solid or powder, flake or granulated in order to achieve a homogeneous premix. Since the leveling agents used are normally liquid, they first have to be converted into a solid form by means of a carrier. Silica is mainly used here. After extrusion, the lacquers are ground to grain sizes of> 100 μm. Leveling aids and related aids are typically used in the processing of powder coatings in order to specifically influence the rheology of the coating melts and to maintain a uniform surface structure. Effects of flow aids are:

• Improvement of raw material wetting during the extrusion process.

• Reduction of surface tension during the melting process.

• Reduction of the melt viscosity during the hardening reaction.

• Improvement of the substrate wetting on the different substrates.

The following connection classes are often used as flow aids:

• Polyalkyl acrylates with average molecular weights from 3000 to 100,000

• Possible alkyl groups are, for example: methyl, ethyl, propyl, butyl, ethyl-hexyl.

Precipitated or pyrogenic silicas with a specific surface area of 50-450 g / m ² are typically used as carriers.

EP-B-737 509 and parallel US-A-5 766 521 describe a process for the preparation of crystallized beads. In this process, a product is melted, the melt is divided into droplets, the droplets are cooled at a temperature which is below the glass transition temperature of the product, so that the droplets harden through glazing. The beads which are vitrified in this way are kept at a temperature below the glass transition temperature and brought together with nuclei, the beads are crystallized by raising the temperature above the glass transition temperature and the beads are then trapped. According to page 3, section [0017] of the EP-A mentioned, the products thus obtained are particularly suitable for the field of pharmacy and agrochemistry. Critical parameters in this method are two factors in particular: It is worked with a supercooled melt; crystallization nuclei are used.

Description of the invention

Leveling agents that are solid at room temperature are usually packaged by spraying the leveling agents onto carriers in discontinuous mixers. This leads in part to an inhomogeneous loading of the active ingredient and to undesired agglomeration with a broad particle size distribution. Furthermore, inorganic carriers often lead to cloudiness in clear lacquers and to undesirable rheology, which results in a less than optimal course.

There is therefore great interest among manufacturers of paint additives in solids based on polyalkyl acrylates with a narrow grain size range. At the same time, there is a desire for products which are no longer tacky on the surface during processing and which dissolve quickly and completely during the extrusion process.

The object of the present invention was to provide new paint additives as leveling agents based on polyalkyl acrylates, which contain a consistency agent in solid form instead of a high proportion of solid support. The paint additives should be provided in the form of small particles if possible, which have a narrow particle size distribution and are characterized by good processability when used as leveling agents. The invention relates to dripped paint additives with a narrow particle size distribution, which can be obtained by liquefying a preparation which is solid at room temperature and which contains one or more flow control agents and one or more consistency agents, dripping the melt by means of a nozzle or pouring plate by vibration and solidifies the drops using a coolant.

As stated, the drops are solidified using a coolant. This can be done by leading a coolant to the drops, which solidifies the drops. However, it may also be desirable to effect the solidification by dropping the drops in a coolant which solidifies the drops. The solidification can also be brought about by bringing the drops into contact with a liquid, vaporizable medium such as nitrogen or carbon dioxide.

Surprisingly, it has been found that mixtures of leveling agents and consistency agents solidify in the form of solid particles and therefore no inert carriers are necessary.

Another advantage of the invention is that the surface of the drops are no longer sticky after solidification and the particles can be filled and stored as free-flowing pearls. In a preferred embodiment, the dripped paint additives have a content of 10-30% by weight of leveling agents and 70-90% by weight of consistency agent.

Surprisingly, it has also been found that, in the case of compositions which contain at least 30% leveling agents and consistency enhancers, the surface of the drops is no longer sticky after solidification if they are coated with a a small proportion of one or more carrier materials are coated (coated). The particles obtained in this way could be filled and stored as free-flowing pearls.

In one embodiment, the proportion of leveling agents in the compositions is 40-60%, the solidified drops, which are still sticky on the surface, being coated with 1-5% of a carrier material.

Possible coating materials are, for example: consistency enhancers in powder form or inert precipitated silicas such as Sipernat (commercial product from Degussa).

The dropletization by means of vibration to be carried out in the context of the present invention is already known for the processing of resins and low-viscosity polyesters. Corresponding components are sold, for example, by Rieter-Automatik under the name "Droppo Line" for use in textile technology, and by Gouda under the name "Jet-Priller".

The throughput of the dropletizing nozzles can preferably be in the range from 0.3 to 6 kg / h / bore, the diameter of the bores is between 0.15 and 1.2 mm. Drops of granules are obtained which have a diameter of 1.6 to 2.7 times the diameter of the bores.

The vibration of the vibration can be generated via an excited membrane, a vibrating plunger, a vibrating plate or sono excitation.

You can work with only a slight overpressure (typically: 100 to 4000 mbar). The temperature at which the feed materials are conveyed into the dropletization tower is limited by the solidification range and is usually in the range from 40 to 160 ° C. Feed temperatures that are 15 to 25 ° C above the solidification point of the feed materials have proven to be particularly effective. A temperature of the melt is preferably set such that the viscosity is less than 100 mPas.

As with the "Jet-Priller" process from Gouda or the Cryogen Rapid Pelletizer from Messer-Griessheim, cooling can in principle be carried out with cold liquid, but for practical reasons cooling in the dropletization tower is carried out according to the process of Rieter with cold air in counterflow is recommended, as is sufficiently described in the prior art. In the Rieter process, the drops in the tower fall vertically with little turbulence. The probability that several drops meet and bake together to form a so-called "raspberry granulate" is low.

The drops are approximately spherical and then, depending on the openings in the perforated plate and the frequency, have average diameters in the range from 1.6 to 2.7 times the diameter of the bores.

For formulations that produce a non-sticky surface, the dust content, ie particles with particle sizes smaller than 0.3 mm, is practically zero. A recycle gas mode of operation is possible without dust, which leads to a reduction in the dehumidification effort for supplied fresh air. Instead of air, inert gas can of course also be used due to the recycle gas procedure. For products with a high level of leveling agents, the solidified particles are still sticky on the surface. Surprisingly, the stickiness could be reduced or completely eliminated by coating. The proportion of coating material is 1-10% low compared to the loading process according to the prior art.

Possible coating processes include:

• Coating in the downstream fluid bed

• Introducing dusty coating material into the cooling gas flow

• Dripping the solidified particles onto a slide bed with coating material and subsequent sieving.

In a preferred embodiment, the solidified drops are coated by an inert consistency generator. In one embodiment, the inert consistency agents are selected from the group consisting of silica, silicon dioxide, zeolites and water glass.

Particularly suitable flow control agents are polyalkyl acrylates with an average molecular weight in the range from 3,000 to 100,000 kg / kmol. The preferred alkyl group in the polyalkyl acrylates is: methyl, ethyl, propyl, butyl, ethylhexyl.

In particular, waxes and / or fatty acids serve as consistency agents to be used according to the invention. Preferred consistency generators are those whose fixed points are in the range from 40 to 120 ° C. and preferably from 50 to 100 ° C.

The waxes are - as is known to the person skilled in the art - esters of a polyol with one or more fatty acids. Possible polyol components of the waxes are, for example: glycerol, ethylene glycol, fatty alcohol; Pentaerythritol, trimethylolpropane. As a fatty acid Building blocks of the waxes come into question, inter alia, palmitic acid, stearic acid, hydroxystearic acid.

Fatty acids can be used as such or in a mixture with one another. They can be saturated and / or unsaturated; this includes hardened and unhardened compounds.

Examples of suitable consistency generators are:

Glycerin esters: glycerol monostearate, palmitin / stearic acid mono- / di- / tri- triglyceride, glycerol hydroxystearate, hardened castor oil.

Ethylene glycol ester: ethylene glycol ester, ethylene glycol monostearate, ethylene glycol distearate, triethylene glycol distearate,

Fatty alcohol esters: esters of C16-C18 fatty acids with C12-C18 fatty alcohols, polyethylene glycol esters such as polyethylene glycol stearate.

Possible fatty acids are: palmitic acid, stearic acid, individually or in a mixture; also: behenic acid, hydroxystearic acid.

Another object of the invention relates to the use of the dripped paint raw materials for the production of powder coatings.

B e i s p i e l e

example 1

In a Droppo system from Rieter Automatik GmbH, 70% ethylene glycol di-stearate Cutina AGS from Cognis and 30% polybutyl acrylate Acronal 4 F from BASF were dripped at 80 ° C and cold in countercurrent at 15 ° C Air freezes. The product temperature was 26 ° C. The product was spherical, free-flowing and did not stick to the surface.

Example 2

In a Droppo system from Rieter Automatik GmbH, 60% hardened castina oil Cutina HR from Cognis and 40% polybutyl acrylate Acronal 4 F from BASF were dripped at 105 ° C with a 300 μm nozzle and countercurrently cold at 3 ° C Air freezes. The product temperature was 23 ° C. The product was spherical, but still sticky. By dripping into a slide bed with silica Sernat 22 S from Degussa, free-flowing, non-sticky beads could be produced. The excess coating material was screened off.

Example 3

In a Droppo plant from Rieter Automatik GmbH, 40% stearic acid Edenor STl from Cognis and 60% polybutyl acrylate Acronal 4 F from BASF were dripped at 85 ° C with a 500 μm nozzle and countercurrent with 3 ° C cold air stiffens. The product temperature was 27 ° C. The product was spherical, but still slightly sticky. By introducing Sipernat 22 S silica from Degussa via an injector into the cooling air stream, free-flowing, non-sticky beads could be produced. The excess coating material was separated from the exhaust gas in the fine particle filter. Example 4

In a Droppo system from Rieter Automatik GmbH, 40% stearic acid Edenor STl from Cognis and 60% polybutyl acrylate Acronal 4 F from BASF were dripped at 85 ° C with a 300 μm nozzle and countercurrent with 5 ° C cold air stiffens. The product temperature was 28 ° C. The product was spherical, but still slightly sticky. By introducing Edenor STl stearic acid powder from Cognis into the cooling air stream via an injector, free-flowing, non-sticky beads could be produced. The excess coating material was separated from the exhaust gas in the fine particle filter.

Claims

Patent claims

1. Dripped paint additives with a narrow particle size distribution, which can be obtained by liquefying a preparation that is solid at room temperature and containing one or more leveling agents and one or more consistency agents, dripping the melt with a nozzle or pouring plate by vibration, and the drops solidifies by means of a coolant.

2. Dripped paint additives according to claim 1, wherein poly-alkyl acrylates with an average molecular weight in the range of 3,000-100,000 kg / kmol are used as leveling agents.

3. Dripped paint additives according to claim 2, wherein the alkyl radicals of the polyalkyl acrylates are selected from the group consisting of methyl, ethyl, propyl, butyl and ethylhexyl.

4. Dripped paint additives according to claim 2 or 3, wherein waxes are used as a consistency agent.

5. Dripped paint additives according to claim 4, wherein the waxes are selected from the group glycerol monostearate, palmitic / stearic acid mono- / di- / tri- triglyceride, glycerol hydroxystearate, hardened castor oil, ethylene glycol ester, ethylene glycol monostearate, ethylene glycol distearate, triethylene glycol, triethylene glycol C16-C18 fatty acids with C12-C18 fatty alcohols, polyethylene glycol stearate.

6. Dripped paint additives according to claim 2 or 3, wherein fatty acids are used as a consistency agent.

7. Use of the dripped lacquer raw materials according to one of claims 1 to 4 for the production of powder coatings.

n