JPH06158579A - Production of paper - Google Patents

Abstract

PURPOSE:To provide paper excellent in both stiffness and smoothness. CONSTITUTION:The paper can be obtained by mixing (A) coniferous pulp (N) 2.0-3.0 in water retention value with (B) hardwood pulp (L) 1.1-1.4 in water retention value at the weight ratio N/L of (5:95) to (20:80) followed by conducting papermaking process. Besides, when the paper produced above is smoothed using a pressurizing nip composed of a heated metallic roll and an elastic roll, especially excellent paper can be obtained. The paper thus obtained, which is low in density and excellent in both stiffness and smoothness, is also excellent in the workability in printers and printed letter quality.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing paper having low density and excellent rigidity and smoothness.

[0002]

2. Description of the Related Art Normally, the standard of paper is defined by basis weight, but the thickness is often more important as a characteristic of printing paper and information paper. In particular, due to the automation of printing machines and printers, sufficient rigidity may be required when it is required to improve workability when feeding paper to the machine and runnability of the paper inside the machine. First of all, it is required to supply the paper with the thickness suitable for the machine or device. In doing so, of course, it is expected that the printing or print-related quality characteristics of the original application, such as smoothness, will remain unchanged or even improved.

In order to meet the above requirements for the thickness of the paper, technical measures such as reducing the degree of beating and reducing the pressure applied by the press are first taken. However, there is a limit to the countermeasures because the occurrence, the decrease in smoothness, the decrease in the desired rigidity, etc. occur. Therefore, it is unavoidable that paper is manufactured with a basis weight exceeding the standard. Recently, however, the review is required from the viewpoint of protecting wood resources.

On the other hand, attempts have been made to improve the paper manufacturing method to actively manufacture low-density paper. They include a method disclosed in Japanese Patent Laid-Open No. 59-43199, in which paper is made to contain fibers crushed by being compressed when wet, as disclosed in Japanese Laid-Open Patent Publication No. 51-132822. A method of adding expandable microspheres to pulp,
JP-B-55-47385, JP-A-58-2400
No. 0, JP-A-58-197400, etc., there is a method of mixing and using lightly beaten pulp and beaten pulp.

[0005]

Various methods have been studied to produce papers having excellent rigidity and smoothness. As a result, the method of containing the fibers crushed by the compression treatment and the method of incorporating the expandable microspheres into the paper can obtain a paper having a low density but not a paper having sufficient rigidity and smoothness. It became clear that I could not. Further, a method of mixing and using a pulp that has been beaten gently and a pulp that has been beaten is also under the conditions disclosed in the above publications, etc., and the water retention of the pulp to be beaten is too low (Japanese Patent Publication No. 55-47385). Or, since it is too high (JP-A-58-24000 and JP-A-58-197400), even if a paper having a low density and excellent rigidity can be produced, it is not enough to obtain a paper having excellent smoothness. Was enough. That is, an object of the present invention is to provide a paper having excellent rigidity and smoothness.

[0006]

[Means for Solving the Problems] In order to solve the above problems, as a result of trying various methods, as a result, a method of mixing and using a pulp that has been softly beaten and a pulp that has been beaten has been significantly changed. Because it can be carried out without
It turned out to be advantageous. Therefore, we focused on improving the point that sufficient smoothness was not obtained, which is a drawback of the conventional method, and examined the effect of pulp type and beating state in detail.
The examination was conducted by paying attention to the flexibility of pulp fiber.

As a result of the above examination, the water retention is 2.0 to 3.
0 softwood pulp (N) and water retention 1.1-1.4 hardwood pulp (L), weight ratio (N / L) 5 / 95-2
It has been revealed that a paper excellent in rigidity and smoothness can be obtained when mixed so as to be 0/80. In addition, the average fiber length of the softwood pulp having a water retention of 2.0 to 3.0 is
It is particularly preferable that the thickness is 1.5 to 2.5 mm, and further smoothness is obtained by smoothing the paper after papermaking through a pressure nip composed of a heated metal roll and elastic roll. It was also made clear that it is possible to manufacture paper.

In the present invention, the water retention is taken as an index of fiber softness and beating degree. From the viewpoint of ease of measurement, freeness is preferable, but since freeness is also easily affected by the fiber morphology and chemical composition of pulp, as a method of defining the flexibility of the fiber, which is the central concept of the present invention, I thought it was inappropriate.

The water retention value is a value measured according to TAPPI standard method UM256, and after centrifugation under predetermined conditions,
The weight of water retained on the wet pulp (W) was expressed as a ratio (W / P) to the dry weight of pulp. However, in the present invention, as the centrifugation conditions, a temperature of 21 ± 3 ° C.
It was set to 3000 g (g = gravitational acceleration) for 15 minutes.

The water retention of the pulp is 2.0 to 3.0 for the softwood pulp having a low content in the base paper and 1.1 to 1.4 for the hardwood pulp. When the water retention of the softwood pulp is less than 2.0, good rigidity cannot be obtained because the reinforcing effect of the interfiber bond is insufficient, and when it exceeds 3.0, the shrinkage during drying is large. Therefore, the smoothness decreases. If the water retention of the hardwood pulp is less than 1.1, sufficient flexibility cannot be obtained due to lack of flexibility of the fiber, and the rigidity becomes low. If it exceeds 1.4,
The thickness is reduced (the density is increased), the rigidity is lowered and the smoothness is lowered, which is not preferable.

The average fiber length of the softwood pulp having a water retention of 2.0 to 3.0 is preferably in the range of 1.5 to 2.5 mm. The average fiber length is J. TAPPI paper pulp test method No. It is the value of the weight average fiber length measured according to 52. Usually, as the beating progresses, the average fiber length decreases, but when the average fiber length is shortened to less than 1.5 mm, the effect of reinforcing the network of hardwood fibers, which occupies a large number in the sheet, decreases, so the rigidity decreases. Not preferable. On the other hand, when the average fiber length is larger than 2.5 mm, the formation is deteriorated, and the smoothness is deteriorated, which is not preferable.

In the present invention, as means for controlling the water retention of pulp, equipment usually used for beating pulp,
That is, a beater, a conical refiner, a disc refiner or the like can be used. For softwood pulp, it is preferable to select a device or blade type capable of viscous beating.

Examples of the pulp used in the paper of the present invention include kraft pulp, sulfite pulp, chemithermo-mechanical pulp and the like. The mixing ratio (N / L) of the softwood pulp and the hardwood pulp is preferably in the range of 5/95 to 20/80. If it is less than 5/95, sufficient rigidity cannot be obtained,
If it exceeds 20/80, the shrinkage during drying becomes large, and good smoothness cannot be obtained.

For smoothing the paper after the papermaking, a machine calender installed at the end of the papermaking machine is usually used, and a super calender composed of a metal roll and an elastic roll, a gloss calender, a soft calender and the like are used. It can also be used on-machine or off-machine. However, it is particularly preferable to smooth the paper after papermaking through a pressure nip composed of a heated metal roll and an elastic roll.

The above metal roll has a thickness of 80 to 250.
A chilled roll heated to ℃, a steel roll, a metal roll having the surface of the roll plated with chromium, and the like are used. Also,
As an elastic roll, Shore D hardness (ASTM D-2
A roll composed of urethane rubber, 240) having a degree of 50 to 98 degrees, an aromatic polyamide resin, a mixture of wool and synthetic fibers, or the like is used.

The paper of the present invention is usually used in papermaking,
A dye, a filler, a sizing agent, a fixing agent, a dry paper strengthening agent and the like are contained as necessary. Furthermore, it is also possible to apply starch, polyvinyl alcohol, or the like to the paper surface by a size press or the like. It is also possible to provide a coating layer on the surface depending on the application. As a coating device at that time, an air knife coater, a gravure coater, a curtain coater, a die coater, a blade coater, or the like is used.

The paper of low density, excellent in rigidity and smoothness according to the present invention can be used as a printing paper, an electrophotographic transfer paper, a thermal transfer image receiving paper or the like which is used in an uncoated state, or a printing coating. It is used as a base paper for engineering paper, thermal recording paper, inkjet recording paper, magnetic recording paper, photographic printing paper, and the like.

[0018]

The softening pulp (N) having a water retention of 2.0 to 3.0 and the hardwood pulp (L) having a water retention of 1.1 to 1.4 according to the present invention have a weight ratio (N / L) of By the manufacturing method of mixing and making paper so as to be 5/95 to 20/80, paper having low density and excellent rigidity and smoothness can be obtained.

[0019]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Examples. The present invention is not limited to the examples. All parts and% in the following are by weight. Further, the value indicating the coating amount is the weight after drying unless otherwise specified.

Example 1 A double disc refiner having a water retention of 2.0 and 2.6.
And the softening rate of softwood kraft pulp (NBKP) beaten at three levels of 3.0 and 3.0, the weight ratio (N /
L) was mixed so as to be 10/90 to prepare pulps of three kinds of blends.

Next, to 100 parts of each pulp, 7 parts of light calcium carbonate (TP121, manufactured by Okutama Kogyo Co., Ltd.) and 0.07 of alkyl ketene dimer size agent (Harcon 11-2, manufactured by Dick Hercules Co., Ltd.) were used.
Part, amphoteric starch (Kate 3210, manufactured by Oji National Co., Ltd.) was added to 0.7 parts, and a fine paper having a basis weight of 64 g / m ² was produced with a Fourdrinier paper machine. The high-quality paper after drying with a multi-cylinder dryer was size-pressed with a 3% aqueous solution of oxidized starch, dried, and then machine calendered under the conditions of 40 kg / cm and 4 nip. These samples
Samples 1-2 and 1 in order of decreasing NBKP water retention
-3 and 1-4.

Comparative Example 1 Fine paper was obtained in the same manner as in Example 1 except that the water retention of NBKP was changed to two levels of 1.9 and 3.1. These samples are respectively sample 1-1
And 1-5. The results of the measured rigidity and smoothness of the above samples are summarized in Table 1.

N / L in Tables 1 to 6 is the weight ratio of the softwood pulp to the hardwood pulp, and the fiber length is the value of the weight average fiber length of the softwood pulp. The density means the sheet density after calendering. Stiffness is JIS P 814
Clarke stiffness measured according to ³ (cm 3/10
0), to obtain a good running property in electrophotographic copying machine or a printer, if the basis weight of 64 g / m ² paper, in the longitudinal direction 55.0 cm ^3/100 or more, more preferably 60
cm ^3/100 or higher is required. The smoothness is a smoothness measured by a Parker Print Surf (manufactured by Lorentzen) under the conditions of measuring pressure of 10 kg / cm ² and using a hard material as a pressure plate in accordance with British Standard Method 6563, and the value (μ
The smaller m) is smoother. To obtain good printing and printability, it is 5.5 μm or less, more preferably 5.0 μm.
It is required to be m or less.

[0024]

[Table 1]

From the results shown in Table 1, it is clear that a fine paper having good smoothness and rigidity can be obtained when the water retention of the softwood pulp is 2.0 to 3.0. Water retention is 2.
When it is less than 0 or more than 3.0, it is not possible to obtain a high-quality paper having excellent rigidity and smoothness.

Example 2 In Example 1, the water retention of NBKP was set to 2.6 and LBKP was used.
A high-quality paper was manufactured in the same manner except that the water retention was changed to two levels of 1.1 and 1.4. These samples are sample 2-2 and 2-in order of decreasing water retention.
Set to 3.

Comparative Example 2 In Example 2, the water retention of LBKP was 1.0 and 1.
Fine paper was obtained by the same method except that the level was changed to 2 of 5. These samples are referred to as samples 2-1 and 2-4. The above results are summarized in Table 2.

[0028]

[Table 2]

From Table 2, the water retention of the hardwood pulp is 1.1.
It can be seen that a paper having excellent rigidity and smoothness can be obtained in the case of ~ 1.4. On the other hand, when it is less than 1.1, the flexibility of the fiber is insufficient and sufficient strength cannot be obtained, so that the rigidity becomes low, and when it exceeds 1.4, the density becomes high and the rigidity decreases. At the same time, it is recognized that the smoothness decreases.

Example 3 In Example 1, NBKP having a water retention of 2.6 and water retention of 1.
Fine paper was obtained by the same method except that the weight ratio (N / L) was changed to 2 levels of 5/95 and 20/80 for 2 LBKPs. These samples are referred to as Samples 3-2 and 3-3 in order of decreasing weight ratio.

Comparative Example 3 In Example 3, the weight ratio of NBKP and LBKP (N /
Fine paper was obtained in the same manner except that L) was changed to 2 levels of 3/97 and 30/70. These samples are referred to as samples 3-1 and 3-4. The above results are summarized in Table 3.

[0032]

[Table 3]

From the results shown in Table 3, the weight ratio (N / L) of the softwood pulp and the hardwood pulp is in the range of 5/95 to 20/80, which is necessary for obtaining paper having excellent rigidity and smoothness. That is, if it is less than 5/95, sufficient rigidity cannot be obtained.
If it exceeds 80, the shrinkage at the time of drying becomes large, and it is apparent that good smoothness cannot be obtained.

Example 4 In Example 1, the water retention of NBKP was set to 2.6, and LBKP was used.
The water retention of 1.2 and the beating conditions of NBKP were changed to obtain weight average fiber lengths of 1.0, 1.5, 2.
Fine paper was manufactured in the same manner except that the levels were changed to 5 and 2.8 mm. In addition, these NB
The freeness of KP is 30, 45, 80, and 10 respectively.
0 ml c. s. f. And greatly differed depending on the fiber length. These samples are referred to as Samples 4-1, 4-2, 4-3 and 4-4 in order from the one having the smallest NBKP fiber length. The above results are summarized in Table 4.

[0035]

[Table 4]

From Table 4, the average fiber length of the softwood pulp is
When the thickness is in the range of 1.5 to 2.5 mm, paper having excellent rigidity and smoothness can be obtained, and the average fiber length is 1.5 mm.
It is clear that when the length is less than 100 mm, the rigidity decreases, and when the average fiber length exceeds 2.5 mm, the smoothness decreases.

Example 5 In Example 1, except that the machine calender was replaced with a soft calender (temperature 150 ° C., linear pressure 100 kg / cm, 2 nip) composed of a heated metal roll and elastic roll. Fine paper was manufactured using the same method. These samples are referred to as Samples 5-2, 5-3, and 5-4 in order of decreasing water retention of NBKP.

Comparative Example 4 In Example 5, the water retention of NBKP was 1.9 and 3.
Fine papers were obtained in the same manner except that the levels were changed to 1 and 2 levels. These samples are referred to as samples 5-1 and 5-5, respectively. The above results are summarized in Table 5.

[0039]

[Table 5]

Comparing Table 5 with Table 1 shows that paper made from softwood pulp having a water retention of 2.0 to 3.0 is subjected to a soft calendering treatment, resulting in much higher rigidity than machine calendering treatment. It is clear that a paper with excellent smoothness can be obtained.

COMPARATIVE EXAMPLE 5 A pulp composition was prepared according to the composition described in JP-B-55-47385 (65 parts of LBKP beaten to 550 ml with a double disc refiner and 400 with a deluxe finer).
20 parts of NBKP beaten up to ml, 15 parts of broke paper), the composition described in JP-A-58-24000 (freeness of 48).
0 ml of NBKP / LBKP = 1/9 mixed pulp 90
Parts, 10 parts of fine fibers that have been beaten with a water retention of 8.1) or a normal high-quality paper blend (freeze with a disc refiner of 35
A high-quality paper was produced in the same manner as in Example 1 except that three levels of LBKP beaten to 0 ml and NBKP beaten to 450 ml were used. These samples
Samples 6-1 and 6-2 are different depending on the pulp composition.
And 6-3. The above results are shown in Table 6. However,
In Table 6, N water retention represents the water retention of heavy beating pulp, and L water retention represents the water retention of light beating pulp.

[0042]

[Table 6]

By comparing Table 6 with Table 1 or Table 5, it can be seen that in Table 6 the water retention of the heavily beaten pulp is different from the water retention of the present invention and that the paper according to the method of the present invention is known. It can be seen that the paper is superior in both rigidity and smoothness to the paper prepared by the method described above and ordinary high-quality paper. That is, it is clear that the method of the present invention is superior to the conventional methods in order to produce a paper having good rigidity and smoothness.

[0044]

From the above, the method for producing paper of the present invention, that is, softwood pulp having a water retention of 2.0 to 3.0 and water retention of 1.
1-1.4 hardwood pulp is mixed so that the weight ratio (N / L) of the softwood pulp and the hardwood pulp is 5/95 to 20/80, and the paper produced by papermaking has excellent rigidity. In addition to having good smoothness and smoothness, the runnability in electrophotographic copying machines and printability in light printing machines were also good.

Claims (3)

[Claims] 1. A softwood pulp (N) having a water retention of 2.0 to 3.0 and a hardwood pulp (L) having a water retention of 1.1 to 1.4.
Is mixed so that the weight ratio (N / L) is from 5/95 to 20/80, and papermaking is performed. 2. The method for producing paper according to claim 1, wherein the softwood pulp having a water retention of 2.0 to 3.0 has an average fiber length of 1.5 to 2.5 mm. 3. The method for producing paper according to claim 1, wherein the paper after papermaking is smoothed through a pressure nip composed of a heated metal roll and an elastic roll.