JPH09118856A - Production of baked pencil lead - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject product high in mechanical strength, good in writing smoothness, and esp. useful e.g. as a mechanical pencil lead, by using a chlorovinyl resin having reactive functional group as a binder for the product. SOLUTION: This baked pencil lead is obtained by kneading, molding and heat treatment, etc., of the major material composed of a reactive functional group-bearing chlorovinyl resin as a binder and a matrix (e.g. graphite, carbon black), and successively followed by appropriately impregnating the resultant sintered compact with e.g. oil-and-fat. Use of a chlorovinyl resin bearing plural reactive groups such as sulfone group, hydroxyl group and epoxy group as the above reactive functional group-bearing chlorovinyl resin develops diversified reaction/crosslinking systems to effect further increase in the mechanical strength of this pencil lead, therefore being preferable. The amount of the reactive functional group-bearing chlorovinyl resin to be used pref. accounts for 50-100wt.% of the whole amount of the binder to be incorporated in the matrix. The chlorovinyl resin is e.g. a vinyl chloride resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a fired pencil lead, and more particularly to a method for producing a fired pencil lead, such as a mechanical pencil lead, which has excellent strength and good writing quality.

[0002]

2. Description of the Related Art A conventional burned pencil lead is prepared by mixing, kneading and molding an inorganic substance such as graphite, boron nitride, talc, mica, carbon black and the like, clay and water as a surfactant and a plasticizer. A clay type produced by heat-treating at high temperature to obtain a sintered body and impregnating the sintered body with various fats and oils, and the above inorganic substance and natural or synthetic resin or pitch such as asphalt The binder, and if necessary, a solvent and / or a plasticizer, a lubricant, etc. are added, and these are mixed, kneaded, molded, and then heat-treated at a high temperature to carbonize the resin and the like, and the carbon is a binder. The sintered body is roughly classified into a carbon type in which various oils and fats are impregnated in the pores.

Basically, the clay type burned pencil lead is mainly used for the wood axis pencil and the carbon type burned pencil lead is used for the mechanical pencil because of its practical strength and cost. In the case of a carbon-type baked pencil lead, that is, a lead for a mechanical pencil, various coupling agents, etc. have been used as one of the means for improving the strength of the core body in order to enhance the adhesive force between the extender and the binder. Modify the surface characteristics of the body material by using the surface treatment agent of
A method of improving the adhesiveness with a resin as a binder to improve the strength of the core, or modifying the resin with a silane coupling agent to prepare a compound containing silicon in the core, A method for improving the strength of is generally known.

For example, the method disclosed in Japanese Patent Laid-Open No. 63-156873 is related to a carbon material such as graphite or carbon black in which an aluminate coupling agent effective for surface modification is added to a compounding composition. This is a method of addition, in which the strength and concentration of the pencil lead using the carbon material are improved by coating the surface of the carbon material as a coloring material with an aluminate coupling agent in advance. However, this method requires a step of coating the surface of the material with the coupling agent,
There is a problem in that the cost becomes high.

In the method disclosed in Japanese Patent Publication No. 64-7632, the resin is modified by compounding a silane coupling agent with the resin to prepare a compound containing silicon in the core, It is an improvement in the strength of the body. However, this method has a problem in that the strength of the core is improved but the writing quality is extremely deteriorated.

[0006]

DISCLOSURE OF THE INVENTION The present invention is stronger than a pencil core made of natural or synthetic resin or pitches such as asphalt which has been conventionally used as a binder for a carbon type baked pencil core. It is an object of the present invention to provide a method for producing a baked pencil lead that is excellent and has a good writing quality.

[0007]

Means for Solving the Problems As a result of earnest research to solve the above-mentioned conventional problems, the present inventor has conducted kneading, molding, heat treatment, etc. on the materials mainly composed of an extender and a binder. The sintered body obtained by applying, by using a chlorine-containing vinyl resin containing a specific functional group in a part or all of the binder, in producing a fired pencil lead by appropriately impregnating fats and oils,
It has been found that a fired pencil lead, which is superior in strength to a pencil lead made of natural or synthetic resin or pitches such as asphalt, which has been conventionally used as a binder, and has good writing quality, is obtained. Has been completed.

That is, in the method for producing a fired pencil lead of the present invention, a sintered body obtained by subjecting a body mainly composed of an extender and a binder to kneading, molding, heat treatment, etc., is appropriately greased. When impregnated to produce a baked pencil lead, a chlorine-containing vinyl resin containing a reactive functional group in a part or all of the binder is used. The "chlorine-containing vinyl resin" defined in the present invention means a vinyl resin containing chlorine, specifically, a vinyl chloride resin, a chlorinated vinyl chloride resin, a copolymer mainly composed of vinyl chloride (for example, , Vinyl chloride-vinyl acetate copolymer, etc.), vinylidene chloride resin, etc.

The reason why the strength and writing quality of the pencil lead are improved by using the chlorine-containing vinyl resin containing a reactive functional group according to the present invention as a part or all of the binder is presumed as follows. . (1) Since the resin contains a reactive functional group, various reaction and cross-linking systems occur with the functional group on the powder surface of the extender, increasing the adhesive strength, resulting in a pencil lead. The intensity of. (2) Since the resin contains a reactive functional group, the dispersibility with the extender is improved, the orientation of the pencil core structure during extrusion is improved, and a normal chlorine-containing vinyl resin is used. The pencil core structure has a denser structure than when used, and the strength of the pencil core increases.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the method for producing a baked pencil lead of the present invention will be described. The chlorine-containing vinyl resin containing a reactive functional group used in the present invention is used as part or all of a binder for a baked pencil lead. Examples of the reactive functional group include a hydroxyl group, an epoxy group, a carboxyl group, and the like, and examples of the chlorine-containing vinyl resin containing a reactive functional group include a vinyl resin containing chlorine as a main component. A resin whose reactive functional group is composed of a sulfone group, a hydroxyl group, an epoxy group, or the like, or a vinyl resin containing chlorine as a main component, which contains vinyl acetate and whose reactive functional group is a carboxyl group (of maleic anhydride). Present in the form) and the like. It is sufficient that at least one of the above various reactive functional groups is contained in the vinyl resin containing chlorine as a main component, and a plurality of reactive functional groups such as a sulfone group, a hydroxyl group and an epoxy group are contained. If it is a chlorinated vinyl resin, as described above, various functional groups on the powder surface of the extender and various reaction / crosslinking systems will occur.
As a result, the strength of the pencil lead can be further increased.

Examples of the extender used in the present invention include natural or artificial graphite, boron nitride, talc, mica, carbon black and the like, which may be used alone or in combination of two or more kinds. You can

In addition, a chlorine-containing vinyl resin containing a reactive functional group such as a sulfone group, a hydroxyl group or a carboxyl group can be used alone as a binder to be used in the present invention. Further, pitches such as natural and synthetic resins or asphalt, which are conventionally known as binders, may be used alone or in combination with two or more kinds in combination with the chlorine-containing vinyl resin containing the reactive functional group. . The amount of the chlorine-containing vinyl resin containing the reactive functional group is 1 with respect to the total amount of the binder.
It is 0 to 100% by weight, preferably 50 to 100% by weight. If the blending amount of the above chlorine-containing vinyl resin is less than 10% by weight based on the entire blending amount of the binder, the effect of increasing the strength due to the reactive functional group is not exhibited, which is not preferable.

In addition, water (purified water), dioctyl phthalate, for the purpose of improving the dispersibility during kneading by applying high shearing force and / or improving the fluidity and moldability during extrusion molding,
At least one plasticizer or solvent such as dibutyl phthalate, tricresyl phosphate, dioctyl adipate, diallyl isophthalate, propylene carbonate, alcohols, ketones, esters and the like can be added as necessary.

In the method for producing a baked pencil lead of the present invention, a blended composition comprising the above-mentioned extender, binder, and optionally solvent and / or plasticizer is thoroughly mixed and kneaded together. , For example, mix and disperse with a Henschel mixer,
It is manufactured by kneading with a pressure kneader, two rolls, etc., extrusion-molding into a thin wire, heating and drying in air, and then heating and firing at about 1000 ° C. in a non-oxidizing atmosphere.
In addition, for the purpose of further improving the writing quality, the pencil lead after firing may be appropriately impregnated with oil or the like.

[0015]

The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

(Example 1) Natural scaly graphite 50 parts by weight Vinyl chloride resin containing a reactive functional group (giving a sulfone group, a hydroxyl group and an epoxy group) 50 parts by weight Dioctyl phthalate 20 parts by weight Zinc stearate 2 Parts by weight The chlorine-containing vinyl resin containing a functional group reactive with the above graphite and the other above-mentioned compounded composition are sufficiently mixed and kneaded, extruded into a thin wire, and dried by heating in air, and then non-oxidized. A core body obtained by heating and firing to about 1000 ° C. in a neutral atmosphere was impregnated with spindle oil to obtain a pencil lead having a core diameter of 0.57 mm.

(Example 2) The vinyl chloride resin (provided with a sulfone group, a hydroxyl group and an epoxy group) used in Example 1 was applied in the form of a vinyl chloride-vinyl acetate copolymer (provided with a carboxyl group: maleic anhydride). And a core diameter of 0.5.
A 7 mm pencil lead was obtained.

(Example 3) A core was prepared in the same manner as in Example 1 except that the natural flake graphite used in Example 1 was changed to boron nitride [produced by Shin-Etsu Chemical Co., Ltd .: average particle diameter of about 2 μm]. A pencil lead having a diameter of 0.57 mm was obtained.

(Example 4) The vinyl chloride resin (provided with a sulfone group, a hydroxyl group and an epoxy group) used in Example 3 was applied in the form of a vinyl chloride-vinyl acetate copolymer (provided with a carboxyl group: maleic anhydride). 0.57 mm in the same manner as in Example 3 except that the carboxyl group is changed to
Got a pencil lead.

(Comparative Example 1) A pencil lead having a core diameter of 0.57 mm was prepared in the same manner as in Example 1 except that the vinyl chloride resin used in Example 1 was replaced with one having no reactive functional group. Obtained.

Comparative Example 2 The vinyl chloride resin having no reactive functional group used in Comparative Example 1 was previously treated with 20 parts by weight of a silane coupling agent [Shin-Etsu Chemical Co., Ltd .: KBM-603]. , Core diameter 0.57 in the same manner as in Comparative Example 1
I got a pencil lead of mm.

Comparative Example 3 A pencil lead having a core diameter of 0.57 mm was obtained in the same manner as in Comparative Example 1 except that the natural flake graphite used in Comparative Example 1 was used instead of the boron nitride of Example 3. It was

The pencil leads obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were subjected to a strength test (bending strength), a writing test (concentration, abrasion degree) and a writing sensory test. The results of these tests are shown in Table 1 below. In addition, the values of the concentration and the abrasion degree in the bending strength test and the writing test were based on the JIS S6005 test method.

[0024]

[Table 1]

(Discussion of Table 1) The first and second embodiments are
A pencil lead (graphite core) obtained by using a natural scaly graphite as an extender and a chlorine-containing vinyl resin containing various reactive functional groups as a binder. Compared with a pencil lead (graphite core) obtained using vinyl resin, a pencil lead using a resin containing a reactive functional group has improved bending strength and writing quality is comparable. There was found. Comparative Example 2 is a pencil lead (graphite core) obtained by modifying an ordinary chlorine-containing vinyl resin as a binder with a silane coupling agent, but a compound containing silicon is formed in the pencil lead structure. In addition, the bending strength of the pencil lead increases, but on the other hand, there is a feeling that the paper surface is scratched for writing.
It turned out to be a very discomforting pencil lead. In addition, Example 3 and Example 4 are pencil cores (BN core) using boron nitride as an extender, and the quality is measured in the same manner as in Example 1 and Example 2, but Comparative Example 3 It was found that the use of a chlorine-containing vinyl resin containing a functional group that is more reactive than the pencil lead (BN core) using the usual chlorine-containing vinyl resin improves bending strength and improves writing quality. .

[0026]

EFFECTS OF THE INVENTION According to the present invention, the reactive functional group provided in the chlorine-containing vinyl resin has the effect of contributing to the adhesion with the extender to improve the strength of the core, and with respect to the writing quality. It is possible to obtain an ideal method for producing a baked pencil lead that is comparable to the above.

Claims (1)

[Claims] 1. A material mainly composed of an extender and a binder,
Chlorine-containing vinyl containing a reactive functional group in a part or all of the binder when a sintered pencil obtained by kneading, molding, heat treatment, etc. is appropriately impregnated with oils and fats to produce a baked pencil lead. A method for producing a baked pencil lead, which comprises using a resin.