Patent GB-1395447-A (GB)
Title: Absorbent fibrous webs and method for making them
IPC: D21G9/00
Filed: 1973-02-28
Abstract: 1395447 Absorbent paper SCOTT PAPER CO 28 Feb 1973 [30 March 1972] 9860/73 Heading D2B A soft, absorbent, creped fibrous web that has substantial stretch in all directions in its own plane comprises randomly arranged contacting lignocellulosic fibres forming stiff web bonds in some places where they contact, and an elastomeric bonding material uniformly distributed through the web to form flexible web bonds between the fibres, the web having a basis weight of 12 to 60 lbs/2880 ft<SP>2</SP>, and the web having a plurality of areas uniformly distributed throughout the web where the web is partially fractured to reduce inter-fibre bonding. The web is formed by first forming a base web and then mechanically working the base web. The base web is formed in a conventional manner e.g. on a Fourdrinier wire from an aqueous slurry of the lignocellulosic fibres, the aqueous slurry containing the elastomeric bonding material. The aqueous slurry may also contain a wet strength resin, a deposition aid to aid the deposition of the elastomeric bonding material onto the fibres, and a debonding agent to reduce the formation of the stiff web bonds between the fibres. The base web may be creped from the surface of a Yankee dryer at 70 to 80% dryness and further dried to more than 90% dryness on a transpiration dryer. The amount of stretch induced by the creping is preferably 18 to 28% but may be 17.1% (example 11). The base web is then mechanically worked by passing it through a pair of embossing rolls (Figure 1, not shown) to produce raised areas 16, depressions 17 and intermediate mechanical worked areas 18, 19. At areas 19, the web may fracture to produce elongated apertures 20. For producing paper towels, the knuckles on the embossing rollers may be 0.05 to 0.1 inches long and 0.024 to 0.04 inches wide, may interleaf a distance of 0.02 inches to 0.06 inches, and may be concentrated at 70 to 300 per square inch, so as to produce apertures 20 of length 0.01 to 0.10 inches. In the examples, the embossed webs produced have machine direction stretches ranging from 11.5 to 18.2% and cross direction stretches ranging from 18.5 to 24.5%. Other physical properties of the webs are listed in the examples. The wood pulp used may comprise 30% bleached Northern Kraft Spruce 40% bleached Southern hardwood and 30% bleached Western sulphite softwood. The elastomeric bonding material preferably forms 3 to 25%. of the dry weight of the web. Suitable elastomeric bonding materials are butadiene-acrylonitrile, acrylic, acrylic copolymers, vinyl chlorideacrylic, acrylic vinyl acetate, butadiene-styrene, carboxylated butadiene styrene, and ethylene vinyl acetate. Polymers such as polyvinyl alcohol or carboxy-methyl-cellulose may also be used with plasticizers added. The wet strength resin may form 0.5 to 2.0% of the dry web weight, and may be urea formaldehyde, melamine formaldehyde, or a mixture thereof. The deposition aid may form 0.1 to 3% of the dry weight of the fibres and may be a vinyl imidazoline polymer, a polyquaternary ammonium compound or a cationic, quaternized imidazoline polymer. The debonding agent may form 0.5 to 2.0% of the dry web weight, and may be a polymeric cationic quaternary ammonium compound such as an imidazolium compound, a quaternised imidazoline, dihydrogenated tallow dimethyl ammonium chloride or dialkylamide diethyl ammonium sulphate, sodium tetradecyl sulphate or the sodium salt of sulphated nonyl phenoxy poly (ethylene oxy) ethanol.