JPH1052316A - Manufacture of brush - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of a burr, and prevent filling failure of resin in a metal mold cavity by using a material on which a resin fluid characteristic value is a specific value and a bending elastic modulus of molding resin is a specific value, as melting resin to be injected into a handle molding metal mold. SOLUTION: Using bristle bundles 1 are introduced into using bristle bundle 1 inserting holding holes 11 provided in a handle molding metal mold 10, and one ends of the using bristle bundles 1 are projected, and projecting end parts are fused on fusion lumps 2 having a cross section larger than a cross section of the holding holes 11 by a heating means, and after the fusion lumps 2 are positioned in a cavity 13, and a melting molding material is introduced, and when a brush where the using bristle bundles 1 are integrally implanted in a handle 3 is formed by handle molding by hardening of the molding material, injection molding is performed under low pressure by using a material on which a resin fluid characteristic value of the melting molding material to be introduced into the handle molding metal mold 10 is in a range of 17 to 40g/10min and a bending elastic modulus of molding resin is 15000 to 30000kgf/cm<2> . Therefore, filling failure is prevented, and a brush having high strength of implanted bristles can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a brush such as a toothbrush, a hairbrush, a body brush or a cleaning brush, and more particularly to a method for forming and integrating a hair bundle and a handle.

[0002]

2. Description of the Related Art Conventionally, in a brush such as a toothbrush, instead of a brush manufactured by fixing a bristle bundle to a large number of flocking holes in a handle with a metal wire, the density of flocking has recently been increased, or the flocking has been increased. Due to the necessity of diversifying the shape, it has been proposed to integrate the handle with a hair bundle when forming the handle with a synthetic resin without using a metal wire. As a method of manufacturing a brush without using a metal wire, a method of fixing a bristle bundle to a brush body by heat fusion (for example, Japanese Patent Application No. 60-1985).
132097, Japanese Patent Application No. 60-16730, Japanese Patent Application No. 1
-215132, etc.) or a method of introducing a hair bundle into a mold, injecting a handle resin material, and integrally molding (insert molding) (for example, Japanese Patent Application No. 59-240403).
No., Japanese Patent Application No. 61-68897, Japanese Patent Application No. 63-5013
No. 77).

[0003]

The problem of this conventional manufacturing method is that, for example, in Japanese Patent Application No. 59-240403, the end of the hair bundle holding hole on the cavity side in the mold is melted and enlarged. The feature is to prevent the occurrence of "burrs" by closing the part, but in this method the molten enlarged part is located directly below the handle flocking surface, so sufficient flocking strength (strength to pull out hair from the molded body) There was a problem that could not be maintained. On the other hand, in the case of Japanese Patent Application Nos. 61-68897 and 63-501377, by providing a sleeve on the extension of the hair bundle holding hole, the hair can be implanted at a distance from the handle implanting surface. However, although the flocking strength can be secured, there is a problem that the mold structure becomes complicated and productivity cannot be increased.

In addition, in the insert molding manufactured without using a metal wire, a complicated mold system is not used, the hair bristle bundle is maintained at an arbitrary flocking strength, and the hair bristle bundle is introduced into the mold. The injection molding resin enters the gap formed between the hair bundle holding hole of the hair bundle and the outer periphery of the hair bundle inserted into the hole, preventing the occurrence of "burrs" and related to resin filling during injection molding. Although it is a useful manufacturing method to prevent molding defects and to obtain a product with excellent usability, a method of fixing a hair bundle to a flocking hole formed in a flocking portion of a handle with a conventional metal wire material. In general, a resin brush having a fluidity of about 9 to 16 g / 10 min has been used for molding the toothbrush handle. However, when in-mold molding is performed under the conventional resin fluidity and molding conditions (such as injection pressure), burrs are generated in which the molding resin protrudes from the gap between the hair bundle holding hole in the mold and the hair bundle. As a preventive measure, low-pressure injection molding can be considered. However, in the conventional handle resin, the flow of the resin has decreased, and other appearance defects (weld, short shot, etc.) have occurred. Furthermore, in the above-mentioned fluid resin,
It is necessary to raise the resin temperature in order to secure a certain degree of fluidity. However, in the case of in-mold molding, since a bristle bundle made of a thermoplastic resin is inserted into the cavity, the resin temperature is higher than the melting point of the bristle. When the molding is carried out, the melted portion at the end of the bristle bundle is melted. As a result, the problem that the flocking strength is lowered occurs. In addition, since the high-flowable resin generally has a low molecular weight, the bending strength and There also arises a problem that the impact strength is reduced, and practically preferable performance cannot be obtained. The present invention is intended to easily eliminate these conventional drawbacks, has a simple mold structure that ensures insert molding of the hair bundle, does not require a special mold system, and does not generate burrs. An object of the present invention is to provide a method of manufacturing a brush having a high flocking strength and improved quality and appearance quality.

[0005]

According to the present invention, a hair bundle made of a thermoplastic synthetic resin is introduced into a plurality of hair bundle insertion holes provided in a mold to project one end of the hair bundle. Then, the protruding end is formed into a fusion mass having a cross section larger than the cross section of the holding hole by the heating means, and after the fusion mass is positioned in the cavity of the handle molding die, the thermoplastic synthetic resin molding material is introduced. In the method of manufacturing a brush in which a hair bundle is planted integrally with a handle by molding a handle by curing the molding material, the molten resin injected into the handle molding die has a resin flow characteristic value of 17 to 40 g / 10 min.
And the bending elastic modulus of the molding resin is 15,000 to 30,
By using a brush of 000 kgf / cm ² , a brush having high flocking strength and good appearance quality can be obtained.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In this method of manufacturing a brush, a fusion lump at one end of a bristle bundle is positioned in an inner space of a handle molding die, and a resin molding material is injected into the mold to form a bristle bundle. When the mold and the handle are integrally molded, the resin flow characteristic value (melt flow index) MI of the molten molding material introduced into the mold is in the range of 17 to 40 g / 10 min, and the bending elastic modulus of the molding resin is 15, 000-30,000
By performing injection molding using a material of kgf / cm ² , low-pressure injection molding becomes possible, and resin does not enter into the gap between the outer periphery of the hair bundle and the hair bundle holding hole of the mold, thereby preventing burrs. Can be prevented, resin filling failure in the mold cavity is prevented, and no special mold system is required.
A high quality brush can be obtained with high flock strength.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. 1 to 3. FIG. 1 is a perspective view of a handle forming die 10 or a hair bundle inserting holding hole 11 provided in a hair bundle inserting die. projecting align the end of use bristle bundle introduced by receiving plate 14 or the piston tresses 1, hot plate or hot air projecting end portion by the heat source 12 _1, the heating means 12 such as an infrared, holding holes 11
Is fused into a fusion mass 2 having a cross section larger than the cross section of the above, the fusion mass 2 is positioned in the cavity 13 of the handle molding die 10, the cavity 13 is closed, and then the molten molding material is introduced. When forming the brush 4 in which the bristle bundle 1 is integrally implanted with the handle 3 by the handle molding by curing of the molding material, the resin flow characteristic value (melt) of the molten molding material introduced into the handle molding die 10 is increased. Flow index) in the range of 17 to 40 g / 10 min, and the bending elastic modulus of the molding resin is 15,000 to 30,000.
kgf / cm ² and low pressure injection molding to prevent poor filling, and
Is embedded in the molding material 3 to hold the fused mass 2 and tufts root portion 1 ₁ a molding material is as small quality good brushes high flocked strength variations.

In this case, the cavity 13 of the molding die 10
The use of the molten molding material having the above-mentioned specific fluidity and physical property values for handle molding to be injected into the inside enables low-pressure injection molding for preventing generation of burrs. For example, the melt flow index (hereinafter referred to as MI) of a resin is represented by a test method defined in JIS K7210 under molding conditions under which a molded article having no appearance defect can be obtained. Therefore, it is necessary to raise the resin temperature, and as a result, there is a problem that the resin temperature melts the bristle bundle melting portion in the cavity, and the flocking strength is reduced. In addition, when the MI is high, the viscosity becomes low, so that the resin temperature is lowered and the flocking strength can be secured. However, there is a problem that burrs are easily generated even in low pressure injection molding. To ensure the strength, as shown in Table 1, MI
= 17 to 40 g / 10 min, it is preferable to increase the fluidity of the resin and perform low-pressure / low-temperature injection molding.

[0009]

[Table 1]

The resin flow characteristic value (melt flow index) of the molding resin is 17 to 40 g / 10 mi.
By using a material having a high fluidity of n, preferably 20 to 30 g / 10 min, it becomes possible to lower the injection pressure which greatly affects the generation of burrs, and to prevent the generation of burrs. In addition, due to high fluidity, poor resin filling (short shot, weld, etc.) even in low pressure injection molding
And a molded article (product) having a good appearance can be obtained. Further, the flexural modulus is 15,000-30,
000 kgf / cm ² , preferably 18,000 to ²
5,000kgf / cm ² · Izod impact value is 1.5
By using a material of kg · cm / cm ² or more, it is possible to maintain the elasticity and strength of the handle and neck which are preferable for practical use in the molded product. "Relationship between handle flexure and usability" and "Relationship between handle flexure and resin flexural modulus" with prototype brushes listed in Table 1, for example, a toothbrush made of polypropylene with a handle thickness of 6.0 mm and handle width of 11.0 mm. FIG. 4 and FIG. FIG. 4 shows a good amount of deflection of the handle from the viewpoint of usability of the handle, and FIG. 5 shows a bending elastic modulus of the handle molding resin for securing a good amount of deflection. The measurement was performed by chucking a position 30 mm from the rear end of the handle at 20 ° C. as shown in FIG.
The amount of deflection when a load of 1 kg was applied to the position of 0 mm was measured with a measuring instrument (height gauge).

Further, as means for adjusting the rigidity of the handle, an elastomer (3 to 15% by weight) is added to the handle molding resin (improvement of impact strength), and a talc (5 to 10% by weight) is added to the handle molding resin. It is effective to also consider the rigidity UP).

A plurality of plungers 15 are provided in each of the hair bundle holding holes 11 provided in the handle molding die 10.
May be slidably inserted so that each bristle bundle 1 is stopped at a predetermined position and the fusion mass 2 is fixedly supported in the cavity 13. However, the bristle bundle holding hole 11 has a diameter larger than the diameter of the plunger 15. The injection molding resin is designed so that the hair bundle is easily supplied and the ratio of the hair bundle cross-sectional area to the cross-sectional area of the hair bundle holding hole (hair filling rate) is stable when the hair bundle is introduced. Is formed so as to prevent entanglement between the bristle bundle and the holding hole of the mold and to prevent generation of burrs. Further, the insertion distance of the hair bundle 1 in the cavity 13 can be arbitrarily selected according to the thickness of the base of the flocked member or the thickness of the brush head.

[0013]

According to the present invention, a bristle bundle made of a thermoplastic synthetic resin is introduced into a plurality of bristle bundle holding holes provided in a mold, and one end of the bristle bundle is protruded. The ends are formed into a fusion mass having a cross section larger than the cross section of the holding hole by the heating means, and the fusion mass is positioned in the cavity of the handle molding die, and then the thermoplastic synthetic resin molding material is introduced.
In a method of manufacturing a brush in which a hair bundle is integrally implanted into a handle by molding a handle by curing the molding material, the molten resin injected into the handle molding die has a resin flow characteristic value of 17 to 40 g / 10 min. And the bending elastic modulus of the molding resin is 15,000 to 30,000 kgf / c.
The use of those m ^2, when manufacturing the brush use tufts are integrally planted on the handle, the gap between the bristle bundle periphery and die use tuft holding hole for enabling the low-pressure injection molding The use of a high-flow resin to prevent resin from entering into the mold, so-called "burrs", prevents poor filling of the resin in the mold cavity (short circuit) even in low-pressure injection molding to prevent burrs. Shot weld) can be prevented, it is possible to obtain a good product in appearance, and it is not necessary to raise the resin temperature, which prevents deformation or melting of the bristle bundle enlargement due to the heat of the handle molding material. In addition, it prevents the reduction and dispersion of the flocking strength of the product, and also prevents the exposed bristle bundles from being exposed to the surface of the molded product, improves the strength of the molded product, and has good quality and reliable appearance quality. With high quality In addition, by using a resin having physical property values, a molded product (product) can maintain the elasticity and strength of the handle and the neck which are preferable for practical use, and the productivity is greatly improved. There is an effect that can be.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a process explanatory view of a production method according to an embodiment of the present invention, wherein (a) is a hair bundle insertion step, (b) is a fusion lump forming step, (c) is a step immediately before injection molding, and (d) is an injection molding step. , (E) show the release step.

FIG. 2 is an enlarged vertical sectional view of a part of a molding process of the example of FIG.

FIG. 3 is a cross-sectional view of the example of FIG.

FIG. 4 is a diagram showing the relationship between the amount of deflection of a handle of a toothbrush product and usability.

FIG. 5 is a graph showing the relationship between the amount of deflection of a handle of a toothbrush product and the flexural modulus of resin.

FIG. 6 is a side view showing a state in which a deflection of the handle portion is measured.

[Explanation of symbols]

Reference Signs List 1 hair bundle for 2 fusion mass 3 handle 4 brush 10 handle forming die 11 hair bundle holding hole 12 heating means 12 ₁ heat source 13 cavity 14 receiving plate 15 plunger

Claims (1)

[Claims] A hair bundle made of a thermoplastic synthetic resin is introduced into a plurality of hair bundle insertion holes provided in a mold, one end of the hair bundle is projected, and the protruding end is heated. Forming a fusion mass having a cross section larger than the cross section of the holding hole by means, placing the fusion mass in the cavity of the handle molding die, introducing the thermoplastic synthetic resin molding material, and curing the molding material. In a method of manufacturing a brush in which a hair bundle is integrally implanted into a handle by handle molding, a molten resin injected into a handle molding die has a resin flow characteristic value of 17 to
40 g / 10 min and the bending elastic modulus of the molding resin is 1
A method for producing a brush, comprising using a brush having a weight of 5000 to 30,000 kgf / cm ² .