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
  • 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
  • D21H21/16—Sizing or water-repelling 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
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/20—Macromolecular organic compounds
  • D21H17/21—Macromolecular organic compounds of natural origin; Derivatives thereof
  • D21H17/24—Polysaccharides
  • D21H17/28—Starch
• • 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
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/20—Macromolecular organic compounds
  • D21H17/21—Macromolecular organic compounds of natural origin; Derivatives thereof
  • D21H17/24—Polysaccharides
  • D21H17/28—Starch
  • D21H17/29—Starch cationic
• • 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
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/20—Macromolecular organic compounds
  • D21H17/33—Synthetic macromolecular compounds
  • D21H17/46—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H17/54—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen
• • 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
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/20—Macromolecular organic compounds
  • D21H17/33—Synthetic macromolecular compounds
  • D21H17/46—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H17/54—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen
  • D21H17/55—Polyamides; Polyaminoamides; Polyester-amides
• • 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
  • D21H19/00—Coated paper; Coating material
  • D21H19/36—Coatings with pigments
  • D21H19/44—Coatings with pigments characterised by the other ingredients, e.g. the binder or dispersing agent
  • D21H19/54—Starch
• • 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
  • D21H19/00—Coated paper; Coating material
  • D21H19/80—Paper comprising more than one coating
  • D21H19/84—Paper comprising more than one coating on both sides of the substrate
• • 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
  • D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
  • D21H23/02—Processes or apparatus for adding material to the pulp or to the paper characterised by the manner in which substances are added
  • D21H23/22—Addition to the formed paper
  • D21H23/24—Addition to the formed paper during paper manufacture
  • D21H23/26—Addition to the formed paper during paper manufacture by selecting point of addition or moisture content of the 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
  • D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
  • D21H23/02—Processes or apparatus for adding material to the pulp or to the paper characterised by the manner in which substances are added
  • D21H23/22—Addition to the formed paper
  • D21H23/32—Addition to the formed paper by contacting paper with an excess of material, e.g. from a reservoir or in a manner necessitating removal of applied excess material from the paper
  • D21H23/42—Paper being at least partly surrounded by the material on both sides
• • 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
  • D21H27/10—Packing paper

Definitions

• the present disclosure relates to the field of paper-based materials to be used in applications requiring barrier properties.
• An objective of the present disclosure is to provide a non-brittle fluorochemical-free paper that provides a grease barrier and/or enables formation of an efficient barrier coating thereon.
• the present disclosure provides a method of producing an impregnated paper, comprising the steps of:
• the present disclosure provides a method of producing an impregnated paper.
• the paper produced by this method obtains its beneficial properties without the addition of fluorochemicals.
• the impregnated paper of the present disclosure is preferably fluorochemical-free.
• the method comprising the steps of:
• step c the paper web was not impregnated to the same extent, which resulted in a more brittle paper product that broke during wind-up.
• a dry matter content of the water-based composition outside the range of 8-18 % results in less efficient impregnation.
• the dry matter content of the water-based composition is 10-15 %.
• a film press is used for the impregnation of the paper web in step c).
• the impregnated paper is an impregnated machine glazed (MG) paper.
• the Bendtsen surface roughness (measured according to ISO 8791-2:2013) of the glazed side of the impregnated paper is preferably below 200 ml/min, such as below 150 ml/min, such as below 120 ml/min.
• the lower limit for the Bendtsen surface roughness (ISO 8791-2:2013) of the glazed side may for example be 50 ml/min.
• the glazed side of an MG paper is particularly suitable for printing also without a pigmented coating thereon.
• the impregnated paper is an impregnated MG paper and the glazed side thereof is not pigment-coated, but printed.
• the non-glazed side may be provided with a barrier coating.
• the impregnated paper of this embodiment is preferably used for at least one wall of a package, wherein the glazed (and printed) side is facing outwards and the non-glazed (and barrier-coated) side is facing inwards.
• the furnish preferably comprises a mixture of hardwood fibres and softwood fibres.
• the dry weight ratio of hardwood fibers to softwood fibers is between 1:1 and 1:3.
• the dry weight ratio of hardwood fibers to softwood fibers is between 1:1.2 and 1:2.0, such as between 1:1.3 and 1:1.8.
• Such a relatively high proportion of softwood fibres is particularly preferred when the impregnated paper has an ash content of at least 3%, such as at least 5%.
• the starch of the water-based composition preferably comprises oxidized starch or dextrin, such as maltodextrin.
• water-based composition preferably comprises oxidized starch and dextrin, such as maltodextrin.
• Oxidized starch and/or dextrin may for example constitute at least 50% of the dry weight of the water-based composition, such as at least 75% of the dry weight of the water-based composition. In one embodiment, oxidized starch and dextrin constitute at least 85% of the dry weight of the water-based composition
• the water-based composition further comprises a crosslinker.
• this crosslinker is capable of crosslinking the starch.
• An example of such a crosslinker is a PAE resin.
• the amount of the crosslinker in the water-based composition may for example be 1-9 %, such as 3-7 %, based on the dry weight of starch.
• the dry amount of water-based composition applied in step c) is 0.4-3.0 g/m 2 , such as 0.6-3.0 g/m 2 . If a higher amount is applied, the risk of obtaining a brittle final product is greater (and brittleness may result in breakage during winding or converting). If the applied amount is too low, the oil barrier properties may be insufficient and/or it may be more difficult to form a continuous film on the surface of the paper product.
• the water-based composition is preferably applied to both sides of the paper web having the moisture content of 10-15 % in step c).
• the dry amount of water-based composition applied to each side is preferably 0.4-1.5 g/m 2 , such as 0.6-1.4 g/m 2 .
• the paper web having the moisture content of 10-15 % has a Gurley value when measured according to ISO 536:2019 of at least 75 s, such as at least 80 s, such as at least 85 s.
• the upper limit is typically 150 s. In one embodiment, the upper limit is 120 s. Such an embodiment maybe preferred since papermaking runnability problems may occur between 120 s and 150 s.
• the measurement according to ISO 536:2019 is carried out on a conditioned sample meaning that the moisture content is no longer 10-15 % when the Gurley value is determined.
• the above-mentioned Gurley values may be achieved by relatively extensive refining of the fibres prior to step a).
• the method of the present disclosure typically further comprises the step of drying the impregnated paper web from step c) to obtain the impregnated paper.
• the impregnation step typically results in a paper of very high air resistance, which reflects high resistance to oil breakthrough and/or low absorption of a barrier coating composition applied thereon.
• the impregnated paper preferably has a Gurley value (measured according to ISO 5636-5:2013) of at least 400 s, such as at least 500 s.
• the Bendtsen porosity (measured according to ISO 5636-3:2013) of the impregnated paper may for example be in the range of 10-50 ml/min.
• the basis weight of the impregnated paper may be 30-65 g/m 2 , such as 35-60 g/m 2 , preferably 35-55 g/m 2 . Higher basis weights are not needed (neither economically motivated) for the intended application. In the present application, basis weight is measured according to ISO 536:2019.
• the ash content of the impregnated paper is 3-9 %, such as 5-9 %, such as 5-8 %.
• a relatively high ash content is the consequence of addition of clay.
• the higher ash contents i.e. 5-9 %) are particularly preferred in case of lower grammages (i.e. 35-45 g/m 2 , such as 35-40 g/m 2 ).
• a reason for adding clay may be to increase opacity.
• clay reduces strength, which impairs runnability.
• Softwood pulp and cationic starch is typically included in the furnish to compensate for this strength reduction.
• the opacity of the impregnated paper is at least 47%, such as at least 53%.
• opacity is measured according to ISO 2471:2008. Strength values are discussed below.
• the burst strength of the impregnated paper is at least 100 kPa and/or the burst strength index is at least 3.3 kN/g, such as 3.3-5.0 kN/g.
• the burst strength is measured according to ISO 2758:2014.
• the tear strength in the machine direction (MD) of the impregnated paper is at least 150 mN and/or the tear strength index in the MD of the impregnated paper is at least 4.0 mNm 2 /g, such as 4.0-6.5 mNm 2 /g.
• the tear strength in the cross direction (CD) of the impregnated paper is at least 155 mN and/or the tear strength index in the CD of the impregnated paper is at least 4.3 mNm 2 /g, such as 4.3-6.8 mNm 2 /g.
• tear strength is measured according to ISO 1974:2012.
• At least one side of the impregnated paper has a Cobb 60 s value of less than 20 g/m 2 , such as less than 19 g/m 2 , such as less than 18.5 g/m 2 .
• both sides of the impregnated paper have a Cobb 60 s value below 21 g/m 2 , such as below 20 g/m 2 .
• the Cobb 60 s value is measured according to ISO 535:2014.
• the Bendtsen surface roughness (ISO 8791-2:2013) of a side of the impregnated paper is in the range of 200-500 ml/min. In case of an MG paper, this side is typically the non-glazed side.
• the tensile strength in the MD of the impregnated paper is preferably above 3.5 kN/m. Further, the tensile index in the MD of the impregnated paper is preferably in the range of 90-145 Nm/g.
• the tensile strength in the CD of the impregnated paper is preferably above 1.8 kN/m. Further, the tensile index in the CD of the impregnated paper is preferably in the range of 50-100 Nm/g, such as 50-85 Nm/g.
• tensile strength is measured according to ISO 1924-3:2005.
• the palm kernel oil breakthrough (measured according to ISO 16532-1) of at least one side of the impregnated paper is above 15 min, preferably above 18 min, such as above 20 min.
• the palm kernel oil breakthrough (measured according to ISO 16532-1) of both sides of the impregnated paper is above 15 min, preferably above 18 min, such as above 20 min.
• a furnish comprising softwood kraft fibres and hardwood kraft fibres in a 60:40 dry weight ratio was provided.
• the furnish contained clay in such an amount that the final ash content of the paper was 6.8%.
• the furnish contained 3.7 kg/tonne dry fibre of cationic starch, 2.5 kg/tonne dry fibre of rosin size and retention polymer.
• NaOH and alum was added to adjust the pH to 5.6.
• the furnish was refined to such an extent that the paper (before impregnation) had a Gurley value of 87 s.
• An MG paper was formed from the furnish on a full-scale paper machine equipped with a Yankee cylinder.
• the degree of drying was such that the paper web leaving the Yankee cylinder had a moisture content of 12%.
• This paper web having a moisture content of 12% was impregnated on both sides in a (full-scale) film press.
• the upper side of the paper web was impregnated with a first water-based composition comprising:
• the wire side (glazed side) of the paper web was impregnated with a second water-based composition comprising:
• the applied dry amount of the first water-based composition was 0.96 g/m 2 .
• the applied dry amount of the second water-based composition was 0.86 g/m 2 .
• the impregnated paper was then dried such that it had 6.2% moisture when rolled up.
• the basis weight at roll-up was 38 g/m 2 . Further properties are provided in table 1 below.
• Bags was formed from the paper of table 1. In the bags, the upper side was facing inwards. Freshly fried hash browns were placed in the bags. After containing the hash browns, the paper of the bags was evaluated and found to have a satisfactory grease barrier, comparatively low sogginess and no tack issues.
• the upper side of the impregnated paper is intended to be provided with a barrier coating, e.g. in an off-line coating operation, it may be preferred to omit the wax from the first water-based composition since it may otherwise be difficult to wet and hence efficiently coat the upper side with a water-based barrier coating composition.
• the wire side (glazed side) of the impregnated paper has low surface roughness and is thus particularly suitable for printing.

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Citations (7)

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• 2022
  • 2022-02-28 EP EP22159305.6A patent/EP4234810B1/de active Active
  • 2022-02-28 FI FIEP22159305.6T patent/FI4234810T3/fi active
  • 2022-04-08 EP EP22167403.9A patent/EP4234811A1/de active Pending
• 2023
  • 2023-02-23 WO PCT/EP2023/054574 patent/WO2023161351A1/en unknown

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