JPS644555B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a colored pencil lead, and more specifically, a so-called sintered body type lead is produced by extruding a kneaded product and then heat-treating it at a high temperature to obtain a sintered body. This invention relates to a method for producing colored pencil leads.

In recent years, as for heat treatment after extrusion molding, so-called sintered type products, which are heat treated to firing or sintering temperatures, are superior in strength to so-called raw core type products, which are simply dried or solidified. In view of the fact that sintered colored pencil leads can be obtained, various types of sintered colored pencil leads are being considered, but in order to obtain a product with a desired color tone, it is necessary to remove the carbonized components in the sintered body. Therefore, it is necessary to use an oxidizing atmosphere during the heat treatment process.

However, conventional treatment in an oxidizing atmosphere takes a long time to sufficiently remove the carbonized components present inside the sintered body, and if the treatment is carried out at high temperatures to complete the process in a short time, the sintered body may crack. It causes swelling and swelling, which is definitely not desirable.

On the other hand, if the material does not contain any organic components, treatment with an oxidizing atmosphere is not necessary.
On the other hand, the manufacturing process such as kneading, extrusion molding, and heat treatment is extremely limited, and
This also increases the variation in quality of the product, which does not lead to favorable results.

The present invention has been made in view of the above points,
The gist is as follows: A colored pencil lead made of at least an inorganic body material, an inorganic binder, and an organic excipient as main materials, kneaded, extruded, heat-treated to obtain a sintered body, and colored as appropriate. A method for producing a colored pencil lead is characterized in that a depolymerizable organic substance is used as an organic excipient.

The depolymerizable organic substances used in the present invention include polyethylene, polypropylene, polybutadiene,
Examples include polyisobutylene, polystyrene, nylon, polymethyl methacrylate, polyethyl methacrylate, poly-α-methylstyrene, polymetamethylstyrene, poly-α-deuterostyrene, natural rubber, butyl rubber, but especially polymethacrylic acid. Methyl is extremely preferred in that it does not require any heat treatment in an oxidizing atmosphere for colored pencil leads of any color.

These depolymerizable organic substances can be used alone or in combination of two or more, but since they function as excipients for extrusion molding, they are used in a softened, plasticized, or solution state. This imparts uniform dispersibility to the kneaded product and a filler to the extruded product. Therefore, kneading or extrusion molding under heating, a plasticizer, a solvent, etc. are used as necessary.

In addition, boron nitride, mica,
Talc, alumina, titanium oxide, heat-resistant pigments, etc. are exemplified as inorganic binders, and kaolin-based, montmorillonite-based, bentonite-based clays, zeolite, diatomaceous earth, activated clay, silica, aluminum phosphate, etc. are exemplified, respectively. species or two
Although these inorganic structural materials and inorganic binding materials are used in combination of more than one type, the same substance can be classified as both of the above from the viewpoint of whether or not it becomes the skeleton of a sintered body through heat treatment. There are also some.

Now, after the above-mentioned materials and appropriate stabilizers and the like are thoroughly kneaded using a triple roll, kneader, Henschel mixer, etc., the mixture is extruded into a thin wire shape. Here, the blending ratio between each material is not essentially limited, but usually the inorganic body material is about 25 to about 70% and the inorganic binder is about 10 to about 70% by weight.
%, depolymerizable organic matter as excipient is about 5 to about 60
It is used in terms of % (relative proportion among the above three).

Next, the extruded product is subjected to an appropriate drying process and then heat-treated to the sintering temperature. During this time, the depolymerized organic matter and the solvent used as necessary are placed in a heat treatment atmosphere such as an inert gas atmosphere, reducing atmosphere, or vacuum atmosphere. Most of them are removed without depending on the
Here, "almost" means that even though it is a depolymerized organic material, there are some that still have carbides. This is because a sintered body of (As mentioned above, in the case of polymethyl methacrylate, a white sintered body can be obtained without passing through an oxidizing atmosphere.) In any case, the carbonized component in the obtained sintered body is zero or almost zero. Therefore, there is no effect on colored pencil leads such as brown, and even if treatment in an oxidizing atmosphere is required, the treatment time is short and does not cause cracks in the sintered body.

The sintered body is further impregnated with ink, if necessary, to obtain a colored pencil lead. Ink impregnation is used here as a coloring method when no heat-resistant pigment is used, but it is a method that may be employed to improve color tone even when a heat-resistant pigment is used.

Examples will be described below, and "parts" simply refer to parts by weight.

<Example 1> (Red core) Boron nitride 40 parts Bentonite 30 parts Polymethyl methacrylate 20 parts Dioctyl phthalate (plasticizer) 10 parts Methyl ethyl ketone (solvent) 100 parts The above materials were heated and kneaded with three rolls, and after extrusion molding. The sintered body was thoroughly dried while raising the temperature to 300°C over 10 hours, and then heat-treated at 950°C for 1 hour in a nitrogen gas atmosphere to obtain a sintered body, which was impregnated with red stamp ink.

<Example 2> (Blue core) Boron nitride 40 parts Bentonite 20 parts Polymethyl methacrylate 15 parts Cerulean blue (pigment) 10 parts Dioctyl phthalate 15 parts Methyl ethyl ketone 100 parts The above materials were sintered in the same manner as in Example 1. ,
The obtained sintered body was impregnated with silicone oil.

<Example 3> (Green core) Boron nitride 30 parts Kaolin 30 parts Methyl methacrylate 20 parts Cobalt green (pigment) 10 parts Dioctyl phthalate 15 parts After kneading the above materials in a kneader, further heat kneading with three rolls and extrusion. After molding, it was thoroughly dried while heating to 350°C over 12 hours, and heat treated at 850°C for 2 hours in an argon gas atmosphere to obtain a sintered body, which was impregnated with spindle oil.

<Example 4> (Red core) A sintered body was obtained in the same manner as in Example 1 except that polymethyl methacrylate was replaced with polystyrene in the material of Example 1. The obtained sintered body was further heat-treated at 600° C. for 1 hour in an oxidizing atmosphere to whiten it, and was impregnated with red stamp ink.

<Example 5> (Brown core) The sintered body that had not been subjected to the treatment under the oxidizing atmosphere in Example 4 was impregnated with a brown water-based ink for writing instruments.

<Comparative Example 1> Boron nitride 40 parts Bentonite 30 parts Polyvinyl alcohol 15 parts Water 70 parts The above materials were heated and kneaded with three rolls, and when the appropriate moisture content was reached, extrusion molded, and then 110 parts
After drying for 12 hours at °C, under an argon gas atmosphere,
Heat treatment was performed at 900°C for 2 hours to obtain a sintered body.

The results obtained in each of the above Examples and Comparative Examples are as follows. First, the products obtained in each example were excellent in color tone, writing quality, etc., and had a strength of about 11,000 to 18,000 g/mm ² (JIS S6019
(based on the measurement method), and the variation within each example was small, but the one obtained in the comparative example was black, and for example, in order to obtain a red core, it was heated again at 600 °C in an oxidizing atmosphere. It requires 5 hours of processing,
In addition, as in Example 4, those treated at 750°C without finishing the treatment in one hour were whitened, but
Many of the products were cracked or swollen, and when the strength was measured, it was about 10,000 to 15,000 g/mm ² , but it varied widely from product to product.

As can be seen from the above explanation, the present invention eliminates problems such as cracking, swelling, and uneven strength caused by processing in an oxidizing atmosphere, and energy waste caused by long-term high-temperature processing. Not only can it be prevented, but it can also be seen to have an effect on strength. This contribution to strength improvement is due to the fact that the inorganic binder is sintered after the depolymerized resin has been substantially removed, that is, the contact between the particles of the inorganic binder is improved. Infer.

Claims (1)

[Claims] 1. A method for producing a colored pencil lead, the main materials being at least an inorganic bulk material, an inorganic binder, and an organic excipient, which are kneaded, extruded, heat-treated to obtain a sintered body, and suitably colored. A method for producing a colored pencil lead, characterized in that a depolymerizable organic substance is used as an organic excipient.