Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H25/00—After-treatment of paper not provided for in groups D21H17/00 - D21H23/00
  • D21H25/04—Physical treatment, e.g. heating, irradiating
  • D21H25/06—Physical treatment, e.g. heating, irradiating of impregnated or coated paper
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
  • D21H21/14—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by function or properties in or on the paper
  • D21H21/18—Reinforcing agents
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
  • D21H27/30—Multi-ply
  • D21H27/40—Multi-ply at least one of the sheets being non-planar, e.g. crêped

Definitions

• This invention relates to the art of papermaking, particularly to treating paper products having additives such as protein, carboxy methyl cellulose, polyvinyl alcohol, latex, milk, or starch with heat and then immediately rewetting the product to improve its properties, including dry and wet stiffness, wet tensile strength and opacity.
• additives such as protein, carboxy methyl cellulose, polyvinyl alcohol, latex, milk, or starch with heat and then immediately rewetting the product to improve its properties, including dry and wet stiffness, wet tensile strength and opacity.
• felted fibers In the art of papermaking, it is customary to subject felted fibers to wet pressing, to consolidate the web, and then to drying on heated rolls.
• wet strength means et tensile strength as measured by American Society for esting and Materials (ASTM) Standard D829-48.
• Folding ndurance is defined as the number of times a board can e folded in two directions without breaking, under conditions pecified in Standard D2176-69.
• Stiffness is defined s flexural rigidity and is determined by the bending moment in g-cm.
• Linerboard as used herein, is a medium-weight paper product used as the facing material in corrugated carton construction. Kraft linerboard_ia linerboard made according to the kraft process, and is well known in the industry. Folding carton board is a medium to heavy weight paper product made of unbleached and/or bleached pulps of basis weights from 40-350 g/m 2 .
• the invention comprises steps of 1) applying one or more additives selected from the group including protein, carboxy methyl cellulose, polyvinyl alcohol, latex, milk or starch to paperboard, 2) heating the paperboard so treated to an internal temperature of at least 400°P (205°C) for a'period of time sufficient to increase the wet strength of the boards and optionally 3) rewetting the board immediately after the heat treatment to at least 11 moisture by weight.
• steps 2 and 3 can be repeated several times.
• Our rewetting treatment differs from conventional conditioning in that we add water, by spraying or otherwise, to a very hot and dry paper or board at the very end of the heat treatment, without intermediate cooling. It is critical that water be applied to the product while it is still hot, certainly above 50°C (122°F), and preferably above 205°C (400°F).
• Another heat treatment or drying step may follow rewetting, on or off the machine, during a subsequent operation such as sizing, coating or calendering.
• the invention can be carried out either on a conventional papermaking machine or off the machine in an oven after a size-press; for high speed production, a papermaking machine is preferred.
• the paper product is first treated by adding to it one or more of the following additives: protein, polyvinyl, alcohol, carboxy methyl cellulose, starch, latex or milk.
• the additive may be mixed with the pulp prior to sheet forming, or it may be added to a formed sheet by spraying or other means. Following wet pressing, the paper product is heat treated.
• the initial water content of the web must be in the range of 1-40% by weight and preferably to within the 10-15% range.
• Sufficient heat is then applied to the board to achieve an internal paper temperature of at least 400°F (205°C).
• the heat can be applied in the form of hot air, superheated steam, heated drying cylinders, infrared heaters, or by other means.
• the invention may be practiced by heating paper product in an oven after a size-press.
• the internal temperature of the board should be brought to at least 400°F for at least 10 sec. Again, the nature of the heat source is not important.
• the paper be immediately rewetted following the heat treating step, and while the paper is still hot.
• Water may be applied by spraying or other means. Even though one effect of the water application is to cool the paper, it is important that the paper not be allowed to cool substantially before the water application.
• the heat treated and rewetted paper is then cooled, conditioned, and calendered according to conventional procedure.
• a commercial.bleached kraft board was sized with different starch protein (casein) mixtures. Both starch and casein solutions had the same concentration of 8% polymer by weight. The size press was adjusted to have a polymer add-on of 2.4% by weight.
• a part of the samples was conventionally dried (C) on Emerson speed drier, model 10 at 230°F (110°C). Another portion of the samples was heat treated (HT) at 400°F (205°C) for 30 seconds and rewetted immediately after heat treated. After conditioning for 48 hours under standard conditions (70°F, 65% relative humidity), the samples were tested for stiffness (Table I).
• Example II Board as in Example I was sized with different starch - whole milk mixtures. Starch and milk concentrations were 8' and 4% by weight respectively. The size press pressure was adjusted to achieve an add-on value of 2.4% by weight. A part of the sized samples was conventionally dried on an Emerson speed drier, model 10 at 230°F (110°C). Another portion of the samples was heat treated at 400°F (205°C) for 30 seconds. All the samples were conditioned for 48 hours under standard conditions. The resultant properties are listed in Table II .
• Example 1 Board as in Example 1 was treated with a 50:50 mixture of starch and acrylic latex (Rohm-Maas Rhoplex HA-16).
• the starch and latex concentrations were 8% and 50% respectively.
• the size press pressure was adjusted to achieve a polymer add-on of 10.5%.
• a portion of the samples was conventionally dried on Emerson.Speed drier, model 10 at 230°F (110°C).
• Another portion of the samples was heat treated at 400°F (250°C) for 30 seconds. All the samples were conditioned for 48 hours under standard conditions.
• the resultant sample properties are listed in Table III.
• Example 4 The same board as in Example 4 was sized and treated as in Example 2. All the samples were conditioned for 48 hours under standard conditions. The resultant board properties are listed in Table V.
• Example 4 The same board as in Example 4 was sized and treated as in Example 3. All the samples were conditioned for 48 hours under standard conditions. The resultant product properties are listed in Table VI.

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• 1986
  • 1986-08-20 EP EP86111506A patent/EP0216145B1/de not_active Expired - Lifetime
  • 1986-08-20 DE DE8686111506T patent/DE3677301D1/de not_active Expired - Lifetime
  • 1986-08-22 BR BR8604012A patent/BR8604012A/pt unknown
  • 1986-08-22 KR KR1019860006956A patent/KR870002330A/ko not_active Withdrawn
  • 1986-08-22 FI FI863422A patent/FI863422L/fi not_active Application Discontinuation
  • 1986-08-22 JP JP61197970A patent/JPS6285097A/ja active Pending

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