JP5530130B2 - Corrugated core paper - Google Patents

Description

  The present invention relates to a core base paper for corrugated cardboard having excellent flexibility and impact resistance.

  In recent years, corrugated cardboard sheets have been widely used in applications other than protective storage cases, taking advantage of their flexibility, shock absorption, cushioning properties, etc. ing.

The quality of corrugated cardboard used as a protective storage case is defined by JIS standards, and the standard for corrugated cardboard core paper is defined by JIS-P3904 “Corrugated cardboard core paper”. In JIS-P3904, the specific compressive strength is determined for each display basis weight of the core raw paper. This core base paper has a high basis weight of 115 to 200 g / m ² and a high specific compressive strength. A corrugated cardboard sheet formed from such a hard and high-strength core base paper has a high plane compressive strength as defined in JIS-Z0403-1 and is a so-called corrugated cardboard sheet that is hard to be dented, but is hard and inferior in cushioning properties. Therefore, there is an inconvenience that sufficient impact absorbability cannot be obtained and it cannot be used for packaging of easily damaged items.

For example, if a high-strength core base paper based on the above-mentioned JIS standard is used as a corrugated cardboard sheet used as a protective sheet for a fluorescent lamp, the surface of the fluorescent lamp is scratched because the specific compressive strength of the core base paper is high. There is a fear. In addition, the flat compressive strength of the corrugated sheet is high and the flexibility is low, so it is inferior in shock absorption, and the fluorescent lamp is not easily damaged. May decrease. Therefore, as a conventional protective sheet for a fluorescent lamp, a single-stage corrugated cardboard sheet made of kraft paper having a weak strength and easily crushed and having a basis weight of about 80 g / m ² is used.

Then, the technique which provides a softness | flexibility and a shock-absorbing property to a core base paper by setting the basic weight of this core base paper small is provided. For example, in Patent Document 1, paper is made with a basis weight of 80 g / m ² or more and 185 g / m ² or less, and a density of 0.5 g / cm ³ or more and 0.7 g / cm ³ or less. A core base paper is disclosed. Further, in Patent Document 2, paper is made with a basis weight set to 70 g / m ² , which can prevent the problem of lowering adhesive strength when manufacturing a thin corrugated cardboard by the fingerless method, and particularly in micro flute corrugated cardboard sheets. A core core paper that is suitably used is disclosed.

  However, as in Patent Document 1, simply setting the basis weight lower than the value defined in JIS-P-3904 balances sufficient flexibility (specific compressive strength) and shock absorption (planar compressive strength). I can't get well. Moreover, even if a corrugated cardboard sheet is prepared from the core base paper disclosed in Patent Document 2 and used as a protection sheet for easily damaged products, sufficient flexibility and shock absorption cannot be obtained in a well-balanced manner.

JP 2008-190064 A JP 2001-162704 A

  The present invention has been made in view of these disadvantages, and aims to provide a core base paper having a basis weight set lower than a value defined in JIS-P3904 and having sufficient flexibility and impact durability in a well-balanced manner. To do.

The invention made to solve the above problems is
A core base paper for corrugated board obtained by papermaking raw material pulp,
The basis weight is 70 g / m ² or more and 100 g / m ² or less,
The number average fiber length distribution of the disaggregated raw pulp has a maximum value in the range of 0.50 mm or more and less than 1.05 mm,
A core base paper for corrugated board, characterized in that, when used as the core of a C-stage corrugated cardboard sheet defined in JIS-Z1516 “Exterior Corrugated Cardboard”, the flat compressive strength of the corrugated cardboard sheet is 124 kPa or more and 168 kPa or less. It is.

The core base paper for corrugated board of the present invention has a basis weight of 70 g / m ² or more and 100 g / m ² or less, and the number average fiber length distribution of the raw pulp has a maximum value in a range of 0.50 mm or more and less than 1.05 mm. Thus, sufficient flexibility and shock absorption can be exhibited in a well-balanced manner. Furthermore, when the flat compressive strength of the corrugated board sheet using the core base paper for corrugated board of the present invention is 124 kPa or more and 168 kPa or less, sufficient shock absorption can be exhibited effectively.

The specific compressive strength of the corrugated core base paper is preferably 40 N · m ² / g or more and 80 N · m ² / g or less. By setting the range of the specific compressive strength within the above range, sufficient flexibility can be effectively exhibited.

  The core base paper for corrugated cardboard preferably contains impurities having a minimum width of 0.25 mm or more, and the content of these impurities is preferably 0.1% by mass or more and 0.5% by mass or less. In this way, it contains impurities having a minimum width of 0.25 mm or more, and by making the content of these impurities within the above range, it effectively inhibits the interfiber bonding contained in the core raw paper, The flexibility of the corrugated cardboard sheet using the core base paper and the core base paper can be improved, and sufficient flexibility and shock absorption can be exhibited with a good balance.

  The raw pulp contains colloidal silica as a flocculant and polyacrylamide as a coagulant, and the content of colloidal silica in the raw pulp is 0.1% by mass or more and 0.8% by mass or less, and the polyacrylamide in the raw pulp The content of is preferably 0.01% by mass or more and 0.10% by mass or less. Thereby, the softness | flexibility and impact-absorbing property of the said core base paper for corrugated cardboard can be improved effectively.

  As described above, the core base paper for corrugated board of the present invention uses raw pulp, and exhibits sufficient flexibility and shock absorption in a well-balanced manner by adjusting basis weight, flat compressive strength, impurities components, etc. can do. Such a core base paper for corrugated cardboard is suitable for recycling because it is low-cost and suitable for recycling.

  Hereinafter, the core base paper for corrugated board according to the present invention will be described in detail.

  The corrugated core base paper mainly contains raw pulp and impurities.

(pulp)
As the pulp used for the core raw paper for corrugated cardboard, used paper pulp, chemical pulp, mechanical pulp and the like can be used. Among these, when used paper pulp is used, it is possible to obtain a core base paper that has a short fiber length and exhibits high flexibility, and can contain a large amount of contaminant components that inhibit interfiber bonding between pulps. In addition, by using waste paper pulp having a short fiber length, as described later, there is an advantage that the number average fiber length distribution of the raw material pulp can be easily adjusted to have a maximum value in a range of 0.50 mm to 1.05 mm.

  Waste paper pulp, for example, corrugated waste paper, tea waste paper, craft envelope waste paper, magazine waste paper, newspaper waste paper, flyer waste paper, office waste paper, Kami white waste paper, Kent waste paper, structured waste paper, ground waste waste paper, etc. Examples include disaggregation / deinked waste paper pulp, deinking / bleached waste paper pulp, and the like.

  Examples of chemical pulp include hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), conifer unbleached kraft pulp (NUKP), hardwood semi-bleached kraft pulp (LSBKP), conifer Semi-bleached kraft pulp (NSBKP), hardwood sulfite pulp, coniferous sulfite pulp and the like.

  Examples of the mechanical pulp include stone ground pulp (SGP), pressurized stone ground pulp (PGW), refiner ground pulp (RGP), chemi-ground pulp (CGP), thermo grand pulp (TGP), ground pulp (GP), and thermo. Examples include mechanical pulp (TMP), chemisermo mechanical pulp (CTMP), refiner mechanical pulp (RMP), and the like.

The number average fiber length distribution of the disaggregated pulp of the core base paper for corrugated cardboard preferably has a maximum value in a range of 0.50 mm or more and less than 1.05 mm, and has a maximum value in a range of 0.60 mm or more and less than 0.95 mm. More preferably, it has a maximum value in the range of 0.70 mm or more and less than 0.85 mm. Even if the basis weight is set to be not less than 70 g / m ^{2 and not} more than 100 g / m ² by setting the maximum value in the number average fiber length distribution of the disaggregated pulp within the above range, sufficient flexibility and impact absorption are achieved. Sex can be obtained in a well-balanced manner. In addition, the number average fiber length distribution of disaggregated pulp is classified into fiber lengths of 0.05 mm for pulp fibers obtained by disaggregating the core base paper according to JIS-P8220: 1998 “pulp-disaggregation method”. This is based on the fiber length distribution obtained as described above.

  When the fiber length of the disaggregated pulp contains many fibers having a fiber length of less than 0.50 mm and the number average fiber length distribution does not have a maximum value in the range of 0.50 mm or more and less than 1.05 mm, fine fibers are This is not preferable because the base paper is densely packed and does not have sufficient plane compressive strength, and as a result, sufficient shock absorption cannot be exhibited. On the other hand, when the fiber length of the disintegrated pulp contains many fibers exceeding 1.05 mm and the number average fiber length distribution does not have a maximum value in the range of 0.50 mm or more and less than 1.05 mm, the long fibers Not only is it excessively large and sufficient impact absorption cannot be exhibited, but also because the surface properties are rough, for example, the surface of an easily damaged product to be protected is easily damaged, which is not preferable.

  In such a fiber length distribution, in order to suitably obtain a pulp fiber having a maximum value in a range where the number average fiber length distribution of the disaggregated pulp is 0.50 mm or more and less than 1.05 mm, a conventionally used beating method is generally used. The freeness may be adjusted by using a beater, a conical refiner, a cylindrical refiner, or a disc refiner (SDR, DDR). Specifically, the freeness may be beaten using DDR under conditions of about 300 ml to 600 ml. When using waste paper pulp obtained by recycling waste paper cardboard, it is preferably adjusted to 350 ml to 580 ml, preferably 400 ml. It is more preferable to adjust to 540 ml or less. The pulp fibers obtained by beating in this way can also be used by mixing with other pulps having different fiber lengths. In that case, the fiber length distribution after the pulp fibers after mixing is 0.50 mm. What is necessary is just to adjust the mixture ratio with other pulp from which fiber length differs so that it may have the maximum value in the range below 1.05 mm. In addition, freeness is the value which measured the freeness by the Canadian standard freeness tester based on JIS-P8121, after disintegrating the sample by the standard breaker based on JIS-P8220.

The Runkel ratio of the disintegrated pulp of the core base paper for corrugated cardboard is preferably 1.3 or more and 2.0 or less, and particularly preferably 1.4 or more and 1.9 or less. In addition to the basis weight of the paper itself, factors contributing to the flexibility and impact absorption of the paper include the physical structure of the pulp fiber itself. The pulp fiber has a lumen (lumen), and when the lumen is crushed, a cushion function as a whole paper is exhibited. The ratio between the lumen and the thickness of the outer ring (cell wall) is important for the cushion function. The Runkel ratio R is a value determined by the width (diameter) L of the lumen of the fiber and the thickness t of the cell wall, and is represented by R = 2 · t / L. If this Runkel ratio is large (wall thickness is large), it is a rigid fiber and is not preferable because it is inferior in shock absorption. If the Runkel ratio is small (wall thickness is small), sufficient shock absorption cannot be exhibited. Therefore, it is not preferable. In the core base paper for corrugated cardboard, the basis weight is 70 g / m ² or more and 100 g / m ² or less by setting the Runkel ratio to 1.3 or more and 2.0 or less, more preferably 1.4 or more and 1.9 or less. Even when it is set to a low value, it is preferable because the impact absorption is high and the bonding property and the surface strength are good. In addition, if the Runkel ratio is less than 1.3, sufficient flexibility cannot be exhibited, and if the Runkel ratio exceeds 2.0, the rigidity of the fiber becomes excessively high and sufficient shock absorption is exhibited. It is not preferable because it cannot be done.

  The Runkel ratio can be adjusted by performing raw material pulp selection, classification, and beating treatment at a minimum. Selection means, for example, that raw material pulp is selected based on conditions such as pulp fibers having a relatively large Runkel ratio can be obtained from pulp made from raw wood or plantation wood obtained from a natural forest. . Classification means using thickeners, screens, cleaners, etc., and other known SP filters, washers, extractors, filter presses, etc. that are generally used in paper and pulp factories. Means to classify while diluting. Beating means beating with a conical refiner, a cylindrical refiner, a disc refiner, or the like.

  When the selection of the raw material pulp is adopted, for example, in conifers, black and pine have a large Runkel ratio (about 4 or more) because the fiber width is small and the wall thickness is large. On the other hand, fir, todomatsu, red pine, and himekomatsu have a large fiber width and a small wall thickness, so the Runkel ratio is small (about 1-2), and larch, spruce, cedar, cypress, and hiba are even smaller (about 1 or less). In broad-leaved trees, beech and red oak have a large Runkel ratio (about 4 or more). Maple is even smaller (less than about 1).

  The impurities contained in the core raw paper for corrugated cardboard inhibit the interfiber bonding between pulps and improve the flexibility of the core raw paper. Examples of the impurities include mixtures such as vinyl strings contained in waste paper, seals, tapes, laminate layers, paper deposits such as magazine back glue and printing ink. These impurities are usually removed in the recycled pulp manufacturing process or the preparation process before the paper machine, but the content and size (minimum width) of these impurities are adjusted in the core raw paper. Thus, sufficient flexibility and impact durability can be exhibited in a well-balanced manner.

  The minimum width of the impurities is preferably 0.25 mm or more, particularly preferably 0.25 mm or more and 5.00 mm or less. Thereby, sufficient softness | flexibility and shock absorption can be exhibited with sufficient balance. If the minimum width of the contaminants is less than 0.25 mm, the interfiber binding inhibition effect of the pulp fibers due to the inclusion of the contaminants cannot be sufficiently obtained, and as a result, the plane compressive strength is excessively high. Therefore, it is not preferable. In addition, if the minimum width of the contaminants exceeds 5.00 mm, the binding inhibition effect between the fibers due to the contaminants becomes excessively large, so that not only a sufficient flat compressive strength cannot be obtained, but also packaging of particularly easily damaged items. In use, it is not preferable because the contact area between the contaminant and the easily damaged product becomes large, and as a result, the easily damaged product is easily damaged.

  The content of impurities is preferably 0.1% by mass or more and 0.5% by mass or less, and particularly preferably 0.15% by mass or more and 0.30% by mass or less. By setting the content of this contaminant within the above range, interfiber bonding contained in the core base paper is likely to be inhibited, and the flexibility of the core base paper and the corrugated cardboard sheet using the core base paper can be improved. it can. When the content of this contaminant is less than 0.1% by mass, the inter-fiber bond of the pulp becomes strong, so that it becomes difficult to be crushed during corrugated sheet, and as a result, the impact absorbability is inferior. On the other hand, if it exceeds 0.5 mass%, the interfiber bond of the pulp becomes excessively weak, and it may not be possible to exhibit sufficient shock absorption, which is not preferable.

  In particular, when there are many pulp fibers having a fiber length of 0.50 mm or more and less than 1.05 mm, as in the case of the core raw paper for corrugated cardboard, the impurities of 0.25 mm or more and 5.00 mm or less are contained in an amount of 0.1% by mass or more and 0.5% or less. It is preferable to contain it by mass% or less, preferably 0.15 mass% or more and 0.30 mass% or less because the flexibility of the core base paper can be further improved.

  In addition, the content rate of the foreign material in the said core raw material for corrugated paper is the value measured using the following method. The core base paper is disaggregated according to JIS-P8220: 1998 “pulp-disaggregation method”, and a screen plate having a slit width of 0.15 mm is used in accordance with TAPPI T275sp98, and 100 g of sample dry pulp is flat screened. The screen residue was made a contaminant. The mass ratio of the impurities to the core base paper in terms of dry weight was taken as the impurities content.

  In order to adjust the content rate of the said foreign material, it is good to adjust the foreign material removal rate in the rough selection process in the used paper processing process and the selective process. When the amount of impurities is small, papermaking sludge discharged from other pulp manufacturing processes, papermaking processes, coating processes, etc. of the papermaking factory, drainage scum of the papermaking factory, and the like can also be used. Moreover, it can prepare also by mixing the rejection obtained from the dust removal apparatus. As such a dust removing device, it is preferable to use a screen having a certain slit width because it is easy to adjust impurities. Specifically, as described above, since it is preferable to adjust the size of the contaminants to 0.25 mm or more and 5.00 mm or less, a slit having a width of 0.25 mm is passed through a hole screen having a size of 5.00 mm. By using a method in which a certain amount of impurities that cannot pass is added to a pulp raw material that has passed through a slit having a width of 0.25 mm, the content of the impurities can be easily adjusted.

(Basis weight)
The basis weight of the core base paper for corrugated cardboard is preferably 70 g / m ² or more and 100 g / m ² or less, more preferably 75 g / m ² or more and 85 g / m ² or less, and 80 g / m ² or more and 81 g / m ² or less. Particularly preferred. By making the range of this basic weight into the said range, sufficient softness | flexibility and impact absorption can be exhibited with sufficient balance. When the basis weight is less than 70 g / m ² , the flexibility is improved, but sufficient impact absorbability cannot be obtained. On the other hand, if the basis weight exceeds 100 g / m ² , both the flexibility and the shock absorption are lowered, which is not preferable.

In the corrugated core base paper, as described above, the pulp having a maximum value in the range where the number average fiber length distribution of the disaggregated pulp is 0.50 mm or more and less than 1.05 mm, the basis weight of the corrugated core base paper is By setting it to 70 g / m ² or more and 100 g / m ² or less, the plane compressive strength can be set to 124 kPa or more and 168 kPa, and therefore, a core base paper having a sufficient balance of flexibility and impact durability can be obtained. .

(Plane compressive strength)
When the core base paper for corrugated cardboard is used as the core of the C-stage corrugated cardboard sheet defined in JIS-Z1516 “Exterior corrugated cardboard”, the plane compressive strength of the corrugated cardboard sheet may be 124 kPa or more and 168 kPa or less. Preferably, it is 134 kPa or more and 161 kPa. By setting the range of the plane compressive strength to the above range, sufficient impact absorbability can be effectively imparted to the corrugated core base paper. In addition, the plane compressive strength of this corrugated board sheet is based on the prescription | regulation of JIS-Z0403-1 "corrugated board-plane compressive strength test method".

(Specific compression strength)
Further, in the case of the core raw paper for corrugated cardboard, specific compression in the case where the lateral compressive strength of the core raw paper is measured according to JIS-P8126: 2005 “Paper and paperboard—Compression strength test method—Ring crush method”. strength is preferably not more than 40N · ^m 2 / g or more 80N · ^m 2 / g, more preferably not more than 44N · ^m 2 / g or more 76N · ^m 2 / g. By setting the range of the specific compressive strength within the above range, sufficient flexibility can be effectively imparted to the corrugated core base paper.

In particular, as described above, the pulp having a maximum value in the range where the number average fiber length distribution of the disaggregated pulp is 0.50 mm or more and less than 1.05 mm is used, and the basis weight of the core base paper for corrugated cardboard is 70 g / m ² or more and 100 g / m. m ² or less, and the plane compressive strength is 124 kPa or more and 168 kPa, and the specific compressive strength when the transverse compressive strength of the core raw paper is measured is 40 N · m ² / g or more and 80 N · m ^2. By setting it to / g, it is possible to obtain a core base paper further having a good balance of flexibility and impact durability.

(Production method)
The method for producing the pulp used for the core raw paper for corrugated cardboard is not particularly limited, and a method generally used for papermaking in the past can be used. For example, a raw material slurry containing pulp, impurities, etc. can be produced by making paper through a wire part, a press part, a dryer part, and a reel part. This slurry may contain chemicals such as a coagulant, a flocculant, and a lubricant, which will be described later.

(Coagulant)
In the core base paper for corrugated cardboard, a coagulant may be used in order to improve the yield of pulp having a fiber length of 0.50 mm or more and less than 1.05 mm. As the coagulant, those conventionally used for papermaking can be used. For example, polyacrylamide (PAM), polyvinylamine (PVAm), polydiallyldimethylammonium chloride (Polydadomac, PDADMAC), polyamine (PAm), polyethyleneimine (PEI), polyethylene oxide (PEO), polyacrylate, methacrylate Etc. Among these, it is preferable to use a polymer having a cationic property. When polyethyleneimine, polyamine, polydadomac, and polyacrylamide are used, the yield of fine fibers can be further improved, and the medium has excellent shock absorption. Since a core base paper can be obtained, it is preferable. In particular, use of polyacrylamide is preferable because a core base paper having the highest impact absorbability, good flexibility, and easy deformation is obtained.

  The addition amount of the coagulant is preferably 0.01% by mass or more and 0.10% by mass or less, and particularly preferably 0.02% by mass or more and 0.08% by mass or less in terms of solid content with respect to the total amount of pulp. If the amount added is less than 0.01% by mass, the yield of fine fibers is lowered and the impact absorption is lowered, which is not preferable. On the other hand, if it exceeds 0.10% by mass, it becomes a hard core base paper, which is not preferable because the impact absorbability is lowered.

(Flocculant)
In the corrugated core base paper, after adding the coagulant, further adding a specific flocculant in the previous stage of the paper making process following the pulp preparation stage, the pulp having a fiber length of 0.50 mm or more and less than 1.05 mm Therefore, the impact absorption can be further improved.

  As the flocculant, a flocculant conventionally used in papermaking applications can be used. For example, inorganic flocculants such as bentonite and colloidal silica; organic polymer flocculants such as polyacrylamide (PAM), polyvinylamine (PVAm), polyamine (PAm), polyethylene oxide (PEO), polyethyleneimine (PEI) alone Or they can be used in combination. Among them, it is preferable to use an inorganic flocculant such as bentonite or colloidal silica, and it is particularly preferable to use colloidal silica. By using such a flocculant, the ability of the fibers to agglomerate is increased. Therefore, even when a pulp having a lot of fine fibers is used, the impact absorbability can be effectively improved.

  In addition, when paper is made after adding colloidal silica, agglomerates may be easily generated, so the aggregating agent is added in front of the screen, and the generated agglomerates are temporarily broken by the screen, so that the agglomerates are moderately cohesive. Is preferably weakened. In such a screen, by using a slit type having an opening of 0.33 mm or more and 0.37 mm or less, the effect of suppressing the generation of aggregates can be more effectively performed.

  The addition amount of the flocculant is preferably 0.1% by mass or more and 0.8% by mass or less, and particularly preferably 0.2% by mass or more and 0.6% by mass or less in terms of solid content with respect to the total amount of pulp. If the amount added is less than 0.1% by mass, the yield of fine fibers is lowered and the density of the resulting paper is lowered. As a result, the impact absorbability is lowered, which is not preferable. On the other hand, if it exceeds 0.8% by mass, the core raw paper becomes hard and the impact absorbability is lowered, which is not preferable.

  Moreover, it is preferable to add the said flocculant between 20 minutes or more and 40 minutes or less after mixing the pulp fiber containing a fine fiber and a coagulant. If the addition timing is less than 20 minutes, the yield of fine fibers decreases, and if it exceeds 40 minutes, agglomerates tend to be generated, which is not preferable.

Thus, by using a cationic polymer, particularly polyacrylamide, as the coagulant and an anionic inorganic particle, particularly colloidal silica, as the coagulant, the fiber length is 0.50 mm or more and less than 1.05 mm, preferably 0.60 mm or more. The yield of pulp having a maximum value in the range of less than 0.95 mm, more preferably in the range of 0.70 mm to less than 0.85 mm can be improved, and a core base paper excellent in impact absorption can be obtained. Furthermore, it is preferable to set the basis weight of the core base paper to 70 g / m ² or more and 100 g / m ² or less because a core base paper and corrugated cardboard excellent in shock absorption can be obtained.

(Lubricant)
The core base paper for corrugated cardboard has, for example, the surface of the core base paper in order to smooth the contact with easily damaged items and prevent the easily damaged products from shaking and rubbing against the core base paper during transportation. A lubricant can be applied.

  As this lubricant, those conventionally used in general can be used. For example, higher fatty acid metal salt such as calcium stearate; aqueous dispersion of low molecular weight polyethylene, liquid hydrocarbon oil, higher fatty acid, higher alcohol, higher fatty acid sulfated oil, aliphatic phosphate ester, polyalkylene glycol or derivative thereof, or These aqueous dispersions; petroleum waxes such as paraffin wax and microcrystalline wax can be used.

  By applying these lubricants to the surface of the core base paper and adjusting the sliding angle of the surface of the core base paper to 20 ° or more and 24 ° or less, as described above, it is preferable to prevent damage to easily damaged products. In particular, in the case of a single-stage sheet that protects fluorescent lamps and bulbs, the fluorescent lamps and bulbs are in direct contact with the core paper, so there is a possibility that scratches may occur during transportation. By adjusting the value within the above range, it is possible to effectively prevent the fluorescent lamp and the bulb from being damaged.

(Additive)
In the core base paper for corrugated cardboard, in addition to the above-mentioned coagulant, coagulant, and lubricant, if necessary, filler, internal sizing agent, fixing agent, paper strength enhancer, paper thickness improver, yield improver, Various paper making aids such as a bulking agent, a cationizing agent, a paper strength enhancer, an antifoaming agent, a colorant, and a dye can be added by appropriately adjusting the type and blending amount thereof.

  In addition, when laminating the core base paper and the liner, step cracks and poor bonding may occur, but by making the slip angle within the above range, step cracks and poor bonding are also effective. Can be prevented.

  The corrugated core base paper of the present invention is not limited to the above embodiment. For example, the paper layer of the core base paper for corrugated cardboard of the present invention may be not a single layer but a plurality of layers of two or more layers that are multilayered in the wire part of the papermaking process.

  EXAMPLES Hereinafter, although this invention is explained in full detail based on an Example, this invention is not interpreted limitedly based on description of this Example.

  In order to confirm the effect of the core raw paper for corrugated cardboard according to the present invention, the following various samples were prepared, and a test for evaluating the quality of each sample was performed.

[Examples 1-27 and Comparative Examples 1-4]
Recycled corrugated waste paper into 100 parts by weight of waste paper pulp adjusted to the freeness listed in Table 1. Rejects the paper machine before the process (passes through a 5.00 mm hole hole screen and passes through a 0.25 mm wide slit screen. Unmixed raw materials) were mixed at the ratio shown in the table in terms of solid content, and then the coagulant and the flocculant shown in Table 1 were mixed at the ratio shown in Table 1 in absolute dry mass to make paper.

(Evaluation method)
The core base paper for corrugated board obtained by the above method was evaluated by the following method.

1) Fiber long maximum value About the pulp fiber obtained by disaggregating core raw paper by JIS-P8220: 1998 "pulp-disaggregation method", FiberLab. The centerline fiber length was measured using (Kajaani Co., Ltd.) and defined as the fiber length. The fiber length distribution was calculated by counting the number of fibers every 0.05 mm of fiber length, and it was determined in which region the maximum value was included.

2) Contaminant content The core base paper is disaggregated according to JIS-P8220: 1998 “pulp-disaggregation method”, and a screen plate having a slit width of 0.15 mm is used according to TAPPI-T275sp98. 100 g of dry pulp was processed with a flat screen, and the residue on the screen was made a contaminant. The mass ratio of the impurities to the core base paper in terms of dry weight was taken as the impurities content.

3) Basis weight About core raw paper, the basis weight was measured according to JIS-P8124: 1998 "Paper and board-Basis weight measuring method".

4) Bonding suitability C-cardboard using the core raw paper of Examples and Comparative Examples as a core, using a commercially available liner (Just Economy, 120 g / m ² , manufactured by Daio Paper Co., Ltd.) as a surface layer liner and a back layer liner. It was processed into. Here, the C-stage cardboard refers to the one described in JIS-Z1516 “Exterior Cardboard”.

The pastability of the core base paper to the surface layer and the back layer liner was evaluated as follows.
(Double-circle): There is no step crack and bonding defect, and it is excellent in bonding suitability.
○: Step cracks and poor bonding occurred slightly, but the bonding suitability was good.
(Triangle | delta): Although the step crack and the bonding defect generate | occur | produced somewhat, bonding suitability is good.
X: Many step cracks and poor bonding occur, resulting in poor bonding suitability.
In addition, ◎, ○, and Δ were actually usable.

5) Specific compressive strength For core raw paper, the lateral compressive strength of the core raw paper is measured according to JIS-P8126: 2005 “Paper and paperboard—Compressive strength test method—Ring crush method”. The compressive strength was calculated.

6) Plane compressive strength About the corrugated sheet adjusted in the said bonding suitability test, according to the prescription | regulation of JIS-Z0403-1 "corrugated cardboard-plane compressive strength test method", test piece 32.2cm < ² > (diameter 64.0mm) The plane compressive strength at was measured.
(Examination of evaluation)

The measurement results of this example and comparative example are shown in Table 1 below.

  From the results shown in Table 1, it is demonstrated that the core base paper for corrugated board of Examples 1 to 27 exhibits good flexibility and shock absorption in a balanced manner as compared with Comparative Examples 1 to 4. Yes.

  The core base paper for corrugated cardboard of the present invention is suitable for recycling at low cost, and can be suitably used particularly for protection of easily damaged products, for example, protection of fluorescent lamps and protection of confectionery.

Claims (3)

A core base paper for corrugated board obtained by papermaking raw material pulp,
The basis weight is 70 g / m ² or more and 100 g / m ² or less,
The number average fiber length distribution of the disaggregated pulp has a maximum value in the range of 0.50 mm or more and less than 1.05 mm,
The specific compressive strength is 40 N · m ² / g or more and 80 N · m ² / g or less,
A core base paper for corrugated board, characterized in that, when used as the core of a C-stage corrugated cardboard sheet defined in JIS-Z1516 “Exterior Corrugated Cardboard”, the flat compressive strength of the corrugated cardboard sheet is 124 kPa or more and 168 kPa or less. . Contain impurities with a minimum width of 0.25 mm or more,
The core base paper for corrugated cardboard according to claim 1, wherein the content of the impurities is 0.1 mass% or more and 0.5 mass% or less. The raw pulp contains colloidal silica as a flocculant and polyacrylamide as a coagulant,
The content of colloidal silica relative to the raw material pulp is 0.1% by mass or more and 0.8% by mass or less,
The core base paper for corrugated board according to claim 1 or 2 , wherein a content of polyacrylamide with respect to the raw material pulp is 0.01% by mass or more and 0.10% by mass or less.