Method of washing a textile product

The present invention relates to a method of washing a textile product, such as a woven fabric, which is to be carried out subsequent to another treatment such as dyeing.

As an apparatus for carrying out a treatment such as dyeing for a textile product, for example, a liquid current treatment apparatus as illustrated in FIG. 4 is generally used. This apparatus has a retention part 2 for a textile product 1 such as a woven fabric, and an annular treatment tank 4 connected between the retention part 2 and a transfer passage 3 for the textile product 1. The retention part 2 has a bottom portion provided with treating liquid suction portions 5 (three in this Figure), through which a treating liquid is sucked. The sucked treating liquid is controlled to a given temperature (generally, a maximum temperature for it is set at a high temperature of 100° C. or higher) and returned to a treating liquid injection part 8 mounted at an end of the transfer passage 3 via a circulating pump 6 and an indirect heat exchanger 7, so that the textile product 1 is treated with a liquid current thereof, while being transferred.

In this liquid current treatment, the treating liquid has various dyes, other chemical agents or auxiliary agents remaining therein at the time when the treatment has been finished. In addition, it contains as products resulting from fiber polymerization, oligomer, shag and scale generated from the textile product 1.

Therefore, when carrying out, for example, polyester deep dyeing, a cooling water is introduced into the indirect heat exchanger 7 subsequent to the finish of the treatment, thereby lowering the temperature of the treating liquid, while circulating the treating liquid; and then once the treating liquid has been lowered to around 80° C., it is kept at this temperature, while hydrosulfite or an alkaline chemical (caustic soda, soda ash or the like) is injected into the treatment tank 4, thereby carrying out a reduction treatment for the aforesaid remaining products. Thus, a so-called reduction washing is carried out. Subsequent to this reduction washing, the treating liquid is again cooled to around 60° C. and discharged. Then, supplying a washing water (generally, water), water washing and discharging water are repeated several times, thereby washing the fabric product 1, and then the fabric product is taken out from the treatment tank 4. An example of a series of the aforesaid dyeing and washing steps is illustrated in FIG. 5.

However, as can be seen from an operation schedule of FIG. 5, the above washing method may pose problems of necessitating a long time washing, not realizing a smooth temperature gradient in cooling, causing wrinkles in the textile product 1, and thus likely deteriorating the quality of the fiber product 1. Also, since oligomer and the like, which have been dissolved at high temperature, are again precipitated, left in the treatment tank 4 and adhered thereto, a so-called tank washing is to be frequently carried out, which is very troublesome and thus poses a problem.

In order to deal with the above problems, the present applicant already proposed and put into practical use an all-new washing method that carries out a treatment by spraying a gas-liquid mixed fluid of a treating liquid and air current onto a textile product while moving and circulating the textile product within the treatment tank, which method involves discharging the treatment liquid at high temperature, and then supplying a washing water while heat exchanging with the discharged treating liquid (cf. Patent Document 1).

Patent Document 1: Japanese Patent Application Laid-open No. Hei-8-269863)

Accordingly, it is conceivable to apply the washing method in the above air current treatment apparatus to the liquid current treatment apparatus. However, it has been found that since the amount of a treating liquid used in the air current treatment apparatus is different from that of the liquid current treatment apparatus, and the structures of the apparatuses are different from each other, it is difficult to apply the aforesaid washing method to the liquid current treatment apparatus without modification.

Consequently, the present applicant has developed a washing method for a textile product that is capable of carrying out effective washing treatment in a shorter time even in a treatment method of a liquid current type that treats a textile product by the circulation of a treating liquid, and already filed an application (Patent Application No. 2004-295212).

FIG. 6 illustrates an example of the apparatus of the above application. The basic structure of this apparatus is similar to that of FIG. 4, and therefore the description thereof will be omitted by allocating the same reference numbers to the same parts or portions. This apparatus has a treating liquid circulation passage 10 provided with the aforesaid circulation pump 6 and indirect heat exchanger 7, a treating liquid discharge conduit 11 for taking out a part of the circulating treating liquid and discharging the same to the outside that is connected on the intake side of the circulation pump 6 to the treating liquid circulation passage 10, and a washing water supply conduit 12 for supplying a washing water into the treating liquid circulation passage 10 that is connected on the downstream side of the connection portion thereof via a check valve 13 to the treating liquid circulation passage 10. Both the treating liquid discharge conduit 11 and the washing water supply conduit 12 extend through the heat exchanger 14 so that a high-temperature treating liquid and a room-temperature washing water are directly heat exchanged with each other. Both the treating liquid discharge conduit 11 and the washing water supply conduit 12 are respectively provided with shut-off valves 15, 16 and fluid meters 17, 18, so that the amount of the treating liquid to be discharged is controlled to be equal to the amount of the washing water to be supplied. Reference numerals 19 and 20 respectively represent a washing-water supply pump and a feed valve.

The washing method of the above application is to treat and wash a textile product 1 by the use of the aforesaid liquid current treatment apparatus, for example, in the following manner. Specifically, in the same manner as a conventional liquid current treatment apparatus, the textile product 1 such as a woven fabric is first loaded into the treatment tank 4, and the treatment is made in the same manner as a regular treatment with the shut-off valves 15, 16 kept closed. Then, upon the finish of the treatment, the water supply valve 20 is opened, the pump 19 is started, and the shut-off valves 15, 16 are opened so that a part of the treating liquid circulating within the treating liquid circulation passage 10 is taken out into the treating liquid discharge conduit 11, and at the same time the washing water is supplied into the treating liquid circulation passage 10. At this moment, they are passed through the heat exchanger 14 so that heat exchanging is made between the high-temperature treating liquid to be discharged and the room-temperature washing water. In addition, the flow control is made by using the fluid meters 17, 18 and the shut-off valves 15, 16 so that the amount of the treating liquid to be discharged and the amount of the washing water to be supplied are controlled to be constantly equal to each other. Whereby, it is possible to carry out the washing while keeping the amount of liquid circulating within the treatment tank 4 (the mixed liquid of the treating liquid and the washing water, in which the treating liquid is gradually replaced with the washing water) constant. This washing step is called as a “liquid replacement washing step”.

As illustrated in the operation schedule of FIG. 7, at the time when the liquid temperature has dropped to a medium temperature range (80° C. in this example) which is higher than a low temperature range in which the liquid can be discharged, the shut-off valve 15 is closed to stop the taking-out of the high-temperature treating liquid from the treating liquid discharge conduit 11, and then the washing water is directly supplied into the treatment tank 4 at a constant feed rate without heat exchanging with the high temperature discharge liquid so as to cool the circulating liquid (direct cooling and washing). The washing water is not necessarily supplied at a constant feed rate in this operation, and the amount of the liquid increased in the treatment tank 4 by the supply of the washing water is gradually discharged through a drain valve. Then, at the time when the temperature of the circulating liquid has reached a predetermined low temperature range (60° C. in this example), the supply of the washing water is stopped, the textile product 1 is taken out and thus a series of the treatments is finished.

According to the above washing method, in the liquid replacement washing step, the high-temperature treating liquid used in the treatment is discharged while keeping the temperature thereof high, and at the same time it is heat exchanged with the room-temperature washing water to be supplied into the treatment tank 4. Thus, the temperature of the washing water becomes much higher than in the conventional method, thereby producing an excellent washing effect. Since the treating liquid is discharged while keeping the temperature thereof high, oligomer, dyeing residue or the like are kept dissolved in the treating liquid when discharged, a reduction washing treatment required in conventional polyester deep dyeing or the like can be omitted. Thus, steam or chemical agents used for increasing the temperature in the reduction cleaning treatment is not required, which contributes to the cost reduction. Since the amount of the oligomer or dyeing residue adhered to the inner wall or the like of the treatment tank and remaining in the treatment tank is decreased, there is an advantage in that the workload in maintenance such as cleaning the treatment tank 4 on regular basis is reduced. In addition, since the amount of the high-temperature treating liquid to be discharged is controlled to be equal to the amount of the washing water to be supplied, the amount of liquid circulating in the treatment tank 4 can be kept constant even when the process transfers from the dyeing or the like treatment to the washing treatment, and thus the textile product 1 is prevented from being subjected to excessive stress and is provided with a good finish.

Meanwhile, in the above washing method, the timing for the transfer from the liquid replacement washing step to the next step (e.g., the aforesaid direct cooling and washing step) is usually determined based on the temperature control, and specifically the liquid temperature within the treatment tank 4 is measured with time by a temperature sensor and when the measured temperature reaches a predetermined temperature (80° C. in the above example), the instruction for actuation is transmitted to an electromagnetic valve or the like of the apparatus, thereby allowing the operation to proceed to the next step.

However, when the timing for the transfer from the liquid replacement washing step to the next step is determined based on the temperature control, the finish time of the liquid replacement washing step may become early or late depending on the liquid temperature, and thus it has been found that poor washing or wasteful consumption of water due to excessive washing is caused. For example, when the amount of the washing water to be supplied is set to enable the washing water to achieve satisfactory washing in 20 minutes in the above liquid replacement washing step, on the condition that the temperature of the washing water to be supplied into the treatment tank is a normal temperature (18-20° C.) and it takes 20 minutes for the liquid temperature within the treatment tank to reach 80° C., the temperature gradient caused by the liquid replacement becomes large when the water is cold in the winter, therefore the temperature of 80° C. is reached, for example, in 15 minutes, causing the operation to proceed to the next step. As a result, the amount of the washing water required for washing becomes insufficient and insufficient washing is encountered. On the contrary, when the water is warm in summer, the temperature gradient caused by the liquid replacement becomes small, and therefore the temperature of 80° C. is reached, for example, in 25 minutes, so that the washing water is excessively supplied and thus is likely to be wastefully consumed.

The present invention has been conceived in consideration of the above circumstances. It is an object of the present invention to provide an excellent method of washing a textile product in a treating method using a treating apparatus of the type, such as a liquid current treatment apparatus that treats a textile product by circulating the treating liquid, which washing method is capable of completely or substantially completely removing oligomer, dyeing residues or the like and is unlikely to cause insufficient washing or excessive washing.

In order to achieve the above object, there is provided a method of washing a textile product, which includes a high-temperature treating step of treating a textile product by loading the textile product in a treatment tank, and bringing a treating liquid circulating the inside and outside of the treatment tank into contact with the textile product while heating the treating liquid to a high temperature by an indirect heat exchanger disposed in a portion of a circulation passage of the treating liquid; and a liquid replacement washing step of gradually supplying a washing water into the treatment tank while gradually discharging the high-temperature treating liquid from the treatment tank, during which the high-temperature treating liquid to be discharged is directly heat exchanged with the washing water to be supplied, and lowering the liquid temperature within the treatment tank to a predetermined temperature while making the amount of the high-temperature treating liquid to be discharged equal to the amount of the washing water to be supplied, thereby keeping the amount of liquid within the treatment tank constant, in which an optimum value of the temperature gradient in the liquid replacement washing step is previously set, so that when the actual temperature gradient is larger than the optimum value, the treating liquid is heated by the indirect heat exchanger, and when the actual temperature gradient is smaller than the optimum value, the treating liquid is cooled by the indirect heat exchanger, thereby bringing the actual temperature gradient at or close to the optimum value.