DE3446178A1 - WATER-DISCOVERABLE PAINT COMPOSITION, METHOD FOR THE PRODUCTION THEREOF AND THEIR USE FOR COATING THE CONTAINERS FOR FOODSTUFFS - Google Patents

Description

Water-thinnable paint composition, method to their manufacture and their use for coating

Containers for food

The present invention relates to hydrous polymer paint compositions and in particular polymer paint compositions for coating interior surfaces of containers for food.

Polymer paint compositions intended for use inside food containers; must meet very strict requirements. In addition to strict requirements for adhesion to the substrate must the polymer to be able to withstand steam treatment must not interact with the food material and must not be discolored or stained by the food material. In addition to these very In the case of strict requirements, there are further limitations with regard to the content of organic solvents Polymer compositions in general.

It is an object of the present invention to provide a water-thinnable paint or coating composition as well as a process for their manufacture to create the meet the strict requirements mentioned and especially for use for coating the interior of containers for food are suitable.

This object is achieved by a composition according to claim 1, a process for its preparation according to claim 5 and solved by their use according to claim 6. Advantageous refinements are the respective to be found in the dependent subclaims.

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The present invention thus relates to a paint composition especially for use in the manufacture of internally coated food containers is suitable, this paint composition being the reaction product of a high molecular weight epoxy resin, which is dissolved in an organic solvent, a phenolic resin which is dissolved in the same solvent as well as a variety of acrylic monomers, at least one of which is an acid monomer and for that by heating in the presence of the epoxy resin and the phenolic resin dissolved in the organic solvent are polymerized. The composition is made water-dilutable by having the functional Carboxyl groups of the polymers formed neutralized with an aqueous amine. The composition obtained is stable in storage, Can be diluted with more water and meets the strict requirements for coatings for food containers. It is believed that the polymer composition obtained is essentially an epoxy-phenolic resin copolymer on which an acrylic copolymer is grafted, although variations and permutations on the The basis of the reactants should also be present in the paint composition.

In another aspect, the present invention relates to a method of making such a paint composition by dissolving the epoxy resin in a water-miscible organic solvent, dissolving the phenolic polymer in the same solvent, adding the acrylic monomers to the solvent composition, and reacting the composition in the presence of at least 3% of an organic oxide (or another radical initiator equivalent) by heating (for example to a temperature below 120 ^° C.).

Any carbonyl functionality of the composition (resulting from the addition of appropriate acrylic monomers

originates) is then neutralized with an aqueous amine solution.

In another aspect, the present invention relates to the use of a paint composition mentioned or prepared in the manner mentioned for coating at least the inner surfaces of containers for foodstuffs, which are coated food containers produced with such use
also encompassed by the present invention.

The following are the above statements, in particular with regard to the problem and solution as well as the features and advantages of the present invention which are important for the solution explained in more detail with reference to preferred exemplary embodiments.

According to the present invention, any
High molecular weight epoxy resin can be used as long as it has the required epoxy functionality.

A particularly suitable class of epoxy resins has
the general formula on:

OH

H ₂ C-HCH ₂ CO-0

in which R is an alkylene group having from 1 to 4 carbon atoms and η is an integer from 1 to 12. the
Epoxy resins used in accordance with the present invention generally contain an average of two terminal 1,2-epoxy groups per molecule and in terms of epoxy equivalent weight are in the range of about 650 to about 5000, preferably in the range of about

1000 to about 4000. A preferred epoxy resin is ΕΡΟΓΓ ^ 1009 (Shell Chemical Corporation).

Other examples of suitable epoxy resins include glycidyl polyethers, sold under the trademark EPON resin 1001, 1004, 1007, etc. Other suitable solid Epoxy resins include the condensates or hot melt resins prepared as described in U.S. Patent 3,477,990 became. Under certain conditions, part of the epoxy resin can be a glycidylated novolak. Other suitable Epoxy compounds include those compounds which are derived from polyhydric phenols and at least have a vicinal epoxy group in which the carbon-carbon bonds are saturated within the six-membered ring. Such epoxy resins can can be produced using at least two well known techniques, namely (1) hydrogenation of glycidyl polyethers of polyhydric phenols or (2) by the reaction of hydrogenated polyhydric phenols with epichlorohydrin in the presence of a suitable catalyst such as a Lewis acid, e.g. Boron trihalides and their complexes, as well as subsequent elimination of hydrogen chloride in an alkaline Medium. The manufacturing process does not form part of the present invention, and that of any of these processes obtained saturated epoxy resins are for that compositions according to the invention suitable.

Epoxy resins that can also be used include the hydrogenated resins made by the process described in U.S. Patent 3,336,241. More preferred are the hydrogenated glycidyl ethers of 2,2-bis (4-hydroxyphenyl) propane, sometimes called the Diglycidyl ether of 2,2-bis (4-cyclohexanol) propane will.

3448178

—Ο-Ι According to the present invention, any phenolic resin can be used can be used as long as it has the methylol functionality required for reactivity. the preferred phenolic resins are the reaction products of phenol, substituted phenols and bisphenol-A with formaldehyde under alkaline conditions. Under such conditions, the methylol group becomes either o or pendent linked to the aromatic ring. Reaction rate studies have shown that the p-position to the hydroxyl group is somewhat more reactive towards formaldehyde, but that in the case of phenol or bisphenol-A, which contain no other substituents, 2 o-positions are present per aromatic nucleus, which is why leads that the o-methylol compound with a faster Total speed is formed. Essentially a mixture of methylol phenols is formed, of which some have more methylol groups than others.

In phenolic resin production, the polymerization or dehydration stage is below the original alkaline Conditions or carried out after the neutralization of the methylol mixture. The obtained methylol-containing Resin, which is called resole resin, is a complex mixture of mononuclear and polynuclear molecules that pass through Methylene or dimethyleneoxy bridges are linked together. These polymer structures contain three methylene groups, which are reactive in subsequent reactions, and they are phenolic resins made according to the present invention can be used. These phenolic resins can under the action of acid and / or heat with the Carboxyl, oxirane and hydroxyl substituents react, present in the epoxy-acrylic resin according to the present invention. The methylol functionality of the Phenolic resin, however, remains under the mild conditions of acrylation required according to the present invention are maintained, essentially intact. It is we-

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essential that the methylol functionality remains intact, because otherwise premature crosslinking and gelation prevent further usefulness. Besides, the preservation will the methylol functionality for the development of paint properties required during the curing step of the paint.

Another suitable phenolic resin that can be used in accordance with the present invention is provided by a Formed alkylation process that causes an etherification of methylol groups. Butanol is the preferred alkylating agent. Alkylation with butanol leads to improved solubility and compatibility of the phenolic resin with the other components (epoxy and acrylic components) of the composition according to the invention. However, the alkylation of the methylol groups does not deteriorate the paint reactivity. Both phenolic resins with free methylol groups as well as phenolic resins with alkylated methylol groups were made in accordance with the present invention used successfully. It should be noted that the phenolic resins described above are known and are commercially available.

The acrylic monomers made according to the present invention can be used include well-known acrylic monomers such as acrylic acid having lower alkyl groups substituted acrylic acids such as methyl, ethyl, butyl, propyl substituted acrylic acids (e.g. methacrylic acid). The lower alkyl esters of such acrylic acids, such as methyl acrylate, Butyl acrylate, methyl methacrylate, etc. corresponding to the acids mentioned above are within the scope of the present Invention also useful (see U.S. Patent 4,308,185 supplementing the present disclosure). It should be It will be understood by those skilled in the art that the COOH groups can also be introduced by using other non-acrylic

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Monomers such as maleic anhydride, itaconic acid etc. copolymerized.

Any water-miscible organic solvent that includes both the epoxy resin and the phenolic resin dissolves can be used in accordance with the present invention. Typical of such solvents are n-butanol, sec-butanol, alkyl ethers of ethylene and propylene glycols, for example ethoxyethanol, propoxypropanol, 2-butoxyethanol, Diethylene glycol monomethyl, ethyl and butyl ethers etc.

For initiating the graft copolymerization of the acrylic monomers Suitable initiators for the epoxy-phenol resins are organic peroxides and their equivalents. Some preferred Initiators are t-butyl peroctoate, t-butyl peroxyacetate, t-butyl perbenzoate, benzoyl peroxide, and 2,2'-azobis (2-methylproprionitrile).

The present invention is based on the discovery that when epoxy and phenolic resins as well as addition polymerizable monomers at elevated temperature (below the curing temperature of the composition, which is typically about 200 ⁰ C, so typically to a temperature below about 120 ⁰ C is heated) in the presence of at least 3% (preferably 3 to 8 wt .-%, based on the weight of the acrylic monomers present) of organic peroxide or an equivalent radical initiator are reacted with one another, so that the addition and graft reactions then take place simultaneously . The grafting occurs (apparently) on the aliphatic groups present in the main chain of carbon atoms of the epoxy-phenolic resin. The reaction mixture obtained contains graft polymers, associatively formed ungrafted addition polymers, as well as a certain proportion of unreacted epoxy-phenol resin,

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The key feature of the reaction to produce valuable paints according to the present invention is that the polymerization-grafting must be carried out in dissolved epoxy and phenolic resins. if the polymerization and the grafting are carried out separately to produce epoxy-acrylic graft copolymers and phenol-acrylic graft copolymers and these, then combined, make the combinations unstable paints. In addition, when cured, opaque films are obtained instead of clear films.

The grafting that occurs has a significant influence on the properties of the reaction mixture. Thus, if the addition of polymerizable monomers is a predominant amount of an acrylic or methacrylic acid contains, both the graft polymers and the ungrafted addition polymers that are formed functional carboxyl groups, and in the presence of an amine solubilizing agent, the reaction products easily dispersed in water to form stable systems. For a satisfactory dispersion should the acid number of the reaction mixture is sufficient to bring the polymer into an aqueous dispersion and in this (e.g. acid numbers from 35 to 86 are common).

In addition, the addition and graft copolymers containing carboxyl groups, which in this reaction obtained a suitable dispersing effect to form all ungrafted epoxy-phenolic resins to keep stable aqueous dispersions.

The ratio of epoxy resin to phenolic resin (the following ratios are all in parts by weight or% by weight unless otherwise stated) is roughly the same, with a lighter if applicable Excess epoxy resin is present. For example, the epoxy should form about 40 to about 60 parts by weight while

the phenolic resin should constitute about 30 to about 40 parts by weight. The acrylic monomers make up about 25% to 35% of the total Acrylic and epoxy-phenolic compositions, with about 30% being preferred. The preferred acrylic composition is from about 20 to about 30% acrylic or methacrylic acid, about 30 to about 40% butyl acrylate, about 30 to about 40 percent methyl methacrylate, about 10 to about 20 percent hydroxymethyl acrylate, and about 20 to about 30 percent styrene are formed.

In use, the mixture of water and organic solvents for coating typically contains about 70 to about 80% water and about 20 to about 30% organic solvent. For coating purposes is the concentration of the epoxy-phenol-acrylic polymer composition in accordance with the present invention typically at about 60 to about 70 weight percent solids in the organic solvent before dilution.

Useful for carrying out the final stage of the reaction Amines to neutralize the unreacted carboxyl groups are: aqueous ammonia and RNH-, where R can be an alkyl radical, e.g. a methyl, propyl, butyl or the like radical or an alkanol radical, e.g. a methanol, ethanol, propanol or the like radical .. A preferred one primary amine is 2-amino-2-methyl-1-propanol.

Suitable secondary amines include amines of the general formula:

■ R ₁

HN
\

in which R and R _{2 are} identical or different hydrocarbon radicals such as, for example, alkyl radicals, e.g. methyl,

_ 1 T _
I -3

34 43-73

Propyl, butyl and similar radicals or alkanol radicals are, for example, methanol, ethanol, propanol and the like Leftovers.

Examples of very suitable secondary amines are N-methylethanolamine, diethanolamine, dimethylamine, diethylamine, Dipropylamine and morpholine.

Suitable tertiary amines include amines of the general formula

I ¹

NR ₂

^R 3
15th

in which R, R ₂ and R _{3 can be} identical or different hydrocarbon radicals such as alkyl radicals, e.g. methyl, propyl, isopropyl, butyl and similar radicals or alkanol radicals, for example methanol, ethanol, propanol, isopropanol and similar remnants.

Examples of preferred tertiary amines include triethylamine, triisopropylamine, tributylamine, dimethylethanolamine and diethylethanolamine. Tertiary amines are particularly preferred and diines are very particularly preferred thy! ethanolamine. The amounts of amine added are sufficient from neutralizing from about 50 to about 100% of the carboxyl groups present.

When used, the compositions of the invention can be applied by any conventional painting or coating process, for example by spraying or rolling. For beverage containers, the preferred method is spraying. For food containers, the preferred method is rolling. The coatings are generally applied in thicknesses up to about 0.54-0.62 mg / cm ² (3.5-4 mg / square inch).

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The present invention is described below on the basis of exemplary embodiments explained in more detail.

example 1

162.0 parts of an epoxy resin (EPON 1009) were added to a mixture of 135.0 parts of n-butanol and 135.0 parts of 2-butoxyethanol, and the mixture was heated to 135 ° C. for dissolution. After the epoxide had dissolved, were added portionwise 216.0 parts of o-cresol-formaldehyde phenolic resin (softening point 65-75 ° C, hot plate cured at 150 ⁰ C, 70-110 s) was added and the slurry was stirred for 30 minutes at 90 ⁰ C stirred until complete dissolution was achieved. A mixture of 59.7 parts of acrylic acid, 51.3 parts of methyl methacrylate, 51.3 parts of butyl acrylate, 15.6 parts of n-butanol, 15.6 parts of 2-butoxyethanol and 12.9 parts of tert-butyl peroctoate were added over a period of time of two hours were added while the reaction temperature was kept ^{at 95 ^ 3 0 C.} After stirring for a further two hours at 95 ± 3 ° C., a mixture of 55.5 parts of dimethylethanolamine and 808.8 parts of deionized water was added, so that 1700 parts of a product with a solids content of 34.89% were obtained, the Brookfield- Viscosity (25 ° C) was 11.4 Pa · s (114 poise) and the pH was 7.3.

Example 2

107.4 parts of EPON 1009 were added to a mixture of 94.5 parts of 2-butoxyethanol and 40.5 parts of n-butanol and the mixture was heated to 135 ° C. until the epoxy resin was dissolved. The temperature was ^{lowered to 95 °} C., and 143.2 parts of phenolic resin (cf. Example 1)

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added and stirred until a solution was achieved. At this point, a mixture of 42.2 parts of butyl acrylate, 31.5 parts of methyl methacrylate, 10.7 parts of hydroxyethyl acrylate, 22.9 parts of acrylic acid, 14.6 parts of 2-butoxyethanol, 6.2 parts of n-butanol and 8.6 parts Parts of tert-butyl peroctoate were added over the course of two hours, while the reaction temperature was kept at 95 ^ 3 ° C. After a further two hours stirring at 95 ⁰ C, a mixture of 21.5 parts of dimethyl ethanolamine and 537.2 parts of deionized water was added so that 1081.0 parts of a product were obtained having a solids content of 31.74%, with the Brookfield viscosity (25 ^° C.) was 0.85 Pa · s (8.5 poise) and the pH was 7.45.

Example 3

14 3.2 parts of EPON 1009 were added to a mixture of 94.5 parts of 2-butoxyethanol and 40.5 parts of n-butanol, and the mixture was heated to 135 ° C. until the epoxy resin had dissolved. The temperature was ^{lowered to 95 °} C. and 107.4 phenolic resin (cf. Example 1) were added, after which the mixture was stirred until it had completely dissolved. At this point, a mixture of 4 2.2 parts of methyl methacrylate, 42.2 parts of butyl acrylate, 22.9 parts of acrylic acid, 14.6 parts of 2-butoxyethanol, 6.2 parts of n-butanol and 8.6 parts of tert-butyl peroctoate was used added within two hours, while the reaction ^{temperature at 95 ^ 3 0} C was kept. After another

QQ two hours of stirring at 95 ° C became a mixture of 21.5 parts of dimethylethanolamine and 537.2 parts of deionized water were added to make 1081.0 parts of a product with a solids content of 31.84% were obtained, the Brookfield viscosity (25 ° C) 1.7 Pa.s (17.0

gg Poise) and the pH was 7.45.

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Example 4

To a solution of 54.0 parts of EPON 1009 resin in a mixture of 19.7 parts of n-butanol and 45.0 parts of 2-butoxyethanol were added at 90 ⁰ C, 97.3 parts of a butylated bisphenol A phenol-formaldehyde resin in n-Butanol with a solids content of 74.0% (72.0 parts resin) was added. A mixture of 19.9 parts of acrylic acid, 17.1 parts of methyl methacrylate, 17.1 parts of butyl acrylate, 4.3 parts of tert-butyl peroctoate, 5.2 parts of n-butanol and 5.2 parts of butoxyethanol was at a constant rate within a two hour period added to the slurry, the reaction temperature was kept ^{at 96_ + 1 0 C.} After another two-hour

Stirring for 2g at 96 + ^ 1 ° C was a mixture of 18.5 parts Dimethylethanolamine and 267.0 parts of deionized water were added and 573 parts of a product were added obtained slurry with a solids content of 33.9%, the Brookfield viscosity 10.3 Pa.s (103 poise)

2Q (25 ⁰ C) and the pH was 7.6.

Example 5

143.2 parts of EPON 1009 were added to 94.5 parts of 2-butoxyethanol, and the mixture was ^{heated to 130 °} C. until the resin had dissolved. The temperature was lowered to 95 ° C and 144.0 parts of butylated phenol-formaldehyde-phenolic resin (74.6% solids at 2950

"Q mPa.s or 2950 cps) and 10.1 parts of n-butanol added, stirring until a homogeneous mixture was achieved. At this point, 38.0 parts of 2-ethylhexyl acrylate, 46.4 parts of methyl methacrylate, 22.9 parts of acrylic acid, 14.6 parts of 2-butoxyethanol and 8.6 parts of t-butyl

_g5 peroctoate added over two hours while maintaining the reaction temperature at 95 + 3 ⁰ C was maintained. To

Another two hours of stirring at 95 ° C was a mixture of 14.2 parts of dimethylethanolamine and 350.0 Parts of deionized water were added and 886.5 parts of product having a solids content of 39.14% obtained, the Brookfield viscosity (25 ° C) 2.62 Pa. s (26.2 poise) and the pH was 7.10.

Paint compositions prepared according to the above examples were further diluted with deionized water to solids contents of 26% to about 32%, a pH of 7.0 to 8.2 and a viscosity of 60-100 s (Ford Cup No. 4), so that the water: cosolvent ratio was 82:18 parts or weight percent. Paint compositions diluted in this manner were rolled directly onto tin-free steel using film weights of 0.54-0.62 mg / cm ² (3.5-4.0 mg / square inch) and the paint was applied at 204.4 ⁰ C (400 ⁰ F) hardened ten minutes. The cured coatings, which were cured in a 204.4 ⁰ C (400 ⁰ F) cure cycle were tough and resistant to chemicals. The applied and cured coatings passed the coating behavior test described below.

The coated metal substrates were flexible, process-resistant, solvent-resistant, food-safe, and storage-stable. For example, the flexibility was measured by reacting 90 minutes a steam of 121.1 ⁰ C (250 ⁰ F) exposing a coated metal sheet, then with acid / copper sulfate-treated to facilitate testing for the presence of micro-cracks. No microcracks were found. The process stability was measured characterized in that the typed plates in partially filled with water and pressure cooking devices there for 90 minutes at 121.1 ⁰ C (250 ⁰ F) held. No blistering, loss of adhesion, or haze was observed. The solvent-resistant

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Speed was measured by taking the coated plate and mechanically rubbing it 200 times with a tissue soaked in methyl ethyl ketone. No delamination, dissolution or penetration of the solvent was observed. The food resistance was measured by applying maintaining the processed into can lids coated plates for 90 minutes at 121.1 ⁰ C (25O ⁰ F) and three weeks at 48.9 ⁰ C (120. ⁰ F) in contact with dog food and tomato paste. No staining or discoloration as a result of interaction between the food and the coating was observed. In addition, high temperature stability, ie shelf life, is a significant problem with water-based compositions. In the past, an increase in viscosity due to a chemical reaction could only be avoided if systems packed in two packs were used. The storage stability of the compositions according to the invention was determined by ^{heating the compositions to 120 °} C. for 1 to 3 weeks. The compositions were stable for more than a week. Such compositions are stable for months at room temperature.

A paint composition is prepared which is particularly suitable for use in coating the Inside of containers for food is suitable, in particular for the coating of metal cans, the contain protein foods. In addition to being non-staining, they are Paint compositions steam resistant and flexible. They can also be thinned with water and are storage-stable. That The polymer present in the paint composition consists of a reaction product of a plurality of Acrylic monomers formed in the presence of a high molecular weight epoxy resin, a phenolic resin and a radical initiator, dissolved in a water mix-

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bar solvent, were implemented. The solution will be made dilutable with water by adding an aqueous amine solution containing the functional carboxyl groups which neutralizes acrylic monomers. "; Although the present invention based on preferred embodiments has been described, it is clear to those skilled in the art that various equivalent embodiments are possible which are not described in detail but fall within the scope of the present claims, such as it is defined by the claims.

Claims (8)

Dfpl.-Ohem. Dr. Stefren ANDflAE 34 46178 Dipl.-Phys. Dieter FLACH & k Dipl.-Ing. Dietmar HAUG, Dipl.-Chem. Dr. Richard KNEISSL * Patent Attorneys Stetnstr. 44, D-8000 Münohen 80 Note: INMONT CORPORATION Clifton, N.J. 07015, V.St.A. Az: 305 AS / sc Water-thinnable paint composition, process for its preparation and its use for coating containers for foodstuffs. Claims 1. Water-dilutable, storage-stable paint composition, characterized in that it is an organic solvent-containing aqueous solution of the reaction product of a high molecular weight epoxy resin, a phenolic resin and a plurality of acrylic monomers, at least one of which is an acid, this composition being converted into a water-miscible organic solvent is prepared and neutralized with an aqueous amine.
10 2. Composition according to claim 1, characterized in that the acrylic monomers in an amount of about 25 to _2— V ^ -i -. 'J about 35% by weight, the epoxy resin in an amount of about 40 to about 60% by weight, and the phenolic resin in an amount from about 30 to about 40 weight percent. 3. Composition according to claim 1 or 2, characterized ι characterized that the epoxy resin is a glycidyl poly ether includes. 4. Composition according to claim 1 or 2, characterized in that the phenolic resin is a phenol, a substituted one Contains phenol or bisphenol A. 5. A process for the preparation of a water-dilutable acrylated epoxy-phenolic paint composition, characterized in that it comprises Dissolving a high molecular weight epoxy resin in a water-miscible organic solvent; Dissolving a phenolic resin in the organic solvent containing the epoxy resin; Adding a variety of acrylic monomers, at least one of which is an acid, to the solution of the Epoxy resin and phenolic resin in the solvent; Polymerizing the acrylic monomers in the solvent for the epoxy resin and the phenolic resin by heating; and Neutralize the carboxyl groups of the acrylic monomers with an aqueous amine to make them stable with water to form dilutable paint composition. 6. Use of the paint composition according to any one of claims 1 to 4 for coating containers for Food. ■ η ο / Ö - 3 - 7. Use according to claim 6, characterized in that the paint composition for coating at least the inner surfaces of the containers is used for food. 8. Use according to claim 6 or 7, characterized in that that the paint composition is applied and the applied coating is cured by heating will. 10