Aqueous semi-finished and primary non-stick coating compositions comprising heterocyclic polymers

Abstract

Provided is an aqueous amine-free coating composition including at least one heterocyclic polymer, wherein the heterocyclic polymer is in the form of powder having a d.sub.90 less than or equal to 20 m. Also provided is an aqueous amine-free non-stick coating composition including such an aqueous composition for a coating, and the respective methods for producing same. Further provided is a method for producing an item on one of the faces of a metal substrate, from at least one layer of coating composition or one layer of non-stick coating composition according to the invention.

Claims

1. Aqueous amine-free coating composition comprising at least one heterocyclic polymer, wherein the heterocyclic polymer is in powder form with a d.sub.90 of less than or equal to 20 m, and wherein the heterocyclic polymer is selected from the group consisting of polyether imides (PEI), polyamide-amic acids, and their mixtures.

2. The coating composition according to claim 1, comprising a maximum of 15% polar aprotic solvent by weight, with respect to the total weight of the coating composition.

3. The coating composition according to claim 1, also comprising at least one aromatic polymer, an acid value of which is equal to 0 mg of KOH/g, and which is in powder form with a d.sub.90 of less than or equal to 20 m, a relative content by weight of the heterocyclic polymer with respect to the aromatic polymer in the coating composition being greater than 50:50 and less than 100:0.

4. The coating composition according to claim 3, in which said aromatic polymer is selected from the group consisting of polyethersulfones (PES), polyether ether sulfones (PEES), polyphenylsulfones (PPSU), polyphenylene sulfides (PPS), polyether ether ketones (PEEK), polyether ketones (PEK), polyether ketone ketones (PEKK), polyether ether ketone ketones (PEEKK), polyether ketone ether ketone ketones (PEKEKK) and mixtures.

5. Aqueous, amine-free, non-stick coating composition, comprising an aqueous coating composition according to claim 1 and at least one fluorocarbon resin.

6. The non-stick coating composition according to claim 5, comprising between 2 and 20% polar aprotic solvent by weight, with respect to the total weight of the non-stick coating composition.

7. The non-stick coating composition according to claim 5, comprising a maximum of 1% toxic polar aprotic solvent by weight, with respect to the total weight of the non-stick coating composition.

8. Process of preparing an aqueous, amine-free coating composition according to claim 1, wherein the process comprises the following steps: a) providing at least one heterocyclic polymer in powder form, the heterocyclic polymer being selected from the group consisting of polyether imides (PEI), polyamide-amic acids, and their mixtures; b) preparing a mixture comprising water and the powder from step (a); and c) grinding of the mixture resulting from step (b) to obtain a ground mixture comprising the heterocyclic polymer in powder form with a d.sub.90 of less than or equal to 20 m.

9. Process of preparing an aqueous, amine-free, non-stick coating composition wherein the process comprises mixing of the aqueous coating composition according to claim 1, with a fluorocarbon resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

Examples

(1) Products

(2) Media Simply degreased, smooth aluminum media

(3) Aqueous Semi-Finished Compositions Triethylamine Heterocyclic polymer resins: Polyamide-amic acid in moist aqueous powder form with 35.5% dry matter (DM), containing less than 5% N-methylpyrrolidone (NMP) by weight, being of food grade and having a degree of polymerization on the order of 8 Polyamide-amic acid in moist aqueous powder form with 90% dry matter (DM), containing less than 5% N-methylpyrrolidone (NMP) by weight, being of food grade and having a degree of polymerization on the order of 10 to 20 Polyamide-imide (PAI) resin with 29% dry matter in N-ethylpyrrolidone (NEP), having a degree of polymerization on the order of 10 to 15 Other polymer resins: Polyethersulfone (PES) resin, micronized grade, having a degree of polymerization of greater than 50 Non-labeled (or in other words, non-toxic, as the term is defined in this invention) polar aprotic solvents: N-formylmorpholine (NFM) Labeled (or in other words, toxic, as the term is defined in this invention) polar aprotic solvents: N-ethylpyrrolidone (NEP)

(4) Aqueous Primary Compositions Non-labeled (or in other words, non-toxic, as the term is defined in this invention) polar aprotic solvents: N-formylmorpholine (NFM) Dimethyl sulfoxide (DMSO) Labeled (or in other words, toxic, as the term is defined in this invention) polar aprotic solvents: N-ethylpyrrolidone (NEP) Filler: Colloidal silica without surface modification, which has a specific surface of approximately 220 m.sup.2/g and which is in the form of an aqueous dispersion of nanoparticles with 30% dry matter Carbon black dispersion at 25% dry matter PTFE dispersion at 60% dry matter Alkylphenol ethoxylate-based non-ionic surfactant system at 13% dry matter Ammonia hydroxide NH.sub.4OH (d=0.9)

(5) Tests

(6) Determining the Dry Matter of an Aqueous Primary or Semi-Finished Composition

(7) Principle

(8) The dry matter of a product is the residual solid portion remaining after evaporation of the volatile materials it contains. The temperature and duration of drying play a major role, as solvents with a high boiling point, monomer fractions, reactive thinners and reaction byproducts (depending on their degree of retention) are very slow to leave the film being formed. It is therefore very important to define, in a very conventional manner, standardized drying conditions that are as close as possible to actual conditions in practice.

(9) Procedure

(10) The procedure to measure this dry matter is as follows: An aluminum dish is weighed: m.sub.0=mass of the dish; 0.5 g to 3 g of the test product is placed in that dish; The filled dish is weighed: m.sub.1=mass of the filled dish; The dish is placed in an oven at 210 C. for two hours; After baking and cooling, the dish is weighed: m.sub.2=mass of the filled dish after baking and cooling; The dry matter is determined by the formula below:
Dry matter=100*[m.sub.2m.sub.0)/(m.sub.1m.sub.0)]

(11) Measurement of the Size and Size Distribution of the Particles by Light Diffraction for Powders in Sizes of Between Approximately 100 nm and Approximately 5 mm

(12) After grinding the products in this invention, the ground powder is collected and its particle size is characterized using a laser diffraction particle size analyzer sold under the commercial name Mastersizer by the company Malvern.

(13) Evaluation of the Adhesion of a Semi-Finished or Primary Layer on a Smooth Aluminum Substrate

(14) A cross-cut test is performed in accordance with ISO standard 2409, followed by an immersion of the coated item for 18 hours (consisting of an alternation of three 3-hour cycles in boiling water and three 3-hour cycles in oil at 200 C.). Then, the non-stick coating is observed for signs of detachment.

(15) The rating is as follows: No square must be detached to obtain a rating of 100 (excellent adhesion); In case of detachment, the rating value is equal to the rating of 100 minus the number of detached squares.

(16) Yellowing Evaluation

(17) After baking, the coated plates are evaluated visually for yellowing by comparison between the plates.

(18) Operating Principle of the Jar Mill (Mechanical Grinding)

(19) Principle

(20) Bead grinding consisting of loading a jar with the sample to be ground and grinding beads, and rotating the jar around its axis at a certain speed. The jar is generally rotated by means of a roller machine. The sample can be ground in dry form or dispersed in an appropriate solvent (e.g. in water, alcohol or a solvent). The dispersion may also contain certain adjuvants (like a dispersing agent or an anti-foaming agent).

(21) Definition of the Main Grinding Parameters

(22) Selection of Grinding Beads (Volume and Diameter(s))

(23) The average diameter of the grinding beads must be appropriate for the size of the particles being ground. The finer the particles, the smaller the diameter of the beads that must be used. The total volume of beads, including the spaces between the beads, will account for approximately 50-60% of the interior volume of the jar. The beads of different sizes are advantageously distributed according to the following proportion by weight, with respect to the total weight of the beads: 25% small beads, 50% medium beads and 25% large beads. The size of the smallest beads is between 2 and 10 mm. Alumina and stabilized zirconia are commonly used as material for the beads.

(24) Volume of Material in the Mill

(25) To limit wear and tear on the grinding beads, the load being ground must cover the load of beads entirely. In general, it will be a volume corresponding to approximately 25% of the volume of the jar.

(26) If the load being ground is a dry powder, the volume of beads will be adjusted after a few minutes of grinding. Because grinding reduces the size of the particles as well as the volume of the spaces between particles, it is necessary to periodically check whether the volume of load being ground is sufficient to cover all of the beads. If this is no longer the case, it is necessary to remove the excess beads in order to limit contamination of the powder as much as possible.

(27) The duration of the grinding depends on the nature of the polymer resin being ground and on the desired final particle size.

(28) Operating Principle of the Discontimill Grinding Mill

(29) This grinding is a mechanical grinding that consists of reducing the size of the particles and grains of the different types of materials, during which the suspension of the particles and grains is maintained under refrigeration.

(30) The grinding operations are performed with a planetary mill, which consists of a disc, attached to which are two grinding jars, each having a volume of 45 mL and being able to hold up to 7 grinding beads that are 15 mm in diameter. The jars and the grinding beads are made of zirconium oxide, a material that is known for its very high resistance to impact and wear, enabling grinding for extended durations.

(31) The grinding system operates by rotating the disc holding the jars around their own axes. The rotation speed is the same for the tray and the jars, varying from 100 rev/min to 800 rev/min. However, the directions of rotation are opposite, so as to generate opposing centrifugal forces.

Example 1: Aqueous Semi-Finished Composition According to the Invention (SF1)

(32) Preparation of an Aqueous Polymer-Based, Amine-Free, Semi-Finished Composition (SF1)

(33) An aqueous semi-finished composition (SF1) is produced with the following components, the respective quantities of which are listed below:

(34) TABLE-US-00001 Polyamide-amic acid (35.5% DM) 616.0 g Demineralized water 726.3 g TOTAL 1342.3 g

(35) To make the aqueous semi-finished composition (SF1), a 3-liter jar mill system is used to obtain a paste consisting of a stable suspension of polyamide-amic acid particles in water, the final particle size of which is significant for spray coating and obtaining adhesion properties in the resulting coating.

(36) The process is as follows: The polyamide-amic acid powder, the initial particle size of which varies from a few hundred microns to mm, is placed into the jar; then, Demineralized water is added; The jar is kept at room temperature with the mixture thus obtained and the beads on rollers for the duration necessary and sufficient to reduce the size of the polyamide-amic acid particles.

(37) The proportion of toxic polar aprotic solvent in the composition (SF1), which is NMP, is less than 2.3% by weight, with respect to the total weight of the composition.

(38) The properties of the aqueous composition (SF1) thus obtained are as follows: Theoretical dry matter: 16.3% Dry matter measured in the composition: 16.2% This is a suspension that is creamy white in color. The pH of this composition is between 3 and 4. Viscosity (in a 2.5-mm flow cup according to standard DIN EN ISO 2433): 45 sec; the composition (SF1) is still stable after 60 days of storage, and the change in viscosity over time is less than 20%. A light diffraction particle sizing measurement using the Mastersizer laser particle size analyzer shows that a main peak is reached at d.sub.50, centered on an average diameter of between 5 and 6 m and a d.sub.90 of 19 m, which confirms that all of the powder has been placed in suspension.

Example 2: Aqueous Semi-Finished Composition According to the Invention (SF2)

(39) Preparation of an Aqueous, Heterocyclic Polymer-Based, Amine-Free, Semi-Finished Composition (SF2) with Non-Labeled Polar Aprotic Solvent.

(40) An aqueous semi-finished composition (SF2) is produced with the following components, the respective quantities of which are listed below:

(41) TABLE-US-00002 Polyamide-amic acid (35.5% DM) 616.0 g N-formylmorpholine 130.0 g Demineralized water 596.3 g TOTAL 1342.3 g

(42) The procedure to produce the aqueous semi-finished composition (SF2), is the same as in Example 1.

(43) The proportion of toxic polar aprotic solvent in the composition (SF2), which is NMP, is less than 2.3% by weight, with respect to the total weight of the composition.

(44) The properties of the aqueous composition (SF2) thus obtained are as follows: Theoretical dry matter: 16.3% Dry matter measured in the composition: 16.2% This is a suspension that is creamy white in color. The pH of this composition is between 3 and 4. Viscosity (in a 2.5-mm flow cup according to standard DIN EN ISO 2433): 50 sec; the composition (SF2) is still stable after 60 days of storage, and the change in viscosity over time is less than 20%. A light diffraction particle sizing measurement using the Mastersizer laser particle size analyzer shows that a main peak is reached at d.sub.50, centered on an average diameter of between 5 and 6 m and a d.sub.90 of 19 m, which confirms that all of the powder has been placed in suspension.

Example 3: Aqueous Semi-Finished Composition According to the Invention (SF3)

(45) Preparation of an Aqueous, Heterocyclic Polymer-Based, Amine-Free, Semi-Finished Composition According to the Invention (SF3) with Labeled Polar Aprotic Solvent.

(46) An aqueous semi-finished composition (SF3) is produced with the following components, the respective quantities of which are listed below:

(47) TABLE-US-00003 Polyamide-amic acid (35.5% DM) 616.0 g N-ethylpyrrolidone 142.0 g Demineralized water 584.0 g TOTAL 1342.0 g

(48) The procedure to produce the aqueous, semi-finished composition (SF3), is the same as in Example 1.

(49) The properties of the aqueous composition (SF3) thus obtained are as follows: Theoretical dry matter: 16.3% Dry matter measured in the composition: 16.2% This is a suspension that is creamy white in color. The pH of this composition is between 3 and 4. Viscosity (in a 2.5-mm flow cup according to standard DIN EN ISO 2433): 50 sec; the composition (SF3) is still stable after 60 days of storage, and the change in viscosity over time is less than 20%. A light diffraction particle sizing measurement using the Mastersizer laser particle size analyzer shows that a main peak is reached at d.sub.50, centered on an average diameter of between 5 and 6 m and a d.sub.90 of 19 m, which confirms that all of the powder has been placed in suspension.

Example 4: Aqueous Semi-Finished Composition According to the Invention (SF4)

(50) Preparation of an Aqueous, Heterocyclic Polymer-Based, Amine-Free, Semi-Finished Composition (SF4) with Non-Labeled Polar Aprotic Solvent.

(51) An aqueous semi-finished composition (SF4) is produced with the following components, the respective quantities of which are listed below:

(52) TABLE-US-00004 Polyamide-amic acid (90% DM) 131.3 g N-formylmorpholine 68.0 g Demineralized water 485.0 g TOTAL 684.3 g

(53) The procedure to produce the aqueous semi-finished composition (SF4) is the same as in Example 1.

(54) The proportion of toxic polar aprotic solvent in the composition (SF4), which is NMP, is less than 1% by weight, with respect to the total weight of the composition.

(55) The properties of the aqueous composition (SF4) thus obtained are as follows: Theoretical dry matter: 17.3% Dry matter measured in the composition: 18.0% This is a suspension that is creamy white in color. The pH of this composition is between 3 and 4. Viscosity (in a 2.5-mm flow cup according to standard DIN EN ISO 2433): 59 sec; the composition (SF4) is still stable after 60 days of storage, and the change in viscosity over time is less than 20%. A light diffraction particle sizing measurement using the Mastersizer laser particle size analyzer shows that a main peak is reached at d.sub.50, centered on an average diameter of between 5 and 6 m and a d.sub.90 of 19 m, which confirms that all of the powder has been placed in suspension.

Comparative Example 1: Aqueous Semi-Finished Composition (SFC1)

(56) Preparation of an Aqueous, Heterocyclic Polymer-Based, Semi-Finished Composition (SFC1) with One Amine and Labeled Polar Aprotic Solvent.

(57) An aqueous semi-finished composition (SFC1) is produced with the following components, the respective quantities of which are listed below:

(58) TABLE-US-00005 PAI resin at 29% dry matter in NEP 327.9 g N-ethylpyrrolidone 117.7 g Triethylamine 32.8 g Demineralized water 521.6 g TOTAL 1000.0 g

(59) Putting the PAI in solution comprises a step for transitioning to the aqueous phase by obtaining a polyamide-amic acid salt. This step is performed in a Discontimill brand bead mill, at room temperature in the presence of amine.

(60) In the composition (SFC1), the weight ratio of water to amine is approximately 94/6. The percentage by weight of amine in the composition (SFC1) is 3.3%.

(61) The weight ratio of polyamide-imide to amine is approximately 74/26. The proportion of polar aprotic solvent in the composition (SFC1) is 35.0% by weight, with respect to the total weight of the composition (SFC1).

(62) The properties of the aqueous composition (SFC1) thus obtained are as follows: Theoretical dry matter: 9.5% Dry matter measured in the composition: 9.3% This is a solution that is translucent yellow in color and very viscous. Viscosity (in a 4-mm flow cup according to standard DIN EN ISO 2433/ASTM D5125): 130 sec; A light diffraction particle sizing measurement using the Mastersizer laser particle size analyzer shows that the particle size is much below 1 m, which confirms that all of the polyamide-imide resin has been placed in emulsion.

Comparative Example 2: Aqueous Semi-Finished Composition (SFC2)

(63) Preparation of an Aqueous, Heterocyclic Polymer-Based, Semi-Finished Composition (SFC2) with a d.sub.90 of Greater than 40 m, without Polar Aprotic Solvent or Amine.

(64) An aqueous semi-finished composition (SFC2) is produced with the following components, the respective quantities of which are listed below:

(65) TABLE-US-00006 Polyamide-amic acid (35.5% DM) 458.9 g Demineralized water 541.1 g TOTAL 1000.0 g

(66) To produce the aqueous semi-finished composition (SFC2), the same procedure is followed as in Example 1 according to the invention.

(67) The properties of the aqueous composition (SFC2) thus obtained are as follows: Theoretical dry matter: 16.3% Dry matter measured in the composition: 16.2% This is a solution that is creamy white in color. The pH of this composition is between 3 and 4. The composition (SFC2) settles in one day. A light diffraction particle sizing measurement using the Mastersizer laser particle size analyzer shows that a main peak is reached at d.sub.50, centered on an average diameter of approximately 20 m and a d.sub.90 of approximately 48 m.

Comparative Example 3: Aqueous Semi-Finished Composition (SFC3)

(68) Preparation of an Aqueous, Heterocyclic Polymer-Based, Semi-Finished Composition (SFC3), without Polar Aprotic Solvent and with One Amine.

(69) An aqueous semi-finished composition (SFC3) is produced with the following components, the respective quantities of which are listed below:

(70) TABLE-US-00007 Polyamide-amic acid (35.5% DM) 149.0 g Triethylamine 26.0 g Demineralized water 710.0 g TOTAL 885.0 g

(71) The procedure to produce the aqueous semi-finished composition (SFC3), is as follows: The water, polyamide-amic acid powder and amine are placed into a reactor; The resulting mixture is agitated, then heated at a temperature of between 50 and 85 C.; The weight ratio of water to amine is approximately 97/3. The percentage by weight of amine in the composition (SFC3) is 2.9%. The proportion of polar aprotic solvent in the composition (SFC3) is less than 1% by weight, with respect to the total weight of the composition.

(72) The properties of the aqueous composition (SFC3) thus obtained are as follows: Theoretical dry matter: 6.0% Dry matter measured in the composition: 6.1% This is a very fluid emulsion that is opalescent white in color. The pH of this composition is between 10 and 11. Viscosity (in a 2.5-mm flow cup according to standard DIN EN ISO 2433/ASTM D5125): 50 sec; after aging at 40 C., the semi-finished composition (SFC3) is still stable after 60 days of storage, and the change in viscosity over time is less than 20%. A light diffraction particle sizing measurement using the Mastersizer laser particle size analyzer shows that the particle size is well below 1 m, which confirms that all of the polyamide-amic acid resin has been placed in emulsion.

Example 5: Aqueous Primary Composition According to the Invention (P1)

(73) Preparation of an Aqueous Primary Composition According to the Invention (P1) Based on the Semi-Finished Composition (SF1) in Example 1.

(74) An aqueous primary composition (P1) for adhesion is produced with the following components, the respective quantities of which are listed below:

(75) TABLE-US-00008 PTFE dispersion 33.3 g Carbon black dispersion 3.8 g Semi-finished composition SF1 30.0 g (16.3% dry matter) N-formylmorpholine 9.9 g Non-ionic surfactant system 5.6 g Colloidal silica 12.0 g NH.sub.4OH 0.8 g Demineralized water 4.6 g TOTAL 100.0 g

(76) Regarding the non-toxic polar aprotic solvent in the composition (P1), the NFM content is 9.9% by weight, with respect to the total weight of the composition (P1).

(77) Regarding the toxic polar aprotic solvent in the composition (P1), the NMP content is less than 0.7% by weight, with respect to the total weight of the composition (P1); the NMP comes from the semi-finished composition (SF1).

(78) The proportion of fluorinated resin in the dry primary composition (P1) is on the order of 66.3% by weight, with respect to the total dry weight of the composition (P1). The relative content by weight of polyamide-amic acid/PTFE is approximately 20:80.

(79) The properties of the primary composition (P1) thus obtained are: Theoretical dry matter in the composition: 30.1% Viscosity (in a 2.5-mm flow cup according to standard DIN EN ISO 2433/ASTM D5125): 48 sec.

Example 6: Aqueous Primary Composition According to the Invention (P2)

(80) Preparation of an Aqueous Primary Composition According to the Invention (P2) Based on the Aqueous Semi-Finished Composition (SF2) in Example 2.

(81) An aqueous primary composition (P2) for adhesion is produced with the following components, the respective quantities of which are listed below:

(82) TABLE-US-00009 PTFE dispersion 36.1 g Carbon black dispersion 4.1 g Semi-finished composition SF2 34.1 g (16.3% dry matter) Non-ionic surfactant system 6.0 g Colloidal silica 13.0 g NH.sub.4OH 0.8 g Demineralized water 5.9 g TOTAL 100.0 g

(83) Regarding the non-labeled polar aprotic solvent in the composition (P2), the NFM content is 3.3% by weight, with respect to the total weight of the composition (P2); the NFM comes from the semi-finished composition (SF2).

(84) Regarding the labeled polar aprotic solvent in the composition (P2), the NMP content is less than 0.8% by weight, with respect to the total weight of the composition (P2); the NMP comes from the semi-finished composition (SF2).

(85) The proportion of fluorinated resin in the dry primary composition (P2) is on the order of 66.6% by weight, with respect to the total dry weight of the composition (P2). The relative content by weight of polyamide-amic acid/PTFE is approximately 20:80.

(86) The properties of the primary composition (P2) thus obtained are as follows: Theoretical dry matter in the composition: 32.9% Viscosity (in a 2.5-mm flow cup according to standard DIN EN ISO 2433/ASTM D5125): 51 sec.

Example 7: Aqueous Primary Composition According to the Invention (P3)

(87) Preparation of an Aqueous Primary Composition According to the Invention (P3) Based on the Semi-Finished Composition (SF3) in Example 3.

(88) An aqueous primary composition (P3) for adhesion is produced with the following components, the respective quantities of which are listed below:

(89) TABLE-US-00010 PTFE dispersion 33.2 g Carbon black dispersion 3.8 g Semi-finished composition SF3 29.1 g (16.3% dry matter) Dimethyl sulfoxide 10.1 g Non-ionic surfactant system 5.6 g Colloidal silica 11.9 g NH.sub.4OH 0.8 g Demineralized water 5.5 g TOTAL 100.0 g

(90) Regarding the non-labeled polar aprotic solvent in the composition (P3), the DMSO content is 10.1% by weight, with respect to the total weight of the composition (P3).

(91) Regarding the labeled polar aprotic solvents in the composition (P3), the NMP content is less than 0.7% by weight, and the NEP content is 3.1% by weight with respect to the total weight of the composition (P3); the NMP and the NEP come from the semi-finished composition (SF3).

(92) The proportion of fluorinated resin in the dry primary composition (P3) is on the order of 66.6% by weight, with respect to the total dry weight of the composition (P3). The relative content by weight of polyamide-amic acid/PTFE is approximately 20:80.

(93) The properties of the primary composition (P3) thus obtained are as follows: Theoretical dry matter in the composition: 30.0% Viscosity (in a 2.5-mm flow cup according to standard DIN EN ISO 2433/ASTM D5125): 49 sec.

Example 8: Aqueous Primary Composition According to the Invention (P4)

(94) Preparation of an Aqueous Primary Composition According to the Invention (P4) Based on the Semi-Finished Composition (SF2) in Example 2 and a Semi-Finished Composition Comprising PES.

(95) First, an aqueous, PES-based, semi-finished composition is produced with the following components, the respective quantities of which are listed below:

(96) TABLE-US-00011 Polyethersulfone (100% dry matter) 119.1 g Demineralized water 625.0 g TOTAL 744.1 g

(97) The aqueous, PES-based, semi-finished composition is produced using an initial polyethersulfone powder, which has a particle size ranging from 20 m to 10 mm, and more specifically, a d.sub.90 of between 40 and 60 m and a d.sub.50 of between 20 and 40 m.

(98) Placing the PES in suspension comprises a grinding step, the grinding being done in a Discontimill brand bead mill at room temperature to reduce the size of the PES particles.

(99) The process is as follows: The polyethersulfone powder is placed into the mill; then, The demineralized water is added to the mill; and finally, The grinding step is performed.

(100) The properties of the aqueous, PES-based composition thus obtained are as follows: Theoretical dry matter in the composition: 16.0% Dry matter measured in the composition: 16.2% This is a suspension that is opaque white in color. The pH of this composition is between 6 and 7. Viscosity (in a 4-mm flow cup according to standard DIN EN ISO 2433/ASTM D5125): >30 sec: after aging at 40 C., the PES-based composition is still stable after 60 days of storage, and the change in viscosity over time is less than 20%. A light diffraction particle sizing measurement using the Mastersizer laser particle size analyzer shows that a main peak is reached at d.sub.50, centered on an average diameter of 5 to 6 m and a d.sub.90 of 19 m, which confirms that all of the powder has been placed in suspension.

(101) An aqueous primary composition (P4) for adhesion is produced with the following components, the respective quantities of which are listed below:

(102) TABLE-US-00012 PTFE dispersion 37.6 g Carbon black dispersion 2.8 g Semi-finished composition SF2 21.9 g (16.3% dry matter) PES-based semi-finished composition 12.5 g (16.0% dry matter) N-formylmorpholine 7.2 g Non-ionic surfactant system 4.2 g Colloidal silica 9.0 g NH.sub.4OH 0.5 g Demineralized water 4.3 g TOTAL 100.0 g

(103) The weight ratio of polyamide-amic acid to polyethersulfone is approximately 64/36.

(104) Regarding the non-labeled polar aprotic solvent in the composition (P4), the NFM content is 9.3% by weight, with respect to the total weight of the composition (P4).

(105) Regarding the labeled polar aprotic solvents in the composition (P4), the NMP content is less than 0.5% by weight, with respect to the total weight of the composition (P4); the NMP comes from the semi-finished composition (SF2).

(106) The proportion of fluorinated resin in the dry primary composition (P4) is on the order of 70% by weight, with respect to the total dry weight of the composition (P4). The relative content by weight of polyamide-amic acid and polyethersulfone/PTFE is approximately 20:80.

(107) The properties of the primary composition (P4) thus obtained are as follows: Theoretical dry matter in the composition: 32.1% Viscosity (in a 2.5-mm flow cup according to standard DIN EN ISO 2433/ASTM D5125): 49 sec

Example 9: Aqueous Primary Composition According to the Invention (P5)

(108) Preparation of an Aqueous Primary Composition According to the Invention (P5) Based on the Semi-Finished Composition (SF4) in Example 4.

(109) An aqueous primary composition (P5) for adhesion is produced with the following components, the respective quantities of which are listed below:

(110) TABLE-US-00013 PTFE dispersion 33.3 g Carbon black dispersion 3.8 g Semi-finished composition SF4 28.5 g (17.3% dry matter) N-formylmorpholine 9.9 g Non-ionic surfactant system 5.6 g Colloidal silica 12.0 g NH.sub.4OH 1.6 g Demineralized water 5.3 g TOTAL 100.0 g

(111) Regarding the non-toxic polar aprotic solvent in the composition (P5), the NFM content is 12.7% by weight, with respect to the total weight of the composition (P5).

(112) Regarding the toxic polar aprotic solvent in the composition (P5), the NMP content is less than 0.3% by weight, with respect to the total weight of the composition (P5); the NMP comes from the semi-finished composition (SF4).

(113) The proportion of fluorinated resin in the dry primary composition (P5) is on the order of 66.2% by weight with respect to the total dry weight of the composition (P5). The relative content by weight of polyamide-amic acid/PTFE is approximately 20:80.

(114) The properties of the primary composition (P5) thus obtained are as follows: Theoretical dry matter in the composition: 30.2% Viscosity (in a 2.5-mm flow cup according to standard DIN EN ISO 2433/ASTM D5125): 58 sec

Comparative Example 4: Aqueous Primary Composition (PC1)

(115) Preparation of an Aqueous Primary Composition (PC1) Based on the Semi-Finished Composition (SF1) in Comparative Example 1.

(116) An aqueous primary composition (PC1) for adhesion is produced with the following components, the respective quantities of which are listed below:

(117) TABLE-US-00014 PTFE dispersion 30.5 g Carbon black dispersion 3.5 g Semi-finished composition SFC1 47.2 g (9.5% dry matter) Non-ionic surfactant system 5.1 g Colloidal silica 11.0 g NH.sub.4OH 1.4 g Demineralized water 1.3 g TOTAL 100.0 g

(118) The proportion of amine in the primary composition (PC1) is 1.5% by weight with respect to the total weight of the composition (PC1); the amine comes from the semi-finished composition (SFC1).

(119) Regarding the labeled polar aprotic solvent in the composition (PC1), the NEP content is 16.5% by weight, with respect to the total weight of the composition (PC1); the NEP comes from the semi-finished composition (SFC1).

(120) The proportion of fluorinated resin in the dry primary composition (PC1) is on the order of 66.6% by weight, with respect to the total dry weight of the composition (PC1). The relative content by weight of polyamide-amic acid/PTFE is approximately 20:80.

(121) The properties of the primary composition (PC1) thus obtained are as follows: Theoretical dry matter in the composition: 27.6% Viscosity (in a 2.5-mm flow cup according to standard DIN EN ISO 2433/ASTM D5125): 55 sec.

Comparative Example 5: Aqueous Primary Composition (PC2)

(122) Preparation of an Aqueous Primary Composition (PC2) Based on the Semi-Finished Composition (SFC2) in Comparative Example 2.

(123) An aqueous primary composition (PC2) for adhesion is produced with the following components, the respective quantities of which are listed below:

(124) TABLE-US-00015 PTFE dispersion 36.9 g Carbon black dispersion 4.2 g Semi-finished composition SFC2 33.6 g (16.3% dry matter) N-ethylpyrrolidone 2.6 g Non-ionic surfactant system 6.2 g Colloidal silica 13.3 g NH.sub.4OH 1.7 g Demineralized water 1.5 g TOTAL 100.0 g

(125) Regarding the labeled polar aprotic solvents in the composition (PC2), the NMP content is less than 0.8% by weight, and the NEP content is 2.6% by weight, with respect to the total weight of the composition (PC2); the NMP comes from the semi-finished composition (SFC2).

(126) The proportion of fluorinated resin in the dry primary composition (PC2) is on the order of 66.6% by weight with respect to the total dry weight of the composition (PC2). The relative content by weight of polyamide-amic acid/PTFE is approximately 20:80.

(127) The properties of the primary composition (PC2) thus obtained are as follows: Theoretical dry matter in the composition: 33.5% Viscosity (in a 2.5-mm flow cup according to standard DIN EN ISO 2433/ASTM D5125): 55 sec.

Comparative Example 6: Aqueous Primary Composition (PC3)

(128) Preparation of an Aqueous Primary Composition (PC3) Based on the Semi-Finished Composition (SF1) in Example 1.

(129) An aqueous primary composition (PC3) for adhesion is produced with the following components, the respective quantities of which are listed below:

(130) TABLE-US-00016 PTFE dispersion 37.5 g Carbon black dispersion 4.3 g Semi-finished composition SF1 34.1 g (16.3% dry matter) Non-ionic surfactant system 6.3 g Colloidal silica 13.5 g NH.sub.4OH 1.8 g Demineralized water 2.5 g TOTAL 100.0 g

(131) Regarding the labeled polar aprotic solvent in the composition (PC3), the NMP content is less than 0.8% by weight with respect to the total weight of the composition (PC3); the NMP comes from the semi-finished composition (SF1).

(132) The proportion of fluorinated resin in the dry primary composition (PC3) is on the order of 66.6% by weight, with respect to the total dry weight of the composition (PC3). The relative content by weight of polyamide-amic acid/PTFE is approximately 20:80.

(133) The properties of the primary composition (PC3) thus obtained are as follows: Theoretical dry matter in the composition: 34.0% Viscosity (in a 2.5-mm flow cup according to standard DIN EN ISO 2433/ASTM D5125): 51 sec.

Comparative Example 7: Aqueous Primary Composition (PC4)

(134) Preparation of an Aqueous Primary Composition (PC4) Based on the Semi-Finished Composition (SFC3) in Comparative Example 3.

(135) An aqueous primary composition (PC4) for adhesion is produced with the following components, the respective quantities of which are listed below:

(136) TABLE-US-00017 PTFE dispersion 23.6 g Carbon black dispersion 2.7 g Semi-finished composition SFC3 59.2 g (6% dry matter) Non-ionic surfactant system 4.0 g Colloidal silica 8.5 g NH.sub.4OH 1.2 g Demineralized water 0.8 g TOTAL 100.0 g

(137) The proportion of amine in the primary composition (PC4) is 1.7% by weight, with respect to the total weight of the composition (PC4); the amine comes from the semi-finished composition (SFC3).

(138) Regarding the labeled polar aprotic solvent in the composition (PC4), the NMP content is less than 0.5% by weight, with respect to the total weight of the composition (PC4); the NMP comes from the semi-finished composition (SFC3).

(139) The proportion of fluorinated resin in the dry primary composition (PC4) is on the order of 66.6% by weight, with respect to the total dry weight of the composition (PC4). The relative content by weight of polyamide-amic acid/PTFE is approximately 20:80.

(140) The properties of the primary composition (PC4) thus obtained are as follows: Theoretical dry matter in the composition: 21.4% Viscosity (in a 2.5-mm flow cup according to standard DIN EN ISO 2433/ASTM D5125): 41 sec.

(141) Results of the Tests Performed

(142) The aqueous semi-finished and primary compositions described above are listed in Table 1 below. The coatings obtained from these various compositions are subject to adhesion testing of the primary composition on the substrate and to coloration testing.

(143) The coloration of the coating, evaluated visually, makes it possible to verify that the formulas produced according to the invention show acceptably little to no yellowing in comparison to the traditional formulations that include amines.

(144) Coating adhesion is ensured when the size of the powder is compliant with the invention.

(145) TABLE-US-00018 TABLE 1 SEMI- Semi- SF1 SF2 SF3 SF2 + SF4 SFC1 SFC2 SF1 SFC3 FIN- finished PES- ISHED compo- based SF sition Example Ex. 1 Ex. 2 Ex. 3 Ex. 4 Comp. Comp. Ex. 1 Comp. Ex. 1 Ex. 2 Ex. 3 Resin PAI PAI PAI PAI PAI PAI PAI PAI PAI type powder powder powder powder + powder solvent powder powder powder PES powder Amine 0 0 0 0 0 TEA = 0 0 TEA = type 3.3% 2.9% Resin d.sub.90 <20 m d.sub.90 <20 m d.sub.90 <20 m d.sub.90 <20 m d.sub.90 <20 m Emulsion d.sub.90 <20 m d.sub.90 <20 m emulsion particle d.sub.50 <10 m d.sub.50 <10 m d.sub.50 <10 m d.sub.50 <10 m d.sub.50 <10 m d.sub.50 <10 m d.sub.50 <10 m size Polar NMP <2.3% NMP <2.3% NMP <2.3% In SF2 NMP <1% NEP = NMP <2.3% NMP <2.3% NMP <1% aprotic NFM = NEP = NMP <2.3% NFM = 35% solvent 9.7% 10.6% NFM = 9.9% 9.7% PRI- Primary P1 P2 P3 P4 P5 PC1 PC2 PC3 PC4 MARY compo- sition Example Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 Comp. Comp. Comp. Comp. Ex. 4 Ex. 5 Ex. 6 Ex.7 Non- NFM = NFM = DMSO = NFM = NFM = 0 0 0 0 labeled 9.9% 3.3% 10.1% 9.3% 12.7% polar aprotic solvent Labeled NMP <0.7% NMP <0.8% NMP <0.7% NMP <0.5% NMP <0.3% NEP = NMP <0.8% NMP <0.8% NMP <0.5% polar NEP = 16.5% NEP = aprotic 3.1% 2.6% solvent TESTS Coating LOW LOW LOW VERY LOW Significant LOW LOW Significant coloration LOW unacceptable unacceptable yellowing yellowing Adhesion Excellent Excellent Good Excellent Excellent Excellent Poor Poor Excellent test on smooth Al substrate