Method for forming an article having a decorative surface

Abstract

The invention refers to a method for forming an article having a decorative surface comprising: a) screen printing an ink composition comprising a curable composition onto at least one major surface of a thermoformable polymeric sheet; b) curing said curable composition to obtain a printed sheet having on at least one major surface an ink comprising a cured composition; and c) thermoforming the printed sheet to obtain a decorated article, wherein said curable composition comprises a polyisocyanate and a component comprising isocyanate reactive groups and wherein said ink composition contains a solvent or solvent blend in which said curable composition is soluble or miscible.

Claims

1. A method for forming an article having a decorative surface comprising: a) screen printing an ink composition comprising a curable composition onto at least one major surface of a thermoformable polymeric sheet; b) curing said curable composition to obtain a printed thermoformable polymeric sheet having on at least one major surface an ink comprising a cured composition; and c) thermoforming the ink and the printed thermoformable polymeric sheet together to obtain a decorated article, wherein said curable composition comprises a polyisocyanate and a component comprising isocyanate reactive groups, and said ink composition contains a solvent or solvent blend in which said curable composition is soluble.

2. The method according to claim 1, wherein said component having reactive groups comprises an acrylic polymer having hydroxyl groups.

3. The method according to claim 1, wherein said polyisocyanate comprises a di-isocyanate or tri-isocyanate.

4. The method according to claim 1, wherein said solvent is selected from ketones, esters, amides, or mixtures thereof.

5. The method according to claim 1, wherein the solvent is selected from cyclohexanone, isophorone, diacetone alcohol, N-methylpyrrolidone, methoxypropyl acetate, isopropoxyethyl acetate, ethoxyethyl propionate, ethyl lactate, and mixtures thereof.

6. The method according to claim 1, wherein the curable ink material further comprises a caprolactone or polycaprolactone compound, optionally having two or more hydroxyl groups.

7. The method according to claim 1, wherein said thermoformable polymeric sheet is made of a material selected from the group comprising polycarbonate, polyethyleneterephthalate glycol (PETG), acrylonitrile butadiene styrene (ABS), thermoplastic polyolefin (TPO), polypropylene, acrylic compounds and mixtures thereof.

8. The method according to claim 1, wherein said thermoformable polymeric sheet is polycarbonate.

9. The method according to claim 1, wherein said curing step b) comprises heating of said printed sheet.

10. The method according to claim 1, wherein said method includes the step of allowing the ink composition to partially penetrate into the thermoformable polymeric sheet.

11. The method according to claim 1, wherein said curing step b) comprises heating the printed thermoformable polymeric sheet before said thermoforming.

12. The method according to claim 2, wherein said polyisocyanate comprises a di-isocyanate or tri-isocyanate.

13. The method according to claim 2, wherein said solvent is selected from ketones, esters, amides, or mixtures thereof.

14. The method according to claim 3, wherein said solvent is selected from ketones, esters, amides, or mixtures thereof.

15. The method according to claim 12, wherein said solvent is selected from ketones, esters, amides, or mixtures thereof.

16. The method according to claim 2, wherein the curable ink material further comprises a caprolactone or polycaprolactone compound, optionally having two or more hydroxyl groups.

17. The method according to claim 12, wherein the curable ink material further comprises a caprolactone or polycaprolactone compound, optionally having two or more hydroxyl groups.

18. The method according to claim 13, wherein the curable ink material further comprises a caprolactone or polycaprolactone compound, optionally having two or more hydroxyl groups.

19. The method according to claim 14, wherein the curable ink material further comprises a caprolactone or polycaprolactone compound, optionally having two or more hydroxyl groups.

20. The method according to claim 15, wherein the curable ink material further comprises a caprolactone or polycaprolactone compound, optionally having two or more hydroxyl groups.

Description

EXAMPLES

Materials for the Ink Composition Examples 1 and 2

(1) D7900: Clear base ink for preparing desired colored inks commercially available from 3M Company. The clear base ink is based on a PVC resin and acrylic resin and containing a solvent mixture of cyclohexanone, aromatic solvents and ethylene glycol butyl ether acetate.

(2) P1 and P2: pigment dispersions commercially available from 3M Company and suitable for blending with D7900.

(3) Joncryl 587: acrylic polyol commercially available from Johnson (Johnson Polymer LLC, Sturtevant, Wis. 53177-0902, US).

(4) TONE 200: polycaprolactone diol commercially available from Dow (Dow, Midland, Mich. 48674, US).

(5) HMDI: hexamethylene di-isocyanate, Desmodur N 3390 BA/SN, commercially available from Bayer (Bayer Material Science AG, 51368 Leverkusen, Germany).

(6) CGS 80: thinner commercially available from 3M Company

(7) The ink composition of Example 1, according to the invention, was prepared having the following composition: a) 50 parts per weight D 7900; b) 40 parts per weight of a pigment dispersion P1; c) 0.87 parts by weight Joncryl 587; d) 0.43 parts by weight of TONE 200; e) 0.0002 parts by weight dibutyltindilaurate; f) 1.8 parts by weight HMDI; g) 5.7 parts by weight CGS 80.

(8) The ink composition of Example 2, according to the invention, was prepared similar as the ink composition of Example 1 but using pigment dispersion P2 to achieve a differently colored ink.

Materials for the Ink Composition of Examples 3 and 4

(9) D7900: Clear base ink for preparing desired colored inks commercially available from 3M Company. The clear base ink is based on a PVC resin and acrylic resin and containing a solvent mixture of cyclohexanone, aromatic solvents and ethylene glycol butyl ether acetate.

(10) P1 and P2: pigment dispersions commercially available from Kiian S.p.a. Luisago, Italy with trade name Mankounian-Argon Thermoplus 49000 series and intended for blending with D7900 clear resin.

(11) Joncryl 587: acrylic polyol commercially available from Johnson (Johnson Polymer LLC, Sturtevant, Wis. 53177-0902, US).

(12) TONE 200: polycaprolactone diol commercially available from Dow (Dow, Midland, Mich. 48674, US).

(13) HMDI: hexamethylene di-isocyanate, Desmodur N 3390 BA/SN, commercially available from Bayer (Bayer Material Science AG, 51368 Leverkusen, Germany).

(14) Desmophen A450M PA/X: acrylic polyol available from Bayer (Bayer Material Science AG, 51368 Leverkusen, Germany).

(15) CGS 80: thinner commercially available from 3M Company.

(16) The ink composition of Example 3, according to the invention, was prepared having the following composition: h) 30 parts per weight D 7900 clear resin; i) 60 parts per weight of a pigment dispersion P1; j) 0.83 parts by weight Joncryl 587; k) 0.41 parts by weight of TONE 200; l ) 0.0002 parts by weight dibutyltindilaurate; m) 0.4 parts by weight HMDI; n) 0.46 parts by weight Desmophen A450M PA/X o) 0.00035 parts by weight Zinc napthenate p) 0.000029 parts by weight Dimethly polysiloxane q) 5.7 parts by weight CGS 80.

(17) The ink composition of Example 4, according to the invention, was prepared similar as the ink composition of Example 3 but using pigment dispersion P2 to achieve a differently colored ink.

Example A

(18) 1. Screen-Printing Step

(19) A sheet of a clear polycarbonate Makrofol (available from Bayer AG, Germany) with a thickness of 200 m was screen-printed, using a commercially available flat-bed screen-printer. The desired design was achieved by screen-printing in two steps using the ink compositions of Examples 1 and 2.

(20) The printed sample was dried in a flat bed oven having four stations. This drying step was done after each color printing. The samples passed through the heating zones at a line speed of 5.5 m per minute. Total oven length was about 5.5 m. Temperature of the four heating zones were as follows: zone 1: 50 C., zone 2: 60 C., zones 3 and 4 room temperature ventilation, maximum temperature 35 C. After the second printing and drying cycle the obtained printed sample was cured at 60 C. for 2 h. The dried ink coating had a thickness of ca. 6 to 10 m.

(21) 2. Thermoforming Step

(22) The printed sheet as obtained above was applied to a Cannon vacuum thermoformer model number Forma1200 (Corso Novara 179-27029 Vigevano (PV)-Italy), in such a way that the printed area was facing the male mold. The male mold was the downside part of the thermoforming equipment. When the sheet became flexible, the vacuum led to a wrap-up of the sheet around the outside of a male mold. The temperature of the polycarbonate's thermoforming process was around 145 C. (following ISO 360 method B50).

(23) The thermoformed sample was then separated from the mold. The final form of the sample was achieved by cutting.

(24) 3. Testing

(25) The resulting multicoloured polycarbonate part was visually inspected for cracks in the printed ink layer. No cracks were found in the printed image.

Comparative Example

(26) Example A was repeated with the exception that an alternative ink, cured by another method, was employed. This ink was UV curable ink Dirasol 916/917_commercially available from SERICOL (Fujifilm Sericol UK Limited, Broadstairs, Kent CT10 2LE). The ink was applied as above and cured using UV lamps as recommended by the manufacturer.

(27) The multicoloured polycarbonate part bearing the UV cured ink was visually inspected for cracking in the printed image. The image showed aesthetically unpleasing cracks in the ink layer that detracted from its appearance.

Materials for the Ink Compositions of Examples 5 to 9

(28) 1903: 3M Screen Printing Ink 1903 White, available from 3M Company (St. Paul, Minn., USA).

(29) 3000: Silberline SPARKLE SILVER 3000-AR (SBR) Aluminum Pigment Paste available from Silberline, Inc. (Tamaqua, Pa., USA).

(30) 3122: Silberline SPARKLE SILVER 3122-AR (SBR) Aluminum Pigment Paste available from Silberline, Inc. (Tamaqua, Pa., USA).

(31) 7900: 3M High Performance Ink, 7900, available from 3M Company (St. Paul, Minn., USA).

(32) 7922: 3M High Performance blue ink, 7922, available from 3M Company (St. Paul, Minn., USA).

(33) 7937: 3M High Performance yellow ink, 7937, available from 3M Company (St. Paul, Minn., USA).

(34) CAPA 2054: polycaprolactone diol, Solvay Caprolactones (Warrington, Cheshire WA4 6HB, United Kingdom).

(35) CAPA 3050: polycaprolactone, Solvay Caprolactones (Warrington, Cheshire, United Kingdom).

(36) DBTDL: Dibutyltin dilaurate catalyst for polymerizing isocyanate reactions, available from PolySciences, Inc. (Warrington, Pa., USA).

(37) Xylene solvent available from Shell Chemical Company (Houston, Tex., USA).

(38) N-100: DESMODUR N 100 aliphatic polyisocyanate resin based on hexamethylene diisocyanate (HMDI) available from Bayer Material Science LLC (Pittsburgh, Pa., USA).

(39) Tone 240: polycaprolactone diol, Dow Chemical Company (Midland, Mich., USA).

(40) HMDI: hexamethylene di-isocyanate, Desmodur N 3390 BA/SN, commercially available from Bayer (Bayer Material Science AG, 51368 Leverkusen, Germany).

(41) Each ink formulation of Examples 5 to 9 was made by mixing the corresponding components together as specified in Table 1. Each Example composition was thinned to approximately 2000 cps with diethyleneglycol monoethyl ether acetate solvent, available from Eastman Chemical Company (Kingsport, Tenn., USA). Then each formulation was silk screen printed onto 1000 micron thick Makrofol 2099UV polycarbonate sheets, available from Bayer AG (Darmstadt, Germany). The ink was printed in a checker board pattern of 25 mm25 mm squares. After printing, the sheets were dried in a forced air oven at 85 C. for 30 minutes. The sheets were then thermoformed as described above.

(42) The percent elongation each sample experienced during thermoforming was calculated by measuring the change in length of each side of the squares after thermoforming. Percent elongation is defined as (new dimension/original dimension100). Screen printed squares that most closely represented percent elongations of 120%, 140%, 160% and 180% were examined and the stress effects on each examined printed ink square after elongation (i.e., their appearance) was rated. The samples were examined for the following changes in ink appearance: color change, pinholes and cracking. The change in appearance of the squares was rated using a 9, 3, 1 and 0 rating system. Squares with very little or no change in appearance after thermoforming were rated a 9. Squares with some acceptable change (i.e., limited color change, limited pinholes, and no visible cracking) in appearance after thermoforming were rated a 3. Ink squares with unacceptable changes in appearance after thermoforming (i.e., noticeable color change, large pin holes and no visible cracking) were rated a 1. Ink squares that exhibited visible cracking after thermoforming were rated a 0. The results are shown in the Table 1 below.

(43) TABLE-US-00001 TABLE 1 Examples (amounts are parts by weight) 5 6 7 8 9 Components 7900 76.00 76.00 76.00 20.00 7922 16.00 16.00 16.00 7937 80 3122 5.00 5.00 5.00 3000 3.00 3.00 3.00 1903 100 DBTDL, 10% in 0.05 0.05 0.05 0.05 0.05 xylene Tone 240 5.00 5 34.19 CAPA 2054 5.00 CAPA 3050 5.00 Admix 770 N-75 HMDI 1.08 5.97 1.00 1 N-100 6.38 Elongation Performance 120% 3 9 9 3 3 140% 1 3 3 3 3 160% 0 3 1 1 3 >180% 0 3 1 1 1