JPH03182308A - Heating of fiber reinforced composite material - Google Patents

Abstract

PURPOSE:To rise temperature uniformly and quickly without generating any temperature gradient in a heating process effected prior to secondary molding by a method wherein a plurality of needle-shaped heaters of a heating device, which are projected at an equal interval substantially, are embedded in a composite material to be heated. CONSTITUTION:A plurality of needle-shaped heaters 1a,... is formed on a heating device 1 with an equal interval substantially like a frog in flower arrangement while penetrating holes 2a,... are formed on a lower surface member 2 in accordance with the size, position and number of pieces of the needle-shaped heaters 1a,.... An upper surface member 4 is formed with a size and a configuration capable of being slid while contacting with the inner surface of a tube member 3 and is provided with penetrating holes 3a,... in accordance with the arrangement of the needle-shaped heaters 1a,.... The needle-shaped heaters 1a,... are retreated downward and the upper surface member 4 is retreated upward while a preformed composite material A is charged into the opened tube member 3 from the upper side thereof. The upper surface member 4 is descended to press the upper surface of the composite material A and the needle-shaped heaters 1a,... are inserted from the lower surface side thereof. When heating sources, connected to respective members, are put ON to heat them, the composite material A is heated by the needle-shaped heaters 1a,... from upper, lower and inside surfaces of the tube whereby the temperature of the composite material A may be increased to a predetermined secondary process temperature in a short period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heating method for fiber-reinforced composite materials, and in particular, a method for heating fiber-reinforced composite materials uniformly and quickly throughout the entire fiber-reinforced composite material. It is related to the method used.

[Prior Art] Composite materials, in which reinforcing fibers are uniformly dispersed in synthetic resin, have excellent physical properties (especially tensile strength and impact strength), so they are used as FRP materials in various panel materials, It is widely used for exterior panel materials, body materials, container materials, etc. These composite materials are commercialized by being preformed into sheet or block shapes (including block and bulk shapes).

There are also those that use thermoplastic properties and those that use thermosetting resin, and the latter are often commercialized in a pre-cured state.

Conventionally, sheet-like preforms have been widely used because they are easy to heat uniformly and have excellent secondary processability, but on the other hand, sheet-like preforms have the following drawbacks.

■-Production costs are high because the synthetic resin must be melted first and then extruded onto a glass fiber mat, etc.; ■The synthetic resin is kneaded in a molten state with chip strands, etc. It is also possible to extrude the material into a sheet, but this method reduces the reinforcing effect because the reinforcing fibers break during the kneading process. Since they must be laminated on a mold and press-formed according to the target thickness, the molding cost is also high.As a result, the cost of pre-forming in bulk has been increasing in recent years.

[Problems to be Solved by the Invention] However, in the case of a material that has been preformed into a block (hereinafter sometimes referred to as a "bulk material"), it is difficult to uniformly heat the preform to the inside prior to secondary forming. That is, heating methods for the preform include heating with infrared heaters, electric heaters, hot air, etc., but in any case, heating is done from the outer periphery, so the preform is heated from the outer periphery to the center. A temperature gradient is formed towards the center, and when the center reaches the predetermined processing temperature, the outer periphery becomes overheated, and in the case of bulk materials made of thermoplastic resin, the outer periphery becomes too soft and fluid, and thermosetting resin In the case of a block material using the above, secondary hardening progresses on the outer peripheral side, and in either case, secondary workability is significantly impaired. Therefore, in order to avoid such problems, it is necessary to minimize the temperature gradient mentioned above by slowing down the rate of temperature rise by heating as much as possible, and it takes a long time to raise the temperature to the secondary processing temperature. As a result, this temperature raising process becomes the rate-determining step, and not only does the productivity of secondary processed products drop significantly, but in the case of bulk materials using thermosetting resins, secondary hardening progresses during this time, resulting in poor workability. do.

The present invention was made with attention to such problems, and its purpose is to uniformly and quickly raise the temperature without creating a temperature gradient during the heating process performed prior to secondary molding. The aim is to provide a heating method that allows for

[Means for Solving Problem 11] The heating method according to the present invention that can solve the above problems is a heating method for a composite material in which reinforcing fibers are uniformly dispersed in a synthetic resin, The gist of this heating device is that a plurality of needle heaters of a heating device are protruded at approximately equal intervals, and the needle heaters are embedded in the composite material and heated.

[Function] In the present invention, as a means for heating a composite material in which reinforcing fibers are uniformly dispersed in a synthetic resin, for example, FIG. Diagram II-■
Use a device like the one shown in the diagram (corresponding to a line cross-section). That is, in these figures, 1 indicates a plurality of needle heaters 1a, Ia,...
2 indicates a lower surface member, 3 indicates a cylindrical member, and 4 indicates an upper surface member, and the heating device 1 includes a plurality of needle heaters 1a, la, . . . arranged at approximately equal intervals. The lower surface member 2 is provided with a needle heater 1a.

Through holes 2a, 2a, . . . are formed corresponding to the dimensions, positions, and numbers of the upper surface member 4
is formed in a size and shape that allows it to slide in contact with the inner surface of the cylindrical member 3, and is a through hole through which the needle heaters 1a, la, . . . formed in the heating member 1 are inserted. 3a, 3a, . . . are formed, and all of these are configured so that they can independently move forward and backward in the upward and downward directions of the drawing, as shown by the arrows in the drawing. And lower surface member 2
, the cylindrical member 3 and the upper surface member 4 are provided with heating means (not shown) such as a plate heater. The object of the present invention can be sufficiently achieved even if the heating means is only provided in the needle heaters 1a, la, . . . .

When heating a block preform using this device, the needle heater 1 of the heating device 1 must be
a, la,... are retracted downward and the upper surface member 4
is retracted upward, and the preformed composite material A is charged from above into the opened cylindrical member 3 (Fig. 3).
As shown in FIG.
If you use a composite material A that has been preformed by mixing synthetic resin powder and reinforcing fibers as described later, the compaction density itself will be small and will be compressed. Since there is some room left, the needle heater 1
Insertion of a, la, . . . is easily accomplished without creating much resistance. However, when using composite material A preformed under high pressure, needle heaters 1a, 1
Since the internal volume decreases by the insertion of the needle heaters 1a, 1a, .
On the other hand, if the compaction density of composite material A is originally small and there is still room for compression even when the needle heaters 1a, la,... are fully inserted, It is desirable to lower the upper surface member 4 and compress it to a desired density to enhance the heat transfer effect during heating. In addition, the composite material A is compressed during the insertion process of the needle heaters 1a, la, .
Since leakage may occur from the holes, a plug body 5a corresponding to the through holes 4a, 4a, . . . is provided on the back side of the upper surface member 4 as shown in FIG.

It is extremely effective to provide a leakage prevention member 5 having projecting portions 5a, . . . .

After the needle heaters 1a, Ia, .

la, . . . , since the upper and lower surfaces and the inner surface of the cylindrical portion are heated simultaneously, the temperature can be quickly raised to the predetermined secondary processing temperature in a short period of time without creating a temperature gradient.

After the temperature has been raised to a predetermined temperature, the heating source is turned off, the needle heaters 1a, la, ... are lowered, and the cylindrical member 3 is retracted upward while the composite material A is held down by the upper surface member 4. Then, after retracting the upper surface member 4 upward, the composite material A remaining on the lower surface member 4 is transferred to a bushar (not shown).
etc., to move it toward the secondary processing device.

A series of steps from charging the composite material A to heating and unloading can be carried out continuously by employing a turntable mechanism as shown in FIG. 6, for example. That is, in FIG. 6, I is the charging part of composite material A, and II is
indicates the needle-like heater insertion part, II+ indicates the needle-like heater extraction part, and ■ indicates the heated softened material delivery part. After being charged into the heating device in the charging part I, the needle-shaped The composite material A into which the heater has been inserted is heated while being moved on the turntable 7 that rotates clockwise to the needle heater extraction section III, and after the needle heater is extracted at this position, it is carried out. In the figure, 8 indicates a drive source for rotating the turntable 7, and 9 indicates a guide roller.

The present invention is constructed, for example, as described above, but the point is that needle-shaped heaters protruding in the shape of a crest at approximately equal intervals are embedded in the composite material A so that the whole can be heated evenly and quickly. The size, number, etc. of the needle heaters may be selected appropriately taking into consideration the size of the composite material A to be heated, the target temperature increase rate, etc.
In the example shown in the figure, the case where the composite material A preformed into a short cylindrical shape was heated was explained, but in addition to this, for example, the third
In the state shown in the figure (however, the composite material A is not charged), a powdered composite material, which is a mixture of synthetic resin and reinforcing fibers, is charged into the cylindrical member 3. At this time, the needle heater 1a , Ia, . . . are the through holes 2a, 2a of the lower surface member 2.
, ... to prevent the composite material from leaking from the through holes 2a, 2a, ...)
Then, by heating in the same manner as above, it becomes possible to heat and preform the composite material at the same time.

As the heating means for the needle heaters 1a, la,..., electric heating, dielectric heating, induction heating, etc. can be adopted.
As the heating means for the cylindrical member 3, a coil-embedded resistance heating, a band heater, etc. are used, and as the heating means for the lower surface member 2 and the upper surface member 4, a coil-embedded resistance heating, a plate heater, etc. are used. Furthermore, although the illustrated example shows an example in which the needle heaters la, la, etc. are inserted from one direction for heating, it is of course possible to adopt a method in which the needle heaters are inserted from the top or bottom for heating. It is possible.

There are no restrictions on the types of synthetic resins or reinforcing fibers that are the raw materials for the composite material to which the present invention is applied, and as synthetic resins, thermoplastic resins and thermosetting resins can be used as appropriate depending on the application and required characteristics. The reinforcing fibers can be selected and used, and in addition to the most common glass fibers and carbon fibers, various metals, whiskers, etc. can be used. In addition, the composite material containing these synthetic resins and reinforcing fibers may be blended with fillers, antioxidants, stabilizers, colorants, plasticizers, antistatic agents, flame retardants, etc., as necessary. .

There are no restrictions on the preforming method used when preforming the composite material as described above, and conventionally known molding methods may be applied as is or suitably modified. The following methods are exemplified as examples.

■Synthetic resin powder and short reinforcing fibers are uniformly mixed in vapor phase (dry mixing) with other additives that may be added as necessary, and this is mixed into a molding space shaped like the one shown in Figure 1, for example. In this case, it is of course effective to use a suitable binder to improve moldability and shape retention. It is also possible to improve the shape retention by slightly heating the powder during the compaction process to partially melt the synthetic resin powder and fuse them together.

■A method of wet-mixing synthetic resin powder and short reinforcing fibers with water as a mixing medium along with other additives as necessary, forming the mixture into an arbitrary shape and drying it, or plunger extrusion. A method in which the product is extruded into a rod shape using a molding device, etc., cut into appropriate lengths, and then dried. In this case, an appropriate binder may also be added as necessary to improve moldability and shape retention. can.

■ A method in which a dry mixture as shown in (■) above is charged into a plunger type extrusion molding device, etc., and the synthetic resin powder is extruded in a partially molten state by heating appropriately at a discharge die.

■The shape of the preform is not limited at all, and in addition to the short cylindrical shape shown in the figure, it can be any shape such as a rectangular shape, a polygonal cylindrical shape, or an elliptical cylindrical shape. It may be determined depending on the shape of the heating device used.

[Example] Using a heating device as shown in Figs. 1 to 5, a homogeneous mixture consisting of 60% by weight of boribrovirene bagdar and 40% by weight of short glass fibers was heated into a short cylindrical shape (200 mm x 200 mm').
) A heating experiment was conducted on a preformed composite material. However, the needle heater is an electric type with 40 needle heaters with a diameter of 16 mm, the cylindrical member uses a band heater heating method from the outside, and the upper and lower surface members use a plate heater heating method, and the surface temperature of both is 260°C. It was controlled so that In addition, nitrogen gas was flowed into the heating device to prevent oxidative deterioration of the composite material.

As a result, it was confirmed that the temperature of the composite material was raised to 220°C in about 2 minutes, the temperature distribution was very small within ±2.5°C, and the heating was extremely uniform.

On the other hand, as a comparative method, the same method was used as above except that the heating with the needle heater was omitted, and heating was performed only from the outer surface side by the cylindrical member, lower surface member, and upper surface member, and the center of the composite material rose to 220 ° C. It took about 30 minutes to heat up, and at that time the temperature on the surface side rose to 260°C and the synthetic resin melted, making it difficult to remove it from the heating device. Furthermore, since there was a temperature gradient of approximately 40° C. between the surface side and the center, compression molding by the secondary processing equipment was also adversely affected.

[Effects of the Invention] The present invention is configured as described above, and by employing a method of embedding a needle heater in the composite material and heating it, the whole can be heated quickly and efficiently.
Subsequent secondary molding can be carried out efficiently and smoothly. Moreover, since no temperature gradient is generated during the heating process, there is no risk of the preform being locally overheated, and there is no risk of deterioration in shape retention due to partial melting, which tends to occur when thermoplastic resins are used. This method does not cause the problem of partial secondary curing reaction that tends to occur when thermosetting resins are used, and it is possible to produce secondary molded bodies of homogeneous and stable quality with good productivity.

[Brief explanation of drawings]

FIG. 1 is a schematic vertical cross-sectional explanatory diagram illustrating a heating device used in carrying out the present invention, and FIG. 2 is a diagram showing II in FIG. 1.
3 to 5 are operation explanatory diagrams illustrating a heating method using the device, and FIG. N6 is a schematic plan explanatory diagram illustrating a continuous heating device using a turntable. 1... Heating device 2... Bottom member 3...
Cylindrical member 1a - Needle heater 7 Turntable I Composite material charging section II Needle heater charging section III Needle heater extraction section ■ Composite material Unloading part -1゜4...Top member 2a, 4a...Through hole A...Composite material missing 0) Kinoe

Claims (1)

[Claims] A method for heating a composite material in which reinforcing fibers are uniformly dispersed in a synthetic resin, the heating device having a plurality of needle heaters protruding at approximately equal intervals, the needle heaters being embedded in the composite material. A method for heating a fiber-reinforced composite material, which comprises heating.