Patent GB-874945-A (GB)
Title: Methods for preparing stable aqueous dispersions of cellulose and applications to coating products such as glass products
IPC: C09K23/52
Filed: 1958-01-16
Abstract: Aqueous dispersions of cellulose are produced by hydrolysing either natural or regenerated cellulose in an acid medium to form "level-off D.P. cellulose," and mechanically disintegrating the hydrolysed cellulose in an aqueous medium.  "Level-off D.P. cellulose" is defined as cellulose which has been hydrolysed, e.g. by treatment with a dilute aqueous solution of a highly ionizable mineral acid, preferably a hot aqueous solution of hydrochloric acid, until it has reached a substantially constant "degree of polymerization" or molecular weight.  The hydrolysed cellulose may be mechanically disintegrated in an acid aqueous medium and then washed free from acid, or may be washed free from acid before disintegration in an aqueous medium.  The latter may have a pH from 1-11, and at least 1% of the cellulose may be reduced to not over one micron particle size. In an example, viscose rayon filaments are contacted for about 15 minutes with a 2,5 normal solution of hydrochloric acid, filtered off and washed first with water and then with a 1% aqueous solution of ammonium hydroxide until neutral.  The treated cellulose (which has a levelling off D.P. of about 40) is air-dried and mixed with water to form suspensions containing 5%, 7%, 9% and 10% of cellulose.  The mixtures are subjected to the action of a Waring Blendor for about one hour to disintegrate the cellulose fibres and diluted with water to 1% concentration.  In other examples, cotton linters (level-off D.P. about 200) and alkali cellulose prepared from wood pulp (level-off D.P. about 80) are similarly treated.  Dispersions made according to the invention may be used for coating glass sheets (see Group III) and glass filaments and fibres (see Group IV(c)).  U.S.A. Specification 2,663,989 is referred to.ALSO:Stable aqueous dispersions of "level-off D.P. cellulose" (see Group IV(a)) are used to form an adherent hydrophilic coating on glass filaments and fibres to facilitate their processing on conventional textile equipment and to permit the application of the conventional yarn finishes applied to cotton and regenerated cellulose fibres and filaments.  The particle size of the cellulose dispersions may not exceed about one micron. When dried, a continuous colourless cellulose film is formed on the filaments &c.  In an example, a bundle of continuous glass filaments having a coating of level-off D.P. cellulose is passed through an emulsion made as described in U.S.A.  Specification 2,663,989 and containing by weight, 0,25 part of polyvinyl alcohol, 0,25 part of sodium oleate, 0,2 part of sorbitan monopalmitate, 0,4 part of castor oil modified with about 127 ethylene oxide groups per mole and 85 parts of water, and the filaments are then passed between rubber rollers so as to remove excess emulsion.ALSO:Shaped articles of glass such as glass sheets are provided with adherent films of cellulose by coating them with stable aqueous dispersions or suspensions of "level-off D.P. cellulose" (see Group IV(a)) and allowing the coating to dry.  The dispersion may be a thixotropic gel or a more dilute, e.g. 1%, dispersion.  If the cellulose particles in the dispersion or suspension are relatively large, a frosted appearance is imparted to the glass, but if the particles do not exceed about one micron in size the dried film on the glass is colourless.  Indicia may be applied to the coated glass and although the films are sufficiently adherent not to be removed by scratching with a fingernail, they may be removed by the application of hot water containing a conventional household detergent.