JPH0447077B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for producing a chitosan-based paper product. The chitosan-based paper product obtained by the method of the present invention can be widely used in the same applications as cellulose-based pulp paper, especially as special paper such as separation membranes, medical materials, and food packaging paper, or as a material for bacteria such as yeast. It can be suitably used as a body fixation material. Also,
It can also be used as a microbially degradable sheet.

Prior Art Chitin is widely present in the cell walls of crustaceans such as shrimp and crabs, insects such as dragonflies and beetles, and fungi, and is produced in large quantities in nature, second only to cellulose. Its chemical structure is poly{β(1-
4)-2-acetamido-2-deoxyglucan}
It is expressed as D-glucose residue of cellulose.
It can also be considered a type of cellulose derivative in which the hydroxyl group at the C2 position is replaced with an acetamide group.

However, while cellulose is widely used in various fields, chitin is hardly used because chitin only dissolves in special solvents. It is also known that fibers and films can be formed from chitin solutions, but these fibers and films have limited applications due to economic reasons and technical issues, and cannot be used in a wide range of applications like ordinary paper. Not provided for any purpose.

When chitin is hydrolyzed with a concentrated sodium hydroxide solution, deacetylation occurs and chitosan is produced. Generally, chitosan has a degree of deacetylation of 70% or more. Chitosan does not dissolve in alkalis or common organic solvents, but it does dissolve in dilute acids.

Chitosan has chitosan properties because it contains amino groups, while cellulose shows anionic properties because of hydroxyl groups and residual carboxyl groups. For this reason,
Chitosan has a high affinity for cellulose, and has been used in paper to improve the surface strength and water resistance of paper. In this case, the amount of chitosan used is as small as 1% or less of the weight of the paper, and paper has been modified by applying a chitosan liquid to the surface of the paper.

By the way, there is a known method for producing chitosan fibers by dissolving chitosan in an acetic acid aqueous solution and extruding this solution into a coagulating liquid, stretching and winding the obtained filament, and then cutting it into lengths of several mm. (Unexamined Japanese Patent Publication No. 1983)
-26049 Publication), the strength of chitosan fibers is weak, which causes various difficulties during spinning, and cutting chitosan fibers requires a large amount of energy, and the strength of paper using chitosan fibers alone is low. However, because paper making was difficult, it was necessary to add a large amount of a binder such as polyvinyl alcohol.

In addition, a method has also been proposed in which powdered chitosan is decomposed into water, passed through a high-pressure homogenizer to produce a chitosan suspension, and then the chitosan suspension is made into paper (Japanese Patent Laid-Open No. 59-84938 Publication No.).

However, this method requires special equipment called a high-pressure homogenizer, which increases production costs and requires harsh conditions such as applying high shear force at high temperatures. The disadvantage is that it involves cutting.

On the other hand, a method for producing a chitosan-based paper product has also been proposed, in which a chitosan suspension is prepared by adding an alkali metal hydroxide to a dilute acid aqueous solution of chitosan while stirring, and then the suspension is made into paper alone or together with pulp. Publication No. 63-59499).

However, this method requires high-speed stirring using a mixer, etc., so the chitosan becomes colloidal.
During papermaking, the wire mesh becomes clogged with fine particles.
It also had drawbacks such as difficulty in dehydration.

Problems to be Solved by the Invention The present invention overcomes these drawbacks in the production of conventional chitosan-based paper products and easily produces cationic chitosan-based paper products that have high strength and excellent water retention and water dispersibility. The purpose of this project was to provide an efficient method for manufacturing.

Means for Solving the Problems As a result of various studies conducted by the present inventors to develop a method for producing a chitosan-based paper product having the above-mentioned excellent properties, the present inventors have developed a cellulose-based pulp containing a predetermined amount of chitosan salt. The inventors have discovered that the objective can be achieved by adding an alkaline solution to the suspension while stirring at high speed to precipitate chitosan, followed by papermaking, and have completed the present invention based on this knowledge.

That is, in the present invention, an alkaline solution is added to a cellulosic pulp suspension containing at least 1% by weight of chitosan salt based on dry weight while stirring at high speed to precipitate chitosan, and this suspension is directly mixed. The present invention provides a method for producing a chitosan-based paper product, which is characterized in that the paper product is produced after being subjected to a disaggregation treatment or a disintegration treatment.

The present invention will be explained in detail below.

The cellulose pulp used in the present invention includes:
Ordinary cellulose pulp obtained from wood or non-wood is common, and in particular, the beaten pulp is made of branched fibers with good water retention and dispersibility, and when dried, the branched pulps bond together. It is preferably used because it intertwines to give a sheet-like material with high strength.

Examples of the chitosan used in the present invention include commercially available chitin or chitosan with a degree of deacetylation of 70% or more obtained by deacetylating chitin collected from shrimp shells, crab shells, etc. by a conventional method, and chitosan with a degree of deacetylation of 70% or more. Examples include low-molecular chitosan obtained by the action of mineral acids or oxidizing agents.

In the method of the present invention, chitosan is first dissolved in a cellulosic pulp suspension. This is usually done as follows.

Beaten or unbeaten cellulose pulp is suspended in water to a concentration of 0.01 to 10%, preferably 0.1 to 5%, and then added to a concentration of 1 to 900% by weight, preferably 10 to 5%, based on the cellulose pulp. Add chitosan to make it 400% by weight and stir using a regular stirrer. Stirring speed is usually 10~
The speed is 1500 rpm, preferably 60 to 1000 rpm, and is adjusted depending on the viscosity of the chitosan. A solvent such as acetic acid is added to the dispersion thus obtained. Examples of solvents for dissolving chitosans include organic acids such as formic acid and acetic acid, and aqueous solutions such as hydrochloric acid. The solvent concentration in the system, for example in the case of acetic acid, is preferably
When the amount is 0.5% or more, chitosan becomes chitosan acetate, dissolves, and becomes mucus.

Next, while stirring the resulting dispersion at high speed, an alkaline solution is added continuously or intermittently to raise the pH of the dispersion to 7 or more. This alkaline solution acts as a coagulant and coats the surface of the pulp with chitosan. At the same time, unexpectedly, a pulpy chitosan with branched fiber length of 1 mm or more is produced, similar to beaten cellulose pulp, and no colloidal chitosan, which normally passes through a 200-mesh wire mesh, is produced. When the dispersion containing cellulose pulp and pulpy chitosan thus obtained is made into paper according to a conventional method, for example, the JISP8209 method, it is easy to produce a chitosan-based paper product with good texture and excellent strength properties and high density. can be obtained.

As the alkali used in the above-mentioned alkaline solution, sodium hydroxide, calcium hydroxide, amines such as ethylenediamine, etc. are usually used, and as a suitable alkaline solution, an aqueous alkali solution or an alkaline methanol solution is used.

Effects of the Invention According to the method of the present invention, the dispersion liquid consisting of cellulose pulp and pulpy chitosan does not contain colloidal substances, and a normal paper-making method can be applied.

The chitosan-based paper product, which is a paper stock made of cellulose pulp and pulp-like chitosan obtained by the method of the present invention, is composed of branched fibers like beaten cellulose pulp, has high strength, high density, and water retention. It has high strength and water resistance, good water dispersibility, and becomes film-like as the concentration of chitosan increases, improving tear strength, so it can be widely used in the same applications as cellulose pulp.

In addition, the chitosan-based paper product of the present invention exhibits cationic properties compared to cellulose-based pulp, which exhibits anionic properties, which makes it possible to produce high-density paper. It can be used for body immobilization carriers, microbially degradable sheets, etc.

EXAMPLES Next, the present invention will be explained in more detail with reference to Examples.

Example 1 2.4 g of beaten pulp NBKP (csf 400 ml) was collected in terms of absolute dry weight, placed in 1 part of water, and thoroughly disintegrated. Next, 2.4 g of chitosan having a degree of deacetylation of 100% (viscosity of 0.5% chitosan-0.5% acetic acid aqueous solution is 385 cp/20°C) was added to form a dispersion containing pulp and chitosan. When 5 g of acetic acid was added to this and stirred for 1 hour, chitosan acetate was produced and a viscous solution was formed. Set the rotation speed of the stirrer to 800 rpm, and drop a 5% aqueous sodium hydroxide solution intermittently until the pH reaches 9.
Pulp-like chitosan with an average fiber length of 1 mm or more was precipitated. The fibers were put into a 200 mesh sieve, thoroughly washed with water, and made into paper according to the JIS method. Note that no colloidal substances passed through the sieve during washing with water. The resulting paper has a thickness of 0.08 mm and a density of 0.93
g/ ^cm3 , the rupture length is 4.15Km, and the specific rupture strength is
It was 3.64. This paper was water resistant and had practically satisfactory strength. It was also found that colloidal substances in white water, which is papermaking wastewater, were significantly reduced.

Example 2 Paper-making was carried out in the same manner as in Example 1, except that 10% by weight of chitosan was added to the pulp. The obtained paper has a thickness of 0.10 mm, a density of 0.60 g/ ^cm2 , and a tear length of
The distance was 4.00km, and the relative strength was 3.37.

Example 3 Paper-making was carried out in the same manner as in Example 1, except that 43% by weight of chitosan was added to the pulp. The obtained paper has a thickness of 0.073 mm, a density of 0.87/ ^cm2 , and a tear length of
6.14km, and the specific bursting strength was 4.10.

Example 4 A sample was prepared in the same manner as in Example 1, except that 400% by weight of chitosan was added to the pulp.
The obtained sample was in the form of a gel, but by applying it to a pulp disintegrator, it became pulp-like and could be made into paper. In this case too, the production of colloidal chitosan was very small. The obtained paper was in the form of a film, with a thickness of 0.063 mm and a density of 0.97 g/cm ² .
The fracture length was 2.24 km, and the specific burst strength was 2.10. The tear strength was also high enough for practical use.

Claims (1)

[Claims] 1. A cellulosic pulp suspension containing at least 1% by weight, based on dry weight, of chitosan salts,
A method for producing a chitosan-based paper product, which comprises adding an alkaline solution to precipitate chitosan while stirring at high speed, and producing a paper from this suspension either as it is or after disintegration treatment.