JP7528630B2 - Manufacturing method for vehicle interior materials - Google Patents

Description

The present invention relates to a method for manufacturing interior materials for vehicles.

Conventionally, a method for manufacturing vehicle interior materials is known, as described in Patent Document 1. In the method for manufacturing vehicle interior materials described in Patent Document 1 (a method for injection molding a foam-molded product), the molding die is closed to form a molding cavity, and then the inside of the molding cavity is pressurized with compressed air or the like to a pressure state equal to or higher than the foaming pressure of the foaming agent in the foaming resin raw material, and the foaming resin raw material is injected and filled in this state.

JP 2004-25696 A

However, in the process disclosed in Patent Document 1, the air pressurizing the molding cavity may get between the injected foaming resin raw material and the molding surface of the molding die, potentially causing relatively large uneven deformations (pockmarks) on the surface of the molded product. On the other hand, if the foaming resin raw material foams before filling the molding cavity, there is a risk of streaky patterns (swirl marks) appearing on the surface of the molded product.

The present invention was developed based on the above circumstances, and aims to provide a manufacturing method for vehicle interior materials that can suppress the occurrence of poor appearance such as pockmarks and swirl marks on the surface. It also aims to manufacture vehicle interior materials with improved lightness and rigidity.

The present invention is a method for manufacturing interior materials for vehicles, which includes an injection process in which a foamable resin is injected into a molding space formed by closing a pair of molds, and a pressurizing process in which a gas is flowed into the molding space and the foamable resin flowing through the molding space is pressurized with the gas. In the injection process, the foamable resin is injected through a first gate and a second gate that communicate with the molding space, and is characterized in that after the foamable resin is injected into the molding space through the first gate, the foamable resin is injected into the molding space through the second gate.

According to this manufacturing method for vehicle interior materials, the foamable resin injected first through the first gate merges with the foamable resin injected later through the second gate, and the merged foamable resin tends to spread in the direction from the first gate side toward the second gate side (downstream direction). This makes it easier to quickly fill the downstream side of the molding space with the foamable resin, whose foaming has been suppressed by gas pressurization.

The manufacturing method for the vehicle interior material may further include an additional injection step of injecting additional foamable resin into the molding space while maintaining the distance between the pair of closed molds after the molding space is filled with foamable resin and before a core back step of expanding the molding space by increasing the distance between the pair of closed molds.

The outer layer of the foamable resin injected into the molding space comes into contact with the molding surface of the mold, and cools and hardens before the inner layer, forming a skin layer. According to the manufacturing method for vehicle interior materials described above, the additionally injected foamable resin flows through the layer inside the skin layer and foams, thereby pressing the skin layer against the molding surface of the mold. This makes it possible to crush any gas that has entered between the foamable resin and the molding surface of the mold.

The manufacturing method for the vehicle interior material also includes a core-back process in which, after the molding space is filled with foamable resin, the distance between the pair of closed molding dies is increased to expand the molding space, and in the core-back process, additional foamable resin can be injected into the molding space.

According to this manufacturing method for vehicle interior materials, the foamable resin additionally injected in the core-back process flows through the layer inside the skin layer, expanding the molding space and foaming, thereby pressing the skin layer against the molding surface side of the mold. This makes it possible to suitably crush any gas that has entered between the foamable resin and the mold, and to expel the gas from the parting line of the mold to the outside of the mold. In addition, the foamable resin can be foamed appropriately in the layer inside the skin layer, making it possible to suitably adjust the thickness of the skin layer and the layer inside it. This makes it possible to obtain vehicle interior materials with improved lightness, rigidity, etc.

In addition, in the pressurizing step, the gas can be made to flow in a direction opposite to the flow direction of the foamable resin injected into the molding space. The foamable resin flowing through the molding space has a tip portion in the flow direction that is exposed to the gas at a relatively high temperature, and is therefore prone to foaming. However, according to the manufacturing method for vehicle interior materials as described above, the tip portion of the foamable resin can be effectively pressurized to suppress foaming.

The first gate can also be connected to a portion of the mold where the injected foamable resin is molded as the end of the vehicle interior material. According to this method of manufacturing a vehicle interior material, the foamable resin injected from the first gate into the molding space flows from the portion of the mold where the end of the vehicle interior material is molded, toward, for example, the portion of the mold where the center of the vehicle interior material is molded. That is, since the flow direction of the foamable resin flowing through the molding space tends to be in one direction, the inlets for the gas flowing into the molding space in the mold can be arranged together, for example, so that the gas flows from a direction opposite to the one direction, and the foamable resin can be efficiently pressurized.

In addition, in the pressurizing step, gas can be made to flow from the portion of the mold between the first gate and the second gate, and from the portion of the mold opposite the first gate with respect to the second gate. With this method of manufacturing vehicle interior materials, gas pressure can be quickly applied to the foamable resin injected from each gate, and foaming of the foamable resin that occurs before the foamable resin fills the molding space can be effectively suppressed.

The present invention makes it possible to provide a manufacturing method for vehicle interior materials that can suppress the occurrence of poor appearance such as pockmarks and swirl marks on the surface. It also makes it possible to manufacture vehicle interior materials with improved lightness and rigidity.

FIG. 1 is a cross-sectional view showing a part of a molding die for molding a door trim according to an embodiment. Top view of the mold A cross-sectional view showing the state in which the foamable resin is injected through the first gate. A cross-sectional view showing the state in which the foamable resin is injected through the second gate. A cross-sectional view showing the state in which the molding space is filled with foamable resin. Cross-sectional view showing the state in which foamable resin is added and injected into the molding space A cross-sectional view showing the state in which the upper die is separated from the lower die to expand the molding space. FIG. 11 is a cross-sectional view showing a state in which foamable resin is additionally injected into the molding space in the modified example.

<Embodiment>
An embodiment of the present invention will be described with reference to Figs. 1 to 7. In this embodiment, a manufacturing method of a door trim (vehicle interior material) to be attached to the door of an automobile (vehicle) will be described. As shown in Fig. 7, the door trim 100 is a plate-shaped body formed by foaming and curing a foamable resin R injected into a molding space S formed by closing a pair of molding dies 1. As the foamable resin R, for example, a mixture of a thermoplastic resin such as a polypropylene resin and a foaming agent can be used. As the foaming agent, for example, a chemical foaming agent or a physical foaming agent can be used. As the chemical foaming agent, for example, inorganic foaming agents such as sodium bicarbonate, ammonium bicarbonate, and ammonium carbonate, nitroso compounds such as N-N'-dinitrosopentamethylenetetramine, azo compounds such as azodicarbonamide and azobisisobutyronitrile, sulfonyl hydrazides such as benzenesulfonyl hydrazide, toluenesulfonyl hydrazide, and diphenylsulfone-3,3'-disulfonyl hydrazide, and organic foaming agents such as p-toluenesulfonyl semicarbazide can be used. As the physical foaming agent, for example, carbon dioxide gas, nitrogen gas, or the like can be used.

As shown in FIG. 1, the pair of molds 1 includes an upper mold 10 and a lower mold 20 disposed below and facing the upper mold 10. The upper mold 10 is a movable mold that can be moved vertically relative to the lower mold 20 by a drive device (e.g., an electric motor, an air cylinder, a hydraulic cylinder, etc.) not shown. FIG. 1 shows the pair of molds 1 in a closed state with the upper mold 10 close to the lower mold 20. In the pair of molds 1 in the closed state, a molding space S is provided between the molding surface 10A of the upper mold 10 and the molding surface 20A of the lower mold 20.

1 and 2, the upper mold 10 has a first gate 11, a second gate 12, and a third gate 13 that serve as a flow path for the foamable resin R injected from the injection device to flow toward the molding space S. The gates 11, 12, and 13 are arranged in this order on a straight line extending in the left-right direction, and each is connected to the molding space S. Each gate 11, 12, and 13 has a control valve (not shown) and is configured to be able to adjust the timing at which the injected foamable resin R flows into the molding space S. As shown in FIG. 2, of the gates 11, 12, and 13, the first gate 11 arranged on the leftmost side is the left part of the upper mold 10 and leads to the end molding part 10L that molds the injected foamable resin R into the end of the door trim 100.

The upper mold 10 has multiple gas inlets 14, 15 that serve as flow paths for air (gas) to flow from an air pump (not shown) into the molding space S. The gas inlets 14, 15 consist of an intermediate gas inlet 14 provided in the upper mold 10 slightly forward (lower in FIG. 2) of the portion between the first gate 11 and the second gate 12, and multiple right gas inlets 15 provided in the right portion of the third gate 13 (the portion opposite the first gate 11 with respect to the second gate 12). The multiple right gas inlets 15 are arranged in a straight line extending in the front-to-rear direction. In addition, in the molding space S, the first gate 11 side (left side) is the upstream side, and the right gas inlet 15 side (right side) is the downstream side.

Next, the manufacturing method of the door trim 100 will be described with reference to each figure. The manufacturing method of the door trim 100 includes, broadly speaking, an injection process in which the foamable resin R is injected into the molding space S, and a pressurizing process in which air is flowed into the molding space S and the foamable resin R flowing through the molding space S is pressurized with the air. In the injection process, as shown in FIG. 1, the upper mold 10 is brought close to the lower mold 20 to close the pair of molds 1, and a molding space S is provided between the upper mold 10 and the lower mold 20 (the distance between the molding surface 10A of the upper mold 10 and the molding surface 20A of the lower mold 20 at this time is L1). Then, the foamable resin R is injected into the molding space S through the first gate 11. At this time, the foamable resin R is injected into the molding space S under the conditions that the pressure for injecting the foamable resin R is 5 MPa and the injection speed is 75 mm/s. Meanwhile, in parallel with the injection process, in the pressurization process, air is introduced from the middle gas inlet section 14 and the multiple right gas inlets 15 (see FIG. 2) to keep the molding space S in a high-pressure state. At this time, air is introduced into the molding space S under the condition that the pressure of the air introduced from each gas inlet section 14, 15 is 10 MPa. The pressurization process may be carried out not only during the injection process, but also before the injection process.

As shown in FIG. 3, the foamable resin R injected into the molding space S through the first gate 11 flows toward the second gate 12 and the third gate 13 (downstream direction). Then, by injecting gas from each gas inlet 14, 15 located in the flow direction of the foamable resin R (from the direction opposite to the flow direction of the foamable resin R), foaming at the tip R1 of the foamable resin R is suppressed. At this time, the part RA of the foamable resin R that touches the molding surface 10A of the upper mold 10 or the molding surface 20A of the lower mold 20 forms a layered skin layer that cools and hardens before the inner layer RB. The inner layer RB of the skin layer RA of the foamable resin R is in an unhardened state and can flow downstream (or upstream). Therefore, the foamable resin R sequentially injected into the molding space S flows downstream as the inner layer RB in the part where the skin layer RA is formed.

As shown in FIG. 4, when the foamable resin R flowing in the downstream direction in the molding space S reaches the second gate 12 (more specifically, when the tip R1 of the foamable resin R flows in the downstream direction beyond the opening 12A that opens on the molding space S side in the second gate 12 in the second gate 12), the foamable resin R2 is injected into the molding space S through the second gate 12. The foamable resin R2 injected into the molding space S through the second gate 12 merges with the foamable resin R flowing in the molding space S and flows toward the downstream side. This makes it difficult for the foamable resin R2 injected into the molding space S through the second gate 12 to flow upstream, and can prevent it from colliding head-on with the foamable resin R injected into the molding space S through the first gate 11 and flowing downstream in the molding space S. If foamable resins with different flow directions merge in a manner that collide head-on, the merged part (called a weld) may have a poor appearance or be easily broken.

Similarly, when the foamable resin R flowing in the downstream direction in the molding space S reaches the third gate 13, the foamable resin is injected into the molding space S through the third gate 13. The foamable resin injected into the molding space S through the third gate 13 merges with the foamable resin R flowing in the molding space S and flows toward the downstream side. By continuously injecting the foamable resin R into the molding space S from each gate 11, 12, 13, the molding space S is filled with the foamable resin R as shown in FIG. 5. In this state, the foamable resin R is in a state where it has spread throughout the molding space S (a state where the foamable resin R has spread and flowed to the left and right ends and the front and rear ends of the molding space S). When the molding space S is filled with the foamable resin R, there are cases where gas has entered between the skin layer RA and the molding surfaces 10A, 20A of the mold 1 (i.e., a part of the skin layer RA is recessed toward the inner layer RB).

Next, while keeping the distance L1 (see FIG. 1) between the upper mold 10 and the lower mold 20 constant, as shown in FIG. 6, additional foamable resin R is injected into the molding space S through each gate 11, 12, 13 (additional injection process). The amount of additional foamable resin R injected into the molding space S can be an amount that is 5% of the weight of the foamable resin R that filled the molding space S before the addition. In order to additionally inject the foamable resin R into the molding space S, for example, the pressure for injecting the foamable resin R from each gate 11, 12, 13 may be increased.

As shown in FIG. 7, after the additional injection process, the upper mold 10 is separated from the lower mold 20 to expand the molding space S (core back process). At this time, the upper mold 10 is separated from the lower mold 20 so that the distance L2 between the upper mold 10 and the lower mold 20 is approximately twice the distance L1 (see FIG. 1) between the upper mold 10 and the lower mold 20 that was maintained from the injection process to the additional injection process. This causes the inner layer RB of the skin layer RA of the foamable resin R to foam. Then, the distance between the upper mold 10 and the lower mold 20 is kept at L2 for a predetermined time to harden the foamable resin R. Thereafter, the upper mold 10 is further separated from the lower mold 20 to open the pair of molding dies 1, and the door trim 100 as a molded body made of the foamable resin R is obtained.

Next, the effects of this embodiment will be described. This embodiment includes an injection process in which the foamable resin R is injected into the molding space S formed by closing a pair of molding dies 1, and a pressurizing process in which gas is flowed into the molding space S and the foamable resin R flowing through the molding space S is pressurized with the gas. In the injection process, the foamable resin R is injected through a first gate 11 and a second gate 12 that communicate with the molding space S, and after the foamable resin R is injected into the molding space S through the first gate 11, the foamable resin R is injected into the molding space S through the second gate 12. This shows a manufacturing method for a door trim 100.

According to this manufacturing method for the door trim 100, the foamable resin R injected first through the first gate 11 merges with the foamable resin R (R2) injected later through the second gate 12, and the merged foamable resin R tends to spread in the direction from the first gate 11 side toward the second gate 12 side (downstream direction). This makes it easier to quickly fill the downstream side of the molding space S with the foamable resin R, whose foaming has been suppressed by gas pressurization.

The manufacturing method of the door trim 100 also includes an additional injection step in which, after the molding space S is filled with the foamable resin R, additional foamable resin R is injected into the molding space S while maintaining the distance L1 between the pair of closed molding dies 1.

The foamable resin R injected into the molding space S forms a skin layer RA in which its outer layer cools and hardens before the inner layer RB by contacting the molding surface of the mold 1. According to the manufacturing method of the door trim 100 described above, the additionally injected foamable resin R flows through the layer RB that is inner than the skin layer RA and foams, so that the skin layer RA can be pressed against the molding surfaces 10A, 20A of the mold 1. This makes it possible to crush any gas that has entered between the foamable resin R and the molding surfaces 10A, 20A of the mold 1.

In addition, in the pressurizing step, gas is caused to flow in a direction opposite to the flow direction of the foamable resin R injected into the molding space S. The foamable resin R flowing through the molding space S has a tip R1 portion in the flow direction that is exposed to air at a relatively high temperature, and is therefore prone to foaming. However, according to the manufacturing method for the door trim 100 as described above, the tip R1 portion of the foamable resin R can be effectively pressurized to suppress foaming.

The first gate 11 also leads to the end molding section 10L in the molding die 1, which molds the injected foamable resin R as the end of the door trim 100. According to this manufacturing method for the door trim 100, the foamable resin R injected from the first gate 11 into the molding space S flows from the end molding section 10L that molds the end of the door trim 100 toward the part that molds the center of the door trim 100 in the molding die 1. That is, since the flow direction of the foamable resin R flowing in the molding space S is easily in one direction, the gas inlet ports (multiple right gas inlet sections 15) that flow into the molding space S in the molding die 1 can be arranged together, for example, so that the gas flows from a direction opposite to the one direction, and the foamable resin R can be efficiently pressurized.

In addition, in the pressurizing step, gas is allowed to flow through an intermediate gas inlet 14 provided in the portion of the molding die 1 between the first gate 11 and the second gate 12, and a right gas inlet 15 provided in the portion of the second gate 12 opposite the first gate 11. This manufacturing method for the door trim 100 allows gas pressure to be quickly applied to the foamable resin R injected from each gate 11, 12, 13, and can effectively suppress foaming of the foamable resin R that occurs before the foamable resin R fills the molding space S.

<Modification>
Next, a modified example of the present invention will be described. In this modified example, the structure, steps, actions, and effects of the above embodiment will not be described in detail. FIG. 8 shows a state during a core-back process in which the molding space S is filled with the foamable resin R, and the distance between the pair of closed molds 1 is increased to expand the molding space S. The distance L3 between the pair of molds 1 at this time is greater than the distance L1 (see FIG. 1) between the pair of molds 1 when the molding space S is filled with the foamable resin R in the above embodiment 1, and is smaller than the distance L2 (see FIG. 7), which is approximately twice the distance L1. In this modified example, the additional injection process described in the above embodiment is not performed.

In the core-back process, the upper mold 10 is gradually moved away from the lower mold 20 to gradually expand the molding space S, while additional foamable resin R is injected into the molding space S through each gate 11, 12, 13. The amount of foamable resin R injected into the molding space S can be an amount that is 5% of the weight of the foamable resin R that filled the molding space S before the addition (before the core-back process). At this time, in order to inject additional foamable resin R into the molding space S, for example, the pressure for injecting the foamable resin R from each gate 11, 12, 13 may be increased.

While resin is being added in this manner, the upper die 10 is moved away from the lower die 20 until the distance between the pair of molding dies 1 reaches L2 (see FIG. 7), allowing the inner layer RB2 of the skin layer RA2 of the foamable resin R to foam completely. The distance between the upper die 10 and the lower die 20 is then maintained at L2 for a predetermined period of time, allowing the foamable resin R to harden. Thereafter, the upper die 10 is moved further away from the lower die 20 to open the pair of molding dies 1, and a door trim is obtained as a molded body made of the foamable resin R.

According to this method of manufacturing door trim, the foamable resin R additionally injected in the core-back process flows through the layer RB2 inside the skin layer RA2, expanding the molding space S and foaming, so that the skin layer RA2 can be pressed against the molding surfaces 10A, 20A of the mold 1. This allows the gas that has entered between the foamable resin R and the mold 1 to be suitably crushed and the gas to be discharged to the outside of the mold 1 through the parting line of the mold 1, etc. Also, the foamable resin R can be suitably foamed in the layer RB2 inside the skin layer RA2, so that the thickness of the skin layer RA2 and the layer RB2 inside it can be made suitable. This makes it possible to obtain a door trim with improved lightness, rigidity, etc.

In this modified example, the foamable resin is injected into the molding space only in the core-back process, but this is not limited to this. For example, after the molding space is filled with the foamable resin, the foamable resin may be injected into the molding space before the core-back process (called the first additional injection process), and the foamable resin may be further injected into the molding space in the core-back process (called the second additional injection process). In this case, in the first additional injection process, an amount of foamable resin is added that is 5% of the weight of the foamable resin that filled the molding space before the addition, and in the second additional injection process, the same amount of foamable resin as the foamable resin added in the first additional injection process may be added.

<Other embodiments>
The present invention is not limited to the embodiments described above and in the drawings. For example, the following embodiments are also included within the technical scope of the present invention. Furthermore, in addition to the embodiments described below, various modifications can be made without departing from the spirit of the present invention.

(1) In addition to the above embodiment, the timing of the pressurizing process can be changed as appropriate. In the above embodiment, the pressurizing process is performed in parallel with the injection process, but this is not limited to this. For example, the pressurizing process may be started when the foamable resin injected from the first gate begins to flow downstream in the molding space.

(2) In addition to the above embodiment, the position, number, and shape of the gas inlet section can be changed as appropriate. For example, the gas inlet section may be arranged between the second gate and the third gate in addition to the ones exemplified in the above embodiment. The gas inlet section may also be arranged downstream and configured to form a long opening into the molding space.

(3) In the above embodiment, the additional injection process involves injecting additional foamable resin from all of the gates, but is not limited to this. For example, the additional injection process may involve injecting additional foamable resin from only the first gate and the second gate.

(4) In the above embodiment, door trim is exemplified as an example of a vehicle interior material, but this is not limited. For example, an instrument panel, roof lining, etc. may be used as a vehicle interior material. Furthermore, the manufacturing method for vehicle interior materials exemplified in the above embodiment is not limited to being provided for vehicles, but may be provided for various types of vehicles. For example, the manufacturing method for vehicle interior materials can be applied to vehicles such as trains and recreational vehicles as ground vehicles, airplanes and helicopters as flying vehicles, and ships and submarines as marine and underwater vehicles.

1...Molding mold, 10...Upper mold, 11...First gate, 12...Second gate, 13...Third gate, 14...Intermediate gas inlet, 15...Right gas inlet, 20...Lower mold, 100...Door trim, R...Foamable resin, S...Molding space

Claims (4)

an injection step of injecting a foamable resin into a molding space formed by closing a pair of molds;
a pressurizing step , which is carried out at least in parallel with the injection step, of flowing a gas into the molding space and pressurizing the foamable resin flowing in the molding space with the gas;
and a core-back process of expanding the molding space by increasing the distance between the pair of closed molding dies after the molding space is filled with the foamable resin,
the molding die is provided with a first gate, a second gate, and a third gate which are gates leading to the molding space and are arranged in that order on a straight line;
In the injection step , after injecting a foamable resin into the molding space through the first gate, when the foamable resin injected from the first gate and flowing through the molding space reaches the second gate, the foamable resin is injected into the molding space through the second gate , and when the foamable resin injected from the first gate and the second gate and flowing through the molding space reaches the third gate, the foamable resin is injected into the molding space through the third gate,
In the pressurizing step, the gas is caused to flow in a direction opposite to a flow direction of the foamable resin injected into the molding space from the first gate,
A manufacturing method for a vehicle interior material includes an additional injection step of injecting additional foamable resin into the molding space while maintaining the distance between the pair of closed molding dies after the molding space has been filled with foamable resin and before the core back step. 2. The method for manufacturing an interior material for a vehicle according to claim 1, further comprising a core-back process for expanding the molding space by increasing the distance between the pair of closed molding dies after the molding space is filled with the foamable resin, and in the core-back process, additional foamable resin is injected into the molding space. 3. The method for manufacturing an interior material for a vehicle according to claim 1, wherein the first gate is connected to a portion of the molding die where the injected foamable resin is molded as an end portion of the interior material for a vehicle. 4. The method for manufacturing a vehicle interior material according to claim 1, wherein in the pressurizing step, gas is caused to flow from a portion of the mold between the first gate and the second gate and from a portion of the mold opposite the first gate with respect to the second gate and the third gate .

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