Process for producing multilayer molded article

Details Process for producing multilayer molded article Process for producing multilayer molded article

2002-02-19

2004-12-28

Lee, Edmund H. (Department: 1732)

Plastic and nonmetallic article shaping or treating: processes

Mechanical shaping or molding to form or reform shaped article

To produce composite, plural part or multilayered article

C264S247000, C264S257000, C264S348000, C264S266000, C425S127000, C425S129100

Reexamination Certificate

active

06835340

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for producing a multilayer molded article in which an skin material having nap on the outer surface, such as a fabric skin material, is attached on the outer surface of a substrate made of synthetic resin.
2. Description of the Related Art
A multilayer molded article that includes a fabric skin material attached thereon is widely used, for example, as an automobile interior component (such as in door trim or on an instrument panel) or as an component mounted on the exterior or in the interior of home electrical appliances.
As a method for producing such a multilayer molded article, a method is known in which, for example, molten thermoplastic resin is supplied to a mold comprising a pair of male and female mold halves after a fabric skin material is placed therein and the mold is held at a predetermined clamping pressure, so that the molten thermoplastic resin is molded into a predetermined configuration and that, at the same time, the fabric skin material is attached on the outer surface of the molded resin. This method offers the advantage that the fabric skin material is attached on the outer surface of the substrate made of thermoplastic resin simultaneously with the molding of the substrate, but the problem exists that the fabric skin material becomes flattened due to the clamping pressure, and the esthetic appeal (i.e., the appearance, feel, etc.) of the resulted article is compromised.
Accordingly, as a method to eliminate the loss in esthetic appeal due to the flattening of the fabric skin material in this fashion, a method has been proposed in which the mold is opened slightly after a clamping and primary cooling step, thereby forming a gap between the outer surface of the fabric skin material and the molding surface of the mold, and this condition is maintained while the thermoplastic resin undergoes secondary cooling (Japanese Patent Laid-Open No. 10-58485, Japanese Patent Laid-Open No. 11-314227). Using this method, a recovery space for the flattened nap on the outer surface of the fabric skin material is maintained, such that the previously flattened nap rises during secondary cooling, enabling a molded article that exhibits little flattening to be obtained.
However, even using this method, there remain the problems that a molded article having a good appearance is not always obtained because sufficient recovery of the flattened nap does not always occur, and that deformation sometimes occurs in the molded article due to inadequate cooling.
Accordingly, an object of the present invention is to provide a method for producing a multilayer molded article in which a fabric skin material is integrally molded with a synthetic resin substrate using a mold comprising a pair of male and female mold halves, wherein the loss in the appearance and feel due to the flattening of the fabric skin material is reliably prevented and deformation of the molded article is prevented as well.
SUMMARY OF THE INVENTION
The present invention is a method for producing a multilayer molded article in which an skin material having nap on the outer surface thereof is integrally molded with a synthetic resin substrate using a mold comprising a pair of male and female mold halves that can be moved toward and away from each other, wherein such method includes a first step of supplying a skin material to the gap between the pair of male and female halves of the mold while they are in an opened state, a second step of supplying molten synthetic resin between the back surface of the skin material and the molding surface of one of the pair of male and female mold halves that faces such back surface, a third step of clamping the mold either after the thermoplastic resin has been supplied or while it is being supplied, a fourth step of carrying out primary cooling of the molten synthetic resin while the mold is being clamped under a predetermined clamping pressure, a fifth step of opening the mold halfway and forming a predetermined gap between the pair of male and female mold halves, a sixth step of carrying out secondary cooling of the molten synthetic resin while the mold is being held in this half-open state, and a seventh step of opening the mold after the molten synthetic resin has hardened and extracting a molded article as a final product.
According to one aspect of the present invention, the time period of the operation of the fifth step to open the mold halfway is set at one second or less.
In other words, if the time period for the operation of the fifth step in which the mold is opened halfway exceeds one second, the nap tends to stay flattened during the half-opening operation, and the rising of the nap during the sixth step in which secondary cooling is performed does not take place completely, but if the half-opening step is carried out in a short interval of one second or less, the nap recovers its shape in a reliable fashion without acquiring the tendency to stay flattened. Furthermore, because the time period between the fourth step, i.e., the primary cooling step, and the sixth step is no more than one second, problems such as inadequate cooling of the molten synthetic resin do not occur. Here, the time period for the half-opening operation is the time period from the beginning of the reduction in the mold clamping pressure to the point at which the mold is halfway open.
In another aspect of the present invention, the gap formed between the pair of male and female mold halves in the fifth step is determined by adjusting in increments of 0.1 mm to ensure that the color of the outer surface of the skin material does not change significantly after molding, as well as to ensure that there is minimal deformation during molding.
The hue of the coloring of the outer surface of the fabric skin material may change due to the degree of flattening nap. Consequently, where the change in the color of the fabric skin material after molding is the smallest, the state of the nap after molding is close to the state of the nap before molding, in which there is a minimum amount of flattening. This is due to the fact that, because the pressure applied by the surface of the mold on the outer surface of the fabric skin material is reduced as the half-opening gap widens and the rising of the nap that was flattened takes place in a more reliable fashion in the sixth (secondary cooling) step, the change in the color of the outer surface of the fabric skin material after molding becomes small. On the other hand, if the half-opening gap becomes too wide, the cooling of the molten thermoplastic resin in the secondary cooling step becomes insufficient and deformation of the molded article can easily occur. Accordingly, by setting the size of the half-opening gap such that the change in the color of the outer surface of the fabric skin material after molding is small and there is minimal deformation in the molded article, insufficiency of cooling of the molten thermoplastic resin is prevented during the second cooling step and the optimal amount of recovery of the flattened nap on the outer surface of the fabric skin material is obtained. Moreover, by adjusting the gap in minute increments of 0.1 mm, the optimal size of the half-opening gap in order to obtain a molded article exhibiting the least amount of flattening and deformation can be reliably determined.
Furthermore, the present invention comprises a method for producing a multilayer molded article by integrally molding an skin material having nap on the outer surface thereof and a synthetic resin substrate using a mold comprising a pair of male and female mold halves that can come into contact with or move away from each other, wherein one of the mold halves has a movable block that is located such that it can be moved closer to or farther away from the other mold half, and the surface of the movable block facing the other mold half comprises part of the molding surface of such one mold half, and wherein such method includes a first step of supplying a skin mate

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