JP2005511916A - Filler for manufacturing base paper and method for manufacturing base paper - Google Patents

Abstract

The invention was made from the use of precipitated calcium carbonate (PCC) with hardwood groundwood and softwood chemical pulp as a filler for making base paper, and hardwood, especially from the wood of the Populus genus The present invention relates to a base paper manufacturing method using pulp and softwood chemical pulp together with a PCC filler. The use of precipitated calcium carbonate (PCC) to produce base paper with hardwood pulp and softwood chemical pulp is used in a fineness fraction in which 20% by weight or more of the hardwood pulp fiber is less than 200 mesh. 10 to 40% by weight of the hardwood pulp fiber is contained in a fineness fraction of 28/48 mesh, the whiteness of the hardwood pulp is 75 or more, and the particle size distribution of the precipitated calcium carbonate However, 9 μm or less is 90%, 5 μm or less is 50%, and 1.5 μm or less is 20%, and the basis weight of the base paper is 25 to 150 g / m ² .

Description

  The present invention relates to the use of precipitated calcium carbonate (PCC) as a filler for producing base paper, together with hardwood (hardwood) groundwood pulp and softwood (softwood) chemical pulp, and hardwood, particularly populus ( The present invention relates to a method for producing a base paper using pulp and softwood chemical pulp produced from wood of the genus Populus) together with a PCC filler.

[Conventional technology]
For base papers, especially thin base papers, kaolin and heavy calcium carbonate (GCC) are used as fillers. Thin base paper is conventionally produced under acidic conditions, and under these conditions, calcium carbonate cannot be used and other compounds are used. Therefore, PCC and GCC are mainly used in fine paper.

  In coated base paper, the coating colorant must be fixed on the paper surface to form a sufficient coating layer so that it cannot penetrate into the base paper during the coating process. In order for the coated paper to have good printability, it is desirable for the coating layer to completely cover the base paper. A thin coating layer should provide excellent coverage and the gloss of the printed paper should be high without interfering with the changes. Furthermore, the bond strength of the paper (measured as the Scott bond value, if necessary) must be sufficiently high so that the paper does not break during printing.

  Paper is usually printed using a heatset offset printer. In this connection, if the strength of the base paper in the z direction is not sufficient, the surface of the finished coated paper may be rough. This phenomenon is especially true for double-sided coated paper when the surface of the paper is dense and vapor generated from the moisture of the paper itself cannot escape through the paper surface in the dryer section of the heat offset press. It is a problem. Considering the quality of the base paper, the filler should further have high opacity (light scattering) and whiteness, while at the same time the filler does not reduce the bond strength of the paper, It is also very important not to increase the porosity of the base paper.

  In sheet-fed offset printing, the strength in the z direction is important even if the printing ink is not dried in another dryer. In the sheet-fed offset, the printing ink is very viscous, and the strength is required due to the fact that a force is liable to cause damage to the paper on the exit side of the printing nip.

  As is known, precipitated calcium carbonate (PCC) is an excellent filler, especially in uncoated fine paper. PCC provides high whiteness and opacity and is bulky compared to other mineral fillers. The resulting advantage is based essentially on the fact that in the PCC manufacturing process, the shape and size of the particles can be controlled by changing the process control parameters. The high whiteness is based on the fact that because the process is synthetic, the end result can be obtained better than heavy calcium carbonate by using pure raw materials. Also, PCC production can be economically competitive in large plants compared to other fillers.

  In view of papermaking, the shape and size of the filler particles can be adjusted in a fairly large range. This allowed PCC pigments to compete with others as coating pigments.

  Calcium carbonate pigments can generally only be used in papermaking processes having a neutral or alkaline pH. Carbonate dissolves under acidic conditions. It is possible to circumvent this limitation by developing PCC pigments that can be used under mildly acidic conditions.

  PCC pigments have established a firm position as fillers for uncoated fine paper, usually with complex particle shapes and quite large sizes. Also, in fine paper coatings, the particles are usually simpler and smaller in size.

  Traditionally, PCC fillers are used in office uncoated paper in proportions exceeding 15% by weight, the purpose of which is to increase whiteness and opacity and reduce costs. The particle morphology of PCC is designed to be as bulky as possible. As a result, the PCC particles are in the form of “sea urchin”, which is also very weak in terms of web density and bond strength. Synthetic precipitated PCC is either gabbro or calcite depending on the production conditions. Usually, the gravel is acicular and is suitable for paper coating. Calcite settles as a scalenohedral, i.e. mainly grain-shaped, or as a light-scattering rhombohedron, i.e. an aggregate of cubes, increasing the bulk of the paper. Alternatively, it settles as prismatic, ie semolina-shaped, spherical or rounded particles. These are often complex in shape and relatively large in size, and from a paper standpoint they represent a compromise on their properties. The attached FIG. 1 shows the particles by SEM photographs. The particles used in the coating of fine paper are of a simpler type and are smaller in size.

  However, PCC pigments have not been successful as a thin base paper filler. In these products, in terms of quality, the filler is desired to have high whiteness and opacity, i.e. light scattering, while at the same time the filler does not reduce the bond strength of the paper while the porosity of the base paper It is very important not to increase. In paper development, opacity generally decreases due to attempts to reduce the basis weight of the paper, but must be compensated for by increasing the light scattering coefficient instead. Furthermore, when the basis weight decreases, the density naturally decreases, i.e. decreases. As the operating speed of paper machines and coaters increases continuously, density becomes even more important. A problem with known PCC fillers is that all the requirements associated with the production of thin base paper are not met simultaneously. Usually, the whiteness and opacity of the base paper may be high, but at the same time the bond strength of the base paper is surprisingly reduced and its density is reduced because the coating colorant penetrates into the base paper .

  Finnish Patent No. 100729 discloses a filler consisting mainly of calcium carbonate used in papermaking and a method for its production. In this method, calcium carbonate settles on the surface of noil fibrils that are produced from cellulose fibers and / or ground pulp fibers by refining. Noyl fibrils with calcium carbonate particles settled on their surface form fibers similar to pearl necklaces, and the calcium carbonate aggregates thus formed are mainly similar to clusters of pearl necklaces. This filler based on cellulosic or ground pulp fibers and calcium carbonate gives the paper good optical properties and good strength.

  Finnish Patent No. 103417 discloses a method for producing a base paper suitable for producing coated fine paper by combining ground wood pulp produced from hardwood and softwood chemical pulp. In this method, a pulp suitable for the production of a base paper is produced with respect to its strength characteristics by using a combination of a groundwood pulp made from wood of Aspen or Populus and a softwood chemical pulp. The advantage of aspen pulp is high whiteness and whiteness stability compared to spruce groundwood. This is especially because the aspen ground pulp or equivalent ground pulp has a low lignin content and a low concentration of carbonyl groups. Thereby, it is possible to manufacture high-quality paper having high whiteness with a basis weight lower than usual.

  As described above, a PCC type filler that is particularly suitable for producing a thin base paper together with hardwood pulp and softwood chemical pulp and that simultaneously satisfies all the requirements required for the base paper filler, and an Aspen or Populus tree It will be noted that there is a need for base paper manufacturing methods that use groundwood pulp and softwood chemical pulp based on hardwood, such as, together with PCC fillers.

[Object of invention]
An object of the present invention is to provide a method for producing a base paper, in particular, a base paper for obtaining a thin base paper having low basis weight, good internal strength and density, and improved light scattering and opacity. is there.

  It is also an object of the present invention to use precipitated calcium carbonate (PCC) as a filler for making base paper, together with hardwood groundwood pulp and softwood chemical pulp, which is particularly as described above. To meet the demands of a new base paper filler.

  Furthermore, an object of the present invention is to provide a method for producing a base paper using a groundwood pulp based on a hardwood such as an Aspen or Populus tree and a softwood chemical pulp together with a PCC filler. All the characteristics required for the base paper can be satisfied at the same time.

[Characteristics unique to the invention]
The use of PCC fillers together with hardwood pulp and softwood chemical pulp in the production of the base paper according to the invention, and the specific features of the base paper production method are described in the claims.

[Description of the Invention]
In the production of base paper, it has been unexpectedly found that the use of hardwood pulp and softwood chemical pulp with PCC fillers can simultaneously achieve all the properties required for base paper. In the method according to the invention, hardwood ground pulp, in particular pressure ground wood (PGW) or chemical ground wood pulp (CTMP) produced from Aspen or Populus wood species is combined with softwood chemical pulp. Is advantageous. Further, a PCC filler having a particle size distribution in which 9 μm or less is 90%, 5 μm or less is 50%, and 1.5 μm or less is 20%, and its form is semolina shape, grain shape, or spherical shape is used. The

  For the base paper, it is possible to use hardwood from Aspen or Populus, i.e. hardwood pulp, which is advantageous to produce from the wood species of Populus, these are P. tremula. , Species of P. tremuloides, P. balsamea, P. balsamifera, P. trichocarpa and P. heterophylla, or It is preferably selected from the group consisting of aspen hybrids from different aspens, such as hybrid aspen species, and genetically produced species, or poplar, or a blend of groundwood pulp produced from the aforementioned species. Particularly preferred wood species are the natural aspen P. tremula, the Canadian aspen P. tremuloides, poplar, and hybrid aspen. Hardwood groundwood pulp may contain up to 70% by weight of spruce or pine as needed.

  It is also possible to use other hardwoods such as birch, eucalyptus or acacia instead of aspen. Such hardwood groundwood pulp can be prepared as a blend containing, for example, two hardwoods and a softwood such as spruce on the hardwood. The percentage of spruce can be up to 70%, preferably up to 50%, particularly preferably less than 30%.

  Hardwood groundwood pulp has shorter fibers than birch chemical pulp or spruce groundwood pulp. Therefore, hardwood groundwood pulp of the same basis weight contains more fibers than birch chemical pulp or spruce groundwood pulp. Thereby, light scattering ability becomes high, favorable formation (namely, there are few fluctuations of basic weight in a small scale), surface roughness becomes low, and also bulkiness is good.

  Hardwood pulp made from other wood species of the genus Aspen or Populus, especially chemical groundwood (CMTP), and pressure groundwood (PGW) contain a large amount of short fibers, which makes the pulp bulky. And light scattering properties are provided. By combining groundwood pulp made from Aspen or Populus wood species and chemical cellulose pulp made from softwood using PCC filler, excellent light scattering and opacity, high whiteness and It is possible to produce a base paper with a uniform surface, good strength and density.

  20-70% by weight hardwood pulp, preferably aspen-CTMP or aspen-PGW, or combinations thereof, and 80-30% by weight bleaching chemistry calculated from dry solids in stock And at least 20% of the hardwood pulp is contained within a fiber size fraction of less than 200 mesh, preferably 10 to 40% by weight of fiber is 28/48 mesh fineness. Included in the fraction. Preferably, at least 30%, particularly preferably at least 50%, by weight of the hardwood pulp is derived from aspen, hybrid aspen and / or poplar.

  After cutting the hardwood material, groundwood, refiner groundwood (TMP) or chemical groundwood (CTMP) is produced from the chips in a manner known per se. When using the groundwood method (GW or PGW), the raw material is supplied to the process as a log. A raw material is prepared from ground wood pulp together with chemical pulp, and a PCC filler having a particle size distribution in which 9 μm or less is 90%, 5 μm or less is 50%, and 1.5 μm or less is 20% is used. In addition, the material can include additives such as various starches, starch derivatives and retention agents. The dry solid content of the material is 0.1 to 5% by weight. As the water phase of the raw material, for example, circulating water of a paper machine can be used. As the chemical pulp, it is preferable to use a soft bleached chemical pulp. Next, calculated from the dry solid of the raw material, the amount of groundwood pulp is 20 to 80% by weight, preferably 30 to 70% by weight, and the amount of bleached chemical pulp of softwood is 80 to 20% by weight, preferably 70 to 30% by weight.

  According to the prior art, a paper web for a paper machine is formed from hardwood groundwood and chemical pulp stock, for example using a gap former.

In laboratory tests, the particle size distribution is 90% 9 μm or less, 50% 5 μm or less, and 20% 1.5 μm or less, preferably 6.3 μm or less 90%, 2.7 μm or less 50%, And a particle size distribution in which 0.8 μm or less is 20%, particularly preferably 4.3 μm or less is 90%, 1.8 μm or less is 50%, and 0.5 μm or less is 20%, Hardwood groundwood pulp, preferably with low freeness, CFS ≦ 150 ml, and high whiteness of 75 or higher, preferably 77 or higher, with PCC fillers in the form of grains, semolina or spheres And softwood chemical pulp, it has been found that it is possible to produce a thin base paper that meets the requirements imposed on the base paper with respect to its quality. The characteristics are shown below.
-Basis weight 25-150 g / m < ² >, preferably 25-80 g / m < ² >
Light scattering coefficient 45 or more, preferably 50 or more, very preferably 55 or more Bond strength 200 or more, preferably 250 or more, very preferably 300 or more Paper porosity 500 ml / min or less, preferably 300 ml / min Or less, very preferably 250 ml / min or less (at a basis weight of 50 g / m ² ),
-Bulk of paper 1.2-1.8cm < ³ > / g
・ Whiteness 75% or more

  The fiber composition of the base paper according to the invention comprises 20-70% by weight hardwood groundwood pulp, preferably aspen-based pulp, most preferably aspen groundwood or aspen-CTMP pulp, very preferably aspen-CTMP pulp, 30% by weight of softwood chemical pulp, preferably pine bleached chemical pulp.

Base paper, it can be coated in any suitable manner known in the art, whereby, 5 to 50 g / m ^2, the coating layer preferably has a basis weight of 5 to 30 g / m ² is , Formed on at least one surface of the paper web, preferably on both surfaces.

  High quality paper is obtained from the base paper according to the invention by application with a suitable pigment-containing coating colorant. The coating colorant can be applied to the material web in a manner known per se. Paper coating can be performed on-line or off-line using conventional coating equipment, ie by blade coating or by film coating or surface spraying.

  The base paper produced by the method according to the invention and the coated paper further produced from this base paper can be calendered by any calendering method known in the prior art. Calendering is preferably done online, like soft calendering, which results in a smooth and glossy product or a matte surface product whose bulk, opacity and stiffness meet requirements It is.

  The invention is further illustrated by the following examples. However, it will be apparent to those skilled in the art that the present invention is not limited only to the example embodiments.

[Laboratory testing with various fillers]
In a series of tests, experimental sheets were produced in a Formette Dynamix sheet mold. In the test, the fiber pulp, waste paper and various fillers described below were used. Standard amounts of retention agent and starch were also used.

The following fiber pulp was used in the test.
・ A bleached chemical pulp of Scandinavian softwood refined to 24 with SR number by Escher Wyss laboratory refiner ・ Voith Sulzer laboratory refiner (consistency 4.2%, specific edge load 0.3 J / m, specific energy Bleached CTMP purified to a CSF value of 48 ml at a consumption of 90 kWh / t) and containing 85% aspen and 15% spruce. The fiber distribution of the pulp and the most important paper technical values measured from the experimental sheets were as follows:
-Length-Weight of the weighted fiber: 0.69 mm
・ McNett classification +28 mesh: 3.3%
・ McNett classification 28/48 mesh: 39.4%
・ McNett classification 48/100 mesh: 22.4%
・ McNett classification 100/200 mesh: 11.0%
-McNett classification -200 mesh: 23.9%
・ Tensile index 37.8Nm / g
・ Tear index 3.4 mNm ² / g
・ Bulk 1.79 cm ³ / g
・ Scott Bond 152J / m ²
-Scattering coefficient 47.4m ² / kg
・ Whiteness 80.9

  In all tests, a total of 12% filler was present. In a paper mill that manufactures coated paper, under actual conditions, the filler for the base paper is both a so-called fresh filler and a filler from the coated paper waste (filler containing mineral pigment in the coating layer). Consists of. For this reason, fillers were administered in several tests as coating waste paper from paper mills. In this spoiled paper, the main mineral component was heavy carbonate contained in the coating. In these tests, the fresh filler comprised 6 percent units of filler and the filler from the waste paper comprised 6 percent units of filler.

  The fillers used are shown in Table 1 below. The attached FIG. 2 is a graph showing the particle size distribution. Values were measured with a Malvern Master Size apparatus.

  The properties of the sheet are shown in Table 2 below. Tensile strength and tear strength are geometric means from mechanical and widthwise results.

  As expected, these results show that the whiteness and scattering coefficient are higher when PCC is used compared to calcium carbonate. However, unexpectedly, in addition to the excellent optical properties, it can be seen that PCC1 and especially PCC2 can also improve the strength properties. This occurred in tests involving splinters regarding Scott Bond bond strength and tear strength. Also, the porosity of the paper remained at a sufficiently low level. Here again, the surprising results of PCC2 are striking.

[Manufacture of base paper on pilot paper machine and its coating and calendering]
The following fiber pulp was used in the test.
-Milled Nordic softwood bleached chemical pulp-Low specific edge load but post-refined with pilot scale refiner with specific energy consumption of 140 kWh / t, containing 85% aspen and 15% spruce Bleach CTMP to do. Prior to post-refining, the pulp had a CSF of 115 ml. After post-refining, the most important properties of the pulp and laboratory sheets were as follows:
・ CSF 59ml
-Length-Weight of the weighted fiber: 0.73 mm
・ McNett classification +16 mesh: 0.0%
・ McNett classification 16/30 mesh: 5.4%
・ McNett classification 30/50 mesh: 31.3%
・ McNett classification 50/200 mesh: 34.1%
-McNett classification -200 mesh: 29.1%
・ Whiteness 78.6
・ Tensile strength: 46.7 Nm / g
・ Tear strength: 3.9 mNm ² / g
・ Density 570 kg / m ³ (bulk 1.75 cm ³ / g)
・ Scott Bond 392J / m ²
-Scattering coefficient 51.5m ² / kg

  Comparing these results with the properties of the post-refined pulp in the laboratory of Example 1, the pilot scale refiner clearly yielded more 200 mesh fractions, whereas in the pilot test the 30/50 mesh fractions It can be seen that there is clearly little (corresponding to fraction 28/48 mesh in Example 1). The results are typical, and in fact, it was found that the refiners used in the pilot tests were in very good agreement with the paper mill conditions. The refiner is similar in structure to the factory refiner, but the pilot refiner is smaller in size.

Base paper was made from pulp on a pilot scale paper machine. The paper machine had a gap former. The same filler as in Example 1 was added to the paper as follows.
-PCC1, decentered triangular face-PCC2, rhombohedral

  No further comparisons with heavy calcium carbonate were made, but two of the best PCCs were included in the study.

  In all tests, a standard amount of starch and the same retention agent were added to the material.

  A base paper was prepared in a roll shape, dried, and then analyzed. The measurement results in the following Table 3 are averages from the measured values of the four rolls. Tensile strength and tear strength are geometric averages in the machine and width direction.

  From Table 3, it can be seen that the properties of the base paper are relatively close to each other. The higher content of PCC1 makes the comparison more difficult. Similar to laboratory tests, better optical properties, ie whiteness and scattering coefficient, were achieved with PCC2.

Thereafter, the base paper was coated with the same coating colorant and super calendered. The target coating amount was 18 g / m ^{2 on} both sides of the paper. The linear pressure for calendering was 280 kN / m.

  The most important properties of the finished paper are shown in Table 4 below (the properties are averages on both sides of the paper).

  According to Table 4, the only obvious difference after coating is whiteness, which is better for PCC2. However, the usual expectation is that if the whiteness is as high as 1.3 units in the finished paper, the opacity of the paper with the higher whiteness is expected to be clearly lower than the paper with the lower whiteness. . Therefore, the optical properties of PCC2 containing paper should be considered superior to PCC1 paper. There is no practical difference in paper surface properties (smoothness, gloss).

The particles of precipitated calcium carbonate are shown by SEM photographs. It is a graph showing the particle size distribution of a filler.

Claims (14)

Use of precipitated calcium carbonate (PCC) to produce a base paper with hardwood groundwood and softwood chemical pulp,
More than 20% by weight of the hardwood pulp fiber is contained in the fineness fraction of less than 200 mesh, and 10-40% by weight of the hardwood pulp fiber is contained in the 28/48 mesh fineness fraction. The hardwood groundwood pulp has a whiteness of 75 or more, and the particle size distribution of the precipitated calcium carbonate is 90% for 9 μm or less, 50% for 5 μm or less, and 20% for 1.5 μm or less, using the basis weight of the base paper is characterized in that it is a 25 to 150 g / ^{m 2.} The whiteness of the hardwood groundwood pulp is 77 or more, and the particle size distribution of the precipitated calcium carbonate is 90% for 6.3 μm or less, 50% for 2.7 μm or less, and 20% for 0.8 μm or less. The use according to claim 1, wherein the base paper has a basis weight of 25 to 80 g / m ² .   Use according to claim 1 or 2, characterized in that the hardwood pulp is produced from aspen and / or Populus wood species.   The hardwood pulp contains CTMP pulp or pressure groundwood (PGW) or a combination thereof, and the hardwood pulp is P. tremula, P. tremuloides, Populus Aspen hybrids from different aspens such as P. balsamea, P. balsamifera, P. trichocarpa, P. heterophylla, hybrid aspen Use according to any of claims 1 to 3, characterized in that it is produced from a wood species of the genus Populus selected from the group consisting of: a genetically engineered species and a poplar group.   Use according to any of claims 1 to 4, characterized in that at least 30% of the hardwood pulp fibers are derived from Aspen and / or Populus wood species.   Use according to any of the preceding claims, characterized in that the hardwood groundwood pulp contains at least 50% of fibers derived from Aspen and / or Populus wood species.   The hardwood groundwood pulp contains 70 to 100% fiber derived from Aspen and / or Populus trees and 0 to 30% fiber derived from softwood and / or other hardwood. Use according to any of claims 1 to 6, characterized in that A method of manufacturing a base paper for forming a paper web from a fiber material for a paper machine,
The fiber raw material is formed by combining precipitated calcium carbonate (PCC) with hardwood ground pulp and softwood chemical pulp, and a fineness fraction in which 20% by weight or more of the fibers of the hardwood groundwood pulp is less than 200 mesh. 10 to 40% by weight of the hardwood pulp fiber is contained in a fineness fraction of 28/48 mesh, the whiteness of the hardwood pulp is 75 or more, and the precipitated calcium carbonate The particle size distribution of the base paper is 90% for 9 μm or less, 50% for 5 μm or less, and 20% for 1.5 μm or less, and the basis weight of the base paper is 25 to 150 g / m ^2. . The whiteness of the hardwood groundwood pulp is 77 or more, and the particle size distribution of the precipitated calcium carbonate is 90% for 6.3 μm or less, 50% for 2.7 μm or less, and 20% for 0.8 μm or less. The method according to claim 8, wherein the basis weight of the base paper is 25 to 80 g / m ² .   The method according to claim 8 or 9, characterized in that the hardwood pulp is produced from an Aspen and / or Populus wood species.   The hardwood pulp contains CTMP pulp or pressure groundwood (PGW) or a combination thereof, and the hardwood pulp is P. tremula, P. tremuloides, Populus Aspen hybrids from different aspens such as P. balsamea, P. balsamifera, P. trichocarpa, P. heterophylla, hybrid aspen The method according to claim 1, wherein the method is produced from a species of Populus genus selected from the group consisting of: a genetically engineered species, and a poplar group.   The method according to any one of claims 8 to 11, wherein at least 30% of the fibers of the hardwood pulp are derived from Aspen and / or Populus wood species.   13. A method according to any one of claims 8 to 12, characterized in that the hardwood groundwood pulp contains at least 50% fibers derived from Aspen and / or Populus wood species. The hardwood groundwood pulp contains 70 to 100% fibers derived from aspen and / or Populus wood species, and 0 to 30% fibers derived from softwood and / or other hardwoods. The method according to claim 8, wherein:

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