JPS58208360A - Production of colored rencil lead - Google Patents

Abstract

PURPOSE:To form a pencil lead having a excellent strength, by heating a raw material compsn. at a given temp. to remove a softening agent, molding the compsn. and burning the molded article in the production of a burning type colored pencil lead. CONSTITUTION:A binder such as clay e.g. kaolin or bentonite, a loading material such as boron nitride, an excipient such as vinyl chloride (co)polymer or polystyrene, a softening agent such as dibutyl phthalate or dioctyl adipate and additives (filler, pigment, lubricant, etc) are kneaded by means of rollers, etc. The resultant compsn. is heat-treated at a temp. not higher than the docomposition temp. of said thermoplastic resin to evaporate and remove the softening agent. The compsn. is crushed and extruded. The molded article is burned at 700-1,000 deg.C and impregnated with ink having the desired color to obtain a colored pencil lead.

Description

[Detailed description of the invention] The present invention relates to a method for producing colored pencil lead by firing.

Conventional colored pencil leads, for example, use colorants and (-) pigments together with extenders, waxes, oils, resins, etc.
After extrusion molding, it is properly dried and made of -Cl, but because of the bond made of carbonized material, its breakage strength is lower than that of the black core obtained by firing, and it is still difficult to erase with an eraser. It had various drawbacks such as being difficult to use.

Research has focused on the production method of so-called fired colored pencil leads impregnated with ink, and it has become possible to achieve a marked improvement in quality compared to the non-fired colored pencil leads mentioned above. However, there is still a significant difference in strength compared to the black core mentioned above.

One of the reasons for the above-mentioned defects in fired colored pencil leads is dryness.
] cannot be considered based on the use of In other words, clay is generally used for the thick black lead used in wood-based pencils even today.As can be seen from 2, viscosity itself generates almost no gas during heat treatment and is carbonized. Compared to the case where the material is manufactured with It is inferior in terms of formability such as plasticity and bondability, and therefore,
When it comes to molding assistance, resins with still movement as excipients and their softening properties, as well as lubricants and stabilizers, are practically indispensable.

However, the molding aid is subjected to high-temperature heat treatment (thus, it escapes, leaving pores at that time, and if the amount of pores is large, the breakage strength or the compressive strength when gripping the zipper of the pencil becomes low). I will do it.

The present invention has been made in view of the above-mentioned viewpoints, and after kneading cuttings containing at least a body material, clay as a binding material, a thermoplastic resin as a filler and a softening agent for the thermoplastic resin, , heat treatment at a temperature below the melting temperature of the thermoplastic resin;
After removing the softened +/3 and extruding it,
The method for producing colored pencil lead is to impregnate the fired body with ink.

Examples of the extending material include boron nitride, Merck, mica, etc., and boron nitride is sometimes preferred. As a binder and as a binder,
Various groups such as kaolin, montmorillonite, and bentonite can be used. Thermoplastic resins used as cedar materials include polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polystyrene, polymethyl methacrylate, polyvinyl butyral, acrylic-styrene copolymer, and acrylic-styrene copolymer. Examples include die/copolymers. Softening agents include phthalate esters such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, butylphthalyl butyl glycolate, dioctyl-rlbate, methyl acetyl lysyllate,
Dioctyl azelate, dibutyl sebacate, dioctyl sebacate, dibutyl maleate, dioctyl fumarate, etc., are generally referred to as plastic phase, and methane, methyl ethyl ketone, toluene, xylene, propylene carbonate, etc. are generally referred to as ablation. Can be used but %
-HI': h of the plastic material is more preferable in relation to the crosstalk process. The valley materials mentioned above are the same as the 11 gods (
In history, it is said that it is used in combination with two Germans.
Depending on the price, we can use photonics such as silica fine powder, pigments,
A) Alternatively, wax, stearic acid, silicone oil, etc., which are used in small amounts, can be used in combination with lubricants and stabilizers.

In addition, the usage ratio of each material mentioned above is set as appropriate depending on the quality of the product, etc. The proportion of thermoplastic resin used is preferably small size, 30% by weight or less,
More preferable (, < is desirable to keep it below 20 East Banchi,
stomach.

Each material is kneaded using a kneader, Henschel mixer, three rolls, etc. Among them, appropriate heating is performed for #, 4, 1, - and +j by applying shearing force to the material.
It is preferable to use a roll because it can crush the particles to an appropriate size and improve the adhesion between the particles, and it is desirable to use it as at least a part of the mixing process. In the above, it was stated that plasticizers are preferable to solvents as softening agents, but this is related to this roll, and
In other words, a large amount of substances with relatively low boiling points evaporate during kneading with rolls, resulting in intercentering that increases the proportion of materials used, and as a result, the improvement in adhesion between materials, which is the effect of rolls, is reduced. Due to not enough company.

The softening agent is removed from the kneaded material by drying.

This drying must be carried out at a temperature below the decomposition temperature of the thermoplastic resin as the excipient; if it is carried out above the decomposition temperature, the shaping effect of the thermoplastic resin will be maintained.

The density of the dried material has decreased due to the removal of the softening agent. This decrease in density can be eliminated by applying pressure during extrusion molding, which is the next step, but once pulverized before extrusion molding, control during extrusion molding becomes easier.

When the dried or pulverized product is extruded, it is preferable to do so under heated conditions. Although it is possible to perform extrusion molding without heating, it is safe to increase the extrusion pressure considerably, and since thermoplastic resin is used as the excipient material, it is better to plasticize it by heating. Power becomes easier to control.

The extruded product is heat treated to the firing temperature, the thermoplastic resin is cleaned, and the binder is fired (sintered). If the material does not leave any carbide, such as methyl methacrylate, there is no need to set up a special atmosphere; for example, it can be heat-treated in a closed container.The firing temperature is viscosity 14.
(It varies depending on the Φ class, but usually 700 to IQ'0'0
' is the extent.

The baked product is impregnated with ink to obtain a product. The ink to be impregnated may be ballpoint pen ink, star ink, etc., but in order to suppress deterioration over time, it is preferable to use an ink solvent with a relatively high boiling point.

In the following explanation using Example F1, parts simply indicate parts by weight.

[Example 1] (,0,5'*m for mechanical pencils (same below); red pencil lead) Boron nitride 40 parts Organic bentonite 22 Vinyl chloride Vinyl acetate Jt [Compound 20 Diethyl phthalate
30〃Stearate (lubricating material) 1〃After thoroughly kneading the materials listed above with three rolls heated at 80°C, 15
Dry at 0'C for 5 hours (-7, then grind it in a pulverizer to 1"am
It was crushed 1-2 by the fake. The pulverized product was extruded into a 1.111 line shape using an extrusion molding machine heated at 160'0, cut into predetermined lengths, and then heat-treated at up to 850°C in an air atmosphere. This was impregnated with red ink for an oil-based ballpoint pen using a vacuum toe of 10 Torr to obtain a red pencil lead.

[Example 2] (Blue pencil lead) Boron nitride 40 parts Organic bentonite 20 Polymethyl methacrylate
16 Dibutyl phthalate 20
[The above material I + 20'C was kneaded for 1 minute with three heated rolls, dried at 210'0 for 4 hours, and the stiffness was crushed with a crusher to a diameter culm resistance of 1-1. The pulverized product was extruded into a thin wire using an extruder heated at 220'0, cut into a predetermined length, and then heat-treated to s s' o 'c in a closed container. This was impregnated with blue stamp ink under a reduced pressure of 10-'''r Or + to obtain a blue pencil lead.

[Comparative Example 1] The same materials as in Example 1 were used (2. After roll-kneading in the same manner, the mixture was extruded into a fine line using an extrusion molding machine heated at 80°C without drying, and heated at 130°C for 50 minutes. After drying for a period of time, it was cut into a predetermined length (2), then heat treated and impregnated with red ink in the same manner as in Example 1.

[Comparative Example 2] The same materials as in Example 1 were used except that diethyl phthalate (softening I) was not used.

However, an attempt was made to roll-knead this, but it remained in a powder state even when heated, and an attempt was made to forcefully extrude it, but it was ultimately unsuccessful.

[Comparative Example 5] The same materials as in Example 2 were used, and after kneading with rolls in the same manner, the mixture was extruded into a thin wire with a heated extruder at 120°C (120°C) without drying, and after drying at 210°C for 4 hours, It was cut into a predetermined length, heat treated and impregnated with blue ink in the same manner as in Example 2. The results of the characteristic test of the obtained colored pencil lead are shown in Figure 1.

6-1 (Note 1) JIS S 6019 [Book 1]
゛-j was measured.

(Note 2) Chuck breakage is 0.5
Hold the colored pencil lead in the zipper of the sill (7, perpendicular to the tip of the lead 1
I put a new book of 9 on it, took it out and folded it (I checked the presence of ingredients, and the values in the clothes are out of 100 each)) 1"
Indicates the number of +u.

(Note 3) The bulk density is calculated from the measured diameter and length of each piece (divided by the volume of 7 x 1 x 11).

As described above, according to the present invention, the softening agent is removed before extrusion molding so as not to impair the shaping effect of the thermoplastic resin, and then the softening agent is extruded and heat treated. (7th, to obtain a pencil lead with excellent strength, the density is still high < 1)
7. It is also possible to increase the amount of writing pleasure per unit length.

Patent applicant: Bentel Co., Ltd.

Claims (1)

[Claims] After kneading a material containing at least a thermoplastic resin, a softening agent of the thermoplastic resin, and a thermoplastic resin as a binder and a binder, after the decomposition temperature of the thermoplastic resin is heated, [2. After extrusion molding, the softening agent is removed [2. After extrusion molding, firing treatment is performed, and the fired body is impregnated with ink.