JPH0525799A - Production of translucent paper - Google Patents

Abstract

PURPOSE:To obtain the title paper having uniform transparency and free from the difference between inside and outside in good productivity by subjecting pulp to super calendering treatment under high temperature and moisture conditions using an elastic roll containing specific amount of blended aramide fiber and satisfying specific conditions in surface roughness. CONSTITUTION:A highly beaten pulp is made into paper using an elastic roll composed of 30-50wt.% aramid fiber and cotton and wool, etc., and satisfying conditions expressed by the formula [Rmax is surface roughness (mum) of the elastic roll after running in; D is shore D surface roughness of the elastic roll; T is surface temperature ( deg.C) (temperature range: 150-350 deg.C) of a metal roll in operation] and then subjected to super calendering treatment at 150-350 deg.C and 150-300kg/m line pressure to provide the objective paper.

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 a translucent paper, and more particularly to a method for producing a high quality translucent paper which has good productivity in surface finishing with a super calender and has no front-back surface difference.

[0002]

2. Description of the Related Art Conventionally, translucent paper such as glassine paper is made of a highly beaten chemical pulp, which is made up of a metal roll and an elastic roll under a condition of high temperature and high pressure after being given appropriate water content. It is generally manufactured by passing it through a super calendar device.

As a super calendering device used in the production of glassine paper, which is a semi-transparent paper, is generally one in which metal rolls and elastic rolls are arranged in multiple stages. The pressure condition is 200 to 300 kg / cm 2. The range and temperature conditions are generally in the range of 150 to 300 ° C. Therefore, if a heat-softening roll is used for the elastic roll that constitutes the super calendering device for producing translucent paper, it will be easily deformed under such harsh conditions, resulting in high quality translucent paper. Can't get

For example, mainly natural fibers such as cotton, fill mat cotton, white cotton, woolen paper, which are used by being incorporated in a super calender device which has been conventionally used in the production of coated paper for printing, etc. Since the elastic roll made of the material (compounding 70% by weight or more) is inferior in heat resistance, even if it is used in the production of translucent paper, the surface roughness deteriorates quickly and it is not suitable for continuous operability. Absent.

Further, for example, an elastic roll made of a synthetic resin obtained by molding a resin such as epoxy, urethane, polyamide, isocyanate, silicon, or vinylidene fluoride in a single layer or a multi-layer by combining a plurality of materials,
Elastic rolls (not mixed with aramid fibers), which are mainly composed of materials such as nylon and tetron, have better heat resistance than those made of natural fibers, but especially for the production of translucent paper. When used at a high temperature of 150 ° C or higher, the rolls are cracked or damaged, and the restorability is poor, and both of them have the drawback that they cannot be used for a long continuous operation.

From the above, as manufacturing of high-quality translucent paper, asbestos, which is excellent in heat resistance and pressure resistance and has little thermal deformation, has been used as a material for the elastic roll. However, recently, it was suggested that asbestos would be a material for inducing lung cancer, so there is a tendency to prohibit the use of asbestos except for existing ones, and the development of elastic rolls made of alternative materials is awaited. It is the current situation.

Therefore, the inventors of the present invention have made earnest studies on the material of the elastic roll as an alternative to asbestos when manufacturing the translucent paper, and as a result, the elastic roll containing aramid fiber has excellent suitability. Found to have.

Incidentally, 10 aramid fibers have been used so far.
Elastic rolls consisting of 0% are known. However, when an elastic roll made of 100% aramid fiber is continuously operated under the conditions of a temperature of 150 ° C or higher and a pressure of 200 kg / cm ² or higher as described above, the roll can withstand these use conditions. However, there is a problem that the roll is damaged. Therefore, it is not possible to continuously and stably obtain a translucent paper having uniform transparency with no difference between front and back sides.

Therefore, the inventors of the present invention blended a mixed amount of aramid fiber in a certain range to form an elastic roll, and when this was used for producing translucent paper, it was as good as when an asbestos roll was used. It was found that a further excellent effect could be obtained, and the present invention was completed.

[0010]

DISCLOSURE OF THE INVENTION The present invention uses an elastic roll made of a material that replaces asbestos, and continuously produces a semi-transparent paper having uniform transparency with high productivity and no front-back difference. It is an object of the present invention to provide a stable production method.

[0011]

[Means for Solving the Problems] In order to solve the above problems, the inventors of the present invention have conducted extensive studies, and as a result, constructed an elastic roll constituting a super calender device with a material containing a specific amount of aramid fiber. However, by specifying the Shore D hardness of the elastic roll and the surface roughness Rmax in relation to the hardness and the surface temperature of the metal roll, the heat resistance is excellent even under high temperature and high pressure conditions and the productivity is good. The inventors have found that a high-quality translucent paper can be obtained, and completed the present invention.

That is, the constitution of the present invention is a method for producing translucent paper by subjecting highly beaten pulp to papermaking and subjecting it to supercalendering treatment under conditions of high temperature and high pressure to constitute the supercalender. An elastic roll containing 30 to 50% by weight of aramid fiber, and having a Shore D hardness of 90 ° or more and a surface roughness Rmax defined by JIS B0651 satisfying the following formula: It is a method for producing translucent paper. Rmax ≤15 + 0.1 D-0.02T In the above formula, each symbol is as follows. Rmax: Surface roughness (μm) after acclimation of the elastic roll D: Shore D hardness of the elastic roll (°) T: Surface temperature of the metal roll during operation (° C) (Temperature range: 150 to 350 ° C)

[0013]

According to the present invention, a translucent paper is produced by applying a paper obtained by making a highly beaten pulp to a super calendering device consisting of a metal roll and an elastic roll under high temperature and high pressure conditions. The present invention, especially as an elastic roll constituting a super calender, the aramid fiber 30 ~
One of the important characteristics is to use an elastic roll containing 50% by weight.

Here, the aramid fiber is a polyamide fiber whose molecular skeleton is aromatic, and aramid is the US FTC (Federa) for this aromatic polyamide.
l Trade Commission is a generic name given by the US Federal Trade Commission. Aramid fiber has excellent strength, flexibility, etc. like nylon, and has even higher heat resistance. The aramid fiber is roughly divided into a linear para-bond system and a zigzag meta-bond system based on its molecular skeleton. Typical examples of the para-binding system include Kevlar manufactured by Du Pont of the United States and Teijin Technora, and examples of meta-bonded systems include Nomex of Du Pont and Teijin Connex.For example, metaphenylenediamine and isophthalic chloride The main component is polymetaphenylene isophthalamide whose main raw material is. The method for producing a sheet of aramid fiber and the method for producing an elastic roll can be produced by a conventionally known method (for example, Japanese Examined Patent Publication Nos. 38-13912 and 55-45771). In the present invention, meta-bonded aramid fiber is preferably used.

As a conventional aramid fiber roll, Du P
Ont's aramid fiber "Nomex" 100% paper made with a paper machine is rolled into Nomex paper, which is superior in heat resistance compared to other cotton and wool. well known.

The present inventors mix a specific amount of aramid fibers with other fibers to form an elastic roll, and the mixed amount of aramid fibers in this case is 30 to 50% by weight. Examples of other fibers include cotton, wool, tetron, nylon and the like, with cotton and wool being particularly preferable.

Incidentally, cotton, wool, etc. are inferior in heat resistance, and the heat-resistant temperature limit thereof is said to be 150 ° C. or lower at the surface temperature of the metal roll constituting the super calendar, but the present inventors have conducted extensive experiments. According to the results, surprisingly, it was found that the heat resistance of the product in which 30 to 50% by weight, preferably 30 to 40% by weight, of aramid fiber is mixed with cotton or wool has a surprisingly improved heat resistance.

By the way, the mixture of aramid fiber is 30% by weight.
In the following, the heat resistance is inferior, and when it is heated to a high temperature in order to obtain a translucent paper, roll burning occurs and continuous operability is deteriorated. On the other hand, if it exceeds 50% by weight, the recoverability is poor and roll breakage is likely to occur, and in this case also the continuous operability is poor.

In the present invention, the hardness of the elastic roll is preferably a Shore D hardness of 90 ° or more in consideration of durability under high temperature and high pressure conditions and resistance to surface roughening under paper passing. ..

In the present invention, the surface roughness R of the elastic roll is
max is measured by the method defined in JIS B0651,
It is necessary to satisfy the following formula. Rmax
≤15 + 0.1 D-0.02T. Preferably, Rmax ≦ 13 + 0.1
D-0.02T. In the above formula, each symbol is as follows. Rmax: Surface roughness (μm) after acclimation of the elastic roll D: Shore D hardness of the elastic roll (°) T: Surface temperature of the metal roll during operation (° C) (Temperature range: 150 to 350 ° C)

Next, regarding Rmax, the measurement is carried out on the entire width of the roll, and the super calender roll used for producing the translucent paper usually has a width of 1500 to 7500.
Since it is about mm, the measured values vary considerably in the width direction of the roll. Therefore, for example, if the roll width is 2000 mm,
As a measuring instrument, for example, Surftest 201 manufactured by Mitoyo Seisakusho Co., Ltd. is used, and the measurement length (L) is set to a maximum measurement length of 8 mm, and the elastic roll is measured at least 10 times over the entire width. The surface roughness Rmax is defined by the average value of the obtained measured values.

Since the surface roughness of the elastic roll under pressure cannot be measured during operation, the roll surface roughness (μm) of the elastic roll at the time of stop is measured and defined in the present invention. ..

Regarding the roll temperature at the time of translucentizing the paper with a super calendar device satisfying the above conditions, the surface temperature of the metal roll is preferably adjusted within the range of 150 to 350 ° C. By the way, when the temperature is higher than 350 ° C, the difference between the front and back surfaces of the translucent paper becomes remarkable due to the roughening of the elastic roll under pressure. Incidentally, the heating method of the metal roll is appropriately selected from conventionally used methods such as steam and electricity, and is not particularly limited. For example, an induction heating method jacket roller (electric heating / No. 41, pages 2 to 8, 19
In 1988, Pulp and Paper Technology Times / December 1987, December 41, pages 41 to 47), temperature uniformity is maintained, and partial roughening due to local heating is avoided, so that it is particularly preferably used.

The pressurizing condition of the roll in the super calender device is preferably in the range of about 150 to 300 Kg / cm in linear pressure. By the way, if the linear pressure is 300 Kg / cm or more, the tightness of the paper becomes too high and the paper strength is lowered, the paper quality is deteriorated such as curling of the paper, and the elastic roll is broken. On the other hand, if it is less than 150 Kg / cm, good translucent paper cannot be obtained due to insufficient pressurization.

From the above, when the elastic roll satisfies the above-mentioned conditions, it is possible to stably obtain a translucent paper having no front and back surface difference even in a continuous operation for a long time.
The number of nips of the super calendar device used in the present invention is not necessarily specified. In the case of a multi-stage super calender device, it is most preferable that all the elastic rolls incorporated therein are constituted by elastic rolls satisfying the above-mentioned conditions, but in particular, the difference between the front and back sides of the translucent paper is greatly affected. Is an elastic roll in the latter half, so that one or two of the elastic rolls in the latter half are elastic rolls satisfying the conditions of the present invention, and other elastic rolls are conventional elastic rolls. It is also possible to use.

According to experiments conducted by the present inventors, the aramid fiber roll used in the present invention has a cotton roll, a woolen paper roll, and a urethane which are mainly made of natural fibers commonly used in conventional super calendering devices. ,
Compared with resin molding rolls such as epoxy and polyamide,
Since it is difficult to obtain polishing accuracy, it is desirable that the elastic roll-in operation be performed more carefully than under normal conditions. The roll-in operation conditions are not specified, but after roll-polishing, for example, while increasing the temperature to 40 ° C, 60 ° C, and 80 ° C without passing the paper through, perform a conditioned operation for 2 hours or more under each temperature condition. Is especially effective.

The paper passing speed of the super calender is greatly influenced by the paper weight of the paper, the paper type, etc., but is generally 100.
It is appropriately adjusted in the range of about 500 m / min. As the base paper for the translucent paper, a high-quality paper of about 40 to 90 g / m ^{2 in} weight is generally used, and the papermaking method is not particularly limited, and any of acidic papermaking, neutral papermaking, and alkaline papermaking may be used. ..

[0028]

EXAMPLES The present invention will be described in more detail with reference to examples, but the scope of the invention is not limited thereto. Unless otherwise specified, "part" and "%" in the examples are
"Part by weight" and "% by weight" are shown, respectively.

Example 1 Commercially available softwood bleached kraft pulp (hereinafter referred to as "NBKP") was mixed with a double refiner at a pulp concentration of 4%,
Beating up to 200 ml of CSF was used as a beatening paper material for preparation.

After 0.25% of rosin (weight ratio to pulp, the same applies below) and 3% of sulfuric acid band were sequentially added to this stock material, papermaking was performed at a speed of 200 m / min using a paper machine, and after cylinder drying. The sheet was dried so as to have a water content of 15%, and immediately passed through a super calendar device to obtain a translucent paper. The paper passing conditions at this time are that the surface temperature of the metal roll is 180 ° C, the linear pressure is 250 Kg / cm, and the operating speed is 2
At 50 m / min, two elastic rolls consisting of 40% aramid fiber and 60% cotton are used for the second and fourth rolls from the bottom (metal roll is the bottom), and the others are cotton rolls (Shore D hardness). : 92 °) was used. Table 1 shows the hardness of the elastic resin roll, the surface roughness after running-in, the surface temperature of the metal roll during operation, and the quality evaluation results of the translucent paper obtained by continuous operation.

Example 2 As the paper passing conditions, the surface temperature of the metal roll was 180 ° C., and the linear pressure was
At 250 Kg / cm, operating speed of 250 m / min, two elastic rolls consisting of 30% aramid fiber and 70% cotton are used for the second and fourth rolls from the bottom (metal roll). A translucent paper was obtained in the same manner as in Example 1 except that a cotton roll (Shore D hardness: 92 °) was used as the elastic roll. Table 1 shows the hardness of the elastic resin roll, the surface roughness after running-in, the surface temperature of the metal roll during operation, and the quality evaluation results of the translucent paper obtained by continuous operation.

Example 3 As the paper passing conditions, the surface temperature of the metal roll was 250 ° C. and the linear pressure was
At 250 Kg / cm, operating speed of 250 m / min, two elastic rolls consisting of 30% aramid fiber and 70% cotton are used for the second and fourth rolls from the bottom (metal roll). A translucent paper was obtained in the same manner as in Example 1 except that a cotton roll (Shore D hardness: 92 °) was used as the elastic roll. Table 1 shows the hardness of the elastic resin roll, the surface roughness after running-in, the surface temperature of the metal roll during operation, and the quality evaluation results of the translucent paper obtained by continuous operation.

Example 4 As the paper passing conditions, the surface temperature of the metal roll was 100 ° C. and the linear pressure was
At 250 Kg / cm, operating speed of 250 m / min, two elastic rolls consisting of 30% aramid fiber and 70% cotton are used as the second and fourth rolls from the bottom (metal roll is the bottom). A translucent paper was obtained in the same manner as in Example 1 except that a cotton roll (Shore D hardness: 92 °) was used as the elastic roll. Table 1 shows the hardness of the elastic resin roll, the surface roughness after running-in, the surface temperature of the metal roll during operation, and the quality evaluation results of the translucent paper obtained by continuous operation.

Example 5 As the paper passing conditions, the surface temperature of the metal roll was 180 ° C. and the linear pressure was
At 250 Kg / cm, operating speed of 250 m / min, two elastic rolls consisting of 50% aramid fiber and 50% cotton are used as the second and fourth rolls from the bottom (metal roll). A translucent paper was obtained in the same manner as in Example 1 except that a cotton roll (Shore D hardness: 91 °) was used as the elastic roll. Table 1 shows the hardness of the elastic resin roll containing the aramid fiber, the surface roughness after the acclimation operation, the surface temperature of the metal roll during the operation, and the quality evaluation results of the translucent paper obtained by the continuous operation.

Comparative Example 1 As the paper passing conditions, the surface temperature of the metal roll was 180 ° C. and the linear pressure was
At 250 Kg / cm, operating speed of 250 m / min, two elastic rolls consisting of 25% aramid fiber and 75% cotton are used for the second and fourth rolls from the lowermost stage (the lowermost stage is a metal roll). A translucent paper was obtained in the same manner as in Example 1 except that a cotton roll (Shore D hardness: 90 °) was used as the elastic roll. Table 1 shows the hardness of the elastic resin roll, the surface roughness after running-in, the surface temperature of the metal roll during operation, and the quality evaluation results of the translucent paper obtained by continuous operation. Comparative Example 2 As the paper passing conditions, the surface temperature of the metal roll was 180 ° C, and the linear pressure was
At 250 Kg / cm, operating speed of 250 m / min, two elastic rolls made of 55% aramid fiber and 45% cotton are used as the second and fourth rolls from the bottom (metal roll). A translucent paper was obtained in the same manner as in Example 1 except that a cotton roll (Shore D hardness: 90 °) was used as the elastic roll. Table 1 shows the hardness of the elastic resin roll, the surface roughness after running-in, the surface temperature of the metal roll during operation, and the quality evaluation results of the translucent paper obtained by continuous operation. Comparative Example 3 As the paper-passing conditions, the surface temperature of the metal roll was 150 ° C, and the linear pressure was
An elastic roll made of 100% urethane resin (Shore D hardness: 85
A semitransparent paper was obtained in the same manner as in Example 1 except that (°) was used. Table 1 shows the hardness of the elastic resin roll, the surface roughness after running-in, the surface temperature of the metal roll during operation, and the quality evaluation results of the translucent paper obtained by continuous operation.

Comparative Example 4 As the paper passing conditions, the surface temperature of the metal roll was 100 ° C. and the linear pressure was
A translucent paper was obtained in the same manner as in Example 1 except that an elastic roll made of 100% cotton (Shore D hardness: 84 °) was used as the elastic roll at 250 kg / cm and an operating speed of 250 m / min.
Table 1 shows the hardness of the elastic resin roll, the surface roughness after running-in, the surface temperature of the metal roll during operation, and the quality evaluation results of the translucent paper obtained by continuous operation.

[0037]

[Table 1]

The evaluation method of each evaluation item is as follows. [Surface Roughness Rmax] The surface length was measured by Surftest 201 manufactured by Mitoyo Seisakusho with a measurement length of 8 mm.

[Transparency of Translucent Paper] The translucent paper was visually observed to determine the uniformity of transparency. A: Very good. ○: Good. Δ: inferior X: Extremely inferior.

[Continuous Operation] The deterioration state of the elastic roll during long-term operation was evaluated. ⊚: Almost no deterioration. ◯: Slightly deteriorated. X;
It deteriorates considerably.

[0041]

As is clear from the results shown in Table 1, according to the present invention, since the elastic roll in which a specific amount of aramid fiber is mixed is used as the elastic roll constituting the super calender, it is excellent in heat resistance and long. Little deterioration even during long-term operation. Therefore, since continuous operation is possible, it is possible to produce high-quality translucent paper which has good productivity and has uniform transparency with no difference in front and back.

Claims (1)

Claim: What is claimed is: 1. A method for producing translucent paper by subjecting highly-beaten pulp to papermaking and subjecting this to supercalendering under conditions of high temperature and high pressure to form the supercalender. 30 to 50% by weight of aramid fiber is mixed in the elastic roll, and the Shore D hardness is 90 ° or more, JI
A method for producing translucent paper, characterized in that an elastic roll whose surface roughness Rmax defined by S B0651 satisfies the following formula is used. Rmax ≤15 + 0.1 D-0.02T In the above formula, each symbol is as follows. Rmax: Surface roughness (μm) after acclimation of the elastic roll D: Shore D hardness of the elastic roll (°) T: Surface temperature of the metal roll during operation (° C) (Temperature range: 150 to 350 ° C)