NL1002153C2 - Radiation curable powder paint binder composition. - Google Patents

Description

- 1 -

RADIATION-CURABLE POWDER PAINT BINDING COMPOSITION

The invention relates to a radiation-curable powder paint binder composition.

As shown in the article "Overview of the powder coatings market worldwide" by G. Maggiore in Pitture e Vernice Europe 1/92, biz. 15-22 and from the 10th lecture by D. Richart "Powder Coating; current

Developments, Future Trends "(Waterborne, High-Solids and Powder Coatings Symposium, February 22-24, 1995) are still looking for powder paint formulations that can be cured at low thermal stress of the substrate and are therefore suitable for application to heat-sensitive substrates such as wood and plastic.

As further shown in the lecture "Radiation curing of powder coating" by Dr. Wittig at the Radtech 20 Europe 1993 Conference (2-6 May 1993) no commercial radiation-curable binder compositions are available yet. The desired combination of good storage stability at relatively high temperatures (for example 40 ° C) on the one hand and a sufficiently low viscosity (to obtain a good flow) on the other hand must be met, on the other hand.

A binder composition is formed by a polymer and optionally a cover netter or crosslinker. In general, the composition contains at least 50 wt% polymer and at most 50 wt% covernetter.

The object of the invention is to provide a radiation-curable powder paint binder composition, which is storage stable at temperatures of, for example, 40 ° C and below, which is good at temperatures between, for example, 80 ° C and 200 ° C. J * 2 - PN 8451 flows, resulting in a powder paint formulation (formed by the binder composition, the photoinitiator and optionally other additives) which can be applied to heat sensitive substrates, especially wood.

The term wood as substrate also includes chipboard, MDF (medium density fiber board) and all substrates that mainly consist of wood.

The invention is characterized in that the binder composition contains polymerizable unsaturation due to itaconic acid or an itaconic acid derivative.

The binder composition according to the invention is curable at a relatively low temperature, is chemically storage stable at 40 ° C, is radiation-curable and exhibits good flow at temperatures between 80 ° C and 200 ° C. The powder paint formulations based on this composition are suitable for application to heat sensitive substrates.

Suitable itaconic acid derivatives are, for example, itaconic anhydride, itaconic acid dichloride and mono or diitaconic esters such as, for example, (Cx-25 C8) alkyl mono- or diaconates. Examples of suitable (mono- or di-) alkylitaconates are mono- or dimethylitaconate, mono- or diethylitaconate, mono- or dibutylitaconate, mono- or dioctylitaconate and mono- or diperfluorooctylitaconate.

Itaconic acid and itaconic anhydride are preferably used.

Another important practical advantage of the radiation-curable binder composition according to the invention is that the coated substrate is directly stackable as a result of the very short drying times after the radiation-curing. The usual storage of physically drying coatings, which is currently a lot for the 10 02 1 53.

- 3 - PN 8451 coating wood is used, in practice it can take up to 24 hours. This storage can be avoided by using a radiation-curable composition according to the invention, which can lead to considerable savings.

According to a preferred embodiment of the invention, more than 40 mol% of the total amount of polymerizable unsaturation of the binder composition due to itaconic acid or an itaconic acid derivative.

The amount of unsaturation of the binder composition can be determined by NMR. Such an assay is described, for example, in Journal of Applied Polymer Science, Vol 15 23, 1979, pp. 25-38.

According to a further preferred embodiment of the invention, more than 80 mol% and more particularly more than 90 mol% of the total amount of polymerizable unsaturation of the binder composition due to itaconic acid or an itaconic acid derivative. It is possible that substantially 100% of the total amount of polymerizable unsaturation of the binder composition is due to itaconic acid or an itaconic acid derivative.

The powder paint formulation can be applied to wood as a substrate, but is also suitable for application to substrates such as, for example, metal, plastic, paper and cardboard.

The binder composition can be formed by the combination of a resin and a cover netter, but it can also consist of only a resin. It is possible that only the resin or only the covernetter contains units of itaconic acid or itaconic acid derivatives, it is also possible that both contain these units.

According to a preferred embodiment of the invention, the resin in the binder composition is based on itaconic acid or itaconic acid derivative units.

.10 02 1 53.

- 4 - PN 8451

Examples of such polymers and oligomers are, for example, polyesters, polyacrylates, polyolefins, polyurethanes, addition products of epoxy resins and itaconic acid and polystyrenes. Preferably 5 polyesters are used.

Generally, the amount of unsaturation in the polymer is between 145 and 3000 grams per mole of unsaturated group (WPU), preferably between 200 and 2000 and more preferably between 400 and 1000 grams per mole of unsaturated group.

The molecular weight (Mn) is generally between 1000 and 10,000 and can be selected depending on the covernetter to be used.

The polymers can be either amorphous or crystalline. Generally, the glass transition temperature of amorphous compounds is greater than 35 ° C and the melting point of crystalline compounds is greater than 50 ° C.

Polyesters are generally based on 20 units of aliphatic polyalcohols and polycarboxylic acids. In addition to the itaconic acid or itaconic acid derivative as an acidic component, the polyester can also contain other polycarboxylic acids, such as, for example, isophthalic acid, terephthalic acid, hexahydroterephthalic acid, 2,6-25 naphthalenedicarboxylic acid and 4,4-oxybisbenzoic acid, 3,6-dichlorophthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, hexahydro-tetrahydric acid, hexahydro-tetrahydric acid, hexahydro-tetrahydric acid, hexahydro-tetrahydric acid , azelaic acid, sebacic acid, decanedicarboxylic acid, adipic acid, succinic acid, trimellitic acid and maleic acid, fumaric acid, citaconic acid and mesaconic acid. These acids can be used as such or, if available, in the form of their anhydrides, acid chlorides or lower alkyl esters.

Hydroxycarboxylic acids and / or optionally lactones, such as for example 12-hydroxystearic acid, hydroxypivalic acid and ε-caprolactone, can also be used. 10-5 PN 8451.

Useful polyalcohols, especially diols, which can be reacted with the carboxylic acids to obtain the polyester include 5 aliphatic diols such as, for example, ethylene glycol, propane-1,2-diol, propane-1,3-diol, butane-1 , 2-diol, butane-1,4-diol, butane-1,3-diol, 2,2-dimethylpropanediol-1,3 (= neopentyl glycol), hexane-2,5-diol, hexane-1,6-diol, 2 , 2-bis- (4-hydroxy-10-cyclohexyl) -propane (hydrogenated bisphenol-A), 1,4-dimethylolcyclohexane, diethylene glycol, dipropylene glycol and 2,2-bis [4-2-hydroxyethoxy) -phenyl] propane, the hydroxypivalin ester of neopentyl glycol.

Small amounts, such as less than about 4 wt%, but preferably less than 2 wt%, of trifunctional alcohols or acids can be used to obtain branched polyesters.

Examples of useful polyols and polyacids are glycerol, hexanetriol, trimethylolethane, trimethylolpropane, tris- (2-hydroxyethyl) isocyanurate and trimellitic acid.

The polyesters can be prepared by esterification or transesterification by conventional methods, optionally in the presence of conventional esterification catalysts such as, for example, dibutyl tin oxide or tetrabutyl titanate. The preparation conditions and the COOH / OH ratio can be selected to give end products that have an acid number or hydroxyl number that is within the intended range of values.

A hydroxyl-functional polymer, such as, for example, a hydroxyl-functional polyester, is preferably used as the polymer. The polymer, for example a polyester, can react with itaconic anhydride to form an acid-functional itaconic acid based polymer, optionally in the presence of a catalyst, such as, for example, dibutyl 1 (· r - 6 - PN 8451 tin laurate), at temperatures between, for example, 70 ° C. The reaction can be carried out, for example, in an extruder or in a static mixer.

As a result, a simple synthesis, in which no side reactions occur, is obtained for a polymer containing itaconic acid units.

. Surprisingly, the resulting polymer after radiation curing, on metal, results in a coating with good mechanical properties. A polyacrylate can also be used as polymer containing itaconic acid units.

Generally, the acrylate polymer is based on alkyl esters of (meth) acrylic acid such as, for example, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, n-propyl (meth) acrylate, isobutyl (meth) acrylate ethylhexyl acrylate and / or cyclohexyl (meth) acrylate, vinyl compounds such as, for example, styrene and vinyl acetate, maleate, fumarate and itaconate.

The acylate resin can be carboxyl, glycidyl or hydroxyl functional. A hydroxyl-functional acrylate polymers are preferably used.

Hydroxyl functional acrylate resins are generally based on hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate and methyl (meth) acrylate.

Acrylic resins can be prepared by a polymerization in which solvent, for example toluene, xylene or butyl acetate, is first added to the reactor. Subsequently, heating takes place to the desired reaction temperature, for example the reflux temperature of the solvent used, after which monomers, initiator and optionally mercaptan are added during a period of, for example, between 2 and 4 hours. The temperature is then kept at reflux temperature for, for example, two hours. The solution is refluxed 10 0 2 Ί *> - 7 - PN 8451 for 1 to 4 hours. The solvent is then distilled off by raising the temperature and then vacuum distillation can be carried out for, for example, one to two hours. The product is then drained and cooled. Itaconic anhydride can then be added to the product obtained, for example a hydroxy-functional polyacrylate, whereby an acid-functional itaconic acid-based acrylate resin is obtained.

Other suitable acrylate polymers are, for example, glycidyl acrylate polymers. The glycidyl groups of these polymers can react with the acid group of a monoester of itaconic acid, for example monoethylitaconate, to obtain an itaconic acid based acrylate resin.

Partly depending on the type and functionality of the itaconic acid based polymer, a cover netter can be chosen.

Suitable cover netters are, for example, solid or liquid compounds which have vinyl ether, vinyl ester or (meth) acrylate functional groups. Such compounds are described, for example, in EP-A-663669. Suitable examples are tripropylene glycol divinylether, di- or triethylene glycol divinylether and di, tri and tetraacrylates, divinylether functionalized urethanes based on, for example, a diisocyanate and hydroxylbutyl or hydroxyethylvinylether and 30 di (meth) acrylate functionalized urethanes based on, for example, a diisethyl acrylate. Fixed covernetters are preferably used.

An itaconic acid-35 derivative, for example triethylene glycol diitaconate or pentaeritritol tetetraaconate, can also be used as cover netter.

According to a further preferred embodiment - PN 8451 of the invention, the binder composition contains an itaconic acid (derivative) as a cover-netter and as a polymer an unsaturated group-containing polymer. Suitable examples of such polymers are an acrylate functional polymer, a vinyl ether functional polymer or an itaconic acid functional polymer already described above.

According to a further preferred embodiment of the invention, a compound with polymerizable unsaturation as a result of itaconic acid or an itaconic acid derivative is processed as such into a powder paint.

The radiation-curable system generally contains a resin, optionally a cover-netter, a photoinitiator and an inhibitor.

According to another preferred embodiment of the invention, the radiation-curable system contains additives that can react with, for example, the double bond of the itaconate groups 20 during the radiation curing. Examples of such reactive additives are monoacrylates, monoaconates and mono vinyl ethers. These additives can be added in amounts between, for example, 0.1 and 15% by weight, relative to the binder composition.

Radiation curing of the binder composition according to the invention preferably takes place by UV and EB curing. These methods are further described in, for example, the article "UV and EB curing" by S.J. Bett et al. In JOCCA 1990 (11), pages 446-453. If desired, the curing can also take place thermally, for instance with thermally latent catalysts.

The UV curing of the binder composition can take place via radically initiated polymerization and cationically initiated polymerization.

10 0 2 "; 9 - 9 - PN 8451

For the UV radiation curing of the powder paint formulation, a photoinitiator is mixed with a binder composition according to the invention at a temperature between, for example, 70 ° C and 150 ° C.

Mixing can be carried out in an extruder (which is preferred) in both solvent and melt. Furthermore, pigments and the desired auxiliary substances, such as, for example, flow agents, fillers, tribo additives, degassing agents and stabilizers, can be added. After this, the paint can be applied to the substrate or sprayed electrostatically. The applied powder paint is melted by placing in an oven, exposure to IR radiation or a combination of both, at temperatures between 15, for example 80 ° C and 200 ° C, into a closed smooth coating film with a layer thickness between, for example, 50 and 200 f / m after which the still warm panel is cured under a light source. Subsequently, a further heating can take place.

Examples of suitable photoinitiators are described in Volume 3 "Photoinitiators for free radical and cationic polymerization" of "Chemistry and Technology of UV and EB formulations" by K. Dietliker (1991; SITA Technology Ltd. London).

Photoinitiators initiate the curing of the compositions of the invention upon exposure to light with wavelengths in the range between 200 and 600 nm. Suitable initiators are ketonic and may be aromatic such as, for example, benzophenone. Darocur 1173® (Merck) is a suitable benzylketal based photoinitiator and contains 2-hydroxy-2-methyl-1-phenylpropan-1-one as the active component. Irgacure 184® (Ciba) is an aryl ketone with hydroxycyclohexyl-phenyl ketone as active component and, like Irgacure 369® (active component 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1), is a suitable photo initiator. Acyl phosphine such as 2,4,6-1,0.

- 10 - PN 8451 trimethylbenzoyl diphenyl phosphine oxide (Lucerine TPO®, BASF) can also be used, as well as Quantacure CPTX® (Octel Chemicals) with the active ingredient l-chloro-4-propoxy thioxanthone. Chemical derivatives of these photoinitiators are also suitable, as well as combinations of these initiators. A suitable combination of photoinitiators is Irgacure 1800® (Ciba) consisting of 75 wt% Irgacure 184® and 25 wt% (bis (2,6-dimethoxy benzoyl) -2,4,4-10 trimethylpentyl phosphine oxide).

A very important advantage of this radiation curing is that the flow of the powder paint (by heat) is completely separated from the curing reaction (by UV or EB radiation), as a result of which powder coatings can be made that exhibit an extremely good flow.

By applying the above-described method of heating and curing, the coating obtains a higher temperature than the substrate, as a result of which a lower thermal load on the substrate occurs, which is very essential for, for example, wood as a substrate.

Powder paint processing is described by Misev in "Powder Coatings, Chemistry and Technology" (biz. 224-300; 1991).

As can be seen from "Powder Paints" in Paintindia (February 1992, biz. 50), from "New developments in powder coatings" in Polymer Paint colors Journal (December 1993, vol. 183, biz. 590-591) 30 and from the lecture "Factors affecting the gloss reducing efficiency of ionomeric flatting agents for powder coatings" by Donald F. Loar at the Waterborne, Higher Solids and Powder Coatings Symposium from February 22-24, 1995 it is very difficult to find matte powder coatings, which also have other desirable properties possess. Furthermore, it appears from "Borders and Möglichkeiten in Sachen Pulverlack" in MetalloberflSche (43 (1989) 3, 100? 1 s> - 11 - PN 8451 biz. 99-101) that powder coatings are generally matted using polyolefins and containing silicon groups connections. However, these additives have a negative influence on the mechanical properties and the adhesion.

It has been found that a powder paint composition based on a binder composition, which contains an itaconic acid or itaconic acid derivative based polymer, after curing on various substrates results in (semi) matt powder coatings, which also have other desirable properties, such as for instance mechanical properties, outer durability, hardness, flow, exhibit color stability, scratch resistance and flow.

This binder composition generally contains as a resin 15 a mixture of polymers.

Preferably, this mixture contains more than 5% by weight of the itaconic acid (derivative) based polymer, the polymer preferably being a polyester. This polymer can be mixed with an unsaturated group-containing polymer, such as, for example, an unsaturated polyester or an unsaturated polyacrylate.

The polymer can also be used with a crystalline polymer, such as, for example, a crystalline polyester.

Suitable cover netters are, for example, solid or liquid compounds which have vinyl ether, vinyl ester or (meth) acrylate functional groups and which are described, for example, in EP-A-663669.

Suitable examples are tripropylene glycol divinylether, di- or triethylene glycol divinylether and di, tri- and tetraacrylates, divinylether functionalized urethanes based on, for example, a diisocyanate and hydroxylbutyl or hydroxyethylvinylether and di (meth) acrylate functionalized urethanes based on, for example, a diisethyl acrylate. At 1 0 0 2 15 5 ...

- 12 - PN 8451 fixed covernetters are preferred.

Preferably, the binder composition comprises as a resin a mixture consisting of an itaconic acid (derivative) based polyester and an unsaturated polyester which is not based on itaconic acid units and as a coverterter a vinyl ether derivative. The polymer: covernetter weight ratio is generally between 95: 5 and 40:60.

Generally, powder coatings have a high gloss with the reflectance (gloss) at 60 ° generally being greater than 95%. With the known fillers as a matting agent, a gloss of about 50% at 60 ° can be obtained.

Generally, the gloss is measured according to ASTM-D-523 by 60 ° and / or 20 °.

With the binder composition according to the invention it is possible to obtain coatings with a gloss between 1% and 50% at 60 °, whereby the desired gloss can be adjusted by choosing the ratio between the polymer components on the one hand and the ratio between the polymer and the polymer. covernetter on the other.

The invention is further illustrated by the following non-limiting experiments and examples.

Exoer iment 1

Preparation of itaconate-containing polyester. A 3 liter round bottom flask equipped with a thermometer, stirrer and distillation attachment was charged with 98.3 grams of trimethylol propane, 113.6 grams of neopentyl glycol and 1.1 grams of butyl chlorotin dihydroxide.

The temperature was raised to 150 ° C under a constant nitrogen flow. 1203.8 grams of terephthalic acid were added in two portions. After this, the temperature was raised to 220 ° C over a period of about 10 hours during which water was distilled off. When an acid number less than about 10 mg KOH / g resin was reached, the reaction mixture was cooled to 165 ° C. Then 286.6 grams of itaconic acid, 1.1 grams of butyl chlorotin dihydroxide and 0.3 grams of mono-tertiar-butylhydroquinone were added, after which the temperature was raised to about 220 ° C until the acid number was less than about 12 mg KOH / g resin. The reaction mixture was cooled to about 180 ° C and placed under vacuum for about an hour.

The resulting polyester had an Mn (theor.) Of 3000, a WPU of 1000 g resin / mol unsaturated group, an acid number of 7.6 mg KOH / g resin, a hydroxy number of 61 mg KOH / g resin, a Tg of 40 ° C 15 (Mettler, TA 3000 at 5 ° C / min) and a viscosity of 105 dPas (Emila at 165 ° C).

Experiment 2

Preparation of itaconic acid determined polyester 20 A 1 liter glass reactor was charged with 400 grams of a hydroxyfunctional polyester (Uralac P 2115®, OH number of 40 mg KOH / gram resin, DSM Resins), 32 grams of itaconic anhydride and 800 mg dibutyltin dilaurate. The reactor was heated to 160 ° for 2 hours, after which an polyester containing itaconic acid groups was drained.

The obtained itaconic acid-terminated polyester had the following characteristics: - acid number: 42 mg KOH / gr resin, 30 - WPU: 1500 grams per mol unsaturated group and

Tg: 49 ° C

Experiment 3

Preparation of itaconic acid-terminated polyester. Experiment 2 was repeated, whereby as hydroxy functional polyester Uralac P1580® (DSM Resins) with an OH number of 75 mg KOH / gram resin was used. i '- 14 - PN 8451 applied.

The product obtained had the following characteristics: acid number: 73 mg KOH / gram resin, 5-WPU: 800 grams per mole unsaturated group and

Tg: 52 ° C

Example I

Preparation of a powder coat 10 170 wt. parts of the resin according to Experiment 1, 30 wt. parts of vinyl ether covernetter (Uralac ZW 3307P, DSM Resins), 2 wt. parts Irgacure 184 * (Ciba) and 1.3 wt. parts of flux (BYK 361®) were homogeneously mixed in a Prism extruder at 70 ° C and 200 rpm. After cooling, the paint was ground and sieved, after which the fraction with a particle size of less than 90fvm was applied to MDF panels in ± 60 µm thick layers using an electrostatic spraying device.

The resulting powder coating was heated with IR lamps for 60 seconds, whereby the surface of the panel reached a temperature of about 120 ° C, after which the still warm panel was cured by UV radiation (1 J / cm2, measured with an IL 390 light bug). .

The obtained coating had a good flow (visually determined), a very good acetone resistance (no damage to the coating after 100 acetone double rubs) and a gloss (according to ASTM-D-523/70) at 20 ° of 7 and at 60 ° from 1.

30

Example II

Preparation of a powder coating

Example I was repeated, 125 wt. parts of the resin according to Experiment 1.41 wt. 35 parts of a non-itaconic acid units-based unsaturated polyester (URALAC XP3125 ™, DSM Resins) and 34 wt. parts of covernetter were mixed.

1 0 ("2" ia.

- 15 - PN 8451

The coating obtained had good flow, very good acetone resistance and a gloss at 20 ° of 7 and 60 ° of 1.

Example III

Preparation of a powder coatina

Example II was repeated, instead of 125 wt. parts of resin 41 wt. parts of resin according to Experiment I and instead of 41 wt. parts Uralac XP3125® 125 wt. parts 10 Uralac XP3125® were used.

The coating obtained had good flow, very good acetone resistance and a gloss at 20 ° of 7 and at 60 ° of 1.

Example IV

Preparation of a powder coatina

A powder coating was prepared from 200 grams of polyester according to Experiment 2 with 2 grams of Irgacure 184® added. After application to an aluminum Q panel, the powder was liquefied at 120 ° C using an IR oven and then cured via UV radiation for 30 seconds using a mercury lamp.

The resulting soft, flexible powder coating had the following characteristics: - acetone resistance (visually determined): very good, - hardness according to Köning: 85 seconds and - impact resistance (reversed impact, test ASTM-2794/69)> 80 inch pound.

30

Example V

Preparation of a powder coatina

Example IV was repeated using the polyester of Experiment 3.

35 The obtained hard, brittle powder coating had the following characteristics: - acetone resistance: very good, 1 0 i 1 - 16 - PN 8451 hardness according to König: 140 seconds and impact resistance (reversed impact, test ATM-2794/69) <20 inch pound .

1 o c? :

Claims (15)

PN 8451 Radiation-curable powder paint binder composition comprising a polymer and optionally a cover-netter, characterized in that the binder composition contains polymerizable unsaturation due to itaconic acid or an itaconic acid derivative. Composition according to claim 1, characterized in that more than 40 mol% of the total amount of polymerizable unsaturation of the binder composition due to itaconic acid or an itaconic acid derivative. Composition according to any one of claims 1-2, characterized in that more than 90 mol% of the total amount of polymerizable unsaturation of the binder composition due to itaconic acid or an itaconic acid derivative. 4. A composition according to any one of claims 1-3, characterized in that the binder composition as polymer contains an itaconic acid (derivative) based polyester, polyacrylate, polyolefin or addition product of epoxy resins and itaconic acid. The composition of claim 4, wherein the polymer binder composition contains an itaconic acid (derivative) based polyester. 6. A composition according to any one of claims 1-3, characterized in that the binder composition contains an itaconic acid (derivative) -based compound as a covernetter and an unsaturated group-containing polymer as a polymer. Use of a binder composition according to any one of claims 1-6 in the preparation of powder paint formulations which are applicable to heat sensitive substrates. 10 02 1 55. 18. PN 8451 The use according to claim 7 wherein the heat sensitive substrate is wood. A powder paint composition comprising a binder composition according to any one of claims 5 to 6. 10. Powder paint composition for (semi-) matte powder coatings comprising a binder composition containing as polymer an itaconic acid (derivative) based polyester and as cover net a vinyl ether derivative. Powder paint composition according to claim 10, characterized in that the polymer is a mixture consisting of more than 5% by weight of itaconic acid (derivative) based polyester and less than 95% by weight of a polymer containing 15 unsaturated groups. Powder coating on the basis of a powder paint composition according to any one of claims 9-11. 13. Fully or partially coated substrate, characterized in that a powder coating according to claim 12 is used as the coating material. 14. Process for the preparation of an acid-functional itaconic acid based polymer, characterized in that a hydroxyl functional polymer reacts with itaconic anhydride at temperatures between 70 ° C and 200 ° C 15. Binder composition, powder paint composition, application, powder coating, substrate and method as substantially described and / or further illustrated in the examples. 10 0 2 1 ", COOPERATION TREATY (PCT) REPORT ON INTERNATIONAL TYPE IDENTIFIKATE OF THE NATIONAL APPLICATION Characteristic of the applicant or of the macnogoe 8451NL No run au application no". filing date 1002153. 23 January 1996 Invited priority claim Applicant (Name) DSM NV Daajm van nel request for a search of mtemaacnaai type By oe insanee for international Search (ISA) to the request for a search of internat »na ai type no. 23 January 1996 SN 26916 NL I. CLASSIFICATION OF THE SUBJECT (when using different ratings) specify all rating symbols) According to the classification (IPC) Int. Cl. 6: C 09 D 5/03 II. FIELD OF TECHNIQUE RESEARCHED Qnoerzoente minimum documentation Classification system _Classificationsvmoolen_ ~ _j Int. Cl.6 C 09 D, C 08 J, C 08 G Onaerzocnte other documentaoe than the minimum documenaM insofar as such documents are included in the investigated geeaeen sentence> (III. ! _1 LACK OF UNIT OF INVENTION (remarks oo supplementolad) I "orm PC7 / ISA / 201tai CS