EP0808337A1 - Composition de resine epoxy capable de durcir a basse temperature - Google Patents

Composition de resine epoxy capable de durcir a basse temperature

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Publication number
EP0808337A1
EP0808337A1 EP95910961A EP95910961A EP0808337A1 EP 0808337 A1 EP0808337 A1 EP 0808337A1 EP 95910961 A EP95910961 A EP 95910961A EP 95910961 A EP95910961 A EP 95910961A EP 0808337 A1 EP0808337 A1 EP 0808337A1
Authority
EP
European Patent Office
Prior art keywords
epoxy
resin
formula
reaction
epoxy resin
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.)
Withdrawn
Application number
EP95910961A
Other languages
German (de)
English (en)
Inventor
Michael David Ravenscroft
Klaus Erich Hoffmann
Terry Wayne Glass
Peter Thompson Keillor, Iii
Jacques Louis Poincloux
William Jay Elms
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Dow Chemical Co
Original Assignee
Dow Chemical Co
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Filing date
Publication date
Application filed by Dow Chemical Co filed Critical Dow Chemical Co
Publication of EP0808337A1 publication Critical patent/EP0808337A1/fr
Withdrawn legal-status Critical Current

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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
    • C08G59/02—Polycondensates containing more than one epoxy group per molecule
    • C08G59/04—Polycondensates containing more than one epoxy group per molecule of polyhydroxy compounds with epihalohydrins or precursors thereof
    • C08G59/06—Polycondensates containing more than one epoxy group per molecule of polyhydroxy compounds with epihalohydrins or precursors thereof of polyhydric phenols
    • C08G59/066—Polycondensates containing more than one epoxy group per molecule of polyhydroxy compounds with epihalohydrins or precursors thereof of polyhydric phenols with chain extension or advancing agents
    • 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
    • C08G59/182—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 using pre-adducts of epoxy compounds with curing agents
    • 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
    • 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

Definitions

  • the present invention relates to epoxy resins, to a process for preparing epoxy resins and to compositions containing epoxy resins. Due to their physical and chemical properties such as resistance to chemical attack, good adhesion to various substrates, solvent resistance and hardness, epoxy resins are useful in a wide variety of commercial applications including the coating of various substrates such as metal, and the preparation of structural and electrical laminates. In many applications, such as the coating of the interior of containers ("cans"), the epoxy resin is applied from an o organic liquid solution or aqueous dispersions. Powder coatings, which eliminate the need for solvents, are also prepared from epoxy resins.
  • the molecular weight of the epoxy resin generally affects the physical properties of the resin, for example: softening point, melt viscosity and solution viscosity of the epoxy resin as well as the physical and chemical properties of the cured product prepared therefrom. 5 A higher molecular weight epoxy resin is generally correlated with increased toughness.
  • High molecular weight resins are the reaction product of a polyepoxide such as the diglycidylether of bisphenol A with a polyhydric phenol such as bisphenol A (so-called “advanced epoxy resins").
  • a polyepoxide such as the diglycidylether of bisphenol A
  • a polyhydric phenol such as bisphenol A
  • the advancement reaction occurs between the epoxide group and the hydroxyl of the phenol forming a ⁇ -hydroxyl group thereby extending the chain of the 0 molecules.
  • Cross-linking is incidental to the advancement reaction.
  • the process of advancement of an epoxy resin is generally a process wherein a lower molecular weight epoxy resin is prepared initially by reacting a polyhydric phenol with epichlorohydrin and alkali metal hydroxide in the presence of a catalyst to produce a polyepoxide. Thereafter, the initial polyepoxide reaction product is advanced by its reaction 5 with additional amounts of polyhydric phenol to form the higher molecular weight material.
  • the reaction of the polyepoxide and polyhydric phenol is typically carried to complete conversion such that the final, advanced epoxy resin contains relatively low amounts of residual phenolic hydroxyl groups.
  • epoxy resins having an EEW (epoxy equivalent weight) between 500 and 700 prepared from 0 bisphenol A and the diglycidyl ether of bisphenol A typically contain less than 800 parts per million (ppm) of phenolic hydroxyl groups which represents more than 98 percent conversion of the phenolic hydroxyl groups employed in preparing the epoxy resin.
  • a higher molecular weight epoxy resin having an EEW from greater than 2000 to 4000 typically contains less than 2500 ppm of phenolic -OH groups which represents more than 95 percent conversion of the 5 phenolic hydroxyl groups.
  • U.S. Patent 3,352,825 teaches condensing a dihydric phenol with an excess of epichlorohydrin in the presence of a catalyst such as an alkali metal or ammonium salt of an inorganic monobasic acid to form an intermediate having a free hydroxyl content in the range of from 0.2 to 0.5 phenolic hydroxyl groups per mole of said dihydric phenol. Subsequently, the excess epichlorohydrin is removed and the intermediate condensate subsequently dehydrohalogenated, using caustic alkali and simultaneously the free phenolic hydroxyl groups are reacted with the epoxy groups ormed in situ.
  • a catalyst such as an alkali metal or ammonium salt of an inorganic monobasic acid
  • One method by which the melt and solution viscosities of an epoxy resin can be reduced for a given EEW is by regulating the chain growth of the advanced resin by the preparation of a reaction product of a polyepoxide and a polyol wherein the reaction product contains both epoxy groups and terminal hydroxyl groups.
  • the prior art U.S. Patent 4,722,981 teaches an epoxy resin having both epoxy and terminal hydroxyl end groups in an amount of at least 0.25 weight percent each of the epoxy groups and the terminal hydroxyl groups, said weight percent being based on the total weight of the epoxy resin reaction product.
  • Such resin is use ul as a starting material for the present invention.
  • Solvent-borne coating systems may be formulated which require no elevated temperature for curing. Consequently, heat-sensitive substrates may be coated with solvent epoxy coating systems.
  • the volatile organic solvents required by solvent-based systems are asserted to be unfriendly to the environment. Powder coatings essentially free of volatile components and curable on temperature-sensitive substrates offer an opportunity to reduce solvent emission to the environment and still provide an effective coating on heat sensitive substrates.
  • a bisphenol A epoxy resin coating may be cured with a bisphenol A type phenolic hardener at 120°C for 20 to 22 minutes. It is generally observed that lower viscosity of the coating at the melt temperature yields better adhesion for otherwise comparable resins (see, P. G. de Lange). Lower molecular weight resins and hardeners generally exhibit lower viscosity than comparable higher molecular weight resins and hardeners. However, a solution to inadequate wet-out, and therefore poor adhesion of the coating to the substrate is not resolvable simply by reducing resin molecular weight. Reduced molecular weight generates a separate countervailing consideration.
  • Reduced molecular weight also generally correlates with reduced softening point and lower glass transition temperature, T g , of the resin.
  • the reduced softening point may result in clumping and adhesion of the resin particles on storage, reducing the shelf-life of the resulting powder coating and producing a coating with unsatisfactory smoothness.
  • the present invention provides an epoxy resin useful for a powder coating having a low viscosity at a low cure temperature, having good flow and coating wet-out, and gloss, with high flexibility and protective coating properties, yet providing a softening point/T sufficient to provide adequate shelf-life.
  • the present invention is an epoxy resin comprising the reaction product of a polyepoxy and a polyol wherein the reaction product contains both epoxy groups and terminal phenolic hydroxyl groups in an amount of at least about 0.2 weight percent of each of the epoxy groups and the terminal phenolic hydroxyl groups, said weight percent being based on the total weight of the epoxy resin reaction product, wherein the improvement comprises addition, subsequent to the first reaction stage, of epoxidized phenol-formaldehyde resin having a M n of at least 450, a ratio of M w /M n greater than 1.05 and having an epoxy functionality greater than 2.
  • the instant invention is an epoxy resin comprising the reaction product of a polyepoxy and a polyol wherein the reaction product contains both epoxy groups and terminal phenolic hydroxyl groups in an amount of at least about 0.2 weight percent of each of the epoxy groups and the terminal phenolic hydroxyl groups, said weight percent being based on the total weight of the epoxy resin reaction product, wherein the improvement comprises addition of an epoxidized phenol-aldehyde resin having an epoxy functionality greater than 2.
  • the instant invention is a method of making an epoxy resin composition
  • each A is independently -S-, -S-S-, -C(O)-, -S(O)-, -S(0) 2 -, a divalent hydrocarbon radical containing from 1 to 8 carbon atoms or an oxygen, sulfur, or nitrogen containing hydrocarbon radical or a covalent bond; also A may be
  • each X is independently hydrogen, halogen, or an alkyl group containing from 1 to 4 carbon atoms, and n has an average value of 0 to 5, preferably from 0 to 2;
  • each R is individually hydrogen or an alkyl radical having from 1 to 4 carbon atoms
  • each Y is independently hydrogen, chlorine, bromine or a lower alkyl group having from one to four carbon atoms and m has an average value from greater than 0 to 10, or mixtures of compositions of Formula I and II and an epoxy reactant according to Formula III
  • R, Y and m are described as above with reference to Formula II; or polyglycidyl ethers of polyglycols such as the diglycidyl ether of polypropylene glycol, or the polyglycidyl ethers of tris(phenol)methane, or a triglycidyl ether of a triazine, for example triglycidyl isocyanurate, or a mixture of such epoxy reactants such that the epoxy component and the hydroxy component are present in a ratio from 0.1 : 1 to 10: 1, a reaction catalyst inhibiting the reaction progress at a predetermined conversion of reactants at which point the resin has at least about 0.2 weight percent terminal hydroxyl end groups and at least about 0.2 weight percent epoxy end groups.
  • polyglycidyl ethers of polyglycols such as the diglycidyl ether of polypropylene glycol, or the polyglycidyl ethers of tris(phenol)methane, or a trigly
  • a resulting coating composition exhibits reduced viscosity upon melting when compared to a similar composition without the epoxidized phenol-formaldehyde resin. Hence, from this resin composition a powder coating with improved flow, therefore greater wet-out and improved adhesion results.
  • the epoxy resins of the present invention offer a significant number of o advantages over conventional epoxy resins, which are converted to the extent that no further significant advancement reaction between epoxy and hydroxyl end-groups occurs in a reasonable time (sometimes called “fully converted") and contain essentially no terminal hydroxyl groups.
  • the melt and solution viscosity of the new resins are reduced when compared to fully converted resins of the prior art having similar composition.
  • the new resins provide a higher T which correlates reasonably well with softening point and therefore longer shelf-life than fully converted resins of the prior art having similar melt viscosities at the same temperature.
  • Such resins Due to the fact that such resins contain both epoxy and terminal hydroxyl groups, they can constitute a convenient, homogeneous, one-component system which need not 0 require an additional hardener. Such resins can be formulated into a powder coating by the addition of an accelerator only.
  • the epoxy resin coating composition of the instant invention is comprised of polyhydric alcohol containing an average of more than one hydroxyl group, preferably 1.8 or more hydroxyl groups per molecule, reactive with the epoxy groups of a polyepoxide.
  • the 5 polyols can be saturated or unsaturated aliphatic, cycloaliphatic, aromatic or heterocyclic compounds which can be substituted with one or more non-interfering substituents such as halogen atoms or ether radicals.
  • the preferred polyols are polyhydric phenols.
  • the polyhydric phenols advantageously employed in preparing the epoxy resins are polyhydric phenols represented by the following structural Formula I: 0
  • each A is independently a covalent bond, -S-, -S-S-, -C(O)-, -S(O)-, -S(0) 2 -, a divalent hydrocarbon radical containing from 1 to 8 carbon atoms or an oxygen, sulfur, or nitrogen- -containing hydrocarbon radical, or a composition according to the following description:
  • each X is independently hydrogen, halogen or an alkyl group containing from 1 to 4 carbon atoms; and n has an average value of 0 to 5, preferably from 0 to 2; and the phenol- aldehyde condensate resins of the Formula (II):
  • each R is individually hydrogen or an alkyl radical having from 1 to 4 carbon atoms
  • each Y is independently hydrogen, chlorine, bromine or a lower alkyl group having from one to four carbon atoms and m has an average value from O to 10.
  • Mixtures of one or more polyhydric phenols are also suitably employed herein.
  • the polyhydric phenol is a polyhydric phenolic compound of the general structural Formula I wherein A is a divalent hydrocarbon radical having from 1 to 8 carbon atoms, each X is hydrogen, and n has an average value of from 0 to 0.5, more preferably 0. Most preferred of the polyhydric phenols is 2,2-bis(4-hydroxyphenyl)propane, commonly referred to as bisphenol A (BPA).
  • BPA bisphenol A
  • the initially reacted polyepoxide component useful in preparing the epoxy resin of the present invention is a compound having two or more epoxide groups.
  • the polyepoxides can be saturated or unsaturated aliphatic, cycloaliphatic, aromatic or heterocyclic compounds and can be substituted with one or more non-interfering substituents such as halogen atoms or ether radicals which are not reactive with the epoxy or hydroxyl groups under the conditions at which the resins are prepared.
  • the polyepoxide component which is reacted with the polyol to form the resin can be monomeric or polymeric.
  • each A and X are as described above in the description of Formula (I) and n has an average value of 0 to 4, preferably 0 to 2, most preferably from 0 to 0.5;
  • the polyglycidyl ethers of a novolac resin that is, phenol-aldehyde condensates of Formula IV:
  • R, Y and m are described as above with reference to Formula (II); polyglycidyl ethers of polyglycols such as the diglycidyl ether of polypropylene glycol; and the polyglycidyl ethers of tris(phenol)methane, or triglycidyl isocyanurate. Mixtures of one or more polyepoxides are also suitably employed herein.
  • Preferred polyepoxides are the liquid polyglycidyl polyethers of a bisphenol, particularly the diglycidyl ether of bisphenol A; the polyglycidyl polyethers of a tetrabromobisphenol, particularly the diglycidylether of tetrabromobisphenol A and mixtures thereof.
  • the polyepoxide and polyol are advantageously employed in an amount such that the number of epoxy equivalents in the polyepoxide to the number of hydroxyl equivalents of the polyol is from 0.1 : 1 to 10: 1.
  • the polyepoxide and polyol components are employed in a ratio from 0.3: 1 to 5: 1, more preferably from 0.3: 1 to 2: 1, epoxy equivalents to hydroxyl equivalents.
  • the relative proportions of the polyepoxide and polyol components most advantageously employed will be dependent on a variety of factors including the specific polyepoxide and polyol employed and the desired properties of the epoxy resin prepared therefrom.
  • the polyol and the polyepoxide components are contacted in the presence of a catalyst for the reaction between the hydroxyl groups of the polyol and the epoxy groups of the polyepoxide and at conditions sufficient to form the desired resin.
  • this reaction is conducted neat, that is, in the absence of any reaction diluent or solvent.
  • catalysts are secondary and tertiary amines, preferably tertiary amines such as benzyl dimethyl amine, triethyl amine and benzyl diethyl amine; the alkali metal hydroxides for example, potassium hydroxide; quaternary ammonium compounds such as tetraalkylammonium halides, for example, tetramethyl ammonium chloride and phosphines and quaternary phosphonium salts such as triphenyl phosphine and ethyl triphenyl phosphonium acetate.
  • tertiary amines such as benzyl dimethyl amine, triethyl amine and benzyl diethyl amine
  • the alkali metal hydroxides for example, potassium hydroxide
  • quaternary ammonium compounds such as tetraalkylammonium halides, for example, tetramethyl ammonium chloride and phosphin
  • the catalyst is typically employed in conventional amounts. These amounts will vary depending on the specific catalyst, polyepoxide and polyol employed but will preferably vary from 0.001 to 1 weight percent based on the total weight of the polyol and polyglycidyl ether components. More preferably, from 0.01 to 0.25 weight percent of the catalyst is employed, said weight percent being based on the total weight of the polyol and polyepoxide components.
  • the reaction of the polyol and polyepoxide components can be conducted in the presence of a reaction diluent. If employed, the reaction diluent is preferably a solvent for, or miscible with, both the polyol and polyepoxide component.
  • Representative solvents which can be employed include various glycol ethers such as ethylene glycol monomethyl ether, or propylene glycol monomethyl ether and esters thereof such as ethylene glycol monoethyl ether acetate; ketones such as methyl isobutyl ketone, methyl ethyl ketone and acetone; and aromatic hydrocarbons such as toluene, xylene or mixtures thereof.
  • the organic liquid reaction diluent is generally employed in an amount from 5 to 300 percent based on the total weight of the polyol and polyepoxide components.
  • the reaction of the polyol and polyepoxide is advantageously carried out at an elevated temperature, preferably from 60°C to 200°C, more preferably from 100°C to 180°C.
  • the reaction is continued until the desired conversion, as determined by monitoring a measurable parameter such as the residual epoxy and terminal hydroxyl content in the resin, or melt viscosity.
  • the reaction is effectively terminated at the desired end point.
  • a convenient method of predicting the approximate time at which a desired characteristic of the resin will be arrived at includes conducting the reaction under essentially isothermal conditions at laboratory scale by terminating the reaction at various times and measuring the extent of reaction by means of measurement of physical or chemical parameters such as melt viscosity and residual hydroxyl content in the ordinary manner known by those skilled in the art.
  • reaction is effectively inhibited when the rate of reaction of the hydroxyl and epoxy group is sufficiently reduced such that further reaction, if any, does not significantly and deleteriously affect the product or its handling characteristics.
  • the reaction is sufficiently inhibited such that the viscosity of the resin remains essentially constant or increases only marginally with time.
  • the reaction mixture can be quenched to stop the reaction.
  • the rapid quenching of the reaction mixture must be conducted carefully to prevent clotting or lumping of the resin and to prevent the resin from forming a large solid mass which cannot subsequently be used.
  • a convenient method for cooling the reaction mixture comprises the addition of a solvent to the mixture, thereby diluting the mixture and reducing its temperature.
  • the amount of organic solvent to be added is dependent on the reaction temperature and the temperature at which reaction is effectively terminated.
  • the addition of organic solvent to the reaction mixture is particularly preferred when the resin is subsequently to be applied from solution.
  • a preferred method for inhibiting the reaction comprises adding a material to the reaction mixture which effectively inhibits further reactions such as by deactivating the catalyst, or by interrupting the reaction mechanism, thereby inhibiting further reactions between the polyol and the polyepoxide.
  • Strong inorganic and organic acids and the anhydrides and esters of said acids have been found to be particularly effective as reaction inhibitors.
  • strong acid it is meant an organic acid having a pK a value below 4, preferably below 2.5.
  • reaction inhibitors include inorganic acids such as hydrochloric acid, sulfuric acid and phosphoric acid; inorganic acid anhydrides such as phosphoric acid anhydride (P 2 0 5 ); esters of inorganic acids such as dimethyl sulfate; the organic acids such as alkyl, aryl and aralkyl and substituted alkyl, aryl and aralkyl sulfonic acids such as p-toluene sulfonic acid and phenyl sulfonic acid and stronger organic carboxylic acids such as trichloroacetic acid and alkyl esters of said acids, such as the alkyl esters of p-toluene sulfonic acid, for example, methyl-p-toluene sulfonate, and ethyl-p-toluene sulfonate and methane sulfonic acid methyl ester.
  • inorganic acids such as hydrochloric acid, sulfur
  • an acid anhydride of a strong organic acid that can be employed herein is p-toluene sulfonic acid anhydride.
  • the alkyl esters of sulfuric acid; the aryl or aralkyl sulfonic acids and the alkyl esters of said acids are preferably employed herein.
  • an alkyl ester of para-toluene sulfonic acid, particularly methyl or ethyl-p-toluene sulfonic acid is employed as the reaction inhibitor herein.
  • the amounts of reaction inhibitor added to the reaction mixture are dependent on the specific inhibitor employed and the catalyst employed in preparing the resin.
  • the inhibitor is added in an amount sufficient to overcome the catalytic activity of the catalyst.
  • at least 0.9, more preferably at least 2 equivalents of the inhibitor are added for each equivalent of the catalyst employed.
  • the maximum amount of inhibitor added to the reaction mixture is dependent on the desired properties of the resin and the expense of adding excess inhibitor, the inhibitor is preferably added in an amount not o exceeding 5 equivalents for each equivalent of catalyst in the reaction mixture.
  • the resin of the instant invention may also be prepared by reducing the temperature of the reaction components. Additional temperature control may be achieved over the reaction components by conducting the reaction in an extruder having zones of temperature control. A zone of high temperature may be useful to heat the reaction 5 components sufficient to destroy the catalytic activity of any catalyst present. Additionally, an inhibitor may be added to the reaction components to interrupt the activity of a catalyst or by another mechanism to halt the reaction of reaction components. Termination of a reaction by temperature reduction has the advantage that the resin does not contain an inhibitor required by quenching the batch-wise reaction by inhibitor addition. 0 The reaction is terminated at a point such that the resulting resin contains the desired amounts of epoxy groups and terminal hydroxyl groups. In this invention, the resin will contain at least 0.2 percent, by weight, of-each of the epoxy and terminal hydroxyl groups.
  • the term "epoxy group” means a radical of the following structural formula:
  • terminal hydroxyl group means a terminal hydroxyl group having an equivalent weight of 17.
  • the weight percent of epoxy groups in epoxy resin may be determined according to the method disclosed in U.S. Patent 4,722,981.
  • weight percentages can also be viewed as the numbers of equivalents of 5 the epoxy and hydroxyl groups per kilogram of the resin reaction product. It has been determined that 0.2 weight percent of the epoxy group is about 0.0465 epoxy equivalents per kilogram resin produced. Similarly, 0.2 weight percent of the hydroxyl group is about 0.12 hydroxyl equivalents per kilogram resin produced.
  • the hydrolyzable chloride content of the resin is generally less than 1 and often less than 0.5 percent based on the total weight of the epoxy resin reaction product. However, a hydrolyzable chloride content of up to 5, preferably not more than 2, weight percent based on the total weight of the epoxy resin reaction product may be tolerated.
  • the amounts of hydrolyzable chloride are determined for the purpose of this invention by the method described in The Handbook of Epoxy Resins pp. 4-29 and 4-30 (Table 4-23).
  • the resin preferably contains at least 0.5, more preferably at least I, weight percent of epoxy groups and at least 0.2 weight percent of terminal hydroxyl groups.
  • the said weight percents are based on the total weight of the resin.
  • the resin preferably comprises less than 20, more preferably less than 12, weight percent of epoxy 5 groups and less than 10, more preferably less than 7 weight percent of the terminal hydroxyl groups.
  • conversion of the polyol and polyepoxide components is controlled such that the resin contains the desired amounts of epoxy and hydroxyl groups. This conversion is dependent on the amount of polyol and epoxide 0 employed.
  • at least 45 percent and up to 95 percent of the deficient component present is reacted. If the components are employed in equivalent amounts, then at least 45 percent and up to 95 percent of both components are reacted.
  • at least 50, more preferably at least 55, and up to 95, more preferably up to 90, most preferably up to 85, percent of the deficient component or the equivalent reactants, as the case may be, are 5 reacted.
  • the number average molecular weight of the resin is dependent on the desired end-use application of the resin and the physical and chemical properties required for said end- use.
  • the resins have a molecular weight of less than 10,000. More preferably, the resins will possess molecular weights of less than 4000, most preferably less than 2000, and 0 more preferably more than 300, most preferably more than 500.
  • the polyepoxide can be advanced with a polyol and, optionally, a polyacid to completion (thereby forming a resin having either only epoxy groups or terminal hydroxyl groups depending on which reactant is employed in excess) in one reaction step and thereafter reacted with a polyol or a polyepoxide component to form 5 the resin.
  • a polyol and, optionally, a polyacid to completion thereby forming a resin having either only epoxy groups or terminal hydroxyl groups depending on which reactant is employed in excess
  • the added compound suitable for crosslinking at the second stage may be either hydroxyl reactive or epoxy reactive.
  • the polyglycidyl ether of an aldehyde-phenol condensate resin described previously with reference to Formula IV are suitable.
  • the range of m should be on average from greater than zero to 5.0, more preferred in a range of from 0.5 to 4.5.
  • the remaining hydroxy reactive components of the secondary addition may have an average functionality of 2 or less, but more than 1.2.
  • Diluents or solvents may be present in the second stage.
  • the diluent content is advantageously less than 50 percent of the total composition, by weight.
  • the polyhydric phenols described with reference to Formula II is suitable.
  • the range of m should be an average from greater than zero to 5.0, preferably from 0.5 to 4.5.
  • the resin can be formulated into a number of different compositions for use in a variety of end- use applications.
  • the resin can be admixed with an accelerator and, optionally, other adjuncts such as flow control agent to form a powder coating composition.
  • a hardener may be added to the resin component, since the resin contains both unreacted epoxy and unreacted terminal hydroxyl groups, the resin may be cured without addition of hardener.
  • Hardeners, catalysts and accelerators conventionally employed in epoxy resin- based powder coating compositions can be employed in a powder coating composition of the resin. Such hardeners and accelerators are well-known in the art and reference is made thereto for the purposes of this invention.
  • Representative accelerators include stannous salts of monocarboxylic acids, such as stannous octoate and stannous laureate, various alkali metal salts such as lithium benzoate, certain heterocyclic compounds such as imidazole and benzimidazole compounds and salts thereof, onium compounds such as quaternary ammonium and phosphonium compounds and tertiary amines phosphines, and phenol carbamates.
  • Preferred accelerators for use in preparing the powder coating formulations are o those which are solid at room temperature and include the imidazoles, particularly the alkyl substituted imidazoles such as 2-methyl imidazole, solid phosphines or amines such as triphenyl phosphine, quaternary phosphonium, and quaternary ammonium compounds.
  • the amount of accelerator most advantageously employed will vary depending on the particular accelerator employed. 5
  • the accelerator will be employed in an amount from 0.01 to 5 weight percent based on the weight of the resin. More preferably, the accelerator is employed in an amount from 0.02 to 3 weight percent based on the weight of the resin.
  • the optionally employed hardeners are phenolic hardeners such as phenolic or cresol novolacs and the phenolic hardeners as described in British Patent 0 Specification No. 1,429,076, dicyandiamide, acid anhydrides such as trimelletic anhydride, the acid functional polyesters, and hydrazides such as adipic dihydrazide and isophthalic dihydrazide. If employed, the hardeners are generally employed in an amount from I to 50 weight percent based on a total weight of the resin.
  • the number of equivalents of epoxy groups per kilogram 5 of resin in the second stage reacted resins suitable for use as powder coatings is 1.54 to 2.1.
  • a maximum number of epoxy equivalents is 5.9. Excess epoxy equivalents results in low softening points.
  • More preferably the range of epoxy equivalents is more than 4.1 per kilogram resin.
  • the resins contain from 5.4 to 5.9 epoxy eq/kg of epoxy resin prior to conversion of any of the epoxy groups to epoxy-derived groups.
  • the resin contains 0.2 to 1.5 0 eq/kg of terminal phenolic hydroxyl groups.
  • the epoxy groups of the controlled conversion resin can be converted to any epoxy-derived functional groups that will not detrimentally affect the curing reaction.
  • the present invention is in noway limited by such theory, it is believed that a hydrolysis reaction of the epoxy group with added water forms alpha-glycols.
  • water addition is a way to conveniently convert the epoxy groups to suitable epoxy-derived groups.
  • the number of equivalents of epoxy groups will determine the amount of water or other reactant necessary to form the alpha-glycol and possibly other types of epoxy-derived groups.
  • water is used in excess amounts of from 0.5 to 20 weight percent based on the total resin weight, preferably 1 to 10 weight percent.
  • Reaction of the resins with water and acid can also be employed to convert the epoxy groups. It is theorized that this is a conversion of the epoxy groups to alpha-glycols and o acid esters and possibly other types of groups derived from the epoxy groups, but the present invention is not to be limited by this theory.
  • Water and acid are used generally in amounts of 0.2 to 10 weight percent acid. These weight percentages are based on the total weight of the resin to which the water and acid are added. More preferably, the respective weight percentages of water and acid are 0.5 to 3 weight percent and 0.2 to 2 weight percent. 5
  • the epoxy groups of the controlled conversion resin are reacted with water and a phosphorous-containing acid.
  • the amounts of water and phosphorous-containing acid are balanced to maximize the mono-esters and minimize the tri-esters. It has been found generally that when the phosphorous-containing acid is used in this way with a controlled 0 conversion resin it should be added in amounts of from 0.1 to 3 weight percent based on the resin weight, preferably from 0.2 to 1.5 weight percent while the water used in conjunction should be added in amounts of from 0.2 to 10 weight percent based on the resin weight, preferably from 0.5 to 3 weight percent.
  • step one amounts of water 5 and acid, preferably a phosphorous-containing acid, are employed as a reaction inhibitor in preparing the controlled conversion resins.
  • the amount of water and acid added is in excess of amounts taught to inhibit the polyol polyepoxide reaction, which excess amount is then able to react with the epoxy groups of the controlled conversion resin to form the epoxy-derived groups.
  • the above-described mixture of such groups comprise alpha-glycols and 0 phosphorous-containing acid esters.
  • the acid is used in amounts of from 0.1 to 3 weight percent based on the weight of resin, preferably from 0.2 to 1.5 weight percent.
  • the resin may be dissolved in an organic liquid for subsequent use.
  • Suitable organic liquids for preparing the organic liquid solution of the resin are dependent on the particular resin and the amounts of terminal hydroxyl and epoxy groups in the resin. In general, alcohols such as n-butanol, glycol ethers such as propylene glycol monomethyl ether and esters thereof, ketones, aliphatic or aromatic hydrocarbons such as xylene and chlorinated aliphatic and aromatic hydrocarbons are preferred.
  • hardener which is also soluble in the organic liquid.
  • Such hardeners are well-known in the art and reference is made thereto for the purposes of this invention.
  • Representative hardeners include phenolic resins such as the reaction product of phenol with an excess of formaldehyde and other hydroxymethyl-containing benzene derivatives and alkylated derivatives thereof and amine-aldehyde condensates, commonly referred to as "aminoplast” or "aminoplastics" which are the condensation products of an aldehyde with an amine such as melamine, urea and benzoguanamine and the alkylated derivatives thereof.
  • the amount of the hardener most advantageously employed is dependent on a variety of factors including the end- use application for the organic liquid solution and the desired physical and chemical properties of said end-use application.
  • the inorganic acid is preferably phosphoric acid and is used in an amount from 0.1 to 5 weight percent based on the total weight of the organic liquid solution.
  • the solids concentration at which the organic liquid solution is prepared is dependent on various factors including the desired viscosity of the resulting solution.
  • the organic liquid solution is formulated such that the solids content is as high as possible while maintaining a sufficiently low viscosity for effective application. Since the resins exhibit a lower solution viscosity than conventional resins which would possess equivalent cured properties, the organic liquid solution of a resin can generally be prepared at higher solids concentrations than an organic liquid solution of a conventional resin.
  • a resin useful in coating applications may be formulated as an organic liquid solution which comprises at least 40 percent of the resin and any hardener employed based on the total weight of the organic liquid solution. More preferably, the liquid solution contains at least 50 percent, most preferably from 50 to 70 weight percent of the resin and hardener.
  • Powder coatings prepared from resins according to the instant invention demonstrate advantageous properties over prior art making such resin particularly useful for coating applications. Coatings advantageously form a uniform surface on the substrate (see, P.G. de Lange).
  • Powder coatings prepared from resin according to the instant invention advantageously demonstrate low viscosity under curing conditions.
  • a particular further advantage of low viscosity may be obtained by the inclusion of an epoxidized phenol- formaldehyde resin to the first stage reactant.
  • the cure of an epoxy resin depends on the temperature of the cure and the duration.
  • the inventive resin cures under conditions of lower temperature than the prior art.
  • the resin curing is achieved over a shorter time than a prior art of a similar composition.
  • cured coating compositions prepared from resin of the instant invention demonstrate coating properties consistent with the prior art, in spite of the milder curing conditions.
  • Prior art resins exist which are curable at similar curing temperatures to the resins of the instant invention.
  • the instant resin exhibits a higher T /softening point and therefore a longer shelf-life.
  • Example 2-9 For Examples 2 through 8, the steps according to Example 1 were repeated incorporating the ingredients as indicated on Table I.
  • Example 9 was prepared using an extruder as described for examples 20 through 24. Resins having the properties noted are prepared.
  • Example 10 (not an example of the invention)
  • the composition has an epoxy equivalent weight of 325.
  • Solid epoxy resin EEW 700- 39.0 750
  • Solid Bis A epoxy resin 4- type 50.3 with 18.6 % of an epoxidized phenol-formaldehyde resin having an epoxy functionality of 3.6, M n 534, M w /M n 1.7.
  • Solid bisphenol A advanced 25.4 epoxy resin with epoxy equivalent weight of 495 - 526.
  • Titanium dioxide available from Kronos Titan GmbH, Leverkusen,
  • BonderTM 1041600C chromate treated, used neat, 1 mm thick. Bonder is a
  • Example 10 Example 11 * (parts by weight) (parts by weight) (parts by weight)
  • Examples 12-17 compare the properties of epoxy resin compositions having the same ratio of epoxy groups to phenolic groups in the starting materials All compositions are mixed in a Mixaco container mixer, then melt extruded in a Werner & Pfleiderer ZSK30 extruder at 63°C After extrusion and cooling, the solid resin is ground to a practical size consistent for all samples from one to one hundred ⁇ m having the average particle size distribution at 25 to
  • Table III presents compositions and coating properties for Examples 11 through 16 Example 18
  • Another resin may be prepared according to Example 17, except that 484 parts of the diglycidyl ether of bisphenol A may be used together with 200 parts of an epoxidized phenol formaldehyde resin having an epoxy unctionality of 3.6, M n of 534 and M w /M n of 1.7. o
  • the other quantities and conditions are the same as in Example 1.
  • the barrel is 1410 millimeters in length excluding the die.
  • the barrel is comprised of 11 single length (900 mm) and 2 double length (180 mm) barrel sections with one 30 mm support plate and one 30 mm end plate.
  • the barrel configuration had a feed section, followed by a solid section, a vent section, then alternating plugged ported or solid sections for the remainder of the barrel.
  • the extruder head has pressure measurement, a rupture disc, and piping connection. There were four extensive mixing sections in the screw design, which extended into the extruder head.
  • the barrel was divided into nine heating and cooling zones. The ninth zone is the extruder head.
  • Epoxy resin is prepared from starting materials at the feed rates indicated in Table IV. Zones 1 - 3 operate at 175°C, zone 4 at 220°C, zones 5 and 6 operate at 240°C, Zones 7 - 9 at 175°C.

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  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Epoxy Resins (AREA)
  • Paints Or Removers (AREA)

Abstract

Résine époxy produite par la réaction d'un polyépoxyde et d'un polyol contenant des groupes époxydes et des groupes hydroxyles phénoliques terminaux d'un pourcentage, en poids, d'au moins 0,2, auxquels on a ajouté une novolaque ayant une fonctionnalité époxyde supérieure à deux. Cette résine époxy convient comme revêtement sous forme de poudre présentant une viscosité de fusion inférieure à celle de résines de l'état de la technique de composition similaire. Ladite résine époxy présente un rapport Tg/point de ramollissement plus élevé que celui de résines de l'état de la technique présentant une viscosité similaire. L'invention décrit également un revêtement en poudre préparé à partir de ladite résine et qui peut être utilisé sur des supports thermosensibles.
EP95910961A 1995-02-10 1995-02-10 Composition de resine epoxy capable de durcir a basse temperature Withdrawn EP0808337A1 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US1995/001674 WO1996024628A1 (fr) 1995-02-10 1995-02-10 Composition de resine epoxy capable de durcir a basse temperature

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EP0808337A1 true EP0808337A1 (fr) 1997-11-26

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AU (1) AU1873795A (fr)
CZ (1) CZ253297A3 (fr)
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CN1347439A (zh) * 1999-04-21 2002-05-01 范蒂科股份公司 可流动的粉末涂料组合物
TWI814925B (zh) 2018-10-29 2023-09-11 美商湛新美國股份有限公司 低烘烤粉末塗料樹脂及塗覆基材的方法

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DE1643309U (de) * 1952-02-11 1952-09-04 Loewe Opta Ag Schallplattengeraet mit mitteln zur inbetriebnahme von schallplatten verschiedener laufgeschwindigkeit.
NL153575B (nl) * 1963-10-09 1977-06-15 Dow Chemical Co Werkwijze voor de vervaardiging van gelamineerde voorwerpen, alsmede gelamineerde voorwerpen verkregen volgens deze werkwijze.
GB8420816D0 (en) * 1984-08-16 1984-09-19 Dow Chemical Rheinwerk Gmbh Epoxy resins
US4596861A (en) * 1985-05-22 1986-06-24 The Dow Chemical Company Advanced epoxy resin for can coating applications
GB8603701D0 (en) * 1986-02-14 1986-03-19 Dow Chemical Rheinwerk Gmbh Epoxy resins
GB9027406D0 (en) * 1990-12-18 1991-02-06 Ciba Geigy Ag Production of compounds

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Title
See references of WO9624628A1 *

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CZ253297A3 (cs) 1998-06-17
MX9706096A (es) 1997-11-29
AU1873795A (en) 1996-08-27
WO1996024628A1 (fr) 1996-08-15

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