DK149976B - METAL PLATE COATED ON AT LEAST ONE SIDE WITH LATEX OF A POLYMER - Google Patents

Description

149976

The present invention relates to a metal plate coated on at least one side with a latex of a polymer.

Prior to the present invention, it was not practical to use a polymer latex as such as a coating agent. Cans made of metal, such as tinned steel and aluminum, are usually coated with a corrosion resistant coating to protect the contents during prolonged storage. This is especially true when food and beverages need to be stored in the cans. Because the coatings, which are usually obtained by using polymeric latexes as a coating agent, are not continuous coatings free of needle holes, voids and the like, polymeric coatings are usually applied to cans by means of organic solvents. The use of organic solvents is both costly and dangerous. From the specification of Danish patent application No. 2119/74 coatings are known for metal cans which can be applied without the use of 2 149976 solvents. These known coatings are latexes of acrylic polymers of particular particle sizes and may contain smaller amounts of acrylonitrile. Highly nitrile copolymers modified with cautious disease have so far only been applied to metals using organic solvents.

It has been found that continuous protective films of good chemical resistance can be made from latexes of certain nitrile copolymer latexes, which are further described below.

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The metal sheet according to the invention is characterized in that the polymer is made by polymerizing a larger amount of a monounsaturated nitrile and a smaller amount of another monovinyl monomeric component copolymerizable with the nitrile in the presence of a preform formed diene rubber.

As a rule, the latex (or mixture of latexes) used according to the invention will contain from ca. 20 to 45% solids and will have an average particle size of 500 to 3000 Å.

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Conjugated diene monomers useful as diene rubber according to the invention include butadiene-1,3, isoprene, chloroprene, bromoprene, cyanoprene, 2,3-dimethylbutadiene-1,3,2-ethylbutadiene-1,3,3,3-di-ethylbutadiene -1,3 and the like. Most preferred for the purposes of the invention are butadiene-1,3 and isoprene because they are readily available and have excellent polymerization properties.

The olefinically unsaturated nitriles useful according to the invention are α, β-olefinically unsaturated mononitriles having the structure CH 2 = C-CN where 30 R

R is hydrogen, a lower alkyl group having 1-4 carbon atoms or halogen. These compounds include acrylonitrile, α-chloroacrylonitrile, α-fluoroacrylonitrile, methacrylonitrile, ethacrylonitrile and the like. The most preferred olefinically unsaturated nitriles of the invention are acrylonitrile and methacrylonitrile and mixtures thereof.

The second monovinyl monomeric component copolymerizable with the olefinically unsaturated nitriles and conjugated dienes includes one or more of the esters of olefinically unsaturated carboxylic acids, vinyl esters, vinyl ethers, oc olefins, vinyl aromatic monomers and others.

The esters of olefinically unsaturated carboxylic acids include those with the structure 2 L of the CH5 = O-C00 R wherein R is hydrogen, an alkyl group having from 1 to 4 carbon-R 12 substance atoms or a halogen and R is an alkyl group having from 1 to 6 carbon atoms. Compounds of this type include methyl acrylate, ethyl acrylate, propyl acrylates, butyl acrylates, amyl acrylates, hexyl acrylates, methyl methacrylate, ethyl methacrylate, propyl methacrylates, butyl methacrylates, amyl methacrylates, hexyl acrylates, hexyl methacrylates and hexyl methacrylates, Most preferred according to the invention are methyl acrylate, ethyl acrylate, methyl methacrylate and ethyl methacrylate.

The α-olefins useful in the invention are those having at least R * f 4 and up to 10 carbon atoms and having the structure 01 ^ = 0, where R 'and R "25 i" are alkyl groups of 1-7 carbon atoms and especially isobutylene, 2-methylethylbutene-1,2-methylpenten-1,2-methylhexene-1,2-methylhepten-1,2-methyloctene-2-ethylbutene-1,2-propylpenten-1 and the like. isobutylene is preferred.

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The vinyl ethers include methyl vinyl ether, ethyl vinyl ether, propyl vin =.

nyl ethers, butyl vinyl ethers, methyl isopropenyl ether, ethyl isopropyl nyl ether and the like. Most preferred are methyl vinyl ether, ethyl = vinyl ether, propyl vinyl ether and butyl vinyl ether.

The vinyl esters include vinyl acetate, vinyl propionate, vinyl butyrates and the like. Most preferred is vinyl acetate.

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Vinyl aromatic monomers include styrene, α-me thyls tyrene, vinyl = toluene, vinyl xylenes and the like. Most preferred is styrene.

Particular polymers useful in the invention are those prepared by polymerizing 100 parts by weight of (A) from 60 to 90% by weight of at least one nitrile having the structure CH9 = O-CR, where R has the

R

and (B) from 10 to 40% by weight based on the total weight of (A) and (B) of at least one representative of the group consisting of (1) an ester of structure CH9 = C-C00R , where R and R have ^ 'in R1 R »den. the aforementioned meaning, (2) an α-olefin having the structure CH 2 C, wherein R "and R 'R"

has the aforementioned meaning, (3) a vinyl ether of the group consisting of methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether and butyl vinyl ether, (4) vinyl acetate and (5) styrene, in the presence of from 0 to 40 parts by weight of (C) a rubbery polymer of a conjugated dienomonomer of the group consisting of butadiene and isoprene and optionally a comonomer of the group consisting of styrene, a nitrile monomer of the structure CH9 = C-CH where R has the aforementioned meaning, and an ester of R

2 12 is the structure 0H9 = 0-C00R, wherein R and R have the aforementioned meaning, C I hvilken R1, which rubber's yolk-like polymer contains from 50 to 100 wt. Of polymerized conjugated diene and from 0 to 50 wt. Comonomer.

The polymeric latexes useful in the invention can be prepared in aqueous emulsion by polymerization technique which involves portionwise, continuous or intermittent addition of monomers 30 and other components. The polymerization is preferably carried out in aqueous medium in the presence of an emulsifier and a free radical polymerization initiator, at a temperature of about

0 to 100 ° C substantially in the absence of molecular oxygen. The preparation of typical latexes useful in accordance with the invention is described in greater detail in U.S. Patent Nos. 3,426,102, No. 3,586,737 and Rir. 31,763.278.

the latexes of the invention are applied to the degreased metal in the can to be coated by means of a spreading knife, a wire rod, a roller, a spray gun, by dipping the metal into the latex, by rinsing or in other known ways within "coating". art.

After the latex coating has dried, the polymeric coating is dried at a temperature in the range of 200 to 300 ° 0. Any of the usual metal sheets used in the manufacture of cans can be used, including steel, tinned steel and aluminum.

The invention is further illustrated by the following examples in which the amounts of the constituents are in parts by weight, unless otherwise stated.

Example 1 A. A rubber latex was prepared by polymerizing with continuous stirring at 45 ° 0 essentially in the absence of oxygen a mixture of the following ingredients:

Ingredients Bele 20 acrylonitrile 40 butadieh-1.3 60 G-afac EE-610 * 2.4 azobisisobutyronitrile 0.3 t-dodecyl mercaptan 0.5 25 water 200 * A mixture of RO-tCHgCHgO- ^ PO ^ Mg and ^ RO- CH2 CH2 O -) ^ 72 ^ 2 ^ quor n is e 'from 1 to 40, E is an alkyl or alkaryl = 30 group and preferably a nonylphenyl group, and M is hydrogen, ammonia or an alkali metal, which agent is sold by GAP Corporation.

Once the reaction was started, the pH of the mixture was adjusted to 3 ^ ea. 8 with EOH. The polymerization was carried out for 22 1/2 hours to a conversion of $ 92 and a total solids content of $ 33.1.

B. A high impact resin and gas blocking properties were prepared by polymerizing a mixture of the following ingredients: 40 6 149976

Ingredients Parts of acrylonitrile 75 methyl acrylate 25 latex A (see above) 31.9 5 potassium persulfate 0.06

Gafac BE-610 3 n-dodecyl mercaptan 1 ethyl diamine tetraacetic acid 0.05 water 200 The pH value "was adjusted to about 7 with KOH. The polymerization" was carried out in the main case in the absence of molecular oxygen at 60 ° C for 20 hours to produce a $ 97 conversion of a latex with $ 33 solids.

Example 2

The procedure of Example 1B was repeated to exclude the component latex A. A latex of the copolymer of aeryl = 20 nitrile and methyl acrylate was obtained.

Example 3

A copolymer of acrylonitrile and styrene was prepared in the presence of a latex of a rubbery butadiene-styrene copolymer (72% by weight butadiene, 28% by weight styrene) using the following composition:

Ingredients Parts of water 419 30 Gafac BE-610 6.3 t-dodecyl mercaptan 0.6 azobisisobutyronitrile 0.5 acrylonitrile 91.05 35 styrene 8.95 s tyrene-butadiene latex 10.8 (solids)

The polymerization was carried out at 60 ° 0 in a nitrogen atmosphere. The molar ratio of acrylonitrile to styrene in the feedstock was 20/1.

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The polymerization time was 130 minutes, and during this time 53 parts of styrene were added to the reaction mixture. A yield of $ 73 polymer was obtained. A sample of the polymeric solid was found to have a nitrogen content of $ 11.19, which corresponds to a molar ratio of aeryl nitrile / styrene in the polymer of 1.44 / 1.

Example 4

A latex of a copolymer of acrylonitrile and styrene was prepared by the procedure of Example 3 except that the latex of butadiene and styrene was omitted by the composition.

Example 5 A. A sample of the polymeric latex described in Example 1B was carefully filtered through coarse filter paper (or cheese cloth) to remove any small particles of polymer that might be present. the latex was then diluted by adding from 0 to 3 parts by weight of distilled water for each part by weight of filtered latex. Ordinary-2 g of fish was used 3 parts water per day. of latex. The diluted latex was then placed in a spray gun (Binks, model # 26). Steel plate, tinned steel plate and aluminum plate were all coated by spraying the latex onto the plate. In each case, the surface of the flat metal plate was first cleaned of any oil and grease that might have remained from the metal rolling. Tetrachloro carbon or a similar solvent was used to clean the metal surface.

The resulting clean, dry metal surfaces were then spray coated with the latex. The spray gun was set to give a fairly light, 3Q fine jet. 1-5 thin, even, latex coatings on the metal surface were prepared, each coating being allowed to air dry for approx. 1 minute before the next coating was applied. After the top layer was air dried, the coated metal plate was placed in an air circulation oven which was held at approx. 200-220 ° C for 1 or 2 minutes. The coated metal plate was then removed from the oven and allowed to cool to room temperature. Care must be taken to avoid overheating of the coating because degradation of polymer can occur by prolonged exposure to high temperature.

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The thickness of the final coating was about 0.0125 mm - 0.0025 mm.

In most cases, the thickness of the applied coatings was in the range of 0.0025 to 0.025 mm. Although the coated metal can have any desired dimensions, for test purposes 3, metal plates of 0.1 to 0.175 mm in thickness and in rectangular pieces of 12.5 x 20 cm were used.

B. The toughness of the polymeric coating applied to the test metal pieces of A above, as well as the adhesion of the coating to the metal surface, were determined by a bending test.

In the bending test, the polymer-coated metal plate was placed in a vice. The plate was bent away from the coated side, it was then removed from the vice and bent all the way in the same direction so that it was folded. Leg coated side was thus bent 180 ° and sharply folded. At this point, the folding on the coated side was examined for peeling off polymer coating from the metal surface.

Then the polymer coated metal plate was again placed in the vice and bent in another place. Once, the coated surface was bent towards itself. Ber was again made a 180 ° bend of the metal plate with the coated surface on the inside of the plate. Again, the folding area was examined for polymer peeling. With all the three types of coated metal sheet, steel, tinned steel and aluminum described above, no peeling of the coating by the bending test was detected.

C. Ber was prepared a punched hole test which is a relatively quicker and more demanding test than the bending test described above under B.

During the punched hole sample, a coated metal plate from B above was placed flat over a partially opened vice or over a metal plate with a hole in it. In both cases, a hard, solid surface was placed under the coated plate except under a small area which was a open space directly below the plate. Directly over this unsupported area of the plate was placed a mandrel and the mandrel was driven through the plate by a sharp blow with a hammer. Bone polymeric coating in the area around the resulting thanked hole was examined for peeling. Absence of peeling means that the coating is good. Poor coatings will show peeling or tearing of the surface extensively around the punched hole and even as far back as 5 3-6 mm from the edge of the hole.

The punched hole test was performed both ways, first with the coated side of the plate at the top and then with the coated side of the plate facing down. In the first part of the sample, the mandrel goes down through the coating, and at the second part the mandrel actually goes up through the coating.

The coated metal sheet samples prepared at B above all showed essentially no peeling or tearing and thus showed that these were good coatings.

D. A sample called the needle punch sample was prepared to determine if the polymeric coatings on the sample plates described under B above were continuous and free of needle holes and voids in the surface of the coating.

A 2% by weight solution of CuSO4, 5H2 O in distilled water was prepared. The pH of this solution was adjusted to 1 with a small amount of HgSO4. The coated sheet metal was then immersed in this solution and in a short time the uncoated side of the sheet metal (steel or tinned steel) was coated with copper metal. However, on the coated side 25 there was no metallic copper deposition if there were no needle holes, cavities or scratches in the polymeric coating. If the polymer-coated side had needle holes, scratches, or voids in the plastic coating, a small surface of the metal surface was exposed and metallic copper deposited on the exposed surface. Mr. fine scratches were intentionally created in good polymeric coatings and the plates immersed in the copper sulfate solution, these scratches invariably appeared as fine, dark red lines on the coated side of the steel or the tinned steel sheets.

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A change of needle punch test was necessary for aluminum plate coated with polymer samples. The copper sulphate solution described above was adjusted to pH 1 with hydrochloric acid instead of sulfuric acid.

With this change, it appeared that copper plated better on aluminum when immersed in the solution.

10 149976

The copper sulphate needle punch test may also be used on polymer coated sheets which have undergone the bending test and the punched punch test described above. The polymer-coated metal sheets described under B above were all found to have excellent continuous tin coatings in the copper sulphate and needle hole samples.

Example 6

A sample of the polymeric latex described in Example 1B was carefully filtered through coarse filter paper and used undiluted. Dip coating was done using aluminum plate and the filtered latex.

The pure, oil and grease-free aluminum sheets were immersed in latex 5 at room temperature and held down for approx. 5-10 seconds. The plates were then taken out of the latex and suspended so that excess latex could drip off, for approx. 5-15 seconds and was air dried for approx. 5 minutes . The resulting coated plates were placed in an air circulation oven for approx. 1-2 minutes at 200-220 ° 0.

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At the dip coating, both sides of the aluminum plate were coated, rather than just one side as described by the spray coating of Example 5A. (The thickness of the coating was determined with one micrometer,! 5

Coatings were made with an average thick ice on one side of 0.0075 to 0.01 mm above most of the plate surface.

With dip coating, the thickness of the coating tends to vary, as it is thinnest at the upper end of the plate and thickest at the lower end of the plate (where draining latex tends to accumulate). To obtain a more uniform thickness on a plate, it is recommended that the plate be rotated during drying. Bone dip-coated aluminum sheet made in this way proved to have an excellent coating (5 in the tests described in Example 5B-B.

Example 7

A latex sample described in Example 1B was filtered and diluted as described in Example 5A. the latex was coated by roller coating

Claims (4)

11 149976 on pure steel and tinned steel. The plate was placed on a flat, even surface and was secured with adhesive tape at both ends. The dilution factor of distilled water / filtered latex was 1: 1 by weight. The latex can thus be used undiluted after filtration. A small amount of diluted latex was poured over one end of the flat metal plate. Then a roll of rubber was slowly rolled over the plate so that it kept pushing a very small wave of latex in front of it. A thin layer of the latex adhered to the metal surface after the roller had passed over it. This coating was allowed to air-dry for several minutes at room temperature. The coated plate was then heated to 200-220 ° C in an air circulation oven. Example 8 The procedure of Example 1 was repeated using the latex described in Example 2. Excellent coatings were obtained on steel, tinned steel and aluminum. Example 9 The procedure of Example 1 was repeated using the latex described in Example 3. Excellent coatings were obtained on steel, tinned steel and aluminum. Example 10 The procedure of Example 1 was repeated using the latex described in Example 4. Excellent coatings were obtained on steel, tinned steel and aluminum. Claims. Metal plate coated on at least one side with a latex of a polymer, characterized in that the polymer is made by polymerizing a greater amount of a monounsaturated nitrile and a smaller amount of another monovinyl monomer component which is copolymeric. mercurable with the nitrile, in the presence of a pre-formed diencote disease.