JP2000342717A - Manufacture rubber sphere - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide manufacture of a rubber sphere which can restrain occurrence of bare without raising manufacturing cost. SOLUTION: A main body cap 4 and a front edge cap 6 are installed in a front edge of an extruder 2. The front edge cap 6 is composed of a frange part 8 and a projecting part 10. A rubber composition is filled in a cylinder of the extruder 2. A through-hole is formed at the main body cap 4 and the front edge cap 6. An inner peripheral face of the through-hole of the main body cap 4 is inclined so as to enlarge a diameter of the inner periphery toward an extruding front direction. The rubber molding body 12 is extruded from the cap then cut by a cutter, thereby a preriminary molding body can be obtained. The rubber sphere can be obtained by compressing and forming the preliminary molding body with a pair of a half metal mold.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a rubber sphere such as a golf ball, a golf ball core, a game ball and the like, and particularly relates to a pair of preforms obtained by extruding a rubber composition. And a method of manufacturing a rubber sphere including a step of compression molding with a half-break mold.

[0002]

2. Description of the Related Art A so-called one-piece golf ball has a structure in which a main body made of a solid rubber alone is coated. In order to obtain the golf ball body, first, a cross-linking agent, a filler, and the like are blended with the unvulcanized rubber using a closed kneader or the like to prepare a rubber composition. Next, this rubber composition is extruded by an extruder provided with a die. The extruded rubber composition is cut by a cutter or the like to obtain a substantially cylindrical preform (also referred to as a “plug”). The preformed body obtained by this extrusion step becomes a golf ball body through a compression molding step.

FIG. 5 is a sectional view showing a state of a compression molding step in a conventional golf ball manufacturing method. The preform 52 is put into a half-split mold including an upper mold 54 and a lower mold 56 having a hemispherical cavity, and is formed into a sphere by a compression molding method. Usually, heating is performed simultaneously with compression molding, and the rubber composition is crosslinked. Thus, the golf ball body is completed.

[0004]

A cutter for cutting a rubber composition in an extrusion step is usually provided immediately near a die of an extruder. Then, cutting is performed at a stage where a predetermined amount of the rubber composition is extruded, and the preform 52 ahead of the cut surface is completed. The rubber composition behind the cut surface is further extruded to a predetermined amount, and the next cut is performed. That is, extrusion and cutting are performed continuously. One cut forms a rear end 60 of the front preform 52 and a front end 58 of the rear preform 52. The cutter is normally controlled by a timer, and it is considered that a predetermined amount of the rubber composition has been extruded after a predetermined time has elapsed, and cutting is performed.

[0005] The rear end portion 60 of the preformed body 52 thus obtained has a shape in which a central portion protrudes forward (ie, a convex shape).
However, the front end 58 tends to be flat or slightly concave. FIG. 5 shows the preform 52 in which the front end 58 is concave. The reason why the front end portion 58 of the preform 52 is flat or concave is unknown in detail, but it is presumed to be due to the influence of the flow rate of the rubber composition, shrinkage of the preform 52, and the like. When compression molding is performed using the preformed body 52, a closed space 62 surrounded by the front end portion 58 and the inner peripheral surface of the mold is formed, and the air accumulated here does not escape, and air is accumulated on the surface of the golf ball ( A so-called bear) occurs.

The weight of the preformed body 52 is increased to a considerable extent, and a large amount of surplus rubber composition is discharged from the joint between the upper mold 54 and the lower mold 56 during compression molding, so that the air at the rear end 58 is cooled. Means for discharging from the mold are also conceivable.
This makes it possible to suppress the occurrence of bears to some extent, but it is difficult to completely eliminate bears. In addition, since the rubber composition that has flowed out from the joint between the upper mold 54 and the lower mold 56 is discarded, there is a problem that the yield of the rubber composition is reduced and the manufacturing cost of the golf ball is increased. .

However, it is difficult to make the extrusion speed from the start to the end of the extrusion completely constant in a normal extrusion process, and there is some variation in the extrusion speed. Therefore, even if cutting is performed at regular intervals by a timer-controlled cutter, the weight of the preform 52 is not uniform. In order to suppress the occurrence of bears in the group of preforms 52, a sufficient amount of the rubber composition is required at the time of compression molding even for the preforms 52 under the variation in weight, that is, the preforms 52 having a small weight. It needs to be drained from the mold. Therefore, it is necessary to increase the safety factor and set the average weight of the preformed body 52 at the time of extrusion to be relatively large. As a result, the yield of the rubber composition is further reduced. For example, assuming that the bear is suppressed by flowing out 3 g of surplus rubber during compression molding when obtaining a 45 g golf ball body, if the variation of the preformed body 52 is an average value plus or minus 2 g,
It is necessary to set the average value of the weight of the preform 52 to 50 g. In this way, even with the lightest preformed body 52 (ie, 48 g of the preformed body 52), 3 g of surplus rubber can flow out, and no bear occurs. In this case, as much as 5 g (50 g minus 45 g) of surplus rubber will be discarded on average.

The present invention has been made in view of the above problems, and has as its object to provide a method of manufacturing a rubber sphere capable of suppressing the occurrence of bears without increasing the manufacturing cost. It is.

[0009]

Means for Solving the Problems The invention made to achieve the above-mentioned object comprises an extruding step of extruding a rubber composition from a die and cutting the same to produce a substantially cylindrical preform. A molding step of performing compression molding on the molded body using a pair of half-split molds, wherein the die is such that the inner peripheral diameter increases in the pre-extrusion direction. A method for producing a rubber sphere, characterized in that the method has a portion whose inner peripheral surface is inclined.

[0010] According to the present invention, since the die is provided with a portion whose inner peripheral surface is inclined so that the inner peripheral diameter increases in the direction before extrusion, the preformed body cut by the cutter. Can be made convex. For this reason,
During compression molding, no sealed space is formed between the front end and the inner peripheral surface of the mold, and air does not accumulate. Therefore, the occurrence of bears can be suppressed even if a large amount of surplus rubber does not flow out during compression molding. The reason why the front end can be made convex by this die is unknown in detail, but it is presumed that the resistance between the rubber composition immediately before being extruded and the inner peripheral surface of the die is reduced.

In the present invention, the use of a die having a length of 15 mm or more in the extrusion direction of the inner peripheral surface, particularly a die having a length of 30 mm or more, can suppress the variation in weight of the preform. Therefore, even if the average weight of the preform is reduced, the weight of the preform below the variation is not so small, and the occurrence of bears can be suppressed.
Therefore, the amount of surplus rubber flowing out during compression molding can be further reduced. There is no particular inconvenience due to the length of the inner peripheral surface of the die in the extrusion direction being too large,
The diameter of a die attached to a general extruder is up to about 150 mm.

In the present invention, the angle between the inner peripheral surface of the portion where the inner peripheral surface of the die is inclined and the extrusion direction (hereinafter, also simply referred to as “inclination angle”) is 0.5 ° or more and 5 ° or more. Or less, and particularly preferably 1.0 ° or more and 3.0 ° or less. If the inclination angle is less than the above range, the front end of the preform may be flat or concave. vice versa,
If the inclination angle exceeds the above range, the weight variation of the preform may increase.

The rubber spheres produced by the present invention include one-piece golf balls, two-piece golf ball cores, multi-piece golf ball centers, thread-wound golf ball centers, game rubber balls, and the like. In particular, the present invention is suitable for manufacturing a golf ball that requires high quality and hates the bear.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view showing a state of an extrusion step of a manufacturing method according to an embodiment of the present invention. At the front end of the extruder 2, a main body base 4 and a front end base 6 are mounted. The front end cap 6 includes a flange portion 8 and a protruding portion 10. The cylinder of the extruder 2 is filled with a rubber composition. Reference numeral 12 denotes a rubber composition extruded forward through the main body base 4 and the front end base 6. A cutter (not shown) is mounted slightly in front of the front end cap 6. This cutter has, for example, a structure in which one end of a blade is axially attached (a so-called rotary cutter).
And the rubber composition 1 extruded by the rotation of the blade
2 is cut.

FIG. 2 shows the main body base 4 and the front end base 6 of FIG.
FIG. In FIG. 2, the left side is the pre-extrusion direction. A through hole 14 is formed in the main body base 4. Similarly, a through hole 16 is formed in the front end cap 6. The inner peripheral surface 18 of the main body base 4 is inclined so that the inner peripheral diameter increases in the direction before extrusion. The inner peripheral surface 20 of the front end cap 6 is continuously formed on the inner peripheral surface 18 of the main body base 4. The inner peripheral surface 20 of the front end cap 6 is parallel to the extrusion direction, and its inner peripheral diameter is constant. The inner diameter of the front end base 6 is the same as the inner diameter of the front end of the main body base 4. In FIG. 2, what is indicated by a double-headed arrow α is the angle formed between the inner peripheral surface 18 and the extrusion direction (hereinafter, referred to as an angle)
This is also referred to as “base tilt angle”). In FIG. 2, what is indicated by a double-headed arrow L is the base inner peripheral surface 18,
20 is the length in the extrusion direction. Although the inner peripheral surface 18 of the main body base 4 has a linearly enlarged diameter in the cross-sectional shape, the inner peripheral surface 18 may have a curvedly enlarged diameter. As used herein, the term "inner peripheral surface is inclined" includes any case.

The rubber composition in the cylinder of the extruder 2 (see FIG. 1) enters the through hole 14 of the main body base 4 from the right side in FIG. It enters the through-hole 16 and is further pushed forward through the through-hole 16. And it cut | disconnects with a cutter as mentioned above, and a preform is formed. Inner peripheral surface 1 of main body base 4
8 is inclined so that the inner peripheral diameter increases in the pre-extrusion direction as described above, so that both ends of the obtained preform are convex.

FIG. 3 is a sectional view showing the state of the compression step of the manufacturing method of the present invention. The preformed body 22 obtained in the extrusion step is put into a half-split mold having an upper mold 54 and a lower mold 56 having a hemispherical cavity, and molded and crosslinked by a compression molding method to form a sphere. Since the front end 24 and the rear end 26 of the preform 22 are convex, a closed space surrounded by the preform 22 and the inner peripheral surface of the mold does not occur.
Therefore, no bear is generated on the surface of the rubber sphere.

[0018]

EXAMPLES The effects of the present invention will be described below with reference to examples. However, it should be understood that the present invention should not be construed as being limited based on the description of the examples.

[Experiment 1] [Example 1] 100 parts by weight of cis 97% butadiene rubber (trade name “BR01” of Nippon Synthetic Rubber Co., Ltd.), 25 parts by weight of zinc acrylate, 22 parts by weight of zinc white, and dicumyl peroxide One part by weight was kneaded with a kneader, further kneaded with an open roll, and heated to 70 ° C. This is extruded with a known plunger type extruder, cut with a cutter, and
000 preforms were obtained. The average weight of the preform was targeted at 50 g. The base used was of a type having a main body base and a front end base as shown in FIG. 2, and the inner peripheral surface of the main body base was inclined so that the inner peripheral diameter increased toward the pre-extrusion direction. And the base inclination angle α is -5
゜. The total length (dimensions indicated by the double-headed arrow L in FIG. 2) of the inner peripheral surface of the main body die and the inner peripheral surface of the front end die in the extrusion direction was 15 mm. The inner diameter of the front end cap was 23 mm. In addition,
The die inclination angle α is minus when the inner diameter increases toward the pre-extrusion direction, and positive when the inner diameter increases toward the post-extrusion direction. When the obtained preform was visually observed, the front end and the rear end were convex.

Next, the preform was subjected to compression molding using a mold having an upper die and a lower die having a cavity radius of 21 mm. A known hydraulic press was used for compression molding. The molding temperature was 160 ° C. and the molding time was 20 minutes. After molding, remove the molded product from the mold, remove the burr generated at the joint between the upper mold and the lower mold by polishing,
A golf ball body having a weight of about 45 g was obtained.

Example 2, Comparative Examples 1 to 3 Each of the bases to be used was preliminarily formed by 1000 pieces in the same manner as in Example 1 except that the base inclination angle α was as shown in Table 1 below. I got a body. When the obtained preform was visually observed, the preform of Example 2 had a convex front end portion and a rear end portion. The preforms of Comparative Example 1, Comparative Example 2, and Comparative Example 3 had many rear-end portions that were convex but front-end portions that were flat or concave. Using these preforms, a golf ball body was formed in the same manner as in Example 1.

[Measurement of Weight of Preformed Body] 100% of the preformed body obtained in the extrusion step of the production method of each of Examples and Comparative Examples.
Samples were extracted at random and weighed. Then, the standard deviation and the width (the difference between the maximum weight and the minimum weight) were calculated. These results are shown in Table 1 below.

[Measurement of Length of Preformed Body] The length (indicated by a double-pointed arrow L1 in FIG. 4) and the total length (shown by double-headed arrow L1 in FIG. 4) of the preformed body obtained in the extrusion step of the production method of each of the examples and comparative examples 4 (indicated by a double arrow L2). Then, the length ratio (L2 / L1) was determined. This length ratio (L
The larger the value of 2 / L1), the greater the degree of protrusion of the front end and the rear end. In addition, 10 preforms extracted at random were used for the measurement. The results are shown in Table 1 below.

[Bear Occurrence Rate] The surface of 1,000 golf balls obtained by the production method of each of Examples and Comparative Examples was visually observed to determine the presence or absence of a bear. Then, the bear occurrence rate was calculated. The results are shown in Table 1 below.

[0025]

[Table 1]

According to the results shown in Table 1, each of the embodiments using a die having a die inclination angle α of minus (that is, the inner peripheral surface is inclined so that the inner peripheral diameter increases toward the pre-extrusion direction). The production method of the example can increase the length ratio of the obtained preformed body as compared with the production method of each comparative example in which the die inclination angle α is zero or positive, and therefore can suppress the bear generation rate. I understand.

[Experiment 2] [Examples 3 to 6] The total length of the inner peripheral surface of the main body die and the inner peripheral surface of the front end die in the extrusion direction was as described in Table 2 below, except that the total length was as shown in Table 2 below. A golf ball body was obtained in the same manner as in Example 1 of Experiment 1. Then, the measurement of the weight of the preformed body, the measurement of the length of the preformed body, and the calculation of the bear occurrence rate were performed in the same manner as in Experiment 1 described above. These results are shown in Table 2 below together with the results of Example 1 of Experiment 1.

[0028]

[Table 2]

From the results shown in Table 2, it was confirmed that the longer the length of the inner peripheral surface of the mouthpiece, the more the variation in the weight of the preform was suppressed and the length ratio of the preform was able to be increased.

[Experiment 3] [Examples 7 to 11] A golf ball body was obtained in the same manner as in Example 1 of Experiment 1 except that the base inclination angle α was as shown in Table 3 below. And measuring the weight of the preform,
The measurement of the length of the preformed body and the calculation of the bear generation rate were performed in the same manner as in Experiment 1 described above. The results are shown in Table 3 below together with the results of Example 5 of Experiment 2.

[0031]

[Table 3]

From Table 3, it was found that a die having a larger inner peripheral diameter in the pre-extrusion direction could have a larger length ratio of the preform. In addition, it was found that a die having a larger inner peripheral diameter in the pre-extrusion direction was disadvantageous in suppressing the variation in weight of the preform. From these results, it was confirmed that the mouthpiece inclination angle α was preferably from −5 ° to −0.5 ° (that is, the absolute value was from 0.5 ° to 5 °).

[0033]

As is clear from the above description, according to the manufacturing method of the present invention, the manufacturing cost is not increased.
It is possible to suppress the occurrence of bears of rubber spheres.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a state of an extrusion step of a manufacturing method according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a main body base and a front end base of FIG. 1;

FIG. 3 is a cross-sectional view showing a state of a compression step of the manufacturing method of the present invention.

FIG. 4 is a front view of a preform obtained in an extrusion step of the production method of the present invention.

FIG. 5 is a cross-sectional view illustrating a compression molding step in a conventional golf ball manufacturing method.

[Explanation of symbols]

 2 Extruder 4 Main body base 6 Front end base 8 Flange part 10 Projection part 12 Rubber composition 14 Through hole 16 Through hole 18 Inner peripheral surface 20 Inner peripheral surface 22 Preform 24 Front end 26 Rear end 54 Upper die 56 Lower Type

Claims (4)

[Claims] 1. An extrusion step of cutting a rubber composition while extruding it from a die to produce a substantially cylindrical preform, and subjecting the preform to compression molding using a pair of half-split molds. A method of manufacturing a rubber sphere including a molding step, wherein the die has a portion whose inner peripheral surface is inclined so that the inner peripheral diameter increases in the direction before extrusion. A method for producing a rubber sphere. 2. The method for producing a rubber sphere according to claim 1, wherein the length of the inner peripheral surface of the die in the extrusion direction is 15 mm or more. 3. The angle between the inner peripheral surface and the extrusion direction of the inclined portion of the inner peripheral surface of the die is 0.5 ° or more.
方法 The method for producing a rubber sphere according to claim 1 or claim 2, wherein 4. The method for producing a rubber sphere according to claim 1, wherein the rubber sphere is a golf ball.