JPH1143880A - Treating of waste paper pulp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain waste paper pulp suitable for a back face layer of a paperboard having improved strength and surface property of the paper by breaking waste paper containing coated paper and subjecting to blending treatment and classifying treatment. SOLUTION: Waste paper pulp obtained by breaking with a pulper the waste paper containing coated paper such as printed waste paper in which a newspaper or a magazine is mixed is adjusted to a range of 25-35 wt.% of pulp concentration and is subjected to blending treatment with a PFI mill, etc. Then, pulp concentration is diluted to 1.5 wt.% with a large amount of water and subjected to classifying treatment with a sulfite pulp filter, and subjected to a beating treatment, as necessary, to obtain the objective waste paper pulp for a back face layer of a paperboard.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating waste paper pulp, and more particularly to a method for improving the surface properties and strength of paper and paperboard using waste paper pulp including coated paper.

[0002]

2. Description of the Related Art In recent years, waste paper is often used as a raw material for pulp from the viewpoint of saving wood resources and recycling paper, and the usage ratio thereof is also increasing. Generally, it is known that the strength of waste paper pulp is lower than that of virgin pulp, and the strength deteriorates as the number of recycling increases. In addition, the ratio of coated paper in the raw material waste paper has been increasing year by year, and the ash content which causes surface foreign matter and strength reduction, such as internal additives and pigments derived from the coating layer, has also increased.
Therefore, when using waste paper, especially waste paper pulp including coated paper, as a raw material for paper and paperboard, some measures are required to prevent deterioration of the surface properties and decrease in strength.

Methods for improving the strength of paper and paperboard include promoting the beating of raw pulp and using a paper-strength enhancer. However, these all lead to an increase in cost, and increasing the degree of beating of the pulp used has the disadvantage that the drainage of the pulp deteriorates and the operability of the papermaking machine is adversely affected.

[0004] In general, coated paper as a product is coated on its surface with a paint using a pigment having high whiteness in order to make the appearance more beautiful. The paint used for the pigment coating is composed of a pigment such as clay and calcium carbonate and a binder such as latex, starch and polyvinyl alcohol. Coated paper is stored and transported after winding or sheeting after paper making, coating, and in that case, in the case of white paperboard etc. which is single-side coated paper, the coated surface of the surface layer and the uncoated surface of the back layer There is a time during which the contact is made under load, and when this is peeled off, a part of the surface of the back layer may be transferred to the surface coated surface. This phenomenon is referred to as "back fluff", and foreign substances adhering to the surface during printing accumulate on the blanket of the printing press, causing a trouble that printing is impaired.

It is said that the frequency of occurrence of back fluff varies depending on the type and lot of raw paper used for the back layer. The more the foreign matter is on the surface of the back layer and the lower the surface strength, the more easily it occurs.
As a method of solving the back fluff, there is a method of reducing the adhesiveness of the coating layer by changing the physical properties of the binder of the coating applied to the surface layer or adding an additive, or coating starch or polyvinyl alcohol on the surface of the back layer. There is known a method of improving the surface strength of the back layer by performing the processing, and preventing the transfer of foreign matter to the coated surface. However, these methods are not desirable in that they lead to an increase in cost and an increase in the number of manufacturing steps similarly to the above. The back fluff is essentially due to the lower quality of the backing layer raw material, such as an increase in ash content and a decrease in strength in the used paper, and it is necessary to take fundamental measures on the used raw paper itself.

[0006] It has been known that pulp containing waste paper is washed and beaten. For example, JP-A-5-311
No. 589 discloses that pulp containing waste paper is washed with water to remove ash and fine fibers, and the Canadian standard freeness is increased, and then beaten to lower the Canadian standard freeness to make paper. It has been proposed. However, when waste paper including coated paper is used as a raw material, ash such as pigment derived from the coated layer is not fragmented by ordinary disintegration, but is present in the pulp as aggregates. Therefore, it is difficult to say that such flocculated ash is sufficiently removed simply by washing, and it is difficult for the pulp to be broken into pieces at a normal pulp concentration even in the subsequent beating treatment. Therefore, most of such agglomerated ash remains in the pulp even after the treatment, and together with the fine fibers generated by beating, causes a reduction in the surface properties and strength of the paper. Therefore, a more effective ash removal method is needed to solve the above-mentioned problem such as back fluffing, and further improvement has been desired.

[0007]

SUMMARY OF THE INVENTION The present invention is directed to a method for removing coagulated ash present in waste paper pulp containing coated paper by a method which does not damage the pulp as much as possible without using a method such as adding or applying a chemical. By selectively slicing and effectively removing, the paper using waste paper pulp containing coated paper, the surface properties and strength of paperboard are improved, and the above-mentioned problems such as back fluffing are solved. Is what you do.

[0008]

The present invention employs the following configuration to solve the above-mentioned problems. That is, the present invention
"A method for treating waste paper pulp for a paperboard back layer, characterized in that waste paper pulp obtained by disintegrating waste paper including coated paper is kneaded and classified. Further, the present invention relates to a method for treating a waste paper pulp for a paperboard back layer, which comprises kneading and classifying waste paper pulp obtained by disintegrating waste paper including coated paper, classifying, and further beating. is there.

The coated paper referred to in the present invention is a coated paper such as a general printing coated paper having a pigment coating layer on both sides or one side of the paper, and a white paperboard used for article packaging and the like. So-called clear coat coated paper coated with a paint that does not use a pigment is not included. The ratio of the coated paper in the raw material wastepaper is not particularly limited, but in the present invention, it is more effective when the above-mentioned coated paper is contained at least 10% by weight or more in the raw material wastepaper. As used paper other than coated paper in the present invention, used paper such as printing paper, newsprint, magazines, and OA used paper can be used.

[0010] The paperboard produced using the treated paper pulp by the present invention is a basis weight 100 g / m ² or more multilayer paper making paperboard. The multilayer paperboard is composed of at least a surface layer, a middle layer and a back layer, and usually has a 5 to 9 layer structure. When the present invention is applied to a multi-layered paperboard, it is applied to a back layer mainly made of used magazine paper containing a large amount of coated pulp and a large amount of coated paper among the front, middle and back layers. . If the waste paper pulp treated according to the present invention is used for the back layer, the strength and the surface properties of the paper are greatly improved, and in the case of white paperboard frequently used for packaging articles, the problem of the back fluff is considered. It is the source of generation, and it is most suitable to be applied to the back layer that becomes the outermost layer as well as the coating layer on the surface when it is processed into a box or the like and is easy to see.

When the waste paper pulp treated in accordance with the present invention (hereinafter referred to as the waste paper pulp) is used for paperboard, it is preferable that the backing layer contains the pulp in an amount of 50 to 100% by weight. In the paperboard, there is no particular limitation on the content of the wastepaper pulp in the other layers, that is, the surface layer, the lower surface layer, and the middle layer. In addition, the used paper pulp other than the used paper pulp may include deinked used paper pulp or non-deinked used paper pulp.

In the kneading treatment in the present invention, the waste paper pulp containing the above-mentioned coated paper, which has been disintegrated with a pulper, is dewatered and concentrated, and then is beaten by a known PFI mill or the like, or a disperser.
This is performed using a kneading device such as a mica processor or a kneader. The pulp concentration at the time of kneading is preferably as high as possible, as far as the performance of the concentrating device or the kneading device allows,
The pulp concentration must be 20% by weight in order to sufficiently promote the fragmentation of the cohesive ash such as the internal filler and the coating layer pigment by kneading.
The above is preferable, and about 25 to 35% is more preferable. Also,
During kneading, the Canadian standard freeness of waste paper pulp (hereinafter CS)
(Abbreviated as F) should be kept as low as possible. When the CSF of the waste paper pulp decreases, not only the operability in the next classification process deteriorates, but also the beating margin in the subsequent beating treatment decreases, which is not preferable.

The classification treatment in the present invention means that the used paper pulp after the kneading treatment is diluted with a large amount of water and washed by a known method. The conditions for the classification treatment are not particularly limited, but it is preferable to use a large amount of water, and it is preferably 65 times or more (pulp concentration of 1.5% by weight or less) with respect to waste paper pulp (air-dried). Further, the classification treatment may be carried out by using a washing step usually performed in a paper or pulp mill. After diluting with a large amount of water, dehydration and concentration are performed using a known SP filter, washer, thickener, extractor, filter press, or the like. In this classification process, it is preferable to wash the pulp until the CSF of the pulp rises by 100 to 250 ml as compared with that before the classification process. It is not preferable because the removal efficiency is small. When the CSF rise is 250 ml or more, the pulp yield tends to decrease.

In the present invention, the pulp after the classification may be further beaten if necessary. In the beating in the present invention, the waste paper pulp after the above classification treatment is beaten using a known beating machine such as various refiners and PFI mills,
This is a process for reducing F by 100 to 250 ml. CSF decline
If it is less than 100 ml, the improvement in strength due to beating is reduced, and 2
If it is more than 50 ml, the drainage of the pulp deteriorates, which is not desirable.

By the kneading treatment and the classification treatment according to the present invention, the waste paper pulp can remove a considerable amount of ash and fine fibers such as flaked fillers and pigments, thereby improving the inter-fiber bonding strength. Further, the beating treatment performed as needed improves the inter-fiber bonding force. The paperboard manufactured using the wastepaper pulp obtained according to the present invention for the back layer is a paperboard using only the conventional wastepaper pulp for the back layer, or the wastepaper prepared without any of the kneading treatment or the classification treatment. Compared with paperboard made by using pulp as the back layer, foreign matters on the back layer surface are reduced, the appearance is improved, and the strength is improved.

A surface layer having a pigment coating layer on the surface layer and using the waste paper pulp obtained according to the present invention as a back layer as the outermost layer,
In a white paperboard having a middle layer and a back layer, the occurrence of the back fluff can be suppressed. In this case, the reject pulp containing the fine fibers, fillers, and pigments obtained by classifying and removing the waste paper pulp used for the back layer is mixed with the middle layer for effective use.

[0017]

In the manufacturing method of the present invention, the surface property and strength of the paper are improved because the waste paper pulp including the coated paper is kneaded in advance, thereby generally inhibiting inter-fiber bonding and reducing the strength of the paper. Agglomeration ash such as pigments derived from the coating layer of the coated paper, which has an effect on the pulp, is sufficiently fragmented and dispersed, and is efficiently removed in the classification process. This is because a wastepaper pulp having a high bonding strength can be obtained. Further, the subsequent beating treatment further improves the inter-fiber bonding strength. If beaten without kneading and classifying treatments, there are disadvantages such as an increase in fine fibers and a decrease in drainage.

[0018]

EXAMPLES The present invention will be described in more detail with reference to examples and comparative examples, but the contents of the present invention are not limited to the examples. In addition, all the pulp concentration% in a present Example and a comparative example means weight%.

<Example 1> Waste paper mixed with a newspaper / magazine ratio of 67/33 was disintegrated with a pulper (CS).
F227ml) and dewatered and concentrated to a pulp concentration of 30%. Subsequently, the mixture was kneaded with a PFI mill at a clearance of 0.2 mm and a rotation of 500 to obtain a waste paper pulp having a CSF of 250 ml. This was diluted to a pulp concentration of 1.5%, disintegrated, 500 g of pulp (air-dried) was diluted in 50 liters of clear water (dilution ratio: 100 times, pulp concentration: 1%), and thoroughly stirred. Classification was performed by concentrating to a concentration of 10%. The obtained pulp had a CSF of 416 ml. Next, the pulp was diluted to a pulp concentration of 4% and beaten to a CSF of 198 ml with a refiner to obtain waste paper pulp. This is referred to as Example 1.

<Second Embodiment> In the first embodiment, the PF
Example 2 is the one processed in the same manner as in Example 1 except that the number of revolutions of the I-mill is set to 600 and the final beating process is not performed.

<Comparative Examples 1 to 3> Conventional waste paper pulp before the kneading and classification treatment of the present invention was used as Comparative Example 1. Waste paper pulp treated in the same manner as in the example except that the kneading treatment was not performed before the classification treatment (Comparative Example 2), waste paper beaten to a CSF equivalent to that of the example without classification after the kneading treatment Pulp (Comparative Example 3) was obtained. Table 1 summarizes the above processing conditions. Examples 1 and 2 and Comparative Examples 1 and 2
Table 2 shows the results obtained by converting the waste paper pulp of No. 3 into a sheet and comparing the quality such as the number of occurrences of back fluff and the strength.

[0022]

[Table 1]

[0023]

[Table 2]

<Test Methods> Various measurements were performed by the following measurement methods. Basis weight Density according to JIS P8124 Density according to JIS P8118 Z-axis strength according to JIS P8113 Complies with TAPPI UM403 Ash content Complies with JIS P8128 (However, the ashing temperature is 500 ° C)

<Method for evaluating back fluff> Both the test sample and the white paperboard are humidified in a constant temperature and humidity chamber (60 ° C., 85%), and the coated surface of the test sample and the white paperboard are overlapped and hot-pressed (surface pressure).
30 kgf / cm ² , 80 ° C., 20 minutes). After the test sample is peeled off from the coated surface after adjusting the humidity at 20 ° C and 65% for 4 hours or more with the test sample and the coated surface still adhered, the color analyzer attached to the coated surface is measured with an image analyzer. Yes (6 × 6
mm, 15 fields of view).

According to the results shown in Table 2, the waste paper pulp of the present invention (Example 1) has a higher density, a breaking length of 75% and an interlayer strength of 52 compared with the conventional waste paper pulp (Comparative Example 1). % Improvement. Further, the ash content, which is the main cause of the back fluff, was significantly reduced, and the number of back flesh generated was reduced by 98%. In Example 2, since the final beating process was not performed, the breaking length was slightly low, but the back fluff was improved as compared with the comparative example. In Comparative Examples 2 and 3 in which the kneading treatment or the classification treatment was omitted, the number of back fluffs generated and the strength were improved as compared with the untreated Comparative Example 1, but the effects were small as compared with the Examples, and the present invention It is clear that this method is superior.

[0027]

According to the method for producing paper and paperboard of the present invention, even when waste paper pulp containing coated paper having a high ash content and low strength is used as a raw material pulp, the pigment derived from the coating layer and the internal The ash content such as filler can be efficiently removed and its content can be reduced, so that the strength and surface properties of the paper can be easily determined during the operation of the paper mill without depending on the method of chemical addition or application. Can be improved. Therefore, it is possible to prevent problems such as back fluff, etc., which are a concern when considering the recycling of coated paper, which is expected to continue to increase as a raw material for waste paper. Contribute greatly.

Claims (2)

[Claims] 1. A method for treating waste paper pulp for a paperboard back layer, wherein waste paper pulp obtained by disintegrating waste paper including coated paper is kneaded and classified. 2. A method for treating waste paper pulp for a paperboard back layer, comprising: kneading, classifying, and beating beaten waste paper pulp obtained by disintegrating waste paper including coated paper.