Title of Invention

A COMPOSITION FOR PRODUCTION OF HEAT SENSITIVE PAPER

Abstract

This invention relates to a composition for the production of heat sensitive paper which comprises Leuco-dye derivative 30-65 parts by weight, bisphenol A250-550 parts by weight, stearamide 70-125 parts by weight, Octadecanamide 50-100 parts by weight, polyvinyl alcohol 50-100 parts by weight, 4-benzyloxy phenol 15-30 parts by weight, copisil clay 25-100 parts by weight, magnesium stearate 70-150 parts by weight, hydroxy ethyl cellulose 25-60 parts by weight and water 2000-2500 parts by weight.

Full Text

This invention relates to a composition for the production of heat sensitive paper. The paper thus prepared is useful in thermorecording machines, more particularly, the invention relates to a process for production of heat sensitive recording paper for use in electrofax machines and computers. The advent of new communication systems and automation in office management, have necessitated the use of many sophisticated instruments, most of which are used either for storage or dissemination of informations. In these instruments, specialised papers, some of which are heat and pressure sensitive, are used for recording informations. Heat sensitive papers have been devised to form a coloured recorded image through heating elements like record head of an instrument. The recording papers used in computers and electrofax machines are very sensitive and the image development takes place within fraction of a second. The coating compositions for making such papers are, therefore, specially formulated, which develop sharp image on the paper surface in contact with the heat source or recording head of such instruments. The use of a heat sensitive material comprising a base paper, having colour developer composition coated into it, is known for a long time. Generally, in all the known thermosensitive papers, the recording on paper is produced by contact of the thermal head of the particular instrument on the sensitive surface of the coated paper. Numerous patent literatures are available on the process for manufacture of heat sensitive papers of different sensitivities. For example, the US Patent 4,251,593 describes a process for producing heat sensitive recording sheet, which comprises a support and a heat sensitive layer formed thereon, consisting of mixtures of solutions A1 B1 C1 D1 and E1 in which solution A1 contains leucodye derivatives in aqueous polyvinyl alcohol, solution B1 - a dispersion of 2 - 2 bis (p-hydroxy phenyl) propane in 5% aqueous polyvinyl alcohol, solution C1 - a condensate of stearic acid amide and formaldehyde in methyl cellulose solution, solution D1 -carnauba wax in aqueous methyl cellulose, while solution E1 contains dispersion of talc in aqueous methyl cellulose. These solutions are mixed together in the proportions A1 : B1 : C1 : D1 : E1 = 1:2:3:4:2 and extra adhesive solution is added for proper binding on the substract. The US Patent 4,247,595 describes a thermographic recording material comprising a support and a thermosensitive colour developer layer and liquids A, B, C, and D are made, wherein liquid A contains leucodye in aqueous polyvinyl alcohol, liquid B -bisphenol A in 10'/. aqueous polyvinyl alcohol, liquid C -kaolin in 5'/. aqueous methyl cellulose, while liquid D contains montan wax modifications in 5'/. aqueous methyl cellulose. The liquids are mixed in definite proportions and 2 then coated on paper to a dry coating weight of 5-6 g/m . Again US Patent 4,644,375 describes a heat sensitive recording sheet in which the heat sensitive colour forming layer comprises a colourless basic dyestuff and an organic developer as the essential ingradients. Here again, solution A contains dye dispersions in 10% aqueous polyvinyl alcohol, solution B - dye developer like 4-isopropoxy-4'-hydroxy diphenyl sulfone in 10% aqueous polyvinyl alcohol, while solution C - contains sensitizer like p - benzyl biphenyl in aqueous polyvinyl alcohol solution. These solutions are mixed together in the proportions, A : B : C = 1 : 4 ; 1.2, and then coated on paper surface to obtain thermosensitive paper. Indian Patent Application No. 1130/DEL/88 describes a process for preparing heat sensitive recording paper, which comprises leuco-dye derivatives, bisphenol A, talcum powder, carnauba wax powder, stearamide, and aqueous solutions of polyvinyl alcohol and methyl cellulose, in which solution A contains reactive dye, talcum powder, carnauba wax powder, methyl cellulose in aqueous medium, while solution B contains bisphenol A, stearamide and polyvinyl alcohol in aqueous medium. Solutions A and B are mixed together in the proportion, AsB = 1:1 and then coated on paper surface to produce heat sensitive paper. The Japanese Patent 225,097 also describes a heat sensitive paper produced by coating with a dispersed mixture of a leucodye such as 2-ani1ino-3-chloro-6-diethyl aminofluorane, a developer such as bisphenol A, a di-aryloxy alkane derivative such as 1,2 diphenoxy ethane as thermoplastic chemical and a binder such as polyvinyl alcohol in water. Again, Japanese Patent 176, 192, describes a heat sensitive paper, which is formed by coating with a composition consisting of a leucodye, a developer such as benzyl 4-hydroxy benzoate, a thermoD1astic chemical such as 1,2-bis (3-methyl phenoxy)ethane, a filler such as calcium carbonate, a bjnder such as methyl cellulose, an antisticking agent such as zinc stearate and also starch in aqueous medium. Japanese Patent 61,585 also describes a heat sensitive paper, which is formed by coating the paper surface with a dispersed mixture of a leuco-dye, a developer such as bisphenol A. a thermoplastic chemical such as 2-ben7ylo*y naphthalene, a filler such as calcium carbonate and a binder such as polyvinyl alcohol in water. In many of the above cited known processes, the heat sensitive paper formed, can be used for recording in sophisticated instruments like Gas chromatograobs. GPC and GLC equipments, but at the same time cannot be used for recording in an electrofa* machine as the coated surface is not sufficiently sensitive to heat generated in a fax machine. Secondly the surface of the coated paper should be extremely uniform and glossy to produce sharp reproduction of the object materials sent from distant placer? through fa* services. At the same time, the paper produced be also suitable for use in other type of sophisticated recording equipments like GPC, HPLC and GLC etc. having computing integrators. Therefore, the main objective of the present invention is to provide an improved process for production of a highly heat sensitive thermal paper devoid of the said drawbacks, preferably for use in electrofax recording machine. Another objective of the present invention is to provide a composition for the production of heat sensitive paper which will produce dark image within very short period of time,on exposure to heat source. Yet another objective of the present invention is to provide a composition for the production of heat sensitive paper exhibiting highly smooth, uniform and bright coated surface to produce intensely dark images. Still yet another objective of the present invention is to provide a composition for the production of heat sensitive paper, sensitive to heat and UV light radiations, thereby forming coloured images on the coated surface, with excellent image density and stability. Still another objective of the present invention is to provide a composition for the production of heat sensitive paper, in which 4-benzyloxy phenol is used as thermo-chromic sensitizer. Still another objective of the present invention is to provide a composition for the production of heat sensi- tive paper, particularly for use in electrofax recording machine, in which a commercially available reactive clay, particularly copisil clay is used, thereby, providing excellent image formation on the coated surface on minimal time of exposure of the paper to light and heat sources. Accordingly, the present invention provides a composition for the production of heat sensitive paper which comprises Leuco-dye derivative 30-65 parts by weight, bisphenol A 250-550 parts by weight, stearamide 70-125 parts by weight, Octadecanamide 50-100 parts by weight, polyvinyl alcohol 50-100 parts by weight, 4-benzy-loxy phenol 15- 30 parts by weight, copisil clay 25-100 parts by weight, magnesium stearate 70- 150 parts by weight, hydroxy ethyl cellulose 25-60 parts by weight and water 2000-2500 parts by weight. Accordingly, the present invention also provides heat sensitive recording paper using coating composi tion for producing heat sensitive paper as detailed above, preferably for use in electrofax recording machine, wherein the coating compositions developed are not mere admixtures of the components resulting in a product having the aggregate properties of the components and is not a product of chemical reaction. The resulting product provides a heat sensitive recording with ther moplastic and antisticking characteristics because of the presence of thermoplastic chemical like octadecanamide and antisticking agent like magnesium stearate, thereby providing a soft and glossy surface to the coated paper. The above mentioned compositions are prepared and coated on the surface of a paper in 3 coating machine, 2 wherein, a coating weight of 6-8 g/m is applied on the paper. The coated paper thus produced is then lightly calendered in a supercalendsr to impart high gloss and smoothness to the coated surface. The following examples are given to illustrate the invention. The examples, should not, however, be construed to limit the scope of the invention. EXAMPLE I PREPARATION OF LIQUID (A) Pergascript Black I BR or - 50 parts React Schwarz SF 7968 Stearamide - 85 parts Hydroxy Ethyl Cellulose - 40 parts Magnesium Stearate - 120 parts Water - 2000 parts I is a colourless leuco-dye derivative manufactured by Ciba-Geigy, Switzerland. II is a colourless leuco-dye derivative manufactured by BASF, Germany. Hydroxy ethyl cellulose (40 parts) is dissolved in a part of water (500 parts) by mild heating and agitation. When the solution is ready, it is allowed to cool to room temperature and then fed into a stainless steel ball mi 11/attritor mill. Either of the dyes (50 parts), stearamide (85 parts) and magnesium stearate (120 parts) are introduced into the mill. Rest of the water (1500 parts) are then added to the ball mi11/attritor mill. The milling is done for sufficient period to get a smooth and uniform paste. This solution is kept ready for use. Unless otherwise mentioned, the parts of solid are taken by weight and the water by volume. PREPARATION OF LIQUID (B) Bisphenol A - 500 parts Polyvinyl alcohol - 75 parts Copisil clay - 50 parts 4-benzyloxy phenol - 25 parts Water - 2500 parts III a reactive clay produced by Sud Chemie A G, Munchen, Germany. Polyvinyl alcohol (75 parts) is dissolved in a part of water (1000 parts) by mild heating. When completely dissolved, put into a ball mi11/attri tor mill. Rest of the chemicals e.g. bisphenol A (500 parts), stearamide (125 parts), copisil clay (50 parts), 4-benzyloxy phenol (25 parts) are added to the mill. The remaining water (1500 parts) is then added and the contents are milled for sufficiently long period to get a smooth and uniform paste. The liquid (A) is maintained at 3 solid content of approximately 15 percent, while in liquid (B), the solid content is maintained between 30-32 percent. Now, liquids (A) and (B) are mixed together in equal proportions by mild agitation and the mixture is used for coating on paper surface in a coating machine, wherein, a dry 2 coating weight of 6-8 g/m is applied on the paper. The coated paper on drying and supercalendering produces heat sensitive recording paper with bright and glossy surface for use in recording instruments, preferably in fax recording machine. The heat sensitive paper, as per the above formulation will produce dark grey prints on imaging. EXAMPLE II PREPARATION OF LIQUID (A) Dye derivative - 55 parts Octadecanamide - 65 parts Hydroxy Ethyl Cellulose 40 parts Magnesium stearate - 120 parts Water - 2000 parts The dye derivative is selected from one of the two as mentioned in Example I. Hydroxy ethyl cellulose is dissolved in a part of water as in Example I. The other components of the composition are put into a bal 1/attri tor mill along with this solution and rest of the water is then added. The mixture is milled for a sufficiently long time to get a smooth and uniform paste. The liquid is kept ready for use. PREPARATION OF LIQUID (B) Bisphenol A - 450 parts Polyvinyl Alcohol - 70 parts Talc - 50 parts Copisil clay - 75 parts Stearamide - 120 parts 4-benzyloxy phenol - 25 parts Water - 2500 parts The procedure for preparation of liquid (B) is same as in Examp1e I. The mixing of liquid (A) and (B) is done as in Example I and applied on paper surface as described in Example I. EXAMPLE III PREPARATION OF LIQUID (A) Dye-derivative - 50 parts Octadecanamide - 60 parts Hydroxy ethyl cellulose 40 parts Magnesium stearate - 120 parts Water - 2000 parts The dye-derivative is selected from Example I. The procedure for preparatoion of solution is same as in Example I. PREPARATION OF LIQUID (B) Bisphenol A - 400 parts Copisil clay - 100 parts Polyvinyl Alcohol - 75 parts Stearamide - 12 0 parts 4-benzyloxy phenol - 2 5 parts Water - 2500 parts Polyvinyl alcohol is dissolved in a part of water as in Example I. The other components of the composition are put into a ball mill or attritor mill along with this solution and rest of the water is added. The mixture is milled for sufficiently long time to get a smooth and uniform paste. The liquids (A) and (B) are mixed in 1:1 proportion by mild agitation. The mixed liuqid is then coated on paper surface. The main advantages and the distinguishing features of the present invention are : 1. The coated paper obtained by the present invention produces dark and clear image of the object materials, when received on a fax system. 2. The coated paper as obtained by the present invention exhibits a soft, glossy and smooth surface on supercalendering and the image development takes place with minimal exposure to light or heat source. 3. The combinations of slip agent like magnesium stearate and thermoplastic chemical like ocatadecana-mide in presence of thermochromic sensitizer like 4-benzyloxy phenol make the product suitable for use in recording instruments where heat exposure time is very short, preferably in electrofax recorders and equipments with computing integrators. WE CLAIM : 1. A composition for the production of heat sensitive paper which comprises Leuco-dye derivative 30-65 parts by weight, bisphenol A 250-550 parts by weight, stearamide 70-125 parts by weight, Octadecana-mide 50-100 parts by weight, polyvinyl alcohol 50-100 parts by weight, 4-benzyloxy phenol 15- 3 0 parts by weight, copisil clay 25-100 parts by weight, magnesium stearate 70- 150 parts by weight, hydroxy ethyl cellulose 25-60 parts by weight and water 2000-2500 parts by weight. 2. A composition as claimed in claim 1 wherein the composition consists of leuco-dye derivatives 50- 55 parts, 4 benzyloxy phenol 25 parts, bisphenol A 400-500 parts, octadecanamide 60 - 65 parts, magnesium stearate 100- 120 parts, copisil clay 50-100 parts, stearamide 85-120 parts, polyvinyl alcohol 70-75 parts, hydroxy ethyl cellulose 40 parts. 3. Heat sensitive recording paper prepared by coating the above said composition on the base paper as claimed in claims 1 and 2 substantially as herein described. 4. A composition of the production of heat, sensitive paper substantially as herein described with reference to the example.

Documents:

438-del-1995-abstract.pdf

438-del-1995-claims.pdf

438-del-1995-correspondence-others.pdf

438-del-1995-correspondence-po.pdf

438-del-1995-description (complete).pdf

438-del-1995-form-1.pdf

438-del-1995-form-2.pdf

438-del-1995-form-4.pdf

438-del-1995-form-6.pdf

438-del-1995-form-9.pdf