JP2000280286A - Method for two-color molding of rim polyurethane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To omit a mold coat which has been conventionally necessary by forming a surface part in such a way that an enough thickness is provided and pinholes are not generated even at a branched part on the midway of a longer main body. SOLUTION: A mold 1 provided with a longer part 4a for molding a ring part, the first branched part 4b for molding the first spoke part and the second branched part 4c for molding the second spoke part is vacuumized. A polyurethane material UN for the surface part is fed into a cavity 4 under a reduced pressure from a gate 6 and is made to flow to the first branched part 4b. An intermittent process for defoaming and curing the material U1 is provided. The material U1 is fed again and is made to flow to the second branched part 4c and another intermittent process for defoaming and curing the material U1 is provided. The material U1 is fed again and is made to flow into approximately the whole region of the longer part 4a. Successively, a polyurethane material for the inner part is fed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an elongated molded product having a branch body in the middle of a longitudinal body, such as a steering wheel having a spoke portion in the middle of a ring portion and an air spoiler having a stay portion in the center. (RIM (reaction injection molding)) for polyurethane two-color molding.

[0002]

2. Description of the Related Art The applicant of the present application has previously described the following RIM.
A two-color polyurethane molding method has been proposed (JP-A-6-14).
No. 3340). Depressurize the mold cavity. The surface polyurethane material is injected into the cavity under reduced pressure. The injected polyurethane material for the surface part is foamed under reduced pressure and flows in the cavity, and the foam is broken and adheres in a film form to almost the entire surface of the cavity, forming a dense surface part with almost no bubbles. You. 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.

This two-color molding method has made it possible to easily perform RIM polyurethane molding of a two-color molded product consisting of a surface portion and an interior. However, the polyurethane material for the surface portion adhered to the cavity surface in the above-mentioned process. When the internal polyurethane material is injected in the above process while the material still has fluidity, the polyurethane material for the surface, particularly attached to the portion of the cavity surface near the gate, is entrained by the internal polyurethane material. As a result of the reduction in thickness, there has been a problem that the surface portion of the portion is transparent and the inside is visible, and the properties of the portion are deteriorated.

Then, the applicant of the present application has proposed a two-color molding method of RIM polyurethane as described below (Japanese Patent Laid-Open No. Hei 9 (1998)).
-207168). FIG. 11 shows a surface portion 9 formed by two-color molding on a metal core 91 of a steering wheel 90 by the same method.
3A and 3B show a polyurethane coating 92 composed of 3 and an inside 94, wherein FIG. 3A is a plan view, and FIG. 3B is a cross-sectional view of a portion near a gate (indicated by an arrow b in FIG.
(C) is a cross-sectional view of the spoke portion (the portion indicated by the arrow c in (a)) at the time of completion of internal molding. Reference numeral 95 denotes a ring portion as a longitudinal main body of the polyurethane coating 92, and reference numeral 96 denotes a spoke portion as a branched body that branches off from the middle of the ring portion 95.

The pressure in the cavity 101 of the mold 100 is reduced. A small amount of polyurethane material for the surface portion is injected from the gate 103 into the cavity 101 under reduced pressure, and adheres to the cavity surface 102 only in the vicinity of the gate on the cavity surface 102 in the form of a film by the scattering action.
Is formed (surface material first injection step). A curing time for curing the surface portion polyurethane material is set (intermittent step). The polyurethane material for the surface portion is again injected into the cavity 101 under reduced pressure, and adheres in a film shape to substantially the entire surface (entire circumference) of the cavity surface 102 by the foaming / defoaming action, thereby forming the remaining surface portion 93 (surface). Material second injection step). The interior polyurethane material is injected into the cavity under reduced pressure to form a foamed interior 94 (internal material injection step).

According to this two-color molding method, FIG.
As shown in (1), the thickness of the surface portion 93 in the vicinity of the gate is prevented from being reduced, and the surface portion 93 having a sufficient thickness can be secured. However, the following problem has not been considered.

[0007]

That is, FIG.
(C) As shown in FIG.
3 is not formed to a sufficient thickness, and there is a problem in that the surface portion 93 can be seen through to see the inside, or the properties of the spoke portion 96 are deteriorated. In addition, as shown in FIG. 11C, air bubbles may remain as pinholes 97 on the surface portion 93 of the spoke portion 96, which may appear to the outside and deteriorate the appearance. Therefore, before molding, the cavity surface 10
It is necessary to apply a colorant to the surface 2 (mold coat) and adhere the colorant to the surface portion 93 at the time of molding to conceal the above-mentioned problems of the surface portion 93, which is troublesome and costly. The causes of these problems are considered as follows.

The mechanism for forming the dense surface portion 93 will be described. The polyurethane material for the surface portion injected into the cavity 101 under reduced pressure is caused by the natural occlusion gas (or added foaming agent) in the material due to the pressure drop. Along with rapid foaming due to bumping, the foam flows in the cavity 101 and breaks (defoams) and adheres to a substantially entire surface of the cavity surface 102 in a film form. Further, in the vicinity of the cavity surface 102, the reaction heat escapes to the mold and the reaction hardening is delayed, and the thickening of the surface polyurethane material is suppressed, so that the foam may be easily broken.

Therefore, in order to form the dense surface portion 93 to a sufficient thickness, it is necessary to cause a certain amount or more of degassing near the cavity surface 102. But,
As shown in FIG. 11C, the cavity 101 of the spoke portion 96 has a cavity surface 102 except for one surface.
Because of the closed space surrounded by the above, the amount of the polyurethane material for the surface portion that needs to be defoamed (the surface area in contact with the cavity surface) can be large. Further, since only one surface of the space is open to the cavity 101 of the ring portion 95, when the surface polyurethane material U1 foamed over the entire cavity 101 of the ring portion 95 flows to lower the degree of vacuum, The defoaming efficiency due to the reduced pressure is reduced. As a result, a defoaming action of a certain level or more cannot be obtained, and the surface portion 93 of the spoke portion 96 becomes thinner, or bubbles remain as pinholes 97.

Accordingly, an object of the present invention is to provide a mold which can be formed to have a sufficient thickness and no pinholes even at a branch portion in the middle of the longitudinal main body. An object of the present invention is to provide a two-color molding method of RIM polyurethane which can eliminate a coat.

[0011]

SUMMARY OF THE INVENTION The present invention is a two-color RIM polyurethane molding method for a long molded article having a branch body in the middle of the longitudinal body, comprising a longitudinal section for molding the longitudinal body and a branch for molding the branch body. Depressurizing the cavity of the mold having a portion and injecting the polyurethane material for the surface portion from the gate into the cavity under reduced pressure, and flowing the material to the branch portion through the longitudinal portion from the gate to the branch portion. A surface material branch region injection step, an intermittent step (delay time) of defoaming and curing the injected surface polyurethane material, and injecting the surface polyurethane material again from the gate into the cavity under reduced pressure, A step of injecting the entire surface material to flow the material over substantially the entire length of the longitudinal section; and an step of injecting an internal polyurethane material into the cavity under reduced pressure.

In the case where the elongated molded article has two or more branches in the middle of the longitudinal body and the cavity has two or more branches for forming the branches, each of the branches is arranged in order from the branch near the gate. It is preferable to repeatedly perform the surface material branch region injection step and the intermittent step as targets.

[0013] At least one of a coloring material, a release agent and a catalyst can be mixed as a secondary component with the polyurethane material for the surface portion. Further, the polyurethane material for the surface portion can be a high-performance material as compared with the polyurethane material for the inside. As the high performance material, a non-yellowing material can be exemplified. Further, the polyurethane material for the surface portion may be a material having a higher urethane reaction rate than the polyurethane material for the inside.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in RIM polyurethane two-color molding of a polyurethane coating of a steering wheel will be described below with reference to FIGS.

FIGS. 6A and 6B show a polyurethane coating 47 including a surface portion 48 and an inner portion 49 formed on the core metal 46 of the steering wheel 45 by two-color molding according to the present method. FIG. 6A is a plan view, and FIG. Is the part near the gate (the part indicated by the arrow b in (a))
7C is a cross-sectional view at the time of completion of the internal molding, and FIG. 7C is a cross-sectional view at the time of completion of the internal molding of the spoke portion (the portion indicated by the arrow c of FIG. 70 indicates a ring portion as a longitudinal main body of the polyurethane coating 47, 71 indicates a pair of first spoke portions as a first branch body branched from the middle of the ring portion 70 (closer to the gate 6), and 72 indicates a ring. In the middle of section 70 (gate 6
Distant from the second spoke) and a pair of second spokes as a second branch body.

The molding apparatus used in this embodiment is as follows:
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. The cavity 4 includes a longitudinal portion 4a for molding the ring portion 70,
A pair of first branch portions 4b for forming the first spoke portions 71
And a pair of second branch portions 4 for forming the second spoke portions 72.
c. 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. 8, 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 at 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, the spool 28 slides between an advanced position indicated by a two-dot chain line in FIG. 8 and a retracted position indicated by a solid line, and the leading end of the retracted spool 28 becomes a mixing chamber 30 for each component described later.

A nozzle 31 for a polyol component and a nozzle 32 for an isocyanate component are provided in the left and right interiors 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 provided in 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. 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 reflux hole 39 → the tank 42b, is formed.

At the center of the spool 28, a third component sub-discharge hole 52 is provided. 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, a two-color RIM polyurethane molding method for polyurethane coating according to the first embodiment, which is performed using the above molding apparatus, will be described in the order of steps. FIG. 9 is a timing chart of material injection in the molding.

(1) 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. (2) 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. The vacuum box 11 is closed. (3) 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. The appropriate degree of vacuum varies depending on the composition of the polyurethane material, the dimensions of the molded product, and the like, and is not particularly limited. In the present embodiment, the appropriate degree of vacuum is 2 to 5 Torr.

(4) Surface Material First Spoke Area (First Branch Area) Injection Step: The spool 28 is retracted, and the polyol component is supplied from the nozzle body 31 and the isocyanate component is supplied from the nozzle body 32 to the mixing chamber 30. The coloring material as the third component is discharged from the sub-discharge hole 52 into the mixing chamber 30 by discharging and the valve 43c is opened, and these are collision-mixed to prepare a polyurethane material U1 for the surface portion. In the present embodiment, the surface portion polyurethane material U
Substantially no blowing agent added to 1

As shown in FIG. 1, FIG. 3 (a), FIG. 4 (a) (b) and FIG. 9, while the pressure in the cavity 4 is continuously reduced, the polyurethane material U1 for the surface portion is injected into the injection nozzle 2
5, and an appropriate amount is injected from the gate 6 into the cavity 4. The injection time is, for example, 0.1 second, and the injection speed is, for example, about 150 g / second. The injected polyurethane material U1 for the surface portion is discharged from the gate 6 as the natural occlusion gas (if a foaming agent is added, the foaming agent is further foamed) rapidly due to bumping due to the pressure drop. The first branch portion 4 passes through the longitudinal portion 4a up to the first branch portion 4b.
b, the bubbles break (the defoaming starts) and adhere to the flowed longitudinal portion 4a and the cavity surface 5 of the first branch portion 4b in a film-like manner. The shaded hatching in FIG. 3A indicates the area where the surface portion polyurethane material U1 is adhered at this time.

As shown in FIG. 4B, the first branch portion 4b of the cavity 4 is a closed space whose entire surface except one surface is surrounded by the cavity surface 5, so that defoaming is necessary. The amount of the polyurethane material U1 for the surface portion is large. Further, since only one surface of the space is open to the cavity 101 of the ring portion 95, it is disadvantageous for defoaming by decompression. However, in this embodiment, the foamed polyurethane material U1 for the surface portion is provided on the longitudinal portion 4a ahead of the first branch portion 4b.
And the appropriate degree of vacuum is maintained, so that the surface polyurethane material U1 near the cavity surface 5 of the first branch portion 4b starts to be efficiently defoamed from the longitudinal portion 4a.

(5) Intermittent Step: The defoaming of the injected polyurethane material U1 for the surface portion is completed to form the surface portion 48 having a sufficient thickness, and a time is left for curing the material U1. (put). In other words, the defoaming started in the previous step is further advanced and completed in this step, and in particular, since the defoaming action of a certain degree or more is obtained even in the first spoke portion 71, the surface portion 48 is formed with a sufficient thickness. No bubbles remain as pinholes. Although the material U1 undergoes reaction curing, the curing at this time is not complete curing, but may be curing to such an extent that it is not entrained by the internal polyurethane material U2 to be injected later. The leaving time in this step is, for example, 1.5 to 2.5 seconds. In order to shorten the standing time, a urethane reaction accelerating catalyst may be added to the third component of the surface polyurethane material U1 to make the surface polyurethane material U1 a material having a high urethane reaction rate. 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.

(6) Surface Material Second Spoke Area (Second Branch Area) Injection Step: In the same manner as in step (4), a polyurethane material U1 for a surface portion is prepared, and as shown in FIG. The surface polyurethane material U1 is injected from the gate 6 into the cavity 4 in an appropriate amount while the pressure is kept low. The injection time is, for example, 0.32 seconds, and the injection speed is, for example, about 150 g / second. The injected polyurethane material U1 for the surface portion flows to the second branch portion 4c through the longitudinal portion 4a from the gate 6 to the second branch portion 4c by the same mechanism as in step (4), and defoams. At the beginning, the fluid adheres to the cavity surface 5 of the flowed longitudinal portion 4a and the second branch portion 4c in a film form. The shaded hatching in FIG. 3B indicates the area where the surface polyurethane material U1 is attached at this time.

Then, for the same reason as in the step (4), the surface polyurethane material U1 near the cavity surface 5 of the second branch portion 4c starts to be efficiently defoamed from the longitudinal portion 4a.

(7) Intermittent step: The defoaming of the injected polyurethane material U1 for the surface portion is completed to form the surface portion 48 having a sufficient thickness, and a time is left for curing the material U1. (put). In other words, the defoaming started in the previous step is further advanced and completed in this step, and in particular, the defoaming action of a certain level or more can be obtained even in the second spoke portion 72, so that the surface portion 48 is formed with a sufficient thickness. No bubbles remain as pinholes. Although the material U1 undergoes reaction curing, the curing at this time is not complete curing, but may be curing to such an extent that it is not entrained by the internal polyurethane material U2 to be injected later. The leaving time in this step is, for example, 1.5 to 2.5 seconds.

(8) Step of injecting the entire surface material: In the same manner as in step (4), a polyurethane material U1 for the surface portion is prepared, and as shown in FIG. An appropriate amount of polyurethane material U1 for the surface portion is injected from the gate 6 into the cavity 4. The injection time is, for example, 0.2 seconds, and the injection speed is, for example, about 150 g / second. The injected polyurethane material U1 for the surface portion flows from the gate 6 to almost the entire area of the longitudinal portion 4a by the same mechanism as in the step (4), and defoaming starts to start the longitudinal portion 4a.
Adhere to the cavity surface 5 in the form of a film. The shaded hatching in FIG. 3 (c) shows the polyurethane material U for the surface at this time.
Pointing to the adhesion area of 1.

(9) Intermittent step: The defoaming of the injected polyurethane material U1 for the surface portion is completed to form the surface portion 48 having a sufficient thickness, and a time is left for curing the material U1. (put). The curing at this time is not a complete curing, but may be a curing that is not carried away by the internal polyurethane material U2 to be injected later.
The leaving time in this step is, for example, 0.5 to 2.0 seconds.
At a location far from the gate 6, the thickness of the surface portion polyurethane material U1 does not substantially decrease. Rather, in some cases, it is better to flow the surface polyurethane material U1 to the final filling position. In this case, it is preferable to omit this intermittent step (9).

(10) Internal Material Injection Step; Valve 43
close c, stop discharging the coloring material as the third component,
The polyol component and the isocyanate component are subsequently discharged, and they are impact-mixed to prepare an internal polyurethane material U2. In this embodiment, a foaming agent is not substantially added to the internal polyurethane material U2. As shown in FIGS. 5 and 6, while the pressure in the cavity 4 is continuously reduced, the internal polyurethane material U2 is discharged from the injection nozzle 25 and injected into the cavity 4 from the same gate 6 as in the surface material injection step. The injection time is, for example, 3.
For 2 seconds, the injection speed is, for example, about 150 g / sec.

The part of the injected internal polyurethane material U2 apart from the cavity surface 5 forms a highly foamed core by bumping the natural occlusion gas in the material U2 under a reduced pressure atmosphere. In addition, a low-foaming dense self-skin layer is formed in a portion of the material U2 near the surface portion 48 by a defoaming action under a reduced-pressure atmosphere. In this way, the interior 49 consisting of the core of the polyurethane coating 47 and the self-skin layer is formed (see FIG. 7). As a result of this injection, the cavity 4 is filled with all the materials U1 and U2, 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.

In this step, since the surface portion 48 is hardened by the above-mentioned intermittent steps to such a degree that it is not entrained by the internal polyurethane material U2, the thickness is prevented from being reduced. However, the inside 49 is not so thin that it can be seen through.

(11) Demolding process: After the internal polyurethane material U2 is cured, the upper mold 2 and the lower mold 3 are opened as shown in FIG.
And the lower box 13 are opened, and the steering wheel 45 with the polyurethane coating 47 is taken out. Polyurethane coating 4
7 is a gate residual portion 10 of an internal polyurethane material U2.
, The remaining gate portion 10 is cut off. As described above, since the thickness of the surface portion 48 is prevented by each intermittent process, the interior 49 cannot be seen through the surface portion 48 and the color density of the surface portion 48 does not become uneven. , Does not hurt the appearance. Therefore, according to the present two-color molding method, there is a possibility that the mold coat conventionally required may be omitted.

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

In the two-color molding method, the internal material injection step can be divided into two steps. That is,
In the first internal material injection step, the discharge of the coloring material is stopped, and in the second internal material injection step, the coloring material is discharged, so that the cutout when the gate remaining portion 10 is cut off is colored. it can.

As shown in FIG. 10, it is also possible to use a six-component mixing head 20 in which two of the three-component mixing heads 22 are connected to a central injection mechanism 55. Upper three-component mixing head 2 in FIG.
2 is a high-performance material (for example, a non-yellowing material with excellent light resistance)
A coloring material obtained by adding a pigment and a urethane reaction accelerating catalyst to a polyol component is used as the third component. In the figure, the lower three-component mixing head 22 is made of an ordinary polyurethane material U (for example, yellowing material).
2. A catalyst and the like as the third component are added as needed. The injection mechanism 55 includes a body 56 that connects the two injection nozzles 25, and the tip of the body 56 is a thin injection nozzle 57. At the center of the body 56, a through hole 58 is formed in which the two injection nozzles 25 are opened. A spool 60 attached to a piston (not shown) of a cylinder 59 is slidably inserted into the through hole 58. I have.

Note that the present invention is not limited to the configuration of the above-described embodiment, and can be embodied by appropriately changing the scope of the invention as follows, for example, as follows. (1) In the case of a steering wheel having only a pair of spokes, steps (6) and (7) of the above embodiment are omitted. (2) In addition to the polyurethane coating of the steering wheel, the present invention can be applied to RIM polyurethane molding of various longitudinal molded products having a branch body in the middle of the longitudinal main body, such as an air spoiler having a stay at the center, for example. it can.

[0045]

As described above in detail, according to the RIM polyurethane two-color molding method of the present invention, even at a branch portion in the middle of the longitudinal main body, the surface portion is made to have a sufficient thickness and no pinhole is formed. Therefore, there is a possibility that the mold coat conventionally required can be omitted.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a molding apparatus and a surface material injection step used in an embodiment of the present invention.

FIG. 2 is a plan view showing a lower die of the molding apparatus and a core of a steering wheel.

FIG. 3 (a) is a surface material first spoke area injection step,
(B) is a schematic plan view of the cavity of the lower die showing the flow state of the polyurethane material for the surface in each of the surface material second spoke area injection step and the (c) whole surface material injection step.

4A is a cross-sectional view taken along the line IVa in FIG. 3, and FIG.
FIG. 4 is a cross-sectional view taken along the line IVb in FIG.

FIG. 5 is a sectional view showing the molding apparatus and an internal material injection step.

6A is a plan view of a polyurethane coating of a steering wheel formed by the same two-color molding, FIG. 6B is a cross-sectional view of a portion indicated by an arrow b in FIG. 6A, and FIG. FIG.

FIG. 7 is a sectional view showing the molding apparatus and a demolding step.

FIG. 8 is a sectional view of a three-component mixing head used for the molding.

FIG. 9 is a timing chart of material injection in the molding.

FIG. 10 is a sectional view of a six-component mixing head that can be used for the molding.

11 is a plan view of a conventional polyurethane coating of a steering wheel formed by two-color molding, FIG. 11 (b) is a cross-sectional view of an arrow b in FIG. 11 (a), and FIG. 11 (c) is a cross-sectional view of an arrow c in FIG. It is.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molding die 2 Upper die 3 Lower die 4 Cavity 4a Long part 4b First branch part 4c Second branch part 5 Cavity surface 6 Gate 45 Steering wheel 46 Core metal 47 Polyurethane coating 48 Surface part 49 Inside 70 Ring part 71 One spoke part 72 Second spoke part U1 Polyurethane material for surface U2 Polyurethane material for internal

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F202 AA42 AB12 AD18 AH19 AM32 CA13 CB01 CB12 CB28 CK11 CP07 4F206 AA42 AB12 AD18 AH19 AM32 JA01 JB12 JB28 JF01 JN12 JN26 JQ81

Claims (2)

[Claims] 1. A method for two-color RIM polyurethane molding of a long molded article having a branch body in the middle of a longitudinal body, the mold comprising a longitudinal section for molding the longitudinal body and a branch section for molding the branch body. And a step of injecting a polyurethane material for a surface portion from the gate into the cavity under the reduced pressure, and flowing the material to the branch portion through the longitudinal portion from the gate to the branch portion. An intermittent step of defoaming and curing the injected polyurethane material for the surface portion, and again injecting the polyurethane material for the surface portion from the gate into the cavity under the reduced pressure, and applying the material over substantially the entire length of the longitudinal portion. A RIM polyurethane comprising: a step of injecting an entire surface material to be flowed; and an step of injecting an internal polyurethane material into the cavity under the reduced pressure. Color molding method. 2. When the elongated molded article has two or more branches in the middle of the longitudinal body and the cavity has two or more branches for molding the branches, the branch is closer to the gate in order. 2. The RI according to claim 1, wherein the surface material branch region injection step and the intermittent step are repeatedly performed for each branch part.
M polyurethane two-color molding method.