FR2644794A1 - POWDER COATING COMPOSITIONS AND PROCESS FOR PRODUCING THE SAME - Google Patents

Abstract

A powder coating composition which is a dry particulate mixture of a thermosetting resin or a thermoplastic resin and vesicular polymer granules. The polymer granules have a volume average diameter of 3 to 30 mum and are formed of a polymeric material which does not melt or degrade under the conditions of time and temperature during the preparation of the compositions or the preparation. subsequent use. The amount of polymer granules in the composition is at least 40% by volume. The powder coating compositions produce a matte finish instead of the glossy finish of the prior art. The polymer granules are preferably spherical and the vesicles occupy 5 to 95% of the volume of the granules. The powder compositions can be used for a wide variety of uses.

Description

l

  The present invention relates to resilient compositions

  neuses and more particularly powder coating compositions. Powder coating compositions are now

  used in increasing quantities and in increasing number of applications

  cations. They have major advantages but due to their application methods, the coatings produced tend to be shiny instead of a matte finish. It is often desirable

to obtain matte finishes.

  In accordance with the present invention, a composition of

  powder coating includes a substantial particulate mixture-

  slightly dry with thermosetting resin or thermosetting resin

  plastic and vesicular polymer granules having a volume average diameter of 3 to 30 µm and forms a polymeric material which does not melt or does not degrade substantially either

  under the temperature and time conditions required for pre-

  to adorn said composition and also to harden said composition

  tion of thermosetting resin, either under the conditions of

  temperature and time required for the application of said com-

  position of thermoplastic resin on a substrate, the quantity of the polymer granules being less than 40% by volume of said mixture. The powder coating compositions of the present invention are based on a resin which may be a resin

  thermosetting or a thermoplastic resin, but the composites

  tions based on thermosetting resins are preferred. Thermosetting resins are those which, when cured, usually by the action of a curing agent, do not

  do not melt or soften on heating.

  Generally, typical thermosetting resins include epoxy resins, polyurethanes, polyester resins, hybrid epoxy-polyester resins and acrylic resins. Epoxy resins that harden by action

  of a hardening agent at various speeds depending on the temperature

  Hardening tures are available. The compositions that work

  tooth, and which harden in 60 s or less can be obtained. Typical hardening agents based on dicyandiamide can be

  used in particular those of the modified and substituted type.

  Polyester resins such as free resins

  saturated oil based on isophthalic acid or terephthalic acid

  Those reacted with diols to produce resins with terminal hydroxyl groups can be used. These resins can be cured by reaction with an amine resin, by

  example a melamine-formaldehyde resin. Poly- resins

  esters with free hydroxyl groups can be cured by isocyanates, such as isophorone diisocyanate which is blocked by a blocking agent, for example caprolactam. These hardened resins contain urethane groups and are

  polyurethanes. Other polyesters containing car-

  boxyles can be used and they can be hardened in use

  health of polyepoxides, for example triglycidyl isocyanurate.

  Polyester hybrids can be used as

  thermosetting resins and can be the product of the reaction

  tion of an epoxy resin and a polyester.

  Thermosetting acrylic resins such as

  those obtained by polymerization of a methacrylate on a sque-

  acrylic can be used. Dibasic acids can be used to crosslink or harden the resin. Others

  suitable hardening agents are polymers with car-

terminal boxyles.

  Thermoplastic resins which can be used to form the powder coating composition of the present

  invention include the following: vinyl polymers, poly-

  amides, thermoplastic polyesters, polyolefins and cellulosic polymers. Typical resins include plasticized polyvinyl chlorides, polyamides having suitable melting temperatures, polyethylene, polypropylene, cellulose acetate butyrate resins, acid-based polyesters

  terephthalic and 1,4-butanediol, ethylene polymers-

  chlorotrifluoroethylene, poly (vinylidene fluoride) and

poly (phenylene sulfide).

  Generally, the powder coating compositions of the present invention, in the case of a thermosetting resin composition, usually and also contain a curing agent for the resin (as described above), a flow additive and vesicular polymer granules. In the case of a powder coating composition based on thermoplastic resin, the composition usually also contains

  plasticizer, stabilizer and vesicle polymer granules

  laire. The resin composition may contain pigments such as titanium dioxide and colored pigments and dyes if necessary or desirable. The titanium dioxide dyes and / or the colored pigments may be present in the composition inside the vesicular polymer granules or

outside of these.

  The polymer granules contain one or more

  vesicles whose walls are formed by the polymer. Preferably

  The granules are substantially spherical and occupy 5% to 95% of the total volume of the granules. More preferably,

  the vesicles occupy from 20% to 80% of the volume of the granules.

  The granules have a size such as the average diameter

  C volume is from 3 to 30 pm and preferably from 5 to 20 pm.

  Typically, the vesicles in the granules pre-

  fairies have a substantially spherical shape and a diameter

  less than 20 pm and preferably 0.1 to 7 pm, more preferable-

0.1 to 1 pm.

  In general, the nature of the polymer of the gra-

  is not critical and the polymer can be a polyester, obtained by condensation of a polycarboxylic acid and a polyol, a polyester amide, a polyurethane, a urea-aldehyde resin,

  a cellulose ester or any other suitable material. Preferably

  rence, the polymer is a crosslinked unsaturated polyester resin

with an unsaturated monomer.

  Although the granules can be formed from a wide variety of different polymers, however, the polymer must

  be the one that doesn't melt or doesn't degrade in a sub-

  tantelle, in the case of a thermosetting resin composition

  curable, under temperature and time conditions When

  mixing or preparing the composition and hardening

  subsequent and, in the case of a thermopLastic composition,

  under the conditions of temperature and time When applying

  tion of the composition on a substrate.

  Other types of polymer particles which can be used in the present invention are those known to be core-coated polymer particles insoluble in

  water and especially those with only one vesicle per part

  cule. In these particles, the nucleus is formed from a poly-

  mother who swells on contact with a suitable substance and coats it

  bage is formed from another polymeric material which is permeable to

  substance required to react with the nucleus.

  Polymer granules, if desired, may contain

  a pigment such as the titanium dioxide pigment which can be pre-

  feels in the vesicles, or in the polymeric material or in both.

  The granules can be formed by an appropriate method.

  any but usually a method which involves the formation of a water-in-oil type emulsion of a polymeric material, such as a polyester resin dissolved in a

  oily material, for example styrene or a crosslinking monomer

  Lation. This emulsion is then dispersed in another phase

  aqueous. The polymerization produces an aqueous dispersion of gr

  polymer beads having vesicles.

  The aqueous dispersion of polymer granules prepared by the preferred method can be dried by the method described in patent application GB 2 205 154A and the dried composition can be used to make the powder coating composition. In the process described and claimed in the application for

  GB patent 2 205 154A, the aqueous dispersion is dried by heating

  fage in an atmosphere containing no oxygen under conditions

  appropriate time and temperature conditions to minimize

  deterioration of said particles.

  When the polymer granules contain a pigment, then the amount of pigment can be from 1 Z to 60 Z by weight of the

  weight of the granules, preferably from 5% by weight to 45% by weight.

  The amount of polymer granules in the powder coating composition can vary over a wide range but should be less than 40% by volume of the composition and

  preferably from 5 X to 30 Z by volume.

  Generally speaking, there are two main methods

  blades for the manufacture of powder coating compositions, namely a method of melt mixing and a method of

dry mixing.

  In the resin melt mixing process, the vesicular polymer granules and any other agent are mixed together in a dry form and then heated during mixing or extrusion before cooling. Heating should be sufficient to melt the resin in the mixture without

  melt the pellets and the temperature and time are not enough

  curing agents to introduce unacceptable premature curing of the thermosetting resin composition. The extruded composition

  or kneaded is cooled and granulated and ground to a part size

  desired final tiles. If desired, any desired final additives can be introduced into the composition before packaging. In a dry mixing process, the resin in the form

  finely divided is mixed with the vesicle polymer granules-

  milk and all other desired ingredients and mixed together in a high speed blender. The mixed composition is cooled and the desired post-mixing operations are carried out. Yes

  if desired, the mixed composition can be classified for

  undermining particles of too large or too small size

before packing.

  Powder coating compositions of the present

  invention can be used in a wide variety of applications

  tions and applied by widely used techniques such as electrostatic spray coating, fluid bed coating, electrostatic fluid bed coating and hot flocking. Electrostatic spray coating

  is the preferred method of application.

  It should be noted that the powder coating compositions of the present invention are particulate mixtures

  substantially dry and are substantially free from soil

or dispersing media.

  The coated products are produced with a mat finish with

  a plain, unspotted appearance. Prior to the use of gra-

  streaks of vesicular polymer, Matt finish products do not pre-

  do not feel the necessary appearance and some have a non-spotted finish. The products of the present invention are useful for the

  coating of a wide variety of products for indoor use

laughing and outdoors.

  The invention is illustrated by the following examples

  in which all the parts are counted by weight.

Example 1 (Pearl production)

  An unsaturated polyester resin is prepared by condensing

  tion of maleic anhydride, phthalic anhydride and propylene glycol in the molar ratio of 3: 1: 4.5. The product has

  an acid number of 16 mg of KOH per gram of solid resin.

  In 44 parts of a 57% by weight solution of solids of the above-mentioned resin in styrene, 3.5 parts of titanium dioxide pigment sold under the name TIOXIDE R-HD6 and 0 are incorporated by grinding. , 18 parts of magnesium oxide, until completely dispersed (about 30 min). To this mixture, parts of styrene and 4.9 parts of hot water (approximately 80 ° C.) are added, and the grinding is continued for 1 min. This oily phase is then left to stand for 1 h. Separately, 0.6 part of a 90% by weight aqueous solids solution of a nonylphenol ammonium ethoxylate sulfate surfactant is mixed with 0.18 part of industrial denatured alcohol and 0.42 part of water. This mixture is incorporated by grinding in 42 parts of water at 50 ° C. to give an aqueous phase which is added slowly to the oily phase with stirring. The mixture formed is ground for 10 min to give an emulsion of the water-in-oil type.

  , 5 parts of this emulsion are added immediately-

  in another aqueous phase containing 5 parts of a solution

  7.5% by weight of polyvinyl alcohol solids (as

  biliary), 1 part of a 1.5% by weight solution of hydroxyethylcellulose solids as thickener and 80 parts of water, and

  the mixture is ground for 3 min, after which a system is formed

  water-in-oil-in-water teme, with oil globules

about 11 µm in average diameter.

  28 parts of hot water are then added, with a

  minimum possible grinding, followed by 0.006 part of iron sulphate

  red, dissolved in a small amount of water, 0.1 part of di-

  ethylenetriamine, also dissolved in a small amount of water, and 0.156 parts of cumene hydroperoxide. The porridge is

  left to stand overnight and the exotherm increases the temperature

  temperature above 50 C, ensuring complete hardening of the unsaturated polyester. A slurry of 16.1% by weight of bead solids of crosslinked vesicular pigmented polyester resin is obtained. This slurry is dried by the method described and claimed in patent application GB 2 205 154A, as follows. To 4,000 parts of slurry, 15 parts of 10% solution are added.

  of ammonia and 40 parts of a 5% solution of flocculating agent.

  The flocculating agent is the selmonoacetate of a diamine derived from a

  fatty acid. The slurry is then heated to 70 ° C. and stirred until

  than flocculation. The preparation is filtered through a conventional vacuum filter, and is washed with clean water until polyvinyl alcohol can no longer be detected in the filtrate. The test for polyvinyl alcohol is to

  mix a sample of the filtrate with ten times its volume of acetate

  tone, and on this The polyvinyl alcohol present precipitates in the form of a white cloudy. The resulting filter cake contains

18.4% by weight of solid pearls.

  2 kg of filter cake are crushed and placed on a plate

  in an oven fitted with a thermostat and swept by nitrogen gas. The cake is then heated at 110 ° C. in a nitrogen atmosphere for 16 h, after which no weight loss can be

detected.

  The dried pearls form a soft, crumbly white mass, which can be passed through a brush through a sieve of

  106 pm of mesh opening without leaving a residue.

Example 2 (Standard)

  A conventional powder coating having a concentration

  15% pigment volume (pvc) is prepared by the following method. 692 parts of pre-chopped epoxy resin in shavings (Dow 663U), 102 parts of master flow control mixture in shavings (Modaflow flow control agent at 5% by weight (an ethyl acrylate copolymer and 2-ethylhexyl acrylate) in the epoxy resin Dow 663U), 40 parts of hardening agent based on accelerated dicyandiamide (Dow DEH 41) and 500 parts of titanium dioxide pigment marketed under the name of TIOXIDE TR92 are mixed in a Henschel water-cooled mixer. The mixing is carried out at a rotor speed of 1800 rpm for 5 min. The side walls and the rotor of the

  machine are scraped off after the initial 3 min of grinding.

  The resulting premix is extruded using an apparatus

  riel PR46 Buss Ko-Kneader, operating at low speed, at 100 C,

  then cooled and chopped into slices in a granular device

  Cumberland Rotary Knife. The chipped extrudate is then ground in a mini-KEK pin-disc disc mill, and the powder produced is passed through a 200 mesh screen to

  remove all particles larger than 75 lim before spraying

tion.

  The powder is applied using a spray unit

  Volstatic manual electrostatic measurement with voltage

  regulated at 90 kV negative, on Bonderite DG12 panels (phos-

  iron phate). The powder is melted and hardened into a comfortable coating

  26447c4 tinu by steaming the panels at 180 C for 10 min. A device

  Permascope-type ES, is used to measure the thickness of the coating

  is lying; the panels are selected with a coating thickness

  hardened between 45 and 55 pm.

  The coloring measurements are made on the panels using a Gardner XL-23 colorimeter. The L and b values are measured on the CIE Lab scale. Gloss is measured using

  a Multigloss Byk-Labotron glossmeter.

Examples 3-6 (Invention)

  We proceed to a series of powder coatings, containing

  nant the beads of dry vesicular pigmented polymer prepared in Example 1. The concentration by volume of pigment is maintained at%, and the concentration by volume of the beads (bvc) varies between 10 × and 40%. The powder coatings are obtained by the same method as that used in Example 2, with the beads added in the same step as the pigment. The quantities used, in parts by weight, are as follows: example 3 4 5 6 pvc 15% 15% 15% 15% t: o 10% 20% 30% 40% epoxy resin 613 531 449 367 masterbatch for controlling flow 90 78 66 54 hardening 35 30 26 21 TiO2 pigment TiO2 pigment 500 500 500 500 pearls 30.4 60.7 91.4 121.4 The test is carried out as in Example 2. The results are

grouped in the table below.

  Example 7 (Comparison) Another powder coating is prepared with a diluent.

  inorganic (calcium carbonate, Durcal 5), having substantial-

  ment The same size as the pearls, and used in their place. The

  volume concentration of pigment is maintained at 15%, and the

  20% diluent volume concentration (evc) is used. The

  powder coating is obtained by the same method as that used

  read in Example 2. The quantities used, in parts by weight, are as follows: example 7 pvc 15% evc 20% epoxy resin 531 flow control masterbatch 78 hardening 30 TiO2 pigment

2,500

  diluent 443 The test leads as in Example 2. The results are given

in the following table.

  Results of examples 2-7 Example pvc bvc evc L b Brillant à Brillant à

  60

2 15% - - 94.8 0.4 77 98

3 15% 10% - 94.9 1.7 32 63

4 15% 20% - 94.9 2.9 9 32

15% 30% - 94.9 3.6 2 8

6 15% 40% - 92.0 6.4 I 2

7 15% - 20% 93.6 0.6 29 75

  In Example 6, with 40% bvc, there is no fusion in a continuous coating, and the system is therefore not usable. In

  Example 7, with 20% evc, we obtain a substantial shine-

  slightly lower than that of the standard, in Example 2, or that of the powder coating with an equivalent volume of pearls, in Example 4. Its gloss is far greater than that of Example 4, and so the pearls are obviously a superior matting agent. The increase in the b value (i.e. the yellow tint) with an increase in bvc is not due to the thermal degradation of the pearls, since a sample of pearl heated in

  the same conditions show very little change in color.

  The particular curing agent used in these examples (Dow DEH41) is believed to be an amine. It is known that amines in general interact with polyesters during heating to

  produce yellowish or brownish products.

  Example 8 (Standard) A conventional powder coating is prepared with a

  15 X pvc by the following method. 691 parts of poly resin

  ester previously chopped into shavings (Uralac P2400, from the firm DSM Resins), 58 parts of triglycidyl isocyanurate (TGIC, Araldite PT810, from the firm Ciba-Geigy), 93 parts of flow modifier in shavings (Urad P2518, from the firm DSM Resins), and 500 parts of a titanium dioxide pigment for general use marketed under the name of TIOXIDE TR92 are mixed in a Henschel mixer cooled by water. Mixing is carried out at a rotor speed of 1,800 rpm for 5 min. The side walls and the rotor of the machine are scraped after an initial grinding period of 3 min. The resulting premix is extruded using an extruder (PR46 Buss Ko-Kneader), operating at low speed, at

   C, then cooled and chopped into chips in a small granule-

  Cumberland Rotary Knife. The chipped extrudate is then ground in a disc mill (mini-KEK pin-disc) and the powder produced is passed through a 200 mesh screen to

  remove all particles larger than 75 µm before spraying

tion.

  The powder is applied using a spray unit

  manual electrostatic application (Volstatic) with a voltage regulated at 90 kV negative, on iron phosphate panels (Bonderite DG 12). The powder is melted and hardened into a coating

  continuous by steaming the panels at 2000 C for 10 min. A dispo-

  sitive Permascope, Type ES, is used to measure the thickness of the coating, and The panels are selected with a thickness of

  hardened coating between 45 and 55 µm.

  The coloring measurements are made on the panels using a Gardner XL-23 colorimeter. The L and b values are measured on the CIE Lab scale. Gloss is measured using

  a Byk-Labotron multigloss glossmeter.

  Examples 9-10 (Invention) Two powder coatings were prepared containing the

  beads of dry vesicular pigmented polymer obtained in Example 1.

  The volume concentration of pigment is maintained at 15%, and the

  volume concentration of pearls (bvc) is fixed at 10% and 20%.

  The powder coatings are prepared by the same method as that used in Example 8, with the pearls added in the same step as the pigment. The quantities used, in parts by weight, are as follows: example 9 10 pvc 15% 15% bvc 10% 20% polyester resin 615 533

TGIC 52 45

  flow modifier 83 72 pigment TiO2 500 500 pearls 30.8 61.6

  The test is carried out as in Example 8. The results are men-

shown in the table below.

  Example 11 (Comparison) Another powder coating is prepared with a diluent

  inorganic (calcium carbonate, Darcal 5), having substantial-

  the same size as the pearls, used in their place. The con-

  volume concentration of pigment is maintained at 15% and a concentration

  20% dilution by volume of diluent (evc) is used. The coating

  The powder is obtained by the same method as that used in Example 8. The quantities used in parts by weight are as follows: example 11 pvc 15 Z evc 20% polyester resin 533

TGIC 45

  flow modifier 72 pigment TiO2 500 diluent 450 The test is carried out as in Example 8. The results

  are listed in the table below.

  Examples 12-13 (Invention; dry mixing)

  Other powder coatings are prepared at concentrations

  volume trations of intermediate pearls, by mixing equal volumes of two coating powders with different bvc, to give a product with an effective bvc equal to the average of the bvc

  individual. As a check, a mixture of a system is prepared.

  teme at 20 X bvc and an O% bvc system (standard), giving

  an effective bvc of 10%. This product behaves identically

  Powder coatings prepared ab inito at a bvc of Z. Thus, mixtures of powders with a bvc of OZ and a bvc of 10% (giving an effective bvc of 5%) and powders of a bvc of 10 X and at a bvc of 20% (giving an effective bvc of 15%) are considered to be equivalent to powder coatings

  prepared ab inito at a 5% bvc and a 15% bvc respectively-

  is lying. The powders are applied and tested as in the example

  8. The results are listed in the table below.

  Results of examples 8-13 Exemole pvc bvc evc L b Brillant à BriLLant à

* 600

8 15% - - 96.1 0.3 87 97

12 15% 5% - 96.4 0.6 48 74

9 15% 10% - 96.3 0.8 24 51

13 15% 15% - 96.4 0.9 8 27

15% 20% - 96.4 1.1 2 9

11 15% - 20% 94.6 0.3 18 60

  In Example 11 with 20% evc, there is a substantially lower brightness than that of the standard, in Example 8, or that of the powder coating with an equivalent volume of pearls, in Example 10. Its gloss is far superior to that of Example 10, and the pearls clearly constitute a superior matting agent. The increase in the b value (i.e. the yellow tint) with an increase in the bvc is much less than that for the corresponding epoxy system, in Examples 2-6, and does not constitute a significant disadvantage for use. It should be noted that when we draw a graph giving the gloss at 60 as a function of the bvc for examples 8, 9, 10, 12 and 13, there is a linear relationship between the two variables. The majority of matting agents have much less direct effect on gloss. Thus, these beads make it easier to select a

  bvc value to give a required result of gloss at 60.

Claims (13)

  1. A powder coating composition comprising a   substantially dry particulate mixture of thermo-resin   curable or of a thermoplastic resin characterized in that the mixture contains granules of vesicular polymer having a   volume average diameter of 3 to 30 μm and formed of a poly-   mother that does not melt or does not deteriorate substantially either under the temperature and time conditions required for   preparing said composition and also for curing said composition   sition of thermosetting resin either under the conditions of   temperature and time required for the application of said com-   position of thermoplastic resin on a substrate, and in that the quantity of polymer granules is less than 40% by volume of said mixture.   2. A composition according to claim 1, characterized in that the granules are spherical and have an average diameter in volume from 5 to 20 pm.   3. A composition according to claim 1 or 2, charac-   terized in that the granules have vesicles which are of substantially spherical shape and which have a diameter less than Pm. 4. A composition according to claim 3, characterized   in that the vesicles have a diameter of 0.1 to 1 µm.   5. A composition according to any one of the claims   above, characterized in that the granules contain   vesicles occupying from 5 Z to 95 Z of the total volume of the granules.   6. A composition according to any one of the claims   above, characterized in that the quantity of the granules   is 5% to 30% of the volume of the mixture.   7. A composition according to any one of the claims   previous reactions, characterized in that the pigment dioxide   titanium is also present in the mixture.   8. A composition according to claim 7, characterized   in that titanium dioxide is present in said granules.   9. A composition according to claim 8, characterized in that the amount of titanium dioxide in said granules   is from 1% to 60% by weight of said granules.   10. A composition according to any one of the claims   above, characterized in that the polymer granules   are polymer particles of the core-coating type.   11. A composition according to claim 10, character-   in fact that each granule has a single vesicle.   12. A process for manufacturing a coating composition   powder which consists of mixing a thermosetting resin   curable or thermoplastic resin with other ingredients   teeth, characterized in that the resin is mixed with gra-   voids of vesicular polymer having an average diameter by volume of 3 to 30 μm and formed of a polymeric material which does not melt or which does not degrade substantially either under the conditions of temperature and time during mixing and during hardening of said thermosetting resin composition is under the temperature and time conditions required for the application of said thermoplastic resin composition to a substrate and the amount of polymer granules being less than 40% by volume of said mixture.   13. A method according to claim 12, characterized in that the mixture is heated to melt the resin and the mixture is extruded and cooled before grinding to the final size desired.