CA1083746A - Hardening agents for filled epoxy resins - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Compounds useful for hardening epoxy resins having the formula

Description

~ i~83746 ` The invention rclates to new and useful compounds suit-able ~or hardenlng epo~y -esins having at lea8t one lJ2-epo~ide group.
~ ovel hardening agents are set rorth that are capable o~
hardening epo~y resins at or below room temperatures ~a8 low as about 5C without having to supply an e~ternsl source Or heat to efr~ct the hardening o~ the resin.
Thi3 invention also relates to compositions and methods o~ using s~id.composition~ and hardening agents to form a resin-ous costing on a ~ubstrate that will protect the ssme against ~:
the deleterious action o~ 8 wide variety o~ materials including ~et ~uels, kerosene, heating oil~, ~cidsJ solvent8, etc. The methods and compositions disclosed are particularly useful for coating ~et ~uel tanks, heating oil tanks and othar containers Or highly fiammable-liqu~ds, due to the absence of volatile solvonts in the coating compositions.
The novel co~pounds use~ul ror hardening epo~y resins ha~ing at least one 1,2-epo~ide group~ng are tho~e compounds o~
the ~ormula:

. _ - _ ~ C~3 ~ L 2 - ~ C~3 ~ ~ _H

NCH2 H3 - H2 ~ H2C ~3 wherein n ha3 a value of at least 2.

The compounds have a value wherein n i9 at lea~t 2, and pre~erably fro~ 2 to 5. Best re~ulfs sre generall~ achicved when n is 2.
The novel co~pounds Or thi~ invention are userul ~or the harden~.ng o~ epo~y resi.n~ or pol~epo~ide~ which comprise those oreanic materials po9sessing at lea3t one vic-epoxy group, i.e., ...

, '..

, ~:
~ : \c/ \c~ ' The compound~ ma~ be saturated or unsaturated aliphatic cycloaliphatic, arom~tic or heterocyclic and msy contain substituents such as halogen atoms, hydroxyl groups, ether radicals, and the like. They may be ~onomeric or poly~eric.
Generally, such epo~ide re~ins compri~e a polyether deri-vative Or a polyhydric or~affic compound, said derivative con-ta~n~ng 1,2-epoxy groups and said compound being selected ~ro~ the group con~ting of polyhydric alcohol~ and phenols ¢ont~ining at least two phenolic hydroxy groups.
¦ A~ong the polyhydr~c phenols which may be used in pre-I par1ng such glycidyl polyethers are the mono-nuclear phenols ¦ such as resorcinol, catechol, hydroguinone, etc., and the polynuclear phenols such a~ bis(4-hydro~yphenyl~-2,2-propane, 4,4~ -dihydroxybenzephenone, bis(4-hydro~yphenyl)-1,1-ethane, bis(4-hydro~yphenyl)~ isobutane, bls(l~-hydro~yphenyl~-

2,2-bubane, bist4-hydroxy-2-methylphenyl)-2,2-propane, bis(4-hydro~y-2-tertiary butylphenyl)-2.2-propane, bis(4-hydro~y-2,5-di¢hlorophenyl)-2,2-propane, 4,4'-dihydroxybis-phenyl-4,4'-dihydroxypentachlorobisphenyl, bi~(2-hydroxynaphthyl) methane, 1,5-dihydro~ynaphthaiene, phloroglucinol, 1,4-di-hydro~ynaphthalene, 1,4-bi~(4-hydroxyphenyl)cyclohe~ane, etc.
a9 well ~8 other oomplex polyhydric phenols, such a p~rogallol, phloroglu¢inol and novalac resin~ from the condensabion Or a phenol with an aldehyde in the presence o~ an acidlc condensa-tion catalyst. For the nature and preparation Or novalac resins, see bhe book by T. S. Car~well, Phenylpla~t, 1947, page 29, et.seQ.
There can al~o be used 1,2-epo~y conbaining ~thers of aliphatic polyhydric alcohols, such ~9 polyglycidyl ethers thereo~, as ~or e~ample, thc diglycidyl ethers o~ ethylene glycol, propylene glycol, trimethylene glycol, butylene glycol, 1~3746 dlethylene ~lycol, 4,4~-dihydro~ydicyclohe~yl triethylene glycol, glycerol, dipropylene glycol, and the like, as w811 as ether containing more than two glycidyl groups such as the glycidyl polyethers, glycerol, mannitol, sorbitol, polyalkyl j alcohol, polyvinyl alcohol, and tbe like.
¦ These epoxide resins, or glycidyl polyethers as they are ~requently called ~ay be prepared by re~cting predetermined amounts Or at least one polyhydric compound and one epihalo-hydrin in an alkaline medium.
~hile it i3 prererred to u~e epichlorohydrin a~ the epi-halohydrin in the preparation o~ the epoxide ~tarting materials, other epihalohydrins such as epibromohydrin may be uqed advantageousl~.
In ~he preparation Or the epoxide resins, aqueous alkali i8 e~ployed to combine with the hsloeen Or tbe epihalohydrin.
The amount Or alkali employed should be substantially equiva-lent to the amount Or halogen present and, prererably, should be omployed in an amount somewhat in e~cess thereof. Aqueous ml~tures Or alkali metal hydroxides, such as potas3ium hydroxide ~;
and llthlum hydroxide m~y be employed; although ror economic rensons, sodium hydroxido is obviously prererred.
The product Or the above-described reaction instead belng a singly slmplo compound i9 gener~lly a complex mixture o~ glycldyl polyethers, but the principal product may be repre-sented by the formula:

-C~2-(0-R-O-CH2-CHOH-CH2)n-0-R-O-CH2- H- ~2 ~ where n is an lnteger o~ a series 0,1,2,3... and prererably having a ma~imum va1ue Or 10~ and R represents a divalent hydrocarbon radical Or a polyhydric co~pound, and preferably a dihydric phenol.
While ror any single molecule n 18 an integer, though the ract that the obtained polyether is a mi~ture Or compounds, cause3 the determined valuo ror n, Q.g., rrom molecular weight measure-.

1~83746 ~ ents to be an ~verage which i9 not neces~arily a whole number.
- ~ Pre,erred polyethers ~or use with the hardening agents Or this invention ~re prep~red rrom bi~t4-hydro~yphenyl)-2,2-propano and contain a chain Or alternating glyceryl and 2,2-bi~s (phenylene) propane radicals, ~epar~ted by intervening ethereal oxygen atoms and hava a 1,2-epoxy equivalency between 1 and 2, snd epoxide equivalent weight Or about 170 to about 250. A
particularly suitable material ror use in the invention i9 a normally liquid glycidyl polyether o~ bisphenol-A having an ' 10 epo~ide equivalent weight o~ about 175 to 200 and a 1,2-epoxy equivalency Or about l.ô to about 1.95.
The term "epoxy equivalency" hae employed in thi~ æpeci-ication refers to the number of epo~y groups contained in the s average molecule Or the de~ired material. The epoxy equivalency is obtained by dividing the average molecular weight o~ the polyepo~ide by the so-called "epoxide equivalent weight". The epoxide equivalent weight i8 determined by heating one gram sample Or the polyepoxide with an exceas Or pyridiniu~ chloride dissolved i ln pyridine at the boiling point ~or twenty minute~. The excess

3 20 pyridiniu~ chloride is then back-titrated with 0.1 N sodium ¦ hydroxide to phenol-phthalein end point. The epoxide value I is calculated by considering 1 HCl as an equivalent Or one i epoxde. This method is u~ed to obtain all epoxide values reported herein.
The novel compound~ o~ this invention are used in an ¦ amount sur~icient to harden the epoxy resin to an in~oluble and inrusible poly~er. Generally, the amount Or hardening agent u~ed should be at least a 5% stoichiometric e~coss, and as used herein, 3toichiometric amount rerers to th~t amount needed to rurnish one amino hydrogen ror every epo~y group to be reacted. Particul~rly superior reaults are obtained when the hardoning agent is e~ployed in rrom 5 to50/~ stoichiometric exce~s .

1'~ 746 ~,~ , The pre~erred hardening ~dditive wherein n has a v~lue 2, is prepared by stirriSng 6 molY phenol, 3 molq formaldehyds ~ (in the ~orm o~ a 36% ~ormalin solution) ~nd 0.5 weight percent :,; of triethyla~ine, for about 2 hours. Nine mols o~ 3,5,5-~:^ trimethyl-3-a~inomethyl cyclohe~yla~ine are then added to the ~1 .
~3 solution and the re3ultant solution is heated for about 1 hour ::~ st 100C. The water produced during the reaction is removed .,. by dist$11ation ~', ' The hardening agent produced ii3 light yellow in color and : 1 10 i8 h~ghly reactive with epo~y resins- Thus, compounds normally ~ used to accelerate the hardening action are not required in .. 1 the practice Or this in~ention due to the high reactivity Or the hardening agent~ o~ this invention with epoxy resin. . . .:
,~ A prererred composition Or the present invention ha~ a luid consi~tency and is cap~ble of being app,lied as a uni~orm coating that hardens to form a smooth, tough and adherent coating, . J
~ possessing good me¢hanical and ¢hemical resistsnt properties. The .~ composition ¢omprises:
(A) a liqu~d ep.oxy resin having terminable epoxy groups and an epoxy equivalent rrom about 185 to 210 and a viscosity below about 900 cps at 25C; ;, (B) a ~iller material in an amount betweGn about 20 and ,~ :
,i 50 weight percent o~ said epoxy resin : (C~ an er~ective a~ount of a dispersing a~ent for said .~:
~iller material; and .
(D) the novel hardening additive of this invention wherein n has a value o~ at lea~t 2, and prererably between 2 ~;~
and 5.
The process o~ the present invention.ror coating a 30 ~ubstrats comprises ~pplying to the surrace the above-idenbi~ied .~.
;~ co~po~ition and thon allowing the coating to cure without the appl,ication of any.heat.
~ The liquid opoxy resins used in thls p~actice e~bod~-:;(, . .. 5 _ 'l ..

)83746 ~ ,nt o~ the invention are the re~ction product3 Or epichlorohydrin .~ . .
~ and diphenylol propane and having the following rormuls:
i-.. :, . ~

C~12-CN-CNz ¦ ~ -O--CCH2- H-CII2 ¦ 0~ ~0CNZ-C~N2 These re~in3 have a viscosty below sbout 900 cp~ at 25 c , and preferably between about 700 to 800 cps at 25C. The preferred ,~ .
value o~ n', in the above structural rormul~, is approximately ~` 0.2, whereby said re~in haa an approximate ~olecular weight 10 o~ 380 although the value o~ n' can vary between about O and 10.
It is understood that when the above epo~y re~in is produced, .
it i~ a mixture of compounds that causes the determined value for n' to be an average which is not neces~arily zero or a whole number such as 1.
A particularly preferred re~in e~ibiting the above .. : . - . . .
~?~` properties is Epon 82~ ~anu~actured by Shell Chem~cal Company.
- Other commercial liquid epoxy rosins which ars equivsl~nt to bhe "~pon 828~' for the purpose~ of this invention, are "DER-331"~
sold by Dbw Corning Corporation and "Ciba Resin 50~, sold by 20 Ciba, Ltd.

D The term "epo~y equ~valent" re~er~ to ~be mesn ~lolec~lar weight o~ the epoxy rssin divided by the number o~ epoxy radicals per molecule, or in any case, the nu~ber Or gra~s Or epo~y resin equivalent to one epoxy group or one gra~ equivalent Or epoxide.
The amount o~ the novel hardener u~eful in the practice Or this e~bodiment o~ tbe lnvention is an er~ective a~ount su~
.~
~icient ror causina the epoxy resin to harden. Generally, the a~ount o~ hardener used i~ betweon about 35 and 40 ~ercent, and 30 prererably 35 percent by weight, based on the total weisht Or the liquld epoxy re~in de3cribed above.

~ * T ~ EMARK -6-; :, .

- It is u~ually desirable to sdd the hardening agent to the composition ~ust prior to use, particuiarly becau3e the hardening agent renders the composition r~adily curable at or near ordinary room temperature a~ well as under cold temperatures.
The compositions of thi3 invention pre~erably contain from about 20 to 50 percent, and prererably 33 percent by weight o~ the de~ired epoxy re~in, and at least one filler which i9 inert with respect to the remaining ingredients Or the co~po~ition and which have a particle ~ize up to about 50 microns. Generally, the ~ize Or the filler particle~ range between about 25 and 50 microns.
Examples o~ suitable inert rillers ~nclude sand, crushed ~hells, rock~, alu~inum powder, copper powder, quartz powder, titanium dioxidel asbesto~, 5ilica, calcium carbon~te, graphite, black iro~ oxide, silicon dioxide, diatomaceous .. . ...
earth, alumino~licates, silicone carbideJ boron carbide, -vermiculite, talc, mica and the like. Best re~ult~, in term~
Or corrosion inhibition are obtained with stainless steel rlakes, steel powder, titaniPerrous ~agnetite oxide or mixtures thereor.
The co~positions Or the invention al~o prererably contaln agent~ to promote the adequate and uni~orm distribution J of ~iller particles in the resin. Best results are achieved when an effective amount Or fumed silica i9 employed. Gsnerally, ~ ~ -between about 5 and 20 percent, and preferably 10 percent by weight Or the liquid epoxy resin is employsd. The ~umed silica not only prevents the settlement of the filler material in ; the composition, but also enhances the over-all anticorrosion propertie3 o~ the coating composition.
As optional ingrsdients ~or the practlce Or this inv~ntion, it i9 desired to include silicic acid in an amount .
o~ ~rom about 1 to 7 percent by weight, and prererably 3 percent by weight of the epoxy resin. The siliclc acid promote~

37~6 ~; the ~dhesion Or the ¢osting compositlon to wet, grea~y or oily ~; sur~aces. Another optional ingredient ~s silicon oil which is employed in an~amount Or between about 1 and 2 ounces p~r 120 pounds o~ the total ba~e composition. The cilicon oil ~acili-i~ tateq pigment distribution when pig~ants are utilized in com-bination with the composition ~ this invention. The silicon oil also decreases the sur~ace tension o~ the composition and facilitate~ the ~preading o~ the ¢omposition on a part~cular - substrateO
Compo~itions o~ this invention can al80 contain ~u~icient amount~ o~ aluminum hydro~ide a~ a flame retardant ~or the compo~ition. It i9 under~tood that other equivalent compounds can be used a~ a substitute ~or aluminum bydroxide altbough this compound iq the preferred ~lame retardant additive ~or the invent~on. Generally, aluminum hydroxide is present in an amount of up to 5 percent by weight of the ¢om-position.
In ~eneral, the ~eparate components o~ the composition can be admi~ed in any desired order and, i~ desired, combi~a-tions of two or more components may be prepared initially withthe remaining components being added ~ubsequently. However, as noted hereinbe~ore, it is usually desired to add the hardening .
agent ~ust prior to use since ~he hardening agent renders the ¢omposition readily curable at or near room temperature with no e~tern~l ~ource of heat be~ng required ~or hardening purposes.
When the above-described compositions are applied to a given substrate, the coatings are ~ound to exhibit highly ,.
sati3~actory chemical resistance to ~et fuels, ga~oline, ~i3 heating oils, solvent~, etc., as well as high compression strength, a low rate o~ shrinkage, good heat resistance, satisfactory thermal coef~icient o~ expansion and adhe~ive propertie~. -The composition~ o~ thi~ invention mny be employed : ..2 ror the coating and~or repair o~ any type o~ surrace. These sur~aces include, ~or example, wood, cement, met~l, gla~s, and the like. The compo~itions are particulsrly suited ~or use in treating metal surraces, such as, for example, copper, aluminum, brass, steel, and iron ~urfaces. The sur~aces may be in any type o~ structure, such as for example, pipes, piling, rsaction ves eis, structural member~ of oil well drilling plat~orms, containers ~or ~et fuel3, heating oils and solvents, well ~ackets, heat exchange tubes, ~old~, and the like.
When the coating co~position~ of this invention are ~` applied to a particular substrate to impart chemical resistance, the coating compositions are applied in an amount ~u~icient to provide the chemical resistance desired. More speci~ically, , the coatings are applied in an amount su~icient to pro~ide , a ~ilm or coating o~ at least about 0.3 ~illimeters thick.
The coatings o~ the compositions can be applied to substrate~ by conventional techniques known in the art including spreading, spraying or dipping, and therea~ter per~itting the .~. ::
composibion to cure at or below room te~perature to ~orm a bard, durable coating having satis~actory chemical resistance and being attractive in appearance.

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Claims (15)

The embodiments of the invention in which an exclus-ive property or privilege is claimed are defined as follows:

1. A hardenable, liquid film forming composition that is capable of being applied as a uniform coating and hardening to a smooth, tough and adherent coating and possessing good mechanical and solvent resistant properties comprising:
A. a liquid epoxy resin having terminable epoxy groups and an epoxy equivalent from about 185 to 210;
B. a filler material in an amount between about 20 and 50 weight percent of said epoxy resin;
C. an effective amount of a dispersing agent for said filler material; and D. a hardening additive for said epoxy resin of the structural formula:
wherein n has a value of between 2 and 5.

2. The composition of claim 1, wherein said filler material is selected from the group consisting of stainless steel flakes, steel powder, titaniferrous magnetite oxide or mixtures thereof.

3. The composition of claim 2, wherein said filler material has a particle size up to about 50 microns.

4. The composition of claim 1, wherein said dispers-ing agent is fumed silica and is present in an amount between 5 and 20 weight percent of said epoxy resin.

5. The composition of claim 1 further comprising silicic acid in an amount between 1 and 7 weight percent of said epoxy resin.

6. The composition of claim 1, further comprising between about 1 and 2 ounces of silicon oil per 120 pounds of said composition.

7. The composition of claim 1, wherein said liquid epoxy resin has an approximate molecular weight of about 380 and a viscosity of below about 900 c.p.s. at 25°C;
said filler material is steel powder and is present in an amount of about 33 weight percent of said epoxy resin; and dispersing agent is fumed silica; said dispersing agent being present in an amount of about 10 weight percent of said epoxy resin; said hardening additive is present in an amount of about 35 weight percent based on the weight of said epoxy resin, and n = 2.

8. The composition of claim 7, further comprising silicic acid in an amount between 1 and 7 weight percent of said epoxy resin.

9. The composition of claim 7, further comprising between about 1 and 2 ounces of silicon oil per 120 pounds of said composition.

10. The cured composition of claim 1.

11. The cured composition of claim 7.

12. A method for forming a corrosion-resistant coating on a metal surface while the surface is immersed in water which comprises applying to said surface the composi-tion of claim 1, and allowing said mixture to harden under said water.

13. The method of claim 12, wherein said filler mate-rial is steel powder and n = 2.

14. A method for repairing a defect in a metal or non-metal surface which comprises applying to said surface the composition of claim 1, and then allowing said com-position to harden to form a smooth, tough and adherent coat-ing and possessing good mechanical and solvent resistant properties.

15. The method of claim 14, wherein said filler mate-rial is steel powder and n = 2.