CA1103387A - Epoxy resin powder coating composition - Google Patents
Epoxy resin powder coating compositionInfo
- Publication number
- CA1103387A CA1103387A CA305,419A CA305419A CA1103387A CA 1103387 A CA1103387 A CA 1103387A CA 305419 A CA305419 A CA 305419A CA 1103387 A CA1103387 A CA 1103387A
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- epoxy
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Classifications
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
- C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
- C08G59/40—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the curing agents used
- C08G59/62—Alcohols or phenols
- C08G59/621—Phenols
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
- C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
- C08G59/20—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the epoxy compounds used
- C08G59/32—Epoxy compounds containing three or more epoxy groups
- C08G59/38—Epoxy compounds containing three or more epoxy groups together with di-epoxy compounds
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/34—Silicon-containing compounds
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L33/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides or nitriles thereof; Compositions of derivatives of such polymers
- C08L33/04—Homopolymers or copolymers of esters
- C08L33/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, which oxygen atoms are present only as part of the carboxyl radical
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L63/00—Compositions of epoxy resins; Compositions of derivatives of epoxy resins
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D163/00—Coating compositions based on epoxy resins; Coating compositions based on derivatives of epoxy resins
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Wood Science & Technology (AREA)
- Paints Or Removers (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Epoxy resin powder coating compositions which have good shelf-life and which are capable of rapid cure are obtained by blending two types of epoxy resins with filler particles and a curing agent. One resin is of the epichlorohydrin-bisphenol-A type. The other resin is an epichlorohydrin-bisphenol-A epoxy modified with an epoxy-novolac. Rapidly curing films are obtained by using a hydroxy-containing, mixed aromatic-aliphatic polyether resin crosslinking agent. The cure is accelerated with an alkylimidazole. These compositions are useful in coating metal substrates, particularly pipe exteriors, when rapid cure, flexibility, and good adhesion are needed.
Epoxy resin powder coating compositions which have good shelf-life and which are capable of rapid cure are obtained by blending two types of epoxy resins with filler particles and a curing agent. One resin is of the epichlorohydrin-bisphenol-A type. The other resin is an epichlorohydrin-bisphenol-A epoxy modified with an epoxy-novolac. Rapidly curing films are obtained by using a hydroxy-containing, mixed aromatic-aliphatic polyether resin crosslinking agent. The cure is accelerated with an alkylimidazole. These compositions are useful in coating metal substrates, particularly pipe exteriors, when rapid cure, flexibility, and good adhesion are needed.
Description
11l~;~;~ 7 BACKGROUND O~ TH~ INVENT~ON
FIELD OF THE Il~VENTION
_ _ _ _ _ This invention is reiated to th~rmosetting powder coating compositions and particularly to compo-sitions containing epoxy resins.
DESCRIPTION OF PRIOR ART
Epoxy resin powder coating compositions which are capable of being crosslinked and various agents which effect the crosslinking are well ~nown. m e prior art contains numerous references to compositions which con-tain epoxy polymers and to conventional crosslinking agents such as anhydrides or amines.
United States Patent 3,882,064 issued May 6, 1975 to W. Pregmon, discloses thermosettin~ powder coating compositions based on an epoxy resin of the epichloro-hydrin-~isphenol-A type crosslinked by- dicyanidiam~de.
Similar powder coatings are shown by Nagel, ~nited States Patent 3,Q28,251, issued April 3, 1962; and Parry, United States Patent 3,400,098, issued September 3, 1968.
Dicyandiamide-cured compositions can be water sensitive and therefore are not well suited to be pipe coatings.
No disclosure ls made in these patents as to the resis-tance of their respective compositions to adhesion loss under cathodic protection.
Powder coatings which cure rapidly and have resistance to adhesion loss when sub~ected to cathodic protection are particularly demanded by the pipe industry.
The prior art coat~ngs capable o~ curing in less than two minutes at 200~C nave been commonly found to lose 3Q adhesion when sub~ected to cathodic protection. Pipes
FIELD OF THE Il~VENTION
_ _ _ _ _ This invention is reiated to th~rmosetting powder coating compositions and particularly to compo-sitions containing epoxy resins.
DESCRIPTION OF PRIOR ART
Epoxy resin powder coating compositions which are capable of being crosslinked and various agents which effect the crosslinking are well ~nown. m e prior art contains numerous references to compositions which con-tain epoxy polymers and to conventional crosslinking agents such as anhydrides or amines.
United States Patent 3,882,064 issued May 6, 1975 to W. Pregmon, discloses thermosettin~ powder coating compositions based on an epoxy resin of the epichloro-hydrin-~isphenol-A type crosslinked by- dicyanidiam~de.
Similar powder coatings are shown by Nagel, ~nited States Patent 3,Q28,251, issued April 3, 1962; and Parry, United States Patent 3,400,098, issued September 3, 1968.
Dicyandiamide-cured compositions can be water sensitive and therefore are not well suited to be pipe coatings.
No disclosure ls made in these patents as to the resis-tance of their respective compositions to adhesion loss under cathodic protection.
Powder coatings which cure rapidly and have resistance to adhesion loss when sub~ected to cathodic protection are particularly demanded by the pipe industry.
The prior art coat~ngs capable o~ curing in less than two minutes at 200~C nave been commonly found to lose 3Q adhesion when sub~ected to cathodic protection. Pipes
- 2 -38'7 are often sub~ected to cat;lodic protection, after burial in the sround, ~y connecting them to the negative terminal of a direct voltage source. It is important that the coating not lose adhesion under these condi-tions.
United States Patent 3,819,564, issued June 25, 1974 to W. Gindrup and A. J. Siegmund, Jr., discloses thermosetting powder coating compositions based on epichlorohydrin-bisphenol-A epoxy resins cured by aromatic anhydrides and hydroxypyridines. This composition i3 said to cure in 45 seconds at 200-230C and has acceptable resistance to adhesion loss during cathodic protection.
~owever, its ~lexibility is less than that exhibited by coatings which require more than two minutes to cure.
The use of blends of epichlorohydrin-bispAenol-A
epoxies and novolac epoxies in powder coating compositions ls ~hown, for example, in United States Patent 3,4~4,398, issued December 16, 1969 to W. I. Childs in whicn a silica filler and anhydride curing agent were used. These compo-sitions, formulated to ser~e either a molding or coatingfunction, are deficient with respect to certain desirable coatlng composition ~roperties, notably cure-time and fle~ibility, when compared to compositions designed .or use solely as coatings.
The use of curing agents other than the conven-tionally used anhydrides and amines is also part of the art.
An agent, belie~ed to be a hydroxy-containing aromatic-aliphatic ether, specially designed for use in curing epoxy resin powder coatings, is shown in Dow Chemical Company Technlcal Data pamphlet entitled "Dow Experimental 33~7 Xardener ~D-8062," dated March 2, 1975. Some o~ the disclosed uses for this curing agent are in compositions based on epoxy resins similar to those used in the present inYention, These compositions exhibit acceptable flex-ibillty and adhesion but require a relatively long cure tlme.
Therefore, there remains a need for an epoxy resin powder coating composition which ~ures rapidly, preferably in less than two minutes at commerclally acceptable ~.emperatures, and which has good adhesion, adhesion retention under cathodlc protection, and flexibility.
SUMMARY OF THE I~VENTION
According to the present invention, there is provided a thermosetting powder coating composition which consists essentially of finely divided particles at least 90 percent by weight of which have a max.imum dimension not exceeding 150 microns. The particles are a blend of a composition of:
(A) 9-25 parts by weight of an epoxy resin of the formula 0\ . 3 OH
CH2 - CH - CH2 - ~ ~, ~ 0-CH2-CH-CH2_ -O-_ CH3 _ n C ~ ~ - - CH2 CH- CH2 C~
where n is suf~iciently large ~o provide a resin having a Gardner-Holdt Viscosity o~ H-L measured at 40 percent 3o polymer solids in diethylene glycol n-butyl ether at ~3387 25C and having an epoxide equivalent weight of 575-7;
(B) 0.9-3 parts by weight of an epoxy resin having the same general formula as (A) ~ut having a value for n sufficiently large to provide a resin having a Gardner-Holdt Viscosity of K-P measured as above and having an epoxide equiYalent weight of 660-810;
(C~ 20-38 parts by weight o~ an epoxy/epoxy no~olac resin which is an epoxy resin of the formula of (A~ modi~ied with an epoxy novolac resin of the ~ormula O c~2 cH c~2 r O cH2 cH c ~2 1 O c~2-C~-cH2 ~2 ~ CH ~ ~
where n o~ the epoxy resin and m of the epoxy novolac resin have values sufficiently large to provide an epoxy~epoxy novolac resin having a Gardner-~oldt Viscosity of W-Z measured as in (A) and having an epoxide equivalent weight o~ 750-860;
(D) 0-25 parts by weight of an epoxy/epoxy novolac resin of the formula of (C~ but having values for n and m sufficiently large to provide an epoxy/epoxy novolac resin having a Gardner-Holdt ~iscosity of 0-S measured as 1n (A) and having an epoxide equivalent weight of 500-575 wherein the parts by weight of components (C) and (D~ total at least 34;
(E~ 10-20 parts by weight of filler particles havlng
United States Patent 3,819,564, issued June 25, 1974 to W. Gindrup and A. J. Siegmund, Jr., discloses thermosetting powder coating compositions based on epichlorohydrin-bisphenol-A epoxy resins cured by aromatic anhydrides and hydroxypyridines. This composition i3 said to cure in 45 seconds at 200-230C and has acceptable resistance to adhesion loss during cathodic protection.
~owever, its ~lexibility is less than that exhibited by coatings which require more than two minutes to cure.
The use of blends of epichlorohydrin-bispAenol-A
epoxies and novolac epoxies in powder coating compositions ls ~hown, for example, in United States Patent 3,4~4,398, issued December 16, 1969 to W. I. Childs in whicn a silica filler and anhydride curing agent were used. These compo-sitions, formulated to ser~e either a molding or coatingfunction, are deficient with respect to certain desirable coatlng composition ~roperties, notably cure-time and fle~ibility, when compared to compositions designed .or use solely as coatings.
The use of curing agents other than the conven-tionally used anhydrides and amines is also part of the art.
An agent, belie~ed to be a hydroxy-containing aromatic-aliphatic ether, specially designed for use in curing epoxy resin powder coatings, is shown in Dow Chemical Company Technlcal Data pamphlet entitled "Dow Experimental 33~7 Xardener ~D-8062," dated March 2, 1975. Some o~ the disclosed uses for this curing agent are in compositions based on epoxy resins similar to those used in the present inYention, These compositions exhibit acceptable flex-ibillty and adhesion but require a relatively long cure tlme.
Therefore, there remains a need for an epoxy resin powder coating composition which ~ures rapidly, preferably in less than two minutes at commerclally acceptable ~.emperatures, and which has good adhesion, adhesion retention under cathodlc protection, and flexibility.
SUMMARY OF THE I~VENTION
According to the present invention, there is provided a thermosetting powder coating composition which consists essentially of finely divided particles at least 90 percent by weight of which have a max.imum dimension not exceeding 150 microns. The particles are a blend of a composition of:
(A) 9-25 parts by weight of an epoxy resin of the formula 0\ . 3 OH
CH2 - CH - CH2 - ~ ~, ~ 0-CH2-CH-CH2_ -O-_ CH3 _ n C ~ ~ - - CH2 CH- CH2 C~
where n is suf~iciently large ~o provide a resin having a Gardner-Holdt Viscosity o~ H-L measured at 40 percent 3o polymer solids in diethylene glycol n-butyl ether at ~3387 25C and having an epoxide equivalent weight of 575-7;
(B) 0.9-3 parts by weight of an epoxy resin having the same general formula as (A) ~ut having a value for n sufficiently large to provide a resin having a Gardner-Holdt Viscosity of K-P measured as above and having an epoxide equiYalent weight of 660-810;
(C~ 20-38 parts by weight o~ an epoxy/epoxy no~olac resin which is an epoxy resin of the formula of (A~ modi~ied with an epoxy novolac resin of the ~ormula O c~2 cH c~2 r O cH2 cH c ~2 1 O c~2-C~-cH2 ~2 ~ CH ~ ~
where n o~ the epoxy resin and m of the epoxy novolac resin have values sufficiently large to provide an epoxy~epoxy novolac resin having a Gardner-~oldt Viscosity of W-Z measured as in (A) and having an epoxide equivalent weight o~ 750-860;
(D) 0-25 parts by weight of an epoxy/epoxy novolac resin of the formula of (C~ but having values for n and m sufficiently large to provide an epoxy/epoxy novolac resin having a Gardner-Holdt ~iscosity of 0-S measured as 1n (A) and having an epoxide equivalent weight of 500-575 wherein the parts by weight of components (C) and (D~ total at least 34;
(E~ 10-20 parts by weight of filler particles havlng
3~7 a ma~imum dimension o~ 10 microns~ and (F) 18-25 parts by weight o~ a reslnous curing agent consisting essentially of:
1. 68-81 parts by weight o~ a compound of the formula E 2 , 2 OH x where Ar= ~ C
and x is a positive number sufficiently large to provide a compound with a weight average molecular weight of 1250-1600, as determined by Gel Permeaticn Chromo-tography based on a linear calibration curve obtained from narrow molecular welght polystyrene standards;
2. 17-30 parts by weight of bisphenol-A; and 2~ 3. 0.6-2~0 parts by welght of an alkyli-midazole in whlch the alkyl group con-tains 1-4 carbon atoms.
DESCRIPTION OF THE INVENTION
-It has been found ~hat the epoxy resin powder coatlng compositlon of this invention unexpectedly elimi-nates the dlsadvantages of the prior art with respect to speed of cure, flexibility, and adhesion retention. The deslrable aspects o~ the prior art coatings have been in-corporated by the new composition to an unexpected degree.
3Q The coating compositlon of this invention has 3~'7 a powder particle size such that at least 90 percent by weight of the particles have a max~mum dimension not exceeding 150 microns and preferably none has a maximum dimension exceeding 200 microns. It is preferred that there be a maximum dimension of 10-120 ~icrons and more preferred that it be 40-100 microns.
About 9-25 parts by weight of the powder coating composition is an epoxy resin whlch is of the epichloro-hydrin-bisphenol-A type, of the formula 1~ _ / \H CH ~ 3 c~3 , r where n is sufficiently large to provide a Gardner-Holdt Viscosity of H-L measured at 40 percent polymer solids in diethylene glycol n-~utyl ether at 25C and the resin has an epoxlde equivalent weight of 575-700. The epoxide equivalent weight is the weight in grams of epoxy resin that contains one gram equivalent of epoxide.
Preferably 10-15 parts by weight and most preferably ahout 11-12 parts by weight o~ this epoxy resin are used in the powder coating composition.
About 0.9-3 parts by weight of another epoxy resin is used in the composition. This epoxy resin has the same general formula as the above resin and has a Gardner-Holdt Vlsco~ity, measured as aDove, of K-P and an epoxide equiv-alent weight of 660-810. Pre~erably, the wei~ht ratio of ~3387 this epoxy resin to the first epoxy resin is approximately .08/1 to .2/1.
About 20-3~ parts by weight of an epoxy/epoxy novolac resin ls used in the composition. m is resin is an epichlorohydrln-bisphenol-A resin of the ~ormula shown above modified with an epoxy novolac resin of the formula O cH2 cH cR2 r O cH2 c~-cH2 1 P cH2 cd c~2 10 ~} CH2~ CH2~
where n of the epoxy resin and m of the epoxy novolac resin have values suf~iciently large to provide an epoxy/epoxy novolac resin having a Gardner-Holdt Vlscosity o~ W-Z, measured at 40 percent polymer soliàs in diethylene glycol n-butyl ether at 25C and having an epoxide equivalent weigh, of 750-860. Preferably, 22~30 parts by weight of this resin is used.
Epoxy/epoxy novolac resins are formed by modifying an epichlorohydrln-bisphenol-A resin with an epoxy novolac resin. It is believed that the modification is either direct crossllnking of the two resins or indirect crosslinklng through reaction o~ both resins with bisphenol-A.
By varylng the ratio o~ epichlorohydrin-bisphenol-A
epoxy to epoxy novolac, the vicosity and epoxide equlvalent weight can be varied and epoxy~epoxy novolac resins o~
dl~ferent reactivity can be provided.
- Optionally, up to 25 parts by weight of an epoxy/
epoxy novolac of the same formula as above, can be used in the compositlon. This resin has a Gardner-Xoldt Viscoslty o~ O-S, measured as above, and an epoxide equivalent wei~ht ~33~37 of 500-575. Preferably this resin is present in the amount of 20-25 parts by weight,and more preferably 22-23 parts by wei~h~ but the parts by weight of both epoxy/epoxy novolac reslns should total at least 34.
To improve abrasion resistance of the coating and to relieve shrinking forces which can occur during curing, the composition contains 10-20 parts by weight of filler particles having a maximum dimension of 10 microns. Con~en-tional particulate fillers which can be used are silica, barium sulfate, calcium car~onate, aluminum silicate, mica, and the like. Preferred fillers are silica, barium sulfate, or mixtures of these. A suitable silica filler, for example, is commercially available under the trademark Min-U-Sil~5 registered to Pennsylvania Glass Sand Company.
When the composition is used to coat rlbbed rein-forcing bars or other sharp-edged articles, more uni~orm edge covering is attained when up to 3 percent by weight, based on the weight of the composition, of fumed silica is added. This is a very fine, amorphous silica formed from silica spheres having an average diameter of 7-14 millimicrons and having large surface area, 200-400 square meters per gram. Such a substance is commercially available from Cabot Corporation as Cab-O-Sil~.
A curing agent in the amount of 18-25 parts by weight is used in the composition. The agent is resinous in nature and contains:
l. 68-81 parts by we~ght o~ a compound of the formula _ , _ HO-Ar- - O-CX2-CX-CH2-0-Ar _ - OH
0~ x ,CH3 where Ar= ~ C
\==/
C~
and x is a positive number sufficiently large to provide a compound with a weight average molecular weight of 1250-1600, as determined by Gel Permeation Chromatogr~phy (GPC) based on a linear calibration curve obtained from narrow molecular weight polystyrene standards;
2. 17-30 parts by weight of bispheno`-A; and 3. 0.6-2.0 parts by weight of an alkylimidazole in which the alkyl group contains 1-4 carbon atoms.
Prefer~bly, the alkyl group is methyl.
With respect to the first component of the curing agent it is preferred for a more flexible coating that the average molecular weight of this component be increased within its range as the parts by weight of the component used ln the curing agent composition is increased.
The composition can be pigmented or unpigmented but is usually plgmented and contains a pigment to binder ratio of 3~100 to 30/100. Any conventional inorganic, organic, or filler pigments can be used. Examples of the pigments that can be used in the composition are:
metallic oxides such as ~i anium dioxide, zinc oxi~e, iro~.
oxide, chrome oxide, and the like; metallic powders;
metal hydroxides; sul~ides; sulfates; and other ~iller pigments.
Flow control agents can be added to the powder coating composition in amounts up to 1.0 percent by weight based on the weight of the composition. Typical flow control agents are poly alkylacrylates where the alkyl group contains 2-8 carbon atoms. A suitable substance ~or this purpose is commercially available under 3~7 the trademark ModaFlow~ registered to Monsanto Corporation.
One method for forming the powder coating compo-sition of this invention ls to blend the components together and then to ~ass the mixture through a conventional extruder. The extrudate can then be reduced to a powder using conventional grinding equipment. After grinding, the powder is passed through a sieve to remove large partlcles. Pre~erably, a sieve which eliminates particles of maximum dimension greater than 150 microns is used but 40-55 percent by weight of the powder should have a maxlmum dimension not exceeding 44 microns.
The powder thus formed has the properties of rapid cure and good shelf~ e to a de~ree mexpected from the components lnvolved. One particularly preferred composition, descr,bed in Example 1, is f~und to cure in 90 seconds at 2~2C. The same cure rate is observed after the powder has been ln storage for 4 weeks at 40ac.
In the prior art, use of epoxy resins and curing agents substantially similar to those used ln the present invention produced powder coating compositions which required cure tlmes, at commercially acceptable tempera-tures, ln excess of two minutes to ~orm smooth, flexible coatings. However~ the present invention combines the components to produce synergist~c results in a powder which not only cures in under two minutes but which also ~orms coatlngs which are adhesive~ ~lexible, and smooth and even.
By comparison, an epoxy resin powder coating composition, shown in the Dow Chemical Company Technical Data pam~hlet entitled "Dow Experimental Hardener XD-8062"
3Q (page 8, Table III), March 2, 1975, is reported to re~uire 3~7 3-5 mlnutes to cure at 232C. The composition shown in this reference contains two epoxy/epoxy novolac resins and a curing a~ent substantially simllar to components which partially comprise the composition of the present invention.
~hile the coating fo~med by the composition is adhesive and impact resistant, it requires a lon~er cure time and exhlbits less fle~ibility.
By way of further com~arison, in the same reference there is shown (page 6, Table II, Column 2) an epoxy resin powder co~ting composition contalning two epoxy resins which, with others, are used in the present invention. ri~is composltlon is cured by a curing agent substantially simllar to that used in the present invention.
This reference composition exhlbits acceptable film proper-tles but re~ulres 15 minutes to cure at 200C.
It has been found that the composition of the present lnventlon comblnes these epoxy and epoxy/epoxy novolac resins with a curing agent to produce a new powder coatlng composition exhibiting unexpected properties. The film properties equal or surpass in quality those exhibited by the compositions of the above reference and these pro-pertles are attained with cures of less tnan two minutes at commercially acceptable temperatures.
It has a~so been found that coatings formed from the compositions of this invention have excellent reslstance to adhesion loss under cathodic protectlon. A procedure used to test this resistance is one in which a metal panel is coated, as described below, with the powder coating composition. A hole ~ m~. ln diameter is drilled through the coating and part way into the panel, A piece of 10 cm 3~3'7 diameter plastic pipe is adhesiYely bonded to the coating to proride a fluid-tlght container ~ith the hole at the center of the flat base of this container. The container is filled with a solution of 5~ i~aCl in water. A platinum wire is placed in the solution and a direct current potential of 6 volts ls applied continuously between the wire and the metal panel, which acts as the cathode in this circuit. A~ter 30 days, the voltage source is disconnected, the solution is poured o~f, and any disbonded co~tlng is scraped away with a sharp knlfe, leaving an uncoated circle, the diameter of which is measured. Prior art pipe coatings which are used commercially leave an uncoated circle of 20-40 mm. diameter when sub~ected to this test. A preferred composition of the present inYention leaves an uncoated circle of only 11-22 mm. diameter when sub~ected to thls test.
The powder coating composition of this invention can be applied to a metal substrate by electrostatic spraying techniques or by using a fluidized bed which can be electrostatic. The preferable method is electrostatic spraying in which a voltage of 20-100 kilovolts is applied to the spray gun. The composition can be ~pplied either in one pass or- in~everal passes to ~rovide variable thicknesses, after cure, of 0.2 - O.5 mm. de-pending on the desired end-use of the coated article.
Some pipes, ~or example, which are to be buried under-ground~ require a coating thickne6s o~ ~pproximately 0.4 mm.
The article to be coated can, optionally, be heated to any temperature up to approximately 270C
3~7 prior to the application of the powder. Preheating the article provides better powder deposition and allows a more uniform coating.
After the application of the powder, the coated article is heated at 200-280C for 1-2 minutes to fuse and to cure the powder particles into a substantially continuous uniform coating. The preferred temperature range is 230-253C when the alkylimidazole content of the curing agent is 1-1.4 weight percent. Curing tem-perat~res above 253~C can sometime~ produce a brittle coating. When the weight percentage of alkylimidazole in the curing agent exceeds 1.6, curing temperatures above 210C can sometimes produce a coating with poor appearance.
The composition of the invention can be applied directly to a .~etal surface, although for some end-uses a primer can be used. It is preferable that the surface to be coated be first cleaned by, for example, grinding or grit blasting.
2Q The following examples illustrate the invention.
Ir. the examples, the components will be referred to according to the following numbering system:
(1~ Epoxy resin having the formula CH2-Ch-C~2 ~ 0 ~ Ch3 0-C~ H-0~ 0 ~ Ch7 0-CH~-Ch-C~z where n is sufficiently large to provide a Gardner-Holdt Viscosity of H-L measured at 40~ polymer solids in diethylene glycol n-butyl ether at 25C and having 3~37 an epoxide equivalent weight of 575-700 (2) Epoxy resin of the above formula but having a value for n such that there is provided a Gardner Holdt Viscosity, measured as above, of K-P and an epoxide equivalent weight of 660-810.
~3) Epoxy/epoxy novolac resin which is an epoxy resin of the fQrmula of (1) modified wlth an epoxy novolac resin of the formula .
O-CX2-CH-CH2 C C/H \CU o-CH2-C --CH2 ~CH2 ~. CH2_~
where n of the epoxy resin and m of the epoxy novolac resln have values sufficiently large to provide an epoxy/epoxy novolac resin having a Gardner-Holdt Viscosity o~ W-Z, measured as in (1) and an epoxlde equivalent weight of 750-860 (4~ Epo~y/epoxy novolac resin o~ the formula of (3) but having values for n and m sufficiently large to pro~ide a Gardner-~oldt Viscosity of 0-S, measured as in (1) and an epoxide equivalent weight of 500-575 (5) Sil~ca partlcles, maximum dimension 10 ~icrons (6) Curing agent which i- a combination of:
a. 70 parts by welght of a resin of the formula 3o ~0-Ar- E O-CH2-CH-CU2-O-Ar ~ -OH
where Ar=
and x is approximately 3.8 corresponding to a weight average GPC molecular weight of 1312 based on a llnear calibratlon curve obtained from narrow molecular weight polystyrene standards;
b. 30 parts by welght bisphenol-A; and c. 1.3 parts by weight of 2-methylimidazole (7~ Titanlum dioxlde pigment (8) Red Iron oxide pigment (9) ModaFlow~
The following components are blended together:
Com~onent Parts by wel~ht 1 11.3 2 1.0 3 22.8
1. 68-81 parts by weight o~ a compound of the formula E 2 , 2 OH x where Ar= ~ C
and x is a positive number sufficiently large to provide a compound with a weight average molecular weight of 1250-1600, as determined by Gel Permeaticn Chromo-tography based on a linear calibration curve obtained from narrow molecular welght polystyrene standards;
2. 17-30 parts by weight of bisphenol-A; and 2~ 3. 0.6-2~0 parts by welght of an alkyli-midazole in whlch the alkyl group con-tains 1-4 carbon atoms.
DESCRIPTION OF THE INVENTION
-It has been found ~hat the epoxy resin powder coatlng compositlon of this invention unexpectedly elimi-nates the dlsadvantages of the prior art with respect to speed of cure, flexibility, and adhesion retention. The deslrable aspects o~ the prior art coatings have been in-corporated by the new composition to an unexpected degree.
3Q The coating compositlon of this invention has 3~'7 a powder particle size such that at least 90 percent by weight of the particles have a max~mum dimension not exceeding 150 microns and preferably none has a maximum dimension exceeding 200 microns. It is preferred that there be a maximum dimension of 10-120 ~icrons and more preferred that it be 40-100 microns.
About 9-25 parts by weight of the powder coating composition is an epoxy resin whlch is of the epichloro-hydrin-bisphenol-A type, of the formula 1~ _ / \H CH ~ 3 c~3 , r where n is sufficiently large to provide a Gardner-Holdt Viscosity of H-L measured at 40 percent polymer solids in diethylene glycol n-~utyl ether at 25C and the resin has an epoxlde equivalent weight of 575-700. The epoxide equivalent weight is the weight in grams of epoxy resin that contains one gram equivalent of epoxide.
Preferably 10-15 parts by weight and most preferably ahout 11-12 parts by weight o~ this epoxy resin are used in the powder coating composition.
About 0.9-3 parts by weight of another epoxy resin is used in the composition. This epoxy resin has the same general formula as the above resin and has a Gardner-Holdt Vlsco~ity, measured as aDove, of K-P and an epoxide equiv-alent weight of 660-810. Pre~erably, the wei~ht ratio of ~3387 this epoxy resin to the first epoxy resin is approximately .08/1 to .2/1.
About 20-3~ parts by weight of an epoxy/epoxy novolac resin ls used in the composition. m is resin is an epichlorohydrln-bisphenol-A resin of the ~ormula shown above modified with an epoxy novolac resin of the formula O cH2 cH cR2 r O cH2 c~-cH2 1 P cH2 cd c~2 10 ~} CH2~ CH2~
where n of the epoxy resin and m of the epoxy novolac resin have values suf~iciently large to provide an epoxy/epoxy novolac resin having a Gardner-Holdt Vlscosity o~ W-Z, measured at 40 percent polymer soliàs in diethylene glycol n-butyl ether at 25C and having an epoxide equivalent weigh, of 750-860. Preferably, 22~30 parts by weight of this resin is used.
Epoxy/epoxy novolac resins are formed by modifying an epichlorohydrln-bisphenol-A resin with an epoxy novolac resin. It is believed that the modification is either direct crossllnking of the two resins or indirect crosslinklng through reaction o~ both resins with bisphenol-A.
By varylng the ratio o~ epichlorohydrin-bisphenol-A
epoxy to epoxy novolac, the vicosity and epoxide equlvalent weight can be varied and epoxy~epoxy novolac resins o~
dl~ferent reactivity can be provided.
- Optionally, up to 25 parts by weight of an epoxy/
epoxy novolac of the same formula as above, can be used in the compositlon. This resin has a Gardner-Xoldt Viscoslty o~ O-S, measured as above, and an epoxide equivalent wei~ht ~33~37 of 500-575. Preferably this resin is present in the amount of 20-25 parts by weight,and more preferably 22-23 parts by wei~h~ but the parts by weight of both epoxy/epoxy novolac reslns should total at least 34.
To improve abrasion resistance of the coating and to relieve shrinking forces which can occur during curing, the composition contains 10-20 parts by weight of filler particles having a maximum dimension of 10 microns. Con~en-tional particulate fillers which can be used are silica, barium sulfate, calcium car~onate, aluminum silicate, mica, and the like. Preferred fillers are silica, barium sulfate, or mixtures of these. A suitable silica filler, for example, is commercially available under the trademark Min-U-Sil~5 registered to Pennsylvania Glass Sand Company.
When the composition is used to coat rlbbed rein-forcing bars or other sharp-edged articles, more uni~orm edge covering is attained when up to 3 percent by weight, based on the weight of the composition, of fumed silica is added. This is a very fine, amorphous silica formed from silica spheres having an average diameter of 7-14 millimicrons and having large surface area, 200-400 square meters per gram. Such a substance is commercially available from Cabot Corporation as Cab-O-Sil~.
A curing agent in the amount of 18-25 parts by weight is used in the composition. The agent is resinous in nature and contains:
l. 68-81 parts by we~ght o~ a compound of the formula _ , _ HO-Ar- - O-CX2-CX-CH2-0-Ar _ - OH
0~ x ,CH3 where Ar= ~ C
\==/
C~
and x is a positive number sufficiently large to provide a compound with a weight average molecular weight of 1250-1600, as determined by Gel Permeation Chromatogr~phy (GPC) based on a linear calibration curve obtained from narrow molecular weight polystyrene standards;
2. 17-30 parts by weight of bispheno`-A; and 3. 0.6-2.0 parts by weight of an alkylimidazole in which the alkyl group contains 1-4 carbon atoms.
Prefer~bly, the alkyl group is methyl.
With respect to the first component of the curing agent it is preferred for a more flexible coating that the average molecular weight of this component be increased within its range as the parts by weight of the component used ln the curing agent composition is increased.
The composition can be pigmented or unpigmented but is usually plgmented and contains a pigment to binder ratio of 3~100 to 30/100. Any conventional inorganic, organic, or filler pigments can be used. Examples of the pigments that can be used in the composition are:
metallic oxides such as ~i anium dioxide, zinc oxi~e, iro~.
oxide, chrome oxide, and the like; metallic powders;
metal hydroxides; sul~ides; sulfates; and other ~iller pigments.
Flow control agents can be added to the powder coating composition in amounts up to 1.0 percent by weight based on the weight of the composition. Typical flow control agents are poly alkylacrylates where the alkyl group contains 2-8 carbon atoms. A suitable substance ~or this purpose is commercially available under 3~7 the trademark ModaFlow~ registered to Monsanto Corporation.
One method for forming the powder coating compo-sition of this invention ls to blend the components together and then to ~ass the mixture through a conventional extruder. The extrudate can then be reduced to a powder using conventional grinding equipment. After grinding, the powder is passed through a sieve to remove large partlcles. Pre~erably, a sieve which eliminates particles of maximum dimension greater than 150 microns is used but 40-55 percent by weight of the powder should have a maxlmum dimension not exceeding 44 microns.
The powder thus formed has the properties of rapid cure and good shelf~ e to a de~ree mexpected from the components lnvolved. One particularly preferred composition, descr,bed in Example 1, is f~und to cure in 90 seconds at 2~2C. The same cure rate is observed after the powder has been ln storage for 4 weeks at 40ac.
In the prior art, use of epoxy resins and curing agents substantially similar to those used ln the present invention produced powder coating compositions which required cure tlmes, at commercially acceptable tempera-tures, ln excess of two minutes to ~orm smooth, flexible coatings. However~ the present invention combines the components to produce synergist~c results in a powder which not only cures in under two minutes but which also ~orms coatlngs which are adhesive~ ~lexible, and smooth and even.
By comparison, an epoxy resin powder coating composition, shown in the Dow Chemical Company Technical Data pam~hlet entitled "Dow Experimental Hardener XD-8062"
3Q (page 8, Table III), March 2, 1975, is reported to re~uire 3~7 3-5 mlnutes to cure at 232C. The composition shown in this reference contains two epoxy/epoxy novolac resins and a curing a~ent substantially simllar to components which partially comprise the composition of the present invention.
~hile the coating fo~med by the composition is adhesive and impact resistant, it requires a lon~er cure time and exhlbits less fle~ibility.
By way of further com~arison, in the same reference there is shown (page 6, Table II, Column 2) an epoxy resin powder co~ting composition contalning two epoxy resins which, with others, are used in the present invention. ri~is composltlon is cured by a curing agent substantially simllar to that used in the present invention.
This reference composition exhlbits acceptable film proper-tles but re~ulres 15 minutes to cure at 200C.
It has been found that the composition of the present lnventlon comblnes these epoxy and epoxy/epoxy novolac resins with a curing agent to produce a new powder coatlng composition exhibiting unexpected properties. The film properties equal or surpass in quality those exhibited by the compositions of the above reference and these pro-pertles are attained with cures of less tnan two minutes at commercially acceptable temperatures.
It has a~so been found that coatings formed from the compositions of this invention have excellent reslstance to adhesion loss under cathodic protectlon. A procedure used to test this resistance is one in which a metal panel is coated, as described below, with the powder coating composition. A hole ~ m~. ln diameter is drilled through the coating and part way into the panel, A piece of 10 cm 3~3'7 diameter plastic pipe is adhesiYely bonded to the coating to proride a fluid-tlght container ~ith the hole at the center of the flat base of this container. The container is filled with a solution of 5~ i~aCl in water. A platinum wire is placed in the solution and a direct current potential of 6 volts ls applied continuously between the wire and the metal panel, which acts as the cathode in this circuit. A~ter 30 days, the voltage source is disconnected, the solution is poured o~f, and any disbonded co~tlng is scraped away with a sharp knlfe, leaving an uncoated circle, the diameter of which is measured. Prior art pipe coatings which are used commercially leave an uncoated circle of 20-40 mm. diameter when sub~ected to this test. A preferred composition of the present inYention leaves an uncoated circle of only 11-22 mm. diameter when sub~ected to thls test.
The powder coating composition of this invention can be applied to a metal substrate by electrostatic spraying techniques or by using a fluidized bed which can be electrostatic. The preferable method is electrostatic spraying in which a voltage of 20-100 kilovolts is applied to the spray gun. The composition can be ~pplied either in one pass or- in~everal passes to ~rovide variable thicknesses, after cure, of 0.2 - O.5 mm. de-pending on the desired end-use of the coated article.
Some pipes, ~or example, which are to be buried under-ground~ require a coating thickne6s o~ ~pproximately 0.4 mm.
The article to be coated can, optionally, be heated to any temperature up to approximately 270C
3~7 prior to the application of the powder. Preheating the article provides better powder deposition and allows a more uniform coating.
After the application of the powder, the coated article is heated at 200-280C for 1-2 minutes to fuse and to cure the powder particles into a substantially continuous uniform coating. The preferred temperature range is 230-253C when the alkylimidazole content of the curing agent is 1-1.4 weight percent. Curing tem-perat~res above 253~C can sometime~ produce a brittle coating. When the weight percentage of alkylimidazole in the curing agent exceeds 1.6, curing temperatures above 210C can sometimes produce a coating with poor appearance.
The composition of the invention can be applied directly to a .~etal surface, although for some end-uses a primer can be used. It is preferable that the surface to be coated be first cleaned by, for example, grinding or grit blasting.
2Q The following examples illustrate the invention.
Ir. the examples, the components will be referred to according to the following numbering system:
(1~ Epoxy resin having the formula CH2-Ch-C~2 ~ 0 ~ Ch3 0-C~ H-0~ 0 ~ Ch7 0-CH~-Ch-C~z where n is sufficiently large to provide a Gardner-Holdt Viscosity of H-L measured at 40~ polymer solids in diethylene glycol n-butyl ether at 25C and having 3~37 an epoxide equivalent weight of 575-700 (2) Epoxy resin of the above formula but having a value for n such that there is provided a Gardner Holdt Viscosity, measured as above, of K-P and an epoxide equivalent weight of 660-810.
~3) Epoxy/epoxy novolac resin which is an epoxy resin of the fQrmula of (1) modified wlth an epoxy novolac resin of the formula .
O-CX2-CH-CH2 C C/H \CU o-CH2-C --CH2 ~CH2 ~. CH2_~
where n of the epoxy resin and m of the epoxy novolac resln have values sufficiently large to provide an epoxy/epoxy novolac resin having a Gardner-Holdt Viscosity o~ W-Z, measured as in (1) and an epoxlde equivalent weight of 750-860 (4~ Epo~y/epoxy novolac resin o~ the formula of (3) but having values for n and m sufficiently large to pro~ide a Gardner-~oldt Viscosity of 0-S, measured as in (1) and an epoxide equivalent weight of 500-575 (5) Sil~ca partlcles, maximum dimension 10 ~icrons (6) Curing agent which i- a combination of:
a. 70 parts by welght of a resin of the formula 3o ~0-Ar- E O-CH2-CH-CU2-O-Ar ~ -OH
where Ar=
and x is approximately 3.8 corresponding to a weight average GPC molecular weight of 1312 based on a llnear calibratlon curve obtained from narrow molecular weight polystyrene standards;
b. 30 parts by welght bisphenol-A; and c. 1.3 parts by weight of 2-methylimidazole (7~ Titanlum dioxlde pigment (8) Red Iron oxide pigment (9) ModaFlow~
The following components are blended together:
Com~onent Parts by wel~ht 1 11.3 2 1.0 3 22.8
4 22.8 16.
~?.~l 7 tJ.Il 8 2.&
9 0.05 The above blentl is char~ed into a melt extruder and extruded at 88-94C. The extrudate is then broken into 3 chips and charged into a grindlng mill where it is ground 3~7 to a fine powder. The powder is then passed through a sieve which removes particles of maximum dimenslon greater than 150 mlcrons.
The powder thus formulated can be stored for four wee~s at 40C without appreciable loss of ability to cure rapidly or to form a smooth film.
Be~ore application o~ the powder, a 3_mm. thick grit blasted steel panel to be coated in this example is heated to 253C. The powder is then applled by Ransburg electro-static powder guns. The guns use 60 volts of the electricityto charge the powder particles and 60 pounds per sauare inch air pressure to propel the particles which are fed to each gun, from a ~luidized bed reservoir, by an air stream. The panel ls then heated for 90 seconds at 232C. The resulting film is smooth and even and is ~ree from popping and cratering.
The film thlckness is approximately 0.3 mm.
The coated steel panel has a frontal impact resistance of 160 inch-pounds using a Gardner impact tester No. 16-1120. No visible cracks in the coating appear when the panel is bent 180 about a conically shaped mandrel varying from 1/8 inch to 1~ inches dlameter over an 8-inch length. After repea~ed tests for adhesion loss under cathodic protection, as described above, the circular coating areas which delaminate have diameters which range fram 11-22 mm., indicating little adhes~on loss.
The following components are blended together:
Component Parts by weight 1 23.0 2 -2.0 3 34.7 16.6 6 20.6 7 0.4 8 2.8 9 0.1 The powder is formed as in Example 1. The powder of thls example also can be stored for 4 weeks at 40C
without appreciable loss of ability to cure rapidly or to form a smooth film.
The powder is applied to a panel as in Example 1.
The panel ls then heated, for purposes of curing, for 2 minutes at 232C. If thls particular composltion is cured at a hlgher temperature, a brlttle film can result.
The coated steel panel of this example has a _~ frontal impact resistance o~ 150 inch-pounds using a Gardner impact tester No. 16-1120. No visible cracks in the coatlng appear when the panel is bent 180 around a conically shaped mandrel varying from 1/8 'nch to 1~ inches diameter over an 8-lnch length.
The composit~on, powder ~ormation and application procedure~ of ~xample 1 are used to coat a l~-foot length o~
l~-inch inside diameter steel pipe. m e edges of the pipe are uniformly coated and the coating along the pipe ~alls is substant~ally uniform, smooth and even, and Lree from popping and cratering.
~?.~l 7 tJ.Il 8 2.&
9 0.05 The above blentl is char~ed into a melt extruder and extruded at 88-94C. The extrudate is then broken into 3 chips and charged into a grindlng mill where it is ground 3~7 to a fine powder. The powder is then passed through a sieve which removes particles of maximum dimenslon greater than 150 mlcrons.
The powder thus formulated can be stored for four wee~s at 40C without appreciable loss of ability to cure rapidly or to form a smooth film.
Be~ore application o~ the powder, a 3_mm. thick grit blasted steel panel to be coated in this example is heated to 253C. The powder is then applled by Ransburg electro-static powder guns. The guns use 60 volts of the electricityto charge the powder particles and 60 pounds per sauare inch air pressure to propel the particles which are fed to each gun, from a ~luidized bed reservoir, by an air stream. The panel ls then heated for 90 seconds at 232C. The resulting film is smooth and even and is ~ree from popping and cratering.
The film thlckness is approximately 0.3 mm.
The coated steel panel has a frontal impact resistance of 160 inch-pounds using a Gardner impact tester No. 16-1120. No visible cracks in the coating appear when the panel is bent 180 about a conically shaped mandrel varying from 1/8 inch to 1~ inches dlameter over an 8-inch length. After repea~ed tests for adhesion loss under cathodic protection, as described above, the circular coating areas which delaminate have diameters which range fram 11-22 mm., indicating little adhes~on loss.
The following components are blended together:
Component Parts by weight 1 23.0 2 -2.0 3 34.7 16.6 6 20.6 7 0.4 8 2.8 9 0.1 The powder is formed as in Example 1. The powder of thls example also can be stored for 4 weeks at 40C
without appreciable loss of ability to cure rapidly or to form a smooth film.
The powder is applied to a panel as in Example 1.
The panel ls then heated, for purposes of curing, for 2 minutes at 232C. If thls particular composltion is cured at a hlgher temperature, a brlttle film can result.
The coated steel panel of this example has a _~ frontal impact resistance o~ 150 inch-pounds using a Gardner impact tester No. 16-1120. No visible cracks in the coatlng appear when the panel is bent 180 around a conically shaped mandrel varying from 1/8 'nch to 1~ inches diameter over an 8-lnch length.
The composit~on, powder ~ormation and application procedure~ of ~xample 1 are used to coat a l~-foot length o~
l~-inch inside diameter steel pipe. m e edges of the pipe are uniformly coated and the coating along the pipe ~alls is substant~ally uniform, smooth and even, and Lree from popping and cratering.
Claims (13)
1. A powder coating composition which consists essentially of finely divided particles at least 90 percent by weight of which have a maximum dimension not exceeding 150 microns wherein the particles are a blend of:
(A) 9-25 parts by weight of an epoxy resin of the formula where n is sufficiently large to provide a resin having a Gardner-Holdt Viscosity of H-L measured at 40 percent polymer solids in diethylene glycol n-butyl ether at 25°C and having an epoxide equiv-alent weight of 575-700;
(B) 0.9-3 parts by weight of an epoxy resin having the same general formula as (A) but having a value for n sufficiently large to provide a resin having a Gardner-Holdt Viscosity of K-P measured as above and having an epoxide equivalent weight of 660-810;
(C) 20-38 parts by weight of an epoxy/epoxy novolac resin which is an epoxy resin of the formula of (A) modified with an epoxy novolac resin of the formula where n of the epoxy resin and m of the epoxy novolac resin have values sufficiently large to provide an epoxy/epoxy novolac resin having a Gardner-Holdt Viscosity of W-Z measured as in (A) and having an epoxide equivalent weight of 750-860;
(D) 0-25 parts by weight of an epoxy/epoxy novolac resin of the formula of (C) but having values for n and m sufficiently large to provide an epoxy/epoxy novolac resin having a Gardner-Holdt Viscosity of 0-S measured as in (A) and having an epoxide equivalent weight of 500-575, wherein the parts by weight of components (C) and (D) total at least 34;
(E) 10-20 parts by weight of filler particles having a maximum dimension of 10 microns;
and (F) 18-25 parts by weight of a resinous curing agent consisting essentially of:
(1) 68-81 parts by weight of a compound of the formula where and where x is a positive number suffi-ciently large to provide a compound with a weight average molecular weight of 1250-1500, as determined by Gel Permeation Chromatography based on a linear calibration curve obtained from narrow molecular weight polystyrene standards;
(2) 17-30 parts by weight of bisphenol-A;
and (3) 0.6-2.0 parts by weight of an alkyl-imidazole in which the alkyl group contains 1-4 carbon atoms.
(A) 9-25 parts by weight of an epoxy resin of the formula where n is sufficiently large to provide a resin having a Gardner-Holdt Viscosity of H-L measured at 40 percent polymer solids in diethylene glycol n-butyl ether at 25°C and having an epoxide equiv-alent weight of 575-700;
(B) 0.9-3 parts by weight of an epoxy resin having the same general formula as (A) but having a value for n sufficiently large to provide a resin having a Gardner-Holdt Viscosity of K-P measured as above and having an epoxide equivalent weight of 660-810;
(C) 20-38 parts by weight of an epoxy/epoxy novolac resin which is an epoxy resin of the formula of (A) modified with an epoxy novolac resin of the formula where n of the epoxy resin and m of the epoxy novolac resin have values sufficiently large to provide an epoxy/epoxy novolac resin having a Gardner-Holdt Viscosity of W-Z measured as in (A) and having an epoxide equivalent weight of 750-860;
(D) 0-25 parts by weight of an epoxy/epoxy novolac resin of the formula of (C) but having values for n and m sufficiently large to provide an epoxy/epoxy novolac resin having a Gardner-Holdt Viscosity of 0-S measured as in (A) and having an epoxide equivalent weight of 500-575, wherein the parts by weight of components (C) and (D) total at least 34;
(E) 10-20 parts by weight of filler particles having a maximum dimension of 10 microns;
and (F) 18-25 parts by weight of a resinous curing agent consisting essentially of:
(1) 68-81 parts by weight of a compound of the formula where and where x is a positive number suffi-ciently large to provide a compound with a weight average molecular weight of 1250-1500, as determined by Gel Permeation Chromatography based on a linear calibration curve obtained from narrow molecular weight polystyrene standards;
(2) 17-30 parts by weight of bisphenol-A;
and (3) 0.6-2.0 parts by weight of an alkyl-imidazole in which the alkyl group contains 1-4 carbon atoms.
2. The powder coating composition of claim 1 containing pigment in a pigment to binder ratio of 3/100 to 30/100.
3. The powder coating composition of claim 1 containing up to 1 percent by weight, based on the weight of the composition, of a poly alkylacrylate as a flow control agent.
4. The powder coating composition of claim 1 containing up to 3 percent by weight, based on the weight of the composition, of fumed silica.
5. The powder coating composition of claim 1 in which the filler particles are silica, barium sulfate, or a mixture of these.
6. The powder coating composition of claim 5 having:
10-15 parts by weight of Component A;
22-30 parts by weight of Component C;
20-25 parts by weight of Component D;
and 21-25 parts by weight of Component F.
10-15 parts by weight of Component A;
22-30 parts by weight of Component C;
20-25 parts by weight of Component D;
and 21-25 parts by weight of Component F.
7. The powder coating composition of claim 6 containing pigment in a pigment to binder ratio of 3/100 to 30/100.
8. The powder coating composition of claim 6 containing up to 1 percent by weight, based on the weight of the composition, of a poly alkylacrylate as a flow control agent.
9. A powder coating composition which consists essentially of finely divided particles at least 90 percent by weight of which have a maximum dimension not exceeding 150 microns wherein the particles are a blend of:
(A) 11-12 parts by weight of an epoxy resin of the formula where n is sufficiently large to provide a resin having a Gardner-Holdt Viscosity of H-L measured at 40 percent polymer solids in diethylene glycol n-butyl ether at 25°C and having an epoxide equiv-alent weight of 575-700;
(B) 1 part by weight of an epoxy resin having the same general formula as (A) but having a value for n sufficiently large to provide a resin having a Gardner-Holdt Viscosity of X-P measured as above and having an epoxide equivalent weight of 660-810, (C) 22-23 parts by weight of an epoxy/epoxy novolac resin which is an epoxy resin of the formula of (A) modified with an epoxy novolac resin of the formula where n of the epoxy resin and m of the epoxy novolac resin have values sufficiently large to provide an epoxy/epoxy novolac resin having a Gardner-Holdt Viscosity of W-Z measured as in (A) and having an epoxide equivalent weight of 750-860;
(D) 22-23 parts by weight of an epoxy/epoxy novolac resin of the formula of (C) but having values for n and m sufficiently large to provide an epoxy/epoxy novolac resin having a Gardner-Holdt Viscosity of 0-S measured as in (A) and having an epoxide equivalent weight of 500-575, wherein the parts by weight of components (C) and (D) total at least 34;
(E) 16-17 parts by weight of filler particles having a maximum dimension of 10 microns wherein the filler particles are silica, barium sulfate, or a mixture of these;
and (F) 22-23 parts by weight of a resinous curing agent consisting essentially of:
(1) 68-81 parts by weight of a compound of the formula and x is a positive number suffi-ciently large to provide a compound with a weight average molecular weight of 1250-1600, as determined by Gel Permeation Chromatography based on a linear calibration curve obtained from narrow molecular weight polystyrene standards;
(2) 17-30 parts by weight of bisphenol-A;
and (3) 0.6-2.0 parts by weight of an alkyl-imidazole in which the alkyl group contains 1-4 carbon atoms.
(A) 11-12 parts by weight of an epoxy resin of the formula where n is sufficiently large to provide a resin having a Gardner-Holdt Viscosity of H-L measured at 40 percent polymer solids in diethylene glycol n-butyl ether at 25°C and having an epoxide equiv-alent weight of 575-700;
(B) 1 part by weight of an epoxy resin having the same general formula as (A) but having a value for n sufficiently large to provide a resin having a Gardner-Holdt Viscosity of X-P measured as above and having an epoxide equivalent weight of 660-810, (C) 22-23 parts by weight of an epoxy/epoxy novolac resin which is an epoxy resin of the formula of (A) modified with an epoxy novolac resin of the formula where n of the epoxy resin and m of the epoxy novolac resin have values sufficiently large to provide an epoxy/epoxy novolac resin having a Gardner-Holdt Viscosity of W-Z measured as in (A) and having an epoxide equivalent weight of 750-860;
(D) 22-23 parts by weight of an epoxy/epoxy novolac resin of the formula of (C) but having values for n and m sufficiently large to provide an epoxy/epoxy novolac resin having a Gardner-Holdt Viscosity of 0-S measured as in (A) and having an epoxide equivalent weight of 500-575, wherein the parts by weight of components (C) and (D) total at least 34;
(E) 16-17 parts by weight of filler particles having a maximum dimension of 10 microns wherein the filler particles are silica, barium sulfate, or a mixture of these;
and (F) 22-23 parts by weight of a resinous curing agent consisting essentially of:
(1) 68-81 parts by weight of a compound of the formula and x is a positive number suffi-ciently large to provide a compound with a weight average molecular weight of 1250-1600, as determined by Gel Permeation Chromatography based on a linear calibration curve obtained from narrow molecular weight polystyrene standards;
(2) 17-30 parts by weight of bisphenol-A;
and (3) 0.6-2.0 parts by weight of an alkyl-imidazole in which the alkyl group contains 1-4 carbon atoms.
10. The powder coating compositing of claim 9 containing pigment in a pigment to binder ratio of 3/100 to 30/100.
11. The powder coating composition of claim 9 containing up to 1 percent by weight, based on the weight of the composition, of a poly alkylacrylate as a flow control agent.
12. The powder coating composition of claim 9 in which;
component 1 of the curing agent is present in the amount of 70 parts by weight and has a molecular weight of 1312;
component 2 of the curing agent is present in the amount of 30 parts by weight;
and component 3 of the curing agent is 2-methylimidazole.
component 1 of the curing agent is present in the amount of 70 parts by weight and has a molecular weight of 1312;
component 2 of the curing agent is present in the amount of 30 parts by weight;
and component 3 of the curing agent is 2-methylimidazole.
13. The powder coating composition of claim 9 containing up to 3 percent by weight, based on the weight of the composition, of fumed silica.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US80705877A | 1977-06-16 | 1977-06-16 | |
| US807,058 | 1977-06-16 | ||
| US05/877,997 US4122060A (en) | 1977-06-16 | 1978-02-15 | Epoxy resin powder coating composition |
| US877,997 | 1978-02-15 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1103387A true CA1103387A (en) | 1981-06-16 |
Family
ID=27122964
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA305,419A Expired CA1103387A (en) | 1977-06-16 | 1978-06-14 | Epoxy resin powder coating composition |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS547437A (en) |
| CA (1) | CA1103387A (en) |
| DE (1) | DE2826556A1 (en) |
| ES (1) | ES470830A1 (en) |
| FR (1) | FR2394590A1 (en) |
| GB (1) | GB1583539A (en) |
| NL (1) | NL7806481A (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4777084A (en) * | 1987-10-08 | 1988-10-11 | Minnesota Mining And Manufacturing Company | Phenolic-modified epoxy adhesive including the reaction product of bisphenol A and the monoglycidyl ether of bisphenol A |
| US4868059A (en) * | 1987-11-16 | 1989-09-19 | The Dow Chemical Company | Curable composition containing a difunctional epoxy resin, a polyfunctional epoxy resin, a difunctional phenol and a polyfunctional phenol |
| JPH02227470A (en) * | 1989-02-28 | 1990-09-10 | Somar Corp | Epoxy resin powder coating composition |
| DE4322437C1 (en) * | 1993-07-06 | 1995-03-30 | Basf Lacke & Farben | Powder coating, process for the external coating of metal pipes and use of the powder coating for single-layer external coating of metal pipes |
| DE69824115T3 (en) * | 1997-11-04 | 2010-07-01 | Rohm And Haas Chemicals Llc | Low Temperature Curable One Component Powder Coating Composition |
| JP6342696B2 (en) * | 2014-04-23 | 2018-06-13 | ソマール株式会社 | Powder coating material and method for producing coating film using powder coating material |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2050777A5 (en) * | 1969-06-24 | 1971-04-02 | Alsthom | |
| US3882064A (en) * | 1973-12-27 | 1975-05-06 | Du Pont | Epoxy resin powder coating composition |
| US4009223A (en) * | 1974-05-08 | 1977-02-22 | Westinghouse Electric Corporation | Thin film electrostatic epoxy coating powder |
-
1978
- 1978-05-18 GB GB20448/78A patent/GB1583539A/en not_active Expired
- 1978-06-14 CA CA305,419A patent/CA1103387A/en not_active Expired
- 1978-06-15 NL NL7806481A patent/NL7806481A/en not_active Application Discontinuation
- 1978-06-15 ES ES470830A patent/ES470830A1/en not_active Expired
- 1978-06-16 JP JP7368278A patent/JPS547437A/en active Pending
- 1978-06-16 FR FR7818109A patent/FR2394590A1/en not_active Withdrawn
- 1978-06-16 DE DE19782826556 patent/DE2826556A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| ES470830A1 (en) | 1979-09-16 |
| NL7806481A (en) | 1978-12-19 |
| GB1583539A (en) | 1981-01-28 |
| JPS547437A (en) | 1979-01-20 |
| DE2826556A1 (en) | 1979-01-04 |
| FR2394590A1 (en) | 1979-01-12 |
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| Date | Code | Title | Description |
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| MKEX | Expiry |