JPH01165431A - Manufacture of fiber molding to be thermally molded - Google Patents

Abstract

PURPOSE:To manufacture a fiber molding to be thermally molded, adapted for an automotive ceiling material having a light weight, excellent rigidity, heat resistance, thermal moldability, sound absorption and bending strength by laminating thermoplastic resin films on both side faces of a nonwoven fiber mat made of mixture fiber of inorganic fiber and thermoplastic resin fiber, thermally compressing the film at a temperature ranged from the melting point of the film to the melting point of the thermoplastic resin fiber, and releasing the pressure. CONSTITUTION:A nonwoven fiber mat made of mixture fiber of inorganic fiber and thermoplastic resin fiber is employed, and its mixture ratio is preferably range by weight at 10:1-1:5 of the inorganic fiber: thermoplastic resin fiber. A laminate formed by laminating films on both side faces of the mat is thermally compressed at a temperature ranged from the melting point of the thermoplastic resin film to the melting point of the thermoplastic resin fiber. Thereafter, the pressure is released thereby to increase the thickness of the mat and it is then cooled. The obtained fiber molding to be thermally molded exhibits an improved thermal adhesive properties, and preferable thermal adhesive properties to a foaming body or a decorative skin material.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing a thermoformable fiber molded article suitable as a ceiling material for an automobile.

(Conventional technique 9) Automotive ceiling materials are lightweight, rigid, heat resistant, sound absorbing,
Materials with excellent properties such as thermal 11R shapeability are required.

As an example of this type of material, for example, Japanese Patent Laid-Open No. 60-83832 discloses an automotive ceiling material in which synthetic resin layers such as polyethylene are laminated on both sides of an inorganic fiber layer such as glass fiber. However, such a laminated molded product is
In particular, it has low sound absorption properties and low bending strength, making it unsatisfactory and problematic as a ceiling material for automobiles.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned problems, and aims to provide lightweight, rigid, heat-resistant, thermal formability, sound absorption, and bending strength. An object of the present invention is to provide a method for producing a thermoformable fiber molded article that has excellent properties and is suitable for automobile ceiling materials.

(Means for Solving the Problems) In the present invention, first, thermoplastic resin films are laminated on both sides of a nonwoven fiber mat made of mixed fibers of inorganic fibers and thermoplastic resin fibers.

Examples of inorganic fibers used include glass fiber, rock wool, ceramic fiber, and carbon fiber.
Glass fibers having a fiber length of ~30 μm and a fiber length of 5 to 200 fibers are suitable. If the fiber thickness and fiber length of the glass fibers are less than the above values, the rigidity of the obtained molded product will decrease. on the other hand,
If the fiber thickness and fiber length exceed the above values, it will not be possible to give the fiber a delicate shape, especially when used as a molded ceiling of an automobile.

As a thermoplastic resin fiber, its melting point is 70.250°C.
90 to 250"C is preferable, and 90 to 250"C is more preferable. Examples of such thermoplastic resin fibers include polyolefin fibers such as polyethylene and polypropylene, polyester fibers, polyamide fibers, and polystyrene fibers.The above-mentioned thermoplastic resins If the melting point of the fiber is below 70°C, the resulting molded product will soften when exposed to high temperatures, resulting in poor dimensional stability.On the other hand, if the melting point is above 250°C, high temperatures will be required during molding. In addition, the molding time becomes longer, resulting in higher costs.

The thermoplastic resin fiber preferably has a fiber thickness of 3 to 50 μm and a fiber length of 5 to 200 mm.

If the fiber thickness and fiber length of the above-mentioned fibers are less than the above-mentioned values, droplets of molten thermoplastic resin fibers become small units during the compression molding process when shaping the molded article into the final shape. Adhesion of inorganic fibers becomes insufficient. On the other hand, when the fiber thickness and fiber length exceed the above values, the droplets of the molten thermoplastic resin fibers become large units, the number of bonding points decreases, and it becomes difficult to obtain a molded article with sufficient strength.

In the present invention, a nonwoven fiber mat made of a mixed fiber of the above-mentioned inorganic fiber and thermoplastic resin fiber is used, and the mixing ratio of the inorganic fiber and thermoplastic resin fiber is 10:1 to 1 by weight. The range of :5 is preferable, and the range of 7:1 to 1:1 is more preferable. When the amount of inorganic fiber increases and the thermoplastic resin fiber decreases, it becomes difficult to mold into a mat shape, and when the compression is released, the thickness becomes difficult to increase properly, and when shaping the molded product into the final shape. In the compression molding process, it becomes difficult to obtain the binder effect of the molten thermoplastic resin fibers. On the other hand, when the amount of thermoplastic resin fibers increases and the amount of inorganic fibers decreases, the strength of the resulting molded product improves, but the porosity of the molded product decreases due to the small amount of inorganic fibers. As a result, sound absorption performance deteriorates.

The above-mentioned nonwoven fiber mat is prepared by a conventional nonwoven fiber mat manufacturing method. For example, it can be obtained by feeding inorganic fibers and thermoplastic resin fibers into a card machine, defibrating them and forming them into a mat shape, and then needle punching the mat.

The density of such a nonwoven fiber mat is 0. O1~0.2g
/cc is preferable. When it is less than 0.01 g/cc, the shape retention as a mat decreases, and the strength of the molded product obtained also decreases. If it exceeds 0.2 g/cc, the weight of the entire molded product obtained will increase, making it unsuitable for use as a molded ceiling for automobiles. The thickness of the nonwoven fiber mat is appropriately determined depending on the use, but is usually 4 to 100 mm. If it is less than 4 mm, the strength of the molded product will be insufficient, which is not preferable. On the other hand, if the number of plates exceeds 100, heat will not be transmitted to the center during thermoforming (this will require a large amount of heat, which is undesirable. When used as a ceiling material for automobiles, 4 to 12 layers is preferable.

As the thermoplastic resin film laminated on both sides of the above-mentioned nonwoven fiber mat, films of polyethylene, polypropylene, ethylene-vinyl acetate copolymer, polyvinyl chloride, polyester, polyamide, etc. are used. The thickness of such a film is preferably in the range of 20 to 500 μm, more preferably in the range of 50 to 200 μm.

If the thickness of the film is less than 20 μm, the rigidity will not improve, and if it exceeds 500 μm, it will take time to completely melt, which is disadvantageous in terms of energy, and the weight of the molded product will increase, which will be disadvantageous in terms of cost.

Therefore, when laminating the above thermoplastic resin films, a thermoplastic resin film having a melting point lower than the melting point of the thermoplastic resin fibers in the nonwoven fiber mat is used. In this case, if the melting points of the above-mentioned fibers and the film are too close to each other, there is a risk that some of the above-mentioned fibers will melt during heat compression. Preferably, a resin film is used. Note that the lamination method may be to simply stack films on both sides of the nonwoven fiber mat, or may be laminated by heat.

Next, in the present invention, a laminate in which films are laminated on both sides of a nonwoven fiber mat is heated and compressed at a temperature higher than the melting point of the thermoplastic resin film and lower than the melting point of the thermoplastic resin fibers.

Any heating method may be employed, such as a hot air heating method, a radiant heating method using an infrared heater, a far-infrared heater, or the like.

Furthermore, any compression method may be employed, such as a pressing method, a method of compressing with a roll, and the like. The compression pressure is preferably in the range of 0.1 to 20 kg/cffl, and the compression time of several seconds is sufficient. This heat compression reduces the thickness of the nonwoven fiber mat. During compression, it is preferable to heat the press or roll to a predetermined temperature.

In addition, when using a press, heating can be performed with this press and compression can be performed subsequently, and in this case, it is not necessary to heat the laminate in advance.

Thereafter, in the present invention, the thickness of the nonwoven fiber mat is increased by releasing the pressure, and the nonwoven fiber mat is cooled.

When decompressed in this way, the compressed nonwoven fiber mat naturally tries to recover its original thickness and increases in thickness. When this amount of recovery is insufficient or takes a long time, the increase in thickness can be promoted by blowing heated air into the interior or by separating both surfaces by vacuum adsorption.

The nonwoven fiber mat with increased thickness is cooled, and the cooling may be done by leaving it to cool or by blowing cold air onto it. In this way, each fiber is partially bonded by the molten resin,
A thermoformable fiber molded article having a large number of voids throughout is obtained.

In order to shape the thermoformable fiber molded article obtained according to the present invention into the final shape, it is sufficient to reheat it to a temperature higher than the melting point of the thermoplastic resin fiber and compression mold it with a press or the like. For use as ceiling materials, woven fabrics can be woven with or without intervening closed-cell or open-cell foams such as polyethylene foam, polypropylene foam, polyvinyl chloride foam, and polyurethane foam during compression molding. Cosmetic skin materials such as , nonwoven fabric, and vinyl chloride leather may be laminated and integrally shaped.

When laminating foams and cosmetic skin materials and shaping them integrally, it is best to provide a heat-melting adhesive layer on the outer surface of the thermoplastic resin sheet that is laminated to the nonwoven fiber mat. The thermal adhesion of the surface of the resulting thermoformable fiber molded article is improved,
Good thermal adhesion to foams and cosmetic skin materials.

(Function) According to the present invention, when a laminate of a non-woven fiber mat and a film is heated and compressed under predetermined conditions, the thickness decreases and the molten resin of the thermoplastic resin film is absorbed into the gaps between each fiber of the non-woven fiber mat. It is well impregnated with.

After that, when the pressure is decompressed, if the non-woven fiber mat is composed only of inorganic fibers, its thickness will be difficult to recover, but in the present invention, since thermoplastic resin fibers are present in the non-woven fiber mat, the thickness of the non-woven fiber mat is Compressed with good elasticity
@The thickness of the fiber mat is well recovered and increased.

As a result, each fiber is partially firmly bonded by the molten resin, and a bulky thermoformable fiber molded article having a large number of voids throughout is obtained.

Furthermore, when the thermoformable fiber molded article obtained according to the present invention is reheated to a temperature higher than the melting point of the thermoplastic resin fiber in order to shape it into the final shape, the thermoplastic resin fiber melts and drops. These droplets adhere to the inorganic fibers and act as a binder together with the melted thermoplastic resin film, allowing for good thermal shaping.

(Example) Examples and comparative examples of the present invention are shown below.

Glass fiber (fiber thickness 9-13 μm, fiber length 40-1
00mm) 65% by weight and high density polyethylene fiber (fiber thickness 6 denier, fiber length 40-100mm melting point 13
5°C) at 35% by weight, defibrated using a card machine to form a cotton-like material, and subjected to needle punching to obtain a non-woven fiber mat having a thickness of 10 mm and a weight of 500 g/bo.

A low-density polyethylene film (thickness 150 um, melting point 107°C) is laminated on both sides of this non-woven fiber mat, and this laminate is compressed by heating at a pressure of Ikg/c+fl for 10 seconds in a press at 120"C to reduce the thickness. After that, the compression was released and the thickness was increased to obtain a flat fiber molded article for thermoforming with a thickness of 8.3 mm.

The above molded body is heated to a surface temperature of 1 from both sides using an infrared heater.
It was heated to 70'C, then immediately placed in a mold at 30°C and compression molded for 1 minute at a pressure of 1 kg/c++1 to form the final shape. The above mold is designed to have a minimum thickness of 2.5nun and a maximum thickness of 5.0mm, and has a recess with a radius of curvature of 5mm (R5). Thermal formability was evaluated by measuring whether or not it was shaped.

The above shaped molded product was held on all four sides in a hot air open at 95° C., and the heat displacement amount (sagging distance) was measured after 24 hours. In addition, a sample piece with a thickness of 5 mm, a width of 50 mm, and a length of 150 mm was cut from the above-described molded product, and its bending strength was evaluated according to JIS K 7211. Furthermore, from the above molded body, a thickness of 8M and a diameter of 9
A sample piece of 0 mm was cut out, and the sound absorption coefficient at 1000 Hz was measured by the normal incidence method according to JIS A 1405. The results are shown in Table 1.

Tsubaraga 1 Example 1 except that high-density polyethylene fiber (melting point 135°C) was changed to polyester fiber (melting point 160°C)
In the same manner as above, a thermoformable fiber molded article having a thickness of 8.7 mm was obtained.

This molded product was used in the same manner as in Example 1 except that the surface temperature of the molded product was changed to 200°C when it was shaped into the final shape. Sound absorption was measured. The results are shown in Table 1.

The process was repeated in the same manner as in Example 1 except that 50% by weight of glass fiber and 50% by weight of high-density polyethylene fiber were mixed in the back mound to a thickness of 7.
．． A 5M thermoformable fiber molded article was obtained.

Using this molded body, heat formability,
The heat displacement, bending strength, and sound absorption properties were measured. The results are shown in Table 1.

2. Compare Example 1 in the same manner as in Example 1 except that the temperature of the press was changed to 150°C. A fiber molded article for thermoforming of 1 mm was obtained.

Since the high-density polyethylene fibers were melted, this molded product had a small increase in thickness and was thin, and could not be formed into the desired thickness with a mold.

4 Comparison ff1u A thermoformable fiber molded article having a thickness of 10.5 mm was obtained in the same manner as in Example 1 except that the temperature of the press was changed to 80°C.

This molded product was a laminated molded product because the thermoplastic resin film was not melted.

Using this molded body, heat formability,
Heat resistance, displacement, bending strength, and sound absorption were measured. The results are shown in Table 1.

The main low-density polyethylene film (melting point 107°C) was replaced with a high-density polyethylene film (melting point 135°C),
A thermoformable fiber molded article having a thickness of 3.2 mm was obtained in the same manner as in Example 1 except that the pressing temperature was changed to 150°C.

Since the high-density polyethylene fibers were melted, this molded product had a small increase in thickness and was thin, and could not be formed into the desired thickness with a mold.

(Hereinafter referred to as a margin) Table 1 (hereinafter referred to as a margin) (Effects of the invention) Since the method for producing a thermoformable fiber molded article of the present invention is configured as described above, inorganic fibers and thermoplastic resin fibers are melted. It is possible to easily obtain an inexpensive thermoformable fiber molded article that is partially firmly bonded with resin, is bulky, and has a large number of voids throughout.

Therefore, this fiber molded article for thermoforming is lightweight due to the presence of inorganic fibers, thermoplastic resin fibers, and voids.
It has excellent rigidity, heat resistance, heat formability, sound absorption, and bending strength, and can be suitably used for automobile ceiling materials.

Claims (1)

[Claims] 1. Thermoplastic resin films are laminated on both sides of a non-woven fiber mat made of mixed fibers of inorganic fibers and thermoplastic resin fibers, and then heated at a temperature higher than the melting point of the thermoplastic resin film and lower than the melting point of the thermoplastic resin fibers. 1. A method for producing a thermoformable fiber molded article, which comprises increasing the thickness of a nonwoven fiber mat by compressing it, then decompressing it, and then cooling it.