JP6921042B2 - Base paper for paper packaging containers - Google Patents

Description

In the present invention, for example, the printability of the outer surface layer portion required for the base paper for paper packaging containers typified by tissue cartons, the processing suitability typified by rule cracking, and the friction between the inclusions and the inner surface of the base paper for paper packaging containers. Regarding base paper for paper packaging containers, which has excellent properties and paper dust control.

In recent years, due to the trend of visualization, paper containers for paper packaging containers are also required to have high-definition printability for improving the product image. In order to ensure high-definition printability, a means for providing a coating layer adopted for conventional printing paper on the surface of a base paper for a paper packaging container is used. However, unlike general printing applications, base paper for paper packaging containers has processing suitability for box making, strength for maintaining the shape of the box and durability during use, and protection and contamination of the contents. Countermeasures exist as further required quality.

For example, as a base paper for paper packaging containers, as disclosed in Japanese Patent Application Laid-Open No. 2006-900955 (Patent Document 1), a carton base paper considering nature-oriented and environmentally friendly has been proposed. There is also a strong need for base paper for paper wrapping containers that improves the product image and ensures high-definition printability, and this is because the conventional base paper for paper wrapping containers is composed of multilayer paper mainly made of used paper. It is required to improve the problem of appearance color tone due to low whiteness, deterioration of strength as a packaging container, particularly surface strength and compression strength, and paper dust and peeling in holding and inserting contents.

Further, as a measure for improving the whiteness, a means for using bleached wood pulp having a high whiteness and excellent printability in the surface layer of a multilayer paper is disclosed in Japanese Patent Application Laid-Open No. 2013-204155 (Patent Document 2). However, bleached wood pulp is inferior in opacity, and in order to conceal the color of used paper pulp with low whiteness used in the lower surface layer and the middle layer, it is necessary to use a large amount of bleached wood pulp, which is expensive, and the surface made of bleached wood pulp. It is necessary to increase the strength of the layer. For example, Japanese Patent Application Laid-Open No. 2008-87854 has proposed that a means for providing a coating layer on the surface layer as a measure for obtaining higher-definition printability and improving the appearance of whiteness also has an air purifying effect. It is disclosed in Patent Document 3).

However, the coating layer (coating layer) has a problem that the coating layer is liable to crack when folded during processing into a paper packaging container, and as described as a problem in Patent Document 2, other than printability. In addition, it is necessary to take measures for processing suitability and stains on the contents, and further improvement is required. There is growing interest in resource protection and environmental recycling, and there is a growing demand for recycling and reduction of packaging materials.

For this reason, the paper density of corrugated cardboard cases for packing products, products, corrugated cardboard base paper used for paper containers, white boards, etc. is becoming lower and lighter, and the paper density of paperboard is 10 to 15% standard. Even if it is downed to reduce the paper density and weight, it is required to have the same or higher strength, processing suitability, and printability as before. For example, Japanese Patent Application Laid-Open No. 2010-150723 (Patent Document 4) describes a multi-layer paperboard used for a corrugated board base paper in which such a point is improved.

The paperboard described in Patent Document 4 is formed by applying a coating liquid containing an organic pigment on at least the surface layer of the base paper to form a coating layer, and the back surface layer of the base paper (on the surface coating layer side). A coating liquid made of a water-soluble resin was applied on the opposite layer), and the wax pick on the back side of the base paper was set to 10 to 20 A. Even if the paper density is reduced and the weight is reduced in this way, the processing suitability of corrugated cardboard, paper containers, etc. can be satisfied, and water-based and oil-based ink is used when paperboard is used for corrugated cardboard cases for fruits and vegetables. It is possible to satisfy the stamp printing suitability suitable for both of the above.

However, although the paperboard described in Patent Document 4 can improve the strength, processing suitability, and printability of the paperboard when used in a corrugated cardboard case, it has an outer surface layer portion required for a base paper for a paper packaging container such as a tissue carton. There was room for improvement in printability, processing suitability typified by rule cracking, scratch resistance between the inclusions (tissue) and the inner surface of the base paper for paper packaging (back surface), and paper dust control. These improvements are the same in Patent Documents 1 to 3.

Japanese Unexamined Patent Publication No. 2006-900955 Japanese Unexamined Patent Publication No. 2013-204155 Japanese Unexamined Patent Publication No. 2008-87854 Japanese Unexamined Patent Publication No. 2010-150723

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is the printability of the outer surface layer portion required for the base paper for a paper packaging container and the processability represented by the rule cracking. An object of the present invention is to provide a base paper for a paper wrapping container which is excellent in scratch resistance between the inclusions and the inner surface of the base paper for a paper wrapping container and suppresses paper dust.

The above-mentioned object of the base paper for a paper packaging container according to the present invention is a multilayer abstract ^{having a basis weight of 250 g / m 2 to} 350 g / m ² and a density of 0.77 to 0.90 g / cm ^{3 having a front surface layer, a front surface layer and a back surface layer.} The base paper for paper packaging containers, the front surface layer of which is mainly made of mixed kraft pulp and high-quality waste paper pulp, the lower surface layer of which is mainly of waste paper pulp, and the back surface layer of which is waste paper derived from machine pulp-containing waste paper. The mixed kraft pulp is a mixture of coniferous bleached kraft pulp and broadleaf bleached kraft pulp, and the ratio of the coniferous bleached kraft pulp / the broadleaf bleached kraft pulp is 15:85 to 85:15. , The compression strength of the vertical grain of the base paper for the paper packaging container is 720 to 840 N.

Further, the above object of the base paper for a paper packaging container according to the present invention is that the surface layer is a mixture of the mixed kraft pulp and the high-quality waste paper pulp at a ratio of 30:70 to 70:30. The waste paper pulp forming the lower layer is selected from Kent, special white, medium white, white Manila, imitation, or color in the waste paper statistical classification, and the product moisture of the base paper for the paper packaging container according to JIS P8127 is 4.0 to 9. By 5%, or the surface layer has ^{a surface coating layer containing 2} to 10 g / m 2 of pigment and an adhesive as main components per side, and the whiteness of the surface coating layer is 73%. As described above, the glossiness of the blank paper is 20% to 50%, or the outer surface of the back surface layer is provided with a back surface coating layer made of polyvinyl alcohol, a paper strength enhancer, and a lubricant, or The polyvinyl alcohol has a degree of polymerization of 1000 to 2000 and a degree of saponification of 98.0 to 99.0, the paper strength enhancer is a modified polyacrylamide-based paper strength enhancer, and the lubricant is polyethylene wax. By being an aqueous dispersion of wax particles, or by further providing at least one or more middle layers between the lower surface layer and the back surface layer, and the middle layer using waste paper pulp derived from machine pulp-containing waste paper as a main raw material. , Achieved more effectively.

According to the base paper for paper packaging containers according to the present invention, a multi- ^{layer paper having a basis weight of 250 g / m 2 to} 350 g / m ² and a density of 0.77 to 0.90 g / cm ³ having a front surface layer, a front surface layer and a back surface layer. Paper packaging container base paper, which has a front surface layer and a front surface layer composed of mixed kraft pulp and waste paper pulp, and waste paper pulp derived from machine pulp-containing waste paper is used for the middle layer and the back surface layer, and has vertical grain. Since the compression strength was set to 720 to 840 N, the printability and processing suitability of the outer surface layer, which are required for the base paper for paper packaging containers, and the scratch resistance between the inclusions and the inner surface of the base paper for paper packaging containers. , It becomes possible to provide a base paper for a paper packaging container excellent in controlling paper dust.

It is a conceptual cross-sectional view which shows one aspect of the base paper for a paper packaging container which concerns on this invention.

Hereinafter, the base paper for paper packaging containers according to the present invention will be described in detail mainly with reference to drawings. The base paper for paper packaging containers according to the present invention is not limited to the following embodiments, and is within the range not deviating from the matters described in the present specification (including the scope of claims and drawings). Needless to say, the configuration can be changed as appropriate.

FIG. 1 is a conceptual cross-sectional view showing an aspect of a base paper for a paper packaging container according to the present invention. The base paper 1 for a paper packaging container shown in FIG. 1 is composed of a base paper 6 having a layer structure of a surface layer 2, a lower surface layer 3, a middle layer 4, and a back surface layer 5, and is a surface layer side surface of the base paper 6 (hereinafter, “upper surface”). A surface coating layer 7 composed of a coating liquid for a front surface layer is provided on the coating liquid for the back surface layer, and the coating liquid for the back surface layer is provided on the back surface layer side surface (hereinafter referred to as “lower surface”) of the base paper 6. The back surface coating layer 8 is provided.

The surface layer and the lower surface layer have a structure composed of mixed kraft pulp and used paper pulp, and a preferred embodiment will be described below. First, the surface layer 2 will be described. The pulp used for the surface layer 2 is mainly a mixed pulp of softwood bleached kraft pulp or hardwood bleached kraft pulp (hereinafter referred to as "mixed bleached kraft pulp"). The ratio of the mixed bleached kraft pulp is (coniferous bleached kraft pulp) :( hardwood bleached kraft pulp) = 15: 85 to 85:15. As a result, by reducing the paper density and weight of the base paper for this paper packaging container, it is possible to strengthen the bond of pulp fibers in the surface layer, satisfy the ruled line cracking resistance required for the use of paper containers, and finely. It is also possible to prevent the loss of fibers and inorganic substances. If the proportion of softwood bleached kraft pulp is less than 15 and the proportion of hardwood bleached kraft pulp exceeds 85, the amount of long fiber pulp is reduced and line cracking is likely to occur. On the other hand, if the proportion of coniferous bleached kraft pulp exceeds 85 and the proportion of broadleaf bleached kraft pulp is less than 15, the surface layer cannot be made uniform (flat) due to too much long fiber pulp. In addition to causing printing defects, the paper is less likely to be squeezed and the rigidity of the base paper for this paper packaging container can be ensured in order to reduce the paper density and weight of the base paper for this paper packaging container. It gets harder. Since the fibers of mixed bleached kraft pulp are soft and the fibers are easily crushed when the calendar treatment is applied, the surface of the base paper is further flattened by applying the calendar treatment to the base paper before forming the surface coating layer. The coating liquid for the surface layer can be uniformly applied on the surface layer.

In addition to the above-mentioned mixed bleached kraft pulp, the surface layer 2 is made of high-quality waste paper pulp (for example, high-quality waste paper, coated paper, etc.) derived from the fine white card in the used paper statistical classification (hereinafter, simply "high-quality type"). "Recycled paper pulp") is added. This further makes it possible for the base paper for paper containers according to the present invention to have a low paper density and a light weight, strengthen the bonding of pulp fibers in the surface layer 2, and prevent ruled line cracking necessary for use in paper containers. It is possible to satisfy the aptitude and prevent the loss of fine fibers (for example, paper dust) and inorganic substances. In the surface layer 2, the high-quality waste paper pulp is preferably mixed with the above-mentioned mixed bleached kraft pulp, that is, (mixed bleached kraft pulp) :( high-quality waste paper pulp) = 30: 70 to 70:30. If the ratio of mixed bleached kraft pulp is less than 30 and the ratio of high-quality waste paper pulp exceeds 70, ruled line cracking is likely to occur due to a decrease in long fiber pulp. On the other hand, when the ratio of mixed bleached kraft pulp exceeds 70 and the ratio of high-quality waste paper pulp is less than 30, the surface layer cannot have a uniform texture (flat) due to too much long fiber pulp. In addition to causing printing defects, it becomes difficult to tighten the paper in order to reduce the paper density and weight of the base paper for this paper packaging container, and it is necessary to ensure the rigidity of the base paper for this paper packaging container. It gets harder.

Although the surface layer 2 is formed only with the above pulp, an internal chemical such as a sizing agent, a sulfate band, and a paper strength enhancer (separate from the surface enhancer described later) may be used. In this case, the sizing agent is preferably about 5 to 10 kg / PT (50% solid content equivalent), the aluminum sulfate band is preferably about 60 to 70 kg / PT, and the paper strength enhancer is 5 to 10 kg / PT (20%). (Solid content equivalent) is preferable because it ensures adjustment of the amount of ink impregnated in printing on the surface layer, fixing of the sizing agent and the paper strength enhancer to the raw material pulp, and improvement of the strength of the surface layer surface. As the sizing agent in this case, an internal sizing agent such as alkyl ketene dimer, alkenyl succinic anhydride, or rosin is used. Further, as the paper strength enhancer, urea formaldehyde resin, melamine formaldehyde resin, polyamide polyamine epichlorohydrin (PAE), polyvinylamine, cationized starch and the like are used.

Next, the lower surface layer 3 will be described. The lower surface layer 3 is made of used paper pulp derived from used paper consisting of Kent, special white, medium white, white Manila or imitation, or colored paper in the used paper statistical classification. By using a raw material pulp whose properties are not significantly different from those of the surface layer raw material pulp while minimizing the influence on the pulp hue of the surface layer, the surface layer peeling and paper quality strength are maintained while maintaining the color tone of the surface layer. Can be maintained.

Further, although the lower surface layer 3 is formed only with the above pulp, an internal chemical such as a sizing agent, a sulfate band, and a paper strength enhancer (separate from the surface enhancer described later) may be used as in the surface layer 2. .. In this case, the sizing agent is preferably about 4 to 8 kg / PT (50% solid content equivalent), the aluminum sulfate band is preferably about 80 to 95 kg / PT, and the paper strength enhancer is 4 to 8 kg / PT (20%). Solid content conversion) is preferable. The lower surface layer does not require as much printability and paper strength as the surface layer, but it has a synergistic effect by suppressing the movement between paper layers during paper-layer transfer of chemicals such as paper strength enhancers, sizing agents, and aluminum sulfate bands in the surface layer. In order to secure it, it is preferable to invite to the above range. In particular, while the paper strength enhancer can increase the strength of the paper, it has a problem of hardening the paper layer, and when the paper layer becomes hard, it is used in a paper packaging container that requires bending, which is the subject of the present invention. Therefore, since there is a problem that the paper layer is torn at so-called creases, it is necessary to adjust the content of the chemicals within a range in which the paper layer can be flexibly bent following the surface layer. As the sizing agent in this case, an internal sizing agent such as alkyl ketene dimer, alkenyl succinic anhydride, or rosin is also used. Further, as the paper strength enhancer, urea formaldehyde resin, melamine formaldehyde resin, polyamide polyamine epichlorohydrin (PAE), polyvinylamine, cationized starch and the like are used.

The middle layer 4 and the back surface layer 5 are made of the same raw material pulp, and the raw material pulp is not particularly limited. Raw material pulp mainly made of balls, used paper for local tickets, etc., that is, used paper pulp derived from used paper is used, and mechanical pulp is also contained. Incidentally, the middle layer 4 and the back surface layer 5 have a two-layer structure in the conceptual cross-sectional view shown in FIG. 1, but may have a multi-layer (plural) structure of three or more layers. On the contrary, the middle layer 4 and the back surface layer 5 may have a one-layer (single-layer) structure. Further, when the middle layer has a multi-layer structure, there is no limitation as long as the above-mentioned used paper is used, whether the same type or different type is used for each layer.

Further, although the middle layer 4 and the back surface layer 5 are formed only with the above pulp, internal additions such as a sizing agent, a sulfate band, and a paper strength enhancer (separate from the surface enhancer described later) are formed as in the surface layer 2 and the lower surface layer 3. Chemicals may be used. In this case, the sizing agent is preferably about 5 to 10 kg / PT (50% solid content equivalent), the aluminum sulfate band is preferably about 40 to 70 kg / PT, and the paper strength enhancer is 2 to 7 kg / PT (20%). (Solid content conversion) is preferable. The middle layer (and / or the back layer) needs to have a cushioning effect when bent when used in a paper packaging container that requires bending, and in order to maintain the original flexible properties of the raw material pulp, the above-mentioned description is made. It is necessary to limit the amount of chemicals used to produce the minimum necessary effect. As the sizing agent in this case, an internal sizing agent such as alkyl ketene dimer, alkenyl succinic anhydride, or rosin is also used. Further, as the paper strength enhancer, urea formaldehyde resin, melamine formaldehyde resin, polyamide polyamine epichlorohydrin (PAE), polyvinylamine, cationized starch and the like are used.

Further, in the base paper 1 for this paper packaging container, the ash content measured according to JIS-P8252 (525 ° C.) is more preferably 10 to 25% and 13 to 20%. If the ash content is less than 10%, the paper density tends to decrease and the compressive strength tends to decrease. On the other hand, if the ash content exceeds 25%, it becomes difficult to satisfy the ruled line cracking resistance.

Further, in the above ash content range, when the paper density of the base paper 6 of the base paper 1 for the main paper packaging container ^{is adjusted to 0.77 to 0.90 g / cm 3} , the absorption balance of the coating liquid for the surface layer on the base paper is adjusted. It is the best, and it is possible to reduce the weight by 10 to 15% compared to the conventional paperboard, and even if the paper density is low and the weight is reduced, the compressive strength of the paperboard is maintained and the processing suitability is maintained. I found that I could do it.

The above-mentioned raw material pulp is subjected to a known papermaking process, for example, a wire part, a press part, a dryer part, a size press, a calendar part, etc. A base paper for a base paper for a paper packaging container having a paper layer is formed. The method of papermaking the base paper 6 of the base paper for this paper packaging container is not particularly limited, and may be any of an acidic papermaking method, a neutral papermaking method, and an alkaline papermaking method. Further, since the paper machine is not particularly limited, various known paper machines such as a long net paper machine, a twin wire paper machine, a circular net paper machine, and a circular net short net combination paper machine can be used. can.

The base paper 6 used for the base paper for this paper packaging container has a base paper basis weight (g / m ² ) of each layer of 36 to 44 for the front surface layer, 49 to 60 for the lower surface layer, and 145 for the middle layer (back surface layer). It was found that it is preferable to adjust the range from to 200 and to have a relationship of surface layer <lower surface layer <middle layer ≤ back surface layer. As a result, it is possible to form a front surface coating layer and a back surface coating layer which can achieve low paper density and weight reduction, which is the object of the present invention, and can maintain rigidity.

It is desirable that the vertical grain of the base paper product for a paper packaging container according to the present invention has a compressive strength of 720 to 840 N. In the use of the present invention in a paper wrapping device, the flow direction of the paper is often used in the direction of supporting the weight and shape of the container. It is preferable to have it.

Further, the basis weight of the base paper product for paper packaging containers according to the present invention is preferably 250 to 350 g / m ² . If the basis weight is ^{less than 250 g / m 2} , there is a problem that the compressive strength of the tissue case becomes low when the base paper for the paper packaging container is used for, for example, a tissue case. On the other hand, if ^{it exceeds 350 g / m 2} , the paper thickness of the base paper for paper packaging according to the present invention also increases, so that when the base paper for paper packaging is bent, the surface stress becomes too strong and the surface coating is applied. There is a problem that cracks occur in the work layer and the surface layer of the base paper.

Further, the base paper 6 of the base paper for this paper packaging container is preferably pressure-welded to a mirror-finished dryer after the pressing process, and particularly preferably pressure-welded to a large-diameter dryer such as a Yankee dryer. Further, it is more preferable that the wet paper moisture of the base paper before pressure welding is 53 to 60%. If the moisture content of the wet paper is less than 53%, the absolute amount of moisture present on the front surface becomes small, and only the front and back surfaces become overdried. The unevenness of the front and back surfaces becomes large, and it becomes difficult to achieve the object of the present invention with the amount of the coating liquid for the front surface layer or the coating liquid for the back surface layer, which will be described later. On the other hand, when the moisture content of the wet paper exceeds 60%, the absolute moisture content distributed in the front surface layer or the back surface layer of the base paper increases, and the amount of water vapor evaporated from the front surface layer or the back surface layer increases. Insufficient contact makes it difficult to obtain good front and back layers. The product moisture content of the base paper for paper packaging containers according to JIS P8127 is 4.0 to 9.5%. Maintaining the flexibility of raw material pulp in combination with refraining from using chemicals that harden the paper layer, such as paper strength enhancers, as a measure for workability in folding machines and tearing of folded parts required for paper packaging containers. It is preferable to adjust the product moisture to a predetermined range for the purpose of

After the base paper 6 is made, the surface coating liquid is applied to the front surface layer and the back surface layer coating liquid by a coating machine such as a printing machine, a bar coater, a rod coater, or an air knife in the secondary processing. The layer 7 and the back surface coating layer 8 are formed to form a base paper for this paper packaging container.

A surface coating layer 7 is formed by coating a surface layer coating liquid containing a pigment and an adhesive as a main component on the surface layer 2 (upper surface) of the base paper for a paper packaging container according to the present invention. , The back surface coating liquid made of a water-soluble resin is coated on the back surface layer (lower surface) of the base paper to form the back surface coating layer 8, and the inclusions (for example, tissue) and the paper packaging on the back surface layer side are formed. It is possible to satisfy the scratch resistance with the inner surface (corresponding to the back surface layer) of the base paper for containers and the effect of suppressing paper dust.

The pigment used for the surface coating layer 7 may be a basic inorganic pigment. As the inorganic pigment, inorganic pigments such as clay, calcium carbonate, and silica can be used, and among them, clay and calcium carbonate are preferable for achieving the object of the present invention of obtaining processability and printability. Regarding the blending amount of the inorganic pigment, the ratio in the case of clay: calcium carbonate is preferably 10 to 90: 90 to 10. As a result, it is possible to maintain the processability for a tissue carton, a paper container, etc., and to have the printability. It is preferable to use clay as an inorganic pigment that brings out flatness and gloss as an inorganic pigment in the surface coating layer, and it is preferable to combine it with calcium carbonate as an inorganic pigment having a high white color that improves the appearance of printing, and the content of clay. If it is less than 10 parts by weight, the problem of poor print fineness occurs, and if it exceeds 90 parts by weight, the problem of lowering the dryness of the printing ink tends to occur. Further, even with respect to the content of calcium carbonate, if it is less than 10 parts by weight, the whiteness tends to decrease, which tends to cause a problem that the print appearance deteriorates, and if it exceeds 90% by weight, the problem that the fineness of printing is lacking. Is likely to occur. In addition, organic pigments can also be used. Although the hardness of organic pigments is lower than that of inorganic pigments, the particles have elasticity, rigidity, and gloss, so that printability, ruled line cracking resistance, and compressive strength can be satisfied in a well-balanced manner. Is preferable to inorganic pigments. Therefore, by including the organic pigment in the coating liquid for the surface layer in this way, the flexibility and rigidity of the surface coating layer can be ensured. As a result, the resistance to bending stress of the surface layer is improved, and the suitability for cracking of the ruled line can be improved, so that the occurrence of cracking of the surface coating layer can be significantly reduced. However, in the case of a tissue carton or a paper container, it does not matter whether or not the organic pigment is used, as long as the processing suitability is maintained and the printing suitability is maintained.

^{The amount of the coating liquid for the surface layer is 2 to} 10 g / m 2 (dry conversion) in the dry state of the surface coating layer 7 (the state of the surface coating layer formed on the base paper). It is preferably 4.5 to 9.5 g / m ² . As a result, the pulp fibers in the surface layer of the base paper in contact with the surface coating layer can be sealed, so that the printability can be improved, and the smoothing of the printed surface and the rigidity of the coating layer can be improved. Can be secured. Further, since the thickness of the surface coating layer is not too thick, the ink easily penetrates into the base paper and the ink adhesiveness is improved, so that high-definition printing with good color reproducibility becomes possible.

If the coating amount of the coating liquid for the surface layer ^{is less than 2 g / m 2} , the sealing effect between the pulp fibers in the surface layer cannot be exhibited, and there is a problem that ink bleeding in printing is likely to occur. , The high-definition printability desired by the present application cannot be sufficiently obtained. On the other hand, if the coating amount ^{exceeds 10 g / m 2} , the thickness of the surface coating layer becomes too thick, and the rigidity of the coating layer is improved, but resistance to bending stress of the surface layer cannot be obtained, and paper container processing is performed. It tends to be inferior in processing suitability such as the suitability for cracking of ruled lines, which is sometimes required.

As the organic pigment contained in the coating liquid for the surface layer, a hollow plastic pigment (PP) is preferable. Although it has a lower hardness than an inorganic pigment, it has rigidity, so that the pigment itself can be easily deformed, and it has the effect of improving the suitability for cracking of ruled lines and improving the processability of the base paper for this paper packaging container.

Further, it is preferable that SBR latex is contained as an adhesive for the surface coating layer 7 (used for the coating liquid for the surface layer). SBR latex has appropriate film-forming property and rigidity, and also has good ink inking property. Therefore, by containing the organic pigment and the SBR latex in the coating liquid for the surface layer, not only the suitability for line cracking resistance as the base paper for paper packaging containers and the ink penetration property, but also the base paper for this paper packaging container can be obtained. Even if the paper density is low and the weight is reduced, the compressive strength is maintained, so that the processing suitability of the base paper for this paper packaging container can be further improved.

In addition to the above SBR latex, the resin used as an adhesive includes acrylamide resin, styrene resin, acrylic resin, polyvinyl resin such as PVA, and resin such as starch. In the present invention, the SBR latex is used. Such a styrene-based resin is particularly preferable.

The amount of SBR latex blended in the coating liquid for the surface layer is preferably 6 to 15 parts by weight, preferably 9 to 12 parts by weight, based on 100 parts by weight of the pigment (inorganic pigment).

When the blending amount of SBR latex is less than 6 parts by weight with respect to the pigment, the amount of adhesive is small and it becomes difficult to satisfy the suitability for cracking of ruled lines. Further, the surface coating layer is easily scratched by rubbing. On the other hand, when the blending amount of SBR latex exceeds 15 parts by weight, the surface of the front surface coating layer tends to have a sticky feeling, and when the wound product is processed, the front surface coating layer and the back surface coating layer become sticky. Since it tends to stick, picking may occur on the paper surface. Further, although the resistance of the surface coating layer to bending stress is improved, the surface coating layer itself loses its flexibility and tends to become hard, so that it becomes difficult to satisfy the ruled line cracking resistance, and in particular, Problems with water-based printability.

The coating method for the surface layer coating liquid may be single coating or multi-stage coating of double coating or more, and the coating equipment includes a bar coater, a blade coater, an air knife coater, and a rod blade coater. , Gate roll coater, roll coater such as size press, bill blade coater, velva equipment coater, calendar roll coater, etc. Further, before applying the surface layer coating liquid on the surface layer of the base paper (before forming the surface coating layer), the surface layer coating liquid is uniformly applied to the surface coating layer 7. It is preferable to surface-treat the base paper in the calendar part in order to smooth the surface.

When the surface coating layer 7 is formed by applying the coating liquid for the surface layer, the whiteness of the coating layer is preferably 73% or more, and the glossiness of the blank paper is preferably 20% to 50%. The base paper for paper packaging containers, which is the main purpose of the present application, needs to have an appearance to motivate the purchase of contents and information on the surface layer, and further, the appearance and information are not stained in transportation and display. It should not lead to missing problems. By setting the whiteness and glossiness within a predetermined range, it is possible to improve the print appearance and improve the purchasing motivation of consumers.

Further, as a preferred configuration of the present invention, the back surface coating layer 8 is formed by coating the back surface layer (lower surface) of the base paper with a coating liquid for the back surface layer made of a water-soluble resin. Examples of the water-soluble resin in the coating liquid for the back surface layer include starch (including various modified starches such as phosphate esterified starch and cationized starch), polyvinyl alcohol (PVA), and polyacrylamide resin (PAM). , Casein, polystyrene-butadiene latex, polyvinyl acetate latex, polyvinyl acrylic latex, polyurethane latex and the like can be used. Among these, considering the film-forming property, rigidity, and permeability to the base material of the base paper 1 for paper packaging containers according to the present invention, it is preferable to use PVA and a lubricant in combination.

It is desirable that the polyvinyl alcohol has a degree of polymerization of 1000 to 2000 and a degree of saponification of 98 to 99. Polyvinyl alcohol has a property that the film strength obtained becomes stronger as the degree of polymerization increases and it becomes difficult to dissolve in water, and the film strength obtained becomes stronger as the degree of saponification increases and it becomes difficult to dissolve in cold water. .. The inventors of the present invention have a problem that the viscosity is increased and the operability is lowered in order to satisfy the required quality of the base paper for packaging containers targeted by the present invention. It has been found that it is preferable to use polyvinyl alcohol having a degree of polymerization. Incidentally, the polyvinyl alcohol is preferably 2 to 3 parts by weight (in terms of 50% solid content) in the coating liquid for the back surface layer. If it is less than 2 parts by weight, the surface coating cannot be formed, the surface strength is low, and paper shaving or the like occurs due to the traversing of the paper surface fibers. If it is 3 parts by weight or more, the film thickness becomes thick and the penetration of the adhesive is hindered, so that the adhesive strength of the adhesive decreases.

In addition to PVA, higher aliphatic hydrocarbons (paraffin wax), higher aliphatic alcohol-based lubricants, higher fatty acid-based lubricants, higher fatty acid amide-based lubricants, higher fatty acid metal salt-based lubricants, and higher fatty acid ester-based lubricants are available as lubricants. Although it can be used, it is preferable to use paraffin wax. The purpose of using paraffin wax is to prevent paper dust and foreign matter from falling off from the back layer. The shape of the paraffin wax is not particularly limited, but an emulsion type wax is preferable. Incidentally, the lubricant (mainly paraffin wax) is preferably 0.04 to 0.2 parts by weight (40% solid content equivalent) in the coating liquid for the back surface layer. If it is less than 0.04 part by weight, the frictional resistance value does not improve, so that the falling off of the paper dust ink residue cannot be improved. If it is 0.2 parts by weight or more, the surface slipperiness is improved, so that troubles such as load collapse when stacking cases are likely to occur.

Further, in addition to PVA and lubricant, 0.24 to 0.4 parts by weight (20% solid content equivalent) of a modified polyacrylamide resin can be used as a surface paper strength enhancer.

Further, the coating liquid for the back surface layer may be adjusted so that the concentration is 1 to 8%, more preferably 2 to 5%. If the concentration of the coating liquid for the back surface layer is less than 1%, the coating liquid for the back surface layer permeates the base paper too well, and it becomes difficult to obtain the rigidity of the paper surface on the back surface layer side of the base paper. It becomes a tendency. Therefore, it becomes difficult to maintain the compressive strength of the base paper for paper packaging containers, and it becomes difficult to satisfy the processing suitability desired by the base paper for paper packaging containers. On the other hand, if the concentration exceeds 8%, the compressive strength can be maintained, but the viscosity of the coating liquid for the back surface layer tends to be too high, so that the coating liquid for the back surface layer penetrates into the base paper. In addition to the problem of deterioration and further deterioration of operability, the surface on the back surface layer side tends to be hard, and it becomes difficult to satisfy processing suitability such as ruled line cracking resistance on the back surface layer side.

The coating amount of such a coating liquid for the back surface layer is 0.08 to 1.62 g / m ² (dry conversion), more preferably 0.05 to 2.0 g / m ² . As a result, the base paper for this paper packaging container maintains the processing suitability required for processing into corrugated cardboard and paper containers, and further, the contents of the container container for paper packaging (for example, tissue) obtained from the base paper for this paper packaging container are soiled. Can be prevented.

If the coating amount of the coating liquid for the back surface layer ^{is less than 0.05 g / m 2} , it becomes difficult to satisfy the desired rigidity of the paper surface on the back surface layer side of the present invention, while 2. If it exceeds 0 g / m ² , the rigidity of the paper surface on the back surface layer side can be satisfied, but the back surface coating layer loses its flexibility and tends to become hard. It becomes difficult to satisfy processing aptitude such as aptitude.

By coating the back surface layer 5 of the base paper with the coating liquid for the back surface layer as described above to form the back surface coating layer 8, not only the surface strength of the back surface coating layer 8 but also the inclusions (for example) , Tissues, paper towels, kitchen paper, etc.) and has excellent effects on paper dust control.

The coating method for the back surface layer may be a single coating or a multi-stage coating of double coating or more, and the coating equipment includes a bar coater, a blade coater, an air knife coater, and a rod blade coater. , Gate roll coater, roll coater such as size press, bill blade coater, velva equipment coater, calendar roll coater, etc. As for the coating equipment, the calendar roll coating method capable of coating under high linear pressure is preferable. Further, the chilled roll is more preferable as the calendar roll. Further, an on-machine calendar, a soft calendar, a gloss calendar, etc. can be used for the surface flattening treatment of the back surface coating layer after coating.

As described above, a coating liquid for a back surface layer having a base paper composed of a plurality of layers and having a specific water-soluble resin, a lubricant, and a paper strength enhancer in a specific blending ratio is applied on the back surface layer of the base paper. By coating to form a back surface coating layer and further defining the ash content of the base paper and the fiber orientation for each layer, the rigidity of the front surface layer and the back surface layer can be increased, so that compared with conventional paperboard. It has become possible to achieve a low paper density and weight reduction of 10 to 15%, and even if the paper density and weight have been further reduced, processing suitability and printability can be satisfied.

Next, the embodiments according to the present invention described above will be described with reference to detailed examples (specific examples). In addition, this embodiment will be described with reference to the description of FIG. 1 as necessary. In addition, the description of "0% solid content conversion" in the section of the mode for carrying out the invention is synonymous with "solid content conversion (0%)" in the section of this "Example" (○ is a number).

In this example, in order to confirm the effect of the base paper for a paper packaging container of multi-layer papermaking according to the present invention, various samples such as the following were prepared and a test for evaluating the quality of each of these samples was conducted. In this example, the numerical values indicating the composition, concentration, etc. are numerical values based on the mass of the solid content or the active ingredient. Further, since the pulp, chemicals, etc. shown in this example are only examples, it goes without saying that the present invention is not limited by these examples and can be appropriately selected.

[Example 1] Preparation of base paper 31 types of base papers for paper packaging containers according to the present invention (referred to as "Example 1" to "Example 31") and Examples 1 to 31 thereof. In order to make a comparative study with the above, three types of base papers for paper packaging containers (referred to as "Comparative Example 1" to "Comparative Example 3") were produced with the configurations shown in Table 1.

Using the following raw materials, a base paper for a paper packaging container having a base paper composed of three layers of a front surface layer, a lower surface layer, and a middle layer (and a back surface layer) was obtained according to the following production method. In addition, "Example 1" will be described as a typical example.

<Base paper>
・ Surface layer Softwood bleached kraft pulp (NBKP) 30% by mass (dry), hardwood bleached kraft pulp 20% by mass (dry), fine white waste paper 15% by mass and coated paper 35% by mass are blended, and the basis weight is 40 g / m. ^{It was set to 2} . In this pulp, a sizing agent (rosin emulsion sizing agent, trade name: R10, manufactured by Hyundai Kagaku Kogyo Co., Ltd.) was added as an internal chemical at 7 kg / PT (50%) in terms of solid content with respect to the weight of the raw material pulp. Absolutely dry pulp ton), sulfuric acid band (manufactured by Sumitomo Chemical Co., Ltd.), 65 kg / PT in solid content with respect to the weight of raw material pulp, and paper strength enhancer (product name: TST153, manufactured by Seikou PMC), weight of raw material pulp. 8 kg / PT was added to the pulp in terms of solid content (20%) to obtain a raw material pulp slurry.

-Lower surface layer 100% by mass of high-quality Kent recycled paper was used as a raw material pulp slurry. Further, in this pulp, as an internal chemical like the surface layer, a sizing agent (rosin emulsion sizing agent, trade name: R10, manufactured by Hyundai Kagaku Kogyo Co., Ltd.) is added to the weight of the raw material pulp in terms of solid content (50%). ), 5.5 kg / PT, sulfuric acid band (manufactured by Sumitomo Chemical Co., Ltd.), 90 kg / PT in solid content relative to the weight of the raw material pulp, and a paper strength enhancer (product name: TST153, manufactured by Seikou PMC). 5.6 kg / PT was added in terms of solid content (20%) to the weight of the pulp to obtain a raw material pulp slurry. The basis weight was 54 g / m ² .

・ Middle layer (back layer)
A raw material slurry containing 50% by mass as a main component was used for both the used ground ticket and the used newspaper. Further, in this pulp, as an internal chemical like the surface layer, a sizing agent (rosin emulsion sizing agent, trade name: R10, manufactured by Hyundai Kagaku Kogyo Co., Ltd.) is added to the weight of the raw material pulp in terms of solid content (50%). ), 7.5 kg / PT, sulfuric acid band (manufactured by Sumitomo Chemical Co., Ltd.), 60 kg / PT in solid content relative to the weight of the raw material pulp, and paper strength enhancer (product name: TST153, manufactured by Seikou PMC). 3.0 kg / PT was added to the weight of the pulp in terms of solid content (20%) to obtain a raw material pulp slurry. In addition, the basis weight was set to 170 g / m ² by a double disc refiner.

Next, the coating liquid for the front surface layer and the coating liquid for the back surface layer were prepared at the blending ratios shown in Table 2. “Examples 1 to 31” and “Comparative Examples 1 to 3” in Table 2 are the same as those in Table 1. Typical examples relating to the adjustment method will be described after Table 2 by taking Example 1 as an example.

<Coating liquid for surface layer>
Next, 23 parts by weight of clay (Amazon Plus JPG) and 77 parts by weight of calcium carbonate (hydrocurve 90, wet heavy cal) were blended as inorganic pigments, and styrene butadiene latex (SBR) (Smartec PA-6082) was blended as a binder. (50% product, manufactured by Nippon A & L Co., Ltd.) was blended in 9 parts by weight to prepare a coating liquid for the surface layer. The numerical value of each blending amount is a numerical value in a dry state.

<Coating liquid for back layer>
As a water-soluble polyvinyl alcohol (PVA) -based resin, PVA (JF-17, manufactured by Japan Vam & Poval Co., Ltd., polymerization degree 1700, saponification degree 98.0-99.0) is converted into solid content (50). %) By 1.3 parts by weight, polyethylene wax emulsion (HITEC E-9015, manufactured by Toho Kagaku Kogyo Co., Ltd.) as a lubricant, 0.08 parts by weight in terms of solid content (40%), modified as a paper strength enhancer A coating liquid for the back surface layer was prepared by blending 0.24 parts by weight of a polyacrylamide-based paper strength enhancer (T-ST153, manufactured by Seikou PMC) in terms of solid content (20%).

This surface layer coating liquid is applied on the surface layer of the base paper with a bar coater at ^{a coating amount of 6.0 g / m 2} to form a front surface coating layer, and the back surface layer coating liquid is applied. A base paper for a paper packaging container (Example 1) was obtained by applying 1.62 g / m2 on the back surface layer of the base paper with a bar coater to form a back surface coating layer. The numerical value of the coating amount is also a numerical value in the dry state.

<Calendar processing>
Next, the calendar processing was performed under the conditions shown in Table 3 below. In addition, "Examples 1 to 31" and "Comparative Examples 1 to 3" in Table 3 are the same as those in Tables 1 and 2. A typical example related to calendar processing will be described after Table 3 by taking Example 1 as an example.

Although it is referred to as "hard calendar" in Table 3, hard nip calendar processing was performed here. Here, the descriptions "NO.1 calendar" and "NO.2 calendar" mean that there are two stacks of calendars. In Example 1, NO. 1 Calendar and NO. Both of the two calendars have one nip. Further, although it is referred to as "soft calendar" in Table 3, the soft calendar processing is performed using a gloss calendar, and in Example 1, the gloss is 195 ° C. and the linear pressure is 110 kgf / cm.

Further, with respect to Examples 2 to 31 and Comparative Examples 1 to 3, the base paper for the paper packaging container according to each Example or Comparative Example is prepared in the same manner as in Example 1 except for the conditions shown in Tables 1, 2 and 3. Made.

[Example 2] Quality evaluation test The results of quality evaluation of all these Examples and Comparative Examples are shown in Table 4. This quality evaluation test was conducted under environmental conditions of a temperature of 23 ± 2 ° C. and a humidity of 50 ± 2% in accordance with JIS-P8111.

First, the "product paper density" in Table 4 is a value measured in accordance with the "paper and paperboard-basis weight measuring method" described in JIS-P8124 (1998).

Next, the "product moisture (%)" in Table 4 is the product moisture of the base paper for paper packaging containers measured by JIS P8127.

"Base paper basis weight + total coating amount" in Table 4 means "base paper basis weight" in Table 1 and "total coating amount (coating amount of coating liquid for surface layer + back surface)" in Table 2. The amount of coating liquid for layers) ”.

“Density (g / cm ³ )” refers to the basis weight of the base paper of the base paper for paper packaging containers as each sample, and the “paper and paperboard-thickness and density test method” described in JIS-P8118 (1998). It is a value calculated from the paper thickness of the base paper measured according to the above.

The "ash content" in Table 4 is the value of the ash content (%) measured in accordance with the "paper, paperboard and pulp-ash content test method-525 ° C. combustion method" described in JIS-P8251 (2003). To tell.

“Paper thickness (μm)” is the thickness of paper as a product according to each Example and Comparative Example.

“Whiteness (%)” is whiteness (pt) measured in accordance with “Paper, Paperboard and Pulp-ISO Whiteness (Diffuse Blue Light Reflectance) Measurement Method” described in JIS-P8148 (2001). Say the value of.

"Blank paper gloss (%)" is the value of the glossiness (%) of unprinted base paper measured in accordance with "Measuring method of paper and paperboard-75 degree mirror surface glossiness" described in JIS-P8142 (2005). To tell.

The "smoothness (seconds)" is a value of smoothness (seconds) measured in accordance with the "paper and paperboard-smoothness test method using a Beck smoothness tester" described in JIS-P8119 (1998).

"Cup water absorption (g / m ² )" is a measured value of "paper and paperboard-water absorption test method-cobb method-based contact time of 2 minutes" described in JIS-P8140 (1991). "Front)" represents the front layer side, and "(back)" represents the back layer side.

"Specific burst strength (kPa / m ² / g)" is the glossiness of unprinted base paper measured in accordance with "Measurement method of paper and paperboard-75 degree mirror surface glossiness" described in JIS-P8142 (2005). %) Say the value.

The "compressive strength (vertical) (N)" is the compressive strength (vertical) measured in accordance with "Paper and paperboard-compressive strength test method-ring crush method" described in JIS-P8126 (2005). Is the value of.

The "printing strength (vertical) (mN)" is a measured value based on "Paper-Tear strength test method-Elmendorf type tear test method" described in JIS-P8116 (1990). The "printing strength (horizontal) (mN)" is a measured value in the width direction in the papermaking direction.

"Wax pick (back) (A)" means JAPAN TAPPI No. It is a value of the wax pick strength (A) on the back surface coating layer side measured in accordance with the "paper and paperboard-surface strength test method using wax" described in 1 (2000).

"Folding resistance (horizontal) (times)" means lateral folding resistance measured according to "Paper and paperboard-Folding strength test method-MIT testing machine method" described in JIS-P8115 (2001). The number of times.

The "box-making property" is evaluated in the process of converting the base paper for a paper packaging container based on the present application into a blank sheet and making the blank sheet into a tissue carton for storing the tissue paper. The evaluation criteria are as follows.

⊚: When the blank sheet is transferred to the molding position, the paper surface is not scratched, and the frictional force between the left and right guide rails when the blank sheet is transferred is different, so that the blank sheet is on a horizontal surface. There is no problem that the blank sheet is tilted diagonally and the position of the blank sheet is displaced with respect to the molding position to reduce the molding accuracy of the mandrel.
◯: When the blank sheet is transferred to the molding position, the paper surface is hardly scratched, and the frictional force between the left and right guide rails when the blank sheet is transferred is different, so that the blank sheet is on the horizontal plane. There is no problem that the blank sheet is tilted diagonally and the position of the blank sheet is displaced with respect to the molding position to reduce the molding accuracy of the mandrel.
Δ: When the blank sheet is transferred to the molding position, scratches are scattered on the paper surface, and the frictional force between the left and right guide rails when the blank sheet is transferred is different, so that the blank sheet is slanted on the horizontal plane. There was a slight problem that the position of the blank sheet was displaced with respect to the molding position and the molding accuracy with the mandrel was lowered.
X: The paper surface is scratched when the blank sheet is transferred to the molding position, and the frictional force between the left and right guide rails when the blank sheet is transferred is different, so that the blank sheet is slanted on the horizontal plane. The position of the blank sheet with respect to the molding position shifts, and the molding accuracy with the mandrel decreases.

"Rule-resistant crack resistance" means that the multi-layered paperboard of each sample printed in the same way as ink removal is cut into A4 size (vertical stitches), folded in half with respect to the long side, and press pressure is 2. After pressing at 0.0 kg / m ² for 5 minutes, the evaluation was made by visually confirming the presence or absence of cracks in the creases. The evaluation criteria are as follows.

⊚: No cracks have occurred.
◯: Cracks occur in which the total total length is less than 15% of the crease length.
Δ: Cracks occur in which the total total length is 15% or more and less than 30% with respect to the crease length.
X: Cracks occur in which the total total length is 30% or more of the crease length.

"RI pick" is a standard tack grade ink (TV = 18) used for the IGT printability tester specified in JIS-P8129, using the KRK universal printability tester manufactured by Kumagai Riki Kogyo Co., Ltd. After printing on the coating layer of the multi-layer paperboard, it was evaluated by the RI printability test. The evaluation criteria are as follows.

⊚: No fluffing or peeling of paper is observed on the surface.
◯: There are two or less fluffing or paper peeling of 0.5 mm or more.
Δ: There are 3 to 5 places of fluffing or paper peeling of 0.5 mm or more.
X: There is fluffing of 0.5 mm or more and paper peeling at 6 or more places.

From Table 4, the multi-layer paperboard according to Examples 1 to 31, that is, the base paper for paper packaging containers according to the present invention, has a paper density of 10 to 15% lower than that of the conventional paperboard, which is a comparative example. It can be seen that the weight can be reduced. Further, it can be seen that the base paper for a paper packaging container according to the present invention can satisfy the processing suitability of a tissue carton or the like even if the paper density is reduced and the weight is reduced in this way.

Although the examples according to the present invention have been described above, the present invention is not limited to the above-described examples, and there are various issues to be examined within the scope of claims and the matters described in the present specification. Needless to say.

The base paper for paper wrapping devices according to the present invention can be applied not only to tissue cartons (tissue cases), but also to wrapping containers such as toilet paper and kitchen towels (paper), wrapping containers for confectionery such as caramel and chocolate, and milk packs. be.

1 Base paper for paper wrapping machine 2 Surface layer 3 Front lower layer 4 Middle layer 5 Back layer 6 Base paper 7 Surface coating layer (coating layer)
8 Backside coating layer (clear coat layer)

Claims (6)

A base paper for a multi-layer paper packaging container ^{having a basis weight of 250 g / m 2 to} 350 g / m ² and a density of 0.77 to 0.90 g / cm ³ having a front surface layer, a lower surface layer and a back surface layer.
The surface layer is mainly made of mixed kraft pulp and high-quality recycled paper pulp.
The lower layer of the surface uses used paper pulp as the main raw material.
The back surface layer is made from recycled paper pulp derived from recycled paper containing mechanical pulp as the main raw material.
The mixed kraft pulp is a mixture of softwood bleached kraft pulp and hardwood bleached kraft pulp.
The softwood bleached kraft pulp / hardwood bleached kraft pulp has a ratio of 15:85 to 85:15.
A base paper for a paper wrapping container, characterized in that the compressive strength of the vertical grain of the base paper for the paper wrapping container is 720 to 840 N. The surface layer is formed by mixing the mixed kraft pulp and the high-quality waste paper pulp at a ratio of 30:70 to 70:30, and the waste paper pulp forming the lower surface layer is Kent and special white in the waste paper statistical classification. The base paper for paper packaging according to claim 1, wherein the product moisture of the base paper for paper packaging according to JIS P8127 is 4.0 to 9.5%, which is selected from medium white, white Manila, imitation, or color. .. The surface layer has ^{a surface coating layer containing 2} to 10 g / m 2 of pigment and an adhesive as main components per side, and the whiteness of the surface coating layer is 73% or more and the glossiness of blank paper is 20%. The base paper for a paper packaging container according to claim 1 or 2, which is ~ 50%. The base paper for a paper packaging container according to any one of claims 1 to 3, wherein a back surface coating layer made of polyvinyl alcohol, a paper strength enhancer, and a lubricant is provided on the outer surface of the back surface layer. The polyvinyl alcohol has a degree of polymerization of 1000 to 2000 and a degree of saponification of 98.0 to 99.0, the paper strength enhancer is a modified polyacrylamide-based paper strength enhancer, and the lubricant is polyethylene wax. The base paper for a paper packaging container according to claim 4, which is an aqueous dispersion of wax particles. The paper according to any one of claims 1 to 5, further comprising at least one middle layer between the lower surface layer and the back surface layer, and the middle layer is made of recycled paper pulp derived from recycled paper containing mechanical pulp as a main raw material. Base paper for packaging containers.

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