CA2020360A1

CA2020360A1 - Preservation of flowers by lyophilization and vacuum deposition polymerization coating

Info

Publication number: CA2020360A1
Application number: CA 2020360
Authority: CA
Inventors: Alex P. Korn
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-07-04
Filing date: 1990-07-04
Publication date: 1992-01-05

Abstract

PRESERVATION OF FLOWERS BY LYOPHILIZATION AND VACUUM DEPOSITION
POLYMERIZATION COATING
ABSTRACT

This invention pertains to the preservation of flowers, and other botanicals for decorative purposes, to a degree that the preserved flower, or other botanical structure, maintains the appearance as if it was still freshly cut.
The method for preserving the material is two-phased. The first phase is the drying in vacuo, preferably while frozen (lyophilization); and the second phase is the coating of the external surface with a polymerizable monomer which adsorbs from the vapour state and polymerizes after deposition onto the flower's surface. The flower is effectively encased in the transparent hydrophobic coating and protected from the deleterious effects of ultraviolet light degradation of pigments, from moisture and from mechanical cracking and breaking of the otherwise brittle petals. The internal water, being removed, cannot now support the normal biochemical degradation of the cellular structures that occurs in non-living plants.

Description

202~360 DISCL~SURE

Preserved flowers are attractive and can be used to make tasteful arrangements by themselves or to decorate gift items.
Those who provide them to the public therefore enjoy a solid commercial market. The techni~ues of ~rying and preserving the flowers depend on the flower type. One method is to hang the flowers upside down for a number of days in a dry room;

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the flowers' internal moisture exits the petals and leaves by evaporation at room temperature via the stomata. Another technique is to bury the flowers in silica gel grains. The hygroscopic property of the silica gel creates extreme dryness in the immediate vicinity of the grains and thereby promotes . .
the removal of water from the buried flowers. The success or -- ~-failure of flower-drying depends on the amount ~f cellular ~.,.~. ,:. ~ .
water relative to the fibrosity of the plant tissue. A high fiber content provides good mechanical support to the drying petals. - ~ -. ~ , , ~ .
As the water evaporates the loss of turgor pressure results in wilting and drooping, A flower with high fiber content ~ -~
will ~ hstand the loss of turgor pressure better. Dryin~ also ~ -~
causes brittlenes, and in some cases causes the petals to drop off. In addition to the limiting of the current methods to certain flower species, another limitation is the loss of colour brilliance. The pigments apparently degrade during the drying and degrade further after drying because of ultra- ~ --violet light from unfiltered sunlight. The result is a dull and ~painted-on" appearance. Some dried flower producers spray hairsprày on the flower to stiffen and protect the petals, but this treatment, with its artificial sheen, makes them look like synthetic flowers.
This invention proposes the use of lyophilization and , vapour phase polymerization coating to preserve freshly-cut flowers. Lyophilization is a process well known in technologies .
such as vaccine production and electron microscopy. Its value is that fragile biological materials can be dried without damage due to surface tension collapse. This is because the water-containing sample is frozen, and thus immobilized . . .
before being placed into the vacuum. The water is removed by sublimation, and, therefore, in the absence of air~water interfaces that cause the surface tension damage. Additional~
caution may be taken by "flash freezing". Ice formation is known to cause microscopic damage to cellular structures.
If the flower is frozen rapidly, no time is given for complete ice crystal formation. Instead, the internal water is frozen in a glassy state Flash freezing can be carried out by -~
immersing the flower into cold (below 0C) liquid such as freon. The freon, or other appropriate liquid, can be cooled in a bath of liquid nitrogen. Liquid nitrogen itself may be used for rapid freezing provided that the flower can withstand the turbulence and bubbling upon its immersion.
After completely removing the water in vacuo, the coating can be carried out. The principle of coating is that a gas phase monomer is released into the chamber. As the monomer adsorbs onto the surface of the flower it polymerizes. This :: ~
method preserves the texture of the surface because the coating procedes~molecule by molecule following the microscopic hills ~20~ and~valleys of the petal or leaf surface. An example o~
polymerizable vapour phase monomer is parylene. The coating te~chnology has been develDped by Nova Tran Corporation~of Clear Lake, Wisconsin, U.S.A. for use, inter alia, in preserving ageing books which have been printed over 50 years ago on ac~id paper. The crumbling and cracking of the pages can be halted because of the flexible nature of the coating. It ~ ;-; is also hydrophobic thereby preventing the entry of water that might cause internal rot. ~ -, In brief, the coating is performed as follows. The monomer ~-is produced by heating the dimeric form in order to vapourize the powder. Next, it is passed into a high temperature pyro- ~-lysis tube to break the dimer into reactive monomers. The monomer passes next to the coating chamber containing the sample to be coated. The monomer condenses and polymerizes on the sample's surface. For more detailed information, see Canadian Chemical News, October 1989, pg. 25: `'Parylene at the Canadian Conservation Institute`t by David W. Grattan. ~ ;
With some kinds of flowers it may be possible to forego ~;~
the freezing and lyophilization process. The coating chamber can operate at relatively low vacuums. It, therefore, may be possible to place the freshly cut flowers into the chamber, and evacuate it at the same time as reactive monomer is being introduced. Thus, as the water evaporates and turgor pressure is lost, the lost mechanical strength is replaced by the depositing and polymerizing parylene. (Water can evaporate continuously because the delicateness of the coating will not block the stomata ~ ~
at the early stages of the coating. At the later stages of the ;
coating the stomata will become blocked, but the water will have been removed by then.) Vapour phase deposition polymerization preserves the texture of petals and leaves, which hairspray or other sprayable ~;~
polymers, oannot. The aromatic rings of the parylene molecule absorbs ultraviolet radiation, thereby protecting the pigments -from bleaching. The polymerized coating prevents the petals from ~20 becoming brittle and from dropping off. Finally, the hydrophobic property of the coating repels water that might cause internal rot. ~T~us, freshly-cut flowers treated by the process described in this invention maintain their freshly-cut appearance almost `
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Claims

1. A process of preserving freshly-cut flowers, or other fresh botanical materials, by freeze-drying (lyophilizing) and polymer coating.

2. The process of claim 1 wherein the flowers, or other botanicals, are slowly frozen before lyophilizing by placing in a freezer for several hours.

3. The process of claim 1 wherein the flowers, or other botanicals, are rapidly frozen by immersion into subzero (less than 0°C) liquid, such as cold freon, before lyophilizing.

4. The process of claim 1 wherein the flowers, or other botanicals are rapidly frozen by immersion into liquid nitrogen before lyophilizing.

5. The process of claim 1, 2, 3 or 4 wherein the polymer coating is by vapour phase deposition of a reactive monomer which subsequently polymerizes on the flower surface.

6. The process of claim 1, 2, 3 or 4 wherein the polymer coating is by vapour phase deposition of monomeric parylene.

7. A process of preserving freshly-cut flowers, or other fresh botanical materials, in a vacuum chamber by vapour phase deposition of a reactive monomer which subsequently polymerizes at a rate slow enough to allow concomitant evaporation of internal water and total drying before the coating is completed.

8. The process of claim 7 wherein the reactive monomer is monomeric parylene.

9. A product consisting of preserved, freshly-cut flowers, or other fresh botanical materials, prepared by lyophilization and polymer coating.

10. The product of claim 9 wherein the lyophilization is performed on slowly-frozen botanical materials, that is, by placing in a freezer for several hours.

11. The product of claim 9 wherein the lyophilization is performed on flowers, or other botanicals, which have bee rapidly frozen by immersion into subzero (less than 0°C) liquid, such as cold freon.

12. The product of claim 9 wherein the lyophilization is performed on flowers, or other botanical materials, which have been rapidly frozen by immersion into liquid nitrogen.

13. The product of claim 9, 10, 11 or 12 wherein the polymer coating is by vapour phase deposition of a reactive monomer which subsequently polymerizes on the flower or leaf surface.

14. The product of claim 9, 10, 11 or 12 wherein the polymer coating is by vapour phase deposition of monomeric parylene which subsequently polymerizes on the flower or leaf surface.

15. A product consisting of preserved, freshly-cut flowers, or other fresh botanical materials, prepared by placing them in a vacuum chamber and depositing reactive monomer from the vapour phase which subsequently polymerizes at a rate slow enough to allow concomitant evaporation of internal water and total drying before the coating 15 completed.

16. The product of claim 14 wherein the reactive monomer is monomeric parylene.