JPH0671735B2 - Molded cotton strain relief dryer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a device for strain-relieving and drying molded cotton used for cushion bodies such as automobile seats, sofas, and beds.

[Conventional technology]

It has been known that molded cotton obtained by binding crimped polyester fibers with a urethane binder has extremely desirable properties as a cushion body. Since this type of molded cotton is molded while reacting the urethane binder with water vapor, for example, it contains about 5 to 10% of water after curing. For this reason, in order to remove water and to improve the sag resistance by removing the internal stress of the molded cotton, the molded cotton after steam curing is subjected to strain relief drying for a certain period of time.

A conventional drying oven used to perform such strain relief drying is, like the hot air drying oven 1 shown in FIG. 3,
While the formed cotton A is being conveyed by the conveyer 2 such as a conveyor provided in the production line, the formed cotton A is blown by the hot air supply device 3 over the length L _{0 of the} furnace.
The water was evaporated and the molded cotton A was kept at a certain temperature. After the strain removal and drying, the cotton was naturally left to cool.

[Problems to be solved by the invention]

As described above, the molded cotton A before drying contains about 5 to 10% of water, and the molded cotton A itself has a heat insulating property. Therefore, when the molded cotton A is put in the conventional hot air drying furnace 1, Shows the temperature rise characteristics as shown in FIG. For example, when placed in a furnace atmosphere temperature of 150 ° C, the surface of the molded cotton A rises relatively quickly as shown by the solid line in the figure, but inside the molded cotton A, the temperature rises as shown by the broken line. Is significantly delayed, and especially during the first five intervals, the water vaporizes and the temperature hardly rises. Therefore, in the drying method using hot air, a temperature difference of about 50 to 60 ° C. occurs between the surface and the inside of the molded cotton A during the heating process, and it takes about 30 minutes for the temperature of the central portion to become steady.

In such a conventional drying oven 1, in order to rapidly raise the temperature of the molded cotton A in a short time, the ambient temperature in the oven is increased or
Alternatively, there is no other way but to improve the heat transfer coefficient by increasing the speed of air blown onto the molded cotton A. However, the heat-resistant temperature of the polyester cotton that constitutes the molded cotton A is approximately 180 ° C, and the urethane binder is approximately 140 ° C.
There is a limit to raising the ambient temperature. On the other hand, even if the speed of the hot air is increased, the pressure loss is large inside the molded cotton A, and it is difficult for the hot air to enter the part, so the internal temperature does not rise so much as the surface temperature of the molded cotton A rises. Therefore, the faster the temperature rises on the surface side, the more the difference between the surface temperature and the internal temperature tends to increase. For this reason, it becomes difficult to perform strain relief drying by uniform heating.

For the above reasons, the conventional heating method using the hot air drying furnace 1 requires a very long drying time, for example, 120 ° C. for 2 hours or 150 ° C. for 30 minutes to perform the desired strain relief drying. It was a cause of a decrease in production efficiency. Not only that, the hot-air drying furnace 1 requires large-scale equipment to raise the ambient temperature, and the thermal efficiency is low, so running costs are high.

Therefore, an object of the present invention is to enable the strain relief drying of the molded cotton to be effectively performed in a short time, and further, to make the equipment compact and save energy as compared with the conventional hot air drying oven. .

[Means for solving problems]

In order to achieve the above object, the strain relief drying apparatus of the present invention provides a microwave heating device for radiating a microwave and a far infrared ray in a heating zone for heating molded cotton made of polyester cotton and urethane binder. A far infrared heater is provided.

[Work]

Molded cotton, which is the object to be heated, is composed of polyester, urethane prepolymer, and water, and is an appropriate load that is convenient for deep penetration of microwaves. As the temperature rises, the water content inside appears on the surface. On the other hand, since the far-infrared heater mainly heats the surface layer of the molded cotton, the moisture that has come out to the surface layer by microwave heating evaporates to the outside by the heating of the far infrared ray, and the heating by the far infrared ray heats the surface layer of the molded cotton. Therefore, the temperature of the surface layer portion, which tends to decrease due to heat radiation, is maintained in the same manner as inside.

Molded cotton is composed of polyester fiber, urethane binder, and water, and they all have a high absorption rate for far infrared rays having a wavelength of 6 to 10 μm. By using heating with far infrared rays and microwave heating together with molded cotton having such far-infrared absorption characteristics, water that has emerged from the inside of the molded cotton to the surface layer can be removed efficiently, and evenly throughout the molded cotton. By being able to raise the temperature by heating, generation of thermal stress and deformation due to the temperature difference do not occur, and effective strain relief drying can be performed in a short time.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

The drying furnace 10 shown in FIG. ₁ has a heating zone 12 having a length L ₁ and a soaking zone 13 having a length L ₂ along a conveying direction of a conveyor 11 as an example of conveying means. L ₃ cooling zone
Consisting of 14 and. Inside the heating device 15 that constitutes the heating zone 12, a microwave heating device 17 that radiates microwaves to the molded cotton A and a far infrared heater 1 that radiates far infrared rays.
8 and 19 are installed.

On the other hand, the soaking zone 13 is provided with a hot air supply means 21 including a heat source and an air blower, so that the dry hot air can be fed to the molded cotton A
Can be sprayed on. Further, the cooling zone 14 is provided with air cooling means 22 equipped with a blower for blowing cooling air to the molded cotton A. The temperature of the air sent from the air cooling means 22 may be equal to room temperature.

Molded cotton A is obtained by adhering a urethane prepolymer, which is a raw material of a urethane binder, onto a crimped polyester cotton and curing it with water vapor to a desired thickness. The fibers are coated and the fibers are bound together by a urethane binder. This molded cotton A
Exhibits suitable air permeability, impact resilience and sag resistance, and has a small specific gravity, and is therefore suitable for a cushion body used in various applications such as an automobile seat.

Molded cotton after steam curing contains about 5 to 10% water. When microwaves (frequency is, for example, 2450 MHz) generated by the microwave heating device 17 are radiated to the molded cotton, the molded cotton A rapidly rises in temperature from the inside thereof. The reason why the temperature can be rapidly raised by microwaves is that the constituent elements of the molded cotton A are polyester, urethane prepolymer and water, and the microwave has an appropriate load amount to be absorbed. Here, when the penetration depth of the microwave is represented by the depth D at which the incident energy is halved, the following equation is obtained.

In the above formula, f: frequency = 2450MHz, εr (specific inductive capacity): water ≈ 56.5, polyester ≈ 5 tan δ (dielectric constant power factor): water ≈ 0.05, (same as): polyester ≈ 0.005, then water D ≈ 0.103 (M), polyester D ≈ 3.50 (m)
Becomes Since the thickness of the molded cotton A is about 10 to 20 cm for general use, the inside can be sufficiently heated.

The degree of temperature rise can be easily changed by changing the amount of heat input. Temperature rise ΔT by microwave
(° C / sec) is calculated by the following formula.

(A) When there is no water (B) When there is water Where P: Heat input (Watt) t: Heating time (sec) W ₁ : Weight of molded cotton (g) C ₁ : Specific heat of molded cotton (cal / g ° C) W ₂ : Evaporated water content (g / sec) C _2: the specific heat of the evaporation water (Cal / g ° C.) (2) and (3) as apparent from the equation, the same input energy is better in the absence of moisture than the moisture in the molding cotton a is present If the amount is high, the temperature is raised quickly. Further, since the temperature rise is proportional to the energy input, the amount of energy input may be doubled if the temperature rise is desired to be doubled, for example. Therefore, compared to the conventional heating method using a hot-air drying oven, the temperature rise can be adjusted very easily, and the tact time can be improved easily. Moreover, since heating by microwave is direct heating without raising the ambient temperature in the furnace,
The thermal efficiency is remarkably better than other heating methods.

As mentioned above, heating using microwaves is
Although there is an advantage that the internal temperature can be raised within a few seconds to a few minutes, since the ambient temperature does not rise, the temperature of the surface of the molded cotton A will drop due to heat radiation to the outside only by heating with microwaves. That is, as indicated by the alternate long and short dash line in FIG. 2, a large temperature difference occurs between the surface temperature and the internal temperature (indicated by the broken line). In this way, if there is a temperature difference during the drying of the molded cotton A, deformation due to thermal stress occurs, and the purpose of strain relief drying cannot be fulfilled.

Therefore, in the heating device 15, the far infrared heaters 18,1
9 is used together. In order to heat the molded cotton A most effectively with far infrared rays, it is necessary that the material forming the molded cotton A be heated at a wavelength that absorbs far infrared rays most. As described above, the molded cotton A is composed of polyester, urethane binder and water, and all of these substances have the lowest transmittance between 6 and 10 μm. That is, the wavelengths at which each material has the highest absorptivity in common are 6 to
Since it is 10 μm, far-infrared heaters 18 and 19 in the present heating device 15 are those having a high emissivity of 6 μm or more.

The temperature T (° K) at which the energy emitted from the far-infrared heaters 18 and 19 becomes maximum can be calculated by the following equation from the Wien displacement law.

T = (2897.8 / [lambda] max-273) [deg.] K ... (4) Here, the heater temperature T for obtaining the wavelength [lambda] max> 6 [mu] m with the best absorptance, T <210 [deg.] C. from the formula (4). That is, by setting the surface temperature of the far infrared heaters 18 and 19 so as not to exceed 210 ° C and adjusting the distance between the molded cotton A and the heaters 18 and 19, the surface temperature of the molded cotton A becomes the specified temperature. Heat to.

As described above, since the surface layer of the molded cotton A can be rapidly heated by the far infrared rays, the moisture that has come out to the surface layer of the molded cotton A is rapidly evaporated by the microwave heating, and the surface layer of the molded cotton A is quickly evaporated. The temperature of is kept equal to the internal temperature. Heat transfer amount Q (kcal /
Since h) has a large value as shown by the following equation, it is optimal for evaporating water and rapidly raising the temperature of the surface.

ε: Emissivity about 0.95 T ₁ : Heater surface temperature (° C) A: Heat transfer surface area (m ² ) T ₂ : Surface temperature of molded cotton (° C) When the molded cotton A is heated by using infrared rays together, the temperature of the molded cotton A is short (L ₁
= 2-3 minutes), the ambient temperature is reached, and there is almost no difference between the internal temperature (broken line) and the surface temperature (solid line).

Thus, the molded cotton A heated to the predetermined temperature in the heating zone 12 is transferred to the soaking zone 13 and is strained by being kept at a constant temperature for a certain time by the hot air blown from the hot air supply means 21. Then, it is transferred to the cooling zone 14 and cooled. Since the molded cotton A thus cooled has a stable shape, it is not deformed even if the operator grips it strongly.

〔The invention's effect〕

As described above, according to the present invention, the moisture contained in the molded cotton after steam curing can be removed in a short time, and the inside and the surface layer of the molded cotton can be adjusted by adjusting the input heat amounts of the microwave and the far infrared ray. Since it can be heated and heated uniformly, effective strain relief drying can be performed. Further, unlike the conventional hot air drying oven, large-scale equipment for raising the atmospheric temperature is not required, and the equipment can be made compact and energy consumption can be reduced.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional side view schematically showing a drying oven according to an embodiment of the present invention, and FIG. 2 is a diagram showing temperature changes of molded cotton when the drying oven shown in FIG. 1 is used. FIG. 3 is a vertical cross-sectional side view schematically showing a conventional drying oven, and FIG. 4 is a diagram showing temperature changes of molded cotton when the conventional drying oven shown in FIG. 3 is used. A: Molded cotton, 10: Drying oven (distortion dryer), 11:
Conveyor (conveying means), 12 ... heating zone, 17 ... microwave heating device, 18, 19 ... far infrared heater.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location F26B 23/08 C 9140-3L

Claims (4)

[Claims] 1. A microwave heating device for radiating microwaves and a far infrared heater for radiating far infrared rays are provided in a heating zone for heating molded cotton made of polyester cotton and urethane binder. A strain relief dryer for molded cotton. 2. The strain relief drying apparatus for molded cotton according to claim 1, wherein far infrared rays having a wavelength of 6 to 10 μm are used. 3. The molding according to claim 1, wherein a soaking zone having a hot air supply means for keeping the temperature of the molded cotton constant is provided on the outlet side of the heating zone. Cotton strain relief drying device. 4. The strain of the molded cotton according to claim 3, wherein a cooling zone having an air cooling means for cooling the molded cotton is provided on the outlet side of the soaking zone. Drying device.