JPH0253948A - Thermo-formable composite material - Google Patents

Abstract

PURPOSE:To obtain the subject composite material having light weight and excellent sound absorptivity and suitable as a ceiling material of automobile, etc., by bonding a heat-weldable resin layer to a surface of a mat having a specific void ratio and produced by bonding a thermoplastic resin to inorganic fibers. CONSTITUTION:A mat having a void ratio of 50-99% is produced by bonding a thermoplastic resin to inorganic fibers e.g., having diameter of 5-30mum and length of 5-200mm at a weight ratio of 1/5-5/1. The objective composite material having high mechanical strength, excellent thermoforming property and capable of absorbing the sound of low-frequency range at about 1kHz can be produced by bonding one surface of the mat almost completely with a heat-weldable resin layer having a thickness of 10-100mum and free from through-holes.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is a thermoformable composite material that is lightweight and has excellent sound absorption properties, particularly a thermoformable composite material that is suitably used as a base material for automobile ceiling materials. Concerning composite materials.

(Prior technology) Cardboard, glass fiber-reinforced thermosetting resin sheets, etc. are used as base materials for ceiling materials, which are one of the interior materials of automobiles.However, cardboard has poor heat formability and is difficult to absorb sound. The thermosetting resin sheet has the disadvantage that it absorbs moisture and becomes heavy or sag when used for a long period of time because it is hygroscopic. Bad,
It also has the disadvantage of being heavy.

Furthermore, Japanese Patent Publication No. 61-17261 discloses that a sound-absorbing skin material is bonded between a base material and a skin material via a fiber network hot melt sheet adhesive, and after bonding, the porosity of the adhesive layer is 20. A ceiling material for automobiles has been proposed in which the amount of carbon dioxide is reduced to 80%.

(Problem to be solved by the invention) However, the ceiling material described in the above publication has a porosity of 20
Because the sound-absorbing skin material is bonded through an adhesive layer with a thickness of ~80%, sound in the high-frequency range can be absorbed relatively well, but the sound absorption coefficient in the low-frequency range decreases. This method has the disadvantage that it cannot effectively attenuate low-frequency sounds generated by automobiles.

Therefore, in conventional ceiling materials, it is necessary to use urethane foam, etc., which has excellent sound absorption properties, as the skin material, and if other skin materials are used, the sound absorption properties are significantly reduced.

The present invention is intended to solve the above-mentioned drawbacks, and aims to be lightweight, have excellent thermal formability, and have excellent sound absorption properties, especially in the low frequency range. Another object of the present invention is to provide a thermoformable composite material that has excellent material selectivity for the skin material.

(Means for Solving the Problems) The thermoformable composite material of the present invention is made by bonding inorganic fibers to each other with a thermoplastic resin and having a porosity of 50 to 99%. It is characterized in that a thermoadhesive resin layer having no through holes is adhered to substantially the entire surface, thereby achieving the above object.

The mat-like material used in the present invention is formed into a mat using inorganic fibers as a main material, and is bonded to each other using a thermoplastic resin.

Examples of inorganic fibers include glass fibers, rock wool fibers, etc. The length thereof is preferably 5 to 200 mm from the viewpoint of ease of forming a mat, and 70% by weight of fibers of 50 mm or more are included. is more preferable. Moreover, the diameter of the inorganic fiber is preferably 5 to 30 μm, more preferably 7 to 20 μm. If the diameter of the inorganic fibers becomes too small, the mechanical strength will decrease, and if the diameter of the inorganic fibers becomes too large, the resulting mat-like material will become heavy and its bulk density will increase.

The above-mentioned thermoplastic resin may be one that mutually bonds a large number of inorganic fibers, and examples thereof include polyethylene, polypropylene, saturated polyester, polyamide, polystyrene, polyvinyl butyral, etc. Organic fibers made of these thermoplastic resins, Used as organic powder and film. It is preferable to add the organic fibers when manufacturing the mat, but the organic powder may be sprinkled after the mat is manufactured. Further, the organic powder may be used in the form of a dry powder, or in the form of a powder dispersion or emulsion. The length and diameter of the organic fibers are preferably such that they can be easily mixed with inorganic fibers to form a mat. That is, the length of the organic fiber is preferably 5 to 200 mm, more preferably 20 to 100 mm,
The diameter of the organic fiber is preferably 3 to 50 μm, more preferably 20 to 40 μm. Also, the diameter of the organic powder is
When added in the form of a powder, it is preferably 50 to 100 meshes, and when added in a state dispersed in a poor solvent or in the form of an emulsion, it may be smaller than that.

The thickness of the thermoplastic resin film is preferably 10 to 300 μm; if the thermoplastic resin film is too thick, it becomes heavy, and if it is too thin, the mechanical strength tends to decrease. Furthermore, when organic fibers or powders are used together, the inorganic fibers are bound by the organic fibers or powders, so the thickness of the thermoplastic resin film used can be reduced.

Furthermore, when organic fibers or powders are used together, it is preferable to use organic fibers whose melting temperature is close to that of the thermoplastic resin film.

At least one type of fiber, powder, and film made of thermoplastic resin is added, and two or more types may be used in combination.If the amount added is small, the adhesion between the inorganic fibers will be reduced, and if the amount is increased, the adhesion between the inorganic fibers will be reduced. Since mechanical strength decreases when the amount is reduced and a composite material is made, a weight ratio of 1=5 to 5:1 with respect to the non-alpha fiber is preferable.

Any method may be used to produce the mat, such as a method in which inorganic fibers and, if necessary, organic fibers are supplied to a card machine, defibrated and mixed to produce a mat. Further, in order to improve the mechanical strength of the mat, needle punching may be performed, and needle punching is preferably performed at 1 to 100 locations, more preferably 10 to 50 locations per 1 ci. The density of the mat is preferably from 0.01 to 0.2 g/cm3, more preferably from 0.03 to 0.07 g/cm3, since the density of the mat becomes heavier as it becomes larger and the mechanical strength decreases as it becomes smaller.

Any method may be used to laminate the thermoplastic resin film; for example, a method of placing the thermoplastic resin film on both sides or one side of the mat, a method of heat-sealing,
Alternatively, there may be a method in which the thermoplastic resin film is laminated onto a matte surface when extruded from a mold. In order to bond the inorganic fibers to each other with a thermoplastic resin, the mat may be heated to melt the thermoplastic resin.

The above heating conditions are 1 from the melting temperature of the thermoplastic resin.
Preferably, the heating is carried out at a temperature of 0 to 70"C for 1 to 10 minutes.

Further, any heating method may be employed, such as a method of heating the entire laminate in an oven, or a method of radiant heating using a far-infrared heater, an infrared heater, or the like.

In addition, when using a thermoplastic resin film or making the bond more dense, it is preferable to compress it. When compressed, the molten thermoplastic resin film is impregnated into the mat and the inorganic fibers are bonded to each other. Ru.

Any method may be used as the compression method, such as press compression, roll compression, etc.

The pressure when compressing with a press is 0.1 to 10 kg/c11
1 is preferable, more preferably 3 to 4 kg/all, and the distance between rolls when compressing with rolls is preferably 115 to 1/20 of the thickness of the mat, more preferably 1/8
~1/15. Also, when the thermoplastic resin cools and solidifies during compression, the thickness of the mat will not recover.
Since the porosity is reduced, it is preferable that the press mold and rolls are also heated to a predetermined temperature.

The thus compressed mat is then preferably decompressed and heated to a temperature equal to or higher than the melting temperature of the thermoplastic resin to restore its thickness in order to increase the porosity. To restore the thickness of the mat, e.g.
This can be done in two ways: One method is to hold the mat for a predetermined period of time under almost no pressure at a temperature higher than the melting temperature of the thermoplastic resin, so that the elastic restoring force of the inorganic fibers restores the thickness of the mat to its original state. Another method is to heat the mat at a temperature higher than the melting temperature of the thermoplastic resin, place a thickness expanding member on both sides of the mat, and adhere the molten resin to the expanding member. By moving the expansion member outward in the thickness direction of the mat, the thickness of the mat is forcibly increased. The thickness expanding member is preferably one that adheres to the molten resin but does not adhere to the cooled resin; for example, Teflon sheets, Teflon-coated iron plates, mylar sheets, polyester films, aluminum plates, etc. can be used. . The thickness expansion member can be moved outward in the thickness direction by, for example, adsorbing a vacuum suction device to the expansion member and moving the vacuum suction device outward.

The time required for the above-mentioned heating is preferably carried out until the thickness of the mat is almost restored to its original thickness, and is generally preferably carried out for 10 seconds to 5 minutes, more preferably 20 seconds to 2 minutes.

The mat whose thickness has been restored is then cooled to obtain a mat-like material. The mat can be cooled by leaving it at room temperature or by blowing cold air onto it.

The interior of the obtained mat-like material has a three-dimensional network structure, is porous with continuous voids, and has a porosity of 50 to 99%. Further, it is preferable that a surface layer in which inorganic fibers and resin are integrated is formed on the surface of the mat-like material, the amount of resin being relatively large compared to the inside.

A thermoadhesive resin layer having substantially no through holes is adhered to one side of the mat-like material over substantially the entire surface. As the heat-adhesive resin layer, any conventionally used hot-melt adhesive can be used, such as polyolefin-based, polyamide-based, polyester-based, and polyurethane-based adhesives. The resin layer has a thickness of 1
A thickness of 0 to 100 μm is preferable. The thickness of the resin layer is 10
If the thickness is less than μm, the adhesive strength is low, and the thickness of the resin layer is 10 μm.
If it exceeds 0 μm, openings will be difficult to form in the resin layer during thermoforming as described below.

The resin layer can be provided on the surface of the mat-like material, for example, as follows.

■Heating the surface of the mat to a temperature above the melting point of the thermoadhesive resin,
A thermoadhesive resin is laminated on the surface of this mat-like material and pressed with a roll or the like.

■Layer a thermoadhesive resin film on a mat-like material, heat it with an infrared heater or hot air, and then press it with a roll or the like.

A thermoformable composite material is constructed by adhering a thermoadhesive resin layer to the surface of the mat-like material as shown in 2, and the composite material can be easily shaped by heating and pressing. Further, the thermoformable composite material may be shaped with a foamed sheet, a cosmetic skin material, etc. laminated and adhered to the surface thereof.

The thermoformable composite material can be shaped, for example, by the following method.

The composite material is heated using an infrared heater, oven, etc. so that the surface temperature reaches a temperature equal to or higher than the melting point of the thermoadhesive resin. Next, a skin material is laminated on the heat-adhesive resin layer. Thereafter, this laminate is molded into a predetermined shape using a press. The press pressure at that time is preferably 0.1 to 2 kg/c+fi, and the press temperature is preferably room temperature to 80°C. In this way, when the composite material is heated, the resin layer melts, and the molten resin aggregates around the inorganic fibers due to surface tension, resulting in the formation of many openings on the surface of the mat-like material. It is.

To give a specific example, on the surface of the mat-like material,
A colored nylon film with a melting point of 120°C was thermally bonded to create a thermoformable composite material, and this composite material was
After heating to 0°C, 1180°C, 1200°C and 1220"C, the surface condition of the thermoadhesive resin film after it was melted by the heat was observed under a 50x microscope. As a result, it was found that the surface state of the inorganic fibers existed on the surface of the inorganic fibers before heating. It was observed that the heat-adhesive resin melted and agglomerated along the inorganic fibers of the mat, forming a large number of openings.In addition, observation of microscopic photographs showed that the opening ratio was statistically is heating temperature 160
It was confirmed that it was 1% at 180°C, 2.5% at 180°C, 5% at 200°C, and 15% at 220°C.

Then, through the openings, the voids inside the mat-like material communicate with the outside, and therefore, the sound waves that hit the surface of the thermoformable composite material reach the voids inside through the openings in the surface layer, and It will be effectively attenuated by the air gap.

Note that the resin layer of the thermoformable composite material is forcibly coated with
For example, a large number of small holes may be formed using a needle or the like. In this way, when the thermoformable composite material is heated, openings are more likely to be formed around the small holes due to the above phenomenon, and the opening ratio can be increased. In this case, the diameter of the small pores formed in the resin layer is 0.1 to 3+ nm, and the aperture ratio is 0.
．． 5 to 15% is preferred. Further, since the aperture ratio of the resin layer increases slightly by heating the composite material, it is preferable to adjust the aperture ratio of the resin layer in the final product to be 1 to 20%. The aperture ratio of this resin layer is 1%
If it is less than 1, the effect of increasing the sound absorption coefficient of the product is small, and the sound absorption coefficient particularly in the high frequency range decreases. In addition, when the aperture ratio of the resin layer exceeds 20%, the sound absorption coefficient in the high frequency region can be increased, but especially in IKII
The sound absorption coefficient in the low frequency region near Z decreases. This seems to be because the pores (size, aperture ratio) on the surface of the mat-like material are controlled within an appropriate range by the resin layer.

Such a thermoformable composite material can be used as a base material for the interior of mobile devices such as automobiles, trains, and airplanes, interior materials for construction, and the like.

(Example) The present invention will be explained in detail below based on examples.

In this example, the porosity was determined as follows. First, the average specific gravity ρ of the resin and inorganic fibers used is determined.

The specific gravity of 1 g of resin is ρ1, and the specific gravity of 1 g of inorganic fiber is ρ2.
Then, ρ-(1+1)/(1/ρ1+1/ρ2)-2/(1/
ρ1+1/ρ2).

Next, the thickness of the specimen to be measured is tc+++, and the size is 1M.
If the weight per unit is wg, the porosity K = 1 w/ (10,000x t x2/ (
1/ρ+ + 1/0g)).

Therefore, for example, a 7 mm thick (0.7 cm) made of polyethylene (specific gravity 0.95) and glass fiber (specific gravity 2.5)
m), the porosity of the plate-shaped specimen with a weight of 800 g/bo is:
1-800/ (10,000X0.7X2/(11
0,95+ 1/2.5))=0.917 (91,
7%).

Further, the aperture ratio was measured as follows. Take a low magnification (40x) surface photo with an electron microscope, approximate the aperture to a circle, triangle, square, etc. to find the area, divide the total area of the aperture by the photographed area to find the aperture ratio, and take the photo. Shown as an average of 10 sheets (10 locations).

A chopped strand of glass fiber with a length of 50 mm and a diameter of 10 μm and a 6 denier, 50 mm cut polyethylene fiber were mixed in a weight ratio of 2:1 and fed to a card machine. , defibrated and mixed to obtain a flocculent material. Next, this cotton-like material was needle punched to obtain a mat having a basis weight of 500 g/m2. The needle punch density was 20 locations/CTl1.

Next, a 100 μm thick high-density polyethylene film is laminated on both sides of this mat, and a 100 μm thick glass fiber reinforced polytetrafluoroethylene sheet is further laminated on the outside of this polyethylene film, and this laminate is fed to a dryer. The material was heated at 200°C for 3 minutes, and compressed by passing it through rolls heated to 200°C at a speed of 10 cm and 7 seconds with a clearance of 1.3 mm. Next, while maintaining the temperature at 200″C, a glass fiber reinforced polytetrafluoroethylene sheet was placed 0.5 m from both sides.
Vacuum suction at a speed of 7 seconds to expand the gap between the sheets to 9 mm, then air cooling for 3 minutes, and then peel the sheets to a thickness of 9 mm.
A matte material of mm in size was obtained.

Next, a resin layer was provided by thermally adhering a nylon film having a thickness of 70 μm and a melting point of 120° C. to one side of the resulting mat to obtain a thermoformable composite material. This composite material was then heated in an oven at 200°C for 2 minutes to
A polyester fiber knit with a thickness of 1 mm was layered on the surface, and this material was fed into a mold with a depth of 10 mm, a distance between the molds of 5 mm, and a radius of curvature of the concave portion of 5 mm (the mold temperature was 25°C). A molded product was obtained by press molding for 2 minutes at a pressure of 3 kg/c+fl. The press temperature was 50°C.
The clearance was 6 mm.

The porosity of the obtained molded article was 93.8%. In addition, the sound absorption coefficient of the obtained molded product was measured using the normal incidence method (JIS A140
5. Measured at a back-to-back distance of 10 mm). The results are shown in Table 1.

In Example 1, a large number of holes with a diameter of 0.5 mm were formed in the resin layer by pressing a hole forming member provided with a large number of needles on the resin layer on the surface of the obtained composite material. A molded product was obtained in the same manner as in Example 1, except that the aperture ratio was set to 5%, and then a polyester fiber knit was layered after heating to 160°C.

The porosity of the obtained molded article was 93.8%. Further, the sound absorption coefficient of the obtained molded article was measured in the same manner as in Example 1. The results are shown in Table 1.

After heating the surface of the matte obtained in Example 1 to 200°C, a hot melt film and a polyester fiber knit were layered one after another, and then pressed in the same manner as in Example 1. A molded product was obtained.

The porosity of the obtained molded article was 90%. Further, the sound absorption coefficient of the obtained molded article was measured in the same manner as in Example 1. The results are shown in Table 1.

(Margins below) From the results in Table 1, it can be seen that by providing a heat-adhesive resin layer on one side of the mat-like material in advance as in this example, it is possible to reduce the sound in the low to high frequency range. It was also confirmed that the material had a high sound absorption coefficient.

This is because openings are formed in the resin layer when the composite material is heated, and the voids inside the material are communicated with the outside through these openings, allowing the voids inside the material to be used appropriately for sound absorption. Seem. Note that when the resin layer of the molded product of the comparative example was observed, no holes were formed in the resin layer.

(Effects of the Invention) As described above, the thermoformable composite material of the present invention has a large number of inorganic fibers bonded with a thermoplastic resin, and has a porosity of 50 to 50.
99%, it is lightweight and has high mechanical strength.
It also has excellent heat formability. Moreover, since a large number of openings are formed in the resin layer during heating, the internal voids can be used appropriately for sound absorption, and the sound absorption coefficient can be particularly increased in the low frequency region near IKIIZ. For example, it can be suitably used as a base material for automobile ceiling materials, architectural interior materials, etc.

that's all

Claims (1)

[Claims] 1. A thermoadhesive resin layer having substantially no through holes is adhered to one side of a mat-like material having a porosity of 50 to 99%, which is made up of inorganic fibers mutually bonded with a thermoplastic resin. A thermoformable composite material characterized by: