JPS6243460B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention particularly relates to a plastic eraser that has excellent tensile strength, bending strength, hardness, and good erasability. A plastic eraser (hereinafter referred to as Plastic erasers (hereinafter referred to as plastic erasers or simply erasers) have been known for a long time, and are widely used for various purposes because of their excellent erasing performance. However, such plastic erasers have the disadvantage that they are generally weaker than rubber erasers and easily break, so plastic erasers cannot be used as replacement erasers for mechanical pencils or pencils with erasers, which require particularly strong strength. A rubber eraser is used. In an attempt to impart strength to a plastic eraser, an eraser was prepared by mixing vinyl chloride resin, about twice the amount of vinylidene chloride resin, and a plasticizer in an amount equal to the total amount of both resins, and heating and gelling the mixture ( Special Publication No. 47-13299), or a hard eraser like a so-called "sand eraser" in which mineral powder such as carborundum, alundum, diamond sand, glass powder, or silicic acid powder is added to the resin (Utility Model Publication No. 51-82539)
) have been proposed. However, the former eraser improves strength but has a problem in that erasing performance deteriorates, and the latter eraser requires approximately 30 to 30% mineral powder to be added.
Because the eraser has coarse particles of 300 microns, it not only damages the paper surface when used, but also causes the eraser itself to become hard but brittle. SUMMARY OF THE INVENTION Therefore, the present invention has been made to solve the above-mentioned problems of conventional plastic erasers and to provide a plastic eraser with excellent strength without impairing erasing performance. That is, the plastic eraser of the present invention has a particle size added to the conventional plastic eraser as a reinforcing agent.
A mixture of inorganic substance powder of 15 to 50μ and inorganic substance powder of particle size of 0.2μ or less in a weight ratio of 1:1 to 10:1 is added to the total amount of the eraser composition.
It is characterized by being blended at 30% by weight. Traditionally, this type of plastic eraser uses inorganic powder with a particle size of approximately 0.5 to 15 μm to adjust the touch and erasability of the eraser.
For example, heavy calcium carbonate, kaolin, and the like are used as fillers, but it has not been possible to impart the desired strength to eraser molded products by adding fillers with such particle sizes. Therefore, in addition to fillers with particle sizes as described above, the present inventors have developed
When we mixed a mixture of ~50μ and inorganic powder with a particle size of 0.2μ or less in a predetermined ratio as a reinforcing agent, we surprisingly found that it was possible to improve the strength of a plastic eraser without reducing its erasing performance. Ta. Furthermore, it was confirmed that the strength-improving effect achieved by blending the above-mentioned inorganic substance powder mixture is achieved regardless of whether or not the conventionally used filler is added. In order to improve the eraser strength in the present invention, it is essential to use a mixture of particles with a particle size of 15 to 50 μm and particles with a particle size of 0.2 μm or less. Particle size 15~50μ
When only particles are blended, the flexural strength (or Young's modulus) and breakage strength decrease because the gaps between the particles are large and the contact area between the particles and the resin surrounding the particles is relatively small. It becomes brittle. On the other hand, when only particles with a particle size of 0.2μ or less are blended, the contact area between the particles and the resin becomes larger, resulting in a higher tensile strength, but the bond between the particles and the resin is too strong, so the eraser cannot be used when erasing. Not enough eraser debris comes out, resulting in poor erasing performance.
As in the present invention, by blending a mixture of particles with a particle size of 15 to 50μ and particles with a particle size of 0.2μ or less with a resin, the small particles enter the gaps between the large particles and fill the gaps. It is presumed that a suitable contact area with the resin can be obtained and that tensile strength and bending strength can be improved without deteriorating erasing performance. In order to obtain the desired strength and good erasing performance, the mixing ratio of [particles with a particle size of 15 to 50 μm]/[particles with a particle size of 0.2 μm or less] must be 1/1 to 10/1 by weight. There is. If the mixing ratio is less than 1/1, that is, if the number of particles with a particle size of 0.2μ or less increases, the eraser density will become too dense, making it difficult to remove eraser debris during erasing, resulting in a decline in erasing performance. . On the other hand, if the mixing ratio is greater than 10/1, that is, if there are too many particles with a particle size of 15 to 50 microns, the eraser density becomes too coarse and sufficient strength cannot be obtained. The ratio of the inorganic powder mixture of particles with a particle size of 15 to 50 μm and particles with a particle size of 0.2 μm or less to the eraser is 5 to 30% by weight based on the total amount of the eraser compound. If the content is less than 5% by weight, a sufficient strength improvement effect cannot be obtained, and 30
If the amount is more than % by weight, it will look like sand eraser and will damage the paper surface when used. Examples of inorganic powders that can be preferably used as the inorganic powder with a particle size of 15 to 50μ in the present invention include mica powders with the above particle size range [e.g. “MICA-400” (particle size
35μ: manufactured by Nippon Mica Co., Ltd.), talc [e.g. ``Talc MS'' (particle size 35μ: manufactured by Tsuchiya Kaolin Co., Ltd.)'', glass fiber powder, aluminum powder, nickel powder, iron powder,
Examples include alumina powder. In addition, as inorganic substance powder with a particle size of 0.2μ or less, fine silica powder [for example, "Aerosil #200" (particle size 0.012μ, manufactured by Nippon Aerosil Co., Ltd.), "Nipseal" (particle size 0.012μ: manufactured by Nippon Silica Co., Ltd.), ) etc.], calcium carbonate fine powder [e.g. "Homocal D" (particle size
0.07μ: manufactured by Shiraishi Kogyo Co., Ltd.), “MSK-C” (particle size 0.03
~0.04μ: manufactured by Kasumori Co., Ltd.], titanium dioxide fine powder [e.g. “Aerosil TiO ₂ , P25” (particle size 0.03μ:
(manufactured by Nippon Aerosil Co., Ltd.)], natural attapulgiaite fine powder (for example, "Atagel" (particle size 0.14 μm, manufactured by Tsuchiya Kaolin Co., Ltd.)), etc. can be preferably used. The above-mentioned inorganic substance powder is merely an example, and any substance can be used as long as it does not react with other components of the eraser composition and have an adverse effect. In manufacturing the eraser of the present invention, conventional methods for manufacturing conventional plastic erasers can be employed. That is, a particle size of 15% is added to a blend of vinyl chloride or vinyl chloride-vinyl acetate copolymer resin, a plasticizer, and optionally stabilizers, pigments, fillers, etc.
A reinforcing agent consisting of an inorganic powder mixture of particles of ~50μ and particles with a particle size of 0.2μ or less is added, mixed uniformly using a device such as a mixer or two rolls, and the resulting uniform mixture is processed using a conventional method. It may be heated and gelled to form a mold. As a molding method, casting, press molding, extrusion molding, injection molding, etc. can be applied. Note that a dry blending method can also be adopted in which the resin and powder components such as fillers and reinforcing agents are stirred in advance at high speed to generate static electricity in the resin and cause the powder components to be electrostatically adsorbed thereto. According to this dry blending method, a sufficient amount of the inorganic substance powder is adsorbed to the resin, so that the particle density in the eraser molded product can be increased. The present invention will be further explained below by giving Examples and Comparative Examples. In addition, all "parts" mean "parts by weight." Example 1 Polyvinyl chloride (“Geon 121” manufactured by Nippon Zeon Co., Ltd.)
150 parts dioctyl phthalate 50 parts dinonyl phthalate 50 parts dioctyl adipate 50 parts TNPP stabilizer ("Mark 1178" made by Adeca Argus Co., Ltd.) 2 parts surfactant ("Twin 65" made by Kao Atlas Co., Ltd.)
4 parts precipitated calcium carbonate ("MSK-C" particle size 0.03~
0.04μ) 20 parts colloidal silicic acid ("Nipseal LP" particle size 0.01
~0.02μ manufactured by Nippon Silica Co., Ltd.) 10 parts Glass fiber powder (particle size 20-50μ) 40 parts After uniformly mixing the above components in a homomixer, this uniform mixture was heated using an extrusion molding machine.
The molded eraser of the present invention was obtained by heat molding at 100 to 130°C. Separately, an eraser molded product was manufactured without adding the glass fiber powder in the formulation of Example 1, and this was used as Comparative Example 1, and an eraser molded product was manufactured without adding precipitated calcium carbonate and colloidal silicic acid. This was designated as Comparative Example 2, and a molded eraser was also produced in which neither precipitated calcium carbonate, colloidal silicic acid, nor glass fiber powder was added, and this was designated as Comparative Example 3. Table 1 shows the results of measuring the tensile strength, Young's modulus, hardness, and erasing rate of the erasers obtained in Example 1 and Comparative Examples 1 to 3.

[Table] As is clear from the values in Table 1, Example 1 in which a mixture of particles with different particle sizes was added is different from Comparative Examples 1 to 3.
It can be seen that the strength, especially the Young's modulus, is improved compared to that of the previous paper without deteriorating the erasing performance. Example 2 Based on the formulation of Example 1 above, particle size 15-50
The same method as in Example 1 was carried out by varying the mixing ratio of μ particles (glass fiber powder) and particles with a particle size of 0.2 μ or less (precipitated calcium carbonate and colloidal silicic acid) in the range of 1/1 to 10/1. An eraser was manufactured by a method using a conventional method, and the strength and hardness of the eraser obtained were measured. Separately, a case where the particle mixing ratio is smaller than 1/1 (more particles with a particle size of 0.2 μ or less than particles with a particle size of 15 to 50 μ) is referred to as Comparative Example 4, and the particle mixing ratio is
Larger than 10/1 (particles with a particle size of 15-50μ are 0.2μ
The strength and hardness of the eraser obtained were measured using Comparative Example 5, in which the number of particles was more than 10 times that of the following particles. The results are shown in Table 2.

[Table] Shows the mixing ratio of the following particles.
** All notes are the same as the notes in Table 1.
As is clear from Table 2, when the mixing ratio of [particles with a particle size of 15 to 50μ]/[particles with a particle size of 0.2μ or less] is 1/1 to 10/1, good values for both strength and hardness are obtained. I was able to get it. On the other hand, in Comparative Example 4, the bending strength was lowered, and the eraser performance was lowered because the eraser dust was difficult to come out during erasing. Furthermore, in Comparative Example 5, the bending strength and breakage strength decreased. Example 3 Based on the formulation of Example 1, the particle size was 15 to 50.
Particle mixtures of μ particles (glass fiber powder) and particles with a particle size of 0.2 μ or less (precipitated calcium carbonate and colloidal silicic acid) were varied in the range of 3 to 30% by weight based on the total amount of the eraser compound. Example 1
An eraser was manufactured in the same manner as above, and the strength and hardness of the eraser obtained were measured. Separately, Comparative Example 6 is a case in which the particle mixture is blended in less than 5% by weight based on the total amount of the eraser compound, and Comparative Example 7 is a case in which the particle mixture is blended in an amount greater than 30% by weight. The hardness of each was measured. The results are shown in Table 3.

[Table] As is clear from Table 3, when the particle mixture was blended in a range of 5 to 30% by weight based on the total amount of the eraser compound, good values for both strength and hardness could be obtained. In Comparative Example 6, the desired improvement in strength and hardness was not observed because the blended amount of the particle mixture was too small, and in Comparative Example 7, both strength and hardness were higher than in Example 3, but as with sand eraser. It gets old and damages the paper surface when erasing it. Example 4 Polyvinyl chloride ("Geon 121") 150 parts dioctyl phthalate 100 parts diisodecyl adipate 40 parts TNPP stabilizer ("Mark 1178") 2 parts surfactant ("Twin 65") 4 parts Filler: heavy carbonate Calcium (particle size 2-10μ)
30 parts colloidal silicic acid ("Nipseal LP") 10 parts mica powder ("MICA-400" particle size 35μ, Nippon Mica
Co., Ltd.) 30 parts The above components were mixed, heated and molded in the same manner as in Example 1 to produce a molded eraser of the present invention. Table 4 shows the results of comparing the strength, hardness, and erasing rate of this eraser with commercially available vinyl chloride and rubber erasers. As can be seen from the results, the eraser of the present invention exhibits extremely superior values in strength, hardness, and erasing rate compared to commercially available erasers.

【table】

[Table] As can be seen from the above description, according to the present invention,
By incorporating an inorganic powder mixture of particles with a particle size of 15 to 50μ and particles with a particle size of 0.2μ or less in a predetermined ratio into a plastic eraser as a reinforcing agent, the excellent erasability of the plastic eraser can be impaired. It is possible to obtain an eraser with excellent tensile strength, bending strength, and hardness. The plastic eraser of the present invention can be preferably used as a replacement eraser for mechanical pencils or a pencil with an eraser, which particularly requires strength.

Claims (1)

[Claims] 1 Vinyl chloride resin and/or vinyl chloride
In a plastic eraser composition formed by heat molding a blend of a vinyl acetate copolymer resin and a plasticizer, an inorganic material powder with a particle size of 15 to 50 μm and an inorganic material powder with a particle size of 0.2 μm or less are used as reinforcing agents. 1. A plastic eraser composition characterized in that the mixture is blended in a ratio of 1:1 to 10:1 in an amount of 5 to 30% by weight based on the total amount of the eraser compound.