A Coating Composition

Abstract

A coating composition, the coating composition comprising: a) a first polyvinyl butyral polymer material having a weight-average molecular weight (Mw) of 10,000 to 20,000 Daltons, b) a second polyvinyl butyral polymer material having a weight-average molecular weight (Mw) of 25,000 to 75,000 Daltons and c) an aminoplast resin.

Claims

1. A coating composition, the coating composition comprising: a) a first polyvinyl butyral polymer material having a weight-average molecular weight (Mw) of 10,000 to 20,000 Daltons, b) a second polyvinyl butyral polymer material having a weight-average molecular weight (Mw) of 25,000 to 75,000 Daltons and c) an aminoplast resin.

2. A coating composition according to claim 1, wherein the first polyvinyl butyral polymer material has an OH content from 1 to 20 mol %.

3. A coating composition according to claim 1 or 2, wherein the second polyvinyl butyral polymer material has an OH content from 10 to 50 mol %.

4. A coating composition according to claims 1-3, wherein the aminoplast resin comprises a melamine resin.

5. A coating composition according to any preceding claim, wherein the aminoplast resin comprises hexa(methoxymethyl) melamine (HMMM).

6. A coating composition according to any preceding claim, wherein the coating composition comprises from 5 to 90 wt % of the first polyvinyl butyral polymer material based on the total solid weight of the coating composition.

7. A coating composition according to any preceding claim, wherein the coating composition comprises from 5 to 90 wt % of the second polyvinyl butyral polymer material based on the total solid weight of the coating composition.

8. A coating composition according to any preceding claim, wherein the coating composition comprises from 0.01 to 10 wt % of the aminoplast resin based on the total solid weight of the coating composition.

9. A coating composition according to any preceding claim, wherein the weight ratio of (a):(b) ranges from 10:1 to 1:10.

10. A coating composition according to any preceding claim, wherein the weight ratio of (a)+(b):(c) ranges from 200:1 to 20:1.

11. A coating composition according to any preceding claim, wherein the coating composition further comprises an additional crosslinking agent.

12. A coated article, coated on at least a portion thereof with a coating composition, the coating composition comprising: a) a first polyvinyl butyral polymer material having a weight-average molecular weight (Mw) of 10,000 to 20,000 Daltons, b) a second polyvinyl butyral polymer material having a weight-average molecular weight (Mw) of 25,000 to 75,000 Daltons and c) an aminoplast resin

13. An aluminium, steel or tin substrate coated on at least a portion thereof with a coating composition, the coating composition comprising: a) a first polyvinyl butyral polymer material having a weight-average molecular weight (Mw) of 10,000 to 20,000 Daltons, b) a second polyvinyl butyral polymer material having a weight-average molecular weight (Mw) of 25,000 to 75,000 Daltons and c) an aminoplast resin.

14. An aerosol can coated on at least a portion thereof with a coating composition, the coating composition comprising: a) a first polyvinyl butyral polymer material having a weight-average molecular weight (Mw) of 10,000 to 20,000 Daltons; b) a second polyvinyl butyral polymer material having a weight-average molecular weight (Mw) of 25,000 to 75,000 Daltons; and c) an aminoplast resin.

15. A food and/or beverage container coated on at least a portion thereof with a coating composition, the coating composition comprising: a) a first polyvinyl butyral polymer material having a weight-average molecular weight (Mw) of 10,000 to 20,000 Daltons; b) a second polyvinyl butyral polymer material having a weight-average molecular weight (Mw) of 25,000 to 75,000 Daltons; and c) an aminoplast resin.

Description

EXAMPLES

[0087] Polyvinyl Butyral Polymer Example 1

[0088] 100 g of polyvinyl butyral powder available commercially as MOWITAL B16S, 120 g dibasic ester (Imsol R), 50 g butyl acetate and 30 g xylene were stirred for approximately 1 hour under a dissolver. After this time the loss due to solvent evaporation was measured as 65 g and completed with xylene. 51 g butyl acetate, 30.2 g xylene, 1 g BYK-313 and 67.3 g dibasic ester (Imsol R) were further added. The solids content of the resultant solution of the first polyvinyl butyral was 19.6%.

[0089] Polyvinyl Butyral Polymer Example 2

[0090] 100 g of polyvinyl butyral powder available commercially as MOWITAL B30HH, 240 g dibasic ester (Imsol R), 100 g butyl acetate and 60 g xylene were stirred for approximately 1 hour under a dissolver. After this time the loss due to solvent evaporation was measured as 111 g and completed with xylene. 1 g BYK-313 and 50 g dibasic ester (Imsol R) were further added. The solids content of the resultant solution of the second polyvinyl butyral was 16 wt %.

[0091] Coating Compositions 1-4

[0092] Coating compositions 1-4 were prepared according to the formulations in Table 1.

[0093] Coating Composition 5

[0094] Comparative coating composition 5 is the commercially available epoxy-phenolic lacquer, PPG 7940 (commercially available from PPG Industries, One PPG Place Pittsburgh, Pa. 15272 USA).

TABLE-US-00001 TABLE 1 Formulations of Coating Compositions Coating Coating Coating Coating Compo- Compo- Compo- Compo- sition 1 sition 2 sition 3 sition 4 Polyvinyl Butyral 24.9 24.9 24.9 24.9 Polymer Example 1/g Polyvinyl Butyral 20.4 20.4 20.4 20.4 Polymer Example 2/g Melamine Resin.sup.1/g 0.1 0.1 0.1 0.1 Isocyanate resin.sup.2/g 8.0 6.0 4.0 Crosslinker 1.sup.3/g 0.5 0.5 0.5 0.5 Crosslinker 2.sup.4/g 8.0 10.0 12.0 16.0 .sup.1Komelol MM90/GE HMMM resin .sup.2Desmodur VP LS 2078/2 IDPI-polyisocyanate, blocked resin .sup.3Phenodur VPM-1150 .sup.4Phenodur VPR 1785/50MP

[0095] The properties of the coatings were tested via the following methods. Results are shown in Table 2.

[0096] Preparation of Test Cans:

[0097] Coatings were coated onto aluminium monobloc cans. About 3 grams of coating formulations 1-4 were filled individually into an aluminium can and then drained for 10 minutes by standing the can upside down with a angle of 45; thereby coating the internal of the can. Subsequently, the can was placed into a convection oven to be cured at 240 C. for 5 minutes.

[0098] The coated cans were tested for coating thickness, for enamel ratings after the impact test, also called falling weight test, solvent resistance, cross cut adhesion and blush and cutting edge adhesion after exposure to boiling water and after sterilisation in water according to the procedures described below.

[0099] Blue Test:

[0100] 1,5% basonyl violet 600 from BASF was dissolved in 10 vol % glycerin/38.30 vol % THFA/50.00 vol % 2-propanon and 0.2 vol % Tego Wet KL 245 from Evonik. Approximately 1-3 ml of this solution was dropped on the surface of the dried coatings. After 5 minutes the solution was removed and the coatings were evaluated for colouring and softening and graded using a scale of 1-5, with 1 being the worst and 5 being the best.

[0101] Coating Thickness:

[0102] Coating thickness was measured according to a non-destructive measurement of anodic coatings applied onto an aluminium base, using an ISOSCOPE MP30, coating thickness measuring instrument. The uncoated aluminium can was used for calibration after it had been flattened. The thickness of the coating of the coated cans was measured both on the side wall and on the bottom of the can. The measured thickness was reported in microns and represented either the average of 10 measurements or the lowest and highest values.

[0103] Impact Test:

[0104] The impact test was carried out according to ASTM D2794. The bottom part of the coated can was cut at a height of 20 mm and then with the coated side facing down on a Teflon coated fixture. A 1 kg weight is dropped from a 1 meter height to strike an indentation. The test was repeated two times under the same conditions on two individual cans. The integrity of the coating was measured using a WACO Enamel Rater Instrument and a 1% salt solution containing 0.1% dioctyl sodium sulfosuccinate and reported in milliamperes (mA).

[0105] Solvent Resistance (NMP Test):

[0106] Flattened parts of the coated cans were immersed in N-methyl pyrrolidone (NMP) in a closed glass container at room temperature for 24 hours. After this period, the coated cans were removed, washed with methyl ethyl ketone (MEK) and then dried. A hard rod coated with PTFE was brought into contact with the coating and moved 10 times over the coated surface with pressure. The coatings were checked for their ability to resist the chemical attack by NMP using a visual scale of 1-5, with 5 being the best.

[0107] Boiling Water Test:

[0108] The coated parts of the can were immersed in boiling water at 100 C. for 15 minutes and subsequently removed and dried. They were then tested for cross-cut adhesion and for cutting edge adhesion. Cross-cut adhesion was measured according to the DIN ISO 2409 standard. Briefly, a crosshatch grid was made in the film using a grid comb and was then covered with tape (grade TESA 4104 clear). Within 60 seconds of its application, the tape was removed rapidly. The grid area is then checked for removal of the coating from the substrate. The adhesion was scored in accordance with the following scale:

TABLE-US-00002 GT0 The edges of the cuts are completely smooth; none of the squares of the grid is detached. GT1 Small flakes of the coating are detached at intersections; less than 5% of the area is affected. GT2 Some flakes of the coating are detached along the edges and/or at intersections of the incisions. The area affected is 5-15% of the grid GT3 The coating has peeled along the edges and on parts of the squares of the grid. The area affected is 15-35% of the grid. GT4 The coating has peeled along the edges of the incisions in large strips and some squares are totally detached. The area affected is 35-65% of the grid. GT5 All degrees of peeling and flecking that can be not classified under GT4.

[0109] Cutting edge adhesion was measured by the following method. The coated parts of the can were cut along the length of the can from the lowest film thickness to the highest film thickness using scissors. The cutting edge adhesion of the coating was evaluated according to the level of peeling from the substrate and using a rating 1-5, with 5 being the best.

[0110] Sterilization in Water:

[0111] The coated parts of the can were immersed in water in a pressurisable metal container and placed into an autoclave where it was retorted at 129 C. for 60 minutes. After this, the parts were removed and dried. Immediately upon removal from the retort solution, the coatings were tested in cross-cut adhesion and in cutting edge adhesion by the methods as described above.

TABLE-US-00003 TABLE 2 Test Results Comparative Coating Coating Coating Coating Coating Composition Composition Composition Composition Composition 1 2 3 4 5 Aluminium monobloc cans curing: 5 mins, 240 C. Blue Test 5 min - B 5 5 5 4 5 Thickness Rim - A/m 13.3 12.4 8 9.6 12.0 Thickness Rim - B/m 12.3 10.8 9.4 10.7 14.0 Enamel rater - A/mA 3.4 0.7 0.1 2.2 0 Enamel rater - B/mA 0.2 0 0 0.1 0.5 Thickness - A (min/max) 6.3/16.3 11.4/17.3 8.2/13.4 9.3/16.4 8/12 Thickness - B (min/max) 11.8/18.3 7.1/15.9 7.9/16.9 11.0/14.8 8/12 Solvent resistance (NMP) Test, 24 hours NMP resistance - A 4.5 5 5 5 5 NMP resistance - B 5 5 5 5 5 Boiling Water Test, 15 mins, 100 C. Cross-cut Adhesion GT0 GT0 GT0 GT0 GT0 body-middle - A Cutting edge Adhesion/ 4.5 5 5 5 5 min thickness - A Cutting edge Adhesion/ 4.5 5 5 4.5 5 max thickness - A Cross-cut Adhesion GT0 GT0 GT0 GT0 GT0 body-middle - B Cutting edge Adhesion/ 5 4 5 5 5 min thickness - B Cutting edge Adhesion/ 4 4 5 5 5 max thickness - B Sterilisation, 1 hour, 129 C., demineralised water Cross-cut Adhesion 5 5 5 5 5 body-middle - A Cutting edge Adhesion/ 2 4 4.5 5 5 min thickness - A Cutting edge Adhesion/ 1.5 4 4.5 4.5 5 max thickness - A Cross-cut Adhesion 5 5 5 5 5 body-middle - B Cutting edge Adhesion/ 4.5 5 5 5 5 min thickness - B Cutting edge Adhesion/ 3 4 4.5 4.5 5 max thickness - B

[0112] The results show that the coating compositions according to the present invention perform as well, or better, than coating compositions comprising epoxy-phenol resins.

[0113] Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

[0114] All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

[0115] Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[0116] The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.