JPH04194098A - Paper having improved dimensional stability - Google Patents

Abstract

PURPOSE:To obtain the subject paper excellent in dimensional stability by applying a mechanical compressive force to a wet pulp sheet for producing a specified pulp, mixing >=a specified amount of the resultant specified pulp, thus varying morphological properties, flexibility, mechanical properties, elasticity, etc., of the raw material pulp single fibers. CONSTITUTION:A mechanical compressive force of 30-500kg/cm<2> is applied to a wet pulp sheet to produce a pulp in which the flatness of swollen pulp fibers in a slurry is >=1.35. The resultant pulp is mixed in an amount of >=30wt.%, thus obtaining the objective paper.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention provides a method for significantly improving the dimensional stability of paper. Paper generally undergoes dimensional changes due to expansion and contraction of the pulp fibers that make up the paper when subjected to changes in moisture or temperature. This dimensional change causes, for example, a shift in the position of the printed portion or an error in the spacing during printing, and especially in the case of multicolor printing, the problem of color shift also occurs, which significantly impairs the commercial value.

In addition, computer human power (optical reader, etc.)
Misalignment of the printed portion is a fatal defect in OCR paper used for. Furthermore, haze has recently increased rapidly in general form paper, form paper for laser printers, and so-called information recording paper such as thermal paper, inkjet paper, thermal transfer paper, PPC paper, and photographic paper for various uses. There are various problems caused by the lack of dimensional stability of paper, especially the problem of paper curling, which causes serious troubles such as impairing the paper's runnability and handling in recording devices. . In recent years, paper and other materials (
Base paper used for special purposes such as so-called composite materials, such as adhesive tapes, adhesives, etc., which are used for special purposes such as bonding with resin films, metal foils, etc., or paper impregnated with other materials (liquid resins, etc.). Curling and dimensional changes in composite materials due to lack of dimensional stability of the base paper have become serious problems in base paper for adhesive release paper that is attached to stickers, etc., and base paper for laminated boards that are formed after being impregnated with resin. There is.

[Conventional technology]

Several proposals have already been made to solve various problems caused by the lack of dimensional stability of paper. For example, as a method of improving dimensional stability by strengthening the constraints during the drying process during the paper manufacturing stage,
It is known to use a Yankee dryer, or to use a humidity control or humidification device that improves dimensional stability by releasing internal stress in paper. However, these methods are no more than minor modifications made at the paper manufacturing stage, and their improvement effects are extremely small, so they are not fundamental solutions.

In addition, pulp that has undergone a drying history as raw material pulp (
Although this method requires a huge amount of heat to dry the pulp once, it significantly increases production costs, and as a practical matter, it is extremely difficult to use. It can only be used in certain fields.

To make matters worse, once pulp fibers have been subjected to a drying history, their cohesiveness becomes extremely poor, and the strength and elastic properties, which are important properties of paper, are significantly impaired.

Other methods include adjusting the operating conditions of the paper machine, controlling the anisotropy of the paper, and balancing the vertical and horizontal dimensions of the dimensional stability. Not yet. There is also a method of improving dimensional stability by adding inorganic pigments to the raw materials, but this also significantly impairs strength and elastic properties, and there is a limit to the amount added, so no significant improvement in dimensional stability can be expected.

[Problem to be solved by the invention]

The present invention provides a method for significantly improving the dimensional stability of paper, which was not possible with the conventional technology, and provides inexpensive and efficient dimensional stability without any loss of other properties of paper. The present invention provides a method for producing paper with extremely good properties.

[Means to solve the problem]

In order to produce paper with extremely good dimensional stability, the present invention applies mechanical compression force to the raw material pulp to improve the morphological characteristics, flexibility, mechanical properties of the raw material pulp single fibers,
This is an epoch-making and fundamental dimensional stability improvement method that aims to improve the dimensional stability of paper by changing its elastic properties and producing paper using the pulp.

It is observed that the pulp fibers in the mechanically compressed pulp are clearly flattened in the swollen state. The inventors of this patent focused on this morphological change of pulp fibers, and as a result of intensive research, they found that flattening pulp fibers changes the mechanical properties of the pulp fibers themselves and their elasticity against moisture, and at the same time, the paper They also changed the network structure during formation, and found that the dimensional stability of the paper was improved as a result. That is, it has been found that the flatness of the pulp single fibers in the swollen state correlates well with the dimensional stability of the paper produced.

The flatness of normal pulp single fibers in the swollen state is 1.1
~1.30 (definition and measurement method will be described later), whereas the flatness in the swollen state of the pulp single fibers subjected to the mechanical compression treatment of the present invention is 1.35 or more, and the As shown, the effect of improving dimensional stability becomes more pronounced as the degree of flatness increases.

The flatness of pulp single fibers in a swollen state is measured as follows. First, 42 mesh-on pulp (long fiber pulp) is separated from the sample pulp using a sieving tester. The water in this separated pulp suspension is repeatedly replaced with a solvent, and finally replaced with an epoxy resin.

Before the epoxy resin is completely cured, the epoxy resin mass in which the pulp fibers are dispersed is stretched slightly to orient the pulp fibers inside. This is to ensure that the cut surface is perpendicular to the fiber axis direction when cutting the pulp fiber cross section. After that, the epoxy resin is cured, and a cross-sectional section of the fiber is cut out using a microtome. This section is observed under a microscope to quantify the shape of the pulp fiber cross section.

The flatness of pulp fibers was defined as fiber cross-sectional area/(minimum width of Ii fibers). This value is an index showing the degree of flatness of the fiber; if the fiber cross section is a perfect circle, it will be 0.79, and if it is a perfect square, it will be 1.00. Become. For example, if it is flattened into an ellipse with a ratio of major axis to minor axis of 2:1, flatness = 1.57,
If it is flattened into a rectangular shape with a long sleeve to short axis ratio of 2:1, the flatness will be 2.00.

Note that since the flatness of the fibers has variations inherent to the fibers, it is necessary to measure at least about 1000 fibers.

There are no particular restrictions on the method of applying mechanical compressibility to the raw pulp, but there are methods such as compressing a pulp sheet dehydrated on a wire mesh using a surface pressure type press device used for press molding, or continuously using a roll press device. A method of applying pressure and compression can be used.

stomach. There is no particular limit to the dry basis weight of the pulp supplied to the mechanical compression device, but from the viewpoint of pulp sheet processing efficiency, it is
g/rrf or higher is usually used, and 3000 g/rrl or lower is suitable from the viewpoint of dehydration treatment efficiency before compression treatment. The pulp may be unbeaten pulp treated under pressure and then re-disintegrated, and used as is or after being beaten to a predetermined end bark depending on the purpose, or the pulp may be beaten to a predetermined end bark beforehand and then subjected to compression treatment. .

The pressure of the compression device is 30kg/in the case of a normal surface pressure type.
A dimensional stability effect was observed at about cIl, and the pressure was increased to 500
The effect increases as the amount of kg/ad increases.

When a pressure of 500 kg and 10 ff or more is applied, there is hardly any further increase in the effect. In the case of the roll press type, the dimensional stability effect is recognized from a linear pressure of about 30 kg/Ci, and the effect increases as the pressure increases up to about 500 kg/Cjl. 500kg
Even if a pressure of /car or more is applied, no further increase in the effect is observed and it is meaningless.

The surface of the mold or roll of the pressurizing device is flat, grooved, or perforated; the effect remains the same, but water is pushed out of the pulp mat when pressurized, making drainage smoother. For this purpose, a grooved type or holed type is suitable. You can also use suction, felt, etc. to assist in water extraction. One stage is sufficient for the number of processing times, but if there are pressure restrictions on the equipment,
Multi-stage processing can also be performed.

In order to make the most of the effect of improving dimensional stability, it is optimal to manufacture paper from 100% pressure-treated pulp, but depending on the application, the effect can be seen with a blend of about 30%.

〔Example〕

Example-1 Unbeaten and beaten LBKP suspensions with a concentration of 1.5% were
5 Dehydrated on mesh wire, basis weight 1000g/m (
A pulp mat with a pulp concentration of 25% was formed. This pulp mat was cut into 500cm x 500m pieces, and after being pressurized with a surface pressure type press device under the conditions shown in Table 1 below,
The mixture was blended in a beaten or unbeaten state, and a paper sheet having a basis weight of 60 g/m and a density of about 0.6 g/ad was made.

The dimensional stability of the paper was evaluated based on the moisture expansion/contraction rate. The moisture expansion/contraction rate is the dimensional change rate per 1% change in moisture content. 1st
As shown in the table, the expansion/contraction ratio of paper made from pressure-compressed pulp shows extremely superior dimensional stability compared to the untreated product (comparative example), and the elastic modulus (ultrasonic propagation It can be seen that the speed (calculated from the speed) has also increased.

(Left below) Table 1 * Beating numbers are Canadian standard wood bark (CSF) Example 2 Unbeaten and beaten LBKP suspensions with a concentration of 1.5%
5 Dehydrated on a mesh round rope, bone dry basis weight 1500 g/n
(A continuous pulp mat with a solid content concentration of 25% was prepared. After passing this pulp mat through a roll press device (30 pitches, chevron grooved roll) under each condition shown in Table 2, Beating and blending, basis weight 60g/m, density approximately 0
．． A sheet of 6 g/a& was made. The dimensional stability of paper was evaluated by the vertical and horizontal geometric mean of the moisture expansion/contraction rate, and the elastic modulus was also expressed by the vertical and horizontal geometric mean.

As shown in Table 2, the dimensional stability of the paper made from the pressure-compressed pulp was extremely superior to that of the untreated product (comparative example).

Table 2 Main beating figures are C3F Procedural amendment (voluntary) May 1991 (Kataguchi 1990 Patent Application No. 314431 2 Name of invention Paper with improved dimensional stability 3, Amendment person case and Relationship between Patent Applicant Address: 2-1-1 Nishi-Shinjuku, Shinjuku-ku, Tokyo, Japan 5, “Detailed Description of the Invention” column 6 of the specification to be amended, Contents of the amendment l) Description page 2, Correct the 4th line "Thermal Paper" to "Thermal Paper J".

2) Correct the "compression ratio" on page 7, line 5 of the specification to "compression force."

3) Page 7 of the specification, lines 199 and 200.
Corrected to ``filt fisheries''.

4) On page 8 of the specification, line 4, ``to the extent'' is corrected to ``to the extent J.''

5) Specification page 8, line 8, line 9, line IO rKg/c
Correct m”J to “Kg/co+1.

6) On page 9 of the specification, line 15, rKg/cm2J is changed to “nig/
/Correct to cm”Jl.

7) Correct "Procedure" on page 9 of the specification, line 155, to r handwritten J.

8) Table 1 on page 11 of the specification is amended as follows.

(Left below) Table 1 * Beating figures are Canadian Standard Filtration Fisheries (C5F) 9) Table 2 on page 13 of the specification has been amended as follows.

Table 2 *The beating number is C5F.

Claims (1)

[Claims] 1) 30kg/cm^2~500k on wet pulp sheet
Dimensionally stable pulp obtained by applying mechanical compression force of g/cm^2, characterized by containing 30% or more of pulp whose swollen pulp fibers have an oblateness of 1.35 or more in the slurry. Paper with improved properties.