JP3358416B2 - RIM polyurethane two-color molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for RIM molding (reaction injection molding) of a two-color molded product having different colors, properties, and the like between a surface portion and an interior portion using a polyurethane material.

[0002]

2. Description of the Related Art The applicant of the present invention has previously proposed a two-color RIM polyurethane molding method (Japanese Patent Laid-Open No. 6-143).
340). First, the mold cavity is depressurized. Next, a small amount of polyurethane material for the surface part is injected into the cavity under reduced pressure. The injected polyurethane material for the surface part is scattered into the cavity due to a sharp pressure drop from the previous pressurized state and adheres in a thin film on almost the entire surface of the cavity, forming the surface part of the two-color molded product Is done. Subsequently, the interior polyurethane material is injected into the cavity under reduced pressure. The injected interior polyurethane material flows and fills the cavity and reacts and cures to form the interior of the two-color molded article.

[0003] According to this two-color molding method, a two-color molded product having a thin film-shaped surface portion covering the inside can be easily subjected to RIM polyurethane molding. For example, if the surface portion contains a release agent, The step of applying a release agent can be omitted, and if a coloring material is included in the surface portion, the application step of the coloring material can be omitted. In addition, by including a predetermined catalyst in the surface portion, etc. By making the internal properties different from each other, the degree of freedom in changing various characteristics such as touch feeling and durability can be increased.

[0004]

However, the above-mentioned two-color molding method still has the following problems. (1) According to the above method, since the internal polyurethane material remains in the gate of the mold and the remaining portion of the gate ends up being attached to the two-color molded product, when the remaining gate portion is cut off from the two-color molded product, the cut end is obtained. , An internal polyurethane material appears. Therefore, when the coloring material is included only in the surface portion polyurethane material and is not included in the internal polyurethane material, an uncolored internal polyurethane material appears at the cut end, and the appearance is deteriorated. Was. FIG.
Reference numeral 4 denotes a part of the steering wheel coating 100 formed in two colors by the above method. As shown by hatching, a gate residual portion (not shown in the figure) is applied to a surface portion 101 made of a colored surface polyurethane material. Cut 10 by excision
3 is an interior 1 made of an uncolored interior polyurethane material.
02 has appeared.

(2) Even if the polyurethane material for the surface portion adheres in a thin film form to almost the entire surface of the cavity surface in the above process, if the urethane reaction speed is slow and the reaction curing is delayed, the polyurethane material for the surface portion is not used. Due to the flow of the polyurethane material for internal use, the cavity surface may be gradually scraped and thinned. This thinning is particularly likely to occur on the cavity surface near the gate where the internal polyurethane material flows for a longer time than other portions. Therefore, when the coloring material is included only in the polyurethane material for the surface portion and not included in the polyurethane material for the interior, the polyurethane material for the surface portion is thinned in the vicinity of the gate, and is not colored through the thinned portion. However, there is a problem that the polyurethane material for internal use is visible on the surface and the appearance is deteriorated. FIG.
Two-color molding of steering wheel by the above method 1
00, a portion 101 away from the gate is provided with a surface portion 101 made of a colored polyurethane material for the surface portion, as shown by hatching, whereas a surface portion 1 near the gate is provided.
01 is thinned and the interior 102 made of uncolored interior polyurethane material is visible.

The problem (1) of the cut edge of the internal polyurethane material and the problem (2) of the exposure of the internal polyurethane material are limited to the deterioration of the appearance due to the absence of the coloring material in the internal polyurethane material. However, when the release agent is not contained in the internal polyurethane material, the releasability is partially deteriorated, and when the internal polyurethane material contains no catalyst, the properties are partially deteriorated.

Accordingly, an object of the present invention is to provide a RIM polyurethane two-color molding method capable of preventing an internal polyurethane material from appearing on a part of the surface of a two-color molded article.

[0008]

To achieve the above object, according to the Invention The, RIM polyurethane two-color molding method of the present invention includes the steps of decompressing the mold cavity, the polyol component and Isoshi
Mixing chamber of mixing head with annate component and third component
And then impact-mix them to form a polyurethane foam for the surface.
Create a tan material, stop the initial step, the discharge of the third component which the said surface portion for polyurethane material under a reduced pressure of the cavity was small volume infusion, to a RIM surface portion of the molded article
The polyol component and the isocyanate component
Subsequently, the mixture is discharged into the mixing chamber, and these are collided and mixed.
Mid-term process to create the internal polyurethane material, the injected the inner polyurethane material cavity under reduced pressure, to RIM molding the majority portion of the interior of the molded article Te, wherein the poly
All component, the isocyanate component and the third component
Is discharged into the mixing chamber, and these are impact-mixed to mix the mixture.
Positive gate near the gate, similar to polyurethane material for the surface
Create a polyurethane material, prior to said cavity under reduced pressure
Serial small volume infusion was near the gate portion for polyurethane materials, see <br/> including a final step of RIM molding near the gate portion of the interior of the molded article, and the polyol component and the isocyanate component
Stop through the above-mentioned initial process, middle process and final process.
Without discharging the mixture into the mixing chamber.
In the initial step and the final step, the third component is mixed with the third component.
In the above-mentioned mid-term process, discharge is stopped
Material switching is controlled.

Here, a common secondary component mixed into the polyurethane material for the surface portion and the polyurethane material for the vicinity of the gate.
Which is a minute the third component, the coloring material can be at least one of the release agent and a catalyst. Further, only the polyurethane material for the surface portion may be a material having a high urethane reaction rate or a non-yellowing material having excellent light resistance.

In another RIM polyurethane two-color molding method of the present invention, a step of depressurizing a cavity of a mold, and injecting a small amount of a polyurethane material for a surface having a high urethane reaction rate into the cavity under the depressurization, RI surface
It is configured to include an initial step of performing M molding, and a subsequent step of injecting an internal polyurethane material having a low reaction rate into the cavity under reduced pressure and performing RIM molding of the inside of the molded article.

[0011] Again, the polyurethane material for the surface portion includes:
At least one of a coloring material, a release agent and a catalyst can be mixed as a secondary component.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing an embodiment of the present invention applied to a two-color RIM polyurethane molding of a polyurethane coating for a steering wheel. First, FIGS. 1 to 9 show a first embodiment, and a molding device used in the present embodiment is, as shown in FIGS.
It comprises a molding die 1, a vacuum box 11, a material injection mechanism 21, and the like, and these parts will be described in detail in order.

The molding die 1 is divided into an upper die 2 and a lower die 3. A cavity surface 5 that forms a ring-shaped cavity 4 when the mold is closed is provided on the PL surfaces of the upper mold 2 and the lower mold 3.
And a gate 6 to the cavity 4 are formed. A vent hole 7 is formed at the final filling position of the polyurethane material in the upper mold 2.

Next, the vacuum box 11 is divided into an upper box 12 and a lower box 13, and the upper die 2 is mounted in the upper box 12.
The lower die 3 is mounted in the lower box 13. The upper box 12 and the lower box 13 are attached to a mold clamping device (not shown).
In the present embodiment, the lower box 13 is moved up and down, so that the upper box 1
The opening and closing of the lower mold 2 and the lower box 13 and the opening and closing of the upper mold 2 and the lower mold 3 are simultaneously performed. An O-ring 14 is attached to a groove formed on the division surface of the upper box 12 and the vacuum box 1
When the cover 1 is closed, the O-ring 14 comes into contact with the divided surface of the lower box 13 to seal between the upper box 12 and the lower box 13.

A suction plug 15 is attached to the lower box 13, and a vacuum pump 18 is connected to the suction plug 15 via a suction hose 16 and a valve 17. Also,
The lower box 13 is provided with a see-through window 19 through which the vicinity of the vent hole 7 can be viewed from the outside of the vacuum box 11 so as to maintain airtightness.

The material injection mechanism 21 has a three-component mixing head 22 as shown in FIG. 6, and can mix a polyol component and an isocyanate component as main components and a third component as a secondary component. ing. The three-component mixing head 22 includes a cylinder 23 and a body 24 attached to the tip of the cylinder 23. The body 24 has a thin injection nozzle 25 at the tip.

A through hole 26 is formed in the center of the body 24, and a spool 28 attached to a piston (not shown) of the cylinder 23 is slidably inserted into the through hole 26. A pair of long grooves 29 extending in the longitudinal direction are provided at positions 180 degrees opposite to the outer periphery of the spool 28. Due to the reciprocating motion of the piston 27, the spool 28 slides between an advanced position indicated by a two-dot chain line in FIG. 6 and a retracted position indicated by a solid line, and the leading end of the retracted spool 28 is a mixing chamber 30 for each component described later.
Becomes

A nozzle 31 for a polyol component and a nozzle 32 for an isocyanate component are provided in the left and right insides of the body 24 so as to face each other. Each of the nozzle bodies 31 and 32 has a tapered orifice 35 that opens into the mixing chamber 30 or the long groove 29. A holder (not shown) for holding each of the nozzle bodies 31 and 32 is mounted on the outer surface of the body 24, and a needle 37 inserted through the holder is provided.
Of the orifice 35 adjusts the opening degree of the orifice 35. Further, a reflux hole 38 for the polyol component and a reflux hole 39 for the isocyanate component are formed adjacent to the nozzle bodies 31 and 32 of the body 24, each of which is open to the long groove 29.

The hose 4 is connected to the nozzle body 31 and the return hole 38.
1a, a polyol component tank 41b and a pump 41
and a tank 41b → pump 41c → nozzle body 31 → long groove 29 → recirculation hole 38 → tank 41b to form a circulation path of the polyol component. Nozzle body 3
The tank 42b of the isocyanate component and the pump 42c are also connected to the second and reflux holes 39 by a hose 42a, and the tank 42b → the pump 42c → the nozzle body 32 → the long groove 29 →
A circulation path for the isocyanate component, that is, the circulation hole 39 → the tank 42b, is formed.

A third component sub-discharge hole 52 is provided at the center of the spool 28. The leading end of the sub-discharge hole 52 opens at the leading end surface of the spool 28, and the trailing end opens at the outer periphery of the spool 28 in the middle. In the rear part of the body 24, there is formed an introduction hole 53 that communicates with the rear end opening of the sub discharge hole 52 only when the spool 28 is retracted. The hose 4 is inserted into the introduction hole 53.
The tank 43b of the third component is connected to the tank 43b via the flow control device 43d and the valve 43c by 3a, and the inside of the tank 43b is constantly pressurized by the air pressurizing device 43e. The valve 43c may be provided at any position from the tank 43b to the body 24. The driving method of the valve 43c is not limited, and may be, for example, an air type or an electric type. Valve 43
The opening and closing of c is controlled by a dedicated timer or an internal timer of the sequence. The coloring material as the third component is obtained by dispersing a pigment in a polyol component.

The injection nozzle 25 of the three-component mixing head 22 is connected to the gate 6 of the lower die 3 through a through hole 40 formed in the lower box 13. The three-component mixing head 22 and the through hole 40 are sealed by a plurality of O-rings 50.

Now, the two-color molding method of the polyurethane coated RIM polyurethane according to the first embodiment, which is performed using the above molding apparatus, will be described in the order of steps. The upper mold 2 and the lower mold 3 of the molding die 1 are opened, and a mold release agent is applied to the cavity surface 5. After setting the metal core 46 of the steering wheel 45 in the lower mold 3, the upper mold 2 and the lower mold 3 are closed to form the cavity 4, and at the same time, the upper box 12 and the lower box 13 are closed to form the vacuum box 11. Is closed. The inside of the vacuum box 11 is depressurized to an appropriate degree of vacuum by the vacuum pump 18, and the cavity 4 is brought into a depressurized atmosphere through the vent hole 7.

Initial step: The spool 28 is retracted, and the polyol component is supplied from the nozzle body 31 to the nozzle body 3.
2, the isocyanate component is discharged into the mixing chamber 30 respectively, and the valve 43c is opened to discharge the coloring material as the third component from the sub-discharge hole 52 into the mixing chamber 30. A polyurethane material U1 is prepared (see FIG. 7). In this embodiment, a foaming agent is not substantially added to the surface polyurethane material U1. As shown in FIG. 1, a small amount of polyurethane material U1 for the surface portion is injected into the cavity 4 from the injection nozzle 25 while the pressure in the cavity 4 is continuously reduced. The injected polyurethane material U1 for the surface portion is scattered into the cavity 4 by the sudden drop of pressure from the pressurized state up to the point where the natural occlusion gas in the material U1 is suddenly boiled. A polyurethane coating 47
Is formed.

Mid-term process; closing the valve 43c,
The discharge of the coloring material as the third component is stopped, the polyol component and the isocyanate component are subsequently discharged, and these are impact-mixed to prepare an internal polyurethane material U2 (see FIG. 7). In this embodiment, a foaming agent is not substantially added to the internal polyurethane material U2. As shown in FIG. 2, the polyurethane material for internal use U2 is injected into the cavity 4 from the injection nozzle 25 while the pressure in the cavity 4 is continuously reduced. In the part of the injected interior polyurethane material U2 that is away from the cavity surface 5, the natural occlusion gas in the material U2 is bumped under reduced pressure to form a highly foamed core. Further, in the portion of the material U2 close to the cavity surface 5, a low foaming dense self-skin layer is formed by degassing under a reduced pressure atmosphere. Thus, the polyurethane coating 4
The majority 49a of the interior 49 composed of the core portion 7 and the self-skin layer is formed (see FIG. 5).

A final step; slightly before the inside polyurethane material U 2 fills the cavity 4, the valve 43 c is opened again, and the coloring material as the third component is discharged from the auxiliary discharge hole 52 into the mixing chamber 30. A polyurethane material U3 for the vicinity of the gate which is substantially the same as the polyurethane material U1 for the surface portion is prepared (see FIG. 7). As shown in FIG. 3, while the pressure in the cavity 4 is continuously reduced, a small amount of the polyurethane material U3 for the vicinity of the gate is injected into the cavity 4 from the injection nozzle 25. The injected polyurethane material U3 for the vicinity of the gate forms a high-foaming core portion and a low-foaming self-skin layer in substantially the same manner as the internal polyurethane material U2. A neighborhood 49b is formed (see FIG. 5). As a result of this injection, the cavity 4 is filled with all the materials U1, U2, U3, and the leading end of the flow of the polyurethane material for internal use U2 is slightly blown out from the vent hole 7 to be hardened, so that the blowout portion 9 is formed.

After all the materials U 1, U 2, U 3 are cured, as shown in FIG. 4, the upper mold 2 and the lower mold 3 are opened, and simultaneously, the upper box 12 and the lower box 13 are opened. Then, as shown in FIG. 5, the steering wheel 45 with the polyurethane coating 47 is taken out. Since the polyurethane coating 47 comes with the gate residual portion 10 of the polyurethane material U3 for the vicinity of the gate, when this is cut off, FIGS.
As shown in FIG. 9, the vicinity of the gate 49 b of the inside 49 made of the polyurethane material for gate vicinity U 3 appears at the cut 8. However, since the vicinity 49b of the gate is colored with the same coloring material as the surface portion 48, the cut 8
Has the same color as the surface portion 48 and is almost inconspicuous and does not impair the appearance.

Further, suppose that a polyurethane material U for a surface portion is used.
As shown by the thick arrow on the steering wheel 45 in FIG. 5 due to the delay in the reaction hardening of No. 1, the surface portion 48 near the gate is made of the internal polyurethane material U2 in the middle stage process.
In the case where the thickness is reduced by the flow of, the near-gate portion 49b of the interior 49 made of the near-gate polyurethane material U3 is visible through the surface of the thinned portion. However, the exposed portion 49b near the gate has the same color as the remaining surface portion 48 and cannot be distinguished, so that the appearance is not impaired.
In order to prevent the surface portion 48 from being thinned near the gate, a urethane reaction promoting catalyst is added to the third component of the surface portion polyurethane material U1 so that the surface portion polyurethane material U1 is subjected to the urethane reaction. A material having a high speed may be used. Further, in order to enhance the light resistance of the surface portion 48, the polyurethane material U1 for the surface portion may be a non-yellowing material having high light resistance.

In addition, according to the RIM polyurethane two-color molding method, the following effects can be obtained. (1) The step of applying a coloring material to the cavity surface 5 before molding can be omitted. (2) The amount of coloring materials used can be reduced to the minimum necessary, and costs can be reduced. (3) The pigment particles contained in the coloring material wear the passing portion in the material injection mechanism 21, and the worn parts need to be replaced. However, since the amount of the coloring material used can be minimized as described above, the abrasion is reduced, the cycle of maintenance and parts replacement of the material injection mechanism 21 is extended, and the man-hour and cost for that can be reduced.

In the material injection mechanism 21, the third component valve 43c is connected to the tank 4 as shown in FIG.
3b and an air pressurizing device 43e.
The same operation and effect as described above can be obtained by opening and closing 3c at the same timing as above.

Next, FIGS. 11 to 13 show a second embodiment. In the present embodiment, as shown in FIG. 11, two of the three-component mixing heads 22 are connected to the central injection mechanism 5.
5 is used. The upper three-component mixing head 22 in the figure is for producing a polyurethane material U1 for the surface portion, and uses a coloring material obtained by adding a pigment and a urethane reaction accelerating catalyst to a polyol component as a third component. The lower three-component mixing head 22 in the figure is for producing an internal polyurethane material U2, and a catalyst or the like as a third component is added as necessary. The injection mechanism 55 includes a body 56 that connects the two injection nozzles 25.
The six tips are thin injection nozzles 57. Body 56
A through hole 58 in which two injection nozzles 25 open
A spool 60 attached to a piston (not shown) of a cylinder 59 is slidably inserted into the through hole 58.

A two-color RIM polyurethane molding method of polyurethane coating according to the second embodiment performed by using the above molding apparatus is as follows. As in the first embodiment, the release agent is applied to the cavity surface 5, the core metal 46 is set, the mold is closed, and the cavity 4 is depressurized.

Initial Step: The spool 28 is retracted by the upper three-component mixing head 22, and the polyol component, the isocyanate component, the coloring component as the third component, and the urethane reaction accelerating catalyst are discharged into the mixing chamber 30. The polyurethane material U1 for the surface portion is prepared by collision mixing (see FIG. 12). In the lower three-component mixing head 22, the spool 28 is advanced to stop the discharge of each component. As in the first embodiment, while continuously reducing the pressure of the cavity 4, the polyurethane material U for the surface portion is used.
A small amount of 1 is injected from the injection nozzle 57 of the injection mechanism 55 into the cavity 4 (substantially the same as in FIG. 1). The injected polyurethane material U1 for the surface portion adheres to a substantially entire surface of the cavity surface 5 in the form of a thin film in the same manner as in the first embodiment.
7 are formed. However, since the polyurethane material U1 for the surface portion of this embodiment contains the urethane reaction accelerating catalyst, the urethane reaction proceeds quickly after the adhesion, and the reaction hardens to some extent. Therefore, the surface portion 48 is prevented from being scraped by the next flow of the internal polyurethane material U2, that is, the thickness is reduced.

Next step: The spool 28 is retracted by the lower three-component mixing head 22, and the polyol component and the isocyanate component (and the third component, if necessary) are discharged into the mixing chamber 30, and these are impact-mixed. An internal polyurethane material U2 is prepared (see FIG. 12). In the upper three-component mixing head 22, the spool 28 is advanced to stop the discharge of each component. As in the first embodiment, the polyurethane material for internal use U2 is injected from the injection nozzle 57 into the cavity 4 while the pressure in the cavity 4 is continuously reduced (substantially the same as in FIG. 2). The injected interior polyurethane material U2 forms an interior 49 consisting of a highly foamed core and a low foamed self-skin layer, as in the first embodiment. However, in this embodiment, the cavity 4 is completely filled with the internal polyurethane material U2, and the injection of the polyurethane material for the vicinity of the gate as in the first embodiment is not performed.

After all the materials U 1 and U 2 are cured, the mold is opened as in the first embodiment, and the steering wheel 45 with the polyurethane coating 47 as shown in FIG. 13 is taken out. In the present embodiment, when the gate remaining portion 10 is cut off, the inside 49 of the colorless internal polyurethane material U2 appears at the cut 8 so that the cut needs to be painted. However, as described above, due to the promotion of the reaction of the polyurethane material U1 for the surface portion, the surface portion 48 is accelerated.
Since the thickness of the inside 49 is prevented, the inside 49 is not seen through, and the appearance is not impaired in this respect.

Note that the present invention is not limited to the configuration of the above-described embodiment, and may be embodied by appropriately changing the scope of the invention as follows, for example, as follows. (1) In the first embodiment, the volume ratio between the majority 49a of the interior 49 and the gate vicinity 49b is not particularly limited, and can be appropriately changed, for example, in the range of 1: 1 to 10: 1. (2) In addition to the polyurethane coating of the steering wheel, for example, the present invention is applied to RIM polyurethane molding of various two-color molded products such as steering wheel pads, console box and glove box lids, armrests, and air spoilers.

[0036]

As described above in detail, according to the RIM polyurethane two-color molding method of the present invention, the appearance of the internal polyurethane material on a part of the surface of the two-color molded article can be prevented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an initial step of forming a surface portion of a polyurethane coating of a steering wheel in a first embodiment embodying the present invention.

FIG. 2 is a cross-sectional view of a middle stage of forming the interior.

FIG. 3 is a cross-sectional view of a final step of forming the vicinity of the gate in the same manner.

FIG. 4 is a cross-sectional view of the same demolding step.

FIG. 5 is a plan view of the same demolding step.

FIG. 6 is a sectional view of a mixing head used for the molding.

FIG. 7 is a timing chart of material switching in the molding.

FIG. 8 is a cross-sectional view of a polyurethane coating formed by the same molding.

FIG. 9 is a front view of a main part of the polyurethane coating.

FIG. 10 is a sectional view of a modification of the mixing head.

FIG. 11 is a cross-sectional view of a mixing head used for molding in a second embodiment.

FIG. 12 is a timing chart of material switching in the molding.

FIG. 13 is a plan view of a polyurethane coating obtained by the molding.

FIG. 14 is a front view of a main part of a polyurethane coating showing a problem of conventional two-color molding.

FIG. 15 is a plan view of a polyurethane coating illustrating another problem of conventional two-color molding.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molding die 2 Upper die 3 Lower die 4 Cavity 5 Cavity surface 11 Vacuum box 12 Upper box 13 Lower box 18 Vacuum pump 21 Material injection mechanism 45 Steering wheel 47 Polyurethane coating 48 Surface part 49 Inside 49a Most part 49b Near gate U1 Polyurethane material for the surface U2 Polyurethane material for the inside U3 Polyurethane material for the vicinity of the gate

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-143340 (JP, A) JP-A-7-186191 (JP, A) JP-A-6-170888 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B29C 45/16 B29C 45/00

Claims (2)

(57) [Claims] 1. A step of depressurizing a cavity of a mold, and mixing a polyol component, an isocyanate component and a third component with each other.
Discharge into mixing chamber of mixing head
Is allowed to create a polyurethane material for surface unit, the polyurethane material for the surface portion and a small amount injected into cavity under reduced pressure, stop and initial step for RIM molding surface portion of the molded article, the discharge of the third component, The polyol component and the
The isocyanate component is subsequently discharged into the mixing chamber.
And impact-mixing them to form an internal polyurethane material.
Create the injecting the inner polyurethane material under reduced pressure of the cavity, the metaphase step of the majority of the interior of the molded article to a RIM, the said polyol component and the isocyanate component a
The three components are discharged into the mixing chamber, and these are impact-mixed.
Near the same gate as the polyurethane material for the surface part.
Create a polyurethane material for near portion, the gate portion near polyurethane material small amount injected, saw including a final step of the gate near the bottom part of the interior of the molded article RIM molded into the cavity under reduced pressure, and the polyol component The isocyanate component and the
Do not stop through the initial, middle and final stages
And discharged into the mixing chamber.
In the initial step and the final step, the third component is placed in the mixing chamber.
In the medium-term process, the material is
RIM polyurethane two-color molding method for controlling switching . 2. A common secondary mixture mixed with the polyurethane material for the surface portion and the polyurethane material for the vicinity of the gate.
The third component is a component, colorant material, according to claim 1 RIM polyurethane two-color molding method according to at least one of the release agent and a catalyst.