PROCESS FOR THE IMPREGNATION OF POLYMER SUBSTRATES

Abstract

Process for the impregnation of a polymer substrate including at least one polymer, which comprises putting said polymer substrate in contact with at least one aqueous emulsion, preferably an aqueous microemulsion, including at least one organic additive. The impregnated polymer substrate obtained from said process can be advantageously used for obtaining polymer end-products having improved aesthetic characteristics (for example, impregnation with at least one dye) or stability characteristics (for example, impregnation with at least one stabilizer), which can be used in various fields such as, for example, the optical field (e.g., advanced optical components, laser applications), the medical field (e.g., the release of pharmaceutical substances), the agricultural field (e.g., release of pesticides), fragrances (e.g., release of fragrances). More specifically, said polymer substrate can be used in luminescent solar concentrators (LSCs) which, in their turn, can be advantageously used together, for example, with photovoltaic cells (or solar cells), or photoelectrolytic cells, in solar devices (i.e. devices for exploiting solar energy). Furthermore, said luminescent solar concentrators (LSCs) can be advantageously used together, for example, with photovoltaic cells (or solar cells), in photovoltaic windows.

Claims

1: A process for impregnating a polymer substrate, the process comprising: contacting the polymer substrate comprising a polymer with at least one aqueous emulsion comprising an organic additive.

2: The process according to claim 1, wherein the polymer is selected from the group consisting of a polyacrylate, a polycarbonate, a polystyrene, a styrene-acrylonitrile copolymer, or a mixture thereof.

3: The process according to claim 1, wherein the organic additive is a photoluminescent dye.

4: The process according to claim 3, wherein the photoluminescent dye is selected from the group consisting of a benzothiadiazole compound, an acene compound, a perylene compound, or a mixture thereof.

5: The process according to claim 1, wherein the aqueous emulsion comprises: from 20% by weight to 90% by weight of water, with respect to a total weight of a surfactant, a co-surfactant, and water; from 3% by weight to 25% by weight of at least one surfactant, with respect to the total weight of the surfactant, the co-surfactant, and water; from 0% by weight to 50% by weight of at least one co-surfactant, with respect to the total weight of the surfactant, the co-surfactant, and water; from 1% by weight to 90% by weight of at least one organic solvent immiscible with water, with respect to a total weight of the organic solvent and water; from 0.02% by weight to 2% by weight of at least one organic additive, with respect to a total weight of the organic additive and the organic solvent.

6: The process according to claim 5, wherein the at least one surfactant is an anionic surfactant.

7: The process according to claim 5, wherein the at least one co-surfactant is present in the aqueous emulsion and is an alcohol.

8: The process according to claim 5, wherein the at least one organic solvent is selected from the group consisting of toluene, cyclohexane, and heptane.

9: The process according to claim 1, which is carried out at a temperature ranging from 15 C. to 40 C.

10: The process according to claim 1, which is carried out for a time ranging from 5 minutes to 3 hours.

11: The process according to claim 1, which is carried out at a pressure ranging from 1 atm to 5 atm.

12: A luminescent solar concentrator, comprising: a polymer substrate obtained by the process according to claim 1.

13: A solar device, comprising: at least one of the luminescent solar concentrator according to claim 12, and a photovoltaic cell or a photoelectrolytic cell.

14: A photovoltaic window, comprising; at least one of the luminescent solar concentrator according to claim 12, and a photovoltaic cell.

Description

EXAMPLE 1

Preparation of Microemulsions Including 4,7-Di-2-Thienyl-2,1,3-Benzothiadiazole (DTB)

Microemulsion EM77

[0061] 16 g of sodium dodecyl sulfate (SDS) (Acros Organics 99%) and 93 ml of pure water MilliQ (MQMillipore) were introduced into a 250 ml flask: the whole mixture was kept under stirring until a limpid solution was obtained. 41.3 ml of 1-butanol (Acros Organics 99%), 83.4 mg of 4,7-di-2-thienyl-2,1,3-benzothiadiazole (DTB) and 7.5 ml of toluene (Aldrich) were subsequently added in sequence: the whole mixture was left, at room temperature (25 C.), under stirring, for about 1 hour and then left to rest for a night, obtaining a transparent orange-coloured microemulsion and a final concentration of 4,7-di-2-thienyl-2,1,3-benzothiadiazole (DTB) in the microemulsion equal to 210.sup.3 M.

Microemulsion EM78

[0062] 161 g of sodium dodecyl sulfate (SDS) (Acros Organics 99%) and 912 ml of pure water MilliQ (MQMillipore) were introduced into a 2.5 litre flask: the whole mixture was kept under stirring until a limpid solution was obtained. 401 ml of 1-butanol (Acros Organics 99%), 958 mg of 4,7-di-2-thienyl-2,1,3-benzothiadiazole (DTB) and 292 ml of toluene (Aldrich) were subsequently added in sequence: the whole mixture was left, at room temperature (25 C.), under stirring, for about 1 hour and then left to rest for a night, obtaining a transparent orange-coloured microemulsion and a final concentration of 4,7-di-2-thienyl-2,1,3-benzothiadiazole (DTB) in the microemulsion equal to 210.sup.3 M.

Microemulsion EM73

[0063] 13 ml of a solution 0.6 M of sodium dodecyl sulfate (SDS) (Acros Organics 98%) in pure water MilliQ (MQMillipore) were poured into a 50 ml flask. 5.7 ml of pure water MilliQ (MQMillipore) and 0.5 ml of a solution 0.05 M of 4,7-di-2-thienyl-2,1,3-benzothiadiazole (DTB) in toluene (Aldrich), were subsequently added in sequence: the whole mixture immediately became limpid and was left, at room temperature (25 C.), under stirring, for 30 minutes, and then left to rest for a night, obtaining a transparent yellow-coloured microemulsion and a final concentration of 4,7-di-2-thienyl-2,1,3-benzothiadiazole (DTB) in the microemulsion equal to 110.sup.3 M.

Microemulsion EM74

[0064] 13 ml of a solution 0.6 M of sodium dodecyl sulfate (SDS) (Acros Organics 98%) in pure water MilliQ (MQMillipore) were poured into a 50 ml flask. 5.7 ml of 1-butanol (Acros Organics 99%) and 0.5 ml of a solution 0.05 M of 4,7-di-2-thienyl-2,1,3-benzothiadiazole (DTB) in toluene (Aldrich), were subsequently added in sequence: the whole mixture immediately became limpid and was left, at room temperature (25 C.), under stirring, for 30 minutes, and then left to rest for a night, obtaining a transparent yellow-coloured microemulsion and a final concentration of 4,7-di-2-thienyl-2,1,3-benzothiadiazole (DTB) in the microemulsion equal to 110.sup.3 M.

EXAMPLE 2

Preparation of Microemulsions Including Various Fluorescent Dyes

Microemulsion EM66

[0065] 13 ml of a solution 0.6 M of sodium dodecyl sulfate (SDS) (Acros Organics 98%) in pure water MilliQ (MQMillipore) were poured into a 50 ml flask. 5.7 ml of 1-butanol (Acros Organics 99%) and 4.2 ml of a solution 210.sup.3 M of 4,7-di-2-thienyl-2,1,3-benzothiadiazole (DTB) in toluene (Aldrich), were subsequently added in sequence: the whole mixture immediately became limpid and was left, at room temperature (25 C.), under stirring, for 30 minutes, and then left to rest for a night, obtaining a transparent light yellow-coloured microemulsion and a final concentration of 4,7-di-2-thienyl-2,1,3-benzothiadiazole (DTB) in the microemulsion equal to 310.sup.4 M.

Microemulsion EM76

[0066] 13 ml of a solution 0.6 M of sodium dodecyl sulfate (SDS) (Acros Organics 98%) in pure water MilliQ (MQMillipore) were poured into a 50 ml flask. 5.7 ml of 1-butanol (Acros Organics 99%) and 4.2 ml of a solution 2.810.sup.3 M of Lumogen F Red 305 in toluene (Aldrich), were subsequently added in sequence: the whole mixture immediately became limpid and was left, at room temperature (25 C.), under stirring, for 30 minutes, and then left to rest for a night, obtaining a transparent dark red-coloured microemulsion and a final concentration of Lumogen F Red 305 in the microemulsion equal to 510.sup.4 M.

Microemulsion EM80

[0067] 13 ml of a solution 0.6 M of sodium dodecyl sulfate (SDS) (Acros Organics 98%) in pure water MilliQ (MQMillipore) were poured into a 50 ml flask. 5.7 ml of 1-butanol (Acros Organics 99%) and 4.2 ml of a solution 210.sup.3 M of 4,7-bis (7,8-dibutylbenzo[1,2-b: 4,3-b]dithien-5-yl)benzo[c][1,2,5]thia-diazole (F500) in toluene (Aldrich) were subsequently added in sequence: the whole mixture immediately became limpid and was left, at room temperature (25 C.), under stirring, for 30 minutes, and then left to rest for a night, obtaining a transparent red-orange-coloured microemulsion and a final concentration of 4,7-bis(7,8-dibutylbenzo[1,2-b:4,3-b ]dithien-5-yl)benzo[c][1,2,5]-thiadiazole (F500) in the microemulsion equal to 410.sup.4 M.

EXAMPLE 3 (COMPARATIVE)

Preparation of a Solution Including 4,7-Di-2-Thienyl-2,1,3-Benzothiadiazole (DTB)

Solution DTB52

[0068] 77.8 ml of toluene (Aldrich) and 40.4 mg of 4,7-di-2-thienyl-2,1,3-benzothiadiazole (DTB) were introduced into a 100 ml flask: the whole mixture was kept under stirring, immediately obtaining a limpid yellow-coloured solution and a final concentration of 4,7-di-2-thienyl-2,1,3-benzothiadiazole (DTB) in the solution equal to 210.sup.3 M.

EXAMPLE 4

Impregnation of Polymer Sheets

[0069] A polymer sheet of polymethylmethacrylate (PMMA) Altuglas (dimensions 2.52.55 mm), obtained by casting, was completely immersed, in a vertical position, in an 80 ml beaker containing the microemulsion EM77 obtained as described in Example 1, and maintained therein at room temperature (25 C.) and at atmospheric pressure. The sheet was then removed from the beaker, washed with abundant distilled water, dried with a cloth and left to dry in the air, at room temperature (25 C.), for a night.

[0070] Other polymer sheets of polymethylmethacrylate (PMMA) Altuglas (dimensions 2.52.55 mm) were impregnated, operating as described above, using: [0071] the microemulsions EM78, EM73 and EM74, obtained as described in Example 1; [0072] the microemulsions EM66, EM76 and EM80, obtained as described in Example 2; [0073] the solution DTB52 obtained as described in Example 3.

[0074] The sheets thus obtained were subjected to determination of the quantity of dye present on the same.

[0075] For this purpose, they were subjected to UV-Vis absorption spectroscopy, measuring the absorbance characteristic of each photoluminescent dye, after calibration using reference sheets containing known quantities of photoluminescent dye dispersed in the same polymer matrix.

[0076] The UV-Vis spectra were acquired by means of a Perkin Elmer Lambda 950 double-ray and double monochromator spectrophotometer: the results obtained are reported in Table 1 and in Table 2. In Table 1 and Table 2, the immersion times of the sheet are also reported.

TABLE-US-00001 TABLE 1 PHOTOLUMINESCENT PHOTOLUMINESCENT DYE TOLUENE DYE TIME SAMPLE (% by wt)* (% by wt) (ppm)** (hours) EM77 0.06 4 33 0.5 EM78 0.06 15 117 0.5 DTB52 0.06 100 12 0.5 DTB52 0.06 100 22 1 EM73 0.04 2 39 2.5 EM74 0.04 2 77 2.5 *wt % percentage of photoluminescent dye in the microemulsion or in the solution; **ppm of photoluminescent dye in the impregnated sheet obtained from the UV-visible absorption curves of the photoluminescent dyes.

[0077] From the data reported in Table 1, it can be seen that the sheets obtained by impregnation with the microemulsions EM77 and EM78 according to the present invention, give better results (i.e. a greater quantity of photoluminescent dye present on the sheet) with respect to the sheets obtained by impregnation with the solution in toluene (DTB52).

[0078] Furthermore, it can be noted that the presence of the co-surfactant (i.e. butanol) in the impregnating microemulsion (EM74) allows a greater quantity of photoluminescent dye to be obtained on the sheet with respect to the microemulsion without co-surfactant (EM73).

TABLE-US-00002 TABLE 2 PHOTOLUMINESCENT PHOTOLUMIINESCENT PHOTOLUMINESCENT DYE (type) TOLUENE DYE (type) TIME SAMPLE DYE (type) (wt %).sup.a (% mmol).sup.a (wt %) ppm/sheet.sup.b mmol/sheet.sup.c (hrs) EM66 DTB 0.009 0.03 15 43 0.14 2 EM76 Lumogen F Red 305 0.05 0.05 15 99 0.09 2 EM80 F500 0.03 0.04 15 45 0.06 2 .sup.awt % and % in mmoles of photoluminescent dye in the microemulsion; .sup.bppm of photoluminescent dye in the impregnated sheet obtained from the UV-visible absorption curves of the photoluminescent dyes; .sup.cmmoles of photoluminescent dye in the impregnated sheet obtained from the ppm values.

[0079] From the data reported in Table 2, it can be seen that the sheet obtained by impregnation with the microemulsion EM66 gives better results (i.e. a greater quantity of photoluminescent dye present on the sheet) with respect to the sheets obtained by impregnation with the microemulsions EM76 and EM80.

EXAMPLE 5

Impregnation of Polymer Sheets on Two Sides in a Vertical Position (EM78f and EM78d)

[0080] A polymer sheet of polymethylmethacrylate (PMMA) Altuglas (dimensions 9205 mm), obtained by casting, was arranged in a vertical position in a basin (dimensions 23237 mm) to which the microemulsion EM78 obtained as described in Example 1 was added, in such a quantity so as to completely cover it and it was maintained therein at room temperature (25 C.) and at atmospheric pressure (1 bar). The sheet was then removed from the basin, washed with abundant distilled water, dried with a cloth and left to dry in the air, at room temperature (25 C.), for a night (EM78f).

[0081] Another polymer sheet of polystyrene-acrylonitrile (SAN) (Kostil B 266 of versalis spa) (dimensions 9205 mm), obtained by extrusion, was impregnated, operating as described above (EM78d).

EXAMPLE 6

Impregnation of Polymer Sheets on One Side in a Horizontal Position (EM78m) and on Two Sides in a Horizontal Position (EM78n)

[0082] A polymer sheet of polymethylmethacrylate (PMMA) Altuglas (dimensions 9205 mm), obtained by casting, was arranged in a horizontal position in a basin (dimensions 24197 mm) to which the microemulsion EM78 obtained as described in Example 1 was added, in such a quantity so as to completely wet the lower part of the sheet, and it was maintained therein at room temperature (25 C.) and at atmospheric pressure (1 bar). The sheet was then removed from the basin, washed with abundant distilled water, dried with a cloth and left to dry in the air, at room temperature (25 C.), for a night (EM78m).

[0083] Another polymer sheet of polymethylmethacrylate (PMMA), on the other hand, was arranged in a horizontal position in a basin (dimensions 24197 mm) to which the microemulsion EM78 obtained as described in Example 1 was added, in such a quantity so as to completely wet the whole of the sheet, and it was maintained therein at room temperature (25 C.) and at atmospheric pressure (1 bar). The sheet was then removed from the basin, washed with abundant distilled water, dried with a cloth and left to dry in the air, at room temperature (25 C.), for a night (EM78n).

EXAMPLE 7

Power Measurements (P.SUB.max.)

[0084] The power measurements were carried out on impregnated polymer sheets obtained as described in Example 5 and Example 6.

[0085] For this purpose, a photovoltaic cell IXYS-XOD17 having a surface of 1.2 cm.sup.2 connected to a digital multimeter, was applied on one of the two shortest edges (i.e. on one of the 9 mm edges) of the sheet to be evaluated.

[0086] The surface of the sheet was then illuminated with a light source, using an ABET solar simulator mod. SUN 2000 equipped with a 550 Watt OF Xenon lamp having a power equal to 1 sun (1,000 W/m.sup.2), for 10 seconds. A first measurement was carried out, illuminating a portion of the sheet (99 cm) and the electric power generated by the illumination was measured.

[0087] Power measurements were subsequently carried out on portions of sheet having the same dimensions, at increasing distances from the edge on which the photovoltaic cell was fixed (a total of 11 measurements).

[0088] The curve for the current intensity (measured in amperes)voltage produced (measured in volts) was registered for each portion of sheet illuminated, and the average effective power (P.sub.max) of the photovoltaic cell was calculated from this. The average effective power (P.sub.max) was calculated ignoring the first and the last measurement (relating to the portions of sheet containing the edge with the photovoltaic cell and the opposite edge, respectively). The values obtained are reported in Table 3. Table 3 also indicates the immersion times of the sheet.

TABLE-US-00003 TABLE 3 PMMA SAN SAM- DTB TIME P.sub.max SAM- DTB TIME P.sub.max PLE (ppm)* (minutes) (mw) PLE (ppm) (minutes) (mW) EM78f 157 40 3.33 EM78d 46 5 2.94 EM78m 84 40 3.06 EM78n 118 40 3.32 *ppm of photoluminescent dye (DTB) in the impregnated sheet.

[0089] From the data reported in Table 3, it can be seen that the impregnation with the microemulsion is equally efficient on both sheets of polymethylmethacrylate (PMMA) and sheets of styrene-acrylonitrile (SAN). The difference in power developed under illumination of the polymethylmethacrylate (PMMA) sheets with respect to that developed by the styrene-acrylonitrile (SAN) sheets, is minimum, considering that the quantity of photoluminescent dye (i.e. DTB) on the styrene-acrylonitrile (SAN) sheets is much lower (EM78f versus EM78d).

[0090] It can also be seen that the position in which the sheet to be impregnated is arranged in the basin (vertical or horizontal) has no influence (EM78f versus EM78n), whereas there is a slight difference (almost negligible) between the power developed by the sheet impregnated on one side only, which, however, also contains less photoluminescent dye (i.e. DTB) and that impregnated on both sides (EM78m versus EM78n).