JPH0675883B2 - Method for producing different hardness foam - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a foam of different hardness having a soft portion and a hard portion. The different hardness foam obtained according to the present invention can be used as a seat, a headrest, etc. by covering a surface skin or the like.

[Prior Art] For example, a headrest of an automobile is required to have a good holding property for supporting the head and a good tactile sensation to the head. However, since it is necessary to make it hard to satisfy the holding property and soft to improve the touch, it is difficult to realize both of these performances with one foaming pair.

Therefore, there is known a different hardness headrest in which the central part of the front part with which the head is in contact is soft and both side parts are hard.
By doing so, both performances described above can be satisfied.

As a method of manufacturing such a different hardness headrest, (1) a method in which a slab foam, a non-woven fabric, or the like is partially disposed in a molding die and integrally molded, and the resin is impregnated to harden the portion ( 2) A method of adhering a soft foam previously cut into a three-dimensional shape to the surface of the foam molded article (3) A method of partially varying the thickness of the backing material formed on the back surface of the skin (4) As disclosed in Japanese Patent Laid-Open No. 63-218317, there is known a method of molding one of a hard foam and a soft foam and then molding the other.

[Problems to be Solved by the Invention] However, the above-described conventional manufacturing method has various problems to be solved as described below.
According to the method (1), it is difficult to position the nonwoven fabric or the like in the mold, and the hardness varies depending on the degree of impregnation of the foamed resin, so that the quality is not stable. In the method (2), the number of steps for cutting into a three-dimensional shape is large, and the number of bonding steps is increased, so that there is a problem in terms of cost. In the method (3), there are cases where the shape is greatly restricted and the work of sewing the outer skin or the work of covering the outer skin becomes difficult. The method (4) requires two molding steps, and the molding cycle time becomes long, so the productivity is low.

The present invention has been made in view of such circumstances,
The object of the present invention is to produce a foam of different hardness, which has high productivity and few man-hours and has stable quality.

[Means and Actions for Solving the Problem] A method for manufacturing a foam with different hardness according to the present invention for solving the above problem is to fix a peripheral portion of a film-shaped partition member to a pair of split molds and to form one mold surface. The partition member forms the first cavity space, the other mold surface of the split mold and the partition member form the second cavity space, and the first cavity space forms the first cavity space.
The foamed resin is foamed, and the partition member is pressed toward the second cavity space by the foaming pressure to form a first foamed body having a convex curved surface, and a composition different from that of the first foamed resin is formed in the second cavity space. The second foamed resin is foamed to form a second foamed body.

In the manufacturing method of the present invention, first, the peripheral portion of the film-shaped partition member is fixed to the pair of split dies. As a method of fixing the peripheral portion of the partition member, the partition member may be adhered to the mold surface with a double-sided tape or the like, or may be sandwiched between the divided surfaces to be fixed. As a result, the partition member and one mold surface form a first cavity space, and the partition member and the other mold surface form a second cavity space.

As the partition member, a member that does not allow the foamed resin to permeate and is easily deformed by the pressure of foaming can be used. For example, urethane film, vinyl chloride film, polyester film, polyolefin film, etc. are used,
It is preferable to use one having excellent adhesiveness to the foamed resin. For example, when urethane foam is used as the resin foam, a urethane film is particularly preferable.

A first foamed resin and a second foamed resin having different compositions are injected into the first cavity space and the second cavity space, respectively, and foam-molded. The partition member is pressed toward the second cavity space by the foaming pressure of the first foamed resin. Since the peripheral edge portion of the partition member is fixed to one mold surface, the partition member has a convex curved surface shape in which the central portion expands by pressing and projects toward the second cavity space. Therefore, the first foam obtained in the first cavity space has a shape in which the thickness gradually increases from the peripheral portion toward the central portion. As a result, if the first foam is made softer than the second foam, the apparent hardness changes continuously, and the feel during use becomes excellent.

To do so, for example, the first foamed resin and the second foamed resin are foamed almost simultaneously. Since the pressure of each foamed resin injected into the first cavity space and the second cavity space is uniquely determined by the composition and amount thereof, the partition member can be pressed with a predetermined pressure difference set in advance. . It is hardly affected by a slight difference in the foaming start time. It is also possible to form the first foam molded body first and then foam the second foam resin. However, in this case, two molding steps are required, which is not preferable because the molding cycle becomes long.

The partition member must be fixed so that it can be easily deformed by the pressure during foaming as described above. For example, as the partition member, it is preferable to use an expansive film that expands in response to the magnitude of the stress when the stress acts. If the expandable film is used, the expandable film can be easily expanded by a predetermined amount to obtain the first foam having a predetermined shape. If the partition member is difficult to expand, the peripheral portion may be fixed in a loosened state. The slack is eliminated by the foaming pressure, and a first foam having a convex curved surface protruding according to the amount of the slack is obtained.

In addition, it is preferable to perform a degassing step in order to prevent gas accumulation during foaming. Since the partition member is pressed from the first cavity space toward the second cavity space, it is particularly desirable to perform degassing in the first cavity space. If a partition member having air permeability is used, it is convenient because the gas accumulation can be prevented without degassing.

The first foam and the second foam are partitioned by the partition member and are not in contact with each other. Therefore, the types of the first foamed resin and the second foamed resin can be freely selected regardless of their compatibility, adhesiveness, or the like. Although the hardness can be freely set, in the case of a seat or a headrest, it is desirable that the first foam be softer than the second foam.

[Effects of the Invention] Therefore, according to the method for producing a foam of different hardness of the present invention,
Since the first foamed resin and the second foamed resin can be foamed at substantially the same time, the time required for molding is almost the same as when molding from one type of conventional foamed resin, and the cycle time does not increase. Further, since the degree of deformation of the partition member is uniquely determined by the composition and injection amount of the first foamed resin and the second foamed resin, the shape and reproducibility of the first foamed body and the second foamed resin are good.
A foam can be formed.

The obtained first foam has a thin peripheral portion and a thicker shape toward the central portion. Therefore, if the hardness of the first foam is softer than that of the second foam, the periphery of the first foam is felt to be hard because the influence of the second foam is great, and the first foam becomes softer toward the central portion. I can feel it,
The change in hardness is continuous and a sudden change in hardness is prevented, resulting in extremely excellent tactile sensation.

[Examples] Hereinafter, specific examples will be described. The present embodiment is an application of the present invention to the production of a foam used for a headrest of an automobile as shown in FIG. The headrest is formed by covering a bag-like skin that is sewn in advance with a foam made of urethane foam. The headrest 1 includes a central portion 10a supporting the occipital region of the human body and a central portion 1a.
It has a front face portion 10 composed of side portions 10b extending slightly curved to the left and right sides of 0a and supporting so as to wrap the occipital region. Two stays 11 that are inserted and held in the seat project from the lower surface.

FIG. 2 shows a plane portion of the molding die used. The molding die includes a first die 2 forming the front half of the headrest 1,
The second mold 3 forms the rear half, and the first mold 2 is further divided into a front mold 20 that forms the front surface portion 10 of the headrest 1 and a side surface mold 21 that forms the side surface portion of the headrest 1. . And the first inlet between the front mold 20 and the side mold 21.
22 is formed, and the second injection port is provided between the first mold 2 and the second mold 3.
30 are formed. Further, a stay hole 31 through which the stay 11 is inserted is provided between the first mold 2 and the second mold 3.

A foam is produced using this molding die as follows.
First, as shown in FIG. 3 and FIG.
An expansive urethane film 4 (thickness: 30 μm) as a partitioning member is arranged on the dividing surface of the core material, and the core material 12 is previously formed by blow molding from PE and integrally joined to the stay 11.
Is placed in the mold, and the first mold 2 and the second mold 3 are clamped.
The urethane film 4 is fixed by sandwiching the peripheral portion between the front mold 20 and the side mold 21, and the mold cavity of the front mold 20 and the urethane film 4 form a first cavity space 23. Thus, the second cavity space 32 is formed. The stay 11 projects from the stay hole 31. Next, the first foamed resin is injected from the first injection port 22 and the second foamed resin is injected from the second injection port 30. Here, as the first foamed resin and the second foamed resin, a general urethane foam raw material for headrest is used, and as shown in Table 1, by changing the mixing ratio of the isocyanate component and the polyol component, a soft and hard foamed product can be obtained. Trying to get. The injection amount of the first foam resin is 60 g, the injection amount of the second foam resin is 210 g, and the second foam resin is injected 10 seconds after the second foam resin is injected.
Foam resin was injected. Then, the first injection port 22 is closed with the injection plug 24 and the second injection port 30 is closed with the injection plug 33, so that the first foamed resin and the second foamed resin are foamed substantially simultaneously. Then, due to the difference in foaming pressure between the first foamed resin and the second foamed resin,
The urethane film 4 is pressed and expanded toward the second cavity space 12, and has a convex curved surface shape protruding toward the second cavity space 12 side as shown in FIGS. 5 and 6. In that state, the soft first foam 25 formed of the first foam resin and the hard second foam 34 formed of the second foam resin fill the first cavity space 23 and the second cavity space 32. As a result, a foam body integrally bonded with the urethane film 4 and the core material 12 is obtained.

The hardness, the density, and the volume occupation rate of the whole of the obtained first foam 25 and second foam 34 were measured, and the results are shown in Table 2. As is clear from Table 2, the first foam 25 is soft and the second foam 34 is hard. And the first foam 25
Accounts for about 20% of the total.

In the obtained foam, the peripheral portion of the protruding urethane film 4 is cut off, and the skin sewn in a predetermined shape is covered to obtain the headrest 1. This headrest 1
Then, the shape of the soft first foam 25 forming the front surface portion 10 is such that the central portion 10a is thicker and becomes thinner toward the side portions 10b. Therefore, the second foam 34 is exposed to the influence of the second foam 34 toward the side portion 10b and gradually hardens, so that the hardness does not suddenly change and the tactile feeling is excellent and the head supportability is excellent. Also central part
In 10a, since the first foam 25 is thick, it is soft and has a good feel.

The headrest was repeatedly manufactured, but no significant change was observed in the numerical values in Table 2, and the reproducibility was excellent. If the injection amount of the first foamed resin and the second foamed resin is constant, the first foam 25 The reproducibility of the convex curved surface shape was also excellent.

Therefore, according to the manufacturing method of this embodiment, the first foam 25
Since the second foam 34 and the second foam 34 can be formed almost at the same time, it is possible to prevent the time required for molding from becoming long. Also obtained first
Since the foam and the second foam have excellent reproducibility of shape and property, a foam having desired performance can be stably and easily manufactured.

[Brief description of drawings]

The drawings relate to a manufacturing method according to an embodiment of the present invention. FIG. 1 is a perspective view of the obtained headrest, FIG. 2 is a plan view of a mold used, and FIGS. 3 and 4 are metal molds before molding. Explanatory sectional views showing the constitution of the mold, FIG. 5 and FIG. 6 are explanatory sectional views showing the constitution of the mold and the foam after molding corresponding to the AA cutting line and the BB cutting line of FIG. 1, respectively. It is a figure. 1 ... Headrest, 2 ... First type, 3 ... Second type, 4
...... Urethane film (partitioning member), 10 …… Front part, 11
...... Stay, 12 …… Core material, 22 …… First inlet, 23 …… First cavity space, 30 …… Second inlet, 32 …… Second cavity space, 25 …… First foam, 34 …… Second foam

Claims (1)

[Claims] 1. A peripheral portion of a film-shaped partition member is fixed to a pair of split molds to form a first cavity space between one mold surface and the partition member, and the other mold surface of the split mold. A second cavity space is formed with the partition member, the first foamed resin is foamed in the first cavity space, and the partition member is pressed toward the second cavity space by the foaming pressure to form a convex curved surface. And a second foamed resin having a composition different from that of the first foamed resin in the second cavity space to form a second foamed body. Method.