NO770723L - PROCEDURES FOR PREPARING A WATER EMULSION OF A COOPOLYMER - Google Patents

Description

The invention relates to an improved method for the aqueous polymerization of α, /?-ethylenically unsaturated monomers whereby latexes are obtained which, when included in coatings, give films with improved resistance to water. The resulting coatings can be used for a wide range of purposes, and examples of such are finish treatment of cars, in paints and for general industrial purposes, e.g. as a coil coating, for metal decoration, as an inner coating in cans, and in resins for electrostatographic

. and "electrofax" copying processes.

The development of a large range of products based on the use of anionic surfactant-stabilized addition polymers is well established. In many coating products there is a need for very good resistance to moisture and water. Products based on conventional anionic emulsion technology have been found to lack satisfactory resistance to moisture and water in certain critical applications. This has been identified as being based on the presence of water soluble "groups", additives and/or

• reaction byproducts.

According to the present invention is provided

a new method by which the alkali metal and alkaline earth metal ions in the latex manufacturing step are replaced with ammonium or amine ions so that surprisingly moisture- and heat-resistant coatings are obtained as a result.

The source of the attacking ions mainly belongs to three classes of substances used in emulsion polymerization;

(a) the catalyst, (b) the buffer system that will maintain the pH value

in the desired range, and (c) the surfactant system used in the emulsion stabilization. Some classic examples are sodium persulphate, peroxides and ferrous ions/or sodium hyposulphite as catalysts, sodium carbonate or bicarbonate as buffers, and sodium lauryl sulphate as a surfactant.

It should be emphasized that the use of the amine salt forms of catalysts and surfactants in aqueous emulsion polymerization is known. However, the method according to the present invention, unlike the methods from the prior art, uses exclusively the amine and ammonium ions, with the intention of avoiding their use. aggressive alkali metal and alkaline earth metals, e.g. sodium ions, in order to achieve an improved end product. This is in contrast to established techniques that are currently recommended commercially and are described in the literature, where the basic raw materials recommended for such

polymerization processes, these introduce attacking ions into one or more of the three basic ingredients mentioned above.

Previous attempts have been made with the intention of removing all ions other than hydrogen and hydroxyl ions from the latex by dialysis or ion exchange techniques so that a very high resistance is obtained and thus water-resistant coatings are obtained. These methods are relatively complicated and involve treatment of the entire volume of the finished product, which certainly makes the methods time-consuming and expensive. This extreme step has been found not to be necessary for most end applications.

It is also theoretically possible to ion-exchange specifically the alkali metal and alkaline earth metal ions from a latex and then replace the hydrogen ions with amine ions. However, this method, in addition to having the above-mentioned disadvantages,

result in a latex that has a very low pH value in one step of the process which could destabilize the emulsion.

Furthermore, in some of the following disclosures, the use of ion exchange techniques for the preparation of certain amine forms of specific surfactants is described. This is simply because the particular surfactants were only commercially available in the highly undesirable sodium ion form and/or contain high levels of undesirable salts resulting from the manufacture of the surfactant. In any case, the ion exchange process used in these examples requires the preparation of only a small fraction of the polymerisation ingredients and presents no stability problems.

Finally, methods have been proposed in the past which expire. on surfactant-free polymerization which produces stable aqueous dispersions for coating ■ masses. - .However, such methods have failed with respect to ; recognize that the absence of substantially any alkali metal or alkaline earth metal ions in the polymerization system results in aqueous copolymer dispersions which, when used to make coating compositions, have increased water resistance. The present invention therefore provides an improved process for producing an aqueous emulsion of a co<p>ol<y>mer comprising polymerization in an aqueous environment of from 99.5 to 30 parts by weight of at least one monomer selected from the group consisting of styrene,-α-methylstyrene\ acrylonitrile, alkyl acrylates, alkyl methacrylates, alkyl fumarates , alkyl maleates, where the alkyl radical includes radicals with 1-12 carbon atoms, vinyl esters of organic and inorganic acids, vinylpyridine, butadiene and ethylene, from 0 to 30 parts by weight of a lower alkyl ether of methyl acrylamide or methylol methacrylamide, from 0 to 25 parts by weight of a hydroxyl group-containing monomer, from 0 to 15 parts by weight of an epoxy group.e-. containing monomer, from 0 to 15 parts by weight of an amino group-containing monomerbg from'0 to 15 parts by weight of a carboxyl group-containing monomer,'the sum of the parts by weight of monomers being 100, whereby the improvement consists in carrying out the plymerization in the absence of practically any alkali metal and alkaline earth metal ions. For some processes, the presence of a surfactant is necessary, e.g. in order to ensure stability of the copolymer. - the emulsions or to form copolymers with very small particle size, i.e. less than 0.5 µm, or to prevent growth of '. reactive bridge surfaces, in such cases a possible surface must be active agent be in the form of a water-soluble amine or ammonium salt. The method according to the invention can be carried out in according to conventional emulsion polymerization techniques. If a surface-active agent is to be used, the following steps are generally practiced: Water is added to a reactor vessel, one or more . surfactants in water-soluble amine or ammonium sulfate form and one or more water-soluble amines or ammonium hydroxide. The vessel is heated to and maintained at temperatures in the range from 30 to 95°C; depending on the catalyst system used, while a pre-emulsified mixture of monomers with additional surfactant, at least one polymerization initiator and water is added.

Further additions of the pre-emulsified feed are made over a period of 4 to 6 hours. When monomers containing

kp-reactive functional groups are included, are used separately

. feeds of each monomer in order to prevent premature cross-linking. Furthermore, after the addition of the first monomer is finished, some water-soluble amine or ammonium hydroxide is added to substantially neutralize the functional group and give the dispersion a minimum pH value of 5. The addition also helps to inhibit the functional groups from reacting.

If the polymerization is to be surfactant-free

.means, then the following technique is usually used: All water is placed in one reactor vessel, and a solution of a polymerization initiator, e.g. ammonium persulphate, and a pH buffer, e.g. ammonia or a water-soluble amine, e.g. dimethylethanolamine, is added to the vessel which is heated to approx. 9o°C. Approximately half of the amount of initiator to be used is added to the vessel together with this first addition. The rest of the initiator solution is added simultaneously, but separately, with the monomers which are then fed to the reaction vessel over a period of from 3 to 6 hours, while the temperature in the vessel is maintained. Additional initiator can be added after this time, if necessary. Again, when monomers having co-reactive functional groups are used, it is best to use split feeds with substantial neutralization of the contents after the first feed is completed. Some solvent can be added instead of the water, e.g. from approx. 10 to 30% by weight. A solvent which has some chain transfer activity, e.g. dipropylene glycol monomethyl ether or propylene glycol monomethyl ether or isobutyl alcohol is preferred. The presence of the solvent helps

to lower the molecular weight of the ethylene resulting copolymer which helps to ensure better film formation.

Any water-soluble amine or ammonium salt forms of surfactants known conventionally to give stable aqueous emulsions can be used, when required, in the process according to the invention. Other salt forms of the surfactants may be more readily available commercially, in which case these surfactants may be treated with an ion exchange hairpin and neutralized with a suitable amine. Such amines as ammonia and water-soluble primary, secondary and tertiary : aliphatic and aromatic amines have been successfully used for such treatment...

The amount of the water-soluble amine salt surfactant used in the method according to the invention is the same amount as for other salt forms that have been proposed to be used in aqueous emulsion polymerization processes, where the only guideline is that the smallest amount that will give stability to the latex should be used.

The buffer system and the polymerization initiators are chosen so that they are in the form of water-soluble amine salts or the free amine (to control the pH value) so that the use of alkali metal and alkaline earth metal ions is avoided. Polymerization initiators

should also be.in amine form, e.g. ammonium persulfate as opposed to sodium persulfate. Suitable buffers. include ammonium hydroxide or the free amine itself. A number of such agents are commercially available and can be used in the method according to the invention.

As discussed earlier, the method according to

the invention is used for the production of latexes for a long

.various" end uses. The polymerization ingredients are easily varied according to the desired use. When the latexes are used in

paints, a small amount of alkali metal or alkaline earth metal ions may be included as part of the mill base. This quantity is so

small that the ions do not exert the decisive influence on the adhesion to the paint. In all cases, the bulk of harmful alkali metal or earth metal ions originate from the latex as opposed to the mill base. The present invention thus attempts to overcome this problem by avoiding the use of or removal of such harmful ions from the latex during its manufacture.

For the production of a latex for use in a car coating recipe, the improved process according to the invention therefore comprises the polymerization of from 93 to 30 parts by weight of styrene and methyl methacrylate, from 0 to 50 parts by weight of butyl acrylate, from 5 to 15 parts by weight of hydroxyethyl methacrylate or hydroxypropyl methacrylate and from 2 to 5 parts by weight of methacrylic acid. For forward-. position of latexes for metal measurements includes the method

.polymerization of 10 parts by weight styrene, 42 parts by weight methyl methacrylate, 40 parts by weight butyl acrylate, 5 parts by weight hydroxypropyl methacrylate

or hydroxyethyl methacrylate and 3 parts by weight of methacrylic acid. For the production of latexes for solid color mixtures, the method comprises the polymerization of 42 parts by weight of styrene, 10 parts by weight of methyl

methacrylate, 40 parts by weight butyl acrylate, 5 parts by weight hydroxypropyl methacrylate or hydroxyethyl methacrylate and 3 parts by weight methacrylic acid. The resulting copolymers have reduced viscosities in the range 0.25-0.8 dl/g, measured in ethylene dichloride/ethanol (95/5) at 0.5 g of copolymer per 100 ml solvent.

The latex copolymers produced by the method according to the present invention can be used in car paints which include melamine/formaldehyde resins. Suitable resins of this type include conventional alkylated melamiri/formaldehyde hair pigments adapted for water-based

coatings and have a ratio between -CI^OR groups and -CH2OH groups where R is lower alkyl, of at least 5:1. The latter resins can be produced by known techniques in which a lower alcohol,

e.g. methanol, ethanol, butane, isobutanol, propanol, isopropanol or 2-butoxyethanol are reacted with a melamine/formaldehyde resin to provide pendant hydroxyl groups. Examples of commercially available resins of this type are "Cymel" 300, "Cymel" 301, "Cymel" 303, "Uformite" MM-83 and "Resimene" .740. In fact, any conventional alkylate, e.g. butylated, melamine/formaldehyde resin is used provided that it satisfies the requirements for water solubility, compatibility or dispersibility in the final system. Generally, the resin will amount to from 8 to 30 parts by weight per 100 parts by weight of the paint.

It may. also included in such car paints is a dissolved,

. compatible copolymer which is present in the range from approx. 0 to approx. 45 parts by weight per 100 parts by weight of the mixtures. The copolymer will usually be acrylic in nature and preferably has a reduced viscosity RV of from approx. 0.15 to approx. 0.50 dl/g, measured in ethylene dichloride/ethanol (95/5) at 0.5 g copolymer per 100 ml solvent...•'..■

The term "compatible", as used in relation to the dissolved copolymer, indicates that the dissolved copolymer must. be compatible with the latex cup polymer and the melamine/formaldehyde resin both in the liquid product and when baked in as a finish. In the liquid phase, compatibility means that the stability of the system is such that no phase separation occurs when dealing with baked-in finishes, and the pigmented baked-in film should not suffer gloss loss.

The term "dissolved" or soluble indicates that the copolymer is dissolved or is soluble (giving clear or slightly hazy solutions), in one or more mixtures of water and water-miscible organic solvents, usually the solvents in which it is manufactured and which satisfy the pollution - provisions with regard to compositions and concentration.

The method according to the invention can also be used for the production of latexes for so-called "trade sales paints". The main monomer for such a method is vinyl acetate copolymerized with one or more monomers from the following selected group and in the following quantities: 10-60 parts by weight alkyl acrylates, e.g. dibutyl or dioctyl fumarate, dibutyl or dioctyl maleate, butyl acrylate, ethylhexyl acrylate, vinyl "Versatate", vinyl caproate, vinyl propionate or

ethylene,.•''•

0-10 parts by weight of a lower alkyl ether of methylacrylamide or methylImethacrylamide,

0-10 parts by weight of a hydroxyalkyl acrylate or a hydroxyalkyl methacrylate,

0-5 parts by weight glycidyl methacrylate,

0-5 parts by weight of acrylic or crotons.yre, and

.0-5 parts by weight dimethylaminoethyl methacrylate or vinylpyridine.

The total parts by weight of monomers comprise 100, with vinyl acetate making up the remaining part.

The above-mentioned copolymer latexes will have glass transition temperatures (Tg) in the range from approx. 5 to approx. 30°C due to minimum film-forming temperatures in the range from approx.0 to approx. 25<"*C. The latexes can be prepared as interior and exterior paints according to

conventional methods.

For the production of a "trade sales" acrylic latex by the method according to the invention, the following are used

monomers are often used in the polymerization process in amounts within de

..designated areas...

These, copolymer latexes, have Tg in the range from approx. 0 to 10°C and minimum film formation temperatures in the range from approx. 0 to approx. 25°C.

The above latexes can also be used in interior and exterior paints according to conventional methods. For the interior paints, the pigment volume concentration can vary in the range of approx. 45-65% and the pH value in the range 8.5-9.0. The white exterior paint generally has a pigment volume concentration of 40-50% and a pH value of 8.5-9.Q. An exterior paint base that breaks down typically has a pigment volume concentration of 30-40% and a similar pH range.

in the same "trade sales" paint area, when the main co-polymers comprise styrene and butadiene monomers, they are preferably polymerized in a weight ratio of 60:40, and the resulting latex has a pH in the range of 7.0-8.5 . When the main copolymers comprise vinyl chloride and acrylic monomers, they are preferably polymerized in a weight ratio of approx. 40:60, and the latex has a pH value of 7.0.

Copolymers of vinyl chloride and ethylene monomers preferably comprise a weight ratio of approx. 70:30 of each monomer respectively, and

it. resulting latex has a pH value of 7.0. In each process they are functional monomers, e.g. acrylic acid, methacrylic acid, dimethyl-;'. aminoethyl methacrylate and glycidyl methacrylate also present in the same weight fraction ranges as. previously. has been described for the acrylic paints.

The method according to the invention has also proved advantageous in the production of latex copolymers for general industrial use, e.g. in coil coatings, metal decoration compounds and coating compounds for the interior of cans.

The Kbpolymers are thermosetting and comprise acrylic-type monomers including one or more monomers that contain reactives

groups,, e.g. acid,. hydroxyl and substituted amide. The latexes can optionally then be combined with 0-30 parts by weight of a water-soluble or water-dispersible cross-linking agent, e.g. melamine/formaldehyde, urea/formaldehyde, epoxy and phenolic resins. The latex copolymers. can be dried to form powders which can then be used as electrostatographic tinting hairpins, coatings, adhesives and molding compounds. Preferred polymerization ingredients are in amounts for making such

latex copolymers are as follows: 0-30 parts by weight of at least one monomer selected from lower alkyl ethers of methylioacrylamide and methylol methacrylamide, 0-25 parts by weight of at least one hydroxyl group-containing monomer, 2-15 parts by weight of at least one carboxyl group-containing monomer,

0-40 parts by weight of at least one hard monomer selected from methyl methacrylate and styrene, and

40-80 parts by weight of at least one soft monomer selected from butyl acrylate and ethyl acrylate.

The resulting latexes are neutralized with water-soluble amines, or ammonia so that they have adequate application characteristics, to pH values of 6-9. In addition, the mixtures may contain water-soluble organic solvents, e.g. the alcohols, ketones and glycol ethers at levels of; from 0 to 30% by weight of the volatile components.

Absence of surface-active agent from the polymerization process when using the ingredients mentioned above has proven to be particularly advantageous in the production of latex copolymers, which can optionally be converted into powders and which are

useful for interior coating of cans and as resins for electrostatographic and "elecfofax" copier processes.

In the following, the invention shall be illustrated by means of examples which do not. shall be considered as limiting the invention in any way. All parts, percentages and ratios are given by weight

.'unless otherwise stated.

Example i - Belegniirgsmiddel for vehicles

In this example, a comparison was made between two latexes which had identical compositions with the exception that one contained sodium ions and the other ammonium ions.

Each latex was mixed with an aminoplast resin for • paints, and the paints were tested for water resistance.

Manufacture of latexes

The above ingredients were combined in a vessel and heated to 80-85°C and held at this temperature while adding the following ingredients:

The mixture was held at 80-85°C for an additional 1/4-1/2 hour. Then additions of pre-emulsified feeds 1 and 2 as indicated below were carried out over a period of 5 hours.

Preparation of monomer mixture

The mixture was held at 80-85°C for an additional 1 hour.

The resulting latexes had the following properties: Total, solids = 45%

Reduced viscosity = 0.32 dl/g pH = 5.0

Production of surfactant solutions

Surfactant solution B

The above ingredients were: mixed in the amounts shown.

Surfactant solution A

The surfactant solution B discussed above was treated with 1000 g "Dowex" 50 W X 8 (acid form) ion exchange resin beads to remove the sodium ions. The beads were filtered

from, and the solution was titrated with sufficient dimethylaminoethanol to give it a pH of 8, whereby the amine salt of the surfactant mixture was formed. As an additional control for

to ensure complete removal of sodium ions from the surfactant solution, the acid number must be at least 146 and should generally be

o' ■ 5

in the area 146-152. The application: of the pH eels as a control is not.

good enough. Acid number can be defined as the number of milligrams of potassium hydroxide needed to neutralize 1.0 g of sample.

Assessment of water sensitivity, indicated by the Cleveland Cohdensing Humidity Cabinet Test (QCT) was performed at 65.5°C.

Example 2 - "Trade Sales" paint

In this example, a comparison was made between latexes containing sodium salt surfactants versus latexes containing ammonium salt surfactants and dimethylethanolamine salt surfactants. The latexes were made into exterior surface finish compounds and applied to a smooth, shiny, gray alkyd surface, aged 3 days. After exposure to moisture overnight (QCT), the films were cross-scored using one comb-shaped template and applied with No. 610 high-adhesion tape. . The tape was then removed, and the adhesion loss was noted.

Manufacture of latex

A latex copolymer with a fixed composition of methyl, methacrylate/butyl acrylate/acrylic acid/glycidyl methacrylate in the respective weight ratios of 44:53:2:1 was prepared using the : sodium salt surfactant (0.8% based on the weight of copolymer) and sodium persulfate as polymerization initiator. With

the amine form of surfactant, ammonium persulfate was used. In non-ionically stabilized systems, 4.3% was required

surfactant based on the weight of copolymer to achieve adequate emulsion stability.

The first four ingredients were combined and heated to 75°C, at which temperature the sodium persulfate was added.

The following ingredients were then added during

1 1/2 hours, keeping the mixture at 75°C.

The mixture was held at 75°C and the following was added during the last 1/3 of the time of the above feed.

The mixture was held at 75°C for a further 1/2 hour and was then cooled to 55°C, after which the following addition was made:

The mixture was cooled to 25°C and the following ingredients were added:

The resulting latex had T.S. = 45% pH = 8.5%

Latex No. 2 (Amine form of surfactant)

The above ingredients bee combined and heated

to 82°C. The following ingredients were added to this mixture over the course of 2 hours, the temperature being held at 82°C:

After the above addition was made, the mixture was kept at 82°C for a further 1/2 hour, it was cooled and the following ingredients were added: . <:->Surface active solution

One solution of the above ingredients was prepared and treated with 1500 g of "Dowex" 50 W X 8. (acid form) ion exchange resin beads to remove the sodium ions. The beads were filtered off, and the solution was titrated with sufficient ammonia to give a pH value of 8, whereby the ammonium salt of the surfactant mixture was formed. As before, the acid number was determined and. turned out to be in the range 146-152:.

16

Latex No. 3. (pimethylethanolamine form of surfactant)

■ A latex identical to latex No. 2 was prepared except that dimethylaminoethanolamine replaced ammonia and

ammonium hydroxide on a 1:1 molar basis.

Latex No. 4

A latex similar to latex no. 2 was produced with the exception that the surfactant solution was not treated with ion exchange resin and that the ammonium hydroxide and ammonium persulfate were replaced with sodium carbonate and sodium persulfate in a 1:1 ratio.

molar base.

Paint recipe

■. Mill base

The above mixture was painted on a Cowles sheet, and

the following premix was added:

To this mill base was added 302 parts of each of four latexes (at 46.5% solids), and each paint was tested for wet adhesion, with the following results:~

The above results indicate that the presence of sodium ions causes weak adhesion.

Example 3

Preparation of typical acrylic copolymer latex for vehicles

. Methyl methacrylate/styrene/butyl acrylate/hydroxypropyl methacrylate/methacrylic acid copolymer in the respective weight ratios 42/10/40/5/3

Preparation of surface-active solution

The above ingredients were mixed and then treated with 1000 g "Dowéx" 50 W X 8 (acid form) ion exchange resin beads

for, removal of the sodium ions. The beads were filtered off and the solution was: titrated with sufficient dimethylaminoethanol to give a pH of 8, whereby the amine salt of the surfactant mixture was formed. •',

Manufacture of latex

An aqueous batch of 230 parts of water and 210 parts of the above surfactant solution was prepared and heated to 80°C. An addition of 15 parts of water and 1.5 parts of ammonium persulfate was made and the whole was kept at 80°C for 30 my. An emulsion (1) of the following ingredients was prepared and added to the above over a period of 3 1/2 - 3 3/4 hours:

A further emulsion (2) of the following ingredients • was prepared and immediately added, to the above emulsion (1) in 1/4 1.1/2 hours.

After the additions were made, the mixture was held for a further 1 hour at 80°C, cooled to 25°C and filtered through a 10 µm bag. The resulting latex had T.S. = 45%, RV = 0.3 3 dl/g.

The following are typical mixtures for aqueous enamels for vehicles where latexes produced by the method according to the invention, as described above, are used:

7.. "v

Color - off-white ..

These two recipes can be applied in relatively high solids, respectively 40-35% and 48-42%, if desired, using

acrylic-latek-s-en 6g the soluble polymers identified below. The range of solids is due to the different viscosity requirements for the different types of application equipment.

In general, the enamel can be reduced to the desired spray viscosity by fbrthinning. with water and/or a pure organic solvent.

Preparation of typical dissolved acrylic copolymer

•A 5 liter flask was prepared with stirring, cooling and monomer addition options.

To the flask was added:

The above was heated to reflux, and

the following was added over the course of 2 hours:

.The above was kept on. reflux for 4 hours. At this time, the solution turned out to have an RV = 0.17 dl/g and a total solids content of 51% by weight. The equipment was converted for distillation, and 7.97 parts by weight of butyl "Cellosolve" was added. The low-boiled distillate (150°C) was removed, and. the total amount of distillate collected was 22.92 parts. The remaining solution was cooled to •100 °C, and 1.89 parts by weight. dimethylaminoethanol was added. While. the temperature was kept at 70-90°C, 29.89 parts became hot, off ionized water added very slowly..'It was all stirred for 1/2 hour and cooled. The resulting solution copolymer had a total solids content of 39.5% by weight and a Gardner-Holdt viscosity equal to Zc-Z,. 5 6 .

- 1 H

Example, 4

a. Methyl methacrylate/styrene/butyl acrylate/hydroxypropyl methacrylate/- methacrylic acid in the respective weight ratios 42/10/40/5/3 RV= 0.37 dl/g. b. A Cowles mix of phthalocyanine blue pigment (14 parts by weight), "Cymel" 301 (20 parts by weight) deionized water (33 parts by weight), butyl "Cellosolve" (33 parts by weight) and a trace amount of triethanolamine was prepared and run 2 times a sand mill. c. Same as b, except that Quindo magenta pigment was used instead of phthalocyanine blue pigment. •. d. Methyl methacrylate/butyl acrylate/hydroxypropyl methacrylate/acrylic-. acid in the respective quantity ratios 20.5/61.6/15.4/2.5 RV= 0.2 dl/g.

This enamel had: Weight% total solids = 3 7.2 (packaging solids)

wt% solvent =20

viscosity in Ford Cup = 65 sec.

No. 4 (packaging

viscosity)

The latex/melamine-formaldehyde/dissolved copolymer was combined in the respective weight ratios of 54/18/28.

Cleveland Condensing Humidity Cabinet Test; (QCT) was performed with the medium blue metallic composition and the off-white composition from Example 3 and the light blue metallic composition from Example 4. These compositions showed no loss in gloss, blistering or whitening, while comparable systems where latexes prepared with the sodium form of surface-active agents, sodium persulfate instead of ammonium persulfate and sodium carbonate instead of the dimethylethanolamine buffer were used, blister formation, losses were shown. of gloss and whitening. Table I shows prescriptions and RV values for latex copolymers which were prepared by the method according to the invention for the purpose of selecting an optimal composition for use in coating mixtures of the type described in the previous examples. In the following table II, prescriptions for various are shown leteks copolymers prepared by the method according to. the invention and dissolved or soluble copolymers which are suitable fpr preparation of coating mixtures. Possible recipes using the copolymers are given.:The melamine/formaldehyde resin is in all cases "Cymel" 3.01. - .

Example 5

Recipes for coating cans

Production of latex (external cross-linking agent required)

A surfactant solution of 0.4% by weight "Aerosol" A196 and "Siponåte" DS-10 (1:2) in water was prepared and converted by

.ion exchange techniques for the amine form of the surfactants. A batch of 3.5% by weight of this surfactant solution in 27.2% by weight of water was prepared. The solution was heated to 80-85°C, and a batch consisting of 0.07 wt% (NH.)<_>S„0o and 0.5 wt% water was

42.2. o

so added.

The following premix was prepared and added to the heated mixture over 5 hours while maintaining the temperature

■ at 80-85°C:

The mixture was then kept for a further hour at a temperature of 80-85°C.

The resulting latex was blended with 10% by weight of "Uformite" MM83 (trade name for a melamine/formaldehyde resin), reduced to application viscosity using a

compatible solvent. When baked in, the films provide a high-hardening, durable tin can coating.

Example 6

•Example 5 was repeated with the exception that sodium carbonate and sodium persulfate replaced the dimethylethanolamine and the ammonium persulfate on a 1:1 molar basis. In addition, the surfactant solution was not converted by ion exchange techniques to the amine form of the surfactants. Example 7. Prescription for can coating Manufacture ay latex (self-crosslinking) Copolymer: styrene/methyl methacrylate/ethyl acrylate/isobutoxymethyl-acrylamide/methacrylic acid (10/20/55/10/5)

The above ingredients were 'heated' to 80-85°C and'

the following was added:

<p>remixes of batches A and B were prepared and each was added simultaneously to the above mixture over 2 hours. • •. '• The following was then added:

Premixes of batches C and D were prepared and each was added simultaneously over a further 2 hours.

The whole mixture was kept at 80-85°C for another 1 hour. The following substances were then added separately: Rate Parts %

Dimethylethanolamine 18,50,4 Butyl-"CéHbsolve" 450 10, 1

Total: 4456 100.0

The latex was cooled to 25°C and filtered. Durable high-curing films for use as can liners

was achieved. Surfactant solution: A solution of 0.4% by weight

"Siponate" DS-10 in water was converted by ion exchange techniques to the amine form of the surfactant.

Beer pasteurization adhesion test

The latexes from Examples 5, 6 and 7 were tested with respect

on adhesion as indicated below.

Sheets of untreated aluminum (dimensions: 50/8 mm x 101.6 mm) were coated with each of the latexes to a thickness of 200 mg/26 cm 2 . The plates were baked in for 5 minutes at 160°C. Each plate was then immersed in cooled beer in a sealed glass jar. The jars were then placed in a water bath and heated to 65°C for 3/4 hour and held at 65°C for another 1/2 hour. The plates were

removed from the jars and washed quickly under cold water, dried and examined for efflorescence or bleaching. A cross was cut into each plate with a sharp scalpel. The crossing was covered with

tape, and. The stump was torn off and the piat examined with regard to

adhesion loss..

A good system will show slight whitening on examination,

but very fast recovery within 30 seconds. A bad system

will remain white for several minutes before turning back on. A system with excellent adhesion will show no peeling when the tape is removed.

Coating compositions made from the latexes according to Examples 5 and 7 showed slight whitening on examination and very rapid gel formation as well as excellent adhesion. A coating composition made from the latex of Example 6 remained white for several minutes and showed peeling upon removal of the tape.

Example 8

Latex that is, free of, surface-active agent, for the interior coating of cans

Copolymer: styrene/butyl acrylate/methyl methacrylate/methacrylic acid in the respective weight ratio 20/60/10/10.

Procedure<0>

Batch A was added to a reactor vessel and heated to 80°C. Batches B and C were added separately, but at the same time during 4-5 hours

while the contents of the vessel were kept at 80°C. Batch D was then added to neutralize the resulting latex.

Example 9

Latex that is free, for surface-active agent, for internal coating of cans

Copolymer; styrene/methyl methacrylate/butyl acrylate/hydroxypropyl methacrylate/methacrylic acid in the respective weight ratio 20.5/13.5/54.5/4.5/7.0.

Approach;

Batches A to D were added as described in Example 8, and then batch É was added.

Example 10

Latex that is free of surfactant, for interior use

coating of cans

Copolymer: styrene/methyl methacrylate/butyl acrylate/hydroxypropyl methacrylate/methacrylic acid in the respective weight ratio 19/5/52/ 10/13.

Approach;

Like for example 9.

Example 11

Latex for interior coating in cans, germ-free and surfactant-free

Copolymer; st<y>ren/but<y>lacryl<y>late/hydroxy<p>rop<y>lmethacrylate/methyl methacrylate/methacrylic acid in the respective weight ratio 20/60/ 5/5 /10.

Approach:

80% of batch B was added to the vessel over 4 hours, while the remaining 20% was added over approx. 30 seconds. The vessel was held at 85°C for a further 1 hour. Rate C was added. at the same time as rate B in the same time period. Batch D was added at 85°C to neutralize the resulting latex.

This latex was released with a mixture of water and butyl-Cellosolve, the maximum amount of butyl-Cellosolve

was less than 30% by weight of volatile matter, while 1% by weight of "Uformite" MM 83 was dissolved in the solvent mixture. The latex

which was thus reduced to spray viscosity, had a total

solids content of 25-35% by weight. This coating composition, after application to an untreated aluminum plate and subjected to the beer paeurization test described above, showed slight whitening

• on examination, but very rapid recurrence.

Example 12

Latex that is free of surfactant, for interior use

coating of cans

Copolymer: styrene/butyl acrylate/methyl methacrylate/hydroxypropyl methacrylate/methacrylic acid in the respective weight ratio 20/57/5/5/13.

Approach;

Like for example 8.

Example 13.

Surfactant-free latex for the interior coating of cans

Copolymer: styrene/butyl acrylate/methyl methacrylate/hydroxypropyl methacrylate/methacrylic acid' in the respective weight ratio 15/60/5/10/10.

Approach;

As in example 8.

Example 14

Latex that is. free of surface-active agent, for internal coating of cans

Copolymer; styrene/butyl acrylate/hydroxypropyl methacrylate/methacrylic acid containing 1% by weight, based on the total monomer weight, of 1,3-butylene dimethacrylate, the monomers being present in the "respective weight ratio 20/60/18/10...

Approach;

Like for example 8.

Example 1-5

Latex that is free of surfactants, medium, for the inner coating of cans

Copolymer: styrene/butyl acrylate/methacrylic acid in the respective weight ratio 20/6 7/13.

Approach;

Like for example .8.

Example 16

Latex that is free of surfactant, for the interior lining of cans

Copolymer; styrene/butyl acrylate/methacrylic acid in the respective

.weight part-forehoid 20/65/15.

Approach:

Like for example'8.

Example 17

. Latex that is free of surface-active agents, for the inner coating of cans

Copolymer; styrene/butyl acrylate/methacrylic acid containing 1% by weight, based on the total monomer weight, of 1,3-butylene dimethacrylate, the monomers being in the respective weight ratio 22.6/75.8/1.5.

Procedure: As for example 8.

Example 18

Latex that is free of surface-active agent, for the inner coating of cans - y

Copolymer: styrene/methyl methacrylate/butyl acrylate/methacrylic acid in the respective weight ratio 22.5/15/60/7.5. ' .

' Approach:

As for example' 8.

, Example 19

Latex that is free of surface-active agents, for the inner coating of cans

Copolymer:•styrene/methyl methacrylate/butyl acrylate/methacrylic acid in the respective weight ratio 22.5/15/60/7.5.

Approach:

Like' for example 8.. »

Example 20

Latex that is free of surface-active agents, for the inner coating of cans

Copolymer: styrene/butyl acrylate/methacrylonitrile/hydroxypropyl methacrylate/methacrylic acid in the respective weight ratio 15/55/l0/l0/l0.

Approach:

Like for example 8.

Example. 21

Latex that is free of surface-active agents, for the inner coating of cans

Copolymer: styrene/methyl methacrylate/butyl acrylate/hydroxypropyl-■.' methacrylate/methacrylic acid in the respective weight ratio 20/57.5/15/7.5.

Approach:

As for example 8. Example 2 2 Latex for internal coating in cans, clear and free of surfactant Copolymer: s.tyrene/methyl methacrylate/butyl acrylate/methacrylic acid/meth- oxymethylacrylamide in the respective parts by weight 19.1/9.5/57.4/9.5/4;5. ' Approach; Batch A was added to a reactor vessel and heated to 82-85°C. Batches B and C were added simultaneously to the vessel for a time room of 2 hours. Batch D was then added over 15 minutes. Batches E and F were added during a further 2 hours while the temperature in the reactor vessel was maintained between 77 and 82°C. The content in the vessel was kept for a further 1 hour at 80°C, and batch C was added over 1/2 hour. The contents of the vessel were cooled to 40°C, and batch H was added over 30 minutes. The contents were cooled to 30°C and filtered; The total solids in the resul tering latex was 36.8%, and the copolymer had a viscosity of 53 sec. (Ford Cup. no. 4).

Example 23

Latex, free of surfactant, for solid tinting resin

Copolymer. : styrene/butyl acrylate/methacrylic acid in the respective weight ratio 80/15/5. '

Batch A was added to a heated reactor vessel and heated to 85°C and held at this temperature for 15-20 minutes. .The monomer mixture included styrene/butyl acrylate/methacrylic acid in the weight ratios indicated above. Batches B and C were added separately, but at the same time during 5 hours while the temperature in the reactor vessel was maintained at temperatures between 85 and 95°C. Once all of the spring was added, the tub was held at temperature for another 1 hour or so. The resulting latex had a reduced viscosity, measured in ethylene dichloride/ethanol (95/5) at a concentration of 0.5 g copolymer per 100.ml solvent, at 0.325 dl/g a total solids content of 45.2%, and the conversion was 100.0%.

The latex was diluted with deionized water to 20-23% total solids content and converted to powder by spray drying in a spray dryer. The yield of solid powder is approx. 80%.

Example 24

Latex, surfactant-free, for solid shading; resin

Copolymer: styrene/methyl methacrylate/butyl acrylate/methacrylic acid in the respective weight ratio 15/67/15/3.

Batch A was placed in one reactor vessel and heated to 85°C.

Batch B was added to batch C under agitation for pre-emulsification, and the emulsion was added to the reactor vessel over 4

hours while the vessel remained. maintained at a temperature between 80 and 85°C.

When all eels were added, the vessel was kept at 85°C for a further 1 hour. The resulting latex had a reduced viscosity of 0.194 dl/g measured in ethylene dichloride/ethanol (95/5) at a concentration of 0.5 g copolymer per 100 ml of solvent, and a total solids content of 44.1%.

Example . 2 5

Latex, free of surfactant, for tinting resins Copolymer: styrene/butyl acrylate/methacrylic acid in the respective weight ratio 75/20/5.

The procedure

Batch A was added to a reactor vessel and heated under agitation and a nitrogen atmosphere to a temperature in the range of 80-85°C. Batches B and C were added simultaneously to the vessel over the course of 5 hours while the temperature was maintained in the range of 85-95°C. When everything was added,

the vessel was held at 95°C for a further 1 hour, after which the resulting latex was cooled and filtered. Spray drying was performed after the latex was diluted to 27% solids.

Example 26

Latex, surfactant-free, for tinting resins Copolymer: styrene/butyl acrylate/methacrylic acid. in the respective weight ratio 80/15/5

Approach;

Like for example 25.

Example 2 7

Latex, surfactant-free, for tinting resins Copolymer. : styrene/butyl acrylate/methacrylic acid in the respective weight ratio 80/15/5.

Approach:

Like for example 25.

Claims (10)

1. Improved process for producing an aqueous emulsion of a copolymer, characterized by polymerization in an aqueous environment of from 99.5 to 30 parts by weight of at least one monomer selected from the group consisting of styrene, cv-methylstyrene, acrylonitrile, alkyl acrylates, alkyl methacrylates, alkyl fumarates, alkyl maleates, where the alkyl radical includes radicals with 1-12 carbon atoms , vinyl esters of organic and inorganic acids, vinylpyridine, butadiene, and ethylene, 0-30 parts by weight of a lower alkyl ether of methyl acrylamide or methylol methacrylamide, 0-25 parts by weight of a monomer containing a hydroxyl group, 0-15 parts by weight of a monomer containing an epoxy group, 0-15 parts by weight of an amino group-containing monomer, 0-15 parts by weight of a carboxyl group-containing monomer, the sum of the weight parts of monomers being 100, whereby the improvement comprises carrying out the polymerization practically in the absence of alkali metal and alkaline earth metal ions. 2. Method as stated in claim 1, characterized in that the polymerization is carried out in the absence of a surfactant. 3. Method as stated in claim 1, characterized in that the polymerization is carried out in the presence of a surface-active agent which is in water-soluble amine or ammonium salt form. 4. Method as stated in claim 1, 2 or 3, characterized in that 93-30 parts by weight styrene and methyl methacrylate, 0-50 parts by weight butyl acrylate, 5-15 parts by weight hydroxyethyl methacrylate or hydroxypropyl methacrylate and 2-5 parts by weight methacrylic acid are polymerised. 5. Method as stated in claim 1, 2 or 3, characterized in that 10 parts by weight of styrene, 42 parts by weight of methyl methacrylate, 40 parts by weight of butyl acrylate, 5 parts by weight of hydroxypropyl methacrylate or hydroxyethyl methacrylate and 3 parts by weight of methacrylic acid are polymerised. 6. Method as specified in claim 1, 2 or 3, characterized in that 42 parts by weight of styrene, 10 parts by weight of methyl methacrylate, 40 parts by weight of butyl acrylate, 5 parts by weight of hydroxypropyl methacrylate or hydroxyethyl methacrylate and 3 parts by weight of methacrylic acid are polymerized. 7. Method as stated in claim 1, 2 or 3, characterized in that 10-60 parts by weight of at least one monomer selected from the group consisting of dibutyl fumarate, dibutyl-. maleate, dioctyl fumarate, dioctyl maleate, butyl acrylate, 2-ethylhexyl acrylate, ethylene, vinyl "Versatate", vinyl caproate, vinyl propionate are polymerized with 0-10 parts by weight of a lower alkyl ether of methyl acrylamide or a lower alkyl ether of methylol methacrylate, d-5 parts by weight of glyceidyl methacrylate, 0-5 parts by weight of vinylpyridine or dimethylaminoethyl methacrylate, 0-5 parts by weight of crotonic acid or acrylic acid, 0-10 parts by weight of a hydroxyalkyl acrylate or a hydroxyalkyl methacrylate, the total parts by weight of monomer being 100, while the remaining parts by weight are made up of vinyl acetate. 8. Method as stated in claim 1, 2 or 3, characterized in that 10-70 parts by weight of at least one monomer selected from the group consisting of methyl methacrylate, styrene, ethyl acrylate, butyl acrylate and 2-ethylhexyl acrylate is polymerized with 0-10 parts by weight isobutoxymethylacrylamide, 0- 10 parts by weight of hydroxypropyl methacrylate, 0-5 parts by weight of dimethylamino methacrylate, 0-5 parts by weight of glycidyl methacrylate and 0-15 parts by weight of acrylic acid or methacrylic acid. 9. Process as stated in claim 1*2 or 3, characterized in that 0-30 parts by weight of at least one monomer selected from lower alkyl ethers of methylacrylamide and methylol methacrylamide is polymerized with 0-25 parts by weight of at least one hydroxyl group-containing monomer* 2-15 parts by weight of at least one carboxyl group main monomer, 0-40 parts by weight of at least one hard monomer selected from methyl methacrylate and styrene, and 40-80 parts by weight of at least one soft monomer selected from butyl acrylate and ethyl acrylate. 10. Improved method for producing ay an aqueous emulsion of a copolymer, comprising polymerizing in an aqueous environment from 99.5 to 60 parts by weight of at least one monomer selected from the group consisting of styrene, α-methylstyrene; acrylonitrile; lower alkyl acrylates in lower alkyl methacrylates, ' lower alkyl fumarates in vinyl acetate in vinyl chloride in butadiene and ethylene, from 0 to 25 parts by weight of a lower alkyl ether of methylolacrylamide or methylol methacrylamide; from 0 to 25 parts by weight of a hydroxyl group-containing monomer, from 0 to 15 parts by weight of an amino group-containing monomer; from 0 to 15 parts by weight of a carboxyl group-containing monomer; the sum of the parts by weight of copolymer being 100 in the presence of at least one surface-active agent, where the improvement consists in carrying out the polymerization in the absence of alkali metal and alkaline earth metal ions in the presence of amine salt formers of the surface-active agent.