JPS62268898A - Conductive paper 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 (Industrial Field of Application) The present invention is a high-strength conductive paper containing conductive fibers and used for antistatic wrapping paper, semiconductor paper for cables, surface heating element-011 recording paper, etc. and its manufacturing method.

(Prior art and problems to be solved by the invention) Conventionally, conductive paper has been used as a conductive paper. Paper made by mixing mm with other paper materials has good electrical conductivity, and compared to the method of mixing other conductive substances, such as carbon pigments, there is no pollution of papermaking equipment or wastewater, etc. The above advantages are great, and it is also used because it does not cause high costs such as expensive conductive substances being handled during the papermaking process or being lost during papermaking (it is also economically advantageous). However, there are many fields in which conductive paper is used in fields that require excellent paper strength, and in order to maintain paper-making properties while maintaining conductivity, and to achieve high paper strength, contradictory measures must be taken. Therefore, conductive fibers are generally expensive, and conductive paper using such fibers is also expensive.Conductive paper Although it has excellent properties, it is said to be sluggish because of the problems mentioned above.

As a prior art, for example, Japanese Patent Publication No. 45-32766 proposes a conductive paper made by mixing carbon fiber with natural pulp. The technology described in the publication is that carbon fibers are
Since it is naturally highly hydrophobic and has a high specific gravity, it has poor dispersibility in water and is unevenly distributed in a sheet of paper, impairing conductivity and reducing commercial value. In order to solve this problem, natural pulp is used, and at the same time, natural pulp is used to increase paper strength. However, although this technology improves paper-making properties, it cannot be used in fields where high paper strength is required for processing or use, such as semiconductor paper for cables and anti-static wrapping paper. It is insufficient.

In general, it is possible to improve paper strength by mixing conductive fibers with other paper materials such as chemical fibers or synthetic fibers and binders (i). On the other hand, if the mixing ratio of conductive fibers is increased, conductivity can be ensured, but
Conductive fibers that are poor in self-adhesion, entanglement, and adhesion with a binder reduce paper strength, and the conductive fibers are expensive, so the resulting conductive paper cannot help but be expensive.

(Preliminary Means to Solve the Problems) The present invention eliminates these conventional drawbacks and provides an inexpensive conductive paper that has excellent conductivity and high paper strength, and a method for manufacturing the same.

The conductive paper according to the present invention is composed of 5 to 30% by weight of conductive fibers and 10 to 60% by weight of synthetic fibers, chemical fibers, and natural fibers, each singly or in a mixture, and these fibers are comprised of 5 to 30% by weight of synthetic fibers, chemical fibers, and natural fibers. It is characterized by the fact that the binder is adhesive and fixed, and its manufacturing method involves wet-processing the mixed paper stock so that the composition in the paper matches the ratio of the conductive fibers and binder, etc., then drying it and heating it further if necessary. It is characterized by:

As the conductive fibers used in the present invention (Yoripon fiber,
Any conductive fibers such as synthetic fibers, plated fibers, and metal fibers containing conductive substances such as carbon particles, tin oxide, or metal powders can be used, but any fiber with excellent conductivity can be used. When obtaining paper, it is desirable that its volume resistivity be 10 7 Ω·a or less. Among these, preferred are carbon fibers obtained by carbonizing pitch-based carbon fibers and polyacrylonitrile-based synthetic fibers, which have excellent electrical conductivity, are relatively inexpensive, and have little change in electrical conductivity due to mechanical treatments such as stirring during paper making.

The inventors of the present invention believe that the fineness and fiber length of these conductive fibers are important in simultaneously satisfying the conductivity, paper strength, and paper-making properties of conductive paper, and as a result of intensive research, they found that the diameter of the conductive fibers (with a circular cross section) We have found that there is an optimal range for the aspect ratio, defined as the ratio of the fiber length (if not the diameter of a circle with equivalent cross-sectional area) and the fiber length.

That is, an appropriate aspect ratio is 250 to 2,000, more preferably 750 to 1,500.

If it is less than 250, the chances of the conductive fibers coming into contact with each other in the paper will be reduced and the conductivity will be inhibited, and if it is more than 2000, the conductive fibers will easily get entangled with each other during paper making (and the conductive fibers will be unevenly distributed in the paper). As a result, not only the conductivity deteriorates, but also the entanglement of the chemical fibers, synthetic fibers, or natural fibers with the conductive fibers causes the paper to become disordered, resulting in a decrease in paper strength, which further deteriorates the appearance and reduces the commercial value. descend.

The mixing ratio of 4-den fiber is 5 within the above aspect ratio range.
30W% is appropriate, more preferably fjlo~
It is 20% by weight. If the paper is less than 5M%, high paper strength and paper-making properties can be obtained easily, but the conductivity is suddenly lost and the resulting paper cannot function as a conductive paper in practice. 30 again!
If it exceeds ffi%, as mentioned above, the paper strength is significantly reduced.

As described above, the present invention is useful! [The fiber mixing ratio 1i is in an unprecedentedly low range, but this is in order to maintain the paper strength of the conductive paper at a high level, along with the mixing ratio and combination of chemical fibers, synthetic fibers, or natural fibers, and binders, which will be described later. This is a necessary condition.

However, in order to ensure excellent conductivity with such a low mixing ratio of conductive fibers, the conditions that must be met are the above-mentioned restrictions on the aspect ratio of the conductive Wl fibers.

That is, only by using the appropriate aspect ratio, excellent np conductivity can be ensured despite the above-mentioned low mixing ratio.

Further, the conductive paper of the present invention having such a low mixing ratio is low in cost and is economically superior.

Next, the chemical fibers, synthetic am-natural fibers (hereinafter these m fibers will be referred to as main fibers), and binders used in the present invention will be described.

The main fiber is not particularly limited and can be used as long as it is not used in ordinary paper making, but in order to obtain high paper strength, strong fibers such as synthetic fibers such as polyester and polyvinyl alcohol are used. , natural fibers such as cellulose-based chemical fibers, hemp, and tripole are preferable.

Furthermore, the combination of the main fiber and the binder is important in obtaining high paper strength, and there are suitable combinations.

For example, a hydrophilic binder such as a polyvinyl alcohol-based fibrous binder is used for hydrophilic main fibers such as polyvinyl alcohol-based synthetic fibers, cellulose-based chemical fibers, and hemp; For the hydrophobic main fiber, a hydrophobic binder such as a polyester fibrous binder or a composite fiber having a polyolefin polymer on the surface layer side is suitable.

In other words, the main fiber and the binder each have similar characteristics, and by selecting a combination with high affinity for each other,
It is possible to obtain high paper strength by strengthening the adhesion and fixation between the main fibers. The most preferred combination is a hydrophilic main fiber and a polyvinyl alcohol-based fibrous binder.

If the main fiber and binder are hydrophobic such as polyester synthetic fibers or polyolefin synthetic fibers, and there are problems with paper-making properties such as dispersibility in water or poor texture, mix natural or synthetic pulp into the paper. It can be resolved by doing this. However, in this case, the addition rate of natural or synthetic pulp is preferably as low as possible within a range not exceeding 50% in order to ensure paper strength.

As mentioned above, the present invention aims to solve the conflicting characteristics of conductivity, paper strength, paper making properties, and cost in conductive paper using conductive fibers by adjusting the aspect ratio of the conductive fibers and the main fibers and binder. This is an excellent method that ensures a high standard by selecting a combination.

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

Example 1 and Comparative Example 1 The conductive fiber was made of pitch-based carbon with a fiber diameter of 15 μml and a fiber length of 12 mm, that is, an aspect ratio of 800, pitch carbon 5 au (volume specific resistance value of 2.1 x 10-2 Ω cm), and a main fiber with a fineness of 1.5 denier and a fiber length. 5- polyvinyl alcohol synthetic 1m fiber, fineness 10 denier, fiber length 3T
r! ! A paper stock was prepared by mixing 20% by weight of a polyvinyl alcohol-based fibrous binder of No. A conductive paper was obtained.

Example 1 and Comparative Example 1 were prepared by changing the mixing ratio of carbon fiber and main fiber as shown in Table 1. The physical properties of the conductive paper obtained in this manner are also shown in Table 1.

Example 2 and Comparative Example 2 10% by weight of carbon fiber (volume resistivity 1.6 x 10-2 Ω-Crn) with a fiber diameter of 8 μ obtained by carbonizing polyacrylonitrile synthetic fiber as a conductive fiber. 75% by weight of the polyvinyl alcohol-based synthetic fiber shown in Example 1 as the main fiber and 15% by weight of the same polyvinyl alcohol-based fibrous binder shown in Example 1 were mixed to prepare a paper stock, and the paper material was prepared by the method shown in Example 1. Paper is made and dried for 30
A conductive paper of y/d was obtained.

The fiber length and aspect ratio of the carbon fibers are as shown in Table 2 (changed to Example 2 and Comparative Example 2).The physical properties of the conductive paper obtained are also shown in Table 2.

Table 1 As is clear from Tables 1 and 2, the conductive paper of the present invention has both superior conductivity and high paper strength compared to the conductive paper of the comparative example. The poor formation observed in Comparative Example 2 indicates entanglement between the conductive fibers or the conductive wam and the polyvinyl alcohol synthetic fibers, and the product has no commercial value in terms of appearance.

The paper strength shown in Table-1 and Table-2 is JIS P-8113.
The volume resistivity was measured using a Wheatstone bridge.

(Effects of the Invention) As detailed above, the conductive paper 1 according to the present invention has both superior conductivity and high paper strength, and can be used for antistatic wrapping paper, semiconductor paper for cables, electrostatic recording paper, surface paper, etc. It is possible to obtain a low-cost conductive product while providing excellent workability and performance when used in a heating element.

Claims (8)

[Claims] (1) 5-30% by weight conductive fiber and 10-60% by weight
1. A conductive paper comprising synthetic fibers, chemical fibers, and natural fibers, each singly or in a mixture, and these fibers are adhesively fixed by 5 to 30% by weight of a binder. (2) The conductive paper according to claim 1, wherein the conductive fibers have an aspect ratio of 250 to 2,000. (3) The conductive paper according to claim 1 or 2, which contains not more than 50% by weight of natural and/or synthetic pulp. (4) The conductive paper according to any one of claims 1 to 3, wherein the synthetic fibers and chemical fibers are hydrophilic fibers, and the binder is a polyvinyl alcohol binder. (5) Paper stock is mixed so that the composition of the paper is 5 to 30% by weight of conductive fibers, 10 to 60% by weight of each of synthetic fibers, chemical fibers, and natural fibers alone or as a mixture, and 5 to 30% by weight of binders. A method for producing conductive paper, which comprises drying after wet papermaking and further heating if necessary. (6) The manufacturing method according to claim 5, wherein the conductive fiber has an aspect ratio of 250 to 2,000. (7) Not exceeding 50% by weight of natural and/or
The manufacturing method according to claim 5 or 6, which uses a paper stock mixed so as to contain synthetic pulp. (8) The manufacturing method according to any one of claims 5 to 7, wherein the synthetic fiber and chemical fiber are hydrophilic, and the binder is a polyvinyl alcohol-based fibrous binder.