JPS5840596B2 - Enpitsu no Seizouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a pencil, and more specifically, the pencil shaft is made of synthetic resin, and the lead is coated with a hot-melt adhesive before being integrally molded with the lead. This is a method of manufacturing pencils that achieves adhesion between the shaft and lead.

Conventionally, various pencils have been devised in which a wooden shaft portion is made of foamable resin, generally referred to as synthetic wood, or its reinforcing agent.

An example of this is a method of extrusion molding in which a crosshead is used to simultaneously extrude the shaft and insert a core at the same time to perform simultaneous molding.

Further, there is no need for drying or firing of the core, and the core and shaft are integrally extruded.

The synthetic pencils manufactured in this manner lack core strength compared to conventional pencils whose shafts are made of wood, and also show cracks when cut, as shown in Figure 1.

Disadvantages of this cutting method include the tendency for the lead to break when cutting with a sharpener and the tendency to break when writing, and was also unfavorable in terms of appearance.

In view of these circumstances, as a result of intensive research, the present invention has improved core removal strength by using an adhesive between the shaft and the core, and has also been developed to prevent bending during cutting and bending during writing. The aim is to obtain good results.

Conventionally, adhesives have only been used in pencils when wood is used as the shaft material.

This is used for the purpose of pasting two boards together by making a groove in the board and inserting a core into it, and also to prevent the core from falling out.

However, the present invention uses a synthetic resin as the shaft material and uses an adhesive in integral continuous molding.

In other words, after the core is molded by an extruder for structural shapes, the surface of the core is coated with a heated and melted adhesive, and then the core enters the crosshead and is coated with synthetic resin as the shaft material, and then molded. .

Types of adhesives generally include solvent type, hot melt type, solventless type, emulsion type, film type, adhesive type, rewetting type, etc., but as a result of various studies conducted by the inventors, the hot melt type is the best. Met.

This product is stable in terms of workability and quality, and is suitable for continuous production.

Hot-melt adhesives are currently made using resins based on thermoplastic polymers that can provide cohesive strength and adhesive strength, such as ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, polyethylene, and polyamide. Those containing modifiers, plasticizers, antioxidants, etc. were effective in the present invention.

These can be selected with a softening point in the range of 70 to 150° C. in consideration of open time, cold and heat resistance, adhesive strength, etc.

In particular, ethylene-vinyl acetate copolymer (E, V, A resin) is compatible with many other components, provides good adhesive properties, and is most suitable for the present invention.

The actual manufacturing method is shown in Figure 2, using an extruder for core molding→
It is manufactured on a line in which the steps of adhesive bath → extruder for shaft molding → cooling water tank → take-off machine are arranged in a straight line, and the known method does not include an adhesive bath.

In addition, in order to apply the adhesive uniformly, an addition nozzle was provided at the outlet of the adhesive bath.

Examples will be described below.

[Example 1] The apparatus shown in Figure 2 described above was used.

For the structured type, use a 30% extruder and have a 2.1 mm diameter at the tip.
A nozzle was installed.

The previously blended materials were placed in a part of the hopper under conditions of a cylinder temperature of 155°C, a head temperature of 160°C, and a die temperature of 150°C to form a core with a diameter of 2 mm.

Next, the core enters an adhesive bath, and this bath has a heating device, and E, V, A resin (Lpax 220, softening point 89°C, manufactured by DuPont) is used as an adhesive in this bath. The bathtub was heated to 150° C., and a 2.1 mm diameter addition nozzle was installed at the rear.

The adhesive-coated core was made using a 40-degree extruder for shaft bottom type, with a crosshead installed at the tip, and the material was extruded under the following conditions: cylinder temperature 180°C, crosshead temperature 190°C, die temperature 205°C. Inorganic mixed polyethylene was placed in a portion of the hopper.

In other words, the lead enters the adhesive bath, coats the area evenly around the lead, and hardens immediately, but then enters the crosshead again, where it melts again and bonds to the shank material, thus defining the resulting pencil. It was cut into pieces and subjected to a stain removal test using the JIS S-6006 method.

[Comparative example]

Put the materials mixed into the extruder for configurations that do not use adhesive into a part of the hopper,
After extrusion molding into a core under the conditions of a cylinder temperature of 155°C, a head temperature of 160°C, and a die temperature of 150°C, a shaft-type extruder (using a low-foaming material of inorganic mixed polyethylene), a cylinder temperature of 180°C, The pencil is extruded under the conditions of crosshead 190℃ and die temperature 205℃), and the pencil whose shaft material is covered has a core strength of 4.3K.
g, and there was a cutting loss.

The pencil manufactured in this way was tested in the same way as in Example 1.
It was tested by the method of S-6006.

The test results are shown in Table 1. [Example 2] The following formulation was used as the adhesive.

Elvac+40 25 parts by weight Chlorinated paraffin 25 W, W rosin 50 Total 100 parts by weight The temperature of the bath was 140°C, and the other conditions were the same as in Example 1.

The results are shown in Table 2 below. As mentioned above, good results were obtained.

[Example 3] Polyamide resin (Persalon 1165, softening point 165-170°C, manufactured by Daiichi General Co., Ltd.) was used as the adhesive, the bath temperature was 190°C, and the other conditions were the same as in Example 1.

The results are shown in Table 3 below.

As described above, good results were obtained.

[Brief explanation of drawings]

FIG. 1 shows a front view of the main parts of the pencil, and FIG. 2 shows a schematic diagram of the manufacturing process of the pencil. 1: Pencil lead, 2: Pencil shaft, 3: Pencil cutter, 4: Extruder for structured shapes, 5: Extruder for shafted shapes, 6: Cross head, 7: Adhesive bath, 8: Addition nozzle , 9: Cooling water tank, 1
0: Pencil lead, 11: Pencil.

Claims (1)

[Claims] 1. A method for manufacturing a pencil in which the core and the synthetic resin shaft surrounding it are continuously molded as one unit, in which the core is coated with a hot-melt adhesive and molded integrally with the shaft.