DK149065B - THERMOUS POWDER COATING MATERIAL BASED ON A POLYESTER RESIN AND A CROSS-BINDING RESIN - Google Patents

Description

in 149065

The present invention relates to a thermosetting powder coating material of good powder stability suitable for application by powder spraying or coating in fluidized bed.

Generally, thermosetting and curable coating materials take the form of solutions of a synthetic resin in an organic solvent serving as a base, and such a solution is applied to the surface of the substrate, which may be of metal, wood, paper or textile material, only the solvent 10 used is evaporated leaving a film of synthetic resin which can then be subjected to a heat curing treatment.

The use of organic solvents as a carrier for the synthetic resin has the disadvantage that in most cases the solvents are flammable or even cause explosions. 15 Furthermore, some organic solvents are physiologically unacceptable as they pose a danger to the health of users. Furthermore, a great deal of energy is required for evaporation of the organic solvent and for the conditioning of the air which is to conduct the solvent vapors away from the furnace in which the coated articles are heat treated.

For these reasons, it has been proposed to replace the organic solvents in whole or in part with water, but the use of water as a carrier for the synthetic resin requires the use of certain types of synthetic resins which in some cases do not provide the desired technological properties such as flow unit. , smoothing and 25 glossy coatings.

Due to these drawbacks of the previously proposed methods, it has also been proposed to apply high melting thermoplastic non-curable coating materials in the form of a homogeneous powder, which powder is mostly applied by the method known as fluidized the rental method. This method is essentially a immersion method in which the article to be coated is preheated to a temperature above the melting point of the coating material and then introduced into a fluidized mass of the coating material powder.

Powdered, thermofixable, curable coating materials can be applied to a substrate in the same way, but this requires two heat treatments, namely first for heating the article to be coated and then the curing of the coated article. For this reason, the electrostatic powder spray application method has been developed which requires only a single heat treatment, namely the cure treatment, and this method has the additional advantage that thinner layers (less than 100 microns) can be applied than by the fluidized bed method. Because of the relatively high viscosity of the molten powder even in a single treatment, coatings which are substantially thicker than those obtainable by conventional coating methods using solutions of the coating material are obtained. Sharp edges or bends are also much better ΙΟ coated by the powder coating method.

The composition of fusible, powdery coating materials for application by powder spraying methods and in fluidized bed results in requirements for the film-forming materials which are quite different from the requirements for the composition of conventional coating materials. Thus, it will be understood that the film-forming material must be a solid which can be readily converted into a free-flowing powder and does not bake together under normal storage conditions and that the material must be capable of fusing at an elevated temperature below its degradation or decomposition temperature.

In practice, the preparation of a thermoplastic powder coating has caused far fewer difficulties than the manufacture of a thermo-fixing powder coating, and this is because the thermoplastic powder coating becomes hard after simple cooling, while in a thermofixing system a crosslinking must take place. , in order to achieve the desired film properties. For this purpose, it is necessary to introduce a curing agent, a crosslinking agent or a catalyst into the system and this causes special problems.

To date, the major thermosetting powder coating systems have been completely based on epoxy resins, whose main drawback, however, is their poor outdoor durability.

Therefore, there is still a need for a powdery, free flowing, fusible, thermosetting coating material which is stable during storage, can be used in electrostatic powder spray coating methods, and has a reduced epoxy resin content and therefore can be heat cured over an acceptable time to a uniform coating with satisfactory chemical and mechanical properties and with acceptable costs.

Pra ans. No. 352/70 discloses a powdery coating material which cures in a condensation reaction between a polyester resin and an amine resin, free hydroxyl groups in the polyester resin reacting with alkoxy groups in the amine resin. This releases volatile products such as water and alcohol.

From German Publication No. 1,937,715, thermosetting resin compositions consisting of a polyepoxy compound, an acidic polyester and a polycarboxylic anhydride are known. These materials are especially intended for use in the electrical engineering and are not suitable in all cases for the production of powdery coating materials, since they have no powder stability.

Pra US Patent No. 3,397,254 discloses acidic polyesters which, together with polyepoxides, can be used for thermosetting coating materials. However, in the preparation, solvents are used such that these known materials are part of the solvent-containing coating materials.

The present invention relates to a thermosetting powder coating material with good powder stability suitable for application by powder spraying or in fluidized bed which does not develop volatiles upon curing and which does not require any solvent and which is in the form of a stable, free flowing powder. The material of the invention is of the kind made by melt blending of two resin components (1) and (2) comprising a film forming component consisting of a polyester resin and a crosslinking resin, preferably in extruders, followed by cooling and grinding to powder. wherein the component i) constituting 75-96, but preferably 85-92, by weight of the mixture consists essentially of a solid polyester resin a) prepared from a dibasic aromatic carboxylic acid of up to 10 mole% of a polybasic aliphatic carboxylic acid or of at least: tribasic aromatic carboxylic acid and an alcohol component comprising 4 149065 a) up to 100 mole%, calculated on the whole alcohol component of the polyester, of an alcohol of the general formula 5 R 5 H - (QR1) χ— 0—] Pp - ^ _ o- (R20) yH, 12 3

wherein R and R represent alkylene groups of 2-4 carbon atoms, R

represents an alkylidene group having 3 or 4 carbon atoms or a cycloalkylidene group having 6 carbon atoms or a carbonyl group or sulfone group, x and y are numbers of at least 1, the sum of x 4,5 and y not being greater than 6 and R and R being a hydrogen atom or an alkyl group of 1-6 carbon atoms, a2) up to 40, but preferably up to 20 mol%, based on the entire alcohol component of the polyester, of a glycidyl ester of the general formula 20 RC-O-CH 2 -CH-CH 2 η 2 \ / 2

ISLAND ISLAND

wherein R is a straight or branched, saturated or unsaturated hydrocarbon group having 4-20 carbon atoms, preferably 4-10 carbon atoms, or is an optionally substituted phenyl group, a3) up to 100, but preferably 75-100 mol%, calculated on the whole the alcohol component of the polyester, of at least one divalent aliphatic alcohol, and a4) up to 10 mol% of an aliphatic trivalent or polyvalent alcohol, the sum of the alcohol components al), a2), a3) and a4) being 100 mol% and peculiar to the material is that the polyester-35 resin a) has a hydroxyl number of 15-50, but preferably 15-40, and a softening point in the range of 60 to 130 ° C, and that this polyester is modified by reaction with an anhydride of a poly organic basic carboxylic acid such that the acid number in the resin component 1) is adjusted to 30-100, but preferably 40-80, and that the component 2) constituting 4-25, but preferably 8-15, weight percent of the mixture , is a polyepoxide resin whose molecule contains 5 at least 2 epoxy groups.

As the dibasic aromatic carboxylic acid in the acid component of the polyester resin, orthophthalic acid, terephthalic acid, isophthalic acid or esters of these acids may be used with lower aliphatic monovalent alcohols such as methanol or ethanol. The dibasic aromatic acids can be used either individually or in combination with each other. The preferred dibasic aromatic acid is terephthalic acid.

In some cases, it has been found advantageous to use up to 10 mole percent (based on the total acid component) of a polybasic aliphatic carboxylic acid such as adipic acid or of a tribasic aromatic carboxylic acid such as trimellitic acid or pyrromellitic acid.

Examples of diols constituting the component (al) of the polyester resin are 2,2-di- (4-p-hydroxyethoxyphenyl) propane, 2,2-di- (4-p-hydroxyethoxyphenyl) butane, 2.2 -di- (4-hydroxypropoxyphenyl) -propane, 2,2-di- (3-methyl-4'-hydroxyethoxyphenyl) -propane and polyoxyethylene-2o or the polyoxypropylene ether of 4,4'-isopropylidene diphenol where both the phenolic groups are oxyethylated or oxypropylated and the average number of oxyethylene or oxypropylene groups is 2-6, as well as di- (4-β-hydroxyethoxyphenyl) ketone and di- (4β-hydroxypropoxyphenyl) ketone.

The preferred diols are 2,2-di- (4-β-hydroxyethoxyphenyl) propane and 2,2-di- (4-hydroxypropoxyphenyl) propane.

The component (a2) of the polyester resin comprises glycidyl esters, examples of which are lauric acid glycidyl ester, benzoic acid glycidyl ester and glycidyl esters of saturated aliphatic monocarboxylic acids with the tertiary or quaternary carbon atoms in the α-position of the carb oxyl group ( "®.

The latter glycidyl esters are preferred.

The component (a3) of the polyester resin comprises divalent aliphatic alcohols such as 2,2-dimethylpropanediol-1,3, propylene glycol-1,2, 1,4-cyclohexanedimethanol and ethylene glycol, which alcohols may contain functional groups other than hydroxyl groups such as f. eg.

diethylene glycol. The divalent aliphatic alcohols can be used either individually or in combination with each other.

6 149065

The component (a4) can e.g. be trimethylolpropane and pentaerythritol.

The polyester resins are prepared by conventional methods for producing polyester resins. Conveniently, they can be prepared by heating all the reactants with stirring to a temperature of bp to 240 ° C, while continuously passing an inert gas (e.g. nitrogen) through the reaction mixture to remove the water formed during the esterification, or the lower alcohol formed 10 by re-esterification reactions. At the end of the esterification reaction, a vacuum of approx. 100 mm Hg and some glycol is distilled off.

Generally, the polyester resin is first melted with stirring in an inert gas atmosphere, then the anhydride of the polybasic organic carboxylic acid is added and the mixture is heated for 1-15 hours, preferably 1-3 hours, to 180 ° C to 250 ° C, preferably l80-210 ° C. The reaction product is then cooled to ca. at 140 ° C and poured into flat containers for solidification. After cooling, the reaction product is crushed into small pieces and then ground, conveniently in a 2o mill with pin-coated discs, to a free flowing powder having the desired particle size range (about 20-150 microns). The obtained free flowing powder can be subjected to a sieve treatment to adjust the desired average particle size according to the particular type of application to be used.

The polyepoxide resins used in the thermosetting coating materials of the invention as a crosslinking agent for the solid modified polyester resin are compounds or mixtures of compounds whose molecules contain, on average, at least two epoxy groups.

Preferably, the average number of epoxy groups in the polypropylene resin molecule is three or more. Particularly suitable for the purpose of the invention is triglycidyl isocyanurate, but various other well-known polyepoxide resins may also be used, provided that they contain at least two epoxy groups in their average molecule and that, in combination with the solid, modified polyester resins, lead to thermosetting good coating materials with thermosetting coating. which will be defined in the following.

1490 * 6

To prepare the stable, powdery, free-flowing resin products of the invention, 75-96 wt.%, Preferably 85-92 wt.% (Based on the total product) of the powdered modified polyester resin is mixed with 4-25 wt.%, Preferably 8-15 wt. total product) of the poly-epoxide resin containing at least two epoxy groups.

The solid modified polyester resin and the polyepoxide resin are mixed at a temperature just above their melting points, e.g. in an extruder whereupon they are cooled to solidify the mixture which is then crushed and ground in a suitable grinding apparatus 10 such as a pin disk mill for a free flowing powder having a particle size range of ea. 20-150 microns. The free flowing powder thus obtained can be subjected to a sieve treatment to adjust the desired average particle size according to the particular type of application to be used.

When filler and pigment components are used, an alternative method of preparation is to melt the polyepoxide resin, then add and mix the filler and pigment components in an extruder and cool the resulting mixture to solidify and then crush and ground to a free flowing powder. with the prescribed particle size range, which powder is then blended with the solid, powdery modified polyester resin of the same prescribed particle size.

The homogeneous powdered coating materials obtained may also contain various well-known functional modifiers such as grinding aids, curing agents or accelerators, flow regulators, surfactants, heat-stable organic or inorganic pigments, inert fillers, inhibitors, abrasives, and emollients.

After application of the coating materials to the substrate, the coatings are cured at a temperature between ca. 120 and approx. 250 ° C for a period of up to approx. 60 minutes. The cure treatment is preferably carried out for 10-40 minutes at 150-200 ° C.

The following examples are intended to further illustrate the invention. In all the examples of the preparation of the final coating material, this is pigmented with an amount of titanium dioxide to give a weight ratio of pigment to binder of 1: 2. In all the examples and claims, all softening points for the polyester resins and modified polyester resins are determined by a modified version of the ball and ring method of A.S.T.M. Specification No. E 28-58 T, this method being modified such that the first measured temperature is the temperature at which the ball begins to move and the last temperature is the temperature at which the ball strikes the base plate, Considering its use as a powder coating, it has been found advantageous to evaluate the properties of the polyester resin to be modified to use these values instead of those mentioned in the ASTM Specification mentioned.

1Q

Example 1 Into a suitable reaction vessel equipped with a thermometer, stirrer, separation column and inert gas inlet tube, 2816 g (9 g mole) of the ethylene glycol diethylene and bisphenol A 1580 g (2 g mole) "Cardura® E" ( a glycidyl ester of branched-chain monocarboxylic acids having 9-11 carbon atoms) and 1660 g (10 g moles) of terephthalic acid. the contents of the container were heated to a temperature of between ca. at 180 ° C and kept at this temperature with stirring, removing the water from the esterification reaction from the reaction mass by bubbling nitrogen gas. The heating was continued until an acid number of 7- The polyester thus obtained had a softening point of 78-96 ° C and a hydroxyl number of 30. Of this polyester resin, 1000 g of a reaction vessel of the same type as that described above was heated to 200-210 ° C while bubbling nitrogen 25 through the molten mass. Then, with stirring, 103 g (0.53 g - mole) of the anhydride of trimellitic acid was added and the mixture was heated to 200-210 ° C for 3 hours until an acid number of 62-63 was reached. Heating was then stopped and the product obtained cooled and solidified. The polyester resin thus obtained had an acid number of 62.8, a hydroxyl number of 0 and a softening point of 99-111.5 ° C. This product will hereinafter be referred to as "Acid A".

9 U9065

Examples 2 and 3 In the same apparatus as described in Example 1, two other polyester resins were prepared using the reactants listed in Table I. The acid numbers (ST), hydroxyl numbers (HT) and the softening points (BP) 1? C for these polyester resins are also listed in Table I.

Table I

10 times mol

Ex. Alcohol Alcohol Acid Acid ST HT BP

2 Neopentyl- 9 TPA ^ 10 8 25 95 -H0 ° C

giycoi DEGBA (1 ^ 0.66 15 "Cardura E" 1.57

Neopentyl TPA 8.5 8.5 32 74-88 ° C

glycol

Ethylene glycol 20 Hexanediol 1.6 1.6 "Cardura E" 2 ^ DEGBA = diethylene of ethylene glycol and bisphenol A ^ TPA = terephthalic acid

Modified polyester resins (2a) 1000 g of the polyester resin of Example 2 were heated in the same apparatus and in the same manner as described in Example 1 with 30 '86.0 g (0.45 g mole) of the anhydride of trimellitic acid to give a modified polyester resin, hereinafter referred to as "Acid B", having an acid number of 51, a hydroxyl number of 5 and a softening point of 96.6 -144 ° C.

(3a) In the same apparatus and in the same manner as in Example 1, 1250 g of the polyester resin of Example 5 was heated with 144 l, 3 g (0.74 g mole) of the anhydride of trimellitic acid to give a modified polyester resin (in the hereinafter referred to as "Acid C") with an acid number of 69, a hydroxyl number of 0 and a softening point of 82-99.5 ° C.

Example 4 10 149065

With "Acid A", a coating material was prepared by mixing 80 g of powdered Acid A, 15 g of a powdered poly-5 glycidyl ether of o-cresol-formaldehyde novolac with an epoxy equivalent weight of 225 and m.p. 73 ° C (Durran1's mercury method as described by Gardner and Sward in "Paint Testing Manual", 12th ed., 1962, page 367) and 0.3% by weight (calculated on Acid A) of tris- (2,4,6- dimethylamino-methyl) -phenol, which is a curing catalyst obtained under the designation "DMP-30" from ROhm and Haas Chemical Corp. (The "epoxy equivalent weight" can be defined as the amount of polyepoxide resin g in weight containing grease equivalent epoxy. The epoxy equivalent weight is determined as follows: 1 g of the polyepoxide resin is dissolved in 25 ml of a 0.2 N solution of pyridinium chloride in pyridine. the sample is.

15 dissolved, the solution is heated under reflux for 25 minutes, then cooled and 50 ml of methanol and 15 drops of phenolphthalein indicator are added. Excess pyridinium chloride is then back-titrated with 0.51 methanolic NaOH to a pink end point. The epoxide equivalent weight is calculated from the fact that fatty HCl molecule is equivalent to phen epoxide group). Of the product obtained by mixing, 80-90 $ had a particle size between 70 and 100 microns. The powdered pigmented resin mixture was applied to 1 mm thick sheets of soft steel by the electrostatic spray application method in such a way that, after curing at 180 ° C for 30 minutes, a uniform coating having a thickness of approx. 80 microns.

Example 5

A coating material was prepared by mixing 88 g of powdered Acid A and 12 g of powdered triglyeyldyl isocyanurate with an epoxy equivalent weight of 102 and m.p. 95-H5 ° C (ring and ball method). Of this mixture, 80-90 $ had a particle size between 70 and 100 microns. The powdery, free-flowing, pigmented resin mixture was applied to 1 mm thick sheets of soft steel by the electrostatic spray coating method in such a way that a uniform coating with a thickness of 180 ° C was obtained for 30 minutes. of approx. 40 microns.

Example 6 11 149O $ 5

A coating material was prepared by mixing 90 g of powdered Acid B and 10 g of the powdered 5 triglycidyl isocyanurate mentioned in Example 5. Of the mixture, 80-90 # had a particle size of between 70 and 100 microns. The powdery, free-flowing, pigmented resin mixture was applied to 1 mm thick sheets of soft steel by the electrostatic spray coating method in such a way that, after curing at 150 ° C for 30 minutes, a uniform coating of thickness, of approx. JO micron.

Example 7

A coating material was prepared by mixing 15 88 g of powdered Acid C and 12 g of the powdery triglycidyl iso cyanurate of Example 5. Of this mixture, 80-90 # had a particle size of between 70 and 100 microns. The powdery, free-flowing, pigmented resin mixture was applied to 1 mm thick sheets of soft steel by the electrostatic spray coating method in such a way that, upon subsequent curing at 150 ° C, for 30 minutes, a uniform coating of approx. 70 microns.

The resin products of Examples 4-7 and the coated steel sheets obtained in these Examples were evaluated for their powder stability and mechanical properties, respectively.

The "powder stability" which will be discussed hereinafter and in the claims is determined in the following manner: 50 g of the pigmented, powdery, free flowing product, of which 80-90 # had a particle size between 70 and 100 µ, was heated. in a beaker to 40 ° C for 30 days. If the resin particles were then not sintered together and.

the powder was still completely free-flowing, the powder dust was judged. the portability as excellent (E). If only some particles in the powder were sintered together to form soft lumps, the powder stability was rated as moderate (M), and if all the particles were sintered together, the powder stability was rated as poor (B).

12 149065

The "flexibility" stated is determined on the basis of samples of 1 mm thick steel sheets, upon which a certain amount of the powdery resin mixture is applied by the electrostatic spray coating method, after which the mixture is cured. The flexibility is rated as good (P) or defective (F) depending on whether or not it was possible to bend the steel plate with the coating 180 ° over a mandrel with a diameter of 18.75 mm without damage to the coating. If the film cracked or broke, it was termed defective. The "ohok resistance" stated is determined by "Eriehsen SehlagprUfgeråt" according to German DIN 53,156 on the same types of tests as used for the assessment of flexibility. The stated "hardness" is determined as "Pendelh'drte nach KOnig" according to German DIN 53,157 on the same kind of tests as used to determine the flexibility. The results are given in Table II:

Table II

Example 4 5

Powder stability E E E M

Flexibility P P P P

20 Shock resistance (mm) 2-3 4-5 '2 3-4 Hardness (sec) 183 195 210 18Ο

Examples 8 and 9 In the same apparatus as described in Example 1, two other polyester resins were prepared using the ingredients listed in Table III using the same abbreviations as in Table I.

30 13 143065 • Table III Mol Mol

Example Alcohol Alcohol Acid Acid ST HT BP

8 Propylene 9 TPA 10 9.2 28 96-113 ° C

glycol

Dipropylene-2 glycol

9 Neopentyl 3 TPA 10 6.4 36.5 80-92 ° C

10 glycol

Ethylene-6 glycol

Diethylene- 1 glycol "Cardura E" 1 15 ---------------------------

Modified polyester resins (8a) 1000 g of the polyester resin of Example 8 were heated 2o in the same apparatus and in the same manner as described in Example 1 with 97 g (0.5 g mole) of trimellitic anhydride to give a modified polyester resin, in the following designated as "Acid D", with an acid number of 57 and a softening point of 108-120 ° C.

(9a) 1000 g of the polyester resin of Example 9 was heated in the same apparatus and in the same manner as described in Example 1 with 126 g (0.65 g mole) of trimellitic anhydride to give a modified polyester resin, hereinafter referred to as "Acid E", with an acid number of 66 and a softening point of 94-104 ° C.

Final Coating Materials 30 (8b) With Acid D, a coating material was prepared by mixing 100 g of powdered Acid D and 11.1 g of powdered triglycodyl - isocyanurate as set forth in Example 5. Of this mixture, more than $ 90 had a particle size of 70 to 100 microns. The powdered, free-flowing, pigmented resin mixture was applied to 1 mm thick sheets of soft steel by the electrostatic spray coating method in such a way that, after curing at 200 ° C for 10 minutes, a uniform coating of thickness ca. 7Ο-8Ο microns. The powder stability and mechanical properties of 4o were as follows: 14 149065

Powder stability E

Flexibility P

Shock resistance 2 mm Hardness 192 sec.

5 (9b) With Acid E, a coating material was prepared by admixing 645s of powdered Acid E and 105g of the powdered triglycidyl isocyanurate specified in Example 5. Of this mixture, more than $ 90 had a particle size of 70 to 100 microns. The 10 powdered, free flowing, pigmented resin mixture was applied to 1 mm thick sheets of soft steel by the electrostatic spray coating method in such a way that upon subsequent curing at 200 ° C for 10 minutes, a uniform coating of about thickness was obtained. 70-80 microns. The powder stability and the mechanical properties of the coating were found to be as follows:

Powder stability M

Flexibility P

Shock resistance 2-5 frame 2q Hardness 197 sec.

Example 10 In the same apparatus as described in Example 1, a polyester resin was prepared from 9 moles of neopentyl glycol, 1 mole of 1,6-hexanediol, 25 moles of "Cardura E" and 10 moles of terephthalic acid. The polyester obtained had an acid number of 8.5, a hydroxyl number of 58.5 and a softening point of 86-105 ° C. Of this polyester, 750 g of the same apparatus and in the same manner as described in Example 1 were heated with a mixture of 49.0 g of trimellitic anhydride and 102.0 g of maleopimeric anhydride, thereby obtaining a modified polyester resin, hereinafter referred to as " Acid P ", with an acid number of 65.6 and a softening point of 92-108 ° C. With this Acid F, a coating material was prepared by mixing 860 g of powdered Acid P and 140 g of the powdered triglycidyl isocyanurate described in Example 5. Of the mixture, 35 more than $ 90 had a particle size of 70-100 microns. The powdery, free-flowing, pigmented resin mixture was applied to 1 mm thick sheets of soft steel by the electrostatic spray coating method in such a way that, after curing at 200 ° C, for 10 minutes, a uniform coating of approx.

15 U9065 50-60 microns. The powder stability and the mechanical properties of the coating were found to be:

Powder stability E

Flexibility P

D

Shock resistance 3-4 mm Hardness 197 sec.

Example II In the same apparatus as described in Example 1, a polyester resin was prepared from 5 moles of ethylene glycol, 3 moles of neopentyl glycol, 1 mole of 1,4-eyclohexanedimethanol, 2 moles of "Cardura E" and 10 moles of terephthalic acid. The polyester obtained had an acid number of 9.3, a hydroxyl number of 32.5 and a softening point of 74-83 ° C. Of this polyester, in 2424, the same apparatus was heated in the same apparatus and in the same manner as described in Example 1 with 218.9 g of trimellitic anhydride to obtain a modified polyester resin, hereinafter referred to as "Acid G", with an acid number of 66 and a softening point of 96-117.5 ° C. With this Acid G, a coating material was prepared by mixing 20 580 g of powdered Acid G and 170 g of powdered diglycidyl terephthalate. Of this mixture, more than $ 90 had a particle size of 70 to 100 microns. The powdery, free-flowing, pigmented resin mixture was applied to 1 mm thick sheets of soft steel by the electrostatic spray coating method in such a way that, upon subsequent curing at 200 ° C for 20 minutes, a uniform coating of approx. 50-60 microns. The powder stability and the mechanical properties of the coating were found to be:

Powder stability M

30 Flexibility P

Shock resistance 1 mm Hardness 197 sec.

35 l6 149066

Example 12 In the same apparatus as described in Example 1, a polyester resin was prepared from 6 moles of ethylene glycol, 3 moles of neopentylglyeol, 5 moles of diethylene glycol, 1 mole of "Cardura E" and 10 moles of terephthalic acid.

The polyester obtained had an acid number of 6.4, a hydroxyl number of 36.5, and a softening point of 81-197 ° C. Of this polyester, 750 g of the same apparatus was heated in the same manner as described in Example 1 with 93.9 g of trimellitic anhydride to give a modified polyester resin, hereinafter referred to as "Acid H", with an acid number of 83.3 and a softening point of 94-104 ° C. With this acid, a coating material was prepared by mixing 600 g of powdered Acid H and 66 g of powdered triglycidyl isocyanurate. Of this mixture, more than 99% had a particle size of 70 to 100 microns. The 15 powdered, free flowing, pigmented resin mixture was applied to 1 mm thick sheets of soft steel by the electrostatic spray coating method in such a way that, after curing at 200 ° C for 10 minutes, a uniform coating of approx. 50-60 microns. The powder stability and mechanical properties of the coating were found to be as follows:

Powder stability E

Flexibility P

Shock resistance 2-3 mm Hardness 200 sec.

25

Examples 13-15 In the same apparatus as described in Example 1, 30 other three polyester resins were prepared using the ingredients listed in Table IV, using the same abbreviations as in Table I.

IT 149065

Table IY

Mol Mol

Ex. Alcohol Alcohol Acid Acid ST HT BP_

Neopentyl TPA 10 5.5 35.1 86-102 ° C

5 glycol

Ethylene-6 glycol 2.2.4-Tri-2-methyl-hexanediol-10 -'6

14 "DEGBA" 5.5 TPA 10 5.9 49 64-84 ° C

"Cardura E" 5 1.4-Cyclo-4.5 hexane-dimethanol

Ethylene TPA 10 6.7 19 84.5-105 ° C

glycol "Cardura E" 2

Neopentyl 5 giycoi

Hexanediol 1.6 1.6

Modified Polyester Resins 25 (15a) 1000 g of the polyester resin of Example 15 are heated in the same apparatus and in the same manner as described in Example 9 with a mixture of 58.5 g of trimellitic anhydride and 30.5 S succinic anhydride to give a modified polyester resin , hereinafter referred to as "Acid K", having an acid number of 50.1 and a softening point of 93-144 ° C.

(14a) 750 g of the polyester of Example 14 was heated in the same apparatus and in the same manner as described in Example 1 with a mixture of 126 g of trimellitic anhydride and 4 g of maleic anhydride to give a modified polyester resin, hereinafter designated 35 as " Acid L ", with an acid number of 94 and a softening point of 112-126 ° C.

(15a) 750g of the polyester resin of Example 15 was heated in the same apparatus and in the same manner as described in Example 1 with a mixture of 4lg of trimellitic anhydride and 14g of maleic anhydride to give a modified polyester resin, hereinafter referred to as " Acid M ", with an acid number of 56 and a softening point of 87 -15 ° c.

18 HS065

Final Coating Materials (lb) With Acid K, a coating material was prepared by mixing 440 g of powdered Acid K and 60 g of the powdered triglycidyl isocyanurate mentioned in Example 5. Of this mixture, more than $ 90 had a particle size of 70 to 100 microns. The powdery, free-flowing, pigmented resin mixture was applied to 1 mm thick sheets of soft steel by the electrostatic spray coating method in such a way that upon subsequent curing 10 at 200 ° C for 10 minutes, a uniform coating of about thickness was obtained. 50-60 microns. The powder stability and mechanical properties of the coating are listed in Table V.

(14b) With Acid L, a coating material was prepared by mixing 625 g of powdered Acid L and 75 g of the powdered triglycidyl isocyanurate mentioned in Example 5. Of this mixture, more than $ 90 had a particle size of 70 to 100 microns. The powdery, free-flowing, pigmented resin mixture was applied to 1 mm thick sheets of soft steel by the electrostatic spray coating method in such a way that, upon subsequent curing 20 at 200 ° C for 10 minutes, a uniform coating of approx. 60-70 microns. The powder stability and mechanical properties of the coating are listed in Table V.

(15b) With Acid M, a coating material was prepared by mixing 650 g of powdered Acid M and 120 g of the powdered triglycidyl isocyanurate mentioned in Example 5. Of this mixture, more than $ 90 had a particle size of 70 to 100 microns. The powdery, free-flowing, pigmented resin mixture was applied to 1 mm thick sheets of soft steel. by the electrostatic spray coating method in such a way that, upon subsequent curing at 30 ° C for 10 minutes, a uniform coating having a thickness of approx. 50-60 microns. The powder stability and mechanical properties of the coating are listed in Table V.

Table V

Example 15 14 15

Powder stability E E M

Flexibility P P P

Shock resistance (mm) 611 Hardness (sec) 192 l80 200

Claims (2)

149066 Patent Claims. A thermosetting powder coating material of good powder stability suitable for application by powder spraying or coating in fluidized bed, prepared by melt blending of two resin components (1) and (2) comprising a filament forming component consisting of a polyester resin and a crosslinking resin, extruder, followed by cooling and grinding to powder, wherein the component 1) constituting 75-96 / but preferably 85-92, weight percent of the mixture consists essentially of a solid polyester resin a) made from a Sibasic aromatic carboxylic acid with up to 10 mol% of a multi-base aliphatic carboxylic acid or of a least tribasic aromatic carboxylic acid and one. alko hol component comprising. al) up to 100 mol%, calculated on the entire alcohol component of the polyester, of an alcohol of the general formula 20 R4 R5 · Η- (° Η11χ-0 - ^ - κ3- ^ Λ- ° - (R wherein R and R represent alkylene groups of 2-4 carbon atoms, 3 R represents an alkylidene group of 3 or 4 carbon atoms or a cycloalkylidene group of 6 carbon atoms or a 30 carbonyl group or sulfone group, x and y are numbers of at least 1, the sum of x and y is not greater than 6, and and is a hydrogen atom or an alkyl group of 1-6 carbon atoms, a Wherein R is a straight-chain or branched, saturated or unsaturated hydrocarbon group having 4-20 carbon atoms,