JP2000282398A - Paperboard - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a bulky paperboard excellent in surface smoothness and having high whiteness and opacity. SOLUTION: In this paperboard having a multilayer structure having two or more layers, an ester compound having <=100 deg.C melting point and selected from an ester compound (A) of a polyhydric alcohol with a fatty acid and an ester compound (B) composed of a polyhydric alcohol with a fatty acid and having 2-4C oxyalkylene group in an amount of average <0 and >12 mol based on 1 mol of the ester compound are contained in at least one layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to paperboard.

[0002]

2. Description of the Related Art Recently, a large amount of used paper has come to be used in newspapers and magazines which are used as raw materials of used paper pulp due to an improvement in a used paper recycling rate. As a result, wood pulp is recycled and used many times, and every time it is recycled, the fibers themselves become keratinized by chemicals added in the used paper processing process, heat in the papermaking process, or oxidation by air. In addition, a negative effect such as a decrease in flexibility and a decrease in bulk due to advancement of hydrophilicity has been realized. It is thought that this problem can be solved to some extent by increasing the amount of virgin pulp used, but this is not desirable from the viewpoint of protection of forest resources. In addition, there has been an increasing movement to directly reduce the use of virgin pulp in order to protect forest resources and, consequently, the global environment.

[0003] In the production of paperboard, it is important to secure the bulk of the paperboard and to reduce the amount of virgin pulp used, but no paperboard satisfying these has been found. For example, a method of including bacterial cellulose in the outermost layer of paperboard to improve surface strength and rigidity (Japanese Patent Application Laid-Open No. 9-137400)
However, the commercial production method of bacterial cellulose has not been established and is expensive. In addition, as the use of waste,
Method for incorporating crushed rice hulls into paperboard (JP-A-5-93395)
However, in the case of white paperboard, for example, there are unsolved problems such as a decrease in smoothness and a decrease in printability, and in both cases, the production of paperboard, which secures the bulk of the paperboard and reduces the amount of virgin pulp used. Was not satisfactory. In the case of white paperboard, there has been an attempt to enhance the deinking process of the deinked waste paper pulp of the middle white layer to increase the whiteness and reduce the amount of white layer, but the adverse effect associated with the increase in whiteness However, there are many unsolved problems such as a decrease in opacity, a decrease in bulk due to excessive hydrophilicity of the fiber, an increase in deinking cost, and an increase in wastewater treatment cost.

[0004]

SUMMARY OF THE INVENTION The present invention provides a paperboard which improves the bulk, whiteness and opacity of each layer constituting the paperboard. Another object of the present invention is to provide a paperboard that saves expensive bleached virgin pulp, reduces production costs, and smoothly promotes waste paper recycling.

[0005]

SUMMARY OF THE INVENTION The present invention provides a paperboard having a multilayer structure of two or more layers, wherein the paperboard contains at least one of the following ester compounds. <Ester compound> An ester compound of a polyhydric alcohol and a fatty acid (A) and an ester compound of a polyhydric alcohol and a fatty acid, wherein the oxyalkylene having 2 to 4 carbon atoms having an average of more than 0 mol and less than 12 mol per mol of the ester compound Ester compounds having a melting point of 100 ° C. or less selected from ester compounds (B) having an OA group

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The ester compound of the present invention is (A) an ester compound of a polyhydric alcohol and a fatty acid (an ester compound containing no OA group) having a melting point of 100 ° C. or lower [hereinafter referred to as an ester compound ( (B) an ester compound of a polyhydric alcohol and a fatty acid, the average being more than 0 mol per 1 mol of the ester compound.
It has less than moles of OA groups having 2 to 4 carbon atoms and a melting point of 100 ° C. or lower [hereinafter referred to as ester compound (B)]. These may be used in combination, or two or more of each may be used.

The polyhydric alcohol constituting the ester compound of the present invention has a total carbon number of 2 which may contain an ether group.
-24 to 2-14 alcohols are preferred. As the dihydric alcohol, the total number of carbon atoms which may contain an ether group is 2 to 2.
10 alcohols such as propylene glycol, dipropylene glycol, butylene glycol, dibutylene glycol, ethylene glycol, diethylene glycol, and polyethylene glycol may have an ether group as the trivalent or higher alcohol, and may have an ether group of 3 to 3 carbon atoms. With 24 alcohols, total number of hydroxyl groups / total carbon number in one molecule = 0.4 to
1, for example, glycerin, poly (n = 2 to 5)
Glycerin, pentaerythritol, dipentaerythritol, arabitol, sorbitol, stachyose,
Erythritol, arabbit, mannitol, glucose,
Sucrose and the like. From the viewpoint of a large bulking effect and availability, it is preferable to use ethylene glycol, diethylene glycol, propylene glycol or an alcohol having a total carbon number of 3 to 12 which may have an ether group.
The number of hydroxyl groups in the molecule / total carbon number = 0.5 to 1; a tri- to dihydric alcohol, more preferably an alcohol having a total of 3 to 12 carbon atoms which may have an ether group, Trihydric to hexahydric alcohols having a total carbon number of 0.5 to 1, particularly preferably glycerin, poly (n = 2 to 4) glycerin and pentaerythritol.

The fatty acids constituting the ester compound of the present invention include fatty acids having 1 to 24 carbon atoms, preferably 10 to 22 carbon atoms, particularly preferably 16 to 22 carbon atoms.
Any of unsaturated, straight chain and branched chain may be used. From the viewpoint that the bulking effect is large and does not affect the size, linear saturated fatty acids are particularly preferable. Preferred fatty acids are lauric acid,
Myristic acid, palmitic acid, stearic acid, oleic acid, arachidic acid and behenic acid, and particularly preferred fatty acids are palmitic acid, stearic acid, arachidic acid and behenic acid.

The ester compound of the present invention can be obtained by performing a conventionally known esterification reaction and alkylene oxide addition reaction. For example, ester compound (A)
Can be obtained by reacting a fatty acid and a polyhydric alcohol at 150 to 250 ° C. in the presence of an esterification catalyst if necessary. The ester compound (B) is an ester compound
It can be obtained by adding an alkylene oxide to (A) in the presence of an alkali catalyst or the like. The ester compound (B) can also be obtained by adding an alkylene oxide to a fatty acid or a polyhydric alcohol and then esterifying it.

The average degree of ester substitution of the ester compound of the present invention refers to the ratio of the hydroxyl group of the polyhydric alcohol being esterified, and is larger than 0, preferably 10 to 95 equivalent%, more preferably 20 to 60 equivalent%. . Those having from 1 to 2 mol of fatty acid groups per mol of polyhydric alcohol are particularly preferred.

In the present invention, when an ester compound (B) containing an OA group having 2 to 4 carbon atoms is used, the number thereof is, on average, more than 0 mol and less than 12 mol, and 0.1 to 6 mol, per mol of the ester compound. Is more preferred. When polyhydric alcohols that can be OA groups, such as ethylene glycol, are used, they are also included in the number of OA groups. OA
The group is formed by adding an alkylene oxide having 2 to 4 carbon atoms (hereinafter referred to as AO) to the ester compound.
Examples of AO include ethylene oxide (hereinafter referred to as EO), propylene oxide (hereinafter referred to as PO), and butylene oxide, and EO and PO are preferred. These are EO, PO
Alternatively, any of a mixture of EO and PO may be used. In the present invention, it is particularly preferable to use an ester compound (A) containing no OA group, from the viewpoint that the bulking effect is large and the size is not affected.

The HLB of the ester compound of the present invention is preferably 1 to 14, more preferably 1.5 to 10, and particularly preferably 2 to 10.
-8, most preferably 2-7. HLB is a measure of the hydrophilicity of a surfactant; the higher the value, the higher the hydrophilicity. In the present invention, each compound is prepared according to the method of Griffin.
HLB is calculated by the following formula.

[0013]

(Equation 1)

However, the hydrophilic group in the present invention means the following group in the ester compound. (1)-(EO)-

[0015]

Embedded image

(3) An alcohol having a total of 3 to 24 carbon atoms which may have an ether group and having 3 to 24 carbon atoms, wherein the total number of hydroxyl groups / total carbon number in one molecule is 0.4 to 1; The residue excluding the acyl group of the ester compound with the fatty acid and the portion of n> 2 in the above (2). (4) An oxygen atom adjacent to the carbonyl group.

Further, the ester compound of the present invention has a melting point of 100 ° C. or less, preferably -15 to 80 ° C., more preferably 20 to 70 ° C., from the viewpoint of handling properties and maintaining size performance.
Particularly preferably, it is 10 to 70 ° C, most preferably 45 to 70 ° C. The melting point is measured by using a differential scanning calorimeter (DSC) to measure an ester compound which has been cooled and solidified in advance (heating rate 2 ° C. /
Min) is the temperature at which the peak rises.

The ester compound of the present invention preferably has an HLB of 2 to 8 and a melting point of 10 to 70 ° C, more preferably an HLB of 2 to 7 and a melting point of 45 to 70 ° C. In this range, favorable results can be obtained due to the bulking effect and the size effect (maintaining the effect of the sizing agent).

Examples of the paperboard of the present invention include paperboard referred to in the classification of paper in "Paper and Pulp Statistical Yearly Report" (Ministry of International Trade and Industry, January 1988), and specifically, paperboard for paperboard, corrugated base paper, Construction material base paper, paper tube base paper, wamp and the like. Specific examples of paperboards for paper containers include white paperboard (manila balls, white balls), yellow paperboard, chip balls, and colored paperboard. Specific examples of the corrugated cardboard include a liner (for exterior and interior) and a middle shin paper (pulp and paper). As the pulp constituting the paperboard of the present invention, any pulp made from wood or herbaceous fiber as a vegetable fiber can be used. That is, chemical pulp (bleached pulp such as NBKP and LBKP, unbleached pulp such as NUKP and LUKP, semi-bleached pulp subjected to weak bleaching, etc.) and mechanical pulp (MP, GP, RGP, etc. and bleached thereof) Pulp), high yield pulp (TMP
, CTMP, CGP, etc. and bleached pulp), and recovered pulp such as waste paper pulp, deinked waste paper pulp (DIP), and bleached pulp (BDIP).

The ester compound of the present invention is preferably used in an amount of 0.01 to 10% by weight, more preferably 0.1 to 10% by weight, based on the absolute dry weight of pulp of at least one layer of paperboard having a multilayer structure of two or more layers.
-5% by weight, more preferably 0.1-3% by weight, particularly preferably 0.1-1% by weight. The "weight%" of the added amount is a percentage with respect to the pulp weight of each layer at the time of papermaking, and does not indicate the ratio in the final paperboard. Bulk of paper,
This addition amount range is preferable from the viewpoint that a favorable effect of improving whiteness and opacity can be obtained and that the strength of the paper can also maintain a required value.

The content of the ester compound in the paperboard is preferably 0.001 to 10% by weight in the paperboard in a completely dry state.
More preferably 0.001 to 5% by weight, even more preferably 0.001% by weight.
It is from 1 to 3% by weight, particularly preferably from 0.001 to 1% by weight. The content of the ester compound in the paperboard is preferably 0.001% by weight or more from the viewpoint that the proportion of the layer having the smallest weight among the layers forming the multilayer structure is about 10% by weight.

The paperboard of the present invention has a multilayer structure of two or more layers. Paperboard having a multilayer structure of three or more layers is more preferred. Further, the paperboard of the present invention is preferably formed by papermaking. The stock forming the multilayer structure of two or more layers may be the same or different. For example, a multi-layered paper using the same stock is also a paperboard of the present invention. Below, white layer,
The white paperboard having a four-layer structure of a middle white layer, a middle layer and a back layer will be specifically described as an example.

Generally, paperboard is manufactured by multilayer papermaking, so that each layer of the paperboard is independently formed and laminated. The weight of the stock in each layer is referred to as a “weight” and is expressed in g /
expressed in m ^2. In addition, the weight per unit area of the paperboard, which is the sum of the weights of the respective layers, is referred to as “basis weight” and is expressed in g / m ² . Each of the following layers is also composed of one or two or more layers according to the amount applied and the paperboard machine used.

The white layer is the surface layer of the paperboard, and is bleached virgin pulp (NBKP, LBKP) to impart whiteness, strength and printability.
Etc.). This pulp is the strongest and most expensive of the raw materials that make up white paperboard, but its properties ensure the whiteness of the surface of the white paperboard and provide a smooth finish. The suitability of processing is also improved. When the ester compound of the present invention is added to this white layer, the bulkiness increases and the whiteness and opacity improve. Therefore, the amount of bleached virgin pulp used can be reduced. The addition amount of the ester compound of the present invention in the white layer is 0.01% per pulp absolute dry weight from the viewpoint of maintaining surface strength and printability.
To 5% by weight, more preferably 0.1 to 3% by weight.

The middle white layer is a layer that economically hides the middle layer, and has a certain degree of whiteness and opacity such as deinked waste paper pulp (DIP), deinked bleached waste paper pulp (BDIP), and mechanical pulp (MP).
Use etc. It is the second most expensive raw material for the white layer. When the ester compound of the present invention is added to the middle white layer, the effect of increasing the bulk and improving the whiteness and opacity is most remarkable. That is, the increase in the whiteness and the opacity effectively hides the middle layer, and the increase in the bulk of the middle white layer enhances the smoothness and cushioning property of the white paperboard, thereby indirectly improving the printability. When the ester compound of the present invention is added to the middle white layer, the amount of the white layer using expensive bleached virgin pulp can be effectively reduced, but if it is too large, the flexural strength decreases. The addition amount of the ester compound of the present invention in the white layer is preferably 0.01 to 5% by weight, more preferably 0.01 to 3% by weight, based on the absolute dry weight of the pulp, since these favorable results can be obtained.

The middle layer is also referred to as an anchor layer. In order to economically secure a predetermined thickness and strength of "strain," unpulled waste paper pulp is used. When the ester compound of the present invention is added to the middle layer, the effect of increasing the bulk appears directly. In addition, it is a layer in which the influence of a decrease in strength is least likely to appear. The addition amount of the ester compound of the present invention in the middle layer is preferably from 0.01 to 10% by weight, more preferably from 0.1 to 5% by weight, based on the absolute dry weight of the pulp.

The back layer is on the back side of the paperboard, and in many cases, unpapered waste paper pulp is used. However, when the back layer is a paper container or the like, it is a part that can be seen by the consumer when the contents are taken out. Therefore, it is preferable to use uniform waste paper pulp sufficiently disintegrated. When the ester compound of the present invention is added to the back layer, an increase in bulk and an improvement in whiteness function to improve the appearance quality of the back side. The amount of the ester compound of the present invention added to the back layer is based on the absolute dry weight of the pulp.
It is preferably from 0.01 to 5% by weight, more preferably from 0.1 to 3% by weight.

The paperboard of the present invention contains the ester compound of the present invention in any one of two or more layers of the multilayer structure. The multilayer structure has a white layer, and the middle layer contains the ester compound. Is preferred.

In each of the layers, chemicals such as a paper strength improver, an internal sizing agent, an interlayer strength improver, a retention improver, a drainage improver and an external sizing agent which are usually used for paperboard papermaking are used. Can be used in combination.

[0030]

According to the present invention, bulkiness, whiteness and opacity can be improved by adding a specific ester compound of the present invention to paperboard. Further, the amount of bleached virgin pulp can be reduced, and a paperboard having good whiteness and smoothness can be obtained. Furthermore, even if the grammage is reduced, the thickness can be ensured, the adverse effects due to the recycling of waste paper can be eliminated, and costs can be reduced and forest resources can be saved.

[0031]

EXAMPLES Reference Examples Table 1 shows the amounts of various pulp used in each layer of white paperboard.
Add pentaerythritol monostearate (HLB = 3.1, melting point 66 ° C, indicated as an ester compound in Table 1), water and the following additives at 25 ° C.
A 1.0% by weight pulp slurry was prepared, mixed with a stirrer for 5 minutes, and then mixed with a TAPPI standard sheet machine at 60 g / m ^2.
Was hand-dried, air-dried, and treated at 105 ° C. for 1 minute with a rotary cylinder drier, and the density, whiteness, and opacity of the obtained sheet were measured.

(Type of Pulp Used and Freeness) BDIP: Newspaper 100%, Freeness 180mL, csf Wastepaper pulp: Newspaper 40% + magazine waste 60%, freeness 230m
L, csf, sufficiently disintegrated NBKP: Freeness 480 mL, csf LBKP: Freeness 360 mL, csf TMP: Freeness 120 mL, csf
10% SF (Asada Flour Milling Co.), 0.5% cationic starch CATO302 (Nippon NNC) as internal paper strengthening agent, 0.5% rosin sizing agent Size Pine N-773 (Arakawa Chemical) as sizing agent, aluminum sulfate 3.0%, and 100 ppm of a polyacrylamide-based retention aid Percoll 47 (Allied Colloid) were added.

(Test Method) The measurement of the freeness of pulp is based on JIS.
P 8121, humidity control and measurement conditions are 20 ° C, 65% RH (JIS P811
1) JIS P 8124 for measuring grammage, J for measuring thickness and density
IS P 8118 and whiteness were measured based on JIS P 8123, and opacity was measured based on JIS P 8138. Table 1 shows the results.

[0034]

[Table 1]

Example 1 Bleached virgin pulp (NBKP / LBKP weight ratio =
50/50), and pulp (3.0% by weight of pulp) containing 0.5% of pentaerythritol monostearate (expressed as an ester compound in Table 2) and 3.0% of aluminum sulfate per absolute dry weight of the pulp. Deinked bleached waste paper pulp (BDIP) is used for the white layer, and a paper material (pulp concentration: 3.0% by weight) is added to the dry weight of the pulp with 0.8% polyacrylamide-based paper strength agent. Paper material (pulp concentration: 3.0% by weight) was used as the backing layer. Separated and used waste paper pulp was used. The paper material (pulp concentration: 3.0% by weight) added with 1% aluminum sulfate per pulp dry weight was used. 10 pulp bone dry weight per
0ppm polyacrylamide-based retention aid (same as Reference Example) was added, and oxidized starch MS-3800 was used as an external sizing agent.
(Nippon Food Processing Co., Ltd.) Apply 1.5 g / m ² with a size press, and apply a short-mesh multi-cylinder multi-layer paper machine at a speed of 300 m / min so that the amount of each layer becomes the value shown in Table 2. White paperboard was made at 40 ° C. The basis weight, thickness, density and whiteness of the obtained white paperboard were measured in the same manner as described above, and the smoothness was measured based on JIS P8119. Table 2 shows the results.

Example 2 White paperboard was made under the same conditions as in Example 1 except that pentaerythritol monostearate was added to the middle white layer instead of the white layer, and the same test was conducted. Table 2 shows the results.

Example 3 A white plate was prepared under the same conditions as in Example 1 except that pentaerythritol monostearate was added not to the white layer but to the middle white layer at 0.5% and to the white layer at 2.0% (all based on the absolute dry weight of the pulp). Paper was made and the same test was performed. Table 2 shows the results.

Example 4 White paperboard was made under the same conditions as in Example 1 except that pentaerythritol monostearate was added to the middle layer instead of the white layer, but to the middle layer, and the same test was conducted. Was. Table 2 shows the results.

Comparative Example 1 White board was made under the same conditions as in Example 1 except that pentaerythritol monostearate was not added to the white layer, and the same test was conducted. Table 2 shows the results.

[0040]

[Table 2]

When Examples 1 and 2 and Comparative Example 1 are compared,
It can be seen that even when the amount of virgin pulp in the white layer is reduced by adding the ester compound and the amount of waste paper pulp in the middle layer is increased, the same whiteness can be obtained and the smoothness can be increased. Comparing Example 3 with Comparative Example 1, even when the basis weight is reduced, the addition of the ester compound increases the bulk, so that the same thickness as in Comparative Example 1 can be secured, and the smoothness and whiteness are further improved. We can see that we can do it. Comparing Example 4 with Comparative Example 1, it can be seen that the thickness equivalent to that of Comparative Example 1 can be ensured even when the basis weight is reduced because the addition of the ester compound only to the middle layer increases the bulk.

Examples 5 to 11 and Comparative Example 2 LBKP was used for the surface layer, a pulp (pulp concentration: 1.0% by weight) containing 3.0% of aluminum sulfate per absolute dry weight of the pulp was used, and BDIP was used for the middle layer. Paper material (pulp concentration: 1.0% by weight) to which various ester compounds shown in Table 3 (addition amounts are shown in Table 4) and 3% of aluminum sulfate based on the absolute dry weight of the pulp were used. , Aluminum sulfate 1.0
% Pulp (pulp concentration 1.0% by weight)
Add 100ppm polyacrylamide-based retention aid per pulp absolute dry weight (same as the reference example) to all paper stocks,
Hand-papermaking was performed under the same conditions as in the Reference Example to obtain a multilayer paper. Table 4 shows the results of measuring the density (bulk) of these papers. In addition, the same multilayer paper was made without adding the ester compound, and the same measurement was performed. The results are shown in Table 4.

[0043]

[Table 3]

[0044]

[Table 4]

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshiyuki Nishimori 1334 Minato, Wakayama-shi, Wakayama Prefecture Inside Kao Corporation Research Laboratory (72) Inventor ▲ Taka ▼ Hashitsu 1334 Minato, Wakayama-shi, Wakayama Prefecture Kao Corporation F Term (Reference) 4F100 AA07 AH02A AH02B AH02H AH02K AK26H BA02 BA03 BA07 BA10A BA10C BA11 CA30 CA30A DG10 DG10A DG10B DG10C JK15 JL16 JL16B JL16C JN02B JN30 4L055 AG10 FA18 EA30 FA10

Claims (4)

[Claims] 1. A paperboard having a multilayer structure of two or more layers, wherein at least one layer contains the following ester compound. <Ester compound> An ester compound of a polyhydric alcohol and a fatty acid (A) and an ester compound of a polyhydric alcohol and a fatty acid, wherein the oxyalkylene having 2 to 4 carbon atoms having an average of more than 0 mol and less than 12 mol per mol of the ester compound Ester compounds having a melting point of 100 ° C. or lower selected from ester compounds having a group (B) 2. The paperboard according to claim 1, wherein the multilayer structure has three or more layers. 3. The paperboard according to claim 2, wherein the multilayer structure has a white layer, wherein the white layer contains the ester compound. 4. The paperboard according to claim 1, wherein the multilayer structure is formed by papermaking.