JPH0984973A - Thermoforming method for fiber assembly - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal molding method capable of thermally molding a fiber assemblage (cotton) into the prescribed position in the cavity of a metal mold while controlling the fiber assemblage to a desired bulk density and is capable of exactly controlling the shape of molded goods after thermal molding. SOLUTION: The thermal molding is executed by dividing a thermal molding cycle to several stages and compressing and forming the fiber assemblage F packed into the respective regions in the cavity at least >=1 times down to the prescribed volume by moving the moving part of the metal mold at the time of packing the fiber assemblage F into the cavity of the metal mold 1 and thermally molding the fiber assemblage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fiber assembly (hereinafter referred to as "cotton") in which a binder fiber having a melting point lower than that of a short fiber of a synthetic fiber having a crimped form is dispersed and mixed in a matrix. Alternatively referred to as "cotton mass").

[0002]

2. Description of the Related Art Generally, urethane foam has been widely used as a cushion material for a seat having a complicated shape such as an automobile and an aircraft. However, urethane foam has problems such as generation of toxic gas at the time of combustion and difficulty in recycling. Therefore, there has been a long-felt need for a molding material that can be used instead.

In view of these problems, in recent years, as a material for substituting for urethane foam, a fiber assembly has been obtained in which a binder fiber having a melting point lower than that of the short fiber is dispersed and mixed in a matrix composed of short fibers of synthetic fiber. The fiber structure used has been attracting attention as a material capable of solving the above problems. This cotton is formed by filling the inside of the cavity of the mold and then thermoforming the binder fibers contained in the cotton by heat fusion.

Conventionally, as a method for filling cotton into a molding die, for example, a lump of cotton is temporarily shaped into a certain size,
A method has been adopted in which provisionally shaped cotton is hand-filled or filled in the cavity of a molding die by an automatic machine such as a robot. However, with this method, it is necessary to temporarily shape the cotton once and then pack the temporarily shaped cotton into the mold, which requires an extra step of temporary shaping, resulting in cost increase and temporary shaping. There is a problem that a temporary storage place for installing cotton is also required.

In order to solve such a problem, a method of pneumatically transporting a small piece of cotton to a shaping mold without temporarily shaping the cotton is disclosed in, for example, Japanese Patent Publication Nos. 56-29556 and 62-62. No. 29069, JP-B 1-27727, etc. In this method, untemporarily shaped cotton is conveyed to a fiber-opening machine by a conveyor, and the fiber-opening machine cuts the cotton into small pieces. Then, by this, the cavity of the mold is filled and thermoformed.

However, in these thermoforming methods,
Since deformation of the fiber assembly during thermoforming is not considered,
Since the molded product taken out of the mold after the molding has undergone heat shrinkage, there is a problem that the size of the molded product after molding is different from the originally planned size.

In order to solve the problem of heat shrinkage at the time of molding, conventionally, an attempt has been made to eliminate the shrinkage error by manufacturing a cavity having a large size in consideration of the shrinkage amount.

However, in order to put such a molding die into practical use, the optimum molding conditions are specified, a large number of expensive molding dies are produced, and after repeated thermoforming experiments by this, However, there is a problem that the shape of the mold cavity must be determined by obtaining the heat shrinkage amount. However, the molding conditions specified to be optimum are not optimum in practice, so that the molding conditions are often changed. In addition, since the actual manufacturing mold has an extremely large shape, a scale-down molding mold is often used in the experiment in order to reduce the cost and simplify the experiment. The molding conditions often differ from those of the molding die.

[0009]

In view of the above-mentioned problems, the problem to be solved by the present invention is that when thermoforming cotton into a predetermined shape, the shape of the molded article after thermoforming is before molding. The object of the present invention is to provide a method capable of thermoforming while maintaining an accurate shape as designed in.

[0010]

According to the present invention, a fiber assembly in which a binder fiber having a melting point lower than that of the short fibers is dispersed and mixed in a matrix composed of short fibers of synthetic fibers having a crimped form. A method for filling the opened fiber assembly into a cavity of a mold to form a body, and thermoforming the fiber assembly, the method comprising: A thermoforming method for a fiber assembly is provided, which comprises performing thermoforming by compressing the fiber assembly at least once during thermoforming to a predetermined volume.

Further, in the method of the present invention, the above-mentioned compression operation is applied to each region in which the fiber assembly filled in the mold cavity is located, whereby the bulk density of the fiber assembly in each region is increased. Is preferably controlled individually.

Here, the fiber assembly used in the present invention will be briefly described.

First, the short fibers of the synthetic fibers constituting the matrix of the fiber assembly are not particularly limited, but for example, ordinary polyethylene terephthalate, polybutylene terephthalate, polyhexamethylene terephthalate, polytetramethylene terephthalate, Poly 1,
A short fiber made of 4-dimethylcyclohexane terephthalate, polypivalolactone, or a copolymerized ester thereof, a cotton blend of these fibers, or a composite fiber made of two or more of the above polymer components is preferable. . Further, the cross-sectional shape of the short fiber may be any of a circle, a flat, an irregular shape, and a hollow.

Further, the crimp in this case is preferably an actual crimp, and the actual crimp is a mechanical method using a crimper or the like, an anisotropic cooling method during spinning, a side-by-side type or an eccentric sheath core. It can be obtained by a method such as heating the type composite fiber.

On the other hand, as the binder fiber, for example, a polyurethane-based elastomer or a polyester-based elastomer may be mixed in accordance with the required performance of the product to be molded.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The embodiments of the present invention described above will be described in detail below with reference to the drawings.

FIG. 1 is a front sectional view exemplifying an apparatus for carrying out the thermoforming method of the present invention, in which F is cotton (fiber assembly), 1 is a molding die, and 2 is a hot air circulating device. Represent each.

FIG. 2 is a front sectional view illustrating a molding die suitable for carrying out the molding method of the present invention. In addition,
The molding die (1) is configured to include a fixed die portion (1a), a fiber supply port (1b), and movable die portions (1c to 1e).

In the cotton thermoforming apparatus configured as described above, first, the molding die (1) having cotton filled in the cavity thereof by air transportation or the like is installed in the hot air circulating apparatus (2). To be done. Then, the hot air is heated to a preset temperature, and the hot air is circulated in the direction of the arrow in FIG. 1 to heat the molding die (1), and the first-stage thermoforming is performed.

Next, the movable mold parts (1c to 1e) are moved by e1 to e3 in the direction of compressing the cotton (F). The movement of the movable mold parts (1c to 1e) is
This step may be performed once, or may be performed in several steps for each thermoforming cycle. As described above, the significance of performing the movement of the movable mold part in several stages for each thermoforming cycle is that the cotton (F) is not significantly compressed at a time, and therefore the molding strain due to the compression of this part. Can be alleviated. Here, the moving amounts (e1 to e3) of the movable mold parts (1c to 1e) can be set independently for each region of the cavity filled with the cotton (F).
The bulk density of the fiber structure (molded product) after molding can be freely controlled.

Finally, the temperature is raised to a predetermined molding temperature to heat-bond the binder fibers to each other, thereby completing the thermoforming. Then, cooling air is circulated to cool the molding die (1). Cooled mold (1)
Is taken out from the hot air circulation device (2), and the molded fiber structure is taken out from the molding die (1).

In the cooling process of the molding die (1), the movable mold parts (1c-1e) of the molding die (1) are moved in the non-compression direction (in some cases, the compression direction). Needless to say, the molding strain at the time of thermoforming may be removed.

[0023]

As described above, according to the present invention, there is an effect that cotton can be filled into a predetermined cavity position in a mold while controlling a desired bulk and high density.
In addition, it is possible to remove molding distortion during thermoforming and to sufficiently cope with shape changes due to heat shrinkage of the molded product during thermoforming, which makes it possible to accurately design the shape intended by the designer before molding. In addition, the extremely remarkable effect that the shape of the molded product can be maintained and thermoforming can be achieved.

[Brief description of drawings]

FIG. 1 is a front sectional view illustrating a device of the present invention.

FIG. 2 is a front cross-sectional view in which only the mold part in FIG. 1 is enlarged.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molding die 1a Fixed die part 1b Fiber supply port 1c-1e Movable die part 2 Hot air circulation device F Fiber assembly (cotton)

Claims (2)

[Claims] 1. In order to form a fiber assembly in which a binder fiber having a melting point lower than that of a short fiber of a synthetic fiber having a crimped form is dispersed and mixed into a matrix, the fiber assembly is introduced into a cavity of a mold. In a method for filling the opened fiber assembly and thermoforming the fiber assembly, the fiber assembly filled in the cavity of the mold is thermoformed at least once during thermoforming. A method of thermoforming a fiber assembly, which comprises thermoforming by compressing to a volume. 2. The compressing operation according to claim 1 is applied to each region where the fiber assembly filled in the mold cavity is located, whereby the bulk density of the fiber assembly in each region is individually increased. The method for thermoforming a fiber assembly according to claim 1, which is controlled.