JPS6183400A - Magnetic cellulosic material and its production - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic cellulosic material and a method for producing the same.

[Industrial application field]

In recent years, digital devices, electronic devices, and ICs have become popular.

With the spread of sophisticated electronic components such as LSI, electromagnetic interference and magnetic interference have become a problem, and electromagnetic shielding, electric plate absorption,
The need for magnetic shielding, etc. is increasing.

The present invention provides a magnetic cellulose-based material that is flexible, lightweight, and highly moldable and suitable for use as an electromagnetic wave shielding material, a radio wave absorbing material, a magnetic shielding material, and other magnetic materials, and a method for producing the same.

[Conventional technology]

Conventionally, the method of imparting magnetism to cellulose-based materials has been to first manufacture a powdered magnetic substance such as a magnetic metal or magnetic oxide, and then use this as a binder to disperse it in a bath liquid and apply a magnetic coating. A method is used in which it is made into a liquid and applied to cellulose-based materials.

However, this coating method requires a long time to operate in order to homogeneously disperse magnetic particles in a resin as a binder when preparing a coating liquid.

In addition, several coating steps are required when coating cellulose-based materials, and in this case, only the surface layer of the cellulose-based material has magnetism.

[Problem that the invention seeks to solve]

The purpose of the present invention is to improve the drawbacks of magnetic cellulose materials obtained by the above-mentioned techniques, and to make use of the characteristics of cellulose materials, such as hydrophilicity and porousness, to make them economical and easy to operate. Specifically, the aim is to obtain a cellulose-based material that is flexible, lightweight, has excellent moldability, and has a high magnetic effect.

That is, (1) without using synthetic resin-based or natural binders, (2) making cellulose-based materials and magnetic substances adhere well, and (3) economically obtaining magnetic cellulose-based materials with excellent magnetic properties. This is the entire purpose.

[Means for solving problems]

The present inventors have discovered that the desired magnetic cellulose material can be obtained by fixing particles of a magnetic substance to a cellulose material or a cellulose material that has been activated in advance, and has achieved the present invention.

That is, the first invention of the present invention is a magnetic cellulose material on which particles of a magnetic substance are fixed. Also,
The second invention is to fix particles of a magnetic substance using a flocculant from a cellulose-based material or a cellulose thread material that has been activated in advance and containing a uniform dispersion of particles of a magnetic substance. This is a method for producing a magnetic cellulose material. This material is of course magnetic, but it has a much lower specific gravity than single metal or metal oxide materials, and can be easily produced into powder, fiber, or sheet magnetic materials, and has good moldability. has.

The magnetic cellulose-based material of the present invention can change the constant N of the magnetic substance from 1 to several hundreds of pounds with respect to cellulose, and is uniformly constant, so it can be used as a magnetic shielding material, an electromagnetic shielding material, etc. As a result, it exhibits superior performance compared to conventional products on the market.

1. Powder 1, fibrous, sheet-like material is obtained in weight and weight, and an excellent magnetic layer is obtained. Magnetism - metal. One-half forestry material - one piece of wood? -Type 4-Low weight of crab--One flexibility → Hitomi Ryo・
[Koiso - Molding - Seiichi] Steller's sea lion ↓. (By combining it with other materials such as plastics and other cellulosic materials, economical and lightweight magnetic materials can be easily obtained.)

In the present invention, particles having a structure similar to the magnetic substance particles are preferably used.

Examples of magnetic metal particles include particles of iron, nickel, cobalt, and their alloys, as well as those with a thin anti-oxidation film formed on their surface to an extent that does not reduce magnetism to improve stability such as preventing oxidation. It will be done. Examples of magnetic metal oxides include chromium oxide, iron oxide, and various ferrites.

The form of the magnetic particles is not particularly limited. The particle size is
Although not particularly limited, it is desirable that the thickness be 100μ or less, preferably 50μ or less.

The magnetic cellulose-based material of the present invention is a slurry made of a cellulose-based material and the above-mentioned magnetic particles dispersed therein.
f. Obtained by flocculating with a flocculant and fixing the magnetic material IR on the surface of the cellulose material.

Examples of the dispersion treatment of the magnetic substance include surface treatment with a surfactant or the like.

Examples of surfactants include fatty acid salts, higher alcohol sulfate ester salts, liquid fatty oil sulfate ester salts, aliphatic amine and aliphatic amide sulfates, aliphatic alcohol phosphate ester salts, and dibasic fatty acid ester sulfone salts. , fatty acid amide sulfonates, alkylaryl sulfonates, formalin-condensed naphthalene sulfonates, other anionic activators, etc., aliphatic amine salts, quaternary ammonium salts, alkylpyridium salts, and other cationic activators. etc., polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenol ethers, polyoxyethylene alkyl esters, sorbitan alkyl esters, polyoxyethylene sorbitan alkyl esters, other nonionic surfactants, alkylamino acids, etc. Examples include amphoteric surfactants. Moreover, not only one type of surfactant but also a combination of multiple types can be used. Furthermore, it is also effective to perform heating during dispersion treatment using a surfactant or the like. A ρU adjuster or the like can also be used if necessary.

Several tens of grams of surfactant is added to the magnetic material and dispersed. The appropriate type and amount of surfactant to be added are as follows:
It varies depending on the type and size of the magnetic particles9, but is not particularly limited. For example, F with an average particle size of 0.1μ or less
e, 0. If sodium oleate is used to disperse
It is about %. In addition, when Fe3O4 and oleic sodium bath solution were mixed, several tens of
When heated for a minute, Fe50 of sodium oleate
．． Adsorption to the surface is promoted and the dispersion effect can be enhanced. For example, when manganese zinc ferrite with an average particle size of 1.5μ is dispersed, linol enemy sodium 't-15wt96,
When 10 wt% of polyoxyethylene nonylphenyl ether f having an HLB of 12 or more is added and thoroughly stirred, a uniform dispersion of manganese zinc ferrite is obtained.

In some cases, the magnetic substance is minute or lightweight, and when it is mixed into a slurry with a cellulose-based material, the magnetic substance can In cases where the particles do not easily settle, the above-mentioned surface treatment is not necessarily necessary.

Examples of flocculants include salts of divalent or higher-valent metals, such as aluminum sulfate, mitten, calcium chloride, ferric iron, and magnesium chloride, and water-bath polymer compounds, such as polyethyleneimine, polyacrylamide, acrylamide, and dimethyl. Examples include ammonium chloride, seratin, starch, various modified products thereof, latex, and the like. The type and amount of flocculant added vary depending on the type and amount of dispersant such as surfactant used, and are not particularly limited, but usually it is applied until the magnetic substance is sufficiently fixed to the cellulose material. added. The method of adding the flocculant is not particularly limited either, and the flocculant can be added either before or at the edge of the magnetic material dispersed in the cellulose material, and can be added continuously or discontinuously. A pn adjuster or the like may be used if necessary.

For example, when fixing F~04 treated with sodium oleate to a cellulose material, the amount of flocculant added is 2 wt% with respect to Fe3O4 for aluminum sulfate.
~3wtfb, about 1.5 for polyethyleneimine
Approximately wt* to 3 wt% is preferable.

Performing the operation of agglomerating and fixing a magnetic substance on a cellulose material in a magnetic field is effective in improving the magnetic properties of the resulting magnetic cellulose material.

A wide range of cellulosic materials can be used, from pure cellulose to lignocellulose, but in sheet form, paper, board, cotton cloth, etc., and in fibrous form, from white pulp to raw material. Water-absorbing pulps up to swimming pulp, cotton, regenerated cellulose cotton, etc., and powdered ones include microcrystalline cellulose, wood powder, cellulose-like polysaccharides (eg, starch), and the like.

These cellulosic materials are subjected to a fixing treatment for magnetic substances either as they are or after being activated in advance. Various methods can be considered as the activation treatment method in this case, and there is a method of increasing functional groups such as aldehyde groups in the material by oxidation treatment using various oxidizing agents, corona discharge treatment, etc.

Alternatively, examples include a method of attaching glyoxal, dialdehyde starch, formaldehyde resin compounds, etc. having aldehyde groups.

[Effect]

In the magnetic cellulose-based material of the present invention, the fixed magnetic substance adheres well to the material and does not fall off even when washed with water, etc., so that the dispersant or flocculant added during the manufacturing process may be removed. Substances that are undesirable when using this magnetic cellulose material can be removed by washing with water or the like. After washing with water and drying, a magnetic cellulose material with excellent weather resistance and abrasion resistance is obtained. This magnetic material is lightweight; for example, if it is in the form of a powder, it can be easily mixed with various resins to form a molded product, and if it is in the form of (lO) fibers, it can be easily made into a sheet by a known method. ,
A very uniform product can be produced. Furthermore, since it is flexible and has sufficient strength, it can be made into rough shapes.

Applications of the magnetic cellulose material of the present invention include radio wave absorbing materials, electromagnetic shielding materials, magnetic shielding materials, gaskets for various electronic devices, and other magnetic materials.

〔Example〕

EXAMPLES Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples.

Example 1 After stirring and pressing 1 ton of water with a homogenizer to dissolve 15 ml of sodium oleate, 10 of barium ferrite having an average particle size of 0.5 μm was gradually added and stirred for 30 minutes to form a dispersion. Add 3f of sodium dodecylbenzenesulfonate to this dispersion, heat it to 90°C, and continue stirring for an additional 30 minutes to obtain a uniform dispersion of barium ferrite.

The entire amount of this dispersion is added to a slurry of 100 tons of softwood bleached pulp beaten to a freeness of 300 dlC and stirred well. Next, polyethyleneimine is gradually added to the barium ferrite so that the agglomeration is 1" and the weight is 2.0, and almost all of the 5 barium ferrite is fixed to the pulp. After washing this barium ferrite-fixed pulp with water, it is made into paper to a paper size of 6097 m2 by a conventional method and dried at 105°C to obtain magnetic paper. The resulting magnetic paper has a barium ferrite adhesion rate of 10% compared to pulp.
0 weight JI#s, its magnetic properties are coercive force 12000e
The magnetic flux density was 25 emu/r.

Example 2 After adding and dissolving 20 tons of IJum (linoleic acid) while stirring 1 ton of water with a homogenizer, the average particle size was 1.
0μ cobalt-containing magnetite 50f? Add gradually to form a dispersion. This dispersion was heated to 90°C and further heated to 30°C.
Stirring is continued for a minute to obtain a homogeneous dispersion of cobalt-containing magnetite.

The entire amount of this dispersion is added to a 1.5-thi slurry of 50 f hardwood unbleached pulp that has been beaten to a freeness of 200 tILt, and stirred well. Next, when aluminum sulfate is added as a coagulant to the cobalt-containing magnetite so as to give a concentration of 3.5 times, almost all of the cobalt-containing magnetite is fixed to the pulp. After washing with water, this cobalt-containing magnetite-fixed pulp is made into paper to a paper size of 9 tsubo M (6097 m2) using a conventional method and dried at 105°C to obtain magnetic paper.

The obtained magnetic paper has a cobalt-containing magnetite adhesion rate of 100% of pulp, and its magnetic properties have a coercive force of 60%.
00e, and the saturation magnetic flux density was 25 emu/7.

Comparative Example 1 Magnetic paper was obtained in the same manner as in Example 1, except that the dispersion treatment with sodium oleate and sodium dodecylbenzenesulfonate was not performed. Only 40 inches of the added barium ferrite was fixed in the paper. The rest is
It fell off and was washed away during washing and paper making processes. On the other hand, in the above-mentioned method for producing magnetic paper, when /M additive was not added, only 3 t of the added barium ferrite was fixed in the paper.

The magnetic properties of the obtained magnetic paper are such that the adhesion rate of barium ferrite to the pulp is 40% by weight, and the coercive force is 6800 s.
, the saturation magnetic flux density ia emu/f , and the latter has an adhesion rate of 3
In weight %, coercive force 2300e, saturation magnetic flux density 3.
It was 3 emu/f.

Comparative Example 2 Magnetic paper was obtained in the same manner as in Example 2, except that the dispersion treatment with sodium linoleate was not performed. Only 50 pieces of the added cobalt-containing magnetite were fixed in the paper. The residue fell off and was washed away during washing and papermaking processes.

On the other hand, when no coagulant was used in the above method for producing magnetic paper, only the added cobalt-containing magnetite 7) 5 was fixed in the paper.

The magnetic properties of the obtained magnetic paper are as follows: the former has a cobalt-containing magnetite adhesion rate of 50 centimeters per bulb, and a coercive force of 45
00e, the saturation magnetic flux density was 16 emu/r, the latter had an adhesion rate of 5 fold i:chi, the coercive force was 3800 s, and the saturation magnetic flux density was 2.5 emu/l.

〔Effect of the invention〕

The results obtained in Example 1.2 and Comparative Example 1.2 above are summarized in Table 1.

Table 1 In the present invention, since almost the entire amount of magnetic substance can be fixed on the cellulose material, its fixed value can be easily controlled freely, and the characteristics of the magnetic substance used can be directly imparted to the cellulose thread material. In addition, it is possible to provide a magnetic cellulose-based material that is flexible, moldable, and has good magnetic effects through simple operations and economically.

Claims (2)

[Claims] (1) A magnetic cellulose material in which particles of a magnetic substance are fixed to a cellulose material. (2) The feature is that a cellulose material or a cellulose material that has been activated in advance is impregnated with a uniform dispersion of magnetic material particles, and then the magnetic material particles are fixed using a coagulant. A method for producing a magnetic cellulose material.