Patent GB-1405701-A (GB)
Title: Thermochromic materials
IPC: C08K9/10
Filed: 1973-09-13
Abstract: 1405701 Thermochromic polymer compositions PILOT INK CO Ltd 13 Sept 1973 43176/73 Headings C3B C3F C3P and C3R [Also in Divisions C4-C5 and B6] Polymers, polymer-based and cellulose-based compositions can be compounded with a thermochromic material comprising (A) at least one electron-donating chromatic organic compound selected from fluoran leuco compounds, triphenylmethane phthalide leuco compounds and lactam leuco compounds, (B) at least one compound having a phenolic hydroxyl group, and (C) at least one alcohol, ester, ketone or ether. The material will undergo reversible metachromatism in the range -100‹ to 200‹ C., the temperature of metachromatism being controlled by selection of (C), the colour being due to (A) and the phenomenon of metachromatism being initiated by (B). Compound (A) may be a diaryl phthalide, polyaryl carbinol, leuco-, acyl-, or aryl-auramine, Rhodamine B lactam, indoline, spiropyrane or fluoran. Compound (B) may be a phenol-formaldehyde resin, or a non- polymeric phenolic compound. The thermochromic material may be formulated into thermochromic polymers, inks, writing instruments, paints or sheets. In one embodiment the thermochromic material is microencapsulated (Examples 63-73), e.g. in polyurethane, polyepoxide, polyester, styrene-divinyl benzene copolymer, aminoplast, or gelatine/gum/formalin and it may then be mixed with microcapsules containing different thermochromic compositions to obtain a composition which gives rise to multiple colour changes. Thermochromic polymers.-The thermochromic material may be incorporated in a polymer in an amount 0À1-40% by wt. of the resulting composition, which may be a block, film, filaments, fine particles, elastomer or liquid. Examples 74-82 disclose thermochromic polymers as follows: 74, 78, polyethylene ; 75, polypropylene; 76, polystyrene; 77, a hydrocarbon resin; 79, polymethyl methacrylate; 80, a polyurethane; 81, an epoxy resin; 82, an unsaturated polyester. Thermochromic polymer-based compositions (1) Inks.-Example 85 is a gravure ink containing a hydrogenated hydrocarbon resin, toluene and methyl-i-butylketone; Example 94 is a ball-pen ink containing a terpene resin, triaryl-dimethane isomers and dioctyl phthalate. (2) Writing instruments.-Example 92 is a pencil lead containing polyethylene, and glass beads; Example 97 is a tube colour containing aqueous polyvinyl alcohol, and polyvinyl acetate emulsion. (3) Paints.-Examples 99-107 disclose thermochromic paints containing the following polymers and, in most cases, conventional solvents: 99, polyethylene + ethylene-vinyl acetate copolymer; 100, polyethylene + terpene resin; 101, terpene resin; 102, chlorinated rubber; 103, maleic anhydride-styrene copolymer; 104, polyvinyl acetate emulsion; 105, rosinmodified maleic resin; 106, an epoxy resin; 107, vinyl chloride-vinyl acetate copolymer; 108 and 109 are polyethylene and polypropylene powder paints. (4) Sheets.-Examples 110-117 disclose the preparation of thermochromic sheets, a first thermochromic layer comprising various polymer-based coatings, and in some cases a second protective polymer layer being superposed thereon. Thermochromic cellulose-based compositions Examples 88, 89 disclose inks; 88 contains aqueous methyl cellulose, and vinyl acetate emulsion; 89 contains ethyl cellulose in xylol and n-butyl acetate. Examples 110, 112 disclose sheets; 110 is a paper sheet coated first with aqueous methyl cellulose and vinyl acetate emulsion (and the thermochromic material), and then with a polyethylene film; 112 is a glass sheet coated first with ethyl cellulose in xylol and n-butyl acetate, and then with polyvinyl butyral.