JP5332332B2 - Injection molding method for mirror cabinet body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molding method not to make a sink mark on each surface of rib joining parts of an outside plate 15 and a front side plate 17 on the outside wall of a body 1 of a mirror cabinet made of a polypropylene resin. <P>SOLUTION: A wall thickness of a jointing part T3 to be jointed with an outside plate 15 in a closed mold cavity 23a, the outside plate 15 for a platy rib 18 in a molding region of the front side plate 17 and the platy rib 18, and with the front side plate 17 is made to be 0.29 to 0.46 times the wall thickness T1 of the outside plate 15, or that of the front side plate 17, the outside plate 15 being an object to joint with the jointing part. When a molten polypropylene resin M is filled into a mold cavity 23a on getting the molten polypropylene resin M is cooled to be solidified, a longitudinal area A inside of each of the outside plate 15 and the front side plate 17 is provided with a cavity 24 for preventing a sink mark side from extending to a halfway before the end point along a corner short direction B and C separating from the jointing corner 20, and the platy rib 18 is cooled to be solidified at the state that the inside pressure of each of the outside plate 15 and the front side plate 17 is raised by a compressed gas G. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an injection molding method for a mirror cabinet body made of polypropylene resin.

Conventionally, a mirror cabinet body has a cross-sectional cross-sectional structure in which an outer side plate and an inner side plate facing each other through a hollow part are connected by a front side plate as a structure of an outer wall extending in a vertical direction that is partitioned into a storage part inside the cabinet and the outside of the cabinet. There are some which are molded into a letter shape to increase the rigidity and increase the strength, and the wall is made thick so that it looks good, and is molded by vacuum molding or injection molding (Patent Document 1, Patent Document 2). The mirror cabinet body is made of impact-resistant polystyrene (HIPS) as its material.
JP-A-5-161557 Japanese Patent Laid-Open No. 5-300815

By the way, the impact-resistant polystyrene part may be broken when a chemical such as cosmetics adheres to it, so that the appearance of a mirror cabinet resistant to the chemical is desired.
In order to meet this demand, the inventors tried to manufacture a mirror cabinet body by injection molding using a chemical-resistant polypropylene resin. Since a large warp occurs in the outer side plate which becomes a free end, ribs are provided in the hollow portion of the outer side wall at appropriate vertical intervals, and the back sides of the outer side plate, the inner side plate and the front side plate are connected by the ribs. We decided to prevent the occurrence.
However, in the outer wall provided with ribs, sink marks are generated on the surfaces of the joint portions of the outer plate, the inner plate, and the front plate that are joined to the ribs. This leads to problems that make the mirror cabinet look bad.

  Then, this invention aims at provision of the injection molding method of the mirror cabinet main body which does not produce sink marks in each surface of the rib joint location of the outer side plate and front side plate in the outer side wall of the mirror cabinet main body made of polypropylene resin.

The means adopted by the present invention includes an outer plate and an inner plate facing each other through a hollow portion, a front plate connected to the outer plate and the inner plate, and a joint disposed on the outer plate, the inner plate and the front plate disposed in the hollow portion. In an injection molding method of molding a mirror cabinet body having a plurality of plate-like ribs and having a longitudinally extending outer wall portion with polypropylene resin, molding of an outer plate, a front plate and plate-like ribs in a cavity of a closed mold and from 0.29 to 0.46 times the outer plate and meat thickness of the outer plate or the front plate is a counterpart of joining wall thickness of the joint portion joined to the front side plate of the plate-shaped rib in the region, and, the plate the shape ribs, shaped as meat thickness as the front plate opposite decreases, is filled with the molten polypropylene resin in the closed mold cavity Zhou the molten polypropylene resin is being cooled and solidified At this time, the compressed ribs are injected toward the joint corners of the outer plate and the front plate inside the filled resin, and the plate-like ribs in the state where the pressure inside each of the outer plate and the front plate is increased by the compressed gas. It is an injection molding method of a mirror cabinet body characterized by cooling and solidifying.

  In the present invention, the compressed gas is injected into the longitudinal direction area inside each of the outer plate and the front plate, in the middle before reaching the separation end along the short direction away from the joint corner of the outer plate and the front plate. An anti-sink cavity that extends to

  In addition, it is preferable to make the plate-like rib contraction amount at the time of cooling and solidification as small as possible by setting the thickness dimension of the joint part joined to the outer side plate and the front side plate of the plate-like rib to 0.8 to 1.3 mm. .

  In the injection molding method of the mirror cabinet body according to the present invention, the wall thickness dimension of the outer plate or the front plate, which is the counterpart to which the thickness dimension of the joint portion to be joined to the outer plate and the front plate of the plate-like rib is joined, is 0.29. By reducing the thickness substantially to 0.46 times, it is possible to reduce the influence of sink marks on the outer plate and the front plate due to the contraction when the plate rib is cooled and solidified, and to join the plate ribs on the outer plate and the front plate. In the region where a cavity for preventing sink marks is provided in the interior, the effect of shrinkage at the time of cooling and solidifying the plate-like ribs is blocked by the cavity so that there is no sink on each surface of the outer plate and the front plate. In the region where the cavity for preventing sink marks is not provided in the joint between the plate and the front plate and the plate-like rib, the outer plate and the front plate in which the internal pressure is increased with compressed gas are cooled and solidified by the plate-like rib. Mold opposite to the shrinkage force at the time Since cooling and solidifying while pressing towards the molding surface of the cavity, it is possible to suppress the shrinkage of about to fail on the surfaces of the outer plates and the front plate. As a result, the present invention can provide a mirror cabinet body free from sink marks on the surface of the outer side plate and the front side plate that face the outside easily.

  An injection molding method for a mirror cabinet body according to the present invention (hereinafter referred to as “the present invention molding method”) will be described based on an embodiment shown in the drawings.

  FIGS. 1 to 9 show an embodiment of the molding method of the present invention. FIG. 1 shows a mirror cabinet in which mirrors 11, 12, and 13 are attached to a mirror cabinet body 1 molded by the molding method of the present invention. It is the partially broken perspective view shown. FIG. 2 shows the vicinity of the left outer wall 2 of the mirror cabinet body 1 obtained by molding. FIG. 2 (A) is a partially broken perspective view, and FIG. 2 (B) forms the outer wall 2. FIG. 6 is a perspective view showing a sink-preventing cavity 24 provided inside the outer side plate 15 and the front side plate 17. FIG. 3 shows each cross section of the outer wall portion 2. FIG. 3 (A) is a plan view enlarged by sectioning along the line III-III in FIG. 2 (A), and FIG. ) Is a cross-sectional front view taken along the line bb, and FIG. 5C is a side view taken along the line cc in FIG. 4 is a front view of the outer wall portion shown in FIG. 2A, in which a portion corresponding to the cross-sectional portion taken along the line IV-IV is being formed, and FIG. 5 is a front view of the outer wall portion being omitted. FIG. 6 is a plan view with the intermediate omitted, showing a state where a portion corresponding to the cross-sectional portion of the outer wall portion of FIG. 2A taken along line VI-VI is formed, and FIG. 7 is a view of FIG. FIG. 8 is a cross-sectional view taken along the line III-III of the outer wall portion of FIG. 2 (A) in FIG. 2A, showing a state in which a portion corresponding to the cross-sectional portion of the outer wall portion taken along the line VII-VII is being molded. It is the top view which abbreviate | omitted intermediate | middle which shows the state which shape | molds the location which corresponds.

  As shown in FIG. 1, the mirror cabinet body 1 obtained by the molding method of the present invention is obtained by injection molding polypropylene resin, and includes left and right outer wall portions 2 and 3 and left and right outer wall portions 2 and 3. And upper and lower horizontal wall portions 4 and 5 and partition walls 6 and 7 that connect intermediate portions of the upper and lower horizontal wall portions 4 and 5, and the upper and lower horizontal wall portions 4 and 5 are arranged between the outer wall portion 2 (3) and the partition wall 6 (7). The left and right storage portions 8 (9) surrounded by the horizontal wall portions 4 and 5 are provided, and the central storage portion 10 surrounded by the upper and lower horizontal wall portions 4 and 5 is provided between the partition walls 6 and 7, The mirrors 11, 12 and the central mirror 13 are attached to open and close the storage units 8, 9, 10. Since the left and right outer wall portions 2, 3 of the mirror cabinet body 1 are formed symmetrically, only the left outer wall portion 2 will be described as follows.

  As shown in FIGS. 2 to 3, the outer wall 2 includes an outer plate 15 and an inner plate 16 facing each other through a hollow portion 19, a front plate 17 connected to the outer plate 15 and the inner plate 16, and a hollow portion 19. And a plurality of plate-like ribs 18 which are joined to the outer plate 15, the inner plate 16 and the front plate 17, and extend in the longitudinal direction A along the vertical direction. The outer wall 2 is connected to the lateral walls 4 and 5 at the top and bottom, and the longitudinal edge on the back side of the inner plate 16 is connected to the back plate 22. The outer wall 2 has a height dimension H (for example, H = 800 mm), a depth dimension D (for example, D = 100 mm), a front width dimension W (for example, W = 25 mm), and a vertical spacing dimension K of the plate-like ribs 18. (See FIG. 3B) (For example, K = 110 mm).

  The outer wall 2 has a thickness T1 (for example, T1 = 2.5 to 4.0 mm, preferably T1 = 2.8 mm) of the outer plate 15, the inner plate 16, and the front plate 17. Further, the plate-like rib 18 of the outer wall portion 2 has a thickness T3a (for example, T3a = 0) on the near side (joining portion to be joined to the front plate 17) that is the thickest with respect to the thickness T3 (see FIG. 3C). .8 to 1.3 mm, preferably T3a = 1.1 mm), and the thickness T3b (for example, T3b = 0.5) on the deepest side (joining portion joined to the outer plate 15 or the inner plate 16). -1.0 mm, preferably T3b = 0.8 mm), and the thickness of the plate-like rib 18 is considerably thinner than the thickness of the outer plate 15 and the front plate 17 (T3 = 0.8-1.3 mm), A draft angle for demolding is provided.

  The outer wall portion 2 is crotched by the outer side plate 15 and the front side plate 17 and inside each of the outer side plate 15 and the front side plate 17 along the longitudinal direction A along the vertical direction and the short side along the front-rear direction perpendicular to the longitudinal direction A. An anti-sink cavity 24 is provided extending in the hand direction B and the short direction C along the left-right direction orthogonal to the longitudinal direction A. The cavity 24 for preventing sink marks is formed at each separation end of the outer plate 15 and the front plate 17 along the short directions B and C that are separated from the joint corner 20 where the outer plate 15 and the front plate 17 are joined (FIG. 3 ( A) is formed so as to extend halfway to the rear end 15a of the outer side plate 15 and the right end 17a) of the front side plate 17 shown in FIG. This prevents the sinking from occurring on the surface. As shown in FIG. 3A, the size of the cavity 24 for preventing sink marks is such that the front-rear dimension E1 of the outer plate 15 along the short-side direction B and the front-rear dimension E2 of the cavity 24 are 10 to 10 of E1. If the left-right dimension F1 of the front side plate 17 along the short-side direction C and the left-right dimension F2 of the cavity 24 are F2, the F2 is about 10 to 80% of F1.

  The procedure of the molding method of the present invention obtained by injection molding the outer wall portion 2 is as follows. First, as shown in FIGS. 4 to 8, a mold 23 is prepared, and a molding region for the outer plate 15, the front plate 17, and the plate-like rib 18 is formed in the cavity 23 a of the closed mold 23. The thickness T3 (see FIG. 5) of the molding region of the joining portion 18a joined to the outer plate 15 and the front plate 17 of the rib 18 is 0.29 of the thickness T1 of the molding region of the outer plate 15 or the front plate 17. The thickness T3 in the molding region of the plate-like rib 18 is 0.8 to 1.3 mm (for example, the thickness T3a on the near side that becomes the thickest (for example, T3a = 0.8 to 1.3 mm (preferably T3a = 1.1 mm) and the thinnest (rear) wall thickness T3b (for example, T3b = 0.5 to 1.0 mm, preferably T3b = 0.8 mm). ) So that the plate-like ribs 18 are cooled and solidified. The amount of shrinkage are as much as possible reduced. Further, in the cavity 23a of the closed mold 23, the thickness in the molding region of the curved joining corner 20 (see FIGS. 6 and 7) for joining the outer plate 15 and the inner plate 16 is set to the outer plate 15 and the front plate. By making the thickness T1 about 0.3 to 0.7 mm thicker than the thickness T1 in the molding region of the side plate 17, the cavity 24 for preventing sink marks can be easily provided along the longitudinal direction A. Further, the mold 23 is provided with a gas injection path 25 that reaches the molding region of the joint corner 20 (see FIGS. 6 and 7) in the closed cavity 23a. If the thickness T3 exceeds 0.46 times the thickness T1 and the thickness T3 of the plate rib 18 is increased, sink marks are generated on the surfaces of the outer plate 15 and the front plate 17, and conversely, When the thickness T3 does not reach 0.29 times the thickness T1 and the thickness T3 of the plate-like rib 18 is thin, there is no sink on the surfaces of the outer plate 15 and the front plate 17.

  Next, molten polypropylene resin M (for example, MFR 15 to 70, which is a block PP, temperature 210 ° C.) is injected and filled into the cavity 23 a of the closed mold 23, and the temperature of the mold 23 is set to 40 to 40 ° C. When the molten polypropylene resin M is being cooled and solidified by cooling to about 45 ° C., the compressed gas G is directed toward the molding region of the joint corner 20 of the outer plate 15 and the front plate 17 via the gas injection path 25. (For example, nitrogen gas having a pressure of 3.8 to 4.2 Mpa, preferably 4.0 Mpa) is injected, and the compressed gas G is injected so as to be pushed in the longitudinal direction A inside the filling resin of the joint corner 20. The outer side plate 15 and the front side plate 17 are pushed along the short side directions B and C separated from the joint corner 20 to the middle before reaching the separation end in the short direction B and C from the joint corner 20. A compressed gas G is injected into each internal longitudinal region to provide an anti-sink cavity 24 (see FIGS. 3A and 2B) extending in the longitudinal direction A and the lateral directions B and C. The plate-like ribs 18 are cooled and solidified in a state where the pressure inside each of the outer plate 15 and the front plate 17 is increased by the compressed gas G. The injection of the compressed gas G is as follows. As shown in FIG. 3A, the size of the cavity 24 for preventing sink marks is such that E2 is about 10 to 60% of E1, and F2 is about 10 to 80% of F1. The injection timing, pressure and pressure are adjusted so that

  When the molten polypropylene resin M is cooled and solidified, the thickness dimension of the joining portion 18a joined to the outer plate 15 and the front plate 17 of each plate-like rib 18 is 0.29 to the thickness of the outer plate 15 or the front plate 17. Since the thickness of the plate-like rib 18 is considerably reduced to 0.46 times, the influence of sink marks on the outer plate 15 and the front plate 17 due to the shrinkage at the time of cooling and solidifying the plate-like ribs 18 can be reduced, and the plate shape in the outer plate 15 and the front plate 17 is reduced. In the area where the cavity 24 for preventing sink marks is provided inside the joint portion with the rib 18, the influence of shrinkage when the plate-like rib 18 is cooled and solidified is blocked by the cavity 24, and each surface of the outer plate 15 and the front plate 17. In the region where the cavity 24 for preventing the sink is not provided in the joint portion between the outer plate 15 and the front plate 17 with the plate-like rib 18, the internal pressure is compressed with the compressed gas G. Elevated state While pressing the outer side plate 15 and the front side plate 17 toward the molding surface in the mold cavity 23a opposite to the contraction force when the plate-like rib 18 is cooled and solidified (arrow P in FIGS. 6 and 7). Reference) Since it is cooled and solidified, sink marks that are likely to occur on the surfaces of the outer plate 15 and the front plate 17 can be suppressed.

  When the molten polypropylene resin M is cooled and solidified, the mold 23 is opened and the mirror cabinet body 1 is removed from the cavity 23a to complete the injection molding. In this way, in the molding method of the present invention, the mirror cabinet main body 1 having no sink marks on the surfaces of the outer side plate 15 and the front side plate 17 that are conspicuous facing outward can be obtained.

In order to confirm the effect of the present invention, the present inventors conducted tests under the following conditions and obtained the test results shown in the table of FIG.
1. External dimensions of the outer wall 2 in the molded product obtained by the test (see FIG. 2A)
Height dimension H = 800mm, depth dimension D = 100mm, front width dimension W25mm
2. Vertical gap dimension K of plate-like ribs 18 in a molded product obtained by the test (see FIG. 3B)
Vertical gap dimension K = 110mm
3. Resin conditions Molten polypropylene resin (MFR60) with a melting temperature of 210 ° C

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an embodiment of the molding method of the present invention, and is a partially broken perspective view showing a mirror cabinet in which a mirror is attached to a mirror cabinet body obtained by molding. The vicinity of the left outer wall portion of the mirror cabinet body obtained by molding is shown, in which FIG. (A) is a partially broken perspective view, and FIG. (B) is an outer side plate and a front side plate forming the outer wall portion. It is a perspective view which shows the cavity for sink marks provided in the inside. FIG. 2 shows each cross section of the left outer wall portion of the mirror cabinet body obtained by molding, and FIG. (A) is a plan view enlarged by sectioning along the III-III line in FIG. 2 (A). (B) is a front view taken along line bb in FIG. (A), and FIG. (C) is a side view taken along line cc in FIG. It is the front view which abbreviate | omitted the intermediate | middle which shows the state which shape | molds the location equivalent to the cross-sectional location of the IV-IV line | wire of the outer wall part of the figure of FIG. It is a left view which abbreviate | omits the intermediate | middle abbreviation and the molding state of an outer wall part. It is the top view which abbreviate | omitted intermediate | middle which shows the state which shape | molds the location corresponded to the cross-sectional location of the VI-VI line of the outer wall part of the figure of FIG. It is the top plan view which omitted the middle which shows the state where the portion equivalent to the section location of the VII-VII line of the outer wall part of Drawing 2 (A) of Drawing 2 is formed. It is the top view which abbreviate | omitted intermediate | middle which shows the state which shape | molds the location corresponded in the cross-sectional location of the III-III line | wire of the outer wall part of the figure of FIG. It is a table | surface which shows a test result.

Explanation of symbols

DESCRIPTION OF SYMBOLS 15 ... Outer plate, 17 ... Front side plate, 18 ... Plate-shaped rib, 20 ... Joining corner, 23 ... Mold, 23a ... Cavity, 24 ... Sink prevention cavity, A ... Longitudinal direction, B, C ... Short Direction, G ... compressed gas, M ... molten polypropylene resin

Claims (2)

An outer plate and an inner plate facing each other through the hollow portion, a front plate connected to the outer plate and the inner plate, and a plurality of plate-like ribs arranged in the hollow portion and joined to the outer plate, the inner plate and the front plate. In an injection molding method for molding a mirror cabinet body having an outer wall portion extending in the longitudinal direction with polypropylene resin,
The outer plate or the front plate which is the counterpart to join the thickness dimension of the outer plate of the plate-like rib in the molding region of the closed mold, the front plate and the plate-like rib, and the joint portion joined to the front plate. 0.29 to 0.46 times the wall thickness dimension, and the plate-like rib is shaped so that the wall thickness dimension becomes smaller toward the opposite side of the front plate,
When the molten polypropylene resin is filled into the cavity of the closed mold and the molten polypropylene resin is being cooled and solidified, a compressed gas is directed toward the joint corner between the outer plate and the front plate inside the filled resin. An injection molding method for a mirror cabinet body, characterized by injecting and cooling and solidifying a plate-like rib in a state in which the pressure inside each of the outer side plate and the front side plate is increased with compressed gas. 2. The outer wall portion according to claim 1, wherein the outer side plate, the inner side plate, and the front side plate surround three sides of the hollow portion, and the opposite side of the hollow portion to the front side plate is open. An injection molding method for a mirror cabinet main body.

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