US 20150247001A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2015/0247001 A1 Lötzsch et al. (43) Pub. Date: Sep. 3, 2015 (54) THERMOCHROMIC MATERIAL MOLDED (30) Foreign Application Priority Data ARTICLE COMPRISING SAD MATERAL AND USE THEREOF Sep. 24, 2012 (DE) ...................... 10 2012 O18813.7 (71) Applicant: FRAUHOFER-GESELLSCHAFT Publication Classification ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG (51) Int. Cl. E.V., Munich (DE) C08G 63/9. (2006.01) (52) U.S. Cl. (72) Inventors: Detlef Lötzsch, Berlin (DE); Ralf CPC .................................... C08G 63/912 (2013.01) Ruhmann, Berlin (DE); Arno Seeboth, Berlin (DE) (57) ABSTRACT (73) Assignee: FRAUNHOFER-GESELLSCHAFT The invention relates to a thermochromic material compris ZUR FORDERUNG DER ing at least one biopolymer, at least one natural dye and at ANGEWANDTEN FORSCHUNG least one reaction medium, selected from the group of fatty E.V., München (DE) acids and derivatives thereof, gallic acid and derivatives thereOThereof and mim1Xtures thereOT.hereof. TheThe ththermochrom1C hromi materiaial (21) Appl. No.: 14/430,419 according to the invention is completely based on non-toxic, 1-1. natural products. Processing into materials or molded articles (22) PCT Filed: Aug. 8, 2013 can occur, according to the invention, by means of conven tional extrusion technology in the form offlat film, blown film (86). PCT No.: PCT/EP2013/066604 or sheets or multi-wall sheets. The thermochromic material S371 (c)(1), can be used in particular in the food industry and medical (2) Date: Mar. 23, 2015 technology. OH iC O N CH 21 OH C HO O HO Patent Application Publication Sep. 3, 2015 US 2015/0247001 A1 Fig. 1 Fig. 2 US 2015/0247001 A1 Sep. 3, 2015 THERMOCHROMIC MATERIAL MOLDED are imprinted with a paint for use in Sun protection or, corre ARTICLE COMPRISING SAD MATERAL sponding to U.S. Pat. No. 4,121,010, polymers are coated AND USE THEREOF with a thermochromic paint, consisting of Sulphates, Sul 0001. The invention relates to a thermochromic material phides, arsenic, bismuth, Zinc and other materials, and the comprising at least one biopolymer, at least one natural dye oxides thereof. As a result, both the field of use is greatly and also at least one reaction medium, selected from the restricted and, as a result of the required additional coating group offatty acids and the derivatives thereof, gallic acid and (printing technique), a cost-reducing continuous technology the derivatives thereof and also mixtures hereof. The thermo is prevented. chromic material according to the invention is thereby based 0007. In DE 103 39 442 B4 and U.S. Pat. No. 7,662,466 entirely on non-toxic natural products. Processing to form B2, thermochromic flat films which are likewise based on the materials or moulded articles can be effected by means of use of the above-mentioned organic dyes are described. conventional extrusion technology in the form of flat films, 0008. This also applies to the invention described in EP 1 blown films or sheets or multiskinsheets. The thermochromic 157 802. Here, in extrusion-blow moulding, thermochromic material is used in particular in the foodstuff industry and in pigments are added only in partial regions of the wall thick medical technology. ness of a plastic material container. This takes place by the 0002 Thermochromism comprises the property of chang addition of a reversible thermochromic pigment in the form of ing the colour of a material, as a function of the temperature, strip-shaped inlays. The thermochromic pigments require in reversibly or irreversibly. This can be effected both by chang addition additional thermostable pigments and are added or ing the intensity and/or the wavelength maximum. Examples fed to the extrudate before discharge from the extrusion head. and theoretical backgrounds relating to the mechanism of the 0009. To date, thermochromic inks, screen printing inks, temperature-controlled colour are described representatively coatings or films have not been used in sensitive areas, such as in Chromic Phenomena by P. Bamfield and M. I. Hutchings the foodstuff sector or medical technology. An essential rea (The Royal Society of Chemistry, 2010) and in Thermochro son is, categorically, the use of toxic compounds. Also the mic Phenomena in Polymers by A. Seeboth and D. Lötzsch most recent thermochromic dyes with a diazapentalene struc (Smithers Rapra Technology, 2008). ture (G. Qian and Z. Y. Wang, Adv. Mater. 24, 2012, page 0003. Materials in the most varied of material forms, 1582) do not offer an approach to the solution. amongst those also polymer films with thermochromic prop 0010 Starting herefrom, it was the object of the present erties, have been patented in the past in various ways. Irre invention to provide a thermochromic material which can be spective of whether the thermochromic effect is of a revers used in many fields of daily life, e.g. in the foodstuff sphere. ible or irreversible nature, inorganic or organic dyes are used, Likewise, the thermochromic material should be produced the latter also in the form of composites with melting agents Such that further processing by means of extrusion technol and/or developers, it is common to all systems that they ogy is possible. always comprise toxic starting materials in Some form. Stan 0011. This object is achieved by the thermochromic mate dard in this respect is the use of bisphenol as developer almost rial having the features of claim 1 and the extruded moulded in all existing organic thermochromic composites. As dyes, articles having the features of claim 11. In claim 13, uses basic structures of triphenylmethane dyes, pyridinium phenol according to the invention are indicated. The further depen betaines, Sulphophthalein structures, thyranines, azo dyes or dent claims reveal advantageous developments. fluoran dyes are used. 0012. According to the invention, a thermochromic mate 0004 Inorganic thermochromic pigments, the colour rial is provided, which material comprises at least one change of which is based on a temperature-controlled change biopolymer, at least one natural dye and also at least one of modification, are based in general on salts of heavy metals. reaction medium selected from the group of fatty acids and A known example is the use of thermochromic inorganic the derivatives thereof, gallic acid and the derivatives thereof pigments as hotspot warning for pans or as Screenprinting for and also mixtures hereof. All the components contained in the bar codes. Encapsulation of heavy metal salts or organic thermochromic material thereby concern components or thermochromic composites likewise does not offer an alter additives which are permitted for foodstuff, i.e. all the com native here; migration effects cannot be stopped permanently. ponents in the dosages used are not toxic. The generally used melamine resins as case for thermochro 0013 Preferably, all the components of the thermochro mic capsules are definitively unsuitable as protective layer mic material are permitted according to the EU regulation No. and in addition are not suitable for extrusion technology. 1333/2008 and corresponding current appendices for food 0005 Thus, the change of a colour effect, based on a stuff and have an E-number. donor-acceptor system, is described in EP 1084 860, which 0014. It is preferred that, as natural dyes, those with an system can be present also in the form of microcapsules with anthocyanidin structure are used. These are subdivided into a diameter of approx. 50 Lum. In EP 1 323 540 A2, a thermo Sugar-free aglycones and glycosides, both Sub-structures chromic material consisting of three components which is being able to be used. As foodstuff additives, anthocyanidins likewise microencapsulated is described. Lack of light stabil with the E-number 163 are permitted. The colour of antho ity of the thermochromic complexes is intended to be coun cyanidins which is dependent upon the pH value in aqueous teracted, corresponding to U.S. Pat. No. 5,527.385, by addi solution is thereby known, whilst the thermochromic proper tives such as hydrazide-, Sulphur- orphosphorus compounds. ties of anthocyanidins have to date not been known. This implies the addition of further toxic compounds. 00.15 Preferred anthocyanidins are cyanidin, delphinidin, 0006. The production of polymeric thermochromic mate aurantinidin, petunidin, peonidin, malvidin, pelargondin, ros rials with the help of imprinting (laminating) of a thermo inidin, europinidin and luteolinidin. The basic structure is chromic paint is a practical solution for Some requirements illustrated in FIG.1. By varying the radicals R to R (R with and wishes of the packaging industry, where toxicity plays a —H. —OH, - OCH), the properties can be widely varied. subordinate role. Thus according to US 2002037421, glasses The formation of dimers, aggregates/chelates, both amongst US 2015/0247001 A1 Sep. 3, 2015 each other and with the biopolymer or the reaction medium, is Applied Chem. 104, 1990, 1310) or also iv) by cooperation of made possible. If a Sugar radical is introduced in positon R. the above-mentioned three effects i, ii, and iii. The process glycoside structures are attained (FIG. 2). can be designed reversibly or irreversibly. As a function of the 0016. As reaction medium, gallic acid and the derivatives temperature, reorientations on a molecular plane are effected, thereof, in particular gallates, saturated, once unsaturated or bonds are reinforced or loosened and a concentration gradient multiply unsaturated fatty acids and the derivatives thereof, in of the natural dye or of the fatty acid and/or gallate in the particular esters, and also branched carboxylic acids are pre polymer volume are enabled reversibly or irreversibly. Thus, ferred. An essential property feature of carboxylic acids is the interaction between the fatty acid and the anthocyanidin is their self-organisation to form dimers. changed as a function of the temperature whilst, at the same 0017.