WO1989006674A1

WO1989006674A1 - Process for preparing powder paints for obtaining surfaces with uniform matt or satin finish

Info

Publication number: WO1989006674A1
Application number: PCT/EP1989/000022
Authority: WO
Inventors: Silvestro Farronato; Gazzea Sergio
Original assignee: Hoechst-Sara S.P.A. Italienische Aktiengesellschaf
Priority date: 1988-01-15
Filing date: 1989-01-11
Publication date: 1989-07-27
Also published as: JPH03503652A; DK167490A; DK167490D0; IT8819081A0; FI903466A0; EP0396598A1; IT1215707B

Abstract

The process disclosed consists in mixing different powder paints composed of various binder systems. By non-intimate mixing (i.e., in the solid state, not in the fused state) of a powder paint consisting of a heat-hardenable binder system with one or more powder paints consisting of one or more different heat-hardenable or thermoplastic binder systems, films with a uniform matt or satin finish after stoving, possessing excellent chemical and mechanical resistance, and suitable for decorative surfaces can be obtained.

Description

"PROCESS FOR THE PREPARATION OF POWDER COATINGSΗ FOR PRODUCTION

EQUAL WATTER OR SEIDTGER SURFACES "

A powder coating usually consists of a thermosetting solid binder system or a thermoplastic solid binder which are above their melting point Temperatures can be co-extruded together with pigments, fillers and various additives. The most commonly used thermosetting binder systems are:

- POLYURETHANE SYSTEMS consisting of hydroxylated polyester and acrylic resins and blocked isocyanate hardeners or thermolabile hardeners that develop isocyanate groups.

- EPQXIDSISTEME consisting of epoxy or glycidyl resins and various hardeners: bases, acids, anhydrides, salts etc.

- MIXING OR HYBEIDSISTEME consisting of aromatic or aliphatic or cycloaliphatic epoxy resins and carboxylated polyester or acrylic resins. - POLYNHYDRIDSISIEME consisting of polyanhydrides and carboxylated polyester or acrylic resins. After application to the object to be painted and before melting and hardening, the powder coating films generally consist of a matt or silky-looking layer of coating particles with a grain size of less than 150 μ (microns); when placed in the oven for a period of time at appropriate temperatures to harden, the particles melt, bake, expand, forming a uniform layer with a smooth, shiny surface. So that the film does not shine, the film surface must logically not expand and become smooth, but should if possible stay finely structured so that it is as little reflective as possible. The harder the film surface expands during the melting and / or curing time, the more the surface remains as it was after application, ie finely structured and non-reflective and therefore matt and silky.

Glossy films are usually required by the industry, but many coatings require films with a certain mattness or a silky sheen for aesthetic reasons or to obtain non-reflective surfaces. A film is generally considered to be matt if 40% of a sunbeam incident at a 60º angle is reflected - referred to as 40 gloss in technical terms - while values between 40 and 70 gloss correspond to a semi-glossy film and over 70 gloss to a glossy film .

In order to obtain silky or matt film, overpigmentation is used in industrial practice or incompatible polymers, such as polyethylene and / or polypropylene and / or fluorine waxes, cellulose esters, fillers with high oil absorption, are added to the main binder system even before extrusion , organic or organometallic salts etc. During the extrusion process, the binder system melts and homogenises perfectly with all other paint components.

There are several patents that claim methods for making matt films from powder coatings. The French patent Mr. For example, 7804685 claims matte film obtained from a powder obtained from an extruder produced intimate mixture of two hydroxylated resins with different hydroxyl number and a polyanhydride hardener.

German patent DE 2324696 claims matt films made from a powder consisting of an intimate mixture of a glycidyl resin produced in the extruder with anhydride salts of polycarboxylic acids.

German patent DE 3232463 claims matt films made from a powder consisting of the intimate mixture of a hydroxylated polyester resin and a blocked isocyanate hardener with carboxyl functions and a crosslinking agent containing glycidyl groups.

Japanese patent JP 101963 dated 25.8.77 claims matt films made from the eutectic mixture of two differently reactive epoxy lacquers, which are produced from the same epoxy resin but with different amounts of the same catalyst.

The present invention is based on the fact that the physical mixing and the lack of homogenization in the extruder of two or more, separately extruded paints, which consist of different binder systems, promote the independent crosslinking of the individual mixed systems, so that one system expands the other systems prevented.

In practice, each of the binder systems, after melting, tends to expand before crosslinking, but it does not succeed because it is from one or more of the others mixed systems are prevented from doing so; So the more difficult the expansion or the shorter the expansion time before the crosslinking of one or more of the mixed binder systems, the more matt or silky the film becomes. In the tests carried out according to the present invention, it has been found that normally the more matte films are obtained, the more the portions of the mixed binder systems are the same.

The kit of the present invention gives uniformly matt and silky films for high-quality surfaces with excellent chemical and mechanical resistance and for decorative surfaces, although the mixed binder systems independently crosslink and prevent each other from expanding; by changing the relationship between the

Binder systems are differently matt or silky

Films achieved.

According to the present invention, the various binder systems which are normally used for the production of powder coatings for glossy films, such as polyurethane systems, hybrid or mixed systems, epoxy systems etc. can be used to obtain matt and silky films. However, an important feature is that the coatings extruded separately and then mixed according to the claims of this invention. Another feature is that at least one of the mixed binder systems is very viscous or thixotropic or very reactive, so that the expansion of the film is prevented during melting and / or baking. The The size distribution of the individual varnishes has no influence on the final appearance of the film.

It is therefore clear how extremely practical the process claimed by this invention is, since the powder coating manufacturer simply needs to dry-blend its various coatings, although it must be borne in mind that at least one coating is the expansion of the film during larding and must prevent burn-in.

According to the invention, the different powder types can be mixed in the desired proportions both in farm van chips or flakes after extrusion and then ground together or first ground individually and then mixed.

As the binder system (A) which prevents the film from expanding, the thermosetting binder systems normally used according to the invention can be used with one of the following compositions: a) Resins with carboxyl end groups + glycidyl resin or hardeners with two or more epoxy groups per column. b) Resin with hydroxyl end groups + polyanhydride. c) Resin with hydroxyl end groups + blocked polyisocyanates. d) Resin with hydroxyl end groups + polyurethane ion isocyanate. e) Resin with hydroxyl end groups + blocked isocyanate with COOH groups. f) epoxy resin + polyanhydride. g) epoxy resin + basic catalyst such as dicyandiamide, substituted dicyandiamide, azelaic acid dihydrazide, isophthalic acid hydrazide, guanamine, etc. One or more of the thermosetting or thermoplastic binder systems (B) which can be used according to the invention for mixing with the expansion-preventing system have the following composition: a) Resins with hydroxyl end groups + blocked polyisocyanate. b) Resin with hydroxyl end groups + polyurethane ion cyanate. c) Resin with hydroxyl end groups + blocked isocyanate with carboxyl groups. d) Resin with hydroxyl end groups + polyanhydride. e) Resin with carboxyl end groups + glycidyl resin or hardener with two or more epoxy groups per Holekül. f) epoxy resin + polyandydride. g) epoxy resin + basic catalyst. h) epoxy resin + compound with epoxy groups. i) Resin with hydroxyl end groups. l) Resin with carboxyl end groups. m) aldehyde resin.

Description of those used in the following examples

Polymers and additives: Alftalat 01844-

Test polyester resin with hydroxyl end groups.

Hydroxyl number = 30 mg KHO / g resin.

Viscosity at 200 ° C C&P = 4500-6000 mPa.s

Glass transition temperature Tg = 50 ° C. Additol XL 432-

Hoechst manufactured and marketed aliphatic blocked isocyanate prepolymer. Total NCO content = 9.5%. Tg = 45 ° C. Additol XL 496- Masterbatch manufactured and marketed leveling agent with 15% virgin content by Hoechst.

Alftalat 01918-

Test polyester resin with hydroxyl end groups.

Hydroxyl number: 100 mg KOH / g resin. Viscosity at 200 ° C C&P = 3500-5000 mPa.s

Tg = about 57 ° C.

Beckpox EH 694-

Polyanhydride manufactured and marketed by Hoechst.

Acid number = 260-280 mg KOH / g melting point = approx. 60 ° C.

Alftalat ANf 721-

Polyester resin manufactured and marketed by Hoechst

Carboxyl end groups.

Acid number: 35-45 mg KOH / g viscosity at 200 ° C C&P = 4000-6000 mPa.s

Tg = approx. 52 * C.

Araldfit PT 810-

Salt produced and marketed by CIBA-GEIGY

Triglycidyl isocyanuric acid (TGIC). Alftalat 01923-

Test polyester resin with carboxyl end groups.

Acid number = approx. 35 mg KOH / g resin. Viscosity at 200 ° C C&P = 6000-8000 mPa.s Tg = approx. 67 ° C. Laropal A 81-

Aldehyde resin manufactured and marketed by BASF. Melting point = 80-90 ° C

Acid number = max. 3 mg KOH / g resin.

example 1

Paint A (aliphatic polyurethane paint), consisting of: ALFTALAT 01844 500 ADDITOL XL 432 110

ADDITOL XL 496 30

BENZOIN 5

TITAH DIOXIDE (rutile) 345

1000 pieces

was mixed dry in the mixer, then thoroughly homogenized in the extruder at 90-100 ° C and, after cooling, ground, ground and sieved through a 106μ sieve. The powder thus obtained, which is sprayed onto sheet metal with an electrostatic gun at a voltage of approx. 60 kV in a layer thickness of 30-60 μ and 30 Hin in the oven. Cured at 180 ° C gave an elastic film with good mechanical strength properties, good adhesion to the backing and a gloss of 90 gloss. Composition B (polyanhydride paint), consisting of: ALFTALAT 01918 456

BECKPOX EH 694 164

ADDITOL XL 496 30 BENZOIN 5

TITAEDIOXIDE (rutile) 345 1000 parts was treated as composition A and gave a film with good chemical and mechanical resistance and a gloss of 92 gloss.

After sieving, the powder coatings of compositions A and B were mixed according to the invention in a mixer dry in various ratios, applied to sheet metal and baked under the conditions used for composition A. The resulting films gave the following values:

Part A / Part B Gloss> 60º

20/80 43

30/70 23

50/50 7 60/40 19

70/30 41

80/20 69

Example 1 was repeated, but the

Compositions A and B were mixed in the proportions given above in farm of chips made after extrusion and then ground together. The resulting powder coatings were screened and coated as composition A and gave films with the same gloss values as those given in the list above.

EXAMPLE 2 COMPARATIVE EXAMPLE Compositions A and B from Example 1 were mixed together in a ratio of 60:40 and 50:50 before extrusion and then extruded together, as in Example 1, ground, sieved, sprayed and fired. Both paints gave a gloss of 85 gloss.

Example 3

Composition A (hydroxylated anhydride varnish) consisting of:

ALFTALAT 01918 456

BECKPOX EH 694 164 ADDITOL XL 496 30

BENZOIN 5

TITAIDIOXIDE (Rutile) 345

1000 parts of composition B (carboxylated glycidyl lacquer), consisting of:

ALFTALAT AN 721 574

ARALDIT PT 810 45

ADDITOL XL 496 30

BENZOIN 4 SOLID WHITE 47 TITANIUM DIOXIDE 300

1000 parts Compositions A and B were extruded separately under the standard conditions (Example 1) and then used in 3 different ways: a) The extruded material was ground and the powder obtained was degreased with an electrostatic gun in a layer thickness of approximately 50 μ Steel plates sprayed and then 30 kin. baked at 180 ° C. Then the gloss was measured with a gloss meter at an angle of incidence of 60 °.

Composition A gave 92 gloss, composition B gave 89 gloss. b) The extruded material was ground and sieved separately and the resulting powders were mixed in different proportions and then sprayed and fired as in .a). c) The extruded material was cooled and chopped into flakes and then mixed together in the form of chips in various ratios and ground, sieved and fired as in a).

The paints prepared according to processes b) and c) with the same ratio between part A and part B had practically the same gloss. The corresponding values are given in the table below: Part A / Part B Gloss> 60º

90/10 73

80/20 43

70/30 32 60/40 23

50/50 22

40/60 23

30/70 34

20/80 44

Example 4

The same procedure as in Example 1. Composition A (aliphatic polyurethane lacquer), consisting of:

ALFTALAT 01844 510 ADDITOL XL 432 110

ADDITOL XL 496 30

BENZOIN 5

TITANIUM DIOXIDE (rutile) 345

1000 pieces

Composition B (carboxylated glycidyl lacquer), consisting of:

ALFTALAT AN 721 574

ARALDIT PT 810 45

ADDITOL XL 496 30

BENZOIN 4

FESTWEISS 47

TITANIUM DIOXIDE 300 1000 pieces

The following values were achieved:

Part A / Part B Gloss> 60º

10/90 63

20/80 42

30/70 30

40/60 22

50/50 20

60/40 24

70/30 42

80/20 66 90/10 81

Example 5

The same procedure as in Example 1 using the following 3 compositions A / B / C in a ratio of 50:40:10. Composition A (carboxylated glycidyl lacquer), consisting of: ALFTALAT 01923 570 ARALDIT PT 810 46

XL 496 30

BEHZOIN 4 FESTVEISS 350

1000 parts of composition B (aliphatic polyurethane lacquer), consisting of: ALFTALAT 01844 510

ADDITOL XL 432 110 ADDITOL XL 496 30

BENZOIN 5

TITAIDIOXIDE 345

1000 parts of composition C (thermoplastic), consisting of: ALFTALAT 01844 510

ADDITOL XL 496 30

BENZOIN 5

TITANIUM DIOXIDE 345

1000 parts after 30 minutes of baking at 180 ° C, the paint had a gloss of 22 gloss.

Example 7

The same procedure as in Example 1. Composition A (hydroxylated anhydride varnish), consisting of: ALFTALAT 01918 456 BECKOPOX EH 694 164 ADDITOL XL 496 30 BENZOIN 5 TITABDIOXIDE 345

1000 pieces

Composition B (thermoplastic), consisting of: LAROPAL A-81 510

ADDITOL XL 496 30 BEHZOIS 5

TITABDIOXIDE 245,

1000 parts In a ratio of 50:50, the gloss of the film was 10 gloss.

Example 8

The same procedure as in Example 1. Composition A (hydroxylated anhydride varnish), consisting of: ALFTALAT 01918. 456

BECKPOX EH 694 164

ADDITOL XL 496 30

BENZOIN 5

TITAS DIOXIDE 345

1000 pieces Composition B (thermoplastic), consisting of: ALFTALAT 01923 570

ADDITOL XL 496 30

BENZOIS 4 TITATE DIOXIDE 350

1000 parts In a ratio of 50:50, the gloss of the film was 18 gloss.

Example 9

The 50:50 mixed paints A / B of Example 1 were sprayed onto electrically non-conductive materials previously heated to 125 ° C and then cured in the oven at 180 ° C for 15 minutes.

As in example 1, the gloss was 7 gloss. The non-conductive materials glass and bisque porcelain were tested.

Claims

1. Process for the production of matt or silky

Powder resins, characterized in that the lacquers consist of physical mixtures (dry blend) and intimate mixtures of two or more powder lacquers which are not achieved by the molten state of the binders and which are composed of different binder systems (A and B).

2. The method according to claim 1, characterized in that the lacquers are extruded separately and mixed before and after the bare and before and after the screening.

3. The method according to claim 1, characterized in that the binder systems from which the paint A consists are thermosetting systems with the following compositions: a) resins with carboxyl end groups + glycidyl resin (or hardener) with two or more epoxy groups per molecule. b) Resin with hydroxyl end groups + polyanhydride. c) Resin with hydroxyl end groups + blocked polyisocyanates. d) Resin with hydroxyl end groups + polyurethane ion isocyanate. e) Resin with hydroxyl end groups + blocked polyisocyanate with carboxyl groups. f) epoxy resin + polyanhydride. g) epoxy resin + acidic or basic catalyst.

4. The method according to claim 1, characterized in that the binder systems from which the paint B consists are thermosetting and / or thermoplastic systems with the following compositions: a) Resin with hydroxyl end groups + blocked polyisocyanate. b) Resin with hydroxyl end groups + polyurethane ion isocyanate. c) Resin with hydroxyl end groups + blocked polyisocyanate with carboxyl groups. d) Resin with hydroxyl end groups + polyanhydride. e) Resin with hydroxyl end groups + glycidyl resin or hardener with two or more epoxy groups per molecule. f) epoxy resin + acidic or basic catalyst.

g) epoxy resin + polyanhydride. h) epoxy resin or compound with epoxy groups. i) Resin with hydroxyl end groups. l) Resin with carboxyl end groups. m) Aldehyde resin.

5. The method according to claim 1, characterized in that the paint mixtures consist of the systems A + B of claims 3 and 4 in a ratio between 90:10 and 10:90, preferably between 70:30 and 30:70, where A is differs from B.

6. The method according to claim 1, characterized in that the lacquers consist of one of the compositions described in claim 3 and one or more of the compositions described in claim 4, the part described in claim 3 in a ratio of 10% to 90%, preferably from 30% to 70%, and has a different composition than that described in claim 4.

7. Composition of matt or silky powder coatings prepared according to claim 5.

8. Composition of matt or silky powder coatings prepared according to claim 6.

9. Electrically conductive and non-conductive objects which are coated with matt or silky paints according to claim 7 or claim 8.