JP2005288961A - Biodegradable resin-molded article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biodegradable resin-molded article which increases strength despite the possession of heat resistance, and which increases the strength, particularly, of a weld line part. <P>SOLUTION: A reinforcing member 13, which is molded of the same resin as a polylactic acid resin (biodegradable resin) for a frame, injected into a cavity 11, and whose crystallizing rate is enhanced, is prearranged in a place, wherein the weld line part 14 appears, in the cavity 11, and the polylactic acid resin is injected into the cavity 11 in this state, so that a decorative frame 8 (molded article) can be obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a biodegradable resin molded product that improves the strength of a weld line portion.

  In recent years when environmental problems are regarded as a problem, the treatment of petroleum-based resins (for example, ABS resin = acrylonitrile / butadiene / styrene resin, etc.) widely used for electric appliances has a large environmental load and has become various problems. For example, when these petroleum resins are incinerated, a large amount of carbon oxides, nitrogen oxides and the like are generated, which causes air pollution. Moreover, since it is not decomposed | disassembled by the natural microorganisms when buried in soil, it is buried in the soil semipermanently and causes soil contamination.

  In order to solve such problems peculiar to petroleum-based resins, recently, bio-derived non-petroleum resins called biodegradable resins (for example, polylactic acid resins) have begun to be used. Unlike the petroleum-based resin, this biodegradable resin has crystals inside in a normal formation state, and has the characteristics that heat resistance and strength are improved by growing the crystals, that is, promoting the crystallization rate. In addition, carbon oxides and nitrogen oxides are hardly generated even when incinerated, and are decomposed by microorganisms in the natural world. Therefore, even if they are buried in soil, they have an excellent merit that they naturally return to soil.

Here, when such a resin is used as a molded product used for, for example, an electric appliance, it is common to melt the resin and then injection-mold it into a cavity (mold) (for example, a patent). Reference 1).
Japanese Patent Laid-Open No. 2003-340889

  By the way, the biodegradable resin has the above-mentioned environmental advantages, but when the crystallization rate is promoted to improve heat resistance and strength, the crystallization rate is extremely slow. It takes time. For this reason, there is a demerit that a molded product of biodegradable resin (biodegradable resin molded product) in a normal molded state, that is, a crystallization rate is not high, is weaker to heat than a molded product of petroleum resin. For this reason, recently, an inorganic filler (for example, talc, calcium carbonate, etc.) is added to a biodegradable resin whose crystallization rate is not promoted to impart heat resistance.

  However, when an inorganic filler is added as described above, the heat resistance is improved, but on the other hand, there is a new problem that the strength of the molded product itself is lowered. Therefore, recently, in order to cope with this, the inorganic filler particles to be added are made fine (diameter of about several nm to about 100 nm), thereby promoting the crystallization rate of the biodegradable resin, It is configured to impart heat resistance and strength to the molded product.

  However, even with the above-described configuration, for example, in a cavity 101 (inside a mold) having an injection port (gate) 100 as shown in FIG. In the case where the resin is formed, it is a reality that a large strength cannot be obtained at a portion where the resins collide with each other, that is, a so-called weld line portion 103 (illustrated by a virtual line in FIG. 8A). Actually, if the tensile strength of the part where the weld line portion 103 does not exist in the molded product is 100%, the tensile strength of the weld line portion 103 is 0% to 20% (0% is peeled off at the stage of measurement preparation) It becomes very brittle.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a biodegradable resin molded product that has heat resistance but also strength, in particular, improved weld line strength. There is.

In order to achieve the above object, the biodegradable resin molded product of the present invention has a block-shaped reinforcing member molded with the same resin as the resin injected into the cavity in a state where the resin is disposed in advance in the cavity. It is formed (Invention of Claim 1).
According to this configuration, when the resins injected into the cavity collide with each other and fuse, the resin melts and encloses the reinforcing member (forms its surface) and forms a weld line portion and hardens. The strength of the line part is improved.

In the above case, the connecting member may be arranged in advance so as to be located at a place where the weld line portion is formed (invention of claim 2).
In addition, the biodegradable resin molded product of the present invention is formed in a state in which a nonwoven fabric formed in the shape of the same resin as the resin injected into the cavity is formed in the cavity in advance. A biodegradable resin molded product characterized in that it has been produced (the invention of claim 8).

  According to this configuration, not only the weld line portion but also the strength of the entire molded product can be improved.

  As described above, according to the biodegradable resin molded product of the present invention, the strength of the weld line portion is improved while having heat resistance.

Hereinafter, a first embodiment in which the biodegradable resin molded product of the present invention is applied to a decorative frame of a circuit breaker operation dial of a unit in a control center (a so-called low voltage motor switching control device) will be described. A description will be given with reference to FIGS.
First, the control center 1 includes a vertical box 2 as shown in FIG. The vertical turbulence 2 is divided into a wiring processing chamber 3, a vertical wiring processing chamber 4, a unit chamber 5, and the like. The unit chamber 5 has an open front, and a unit 6 for controlling the opening and closing of the low-voltage machine can be inserted and placed. The unit 6 has a circular circuit breaker operation dial 7 as shown in FIG. 3 on the front surface thereof, and a decorative frame 8 is provided around the circuit breaker operation dial 7. The decorative frame 8 is fixed to the unit 6 with screws 8a (see FIG. 3).

  As shown in FIG. 3, the decorative frame 8 has printing such as “ON”, “TRIP”, and “OFF” on its surface, and the operation dial 7 for the circuit breaker is rotated with respect to this printing. By positioning each of them, a circuit breaker (not shown) performs a predetermined operation. As shown in FIG. 1, the decorative frame 8 injects, for example, polylactic acid resin (hereinafter referred to as “polylactic acid resin for frame”) as a biodegradable resin into a cavity 11 composed of an upper mold 9 and a lower mold 10. It is formed on the basis of molding, and the shape thereof is a square as a whole, and a hole 12 (see FIGS. 2 and 3) through which the circuit breaker operation dial 7 is inserted is formed in the center. It is what. FIG. 1 shows a state before the frame polylactic acid resin is injected into the cavity 11.

  In the upper mold 9 and the lower mold 10 constituting the cavity 11, first, the upper mold 9 is centered as shown in FIG. 1 (b) showing a cutaway perspective view along the line AA in FIG. 1 (a). The part has a core 9a that protrudes downward in a columnar shape, and surrounds the core 9a in a square shape and is provided with a recess 9b that is shorter in the depth direction than the core 9a. Furthermore, an injection port 9c is provided in one side wall (the lower side wall in FIG. 1) of the recess 9b, and the frame polylactic acid resin can flow into the cavity 11 from the injection port 9c. ing. Further, at the four corners of the concave portion 9b of the upper die 9, there are provided screw hole forming projections 9d for forming the screw holes of the screw 8a so as to protrude downward. On the other hand, the lower mold 10 has a recess 10a that forms a cavity 11 together with the recess 9b.

  Incidentally, a block-shaped reinforcing member 13 is placed in the back of the lower mold 10 as shown in FIG. The reinforcing member 13 is shown in FIG. 4 showing a cross-sectional view taken along the line BB in FIG. 1A (this FIG. 4 shows the upper mold 9 and the lower mold 10 in a closed state). Furthermore, it has a height and a width (see also FIG. 1) so as to be placed with a predetermined gap between the upper mold 9 and the lower mold 10. The reinforcing member 13 is composed of a mixture of the polylactic acid resin (hereinafter referred to as a polylactic acid resin for reinforcing member) and an inorganic filler (for example, calcium carbonate), and the following method is used. Thus, it is formed so that the crystallization rate is increased (than the normal molding state).

  In forming the reinforcing member 13, first, calcium carbonate (powder) formed to a diameter of about several to 100 nm is added to and mixed with the polylactic acid resin for reinforcing member, and the polylactic acid resin for reinforcing member is mixed. And obtain a mixture of calcium carbonate. And this mixture is stored in the storage tank of the injection molding machine which is not illustrated, and the temperature (plasticization temperature) of this storage tank is about 200 degreeC, and the temperature in a normal shaping | molding state (about about 180 degreeC is common. Higher than that).

  Then, the temperature of a block-shaped (rectangular) reinforcing member cavity (mold) (not shown) for injecting the mixture is about 110 ° C. and a temperature in a normal molding state (about about 60 ° C. is common). In this state, the mixture is injected into the reinforcing member cavity. The in-mold holding time after injection (so-called cooling time) is about 60 seconds, which is longer than the holding time in a normal molding state (generally about 10 seconds). By such a series of operations, the reinforcing member 13 has a higher crystallization rate, and thus the reinforcing member 13 with improved heat resistance and strength can be obtained.

Now, the reinforcing member 13 formed in this way is placed behind the recess 10a of the lower mold 10 in the cavity 11 as described above (see FIGS. 1 and 4). 11, in other words, each of the upper mold 9 and the lower mold 10 is configured so that the temperature is maintained at around 110 ° C. The frame polylactic acid resin is injected into the cavity 11 at a high pressure of about 700 kg to 1000 kg / cm ² from the injection port 9c. In the case of the present embodiment, also in the polylactic acid resin for the frame injected into the cavity 11, calcium carbonate is added in advance as in the case of the polylactic acid resin for the reinforcing member, and an appropriate crystallization rate (the polylactic acid for the reinforcing member is added). Resin grade).

  As shown by arrow C in FIG. 1A, the frame polylactic acid resin injected into the cavity 11 is first centered on the front surface of the cylindrical core 9a (the lower surface in FIG. 1A). It divides into two hands and flows so as to go around both sides from the front surface of the core 9a. Then, the polylactic acid resin for a frame divided into two is circulated around the side surfaces along the shape of the core 9a, and finally, in the cavity 11, as shown by the arrow D in FIG. It reaches from behind in both directions (upward in FIG. 1 (a)). At this time, since the reinforcing member 13 is placed behind the core 9a as described above, the frame polylactic acid resin is formed in the cavity 11, that is, the upper die 9 and the lower die 10, the reinforcing member 13, The reinforcing member 13 is wrapped in the gap. However, the resin hardly flows into the mounting surface for the lower mold 10 of the reinforcing member 13.

  As described above, when the frame polylactic acid resin wraps the reinforcing member 13, the inside of the cavity 11 is at a temperature higher than a general temperature (about 110 ° C.) as described above. Although some heat is taken away in the middle of reaching the rear of the core 9a from the base 9c, the temperature does not rapidly decrease, so it flows into the gap between the upper mold 9 and the lower mold 10 and the reinforcing member 13. Even at that time, it has a relatively high temperature (a temperature with a certain degree of fluidity) and a low viscosity. As a result, the frame polylactic acid resin melts the reinforcing member 13 (the surface thereof) by the heat of the frame itself and encloses the reinforcing member 13 integrally, and the frame polylactic acid resin is separated into two hands. Also, each other collides and fuses to form the weld line portion 14 (illustrated by phantom lines in FIG. 1A), and each is cured.

Then, after that, by separating the upper mold 9 and the lower mold 10 from each other, it is possible to obtain the decorative frame 8 molded from the polylactic acid resin for frames. Although not shown precisely, the upper mold 9 and the lower mold 10 are configured to have a slight taper so that the decorative frame 8 (molded product) can be easily pulled out.
As described above, in the first embodiment, first, the temperature of the storage tank (not shown) of the mixture of polylactic acid resin and calcium carbonate forming the reinforcing member 13 and the direction of injecting this mixture The temperature of the body cavity (not shown) is set to be higher than the temperature in the normal molding state, and the in-mold holding time after injection (so-called cooling time) is set to be higher than the holding time in the normal molding state. Also for a long time. For this reason, the crystallization rate of the reinforcing member 13 is increased, and the reinforcing member 13 having heat resistance and strength can be obtained.

  In addition, the reinforcing member 13 with the increased crystallization rate is placed in the depth of the lower mold 10, in other words, in a place where the weld line portion 14 is formed, and the temperature of the cavity 11 is set to normal molding. The temperature was higher than the temperature in the state. For this reason, the polylactic acid resin colliding from both directions behind the core 9a has a relatively high temperature, and is cured so as to contain the reinforcing member 13 by melting the surface of the reinforcing member 13, so that the weld A line portion 14 is formed.

Here, FIG. 5 shows an experimental result by the present inventors. As shown in FIG. 5, the strength of the weld line portion 14 is 60% as compared with the strength of a so-called non-weld line portion where the weld line portion 14 does not exist in the decorative frame 8 as 100 (%). -80 (%), which is a dramatic improvement over the conventional 0-10 (%).
In the first embodiment, the shape of the reinforcing member 13 is a rectangular parallelepiped. However, the shape is not limited to this. For example, the reinforcing member 13 may be a long rod shape, a spherical shape, and the like. In addition, irregularities may be formed on the surface of the reinforcing member so as to be easily entangled with the frame polylactic acid resin injected into the cavity 11.

Further, although the reinforcing member 13 is placed behind the lower mold 10, the present invention is not limited to this. Actually, the reinforcing member 13 is pushed by the injected polylactic acid resin for the frame, and finally However, it may be placed in any part of the cavity 11, but preferably in the vicinity of the weld line part 14.
Next, a second embodiment of the present invention will be described with reference to FIG. The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 4A, a sheet-like nonwoven fabric 20 having substantially the same shape as the cavity 11 is placed on the lower mold 10. The thickness of the nonwoven fabric 20 is slightly smaller than the depth of the concave portion 10a of the lower mold 10, that is, located below the injection port 9c of the upper mold 9. This non-woven fabric 20 is composed of a mixture of the polylactic acid resin (hereinafter referred to as polylactic acid resin for non-woven fabric) and an inorganic filler (for example, calcium carbonate). It is formed so that the crystallization rate can be increased.

  In forming the nonwoven fabric 20, first, calcium carbonate (powder) formed to have a diameter of about several nm to 100 nm is added to and mixed with the polylactic acid resin for nonwoven fabric, and the nonwoven fabric polylactic acid resin and calcium carbonate are mixed. And get a mixture with. Next, the mixture is made into a plurality of lines (fibrous), and these are entangled with each other by, for example, wind power, etc., so that the surface portion 20a and the interior 20b communicate with each other in large, small, vertical, and horizontal directions ( (Not shown).

  And, this entangled, the surface portion 20a and the interior 20b having a space (not shown) that communicated with each other in the vertical and horizontal directions, a mixture is formed into a sheet by applying a hot roll or the like to the mixture formed in this sheet, The non-woven fabric 20 having the above shape is formed by punching. Then, this nonwoven fabric 20 is accommodated for about 1 hour in a storage tank (not shown), which is maintained at about 110 ° C. by hot air from an electric heater (not shown) as superheating means. By this operation, the non-woven fabric 20 has an increased crystallization rate, whereby the non-woven fabric 20 with improved heat resistance and strength can be obtained.

  The nonwoven fabric 20 thus formed is placed on the lower mold 10 in the cavity 11 as described above. When the frame polylactic acid resin is injected into the cavity 11 from the injection port 9c. The frame polylactic acid resin first melts the surface portion 20 a on the nonwoven fabric 20. Furthermore, since the space is formed in the surface portion 20a and the inside 20b of the nonwoven fabric 20 as described above, the polylactic acid resin for a frame is transmitted through the inside space and is deepened while melting the inside of the nonwoven fabric 20. It gradually penetrates in the right direction.

  By the way, this polylactic acid resin for a frame is slightly deprived of its own heat while flowing in the cavity 11 as described above, but also slightly deprived of heat when it penetrates into the inside 20b of the nonwoven fabric 20. For this reason, the polylactic acid resin for a frame that penetrates in the depth direction of the nonwoven fabric 20, particularly the polylactic acid resin for a frame that penetrates in the vicinity of the weld line portion 21 melts the entire inside 20 b of the nonwoven fabric 20. Just don't have heat. Therefore, in such a case, a part of the inside of the non-woven fabric 20 is included in the polylactic acid resin for a frame without melting, and the non-woven fabric 20 is cured as an aggregate.

As described above, according to the second example, first, the molded nonwoven fabric 20 was accommodated in an accommodation strap maintained at about 110 ° C. for about 1 hour. For this reason, the crystallization rate of the nonwoven fabric 20 is increased, and the nonwoven fabric 20 having heat resistance and strength can be obtained.
Further, since the nonwoven fabric 20 has a space (not shown) in which the surface portion 20a and the interior 20b communicate with each other in large, small, vertical, and horizontal directions, the polylactic acid resin for the frame is easily entangled, and particularly in the weld line portion 21, As shown in FIG. 5, the strength of the weld line portion 21 is 100% that of the non-weld line portion so that the nonwoven fabric 20 is contained in the polylactic acid resin as an aggregate without melting. When compared as (%), the value is 50 to 70 (%), which is a dramatic improvement over the conventional 0 to 10 (%).

  By the way, if it is comprised so that the nonwoven fabric 20 may be located in the whole cavity (molded article) 11 as mentioned above, an effect will be exhibited also in suppression of a curvature. This is because in the decorative frame (molded product) 8, the warp is different in the curing rate in the thickness direction of the decorative frame 8, that is, the polylactic acid resin for the frame flows from the lower mold 10 first due to gravity. This is caused by a time difference in curing speed in which the polylactic acid resin on the side is cooled and cured quickly, and then the resin of the upper mold 9 is gradually cured.

  However, according to the present embodiment, the nonwoven fabric 20 is placed on the lower mold 10, and as described above, the nonwoven fabric 20 has a space in the surface portion 20a and the inside 20b due to the complex intertwining of linear fibers. It has a structure. For this reason, the polylactic acid resin does not reach the lower mold 10 all at once, but gradually penetrates in the depth direction (lower mold 10) by the nonwoven fabric 20 (internal space) as described above. At the same time, the upper mold 9 is gradually filled. Therefore, the time difference of the curing speed in the thickness direction of the decorative frame 8 can be reduced, and thus warpage generated in the decorative frame (molded product) 8 can be suppressed.

In addition, in the said 2nd Example, although the thickness of the nonwoven fabric 20 was made into the grade accommodated in the lower mold | type 10, when the intensity | strength etc. should be pursued, the thickness should just be increased, In addition, when it is desired to make it completely integrated with the polylactic acid resin, it may be appropriately changed according to the purpose, for example, to reduce its thickness.
Moreover, although the shape of the nonwoven fabric 20 was made substantially the same as that of the cavity 11, it is not limited to this. For example, it is a circular shape surrounding the core 9a, or a simple annular line shape. There is no particular limitation.

In the first and second embodiments, the polylactic acid resin for the frame is preliminarily added with calcium carbonate to an appropriate crystallization rate (similar to the polylactic acid resin for reinforcing member and the polylactic acid resin for nonwoven fabric). Although it is increased, the injection may be performed without particularly increasing the crystallization.
Next, a third embodiment of the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the location similar to the said 1st and 2nd Example, The detailed description is abbreviate | omitted.

A block-shaped reinforcing member 30 is placed behind the lower mold 10 as shown in FIG. The reinforcing member 30 is composed only of the polylactic acid resin (hereinafter referred to as “polylactic acid resin for reinforcing member”), and has a lower crystallization rate (than a normal molding state) by the following method. It is formed so that.
In the formation of the reinforcing member 30, first, the polylactic acid resin for reinforcing member is stored in a storage tank of an injection molding machine (not shown), and the temperature (plasticization temperature) of this storage tank is about 160 ° C., which is a normal molding. The temperature is lower than the temperature in the state (generally around 180 ° C.). And the temperature of the block-shaped (rectangular) reinforcing member cavity (mold) (not shown) for injecting the polylactic acid resin for reinforcing member is about 20 ° C., and the temperature in a normal molding state (about about 60 ° C.). In this state, the polylactic acid resin for reinforcing member is injected into the cavity for reinforcing member.

  The in-mold holding time after injection (so-called cooling time) is about 3 seconds, which is shorter than the holding time in the normal molding state (generally about 10 seconds). By such a series of operations, the reinforcing member 30 has a low crystallization rate, and the reinforcing member 30 that is easily melted even at a relatively low temperature can be obtained. In this embodiment, the polylactic acid resin for a frame injected into the cavity 11 is not particularly increased in its crystallization rate by adding calcium carbonate.

  According to the third embodiment, even if the temperature of the polylactic acid resin for a frame in the weld line portion 31 is slightly low for some reason, the reinforcing member 30 is reliably used for the frame. Since it is fused and integrated with the polylactic acid member, as shown in FIG. 3, the strength of the weld line portion 31 is 40 to 60 (%) when compared with the strength of the non-weld line portion being 100 (%). ), Which is a dramatic improvement over the conventional 0-10%.

In addition, although the shape of the reinforcing member 30 is a rectangular parallelepiped, it is not limited thereto, and may be, for example, a long rod shape or a spherical shape, and further, although not illustrated, unevenness is formed on the surface of the reinforcing member. Then, it may be easily entangled with the frame polylactic acid resin injected into the cavity 11.
Further, although the reinforcing member 30 is placed in the back of the lower mold 10, the present invention is not limited to this, and may be placed in any portion in the cavity 11, but preferably the weld line portion 31. It is a neighborhood.

In addition, the frame polylactic acid resin injected into the cavity 11 is configured not to have a particularly high crystallization rate, but may be one having an increased crystallization.
Moreover, in the said 1st-3rd Example, although it was set as the decorative frame 8 of the operation dial 7 for a circuit breaker as a biodegradable resin molded product, it is not limited to this, For example, it is a machine of various uses There are no particular limitations on the use of gears, gears, bolts, nuts, hammers, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS It shows the first embodiment of the present invention, (a) is a plan view of the cavity, (b) is a broken perspective view along the AA line of (a). Perspective view of control center Enlarged front view of breaker operation dial Sectional drawing which follows the BB line of FIG. Figure showing the experimental results of tensile strength FIG. 2 shows a second embodiment of the present invention and is equivalent to FIG. FIG. 3 shows a third embodiment of the present invention and is equivalent to FIG. FIG. 1 shows a conventional example and is equivalent to FIG.

Explanation of symbols

In the drawing, 8 is a decorative frame (biodegradable resin molded product), 9 is an upper mold, 10 is a lower mold, 11 is a cavity, 13 is a reinforcing member, and 14, 21 and 31 are weld line portions (the resins are fused together). , 20 is a nonwoven fabric, and 30 is a reinforcing member.

Claims (10)

  A biodegradable resin molded product, wherein a block-shaped reinforcing member molded with the same resin as the resin injected into the cavity is resin-molded in a state of being placed in the cavity in advance.   2. The biodegradable resin molded product according to claim 1, wherein the reinforcing member is disposed at a location where the resins injected into the cavity are fused together in the cavity.   The biodegradable resin molded product according to claim 1, wherein unevenness is formed on a surface of the reinforcing member.   The biodegradable resin molded product according to any one of claims 1 to 3, wherein the reinforcing member has a higher crystallization rate than a normal molded state.   The biodegradable resin molded product according to any one of claims 1 to 3, wherein the reinforcing member has a crystallization rate lower than that of a normal molded state.   The reinforcing member has a plasticizing temperature higher than that in a normal molding state at the time of molding, a temperature of a mold to be injection-molded is higher than that at the time of normal molding, and an in-mold holding time after injection. The biodegradable resin molded article according to claim 4, wherein the crystallization rate is increased by executing at least one of making the length longer than that during normal molding.   The reinforcing member has a plasticizing temperature lower than that in a normal molding state at the time of molding, a temperature of a mold to be injection-molded lower than that in normal molding, and an in-mold holding time after injection. 6. The biodegradable resin molded article according to claim 5, wherein the crystallization rate is lowered by executing at least one of making the length shorter than that during normal molding.   A biodegradable resin molding characterized in that a non-woven fabric formed in the shape of the same resin as the resin injected into the cavity along the shape of the cavity is molded in advance in the cavity. Goods.   The biodegradable resin molded product according to claim 8, wherein the nonwoven fabric has a higher crystallization rate than a normal molded state. The biodegradable resin molded article according to claim 9, wherein the non-woven fabric is heated by a heating means after molding to increase its crystallization rate.

Images