JP5486824B2 - Metal paper - Google Patents

Description

  The present invention relates to a metal slip sheet. More specifically, although the paper thickness is small and extremely light, it has excellent adhesion to the metal foil, the fluctuation range of the paper thickness is small, and there is little wrinkling due to paper misalignment or moisture absorption during use. In particular, the present invention relates to a metal sheet for a thin metal foil having a thickness of a target metal foil of about 45 μm or less.

  The main application of the metal foil is, for example, a precision part used for a flexible printed circuit board or a hard disk, and a slip sheet, so-called metal slip sheet, is used to prevent scratches due to friction between parts.

  Interleaving paper used for general metal products is not easily corroded even when it comes into contact with a metal surface or metal plating surface, and fine protrusions on the surface of the interleaving paper due to pressure when the interleaving paper and metal are wound up. The part is pressed against the metal surface, and it is required that there is little foreign matter in the paper so that scratches called dents do not enter.For example, the chlorine ion concentration is adjusted to a predetermined range, and vegetable oil is used as the main raw material release agent. Neutral metal interleaving paper (see Patent Document 1), neutral metal interleaving paper in which cationic starch, anti-slip agent and release agent are blended at a predetermined ratio and the aluminum sulfate concentration is adjusted to a predetermined range (Patent Document) 2) has been proposed.

  However, the metal foil particularly targeted by the present invention itself is as thin as about 45 μm, further about 30 μm, and precision parts made of the metal foil are more likely to be scratched than general metal products. There is a big problem that scratches due to the unevenness of the product cause a decrease in product yield. Furthermore, if the slip sheet is made thinner, not only wrinkles due to shrinkage are likely to occur, but also the metal foil and slip sheet are slippery, so there is a problem that the metal foil is damaged when the slip sheet is inserted and the sheet slips. . Usually, metal interleaving paper is repeatedly used in the process. However, if the interleaving paper is thinned, reusability is inferior due to insufficient strength or wrinkles.

  Therefore, compared to conventional metal interleaving paper, of course, it is thin enough to be applied to metal foil, especially in the interleaving paper where there is less foreign matter in the paper and wrinkles during use, and it is difficult to damage precision parts. Although development is underway, it is the actual situation that metal interleaving paper having sufficient quality such as wrinkling due to shrinkage, improvement of slipping between metal foil and interleaving paper, and cushioning properties has not yet been obtained.

JP 2008-057080 A Japanese Patent Application Laid-Open No. 2005-154979

  The present invention has been made in view of the above-mentioned background art, and despite having a small paper thickness and extremely light weight, it has excellent adhesion to a metal foil, has a small fluctuation range of paper thickness, and generates wrinkles during use. An object of the present invention is to provide a slip sheet suitable for metal foil products.

That is, the present invention
JAPAN TAPPI Paper Pulp Test Method No. 49-2: Metal interleaving paper having a pH of 6-8 measured according to 2000 and a chlorine ion concentration measured according to JIS K 0101 of 80 ppm or less,
The raw pulp is composed of 100% by weight of bleached kraft pulp, and the Runkel ratio of the bleached kraft pulp is 0.9 or less,
The basis weight measured according to JIS P 8124 is 23 g / m ² or less, the paper thickness measured according to JIS P 8118 is 28 μm or less, and the density measured according to JIS P 8118 is 0.82 g / cm. ³ or less, and the Beck smoothness of one side measured in accordance with JIS P 8119 is 1000 seconds or more and the Beck smoothness of the other side is 100 seconds or less,
Paper that has been dried with a Yankee dryer is flattened with a thermal soft calender with one nip stage, and it causes wrinkles due to paper misalignment and moisture absorption when inserted between metal foils. The present invention relates to a metal interleaving paper characterized in that there are few marks and fluctuations in paper thickness hardly occur.

  The metal foil referred to in this specification refers to an extremely thin metal foil obtained by extending a metal such as stainless steel or copper to a thickness of, for example, about 45 μm, or about 30 μm.

  The metal interleaving paper of the present invention has excellent adhesion to the metal foil, small fluctuation width of the paper thickness, less wrinkles during use, and reusability despite its small thickness and extremely light weight. It is an excellent slip sheet suitable for metal foil products.

  The metal interleaving paper of the present invention has a JAPAN TAPPI paper pulp test method no. 49-2: 2000 “Paper and paperboard—Surface pH test method—Part 2: Indicator method” pH measured in accordance with 6-8, according to JIS K 0101 “Industrial water test method” It has the physical properties normally required for metal interleaving paper, such as a chlorine ion concentration measured according to the method of 80 ppm or less, preferably 50 ppm or less, and is manufactured from a base paper in which a sizing agent is internally added to raw pulp. Can do.

  The raw material pulp used for the base paper is not particularly limited, and for example, kraft pulp such as hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP) can be suitably used, and if necessary, thermomechanical pulp (TMP), mechanical pulp such as pressurized stone grand pulp (PGW), etc .; select one or more from among waste paper pulp made of city-collected waste paper such as deinking pulp (DIP) and waist pulp (WP), What is necessary is just to use a kraft pulp as a main component suitably.

  In addition, it is not preferable to use mechanical pulp or waste paper pulp as raw material pulp because it contains little foreign matter or contains almost no binding fibers, and it has less influence on the metal foil surface due to formation. Therefore, it is preferable to use kraft pulp as the raw material pulp. Particularly preferably, bleached kraft pulp that has been bleached to remove the resin content in the pulp is used in an amount of 100% by mass. Among them, hardwood bleached kraft pulp (LBKP) capable of forming formation and obtaining a uniform paper thickness. ) Is preferably used in an amount of 100% by mass.

  The preferred raw material pulp composition found by the present inventor uses the hardwood bleached kraft pulp, and the raw pulp has a Runkel ratio ((pulp fiber cell wall thickness × 2) / pulp fiber cell cavity diameter) of 0. .9 or less. When the Runckel ratio of the raw material pulp is small, there is an advantage that papermaking suitability is improved and a base paper with the same basis weight and a small paper thickness can be obtained. Therefore, in the present invention, it is particularly preferable to adjust the Runkel ratio of the bleached kraft pulp, particularly hardwood bleached kraft pulp, to 0.9 or less, more preferably 0.85 or less.

  The Runkel ratio can be adjusted by using pulp made from young plantation trees as raw pulp or by performing a viscous beating process.

In the present invention, it is preferable that the raw material pulp be beaten in the form of a beating concentration of 2 to 5%. If the beating concentration of the raw material pulp is less than 2%, the required internal fibrillation and external fibrillation do not proceed sufficiently due to the beating effect, and cutting of the pulp fibers occurs. Bulkiness may be difficult to obtain. Conversely, if the beating concentration of the raw pulp exceeds 5%, the amount of power consumed at the time of beating increases and the cost effectiveness is reduced, which is not preferable. The optimum beating concentration of the raw pulp is 2 to 4%, and the power consumption during beating is preferably 70 to 100 kW / t, and the bulk becomes highest in the vicinity of about 80 kW / t. Therefore, such beating conditions are as follows: the basis weight is 23 g / m ² or less, the paper thickness is 28 μm or less, the density is 0.82 g / cm ³ or less, and the Beck smoothness on one side is 1000 seconds or more. This is a preferable condition for obtaining the metal interleaving paper of the present invention in which the Beck smoothness on one side is 100 seconds or less.

  For example, a normal disc refiner can be used for the viscous beating process. However, the disc refiner is limited to a temporary viscous beating process performed by centrifugal force generated by high-speed rotation of the refiner. In contrast, a conical disc refiner is a centrifugal force generated by high-speed rotation of the refiner, and the raw pulp fibers are repeatedly beaten with the beating blade by the flow vortex of the raw material generated in the groove between the beating blade and the beating blade. Frequency increases and sticky beating progresses. Therefore, it is preferable to use a conical disc refiner for the viscous beating process.

  In particular, the blade width and the groove width are in a relationship of “blade width <groove width”, and unlike conventional refiners having a blade width of 2.0 mm or more, the blade width is 1.5 mm or less, and further 1.0 mm or less. Then, using a conical type refiner equipped with a rotary blade and / or a fixed blade having a groove width of 1.5 mm or more and a groove depth more than three times the blade width, a large amount of raw material flow vortex is generated. By applying the beating process, the Runkel ratio can be suitably adjusted. The optimum blade width and groove width are 1.3 mm and 2.4 mm, respectively. When using a conical type disc refiner under such conditions, even a raw pulp made of a tree species having a high Runkel ratio can be internally fibrillated, and by using the raw pulp thus treated, Despite its small paper thickness and extremely light weight, it is suitable for metal foil products with excellent adhesion to metal foil, small variation in paper thickness, little wrinkling during use, and excellent reusability Can be obtained easily.

  It is preferable to add a sizing agent to the pulp slurry made of the raw material pulp. By internally adding the sizing agent, generation of wrinkles due to moisture absorption can be sufficiently suppressed when the metal interleaving paper is used.

  There are no particular limitations on the type of sizing agent, but considering the reduction of the pitch component due to the resin component, for example, cationic styrene-acrylic polymer, styrene maleic acid-acrylic cation, etc., compared to rosin sizing agent Styrenic sizing agents represented by basic styrenic sizing agents have a small resin component as a pitch component, good sizing properties in neutral formulations, and the effect of suppressing wrinkles due to moisture absorption when using metal interleaving paper Is particularly preferable in that it is large and the reusability of the metal interleaving paper can be further improved.

  Examples of the styrenic sizing agent include styrene / acrylic acid copolymer and styrene / (meth) acrylic acid copolymer (“(meth) acrylic acid” means “acrylic acid and / or methacrylic acid”). (Hereinafter the same)), styrene / (meth) acrylic acid / (meth) acrylic acid ester copolymer, styrene / maleic acid copolymer, styrene / maleic acid half ester copolymer, styrene / maleic acid ester copolymer Etc., and one or more of these can be appropriately selected and used.

  Styrene-based sizing agents are highly dispersible in raw pulp and have a high effect of size, so it is easy to obtain uniform paper thickness and flatness in combination with the thermal soft calender used in the present invention. In spite of the fact that the paper thickness is small and extremely light, the metal foil product has excellent adhesion to the metal foil, small variation in paper thickness, little wrinkling during use, and excellent reusability. A suitable slip sheet can be easily obtained.

  As the sizing agent, in addition to the styrene sizing agent, for example, ethylene / acrylic acid copolymer, isobutylene / acrylic acid copolymer, n-butylene / (meth) acrylic acid / (meth) acrylic acid. Olefin-based sizing agents such as ester copolymers, propylene / maleic acid copolymers, and ethylene / maleic acid copolymers are exemplified, and one or more of them can be appropriately selected and used.

  The blending amount of the sizing agent is 0.05 parts by mass or more with respect to 100 parts by mass of the raw material pulp, and further 0.1 It is preferable that it is more than a mass part. In addition, the amount of the sizing agent is 3 parts by mass or less, further 2 parts by mass with respect to 100 parts by mass of the raw material pulp from the viewpoints of influence on the base paper formation, operability such as dryer peelability, and the upper limit of the size performance. The following is preferable.

  Since the metal interleaving paper in the present invention is made in a neutral region so that the pH is 6 to 8, it may tend to stick to the dryer surface during drying. Therefore, in addition to the sizing agent, for example, a release agent may be added to the pulp slurry made of raw material pulp. The type of the release agent is not particularly limited, and examples thereof include vegetable oils, mineral oils, surfactants, and the like, and one or more of these can be appropriately selected and used.

  The compounding amount of the release agent is preferably 0.1 parts by mass or more with respect to 100 parts by mass of the raw material pulp in order to develop good slipperiness. Moreover, it is preferable that the compounding quantity of a release agent is 1.0 mass part or less with respect to 100 mass parts of raw material pulp for prevention of slip with metal foil.

  In addition to the above sizing agent and release agent, the pulp slurry made of raw material pulp, for example, a paper strength enhancer such as starch, a fixing agent such as a sulfuric acid band, a pitch control agent, an antifoaming agent, a dye, etc. Various additives to be blended can be blended by appropriately adjusting the kind and amount thereof as necessary.

  Pulp slurries such as those described above are made by appropriately adjusting the papermaking conditions with a paper machine such as a long paper machine, a round paper machine, or a twin wire paper machine, and a dryer such as a Yankee dryer or a multi-cylinder dryer. To obtain a base paper. Among them, in order to reduce the generation of wrinkles and scratches during use, it is preferable to dry using a Yankee dryer having good dimensional stability and high surface smoothness.

  The release agent may be blended in the pulp slurry as described above, but can also be applied to the surface of the base paper by, for example, spray application to a dryer cylinder or application with a size press.

  Next, the obtained base paper (paper) is passed through a thermal soft calendar, and the paper is smoothed. By performing this smoothing process under the conditions described below, for example, the paper thickness is small and extremely light, but it has excellent adhesion to the metal foil, and the fluctuation range of the paper thickness is small. It is possible to easily obtain a metal interleaving paper that is less generated and excellent in reusability.

  In the present invention, a thermal soft calender provided with an elastic roll and a rigid roll is preferably used.

  As the thermal soft calender, both off-type and on-type can be used, but an on-type one that performs a series of flattening processes from paper making using a thermal soft calender, for example, preferably using a Yankee dryer. It is preferable from the viewpoints of drying treatment, imparting sizing properties with a styrenic sizing agent, reducing the fluctuation range of paper thickness, ease of obtaining paper strength, and productivity.

  Thermal soft calenders include elastic rolls such as urethane, epoxy, polyamide, phenolic and polyacrylate resin rolls, rolls made of cotton, nylon, asbestos, aramid fibers, etc., Roll Shore D hardness It is preferably used at 80 or more. As the rigid roll, a metal roll, a roll whose surface is mirror-finished with hard chrome plating or the like, a roll whose surface is roughened, and the like are appropriately used.

  Also, when passing the paper through the thermal soft calender, for example, under the conditions such as the nip temperature shown below, the glossy surface of the paper is on the elastic roll side and the non-glossy surface is on the rigid roll side. By treating the non-glossy surface with a rigid roll with an elastic roll, it prevents excessive flatness and excessive protrusion on the non-glossy surface, and smoothes the front and back surfaces within an appropriate range. It is possible to obtain a metal interleaving paper that can be carried out and that has a very small variation in paper thickness.

  It is preferable to appropriately adjust the nip temperature as the condition for the smoothing treatment. When the nip temperature is too low, the minimum smoothness for preventing the metal foil from being scratched cannot be obtained. Therefore, the temperature is set to 70 ° C. or higher, more preferably 75 ° C. or higher, particularly 78 ° C. or higher. preferable. On the other hand, if the nip temperature is too high, the density will increase and the cushioning properties will decrease, and scratches will occur on the metal foil. Therefore, the temperature should be 88 ° C or lower, more preferably 85 ° C or lower, especially 83 ° C or lower. Is preferred.

  The number of nip stages can be adjusted by appropriately combining multiple stages and the number of stacks of the thermal soft calender, but in the thin metal foil application, which is a particularly preferred application of the metal interleaving paper of the present invention, a desired density, In order to obtain flatness, rigidity, and paper strength, it is preferable to use one stage. By applying a flattening treatment with a thermal soft calender with one nip step, it is possible to provide a difference in smoothness between the front and back surfaces of the paper in particular. It is done. Furthermore, the nip pressure is preferably 90 kg / cm or more, and more preferably 95 kg / cm or more from the viewpoint of obtaining a suitable smoothness to prevent scratches on the metal foil. If the nip pressure is too high, the density increases and the cushioning property decreases, so there is a risk of scratches on the metal foil, so 150 kg / cm or less, further 120 kg / cm or less. Preferably there is.

  Further, in order to further improve the smoothness of the obtained metal interleaving paper, in addition to the adjustment of the nip temperature, the number of nip steps, the nip pressure, etc., the paper moisture of the paper before passing through the thermal soft calender is, for example, It is preferable to adjust to about 3.5-4.5 mass%. If the water content of the paper before passing through the thermal soft calender is less than 3.5% by mass, the effect of obtaining flatness is low, causing a problem that static electricity is likely to occur, and workability may be reduced. On the other hand, if the paper moisture of the paper before passing through the thermal soft calender exceeds 4.5% by mass, excessive smoothness tends to occur, and curling and dimensional stability may be reduced.

The metal interleaving paper thus obtained has a basis weight measured in accordance with the method described in JIS P 8124 “Method for measuring basis weight” of 23 g / m ² or less, JIS P 8118 “Paper and paperboard—Test for thickness and density”. The paper thickness measured in accordance with the method described in “Method” is 28 μm or less, and the density measured in accordance with JIS P 8118 is 0.82 g / cm ³ or less. Further, JIS P 8119 “paper and The Beck smoothness on one side measured in accordance with the method described in “Smoothness test method using paperboard-Beck smoothness tester” is 1000 seconds or more, and the Beck smoothness on the other side is 100 seconds or less.

  As described above, the metal interleaving paper according to the present invention has the basis weight, paper thickness, density and smoothness all adjusted within a specific range, so that the paper thickness is small and extremely light. It is a metal interleaving paper suitable for a metal foil product, which has excellent adhesion to a metal foil, has a small variation in paper thickness, has little wrinkling during use, and is excellent in reusability.

The basis weight is 23 g / m as measured according to JIS P 8124 in order to reduce the weight so that it can be suitably used as a slip sheet for a metal foil product compared to a conventional slip sheet. ² or less, preferably 22 g / m ² or less, more preferably 21 g / m ² or less. In addition, when the basis weight is too small, there arises a problem that the cushioning property is deteriorated or the paper is cut due to insufficient strength. Therefore, the basis weight may be 14 g / m ² or more, further 16 g / m ² or more. preferable. If the basis weight exceeds 23 g / m ² , the variation in paper thickness becomes large, or it becomes difficult to maintain a desired small paper thickness.

  The paper thickness is a thickness that can be suitably used as a slip sheet for a metal foil product as compared with a conventional metal slip sheet, and is 28 μm or less, preferably 27 μm or less as measured in accordance with JIS P 8118. More preferably, it is 26 μm or less. In addition, when the paper thickness is too small, the strength may be lowered. Therefore, the thickness is preferably 20 μm or more, and more preferably 22 μm or more. When the paper thickness exceeds 28 μm, the variation in the paper thickness increases, and dents on the metal foil easily occur due to the unevenness of the slip sheet.

  In addition, regarding the metal interleaving paper of the present invention, when 40 paper thicknesses in the width direction were measured at intervals of 2 cm in accordance with JIS P 8118, the maximum paper thickness difference between adjacent measurement points (hereinafter referred to as “maximum adjacent difference”). Is also preferably 3 μm or less, more preferably 1 to 3 μm, particularly preferably 1 to 2 μm, and the difference between the maximum value and the minimum value of the paper thickness at 40 locations is 5 μm or less, further 4 μm or less, It is preferable that it is 3 micrometers or less.

  The measurement of the paper thickness in the width direction when obtaining the maximum adjacent difference and the difference between the maximum value and the minimum value is preferably performed at intervals of 2 cm since the size of the floc in the paper is about 2 cm. . When the measurement is performed at intervals exceeding 2 cm, it is difficult to catch irregularities in the paper and the maximum adjacent difference is small, so that a difference according to the papermaking conditions is difficult to occur. Conversely, even if measurement is performed at intervals of less than 2 cm, there is no change in the maximum adjacent difference or the difference between the maximum value and the minimum value compared to the result measured at intervals of 2 cm. Therefore, by measuring at intervals of 2 cm, a reliable measurement value can be obtained with the minimum number of measurements.

  The paper thickness is adjusted mainly by means of the thermal soft calender, but kraft pulp with a Runkel ratio of 0.9 or less is used as the raw pulp, and the paper moisture of the paper before passing through the thermal soft calender. It is also possible to adjust easily to about 3.5 to 4.5% by mass. As a result, even though the paper thickness is small and extremely light, the metal foil has excellent adhesion to the metal foil, small variation in paper thickness, little wrinkling during use, and excellent reusability. Metal interleaving paper suitable for products can be easily obtained.

The density is 0.82 g / cm ³ or less, preferably 0.8, as measured according to JIS P 8118 in order to obtain a cushioning property that can be suitably used as a slip sheet for metal foil products. It is 81 g / cm ³ or less, more preferably 0.80 g / cm ³ or less. In addition, when the density is too small, it is difficult to maintain a desired small paper thickness, and there is a possibility that the paper becomes stiff and difficult to bend, so 0.70 g / m ³ or more, Is preferably 0.72 g / m ³ or more. When the density exceeds 0.82 g / cm ³ , cushioning properties are lowered, and scratches on the metal foil are likely to occur.

  For the smoothness, in order to prevent dents and scratches on the metal foil during use, the Beck smoothness measured according to JIS P 8119 on one side is 1000 seconds or more, preferably 1100 seconds or more, more preferably Is 1500 seconds or longer, and on the other side, the Beck smoothness is 100 seconds or shorter, preferably 90 seconds or shorter, more preferably 80 seconds or shorter. When the Beck smoothness on one side is less than 1000 seconds, when the slip sheet is inserted into the metal foil coil, the unevenness on the surface of the slip sheet is transferred to the metal foil and becomes a dent. Further, when the Beck smoothness of the other surface exceeds 100 seconds, paper misalignment occurs during insertion, and scratches are likely to occur in the metal foil. Since it is difficult to extremely reduce the smoothness of one surface, the Beck smoothness of one surface is preferably 30 seconds or more, and more preferably 40 seconds or more.

  The metal interleaving paper of the present invention has sufficient strength as an interleaving paper for metal foil products, and when a hard inorganic substance is present in the paper, a dent is generated on the metal foil. Therefore, JIS P 8251 “paper, paperboard and It is preferable that the ash content in paper measured in accordance with the method described in “Pulp-Ash Content Test Method—525 ° C. Combustion Method” is 0.5 mass% or less, and further 0.3 mass% or less.

  The metal interleaving paper of the present invention is measured in accordance with the method described in JIS P 8147 “Friction coefficient test method for paper and paperboard” from the viewpoint of preventing slipping when inserting interleaving paper. It is preferable that the static friction coefficient in the flow direction (longitudinal direction) of the front and back paper is 0.47 to 0.57 on one side and 0.33 to 0.43 on the other side.

  The adjustment of the coefficient of static friction is mainly carried out by means of the thermal soft calender, but it can be easily performed in more detail by the internal addition of a styrenic sizing agent, and the raw pulp has a Runkel ratio of 0.9. It is also possible to easily use the following kraft pulp and adjust the paper moisture of the paper before passing through the thermal soft calender to about 3.5 to 4.5% by mass. As a result, even though the paper thickness is small and extremely light, the metal foil has excellent adhesion to the metal foil, small variation in paper thickness, little wrinkling during use, and excellent reusability. Metal interleaving paper suitable for products can be easily obtained.

The metal interleaving paper of the present invention has a temperature of 23 ± in accordance with the description in JIS P 8111 “Paper, paperboard and pulp—standard conditions for humidity conditioning and testing” in order to prevent adhesion due to static electricity when inserting the interleaving paper. The volume electrical resistance measured in accordance with the method described in JIS K 6911 “General Test Method for Thermosetting Plastics” at 1.0 ° C. and relative humidity of 50 ± 2% is 1.0 × 10 ¹² -1. It is preferably 0 × 10 ¹⁴ Ω · cm, more preferably 1.0 × 10 ^{13 to} 5.0 × 10 ¹³ Ω · cm.

  For adjusting the volume electric resistance, for example, a known static electricity adjusting agent can be used, and preferably provided on the surface of the metal interleaving paper together with a release agent in a size press or a dryer, the paper thickness is small and extremely lightweight. In spite of this, it is easy to obtain metal interleaving paper suitable for metal foil products with excellent adhesion to metal foil, small fluctuation of paper thickness, low wrinkling during use, and excellent reusability. It is preferable in that it is.

The metal interleaving paper of the present invention is measured in accordance with the method described in JIS P 8143 “Stiffness testing method using paper Clark stiffness tester” in consideration of workability at the time of use and elimination of wrinkles when inserting the interleaving paper. the stiffness (stiffness) is in the longitudinal direction 3.5~5.5cm ^3/100, more in 3.8~5.2cm ^3/100, in the transverse direction 2.2~3.2cm ^3/100, further it is 2.5~3.0cm ^3/100 is, regardless it is a sheet thickness is small very light, excellent adhesion to the metal foil, the variation width of the paper thickness is small, the wrinkles at the time of use It is preferable in that a metal interleaving paper suitable for a metal foil product can be easily obtained with little generation and excellent reusability.

  The stiffness can be easily adjusted by using a kraft pulp having a Runkel ratio of 0.9 or less as a raw material pulp, a flattening treatment using a thermal soft calender, and a styrene sizing agent. As a result, even though the paper thickness is small and extremely light, the metal foil has excellent adhesion to the metal foil, small variation in paper thickness, little wrinkling during use, and excellent reusability. Metal interleaving paper suitable for products can be easily obtained.

  In consideration of workability during use, reusability, and prevention of sheet breakage due to insufficient strength, the metal interleaving paper of the present invention is JIS P 8113 “Paper and Paperboard—Testing Method for Tensile Properties—Part 2: Constant Speed Extension Method” The tensile strength measured in accordance with the method described in the above description is 1.10 to 1.50 kN / m in the machine direction, more preferably 1.15 to 1.45 kN / m, and 0.75 to 1.5 in the transverse direction. 10 kN / m, further 0.80 to 1.05 kN / m, although the paper thickness is small and extremely light, it has excellent adhesion between the metal foil and the interleaf, and the fluctuation range of the paper thickness. It is preferable in that it is easy to obtain a metal interleaving paper suitable for a metal foil product, which is small, has little wrinkling during use, and is excellent in reusability.

  The tensile strength can be easily adjusted by using kraft pulp having a Runkel ratio of 0.9 or less as raw material pulp, combining a flattening treatment with a thermal soft calender, and a styrene sizing agent. As a result, even though the paper thickness is small and extremely light, the metal foil has excellent adhesion to the metal foil, small variation in paper thickness, little wrinkling during use, and excellent reusability. Metal interleaving paper suitable for products can be easily obtained.

  Next, although the metal interleaving paper of this invention is demonstrated still in detail based on an Example, this invention is not limited only to these Examples.

Examples 1-9 and Comparative Examples 1-5 (Manufacture of metal interleaving paper)
The following were prepared as pulp, sizing agent, release agent and paper strength enhancer.
(A) Pulp LBKP
(Canadian Standard Freeness: 300-400mL)
NBKP
(Canadian Standard Freeness: 400-500mL)
PGW
(Canadian Standard Freeness: 100-200mL)
(B) Sizing agent / Styrenic sizing agent (Arakawa Chemical Industries, product number: NA size)
・ Rosin sizing agent (manufactured by Seiko PMC, product number: AL1302)
AKD sizing agent (manufactured by Seiko PMC, product number: AD1624)
(C) Release agent-containing mineral oil (manufactured by Seiko PMC Co., Ltd., product number: CR 6102)
(D) Paper strength enhancer cationic starch (manufactured by Shikishima Starch Co., Ltd., product number: Mermaid C-50)

  As shown in Table 1, with respect to 1 t of absolutely dry pulp, sizing agent 1.8 kg, release agent 2 kg, paper strength enhancer 5 kg, pitch control agent 0.5 kg, antifoaming agent appropriate amount and dye (Nipponization) A suitable amount of Yakuhin Co., Ltd., trade name: Violet P Liquid) was added to prepare a pulp slurry. This pulp slurry was made using a long paper machine at a paper making speed of about 350 m / min, and dried with a Yankee dryer to obtain a base paper.

  In Comparative Example 4, the drying treatment was performed using a multi-cylinder dryer instead of the Yankee dryer.

  Next, the obtained base paper was passed through a thermal soft calender having the following elastic roll and rigid roll in a series (on-machine), and the glossy surface (surface) of the base paper was elastic under the conditions shown in Table 2. The roll side was subjected to a smoothing treatment such that the non-glossy surface (back surface) was in contact with the rigid roll side to obtain a metal interleaving paper. Table 2 shows the water content of the base paper before passing through the calendar.

  In Comparative Example 1, the base paper is not flattened, and in Comparative Example 2, smoothing is performed using a machine calender having two rigid rolls instead of a thermal soft calender having an elastic roll and a rigid roll. In Comparative Example 4, a smoothing process was performed using a thermal soft calender provided with a combination of an elastic roll / rigid roll and a rigid roll / elastic roll.

Elastic roll (manufactured by Yodogawa Steel Works)
Material: Mirror mat (YCR5100), Hardness: 85SD, Single wall: 25mm
Rigid roll: (manufactured by Yodogawa Steel Works)
Material: Alloy chilled, Hardness: 78HS

  In addition, the hot water extraction pH (measured according to JAPAN TAPPI paper pulp test method No. 49-2: 2000) of the obtained metal interleaving paper is in the range of 6.0 to 8.0, and the chloride ion concentration (Measured according to JIS K 0101) is 80 ppm or less.

  Furthermore, about the obtained metal interleaving paper, each physical property and characteristic were investigated in accordance with the method shown below. The results are shown in Tables 3-5.

  In addition, the physical properties and characteristics of the commercially available metal interleaving paper were similarly examined. The results are shown in Tables 3 to 5 as Comparative Example 6.

(1) Physical property (a) Basis weight It measured based on JISP8124.

(B) Paper thickness and density It measured based on JISP8118.

(C) Beck smoothness Based on JIS P 8119, the Beck smoothness of the front and back surfaces was measured.

(D) Ash content in paper Measured according to JIS P8251.

(E) Static friction coefficient Based on JISP8147, the static friction coefficient of the paper flow direction (longitudinal direction) of the paper of front and back was measured between the metal interleaving paper front surfaces or back surfaces.

(F) Volume electric resistance It was measured according to JIS K 6911 in a standard state of a temperature of 23 ± 1 ° C. and a relative humidity of 50 ± 2% according to JIS P8111.

(G) Stiffness
In accordance with JIS P 8143, the longitudinal and lateral stiffnesses were measured.

(H) Tensile strength In accordance with JIS P8113, the tensile strength in the longitudinal direction and the transverse direction was measured.

(2) Characteristics (A) Variation width of paper thickness In the width direction of the metal interleaving paper, 40 thicknesses were measured at intervals of 2 cm in accordance with JIS P 8118, and the variation width was obtained.

(A) Presence / absence of dents Stainless steel foil (thickness: about 30 μm) After inserting metal interleaving paper into the coil and rewinding, visually observe the presence or absence of dents on the stainless steel foil, and the following evaluation criteria Based on the evaluation.
(Evaluation criteria)
5: The number of dents per 20 m ² is less than 0.5 4: The number of dents per 20 m ² is 0.5 or more, less than 1 3: The number of dents per 20 m ² is 1 or more, 3 Less than 2: The number of dents per 20 m ² is 3 or more. Less than 5: The number of dents per 20 m ² is 5 or more. If the evaluation is 3 to 5, it is actually used as a slip sheet for metal foil. Is possible.

(C) Paper misalignment at the time of insertion After inserting 10,000 m of metal interleaving paper into the traveling stainless steel foil (thickness: about 30 μm), measure the misalignment between stainless steel foil and metal interleaving paper, and determine the maximum value. Evaluation was made based on the following evaluation criteria.
(Evaluation criteria)
5: Maximum value is less than 0.5 mm 4: Maximum value is 0.5 mm or more, less than 1.0 mm 3: Maximum value is 1.0 mm or more, less than 1.5 mm 2: Maximum value is 1.5 mm or more, 2.0 mm Less than 1: Maximum value is 2.0 mm or more If the evaluation is 3 to 5, it can be actually used as a slip sheet for metal foil.

(D) Wrinkles due to moisture absorption After inserting 10,000m of metal interleaving paper into the traveling stainless steel foil (thickness: about 30μm), it is rewound to collect the metal interleaving paper and visually check for wrinkles due to moisture absorption of the top 10m. Observed and evaluated based on the following evaluation criteria.
(Evaluation criteria)
5: No change in shape due to moisture absorption.
4: Although expansion and contraction is observed in a part of the paper due to moisture absorption, no wrinkle is generated.
3: Although the paper expands and contracts due to moisture absorption, wrinkles are not generated.
2: Wrinkles are generated in part of the paper due to moisture absorption.
1: Wrinkles are generated on the entire paper due to moisture absorption.
In addition, if it is evaluation 3-5, it can be actually used as a slip sheet for metal foil.

  From the results shown in Tables 3 to 5, the metal interleaving papers of Examples 1 to 9 were produced by subjecting paper dried with a dryer to a flattening treatment with a thermal soft calender, and thus usually metal. Not only have the pH and chloride ion concentration required for slip paper, but also their basis weight, paper thickness, density and smoothness are all adjusted within a specific range, but also for metal foil products. It can be seen that it has various physical properties suitable as interleaving paper.

  Thus, although the metal interleaving papers of Examples 1 to 9 are small and extremely lightweight, the variation width of the paper thickness is small, there is little dent on the metal foil, and the metal foil is in close contact with the metal foil. It has excellent properties and there is almost no paper misalignment at the time of insertion.

  On the other hand, the metal interleaving papers of Comparative Examples 1 to 5 do not have a suitable basis weight, paper thickness, density and smoothness as interleaving paper for the metal foil, and the fluctuation width of the paper thickness is large. There are many dents on the metal foil, paper misalignment occurs during insertion, and wrinkles occur during use.

  In addition, commercially available metal interleaving paper has a small variation in paper thickness and few dents on metal foil, but paper misalignment occurs during insertion and wrinkles occur during use. There is no problem with this, but it is inappropriate as a slip sheet for metal foil.

  The metal interleaving paper of the present invention can be suitably used as interleaving paper for metal foil products such as flexible printed boards and precision parts used for hard disks.

Claims (3)

JAPAN TAPPI Paper Pulp Test Method No. 49-2: Metal interleaving paper having a pH of 6-8 measured according to 2000 and a chlorine ion concentration measured according to JIS K 0101 of 80 ppm or less,
The raw pulp is composed of 100% by weight of bleached kraft pulp, and the Runkel ratio of the bleached kraft pulp is 0.9 or less,
The basis weight measured according to JIS P 8124 is 23 g / m ² or less, the paper thickness measured according to JIS P 8118 is 28 μm or less, and the density measured according to JIS P 8118 is 0.82 g / cm. ³ or less, and the Beck smoothness of one side measured in accordance with JIS P 8119 is 1000 seconds or more and the Beck smoothness of the other side is 100 seconds or less,
Metal interleaving paper, characterized in that a paper subjected to a drying process with a Yankee dryer is subjected to a flattening process with a thermal soft calender having one nip stage . The metal interleaving paper according to claim 1 , wherein the paper is made of a base paper in which a styrene-based sizing agent is internally added to the raw pulp. The nip temperature of the thermal soft calender is 70 to 88 ° C. , one side of the paper is treated with an elastic roll, the other side of the paper is treated with a rigid roll, and the paper before passing through the thermal soft calender Metal interleaving paper of Claim 1 or 2 whose moisture is 3.5-4.5 mass% .