CA1093909A - Metal substrate coated with mixture of epoxy resin and imidazoline derivative - Google Patents
Metal substrate coated with mixture of epoxy resin and imidazoline derivativeInfo
- Publication number
- CA1093909A CA1093909A CA218,802A CA218802A CA1093909A CA 1093909 A CA1093909 A CA 1093909A CA 218802 A CA218802 A CA 218802A CA 1093909 A CA1093909 A CA 1093909A
- Authority
- CA
- Canada
- Prior art keywords
- epoxy resin
- coating
- substrate
- weight
- article
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- 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
- C08G59/50—Amines
- C08G59/5046—Amines heterocyclic
- C08G59/5053—Amines heterocyclic containing only nitrogen as a heteroatom
- C08G59/5073—Amines heterocyclic containing only nitrogen as a heteroatom having two nitrogen atoms in the ring
-
- 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
Abstract
A b s t r a c t An article comprising a metal substrate in the form of a pipe or a container, said substrate being coated with a hardened epoxy resin composition formed from A) a solid epoxy resin based on epichlorohydrin and 4,4'-diphenylolpropane or 4,4'-diphenylol-methane or both, B) from 1 to 12% by weight based on the epoxy resin of a compound of formula (I) or of formula
Description
~1093909 "Metal substrate coated with mixture of epoxy resin and imidazoline derivatives"
Thè învention relates to metal substrates in the form Or pipe~ or containers coated with a hardened epoxy resin composition and to a process for the manufacture thereof.
The invention i3 especially concerned with large pipes coated with a coating composition of low toxicity which is resistant to heat and chemic~l corrosion and which i8 also ~electrically insulating.
It has been proposed to coat metal pipes, e~pecially large pipes, with an outer coating of bitumen ~r high pres-qure polyethylene. Since high pressure polyethylene is very sort, good protection from mechanical stress, in particular blows, knocks and abrasions, is difficult to obtain. In this respect, bitumen coatin~s have an even wor~e re~istan-ce to such mechanical treatment. Damage to the coating may cause corrosion of the metal and, fo~reasons of safety, make~ large pipes unusable for the transporting of natural ga~, mineral oil, petrochemicals, hot water, waYte water and other gaseou~ and liquid chemical substances.
Furthermore, it has been proposed to coat pipes with a layer of a hardenable resin, for example a mixture of epoxy resin and coal tar asphalt in which coarse-grained fillers are embedded. In addition a method has been pro-posed for covering pipes with multiple coatings, in whicha preheated pipe rotating about i~s longitudinal axis is provided with a thermosetting liquid coating mixture, and is subsequently hardened in a separated hardenin~ rocess.
, lU~3909 It has al~o been proposed to use powdered hardenable epoxy resin compositions containing, as curing agents, aro-matic amines, acid anhydrides, dicyanodiamide or modified dicyanodiamides, i.e. dicyanodiamides activated by small quantities of accelerators. These so-called accelerators, which a~ect the hardening rate of the curing agents, are for example, mixtures o~ carboxylates of the metal lead, iron, cobalt, manganese~ zinc or tin, with carboxylic acids or anhydrides or adducts of epoxy re~ins ~ith imida-zole derivatives, e.g. 2-methyl-4-ethyl-imidazole.
The hardenable epoxy resin compositions proposed hitherto howeverhave the disadvantage that they have low heat-resi3tance; moreover, when the epoxy layer i8 damaged, the actio~of warm alkali solutions, hot water or hot steam, leads to a los8 of adhesion at the junction of the metal and the epo~y resin coating, resulting in corrosion under-neath the coating. The sensitivity to alkalis is important in many fields of application, for example in building projects, where materials with an alkaline reaotion~ such 20~ as for example lime and cement, are usually pre~ent.
A coating moreover often contains pores, i.e. micros-copic cavitie~ which extend as fas as the metal surface.
Such pores are formed, for example, by the pre~ence or for-mation of gaseous and other products when the hardening pro-cess is subject to side-reactions. These microscopic cavities are very often the cause of so-called point corro-sion of the metal wall. The above-mentioned disadvantages .., lVg3909 are especially undesirable in the coating of large pipes, ~ince they lead to so-called delayed damage, which, for economic and technical reasons, is unacceptable. In addi-tion the epoxy resin coating materials used hitherto often contain toxic components, such as aromatic amines as hardener~ or lead-containing compounds as accelerators.
We have now found that metal pipes, containers and other articles may be provided with a coating which is more ; durable than the aforementioned coatings and i~ non-toxic.
Thus according to the present invention we now provide an article comprising a metal substrate in the ~orm of a pipe or a container, said substrate being coated with a hardened epoxy resin composition formed from A) a solid epoxy resin based onepichlorohydrin and 4,4'-diphenylolpropane or 4,4'-diphenylolmethane or both, B) from 1 to 12~ preferably from 3 to 9~ by weight based on the epoxy resin of a compound of formula ! CH - N
~ - - R (I) CH CH
\ /
Nl H
; or of ~ormula ~ R (II) C ~ / H
N
H
~09390~
(wherein R represents an alkyl group with 1 to 6 carbon atoms, or an aromatic hydrocarbon residue with 6 to 10 car-bon atoms), C) a flow agent and D) a thixotropic agent. The term "aromatic hydrocarbon" includes phenyl, benzyl and toluyl.
According to a further feature of the present invention we provide a method oP coating a metal substrate which com-prises heating said substrat~ , for example a pipe or con-tainer, to a temperature above the melting temperature of the epoxy resin component of an epoxy resin coating composition as hereinbefore defined and sufficient to cure the 3aid epoxy resin, ror example to a temperature in the range 250 to 330C, and powder-coating, conveniently electrostatically or by powder-spraying, the said epoxy resin coating composi-tion on to the hot surface of the substrate to provide a substantially uni~orm coating thereon.
As will be understood, prior to coating the metal sub-strates ~hould be thoroughly cleaned, for example by sand-blasting.
The method of coating should be 80 carried out that the composition melts to~orm as even film over the surface of the substrate and i5 immediately hardened, no further processing steps being required. The heat capacity of the hot metal substrate is itself generally sufficient with large metallic articles to cross-link the epoxy resin in a short time, for example less than a minute, without any further heating. It i3 surprising that despite the high temperature of the sub-strate during the application of the coating composition and the hardening thereof, no cracking of the coating occurs and neither a deterioration of the properties.
The epoxy resins used as component A) of the coating compo-sitions preferably have an epoxy equivalent weight in the range 600 to 2000, more preferably 700 to 1500 and particularly 875 to 1100. It may be advantageous to use mixtures of epoxy resins with different epoxy equivalent weights in order to improve the mechanical or other properties of the coating. Then the content of epoxy resins having an epoxy equiva-lent weight in the range 1500 to 2000 is preferably above 5 and not more than 20% by weight to avoid a deleterious effect on the flow properties.
The curing agent (component B) of the coating composition) is preferably a compound of formula I or II wherein R represents a methyl, ethyl, n-propyl, n-butyl, n-hexyl, isopropyl, isobutyl, tert.-butyl, phenyl, benzyl group or any of the various toluyl groups, the R
substituent being preferably in the 2-position. Aryl substituted imidazolines of general formula II are particularly preferred since these compounds retain their ability to cross-link epoxy resins at the high baking temperatures used and moreover due to their chemical stabil-ity improve the storability of the powdered coating composition. In particular 2-phenyl-2-imidazoline has been demonstrated to be an especially suitable curing agent. The baking temperatures generally used in~the manufacture of the resin coated metal substrates according to the in-vention, such as pipes and containers, are generally in the range 250 to 330C and the curing agent selected should ~r~
,~A
. ,. . . .
.. . .
... . . .. . . ~ ~; .. .
...... . ~ . .. .
390~
therefore be one which retains its ability to harden the resin at these temperatures. On the other hand dicyanodiamide, a conventional curing agent which is frequently used in other hardening processes, melts at 211C under decomposition and its properties as a hardener are therefore seriously impaired above this temperature.
The flow agent ~component C) of the coating composition) serves to improve the flow properties of the composition and at the same time to facilitate the wetting of the substrate and of any pigments which may be present. The quantity used is generally up to 5% preferably from 3 to 3.75% by weight based on the epoxy resin. Preferred flow agents include for example polyvinylbutyral, silicone oils, silicone resin or a poly-acrylate, for example a concentrate of an epoxy resin and a polyacrylate marketed by Monsanto under the trade name Modaflow*.
The coating composition according to the invention also contains a thixotropic agent which serves to increase the viscosity of the molten composition on the substrate and thus produce an even coating. The presence of fillers is in addition made redundant. The thixotropic agent is con-veniently present in an amount of 1 to 5%, preferably 2 to 3% by weight based on the total composition. A preferred thixotropic agent is finely divided silicon dioxide.
The coating may if desired additionally contain pigments, for example non-toxic pigments which are conventionally used in coatings for metal pipes. Such pigments, preferably used in low concentrations, are preferably lead-free, *Trade Mark 1(~93909 resistant to high temperatures and to chemical attack,for example by water, acids, alkalis, soil, lime and cement.
Titanium dioxide and chromium oxide green are two examples of pigments which may be present in the coating compositions used in the present invention. The total pigment content is generally not more than 40%, preferably not more than 20%
by weight of the total composition. The pigment concentration i~ gen~rally selected so as to affect the mechanical proper-ties of the coating as¦little as possible. Pigment concentra-tions of more than 40% by weight are generally to be aboidedsince excessively high pigment contents result in poor resi-stance of the coating to mechanical stresses, poor wetting of the pigment and inhomogeneity of the coating.
The epoxy resin coating compositions used according to the invention are conveniently prepared rrom finely-divi~ed starting materials so that the homogeneity of the starting mixture is improved and at least partial addition of the curin ~gent, for example the imidazoline, to the epoxy resin i3 pos~ible during the molten-liquid stage. The starting ma-terials are mixed, for example in an extruder suited to duro-plastic materials. After extrusion, which usually takes several minutes, e.g. 1 or 2 minutes, the reaction is imme-diately terminated by means of intensive cooling to prevent further enlargement of the molecules. After cooling the epoxy resin composition is ground to a fine particle ~ize, for example to a powder with a maximum particle size of 60 to 100 microns.
. . .: .
10~3909 Pipes and containers are~generally coated on the outer sur~aces only for economic reasons, but it is also possible to coat only the inner surface~ or to coat both the outer and the inner surfaces. Thus the properties required of the coating depend on the particular application: in the case of internal coatings only the durability and possibly the resistance to temperatures up to, for example 130 or 140C, are of importance, the mechanical strength being less critical since knocks and blows will occur only rarely.
We have found that a coating thickness of 100 to 2000 microns is generally adequate. However, thicker coatings may also be applied.
The invention relates in particular to the coating of large pipes, for example such pipes having an internal dia-meter of more than 100 mm and more usually pipes having adiameter of 300 to 1600 mm, Such pipes are often used for transporting petrochemicals and other ga~e~us and liquid chemicals at various temperatures and are laid above;or below ground or under water. They may be made of various metals , but especially from iron and its alloys.
Coated metal substrates according to the invention have been subjected to a number of tests, the reQults of which are shown in the following Table. The test articles consi-ted of resin coated pipe sections and steel sheets mea-suring 300 x 100 x 10 mm. The metal substrates were rirstlpretreated with steel shots STS 20 to remove rust to grade _ g _ ~. . . .
' . ' : '- ,! . ' -109390~
1 according to DIN 18 364. Subsequently they were heated by gas burners to a surface temperature of 290 + 10C, after which th~owdered coating composition was electrostatically applied and hardened.
The following tests were carried out using test articles of sheet steel measuring 300 x 100 x 10 mm coated with a 300 micron thick epoxy resin composition prepared according to Example 1 which follows. In tests A) to D) the coating was scored by the lattice cut method according to DIN 53 151, 10 The!score marks produced were not sealed.
Test A): Storage in lN NaOH solution at 50C
The test articles were stored for 6 months at 50C
in a lN NaOH solution. Afterwards the loss of adhesion at the point contact of the steel and the coating was estimated (evaluated according to DIN 53151).
Test B): Boiling test, in distilled water The test was carried out as an alternating boiling test over 10 cycles, each cycle comprising heating for 20 hours at boiling temperature and storing at room temperature for
Thè învention relates to metal substrates in the form Or pipe~ or containers coated with a hardened epoxy resin composition and to a process for the manufacture thereof.
The invention i3 especially concerned with large pipes coated with a coating composition of low toxicity which is resistant to heat and chemic~l corrosion and which i8 also ~electrically insulating.
It has been proposed to coat metal pipes, e~pecially large pipes, with an outer coating of bitumen ~r high pres-qure polyethylene. Since high pressure polyethylene is very sort, good protection from mechanical stress, in particular blows, knocks and abrasions, is difficult to obtain. In this respect, bitumen coatin~s have an even wor~e re~istan-ce to such mechanical treatment. Damage to the coating may cause corrosion of the metal and, fo~reasons of safety, make~ large pipes unusable for the transporting of natural ga~, mineral oil, petrochemicals, hot water, waYte water and other gaseou~ and liquid chemical substances.
Furthermore, it has been proposed to coat pipes with a layer of a hardenable resin, for example a mixture of epoxy resin and coal tar asphalt in which coarse-grained fillers are embedded. In addition a method has been pro-posed for covering pipes with multiple coatings, in whicha preheated pipe rotating about i~s longitudinal axis is provided with a thermosetting liquid coating mixture, and is subsequently hardened in a separated hardenin~ rocess.
, lU~3909 It has al~o been proposed to use powdered hardenable epoxy resin compositions containing, as curing agents, aro-matic amines, acid anhydrides, dicyanodiamide or modified dicyanodiamides, i.e. dicyanodiamides activated by small quantities of accelerators. These so-called accelerators, which a~ect the hardening rate of the curing agents, are for example, mixtures o~ carboxylates of the metal lead, iron, cobalt, manganese~ zinc or tin, with carboxylic acids or anhydrides or adducts of epoxy re~ins ~ith imida-zole derivatives, e.g. 2-methyl-4-ethyl-imidazole.
The hardenable epoxy resin compositions proposed hitherto howeverhave the disadvantage that they have low heat-resi3tance; moreover, when the epoxy layer i8 damaged, the actio~of warm alkali solutions, hot water or hot steam, leads to a los8 of adhesion at the junction of the metal and the epo~y resin coating, resulting in corrosion under-neath the coating. The sensitivity to alkalis is important in many fields of application, for example in building projects, where materials with an alkaline reaotion~ such 20~ as for example lime and cement, are usually pre~ent.
A coating moreover often contains pores, i.e. micros-copic cavitie~ which extend as fas as the metal surface.
Such pores are formed, for example, by the pre~ence or for-mation of gaseous and other products when the hardening pro-cess is subject to side-reactions. These microscopic cavities are very often the cause of so-called point corro-sion of the metal wall. The above-mentioned disadvantages .., lVg3909 are especially undesirable in the coating of large pipes, ~ince they lead to so-called delayed damage, which, for economic and technical reasons, is unacceptable. In addi-tion the epoxy resin coating materials used hitherto often contain toxic components, such as aromatic amines as hardener~ or lead-containing compounds as accelerators.
We have now found that metal pipes, containers and other articles may be provided with a coating which is more ; durable than the aforementioned coatings and i~ non-toxic.
Thus according to the present invention we now provide an article comprising a metal substrate in the ~orm of a pipe or a container, said substrate being coated with a hardened epoxy resin composition formed from A) a solid epoxy resin based onepichlorohydrin and 4,4'-diphenylolpropane or 4,4'-diphenylolmethane or both, B) from 1 to 12~ preferably from 3 to 9~ by weight based on the epoxy resin of a compound of formula ! CH - N
~ - - R (I) CH CH
\ /
Nl H
; or of ~ormula ~ R (II) C ~ / H
N
H
~09390~
(wherein R represents an alkyl group with 1 to 6 carbon atoms, or an aromatic hydrocarbon residue with 6 to 10 car-bon atoms), C) a flow agent and D) a thixotropic agent. The term "aromatic hydrocarbon" includes phenyl, benzyl and toluyl.
According to a further feature of the present invention we provide a method oP coating a metal substrate which com-prises heating said substrat~ , for example a pipe or con-tainer, to a temperature above the melting temperature of the epoxy resin component of an epoxy resin coating composition as hereinbefore defined and sufficient to cure the 3aid epoxy resin, ror example to a temperature in the range 250 to 330C, and powder-coating, conveniently electrostatically or by powder-spraying, the said epoxy resin coating composi-tion on to the hot surface of the substrate to provide a substantially uni~orm coating thereon.
As will be understood, prior to coating the metal sub-strates ~hould be thoroughly cleaned, for example by sand-blasting.
The method of coating should be 80 carried out that the composition melts to~orm as even film over the surface of the substrate and i5 immediately hardened, no further processing steps being required. The heat capacity of the hot metal substrate is itself generally sufficient with large metallic articles to cross-link the epoxy resin in a short time, for example less than a minute, without any further heating. It i3 surprising that despite the high temperature of the sub-strate during the application of the coating composition and the hardening thereof, no cracking of the coating occurs and neither a deterioration of the properties.
The epoxy resins used as component A) of the coating compo-sitions preferably have an epoxy equivalent weight in the range 600 to 2000, more preferably 700 to 1500 and particularly 875 to 1100. It may be advantageous to use mixtures of epoxy resins with different epoxy equivalent weights in order to improve the mechanical or other properties of the coating. Then the content of epoxy resins having an epoxy equiva-lent weight in the range 1500 to 2000 is preferably above 5 and not more than 20% by weight to avoid a deleterious effect on the flow properties.
The curing agent (component B) of the coating composition) is preferably a compound of formula I or II wherein R represents a methyl, ethyl, n-propyl, n-butyl, n-hexyl, isopropyl, isobutyl, tert.-butyl, phenyl, benzyl group or any of the various toluyl groups, the R
substituent being preferably in the 2-position. Aryl substituted imidazolines of general formula II are particularly preferred since these compounds retain their ability to cross-link epoxy resins at the high baking temperatures used and moreover due to their chemical stabil-ity improve the storability of the powdered coating composition. In particular 2-phenyl-2-imidazoline has been demonstrated to be an especially suitable curing agent. The baking temperatures generally used in~the manufacture of the resin coated metal substrates according to the in-vention, such as pipes and containers, are generally in the range 250 to 330C and the curing agent selected should ~r~
,~A
. ,. . . .
.. . .
... . . .. . . ~ ~; .. .
...... . ~ . .. .
390~
therefore be one which retains its ability to harden the resin at these temperatures. On the other hand dicyanodiamide, a conventional curing agent which is frequently used in other hardening processes, melts at 211C under decomposition and its properties as a hardener are therefore seriously impaired above this temperature.
The flow agent ~component C) of the coating composition) serves to improve the flow properties of the composition and at the same time to facilitate the wetting of the substrate and of any pigments which may be present. The quantity used is generally up to 5% preferably from 3 to 3.75% by weight based on the epoxy resin. Preferred flow agents include for example polyvinylbutyral, silicone oils, silicone resin or a poly-acrylate, for example a concentrate of an epoxy resin and a polyacrylate marketed by Monsanto under the trade name Modaflow*.
The coating composition according to the invention also contains a thixotropic agent which serves to increase the viscosity of the molten composition on the substrate and thus produce an even coating. The presence of fillers is in addition made redundant. The thixotropic agent is con-veniently present in an amount of 1 to 5%, preferably 2 to 3% by weight based on the total composition. A preferred thixotropic agent is finely divided silicon dioxide.
The coating may if desired additionally contain pigments, for example non-toxic pigments which are conventionally used in coatings for metal pipes. Such pigments, preferably used in low concentrations, are preferably lead-free, *Trade Mark 1(~93909 resistant to high temperatures and to chemical attack,for example by water, acids, alkalis, soil, lime and cement.
Titanium dioxide and chromium oxide green are two examples of pigments which may be present in the coating compositions used in the present invention. The total pigment content is generally not more than 40%, preferably not more than 20%
by weight of the total composition. The pigment concentration i~ gen~rally selected so as to affect the mechanical proper-ties of the coating as¦little as possible. Pigment concentra-tions of more than 40% by weight are generally to be aboidedsince excessively high pigment contents result in poor resi-stance of the coating to mechanical stresses, poor wetting of the pigment and inhomogeneity of the coating.
The epoxy resin coating compositions used according to the invention are conveniently prepared rrom finely-divi~ed starting materials so that the homogeneity of the starting mixture is improved and at least partial addition of the curin ~gent, for example the imidazoline, to the epoxy resin i3 pos~ible during the molten-liquid stage. The starting ma-terials are mixed, for example in an extruder suited to duro-plastic materials. After extrusion, which usually takes several minutes, e.g. 1 or 2 minutes, the reaction is imme-diately terminated by means of intensive cooling to prevent further enlargement of the molecules. After cooling the epoxy resin composition is ground to a fine particle ~ize, for example to a powder with a maximum particle size of 60 to 100 microns.
. . .: .
10~3909 Pipes and containers are~generally coated on the outer sur~aces only for economic reasons, but it is also possible to coat only the inner surface~ or to coat both the outer and the inner surfaces. Thus the properties required of the coating depend on the particular application: in the case of internal coatings only the durability and possibly the resistance to temperatures up to, for example 130 or 140C, are of importance, the mechanical strength being less critical since knocks and blows will occur only rarely.
We have found that a coating thickness of 100 to 2000 microns is generally adequate. However, thicker coatings may also be applied.
The invention relates in particular to the coating of large pipes, for example such pipes having an internal dia-meter of more than 100 mm and more usually pipes having adiameter of 300 to 1600 mm, Such pipes are often used for transporting petrochemicals and other ga~e~us and liquid chemicals at various temperatures and are laid above;or below ground or under water. They may be made of various metals , but especially from iron and its alloys.
Coated metal substrates according to the invention have been subjected to a number of tests, the reQults of which are shown in the following Table. The test articles consi-ted of resin coated pipe sections and steel sheets mea-suring 300 x 100 x 10 mm. The metal substrates were rirstlpretreated with steel shots STS 20 to remove rust to grade _ g _ ~. . . .
' . ' : '- ,! . ' -109390~
1 according to DIN 18 364. Subsequently they were heated by gas burners to a surface temperature of 290 + 10C, after which th~owdered coating composition was electrostatically applied and hardened.
The following tests were carried out using test articles of sheet steel measuring 300 x 100 x 10 mm coated with a 300 micron thick epoxy resin composition prepared according to Example 1 which follows. In tests A) to D) the coating was scored by the lattice cut method according to DIN 53 151, 10 The!score marks produced were not sealed.
Test A): Storage in lN NaOH solution at 50C
The test articles were stored for 6 months at 50C
in a lN NaOH solution. Afterwards the loss of adhesion at the point contact of the steel and the coating was estimated (evaluated according to DIN 53151).
Test B): Boiling test, in distilled water The test was carried out as an alternating boiling test over 10 cycles, each cycle comprising heating for 20 hours at boiling temperature and storing at room temperature for
2~ 4 hours. The formation of bubbles (evaluated according to DIN 53209) and the loss o~ adhesion at the contact Or steel and coating (evaluated according to DIN 53151) were estimated.
Test C): Boilin~ test in tap water ~ . . _ . . . _ The test was carried out analogously to Test B) except 25 that instead of distilled water tap water of pH 6.9 with a carbonate hardness of 13.7dH and a constant hardness of 10.9dH was used.
10~3~05~
Test D): Bending test according to DIN 53152 and DIN_1605 Bending pegs of 20, 30 and 40 mm diameter were used.
The tests were carried out at -5C, +23C, ~50C and+ 130C.
In the further tests, articles with unscored coatings 5 were used.
- Tbst E): Presence of pores according to preliminary standard _ _ The test articles were scanned with an electrode at a test voltage of 5kV + 5kV per mm thickness of coating. The ;~ -~
10 presence of pores on the coated surface rather than the cut edge was studied.
Test F): Impact resistance according to preliminary standard ~; DIN 30670 tsecond 3.2.1_and 5.6) ;~ For a coating thickness of 300 micron, an impact energy 15 of 3 Nm was used:
`~ The following Examples illustrate the production of articles according to the present invention. T indicates parts by weight.
Example 1 20 Preparation of a powdered epoxy resin coating composition.
73.0 T o~ a coarsely ground epoxy resin (maximum particle size approximately l mm) based on 4,4'-diphenyiolpropane and epichlorohydrin ~ softening point (according to Durrans):93C
to 104C, epoxy equivalent weight: 875 - 1000; viscosity:
25 430 630 cP in 40 % solution (measured in ethylene glycol dibutyl ether at 250~) 7, 3.0 T of a flow agent concentrate -- 11 -- .
lU9390~
(MODAFLOW manufactured by Monsanto) consisting of the above-mentioned epoxy resin and a polyacrylate in a weight ratio of 9:1, 4.0 T of 2-phenyl-2-imidazoline (melting point 101C -103C, determined according to the capillary method), 13.0 T
5 of titanium dioxide Kronos RN 57 P (Kronos is a trade mark, manufactured by Kronos Titan_gesellschaft mbH), 5.0 T of chromium oxide GX (manufactured by Bayer AG ) and 2.0 highly dispersed silicon dioxide were mixed in a sealed, fast-ro;tating mixer, firstly for 1 minute at 800 rpm (revolutions lO per minute)~ then for 1 minute at 1600 rpm and finally for 30 seconds at 800 rpm, the mixer being simultaneously cooled with water.
The mixture was plasticised and homogenised under the following conditions in a Buss-Ko-Kneader PR 46 (manufactured 15 by Buss AG., Basle, Switæerland). Temperature of screw:
100C~ temperature of central part of housing: 105C;
temperature of outlet part of housing: 105C; temperature of nozzle: 100C; temperature of the molten homogenised mixture: llOaC; revolution rate of the proportioning screw:
20 18 rpm; revolution rate of the kneading screw: 62 rpm. The molten homogenised epoxy resin material was rolled out flat on two rollers, rotating in opposite directions and filled with cooling brine, whereby it was intensively cooled, and then was passed via an outlet caterpillar track on to a 25 water-cooled steel belt, where an additional countercurrent of cold air was blown on to the epoxy resin material .... .. . . ~: . -~V5~3909 from above. The cooled epoxy resin material was coarsely ground, in known manner, e.g. in a blade mill (maximum particle size 4 - 5 mm). It was then finely ground in a sifter mill while being classified at the same time. The maximum particle size 5 of the powdered composition was in the range 60 to 100 micron.
b) Manufacture of coated p pes Large pipes were heated by means of ring or line burners arranged in a star shape. The pipes were moved along and rotated until they showed a constant temperature of 290 ~ 104C
10 over the,total length of the pipe. The subsequent electrostatic application of the powdered coating composition to form a layer 300 microns thlck was carried out according to conventional methods. The heat capacity of the large heated pipes was quite 'adequate to effect chemical cross-linking. The properties of 15 the coating were tested as described hereinbefore and the results are given in the following Table.
Example 2 ~ An epoxy resln coating composition was prepared ,~
analogously to Example la) except that the ratio of expoy resin:
20 2-phenyl-2-imidazoline was 74T:3T. Large pipes were coated with this composition analogously to Example lb) and the same good test values of the coatings were abtained as in Example 1.
Example 3 An epoxy resin coating composition was prepared analogously 25 to Example la) except that the ratio of epoxy resin:
2-phenyl-2-imidazoline was 71 T : 6 T. Large pipes were coated with this composition analogously to Example lb) and the same ~ood test values o~ the coatin,~,,s were obtained ~0~3909 as in Example 1.
Example 4 An epoxy resin coating composition was prepared analogouslyto Example la) except that an epoxy resin mixture containing 590 % by weight of the epoxy resin used in Example la) and 10 %
by weight of an epoxy resin with an epoxy equivalent weight of 1500 to 2000 was used, and the ratio o~ epoxy resin: 2-phenyl-2-imidazoline was 73.4T:3.6T. Pipes were coated with this composition analogously to Example lb) and the same good test 0values of the coatings were obtained as in Example 1.
Example 5 An epoxy resin coating composition was prepared analogously to Example la) except that the ratio o~ epoxy resin: 2-phenyl-2-imidazoline was 71T:6T, no pigment was used and the amount 15 of silicon dioxide was increased to 3 % by-weight. Coated pipes extraordinarily high impact strength.
Comparison Example 1 An epoxy resin coating composition was prepared analogously to Éxample la) but using only 61T o~ epoxy re8in and~instead o~
20 the 2-phenyl-2-imidazoline, 16T o~ 2-acetyl-glycerine esteriried in the 1- and 3-positions with one molecule o~ trimellitic anhydride. Pipes were coated with this composition analogously to Example lb) andlthe test values of the coating are given in the Table.
., ~093909 Comparison Example 2 An epoxy resin coating composition was prepared analogously to Example la) but using as component B) instead of 2-phenyl-2-imidazoline, a modified dicyanodiamide containing 5 85 T of dicyanodiamide, 9.5 T of 2-ethyl-4-methyl-imidazole and 5.3 T of an epoxy resin based on Bisphenol A with an epox~
number of 190.
_BLE
Test methods for 10 large iaminated pipes Exarnple 1 Compar. 1 Compar,?
A) Storage in 1 N NaOH solution at 50C
` Duration of test: 6 months 0 3 3 B) Boi.ling test in distilled water Duration of test: 240 hours 0 3 3 C) Boiling test in tap water Duration of test: 240 hours 0 3 3 D) Bendin~ test according to DIN 53152 and DIN 1605 0 1 2 `
E) Absence of pores according to preliminary standard`
~) Impact reslstance accor-dingtO preliminarY standard Evaluation:
(according to DIN 53230 0 = best mark 5 = worst mark
Test C): Boilin~ test in tap water ~ . . _ . . . _ The test was carried out analogously to Test B) except 25 that instead of distilled water tap water of pH 6.9 with a carbonate hardness of 13.7dH and a constant hardness of 10.9dH was used.
10~3~05~
Test D): Bending test according to DIN 53152 and DIN_1605 Bending pegs of 20, 30 and 40 mm diameter were used.
The tests were carried out at -5C, +23C, ~50C and+ 130C.
In the further tests, articles with unscored coatings 5 were used.
- Tbst E): Presence of pores according to preliminary standard _ _ The test articles were scanned with an electrode at a test voltage of 5kV + 5kV per mm thickness of coating. The ;~ -~
10 presence of pores on the coated surface rather than the cut edge was studied.
Test F): Impact resistance according to preliminary standard ~; DIN 30670 tsecond 3.2.1_and 5.6) ;~ For a coating thickness of 300 micron, an impact energy 15 of 3 Nm was used:
`~ The following Examples illustrate the production of articles according to the present invention. T indicates parts by weight.
Example 1 20 Preparation of a powdered epoxy resin coating composition.
73.0 T o~ a coarsely ground epoxy resin (maximum particle size approximately l mm) based on 4,4'-diphenyiolpropane and epichlorohydrin ~ softening point (according to Durrans):93C
to 104C, epoxy equivalent weight: 875 - 1000; viscosity:
25 430 630 cP in 40 % solution (measured in ethylene glycol dibutyl ether at 250~) 7, 3.0 T of a flow agent concentrate -- 11 -- .
lU9390~
(MODAFLOW manufactured by Monsanto) consisting of the above-mentioned epoxy resin and a polyacrylate in a weight ratio of 9:1, 4.0 T of 2-phenyl-2-imidazoline (melting point 101C -103C, determined according to the capillary method), 13.0 T
5 of titanium dioxide Kronos RN 57 P (Kronos is a trade mark, manufactured by Kronos Titan_gesellschaft mbH), 5.0 T of chromium oxide GX (manufactured by Bayer AG ) and 2.0 highly dispersed silicon dioxide were mixed in a sealed, fast-ro;tating mixer, firstly for 1 minute at 800 rpm (revolutions lO per minute)~ then for 1 minute at 1600 rpm and finally for 30 seconds at 800 rpm, the mixer being simultaneously cooled with water.
The mixture was plasticised and homogenised under the following conditions in a Buss-Ko-Kneader PR 46 (manufactured 15 by Buss AG., Basle, Switæerland). Temperature of screw:
100C~ temperature of central part of housing: 105C;
temperature of outlet part of housing: 105C; temperature of nozzle: 100C; temperature of the molten homogenised mixture: llOaC; revolution rate of the proportioning screw:
20 18 rpm; revolution rate of the kneading screw: 62 rpm. The molten homogenised epoxy resin material was rolled out flat on two rollers, rotating in opposite directions and filled with cooling brine, whereby it was intensively cooled, and then was passed via an outlet caterpillar track on to a 25 water-cooled steel belt, where an additional countercurrent of cold air was blown on to the epoxy resin material .... .. . . ~: . -~V5~3909 from above. The cooled epoxy resin material was coarsely ground, in known manner, e.g. in a blade mill (maximum particle size 4 - 5 mm). It was then finely ground in a sifter mill while being classified at the same time. The maximum particle size 5 of the powdered composition was in the range 60 to 100 micron.
b) Manufacture of coated p pes Large pipes were heated by means of ring or line burners arranged in a star shape. The pipes were moved along and rotated until they showed a constant temperature of 290 ~ 104C
10 over the,total length of the pipe. The subsequent electrostatic application of the powdered coating composition to form a layer 300 microns thlck was carried out according to conventional methods. The heat capacity of the large heated pipes was quite 'adequate to effect chemical cross-linking. The properties of 15 the coating were tested as described hereinbefore and the results are given in the following Table.
Example 2 ~ An epoxy resln coating composition was prepared ,~
analogously to Example la) except that the ratio of expoy resin:
20 2-phenyl-2-imidazoline was 74T:3T. Large pipes were coated with this composition analogously to Example lb) and the same good test values of the coatings were abtained as in Example 1.
Example 3 An epoxy resin coating composition was prepared analogously 25 to Example la) except that the ratio of epoxy resin:
2-phenyl-2-imidazoline was 71 T : 6 T. Large pipes were coated with this composition analogously to Example lb) and the same ~ood test values o~ the coatin,~,,s were obtained ~0~3909 as in Example 1.
Example 4 An epoxy resin coating composition was prepared analogouslyto Example la) except that an epoxy resin mixture containing 590 % by weight of the epoxy resin used in Example la) and 10 %
by weight of an epoxy resin with an epoxy equivalent weight of 1500 to 2000 was used, and the ratio o~ epoxy resin: 2-phenyl-2-imidazoline was 73.4T:3.6T. Pipes were coated with this composition analogously to Example lb) and the same good test 0values of the coatings were obtained as in Example 1.
Example 5 An epoxy resin coating composition was prepared analogously to Example la) except that the ratio o~ epoxy resin: 2-phenyl-2-imidazoline was 71T:6T, no pigment was used and the amount 15 of silicon dioxide was increased to 3 % by-weight. Coated pipes extraordinarily high impact strength.
Comparison Example 1 An epoxy resin coating composition was prepared analogously to Éxample la) but using only 61T o~ epoxy re8in and~instead o~
20 the 2-phenyl-2-imidazoline, 16T o~ 2-acetyl-glycerine esteriried in the 1- and 3-positions with one molecule o~ trimellitic anhydride. Pipes were coated with this composition analogously to Example lb) andlthe test values of the coating are given in the Table.
., ~093909 Comparison Example 2 An epoxy resin coating composition was prepared analogously to Example la) but using as component B) instead of 2-phenyl-2-imidazoline, a modified dicyanodiamide containing 5 85 T of dicyanodiamide, 9.5 T of 2-ethyl-4-methyl-imidazole and 5.3 T of an epoxy resin based on Bisphenol A with an epox~
number of 190.
_BLE
Test methods for 10 large iaminated pipes Exarnple 1 Compar. 1 Compar,?
A) Storage in 1 N NaOH solution at 50C
` Duration of test: 6 months 0 3 3 B) Boi.ling test in distilled water Duration of test: 240 hours 0 3 3 C) Boiling test in tap water Duration of test: 240 hours 0 3 3 D) Bendin~ test according to DIN 53152 and DIN 1605 0 1 2 `
E) Absence of pores according to preliminary standard`
~) Impact reslstance accor-dingtO preliminarY standard Evaluation:
(according to DIN 53230 0 = best mark 5 = worst mark
Claims (11)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An article comprising a metal substrate in the form of a pipe or a container, said substrate being coated with a hardened epoxy resin composition formed from A) a solid epoxy resin based on epichlorohydrin and 4,4'-diphenylolpropane or 4,4'-diphenylolmethane, or both, with an epoxy equivalent weight in the range of from 600 to 2000, B) from l to 12%
by weight based on the epoxy resin of a compound of formula (I) or of formula (II) (wherein R represents an alkyl group having 1 to 6 carbon atoms, or an aromatic hydrocarbon residue having 6 to 10 carbon atoms), C) up to about 5% by weight, based on therein of a flow agent and D) a thixotropic agent, in an amount of 1% to 5% by weight, based on the total composition.
by weight based on the epoxy resin of a compound of formula (I) or of formula (II) (wherein R represents an alkyl group having 1 to 6 carbon atoms, or an aromatic hydrocarbon residue having 6 to 10 carbon atoms), C) up to about 5% by weight, based on therein of a flow agent and D) a thixotropic agent, in an amount of 1% to 5% by weight, based on the total composition.
2. An article as claimed in claim 1 wherein component B) is present in an amount of from 3 to 9% by weight of the epoxy resin.
3. An article as claimed in claim 1 wherein the epoxy resin component A) has an epoxy equivalent weight of from 700 to 1500.
4. An article as claimed in claim 1, 2 or 3 wherein the epoxy resin component A) is a mixture of epoxy resins with different epoxy equivalent weights and which contains from 5 to 20% by weight of an epoxy resin with an epoxy equivalent weight of 1500 to 2000.
5. An article as claimed in claim 1, 2 or 3 wherein the coating composition additionally contains a pigment up to 40% by weight of the total composition.
6. An article as claimed in claim 1, 2 or 3 wherein the thickness of the coating is from 100 to 2000 micron.
7. An article as claimed in claim 1, 2 or 3 wherein the metal substrate is a pipe of at least 100 mm internal diameter.
8. An article as claimed in claim 1, wherein at least one of the following features is applied:
(h) the epoxy resin of component A) has an epoxy equivalent weight of from 700 to 1500;
(i) component B) comprises 2-phenyl-2-imidazoline;
(j) component C) is present in an amount of 3% to 3.75% by weight based on the epoxy resin and component D) is present in an amount of 2% to 3% by weight of the total composition; and (k) the thickness of the coating is from 100 to 2000 micron.
(h) the epoxy resin of component A) has an epoxy equivalent weight of from 700 to 1500;
(i) component B) comprises 2-phenyl-2-imidazoline;
(j) component C) is present in an amount of 3% to 3.75% by weight based on the epoxy resin and component D) is present in an amount of 2% to 3% by weight of the total composition; and (k) the thickness of the coating is from 100 to 2000 micron.
9. A process of coating a metal substrate in the form of a pipe or a container which comprises heating said substrate to a temperature above the melting temperature of the epoxy resin component of an epoxy resin coating composition as defined in claim 1 and sufficient to cure the said epoxy resin, and powder-coating the said epoxy resin composition onto the hot surface of the substrate to provide a substantially uniform coating thereon by immediate hardening without any further processing step by means of the heat capacity of the hot substrate.
10. A process as claimed in claim 9 wherein the substrate is heated to a temperature of 250 to 330°C.
11. A process as claimed in claim 9 or 10, wherein at least one of the following features is applied:
(l) the maximum particle size of the epoxy resin composition applied to the substrate is 60 to 100 microns;
(m) the epoxy resin composition is coated onto the surface of the metal substrate by powder-spraying; and (n) the epoxy resin composition is coated onto the surface of the metal substrate electrostatically.
(l) the maximum particle size of the epoxy resin composition applied to the substrate is 60 to 100 microns;
(m) the epoxy resin composition is coated onto the surface of the metal substrate by powder-spraying; and (n) the epoxy resin composition is coated onto the surface of the metal substrate electrostatically.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE2405111A DE2405111C3 (en) | 1974-02-02 | 1974-02-02 | Process for the production of metal substrates coated with cured epoxy resin compositions |
| DEP2405111.4 | 1974-02-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1093909A true CA1093909A (en) | 1981-01-20 |
Family
ID=5906493
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA218,802A Expired CA1093909A (en) | 1974-02-02 | 1975-01-28 | Metal substrate coated with mixture of epoxy resin and imidazoline derivative |
Country Status (18)
| Country | Link |
|---|---|
| JP (1) | JPS5329336B2 (en) |
| AR (1) | AR209921A1 (en) |
| AT (1) | AT345945B (en) |
| BE (1) | BE824901A (en) |
| BR (1) | BR7500661A (en) |
| CA (1) | CA1093909A (en) |
| CH (1) | CH613757A5 (en) |
| DE (1) | DE2405111C3 (en) |
| DK (1) | DK34775A (en) |
| ES (1) | ES434383A1 (en) |
| FR (1) | FR2260060B1 (en) |
| GB (1) | GB1475034A (en) |
| IN (1) | IN143816B (en) |
| IT (1) | IT1031384B (en) |
| NL (1) | NL7500891A (en) |
| NO (1) | NO149270C (en) |
| SE (1) | SE419555B (en) |
| ZA (1) | ZA75550B (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2557278C2 (en) * | 1975-12-19 | 1982-04-01 | Hoechst Ag, 6000 Frankfurt | Pipes and containers made of metal coated with hardened epoxy resin compounds and processes for their manufacture |
| US4285783A (en) * | 1979-07-06 | 1981-08-25 | Metropolitan Wire Corporation | Coating for metal shelving and method of applying same |
| GB2145639A (en) * | 1983-08-25 | 1985-04-03 | Shaw Ind Ltd | Impact-resistant, moisture-impermeable resinous coatings and method of applying the same to an object |
| US5189118A (en) * | 1991-02-28 | 1993-02-23 | Texaco Chemical Company | Mixtures of 1-isopropyl-2-aryl imidazole and 1-isopropyl-2-aryl imidazoline as epoxy resin curatives |
| US5721052A (en) * | 1996-05-06 | 1998-02-24 | Morton International, Inc. | Textured epoxy powder coating compositions for wood substrates and method of coating wood therewith |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AT125665B (en) * | 1929-04-30 | 1931-11-25 | Herold Ag | Method of applying varnishes. |
| NL246775A (en) * | 1958-12-27 | |||
| BE613493A (en) * | 1961-02-06 | 1900-01-01 | ||
| US3258032A (en) * | 1961-07-14 | 1966-06-28 | United States Steel Corp | Coating |
| US3369922A (en) * | 1966-08-09 | 1968-02-20 | Joseph G. Svrchek | Method for applying heat reactive coatings |
| US3598636A (en) * | 1968-06-17 | 1971-08-10 | Desoto Inc | Coating of interior surfaces of pipe |
| DE1908772A1 (en) * | 1969-02-21 | 1970-09-10 | Kabel Metallwerke Ghh | Covering for electric cable |
| DE2034488A1 (en) * | 1970-07-11 | 1972-01-27 | Kabel Metallwerke Ghh | Plastics coated metal pipe |
| DE2248776C3 (en) * | 1972-10-05 | 1978-04-13 | Veba-Chemie Ag, 4660 Gelsenkirchen- Buer | Process for the production of coatings based on powder paints |
-
1974
- 1974-02-02 DE DE2405111A patent/DE2405111C3/en not_active Expired
-
1975
- 1975-01-25 NL NL7500891A patent/NL7500891A/en not_active Application Discontinuation
- 1975-01-27 ZA ZA00750550A patent/ZA75550B/en unknown
- 1975-01-28 CA CA218,802A patent/CA1093909A/en not_active Expired
- 1975-01-29 BE BE152807A patent/BE824901A/en not_active IP Right Cessation
- 1975-01-30 IN IN184/CAL/75A patent/IN143816B/en unknown
- 1975-01-31 GB GB434875A patent/GB1475034A/en not_active Expired
- 1975-01-31 DK DK34775*#A patent/DK34775A/da not_active Application Discontinuation
- 1975-01-31 AT AT71575A patent/AT345945B/en not_active IP Right Cessation
- 1975-01-31 FR FR7503028A patent/FR2260060B1/fr not_active Expired
- 1975-01-31 CH CH114475A patent/CH613757A5/en not_active IP Right Cessation
- 1975-01-31 SE SE7501106A patent/SE419555B/en unknown
- 1975-01-31 BR BR661/75A patent/BR7500661A/en unknown
- 1975-01-31 NO NO750305A patent/NO149270C/en unknown
- 1975-01-31 JP JP1264075A patent/JPS5329336B2/ja not_active Expired
- 1975-01-31 IT IT19862/75A patent/IT1031384B/en active
- 1975-02-01 ES ES434383A patent/ES434383A1/en not_active Expired
- 1975-02-03 AR AR257502A patent/AR209921A1/en active
Also Published As
| Publication number | Publication date |
|---|---|
| AU7772675A (en) | 1976-08-05 |
| NO750305L (en) | 1975-09-01 |
| JPS5329336B2 (en) | 1978-08-19 |
| NO149270B (en) | 1983-12-12 |
| IT1031384B (en) | 1979-04-30 |
| CH613757A5 (en) | 1979-10-15 |
| DK34775A (en) | 1975-09-29 |
| NO149270C (en) | 1984-03-21 |
| ZA75550B (en) | 1976-01-28 |
| DE2405111C3 (en) | 1982-08-12 |
| AR209921A1 (en) | 1977-06-15 |
| IN143816B (en) | 1978-02-11 |
| FR2260060A1 (en) | 1975-08-29 |
| SE419555B (en) | 1981-08-10 |
| FR2260060B1 (en) | 1979-09-28 |
| AT345945B (en) | 1978-10-10 |
| ATA71575A (en) | 1978-02-15 |
| BE824901A (en) | 1975-07-29 |
| DE2405111B2 (en) | 1976-08-12 |
| JPS50126719A (en) | 1975-10-06 |
| DE2405111A1 (en) | 1975-08-14 |
| ES434383A1 (en) | 1976-12-16 |
| GB1475034A (en) | 1977-06-01 |
| NL7500891A (en) | 1975-08-05 |
| BR7500661A (en) | 1975-11-11 |
| SE7501106L (en) | 1975-08-04 |
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| MKEX | Expiry |