FLUOROPOLYMER COMPOSITION FOR COMPONENTS OF LIGHT EMITTING APPARATUS

Abstract

The invention pertains to a white pigmented fluoropolymer composition comprising certain thermoprocessable tetrafluoroethylene copolymers, certain amounts of specific PTFE micropowders, which possesses advantageous properties for being used for manufacturing shaped articles, and to shaped articles therefrom, including components of light emitting apparatuses, e.g. LED assemblies, including those having junctions emitting in the UV region.

Claims

1.-16. (canceled)

17. A fluoropolymer composition [composition (C)] comprising: (i) a major amount of at least one melt-processible perfluorinated tetrafluoroethylene copolymer [polymer (F)], (ii) from 1 to less than 50% wt., with respect to the total weight of the composition (C) of at least one pigment selected from the group consisting of titanium dioxide (TiO.sub.2), zinc disulfide (ZnS.sub.2), zinc oxide (ZnO) and barium sulfate (BaSO.sub.4) [pigment (P)]; (iii) from 0.5 to 20% wt., with respect to the total weight of the composition (C) of at least one PTFE micropowder possessing a B.E.T. surface area of exceeding 5.0 m.sup.2/g [powder (PTFE)]; and optionally, (iii) at least one reinforcing filler [filler (F)], different from pigment (P).

18. The composition (C) of claim 17, wherein polymer (F) is selected from the group consisting of TFE copolymers comprising recurring units derived from hexafluoropropylene (HFP) and optionally from at least one CF.sub.2CFOR.sub.f perfluoroalkylvinylether (PAVE), wherein R.sub.f is a C.sub.1-C.sub.6 perfluoroalkyl.

19. The composition (C) of claim 17, wherein the polymer (F) is selected from the group consisting of TFE copolymers comprising recurring units derived from at least one CF.sub.2CFOR.sub.f perfluoroalkylvinylether (PAVE), wherein R.sub.f is a C.sub.1-C.sub.6 perfluoroalkyl, and optionally further comprising recurring units derived from at least one C.sub.3-C.sub.8 perfluoroolefin.

20. The composition (C) of claim 19, wherein polymer (F) is a TFE/PMVE copolymer consisting essentially of: (a) from 3 to 13%, preferably from 5 to 12% by weight of recurring units derived from perfluoromethylvinylether; (b) from 0 to 6% by weight of recurring units derived from one or more than one fluorinated comonomer different from perfluoromethylvinylether and selected from the group consisting of perfluoroalkylvinylethers as detailed above, and perfluorooxyalkylvinylethers as detailed above; (c) recurring units derived from tetrafluoroethylene, in such an amount that the sum of the percentages of the recurring units (a), (b) and (c) is equal to 100% by weight.

21. The composition (C) of claim 19, wherein the polymer (F) is a TFE copolymer consisting essentially of: (a) from 0.5 to 5% by weight of recurring units derived from perfluoromethylvinylether; (b) from 0.4 to 4.5% by weight of recurring units derived from one or more than one fluorinated comonomer different from perfluoromethylvinylether and selected from the group consisting of perfluoroalkylvinylethers, as above detailed and perfluorooxyalkylvinylethers, as above detailed; (c) from 0 to 6% weight of recurring units derived from at least one C.sub.3-C.sub.8 perfluoroolefins, preferably derived from hexafluoropropylene; and (d) recurring units derived from tetrafluoroethylene, in such an amount that the sum of the percentages of the recurring units (a), (b), (c) and (d) is equal to 100% by weight.

22. The composition (C) of claim 16, wherein the polymer (F) is a TFE copolymer consisting essentially of: (a) from 0.5 to 8%, preferably from 0.7 to 6% by weight of recurring units derived from perfluoropropylvinylether (PPVE); (b) recurring units derived from TFE, in such an amount that the sum of the percentages of the recurring units (a) and (b) is equal to 100% by weight.

23. The composition (C) of claim 17 wherein pigment (P) is Barium sulfate (BaSO.sub.4).

24. The composition (C) of claim 17, wherein the weight percent of the pigment (P) in the composition (C) is of at least 3 wt. %, based on the total weight of the composition (C) and/or is of at most 45 wt. %, based on the total weight of the composition (C).

25. The composition (C) of claim 17, wherein the powder (PTFE) possesses a B.E.T. surface area of exceeding 6.0 m.sup.2/g, and/or possesses a bulk density of less than 380 g/l.

26. The composition (C) of claim 17, wherein the weight percent of the powder (PTFE) in the composition (C) is of at least 1 wt. %, based on the total weight of the composition (C), and/or is of at most 18 wt. %, based on the total weight of the composition (C).

27. An article comprising at least one component comprising the fluoropolymer composition (C) according to claim 17.

28. The article of claim 27, said article being a light emission apparatus selected from the group consisting of keyless entry systems of an automobile, lightings in a refrigerator, liquid crystal display apparatuses, automobile front panel lighting apparatuses, desk lamps, headlights, household electrical appliance indicators and outdoor display apparatuses, and optoelectronic devices comprising at least one semi-conductor chip that emits and/or transmits electromagnetic radiation.

29. The article of claim 28, wherein the at least one semi-conductor chip that emits and/or transmits electromagnetic radiation is a Light Emitting Diode device possessing junctions emitting in the UV region.

30. A method for making the article of anyone of claim 27, the method comprising processing the composition (C) of anyone of claim 1 by compression molding, extrusion molding, injection molding, or other melt-processing technique.

31. The method of making of claim 30, said method comprising a step of injection molding the composition (C).

32. The method of making of claim 31, wherein the step of injection moulding uses a ram or screw-type plunger to force molten composition (C) into a mould cavity; and wherein within the cavity of the said mould, the composition (C) solidifies into a shape that has conformed to the contour of the mould.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0022] FIG. 1 is a top view LED comprising one or more component made from the composition of the invention.

[0023] FIG. 2 is a power LED comprising one or more component made from the composition of the invention.

DESCRIPTION OF EMBODIMENTS

[0024] The composition (C) may comprise one or more than one melt processable tetrafluoroethylene copolymer, as above detailed, more particularly of a polymer formed of tetrafluoroethylene (TFE) copolymer with one or more perfluorinated comonomers [comonomer (F)]. For the purpose of the present invention, a melt-processible polymer refers to a polymer that can be processed (i.e. fabricated into shaped articles of whichever shape) by conventional melt extruding, molding, injecting or coating means. This generally requires that the melt viscosity of the polymer at the processing temperature be no more than 10.sup.8 Pasec, preferably from 10 to 10.sup.6 Pasec.

[0025] Preferably, the polymer (F) of the present invention is semi-crystalline. For the purpose of the present invention, the term semi-crystalline is intended to denote a polymer having a heat of fusion of more than 1 J/g when measured by Differential Scanning calorimetry (DSC) at a heating rate of 10 C./min, according to ASTM D 3418. Preferably, the semi-crystalline polymer (F) of the invention has a heat of fusion of at least 15 J/g, more preferably of at least 25 J/g, most preferably at least 35 J/g.

[0026] The polymer (F) comprises advantageously more than 0.5% wt, preferably more than 2.0% wt, and more preferably at least 2.5% wt of comonomer (F).

[0027] The polymer (F) as above detailed comprises advantageously at most 20% wt, preferably at most 15% wt, and more preferably 10% wt of comonomer (F).

[0028] Good results have been obtained with the polymer (F) comprising at least 0.7% wt and at most 10% wt of comonomer (F).

[0029] Among suitable comonomers (F), mentions can be made of: [0030] C.sub.3-C.sub.8 perfluoroolefins, e.g. hexafluoropropene (HFP), hexafluoroisobute-ne; [0031] CF.sub.2CFOR.sub.f perfluoroalkylvinylethers (PAVE), wherein R.sub.f is a C.sub.1-C.sub.6 perfluoroalkyl, e.g., CF.sub.3, C.sub.2F.sub.5, or C.sub.3F.sub.7; [0032] CF.sub.2CFOX perfluorooxyalkylvinylethers wherein X is a C.sub.1-C.sub.12 perfluorooxyalkyl having one or more ether groups; and [0033] perfluorodioxoles.

[0034] Preferably, said comonomer (F) is selected from the following comonomers: [0035] PAVEs of formula CF.sub.2CFOR.sub.f1, wherein R.sub.f1 is selected from CF.sub.3, C.sub.2F.sub.5, and C.sub.3F.sub.7, namely, [0036] perfluoromethylvinylether (PMVE of formula CF.sub.2CFOCF.sub.3), [0037] perfluoroethylvinylether (PEVE of formula CF.sub.2CFOC.sub.2F.sub.5), [0038] perfluoropropylvinylether (PPVE of formula CF.sub.2CFOC.sub.3F.sub.7), and mixtures thereof; [0039] perfluoromethoxy vinyl ether (MOVE) of general formula CF.sub.2CFOCF.sub.2OR.sub.f2, wherein R.sub.f2 is a linear or branched C.sub.1-C.sub.6 perfluoroalkyl group, cyclic C.sub.5-C.sub.6 perfluoroalkyl group, a linear or branched C.sub.2-C.sub.6 perfluoroxyalkyl group; preferably, R.sub.f2 is CF.sub.2CF.sub.3 (MOVE1), CF.sub.2CF.sub.2OCF.sub.3 (MOVE2), or CF.sub.3 (MOVE3); and [0040] perfluorodioxoles having the following formula:

##STR00001##

[0041] wherein X.sub.1 and X.sub.2, equal to or different from each other, are selected between F and CF.sub.3, preferably F.

[0042] According to a first embodiment of the invention, the polymer (F) is selected from the group consisting of TFE copolymers comprising recurring units derived from hexafluoropropylene (HFP) and optionally from at least one perfluoroalkylvinylether, as above defined.

[0043] Preferred polymers (F) according to this embodiment are selected among TFE copolymers comprising (preferably consisting essentially of) recurring units derived from tetrafluoroethylene (TFE) and hexafluoropropylene (HFP) in an amount ranging from 3 to 15 wt % and, optionally, from 0.5 to 3 wt % of at least one perfluoroalkylvinylether, as above defined.

[0044] The expression consisting essentially of is used within the context of the present invention for defining constituents of a polymer to take into account end chains, defects, irregularities and monomer rearrangements which might be comprised in said polymers in minor amounts, without this modifying essential properties of the polymer.

[0045] A description of such polymers (F) can be found notably in U.S. Pat. No. 4,029,868 (DUPONT) 14 Jun. 1977, in U.S. Pat. No. 5,677,404 (DUPONT) 14 Oct. 1997, in U.S. Pat. No. 5,703,185 (DUPONT) 30 Dec. 1997, and in U.S. Pat. No. 5,688,885 (DUPONT) 18 Nov. 1997.

[0046] Polymers (F) according to this embodiment are commercially available under the trademark TEFLON FEP 9494, 6100 and 5100 from E.I. DuPont de Nemours, or from Daikin (e.g. FEP NP-101 material), or from Dyneon LLC (FEP 6322).

[0047] Best results within this embodiment have been obtained with TFE copolymers comprising (preferably consisting essentially of) recurring units derived from tetrafluoroethylene (TFE) and hexafluoropropylene (HFP) in an amount ranging from 4 to 12 wt % and either perfluoro(ethyl vinyl ether) or perfluoro(propyl vinyl ether) in an amount from 0.5 to 3% wt.

[0048] According to a second embodiment of the invention, the polymer (F) is selected from the group consisting of TFE copolymers comprising recurring units derived from at least one perfluoroalkylvinylether, as above defined and optionally further comprising recurring units derived from at least one C.sub.3-C.sub.8 perfluoroolefin, as detailed above.

[0049] Good results within this second embodiment have been obtained with TFE copolymers comprising recurring units derived from one or more than one perfluoroalkylvinylether as above specified; particularly good results have been achieved with TFE copolymers wherein the perfluoroalkylvinylether is selected from the group consisting of PMVE, PEVE, PPVE and mixtures thereof.

[0050] According to a preferred variant of the second embodiment of the invention, the polymer (F) is advantageously a TFE/PMVE copolymer consisting essentially of:

(a) from 3 to 13%, preferably from 5 to 12% by weight of recurring units derived from perfluoromethylvinylether;
(b) from 0 to 6% by weight of recurring units derived from one or more than one fluorinated comonomer different from perfluoromethylvinylether and selected from the group consisting of perfluoroalkylvinylethers as detailed above, and perfluorooxyalkylvinylethers as detailed above; preferably derived from perfluoroethylvinylether and/or perfluoropropylvinylether;
(c) recurring units derived from tetrafluoroethylene, in such an amount that the sum of the percentages of the recurring units (a), (b) and (c) is equal to 100% by weight.

[0051] The said TFE/PMVE copolymer generally possesses a melting point, determined according to ASTM D3418 of at least 265 C., preferably at least 270 C., and generally at most 290 C., preferably at most 285 C.

[0052] As said, the said TFE/PMVE copolymer possesses a MFR of more than 5 g/10 min, when determined at 372 C. under a piston load of 5 kg. Upper boundaries for the MFR are not particularly critical. Nevertheless, it is generally preferred to use in the composition (C) a TFE/PMVE copolymer having a MFR of less than 800 g/10 min, advantageously of less than 700 g/10 min, preferably less than 600 g/10 min, more preferably less than 550 g/10 min, measured as above detailed, to the sake of optimizing processability without detrimentally affecting mechanical properties.

[0053] The TFE/PMVE copolymer of this variant is most preferably a copolymer preferably essentially consists of: [0054] from 3.7 to 5.8% moles of recurring units derived from perfluoromethylvinylether (PMVE); [0055] from 94.2 to 96.3% moles of recurring units derived from tetrafluoroethylene (TFE).

[0056] According to another preferred variant of this second embodiment of the invention, the polymer (F) is advantageously a TFE copolymer consisting essentially of:

(a) from 0.5 to 5% by weight of recurring units derived from perfluoromethylvinylether;
(b) from 0.4 to 4.5% by weight of recurring units derived from one or more than one fluorinated comonomer different from perfluoromethylvinylether and selected from the group consisting of perfluoroalkylvinylethers, as above detailed and perfluorooxyalkylvinylethers, as above detailed; preferably derived from perfluoroethylvinylether and/or perfluoropropylvinylether;
(c) from 0 to 6% weight of recurring units derived from at least one C.sub.3-C.sub.8 perfluoroolefins, preferably derived from hexafluoropropylene; and
(d) recurring units derived from tetrafluoroethylene, in such an amount that the sum of the percentages of the recurring units (a), (b), (c) and (d) is equal to 100% by weight.

[0057] According to yet another variant of this second embodiment, polymer (F) is advantageously a TFE copolymer consisting essentially of:

(a) from 0.5 to 8%, preferably from 0.7 to 6% by weight of recurring units derived from PPVE;
(b) recurring units derived from TFE, in such an amount that the sum of the percentages of the recurring units (a) and (b) is equal to 100% by weight.

[0058] MFA and PFA suitable to be used for the composition of the invention are commercially available from Solvay Specialty Polymers Italy S.p.A. under the trade name of HYFLON PFA P and M series and HYFLON MFA and HYFLON F.

[0059] As said, the polymer (F) is the major constituent of the composition (C). The weight percent of the polymer (F) in the composition (C) is generally of at least 50 wt. %, preferably of at least 55 wt. %, and more preferably of at least 60 wt. %, based on the total weight of the composition (C). It is further understood that the weight percent of the polymer (F) in the composition (C) will generally be of at most 95 wt. %, preferably of at most 85 wt. % and most preferably of at most 80 wt. %, based on the total weight of the composition (C).

[0060] Excellent results were obtained when the composition (C) comprised the polymer (F) in an amount of 65-95 wt. %, preferably of 70-93 wt. %, more preferably 75-92 wt. %, based on the total weight of the composition (C).

[0061] Reinforcing fillers [fillers (F)] which are suitable to be possibly used in the composition (C) of the invention are well known by the skilled in the art.

[0062] Having regards to its morphology, the filler (F) of the composition (C) can be generally selected from the group consisting of fibrous fillers and particulate fillers.

[0063] Typically, the filler (F) is selected from the group consisting of mineral fillers (such as talc, mica, kaolin, calcium carbonate, calcium silicate, magnesium carbonate), glass fiber, carbon fibers, synthetic polymeric fiber, aramid fiber, aluminum fiber, titanium fiber, magnesium fiber, boron carbide fibers, rock wool fiber, steel fiber, wollastonite, inorganic whiskers. Still more preferably, it is selected from mica, kaolin, calcium silicate, magnesium carbonate, inorganic whiskers, glass fiber and wollastonite.

[0064] A particular class of fibrous fillers which are advantageously usable in the composition (C) consists of whiskers, i.e. single crystal fibers made from various raw materials, such as Al.sub.2O.sub.3, SiC, BC, Fe and Ni.

[0065] According to certain embodiments, the filler (F) can be selected from the group consisting of fibrous fillers. Among fibrous fillers, glass fibers are preferred; non (imitative examples of glass fibers include notably chopped strand A-, E-, C-, D-, S- and R-glass fibers, as described in chapter 5.2.3, p. 43-48 of Additives for Plastics Handbook, 2nd edition, John Murphy, the whole content of which is herein incorporated by reference. Glass fibers fillers useful in composition (C) may have a round cross-section or a non-circular cross-section.

[0066] In certain embodiment's of the present invention, the filler (F) is selected from the group consisting of wollastonite fillers and glass fiber fillers.

[0067] When present, the weight percent of the filler (F) in the composition (C) is generally of at least 0.1 wt. %, preferably of at least 0.5 wt. %, more preferably of at least 1 wt. % and most preferably of at least 2 wt. %, based on the total weight of composition (C). The weight percent of the filler (F) is generally of at most 30 wt. %, preferably of at most 20 wt. % and most preferably of at most 15 wt. %, based on the total weight of the composition (C).

[0068] Nevertheless, preferred compositions (C) are those wherein no additional filler (F) is added to the combination of polymer (F), powder (PTFE) and pigment (P).

[0069] Above mentioned pigments (P) are typically known as white pigments, in that they absorb limited incident visible radiation and scatter most of said incident visible radiation. Otherwise stated, the pigments (P) used in the composition (C) generally absorb essentially no light in the visible region (wavelength 400-800 nm), and in certain cases some of them generally absorb no light in the UV region (wavelength 100-400 nm), but they disperse incident radiation in this region as completely as possible.

[0070] The pigment (P) is selected from the group consisting of titanium dioxide (TiO.sub.2), zinc disulfide (ZnS.sub.2), zinc oxide (ZnO) and barium sulfate (BaSO.sub.4).

[0071] According to certain embodiments, the pigment (P) may be titanium dioxide. Suitable titanium dioxide pigments can be supplied from a variety of commercial sources, including notably Chemours, ISK, and the like. The nature of the titanium dioxide pigment is not particularly limited, and a variety of crystalline forms such as the anatase form, the rutile form and the monoclinic type can be advantageously used. However, the rutile form is generally preferred due its higher refraction index and its superior light stability. Titanium dioxide pigment may be treated on its surface with at least one treatment agent, even if embodiments wherein titanium dioxide pigments have no surface treatment are also suitable. Preferably the APS of the titanium dioxide pigment is in the range of 0.05 m to 0.40 m.

[0072] Barium sulfate (BaSO.sub.4) is particularly preferred when the composition is intended for use in UV LED, with emitting wavelengths between 100-410 nm, whereas TiO.sub.2 cannot be used, because of its absorption. Hence, in preferred composition intended for UV-LED devices, the pigment (P) is preferably BaSO.sub.4.

[0073] When using BaSO.sub.4 as pigment (P), at least one of the following pre-treatment may be applied to commercially sourced BaSO.sub.4, before incorporation into the composition (C) of the present invention: [0074] washing/rinsing with water, for removal of water-soluble contaminants; and [0075] thermal pre-treatment, e.g. at temperatures of 80 C. or beyond, for instance, under vacuum or in air or under inert gas (e.g. N.sub.2), generally for a suitable time enabling advantageously extensive moisture or contaminants removal.

[0076] The pigment (P) is advantageously present in the composition (C) under the form of particles having an average particle size (APS, expressed as D.sub.50) of generally less than 250 m, preferably less than 100 m, more preferably of less than 5 m. Larger sizes may deleteriously affect the properties of the composition.

[0077] While pigments (P) having larger APS can be used, these pigments (P) are less advantageous, in that they might impair other relevant properties (e.g. mechanical properties) of the composition (C).

[0078] Preferably, the APS of the pigment (P) is of below 5 m. While lower boundaries for APS of pigment (P) are not particularly critical, it is generally understood that pigment (P) will have an APS of at least 0.1 m.

[0079] Average particle size of pigment (P) is generally determined by laser diffraction method, where the average size is determined as D50, i.e. is the diameter of the particle that 50% of a sample's mass is smaller than and 50% of a sample's mass is larger than.

[0080] The shape of the particles of pigment (P) is not particularly limited; the said particles may be notably round, flaky, flat and so on.

[0081] The weight percent of the pigment (P) in the composition (C) is generally of at least 1 wt. %, preferably of at least 3 wt. %, more preferably of at least 5 wt. % and most preferably of at least 6 wt. %, based on the total weight of the composition (C). Besides, the weight percent of the pigment (P) is generally of less than 50 wt. %, preferably of at most 45 wt. %, more preferably of at most 30 wt. %, even more preferably of at most 25 wt. % and most preferably of at most 20 wt. %, based on the total weight of the composition (C).

[0082] Excellent results were obtained when the pigment (P) was used in an amount of 3-35 wt. %, preferably of 5-25 wt. %, based on the total weight of the composition (C).

[0083] PTFE micropowders are well known in the art, and are low molecular weight derivatives of non-melt flowable PTFE polymers, which may be obtained by direct polymerization under conditions that prevent very long polymer chains from forming, or by irradiation degradation of non-melt flowable PTFE polymers. Generally, nevertheless, PTFE micropowders are resulting from irradiation degradation of non-melt flowable PTFE polymers.

[0084] As mentioned above, it is essential for the powder (PTFE) to possess a B.E.T. surface area of exceeding 5.0 m.sup.2/g, preferably of exceeding 6.0 m.sup.2/g, more preferably of exceeding 7.0 m.sup.2/g.

[0085] B.E.T. surface area determination is carried out measuring the volume of nitrogen adsorbed to the surface of the particles at the boiling point of nitrogen (196 C.). The amount of adsorbed nitrogen is correlated to the total surface area of the particles including pores in the surface based on the BET (Brunauer, Emmett and Teller) theory.

[0086] Generally, such high B.E.T. surface area is also accompanied in powder (PTFE) by a bulk density of less than 380, preferably less than 350, more preferably less than 340 g/I, whereas bulk density is measured according to ASTM D 4895 standard, referring back to ASTM D1895.

[0087] From a compositional standpoint, the PTFE micropowder may be a homopolymer of TFE or a copolymer thereof with at least one other fluorine-containing monomer in an amount of not larger than about 1% by weight. Such copolymers are known as modified PTFEs and is distinguished from a melt processable TFE copolymer. As the modifier, copolymerizable monomers including per(halo)fluoroolefins different from TFE, e.g. tetrafluoroethylene, chlorotrifluoroethylene, perfluoroalkylvinylethers, perfluorodioxoles have been used for manufacturing modified PTFE. In general, nevertheless, powder (PTFE) are homopolymers of TFE.

[0088] The powder (PTFE) can also be characterized by high crystallinity, preferably exhibiting a heat of crystallization of at least 50 J/g.

[0089] The powder (PTFE) is advantageously melt flowable. By melt flowable it is meant that the PTFE has a non-zero melt flow rate that is measurable by ASTM D 1238, when measured at 372 C., under a piston load of 10 kg.

[0090] The powder (PTFE) has generally melt flowability such that its melt flow rate (MFR) is of at least 0.01 g/10 min, preferably at least 0.1 g/10 min and more preferably at least 0.5 g/10 min, as measured in accordance with ASTM D 1238, at 372 C., using a 10 kg weight on the molten polymer.

[0091] While the powder (PTFE) has low molecular weight, it nevertheless has sufficient molecular weight to be solid up to high temperatures, e.g. possessing a melting point of at least 300 C., more preferably at least 310, even more preferably, at least 318 C. In a particularly preferred manner, melting point of powder (PTFE) is of at least 328 C., more preferably at least 329 C., when determined according to ASTM D 3418 standard.

[0092] The powder (PTFE) can be obtained from Solvay Specialty Polymers Italy S.p.A. under the trade name of Algoflon L.

[0093] The pigment (PTFE) is advantageously present in the composition (C) under the form of particles having an average particle size (APS, expressed as D50, as detailed above) of generally less than 25 m, preferably less than 15 m, more preferably of less than 10 m, most preferably of less than 7.5 m. Larger sizes may deleteriously affect the properties of the composition.

[0094] Preferably, the APS (D.sub.50) of pigment (PTFE) is of about 5 m or below 5 m. While lower boundaries for APS (D.sub.50) of pigment (PTFE) are not particularly critical, it is generally understood that pigment (PTFE) will have an APS of at least 0.1 m.

[0095] The weight percent of the powder (PTFE) in the composition (C) is generally of at least 1 wt. %, preferably of at least 3 wt. %, more preferably of at least 5 wt. %, based on the total weight of the composition (C). Besides, the weight percent of the powder (PTFE) is generally of at most 18 wt. %, preferably of at most 17 wt. %, more preferably of at most 16 wt. % and most preferably of at most 15 wt. %, based on the total weight of the composition (C).

Optional Ingredients

[0096] The composition (C) can optionally comprise additional components such as stabilizing additive, notably mould release agents, plasticizers, lubricants, thermal stabilizers, light stabilizers and antioxidants etc.

The Article

[0097] An aspect of the present invention also provides an article comprising at least one component comprising the fluoropolymer composition (C), as above detailed, which provides various advantages over prior art parts and articles, in particular an increased resistance to concurrent exposure to heat and radiation (both visible and UV) while maintaining all their other properties at a high level. Preferably, the article or part of the article consists of the composition (C) as above detailed.

[0098] In a particular embodiment, the article is a light emission apparatus.

[0099] Non limitative examples of light emission apparatuses are keyless entry systems of an automobile, lightings in a refrigerator, liquid crystal display apparatuses, automobile front panel lighting apparatuses, desk lamps, headlights, household electrical appliance indicators and outdoor display apparatuses such as traffic signs, and optoelectronic devices comprising at least one semi-conductor chip that emits and/or transmits electromagnetic radiation commonly known as Light Emitting Diodes devices (LEDs). Preferably, the light emission apparatus is a Light Emitting Diode device (LED).

[0100] Depending on the electroluminescence characteristic of the junction diode comprised in the LED device as emitting source, the LED of the invention may notably emit in the visible region or in the UV region.

[0101] LED devices emitting in the visible region typically possess one or more than one junctions emitting at different wavelength in the visible spectral region. Red LED junctions may emit between 620 and 645 nm; red-orange LED junctions may emit between 610 and 620 nm, green LED junction may emit between 520 and 550 nm, cyan LED junctions may emit between 490 and 520 nm, and blue LED junctions may emit between 460 and 490 nm. Any combination thereof may be used to provide for white light; as an alternative, phosphor(s) may be used in combination with single-color LED junctions to convert monochromatic light from a blue or UV LED to broad-spectrum white light, through Stokes shift of the phorphor(s) used.

[0102] LED devices possessing junctions emitting in the UV region may emit Ultraviolet A (or UVA) in the region of 315-400 nm in wavelength, Ultraviolet B (or UVB) in the region of 280-315 nm in wavelength, and Ultraviolet C (or UVC) in the region of 100-280 nm in wavelength.

[0103] LED devices emitting in the UV region are e.g. designed to be used for UV curing applications, for instance in digital print applications and inert UV curing environments, but also for other general purposes curing systems, e.g. in dental fields or even for nail polishes and lacquers; still, UV LEDs (in particular UV-C LEDs) are suitable to be used in disinfection (e.g. for air or aqueous media disinfection) and as line sources to replace deuterium lamps in liquid chromatography instruments; yet, UV-LED may be used as sensors/detectors, e.g. for counterfeit banknotes detection, for verifying identity documents/passports or for controlling other goods against counterfeit.

[0104] Structurally, LEDs are preferably chosen from the group of top view LEDs, side view LEDs and power LEDs. Top view and side view LEDs comprise usually a basic housing, which, in general, acts as reflector; besides, top view and side view LEDs usually do not comprise any heatsink slug. On the other hand, power LEDs comprise usually a heatsink slug, which, in general, acts as reflector; power LEDs usually further comprise a basic housing, which is a part distinct from the heatsink slug.

[0105] The top view LEDs are notably used in automotive lighting applications such as instrumental panel displays, stop lights and turn signals. The side view LEDs are notably used for mobile appliance applications such as, for example, cell phones and PDAs. The power LEDs are notably used in flashlights, automotive day light running lights, signs and as backlight for LCD displays and TVs.

[0106] The LED according to the present invention comprises at least one part comprising the composition (C) as above described. The part is preferably selected from the group consisting of basic housings and heatsink slugs. The part made from the composition (C), as above detailed, is generally intended to act as reflector in a LED device.

[0107] Preferably at least 50 wt. % and more preferably more than 80 wt. % of the part comprises the composition (C), being understood that the part may possibly further contain other materials, e.g. a metal; for example, for certain end uses, the surface of certain parts made from the composition (C), as above detailed, and acting as reflector, may be metal plated. More preferably, more than 90 wt. % of the part comprises the composition (C). Still more preferably, the part consists essentially of the composition (C). The most preferably, the part consists of the composition (C).

[0108] An exemplary embodiment of a top view LED is provided in FIG. 1, which illustrates a sectional view of said embodiment. The top view LED 1 comprises a basic housing 2 comprising, and preferably consisting of, the composition (C) as above detailed. As will be detailed hereafter, the basic housing 2 acts also as reflector cup. No heatsink slug is present. Usually, the LED 1 further comprises a prefabricated electrical lead frame 3. Lead frame 3 can be advantageously encapsulated by injection moulding with the composition (C) included in the basic housing 2.

[0109] The basic housing 2 has a cavity 6. A semiconductor chip 4 that emits electromagnetic radiations, such as a LED chip, is mounted inside such cavity. The semiconductor chip 4 is generally bonded and electrically contact-connected on one of the lead frame terminals by means of a bonding wire 5.

[0110] A transparent or translucent potting compound (e.g. an epoxy, a polycarbonate or a silicone resin, not shown in FIG. 1) is generally built into the cavity in order to protect the LED chip. It is customary, for the purpose of increasing the external efficiency of the LED chip, to shape the cavity of the basic housing with non-perpendicular inner areas in such a way that the cavity acquires a form opening towards the front side (the sectional view of the inner wall of the cavity may have, for instance, the form of an oblique straight line, as in the exemplary embodiment in accordance with FIG. 1, or that of a parabola).

[0111] Thus, the inner walls 7 of the cavity serve as reflector cup for the radiation which is emitted laterally by the semiconductor chip or junction, notably reflecting this radiation towards the front side of the basic housing.

[0112] It is understood that the number of chips or junctions which can be mounted in the cavity of the basic housing, as well as the number of cavities which can be formed inside a basic housing, is not restricted to one.

[0113] An exemplary embodiment of a power LED is provided in FIG. 2, which illustrates a sectional view of said embodiment. The power LED 8 comprises advantageously an aspherical lens 1 and a basic housing 2 comprising, and preferably consisting of, the composition (C), as above detailed. As in the previous embodiment, the LED 8 further comprises a prefabricated electrical lead frame 3.

[0114] The power LED 8 also comprises a carrier body or heatsink slug 9 which may comprise, or consist of, the composition (C) as above detailed. A cavity 6 is realized in the upper portion of the heatsink slug 9. A semiconductor LED chip or junction 4 that emits electromagnetic radiations is mounted on the bottom area of cavity 6 and it is generally fixed by means of a carrier substrate or solder connection 10 to the heatsink slug 9. The solder connection 10 is generally an epoxy resin or another equivalent adhesive material. The LED chip or junction is generally conductively connected to the electric terminals of the lead frame 3 via the bonding wires 5.

[0115] The inner walls 7 of the cavity 6 run generally from the bottom area of the cavity to the front side so as to form a reflector cup increasing the external efficiency of the LED chip. The inner walls 7 of the reflector cup may be, for example, straight and oblique or concavely curved (like in the exemplary embodiment in accordance with FIG. 2).

[0116] The lead frame 3 and the heatsink slug 9 are generally encapsulated within the basic housing 2. In order to protect the LED chip or junction 4, the cavity is generally completely filled, likewise in the first exemplary embodiment of FIG. 1, with a radiation-transmissive, for example transparent, encapsulation compound (the encapsulant is not shown in FIG. 2). The composition (C) as above detailed is particularly suitable for making basic housings and/or heatsink slugs as above described, because, besides having excellent thermal conductivity thus allowing the heat produced by the optoelectronic device to be easily dissipated, it has also good mechanical properties, high heat deflection temperature, good plateability, good adhesion to lead frame, excellent optical properties, notably excellent initial whiteness and high retention of reflectance, even after prolonged exposure to heat and radiation.

Method of Making the Article

[0117] The article as above detailed can be manufactured processing the composition (C) as above detailed through standard techniques, including notably compression molding, extrusion molding, injection molding, or other melt-processing techniques.

[0118] It is nevertheless generally understood that the method of making the article, as above detailed, generally comprises a step of injection molding the composition (C), as detailed above.

[0119] The step of injection moulding generally uses a ram or screw-type plunger to force molten composition (C) into a mould cavity; within the cavity of the said mould, the composition (C) solidifies into a shape that has conformed to the contour of the mould.

[0120] Moulds which can be used can be single cavity moulds or multiple cavities moulds.

[0121] The invention will now be described in more details with reference to the following examples whose purpose is merely illustrative and not intended to limit the scope of the present invention.

EXAMPLES

Raw Materials

[0122] Hyflon SBS91000850P MFA commercial powder grade, having a melting point of about 270 C., and a melt mass-flow rate (MFI) (372 C./5.0 kg) of 8.0 to 18.0 g/10 min [MFA-1, herein below)

[0123] Hyflon polymer based on TFE/PMVE/PPVE terpolymer (about 91.1/8/0.9 moles) having MFI of 500 g/10 min, and melting point of about 240 C. (MFA-2, herein below)

[0124] Barium sulfate EMPROVE ESSENTIAL Ph Eur,BP,USP, available from Merck (BaSO.sub.4, herein below)

[0125] Polymist F.sub.5A PTFE is a PTFE micropowder commercially available from Solvay Specialty Polymers Italy SpA, possessing a B.E.T. surface area of less than 4.0 m.sup.2/g, a D50 of about 4.0 m, a bulk density of about 400 g/I a melting point of about 325 C. and a non-measurable MFI (372 C./10 kg) [-PTFE-1, herein after].

[0126] Algoflon L 2013 PTFE is a PTFE micropowder commercially available from Solvay Specialty Polymers Italy SpA, possessing a B.E.T. surface area of more than 7.5 m.sup.2/g, a D50 of about 5.0 m, a bulk density of about 330 g/I a melting point of about 329 C. and a MFI (372 C./10 kg) of 1.2 g/10 min [-PTFE-2, herein after].

Example 1C (of Comparison)

[0127] The powders of MFA-1 were mixed in a turbo-mixer for 3 with BaSO.sub.4 in a ratio 90/10% w, then the powdered blend was pelletized in a Brabender conical twin screw extruder. The temperature profile was set in order to have a melt temperature in a range between 280 C. and 320 C. depending on the melt viscosity and the melting point of the polymer. Then the pellets underwent melt-compression moulding at 270-320 C. in a vertical press in order to make a plaque with a thickness of about 1.5 mm. The reflectance of the sample was measured on the plaque at room temperature and results were summarized in Table A. MFI was determined on extruded pellets at 372 C. under 5 kg as load.

Example 2C (of Comparison)

[0128] The procedures are the same described in Ex 1 except the ratio between BaSO.sub.4 and MFA-1 was set to 80/20% wt.

Example 3C (of Comparison)

[0129] The powders of MFA-1 were mixed in a turbo-mixer for 3 with BaSO.sub.4 and -PTFE-1 in a ratio 75/20/5% w, then the powdered blend composition was pelletized in a Brabender conical twin screw extruder. Otherwise, same procedure of Ex 1 was followed.

Example 4 (According to the Invention)

[0130] The procedures of compounding preparation and palletisation and compression moulding are the same described in Ex 3C but the formulation was based on MFA-1, BaSO.sub.4 and -PTFE-2 in a ratio 75/25/5% wt.

Example 5 (According to the Invention)

[0131] The procedures of compounding preparation and pelletization and compression moulding are the same described in Ex 4 except the ratio between the ingredients MFA-1, BaSO.sub.4 and -PTFE-2 was 60/30/10% wt.

Example 6C (of Comparison)

[0132] The procedures of compounding preparation and pelletization and compression moulding are the same described in Ex 4 except that no BaSO.sub.4 was used and the ingredients MFA-1 and -PTFE-1 were used in a ratio 90/10% wt.

Example 7C (of Comparison)

[0133] The procedures of compounding preparation and pelletization and compression moulding are the same described in Ex 4 except that no BaSO.sub.4 was used and the ingredients MFA-1 and -PTFE-1 were used in a ratio 90/10% wt.

Example 8C (of Comparison)

[0134] BaSO.sub.4 was treated in oven at 120 C. for 2 hrs under vacuum to have a drier, clearer filler and then compounded with the powders of MFA-2 in a ratio 80/20% wt, and then mixed in a turbomixer for 3. The powders composition was pelletized in a Brabender conical twin screw extruder and the temperature profile was set in order to have a melt temperature in a range between 280 C. and 300 C. depending on the melt viscosity and the melting point of the polymer. Then the pellets underwent melt-compression moulding at 270-320 C. in a vertical press in order to make a plaque with a thickness of about 1.5 mm.

Example 9 (According to the Invention)

[0135] An amount of -PTFE-2 was added to ingredients of Ex. 8C so that the weight ration MFA-2/BaSO.sub.4/-PTFE-2 was set to 70/20/10. Powders were blended in a turbo-mixer for 3 and then pelletized in order to have a melt temperature in a range between 280 C. and 300 C. and then the pellet underwent melt-compression moulding at 300 C. as described above.

Example 10C (of Comparison)

[0136] The procedures of compounding preparation and pelletization and compression moulding are the same described in Ex 8 except that BaSO.sub.4 was used as supplied, without thermal treatment.

Reflectivity Measurements

[0137] In tables below, reflectivity is intended to designate the % ratio of reflected radiant flux over incident radiant flux. A compression molded specimen was inserted in a UV-Vis spectrophotometer (Shimadzu 3600), equipped with halogen and xenon light sources that emit from UV to IR region, and the radiation reflected over the full solid angle was determined by means of an integrating sphere, i.e. a spherical cavity with a diameter of 15 cm, internally coated with a BaSO.sub.4 layer, that absorbs all the impinging radiation via multiple reflections. Measurements were carried out according to ASTM E 903 standard (Standard Test Method for Solar Absorptance, Reflectance, and Transmittance of Materials Using Integrating Spheres).

TABLE-US-00001 TABLE 1 Ingredients MFA-1 BaSO.sub.4 -PTFE-1 -PTFE-2 Run (% wt) (% wt) (% wt) % w Ref. 100 1C 90 10 2C 80 20 3C 75 20 5 4 75 20 5 5 60 30 10 6C 90 10 7C 90 10

TABLE-US-00002 TABLE 2 Reflectivity* MFI** 280 nm 315 nm 380 nm 405 nm Run g/10 % % % % Ref. 12 1C 69.4 69.7 72.4 73.7 2C 10 71.1 72.9 76.6 78 3C 10.4 71.6 71.9 74.5 75.6 4 9.5 76 76 78.8 79.8 5 4.6 79 79.5 82 83.1 6C 34.6 31.9 29 27.6 7C 47.6 41 33 30.4 *measured on compression molded plaques having thickness of 1.5 mm; **MFI measures at 372 C. under a piston load of 5 kg, according to ASTM D 1238 standard.

TABLE-US-00003 TABLE 3 Ingredients MFA-2 BaSO.sub.4 -PTFE-2 Run (% wt) (% wt) () (% wt) 100 8C 80 20 TT 9 70 20 TT 10 10C 80 20 no TT () TT means thermal treatment of BaSO.sub.4 under vacuum for 2 hours at 120 C. before mixing and compounding; no TT means no thermal treatment of BaSO.sub.4 before mixing and compounding.

TABLE-US-00004 TABLE 4 Reflectivity* MFI** 240 nm 280 nm 315 nm 380 nm 405 nm Run g/10 % % % % % 500 80 285 78.9 81.1 81.2 83.7 85.6 9 261 83.5 84.3 83.7 84.8 85.9 10C 74.7 76.7 78 80.6 82.2 (*) measured on compression molded plaques having thickness of 1.5 mm; (**) MFI measures at 372 C. under a piston load of 5 kg, according to ASTM D 1238 standard.

TABLE-US-00005 TABLE 5 Run WI* Stensby** YI*** Ex 2C 72 86 7 Ex 8C 73 88 6 Ex 9 76 89 5

[0138] All colour characteristics determined on compression molded plaques having a thickness of 1.5 mm. *WI: White index determined according to ASTM E313-00 standard, using a D65 illuminant/10 geometry, using K Color View Instrument; **Stensby: Stensby Whiteness Index, determined according to E313-00 standard; ***YI: Yellow index determined according to ASTM E313-00 standard, using a D65 illuminant/10 geometry, using K Color View Instrument