Treatment method for preserving cut flowers

Abstract: The present invention is a treatment method for preserving cut flowers, which has a dehydration process for removing the tissue water of cut flowers using a solvent, and a permeation process for letting polyethylene glycol permeate after dehydration, to substitute the solvent by polyethylene glycol, characterized in that the dehydration process is effected while the cut flowers are fixed in a container having a proper amount of a molecular sieve spread over its bottom and filled with a solvent having a specific gravity smaller than that of water, wherein the specific gravity of the solvent is measured to monitor the change of the solvent in dehydratability, and the time when the specific gravity suddenly rises is detected as the time for exchanging the molecular sieve for a new one, to restore the dehydratability of the solvent, thereby allowing the solvent to be used continuously and allowing the dehydration process to be continued without waste of time. Furthermore, if a washing process for washing the cut flowers containing polyethylene glycol as a substitute of the tissue water by a solvent not containing polyethylene glycol is added, the stickiness of the cut flowers otherwise caused after a drying process can be prevented.

Description: FIELD OF THE INVENTION The present invention relates to a treatment method for preserving cut flowers. BACKGROUND OF THE INVENTION Treatment methods for preserving cut flowers such as roses, to keep them appearing like natural flowers for a long period time for decoration are proposed, for example, in PCT international Publication No. WO91/03160 and US Pat. No. 4,828,890, etc. In the treatment methods disclosed in these documents, the water in the cellular structures of cut flowers, i.e., the tissue water is removed and substituted by permeating polyethylene glycol, with dyeing as required, and as shown in Fig. 2, cut flowers are treated generally through a dehydration process, permeation process and drying process in this order, to obtain cut flowers as products appearing like natural flowers. The dehydration process is effected while the cut flowers are fixed in a container having a proper amount of a molecular sieve spread over its bottom and filled with a solvent having a specific gravity smaller than that of water, for example, an anhydrous organic solvent such as acetone. In the dehydration process, the water in the tissue of cut flowers, i.e., tissue water is gradually dissolved into the solvent while the solvent migrates into the tissue. So, in the tissue of cut flowers, tissue water is removed and substituted by the solvent, while the mechanical structure of the tissue is maintained. Then, the permeation process is effected while the cut flowers are fixed in a container filled with a permeating solution obtained by dissolving substitutive polyethylene glycol into acetone and a cellosolve. In this case, the polyethylene glycol used is a mixture consisting of polyethylene glycol compounds different in molecular weight suitable for the kind of cut flowers to be treated. In this case, if the permeating solution contains a coloring matter such as a textile dye for acrylic fibers, the coloring matter permeates the tissue of cut flowers together with polyethylene glycol for dyeing them. That is, the permeation process and the dyeing process take place simultaneously. After lapse of a certain time in the permeation process, the permeating solution is discharged, and the cut flowers are taken out and dried in the subsequent drying process, to obtain cut flowers as products. The prior art has the following problems. A. Dehydration process The prior art has the following problem in the dehydration process. As described above, since the water dissolved into the solvent from the tissue of cut flowers in the dehydration process is larger in specific gravity than the solvent, the specific gravity of acetone tends to gradually rise due to the dissolved water. While the molecular sieve remains new, most of the dissolved water is adsorbed by the molecular sieve. So, the dehydration by the solvent continues without causing the specific gravity of the solvent affected by the dissolved water to rise greatly. However, if the total amount of dissolved water exceeds the water adsorbability of the molecular sieve with the progression of the dehydration process, the water remaining without being adsorbed raises the specific gravity of the solvent sharply, to quickly deprive the solvent of its adsorbability. Since the prior art does not monitor the change of dehydratability, the dehydration process may be continued to waste time even though the dehydratability of the solvent is lost. Thus, efficient dehydration is difficult. B. Drying process The prior art has the following problem since the cut flowers delivered from the permeation process are dried into products without being washed. Since the acetone and cellosolve in the permeating solution are volatile, they are diffused into air in the drying process, but polyethylene glycol as a high molecular material remains deposited on the outside surfaces of petals. The polyethylene glycol remaining deposited on the outside surfaces of petals like this absorbs water in air if the humidity is higher than a certain level, and becomes sticky to touch. So, the phenomenon remarkably lowers the commercial value of cut flowers. C. Dyeing process In the prior art, depending on the kinds of cut flowers, uneven dyeing can happen without allowing even dyeing, to remarkably lower the commercial value of cut flowers. The inventor intensively experimentally studied and found that the uneven dyeing is caused because the permeation of the permeating solution into the cellular structures of petals occurs differently from portion to portion in the petals. In the prior art, the water in the cellular structures is substituted by an anhydrous organic solvent such as acetone in the dehydration process, and the solvent is substituted by the permeating solution containing polyethylene glycol in the permeation process. In this case, the substitution rate is different from cellular structure to cellular structure. Therefore, after lapse of a certain time in the permeation process, the solvent is fully substituted by the permeating solution in the cellular structures higher in substitution rate, to dye the cellular structures by the coloring matter contained in the solvent, but in the cellular structures lower in substitution rate, the solvent is less substituted by the permeating solution, to keep the color remaining diluted. D. Permeating solution, etc. In the prior art, when the cut flowers to be treated include plural colors and are intended to be treated simultaneously, permeating solutions as many as the number of colors are necessary since each permeating solution contains one coloring matter for each color of flowers, and they occupy a vast space. Furthermore, if the permeating solution for any disused color is dumped, such problems as waste treatment and resource wastage arise because of the organic solvent contained, and if the permeating solution is stored as contained in a container, it needs an extra storage space. GB-A-2 287 637 discloses a method of making preserved plant material having the colour and texture of fresh plant material and substantially free from curling or distortion, which method comprises the step of immersing the plant material in an aqueous solution comprising from 40 % to 95 % by volume of one or more C 3 -C 6 dihydric alcohols at a temperature of from 60 to 95 °C. The dihydric alcohols preferably comprise a major fraction of propylene glycol. The immersion is preferably carried out for from 5 to 90 minutes at a temperature of from 65 to 85 °C. The aqueous solution may also contain dehydrating alcohols and/or polyethylene glycol. The aqueous solution of the dihydric alcohols exchanges for aqueous sap and juices in the plant material, e.g. cut green foliage or cut flowers, without changing the colour or texture of the material. The plant material may also be preserved by dipping in an aqueous solution or suspension of a polymer and drying to leave a layer of polymer on the surface of the plant material. SUMMARY OF THE INVENTION An object of the present invention is to solve the problem described in the above A, and the object can be achieved by a treatment method for preserving cut flowers, which has a dehydration process for removing the tissue water of cut flowers using a solvent, and a permeation process for letting polyethylene glycol permeate after dehydration, to substitute the solvent by polyethylene glycol, characterized in that the dehydration process is effected while cut flowers are fixed in a container having a proper amount of a molecular sieve spread over its bottom and filled with a solvent having a specific gravity smaller than that of water, wherein the specific gravity of the solvent is measured to monitor the dehydratability with the progression of dehydration, for detecting the time for exchanging the molecular sieve. According to this method, the change in the dehydratability of the solvent can be monitored by measuring the specific gravity of the solvent, and the time when the specific gravity sharply rises is detected as the time for exchanging the molecular sieve for a new one, to restore the dehydratability of the solvent, thereby allowing the solvent to be continuously used and allowing the dehydration process to be continued without waste of time. The molecular sieve removed from the container for exchange can be dried for re-use. In the present invention, the cut flowers to be treated for preservation also include leaves and stems. Fig. 1 is a process flow chart as a first embodiment of the treatment method for preserving cut flowers of the present invention. Fig. 2 is a process flow chart of the treatment method for preserving cut flowers as the prior art. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention are described below in more detail in reference to the attached drawings. [EMBODIMENT 1] Fig. 1 is a process flow chart as embodiment 1 of the treatment method for preserving cut flowers of the present invention. The embodiment 1 has a dehydration process, permeation process, washing process and drying process, and in the dehydration process and the permeation process, a coloring matter for dyeing is added. That is, the dyeing process takes place concurrently with the dehydration process and the permeation process. a. Dehydration process At first in the dehydration process, as in the above prior art, a molecular sieve (zeolite) for adsorbing the water dissolved from petals was spread with a thickness of about 2 cm over the bottom of a dehydration container with a proper size, i.e., with a size suitable for the quantity of the cut flowers to be treated simultaneously, and the cut flowers were fixed in the dehydration container by proper supports. The container was filled with a solvent having a specific gravity smaller than that of water, for example, 100% acetone as a solvent for dehydration treatment. In this case, in the present invention, a coloring matter for desired dyeing was added to the dehydrating solvent. The added coloring matter and the concentration are described later, since they were the same as those used in the permeation process described later. In this state, the dehydration process was effected at room temperature (20 ∼ 30°C), and by treatment for at least 24 hours, dehydration could be achieved. Even if the dehydration process was effected for 48 hours, no special advantage was found. During the dehydration process, the specific gravity of the solvent was incessantly measured by a specific gravity meter, to be monitored. In an experiment, during the dehydration process, the specific gravity of the solvent, 100% acetone, gradually increased from 0.78, but after it exceeded 0.82, it rose sharply. At a specific gravity of 0.85, the effect of dehydration was little observed. From the above, it can be estimated that under the experimental conditions, the total quantity of dissolved water exceeded the water adsorbability of the molecular sieve about the time when the specific gravity of the solvent became 0.82. Therefore, if the molecular sieve is exchanged for a new one, the dehydratability of the solvent can be restored and the solvent can be used continuously. So, without waste of time, the dehydration process can proceed. The molecular sieve removed from the container for exchange can be dried for re-use. In the above dehydration process, the water in the cellular structures of cut flowers, i.e., tissue water was gradually dissolved out into acetone, while acetone migrated into the tissue together with the coloring matter dissolved in it. So, while the mechanical structure of the cut flowers was maintained, the tissue water was gradually substituted by acetone, to be removed. Since the acetone occupying the tissue of the cut flowers, to substitute the tissue water contained the coloring matter at a predetermined concentration, the cellular structures were dyed by the coloring matter. b. Permeation process Then, in the permeation process, a permeating solution obtained by dissolving substitutive polyethylene glycol into acetone and a cellosolve was supplied into a permeation container having cut flowers fixed in it. The permeating solution was prepared by mixing polyethylene glycol compounds different in molecular weight (e.g., PEG 1000 and PEG 400) at a proper ratio, for example, at the following ratio, dissolving the mixture into a mixed solvent consisting of acetone : a cellosolve = 1 : 1, etc., and adding the same coloring matter as used in the dehydration process to the solution at a predetermined concentration. Example of permeating solution PEG 1000 500 g PEG 400 100 ml A mixed solvent consisting of acetone : a cellosolve = 1 : 1 is added to make one liter as the total amount. The permeating solution in this composition ratio is solidified at 15°C or lower. So it was kept at a treatment temperature higher than the solidification temperature, for example, about 25 ∼ 35°C on a hot water bath or in an incubator, etc. for treatment for about 24 hours, to achieve the optimum permeation effect. Theoretically, permeation treatment at a higher temperature is expected to be completed in a shorter time, but in an actual experiment, polyethylene glycol could permeate more evenly by treatment at room temperature (20 ∼ 30°C) for 24 hours than by treatment at 50°C for 12 hours. Examples of coloring matters to be added in the dehydration process and the permeation process: Example 1 Coloring matter ... Methyl Red Color... Vermilion Concentration: 3 (g/l) Example 2 Coloring matter ... Tartrazine Color... Yellow Concentration... 1 (g/l) Example 3 Coloring matter ... Acid Green 25 Color ... Green Concentration ... 2 (g/l) Example 4 Coloring matter ... Acid Blue 80 Color ... Blue Concentration... 2 (g/l) The above coloring matters are solids (powders), and each concentration is based on the amount of the dehydrating solvent or the permeating solution. For dyeing cut flowers in primary colors, the above coloring matters are used respectively singly, but for dyeing in any intermediate color, these coloring matters can be mixed adequately. In the above permeation process, the acetone substituting the tissue water in the cellular structures is substituted by the permeating solution containing polyethylene glycol, and the permeating rate is different from cellular structure to cellular structure. That is, in the cellular structures higher in substitution rate, acetone is soon replaced by the permeating solution, but in the cellular structures lower in substitution rate, acetone remains in the cellular structures without being replaced by the permeating solution unless a sufficient time elapses. For this reason, in the prior art in which a coloring matter is added only to the permeating solution for dyeing only in the permeation process, unless a sufficient time is taken to allow acetone to be replaced by the permeating solution in all the cellular structures, the quantity of the coloring matter migrating into the cellular structures lower in substitution rate becomes smaller in inverse proportion to the amount of remaining acetone. So, the coloring matter concentration of the cellular structures remains low, keeping the color of the cellular structures remaining diluted, to cause uneven dyeing. In other words, the reason why uneven dyeing occurs in the prior art is that the permeation of the permeating solution into the cellular structures occurs differently from portion to portion, that is, the amount of permeating polyethylene glycol is different from petal portion to petal portion in the cut flowers. On the contrary, in the embodiment 1, since the coloring matter is added also for dehydrating acetone, the acetone substituting the tissue water in the cell structures also contains the coloring matter, and even if acetone remains in the cellular structures lower in substitution rate, the coloring matter concentration in the cell tissue remains unchanged, allowing uneven dyeing to be avoided. However, though the present invention in which the coloring matter is added in the dehydration process can avoid uneven dyeing, the substitution rate different from cellular structure to cellar structure cannot be raised. So, the treatment time in the permeation process must be decided considering undesirable effects such as the strain of cut flowers and partial excessive drying caused by different amounts of permeating polyethylene glycol, in relation with the productivity of cut flowers to be dyed. That is, in general, when unevenly dyed products are compared with evenly dyed products rather uneven in the permeating amount of polyethylene glycol, the unevenly dyed products are evaluated very low. Therefore if the effect due to some unevenness in the quantity of polyethylene glycol is practically negligible, the embodiment 1 has an advantage that the productivity does not decline since the uneven dyeing can be avoided without extending the treatment time in the permeation process. It is suitable that the coloring matter concentration in the dehydration process is equal to or rather lower than the coloring matter concentration in the permeation process. c. Washing process In the washing process, the cut flowers delivered from the permeation process were immersed for washing in a mixed solvent of acetone : a cellosolve = 1 : 1 for a predetermined time, say, 2 to 8 hours. In this case, if the cut flowers are immersed in the solvent for a period of time longer than necessary, the polyethylene glycol contained in the cellular structures of petals in the permeation process also comes out. So, time control is necessary. The immersion time can be set based on the data obtained by a preliminary experiment performed for the kind, size, etc. of the cut flowers. d. Drying process After the washing process, the cut flowers are dried in any adequate drying process as described in the above prior art, to obtain cut flower products which can remain appearing like natural flowers for a long time for decoration. [EMBODIMENT 2 ] In embodiment 2, the coloring matter used for dyeing in embodiment 1 is a coloring matter which develops different colors depending on whether it is exposed to natural light and ordinary artificial light or to ultraviolet rays, as shown in the following examples. Example 1 Coloring matter ...Yellow No. 4 food dye, tartrazine Colors Natural light and ordinary artificial light: Yellow Ultraviolet rays: Orange Concentration ... 1 (g/l) This coloring matter is a solid (powder), and the concentration is based on the amount of the dehydrating solvent or the permeating solution. Example 2 Coloring matter ... Red No. 104 food dye, Acid Red 92 Colors Natural light and ordinary artificial light: Red Ultraviolet rays: Greenish yellow Example 3 Coloring matter ... Red No. 106 food dye, Acid Red 52 Colors ... Natural light and ordinary artificial light: Bluish red Ultraviolet rays: Light yellow The above Examples 1 to 3 use food dyes, and in addition, other food dyes such as Acid Green 25 and Acid Blue 80 can also be used. Their concentrations can be set adequately. These coloring matters are respectively singly used for dyeing cut flowers in primary colors, but can be adequately mixed for dyeing in intermediate colors. The above coloring matters develop different colors depending on whether they are exposed to natural light and ordinary artificial light or to ultraviolet rays. These coloring matters can be selected from food dyes as described above. However, in the present invention, coloring matters obtained by adding a fluorescent material to coloring matters without having such a nature can also be used. For example, a coloring matter obtained by mixing a fluorescent material such as fluorescein or rhodamine used for fluorescent dyes, etc. to an ordinary coloring matter such as Methyl Red (color: vermilion) can also be used. The cut flowers produced according to the embodiment 2 can develop a color of petals different from that in the daytime, by irradiating them with ultraviolet rays such as a black light at night, and an outstanding decorative effect which cannot be achieved with natural flowers can be obtained. Industrial Applicability The present invention as described above can provide the following advantages by applying the above respective embodiments. a. In the dehydration process, it can be avoided that the dehydration process is kept proceeding even though the dehydratability of the solvent is lost. Therefore, the dehydration process can be kept proceeding efficiently without waste of time. b. The polyethylene glycol remaining deposited on the outside surfaces of petals after the permeation process can be washed away by a solvent, and since the stickiness otherwise caused after the drying process can be prevented by removing the extra polyethylene glycol remaining on the outside surfaces of petals, the commercial value of the products can be significantly raised. c. Uneven dyeing can be avoided without extending the treatment time in the permeation process, hence without lowering the productivity. d. Since the permeating solution, dehydrating solvent and washing solvent respectively containing a coloring matter for dyeing are decolored, to be re-used, it is not necessary to dump the permeating solution, dehydrating solvent or washing solvent of any disused color. So, such problems as waste treatment and resource wastage can be avoided, and the extra storage space for them is not required. e. The cut flowers treated to be preserved can develop a color different from that developed in the daytime, by exposing them to ultraviolet rays such as a black light at night, and an outstanding decorative effect which cannot be achieved with natural flowers can be achieved.

Claims: A treatment method for preserving cut flowers, which has a dehydration process for removing the tissue water of cut flowers using a solvent, and a permeation process for letting polyethylene glycol permeate after dehydration, to substitute the solvent by polyethylene glycol, characterized in that the dehydration process is effected while the cut flowers are fixed in a container having a proper quantity of a molecular sieve spread over its bottom and filled with a solvent having a specific gravity smaller than that of water, wherein the specific gravity of the solvent is measured to monitor the change of dehydratability with the progression of dehydration, for detecting the time for exchanging the molecular sieve. A treatment method for preserving cut flowers, according to claim 1, wherein the solvent in the dehydration process is acetone. A treatment method for preserving cut flowers, according to claim 1, wherein the solvent in the permeation process is a mixed solvent consisting of acetone and a cellosolve. A treatment method for preserving cut flowers, according to claim 1, wherein a coloring matter for dyeing is added to the permeating solution in the permeation process after dehydration. A treatment method for preserving cut flowers, according to claim 4, wherein the coloring matter develops different colors depending on whether it is exposed to natural light and ordinary artificial light or to ultraviolet rays. A treatment method for preserving cut flowers, according to claim 5, wherein the coloring matter has a nature of developing different colors depending on whether it is exposed to natural light and ordinary artificial light or to ultraviolet rays. A treatment method for preserving cut flowers, according to claim 6, wherein the coloring matter is selected from food dyes. A treatment method for preserving cut flowers, according to claim 5, wherein the coloring matter is a coloring matter obtained by mixing a fluorescent material.

Inventors: ANDO TOSHIO, KOKUBUN TAKASHI, SEKIYAMA TADASHI, ANDO, TOSHIO, KOKUBUN, TAKASHI, SEKIYAMA, TADASHI
Applicants: NIKKEN RENTACOM COMPANY LTD, NIKKEN RENTACOM COMPANY LIMITED
Application year: 1999
Main classification: A01N3
IPC codes: A01N3