JPH0892893A - Reinforced sheet - Google Patents

Abstract

PURPOSE: To reinforce mechanical strength of a sheet by impregnating a sheet such as paper with a bacterial cellulose suspension and drying the sheet. CONSTITUTION: This method for reinforcing a deteriorated sheet with bacterial cellulose is to culture a bacterial strain belonging to the genus Acetobacter, etc., capable of producing bacterial cellulose, purify the bacterial cellulose, defibrate the cellulose with a homogenizer, prepare fine fiber suspension of the bacterial cellulose, impregnate deteriorated paper of books or documents with the fine fiber suspension and dry the paper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanically reinforced sheet.

[0002]

2. Description of the Related Art The mechanical strength of sheets such as nonwoven fabric and paper has been conventionally reinforced by various methods.

However, there is no report that the strength of such a sheet could be reinforced by utilizing the characteristics of bacterial cellulose. Although a method of treating the paper surface with bacterial cellulose to improve the gloss and printing gloss of the paper has been proposed (see US Pat. No. 4,861,427 and JP-A-5-9895 as an improved method thereof). Method),
There are few places that contribute to the reinforcement of paper strength.

In particular, the prior art relating to deteriorated paper is as follows.

For example, various restoration methods have heretofore been used for restoration of deteriorated and weakened old documents and works of art. Typical methods include the following.

I) Peeling and laminating method: This is a method that has been practiced in Europe for old documents. Paper materials are divided into two layers, thin paper is inserted between them, and they are laminated with an adhesive. The reinforcing effect is high, but the drawback is that it takes time and effort.

Ii) Lining method with Japanese paper: A method which is often used in Japanese surface equipment, and a strong thin paper is attached to the front surface or the back side of an object. It can only be applied to one side.

Iii) Paper-fitting method: The target material is placed on a net, and the pulp suspension is added on the net and suction filtration is performed from below the net to collect and repair fibers in the missing part of the material. To do. Suitable for repairing partial defects, but cannot reinforce the whole.

Iv) Chemical reinforcement method: (a) A transparent film is applied to an object and laminated by an adhesive or heat fusion. (b) The object is impregnated with the polymerizable monomer and then polymerized by radiation or heat. Both (a) and (b) have a high reinforcing effect, but they irreversibly denature the object,
It is difficult to use for valuable materials.

Each of these methods has its advantages and disadvantages and is used depending on the characteristics of the object to be repaired. For the purpose of merely imparting physical strength, a method of coating or filling with a synthetic material as in iv) is effective. However, in the restoration of old documents and works of art, there is a demand to avoid irreversible changes to the original materials, and in that sense, the use of synthetic products, non-aqueous solvents and adhesives is not desirable. In that sense, “i” and “ii”, which use adhesives to reinforce the entire paper, have traditionally used “paste” with intentionally reduced adhesive strength.

The method of the invention described below is similar to ii) with respect to degraded paper, but uses fine fibers formed from an aqueous suspension of bacterial cellulose as a reinforcing material, and It is characterized in that no or almost no adhesive is used in bonding.

[0012]

Under the background of the prior art described in the preceding paragraph, the present invention has developed a novel method for reinforcing a sheet such as a non-woven fabric, a paper, etc., and by extension, was reinforced by such a method. It is intended to provide a reinforcing sheet.

[0013]

Means for Solving the Problems As a result of earnest research to achieve the object described in the preceding paragraph, the present inventor found that the mechanical strength of a sheet can be reinforced by utilizing bacterial cellulotis as a reinforcing agent. Based on such knowledge, the present invention has been completed.

That is, the present invention relates to a reinforcing sheet produced by a method characterized in that the sheet is impregnated with a suspension of bacterial cellulose and then dried.

The present invention will be described below in detail.

The sheet to be reinforced according to the present invention is
A fibrous sheet having appropriate voids therein, which is generally produced by a wet or dry papermaking method, for example, ordinary paper made of pulp, nonwoven fabric made of a material such as polyester or polyamide, or The cloth etc. can be mentioned. The paper also includes paper materials (aged paper) that have been aged or deteriorated, such as library books and archive documents. Of course, not only such deteriorated paper with time but also deteriorated paper due to some other cause can be reinforced by the present invention.

As is well known, bacterial cellulose is cellulose produced by microorganisms such as the genus Acetobacter. This bacterial cellulose may be produced by either static culture or stirred culture of microorganisms.

Bacterial cellulose is known to have characteristics such as being composed of very fine fibers and having high strength as compared with the cellulose of essential pulp, and according to the present invention, the utilization of such characteristics is considered. The method for reinforcing deteriorated paper is superior to conventional methods for reinforcing deteriorated paper in that it can reinforce the entire surface or both sides, does not involve modification, and does not use solvents or adhesives.

The suspension of bacterial cellulose is not particularly limited as long as the object of the present invention is achieved, and can be carried out by a known method. See, for example, JP-A-61-113601.

Such a bacterial cellulose suspension contains a dispersant such as carboxymethyl cellulose and an additive such as an aggregating agent such as acrylamide unless the object of the present invention is hindered. It goes without saying that liquid is also included.

The term "impregnating a sheet with a suspension of bacterial cellulose" as used in the present invention means, in short, that an interfiber bond or an entanglement is positively produced between fine fibers of bacterial cellulose and the fibers constituting the sheet. In order to tighten, it means to fill the defibrated material of bacterial cellulose in the gap between the fibers and the fibers constituting the sheet, for example,
The suspension of bacterial cellulose can be applied to the sheet (including spray application), and then suction, pressurization, or the like.

The sheet impregnated with the suspension of bacterial cellulose in this manner is then dried to be a target reinforcing sheet. This drying is also not particularly limited, and the method conventionally used for drying this kind of sheet, for example,
Steam cylinder system drying, air dryer system drying, infrared (heat ray) system drying, dielectric heating system drying, microwave (high frequency) system drying and the like can be appropriately applied.

The present invention also purifies cellulose produced by acetic acid bacteria, and disintegrates fine fibers disintegrated from water to deposit on the surface or inside of deteriorated paper material to form a bond with the material. The present invention relates to a method for reinforcing deteriorated paper, which is characterized in that the deteriorated paper is reinforced with cellulose fine fibers produced by acetic acid bacteria.

This will be described in detail below.

The cellulose produced by the acetic acid bacterium is a high-purity, highly crystalline cellulose and is composed of very fine fibers. Therefore, when it is dried in a state swollen with water, it is as strong as an ordinary paper. A bond is formed. The present invention
By utilizing this property of bacterial cellulose, we propose a new method for reinforcing paper materials instead of the conventional method.

In the method of the present invention, bacterial cellulose fine fibers can be obtained, for example, by washing and purifying bacterial cellulose formed in a liquid medium and then defibrating it into fine fibrous forms. .

The bacterial cellulose fine fibers thus obtained are made into an aqueous suspension having an appropriate solid content concentration, applied to the surface of the object to be reinforced or deposited on the inside by filtration, and dried to give bacterial cellulose. The fine fibers form a bond with the fibers in the degraded paper material.

The reinforcing structure thus formed or the deteriorated paper reinforced by such a reinforcing structure has the following features.

That is, 1) There is a remarkable reinforcing effect even with a small amount of about 1 g in basis weight. In particular, the folding strength, which is important for handling materials, is remarkably improved. 2) High transparency makes it possible to maintain the visibility of the characters etc. recorded on the material. 3) Since it is made of pure cellulose, it is chemically stable and easy to manage. 4) Since no adhesive is used, there is no fear of secondary deterioration (rotting, worming, etc.) as in the case of using starch or glue. 5) If the coating and deposition conditions are appropriately selected, the deposited layer can be easily peeled off by swelling with water. And 6)
As we do not use materials such as Japanese paper and old glue that are difficult to control quality,
A stable effect can be obtained.

[0030]

The reinforcement of the sheet according to the present invention is believed to be due to the mutual connection and entanglement between the fibers of the bacterial cellulose and the fibers of the sheet to be reinforced.

[0031]

EXAMPLES The present invention will be further described below with reference to examples.

Example 1 (Preparation of bacterial cellulose suspension) After washing the bacterial cellulose with water to remove the medium, 2
Boil in 30% sodium hydroxide for 30 minutes and wash with water to give pure cellulose. This is decomposed into 10 to 30 fibers with a rotary blade type strong homogenizer to obtain a fine fiber suspension. A small amount of this liquid is sampled to obtain the dry weight, and the solid content concentration is obtained.

Incidentally, bacterial cellulose is
For example, Acetobocter xylinum ATCC 237
69) as a standard medium (Schramm-Hestrin medium: 1 L of water, 20 g of glucose, 5 g of peptone, 5 g of yeast extract, 6.8 g of disodium hydrogen phosphate dodecahydrate and 1.15 of citric acid).
It can be obtained as gel-like bacterial cellulose by statically culturing for 5 to 7 days in a solution obtained by dissolving g and sterilizing it. Of course, stirring culture can also be used.

Example 2 A paper sample was used as a standard hand-made machine (JIS-P-
8209) on the wire, fix the water retaining cylinder from above, and sandwich the paper sample. About 1 L of water is added on the paper sample, and the required amount of bacterial cellulose suspension is added thereto. This required amount is determined to be, for example, 1 g / m ^{2 in} basis weight conversion based on the solid content concentration of the suspension determined above.

After appropriately stirring the suspension in accordance with the usual method, when the cock under the wire is opened, the suspension drops due to gravity, but the fine fibers of bacterial cellulose are placed on the upper surface or inside due to the filtering action of the paper sample. Deposit to form a reinforced structure.

When the water has run out, it is removed from the wine, placed on a plate and left in a constant temperature and constant temperature room to dry.

The effect of such reinforcement by bacterial cellulose was examined on the overlay paper.

In order to reproduce the deteriorated state corresponding to the lower limit of the practical strength at which a library or a document library can withstand handling, the upper cover sheet was subjected to a rapid deterioration treatment using a blower dryer. That is, the deterioration treatment was performed for 10 days and 20 days under the dry heat deterioration condition at a temperature of 125 ° C.

The samples subjected to the rapid deterioration treatment and the samples subjected to the reinforcing operation were subjected to various tests after conditioning the humidity in a constant temperature and humidity chamber at a temperature of 20 ° C. and a relative temperature of 65% for 4 hours or more.

The test method is as follows.

(A) Folding endurance test According to JIS P8115, temperature 20 ° C., relative humidity 65
% In a constant temperature and constant humidity chamber using a MIT type tester. The load was changed depending on the sample so that a value of 3 to 4 digits could be obtained. The measurement was performed in the papermaking direction (MD).
For each sample, 10 pieces were tested and an average value was obtained.

(B) Tensile Strength and Elongation Test According to JIS P8113, temperature 20 ° C., relative temperature 6
The test was performed in a constant temperature and humidity room of 5% using a constant-speed extension type tensile tester. The test conditions were a paper piece width of 15 mm, a span length of 10 cm, a pulling speed of 10 mm / min, and a chart feed speed of 150 mm / min. The measurement was performed in the papermaking direction (MD). For each sample, 10 pieces were tested and an average value was obtained.

The elongation of each sample was read from the chart of the tensile test and the average value of 10 samples was obtained.

(C) Tear strength test According to JIS P8116, temperature 20 ° C., relative temperature 65
% Constant temperature and humidity chamber. The tear strength in the transverse direction of the paper (value obtained by tearing in parallel to the transverse direction of the paper, that is, a method of cutting fibers by tearing) was performed.

The results are shown in Table 1 below.

[0046]

[Table 1]

As can be seen from the above table, all of the values of folding endurance, tensile strength, elongation and tear strength are increasing, but there is a remarkable effect particularly in improving the folding endurance. .
This is similar to the result of the increase in folding endurance in the state where wood pulp was very thin on the deteriorated sample during reinforcement of the past hole-treated sample by the Leaf Casting method. It is noteworthy that in the case of bacterial cellulose, the value of tear strength is also increased.

Example 3 In Example 2, a vacuum filtration device is used instead of the standard hand-made machine to drain water in a corrective manner. The reinforcing effect is the same as in Example 2, but the dehydration is performed quickly, so that the time required for the treatment is shortened.

Example 4 The same bacterial cellulose as in Example 1 was added to 0.1-1.
A 5% water suspension is formed, and this is uniformly applied onto the sheet to be reinforced using an appropriate device and dried to form a reinforced structure.

Example 5 (combined use of paper strengthening agent) In the bacterial cellulose suspensions used in Examples 2 to 4, 0.1 to 5% of a water-soluble polymer as a paper strengthening agent, for example, CMC, The reinforcing effect can be enhanced by adding polyacrylamide or the like.

[0051]

INDUSTRIAL APPLICABILITY According to the present invention, the mechanical strength of a fibrous sheet such as a nonwoven fabric or paper is easily enhanced by bacterial cellulose.

Claims (3)

[Claims] 1. Reinforcement sheet produced by a process characterized in that the sheet is impregnated with a suspension of bacterial cellulose and then dried. 2. The reinforcing sheet according to claim 1, wherein the sheet is a deteriorated paper. 3. Cellulose produced by acetic acid bacteria is purified, and fine fibers disintegrated are deposited on the surface or inside of deteriorated paper material in a state of being suspended in water to form a bond with the material. And a method of reinforcing deteriorated paper.