JPH10653A - Rim polyurethane bicolor molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of defect in its appearance by making the surface part of a square part to be often rubbed with another object during use hard to abrase in an RIM polyurethane bicolor molded item. SOLUTION: The polyurethane sheath 74 of a steering wheel 70 is an RIM polyurethane bicolor molding provided with a ring part 71 comprising a surface part 75 formed by pouring surface forming polyurethane material U1 into the decompressed cavity and an inner part 76 formed by pouring an Inner part forming polyurethane material U2 into the decompressed cavity. The thickness of a surface part 75a at the outer peripheral side of the ring part 71 is formed thicker than that of a surface part 75b at the inner peripheral side of the ring part 71.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-color RIM (reaction injection molding) polyurethane molded article which uses different materials for the surface portion and the inside.

[0002]

2. Description of the Related Art In a steering wheel 100 shown in FIGS. 8 and 9, a ring portion 101 and a spoke portion 102 include
It is composed of a core bar 103 and a polyurethane coating 104. The conventional polyurethane coating 104 is made of a single polyurethane material, and a skin layer 105 having extremely few air bubbles.
There were many integral skin foams obtained by simultaneously RIM-molding the core part 106 and the core 106 having many bubbles.

[Problems to be solved by the invention]

The skin layer 1 on the outer peripheral side of the ring portion 101
05a is a part which is easily rubbed by a hand during steering operation. In particular, the left and right side portions 10 of the ring portion 101
7 and 107 are portions that are always gripped by the driver, so that the skin layer 105a on the outer peripheral side of the side portions 107 and 107 is the portion that is most easily rubbed by hand.

[0004] Here, the skin layer 105 made of integral skin foam is generally thin, and it is particularly difficult to make the thickness more than 1 mm. Therefore, elasticity and shock absorption in the skin layer 105 cannot be expected. For this reason, the ring 1
01 has an inconvenience that the skin layer 105a on the outer peripheral side is liable to be worn when rubbed by hand as described above, and the appearance is deteriorated by long-term use.

Accordingly, an object of the present invention is to provide an RI which can make it difficult to wear the outer peripheral surface of a curved portion such as a ring portion which is liable to be rubbed at the time of use, so that appearance defects do not occur.
An object of the present invention is to provide an M polyurethane two-color molded article.

[0006]

In order to achieve the above object, a RIM polyurethane two-color molded article of the present invention comprises a surface portion formed by injecting a polyurethane material for a surface portion into a cavity under reduced pressure; A curved portion including an interior formed by injecting an internal polyurethane material into the cavity under reduced pressure, and a surface portion on an outer peripheral side of the curved portion is thicker than a surface portion on an inner peripheral side of the curved portion. It is characterized by being formed.

Here, the thickness of the surface portion on the inner peripheral side of the curved portion can be changed as appropriate by increasing or decreasing the injection amount of the polyurethane material for the surface portion, but is set in the range of 0.2 to 1.5 mm. It is more preferable that the thickness be in the range of 0.5 to 1.0 mm. If the thickness is less than 0.2 mm, the inside can be seen through, and if it exceeds 1.5 mm, the cost increases.

[0008] The thickness of the surface portion on the outer peripheral side of the curved portion can be changed as the injection amount of the polyurethane material for the surface portion increases or decreases, but is preferably 1.5 mm or more. If the thickness is less than 1.5 mm, the effect of making the surface hard to wear is small. Preferably, the thickness of the outer surface of the curved portion is 1.5 times or more the thickness of the inner surface of the curved portion.

Further, if the surface polyurethane material is a coloring material and the interior polyurethane material is a non-coloring material, the amount of the coloring material, which is generally expensive, can be reduced to the required minimum and the cost can be reduced.

If the surface polyurethane material is made of a material having high abrasion resistance and the interior polyurethane material is made of a material having low abrasion resistance, it is necessary to use a generally expensive material having a high abrasion resistance. Minimal savings and cost savings.

In addition, for example, if the surface polyurethane material is a material having a high urethane reaction rate, the thickness of the surface polyurethane material due to the flow of the internal polyurethane material can be prevented. Further, if a release agent is mixed with the surface polyurethane material, the release property can be improved. In addition, if the surface portion polyurethane material is a non-yellowing material having excellent light resistance, discoloration of the surface portion can be prevented. Further, if the surface polyurethane material is a material containing an antibacterial agent, sanitary properties can be improved.
Also, if the internal polyurethane material is made of a highly elastic material,
Soft feeling can be improved. As described above, various materials can be selectively used.

[0012]

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.

First, as shown in FIGS. 5 and 7, a steering wheel 70 manufactured in this embodiment has a ring portion 71 as a curved portion, four spoke portions 72, and a central pad portion in the present invention. 80. Ring part 7
1 and spoke portions 72 are made of core metal 73 and polyurethane coating 7
The polyurethane coating 74 comprises a surface portion 75 formed by injecting a small amount of a polyurethane material for a surface portion into a cavity under reduced pressure, and an polyurethane material for an interior into a cavity under reduced pressure, as described later. This is an RIM polyurethane two-color molded product comprising an inner portion 76 formed by the above-described process. The pad section 80 includes the ring section 7
1 and the spoke portion 72 are formed as separate parts, and are attached to the polyurethane coating 74 of the spoke portion 72 by mechanical fitting (not shown).

The outer surface 75a of the ring 71 is
This part is easily rubbed by the hand during steering operation. Therefore, while the thickness of the surface portion 75b on the inner peripheral side of the ring portion 71 is 0.2 to 1.0 mm, the ring portion 71
The thickness of the surface portion 75a on the outer peripheral side of
It is 5.0 mm. The details differ depending on the site as follows.

(A) In the lower portion 79 of the ring portion 71, the thickness of the outer surface portion 75a is 1.0 to 2.0 mm. This part is the part closest to the gate in RIM molding described later. (B) Since the left and right side portions 77, 77 of the ring portion 71 are always gripped by the driver, and the outer surface portion 75a is the portion that is most easily rubbed with the hand, the thickness of the surface portion 75a is Particularly, the thickness is set to 2.0 to 5.0 mm. This part is a part slightly away from the gate in RIM molding described later. (C) In the upper portion 78 of the ring portion 71, the outer surface side surface portion 7
The thickness of 5a is set to 2.0 to 3.0 mm. This part is a part farthest from the gate in RIM molding described later.

The molding apparatus for molding the polyurethane coating 74 includes a molding die 1, a vacuum box 11, and a material injection mechanism 21.
These components will be described in detail in order.

The molding die 1 is divided into an upper die 2 and a lower die 3. On the PL surfaces of the upper mold 2 and the lower mold 3, a cavity surface 5 that forms the cavity 4 when the mold is closed, 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. The cavity 4 includes a portion for forming the polyurethane coating 74 of the ring portion 71 and a portion for forming the polyurethane coating 74 of the spoke portion 72.

The vacuum box 11 is divided into an upper box 12 and a lower box 13, and an upper mold 2 is mounted in the upper box 12, and the lower box 1
The lower die 3 is mounted in the lower die 3. 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 to open and close the upper box 12 and the lower box 13 and the upper mold 2 and the lower mold 3. And opening and closing are performed at the same time. An O-ring 14 is attached to a groove formed on the division surface of the upper box 12, and when the vacuum box 11 is closed, the O-ring 14 comes into contact with the division surface of the lower box 13 and Seal between

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 is configured as shown in FIG.
The two three-component mixing heads 22 are connected to the central injection mechanism 5.
5 is provided with a six-component mixing head 20.

The upper three-component mixing head 22 in the figure is for producing a polyurethane material U1 for a surface portion, and is capable of mixing a polyol component and an isocyanate component as main components with a third component. .
The coloring material may be blended with the polyol component instead of the third component. In this embodiment, the composition of each component is selected so that the surface polyurethane material U1 is a coloring material, a non-yellowing material and a material having high abrasion resistance, and an appropriate amount of an antibacterial agent is further mixed. I have. Also, an appropriate amount of a release agent can be added to the polyol main component or the third component.

The lower three-component mixing head 22 in FIG. 1 is for producing an internal polyurethane material U2, and is capable of mixing a polyol component and an isocyanate component as main components with a third component. . In this embodiment, the composition of each component is selected such that the polyurethane material for internal use U2 is a non-colored material, a highly elastic material, and a material having low abrasion resistance.

Each of the upper and lower three-component mixing heads 22 comprises a cylinder 23 and a body 24 attached to the tip of the cylinder 23. The body 24 has an 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 movement of the piston, the spool 28 slides between an advanced position and a retracted position, 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 insides of the body 24 so as to face each other. Each of the nozzle bodies 31 and 32 has a tapered orifice opening to the mixing chamber 30 or the long groove 29. Body 24
A holder (not shown) for holding each of the nozzle bodies 31 and 32 is mounted on the outer surface thereof, and the tip of the needle 37 inserted through the holder adjusts the opening degree of the orifice. 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. 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.

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 injection mechanism 55 includes two upper and lower injection nozzles 2.
5 is formed, and a through hole 58 is formed in the center of the body 56 to open the two injection nozzles 25. The through hole 58 has a spool attached to a piston (not shown) of a cylinder 59. 60 is slidably inserted. The tip of the body 56 becomes a thin injection nozzle 57,
It is connected to the gate 6 of the lower mold 3 through a through hole 40 formed in the lower box 13. The injection mechanism 55 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 of the present 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. When an appropriate amount of a release agent is added to the surface RIM polyurethane material U1, the step of applying the release agent can be omitted. In the present embodiment, the step of applying a coloring material to the cavity surface can also be omitted. After setting the metal core 73 of the steering wheel 70 on 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 and the vacuum box 11 is closed. Is closed. The inside of the vacuum box 11 is depressurized to a suitable degree of vacuum by the vacuum pump 18, and the cavity 4 is set in a depressurized atmosphere through the vent hole 7 and the gap between the PL surfaces of the upper die 2 and the lower die 3.

Surface material injecting step: The spool 28 is retracted by the three-component mixing head 22 on the upper side of FIG.
2, the isocyanate component is discharged into the mixing chamber 30 respectively, and the valve 43c is opened to discharge the third component from the sub-discharge hole 52 into the mixing chamber 30. create. In addition,
In the lower three-component mixing head 22, the spool 28
To stop the discharge of each component.

As shown in FIG. 1, while the pressure in the cavity 4 is continuously reduced, the polyurethane material U1 for the surface portion is discharged from the injection nozzle 57 of the injection mechanism 55, and the gate 6 is discharged.
Into the cavity 4. The injected polyurethane material U1 for the surface portion is divided into two directions as shown by arrows in FIG. 2 due to sudden boiling of the natural storage gas in the material U1 due to a sudden pressure drop from the pressurized state up to that time. The particles are scattered in the cavity 4 and adhere to a substantially entire surface of the cavity surface 5 in a thin film form to form a surface portion 75 of the polyurethane coating 74. The thickness of the surface portion 75 is determined by the polyurethane material U for the surface portion.
1 can be changed as appropriate by increasing or decreasing the injection amount, and differs depending on the site as in the following (a), (b), and (c).

(A) At the portion near the gate 6, the surface polyurethane material U1 adheres thickest to the cavity surface 5. As shown by the arrow in FIG. 2, the surface polyurethane material U1 always flows in the cavity 4 in the tangential direction with respect to the product shape, and more material flows from the inner peripheral side of the cavity surface 5 to the outer peripheral side. Is pressed, so that it adheres thicker on the outer peripheral side than on the inner peripheral side of the cavity surface 5. (B) Even at a portion near the spoke portion slightly away from the gate 6, the surface polyurethane material U1 always flows in a tangential direction to the product shape, so that the cavity surface 5 is formed.
Thicker on the outer circumference than on the inner circumference. (C) At the part farthest from the gate 6, although the adhesion thickness is slightly reduced, the surface polyurethane material U1 always flows in a tangential direction to the product shape, so that the polyurethane material U1 from the inner peripheral side of the cavity surface 5 Thickly adheres to the outer peripheral side.

Injected polyurethane material U1 for the surface part
Allow a curing time for the composition to cure. The curing at this time is
Rather than a complete cure, it may be a cure that is less likely to be entrained by the internal polyurethane material U2 to be injected later.

Internal material injecting step: The spool 28 is retracted by the lower three-component mixing head 22 in FIG. 6, and the polyol component, the isocyanate component, and the coloring component as the third component are put into the mixing chamber 30 in the same manner as described above. The polyurethane material for internal use U
Create 2. The upper three-component mixing head 2
In step 2, the spool 28 is advanced to stop the discharge of each component.

As shown in FIG. 3, while continuously reducing the pressure in the cavity 4, the internal polyurethane material U2 is discharged from the injection nozzle 57 and injected into the cavity 4 from the same gate 6 as in the surface material injection step. At this time, as described above, since the surface portion 75 is hardened to such a degree that it is not entrained by the internal polyurethane material U2, the thinning is prevented. Specifically, there are two types as in the following (A) and (B).

(A) If the surface portion 75 is almost completely cured, the thinning of the surface portion 75 is almost completely prevented in a portion close to the gate 6 where the collision of the internal polyurethane material U 2 is severe and in other portions. Therefore, the thickness of the surface portion 75 is, in order from the thicker one, a portion near the gate 6 → a portion near the spoke portion slightly away from the gate 6 → a portion farthest from the gate 6.

(B) If the surface portion 75 is hardened to some extent, the surface portion 75 is slightly thinned in a portion near the gate 6 where the collision of the internal polyurethane material U 2 is severe, and in other portions, the surface portion 75 is hardened. Thinning is almost completely prevented, and the thickness of the left and right side portions 77, 77 and the upper portion 78 is increased by the surface polyurethane material U1 drawn from the portion near the gate 6, so that the surface portion 75 From the thick side, the part near the spoke part slightly away from the gate 6 → the part farthest from the gate 6 → the part near the gate 6,
It becomes in order. Paragraph [0015] is this example.

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. Further, in the portion of the material U2 near the cavity surface 5, a low-foaming dense portion is formed by degassing under a reduced pressure atmosphere. In this way, the interior 76 of the polyurethane coating 74 consisting of the core and the dense portion is formed (see FIG. 7). Thus, the interior polyurethane material U2 fills the cavity 4. Then, the flowing front end of the polyurethane material for internal use U2 is slightly blown out from the vent hole 7 and hardened to form a blowout portion 9.

Demolding process: After the internal polyurethane material U 2 is cured, the upper mold 2 and the lower mold 3 are opened as shown in FIG. And open the polyurethane coating 7 as shown in FIG.
Take out the steering wheel 70 with 4. Since the polyurethane coating 74 comes with a gate residual portion 10 of the polyurethane material for internal use U2, the gate residual portion 10 is cut off.

As described above, according to the present embodiment, the outer surface portion 75a of the ring portion 71 is replaced with the inner surface portion 75b.
Since it is formed thicker and has appropriate elasticity and shock absorption in the outer peripheral surface portion 75a, the outer peripheral surface portion 75a is less likely to be worn even if it is rubbed with a hand by a steering operation. Therefore, there is no problem that the appearance is deteriorated even after long use.

In addition, according to the present embodiment, 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 amount of non-yellowing materials, which are generally expensive, can be reduced to the minimum necessary, and costs can be reduced. (4) It is possible to reduce the use amount of generally expensive and highly wear-resistant material to a necessary minimum and reduce costs. (5) Since the surface portion polyurethane material U1 contains an antibacterial agent, hygiene can be improved. (6) Antioxidants and other additives added to the internal polyurethane material U2 can be reduced. (7) Since the internal polyurethane material U2 is made of a highly elastic material, the soft feeling can be improved.

Note that the present invention is not limited to the configuration of the above-described embodiment, and may be embodied with appropriate modifications without departing from the spirit of the invention, for example, as follows. (1) 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 having a curved portion such as an armrest and an air spoiler.

[0043]

As described above in detail, according to the RIM polyurethane two-color molded product of the first aspect, the outer surface of the curved portion such as the ring portion, which is easily rubbed during use, can be hardly worn, and the appearance can be improved. Can be prevented from occurring.

In addition to the above effects, according to the RIM polyurethane two-color molded product of claim 2, the amount of the generally expensive coloring material used can be reduced to the required minimum and the cost can be reduced.

Further, according to the RIM polyurethane two-color molded product of the third aspect, it is possible to reduce the amount of a generally expensive material having high abrasion resistance to a required minimum and reduce the cost.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a step of forming a surface portion of a polyurethane coating of a steering wheel according to an embodiment of the present invention.

FIG. 2 is a plan view showing the inside of a mold (lower mold) in the same step.

FIG. 3 is a cross-sectional view of a step of similarly forming the inside.

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 sectional view taken along line VII-VII of FIG. 5;

FIG. 8 is a front view of a conventional steering wheel.

FIG. 9 is a sectional view taken along line IX-IX of FIG. 8;

[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 20 Six component mixing head 21 Material injection mechanism 70 Steering wheel 71 Ring part 72 Spoke part 73 Core metal 74 Polyurethane coating 75 Surface 75a Outer surface 75b Inner surface 76 Inside U1 Polyurethane material for surface U2 Polyurethane material for inside

Claims (3)

[Claims] 1. A curved portion including a surface portion formed by injecting a polyurethane material for a surface portion into a cavity under reduced pressure, and an interior formed by injecting a polyurethane material for an interior into the cavity under reduced pressure. Part,
An RIM polyurethane two-color molded product, wherein a surface portion on an outer peripheral side of the curved portion is formed thicker than a surface portion on an inner peripheral side of the curved portion. 2. The RIM polyurethane two-color molded article according to claim 1, wherein the surface polyurethane material is a colored material, and the internal polyurethane material is a non-colored material. 3. The RI according to claim 1, wherein the surface polyurethane material is a material having high wear resistance, and the internal polyurethane material is a material having low wear resistance.
M polyurethane two-color molded product.