JPH021482B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a pencil-shaped cosmetic shaft made of synthetic resin and a method for manufacturing the same. [Background technology] Wooden shafts are generally used for pencil-shaped shafts, that is, shafts for pencil-shaped cosmetics and ordinary pencil shafts, and American incense cedar wood was particularly used, but resources have been decreasing in recent years. As wooden shafts have become difficult to obtain and expensive, various synthetic shafts have been researched and developed to replace wooden shafts. However, none of them were satisfactory enough to completely replace wooden shafts, and issues still remained. That is, this type of pencil-shaped shaft is required to have various properties, particularly physical properties such as cutting ability, bending resistance (rigidity), and resistance to oil and fat penetration. Furthermore, the subtle tactile sensations of a product, such as how easy it is to hold and how light it is when held in the user's hand, have a great impact on the success of the product. Generally speaking, to improve the cutting properties of a synthetic resin pencil shaft, it is sufficient to foam the resin, but simply foaming the shaft weakens the strength of the shaft, so it has been traditionally made using wood flour or other materials. Mixing fibrous fillers has been practiced. but,
When such a conventional filler is added, the degree of foaming of the resin is lowered accordingly, resulting in a disadvantage in that the machinability is deteriorated. For example, when a shaft is shaved, the shavings become powdery and do not form a continuous ribbon-like flake like when whittling a wooden shaft, and the sharpness is not good. Another method for reinforcing the rigidity of the foamed resin shaft is to mix inorganic materials such as gypsum or glass fibers into the synthetic resin. Although reinforcement with such an inorganic material is useful for increasing rigidity, it has the disadvantage that it reduces moldability and also reduces the machinability of the product. For example, when cutting, it has a hard, hard, low-resistance feel that makes it extremely difficult to sharpen, and there is a risk that the knife will wear out quickly. In addition, the inorganic reinforced shaft feels cold and heavy when held in the hand, which is not desirable in practical terms as a product. [Object of the Invention] Therefore, the present invention provides a pencil that has good cutting properties, sufficient strength (rigidity), feels light in the hand and does not feel cold, and is suitable for mass production at low cost. The purpose of the present invention is to provide a synthetic resin shaft for molded cosmetics. Furthermore, the present invention also aims at a method for manufacturing the novel pencil-shaped shaft as described above. [Summary of the Invention] To summarize, the pencil-shaped synthetic shaft of the present invention has a diameter of about 75 to
85% (weight, same below) thermoplastic synthetic resin,
The shaft is made of a foamed synthetic resin made of a mixture of about 8 to 15% fine pulp, about 1 to 7% mineral wool, and about 0.5 to 6% inorganic minute hollow spheres. The composition ratio of each component will be explained in detail in Examples below. Thermoplastic synthetic resins that can be used in the present invention include polystyrene, high impact polystyrene, ABS
The material is appropriately selected from among resins, polypropylene resins, and the like. Fine pulp is an organic filler that is added mainly to give synthetic resin machinability and to supplement the strength of foamed resin.
A size of 300 mesh passes, or about 60 to 48 microns, is preferably used. The pulp that can be used in the present invention is hardwood chemical pulp (LP),
In particular, bleached pulp (BP) of sulfate pulp (KP) is recognized as the best (L・B・KP). Mineral cotton is an inorganic filler added mainly for the purpose of reinforcing rigidity, and is an inorganic fine short fiber obtained from blast furnace slag in the steel manufacturing process. are preferably used. By using mineral cotton as an inorganic filler, it is possible to reinforce the rigidity of the pencil-shaped synthetic shaft, and it does not cause the cold feel that occurs when other inorganic substances are added, making it durable, hard to break, and comfortable to use. A composite axis with is obtained. The inorganic micro hollow spheres are micro hollow spheres made of polysilicate-based inorganic material with a particle size of about 60 to 80 microns, and are commercially available under the name of silica balloons. This mainly contributes to lowering the density of the synthetic shaft, and together with the aforementioned mineral wool, it is possible to achieve the effect of stiffness reinforcement by inorganic material without feeling cold and heavy. Furthermore, the machinability does not deteriorate due to the addition of inorganic substances as in the conventional method. According to the present invention, the strength of the foam shaft is improved by skillfully combining an organic filler (fine pulp) and an inorganic filler (slag and silica balloon) with the foamable thermoplastic synthetic resin used as the main material. While reinforcing the material, we were able to improve cutting properties and make the feel during use feel light and warm, similar to the skin of wood, making it possible to solve the problems of the past all at once. [Specific Disclosure of the Invention] Next, the synthetic shaft manufacturing method of the present invention will be explained. First, fine pulp (approximately 8-15% by weight), mineral wool (approximately 1-7% by weight) and silica balloon (approximately 0.5-15% by weight)
6% by weight) in a mixer and thoroughly mixed to prepare a filler mixture. Separately, a thermoplastic synthetic resin is fed in a quantitative amount to an appropriate kneading machine, for example, a Busco kneader, to melt the synthetic resin, and the filler mixture is fed in a quantitative amount to this, kneaded at about 150 to 180°C, and then extruded to form hot cuts. Knead into pellets. The proportions of the main material and each filler are approximately 75 to 85% by weight of thermoplastic synthetic resin, approximately 8 to 15% of fine pulp, approximately 1 to 7% of mineral wool, and approximately 0.5 to 6% of silica balloon (both weight). Next, 0.4 to 0.5 parts of an appropriate blowing agent, such as azodicarboxylic acid, was added to 100 parts of the kneaded pellets, mixed thoroughly in a blender, and then molded using a pipe die in a 50 mm single screw extruder at a temperature of 160 to 180°C.
extrusion molding. Molded product has an outer diameter of approximately 7.65
mm, obtained as a foam pipe with an inner diameter of about 4 mm. Next, Table 1 shows specific formulation examples of the pencil-shaped synthetic shaft of the present invention formed as described above.

[Table] The foamed synthetic resin shafts of the present invention extruded using these compounding ratios all have extremely good machinability, do not feel heavy or hard against cutting tools, and are free of shavings with thin skin. It was produced continuously in a shape, and the cutting feeling was comparable to that of a wooden shaft. When you hold it in your hand, it doesn't feel cold or heavy at all, even though it contains up to 10% inorganic filler. In order to use such a foamed synthetic shaft as a pencil-shaped shaft for cosmetics, it is necessary to have good cutting ability, feel in the hand, strength, etc., as well as to prevent oils and fats from the cosmetic core that is filled or inserted into the shaft from penetrating into the shaft. It is necessary to have oil and fat resistance. The results of this comparative test are
Shown in Table and Table 3.

【table】

【table】

[Table] Regarding the bending strength and bending strength of the foamed synthetic resin shaft according to the present invention, the test shaft was supported horizontally at two points 60 mm apart, a load was applied from above, and the amount of deflection and bending strength were measured. The results are shown in Table 4.

[Table] As explained above, according to the present invention, inorganic and organic fillers are skillfully blended into the foamable thermoplastic synthetic resin so as to improve machinability, strength, and usability. This problem is solved at once, and a synthetic shaft that is strong, easy to sharpen, and comfortable to use is obtained, and it also has physicochemical properties that can withstand the penetration of cosmetic cores containing a lot of oil and fat components. It has the effect that it can be used widely and inexpensively as a synthetic shaft for pencil-shaped cosmetics instead of a wooden shaft.

Claims (1)

[Scope of Claims] 1 Thermoplastic synthetic resin, fine pulp, mineral cotton,
and inorganic hollow spheres, and the mixture is extruded and foam-molded to form a pencil-shaped synthetic shaft for cosmetics. 2. Mixing fine pulp, mineral wool, and inorganic hollow spheres to produce a filler mixture, melting a thermoplastic synthetic resin, adding and kneading the filler mixture thereto, and forming kneaded pellets by extrusion; A method for producing a synthetic shaft, which comprises adding a foaming agent to the material and extruding it into a hollow cylindrical body.