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
  • D21H19/00—Coated paper; Coating material
  • D21H19/36—Coatings with pigments
  • D21H19/38—Coatings with pigments characterised by the pigments
  • D21H19/40—Coatings with pigments characterised by the pigments siliceous, e.g. clays
• • 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
  • D21H19/38—Coatings with pigments characterised by the pigments
  • D21H19/42—Coatings with pigments characterised by the pigments at least partly organic
• • 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
  • D21H19/66—Coatings characterised by a special visual effect, e.g. patterned, textured
  • D21H19/70—Coatings characterised by a special visual effect, e.g. patterned, textured with internal voids, e.g. bubble coatings
• • 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
  • D21H19/82—Paper comprising more than one coating superposed
• • 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
  • 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
  • D21H21/50—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 form
  • D21H21/52—Additives of definite length or shape
  • D21H21/54—Additives of definite length or shape being spherical, e.g. microcapsules, beads

Definitions

• This disclosure relates to coated paperboard having good smoothness and printability at low coat weights.
• Paper and paperboard are used for many printing and packaging applications. Paperboard grades are heavier than paper grades, and are typically characterized as having a caliper (thickness) of at least 254 ⁇ (0.010") or 305 ⁇ (0.012"); such calipers are also commonly called 10 point (10 pt) or 12 point (12 pt). It is often desirable for paperboard to have a surface well suited for printing, which may be characterized by various properties including smoothness, gloss, ink receptivity, and other measurements.
• certain inventive coatings are able to provide superior smoothness and printability with a single layer of coating applied at remarkably low coat weight compared with the typical total coat weight of double coating.
• Parker Print Surf smoothness values of 2.5 microns and lower are achieved with a single layer of the inventive coatings having coat weights of 9.8 g/m 2 (6 lbs/3000 ft 2 ) and higher.
• certain inventive base coats are disclosed which may be used with various top coats to achieve superior smoothness and printability.
• FIG. 1 illustrates a method for producing a base stock on a paperboard machine
• FIG. 2 illustrates a method for treating the base stock from FIG. 1 by applying coatings to both sides on a paperboard machine
• FIG. 3 illustrates a method for treating the base stock from FIG. 1 by applying coatings to one side on a paperboard machine
• FIG. 4 illustrates a method for treating the base stock from FIG. 1 by applying coatings to one side on an off-machine coater
• FIG. 5 illustrates the effect of coat weight on Parker PrintSurf (PPS) smoothness for single-coated samples
• FIG. 6 illustrates the effect of various pigments on ink gloss for single-coated samples
• FIG. 7 illustrates the effect of coat weight and LDOP particle size on PPS smoothness for single-coated samples
• FIG. 8 illustrates the effect of LDOP particle size on PPS smoothness for single- coated samples at 13.0 g/m 2 (8 lb/3000ft 2 ) coat weight;
• FIG. 9 illustrates the effect of LDOP particle size on ink gloss for single-coated samples
• FIG. 10 illustrates the effect of coat weight and LDOP concentration on PPS smoothness for single-coated samples
• FIG. 11 illustrates the effect of LDOP concentration on PPS smoothness for single- coated samples at 13.0 g/m 2 (8 lb/3000ft 2 ) coat weight;
• FIG. 12 illustrates the effect of LDOP concentration on ink gloss for single-coated samples
• FIG. 13 illustrates the effect of coat weight and various mineral pigments on PPS smoothness for single-coated samples
• FIG. 14 illustrates the effect of mineral pigments on ink gloss for single-coated samples
• FIG. 15 illustrates the effect of LDOP and their percent on pigment packing void volume
• FIG. 16 shows the effect on percent void volume of blending LDOP with a mineral pigment and a hyperplaty clay
• FIG. 17 shows the effect on percent void volume of blending LDOP with a mineral pigment
• FIG. 18 illustrates the effect of coat weight and LDOP concentration on PPS smoothness for based coated samples
• FIG. 19 illustrates the effect of coat weight and LDOP concentration on Sheffield smoothness for based coated samples.
• FIG. 20 illustrates the effect of LDOP concentration on PPS smoothness of top coated, uncalendered samples.
• FIG.1 and FIG 2 illustrate an exemplary on-paper machine method for coating a paperboard web with one or more layers of aqueous coating.
• a forming wire 110 in the form of an endless belt passes over a breast roll 115 that rotates proximate to a headbox 120.
• the headbox provides a fiber slurry in water with a fairly low consistency (for example, about 0.5% solids) that passes onto the moving forming wire 110.
• a first distance 230 water drains from the slurry and through the forming wire 110, forming a web 300 of wet fibers.
• the slurry during distance 130 may yet have a wet appearance as there is free water on its surface. At some point as drainage continues the free water may disappear from the surface, and over distance 231 , water may continue to drain although the surface appears free from water.
• the web is carried by a transfer felt or press felt through one or more pressing devices such as press rolls 130 that help to further dewatering the web, usually with the application of pressure, vacuum, and sometimes heat.
• the still relatively wet web 300 is dried, for example using dryer or drying sections 401, 402 to produce a dry web ("raw stock") 310 which may then be run through a size press 510 that applies a surface sizing to produce a sized "base stock” 320 which may then be run through additional dryer sections 403 and (on FIG. 2) smoothing steps such as calendar 520.
• the base stock 320 may then be run through one or more coaters.
• coater 530 may apply a first coat ("BC") to a first side ("CI") of the web, and the first coat may be dried in one or more dryer sections 404.
• Coater 540 may apply a second coat ("TC") to the first side of the web, and the second coat may be dried in one or more dryer sections 405.
• coater 550 may apply a first coat to the second side ("C2") of the web, and this coat may be dried in one or more dryer sections 406.
• Coater 560 may apply a second coat to the second side of the web, and this coat may be dried in one or more dryer sections 407.
• the order of coaters 540, 550 may be swapped, so that both sides CI and C2 are first given a first coat, and then one side or both sides are given a second coat. In some instances, only one side will be coated as shown in FIG. 3, or only a first coat may be applied. In some instances, a third coat may be applied to one side.
• coating may be applied by an off-machine coater as shown in Fig. 4.
• the paperboard having been produced on the paper machine and wound onto reel 572 may then be transported (as a reel or as smaller rolls) to an off machine coater 600, where the paperboard is unwound from reel 572, given a first coating by coater 610, dried in dryer(s) 601, given an optional second coating by coater 620, dried in dryer(s) 602, optionally given further treatment (such as gloss calendaring) and then wound onto reel 573.
• An off machine coater could instead apply a single coat to one side of the paperboard, or could apply a single coat to each side, or could apply more than one coat to either or both sides. Alternately some coating may be done on the paper machine, with additional coating done on an off-machine coater.
• FIGs. 2-4 are devices where a coating is held in a pan, transferred by a roll to the lower surface of the web (which may be either the first side or the second side depending on the web path), and then the excess coating scraped off by a blade as the web wraps partially around a backing roll.
• coater types including but not limited to curtain coater, air knife coater, rod coater, film coater, short-dwell coater, spray coater, and metering film size press.
• the particular materials used in the coatings may be selected according to the desired properties of the finished paperboard.
• the coating(s) may provide desired printability, as indicated by various measurements including smoothness, gloss, ink hold out, etc.
• Coated board whether bleached, unbleached or recycled, is conventionally made by applying two layers of coating to the board surface. This is required due to the high level of roughness of the board surface.
• the first coating referred to as a basecoat
• the second coating is typically made from fine pigments, and its purpose is to make a smooth ink receptive surface for printed images.
• the current invention as described in PART I below is a method for producing a quality printing surface using only a single layer of coating.
• the current invention is a method for producing a quality printing surface using a specialized base coat over which a top coat may be applied.
• Two key performance parameters for coated board are smoothness and printability.
• Parker PrintSurf (PPS) smoothness is used as the smoothness test, with 68.9 kPa (10 psi) pressure and a soft backing.
• PPS Parker PrintSurf
• a Prufbau printability tester was used to apply a uniform layer of cyan ink. 15 ⁇ 1 of Prufbau cyan ink to the inking roller for each sample. The printing pressure was 1100 N, and the speed was 2.5 m/sec.
• Print gloss was measured using the standard TAPPI gloss method.
• Paperboard samples were made using solid bleached sulphate (SBS) substrate with a caliper of 267 ⁇ (10.5 pt; 0.0105"). The samples were coated on one side using a pilot blade coater with either one layer or two layers of coating. The pilot results are expected to be representative of results that might be achieved on a production paper machine or a production off-machine coater.
• SBS solid bleached sulphate
• the pigments had a wide range of densities, so the coatings were formulated based on volume percent.
• the inorganic pigments were:
• Hydrocarb 60 - A coarse GCC from Omya
• Hydrocarb 90 - A fine GCC from Omya
• LDOP Low density organic pigments
• LDOP pigments tested here did not include pigments that substantially expand during drying.
• non-expanding pigments is meant that the pigments do not expand more than 10% by volume during drying of the coating.
• Ropaque OP-96 - a low density pigment with a 0.6 ⁇ diameter
• Ropaque AF-1055 - a low density pigment with a ⁇ . ⁇ diameter
• Ropaque AF-1353 - a low density pigment with a 1.3 ⁇ diameter
• Ropaque TH-2000AF - a low density pigment with a 1.5 ⁇ diameter
• the binder used in all coatings was Basanol X497AB, a styrene acrylate latex from BASF.
• the addition level of this latex binder was the same for all coatings, and was 26.4% based on total dry pigment volume.
• the experimental design was based on pigment blends and ratios, so in the following tables, only the pigment portion is presented. All pigments total 100% for each formulation.
• Coating formulations A-P are shown in Table 1.
• a double coated sample was made using approximately (13.0 g/m 2 (8 lb/3000 ft 2 ) of coating A as a basecoat and 9.8 g/m 2 (6 lb/3000 ft 2 ) of coating B as a topcoat.
• the coatings were applied onto solid bleached sulfate paperboard which had an initial (uncoated) basis weight of 167 g/m 2 (103 lb/3000 ft 2 ) and a PPS value of 7.7 ⁇ .
• Coatings were applied at 4.1 m/sec (800 fpm) using a bent blade configuration. For each coating multiple coat weights were applied to the board.
• the samples were single-coated with range of coat weights from approximately 9.8-14.6 g/m 2 (6-9 lb/3000 ft 2 ) being run for each sample.
• Table 2 shows ink gloss data for calendered single-coated samples with coat weights closest to 11.4 g/m 2 (7 lb/3000 ft 2 ). Ink gloss is reported as a percent of the reference standard. Measurements were made using a Glossmeter Model T480A from Technidyne Corporation.
• Table 3 shows PPS smoothness for single-coated samples after they were hot soft roll calendered at 1.5 m/sec (300 fpm), 107°C (225°F) and 21900 N/m (125 pli). PPS
• FIG. 5 shows PPS smoothness results for single-coated samples after calendering.
• a typical basecoat (A) or topcoat (B) formulation (upper portion of the graph) do not sufficiently reduce the surface roughness.
• a coating (C) of hyperplaty clay with coarse carbonate greatly reduced the roughness (lower portion of the graph). Additional improvement was realized with a coating (G) using a LDOP as the co-pigment instead of carbonate.
• FIG. 6 shows that printability (of the single-coated samples after calendering) as measured by ink gloss, is poor (upper three graph bars) for the all-carbonate basecoat (A), clay/carbonate topcoat (B), and improved platy clay/carbonate basecoat formulation (C) compared to the double coated reference (bottom graph bar). Only the combination of platy clay and LDOP (G) gives single-coated ink gloss similar to the double coated reference.
• FIG. 10 shows that PPS smoothness (of single-coated samples after calendaring) improves (roughness decreases) as the addition level increases to about 43%, then the PPS smoothness levels off. This is more clearly evident in FIG. 11 which is graphs the smoothness values of FIG. 10 regressed to a 13.0 g/m 2 (8 lb/3000ft 2 ) coat weight.
• FIG. 12 shows corresponding ink gloss results (on single-coated samples after calendaring) for the same formulations as in FIG. 11. Ink gloss gradually increases as the LDOP level increases until about 36%, but further addition of LDOP does not increase ink gloss.
• FIG. 13 shows the effect on smoothness (on single-coated samples after calendaring) of including other pigments with a formulation including 50 parts (volume) platy clay.
• a formulation upper line
• LDOP improved smoothness (PPS decreased) as seen in the bottom three lines.
• PPS smoothness
• FIG. 14 likewise shows that compared with the reference (upper bar), the best improvements in printability (as reflected by higher ink gloss on single-coated samples after calendering) were achieved with 50 parts LDOP replacing the coarse GCC (second bar). However, significant improvements in ink gloss (lower two bars) can still be obtained when other pigments (GCC) replace some of the LDOP.
• a die cutter was used to cut a 7.6cm x 15.2cm (3" x 6") area from both the coated and uncoated portion of the Mylar. These coupons were weighed to determine the weight of coating applied. The coated coupon was then saturated with mineral oil, then the excess was wiped away. The oil-saturated coupon was then weighed to determine the amount of oil picked up. The void volume can be calculated using the formulation, the weights, the densities of the components and the density of the oil. The volume of the binder was added to give the final void volume value. Pigment blends were initially made with 8% binder added. The coatings comprised of LDOP without any other pigment crazed and were not testable.
• FIG. 15 shows the effects of the LDOP level when blended with a hyperplaty clay.
• a curve "FTX/H60" denoted by the circle symbols for blends of clay with coarse ground calcium carbonate is given as a reference (as shown in U.S. Patent 8142887).
• the void volume values increase as the addition level of LDOP increases. This demonstrates that LDOP give void volumes greater than those achieved in the U.S. Patent 8142887.
• Table 5 has data for pigments blends containing both coarse GCC and LDOP with hyperplaty clay.
• Figure 16 shows the effect of blending Ropaque 1353 LDOP with
• Hydrocarb 60 as the counter pigment to Barrisurf HX.
• the Barrisurf HX volume content was held constant at 50%, and the ratio of 1353 and Hydrocarb 60 was varied.
• the results show that blends containing HX, GCC and LDOP can give equal or better void volume compared to clay carbonate blends (at 0 parts LDOP in FIG.16, and as discussed in U.S. Patent 8142887).
• Paperboard samples were made using solid bleached sulphate (SBS) substrate with a caliper of 267 ⁇ (10.5 pt). The samples were coated on one side using a pilot blade coater to apply a base coat, followed by a top coat. The pilot results are expected to be representative of results that might be achieved on a production paper machine or a production off-machine coater.
• SBS solid bleached sulphate
• the pigments had a wide range of densities, so the coatings were formulated based on volume percent.
• the inorganic pigments were:
• Hydrocarb 60 - A coarse GCC from Omya, previously mentioned
• Hydrocarb 90 - A fine GCC from Omya, previously mentioned
• a low density organic pigment was used in the basecoat only.
• One LDOP was used, which does not expand substantially during drying.
• Ropaque AF-1353 - a low density pigment with a 1.3 ⁇ diameter from Dow, previously mentioned
• Figure 17 shows a graph of pigment packing void volume for mixtures of the Ropaque AF-1353 LDOP pigment with Hydrocarb 60, a coarse ground calcium carbonate (GCC) used in the base coat formulations.
• the method described above was used, with absorption of mineral oil into layers of pigment blends to measure the void volume within packed pigments.
• the pigment packing void volume was about 33% with no LDOP, and rose steadily with increased amounts of LDOP.
• the increase in pigment packing volume was approximately linear between 30 and 90% LDOP by volume.
• Resyn 1103 - a latex from Celanese
• the binder levels (based on 100 parts of pigment) were about 18-21 parts for the various basecoat formulations, and about 14 parts for the topcoat formulation.
• Base coat formulations Q through T are shown in Table 6, which include a "standard” formulation Q (no LDOP), a 25%(volume) LDOP formulation R, a 41 %(volume) LDOP formulation S, and a "platy-clay” formulation T (no LDOP).
• Table 7 gives the ingredients for a single formulation used as a top coat as will be explained below.
• the amount (weight) of LDOP to give a desired volume percent in the base coating is determined as follows. Although the density of calcium carbonate varies slightly due to impurities, a density value of 2.6 g/cc was used here for the Hydrocarb 60.
• the Ropaque 1353 LDOP, as specified by the manufacturer, has a void volume of 53% giving it an equivalent density of .484 g/cc. Assuming we want 25% by volume of LDOP, our calculations will be as follows:
• the base coat formulations were applied onto solid bleached sulfate paperboard which had an initial (uncoated) basis weight of 167 g/m 2 (103 lb/3000 ft 2 ).
• the uncoated paperboard has a PPS smoothness of 7.7 ⁇ and a Sheffield smoothness of 200.
• the base coatings were applied at 7.6 m/sec (1500 fpm) using a bent blade configuration.
• a single base coat was applied, with the basecoat weight ranging from 8.1 to 16.2 g/m 2 (5 to 10 lb/3000 ft 2 ). After drying, the samples in uncalendared condition were tested for Parker PrintSurf (PPS) smoothness and Sheffield smoothness.
• Table 9 shows the Parker PrintSurf (PPS) results.
• PPS Parker PrintSurf
• the results of PART II show that a based-coated paperboard with improved smoothness relative to typical basecoats or platy-clay basecoats is achieved by the inventive coating.
• the improvement in smoothness is maintained.
• the improvement in smoothness would be maintained if more than one coating is applied over the base coat (for example, a second coat and a third coat).
• Figures 18-20 show that where LDOP is used in the base coat, the Parker PrintSurf typically improves (decreases) in both the base coated condition and the top coated condition, as the percent LDOP in the base coating is increased.
• Figure 17 shows that the percent void volume generally increases as the LDOP in the base coating increases.
• high void volumes in the base coating are associated with improved smoothness.

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  • 2017-11-10 MX MX2019005114A patent/MX2019005114A/es unknown
  • 2017-11-10 EP EP17804757.7A patent/EP3538709A1/de active Pending
  • 2017-11-10 CN CN201780069762.9A patent/CN109937278A/zh active Pending
  • 2017-11-10 WO PCT/US2017/061008 patent/WO2018089739A1/en unknown

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