Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
57~
This application relates to a coagulation coating
process which is useful for applying coatings to various sub-
strates.
) More particularly, the process relates to the
deposition of organic resins, which may be admixed with reac-
tive or nonreactive particles, by coagulation on the surface
of various substrates, followed by curing, aging or other
treatments to provide the desired properties for the coating.
The process may be employed to provide numerous types of
coatings on many different substrates or articles. For
example, coatings may be applied to: (1) improve corrosion
and oxidakion resistance at ambient and elevated temperatures
of metal substrates such as turbine engine components, auto-
motive exhaust train components,and automotive interior and
exterlor components; (2) reduce or eliminate water and/or
solvent permeability of porous materials such as wood, un-
glazed ceramics, paper and fabrics; (3) improve solvent
resistance of organic surfaces; (4) enhance the decorative
value of metallic and nonmetallic surfaces such as on the
interior and exterior of automobiles, (5) provide electrical
insulation on conductive surfaces; (6) provide conductive
sur~aces on nonconductive substrates; (7) provide lubricants
on metallic and nonmetallic surfaces such as graphite lubri-
cant coatings for forged articles; and (8) provide acid and
alkali resistant glass coatings for items such as water
heaters.
Methods for coating surfaces by coagulation from
both acid and alkaline aqueous dispersions of polymeric
particles are known in the art. Representative methods of
coagulation coating from an acidic aqueous solution are
discussed in U~S. Patents 3,709,743 and 3,7913431. U.S. Patent
No. 3,791,431 discusses a method wherein an organic coating
787
is applied to a metallic surface by immersing the surface in
an acidic aqueous coating composition containing particles
of an organic coating-forming material. The organic material
may be in either dissolved, emulsified, or dispersed form.
The coating composition is acidic as a result of the inclu-
sion of an acidic oxidizing agent such as a mineral acid.
This acidic oxidizing agent attacks the metal substrate
causing metal ions to be dissolved from the surface. These
ions cause the coating-forming material to be unstable in
the region of the surface and, as a result, it deposits on
the surface. One of the problems with this type of process
is that the coating composition tends to become unstable as
metal ions build up with repeated use. U.S. Patent No. 3,791,431
seeks to remedy this problem by removing metal ions from the
composition or adding a mater~al to render the metal ions
innocuous. The necessity of this additional step~ of courseg
complicates the process and adds a further parameter which
must be monitored and controlled during processing.
The process of ~.S. Patent No. 3,709,743 , which is
slmilar to the above-discussed process also employs an oxi-
dizing acid which attacks a metallic substrate causing metal
ions to form which, in turn, cause coagulation of an organic
coating. Thus, this suffers the same disadvantages with
respect to metallic ion build-up. The procSess of U.S. Patent N~.
3,7~r743 also employs an~q~us ~h CGnt~n~ an anicnic surfac~nt
stabilized emulsion of the synthetic resinous ~ilm-forming
composition and, as a result, suffers from certain other
serious deficiencies which are treated more thoroughly ln the
dissussion of prior art alkaline bath coagulation methods set
3~ forth below. Of course, it will also be noted that both of
the acidic bath embodiments disclosed in the above referenced
.
s~ ~ - 3 -
~95787
patents are useful only to coat certain metallic substrates.
~It should also be noted that both of these prior art pro-
cesses also are unsuitable for the application of aluminide
coatings because of the presence of strong oxidizing acids.
~ .
- 3a -
5'7~7
1 Many prior art references disclose applying coat-
2 ings such as natural latex or synthetic latices by coagula-
3 tion from alkaline aqueous dispersions of essentially
, 4 insoluble particles. U.S. Patent Nos. 3,411,982 and
3,856,561 teach processes which are representative of these
6 alkaline bath processes. These processes involve deposition
7 of synthetic latices, which may contain small amounts of
8 acrylic or methacrylic acid and which can be used alone or
9 in combination with styrene, polystyrene, polyethylene
chloride, polyvinyl chloride, polyvinyledene chloride and
11 polyacrylate resins, and vinyl chloride butyl acrylate
12 copolymers, by polyvalent destablization of stabilized
13 polymers. In that process the polymers are anionically
14 stabilized or stabilized with anionic surfactants in com-
bination with nonionic surfactants or reaction products of
16 such. Soluble alkalies such as potassium hydroxide or
17 ammonium hydroxide are also added in some cases to control
18 pH and/or to assist the stabilizer in producing emulsions
19 of the particles in water.
The presence of such anionic and nonionic sur-
21 factants or mixtures of nonionic and anionic surfactants or
22 reaction products of such can have a deleterious ef~ect on
23 the final properties of coagulated polymer coatings by
24 building up in the bath and~or in the coagulated film.
Another disadvantage of such processes is the tendency of
26 the emulsions to be unstable in the presence of chemically
27 reactive substances such as pigments that release ions into
28 solution and cause coagulation of dispersed film former.
29 Still another disadvantage of such processes is thal the
~95787
dispersed latices have a tendency to swell in the presence
of various solvenks.
The improved proce~sof this invention, which over-
comes the deficiencies of prior art techniques, involves
the controlled coagulation of water soluble polymers along
with, if desired, pigments which may be either inert or
chemically reactive. The coagulation or desolubilization
o~ the chemically soluble or solubilized polymer is effected
as a result of contact of the polymer with a coagulating
compound which is applied to the substrate to be coated
prior to exposure of the substrate in the aqueous bath con-
taining the polymer.
The improved process has many advantages including:
1. A high degree of bath stability;
2. Uniformiky and homogeneity of coagulated film;
3. Elimination of the use of anionic or nonionic
stabilizers or reaction products thereof and/or
mixtures of such stabllizers to provide disper-
sions of polymers in water;
4. Improved film thickness control;
5. Minimization of polymer swelling, thus avoiding
coagulation through dehydration;
6. Minimization of coagulation by reactive pigments
such as finely divided powders of aluminum,
catalytic platinum~ lead pigment extenders alkali
earth silicates and borates, etc.;
lass7s7
1 7. Improved corrosion protection for metallic sur-
2 faces especially when the polymers are: (a)
3 coagulated as a mixture of corrosion inhibiting
4 pigments and pigment extenders where the resin
comprises the bulk of said mixture (commonly
6 referred to as paints); ~b) coagulated onto
7 metal surfaces as a mixture of a minor amount
8 of polymer and a ma~or amount of metal pigments
9 and heat treated at a temperature below the melting point
of the metal particles in an atmosphere essentially
11 inert to said particles to vaporize or thermally
12 degrade the polymer so that metal particles may
13 then be heated so as to react with and modify the
14 metal substrate; (c) coagulated as a mixture of a
minor amount of polymer and a major amount of
16 refractory or ceramic enamel frit, and heat
17 treated in an oxidizing atmosphere at temperatures
18 above the point where the polymer vaporizes or
19 thermally degrades so that the frit particles may
then be fused with said metal substrate to form an
21 adherent acid, alkali, high temperature or elec-
22 trically resistant coating depending upon char-
23 acteristics of the frit;
24 8. Improved water impermeability of porous surfaces
such as wood (laminated or unlaminated) by coagula-
26 tion of a coating consisting of a mixture of a major
27 amount of polymer and a minor amount of pigments so
28 that when such coatings are heated below the thermal
29 flash point of the coated article and essentially
-- 6 --
787
: at the cure temperature of the coagulated coating,
an adherent water resistant coating is formed;
and
9. Limits the use of toxic and/or corrosive oxidizing
and reducing mineral acids such as hydrochloric,
sulfuric, nitric, chromic, hydrofluoric, hydro-
bromic, oxychloroacetic, chloroacetic acid, etc.,
and low molecular weight organic acids, as coagu-
lants.
10These and other advantages will be more re~dily
apparent after reading the ~ollowing detailed description
of the invention.
The process claimed in this application relates to
a coating process which comprises (A) providing the sub-
strate to be coated with a dry coagulating compound surface;
and (B) exposing said substrate to an aqueous composition !,
which, except for solvents, reactive and non-reactive pig-
ments and other non-reactive particulate material, consists
essentially of an organic film-forming material consisting
essentially of (i) at least fifty (50) weight percent of a
chemically ionizable organic film former which (a) has at
least 12 carbon atoms per molecule; (b) is at least partially
ionized such that it is substantially soluble in said aqueous
co~position; and (c) coagulates and deposits in the presence
of said coagulating compound; and (ii) a remainder of an
organic film-former which is not chemically ionizable.
In one preferred embodiment of the process the
coagulating compound employed has a pH of less than 7.0
and the organic film-former is a synthetic polycarboxylic
acid resin which ~i~ is at least partially neutralized with a
- 7 -
.~ .
~ 5'787
1 water soluble base, (ii) advantageously has an electrical
2 equivalent weight between about 1,000 and about 20,000, and
3 ~iii) advantageously has an acid number between about 30
4 and about 300.
In a second pre~erred embodiment of the process,
6 the coagulating compound employed has a pH greater than 7.0
7 and the organic film-former is selected ~rom basic monomers
8 and resins having one or more nitrogens in their molecular
9 structure and is at least partially neutralized by a water
soluble acid compound (including a compound which can pro-
11 duce an acid compound when recited with a basic resin)~
12 Coagulating Compounds
13 In accordance with the process o~ the invention,
14 the substrate to be coated is ~irst provided with a dry
coagulating compound surface. This can be accomplished in
16 a number o~ ways which will be apparent to those skilled in
17 the art. For example, the compound or mixture of compounds
18 may be dissolved in suitable volatile solvents or mixtures
19 o~ such suitable solvents (e.g. water, alcohols, acetones,
cellosolves, etc.) and the solution then applied to the sub-
21 strate by known means such as dipping, roll coating, spray-
22 ing, etc. The coated substrate is then dried to remove the
23 volatile solvent(s), thus leaving a surface coating of dry
24 coagulating compound. I~ desired, the compound solution
may include soluble or partially insoluble conditioning
26 agents such as cellulose, cellulose acetates, colloidal
27 silicates, polyvinylp-yrolidones, etc. to promote uni~orm
28 application o~ the compound on the substrate. Generally,
29 the coagulating compound will comprise between about 1 and
1~5~787
1 about 40 weight percent of such solution. The coagulating
2 compound surface may also be provided, for example, by
3 application of the compound or mixture of compounds in dry
4 form in combination with conditioning agents, if required,
such as finely divided aluminum oxide, silica, mica, glass,
6 etc. to promote the uniform application of the compound(s)
7 on the surface by any known prior art techniques such as
8 dry dipping, blasting, surface grinding, fluidized bed,
9 etc. By way of a still further example, the coagulating
compound may be formed on the substrate surface by applica-
11 tion of a material to the substrate which reacts with or
12 otherwise modifies the substrate surface to form a coagula-
13 ting compound surface.
14 As mentioned above when the organic film-former
is a synthetic polycarboxylic acid resin, the coagulating
16 compound must have a pH less than 7Ø The preferred
17 coagulating compound for use in this embodiment of the
18 process is a salt. Preferred salts are salts of polyvalent
19 metals. The salts of bivalent metals such as magnesium,
the alkaline earths, zinc, copper, cobalt~ cadmium, ferrous
21 iron, lead, nickel and manganese are preferred, but the
22 salts of polyvalent metals such as aluminum, ferric iron,
23 antamony, chromium, molybdenum, tin, thorium and zirconium
24 may also be used. In general, the chlorides and nitrates
of these metals are the most useful because of their avail-
26 ability and great solubility in water and organic solvents,
27 but the bromides iodides, fluorides, chlorates, bromates,
28 perchlorates, sulphates, persulfates, thiosulphates,
29 permanganates, chromates, hypophosphites, thiocyanates,
~6~957~37
1 nitrites~ acetates, formates~ oxalates, etc. of some of the
2 metals are suf iciently soluble to merit consideration. Of
3 all the salts mentioned, the salts of metal of the First
4 Transition Series are preferred, with nickel being most
preferable. The salts are also preferably salts of strong
6 acids, i.e., pH less than 4.5, and most preferably exhibit
7 a pH in the range of 3.5 to 4.5. A list of salts which are
8 ideal for use in this embodiment and their pH (10% by
9 weight Aqueous) is as follows:
FormulapH (10% by Weight Aqueous)
11 NiC12 6H20 (Nickel Chloride) 4.0
12 CuC12-2H20 (Cupric Chloride)3.6
13 CoC12 6H2o (Cobaltous Chloride) 4.5
14 CuN03-6H2o (Cupric Nitrate) 4.0
NiNo3-6H2o (Nickel Nitrate) 4.0
16 CuS04 5H20 (Cupric Sulfate)4.0
17 ZnC12 6H20 (Zinc Chloride) 4.0
18 Xn this embodiment of the process another pre-
19 ferred manner of forming the metal salt when the substrate
is metal is to apply an acid which will react with the
21 metal to form a metal salt. Such acids may include acids
22 such as formic, acetic, oxalic, hydrochloric and sulphuric
23 and preferably are strong mineral acids.
24 In the course of the coagulation process of the
embodiment, the dry metal salt hydrate, when wetted, forms
26 ions at the salt layer interface, which ions react with the
27 polycarboxylic acid moiety of the acid resin. It i5
28 thought that the metal ions are free to react with the
29 resin to form complex organometallic compounds which, in
-- 10 --
5~7
1 turn, coagulate to form a film of resin on the continuously
2 reacting salt (see "Electrodeposition of Epoxy Resin on
3 Electrodes of Iron and Platinum't, Journal of Paint
4 Technology, Vol. 12, No. 515, June3 1970). As suggested
in the above reference, coagulation by formation of
6 metallic complexes may occur as follows:
n~ _
8 M ----~ ---- M + ne
n+
n(RCOO~) + M _________----- M (RCOO)n
11
12 A secondary reaction which may take place at the salt bath
13 interface and which is possibly coupled with the first
14 reaction is the precipitation of the acid resin in an acid
form as follows:
16
+
17 RCOO + H -----------~ - RCOOH
18
19 Complexing throughchelation and formation of other complex
coordination compounds may play an important role in the
21 first reaction.
22 The reactions set forth above are merely sugges-
23 tions with respect to the possible mechanism of coagulation
24 and should not be considered limitations on the process of
the invention.
26 As also mentioned above, when the organic film-
27 former is selected from basic monomers and resins having
28 one or more nitrogens in their molecular structure, the
29 compound must have a pH greater than 7Ø Preferred
~95~787
1 coagulating compounds for use in this embodiment include:
2 any or all of the soluble alkali earth metal salts such as
3 sodium, potassium and lithium salts and/or other salts of
4 strong bases and weak acids and/or mixtures of said salts
which exhibit a pH in solution greater than 7.0 and
6 preferably greater than 10Ø Exemplary of the many salts
7 which fall within this category and which will be apparent
8 to those skilled ln the art are: carbonates, silicates,
9 oxalates, salicylates and formates of alkali earth metals
sodlum, potassium and lithium.
11 A second preferred type of coagulating compound
12 for use in this embodiment of the process includes strong
13 bases, i.e., those with a pH greater than 10.0~ such as the
14 alkali earth metal hydroxides.
Film-Former
16 All embodiments of the invention employ an organic
17 film-forming material, at least fifty (50) weight percent of
18 which is a chemically ionizable, organic film-former which
19 (i) has at least 12 carbon atoms per molecule; (ii) is at
least partially ionized such that it is substantially
21 soluble in said aqueous bath, i.e., sufficiently soluble
22 that the film-former molecule would behave in the manner of
23 an anionic (or cationic as the case may be) polyelectrolyte
24 under the influence of a direct electric current when such
aqueous bath is employed as the bath of an electrodeposi-
26 tion cell (in contrast to the behavior in the manner of a
27 hydrophilic colloid, e.g., an inert resin globule encased
28 in a soap film and emulsified; and (~ii) coagulates in the
29 presence of said coagulating compound.
- 12 -
~57~7
1 The organic film-former used in the process of
2 this invention, unlike the film-formers used in processes
3 discussed previously wherein ionic or nonionic stabilizers
4 and/or reaction products of such are used, is a coating
salt which is substantially soluble in water. In the
6 prior art processes referred to the anionic or nonionic
7 stabilizers and~or reaction products thereof are required
8 to form emulsions of discretely insoluble particles in
9 water. Essentially, the stability of such conventional
emulsions used for the coagulation of a coating on a
11 surface is provided by (1) anionic (e.g. alkyl-aryl
12 sulfonates) or soap-like stabilizers which form a protec-
13 tive film around essentially insoluble particles keeping
14 them from coalescing. The same pertains to nonionic
stabilizers, except these materials (e.g. reaction product
16 o~ ethylene oxide and oleyl alcohol or octyl phenoxy
17 polyethoxyethanol) are used most commonly in combination
18 with one or more anionic stabilizers which are salts or
19 alkali metal salts or organic acids, particularly sulfates,
phosphates or carboxylates.
21 In the coagulation mechanism of such conventional
22 methods~ the coagulating ion acts on the stabilizers,
23 destroying the protective film around the particles and
24 causing them to coalesce. It is the stabilizer which is
antagonized in such a process. In the process of this
26 invention, on the other hand, it is the solubilized polymer
27 which is antagonized.
28 In the first embodiment of the process, discussed
29 above, the coagulating compound has a pH of less than 7.0
5787
1 and the organic film-former is a synthetic polycarboxylic
2 acid resin which (i) is at least partially neutralized with
3 a water-soluble base, (ii) advantageously has an electrical
4 equivalent weight between about 1,000 and about 20,000, and
(iii) has an acid number between above 30 and about 300.
6 - The electrical equivalent weight of a given resin
7 or resin mixture is herein defined as that amount of resin
8 or resin mixture that will deposit per Faraday of electrical
9 energy input under the conditions of operation set forth in
detail below. For this purpose, the value of one Faraday
11 in coulombs is herein taken to be 107.88 (atomic weight of
12 silver) . 0.001118 (grams of silver deposited by one
13 coulomb from silver nitrate solution) or 96.493. Thus, if
14 0.015 gram of coating, the binder polycarbox~lic acid resin
moiety of which is 90% by weight and the balance of which
16 is amino compound used to disperse it in the bath is trans-
17 ferred and coated on the anode per coulomb input to the
18 process, the electrical equivalent weight of the resin is
19 about 1303 or 0.015 x 0.9 x 107.88 . 0.001118. By way of
further illustration I find electrical equivalent weight
21 (in the nature of a gram equivalent weight in accordance
22 with Faraday's laws) of a particular polycarboxylic acid
23 resin or resin mixture simply and conveniently for typical
24 process conditions standardized on as follows: a poly-
carboxylic acid resin concentrate is made up at 65.56C.
26 (150F.) by thoroughly mixing 50 grams of polycarboxylic
27 acid resin, 8 grams of distilled water and diisopropanol
28 amine in an amount sufficient to yield resin dispersion pH
29 of 9~0 or slighly lower after the concentrate has been
- 14 _
~ 5\5i~87
1 reduced to 5% by weight resin concentration wikh additional
2 distilled water. The concentrate is then diluted to one
3 liter with additional distilled water to give 5% resin con-
4 centration in the resulting dispersion. (If a slight
insufficiency of the amine has been used, and the dispersion
6 pH is below 9.0, pH is brought up to 9.0 with additional
7 diisopropanol amine.) The dispersion is poured into a
8 metal tank, the broadest side walls of which are substan-
9 tially parallel with and 2.54 cm. out from the surfaces of
a thin metal panel anode. The tank is wired as a direct
11 current cathode, and the direct current anode is a 20
12 gauge, 10.17 cm. (4 inches) wide, tared steel panel
13 immersed in the bath 7.62 cm. (3.5 inches) deep. At
14 26.67C. (80F.) bath temperature and while the bath is
agitated sufficiently to provide turbulent flow direct
16 current is impressed from anode to cathode at 100 volts for
17 for one ~inute from an external power source, the current
18 measured by use of a coulometer, and the current turned off.
19 The anode panel is removed immediately, rinsed with distilled
water, baked for 20 minutes at 176.67C. (350F.) and
21 weighed. All volatile material such as water and amine is
22 presumed to be removed from the film for practical purposes
23 by the baking operation. The difference between tared
24 weight of the fresh panel and final weight of the baked
panel divided by the coulombs of current used, times 107.88,
26 divided by 0.001118 gives the electrical equivalent weight
27 of the resin for purposes of this invention.
28 The polycarboxylic acid resins use~ul in the
29 process include any of the polycarboxylic acid resins
- 15 -
5~7
1 useful in the electrodeposition of paint ~rom an aqueous
2 bath. These acidic film-forming materials include, but not
3 by way of limitation coupled oils such as sunflower,
4 safflower, perilla, hempseed, walnut seed, dehydrated
castor oil, rapeseed, tomato seed, menhaden, corn, tung,
6 soya, oiticia, or the like, the olefinic double bonds in
7 the oil being conjugated or nonconjugated or a mixture,
8 the coupling agent being an acyclic oxefinic acid or
9 anhydride, preferably maleic anhydride, but also crotonic
acid, citraconic acid or anhydride, fumaric acid, or an
11 acyclic olefinic aldehyde or ester of an acyclic olefinic
12 ester such as acrolein, vinyl acetate, methyl maleate, etc.,
13 or even a polybasic acid such as phthalic or succinic,
14 particularly coupled glyceride oils that are further
reacted with about 2 to about 25% of a polymerizable vinyl
16 monomer; maleinized unsaturated fatty acids; maleinized
17 r~sin acids, alkyd resins, e.g., the esterification
18 products of a polyol with polybasic acid, particularly
19 glyceride drying oil-extended alkyd resins; acidic hydro-
carbon drying oil polymers such as those made from
21 maleinized copolymers of butadiene and diisobutylene;
22 diphenolic acid and the like polymer resins; and acrylic
23 vinyl polymers and copolymers having carboxylic acid
24 groups such as butyl acrylate-methyl methacrylate-methacrylic
acid copolymers, acrylic acid and lower alkyl (Cl to C4)
26 substituted acrylic acid-containing polymers, i.e., those
27 having carboxyl groups contributed by alpha-beta unsaturated
28 carboxylic acids or residues of these acids, etc.
- 16 -
5'7i~7
1 These and other suitable resins are described in
2 detall in many patents of which U.S. Patents 3,230,162;
3 3,335,103; 3,378,477 and 3,403,088 are illustrative.
4 As discussed in the cited patents the poly-
carboxylic acid resin can also be modified and extended in
6 various ways ~ithout impairing its useful characteristics.
7 Thus, one may use polycarboxylic acid resins wherein there
8 is blended thermoplastic, non-heat reactive phenolic resins
9 into the polycarboxylic acid resin batches, which extended
resins then were dispersed in water with the polyfunctional
ll amino compound. The heating together, preferably with
12 agitation, of the polycarboxylic acid resin with such
13 phenolic resin for at least about 1/2 hour, and preferably
14 about one to two hours or more, at a temperature between
about 200 and about 260c. appears to give a chemical
16 bonding between those two components and no free phenolic
17 resin mixtu:re. Thus, when the resulting resin is used in
18 the process, the coating is essentially homogenous~ and in
19 a bath containing the resulting resin product there is no
appreciable accumulation of free phenolic bodies dissociated
21 from the resln in an appreciable operating time.
22 Other suitable extenders for the polycarboxylic
23 acid resins include hydrocarbon resins such as cumarone-in-
24 dene resins, which are generally inert and thermoplastic,
and diolefinic petroleum resins such as those or essen-
26 tially naphthenic structure which are heat-reactivey e.g.,
27 cyclopentadiene resins. Addition of resins such as this
28 also can give increased chemical resistance to the result-
29 ing cured film. Many other resinous extenders and film
- 17 -
35~7~37
1 plasticizers of conventional nature, e.g., amino aldehyde
2 resins, butadiene-styrene latices, vinyl chloride and
3 vinylidene chloride homopolymer and copolymer latices,
4 polyethylene resins, fluorocarbon resins, bis phenol-
glycidyl ether resins, dicyclo diepoxy carboxy~ate resins,
6 etc., are permissible also, provided, howe~er, that their
7 concentration is not so high as to mask the characteristics
8 of the polycarboxylic acid resin.
9 Another acidic material which may be employed is
an organic acid contalning at least about 12 carbon atoms,
11 e.g., lauric acid (dodecanoic acid), stearic acid
12 (octodecanoic acid), etc. These are preferably used in con-
13 ~unction with a minor amount of neutral or essentially
14 neutral filmforming polymers, e.g., polyesters, hydrocar-
bon resins, polyacrylates, polymethacrylates, etc., but
16 may be used alone or with the aforementioned carboxylic
17 acid resins.
18 As mentioned above, the carboxylic acid is at
19 least partially neutralized in the coagulati.on bath with a
suitable water soluble base. The preferred water soluble
21 bases are alkaline earth metal hydroxides with sodium
22 hydroxide being most preferred. Other water soluble bases
23 which may be effectively used include water soluble amino
24 compounds and ammonia.
The especially suitable water soluble amino
26 compounds are soluble in water at 20C. to the extent of
27 at least about 1% basis weight of solution and include
28 hydroxy amines, polyamines and di- and polyfunctional
29 monomericamines such as: monoethanolamine, diethanolamine3
- 18 -
~S~87
1 triethanolamine, N-methyl ethanolamine, N-aminoethylethano-
2 lamine, N-methyldiethanolamine, monoisopropanolamine,
3 diiopropanolamine, triisopropanolamine, "Polyglycol amines"
4 such as HO(C2H40)2C3H6NH2, hydroxylamine, butanolamine,
hexanolamine, methyldiethanolamine, octanolamine, and
6 alkylene oxide reaction products of mono- and polyamines
7 such as the reaction product of ethylene diamine with
8 ethylene oxide or propylene oxide, laurylamine with
g ethylene oxide, etc.; ethylene diamine, diethylene triamine,
triethylene tetramine, hexamethylene tetramine, tetrae-
11 thylene pentamine, propylene diamine 1,3 diaminopropane,
12 imino-bis-propyl amine, and the like; and mono-di-and
13 tri-lower alkyl (Cl 8) amines such as mono-, di- and tri-
14 ethyl amine.
When using amines we have found that the best
16 films are deposited when about 30-60% total amino equiva-
17 lents present in the bath, both combined and free, are
18 contributed by water soluble polyamine, and thus I prefer
19 to operate that way when using amines. Preferably, when
using amines diethylene triamine is employed for efficiency
21 and economy. The polyamine can be added to the bath along
22 with supplemental binder concentrate composition dosing or
23 separately.
24 The hydroxy amines, particularly those that are
aliphatic in nature at points of hydroxyl attachment, such
26 as the alkanol amines are also very useful for treating the
27 polycarboxylic acid resin for dispersion and appear to have
28 some desirable resin solubilizing effect in water over and
29 above their neutralizing action~
-- 19 --
~5787
1 In the second above mentioned embodiment, the
2 coagulating compound has a pH greater than 7.0 and the
3 organic film-former is selected from basic monomers and
4 resins having one or more nitrogens in their molecular
structure. This basic material contains at least 12
6 carbon atoms, e.g., lauryl amine, stearyl amine, etc.
7 Obviously, when the basic material is polymeric, it will
8 be of substantially greater molecular weight.
9 Examples of the basic resins containing nitrogen
atoms in the molecule are amino group-added epoxy resins
11 (aminoepoxy resins), amino group-containing acrylates
12 (aminoacryl resins), amino group-containing vinyl compound
13 copolymers (aminovinyl resins) and polyamide resins.
14 The aminoepoxy resins may be obtained by adding
any organic amino compound to an epoxy group in an epoxy
16 resin or epoxy modified resin. A glycidyl ether of phenol
17 or a ~lycidyl ether of a phenol-aldehyde condensate is
18 suitable as such epoxy compound. Among commercial products
19 thereof are Epikote 828, Epikote 1001, Epikote 1002,
Epikote 1004, Epikote 1007 and Epikote 1009 (trademarks)
21 produced by Shell Oil Co., Araldite 6071, Araldite 6084,
22 Araldite 6097, Araldite 6099 and Araldite 7072 (trade
23 marks) produced by Ciba Ltd. and Epichlon 800, Epichlon
24 1000 and Epichlon 1010 (trade marks) produced by Dainippon
Ink Co. Polyalkadiene epoxide such as polybutadiene epoxide
26 can also be used. Further, a copolymer of unsaturated
27 compound containing an epoxy group such as glycidyl
28 methacrylate, glycidyl acrylate, N-glycidylacrylamide,
29 allylglycidylether or N-glycidylmethacrylamide with another
- 20 -
~57~3~
1 with another unsaturated monomer copolymerizable therewith
2 is also useful. As an organic amino compound to be added
3 to such epoxy group, a secondary monoamine is most prefer-
4 able. However, a primary monoamine or polyvalent amine
can also be used together with such secondary monoamine.
6 Example of these amino compounds are diethylamine, dieth-
7 anolamine, diisopropylamine, dibutylamine, diamylamine,
8 diisopropanolamine, ethylaminoethanol, ethylaminoisopro-
9 panol, n-butylamine, ethanolamine, ethylenediamine and
diethylenetriamine.
11 The aminoacryl resins or aminovinyl resins are
12 basic resins obtained by copolymerizing an acrylate or
13 methacrylate having an amino group or a nitrogen-containing
14 acrylic or vinyl compound such as vinyl pyridine or vinyli-
midazole with a vinyl compound having no free acid group.
16 Example of such acrylic acid esters having amino groups are
17 esters of acrylic acids or methacrylic acids and amino
18 alcohols, such as aminoethyl acrylate, aminobutyl acrylate,
19 methylaminoethyl acrylate, dimethylaminoethyl acrylate,
hydroxyethylaminoethyl acrylate, aminoethyl methacrylate
21 and dimethylaminoethyl methacrylate. Examples of vinyl
22 compounds having no free acid group and to be copolymerized
23 with the above amino- or nitrogen-containing compounds are
24 acrylic acid and methacrylic acid derivatives such as
methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethyl-
26 hexyl acrylate, acrylamide. N-methylolacrylamide, N-
27 butoxymethylacrylamide, acrylonitrile, methyl methacrylate,
28 ethyl methacrylate, n-butyl methacrylate, isobutyl metha-
29 crylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate,
- 21 -
~5'7~7
1 and methacrylamide, etc., aromatic vinyl compounds such as
2 styrene, a-methyl styrene, vinyl toluene, etc. and other
3 vinyl compounds such as vinyl acetate, vinyl chloride and
4 vinyl isobutyl ether.
The polyamide resins are condensates of a dibasic
6 acid and a polyvalent amine. Examples of dibasic acids are
7 isophthalic acid, adipic acid and dimer acid~ and examples
8 of polyvalent amines are ethylene diamine and diethylene
9 triamine.
As mentioned previously, the basic monomers and
11 resins are at least partially neutralized by a water soluble
12 acid compound.
13 Examples of acid compounds to be used for the
14 reaction with the basic resin are hydrochloric acid, phos-
phoric acid, formic acid, acetic acid, propionic acid,
16 citric acid, malic acid, tartaric and acrylic acid, but any
17 other inorganic acids and organic acids may also be used.
18 A water-dilutable or thinnable organic film-former
19 resin may be obtained by adding to the basic resin 0.2 to 3
equivalents, preferably 0.5 to 1.5 equivalents of the acid
21 compound to the amino groups or basic nitrogen atoms in the
22 basic resin and agitating the mixture at the normal or room
23 temperature.
24 As a compound which can produce an acid substance
by reacting with the amino group or basic nitrogen in the
26 basic resin at the time of the neutralization or modifica-
27 tion of the basic resin, there may be mentioned epihalo-
28 hydrinssuch as epichlorohydrin or epibromohydrin. The
29 amount of this modifier may be 0.5 to 2 equivalents to the
~t~95787
1 amino groups or basic nitrogen atoms in the basic resin. A
2 mixture of the basic resin and modifier are heated to 504
3 to 100C. The acid produced in the mixed system at the
4 time of such modification will react with the amino groups
in the basic resin to obtain a water-dilutable or thinnable
6 cationic binder resin.
7 The non-ionic synthetic resins in the form of
8 powder and to be used together with the cationic binder
9 resin are those which are solid at the normal or room tem-
perature and can melt when heated in the subsequent baking
11 operation, and may or may not be compatible with the binder
12 resin in the fused film formed at an elevated temperature.
13 The non-ionic synthetic resin should be used in the form of
14 fine powder with an average particle size of 0 n 5 to 100
microns. Further, the non-ionic resin may be thermosetting
16 by itself or thermoplastic but, preferably, is curable with
17 a curing agent or catalyst which is known per se in the art.
18 The non-ionic synthetic resins which may be
j 19 included with the basic resin include those selected from
the group consisting of epoxy-resins, polyester resins,
21 acrylic resins, polyurethane resins, polyamide resins, poly-
~ 22 olefin resins and cellulose derivative resins.
j 23 The epoxy resin is a ~lycidyl etheride of phenol,
24 a glycidyl etheride of a phenol aldehyde condensate or a
phenol glycidyl etheride esterified with 10 to 20% dimer
26 acid. As for the polyester resin there may be used a blend
27 of a melamine resin with a saturated linear polyester or an
28 oil-free alkyd resin.
- 23 -
l#gS7~
The acrylic resin is a polymer or copolymer of an
acrylate or methacrylate or its copolymer with any other
copolymerizable unsaturated monomer. For example, it is a
copolymer of an acrylate and styrene, or a copolymer con-
sisting of a methacrylate and unsaturated carboxylic acid.
Such acrylic resin may be mixed with a cross-linking agent
or curing catalyst such as an amino resin or epoxy resin.
The polyurethane resin is a copolymer produced by
the poly-addition of diisocyanate such as trilenediiso-
cyanate or hexamethylenediisocyanate with polyol such as
glycol or polyesterglycol, having more than two urethane
groups in the molecule.
The polyamide resin is a copolymer produced by the
co-condensation of dicarboxylic acid such as aliphatic
dicarboxylic acid having more than 6 carbon atoms with
diamine such as aliphatic diamine having more than 6 carbon
atoms, or by the polycondensation of w-amino acid having
more than 6 carbon atoms, or by the ring-opening polymeriza-
tion of lactam having more than 4 carbon atoms. For
examples of said polyamide resin are Tohmide (trade mark of
Fuji Chemicals Co.) derived from dimer acid and diamine,
6.6-nylon, 6.10-nylon, mixed type nylon Zytel 3606 (trade
mark o~ DuPont), alcohol soluble nylon Amilan CM-4000,
CM-8000 (trade mark of Toray Co.) produced by the co-
condensation of caprolactam with 6.10-nylon salt, and N-
methoxymethyl substituted nylon Toresin F-30, HF-30 (trade
mark of Teikoku Chemical Ind.).
The polyolefin resin may be exemplified as
polyethylene or polypropylene having a molecular weight of
- 24 -
3S787
1 less than 100 thousand and a particle size (as chemically
2 grinded) of about 1 micron to about 50 microns.
3 The cellulose derivate resin may be such as
4 cellulose acetate or cellulose acetatebutyrate and may be
used supplementally in order to facilitate the flow of the
6 deposited film in the baking step.
7 The above explained basic resins, cationic binder
8 resins and non-ionic synthetic resins are all when known
9 in the art and mostly commercially available, and therefore
no further explanation thereabout will be necessary.
11 In any case, it will be understood that these
12 resins in the state as used in the-deposition bath
13 are in the form of prepolymers or precondensates which are
14 curable by themselves or in the presence of a cross-linking
agent or catalyst upon the subsequent heat treatment or
16 baking to form a rigid or tough film.
17 If desired a mixture of two or more different
18 cationic binder resins, and/or two or more different non-
19 ionic synthetic resins may be employed. In case the
cationic binder resin is not compatible with the non-ionic
21 synthetic there is a tendency that there is formed a two-
22 layer film upon the subsequent baking.
23 While positive employment of a neutralizing
24 solubilizer has been described for both of the above
discussed process embodiments, it is within the scope of
26 the invention to employ a film-former that ionizes in water
27 without the addition of a neutralizer.
- 25 -
~5787
l Coating Bath
2 The coating bath used in the process of the in-
3 vention comprises an aqueous suspension of the solubilized
4 carrier of organic film-forming resin. The bath may
optionally contain thickeners and suspending agents.
6 Pigments or other particulate material which is applied as
7 the final coating on the substrate or as a part of that
8 coating are also included in the coating bath. As mentioned
9 previously, both reactive and nonreactive pigments or other
particulate materials and mixtures thereof may be employed
ll in the process. Of course, the coating may consist entirely
12 of the organic film-formlng material and need not include
13 particulate material. In any event, the concentration of
14 the organic film-forming in the bath is preferably maintained
in the range of about 0.2 to 40 weight percent.
16 When pigment or other particulate material is
17 included in the bath, the total amount of nonvolatile solids,
18 i.e., particulate material pius resin, preferably is between
19 about 3 and about 60 weight percent of the bath most prefer-
ably between lO and 50 weight percent. The weight ratio of
21 particulate material to resin nonvolatiles is preferably in
22 the range of 1/9 to 30/l, most preferably 1/4 to 20/l.
23 The concentration of thickeners, when used, is
24 preferably in the range of l to 15 grams per kilogram of
bath. For example, the preferred concentration of a cellu-
26 lose thickener is l to 3 grams per kilogram of bath and the
27 preferred concentration for a polyvinylpyrrolidone thickener
28 is 9 to 12 grams per kilogram of bath. The bath may also
29 contain a small amount of a curing agent for the organic
- 26 -
~S'~7
1 film-forming material, flow adjusting agent and other
2 additives which are usually used in the art of synthetic
3 resin type paints. Further, the bath may also contain a
4 small amount (i.e., 0-100 parts by weight per 100 parts of
the organic film~forming material) of an organic solvent.
6 The organic solvent is useful to increase the adhesiveness
7 of the organic film-forming material, to improve the
8 appearance of the coating film and to improve the stability
9 of the paint.
By way of illustration of the preparation of coat-
11 ing bath, the bath for practicing the first aforementioned
12 embodiment of the process may be prepared by solubilizing
13 a weighed amount of a polycarboxylic acid resin with 1
14 normal sodium hydroxide to produce a homogeneous dispersion.
Pigment and water are then added to produce a viscous
16 product which is mixed for a suitable time to insure proper
17 wetting of the pigment by the resin and the mixture is
18 diluted with water to glve the desired bath solids content.
19 Of course, the weight ratio of particulate
material to organic film-forming material will vary widely
21 depending upon the substrate being coated and the type of
22 particulate material being applied. For example, when the
23 particulate material being applied is metal and/or ceramic
24 frit or other refractory material it is preferable to
employ a particulate material to organic film-forming
26 material weight ratio in the range of 1/1 to 20/1.
27 Coatin~ by Coagulation
28 After the substrate to be coated is provided with
29 a coagulating compound surface as discussed above, it is
5'7~3~
1 exposed to the coating bath by such known techniques as
2 immersion, flow coating, etc. for a time period, preferably
3 greater than 5 seconds and less than 20 minutes, to obtain
4 a coating of the desired thickness, e.g., in the range of
0.25 mils (0.00025 inches) to 35 mils (0.035 inches).
6 As will be apparent to those skilled in the art,
7 the coating bath is preferably agitated as necessary to
8 maintain the dispersion of materials therein during coating.
9 The completeness and thickness of the coating film
which is applied, o course, will vary depending on a
11 number of factors. Perhaps the most important factor is
12 the concentration of coagulating compound sites (e.g. salt
13 sites) per unit area of the substrate. Other factors which
14 will affect the completeness and thickness of the film are
bath variables such as the pigment to binder weight ratio
16 as well as the type of organic film-forming material being
17 applied and the type of coagulating compound employed. For
18 example, a polycarboxylic acid resin of 200 acid number was
19 reacted with sodium hydroxide to form a 2% by weight aqueous
solution of a salt of the resin. The pigment (Reynolds 400
21 Aluminum Powder) was added to increase the pigment to binder
22 ratio of the bath. Film thicknesses of the coatings, which
23 were determined at various pigment to organic film-forming
24 ratios are set forth below:
_ 28 -
~S787
Pigment/Organic Film-
1 Formin~_Material Film Thickness
2 0/1 0.5 mil
3 0.5/1 o.8 mil
4 1/1 1.5 mil
2/1 2.5 mil
. 6 4~1 4.8 mll
7 8/1 4.8 mil
8 .
9Post Coating Treatment
As will be apparent from the various examples set
11 forth in this application, various post coating treatments
12 of the coated substrate may be desirable. For example, the
13 coated substrate is desirably heated to remove solvent or
14 water from the coating, particularly if extensive handling
of the part is contemplated shortly after coating. Depend-
16 ing on the nature of the organic film-forming material,
17 heating to cure the resin may also be desirable. Also, it
18 may be desirable to heat the substrate to remove the
19 organic film-forming material. If the coating is intended
to further modify the substrate surfaces, such as in diffu-
21 sion coating of metals, further heat treating may be nec-
22 essary. For example, ~hen the coating applied to a metal
23 substrate includes partlculate material comprising metal
24 particles or mixtures of various metal particles and it is
desired to diffuse the metal coating into the surface, it
26 is desirable to heat the coated substrate in an ambient
27 essentially inert to the metal particles in said coating to
28 a decomposition temperature above the temperature required
29 to decompose the organic film-forming material in the
- 29 -
5~787
1 coating and below the diffusion temperature of the metal,
2 maintain that decomposition temperature until the coating
3 is essentially decomposed and gaseous products thereof are
4 formed, evacuate the gaseous products from the heating
zone, maintain the substrate in an ambient essentially
6 inert to the metal particles and raise the temperature to
7 a suitable diffusion temperature for a suitable time to
8 diffuse the coating into the substrate.
9 Preferred Uses of Process
A first preferred use of the process of the inven-
11 tion is in a process for modifying the surface of a metal
12 substrate of which the ma~or component by weight is selected
13 from cobalt, nickel and iron and constitutes at least 40
14 weight percent of the substrate. The process comprises:
(a) providing said substrate with a dry coagulating
16 compound, preferably a salt surface;
17 (b) codepositing by coagulation on said metal sub-
18 strate a coating of
19 (I) ~etal particles having an average diameter
in the range of 0.5 to 20 microns and
21 selected from
22 (A) aluminum comprising particles wherein
23 the weight ratio of aluminum to other
24 metal is in the range of 200:1 to 1:3
and which are selected from
26 (1) aluminum alloy particles,
2~ (2) a mixture of aluminum particles
28 and particles of at least one
29 other metal,
- 30 -
5787
(3) a mixture of aluminum particles
and particles of at least one
alloy, or
(B) aluminum particles;
(II) a heat fugitive organic film-forming material,
consisting essentially of at least S0 weisht
percent of which is a chemically ionizable
organic film-former having at least 12 carbon
`~ atoms per molecule and a xemainder of organic
101 film-former which is not chemically ionizable,
in a metal particle to organic film-forming
material weight ratio in excess of 3~1,
from an aqueous dispersion forming a coating bath which,
except for solvent, consists essentially of said metal parti-
cles and said organic film-forming material, said chemically
ionizable organic film-former being at least partially ionized
and adapted to coagulate and deposit in the presence of
said coagulating compound, and wherein
(A) the weight ratio of metal particles in
said bath to organic film-forming
material in said bath is maintained
above 3:1,
(B) the concentration of organic film-
forming material in said bath is
maintained in the range of about
0.2 to about 7 weight percent, and
(C) the total weight of non-volatile
solids in said bath is maintained
below about 35 weight percent of
said bath, and
(c) heating the substrate and resultant coagulation
coating thereon in a heating zone in an ambient
31 -
~5787
essentially inert to the metal particles in said
ccating to a decomposition temperature above the
temperature required to decompose the organic
film-forming material in said coating and below
31 a -
~a3~5787
1 the diffusion temperature hereinafter set forth,
2 maintaining said decomposition temperature until
3 said coating is essentially decomposed and gaseous
4 products thereof are formed in said heating zone,
essentially evacuating said gaseous products from
6 said heating zone, maintaining the substrate in
7 the heating zone in an ambient essentially inert
8 to the metal particles and raising the temperature
9 of the heating zone to the diffusion temperature
and maintaining said diffusion temperature
ll and said ambient for a time sufficient to obtain
12 the desired diffusion.
13 The metallic substrate upon which the particulate
14 metal is deposited is preferably a substrate which after be-
ing processed in accordance with this invention exhibits
16 corrosion resistance at high temperatures. Obviously, various
17 uses of metal parts sub~ected to high temperatures require
18 varying degrees of high temperature corrosion resistance.
19 Iron alloys which can be surface modified in
accordance with this invention include those which contain
21 very small amounts of alloying components, e.g., carbon
22 steel, as well as those alloys wherein the alloying component
23 or components constitute a substantial percentage of the
24 alloy. The iron alloys contain a minimum of 50 weight
percent iron and commonly much more, e.g., about 60 to about
26 99 weight percent iron. Thus, a broad spectrum of iron
27 base materials are suitable for treatment in accordance with
28 this process including carbon steels, stainless steels and
29 nodular irons. Both cast and wrought alloys of these types
~5787
1 can be processed provided heat treatment in a non-oxidizing
2 atmosphere at 1300F. or above is permissable, i.e., pro-
3 vided that the temperature selected in this range is com-
4 patible with recognized metallurgical practices for such
alloy.
6 The nickel and cobalt base materials which may be
7 processed typically contain from about 5 to about 25 weight
8 percent chromium for oxidation resistance, although nickel
9 and cobalt alloys without chromium exist and can be surface
modified by this process. Various amounts of refractory
11 elements such as tungsten, tantalum, columbium, molybdenum,
12 zirconium and hafnium are commonly added as solid solution
13 strengtheners and/or carbide formers to improve high
14 temperature strength. Aluminum and/or titanium are added
to certain of the nickel base materials to produce age
16 hardening response for additional high temperature strength
17 In such alloys, the total aluminum plus titanium contents
18 may be as high as 10 weight percent in some.
19 The nickel alloys contain about 40 weight percent
nickel, commonly about 50 to about 80 weight percent. Even
21 when the nickel content of the alloy is between 40 and 50
22 weight percent, it is the largest single component of the
23 alloy. Correspondingly, the cobalt alloys contain above 40
24 weight percent cobalt, commonly about 50 to about 80 weight
percent. Similarly, when the cobalt content of the alloy
26 is between 40 and 50 weight percent, it is the largest
27 single component of the alloy.
28 As discussed previously, various factors will
29 affect the thickness of the coating initially applied by
~957~7
1 coagulation. For a given thickness of coagulated coating,
2 it will be appreciated that the time required for providing
3 a desired depth of diffusion coating will vary depending
4 on the substrate being coated and the coating being applied.
In the preferred use of the process as in others,
6 the areas to be coated are preferably cleaned by conven-
7 tional processes such as pickling, grit blasting with suit-
8 able particulate abrasive, e.g.~ aluminum oxide particles
9 of about 140-325 mesh, preferably about 220 mesh using a
pressure in the range of 40-80 psi, etc. This cleaning is
11 preferably performed not longer than 30 minutes prior to
12 exposure of the part to the coating bath.
13 Areas not requiring coating may be left uncoated
14 by leaving these portions out of the coating bath during
deposition whenever this is feasible. In the alternative,
16 these portions may be masked to prevent coating although
17 exposed to coating bath. Any suitable masking material
18 may be used. For such a process, a suitable masking material
19 is one that will remain in place during the coagulation
process, ~ill prevent surface contact of the masked area by
21 the bath during the processing and which will not signif-
22 icantly interfere with the chemical composition of the bath.
23 Examples of a suitable insulative masking material are
24 rubber, wax, pla~tic, a removable sleeve of metal, etc.
The particulate metal to be deposited and sub-
26 sequently diffused into the substrate advisedly has an
27 average particle diameter in the range of about 0.05 to
28 about 20, preferably about 4 to about 9 microns in the case
29 of aluminum. Preferably, the median particle size range is
- 34 -
5787
1 (50 wt. percent is greater than and 50 wt. percent is less
2 than) 6 to 30 microns in the case of aluminum. For even
3 and homogeneous deposits, it is advisable that 0 percent of
4 the particles exceed 74 microns in particle size with not
more than 5 percent having particle size above 44 microns.
6 However, small quantities of undesirably large particles
7 may be removed by sieving or by gravitational settling from
8 the coagulation bath.
9 The particulate metal used in this process is one
that when diffused into the surface of the substrate pro-
11 vides a change in surface characteristics that increases the
12 high temperature corrosion resistance of the surface treated.
13 The preferred metallic particles are aluminum particles,
14 aluminum alloy particles, e.g., 60 wt. percent Al-40 wt.
percent Pt. 50 wt. percent Al-50 wt. percent Pd. 99 wt.
16 percent Al-l wt. percent Y, a particulate mixture of alumi-
17 num and at least one other metal or metal oxide, e.g.,
18 platinum, palladium, chromium Cr203, cobalt, rare earth
19 metals, etc. and a mixture of aluminum particles and the
particles of at least one alloy, e.g., 75 wt. percent Al+25
21 wt. percent (63 wt. percent Co-23 wt. percent Cr-13 wt.
22 percent Al-0.65 wt. percent Y) alloy, 50 wt. percent A1~50
23 wt. percent (69 wt. percent Al-30 wt. percent Co-l single
24 wt. percent Y) alloy. While a single coagulation providing
a coating containing all of the particulate metal to be
26 deposited is ordinarily preferred, it is within the scope
27 of the invention to carry out successive coagulation steps
28 of different particulate materials.
- 35 -
~957B7
1 A typical composition of the aluminum powder or
2 flake used is as follows:
3 ~eight Percent
4 Aluminum 97.0 min.
A12O3 2.0 max.
6 Fe 0.25 max.
7 Si 0.15 max.
8 Other metallics, each 0.03 max.
9 Other metallics, each 0.15 max.
The ~eight ratio of aluminum to other metal or
11 metals in the particulate metal in those embodiments
12 wherein at least one other metal is employed either in
13 separate particulate form or in the form of particulate
14 alloy is in the range of about 200:1 to about 1:3.
- 36 -
~95'787
1 Immediately following coating by coagulation, the
2 coated part should be rinsed with water to remove loose
3 adhering bath materials. After removing the masking material,
4 if any, the parts are then oven dried advisedly at a temperature
of 160F to about 180F for about 5 minutes or more to eliminate
6 any residual water from the coating followed by a bake at
7 about 350F metal temperature for about 10 minutes to cure
8 - the polymer. Of course, where the part will not be handled
9 extensively prior to further processing, the curing step
may be omitted.
11 Following oven drying, the coated parts are heat
12 treated in an ambient inert to the particles deposited. In
13 one e~bodiment, the heat diffusion step is carried out in a
14 vacuum of about 10-4 mm. Hg or greater, i.e., a lower pressure,
preferably at a pressure not in excess of 5xlO 5 mm. Hg.
16 In another embodiment, the heat diffusion ~s carried out in
17 a hydrogen atmosphere having dew point below about -75F.
18 In firing, the coated article is supported on a support that
19 does not undergo chemical reaction in the firing process,
e.g., aluminu~ oxide.
21 When the process is carried out in vacuum, the
22 follo~ing procedure can be used. The coated part is
23 charged to the heating zone. The vacuum is established and
24 the heating zone is heated to a metal temperature of about
800 to about 1100F and held at that temperature until the
26 initial vacuum is restored and the organic portion of the
27 coating has essentially decomposed and the vapors therefrom
28 are removed from the heating zone before heating the part
- 37 -
~5 ;~87
1 to diffusion temperature. Diffusion is carried out by heating
2 the article to a metal temperature between ab~ut 1300 and
3 about 2200F., commonly between about 1500F and about
4 1900F until the desired diffusion of metal from the deposit
into the alloy substrate is achieved.
6 Diffused coating thickness can be determined on
7 parts by microscopic inspection of cross sectional test
8 samples. The average depth will ordinarily be in the
9 range of about 2 to about 5, preferably about 3 to about 4
mills.
11 By way of further example, a typical heat treat
12 cycle for low carbon steel of a thickness ranging from
13 about 0.035-0.125 inches comprises heating to a metal
14 temperature of 900-1100F for 5 to 15 minutes followed
by heating to a metal temperature of 1400-1600F for a period
16 of about 5 to about 15 minutes to produce a diffusion coating
17 with an average thickness of about 3 mils. Of course,
18 depending on such factors as the type of material being
19 coated, the coating material being applied, the temperature
at which diffusion is carried out, the thickness of the
21 material and the thickness of the desired diffusion coating,
22 heat treatments of 1 hour or more and even 8 hours or more
23 may be desirable.
24 ~ A second preferred use of the ~rocess of this
invention is in a process for coating a substrate with
. . .
26 inorganic particulate solids such as ceramic frit or other
27 refractory~material. That process comprises~
28 (A) providing the substrate with a dry coagulating
29 compound, e.g., a salt, surface;
- 38 -
~ S787
l (B) codepositing by coagulation on the substrate
2 a coating having a particulate solids to
3 organic film-forming m~terial weight ratio in
4 excess of 2.5:1 from an aqueous dispersion
comprlsing a vaporizable and chemically ionizable
6 organic film-former which
7 (~) has at least 12 carbon atoms per molecule
8 (ii) is at least partially ionized such
9 that it is substantially soluble in
said aqueous bath, and
ll (iii) coagulates and deposits in the presence
12 of said coagulating compound and
13 inorganic particulate solids selected from ceramic frit and
14 metal and having an average ma~or dimension between about
2 and about 70 microns.
16 In accordance with this process, the following
17 limitations on bath parameters are desirable:
18 (1) The concentration of organic film-forming
l9 material in the bath is preferably within
the range of about 0.02 to about 2,
21 preferably about 0.5 to about 2, parts by
22 weight of organic film-forming material to
23 100 part~ by weight of coating bath.
24 (2) The weight to weight ratio of particulate
material in said bath to organic film-
26 forming material in the bath is preferably
27 within the range of about 2.5 ~o about 35
28 to l, preferably about 3.5 to about 20 to l.
- 39 -
~ 5787
1 (3) The concentration of depositables in the
2 bath is preferably within the range of
3 about 1.7 to about 30, preferably about 5
4 to about 25, parts by weight total depositables
per 100 parts by weight of bath.
6 When the particulate material is ceramic frit, the
7 organic film-forming materials must be materials that will
8 vaporize during the firing cycle through which the particu~
9 late frit is converted to a continuous film. This vapor-
ization generally should take place at temperatures below
11 about 1500F, preferably between about 900 and about
12 1100F, most preferably below about 1000F.
13 The invention will be more fully understood after
14 reading the specific examples which follow. However, it
should be understood that the examples are merely intended
16 to be illustrative of certain embodiments of the invention
17 and are not to be considered limiting.
Example 1
Coagulation deposition of a paint is carried out
19 with the materials and method hereinafter set forth:
Pre~aration_of Coating Bath
21 A linseed oil coupled with maleic anhydride,
22 diluted with water and solubilized with diisopropanol amine
23 was prepared as follows:
- 40 -
~9S'787
1 (A) 6,197 parts - Linseed oil and
2 (B) 1,484 parts - maleic anhydride were reacted in an
3 agitation tank for 3 hours at 232C
4 and then cooked at 157C.
~C) 1,309 parts - Vinyl toluene containing 35 parts
6 tertiary butyl peroxide was added to
7 (B~ and the mixture reacted at 218C
8 for 1 hour. The mixture was cooled to
9 157C.
10 (D) 3,875 parts - Oil soluble phenolic resin was added
11 to (C) and the mixture reacted for 1
12 hour at 176C. The mixture was cooled
13 to 93C and
14 (E) 3,000 parts - Deionized water was added
15 (F) 2,060 parts Diisopropanol anine was added to (E)
16 at 75-90C to neutralize the resin.
17 (G) 17,179 parts - Deionized water was added to further
18 reduce the vehicle. Based on the
19 resin solids of the vehicle 2% by
weight carbon black and 8% by weight
21 corrosion inhibiting pigments were
22 added. The resultant bath had a pH
23 of 8.5.
24 Coagulation Process
The bath prepared as above is placed in a metal
26 or plastic container and agitated to provide uniform
27 suspension of the paint pigments. The bath temperature
28 is maintained at about 40 to 125F, most preferably between
29 65 to 75F.
_ 41 -
~ 57~37
1 An article of 1010 steel is alkali cleaned in a
2 2 oz./gal. solution of Stauffer 128NP cleaner for 5 minutes
3 at 160F to 170F~ removed~ tap water rinsed, hot air dried
4 and permitted to cool to room temperature. The article is
immersed in a 10% by weight nickel chloride hexahydrate in
6 methanol solution, withdrawn at a rate of 12 inches per minute
7 and heated in a convection oven for 5 minutes at 160F,
8 removed and permitted to cool to room temperature. The
9 article is then immersed in the coating bath for one minute,
removed and tap water rinsed and the resultant film cured at
11 3600F for 25 minutes which resulted in 2 smooth, glossy,
12 adherent o.6 mil coating. Additional articles were coated
13 and salt spray tested according to ASTM Test Method
14 No. B117-64. The coating exhibited exeellent corrosion
protection after 240 hours exposure. In addition good
16 adhesion, cross hatch and other good physical properties
17 were obtained.
Example 2
18 A coagulation coating bath consisting of an
19 aminoepoxy resin was prepared as follows:
(A) 488 parts - Epikote 1001, and
21 (B~ ].05 parts - Diethanolamine and
22 (C) 250 parts - Isopropyl alcohol were reacted under reflux
23 for 3 hours at 80C to gi~e an amino-
24 epoxy resin.
~ 42 -
' ` li~9578~
1 (D) 100 parts - Epoxy resin powder (~pikote 1004) 3 and
2 (E) 3 parts - Butvar D 510 leveling agent, a product
3 of Monsanto Co. and
4 (F) 40 parts - Rutile type titanium oxide and
5 (G) 5 parts - ~icyandiamide were melted and kneaded
6 together to produce a solidified mixture
7 which was pulverized into a powder having
8 a maximum particle diameter of 100 microns
9 and an average particle diameter of 40
microns.
11 (H) 6.2 parts - Glacial acetic acid and
12 (I) 500 parts - Deionized water are added to
13 (J) 143 parta - of the resin of (C) and the mixture
14 agitated in a dissolver.
(K) 634 parts - Powder (G) is added to the resulting
16 mixture from (J), dispersed in a homogenizer
17 for 30 minutes and then diluted with
18 deionized water to give a coating bath
19 of 12% solids. Glacial acetic acid is
then added to ad~ust the pH to 4.4-4.5.
21 The coating both from (K) is placed into a plastic
22 container and agitated to maintain uniform suspension of
23 the pigment.
24 An article of 1010 steel is alkali cleaned and
rinsed and dried as in Example 1. The article is then
26 immersed in a 2.6% by weight sodium hydroxide in methanol
27 solution, withdrawn at a rate of 12 inches per minute and
28 heated and cooled as in ~xample 1. The article is then
- 43 -
~ 5787
1 immersed in the coating bath for 1 minute, withdrawn, rinsed
2 and baked for 25 minutes at 3600F which resulted in a 0.7
3 mil coating.
Example 3
4 A coating bath consisting of 20% bath solids, in
which 89.9% b~ weight of the solids is metallic aluminum
6 powder and 11.1% by weight of a polycarboxylated heat
7 fugitive~ acrylic acid resin is prepared as follows:
8 (A) 111 grams - Acrylic acid resinl in butyl cellosolve
9 which contains 77.8 grams of resin solids
is reacted with 2.5 grams of sodium
11 hydroxide (62.2 milliliters 1 normal
12 sodium hydroxide).
13 tB) 624 grams - Reynolds 400 atomized aluminum powder
14 (406 micron APD) and
15 (C~ 435 grams - Deionized water are added to (A) and the
16 mixture is blended for 2 hours under high
17 shear agitation to give
18 (D) 1170 grams - 60% (by weight) bath.
19 ~E) 2330 grams - Deionized water is ~lowly added to (D)
to give
21 (F) 3500 grams - Coating bath.
22 The above bath from (F) is placed under agitation to insure
23 uniform suspension of the metal powder.
24 An article of 1010 steel or Tinamel (Titanimum
strengthened low carbon steel) is processed the same way
26 as in Example 1 using a 10% (by weight) nickel chloride
_ ~4 -
~gS~787
1 hexahydrate in ethanol solution for application of coagulant
2 by immersion. The part is immersed in the coating bath for
3 1 minute, withdrawn, rinsed with tap water and the aluminum
4 coated article is baked for 1/2 hour at 180F, The article
with its smooth, adherent 4.0-5.0 mil coating is placed into
6 a furnace whose atmosphere is essentially inert to the metal
7 particles. The coated article is heat treated at a metal
8 temperature of 900F for 5 minutes to vaporize the heat
9 fugitive resin and is then heat treated at a metal temperature
of 1500~' for 5-10 minutes. The result is a highly oxidation
11 and corrosion resistant coating essentially of iron aluminide.
12 1 ~his resin is prepared from the following materials in
13 the following manner:
14 (a~ To a reaction vessel is charged 900 parts by weight
Cellosolve and the same is heated to 140C.
16 (b) While mP~ntaining this temperature~ there is added
17 dropwise over a 3.5 hour period a mixture of
18 Parts by weight
19 Methacrylic acid 226
2-ethyl hexyl acrylate 630
21 Styrene 1034
22 ~ydroxy ethyl methacrylate 210
23 Azoblsisobutyronitrile 21
24 ~c) After addition is complete, the temperature of 140C
is held for 0.5 hour and the resin recoveredl The
26 resin has an acid value of about 71 and an X-Y
27 Gardener-Holdt viscosity at 50% solids in butyl
28 Cellosolve.
- 45 -
~ 57~37
Example 4
1 A coating bath consisting of 48% by weight bath
2 solids, o~ which 4.8% by weight is a heat fugitive poly-
3 carboxyl acrylic acid resin and 95.2% by weight is a
4 ceramlc enamel frit is prepared as follows:
(A) 447 grams - Sodium hydroxide presolubilized acrylic
6 acid resin prepared in Example 3 which
7 contains 174 grams of resin solids is
8 mixed under agitation with
9 (B) 4941 grams - Ceramic mill slip of Ferro Frit #234
which contains 3459 grams pigment solids,
11 4% of which is retained in a USA
12 Standard Sieve No. 400 until a homo-
13 geneous blend results to give
14 tC) 5388 grams - Viscous slurry containing 64.4~ solids
by weight.
16 (D~ 1136 grams - Hydroxy propyl methyl cellulose aqueous
17 dispersion containing 11.4 grams of the
18 thickener is blended into (C) to give
19 (E) 6524 grams - Bath which is diluted with
(F) 1046 grams - Deionized water to give
21 (G) 7570 grams - Coating Bath at 48% solids by weight.
22 Bath (G) is placed into a stainless container and agitated
23 to maintain uniform suspension of the plgment.
24 An article of Tinamel is aluminum o~ide blasted
(200 Mesh) at 100 psi. The article is immersed into a 20% ..
26 by weight nickel chloride hexahydrate in ethanol solution,
27 removed at a controlled rate as in Example 1 and the
- 46 -
~S787
1 coagulant dried at 160F for 5 minutes and cooled to room
2 temperature for 5 minutes. The pretreated article is immersed
3 into bath (G) for 1 minute, withdrawn and the coated article
4 tap water rinsed, dried at 360F for 30 minutes. An 8-10
mil coating is formed on the article which is then fired at
6 160F for 6 minutes which results in a ~3.0-~.0 mil oxidation
7 and corrosion resistant glass coating.
~ le 5
8 A paint comprising approximately 15% by weight of
9 the bath solids in which approximately 80% by weight of the
solids consists of an amine solubilized polybutadiene resin
11 and approximately 20% by weight pigment was prepared as
12 follows:
13 (A) 1514 grams - Polybutadiene paint2 containing appro~i-
14 mately 908 grams resins solids and 227
grams pigment is solubilized with 38.8
16 t grams o~ diethylamine under high shear
17 stirring.
18 tB) 6056 grams - Deionized water is slowly worked into
19 (A) to give
(C~ 7570 grams - Coating bath at 15% solids.
21 The ~ath ~C) was placed into a container and agitated as in
22 Example 1. An article of low carbon steel is processed in
23 the same manner as in Example 1 except the coagulant solution
24 is a 5% by weight cupric chloride dihydrate in ethanol. me
coated article is tap water rinsed and cured at 360F for 25
26 minutes which resulted in a smooth, adherent 0.4 mil coating.
_
27 A water dispersable paint PPG-1260, comprlsing 1.4 poly-
28 butadiene, developed by PPG Industries.
- 47 _
lQ~35787
Example 6
1 The coating bath of Example 1 is used to apply a
2 0. 6-o. 7 mil opaque decorative coating on a glass article.
3 The article is etched by mild blasting using finely
4 divided powdered glass beads, and is immersed into a 10%
by weight aqueous solution of aluminum chloride and the
6 coagulant dried at 160F for 5 minutes and allowed to cool
7 at room temperature for 5 minutes. The glass article is
8 immersed for 1 minute into bath (G) of Example 1. The
~ article is withdrawn and the film is baked at 360F for
30 minutes which gives a 0.6-0.7 mil adherent, decorative
11 coating.
Example 7
12 The same procedure for application of the coagulant
13 f Example 6 is used to coat a plastic article and~a
14 decorative paint film is applied by immersing the article
in bath (G) of Example 1.
ExamPle 8
16 The same procedure in Example 6 is used to apply
17 the coagulant of Example 3 onto a glass article except an
18 aluminum coating is applied by immersing the article lnto
19 bath ~) of Example 3.
_ 48 -
~t~5~
Example 9
1 The coating bath is the same as in Example 3
2 except the metal article to be coated is a nickel base
3 alloy (58% Ni, 9% Cr, lC% Co, 10% W, 6% Al, 2% Mo, 4% Ta,
4 1% Ti) containing approximately 59 weight percent nicKel.
5` The coagulant is a 10% by weight solution of cobaltous
6 chloride hexahydrate in n-propanol. The article prior to
7 application of cobaltous chloride was aluminum oxide grit
8 blasted at 80 psi. Immersion time in bath tF) of Example 3
9 is 1 minute. The coated particle was tap water rinsed, and
dried at 180F for 1/2 hour. The coated article is heat
11 treated in vacuum for 4 hours at a metal temperature of
12 1900F. The surface modification or coating of nickel
13 aluminlde is capable of providing oxidation protection for
14 the~articie at high temperatures.
Example 10
A process for the application of a water imper-
16 meable coating on porou~ articles such as wood (laminated
17 or unlzminated) is accomplished by immersing said article
18 into the coagulant of Example 1, withdrawing the article
19 and drying the coagulant at 160F for 5 minufes. After the
article is cool, it is immersed into bath (G) of Example 1
21 for 2 minutes, withdrawn, tap water rinsed, and baked at
22 180F for 1/2 hour.
- 49 -
gS787
Example 11
1 The coating bath (F) of Example 3 is used to apply
2 a coating of aluminum on a glass article. The article is
3 lightly blasted witn 2~ mesh alumlnum oxide, and immersed
4 into a 10% by weight aqueous solution of hydrofluoric acid,
withdrawn and the applied salt dried. After immersing the
6 article in the coagulation coating bath for 1 minute, it
7 is withdrawn, rinsed and baked for 30 minutes at 360F.
8 An adherent 2.5 mil coating resulted.
Example 12
9 The coating bath (G) of Example 1 was used to apply
protective coating to a steel metal article. The article
11 was cleaned as in Example 1 and immersed into a 10% by weight
12 nickel chloride, 3.5% by weight hydrochloric acid in methanol
13 solution. The article was coated in bath (G), Ex~mple 1,
14 rinsed and baked at 3600F. An adherent, smooth 1.0 mil
coating resulted.
Example 13
16 The coating bath (G) of Example 1 was used to apply
17 a protective coating on a steel article. The article was
18 cleaned as in Example 1, except the article was immersed
19 into a 5% by weight hydrochloric acid in ethanol solution.
After the article was withdrawn, and dried, it was immersed
21 ~or 1 minute into the coating bath. The article was with_
22 drawn, rinsed and baked at 360F which resulted in an adherent,
23 smooth 0.5 mil coating.
- 50 -
~95787
Example 14
l The same procedure for coating a glass article
2 was used to apply an aluminum powder coating as in
3 Example ll, except the coagulant was an aqueous 10% by
4 weight h~drofluoric acid, 5~ by weight cobaltous nitrate
solution. The coating which resulted was 9.0 mils.
Example 15
6 An acrylic polymer as prepared in Example 3 was
7 solubilized by reacting the total acid number with ~n
8 equivalent amount of sodium hydroxide. A steel article is
9 cleaned by the procedure in Example l and immersed into a
10% by weight nickel chloride in ethanol solution, withdrawn
ll and dried. The article was immersed into the resin coating
12 bath for 1 minute, withdrawn, and the coated article baked
13 for 25 minutes at 360F. A glossy, adherent, smooth 0.8
14 mil coating resulted.
` Example 16
The coating bath in Example 5 is used to apply a
16 paint film on a 1010 steel article, prevlously zinc
17 phosphate coated by Parker Chemical Company's Bonderite
18 411~P-85 phosphating process. The article is immersed into
19 a 15% by weight nickel chloride in ethanol solution and
withdrawn at a controlled rate, dried and cooled as in
21 Example 1. After immersion of the article into bath (C)
22 of Example 5 for 1 minute, it is withdrawn, tap water
23 rinsed and the resultant film cured. The coating which
- 51 -
9st787
1 resulted was o.7_0.8 mil thick, smooth, adherent and
2 provided excellent salt corrosion protection when tested as
3 in ~xample 1.
Example 17
4 ~he coating bath in Example 5 was used to apply a
paint film on 1010 steel article except the article was grit
6 blasted with 200 mesh aluminum oxide powder prior to immersion
7 into the salt solution of Example 5. In this case the
8 paint fllm was applied by flowing the bath at a controlled
9 rate over the surface of the article for a period of
1 minute. The resultant film after rinsing and curing was
11 continuous, adherent and 0.7 to 0.75 mils.thick.
Example 18
12 A coating was applied on a steel article using the
13 coating bath (C) in Example 5 except the coagulating salt
14 was applied by blasting the surface of the article with a
mixture composed of 2.5% by weight nickel chloride in a
16 200 mesh aluminum oxide powder at a pressure of 60-80 psi.
17 The powder mixture was uniformly blended prior to blasting
18 using a high speed blender. The article was dried at
19 160F and cooled to room temperature. Immersing the part
into the coating both for 1 minute followed by a top water
21 rinse and curlng of the film resulted in a continuous 0 5
22 mil coating.
23 It will be understood by those skilled in the art
24 that modifications can be made in the foregoing examples and
within the scope of the invention as hereinbefore described
26 and hereafter claimed.
_ 52 -
