JP2014117814A - Method for producing gasket for battery made of pps resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a gasket for a battery made of a PPS resin capable of obtaining a gasket in which the reduction of cost is possible, and sufficiently satisfying out-of-roundness and strength.SOLUTION: In the method for producing a gasket for a battery made of a PPS resin using an injection mold having a sprue 2, runners 3 and cavities 5, using the mold provided with a plurality of the cavities 5, and pin gates 4 or submarine gates at three or more parts to the respective cavities 5, using mainly a PPS resin melted in such a manner that the cross-sectional area of the runners 3 leading to the respective gates 4 is controlled to 7.0 mmor less, and thereby injection molding is performed.

Description

  The present invention relates to a method for manufacturing a gasket for a PPS resin battery, and more particularly to a method for manufacturing a gasket for a PPS resin battery for coin or button type lithium batteries.

  For example, a coin-type battery is sealed at the opening of a bottomed positive electrode can serving as a positive electrode terminal in order to seal the positive electrode material / negative electrode material, electrolyte, etc. so as not to leak and maintain insulation from the positive electrode terminal / negative electrode terminal. When a sealing plate serving as a negative electrode terminal is attached, a resin ring-shaped gasket is interposed between the opening and the sealing plate (see Patent Document 1).

  In particular, a coin-type lithium battery may be used at an environmental temperature of −40 to 100 ° C., and a gasket used in such an environment needs to maintain performance in the same temperature range, so that it has an electrical insulation property. A gasket made of PPS (polyphenylene sulfide) resin, which is excellent in chemical resistance and heat resistance, is used.

JP 2005-259578 A

  By the way, conventionally, when manufacturing a ring-shaped gasket, injection molding which can be manufactured in large quantities at low cost has been performed. In particular, a gasket made of PPS resin for coin or button type lithium batteries has a ring shape, and is made using a mold having a disk gate because of problems of weld strength and roundness.

However, gaskets molded with a mold with a disk gate not only make the mold expensive because the mold structure is very complex, but also has a short mold life and is difficult to maintain quality. Therefore, there is a problem that the product cost of the gasket becomes very expensive.
In addition, the resin portion formed by the sprue, the runner, and the disk gate is discarded. The amount of resin molded in the disk gate part is higher than the waste resin ratio compared to using a pin gate or submarine gate, and if the product is small, it is more than the resin amount used in the product part. In some cases, however, the amount of resin to be discarded becomes larger. In this case, there is a problem that the product cost is further increased in addition to the cost required for the mold.

  Therefore, it is conceivable to recycle the discarded part of the resin. However, since the gasket used for the lithium battery needs to maintain the physical properties for more than 10 years, only the virgin material having stable physical properties is used. Runners that cannot be managed and recycled materials of resin molded with disk gates cannot be used. Therefore, there is a need for a technique that minimizes the amount of resin molded by the gate and runner to be discarded.

  The present invention has been made in view of the above circumstances, and is made of PPS resin that can ensure the quality required as a PPS resin battery gasket and can be manufactured at low cost using an inexpensive mold. It aims at providing the manufacturing method of the gasket for batteries.

A method for producing a gasket for a PPS resin battery according to the present invention is a method for producing a gasket for a PPS resin battery using an injection mold having a sprue, a runner and a cavity.
Using a mold having a plurality of cavities and three or more pin gates or submarine gates for each cavity, the melted mainly PPS resin with the cross-sectional area of the runner leading to each gate being 7.0 mm ² or less It is used for injection molding.

  By the way, until now, in injection molding using PPS resin, if the cross-sectional area of the runner is too small, pressure transmission is not efficient and weld adhesion becomes weak, and dimensional accuracy and mechanical strength such as gaskets. However, it was thought that it was not appropriate to make the necessary molded product. However, as a result of intensive studies, the inventors have surprisingly found that the melt viscosity is reduced by setting the cross-sectional area of the runner to a predetermined size or less and the number of pin gates or submarine gates to the cavity to 3 or more. Even if a pin gate or submarine gate with a small flow path area is used as the gate even though the PPS resin is relatively high, the fluidity is improved while the molten resin injected from the injection molding machine flows through the runner, and the inside of the cavity The present inventors have found that a molten resin can be satisfactorily flowed into the mold, and that a molded product with excellent weld strength and dimensional accuracy can be molded, thereby completing the present invention.

According to the PPS resin battery gasket manufacturing method of the present invention, a molten resin injected from an injection molding machine passes through a runner connected to a plurality of pin gates or submarine gates connected to a cavity through a sprue. When filling into the cavity, the molten resin flows from the sprue to the runner with a very small cross-sectional area, the temperature of the molten resin increases due to the passage resistance, and the viscosity decreases, and the molten resin passes through each pin gate or submarine gate from the runner. The fluidity of the resin becomes very good, and the cavity is filled with the molten resin.
As a result, a gasket that satisfies the same roundness and strength as a gasket molded by a mold having a disk gate, and can be manufactured at a lower cost than an injection molded product by a mold having a disk gate. Can be molded.
Furthermore, since the runner can also be made thinner than before, the amount of resin in the runner portion is reduced, and the overall cost for producing a molded product can be reduced. In particular, when the size of the gasket is small, the amount of resin molded by the runner and gate may be larger than the amount of resin used for molding the gasket in a mold equipped with a disk gate. According to the manufacturing method of the invention, the amount of waste resin can be reduced as much as possible.

Furthermore, it is preferable that the cross-sectional area of a runner shall be 2.4 mm < ² > or less as for the manufacturing method of the battery gasket for PPS resin of this invention.
By setting the cross-sectional area of the runner in this way, the fluidity of the molten resin is further improved and the amount of waste resin can be further reduced.

As described above, the PPS resin battery gasket manufacturing method of the present invention satisfies the same roundness and strength as those of a gasket molded by injection using a mold having a disk gate, and includes the disk gate. It is possible to mold a gasket that can be reduced in cost as compared with the case of using a mold.
As a result, the amount of resin used can be reduced, the gasket productivity can be greatly improved, and the production cost can be greatly reduced.

Resin of gasket corresponding to sprue, runner and pin gate molded by mold of molding apparatus for manufacturing battery gasket made of PPS resin according to embodiment of present invention, and connected to resin portion of pin gate It is the perspective view which showed the part. It is sectional drawing of the metal mold | die of the shaping | molding apparatus which manufactures the gasket for battery made from PPS resin which concerns on this embodiment.

  Hereinafter, embodiments of the present invention will be described. In this embodiment, a coin-type lithium battery is used as a battery in which a gasket manufactured by the manufacturing method of the present invention is incorporated. This coin-type lithium battery is mainly used for in-vehicle applications and has a low-cylindrical shape with high heat resistance and high reliability. A liquid and a separator are accommodated, and the opening of the metal can is sealed with a plate-like negative electrode terminal. And it has the structure where the positive electrode terminal and the negative electrode terminal were sealed via the ring-shaped gasket.

  The gasket used in this coin-type lithium battery is made of a thermoplastic resin that is mainly composed of PPS resin because it requires excellent electrical insulation, chemical resistance to electrolytes, and constant heat resistance of 100 ° C or higher. ing.

  PPS resin is a thermoplastic resin obtained by synthesizing paradichlorobenzene and sodium sulfide. Furthermore, it is preferable to add a heat-resistant rubber or elastomer such as fluororubber to the PPS resin in order to impart flexibility as a gasket. If necessary, a heat stabilizer, a release material, a sliding material, an inorganic additive such as glass fiber, and a small amount of other plastics may be added.

FIG. 1 shows a resin portion corresponding to a sprue 2, a runner 3, and a pin gate 4 of a mold that is injection-molded by a mold of a molding apparatus that manufactures a PPS resin battery gasket, and a cavity 5 that is connected by the pin gate 4. The positional relationship with the resin part used as the corresponding gasket 1 is shown.
FIG. 2 is a cross-sectional view of a mold including the cavity 5, the pin gate 4, and the runner 3.

As shown in FIG. 2, the mold used in the injection molding includes an upper mold 61, an intermediate mold 62, and a lower mold 63.
The upper mold 61 is fixed so as not to move, and a sprue 2 for receiving a molten resin sent from an injection molding machine is formed inside.

  The intermediate mold 62 moves up and down so as to be movable back and forth with respect to the upper mold 61, and a number of fifth runners 35 to be described later of the runners 3 are formed to penetrate vertically. A pin gate 4 that opens to the cavity 5 is formed at the lower end. A first runner 31 to a fourth runner 34, which will be described later, of the runner 3 are formed between the upper mold 61 and the intermediate mold 62.

  The lower mold 63 moves up and down to be movable back and forth with respect to the intermediate mold 62. With the intermediate mold 62 in contact with the upper mold 61, the lower mold 63 moves downward. It moves away from the intermediate mold 62. A cavity 5 for molding the gasket 1 is formed between the intermediate mold 62 and the lower mold 63, and the cavity 5 communicates with the three pin gates 4.

The sprue 2 is a portion through which molten resin flows from the nozzle portion of the injection molding machine.
The runner 3 is a portion that is continuous with the sprue 2 and flows through the sprue 2. The runner 3 branches from the sprue 2 to each cavity 5 and extends. The cross-sectional shape of the runner 3 may be rectangular, but is preferably circular or elliptical. The pin gate 4 connects the cavity 5 and the runner 3 and is provided as a portion to be cut after the resin in the gasket 1 and the runner 3 as a molded product is cooled and solidified.

  In the present embodiment, three pin gates 4 are provided for one cavity 5, but the number can be four or more depending on the size of the gasket 1 that is a molded product. Further, a submarine gate can be used instead of the pin gate 4. In addition, various gate shapes such as direct gate, side gate, tab gate, fan gate, film gate, disc gate, pin gate, and submarine gate can be used, but the mold structure is simple to make gasket 1 at low cost. A pin gate and a submarine gate are preferred in which the gate is automatically cut when the molded product is taken out. In the present invention, it is preferable to form at least three gates connected to one cavity 5 in order to obtain a gasket 1 with good weld strength and roundness.

  When the molten resin injected from the injection molding machine flows into the runner 3 from the sprue 2, the molten resin flows toward the cavities 5 while branching, and is filled into the cavities 5 from the three pin gates 4. When the molten resin is cooled and solidified in the cavity 5, the gasket 1 having a shape as shown in FIG. 1 is formed. Further, the runner 3 and the pin gate 4 also form resin moldings of those shapes as shown in FIG.

  A specific injection molding process for this embodiment will be described. When molten resin is supplied to the sprue 2 from the injection molding machine with the upper mold 61, the intermediate mold 62, and the lower mold 63 connected to each other, Resin is filled into each cavity 5 from the pin gate 4 through the runner 3 from the sprue 2. As shown in FIG. 1, the runner 3 formed between the upper mold 61 and the intermediate mold 62 includes a first runner 31 that branches in two directions from the sprue 2, and an end portion of the first runner 31. A second runner 32 that further branches in two directions, a third runner 33 that further branches in two directions from the end portion of the second runner 32, and a fourth runner that extends radially in three directions from the end portion of the third runner 33 34. Then, a fifth runner 35 is formed continuously downward from the end portions of these fourth runners 34, and a pin gate 4 that opens to the cavity 5 is formed at the lower end of the fifth runner 35. The three fourth runners 34 that extend radially are connected to the third runner 33 at the center of the cavity 5.

In the present embodiment, the first runner 31, the second runner 32, the third runner 33, and the fourth runner 34 have a circular cross-sectional shape, and the cross-sectional areas are all formed in the same size, and the fifth runner 35 is downward. It is formed in a tapering shape toward. The first runner 31, the second runner 32, the third runner 33, the fourth runner 34, and the fifth runner 35 are formed so that the cross-sectional areas are 7.0 mm ² or less.

  When the resin in the cavity 5 is solidified, the lower mold 63 moves downward in the direction away from the intermediate mold 62, and the molded product to be the gasket 1 molded in the cavity 5 is separated from the lower mold 63. . Next, by moving the intermediate mold 62 downward in a direction away from the upper mold 61, the resin portion molded by the pin gate 4 from the gasket 1 is cut, and the gasket 1 is detached from the intermediate mold 62. Then, the resin portions of the runner 3, the pin gate 4 and the sprue 2 are removed from between the upper mold 61 and the intermediate mold 62.

In the present embodiment, as described above, the cross-sectional area of the runner 3 is 7 mm ² or less, but the cross-sectional area of the runner 3 is 3 mm ² to ² mm ² depending on the capacity of the molding apparatus and the number of mold cavities 5. Preferably, it is 2.4 mm ² or less.

  The number of cavities 5 is not particularly limited as long as the runner 3 having a small cross-sectional area can be used. However, if the number of cavities 5 is too large, the runners 3 become longer and the injection pressure increases. Depending on ability, 16 or less is preferable.

In addition, when the runner 3 having a cross-sectional area exceeding 7.0 mm ² is used, the fluidity tends to decrease, and the resin filling into the cavity 5 in the mold becomes insufficient, and a good molded product is obtained. This tends to be difficult to obtain, which is not preferable.

Moreover, as a minimum of the cross-sectional area of a runner, there exists an area which can degas in a runner, and the cross-sectional area where the fluidity | liquidity of resin in a runner is favorable is required. Preferably it is 0.1 mm ² or more. If the cross-sectional area is too small, it is not preferable because the molten resin hardly flows from the sprue 2 to the runner 3.

  Furthermore, in the connection part of the sprue 2 and the runner 3, the opening area to the sprue 2 of the runner 3 is made larger than the intermediate flow path area of the runner 3, and a taper-shaped taper part is formed in the inlet part of the runner 3. It is preferable. In this way, the inlet of the runner 3 is tapered, so that the molten resin easily enters the runner 3 from the sprue 2 even if the cross-sectional area of the runner 3 is considerably reduced.

  About the cross-sectional shape of the runner 3, well-known arbitrary shapes are applicable, for example, shapes, such as a circle, a semicircle, a trapezoid, a rectangle, a triangle, can be illustrated. The length of the runner 3 is not particularly limited, and can be set as usual in accordance with the layout of the cavity 5.

  In addition, the cross-sectional area of the runner 3 may be uniform over the entire length of the runner 3 or may be changed stepwise. When the cross-sectional area is changed stepwise, the length of the runner 3 whose cross-sectional area falls within the scope of the present invention is 1/4 or more, preferably 1/3 or more, more preferably 1 of the length of all runners 3. It is preferable that the cross-sectional area on the side of the cavity 5 is reduced so as to be not less than / 2.

  Thus, by setting the proportion of the volume occupied by the runner 3 and the pin gate 4 in the mold as small as possible, the waste of resin is reduced and the productivity of the gasket is improved. In the present embodiment, the weight per gasket molded product, that is, the amount of resin filled in one cavity 5 is less than 1 g. Thus, even if the molded product is small, the amount of discarded resin can be reduced as much as possible, and the gasket productivity can be improved.

  In the present embodiment, the number of cavities 5 provided in one mold is eight, but one may be used. Preferably, the number of cavities 5 is four or more. Even when the number of the cavities 5 is increased to 8, 16, and 32, the fluidity of the molten resin is improved and the productivity of the gasket is improved by the manufacturing method of the present invention.

  The following results were obtained for the quality and moldability of the gaskets produced by the method for producing a PPS resin battery gasket according to the present invention. As an example, PPS resin was used.

  The mold has eight cavities for molding the gasket 1 having the shape shown in FIG. 1, and the shape of the gate, the number of gates, and the cross-sectional area of the runner can be changed to the shape, number, and numerical value shown in Table 1, respectively. used. In addition, the cross-sectional shape of the runner of the Example and comparative example which are shown in Table 1 is circular, and Table 1 also shows the runner diameter corresponding to the cross-sectional area of the runner. The cavity formed in the mold was such that a ring-shaped gasket having an outer diameter of 24 mm and a weight of 0.15 g could be injection molded.

The injection molding machine used in the examples was a screw having a screw diameter of 32 mm and a clamping force of 100 tons.
The injection molding conditions for PPS resin are: the cylinder temperature of the injection molding machine is set so that the resin temperature is 310 ° C, the mold temperature is set to 145 ° C, and the injection speed and holding pressure are checked while checking the quality of the molded product. Adjustments were made.

  The roundness of the gasket molded product obtained was evaluated by measuring the outer diameter of the gasket using a line connecting the marking position and the gasket center point at one place on the outer periphery of the ring of the molded product. The value is the direction of the outer diameter x. Further, a value obtained by measuring the outer diameter orthogonal to the outer diameter x direction is defined as an outer diameter y direction. When the value obtained by subtracting the outer diameter y direction from the outer diameter x direction is 0.05 mm or less with respect to all the gaskets formed of eight cavities, the roundness is OK, and even one exceeds 0.05 mm. The roundness was NG. In addition, the target of the measured value of the outer diameter is 24.0 mm.

  Further, in order to fix the position of the marking as the measurement position of the molded product, the gasket was injection-molded with a mold in which a shape to be the marking was previously formed on the mold so that the marking was transferred to the gasket molded product.

  As a method for evaluating the strength of the gasket, the tensile strength was measured using a predetermined tensile test apparatus. The tensile test apparatus is a disk-like state by abutting the straight portions of a pair of semi-discs, forming a semi-cylindrical protrusion at the center of the straight-line portion of each semi-disc, and forming a cylindrical shape by the abutting state. A ring gasket is fitted to a pair of semi-cylindrical protrusions, one half disk is fixed, the other half disk is slid and the gasket is pulled from the inner periphery, thereby pulling the ring gasket. What measured the intensity was used.

  Table 1 shows the average value of the tensile strength of the molded product formed with eight cavities. In addition, in order for a gasket to show a favorable state as a battery, the tensile strength needs to be 176 N or more. As a comparative example with the gasket manufactured by the manufacturing method of the present invention, Table 1 shows that the cross-sectional area of the runner is small as a result of the gasket performance evaluation when the cross-sectional area of the runner is large and the number of pin gates is one and three. The results of gasket performance evaluation in the case of one and two pin gates are shown.

  Table 1 shows the evaluation results of gasket molded products by each runner / gate shape.

  As shown in the results of the above examples and comparative examples, by using the manufacturing method by injection molding according to the present invention, a PPS resin gasket that satisfies the quality requirements of a coin-type lithium battery can be obtained using an inexpensive mold. It was found that it can be manufactured at low cost.

As shown in Comparative Example 1, when a pin gate is provided in place of the disk gate and the cross-sectional area of the runner is 13.0 mm ² , the roundness and strength do not match the gasket specifications, and the gasket The shape became an ellipse and the strength was insufficient.

As shown in Comparative Example 2, the cross-sectional area of the mold runner is 20.0 mm ² as in the current disk gate type, and even when the gasket is molded with the number of pin gates increased to three, The strength and strength did not match the gasket specifications, the gasket shape was elliptical, and the strength was insufficient.

  As shown in Comparative Example 3, when the mold runner cross-sectional area is 13.0 mm and the number of pin gates is increased to three and the gasket is molded, the roundness matches the gasket specifications, but the strength Did not satisfy the gasket specifications.

As shown in Comparative Example 4, when one pin gate was provided and the cross-sectional area of the runner was 5.0 mm ² , the strength was within the allowable range, but the roundness did not match the gasket specifications. It became.

As shown in Comparative Example 5, when one pin gate was provided and the runner cross-sectional area was 2.4 mm ² , the strength was acceptable, but the roundness did not meet the gasket specifications. It became.

As shown in Comparative Example 6, when two pin gates were provided and the cross-sectional area of the runner was 5.0 mm ² , the strength was good, but the roundness did not match the gasket specifications. became.

As shown in Comparative Example 7, when two pin gates were provided and the cross-sectional area of the runner was 2.4 mm ² , the strength was good, but the roundness did not match the gasket specifications. became.

In contrast to the comparative example, in Example 1, the number of pin gates is three, the cross-sectional area of the runner is reduced to 7 mm ² , and the gasket is molded. The roundness matches the gasket specification, and the strength is also the gasket specification. A strength sufficiently satisfying the above was obtained.

In the second embodiment, the number of pin gates is three, the gasket is molded by further reducing the cross-sectional area of the runner to 3 mm ² , the roundness matches the gasket specifications, and the strength is the runner of the first embodiment. The cross-sectional area was further improved as compared with the case where the cross-sectional area was 7 mm ² .

In Example 3, the number of pin gates is three, and the cross section of the runner is reduced to 2 mm ² to form a gasket. The roundness matches the gasket specifications, and the strength is the same as that of the runner of Example 1. The area was improved as compared with the case where the area was 7 mm ² .

In Example 4, the number of pin gates was four, the gasket was molded with the cross-sectional area of the runner being 7 mm ² , the roundness matched the gasket specifications, and the strength was also the number of pin gates of Example 1 was three. Improved than the case.

In Example 5, the number of submarine gates is set to 3 and the cross-sectional area of the runner is set to 7 mm ² , and the gasket is molded. As in the case of Example 1 having 3 pin gates, the roundness is the gasket specification. The strength was sufficient to satisfy the gasket specifications.

In Example 6, the number of submarine gates was set to 4 and the cross-sectional area of the runner was set to 5 mm ² , and the gasket was molded. As in the case of Example 4 having 4 pin gates, the roundness is the gasket specification. The strength was improved as compared with the case where the number of submarine gates in Example 5 was three.

In Example 7, the number of pin gates was four, the gasket was molded with the cross-sectional area of the runner being 5 mm ² , the roundness matched the gasket specifications, and the strength was three in the number of pin gates of Example 1. Therefore, the cross-sectional area of the runner was improved to 7 mm ^2, and the number of pin gates in Example 2 was 3 and the cross-sectional area of the runner was 3 mm ² .

In Example 8, the number of pin gates is four, the gasket is molded with a cross-sectional area of the runner of 2.4 mm ² , the roundness matches the gasket specifications, and the strength is the number of pin gates of Example 1. Three improved the cross-sectional area of the runner to 7 mm ^2, and further improved compared to the case where the number of pin gates in Example 7 was four and the cross-sectional area of the runner was 5 mm ² .

In the ninth embodiment, the number of pin gates is three, the gasket is molded with a runner cross-sectional area of 2.4 mm ² , the roundness matches the gasket specifications, and the strength is the number of pin gates of the first embodiment. Three improved the cross-sectional area of the runner to 7 mm ^2, and further improved compared to the case where the number of pin gates in Example 2 was three and the cross-sectional area of the runner was 3 mm ² .

In Example 10, the number of pin gates was 5, the cross-sectional area of the runner was 5 mm ² , and the gasket was molded. The roundness matched the gasket specifications, and the strength was 3 for the number of pin gates of Example 1. Thus, the cross-sectional area of the runner was improved to 7 mm ^2, and the number of pin gates in Example 7 was 4 and the cross-sectional area of the runner was 5 mm ² .

In Example 11, the number of pin gates was set to 5 and the gasket was molded with the cross-sectional area of the runner set to 2.4 mm ² , the roundness matched the gasket specifications, and the strength was the number of pin gates of Example 1. Three improved the cross-sectional area of the runner to 7 mm ^2, and further improved compared to the case where the number of pin gates in Example 10 was five and the cross-sectional area of the runner was 5 mm ² .

  The method for manufacturing a gasket for a battery made of PPS resin of the present invention can reduce the cost, and is suitable for molding a gasket that sufficiently satisfies roundness and strength.

DESCRIPTION OF SYMBOLS 1 Gasket 2 Sprue 3 Runner 31 1st runner 32 2nd runner 33 3rd runner 34 4th runner 35 5th runner 4 Pin gate 5 Cavity 61 Upper mold 62 Intermediate mold 63 Lower mold

Claims (2)

In the manufacturing method of a battery gasket made of PPS (polyphenylene sulfide) resin using an injection mold having a sprue, a runner and a cavity,
Using a mold having a plurality of cavities and three or more pin gates or submarine gates for each cavity, the melted mainly PPS resin with the cross-sectional area of the runner leading to each gate being 7.0 mm ² or less A method for producing a gasket for a battery made of PPS resin, characterized by using injection molding. The method for producing a PPS resin battery gasket according to claim 1, wherein the runner has a cross-sectional area of 2.4 mm ² or less.

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