DE4104681A1 - Powder coating compsn. for prodn. of structured effect coatings - comprises particles with specified particle size ranges in specified proportions - Google Patents

Abstract

Comosn. (I) comprises; (1) particles based on conventional heat-fusible and hardenable binders (2) conventional auxiliaries and additives, and, if necessary (3) hardeners, the powder particles being up to 700 merons and 20-40% (all pts.wt.) thereof being in range over 250-500 microns. Prepn. of structured coatings with so-called 'Spucker' effect by electrostatic or triboelectric spray application of (I). Pref. (I) comprises; (A) 0-50% particles up to 100 microns (B) 100-50% particles of over 100-700 microns, of which 20-40% on total (I), are over 250-500 microns, sum of (A) and (B) being 100%. Binders of (A) and (B) have same or different chemical structure. (B) has poorer flow properties on heat-hardening than has (A). USE/ADVANTAGE - Forming 'Spucker' effect, with fine structure and 'Spucker' of 0.2-1.5mm, roughness up to 150 m:rons, on lass, ceramic, plastic, wood or woodlike substrates, partic. on metal furniture such as office furniture and circuit cupboards, household appts., small articles, and equipment such as sewing machines. 'Spucker' effect was perviously obtainable only by using liq. paints.

Description

The invention relates to a powder coating composition for the electrostatic powder coating, used for the production of structured Effect coatings with spit effect is suitable.

Powder coatings are used for coating various objects, in particular metallic articles used, such as for Painting of metal furniture, such as office furniture and control cabinets, Household appliances, small items and utensils, such as sewing machines and bicycles.

Powder coatings can be applied solvent-free and are therefore environmentally friendly and cost-saving. The paint systems on Solvent based necessary disposal and safety measures omitted. Also, no long drying times are required.

Powder coatings consist of powder particles, which in space or application temperature are solid and melted by heat and run, so that a paint layer forms, which then in the course of the baking process cures. The powders of powder coatings consist of binders (Resins), which aids and additives, such as pigments, fillers and Additives, e.g. B. leveling agents are admixed. If the binders are not self-curing, the powder particles also contain corresponding Harder. The particle sizes of such powder coatings are substantially (Up to 99 wt .-%) Below 100 microns, with about 50 to 60 wt .-% of the powder between 30 and 80 microns have.

The powder coatings, for example, by electrostatic or triboelectric spray application on surfaces to be coated be applied. For example, for the electrostatic process conventional corona processes in which the powder of a corona Charging is subjected. In the triboelectric method, the Utilized by friction electricity.  

JP Patent Publication 37-14,229 describes powder paints which in addition to the usual grain size and grain sizes up to 250 microns included. This should be multi-colored patterns and, for example, hammer blow effects be achieved. So far, it has not been common for larger particle sizes for to use electrostatically applicable powder coatings. Even at so-called vortex sintering powders, which in the fluidized bed process without electrostatic charge deposited on heated objects, Only particle sizes up to 300 microns are used in practice.

For certain devices, such as metal furniture, such as control cabinets and Office furniture as well as various appliances often become surface textures used with a special decorative effect, in particular by so-called spit is characterized. Such surface structures could be achieved so far only with liquid paints.

The object of the invention is to provide a powder coating, the purpose suitable is surface effect structures, in particular by so-called spiters are labeled, and for the previously the use of Liquid paints was required to produce.

This task is surprisingly by a Powder coating composition dissolved for the electrostatic and triboelectric powder coating is suitable and made of powder on the base of usual heat-fusible and curable Binders, with customary auxiliaries and additives and, if necessary, for the binder suitable hardeners and characterized is that the powder particles are present in particle sizes up to 700 microns, wherein 20 to 40 wt .-% of the powder particles have particle sizes in the range of have over 250 microns to 500 microns.

Such particle sizes have hitherto been used for the electrostatic and triboelectric powder coating not used. As part of the Invention it has been found that using such Particle sizes can be achieved excellent decorative effects, in particular characterized by the so-called spitters.  

The powder coating compositions according to the invention preferably have one Content of A) 0 to 50% by weight of powder particles with particle sizes from to to 100 microns and B) 100 to 50 wt .-% of powder particles with particle sizes from about 100 to 700 microns, wherein 20 to 40 wt .-% (based on the Total weight of the powder) particles of over 250 to 500 microns. The given weight percent refer to the powdered Binder. They add up to 100 wt .-%.

A preferred example of an inventive Powder coating composition has the following particle size distribution Powder particles on:

• A) up to 50 wt .-% in particle sizes up to 100 microns,
• B1) from 20 to 40% by weight in particle sizes of more than 100 to 250 μm,
• B2) 20 to 40 wt .-% in particle sizes of about 250 to 500 microns and
• B3) up to 15% by weight in particle sizes of more than 500 to 700 μm,

wherein the weight percent add up to 100 wt .-%.

According to a particularly preferred embodiment, the Powder coating composition of the invention following grain size distribution the powder particles on:

• A) up to 40 wt .-% in particle sizes up to 100 microns,
• B1) from 30 to 40% by weight in particle sizes of more than 100 to 250 μm,
• B2) 25 to 35 wt .-% in particle sizes of about 250 to 500 microns and
• B3) up to 10 wt .-% in particle sizes of about 500 to 700 microns,

wherein the weight percentages also add up to 100 wt .-%.  

The small-grain component A) and the coarse-grained component B) of The powder coating composition of the present invention may be the same Binder resin systems included. However, it is also possible that the both components contain different resins. For example it has proved to be favorable when the two components A) and B) due to different flow properties of the two powders differ. For example, then good spit structures become achieved when the component A) preferably better flow properties has as the component B). For example, component A) have normal flow properties for powder coating compositions, whereas the coarse-grained component B) has worse flow properties as they are common for powder coatings.

The different flow properties of components A) and B) can be achieved in different ways. They arise for example, by choosing different binder resins for the both components; however, it can also be the same resins with different addition of the flow properties improving or worsening agents are used. worse Gradient properties arise when choosing different Binders whenever powders with higher reactivity are used become. Due to the higher reactivity, a faster curing, so that the course is hampered.

To achieve the desired structured according to the invention Effect coatings with spit effect can all conventional binders, as used in powder coatings can be used. the Those skilled in such binders are familiar. It is about thermosetting binders based on various epoxides, Polyesters, polyurethanes, polyacrylates and polymethacrylates. These Binders can be used either alone or in admixture. Unless they are self-crosslinking, they will be with you for this suitable conventional hardeners, such as capped polyisocyanate, acid or basic crosslinker resins. Such systems are used in the Literature, for example in H. Kittel, textbook of the lacquers and Coatings, Volume VIII-2, 1980, in particular pages 12 and 13, or User's Guide to Powder Coating, AFP / SME Powder Coating Division, 1987, and  The Technology of Powder, Modern Paint and Coatings, November 1988, pages 52 to 54 and 68.

Examples of usable thermosetting binders are epoxy resins, for example, of the bisphenol A type; Hardeners for this are dicyandiamide and its derivatives, polyaminoamide resins, carboxylic acid anhydrides, acidic Polyester resins and capped polyisocyanates; hydroxyl Polyester resins, for which hardeners, carboxylic acid anhydrides, acid polyester resins, Amino resins and capped polyisocyanates; carboxyl Polyester resins, for which hardeners epoxy resins (bisphenol A type), Triglycidyl isocyanurate (TGIC), oxazolines and hydroxyl groups Polyester resins are; epoxy-containing polyacrylates, for which hardeners, Carboxylic acid anhydrides, acidic polyester resins, acidic polyacrylates and amino- / amide group-containing crosslinkers are; hydroxyl-containing polyacrylates, for which crosslinkers, carboxylic anhydrides, acidic polyester resins, acidic Polyacrylates and capped polyisocyanates; and carboxyl group-containing Polyacrylates, for which crosslinkers triglycidyl isocyanurate, oxazolines, hydroxyl-containing polyester resins, hydroxyl-containing polyacrylates and epoxy group-containing polyacrylates.

Examples of favorable binder mixing systems are mixtures of Epoxies with different hardnesses, mixtures of epoxides with acidic ones Polyesters and mixtures of different polyesters. These mixtures are, if they are not self-crosslinking, with hardeners before. In the Preparation of such mixtures are the resin components and optionally hardener and optionally present pigments, fillers and additives co-extruded and optionally to the desired Grinding grain size distribution.

As mentioned above, it may be beneficial if the small-grained Components A) and the coarse-grained components B) different Have compositions, so that in particular the flow properties the two powders are different. Examples of favorable mixtures are a mixture of an epoxy / acid polyester mixed powder for component A) with a mixed powder Polyester / triglycidyl isocyanurate for component B), a mixed powder of epoxy and acidic polyester for component A) with a Epoxy powder for component B).  

Different flow properties of the components A) and B) can can also be achieved when the PVK (pigment volume concentration; percentage of total paint volume, which is solid, not fusible or soluble parts, such as pigments and fillers) both components is different. It is particularly favorable if the Component A) a lower PVK and thus a better course than the Component B), which has a higher PVK in worse Has gradient properties.

The powder coatings according to the invention with chemically identical constitution of Components A) and B) can be prepared by the to be used resin or mixtures of resins and optionally necessary hardener as well as pigments, fillers and other additives be prepared, extruded these mixtures and then to the desired Grain size range are ground, the grinding must be done so that the desired proportion of coarse grain is available up to 700 microns.

For powder coatings based on different components A) and B) the components A) and B) are extruded separately, separated on the milled desired grain size ranges and then together mixed. However, it is also possible to separate components A) and B) to extrude, to mix the extrudate and then together to ground.

The mixing process can be carried out in the usual way as it is made The prior art is familiar, for example, drum mixer be used. The grinding process is carried out in the usual way. It For example, mills are used in which the set different desired grain sizes of the final product such as micro pin mills.

In the binder used in the powders of the invention can conventional additives and auxiliaries incorporated in the usual way become. Examples of such additives are conventional Wetting agents, leveling agents and structurants such as silicone oil. Further Fillers, as they are common in powder coatings used be such. As barium sulfate, calcium carbonate, silicates and talc. It has been shown that by different selection of additives to the  Binders, such as fillers, differences in gloss can be achieved. This is especially advantageous if different fine components A) and coarse components B) used become. In this case, the structural effect, in particular the Spitereffekt, reinforced, if the degrees of gloss are different, if For example, the fine component A) a lower gloss, for example of the order of 50 to 60, and the coarse one Component B) a higher gloss level, for example of the order of magnitude of 80 has. The gloss level is at the non-textured surface with a reflectometer measured, z. B. according to DIN 67 530, ISO 2813 or ASCM-D 523. The gloss of the textured surface is then visually adjacent to the appropriate smooth surface assessed.

The powder particles of the powder coatings according to the invention can be used as Additives contain conventional pigments, as in the field of Powder coatings are familiar to the expert. It can be inorganic or act organic pigments. It may be favorable if the components A) and B) have a slight color difference. So can according to a Preferred embodiment, the fine-grained component A) of Powder coatings of the invention have a hue that differs from the the coarse-grained component is different.

This can be achieved by using different pigments, but also by Use of different pigment concentrations can be achieved. to Achieving different shades, for example, can be beneficial the fine-grained component A) 10 to 25 vol.%, preferably 15 to 20 vol.% Add pigment, and the coarse-grained component B) 15 to 40 vol .-%, preferably 25 to 35 vol .-% pigment to add. Refer to the volume percent on the total volume of the binder, pigment and optionally Hardener and other additives containing powder paint particle.

Using the powder coating composition of the present invention by electrostatic and triboelectric powder coating, in particular by appropriate spray application or spray application, decorative structures with the so-called Spuckereffekt be achieved, as previously only by Liquid coatings could be achieved. There are fine structures with very coarse spit from 0.2 to 1.5 mm. The achieved roughness depths of Effect coating can be up to 150 μm.  

As substrates for the powder coatings according to the invention are very different Materials suitable. Particularly favorable are metals, but can also For example, glass, ceramics, plastics and wood or woody Substrates are coated. Since the curing of the powder coatings thermally is done to the substrates only in terms of their thermal Resistance set a limit. The substrates can be as such be coated, for example, as mentioned above by electrostatic spray application. However, it can also be beneficial to them for To make powder coatings "sensitive", for example, by preheating or by using a conductive primer.

Curing takes place in the usual way, depending on the used Binder and hardener material by heating, for example Temperatures up to 200 ° C during normal heating times in the Magnitude of, for example, up to about 20 minutes.

In practice, it has been found that with the inventive Powder coatings decor structures achieved with the so-called Spuckereffekt can be, in particular in the field of metal furniture, such as Office furniture and control cabinets, household appliances, small items and Operating devices are desired.

The following examples serve to illustrate the invention. Unless otherwise stated, all parts are by weight.  

Example 1 Production of a textured powder coating with spit effect

Component A) (fine-grained fraction) Epoxy resin (epoxy number 850-1000) 194 parts Polyester, acid number about 73 192 parts commercial hardener for epoxies (Matthärter, which gives a low degree of gloss) 3 parts Cellulose acetobutyrate (10% in the masterbatch) 4 parts Titanium dioxide 80 parts Yellow iron oxide 2.2 parts Iron oxide red (10% in masterbatch) 0.9 parts Iron oxide black (10% in masterbatch) 4.4 parts calcium carbonate 200 parts

The above raw materials were premixed, extruded and made into one Powder with a grain size of max. 40% <32 μm max. 5% <80 μm.

Was this powder sprayed electrostatically and for 10 minutes at 200 ° C. baked, so we obtained a regular surface medium-fine Structure.

Component B) (coarse fraction) Epoxy resin (epoxy equivalent weight 850-1000) 162 parts Polyester, acid number about 73 162 parts commercial epoxy hardener (Matthärter) 3 parts Titanium dioxide 80 parts Yellow iron oxide 2.2 parts Iron oxide red (10% in masterbatch) 0.9 parts Iron oxide black (10% in masterbatch) 4.4 parts calcium carbonate 300 parts

The above raw materials were mixed and extruded. The extrudate was coarsely ground and screened through a sieve of 750 microns.

The two powders A) and B) were in the following proportions mixed:

A B 30 70 20 80 15 85 - 100

The resulting mixtures were electrostatically sprayed and 10 minutes baked at 200 ° C.

In all cases, a spit effect structure was obtained, with the Products with the mixing ratio A / B = 20/80 and 15/85 the optical most beautiful spit effects resulted.

example 2 Production of a textured powder coating with spit effect Component A) (fine-grained fraction)

It was a mixed powder based on an epoxy resin with a Epoxy equivalent weight of 700-875 and a polyester having a Acid number of about 73 produced. As fillers served Barimsulfat and Calcium carbonate. The pigmentation was carried out as in Example 1. It was proceed as in Example 1 and ground to the same particle sizes.

Component B) (coarse powder content)

It was an outdoor resistant powder based on a Polyester binder with an acid number of about 30 and Triglycidyl isocyanurate provided as a hardener. It was with a Combination of titanium dioxide with yellow, red and black pigments, such as  described in Example 1, pigmented to a hue to RAL 7032 result. Further, conventional polyester powder coatings have become commonplace Fillers and auxiliaries added. The powder became as in Example 1 described prepared.

After mixing, spraying and baking were excellent Spit effects achieved; a visually particularly favorable spit effect resulted in a mixing ratio of A / B = 5/95.

example 3 Component A) (fine-grained powder portion)

The procedure was as in Example 2.

Component B) (coarse powder content)

It was an epoxy-based powder coating with an epoxy equivalent weight from 850-1000 and a hardener based on cyclic amidines and their salts, provided. The pigmentation was carried out as in the example 2, component B). There were usual excipients and Structural auxiliaries and barium sulfate, calcium carbonate and talc as Added fillers such that the pigment volume concentration (PVK) totaled 40%.

It was pulverized and sieved as in Example 1.

Best spit results were obtained at a mixing ratio of A / B = 10 / 90-5 / 95 achieved.

example 4

Examples 1 to 3 were followed, but the component B) was screened through a sieve of 500 microns mesh size. Even in these cases, one obtained excellent Spuckereffekte, the But spit structures were a bit finer.  

example 5 Production of a structured powder coating from a chemically uniform powder component

The following mixture was provided:

Polyester with an acid number of about 73 62.5 parts Epoxy resin (epoxy equivalent weight 700 to 875) 133.5 parts Epoxy hardener (Matthärter as in Example 1) 7 parts fillers 155 parts Pigmentation for RAL 7035 35 parts

The above ingredients were mixed and extruded together. After cooling, the extrudate was ground and passed through a sieve of Sieved 750 μm.

After electrostatic spraying and baking for 10 minutes 190 ° C surfaces were achieved with excellent Spuckerstrukturen.

Claims (12)

1. Powder coating composition of powder particles based on conventional heat-fusible and curable binder with conventional auxiliaries and additives and, if necessary, curing agents, characterized in that the powder particles are present in particle sizes up to 700 microns, wherein 20 to 40 wt .-% of Powder particles in the range of particle sizes of about 250 microns to 500 microns. 2. Powder coating composition according to claim 1, characterized in that

• A) 0 to 50 wt .-% of the powder particles particle sizes of up to 100 microns and
• B) 100 to 50 wt .-% of the powder particles have particle sizes of about 100 to 700 microns, of which 20 to 40 wt .-% (based on the total weight of the powder) have particle sizes of about 250 to 500 microns,

wherein the specified percentages by weight add up to 100% by weight. 3. Powder coating composition according to claim 2, characterized in that the binder of components A) and B) the same chemical Have structure. 4. Powder coating composition according to claim 2, characterized in that the binders of components A) and B) different chemical Have structure. 5. Powder coating composition according to claim 2, characterized in that the component B) worse flow properties in the have thermal curing than that of component A).   6. Process for the preparation of structured effect coatings with Spitereffekt, by electrostatic or triboelectric Spray application of powder coatings of powder particles on the base conventional heat-fusible and curable binder customary auxiliaries and additives and, if necessary, hardeners, characterized in that powder paints of powder particles with Particle sizes up to 700 microns used, wherein 20 to 40 wt .-% of Powder particles in the range of particle sizes of over 250 microns to 500 microns are. 7. The method according to claim 6, characterized in that a Powder coating composition is used, wherein A) 0 to 50 wt .-% of Powder particles have particle size of up to 100 microns and B) 100 to 50 wt .-% of the powder particles particle sizes of about 100 to 700 microns, of which 20 to 40 wt .-% (based on the Total weight of the powder) particle sizes of over 250 to 500 microns have, wherein the specified percentages by weight to 100 wt .-% add. 8. The method according to claim 7, characterized in that a Powder coating composition is used, wherein the binders of the Components A) and B) have the same chemical structure. 9. The method according to claim 7, characterized in that a Powder coating composition is used, wherein the binders of the Components A) and B) have a different chemical structure. 10. The method according to claim 7 or 9, characterized in that a Powder coating composition is used, wherein component B) poorer flow properties during thermal curing has as the component A). 11. Use of the powder coating compositions according to any one of the claims 1 to 5 for the production of structured effect coatings with Spuckereffekt.