JPH06287896A - Production of transparent paper - Google Patents

Abstract

PURPOSE:To improve various properties of a transparent paper manufactured by coating method. CONSTITUTION:A thermoplastic transparent finishing agent dissolved in an organic solvent is applied to a base paper in an amount less than the void volume of the paper and the paper is dried and aged. In the case of using a base paper having almost uniform fiber quantity in the direction of thickness and imparted with protrusion patterns and non-patterned parts, the amount of the transparent finishing agent is less than the void volume of the non- patterned part. When the patterned part of the base paper is formed by the difference of the fiber quantity in the direction of thickness, the coating amount of the transparent finishing agent is less than the void volume in the patterned part having low fiber content. The microscopic fluctuation of the transparent feeling caused by the formation of the base paper can be suppressed to decrease the uneven feeling. The contrast between the patterned part and the non- patterned part can be increased in the case of a base paper having patterned part.

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 transparent paper. More specifically, it relates to a method for improving various properties of transparent paper produced by a coating method.

[0002]

2. Description of the Related Art Conventionally, various methods for producing transparent paper are known.
As a typical method, a method of treating paper with concentrated sulfuric acid, a method of highly beaten chemical pulp to make paper, a method of treating base paper with a clarifying agent such as wax or synthetic resin, synthetic fiber or synthetic pulp mixed paper There is a method of heating and pressurizing to make it transparent.

On the other hand, various methods for producing a design paper in which the pattern portion is opaque and the non-pattern portion is transparent have been proposed. For example, in Japanese Patent Publication No. 50-25048, a method of heat-pressing a polyolefin fiber mixed paper with an embossing roll having a smooth convex part is disclosed in Japanese Patent Publication No. 50-3802 and Japanese Patent Publication No. 61-7.
No. 0092 and JP-A No. 63-256798 propose a method of partially treating a base paper with a specific resin and a solvent. However, these conventional methods are poor in elegance because there is no difference in the unevenness between the pattern portion and the non-pattern portion, or even if there is a small difference, the method of Japanese Patent Publication No. 50-25048 has a uniform transparency in the non-pattern portion. However, it is difficult to continuously operate because the resin adheres to and accumulates on the hot roll during manufacturing, and it is difficult to make the base paper transparent when the method of JP-B-50-3802 is thick. It has a big problem.

The present applicant has applied for a design paper, which solves the problems of these conventional methods, as Japanese Patent Application No. 2-258652. This application applies convex and non-patterned parts to a base paper having a substantially uniform amount of fibers in the thickness direction, and applies a clarifying agent dissolved in an organic solvent to a void volume or less occupied by the non-patterned parts. The present invention relates to a design paper, which is characterized by having a large difference in transparency between a convex pattern and a non-pattern part after drying. Further, the design paper is characterized in that the base paper is provided with a convex pattern only on one surface, and the transparentizing agent is applied from the surface (smooth surface) opposite to the surface having the convex pattern.

As a result, it was possible to obtain a design paper in which the transparent contrast of the convex pattern portion and the non-pattern portion was emphasized. The reason why the contrast is enhanced can be explained as follows, as described in detail in the application. 1 and 2 are examples in which a partially enlarged sectional view of a base paper used in the present invention is schematically shown. The base paper P in FIG. 1 has, for example, a water content of 5 on the paper machine.
It is produced by a method of press-molding a wet paper of about 0% with felt having a knitting pattern, a method of press-molding with two embossing rolls engraved with the pattern, and the like. In the base paper P ′ of FIG. 2, a wet paper having a water content of about 15% which is hydrated on a paper machine or formed paper is pressed through an embossing roll having an uneven pattern and a counter roll having a flat surface. It is manufactured by the method.

Volumes of the convex pattern portions 1 and 1'are V ₁ and V ₁ ', and non-pattern portions 2 and 2'of the same area as that.
Is defined as V ₂ and V ₂ ′, V ₁ is formed from fibers of volume F ₁ and voids (corresponding to air) A ₁ , and V ₁ ′ is formed from fibers of volume F ₁ ′ and voids A ₁ ′. Be present. Also,
It is assumed that V ₂ is formed by the fiber of the volume F ₂ and the void A 2, and V ₂ ′ is formed by the fiber of the volume F ₂ ′ and the void A 2 ′. Since the amount of fibers in the thickness direction of the paper is almost uniform, F ₁
≈F ₂ and F ₁ ′ ≈F ₂ ′. Also, V ₁ > V ₂ ,
V ₁ '> V ₂ '. If this base paper is impregnated with a clarifying agent having a concentration of 30% (specific gravity of 1), the clarifying agent fills the void volumes A ₁ and A ₁ ′ in the convex pattern portions 1 and 1 ′. Therefore, the adhering amounts of the clarifying agent after drying are 0.3A ₁ and 0.3A ₁ ', and similarly, the non-patterned portions 2 and 2'are 0.3A ₂ and 0.3A ₂ '. A ₁ > A ₂ and A ₁ '
Since> A ₂ ', the amount of the transparentizing agent deposited on the convex pattern is
More than non-patterned areas.

On the other hand, in the method of applying the clarifying agent, both the convex and non-patterned portions can be obtained by applying the amount of 0.3A ₂ and 0.3A ₂ 'after drying. The amount of adhesion is the same (0.3A ₂ and 0.3A ₂ '). That is,
According to the coating method, the amount of resin adhering to the convex pattern portion can be made smaller than that in the impregnation method, and the contrast of transparency of the convex pattern portion and the non-pattern portion can be further emphasized.

In the case of the impregnation method, the base paper actually passes through the impregnating liquid in the impregnation tank, so that the clarifying agent is excessively supplied and tends to stay in the non-patterned portion. When it is dried, it becomes as if a resin film had been formed on the surface of the non-patterned portion, which causes a defect called "shining" in which a large amount of light is reflected at that portion. On the other hand, in the coating method, the necessary amount of the clarifying agent can be freely controlled in advance, so that this drawback can be reduced. In particular, if a base paper with a convex pattern on only one side (schematically shown in FIG. 2) is used and coating is applied from the surface opposite to the convex surface (smooth surface), there will be no retention of the clarifying agent. We were able to manufacture a design paper that had no "shine". Further, in the impregnation method, the clarifying agent gradually accumulates on the guide rolls in the drying zone and dries, so that it is necessary to take measures against it, but in the coating method of the present invention, this problem hardly occurs. There was also an advantage. Further, there is an advantage that the transparency of the pattern portion and the non-pattern portion can be freely controlled by changing the coating amount.

[0009]

DISCLOSURE OF THE INVENTION The inventors of the present invention have further studied the production of transparent paper by the above method. As a result, the transparent paper produced by this method has a high density (corresponding to portions 2 and 2'in the figure) and a low density (corresponding to portions 1 and 1'in the figure). It has been found that there is a large difference in printability, especially ink absorbency. It was presumed that this phenomenon was caused by the fact that the clarifying agent applied to a high-density portion was ubiquitous near the surface. In other words, when the density is low, the applied transparency agent penetrates the inside of the base paper faster, and compared to areas where the density is high, the proportion of the transparency agent that is ubiquitous near the surface is low, so ink absorption It was estimated that there was a large difference in sex. This phenomenon becomes a problem when the transparent paper is used for printing. Further, if the transparentizing agent is ubiquitous near the surface, there is a problem in that a problem of poor posture (curl or the like) is likely to occur and the tactile sensation becomes poor. The present invention mainly aims to solve these problems.

[0010]

The present inventors have newly found that the above problems can be solved by treating the base paper with a specific clarifying agent and then subjecting it to aging treatment, and completed the present invention. . We also found that a specific effect can be obtained even when a flat base paper without a pattern is used. That is, the gist of the present invention is a method for producing a transparent paper, which comprises coating a thermoplastic clarifying agent dissolved in an organic solvent to a void volume or less of the base paper, drying and further aging treatment. . In the method,
Having a substantially uniform fiber amount in the thickness direction, and using a base paper provided with a convex pattern and a non-patterned portion, coating a transparentizing agent to the void volume or less occupied by the non-patterned portion, A method for producing transparent paper, which comprises using a base paper having a pattern portion provided with a difference in the amount of fibers in the thickness direction, and applying a clarifying agent to a void volume or less occupied by the pattern portion having a small amount of fibers. Is.

The base paper used in the present invention is a flat base paper without a pattern, a base paper having a substantially uniform fiber amount in the thickness direction, and having a convex pattern and a non-pattern portion, in the thickness direction. It is possible to use any of the base papers provided with a pattern portion due to the difference in fiber amount. The materials used for the base paper are bleached softwood kraft pulp (NBKP), bleached hardwood kraft pulp (LBKP), bleached softwood sulphide pulp (NBS).
P), wood pulp such as thermo-mechanical pulp (TMP), bast fiber such as hemp, swordfish, goose bark, sanpei, non-wood pulp such as straw and bamboo, synthetic pulp such as polyolefin, rayon, vinylon, nylon, polyester, etc. If necessary, clay, kaolin, talc, titanium dioxide, calcium carbonate, aluminum hydroxide, silicon dioxide, magnesium hydroxide, and other various fillers, coloring agents, sizing agents, Freeness is usually 100-500ml, using paper strength enhancer as appropriate.
C. S. F. In the conventional method, a base paper is usually produced with a basis weight of 50 to 200 g / m ² using a paper machine such as a Fourdrinier paper machine or a cylinder paper machine.

The base paper having a substantially uniform fiber amount in the thickness direction and having a convex pattern and a non-patterned portion is generally formed by embossing a formed paper or a wet paper on a paper machine. It is manufactured by pressing with an embossing roll or felt. Specifically, the water content on the paper machine or the water content of the formed paper is 15
% Wet paper with an embossing roll of rubber, metal, synthetic resin, etc., or wet paper with a water content of about 50% on a paper machine is pressed with felt with a knitting pattern. It is manufactured by the method.

The base paper provided with a pattern portion due to the difference in the amount of fibers in the thickness direction is a transparent paper having a pattern mesh attached to a cylinder cylinder of a cylinder paper machine or a dandy roll of a Fourdrinier paper machine. It can be manufactured using manufacturing technology. As the method for producing the pattern net for producing these transparent paper, a method of winding a metal cage or bamboo cage around an upper net of a cylinder cylinder or a dandy roll, a wire pattern made of wire, metal, resin, paper, etc. on the upper net is used. Attaching with thin wires, soldering, sticking with adhesive, drawing pattern etc. with paint or resin on the upper net,
A method of closing the mesh, a method of directly forming an uneven pattern on the paper making mesh itself, a method of forming a pattern using a photosensitive resin, etc. are known, but any of these methods can be used in the present invention. .

In the present invention, the base paper thus produced is coated with a thermoplastic clarifying agent dissolved in an organic solvent. The clarifying agent used in the present invention needs to be thermoplastic because the thermosetting clarifying agent does not exhibit the aging effect described later. Further, it is necessary to apply the clarifying agent so that it is not more than the void volume in the thickness direction of the base paper. The reason is that it is possible to manufacture transparent paper that has no "shining" and that also has an aging effect.

Even if a water-based clearing agent of water-soluble polymer such as polyvinyl alcohol, starch, casein, carboxymethylcellulose, polyvinylpyrrolidone, polyacrylamide, polyethylene oxide, etc. is applied, it hardly penetrates into the base paper and stays on the surface. This is not suitable for the present invention because it tends to cause "shining" and the resin adhesion amount is small, resulting in a low transparency effect.

On the other hand, a clarifying agent prepared by dissolving a synthetic resin or the like in an organic solvent can easily obtain a solution having a high concentration and a low viscosity as compared with a water-soluble clarifying agent, and has a permeability to the base paper. Since it is also large and the resin adhesion amount can be large, it can be suitably used in the present invention. As the clarifying agent that can be used in the present invention,
Any transparentizing agent that is soluble in an organic solvent and has thermoplasticity can be used. Examples include paraffin,
Waxes such as higher fatty acids, fatty acid amides, fatty acid alcohol esters, polyacrylic acid esters, polymethacrylic acid esters, polyvinyl chloride, polyvinyl acetate, polystyrene, polybutene, polyesters, polyurethanes, polyamides and acetobutyrate, hydroxyethyl cellulose , Cellulose or polysaccharide derivatives such as sucrose acetate isobutyrate, rosin, rosin ester, dammar resin, shellac, etc., or resins modified with these, or prepolymers having radically polymerizable unsaturated groups in the molecule UV curable resin consisting of liquid vinyl monomer such as styrene and methyl methacrylate and photosensitizer (cured by UV lamp)
And prepolymers with radically polymerizable unsaturated groups in the molecule and liquid vinyl monomers such as styrene and methyl methacrylate and unsaturated polyesters, diacrylic phthalates, modified acrylics, modified epoxies, modified urethanes, polyfunctional It is a resin (cured by an electron beam generator or the like) which is polymerizable by radiation such as an electron beam and is composed of a monomer or the like, and these are used alone or in combination of several kinds.

In the present invention, these clarifying agents are dissolved in an organic solvent. Examples of usable solvents are benzene,
Toluene, aromatic hydrocarbon solvents such as xylene, gasoline, petroleum solvents such as petroleum ether, ethyl acetate, ester solvents such as butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, ketone solvents such as cyclohexanone, Examples thereof include chlorinated hydrocarbon solvents such as methylene chloride and trichlorethylene, alcohol solvents such as methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol and methyl cellosolve, and these solvents may be used alone or as a mixed solvent. The concentration of the clarifying agent dissolved in an organic solvent is 15% or more, and the viscosity thereof is preferably 80 cps (centipoise, measured with a B type viscometer at 60 rpm with a # 1 rotor, the same applies hereinafter). . If the concentration is 15% or less, the resin adhesion amount necessary for transparency cannot be obtained, and if it is 80 cps or more, the penetration into the base paper is insufficient, the transparency effect is also insufficient, and the surface "shine" is large. There is a drawback. A hardening agent, a coloring agent, a surfactant, a plasticizer and the like can be appropriately mixed and used as the clarifying agent.

In the present invention, the transparentizing agent thus prepared is applied to the base paper. As a coating machine, known coating machines such as a gravure coater and a roll coater which can accurately control the coating amount can be used. . When a flat base paper without a pattern is used as the base paper, it is preferable to apply a clarifying agent in an amount not more than the void volume in the thickness direction of the base paper, which has a substantially uniform fiber amount in the thickness direction. In addition, when using a base paper having a convex pattern and a non-patterned portion, it is necessary to coat the base paper with a volume not more than the void volume occupied by the non-patterned portion. When the base paper is used, it is necessary to apply a clarifying agent to the volume of voids occupied by the pattern portion having a small amount of fibers.

According to the present invention, the base paper is coated with the clarifying agent, then dried to volatilize the solvent and further subjected to the aging treatment. This is the greatest feature of the present invention. The aging treatment is performed by keeping the transparent paper after the transparency treatment at a high temperature for a certain period of time. The treatment temperature is usually 45 to 120, although it depends on the type of the clarifying agent used.
The temperature and the treatment time are preferably 10 minutes to 3 days.
If the temperature is lower than 40 ° C, it becomes difficult to obtain the effect, and 120
If the temperature is higher than ℃, the risk that the paper will be thermally discolored increases.

By the aging treatment, the transparentizing agent near the surface is uniformly diffused into the inside of the base paper, so that the defect of "shining" becomes inconspicuous, the unevenness of ink absorption during printing is reduced, and the whitening caused by folding is reduced. It was found that the degree of reduction is small, unevenness of formation appears to be reduced (microscopic difference in transparency due to unevenness of formation is reduced), and dimensional stability of paper is improved.

In particular, as the base paper, a base paper having a substantially uniform fiber amount in the thickness direction and provided with a convex pattern and a non-patterned portion is used, and a transparentizing agent is added to the void volume occupied by the non-patterned portion or less. When applied, the aging effect is remarkable. Specifically, the difference in transparency between the patterned and non-patterned areas increases due to aging, and the contrast becomes clear,
The design effect can be significantly improved.

The present inventors conducted the following experiments to clarify this phenomenon. First, the present inventors
Pulp with a ratio of P: LBKP = 60: 40 was beaten to a freeness of 300 ml, and a base paper having a basis weight of 80 g / m ² and a density changed in three stages (1.2, 0.9, 0.7) was produced. . A thermoplastic transparency agent (alkyd resin type) was applied to this base paper in an amount of 12% by weight based on the base paper to produce a transparent paper. Table 1 shows the results of measuring the transparency immediately after processing and the transparency after aging (45 ° C. × 3 days). The transparency is JIS
Obtain the opacity specified in P8138, transparency = 100
-Calculated by opacity.

[0023]

[Table 1]

As is clear from Table 1, there is a difference in the change in transparency after the aging treatment depending on the density of the base paper. That is,
When the density of the base paper is high, the transparency after the aging treatment is higher than the transparency immediately after processing, and when the density of the base paper is low, the opposite is true. Of course, this value varies depending on the type of pulp used, the thickness of the base paper, etc., but the tendency does not change. The present inventors estimated this phenomenon as follows. When the density of the base paper is high, the speed of penetration of the applied transparentizing agent into the base paper is slower than that of the low-density base paper, and the ratio of the transparentizing agent remaining near the surface is large. By the aging treatment, the transparency agent is diffused in the thickness direction of the paper to improve the transparency. When the density of the base paper is low, the coated clarifying agent quickly penetrates into the base paper, but since it is applied in a volume not more than the void volume, it rarely reaches the side opposite to the coated surface. By the aging treatment, the clarifying agent diffuses in the thickness direction and the transparency decreases.

Using a base paper having a substantially uniform fiber amount in the thickness direction and having a convex pattern and a non-pattern part,
In the case of transparent paper produced by applying a clarifying agent to the void volume occupied by the non-patterned portion, the density of the base paper in the convex pattern part is lower than the density of the base paper in the non-patterned part. The transparency of the part decreases and the transparency of the non-pattern part improves. This significantly improves the design effect (contrast due to the difference in transparency).

The same applies to a transparent paper produced by a method in which a base paper having a pattern portion with a difference in the amount of fibers in the thickness direction is used, and a transparentizing agent is applied to a volume less than the void volume occupied by the pattern portion having a small amount of fibers. The effect of is obtained.

[0027]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples. Example. 1 part papermaking NBKP 30 parts by weight, LBKP 70 parts by weight,
430 ml C.I. S. F. Beaten up. Next, sizing agent (trade name "Size Pine E", manufactured by Arakawa Hayashi Chemical Co., Ltd.)
Solid content of 1% and starch (trade name "Amicol 60
2 ", manufactured by Nitto Co., Ltd.) was added to the pulp solid content of 1%, and the pH was adjusted to 4.5 with aluminum sulfate. The slurry was used to make a paper with a Fourdrinier paper machine to obtain a base paper having a basis weight of 100 g / cm ² . 62 parts by weight of transparentized polyacrylic ester resin (trade name "Tesfine 404", manufactured by Hitachi Chemical Co., Ltd.), 5 parts by weight of polyethylene glycol, 28 parts by weight of toluene,
A clearing treatment liquid containing 5 parts by weight of methyl ethyl ketone and having a coating concentration of 25% by weight and a viscosity of 60 cps was prepared. This solution was dried with a gravure roll coater to give a dry solid weight of 10 g / m 2.
² was coated on the back surface (smooth surface) of the base paper, the solvent was volatilized in the drying zone, and a roll having a diameter of 2 m was manufactured. Aging Treatment Next, this winding was left in an aging chamber at 50 ° C. for 3 days to perform an aging treatment.

Example. 2 papermaking in the papermaking Example 1 and same slurry using long paper machine of the base paper, and preliminarily dried after dewatering press, the overall when water content of 15%, an embossing roll (cloth pattern Was formed by engraving so as to correspond to 25% of the area of the above) and a counter roll having a flat surface, and pressed with a linear pressure of 100 kg / cm, and dried to obtain a base paper having a basis weight of 100 g / cm ² . Then, the same clearing treatment and aging treatment as in Example 1 were performed.

Example. 3 A wire net formed with a raid pattern was attached as an upper net of a dandy roll of a Fourdrinier paper machine. Dandy rolls are pressed against a web of paper made from the same slurry as in Example 1 to give a transparent pattern of a raid pattern, which is dried by a cylinder dryer according to a conventional method, and the basis weight is 100 g /
A transparent pattern paper of m ² was obtained. Then, the same clearing treatment and aging treatment as in Example 1 were performed.

[0030]

The transparent paper produced as described above has the following advantages over the transparent paper which is not subjected to the aging treatment. (1) It is possible to eliminate the phenomenon of so-called "shining" in which the glossiness of the transparent paper surface partially looks large depending on the angle of the incident light beam. (2) Transparent paper is often used for printing on its front and back surfaces, but the degree of unevenness in ink absorption can be significantly reduced. (3) Since the clarifying agent is evenly distributed in the thickness direction of the paper,
It is possible to reduce the "whitening" phenomenon that appears as white streaks when the transparent paper is folded. (4) Since it is possible to reduce a microscopic difference in transparency due to texture unevenness, it is possible to reduce unevenness feeling. (5) The transparent paper using the pattern-provided base paper can have a large contrast difference in transparency between the pattern portion and the non-pattern portion, and the design effect can be remarkably improved. (6) The dimensional stability is improved by uniformly distributing the clarifying agent.

[Brief description of drawings]

FIG. 1 is a partially enlarged sectional view of an example of a base paper used in the present invention.

FIG. 2 is a partially enlarged sectional view of an example of a base paper used in the present invention.

[Explanation of symbols]

P sheet P 'volume V ₁ of the the non-pattern portion V ₁ convex pattern portion 1 of the same area' convex pattern portions 2'1 'fiberboard first convex pattern portion 2 1 and a non-pattern portion 1 of the same area' convex pattern portion 1 ' Volume of V ₂ Volume of non-patterned part 2 V ₂ Volume of non-patterned part 2 '

Claims (3)

[Claims] 1. A method for producing a transparent paper, which comprises applying a thermoplastic clarifying agent dissolved in an organic solvent so that the void volume of the raw paper is equal to or less than that, drying and further aging treatment. 2. A base paper having a substantially uniform amount of fibers in the thickness direction and provided with convex and non-patterned parts,
The method for producing transparent paper according to claim 1, wherein the transparentizing agent is applied to a volume of voids occupied by the non-patterned portion or less. 3. A stencil sheet having a pattern portion provided with a difference in the amount of fibers in the thickness direction is used, and a transparentizing agent is applied to a volume of the void portion occupied by the pattern portion having a small amount of fibers. The method for producing transparent paper according to claim 1.