JP6883399B2 - Manufacturing method of kraft paper for reinforcing paper and kraft paper for reinforcing paper - Google Patents

Description

The present invention relates to kraft paper for reinforcing paper and a method for producing kraft paper for reinforcing paper.

Kraft paper bags are widely used for filling, transporting and storing granules such as rice, sugar, cement and resin, powders and pellets. The kraft paper bag is usually filled with 20 to 50 kg of contents, and since it is required not to break from the filling, transportation and storage stages to the opening of the bag, the kraft paper bag is given high strength. To. Then, in order to further impart strength to the kraft paper bag, paper called reinforcing paper is often sewn or glued to the perforated portion or the glued portion at the upper or lower part of the kraft paper bag.

Heavy-duty kraft paper and stretched paper are generally used as the material for this reinforcing paper, but since heavy-wrapped kraft paper and stretched paper are also used for the body of the kraft paper bag, high strength is imparted as described above. When these are used as the materials for the reinforcing paper, the reinforcing paper may not be easily broken and the bag may not be easily opened.

Therefore, in order to facilitate the breakage of the reinforcing paper, a kraft paper bag (hereinafter, also referred to as "easy open type paper bag") in which a tape equipped with an opening mechanism (hereinafter, also referred to as "cut tape") is attached to the reinforcing paper is put on the market. Also, a technique related to a cut tape is disclosed (see Patent Document 1 below).

Japanese Unexamined Patent Publication No. 2000-85792

However, in the existing easy-open type paper bag, the reinforcing paper can be easily broken by pulling the cut tape from either the left or right end of the cut tape, but the reinforcing paper can be easily broken by pulling the cut tape from the other end. It cannot be broken, and if you try to break it forcibly, the reinforcing paper will tear in a V shape and you will not be able to easily open the bag, or fragments of the reinforcing paper generated at the time of breaking will enter the inside of the bag and foreign matter will enter. There are problems such as causing. Further, it is not preferable that the bag can be easily opened only from one of the left and right ends of the cut tape because both right-handed and left-handed persons can open the bag. Further, the technique described in Patent Document 1 prevents the cut tape from entering the inside of the bag at the time of opening, and does not improve the breakability of the reinforcing paper.

The present invention has been made in view of the above circumstances, and the reinforcement is easily broken even if the cut tape is pulled from either the left or right end of the cut tape, and the reinforcing paper is not broken at the time of breakage. An object of the present invention is to provide kraft paper for paper and a method for producing kraft paper for reinforcing paper.

In the case where the pulp fibers contained in the kraft paper for reinforcing paper form a uniform texture that is substantially the same in both the front and back surfaces of the kraft paper, and also in both the MD and CD directions, the present inventor determines in which direction the pulp fibers break. Regardless of this, it was found that the reinforcing paper could be easily broken, and the present invention was completed based on this finding. Here, the MD direction refers to the direction of papermaking flow, and the CD direction refers to a direction orthogonal to the MD direction in the horizontal plane.

The invention made to solve the above problems is composed of a single layer containing unbleached kraft pulp fiber as a main component and having a basis weight of 70 g / m ² or more and 120 g / m ² or less, and has a fiber orientation ratio of one surface. The absolute value of the absolute value and the absolute value of the fiber orientation ratio of the other surface are both 3 or less, and the absolute value of the difference between the fiber orientation ratio of the one surface and the fiber orientation ratio of the other surface is 0.5 or less. It is a kraft paper for reinforcing paper.

According to the kraft paper for reinforcing paper, unbleached kraft pulp is the main component, a single layer having a basis weight in the above range is used, and the fiber orientation ratio is adjusted as described above, thereby impairing workability as a kraft paper bag. While having sufficient strength as a reinforcing paper, the pulp fibers constituting the paper layer as a whole of the kraft paper have substantially the same uniform texture properties on the front and back surfaces, and also in both the MD and CD directions. Therefore, even if the reinforcing paper is broken in the same direction as the MD direction or in the same direction as the CD direction, the broken portion does not spread in a C shape and can be easily broken. As a result, even if the cut tape is pulled from either the left or right end of the cut tape, the broken portion does not spread in a V shape, and the reinforcing paper can be easily broken.

The kraft paper for reinforcing paper has an absolute value of 1.5 ° or less between the fiber orientation angle in the MD direction of one surface and the fiber orientation angle in the CD direction, and the fiber orientation of the other surface in the MD direction. The absolute value of the difference between the angle and the fiber orientation angle in the CD direction is also preferably 1.5 ° or less. By setting the absolute value of the difference to 1.5 ° or less on both one surface and the other surface, the uniformity of the paper layer on the front and back surfaces of the kraft paper for reinforcing paper can be more ensured, which is easier. You will be able to break the reinforcing paper.

The kraft paper for reinforcing paper has a stakehito size degree of 30 seconds or less, and an interlayer strength measured using an internal bond tester in accordance with JAPAN TAPPI pulp and paper test method 18-2 is 200 mJ or more and 400 mJ or less. Is preferable. By lowering the degree of stakehito size in this way, the strength of the reinforcing paper is strengthened, and by further setting the interlayer strength within the above range, the reinforcing paper can be broken more easily. Further, as the kraft paper for reinforcing paper, the ratio of the tensile strength in the CD direction to the tensile strength in the MD direction is 30% or more and 65% or less, and the elongation measured in accordance with JIS-P-8113 (2006). Is preferably 1.3% or more in the MD direction and 3.5% or more in the CD direction. If the above ratio is less than 30%, the tensile strength in the CD direction may be insufficient. On the other hand, when the above ratio exceeds 65%, the pulp fibers tend to be oriented in the CD direction, making it difficult to obtain a uniform texture, and when the reinforcing paper is broken, the broken portion easily spreads in a V shape. There is a risk that it will not break. Here, the tensile strength means a tensile strength (kN / m) measured in accordance with JIS-P-8113 (2006). Further, when the elongation is at least the above lower limit, the amount of tensile energy absorbed by the kraft paper for reinforcing paper is increased, and the strength of the reinforcing paper is improved. Here, the tensile energy absorption amount refers to the work amount (J / m ² ) per unit area required to stretch and break the kraft paper, and is measured in accordance with JIS-P-8113 (2006).

Another invention made to solve the above problems is a step of preparing a pulp slurry containing unbleached kraft pulp fiber as a main component, a step of discharging the pulp slurry to a papermaking wire, and a step of discharging the pulp slurry. In a step of making a wet paper from a pulp slurry using the papermaking wire and a step of further dehydrating and drying the wet paper, in a step of discharging the pulp slurry to the papermaking wire, the pulp at the time of ejection is provided. The ratio of the speed of the slurry to the speed of the papermaking wire is 0.98 or less or 1.03 or more, and ^{the single layer has a basis weight of 70 g / m 2} or more and 120 g / m ² or less, and the fiber orientation ratio on one surface. This is a method for producing kraft paper for reinforcing paper, which is made so that the absolute value of the difference between the pulp and the fiber orientation ratio on the other surface is 0.5 or less.

According to the method for producing kraft paper for reinforcing paper, kraft paper for reinforcing paper having substantially the same uniform texture on the front and back surfaces, and also in both the MD and CD directions can be obtained. Therefore, according to the method for manufacturing the kraft paper for reinforcing paper, the reinforcing paper is easily broken even if the cut tape is pulled from either the left or right end of the cut tape by a relatively easy method, and the reinforcing paper is broken at the time of breaking. It is possible to obtain kraft paper for reinforcing paper that does not generate debris.

According to the kraft paper for reinforcing paper of the present invention, in an easy-open type kraft paper bag in which a tape provided with an opening mechanism is attached to the reinforcing paper, it is easy to pull the tape from either the left end or the right end of the tape attachment port. The reinforcing paper can be broken, and there is no possibility that fragments of the reinforcing paper will be generated and mixed into the inside of the bag at the time of breaking. Further, since the kraft paper for reinforcing paper has sufficient strength and excellent processing suitability as shown in Examples described later, the body portion of the entire kraft paper bag including the kraft paper bag for heavy packaging is not limited to the reinforcing paper. Can also be used for. On the other hand, according to the method for producing kraft paper for reinforcing paper of the present invention, in the above-mentioned easy-open type kraft paper bag, the reinforcing paper can be easily broken even if the tape is pulled from either the left end or the right end of the tape attachment port. It is possible to easily obtain kraft paper for reinforcing paper, which is capable of forming and does not cause fragments of reinforcing paper to be generated and mixed inside the bag when broken.

Hereinafter, a method for producing kraft paper for reinforcing paper according to one embodiment of the present invention and a method for producing kraft paper for reinforcing paper according to another embodiment of the present invention will be described. The scope of the present invention is not limited to the configurations of these embodiments, and is intended to include all modifications within the meaning and scope equivalent to the claims.

<Kraft paper for reinforcing paper>
The kraft paper for reinforcing paper according to one embodiment of the present invention contains unbleached kraft pulp fiber as a main component, and is composed of ^{a single layer having a basis weight of 70 g / m 2} or more and 120 g / m ² or less, and has one surface. The absolute value of the fiber orientation ratio and the absolute value of the fiber orientation ratio of the other surface are both 3 or less, and the absolute value of the difference between the fiber orientation ratio of the one surface and the fiber orientation ratio of the other surface is 0. It is a kraft paper for reinforcing paper that is 5.5 or less. In the present specification, the "one side" refers to either the front surface or the back surface of the kraft paper, and the "other side" refers to the above-mentioned "one side" of the front surface and the back surface of the kraft paper. It means a side that is not.

(Raw material pulp)
Examples of the unbleached kraft pulp which is the main component of the kraft paper for reinforcing paper include softwood unbleached kraft pulp (NUKP) and hardwood unbleached kraft pulp (LUKP). The mass ratio of NUKP to LUKP is preferably 75:25, more preferably 80:20, even more preferably 90:10, and particularly preferably 100: 0. When the mass ratio is less than 75:25, the content of NUKP having a long fiber length and a large fiber diameter is insufficient, the bond between pulp fibers is weakened, and the strength as a reinforcing paper may be insufficient. The main component refers to the raw material having the highest content among all the raw materials excluding water in the pulp slurry, preferably occupying 50% by mass or more, more preferably 70% by mass or more.

Further, as the raw material pulp of the kraft paper for reinforcing paper, pulp other than unbleached kraft pulp can be used as long as the strength required for the reinforcing paper is not lost. The mass ratio of unbleached kraft pulp to pulp other than unbleached kraft pulp is preferably 75:25, more preferably 80:20, even more preferably 90:10, and particularly preferably 100: 0. If the mass ratio is less than 75:25, the strength of the reinforcing paper may be insufficient. Examples of pulp other than unbleached kraft pulp include coniferous bleached kraft pulp (NBKP), broadleaf bleached kraft pulp (LBKP), coniferous semi-bleached kraft pulp (NSBKP), broadleaf semi-bleached kraft pulp (LSBKP), coniferous sulfite pulp, and broadleaf sulfite. Chemical pulp such as pulp, stone ground pulp (SGP), pressurized stone ground pulp (PGW), refiner ground pulp (RGP), thermogrand pulp (TGP), chemigrand pulp (CGP), crushed wood pulp (GP), thermo Mechanical pulp such as mechanical pulp (TMP), disintegrated waste paper pulp, disintegrated / deinked waste paper pulp, disintegrated / deinked / bleached waste paper pulp, etc. Examples thereof include various pulps such as non-wood pulp produced in Japan. It is preferable to mix as much recycled paper pulp as possible within a range that does not affect the tensile strength, elongation, air permeation resistance, etc. from the viewpoint of reducing the energy intensity and the environmental load.

(Freeness of raw pulp)
The freeness of the raw material pulp of the kraft paper for reinforcing paper is preferably 450 cc or more and 700 cc or less, and more preferably 500 cc or more and 650 cc or less. When the freeness of the raw material pulp is less than 450 cc, the fiber length of the raw material pulp is shortened and the air permeability resistance of the kraft paper is increased, so that when the kraft paper bag is dropped, a large air pressure is generated inside the bag and the bag is broken. There is a risk of creating a bag. On the other hand, when the freeness of the raw material pulp exceeds 700 cc, the bond between the pulp fibers is weakened and the tensile strength and elongation of the kraft paper are lowered, so that bag breakage may easily occur. Here, the freeness of the raw material pulp refers to the Canadian standard freeness measured in accordance with JIS-P-8121-2 (2012).

(Additive)
Similar to general kraft paper, the kraft paper for reinforcing paper also contains sizing agents, chemical fixing agents, paper strength enhancers, yield improvers, water resistant agents, oil resistant agents, defoaming agents, fillers, dyes, etc. Various chemicals such as pigments can be added.

The type of sizing agent is not particularly limited, and for example, a rosin-based sizing agent, an internal sizing agent such as alkyl ketene dimer (AKD), alkenyl anhydride succinic acid (ASA), polyvinyl alcohol (PVA), oxidized starch, and styrene-acrylic acid. Examples thereof include surface sizing agents such as system copolymers and styrene-methacrylic acid-based copolymers. The blending amount of the sizing agent is also not particularly limited, but in the case of the rosin-based sizing agent, for example, it can be 0.1 kg or more and 7 kg or less with respect to 1 ton of the raw material pulp solid content.

The type of the paper strength enhancer is also not particularly limited, and for example, a dry paper strength enhancer such as cationized starch, amphoteric starch, polyacrylamide (PAM), and carboxymethyl cellulose (CMC), urea resin, acid colloid / melamine resin, and thermal cross-linking. Examples thereof include a wet paper strength enhancer such as sexually imparting PAGE. By appropriately adding the paper strength enhancer, debris is less likely to be generated when the reinforcing paper is broken, and the breakability is also improved. The blending amount of the paper strength enhancer is also not particularly limited, but in the case of polyacrylamide, for example, it can be 3 kg or more and 30 kg or less with respect to 1 ton of the raw material pulp solid content. However, it is desirable to keep the amount of the paper strength enhancer to the minimum necessary so that the reinforcing paper can be easily broken with the cut tape.

Further, the kraft paper for reinforcing paper includes a chemical fixing agent such as a sulfuric acid band, a yield improving agent such as cationized starch, polyethyleneimine, and polyethylene oxide, polyamide, polyamine, epichlorohydrin, etc., as long as the object of the present invention is not violated. Water resistant agents, fluororesin, oil resistant agents such as silicone oil, silicone defoaming agents, defoaming agents such as nonionic polyethylene defoaming agents, fillers such as kaolin, clay, talc, calcium carbonate, and various dyes. Pigments and the like can also be added.

(Basis weight)
The basis weight of the reinforcing sheet for kraft paper, and a 70 g / ^{m 2} or more 120 g / ^{m 2} or less, 75 g / ^m, more preferably ² or more 110g / ^{m 2} or less, 80 g / ^{m 2} or more 100 g / ^{m 2} or less More preferred. If the basis weight is ^{less than 70 g / m 2} , the strength of the reinforcing paper may be insufficient. On the other hand, when the basis weight ^{exceeds 120 g / m 2} , the strength may be excessive and the reinforcing paper may not be easily broken, and the kraft paper bag to which the reinforcing paper is attached may become too heavy. Here, the basis weight means the value of rice tsubo measured in accordance with JIS-P-8124 (2011). Further, the kraft paper for reinforcing paper is composed of a single layer instead of multi-layered so that it can be easily broken when it is made into a reinforcing paper.

(Fiber orientation ratio and fiber orientation angle)
Paper has the property of being easily torn along the orientation of the pulp fibers, and when the pulp fibers are torn diagonally in the MD direction in the same direction as the MD direction, the break site is in the MD direction along the fiber orientation. It tends to be slanted. However, in the present invention, the absolute value of the fiber orientation ratio of one surface and the absolute value of the fiber orientation ratio of the other surface are both 3 or less, and the fiber orientation ratio of the one surface and the fiber of the other surface are both. When the absolute value of the difference from the orientation ratio is 0.5 or less, it becomes possible to achieve the uniformity of the fiber composition itself on the exposed surface of the kraft paper for reinforcing paper and the texture of the exposed surface. As a whole, kraft paper for reinforcing paper has an extremely good texture with no uneven orientation of the fibers themselves constituting the paper layer, which makes it difficult for uneven paper quality differences to occur in the MD direction, CD direction or thickness direction. Is obtained. Therefore, even when the kraft paper for reinforcing paper is made into reinforcing paper and broken in the same direction as the MD direction, the broken portion does not have a C shape and is easily broken.

Various methods for measuring the fiber orientation ratio or fiber orientation angle, such as dyed fiber mixed extraction method, X-ray diffraction method, soft X-ray method, light diffraction method, light scattering method, mechanical breaking strength method, ultrasonic method, microwave method, etc. Although the method is used, the fiber orientation ratio and fiber orientation angle of the front and back surfaces can be easily measured by, for example, an ultrasonic conduction type orientation measuring machine "SST-4000" manufactured by Nomura Shoji Co., Ltd. In the present specification, the "fiber orientation ratio" means a value obtained by dividing the physical characteristic value of kraft paper in the MD direction by the characteristic value in the CD direction, and when measuring the fiber orientation ratio by the ultrasonic method, The value obtained by dividing the ultrasonic propagation velocity in the MD direction by the ultrasonic propagation velocity in the CD direction. On the other hand, the "fiber orientation angle" refers to the angle (°) of the pulp fiber orientation with respect to the MD direction or the CD direction.

(Tensile strength in the CD direction)
The tensile strength of the kraft paper for reinforcing paper in the CD direction is preferably 2.8 kN / m or more and 5.6 kN / m or less, and more preferably 3.5 kN / m or more and 5.6 kN / m or less. If the tensile strength in the CD direction is less than 2.8 kN / m, the strength as a reinforcing paper may be insufficient. On the other hand, when the tensile strength in the CD direction exceeds 5.6 kN / m, it is necessary to use a special raw material for high strength, and if it is made of reinforcing paper, it may not be easily broken.

(Tensile strength in MD direction)
The tensile strength of the kraft paper for reinforcing paper in the MD direction is preferably 6.0 kN / m or more and 10.0 kN / m or less, and more preferably 8.0 kN / m or more and 10.0 kN / m or less. If the tensile strength in the MD direction is less than 6.0 kN / m, the strength as a reinforcing paper may be insufficient, and the pulp fibers may be excessively oriented in the CD direction, causing uneven formation. There is. On the other hand, when the tensile strength in the MD direction exceeds 10.0 kN / m, the pulp fibers may be excessively oriented in the MD direction, and the reinforcing paper may not be easily broken.

(Ratio of tensile strength in the CD direction to tensile strength in the MD direction)
In the production of the kraft paper for reinforcing paper, the ratio of the ejection speed of the pulp slurry to the speed of the papermaking wire (hereinafter, also referred to as “J / W ratio”) and the position where the ejected pulp slurry lands on the papermaking wire (hereinafter, referred to as “papermaking wire”). By changing the papermaking conditions such as (also called "jet landing position"), the position of the forming board, the arrangement / number / angle of foil, the basis weight, and the fiber orientation ratio of the front and back surfaces, the formation on the front and back surfaces and in the MD and CD directions. The ratio of the tensile strength in the CD direction to the tensile strength in the MD direction (hereinafter, also referred to as “Y / T ratio”) is preferably 30% or more and 65% or less, more preferably 35% or more. Control so that it is 45% or less. When the Y / T ratio is in the above range, the cut tape can be easily broken even if the cut tape is pulled from either the left or right end of the cut tape.

(Growth)
Since the kraft paper for reinforcing paper is used to reinforce the perforated portion and the glued portion of the kraft paper bag, strength is particularly required in the CD direction where a large stress is likely to be applied. Therefore, the elongation of the kraft paper for reinforcing paper in the CD direction is preferably 3.5% or more and 10.0% or less, more preferably 4.5% or more and 10.0% or less, and 5.5% or more and 10%. More preferably, it is 0.0% or less. If the elongation is less than 3.5%, the strength in the CD direction may be insufficient. On the contrary, when the elongation exceeds 10.0%, there is a possibility that the reinforcing paper cannot be easily broken. On the other hand, the elongation of the kraft paper for reinforcing paper in the MD direction is preferably 1.3% or more. If the elongation is less than 1.3%, the strength in the MD direction may be insufficient. Here, the elongation means an elongation (%) measured in accordance with JIS-P-8113 (2006).

(Interlayer strength)
The interlayer strength of the kraft paper for reinforcing paper is preferably 200 mJ or more and 400 mJ or less. If the interlayer strength is less than 200 mJ, the strength as a reinforcing paper may be insufficient. On the contrary, when the interlayer strength exceeds 400 mJ, there is a possibility that the reinforcing paper cannot be easily broken. Here, the interlayer strength refers to the load required for delamination of kraft paper measured using an internal bond tester in the thickness direction in accordance with the JAPAN TAPPI pulp and paper test method 18-2.

(Sutekihito size degree)
The degree of sizing of the kraft paper for reinforcing paper is preferably 30 seconds or less. If it exceeds 30 seconds, the strength of the reinforcing paper may be insufficient. Here, the degree of stekihito size means the degree of size (water penetration resistance) measured in accordance with JIS-P-8122 (2004).

(Air permeability resistance)
The air permeation resistance of the kraft paper for reinforcing paper is preferably 10 seconds or more and 120 seconds or less, more preferably 10 seconds or more and 60 seconds or less, and further preferably 10 seconds or more and 30 seconds or less. If the air permeation resistance is less than 10 seconds, it is necessary to take measures such as increasing the freeness of the raw material pulp, and it may be difficult to obtain a constant tensile strength and elongation. On the other hand, if the air permeation resistance exceeds 120 seconds, the air permeability is poor, and if a kraft paper bag filled with the contents is dropped, a large air pressure is generated inside the bag, which may cause the bag to break. Here, the air permeation resistance refers to the time (seconds) required for 100 mL of air to pass through the kraft paper, which is measured in accordance with JIS-P-8117 (2009).

<Manufacturing method of kraft paper for reinforcing paper>
The method for producing kraft paper for reinforcing paper according to another embodiment of the present invention includes a step of preparing a pulp slurry containing unbleached kraft pulp fiber as a main component and a step of discharging the pulp slurry onto a papermaking wire. In the step of making a wet paper from the discharged pulp slurry using the papermaking wire and further dehydrating and drying the wet paper, in the step of discharging the pulp slurry to the papermaking wire. The ratio of the speed of the pulp slurry at the time of discharge to the speed of the papermaking wire is 0.98 or less or 1.03 or more, and the basis weight is 70 g / m ² or more and 120 g / m ² or less in a single layer. This is a method for producing kraft paper for reinforcing paper, in which the absolute value of the difference between the fiber orientation ratio of one surface and the fiber orientation ratio of the other surface is 0.5 or less.

(Papermaking method / paper machine)
The method for producing the kraft paper for reinforcing paper is not particularly limited as to the papermaking method, and may be any of an acidic papermaking method, a neutral papermaking method, and an alkaline papermaking method. The paper machine is not particularly limited, and various known paper machines such as a long net paper machine, a twin wire paper machine, a gap former paper machine, and a circular net paper machine can be used.

(Control of jet landing position)
In the papermaking process, the closer the jet landing position is to the discharge device (stock inlet) side, the stronger the tendency for the pulp fibers of kraft paper to be oriented in the MD direction, and conversely, the next process (press part) within a certain range of the jet landing position. The closer to the) side, the stronger the tendency for the pulp fibers of kraft paper to be oriented in the CD direction. Further, when the jet landing position exceeds the above-mentioned certain range and approaches the press part side, the pulp fibers tend to be oriented in the MD direction again. Here, the jet landing positions are mainly (1) the relative speed difference between the pulp slurry and the papermaking wire, (2) the pulp slurry discharge angle (particularly the elevation angle or the depression angle), and (3) the upper surface of the papermaking wire. Although it is affected by the height of the pulp slurry discharge port (slice lip) with respect to the above, it is not always easy to adjust the discharge angle of (2), and the height adjustment of (3) is often restricted in terms of equipment. Therefore, the present inventor controls the jet landing position by the J / W ratio, which is relatively easy to adjust and has a strong correlation with the relative velocity difference in (1), thereby the fiber orientation in the MD direction and the CD direction. It was decided to coordinate with the fiber orientation to. That is, as shown in claim 4, the jet landing position is brought closer to the stock inlet side by setting the J / W ratio to 0.98 or less, or the jet landing position is set to 1.03 or more by setting the J / W ratio to 1.03 or more. Was brought closer to the press part side beyond the above-mentioned certain range to promote the orientation of the pulp fibers in the MD direction and to balance the fiber orientation in the MD direction and the fiber orientation in the CD direction.

(Measurement of fiber orientation ratio)
In this manufacturing method, the absolute value of the difference between the fiber orientation ratio on one surface and the fiber orientation ratio on the other surface is 0.5 or less in order to achieve uniformity of the formation in the thickness direction of kraft paper. To control. At that time, the fiber orientation ratio of the front surface and the back surface of the kraft paper may be measured by measuring the front surface and the back surface of the wet paper on the paper machine with an online fiber orientation measuring machine, and the front surface and the back surface of the manufactured kraft paper. May be measured by the above-mentioned ultrasonic conduction type orientation measuring machine or the like. The former has the advantage that the measurement result can be immediately reflected in the control of the fiber orientation ratio, and the latter has the advantage that the fiber orientation ratio can be measured more accurately.

(Crepe processing)
Since the kraft paper for reinforcing paper is used as reinforcing paper, in the manufacturing method, it is possible to perform a crepe process in which the paper is finely shrunk to enhance impact resistance, if necessary. Generally, crepe processing is performed on wet paper having a water content of 20% or more and 45% or less, preferably 30% or more and 45% or less. Therefore, for example, a crepe processing device may be installed in the middle of the dryer part to perform crepe processing. it can. At the time of this processing, if the ratio of the speed on the exit side of the Kurupak device to the speed on the inlet side of the Kurupak device is set to about 92%, the elongation in the CD direction can be significantly increased. For example, assuming that the pressurization by the nip bar is 2.5 kg / cm, the speed on the inlet side of the Kurupak device is 600 m / min, and the speed on the outlet side of the Kurupak device is 550 m / min, the elongation in the CD direction is 7.00 to 10.0. Can be%. In addition, instead of the crepe processing, the elongation in the CD direction can be significantly increased by the free drying process in which the paper is freely shrunk and dried.

(Smoothing process)
In the manufacturing method, the surface of the kraft paper for reinforcing paper may be smoothed in order to improve the surface strength, the adhesiveness to the adhesive, and the like. This smoothing treatment is preferably carried out, for example, by performing a pressure treatment between reels that can be pressurized. Further, the roll in contact with the surface of the kraft paper for reinforcing paper is preferably a metal roll having a smooth surface and can be heated. In addition, smoothing can be performed by calendar processing using a machine calendar, soft calendar, etc., drying processing using a Yankee dryer, or the like. Further, a coating treatment or an impregnation treatment can be performed in order to improve oil resistance, water resistance, glossiness, printability and the like within a range not contrary to the object of the present invention.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the scope of the present invention is not limited to these Examples. The blending amount of the raw material of each pulp slurry of the following Examples and Comparative Examples is a numerical value based on the mass of the solid content excluding water or the active ingredient.

[Example 1]
9900 parts by mass of tap water was added to 100 parts by mass of NUKP adjusted by beating and adjusting with a refiner so that the freeness of the raw material pulp became 650 cc, and mixed. "NES-500P") 0.20 parts by mass, sulfuric acid band (Asahi Chemical Industry Co., Ltd.) 3.20 parts by mass and polyacrylamide as a paper strength enhancer ("DS-95" of Seikou PMC Co., Ltd.) 2.45 Parts by mass were added and mixed well to prepare a pulp slurry. This pulp slurry is provided on a wire part of a twin wire type paper machine (Bellbond Former) equipped with a wire part, a press part, a dryer part, a size press part and a calendar part and operating at a speed of 600 m / min at a speed of 618 m / min. ^{A single layer with a basis weight of 85 g / m 2 at} a minute (J / W ratio of 1.03), discharged so that the fiber orientation ratios of both surfaces are 1.9, and the single layer is made by papermaking. Obtained kraft paper for reinforcing paper. The manufactured kraft paper for reinforcing paper is humidity-controlled at a temperature of 23 ° C. ± 1 ° C. and a relative humidity of 50 ± 2% in accordance with JIS-P-8111 (1998), and a part of it is a sample for measuring fiber orientation angle, etc. The rest was used as the material for reinforcing paper at the time of trial production of the kraft paper bag described later.

[Examples 2 to 3]
Kraft paper for reinforcing paper was obtained in the same manner as in Example 1 except that the mass ratio of NULP and LUKP, the raw material pulp freeness and the J / W ratio were changed as shown in Table 1.
[Examples 4 to 5]
Kraft paper for reinforcing paper was obtained in the same manner as in Example 1 except that the sizing agent addition rate and the J / W ratio were changed as shown in Table 1.
[Examples 6 to 7]
Kraft paper for reinforcing paper was obtained in the same manner as in Example 1 except that the aluminum sulfate band addition rate and the J / W ratio were changed as shown in Table 1.
[Examples 8 to 9]
Kraft paper for reinforcing paper was obtained in the same manner as in Example 1 except that the addition rate of the paper strength enhancer, the basis weight and the J / W ratio were changed as shown in Table 1.
[Examples 10 to 11]
Kraft paper for reinforcing paper was obtained in the same manner as in Example 1 except that the J / W ratio was changed as shown in Table 1.
[Examples 12 to 13]
Kraft paper for reinforcing paper was obtained in the same manner as in Example 1 except that the basis weight and the J / W ratio were changed as shown in Table 1.
[Comparative Example 1]
Kraft paper for reinforcing paper in the same manner as in Example 1 except that the absolute values of the mass ratio of NULP and LUKP, the raw material pulp freeness, and the difference in the fiber orientation ratio of both surfaces were changed as shown in Table 1. Got
[Comparative Examples 2-3]
Kraft for reinforcing paper in the same manner as in Example 1 except that the addition rate of the sizing agent, the basis weight, the absolute value of the difference in the fiber orientation ratios on both surfaces, and the J / W ratio were changed as shown in Table 1. I got the paper.
[Comparative Example 4]
The same as in Example 1 except that the addition rate of the sizing agent, the addition rate of the paper strength enhancer, the absolute value of the difference in the fiber orientation ratios on both surfaces, and the J / W ratio were changed as shown in Table 1. Obtained kraft paper for reinforcing paper.
[Comparative Example 5]
Reinforcing paper in the same manner as in Example 1 except that the addition rate of the sizing agent, the addition rate of the aluminum sulfate band, the absolute value of the difference in the fiber orientation ratios on both surfaces, and the J / W ratio were changed as shown in Table 1. I got kraft paper for.
[Comparative Example 6]
Kraft paper for reinforcing paper was obtained in the same manner as in Example 1 except that the addition rate of the sizing agent, the absolute value of the difference in the fiber orientation ratios on both surfaces, and the J / W ratio were changed as shown in Table 1. It was.

(Prototype conditions)

<Prototype evaluation>
Basis weight of measurement sample of each Example / Comparative example, fiber orientation ratio of one surface and the other surface, fiber orientation angle of one surface and the other surface in the CD direction and MD direction, CD direction and MD direction. Tensile strength and elongation, interlayer strength, stakehito size, and air permeation resistance were measured. Further, using the kraft paper of each Example / Comparative Example as a reinforcing paper, JIS-Z-0102 3. The "bottom bag with foldless valve" specified in B-1 (2004) was manufactured. At this time, a cut tape was attached to the reinforcing paper to form an easy-open type paper bag. At the time of this production, the "bag making suitability" described later was evaluated. Then, after adjusting the humidity of these paper bags at a temperature of 23 ° C. ± 1 ° C. and a relative humidity of 50 ± 2% in accordance with JIS-P-8111 (1998), the "bag rupture evaluation" described later and "from both the left and right sides" will be described later. "Easy to open" and "presence or absence of debris" were evaluated. These results are shown in Tables 1 to 4.

(Basis weight)
The “basis weight (g / m ² )” in Table 1 was measured according to JIS-P-8124 (2011).

(Fiber orientation ratio and fiber orientation angle)
The "fiber orientation ratio" in Table 1 and the "fiber orientation angle (°)" in Table 2 are set separately for the front and back surfaces of kraft paper using the above-mentioned ultrasonic conduction type orientation measuring machine "SST-4000". It was measured. The "absolute value of the difference in the fiber orientation angle of one surface" in Table 2 is the difference between the "fiber orientation angle in the MD direction of one surface" and the "fiber orientation angle in the CD direction of one surface" in Table 2. Is the absolute value of. The same applies to the "absolute value of the difference in the fiber orientation angles of the other surface".

(Tensile strength, Y / T ratio)
The tensile strength (kN / m) in the CD direction and the MD direction in Table 3 was measured in accordance with JIS-P-8113 (2006), and the "Y / T ratio" was calculated based on these measured values.

(Growth)
The elongation (%) in the CD direction and the MD direction in Table 3 was measured according to JIS-P-8113 (2006).

(Production of tensile strength and elongation in the CD direction)
In Table 3, "Production of tensile strength in the CD direction and elongation" shows the measured value of the tensile strength in the CD direction (kN / m) and the CD direction in order to examine in detail the strength in the CD direction where a large stress is likely to be applied. It was calculated as the product of the measured value (%) of the elongation of. If this value is about 10 or more, it can be said that the strength in the CD direction is sufficient.

(Interlayer strength)
The “interlayer strength (mJ)” in Table 3 was measured using an internal bond tester according to the JAPAN TAPPI pulp and paper test method 18-2.

(Sutekihito size degree)
The “Sutekihito size degree (seconds)” in Table 3 was measured according to JIS-P-8122 (2004).

(Air permeability resistance)
The “air permeation resistance (seconds)” in Table 3 was measured according to JIS-P-8117 (2009).

(Aptitude for bag making)
In “Aptitude for bag making” in Table 4, JIS-Z-0102 3. Using the kraft paper for reinforcing paper of each Example / Comparative Example as the reinforcing paper. Ease of manufacturing (easy to process on reinforcing paper, easy to attach reinforcing paper, etc.) when manufacturing "bottom burrs with foldless valves" specified in B-1 (2004). , The evaluation was made on a three-point scale as follows.
◯: Easy to manufacture than conventional products.
Δ: Ease of manufacture equivalent to that of the conventional product.
X: It is harder to manufacture and cannot be used than conventional products.

(Evaluation of broken bag)
In the “bag rupture evaluation” of Table 4, JIS-Z-0102, which was manufactured by using the kraft paper for reinforcing paper of each Example / Comparative Example as the reinforcing paper, 3. 25 kg of flour is filled and packaged in the "bottom bag with foldless valve" specified in B-1 (2004), and the next day, these filled and packaged bags are packed in accordance with JIS-Z-0217 (1998). The number of repetitions when the bag was repeatedly dropped horizontally from a height of 1.2 m until the bag was broken on the resin floor was measured, and based on the number of repetitions, the evaluation was made in three stages as described below. In the following, d = (number of times of each example / comparative example)-(number of times of conventional product).
◯: It is harder to break the bag than the conventional product (d ≧ 2).
Δ: The bag is as easy to break as the conventional product (1 ≧ d ≧ -1).
X: The bag is easier to break than the conventional product and cannot be used (-2 ≧ d).

(Easy to open from both left and right sides)
In Table 4, "Easy to open from both left and right sides", 25 kg of flour is filled and packaged in each of the above "bottom burrs with foldless valves", and the next day, cut tape is pulled from each of the left and right ends of the cut tape to reinforce it. The breakability of the reinforcing paper when the paper was broken was evaluated on a three-point scale as follows.
◯: Even if the cut tape is pulled from either the left end or the right end, the breaking portion does not spread in a V shape and the reinforcing paper is easily broken.
Δ: When the cut tape is pulled from either the left end or the right end, the broken part does not spread in a C shape and the reinforcing paper is easily broken, but when the cut tape is pulled from the other, the broken part is slightly C-shaped. The reinforcing paper is slightly hard to break.
×: When the cut tape is pulled from either the left end or the right end, the broken part does not spread in a V shape and the reinforcing paper is easily broken, but when the cut tape is pulled from the other, the broken part becomes a C shape. Spreads and the reinforcing paper is hard to break (easy to open as easy as conventional products).

(Presence / absence of debris)
In Table 4, "Presence or absence of debris", 25 kg of flour is filled and packaged in each of the above "bottom bag with foldless valve", and the next day, the cut tape is pulled from each of the left and right ends of the cut tape to remove the reinforcing paper. The generation of fragments of the reinforcing paper when broken was evaluated on a three-point scale as follows.
◯: No debris is generated even if the cut tape is pulled from either the left end or the right end.
Δ: When the cut tape is pulled from either the left end or the right end, no debris is generated, but when the cut tape is pulled from the other, debris may be generated.
X: When the cut tape is pulled from either the left end or the right end, no debris is generated, but when the cut tape is pulled from the other, debris is frequently generated (the frequency of debris generation is about the same as that of the conventional product).

(Prototype evaluation)

(Comprehensive evaluation)
In all of Examples 1 to 13 of the present invention, the bag making suitability, the bag breaking evaluation, the ease of opening from both the left and right sides, and the prevention of debris generation at the time of opening are excellent, and the cut tape is pulled from either the left or right end of the cut tape. However, the problem that the reinforcing paper is easily broken and fragments of the reinforcing paper are not generated at the time of breaking is solved.

The kraft paper for reinforcing paper of the present invention is cut because it has sufficient strength and durability as a reinforcing paper, is easily broken in any direction, and does not generate fragments of the reinforcing paper when broken. It can be suitably used as a reinforcing paper for an easy-open type kraft paper bag in which a tape and a reinforcing paper are bonded. In addition, since the kraft paper for reinforcing paper has sufficient strength and durability and is also excellent in processing suitability, it can be used on the body of all kraft paper bags including kraft paper bags for heavy packaging such as for rice and wheat and cement. It can be preferably used.

Claims (4)

Contains unbleached kraft pulp fiber as the main component
It is composed of a single layer with a basis weight of 70 g / m ² or more and 120 g / m ^{2 or less.}
The absolute value of the fiber orientation ratio on one surface and the absolute value of the fiber orientation ratio on the other surface are both 3 or less.
The absolute value of the difference between the fiber orientation ratio and fiber orientation ratio of the other surface of the one surface described above Ri der 0.5 or less,
The fiber orientation ratio ultrasonic conduction orientation of kraft paper for reinforcement paper that by the measurement. The absolute value of the difference between the fiber orientation angle in the MD direction and the fiber orientation angle in the CD direction on one surface is 1.5 ° or less.
Absolute value even 1.5 ° der less of a difference between fiber orientation in the other fiber orientation and CD direction MD direction of the surface is,
Kraft paper reinforcing sheet of claim 1 wherein said fiber orientation is that by the ultrasonic transmission and orientation measurements. The degree of wonderful human size is 30 seconds or less,
The interlayer strength measured using an internal bond tester according to the JAPAN TAPPI pulp and paper test method 18-2 is 200 mJ or more and 400 mJ or less.
The ratio of the tensile strength in the CD direction to the tensile strength in the MD direction is 30% or more and 65% or less.
The reinforcing paper according to claim 1 or 2, wherein the elongation measured in accordance with JIS-P-8113 (2006) is 1.3% or more in the MD direction and 3.5% or more in the CD direction. Kraft paper. The process of preparing a pulp slurry containing unbleached kraft pulp fiber as the main component,
The process of discharging the pulp slurry to the papermaking wire and
The process of making wet paper from the discharged pulp slurry using the papermaking wire, and
It is provided with a step of further dehydrating and drying the wet paper.
In the step of discharging the pulp slurry to the papermaking wire, the ratio of the speed of the pulp slurry at the time of discharge to the speed of the papermaking wire is 0.98 or less or 1.03 or more, and the basis weight is 70 g / m. in ^more 120 g / m ² or less of a single layer, the absolute value of the difference between fiber orientation ratio and the other surface fiber orientation ratio of the one surface is a paper to be 0.5 or less,
Method for producing the fiber orientation ratio ultrasonic conduction orientation by that reinforcing Kraft paper for paper measurement.