JP5775271B2 - Paper containing recycled pulp - Google Patents

Description

  The present invention relates to paper containing recycled pulp, and more particularly to paper suitable for postcard paper.

  In general, paper is roughly classified into paper and paperboard. There are various uses of the former paper, and postcards called “public postcards” (or “postcards”) and “private postcards” are one of them. A postcard is usually a postcard paper made from raw pulp and cut into a predetermined size. In the case of a government-made postcard, a postage stamp face with a face value that has the same effect as a postal code box or stamp is printed on the surface. Printed. New year's cards with New Year's cards and summer letter postcards are printed with a group number and lottery number at the bottom. These printings are usually performed by an offset printing method.

  As such a postcard paper, for example, Patent Document 1 (Japanese Patent No. 3755483) describes that chemical pulp, deinked pulp, or the like is mixed and calcium carbonate is used as a filler. Patent Document 2 (Japanese Patent Application Laid-Open No. 2004-1000049) describes that an ink receiving layer is provided on one surface of a multi-layer support so as to be suitable for ink jet recording. Patent Document 3 (Japanese Patent Laid-Open No. 2003-291515), Patent Document 4 (Japanese Patent Laid-Open No. 2002-127492), Patent Document 5 (Japanese Patent Laid-Open No. 10-297148), and Patent Document 6 (Japanese Patent No. 4031277) Describes that it is excellent in ink absorbability as a support having a multilayer structure of two or more layers.

  In recent years, in the manufacture of paper, the use of waste paper as a raw material pulp has been promoted with an increase in environmental awareness such as recycling and resource saving. There is a very high demand for the use of used paper even for postcard paper and sealed paper. For example, Patent Document 7 (Japanese Patent Laid-Open No. 2005-35224) describes a transportation system for postcards containing recycled pulp obtained from waste paper as raw pulp.

On the other hand, the post office can read the postal code and address name written by the sender in the postal item with OCR, print the destination information as a bar code, and sort and convey it by machine processing with an automatic sorter. Has been done. The bar code is printed as invisible information that cannot be seen by the eyes using infrared or ultraviolet excited fluorescent stealth ink. For example, Patent Document 8 (Japanese Patent Laid-Open No. 11-076950) describes a barcode printing system for sorting mail items.
Patent Document 9 describes a recycled postcard paper that contains 40% by mass or more of waste paper pulp in paper and is made by multi-layer stitching of three or more layers.

Japanese Patent No. 3755483 JP 2004-100049 A JP 2003-291515 A JP 2002-127582 A JP-A-10-297148 Patent No. 4031277 JP 2005-035224 A Japanese Patent Application Laid-Open No. 11-076950 JP 2010-047894 A

  As described above, the mail is a system that is efficiently transported by optically reading the destination information described by the sender and converting it into a stealth bar code. However, in the manufacture of paper, dust, pitch, and other contaminants such as ink fountain and toner fountain derived from waste paper are likely to be mixed, and the destination information can be read by these dust and dirt (spots and foreign matter due to the foreign matter). There is a problem that the accuracy is lowered and the barcode is not accurately generated. In addition, fluorescent materials such as fluorescent dyes contained in waste paper reduce the contrast between the barcode printing area and the ground color area, hinder barcode reading with an automatic sorting machine, and are not transported correctly. There is. And when mix | blending a large amount of the recycled pulp which uses waste paper as a raw material, the reading accuracy of the destination information and the stealth barcode which the sender described will deteriorate further. In addition, when the recycled pulp is highly blended, there is a problem that the appearance of the product such as whiteness is impaired.

  As described above, the promotion of waste paper use and the efficiency of the postal transport system are inversely proportional, and it is desired to increase the number of recycled pulp without deteriorating the reading accuracy of destination information and barcode. Accordingly, an object of the present invention is to provide a paper suitable for a postcard paper that is excellent in whiteness, low in fluorescence intensity, and less in dust and dirt while containing a high proportion of recycled pulp.

  The inventors of the present invention have solved the above problems by using a pulp having a high whiteness among recycled pulps, and have reached the present invention. Specifically, it is a multi-layered structure with three or more layers of pulp as the main raw material, and is a paper containing recycled pulp in at least one inner layer formed between the surface layer and the back layer, and is regenerated with respect to the total pulp solid content It has been found that the problem can be achieved by containing 20% by mass or more of pulp and 50% by mass or more of regenerated pulp having a whiteness of 60% or more with respect to the total solid content of the regenerated pulp.

  According to the present invention, recycled pulp can be blended in a high amount, and an environmentally friendly paper can be obtained. Further, even if the recycled pulp is highly blended, it is possible to provide a postcard paper that is excellent in whiteness, low in fluorescence intensity, less dust and dirt, and suitable for a mail transport system.

  The paper in the present invention does not include paperboard. Hereinafter, the present invention will be described in detail by taking the case of postcard paper as an example.

(Structure of postcard paper)
The postcard paper of the present invention has a multilayer structure of three or more layers using pulp as a main raw material, and is manufactured by papermaking or multilayer papermaking. For example, in the case of 3 layers, “surface layer”, “middle layer”, “back layer”, in the case of 4 layers, “surface layer” “front layer” “back layer” “back layer”, in case of 5 layers “surface layer” “surface layer” ”,“ Middle layer ”,“ back layer ”, and“ back layer ”. The number of stacked layers is not limited to these. The surface layer includes a stealth barcode printed surface. The inner layer formed between the surface layer and the back layer in the present invention means “front layer”, “middle layer”, “back layer” and the like.

  The postcard paper of the present invention has at least one inner layer, that is, for example, “medium layer” in the case of three layers, “front lower layer” in the case of four layers, and / or “back lower layer” in the case of five layers. Any one or more of the “lower layer”, “middle layer”, and “back lower layer” contains recycled pulp made from waste paper as a raw material. In the present invention, by containing recycled pulp in the inner layer as described above, the whiteness is high while the recycled pulp is highly blended, and the influence of dust, dirt, and fluorescent substances contained in the recycled pulp is kept low. It becomes possible. In the present invention, the content of recycled pulp is preferably as much as possible from the viewpoint of the environment, and is 20% by mass or more, more preferably 40% by mass or more, and further preferably 60% by mass or more, based on the total pulp solid content.

(Pulp raw material)
In the present invention, recycled pulp having a whiteness of 60% or more is used, and it is contained at a ratio of 50% by mass or more based on the solid content of all recycled pulp, so that dust, dirt, fluorescence intensity, etc. are regenerated. In addition to resolving problems in the case of high blending of pulp, excellent whiteness can be obtained. The whiteness of the recycled pulp is more preferably 65% or more, and further preferably 70% or more.

  In the present invention, it is preferable to use deinked waste paper pulp (DIP) as the recycled pulp having such whiteness. In general, DIP includes each process of waste paper decontamination, dust removal using a cleaner or screen, deinking (ink separation) using a floatator, bleaching, dispersion using a kneader or disperser, and washing / dehydration using a DNT washer. It is manufactured after. Washing is performed in each step as necessary. The whiteness of DIP can be adjusted by bleaching or washing. In addition, the whiteness of the pulp and postcard paper in the present invention is measured according to JIS P 8148.

  In the present invention, the ash content in the regenerated pulp is preferably less than 20% by mass and more preferably less than 10% by mass in the regenerated pulp from the viewpoint of reducing dust and dirt. Thus, since there is little ash content in a regenerated pulp, the internal bond strength in a multilayer structure also becomes favorable. Ash content in the recycled pulp can be adjusted by dust removal, deinking, washing with a dehydrator, and the like. Further, by sufficiently performing these treatments, the amount of fine fibers contained in the regenerated pulp is reduced, and the content ratio of fine fibers having a length of 0.1 mm or less is less than 10% by mass, and further less than 5% by mass. It becomes. The ash content in the recycled pulp is measured according to the 525 ° C. combustion method defined in JIS P 8251. The amount of fine fibers is measured according to a fiber length measurement method by an optical automatic analysis method stipulated in JIS P 8226. Specifically, when measured with a pulp analyzer “FiberLab” manufactured by Kajaanisy The frequency of 0.1 mm or less in the fiber length distribution at the time of the average length calculation.

  In the present invention, when the recycled pulp is blended in a plurality of inner layers with four or more layers, the recycled pulp blended in each inner layer may be the same or different. When the whiteness of the regenerated pulp used for each layer is different, for example, when there are 5 or more layers, the whiteness of the regenerated pulp used for the front lower layer and the back lower layer is higher than the whiteness of the regenerated pulp used for the middle layer It is preferable. As a result, when the postcard paper is divided into layers, it is preferable that the whiteness of the front and back lower layer papers is higher than the whiteness of the middle layer paper.

  Furthermore, if necessary, the inner layer can be recycled with one or more of the commonly used papermaking materials such as mechanical pulp (MP), hardwood kraft pulp (LKP), and softwood kraft pulp (NKP). It can be used by mixing with pulp. Examples of the mechanical pulp include groundwood pulp (GP), refiner groundwood pulp (RGP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), chemiground pulp (CGP), semi-chemical pulp (SCP), and the like. . From the environmental viewpoint, it is desirable that the amount of recycled pulp used is large. When the recycled pulp and other pulp are mixed and used, the ratio of the two in each inner layer can be arbitrarily set and is not particularly limited, but recycled pulp: other pulp = 50: 50 to 100: 0 is preferable. is there.

  Used paper for recycled pulp includes high-quality paper, medium-quality paper, low-grade paper, newspaper, flyers, magazines, and other sorts of waste paper, unsorted waste paper mixed with these, copy paper, thermal paper, and carbonless paper. Office waste paper including the like can be suitably used.

  On the other hand, recycled pulp may be blended in the surface layer and the back layer, but chemical pulp such as softwood kraft pulp, hardwood kraft pulp, etc. may be used from the viewpoints of product whiteness, fluorescence intensity, dust, dirt, etc. preferable. In particular, since the surface layer determines the appearance of the paper and is also the surface side on which the stealth barcode is printed, 100% by mass of chemical pulp is preferable.

  According to the present invention, it is possible to obtain a postcard paper excellent in appearance whiteness. As a postcard paper using recycled pulp, the whiteness of the front and back surfaces of the paper is preferably about 74%, but according to the present invention, a whiteness of 76% or more can be obtained.

(Fluorescence deactivation treatment)
In the present invention, it is desirable to subject the recycled pulp to fluorescence deactivation treatment from the viewpoint of lowering the fluorescence intensity. Fluorescence deactivation treatment includes addition of a fluorescence deactivator to the recycled pulp slurry, polyvalent metal treatment, enzyme treatment, peroxide treatment, ozone treatment, masking treatment, treatment of the pulp after deinking with chlorine dioxide, etc. Is mentioned.

  In the present invention, it is desirable to use recycled pulp to which a fluorescence quencher has been added. Examples of the fluorescence quencher include dichloroisocyanurate, N-vinylformamide polymer, aromatic carboxylic acid / amine condensate, and the like, but are not limited thereto.

  The addition amount of the fluorescence deactivator is preferably 0.01 to 2%, more preferably 0.03 to 1.5% in terms of solid content per solid content of the recycled pulp. Even if the amount of the fluorescent deactivator added is large, the effect of removing the fluorescence is peaking out, and when it is too much, the whiteness of the pulp tends to decrease, whereas when the amount of the fluorescent deactivator is too small, the effect is insufficient. It is. In particular, for example, in the case of 5 layers, it is preferable to add to the recycled pulp contained in the front and lower layers and / or the back and bottom layers. It is considered that the detrimental effect of the fluorescent dye derived from recycled pulp can be more efficiently suppressed by deactivating the fluorescent dye present in the inner layer close to the surface layer or the back layer.

  In order to add the fluorescence quencher to the recycled pulp, it is preferable after the production of the recycled pulp. In the present invention, it is presumed that the fluorescence intensity decreases due to the masking action of the fluorescence quencher. If it is added before or during the production of regenerated pulp, it is considered that it does not flow out together with water in the treatment step or does not sufficiently adhere to the pulp fiber due to stirring or the like.

(Paper making method)
The method for producing the postcard paper of the present invention is not particularly limited, and can be obtained by preparing each layer of paper stock, for example, by making each layer together with a long net type wet paper machine to form a multilayer structure. . Moreover, the paper stock of each layer may be ejected from the multi-layer head box to make a multi-layer paper. In addition to the above, examples of the paper machine include a twin wire type paper machine, a circular net paper machine, and a short net paper machine.

  In the present invention, in order to increase the internal bond strength of the multilayer structure, starch or other adhesive may be applied between the layers, or a paper strength enhancer may be blended. However, it is desirable that the internal bond strength is not too high from the viewpoint of disintegration during recycling. In the present invention, JAPAN TAPPI No. The measured value along 18-1 is preferably less than 500 KPa, more preferably 450 KPa or less, and still more preferably 400 KPa or less. Alternatively, JAPAN TAPPI No. The measured value along 18-2 is preferably less than 1650 KPa, more preferably 1600 KPa or less. As a method for obtaining a paper having a multi-layer structure having an internal bond strength in such a range, for example, a layer to which starch and an adhesive are applied and a layer to which a paper strength enhancer is blended are provided, and a layer not containing a paper strength enhancer is provided. However, it is not limited to this.

  In order to prevent the occurrence of paper dust when cutting to a postcard paper size and the peeling of paper during printing or automatic sorter processing, the JAPAN TAPPI No. More than 300 KPa in the measured value according to 18-1, JAPAN TAPPI No. The measured value along 18-2 may be 1300 KPa or more.

(Basis weight)
The basis weight of the postcard paper is desirably 180 to 200 g / m ² . The basis weight range of each layer in the sheeting can be adjusted within a range not impairing the effect of the present invention, but the basis weights of the surface layer and the back layer are each preferably 20 to 60 g / m ² , 25 More preferably, it is ˜50 g / m ² . If the basis weight of the surface layer and the back layer is too low, there is a concern that the fluorescence intensity derived from the recycled pulp will be high. On the other hand, if the basis weight of the surface layer and the back layer is too high, the surface layer is good in terms of fluorescence intensity and dirt. The amount of chemical pulp used in the back layer is large, which is undesirable from a cost and environmental standpoint.

The basis weight of the inner layer is about 60 to 160 / ^{m 2} is preferred. Moreover, when manufacturing a paper by making four or more layers (inner layers are two or more layers), the basis weight of each layer is more preferably 30 to 80 g / m ² . If the basis weight of the inner layer is too low, the proportion of recycled pulp cannot be increased. On the other hand, if the basis weight of the inner layer is too high, the basis weight of the surface layer and the back layer will be reduced, and the fluorescence intensity derived from the recycled pulp will increase. There may be a problem in the readability of the destination information barcode.

(Filler)
Further, the postcard paper of the present invention may contain a filler. In particular, in order to increase opacity, the surface layer and / or the back layer preferably contains a filler. The type of filler is not particularly limited. For example, calcium carbonate such as heavy calcium carbonate and light calcium carbonate, calcium carbonate-silica composite, titanium oxide, clay, silica, talc, kaolin, calcined kaolin, deramikaolin, magnesium carbonate , Inorganic fillers such as barium carbonate, zinc oxide, silicon oxide, amorphous silica, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, titanium oxide, bentonite; urea-formalin resin, polystyrene resin, melamine resin , Organic fillers such as phenol resin and fine hollow particles can be used alone or in appropriate combination of two or more. In addition, recycled fillers made from papermaking sludge, deinking floss, etc. can also be used. In the case of acidic papermaking, a filler obtained by removing acid-soluble ones from the filler is used, and the filler is used alone or in combination of two or more.

  In the present invention, among others, it is recyclable and can improve the opacity and whiteness of the paper at a relatively low cost, so that the pH of the paper surface becomes 6.0 to 9.5 using calcium carbonate. It is preferable to make a paper. If the content of the filler is too small, the opacity is inferior, and if it is too large, paper dust is likely to be generated during offset printing or cutting. The filler content mentioned here includes both those derived from recycled pulp and those added during papermaking.

(Paper chemicals)
In the present invention, various papermaking chemicals can be added as necessary. Specifically, polyacrylamide polymer, polyvinyl alcohol polymer, cationic starch, various modified starches, internal paper strength enhancers such as urea / formalin resin, melamine / formalin resin; rosin sizing agent, AKD type Sizing agents, ASA sizing agents, petroleum sizing agents, internal sizing agents such as neutral rosin sizing agents, and the like. In addition, a retention agent, a drainage improver, a coagulant, a sulfate band, bentonite, silica, a dye, an antifoaming agent, an ultraviolet ray inhibitor, a fading inhibitor, a pitch control agent, a slime control agent, and the like can be used.

(surface treatment)
In addition, a surface treatment agent can be applied to the front surface and / or the back surface of the postcard paper of the present invention as required. There are no particular limitations on the type and composition of the surface treatment agent, but examples of water-soluble polymeric substances for the purpose of improving surface strength include raw starch, oxidized starch, esterified starch, cationized starch, enzyme-modified starch, and aldehyde. Starch, hydroxyethylated starch, hydroxypropylated starch, etc .; cellulose derivatives such as carboxymethylcellulose, hydroxyethylcellulose, methylcellulose; modified alcohols such as polyvinyl alcohol, carboxyl-modified polyvinyl alcohol; styrene-butadiene copolymer, polyvinyl acetate, A vinyl chloride-vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, polyacrylic acid ester, polyacrylamide or the like is used alone or in combination. Further, in the present invention, for the writing suitability or the printability with a printer, the Steecht sizing degree is preferably 250 to 600 seconds. In order to increase the water absorption resistance, in addition to the water-soluble polymer substance, Surface sizing agents such as styrene acrylic acid, styrene maleic acid, and olefinic compounds may be applied together. The coating amount of the surface treatment agent is not particularly limited, and is usually about 0.5 to 5 g / m ² per both sides. Further, when a surface treatment agent comprising a water-soluble polymer substance and a surface sizing agent is applied, the mixing ratio of the water-soluble polymer substance and the surface sizing agent may be within a public range.

  In the case of applying the above-described surface treatment agent, a commonly used coating apparatus can be used. For example, a 2-roll size press, a gate roll coater, a rod metering size press, a blade coater, a bar blade coater, an air knife. A coater, curtain coater, spray coater or the like can be used on-machine or off-machine. Furthermore, in the present invention, a calendar process can be applied to the paper surface. There are no particular limitations on the type and processing conditions of the calendar device, and public devices such as ordinary calenders made of metal rolls, soft nip calenders, and high-temperature soft nip calenders are appropriately selected, and according to the quality target values, What is necessary is just to set conditions within the controllable range.

  In addition, the postcard paper of the present invention can be provided with a coating layer containing a pigment on the front surface and / or the back surface, if necessary, in order to enhance printability. Moreover, as a method for improving the suitability of the ink jet printer, there can be mentioned the internal addition of an oil-absorbing filler or an internal sizing agent, and the application of a cationic resin or the like as a dye fixing agent.

(Other uses)
In addition to postcard paper, the paper of the present invention can be used for printing paper, information paper, newsprint, packaging paper, and the like. What is necessary is just to set suitably various physical properties, such as basic weight, a manufacturing method, etc. according to each use.

  Hereinafter, the present invention will be described in more detail based on examples. In addition, this invention is not restrict | limited to these Examples. In the examples and comparative examples, parts and% represent solid parts by mass and solids mass%. In the following examples, five layers were combined, and each layer was described in the order of “surface layer”, “front layer”, “middle layer”, “back layer”, and “back layer”.

[Manufacture of recycled pulp]
(DIP-A)
Waste paper was fed into the high-concentration pulper at a ratio of waste newspaper: magazine waste paper: Kent waste paper: flyer waste paper = 65: 16: 11: 8. The chemical | medical agent was added here and it adjusted so that a pulp density | concentration might be 15 mass%, and the disaggregation process was performed. The chemicals used were 2.0% caustic soda and 0.2% higher alcohol deinking agent, respectively, in proportion to the weight of used paper. Subsequently, DIP (deinked recycled pulp) was produced through a coarse selection screen, a floater, a selection screen, and a disperser. Formamidine sulfinic acid (FAS) is further added to this DIP, and after dispersion treatment with a disperser, it is diluted with water and washed with a high-speed wire belt type dehydrator (DNT washer). Obtained. The whiteness of DIP-A was 70%, the ash content was 3%, and the amount of fine fibers of 0.1 mm or less was 1.4%.

(DIP-B)
DIP-B was obtained in the same manner as DIP-A, except that the steps after the addition of formamidinesulfinic acid (FAS) were not performed. The whiteness of DIP-B was 55%, the ash content was 12%, and the amount of fine fibers of 0.1 mm or less was 10%.

[Example 1]
(Surface and back layers)
Add 100 parts of LBKP beaten to 400 ml of Canadian Standard Freeness (CSF), add 2 parts of calcium carbonate as filler, 0.4 part of internal sizing agent, 0.1 part of retention agent, and 2 parts of sulfuric acid band. A slurry was prepared.
(Front lower layer, back lower layer)
Mixing 50 parts of LBKP with 400 ml of CSF and 50 parts of recycled pulp (hereinafter referred to as DIP-A) with a whiteness of 70%, adding 0.75 parts of internal sizing agent and 2.5 parts of sulfuric acid band, and adding slurry Was prepared.
(Middle layer)
A slurry was prepared by adding 0.75 parts of an internal sizing agent and 2.5 parts of a sulfuric acid band to 100 parts of recycled pulp (DIP-A) having a whiteness of 70%.
(Making)
The above three types of paper stock slurry were paper-made with a long paper machine so that the surface layer = 28 g / m ² , the lower layer / middle layer / back layer = 44 g / m ² each, and the back layer = 30 g / m ² , Paper was made in the state of paper and dried, and a base paper was made to have a basis weight of 190 g / m ² . During the papermaking, a 2.3% aqueous solution of granular starch was spray-coated at a coating amount of 1 g / m ² between each layer except between the back layer and the back layer. This base paper was coated with 1.8 g / m ² of polyvinyl alcohol on both sides with a two-roll size press and subjected to calendar treatment so that the Beck smoothness was 30 seconds to obtain a postcard paper.

[Example 2]
Example 1 except that in the pulp slurry of the lower and lower layers of Example 1, 100 parts of regenerated pulp (DIP-A) was used instead of 50 parts of LBKP and 50 parts of regenerated pulp (DIP-A). A postcard paper was obtained in the same manner.
[Example 3]
In Example 1, aromatic carboxylic acid / amine condensate (satoda processed FQ-50), LBKP, and recycled pulp (DIP-A) were used as a fluorescence quencher when preparing pulp slurries for the front and back lower layers and the back lower layer. A postcard paper was obtained in the same manner as in Example 1 except that 0.05% was added per pulp combined with (corresponding to 0.1% addition to DIP-A).

[Example 4]
In the middle-layer pulp slurry of Example 1, in the same manner as Example 1 except that 100 parts of recycled pulp (DIP-B) having a whiteness of 55% was used instead of 100 parts of recycled pulp (DIP-A). I got a postcard paper.

[Comparative Example 1]
Mix 60 parts of LBKP (400 ml of CSF) and 40 parts of regenerated pulp (DIP-A), add 5 parts of calcium carbonate as a filler, 1.4 parts of internal sizing agent, and 2 parts of sulfuric acid band to prepare a paper slurry. Prepared. This stock slurry is made with a long paper machine so that the basis weight is 190 g / m ^2, and 1.8 g / m ² of polyvinyl alcohol is applied with a size press, and the calendar is adjusted so that the Beck smoothness is 30 seconds. After processing, a postcard paper was obtained.

[Comparative Example 2]
A postcard paper was obtained in the same manner as in Comparative Example 1 except that 40 parts of recycled pulp (DIP-B) having a whiteness of 55% was used instead of 40 parts of recycled pulp (DIP-A).

[Comparative Example 3]
Similar to Example 2 except that 100 parts of regenerated pulp (DIP-B) was used instead of 100 parts of regenerated pulp (DIP-A) in the pulp slurry of the lower layer, middle layer and back layer of Example 2. A postcard paper was obtained.

[Evaluation method]
Evaluation of the postcard paper obtained in each example and comparative example was performed by the following method. The evaluation results are summarized in Table 1.

<Whiteness>
The pulp and postcard paper were measured according to JIS P 8148.
<Fluorescence intensity>
According to JIS P 8148, the whiteness (X) when irradiated with light including an ultraviolet region and the whiteness (Y) when irradiated with light not including ultraviolet light were measured, and the difference between the two (X−Y ) To obtain the fluorescence intensity. It shows that fluorescence intensity is so small that a value is small.
<Chile Dirt>
Visual evaluation was performed and the following criteria were used.
◎ Chile Dirt is inconspicuous ○ Chile Dirt is almost inconspicuous △ Chile Dirt is slightly conspicuous × Lots of Chile Dirt <DIP fine fiber amount>
A frequency of 0.1 mm or less in the fiber length distribution at the time of length average calculation was measured using a pulp analyzer “FiberLab” manufactured by Kajaanisy.
<Internal bond strength>
JAPAN TAPPI No. 18-1 and no. Measured along 18-2. The former represents tension in the Z-axis direction, and the latter represents internal bonding.
<Automatic sorting machine processing test>
The results of the processing test using the automatic sorting machine are shown below.
○ Good △ Somewhat bad × Bad

表１中の＊印の白色度６０％以上は、再生パルプに対する白色度６０％以上の再生パルプの割合である。

The whiteness of 60% or more indicated by * in Table 1 is the ratio of the regenerated pulp having a whiteness of 60% or more with respect to the regenerated pulp.

  From Table 1, the postcard papers of Examples 1 to 4 were excellent in whiteness, low in fluorescence intensity, and at a level where there was no problem with dust and dirt, and the results of the automatic sorter treatment were good. In particular, Example 3 to which the fluorescence deactivator was added had a lower fluorescence intensity. On the other hand, in Comparative Example 1 using a regenerated pulp having a high whiteness in single-layer papermaking, the fluorescent intensity was high and the influence of the regenerated pulp-derived fluorescent dye was strong, and dust and dirt were also increased. Furthermore, in Comparative Example 2 using a single layer paper-making recycled pulp with low whiteness, whiteness was inferior, fluorescence intensity was high, and dust and dirt were also increased. Moreover, in Comparative Example 3 using a recycled pulp having a multilayer structure but low whiteness, dust and dirt increased.

  The paper of the present invention can be used as an environmentally friendly postcard utilizing waste paper.

Claims (5)

It has three or more layers structure in which the pulp as the main raw material, at least one layer of the inner layer which is formed between the surface layer and the backing layer is a paper as a layer containing a recycled pulp, the surface layer and back layer contains no recycled pulp together, the basis weight of the surface layer and the back layer are each 20 to 60 g / m ^2, relative to the total pulp solids containing recycled pulp least 20 mass%, furthermore, the reproduction At least one of the pulp- containing layers contains 0.01 to 2% of a fluorescence deactivator in solid mass per solid content , and the whiteness of the total solid content of the recycled pulp. A postcard paper containing 50% by mass or more of recycled pulp having a content of 60% or more . 2. The postcard paper according to claim 1, wherein a basis weight of the postcard paper is 180 to 200 g / m ² , and a total weight of the inner layers is 60 to 160 g / m ² .   The postcard according to claim 1 or 2, which has a multilayer structure of 3 to 5 layers. JAPAN TAPPI No. The postcard paper according to any one of claims 1 to 3, wherein the internal bond strength defined by 18-1 is less than 500 KPa. JAPAN TAPPI No. The postcard paper according to any one of claims 1 to 4, wherein the internal bond strength defined by 18-1 is 300 KPa or more.