JPH0437634A - Method and device for drying wet chopped strand - Google Patents

Abstract

PURPOSE:To shorten the time for drying by irradiating the specific laminar chopped strands deposited on a conveyor with high-frequency electric energy or electromagnetic waves from above the strands and ejecting and conducting heating air from below. CONSTITUTION:A binder is applied by a coating device 12 on the many glass filaments 11 drawn out of a bushing 10, and thereafter, the filaments are cut to prescribed lengths by a cutter 15 consisting of a feed roller 17 and a cutter roller 19 to form the chopped strands 20. The chopped strands 20 of about 10 to 15wt.% moisture content are deposited on the ventilatable vibration conveyor 22 and are transferred by vibration at about 500 to 3000Hz oscillation frequency into a microwave cavity 25, where the moisture is evaporated by the heating air of about 120 to 180 deg.C from a heating ventilation chamber 29 and the internal heating by >=100MHz high-frequency from a microwave irradiation section 46. The dried and chopped strands 20 are sent into an electromagnetic shielding device 26 of the outlet part and are cooled by the cooling air from a cooling ventilation chamber 30 in the lower part of this device. The dried products are delivered by the conveyor 50 in about 1 to 3 minutes total drying time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method and apparatus for drying a wet chopped glass fiber N strand.

[Prior Art] Conventionally, wet chopped strands of glass Milli are dried by depositing them on a conveyor, passing them through a tunnel-type hot air dryer, and leaving them to dry, or by drying the wet chopped strands in a suitable can. A method was adopted in which the material was deposited on a drying surface, left undisturbed in a hot air drying chamber, and directly heated with hot air. These drying methods require a very long drying time of about 10 to 20 hours.

In order to shorten this time, the inventors of the present invention
In No. 9541, a method for drying wet chopped strands using a dynamic drying method was proposed. Said Special Public Service 1986-
In No. 9541, a large number of fine heated air streams are ejected and conducted from the F direction to the chopped strand layer under vibration,
We succeeded in significantly shortening the drying time to 15 to 30 minutes.

Furthermore, in Japanese Patent Application No. 1-8240, the present inventors irradiated high-frequency electric energy from the upper part of wet chopped strands deposited on a ventilation conveyor, and at the same time, a large number of fine heated air streams were ejected and conducted from below. A drying method was proposed. According to this drying method, it is possible to further shorten the drying time to about 1 to 4 minutes, which makes it possible to directly connect the spinning process and drying process, and also prevents the formation of lumps due to migration and post-heating. However, with the recent use of large bushings, new problems have arisen with the use of large bushings.

[Problems to be Solved by the Invention] Glass 1IIi chopped strands are widely used in glass fiber reinforced thermoplastic resin products, but these glass m miscellaneous reinforced thermoplastic products are generally combined with thermoplastic resin pellets. It is manufactured by pelletizing a mixture of chopped glass fiber strands using an extruder and molding the resulting pellets containing glass fibers using an injection molding machine or the like.

However, chopped strands, which are produced by applying a binder to a large number of filaments pulled out from a large bushing and converging them into one strand, are cut in a wet state and dried to produce a product, whereas each filament is made up of many filaments. Since it is solidified as an aggregate, a problem arises in that it is poorly dispersed in a molded product that is mixed with a thermoplastic resin, pelletized using an extruder, and then molded using an injection molding machine.

Normally, to solve this problem, methods are taken to reduce the number of monofilaments in the strand that enters the saw starter, that is, to feed them in parts, or to use a type of binder with weak adhesive strength, but the former method is difficult to work with. Moreover, the latter requires a large-sized cutting device, and the latter has the problem of generating yarn cracks, fuzz, etc., which impede processability and moldability in the process of mixing chopped strands and resin pellets.

In order to solve the above problems, the present invention converges and cuts a large number of filaments drawn from a large bushing into one strand without dividing them, and does not impair processability and moldability of the mixing process. The object of the present invention is to provide a method for producing chopped glass fiber strands that does not induce poor dispersion of chopped strands after injection molding even when a binder with low adhesiveness is used.

Another object of the present invention is to eliminate the need to increase the size of the apparatus and to obtain a compact facility in which the spinning process and the cutting/drying process are directly connected.

Furthermore, the present invention solves problems such as yarn breakage in conventional dynamic drying methods, reduced product quality and yield caused by mutual adhesion of chopped strands and binder migration in static drying methods, and long-term thermal history. The purpose of this invention is to solve the problem of deterioration of the physical properties of molded products and insufficient hardening of the binder due to the oxidation process, and to obtain chopped strand products of good quality.

[Means for Solving Problem 7a] In two aspects of the present invention to achieve the above object,
A large number of glass filaments spun from a large-capacity bushing are concentrated into one glass fiber strand without splitting, and the glass fiber strand is cut into chopped strands in a wet state and then layered on a ventilated conveyor. The layered chopped strands are deposited and transported continuously while applying a vibration effect, and high-frequency electric energy or electromagnetic waves are irradiated from the top of the layered chopped strands, and a heated air flow is ejected and conducted from below. A method of drying wet chopped glass fiber strands is provided.

In another aspect of the present invention, there is provided a cavity which is irradiated with high-frequency energy from above by the same pump, and an air vent which is integrally attached below the cavity and on which wet chopped strands are deposited in a layered manner. sex conveyor,
a vibration generator for vibrating the ventilation conveyor so as to horizontally vibrate the wet chopped strands deposited on the ventilation conveyor A7; Drying of wet chopped strands of glass 5iIs is provided, which is characterized in that it has a heated ventilation chamber above which heated air is passed.

The high-frequency electric energy source used in the present invention may be any source as long as it can efficiently generate dielectric heating in the substance, but microwaves with a frequency of 100 MHz or more have a high drying efficiency and a short wavelength. It is excellent in that uniform heating can be obtained because it is easy to cause diffused reflection, and it is easy to take measures against leakage radio waves and is preferable from a safety standpoint. The wavelengths currently available in our country are 245.
0 MHz, 915 MHz, but 2450 MHz is preferred for the present invention.

The aperture ratio of the through holes of the ventilation vibrating conveyor is approximately uniform over the entire area, approximately 1.5 to 10%, preferably approximately 2 to 3%, and the diameter thereof is 0.5 to 5 mm, preferably 1 to 2 mm. It is. To ensure proper transport and flow of chopped strands, ventilated vibratory conveyors typically
It is appropriate to vibrate at a frequency of 3000 H2, preferably 1000 to 2000 Hz, and a width of about 1.5 to 3 am, for example, and it is preferable that the trajectory of the movement is an ellipse.

It is necessary for the heated air to have a predetermined temperature as well as a predetermined velocity and ejection volume, and these conditions depend on the shape and length of the chopped strands, the properties and history of the binder, and the various conditions of the vibrating conveyor. Although it is not possible to specify comprehensively,
Generally the temperature is about 120-180°C, preferably 140-1
60℃ range, jet volume is approximately 10-40m for each small hole
Suitable amounts are such that an ejection velocity of about 20 to 30 m/sec is achieved.

Furthermore, in a preferred embodiment of the present invention, the ventilation vibrating conveyor immediately cools the chopped strands that have been heated and dried by passing a cooling air stream from below on the downstream side of the point where the heated air stream is blown out. is configured to do so. In this example, outside air at room temperature is used as the cooling air, and is blown out to each small hole of the conveyor at a speed of 10 to 25 m/s, but if necessary, it can be further cooled through an air cooling device. Air may also be used.

[Function] Conventionally, the form of chopped glass fiber strands that does not cause poor dispersion after injection molding is an aggregate of about 800 to 2000 monofilaments, depending on the viscosity of the resin during the kneading process. However, the number of monofilaments of chopped glass fiber strands formed using recent large bushings is increasing from 2000 to 4000 or more. Chopped strands made of a large number of monofilaments can be dried using conventional static drying or ventilation drying using hot air, dynamic ventilation drying,
Furthermore, if you use microwave drying alone, it will cost 800
It is not possible to obtain chopped strands divided into the appropriate number of ~2000 strands. In the present invention, wet chopped strands are placed under the action of vibration and conductive heating air, and are irradiated with high-frequency electrical energy such as microwaves to perform internal heating drying, thereby dividing the wet chopped strands into an appropriate number of strands that will not cause poor dispersion. It was discovered that chopped strands can be obtained.

According to the present invention, the chopped wet glass fiber strands having a moisture content of 10 to 15% are fed onto a vibrating ventilation conveyor, and are first subjected to the action of heated air ejected from below the conveyor to form glass fibers and chopped strands. After the temperature of the water starts to rise, it enters the microwave cavity, which is the drying area, and is irradiated with microwaves. Chopped strands irradiated with microwaves are exposed from the inside! The chopped strands are heated in a very short time, and the moisture adhering to the chopped strands is simultaneously heated and evaporated. Looking at this state for one chopped chopped strand, it is estimated that water evaporation starts from the inside of the chopped strand, and the saturated vapor pressure is high inside and low outside. Since the chopped strand dielectrically heated by microwaves is in such a state, it is assumed that when it receives an external force, that is, an excitation force from a vibrating conveyor, it will be divided into chopped strands consisting of an appropriate number of monofilaments. Presumed. In addition, since the drying speed is very fast, it is presumed that the divided chopped strands are solidified without being separated, and a suitable number of chopped strands of good quality can be obtained.

Furthermore, the reason why fiber separation is small is that the heated air ejected from below the conveyor provides a cushioning effect, and the chopped strands receive an appropriately weakened excitation force as a whole without coming into direct contact with the vibrating surface. It is also thought to be for the purpose of division. The heated air that is ejected and conducted immediately removes the steam generated when the chopped strands are dried, and the chopped strands themselves move up and down on the ventilation vibration conveyor, so the microwaves are evenly applied to the entire chopped strand. This results in improved drying efficiency and more uniform drying. In this way, the drawback of drying using only microwaves, namely, that after water evaporates, electromagnetic wave energy becomes difficult to absorb, the binder curing becomes insufficient can be overcome.

In addition, in external heating drying such as hot air, drying begins sequentially from the outer surface filament of the chopped strand, and it is necessary to lengthen the drying time, so if vibration is applied under such conditions, drying and solidification will occur. Separation begins from the outer surface filaments of the chopped strand, resulting in a chopped strand with many fibers, making it impossible to obtain a chopped strand product of good quality that is divided into the desired number of pieces.

[Embodiment] In FIG. 1, a large number of filaments 11 drawn out from a bushing 10 are coated with a binder by a coating Vt 12, and then directly guided to a cutting device 15. The cutting device includes a guide roller 16, a feed roller 17 whose surface is made of an elastic material such as rubber or synthetic resin that has a large coefficient of friction against the glass ia* and can rotate freely, and a large number of blades 18 that protrude radially from the surface. and a cutter roller 19 which is planted in pressure contact with a feed roller 17 and is actively driven by a motor. The strand 14 guided to the cutting 81115 passes through the guide roller 16 and is cut into a length determined by the blade spacing by the blade 18 biting into the feed loaf surface at the pressure contact point between the feed roller 17 and the cutter roller 19 to form the chopped strand 20. Form.

The chopped strands 20 thus formed have a moisture content which may vary depending on the amount of binder applied during spinning, but typically ranges from 10 to 15% in a hexagonal cutting method such as the present method. The chopped strands 20 cut by the cutting device 15 fall from the hopper 21 to the front part of the ventilation vibrating conveyor 22, and are supplied to the drying device 23 while being heated and heated.

The drying device 23 is divided into a ventilation conveyor 22, an entrance radio wave shielding device 124, a microwave cavity 25, and an exit radio wave shielding device 26, which have an integrated structure. The ventilation vibration conveyor 22 has a width of 400 rin,
It consists of a multi-hole transfer plate 27 with a length of 2,500 feet, with an exhaust air 28 on the top and a heating ventilation chamber 29 and a cooling ventilation chamber 30 on the bottom.
and has.

The entire drying device 23, including the ventilation conveyor and these chambers, is supported on a support 33 via a spring 32, and is vibrated by a vibration generator 31 attached to the outside of the heating ventilation chamber 29. Also, the porous transfer plate 27 constituting the ventilation conveyor has a cavity 2 which is irradiated with frequency electric energy.
5, on a substrate 34 made of a metallic material that reflects microwaves, such as stainless steel, as shown in FIG.
A plate 35 made of a material with a low dielectric constant such as Teflon and having a thickness of about 30ag+ is fixed by bolts or adhesive made of the same material, and the irradiated microwave is reflected by the substrate 34, and the plate 35 made of a material with a low dielectric constant is heated. It is designed so that it can be applied efficiently to the chopped strands. Further polymerized substrate 34 and plate 35
A large number of small holes 37 pass through it. It is preferable that the multi-hole transfer plate 27 has a flat surface with no steps from the inlet to the outlet, and is either horizontal or slightly inclined upward toward the outlet.

Heated air is supplied to the heating ventilation chamber 29 through a ventilation device. As shown in FIG. 2, the heated air blower and exhaust fan 38 is connected to the heating ventilation chamber 29 via a campus duct 39 that can absorb vibrations, and the exhaust fan 38 is connected to the exhaust chamber 28 via a campus duct 41 as well. An exhaust fan 40 that is connected to suck air whose temperature has dropped, a W collecting device 42 that is connected between the exhaust fan 40 and the blower fan 38, and a heating device 43 that heats the air whose temperature has dropped to a desired temperature. It has become. Furthermore, in the illustrated embodiment the ventilated conveyor 2
The second porous transfer plate 27 has a cooling ventilation chamber 3 integrated with the outlet radio wave shielding device 26 below the portion passing below it.
A cold air fan 49 is connected to the cooling ventilation chamber 30 via a campus duct 48 to supply outside air. The cooling air that has passed upward through the ventilation conveyor 22 from the cooling ventilation chamber 30 passes through a duct connected above the exit radio wave shielding device f26 (Fig. It is sucked into the exhaust fan 40. Furthermore, the exhaust gas sucked into the exhaust fan 40 is sent to the dust collector 42.
After entering and removing fluff, etc., it is reheated by the heating device 43 and then returned to the ventilation fan 38 to be heated in the heating ventilation chamber 29.
is recirculated to Although not shown, there is an air volume adjustment damper between the ventilation fan 38 and the campus duct 39, an exhaust volume adjustment damper between the dust collector 42 and the heating device 43, and between the cold air fan 49 and the campus duct 48. It has a feed f411 adjustment damper, and ducts for exhausting dry steam are installed at appropriate locations. Although the above-mentioned embodiment is configured to suck in and exhaust the heated air and the cooling air in one go, they may be configured to suck in and exhaust the air separately. Further, an air cooler M for cooling the outside air supplied to the cooling ventilation chamber 30 may be provided as necessary.

Two microwave irradiation units 46 are provided in the upper part of the microwave cavity 25, one on the entrance side and the other on the exit side.

The microwave irradiation unit 46 includes a microwave oscillator 45 that can be adjusted to 0.5 to 5 W, a waveguide 51 that guides the microwave oscillated by the microwave oscillator, and a waveguide 51 that is configured to reduce reflected radio waves of the microwave. Microwaves are generated by a matching device 52 that adjusts and supplies maximum radio wave output to the load side, and a flexible waveguide 44 connected to guide the microwaves matched by the matching device to the upper part of the vibrating cavity. be guided. Furthermore, a radio wave diffusion vane 47 is installed above the cavity and rotated at an appropriate speed so that the chopped strands are uniformly irradiated (the rotating device is not shown).

The chopped strands 20 deposited on the ventilation conveyor 22 and vibrationally transferred into the microwave cavity are internally and externally heated by the heated air from the heating ventilation chamber 29 and the 245 QHz microwave, and moisture evaporation progresses. , the splitting and hardening action begins. The dried chopped strands 20 are then sent to an exit power shield device 26 having a microwave absorber. In the exit radio wave shielding device 26, the chopped strands are cooled by cooling air ejected from the cooling ventilation chamber 30 below. The completely dried and cooled chopped strands are sent to the next process by a conveyor 50.

In the above embodiment, the microwave cavity 25 is configured integrally with the ventilation vibration conveyor and the vibration conveyance means, but the microwave cavity 25 has a structure that does not affect the microwave cavity even if the ventilation conveyor vibrates, and The microwave cavity may be separated from the vibration conveying means if it can be shielded from radio waves. At this time, since the microwave cavity does not vibrate, the flexible waveguide can be used as a fixed waveguide. Further, the alignment device is provided as necessary, and the present invention is not limited to this embodiment.

The results of actually applying the apparatus of the above embodiment are as follows.

A glass fiber strand consisting of a filament with a diameter of 13 microns spun from a bushing having a 3200-hole nozzle and coated with an epoxy binder was introduced into a cutting device to form chopped strands. Cut water percentage 1
The 2% chopped strands were placed on a ventilation vibrating conveyor, dried and cooled by heated vibrating ventilation and microwave drying equipment, and then taken out as a product. The moisture content of these products is 0.01%, and the constant moisture content of glass fiber is 0.
．． 0.3% or less, and was substantially completely dried. Furthermore, the number of monofilaments of each dried strand was about 1450 on average, and there was little fluff due to fiber splitting.

The ventilation vibratory conveyor had an aperture ratio of 2%, a swing width of 2 steel, a vibration frequency of 1450H2, a small hole penetration air velocity of 25TrL/sec, and the heated air 1111 at that time was set to 150°C.

The amount of chopped strands supplied in the drying process is approximately 9
At 0 kg/hour, the layer thickness of the ventilated vibratory conveyor was 5-6 shoes. Also, the microwave output is set to 4.5Kwx2,
The cooling air was air at room temperature, and the jetting speed was set at about 15 m/sec with respect to the small holes. The drying time according to this specification was about 2 minutes and the cooling time was 30 seconds.

As comparative examples, Table 1 shows the characteristic results for the case of microwave drying using a conveyor as disclosed in Japanese Patent Application No. 1-8240, the case of aeration vibration drying as described in Japanese Patent Publication No. 629541, and the case of fluidized bed drying.

Table 1 In Table 1, the number of cut monofilaments indicates the total number of filaments in the bushing, and the number of product monofilaments indicates the average number of monofilaments in each chopped strand after drying.

The number of monofilaments in each chopped strand after drying naturally has a wide distribution, but the numerical value is the average value. The adhesion rate indicates the adhesion rate of the binder to the chopped strands, and the degree of insolubilization indicates the adhesion rate of the binder to the chopped strands.
This is the ratio of insoluble binder when boiling for a period of time, and is a measure of the degree of hardening of the binder. The apparent density is calculated by uniformly charging 2009 chopped strands into a 1000 d measuring cylinder and expressing the volume in g/13. Experience has shown that chopped strands with a high apparent density have less fluff and fiber splitting. For drum-style cotton, 5 chopped strands are put into a 1351 ■-shaped container, sealed, and rotated at 30 rpm for 5 minutes to force defibration. After rotation, take out the sample inside the container 2.5
Sieve through a mesh standard sieve and measure the amount of fluff remaining at the top. The flow value was determined by placing chopped strands in a test 11i device, which had a length of 500 mm, medium 10 mm steel, and a depth of 50 m + trough, with a slit weir at 100 mm from the rear of the vibrating device with an interval of 10 is + from the bottom. The material is fed until it is completely rubbed, and the weight flowing down from the slit due to vibration is measured. The frequency of the vibration device is 3000H
7 and the swing width is 0.4 shoes. The drying efficiency is the value when the case of fluidized bed drying is set to 1.0, and is the product of the throughput ratio, time efficiency ratio, and energy efficiency ratio.

As can be seen from the results in Table 1, the number of monofilaments in the product is approximately 55% lower than the number of monofilaments during spinning, but the characteristics as chopped strands are the same as those obtained using the conventional method. or even more.

"Effects of the Invention" According to the drying method of the present invention, an appropriate chopped strand shape can be achieved using a large-capacity spinning furnace, which was difficult with conventional dynamic drying methods, fluidized bed drying, hot air drying, or microwave stationary drying. It is easy to obtain a strand, and the spinning workability is improved, and the chopped strand obtained without the use of a special binder has the advantage of being of good quality with less fuzz and fiber splitting. .

Furthermore, by using microwave drying and dynamic hot air drying in combination, the present invention can greatly shorten the drying time to about 1 to 3 minutes, and in addition, the amount of hot air can be reduced to dry the entire amount of moisture with hot air. The amount can be reduced compared to the conventional method. Therefore, in terms of process control, it is possible to greatly save labor by shortening the process, and since the spinning and cutting process and drying process can be directly connected, it is convenient for production control and quality control, and it also reduces the space occupied by equipment. Considering the overall effects such as effective utilization, considerable cost reductions can be expected as a whole.

Furthermore, the internal heating characteristics and shortened drying time achieved by microwave drying have the effect of suppressing the migration of chopped strands.

Further, Japanese Patent Application No. 1-8240 is similar to the present invention in that microwave drying and ventilation drying using a ventilation conveyor are used in combination, but differs from the present invention in that the ventilation conveyor does not vibrate. Therefore, when viewed in the width direction of the conveyor, the chopped strands fed onto the conveyor from above tend to be piled up high in the center of the width, and the piled strands tend to become smaller toward both ends. Drying is difficult, drying is uneven, and drying efficiency is still not sufficient. In contrast, in the present invention, since the ventilation conveyor vibrates, the chopped strands deposited on the conveyor vibrate while forming a layer of uniform thickness. Therefore, heated air can escape easily and drying efficiency is high. Furthermore, since the separated filaments tend to adhere to the chopped strands due to rolling action, there is less fluffing of the product, and there is also less chance of the separated monofilaments adhering to the conveyor and contaminating the conveyor.

[Brief explanation of drawings]

FIG. 1 is a side view schematically showing the process of spinning and cutting glass fiber strands and an embodiment of a chopped strand drying apparatus according to the present invention. FIG. 2 is a schematic diagram showing an air blower/exhaust system and a high frequency electric energy supply system used in the embodiment of FIG. 1. FIG. 3 is an enlarged cross-sectional view of the microwave cavity portion of FIG. 2, showing in particular the detailed structure of the chopped strand vibration transfer surface. DESCRIPTION OF SYMBOLS 10... Bushing, 11... Filament 12... Binder application II, 14... Strand, 15... Cutting device, 20... Chopped strand, 22... Ventilated vibration conveyor, 25... Microwave cavity, 27... Porous transfer plate, 28... Exhaust chamber, 29... Heating ventilation chamber, 30... Cooling ventilation chamber, 31... Vibration generator, 38...・Blower fan, 40...exhaust fan,
42... Dust collector, 43... Heating device, 45
...Microwave oscillator 46...Microwave irradiation section, 49...Cooling fan.

Claims (6)

[Claims] (1) A large number of glass filaments spun from a large-capacity bushing are gathered into one glass fiber strand without splitting, and the glass fiber strand is cut into chopped strands in a wet state and then placed on a ventilated conveyor. Glass that is deposited in a layered manner and transported continuously while applying a vibrating effect, and is irradiated with high-frequency electric energy or electromagnetic waves from the upper part of the layered chopped strands, and at the same time, a heated air flow is ejected and conducted from below. Method of drying fiber wet chopped strands. (2) A cooling air flow is ejected and conducted from below the chopped strand layer on the downstream side of the point where the heated air flow is ejected and conducted as viewed in the transport direction of the chopped strand layer. How to dry wet chopped strands. (3) a cavity that is irradiated with high-frequency energy from above toward the inside; a ventilated conveyor that is integrally attached below the cavity and on which wet chopped strands are deposited in layers; a vibration generating device for vibrating the ventilated conveyor so as to horizontally vibrate the deposited wet chopped strands; and a heating vent disposed below the ventilating conveyor for conducting heated air upwardly through the ventilating conveyor. A drying device for wet chopped glass fiber strands, characterized in that the drying device has a chamber. (4) A cooling ventilation chamber arranged below the ventilation conveyor and allowing cooling air to flow upward through the ventilation conveyor is provided on the downstream side of the heating ventilation chamber. Equipment for drying wet chopped strands. (5) The heated air and the cooled air ejected through the ventilation conveyor are collected together to remove dust, and then reheated to a desired temperature and recirculated as a heated air stream to the heated ventilation chamber. The wet chopped strand drying apparatus according to claim 4, characterized in that: (6) The ventilated conveyor has a metal substrate and a plate made of a material with low dielectric loss that is pasted on the substrate and has a thickness that prevents electromagnetic waves from penetrating to the substrate. (3) The wet chopped strand drying device described in (3).