JP7501833B2 - paper - Google Patents

Description

The present invention relates to paper.

Recycling systems have been established for newspapers, magazines, cardboard, milk cartons, etc., and after collection, they are reused as waste paper pulp. In recent years, environmental awareness has increased, and there is a demand for further increased use of waste paper pulp, which will lead to reduced carbon dioxide emissions. For example, Patent Document 1 proposes a multi-layered paperboard in which the waste paper pulp content of the total pulp is 70 mass% or more.

Recycled paper pulp has shorter fiber length than virgin pulp, and repeated reuse increases the amount of short fibers, while at the same time tends to reduce the beating freeness. Therefore, paper with a high recycled paper pulp content has the problem of being prone to strength loss.
The strength of paper can be improved by adjusting the raw pulp, external additives, internal additives, etc.
Known internal additives for improving paper strength include cationic starch, polyacrylamide (PAM), polyamide epichlorohydrin (PAE), etc. Carboxymethyl cellulose (hereinafter also referred to as CMC) has also long been known to improve paper strength. However, its strength-improving effect is smaller than that of PAM, etc., and it is hardly used at present.

JP 2020-020065 A

The objective of the present invention is to provide paper with improved strength.

The means for solving the above problems are as follows.
1. A paper comprising pulp and carboxymethyl cellulose having a 1% B type viscosity of 3 mPa·s or more and 16,000 mPa·s or less and a degree of carboxymethyl group substitution of 0.65 or more.
2. For a total of 100% by weight of the pulp and the carboxymethyl cellulose,
2. The paper according to 1., characterized in that the carboxymethyl cellulose is contained in an amount of 0.2% by weight or more and 10% by weight or less.
3. The paper according to 1. or 2., characterized in that the pulp contains 50% by weight or more of recycled paper pulp.

The paper of the present invention has improved strength compared to paper that does not contain CMC and is otherwise the same. The paper of the present invention has excellent strength even when it contains a large amount of recycled paper pulp. The paper of the present invention can be suitably used for cardboard, cardboard liners, medium base paper, paperboard for paper containers, paperboard for box making, paperboard for laminated paper, etc.

The present invention relates to paper containing pulp and carboxymethylcellulose having a 1% B-type viscosity of 3 mPa·s or more and 16,000 mPa·s or less and a degree of carboxymethyl group substitution of 0.65 or more.

Pulp Examples of pulp that can be used include chemical pulps made from wood, such as bleached softwood kraft pulp (NBKP), unbleached softwood kraft pulp (NUKP), bleached hardwood kraft pulp (LBKP), unbleached hardwood kraft pulp (LUKP), and sulfite pulp (SP); mechanical pulps made from wood, such as ground pulp (GP), refiner ground pulp (RGP), stone ground pulp (SGP), chemi-ground pulp (CGP), semi-chemical pulp (SCP), thermomechanical pulp (TMP), and chemi-thermomechanical pulp (CTMP); non-wood pulp obtained from kenaf, bagasse, bamboo, hemp, straw, and the like; and waste paper pulp made from waste paper, from which ink contained in the waste paper has been removed in a deinking process. Any of these known pulps can be appropriately blended and used.

The paper of the present invention has excellent strength, so it can be blended with a large amount of recycled paper pulp, and preferably contains 50% or more by weight of recycled paper pulp relative to the total amount of pulp, more preferably 70% or more by weight, even more preferably 80% or more by weight, and can be 90% or more by weight, or even 100% by weight. Examples of recycled paper pulp that can be used include recycled cardboard, recycled white, extra white, medium white, and white damage paper that has been disintegrated and unprinted, recycled paper that has been printed on fine paper, fine coated paper, medium paper, medium coated paper, and recycled paper, and pulp (DIP) that has been disintegrated and deinked from discarded confidential documents, recycled magazines, and recycled newspapers.

・Carboxymethylcellulose (CMC)
The present invention uses a CMC having a 1% Brookfield viscosity of 3 mPa·s or more and 16,000 mPa·s or less and a degree of carboxymethyl group substitution (hereinafter also referred to as DS) of 0.65 or more.
If the 1% B type viscosity of CMC is less than 3 mPa·s, the strength may not be improved, and if it exceeds 16,000 mPa·s, the viscosity may become too high and the papermaking properties may deteriorate. The 1% B type viscosity of CMC is preferably 50 mPa·s or more and 10,000 mPa·s or less, more preferably 90 mPa·s or more and 7,000 mPa·s or less, and even more preferably 100 mPa·s or more and 6,000 mPa·s or less.
If the DS of CMC is less than 0.65, the strength may not be improved. The upper limit of the DS of CMC is 3. Since CMC has anionic properties, when a cationic fixing agent described later is used, the formation of the paper may be deteriorated due to the aggregation action with the cationic fixing agent. Therefore, the DS of the CMC used in the present invention is preferably 1.8 or less, and more preferably 1.6 or less.

The amount of CMC is not particularly limited as long as it is within a range that improves strength compared to paper that does not contain CMC, but it is usually preferable to use 0.2 to 10 weight percent CMC relative to 100 weight percent of the total of pulp and CMC. If the amount of CMC is less than 0.2 weight percent, strength may not improve significantly, and if it exceeds 10 weight percent, the effect may saturate and the strength may not improve any further, and costs may increase. The amount of CMC is preferably 0.5 to 7 weight percent, and more preferably 1.0 to 5 weight percent.

Cationic fixing agent The paper of the present invention preferably contains a cationic fixing agent. By containing a cationic fixing agent, CMC can be effectively fixed to the pulp. Examples of the cationic fixing agent include cationic polymers such as aluminum sulfate (aluminum sulfate), polyaluminum chloride (PAC), ferric chloride, polyferric sulfate, cationized starch, cationic polyacrylamide (PAM), polyvinylamine, polydiallyldimethylammonium chloride (polyDADMAC), polyamide epichlorohydrin (PAE), and polyethyleneimine (PEI).
The amount of the cationic fixing agent to be added is not particularly limited as long as it is within a range in which the agent can exert its effect.

Furthermore, the paper of the present invention may contain known fillers and papermaking auxiliaries, if necessary.
Examples of the filler that can be used include known fillers such as inorganic fillers such as talc, kaolin, calcined kaolin, clay, heavy calcium carbonate, light calcium carbonate, white carbon, zeolite, magnesium carbonate, barium carbonate, titanium dioxide, zinc oxide, silicon oxide, amorphous silica, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, barium sulfate, and calcium sulfate; and organic fillers such as urea-formalin resin, polystyrene resin, phenol resin, and hollow microparticles.

Examples of papermaking auxiliaries include various internal sizing agents such as rosin, alkyl ketene dimer (AKD), and alkenyl succinic anhydride (ASA), various nonionic, cationic, and amphoteric retention improvers, freeness improvers, paper strength improvers, various starches, polyacrylamide, urea resin, melamine resin, epoxy resin, polyamide resin, polyamine resin, polyethyleneimine, vegetable gum, polyvinyl alcohol, latex, polyethylene oxide, hydrophilic crosslinked polymer particle dispersions and their derivatives or modified products, basic aluminum compounds such as aluminum sulfate, aluminum chloride, sodium aluminate, basic aluminum chloride, and basic polyaluminum hydroxide, water-soluble aluminum compounds such as alumina sol that is easily decomposed in water, polyvalent metal compounds such as ferrous sulfate and ferric sulfate, silica sol, defoamers, coloring dyes, coloring pigments, pH adjusters, pitch control agents, and slime control agents, and can be selected and used as needed.

The uses of the paper of the present invention are not particularly limited. However, when the paper contains a large amount of recycled paper pulp, the uses may be limited due to the risk of contamination with foreign matter. When the paper contains recycled paper pulp, the paper can be suitably used as cardboard, particularly cardboard liners for packaging, corrugating medium, paperboard for paper containers, paperboard for box making, paperboard for laminated paper, etc.
The basis weight of the paper of the present invention is not particularly limited, but can be, for example, 10 g/m ² or more and 900 g/m ² or less. The basis weight can be selected according to the application, and for example, when used as a single-ply paper, it can be appropriately set in the range of 10 g/m ² or more and 500 g/m ² or less, more preferably 30 g/m ² or more and 300 g/m ² or less. In addition, when it is a multi-layer paperboard having two or more paper layers, one layer may be in the above range, but the total of all layers can be appropriately set in the range of 70 g/m ² or more and 900 g/m ² or less, and for example, when used as a liner for corrugated cardboard, it can be 70 g/m ² or more and 550 g/m ² or less.

The paper manufacturing (papermaking) method and the type of papermaking machine are not particularly limited, and any known manufacturing (papermaking) method and papermaking machine can be selected, such as a Fourdrinier papermaking machine, a twin-wire papermaking machine, a cylinder papermaking machine, a gap former, a hybrid former (on-top former), or a combination of these. In addition, the pH during papermaking may be in the acidic range (acidic papermaking), pseudo-neutral range (pseudo-neutral papermaking), neutral range (neutral papermaking), or alkaline range (alkaline papermaking), and after papermaking in the acidic range, an alkaline agent may be applied to the surface of the paper layer.

After papermaking, a surface treatment agent can be applied to the paper as needed. When applying a surface treatment agent, known surface treatment chemicals such as water-soluble polymeric substances and surface sizing agents can be used alone or in combination depending on the quality required for the paper.
The type of size press for applying the surface treatment agent is not particularly limited, and the surface treatment agent can be externally added by appropriately using a known device such as a two-roll size press, a gate roll coater, a shim sizer, etc. The calender may be bypassed or may be treated within the normal operating range.

The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.
The papers obtained in the following Examples and Comparative Examples were measured by the following methods. The results are shown in Table 1.
Basis weight: Measured with reference to JIS P 8223.
Bulk thickness: Measured with reference to JIS P 8118 and JIS P 8223.
Bulk density: Calculated from basis weight and bulk thickness with reference to JIS P 8118 and JIS P 8223.
Tensile index: Measured with reference to JIS P 8113 and JIS P 8223.
Burst strength index: Measured according to JIS P 8131.

"Example 1"
The pulp used was a mixture (CSF 370 ml) of 88% by weight of recycled paper pulp from cardboard and 12% by weight of recycled paper pulp from magazines. 99.5% by weight of this pulp and 0.5% by weight of CMC (Sunrose F600LC, 1% B-type viscosity 6000 mPa·s, DS 0.7, manufactured by Nippon Paper Industries Co., Ltd.) were mixed with water to a concentration of 1%, and stirred at 3000 rpm for 30 minutes. Next, 1% by weight of aluminum sulfate, 0.15% by weight of dry strength agent, 70 ppm of retention aid, and 100 ppm of colloidal silica were added and stirred to prepare a paper stock.
The obtained paper stock was diluted to about 0.7% solids concentration, and then formed into a sheet, pressed, and dried in accordance with JIS P 8222 to produce handsheets.

"Example 2"
Paper was obtained in the same manner as in Example 1, except that the proportions of pulp and CMC were 99% by weight and 1% by weight, respectively.
"Example 3"
Paper was obtained in the same manner as in Example 1, except that the proportions of pulp and CMC were 98% by weight and 2% by weight, respectively.
"Example 4"
Paper was obtained in the same manner as in Example 1, except that the proportions of pulp and CMC were 96% by weight and 4% by weight, respectively.

"Example 5"
Paper was obtained in the same manner as in Example 1, except that CMC (Sunrose F1400MC, manufactured by Nippon Paper Industries Co., Ltd., 1% B-type viscosity 14,000 mPa·s, DS 0.75) was used.
"Example 6"
Paper was obtained in the same manner as in Example 5, except that the proportions of pulp and CMC were 99% by weight and 1% by weight, respectively.
"Example 7"
Paper was obtained in the same manner as in Example 5, except that the proportions of pulp and CMC were 98% by weight and 2% by weight, respectively.

"Comparative Example 1"
Paper was obtained in the same manner as in Example 1, except that CMC was not added.

"Example 8"
A mixture (CSF 390 ml) of 73% by weight recycled paper pulp from cardboard, 20% by weight recycled paper pulp from magazines, and 7% by weight unbleached softwood kraft pulp (NUKP) was used as the pulp. Paper was obtained in the same manner as in Example 4, except that CMC (Sunrose A10SH, manufactured by Nippon Paper Industries Co., Ltd., 1% B-type viscosity 100 mPa·s, DS 1.4) was used.
"Example 9"
Paper was obtained in the same manner as in Example 8, except that CMC (Sunrose F10LC, 1% B type viscosity 100 mPa·s, DS 0.7, manufactured by Nippon Paper Industries Co., Ltd.) was used.
"Example 10"
Paper was obtained in the same manner as in Example 8, except that CMC (Sunrose F350HC, 1% B type viscosity 3500 mPa·s, DS 0.9, manufactured by Nippon Paper Industries Co., Ltd.) was used.
"Example 11"
Paper was obtained in the same manner as in Example 8, except that CMC (manufactured by Nippon Paper Industries Co., Ltd., Sunrose F600LC, 1% B type viscosity 6000 mPa·s, DS 0.7) was used.

"Comparative Example 2"
Paper was obtained in the same manner as in Example 8, except that CMC was not added.

The papers obtained in Examples 1 to 11 of the present invention had improved burst strength index and tensile strength index compared to the papers not containing CMC obtained in Comparative Examples 1 and 2. It was confirmed that the strength of paper made from recycled paper pulp can be improved by the present invention.

Claims (2)

The present invention relates to a pulp composition and a carboxymethyl cellulose composition having a 1% B type viscosity of 3,500 mPa·s or more and 16,000 mPa·s or less and a degree of carboxymethyl group substitution of 0.65 or more,
The pulp contains 50% by weight or more of recycled paper pulp,
The carboxymethyl cellulose is contained in an amount of 0.5% by weight or more and 10% by weight or less relative to 100% by weight of the total of the pulp and the carboxymethyl cellulose,
A paperboard having the carboxymethyl cellulose incorporated therein. 2. The paperboard according to claim 1, wherein the carboxymethyl cellulose is contained in an amount of 1% by weight or more relative to 100% by weight of the total of the pulp and the carboxymethyl cellulose.