US 2811468 A
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United States Patent IMPERMEABLE POLYETHYLENE FILM AND CfiN- TAINERS AND PROCESS OF MAKING SAME Stephen P. Jotfre, Little Falls, N. .L, assignor to Shulton Inc., Clifton, N. J., a corporation of New Jersey No Drawing. Application June 28, 1956, Serial Nor 594,342
16' Claims. (Cl. 117-95) This invention relates to polyethylene film and containers and more particularly to polyethylene film suitable for use as a wrapping material for foodstuffs and other perishable materials and to containers for perfume compositions, synthetic aromatic chemicals, natural isolates (fractions derived from natural sources, such, for example, as aromatic woods, barks, branches, flowers and fruits), other materials which are deleteriously affected either by the escape of vapors from the interior of the container through the walls thereof or by entry of constituents of the surrounding atmosphere through the walls of the container into contact with its contents, mineral and vegetable oils, aromatic hydrocarbons, e. g., toluene, aerosols in which a pressurized gas, such as nitrous oxide or the Freons are usedas the propellants, emulsions in which the oil phase is the continuous phase, etc. The expression container is used herein in a broad sense to include bottles, boxes, envelopes, and the like.
Polyethylene containers, particularly bottles, are widely used for storing and transporting perfume compositions containing synthetic aromatic materials, such as citrus oils, clove oils, eugenol, isoeugenol, ionones, orange oils, lemon oils, etc., and other materials. Examples of such containers are the flexible polyethylene bottles including the now popular polyethylene squeeze bottles and bottles made from filled polyethylene compositions, such, for example, as mixtures of polyethylene and pigments and/or fillers such as barium sulfate, metal powders, talc, clay, etc. The latter type of bottle, while lacking the flexibility of the former, like the former has the advantage of unbreakability as contrasted with glass, lightness in weight and the other advantages of polyethylene.
It is known that polyethylene is chemically inert to perfume compositions and aromatic chemicals, e. g., it will not dissolve therein or react therewith. Nor are the individual constituents of perfume compositions adversely affected by contact with polyethylene. Yet when perfume compositions are packaged in polyethylene containers not only does a rapid change in the character of the perfume occur but also Weight losses from the sealed containers are considerable. In addition, distortion' of the container frequently occurs. These changes in the composition of the perfume and the consequent weight losses are due to escape of the light notes (the fugitive or more volatile constituents), and sometimes also the medium notes through the Walls of the poly* ethylene container, i. e. polyethylene is permeable to the constituents present in the perfume and the solvent employed (usually alcohol), permitting their escape in vapor or gaseous formthrough the walls of the sealed polyethylene container.
fragrance, light, medium and heavy notes must be blended judiciously. It has been the uniform experience of the perfume industry that any well constituted odor containing these three phases becomes unbalanced after storage in a sealed polyethylene container, even though no liquid leakage takes place from the container. The lighter notes disappear far more rapidly than the medium notes and the medium notes permeate the polyethylene walls more rapidly than the heavy notes. After awhile the unequal rate of permeation throws the fragrance completely out of balance.
Polyethylene containers can not be used, as a practical matter, for the storage of mineral or vegetable oils or emulsions in which oil is the continuous phase, because such oils ditiuse through the walls. Attempts to' store aromatic hydrocarbons, such as toluene, in polyethylene containers has resulted in the collapse and distortion of such containers. Nor have polyethylene containers been found suitable for packaging aerosols in which a pres surized gas such as nitrous oxide or theFreo'n s chloro fl-uoro methanes or ethanes) including Freon 1 14 (di chlorotetrafluoro' ethane) is used as the propellant because such pressurized gases escape through the walls with consequent loss of pressure within the container.-
Polyethylene film, because of its" clarity, tensile strength, relatively low moisture permeability, ease of handling, heat sealing ability and prope'rfy of transmitting ultra-violet light, permitting surface" sterilization of material wrapped with such film by means of ultra-violet light, is an eminently satisfactory wrapping material for materials which are not deleteriously infected by atmosphen'c' gases, such as oxygen, air, carbon dioxide, or which donot contain flavor or odor constituents which escape through the polyethylene. The use ofpol y'ethyl'ene film for packaging foodstuffs and other perishable mater-ials deleteriously affected by atmospheric gases; has been discouraged, if not substantially completelyavoided, because of the relatively high permeability of polyethylene to atmospheric gases, particularly air and ox yg" cause spoilage, including changes'in odor, flavor. Likewise, the packaging of meats; che'e's cooked foods, dried fruits, etc., in polyethylene filrmwrapriers, has frequently resulted in' discoloration, rancidity and poor flavor or" the packaged material.
ethylenes, including polymeric trifluorochlo'roethyl'enev and copolymers of vinyl chloride and vin'ylidene' .chlo?" ride from which containers may be made by injection into a mold or by blowing into a mold, etc. However, containers made from such polymers either sacrifice the desirable flexibility characteristics of polyethylene; are
prohibitively expensive, or are objectionable for other reasons.
In'the case of wraps for foodstufis and otherperishable materials, development has proceeded along the dir'ec tion of (1) laminated films in which one film which isa good gas or vapor barrier but lacking in other desirable characteristics is bonded to another film'h'aving the desired qualities, e. g., polyethylene bonded to cellophane; (2) coated films, e; g., films coated with waxes'orr s'insi includingthe polyvinyls; and (3) special plastics, such as- Afck Saran (polyvinylidene chloride), Mylar (polyester), which, while substantially impermeable to gases, are difficult to handle, lack ultra-violet transmission necessary for the sterilization of the surface of goods packaged therein, e. g., fresh meat, generate static electricity when handled, lack heat-scalability, are excessively costly, etc.
It is among the objects of the present invention to provide a polyethylene film and/or container, which film and walls of which container are relatively impermeable to the passage of atmospheric gases therethrough, and this without sacrifice to the desirable properties of the polyethylene, such as its clarity, tensile strength, ability to transmit ultra-violet light, and heat-sealing ability.
It is another object of this invention to provide polyethylene containers which are of improved impermeability to the passage of gases or vapors through the walls thereof and which containers, in the case of flexible polyethylene containers, such as squeeze bottle, retain the flexibility and other desirable characteristics of polyethylene, i. e., the improvement in the impermeability of the container is without sacrifice to the other desirable properties of polyethylene.
It is still another object of this invention to provide a polyethylene wrap or container which minimizes, if not completely prevents, the loss of aromatic flavor constituents from foods like cheese packaged in such wraps or containers; such loss, it will be appreciated, not only reduces customer acceptance of the food item but can also lead to flavor contamination of other food items stored in proximity therewith.
Still another object of the present invention is to provide a process for producing such polyethylene films or containers of improved impermeability which process is relatively simple and economical to carry out.
Other objects and advantages of this invention will be apparent from the following detailed description thereof. In accordance with this invention, polyethylene film and/ or containers are fluorinated to produce fluorinated polyethylene film and/ or container walls containing from 0.03% to 3.5%, preferably from 0.05% to 1.5% by weight of fluorine based on the weight of the polyethylene. Surprisingly, I have found that the formation of such fluorinated polyethylenes results in a polyethylene film and/or container which is of surprisingly improved impermeability, and this without sacrifice to the desirable properties of the polyethylene.
It is important that the fluorination be carried out so as to produce a fluorinated polyethylene containing from 0.03% to 3.5% by weight of fluorine, based on the weight of the polyethylene. The desired improvement in the impermeability of the polyethylene is obtained as long as it is reacted with the fluorine to form fluorinated polyethylene containing fluorine in the amounts above indicated. While the explanation for the improvement in impermeability is not fully understood, it is believed due to the replacement of some of the hydrogen atoms of the polyethylene with fluorine which form an electrical lattice-work to prevent passage therethrough af vapors and/or gases. It will be understood that the above explanation is advanced for the purpose of facilitating a better understanding of the invention and that this invention is not to be confined to or limited by the above explanation.
Fluorination of the polyethylene to an. extent to introduce more than approximately 3.5% by weight of fluorine does not result in the desired improvement in the impermeability of the polyethylene and may deleteriously' affect other desirable properties of the polyethylene, such as its tensile strength and clarity. On the other hand; the fluorination of polyethylene so as to introduce fluorine in amount less than 0.03% based on the weight of the polyethylene does not result in the desired improvement in the impermeability.
The polyethylene, such as bottles and film, subjected to fluon'nation may have a thickness of from 0.25 to I 250 mils; in the case of film the thickness is from 0.25 to 25 mils. All commercial polyethylenes employed for the production of containers or in the form of film may be fluorinated in accordance with this invention to render them substantially impermeable. Such polyethylene usually consists of polymers of ethylene having a molecular weight of at least 10,000, preferably from 14,000 to 60,000.
In the fluorination of the polyethylene film, the film should be free of lint and grease. This is preferably accomplished by washing the film with a low boiling grease removing solvent, such as carbon tetrachloride, acetone, ether or perchloroethylenes, to remove all grease, dust and foreign matter which, if not removed, might cause ignition of the polyethylene. Thereafter, the film is contacted with pure fluorine or a mixture of fluorine and an inert gas containing at least about 10% fluorine. The fluorination may be continuous by continuously passing the film through the fluorine or fluorine mixture maintained in a suitable sealed chamber provided with gas-tight seals through which the film enters and leaves. Alternatively a wound reel of the film can be unrolled and rerolled in the treatment chamber.
Instead of the continuous treatment hereinabove described, the treatment may be a batch operation involving festooning or otherwise arranging the clean film within the reactor to expose both sides, then introducing the fluorine or fluorine mixture into the reactor and permititng the film to remain in contact with the fluorine for the desired time interval. While not preferred, if desired the fluorination treatment may be carried out so that only one side of the film is fluorinated to form a layer of fluorinated polyethylene containing from 0.03% to 3.5%, preferably from 0.05% to 1.5% fluorine.
The time of treatment will depend on the particular equipment used, the film to be treated, the concentration of fluorine used, and the temperature. In general, a treatment time (contact time between the polyethylene and the fluorine) of from about 5 minutes to about 3 hours will give satisfactory results at room temperature (2025 C.). It is preferred to operate at room temperature, although temperatures as high as 50 C. may be employed. The more concentrated the fluorine atmosphere, the shorter the treatment time. Also, elevating the temperature to not exceeding 50 C. will permit Shortening the treatment time. In the case of films in the lower portion of the 0.25 to 25 mils thickness range, it is preferred to use a relatively short treatment time. Treatment times exceeding 3 hours may be used but are not preferred because they do not result in material further improvement in the impermeability of the polyethylene.
Following the above noted conditions, it has been found the film is not charred nor is there any material loss of clarity or tensile strength; the impermeability of the film to gases is, however, greatly improved as will be evident from the test data given below.
The fluorination of polyethylene containers is carried out by first cleaning each container so that it is free from lint and oil, introducing the clean container into a chamber, evacuating this chamber, then introducing fluorine gas into this chamber and continuing this introduction to the desired extent. Maintenance of each container in the chamber in contact with the fluorine gas for from 20 to minutes usually suflices to produce the desired level of fluorination. Thereafter, the container is removed from the chamber and its interior and exterior flushed with air or other inert gas, such as nitrogen, to remove residual fluorine gas.
. In lieu of the above procedure, each container after cleaning, as above described, may be introduced into an The time of treatment of the containers will depend on the equipment used, the containers to be treated, the concentration of fluorine used and the temperature. At
atmospheric temperature, a treatment time of from min-.
utes to 3 hours will give satisfactory results. Elevating the temperature or using more concentrated fluorine atmospheres, or both, will permit the use of shorter treatment times. Treatment times exceeding 3 hours may be employed but are not preferred because they do not result in further improvement in the impermeability of the polyethylene. Excessively long treatment times should not be used because they adversely affect the tensile strength of the polyethylene.
The cleaning of the containers before they are subjected to fluorination is desirably efiected by washing the container with a suitable solvent for oil or grease, such as carbon tetrachloride, acetone, ether or perchloroethylene, and thereafter removing residual traces of the solvent, for example, by blowing clean air over and through the washed containers. Unless the containers are clean when subjected to fluorination, particularly at temperatures above room temperature, there is the danger that when the container is fluorinated the polyethylene will ignite. By observing the conditions hereinabove set forth, namely, at temperatures below 50 C., preferably at room temperature, and utilizing clean containers, particularly in that they are free of lint and oil or grease, this danger is eliminated.
While it is preferred to fluorinate both the interior and exterior of the container, as hereinabove described, only the interior or only the exterior of the container may be so treated and still obtain the desired improvement in theimpermeability of the walls of the container.
In all modifications, including the fluorination of polyethylene film, instead of an atmosphere containing 100% fluorine, the fluorine may be diluted with an inert gas. The fluorine concentration may vary from 2% to 100% by weight, the balance, if any, being the inert gas, such as nitrogen, air, Freon (chlorofluoro alkanes, e. g., methanes and ethanes), etc. When a diluted fluorine is used, it is important to dry the diluent, i. e., substantially anhydrous conditions should be maintained during the fluorination. The presence of moisture tends to result inundesirable side reactions with the fluorine.
While the fluorination desirably is carried out at room temperature (2025 C.) any desired temperature below 50 C. may be used.
The following comparative data shows the surprising improvement in impermeability of polyethylene films and containers effected by the present invention.
CONTAINERS In all of the container examples, flexible bottles were employed made of a commercial polyethylene having an average molecular weight of 21,000; the bottles were oval shaped and the walls thereof varied in thickness from 20 to 60 mils.
Example] Pre-formed clean polyethylene bottles, each of 5% 02. capacity, were treated with a stream of fluorine gas at room temperature (20-25 C.) for six hours and for twelve hours. A 1 cm. diameter punch taken from the thickest aspect of the bottle wall from bottles which were fluorinated for 6 hours contained approximately 0.3% fluorine. The bottles fluorinated for 12 hours contained approximately 1.5% fluorine. The bottles were then flushed with air until no residual odor remained and filled to capacity with liquid allyl caproate and then sealed. This material was used as a test liquid because of its high volatility and distinctive odor and also because it has been found to be an excellent medium for indicating the permeability characteristics of polyethylene.
1 The filled bottles were then weighed, stored on open 6 shelves at room'temperature for the periods indicated in the table which follows and at the termination of each' of these periods the bottles again weighed and the gross losses in weight noted. An identical, fluorine untreated bottle was subjected to the same test for control purposes. The data on this test is given in Table 1 which follows:
i TABLE 1 Percent Loss in Gross Weight Bottle Type 10 days 21 days 40 days (a; Untreated bottle 0.8 2. 42 5.67 (b fihnfluorlne treatment 0.0009 0.007 0. 0512 (c) 12 hr. fluorine treatment 0.020 0.104 0.400
From the above data, it will be noted the untreated bottle lost at the end of 40 days times more weight than the bottle treated for 6 hours. The strong characteristic odor of allyl caproate was readily detectable from the untreated bottle whereas it was not noticeable from the outer walls of the treated bottles.
Example II Clean polyethylene bottles of 5% oz. capacity were fluorinated by passing a stream of gas from the inside of one bottle to the inside of the next bottle, the bottles being connected with fluorine resistant tubing. The bottles were treated with a stream of fluorine at room temperature for diiferent periods of time indicated in the table which TABLE 2 Time of Percent Bottle Treatment, Gross Loss hours in Weight Control (untreated) None 4. 0 Treated it 0. 00174 130.- 1 0. 00224 Do." 2 0. 00199 D0 3 0. 00542 Do 4 0.00293 During and at the end of the test, the strong character istic odor of allyl caproate was readily detected from the untreated bottle, whereas the outer walls of the treated bottles did not have any noticeable odor.
Example 111 The polyethylene bottles were first thoroughly cleaned to remove lint, oil and grease and then were placed in a chamber at room temperature. The air was evacuated from this chamber. Fluorine gas was slowly fed into the chamber so that at the end of an hour atmospheric pressure was established in the chamber. The fluorine gas was then permitted to remain in contact with the polyethylene bottles for another hour and thereafter the entire system was flushed with air until no residual odors remained.
Bottles thus treated were then filled with (a) the test liquid allyl caproate, (b) with a fragrance sold commercially under the trade name of Desert Flower Toilet Water and (c) with a lotion sold commercially under the trade name of Old Spice After-Shave Lotion. The bottles were weighed, stored on open shelves at room-temperature, again weighed at the end of the test period indicated in the table which follows, and the gross loss in weight noted. Untreated polyethylene bottles were subjected to the same treatment for control purposes. The data otbained on this test is given in Table 3 which follows:
During and at the end of the test period the strong characteristic odor of allyl capr oate and Desert Flower Toilet Water Was readily detected from the outer walls of the untreated bottles (the control bottles) whereas there was no noticeable odor of the test liquids on the outer walls of the treated bottles. Likewise, the untreated bottles containing Old Spice After-Shave Lotion had a faint spice odor on their outer walls, while this was not noticeable with the treated ones. In Table 3-A below is given the concentration of fluorine and the diluent used in treating polyethylene bottles made from polyethylene having an average molecular weight of 21,000 to 23,000; this table also gives the fluorine content and treatment times of the resultant bottles.
1 In this example, the bottles were placed in a closed chamber, the chamber sealed and evacuated and an amount of fluorine introduced into the chamber equal to 5- of the volume of the chamber.
FILMS All film permeability data hereinafter given was obtained using the apparatus and the test procedure described in the article by A. Cornwell Sherman, entitled Apparatus for measuring the gas permeability of film materials of low permeability, published in Industrial and Engineering Chemistry, Analytical Edition, vol. 16 (No. 1), pages 58 through 60, January 15, 1944.
Example IV In the film examples, the molecular weight of the polyethylene was about 23,000.
25 ft. of polyethylene film, 8 inches wide and 1.2 mils in thickness were washed with carbon tetrachloride to remove oily residues and foreign matter. The fihn was then air dried and festooned in the gas-tight treatment chamber to expose both sides of the film. The chamber was then evacuated and filled with dry nitrogen. This evacuation and filling process was twice repeated in order to flush the treatment chamber of any initial undried moisture-bearing atmospheric air. The treatment chamber, after this flushing, was evacuated to approximately 28 inches of vacuum and then filled with fluorine gas, over a 30 to 40 minute time interval until the vacuum was about 14 inches. At this point, the fiow of fluorine gas into the chamber was stoppedv and dry nitrogen gas was introduced into the chamber until the pressure was one atmosphere. The treatment chamber then contained 50% fluorine gas and 50% nitrogen.
The polyethylene film was permitted to remain in the treatment chamber for 30 minutes and thereafter the chamber was flushed with dry nitrogen to remove substantially all of the fluorine gas. The chamber was then opened, the film removed, washed with cold tap water, air dried and stored for 48 hours in an air conditioned room having a relative humidity of 45-50% and at a temperature of 7678 F.
The resultant film was clear and showed no reduction in tensile strength. The film before and after treatment was tested to determine its permeability to oxygen and carbon dioxide with the following results:
OXYGEN PERMEABILITY Film before treatment 303 Film after treatment 46 CARBON DIOXIDE PERMEABILITY Filmv before treatment 995 Film after treatment 148 The above values and all permeability values hereinafter given are in terms of the number of cubic centimeters of the particular gas under test transmitted per hundred square inches of film surface per 24 hours.
Example V Sheets of polyethylene film 8" wide, 10 long, and 2 mils in thickness, were washed with carbon tetrachloride to remove anyoily residues and foreign matter. The film was air dried and placed in the gas-tight treatment chamber, which was flushed with dried air. The treatment chamber was then filled with a mixture of 50% by volume fluorine gas and 50% by volume of dried air and the film permitted to remain in this mixture for 30 minutes. The chamber was then flushed with dried air to remove substantially all of the fluorine gas. The chamber was then opened to the atmosphere; the film removed, washed with cold water, dried in air, and then stored for 48 hours in an air conditioned room, as in Example IV.
Tests on this film before and after treatment, to determine air and Freon 114 (dichloro-tetrafluoro ethane) permeability, gave the following results:
am PERMEABILITY before treatment 135 A sheet of polyethylene film 8 wide, 12' long, and 5 mils in thickness, was washed with acetone to remove any oily residues and foreign matter, then air dried, and placed in the gas-tight treatment chamber, which was thereafter flushed with dried air. The treatment chamber was then filled with a mixture of fluorine and dried air so as to contain 40% fluorine by volume. The film remained in this atmosphere within the treatment chamber for 10 hours. Thereafter, the treatment chamber was flushed with dried air to remove substantially all of the fluorine. The film was thereafter removed from the chamber, washed in cold tap water and dried. It was then tested for oxygen permeability, with the following results:
Film before treatment Film after treatment 28 In Table 4, which follows, there are given the permeability values for different thicknesses of film, before and after treatment, subjected to fluorination treatment, using g the different concentrations of fluorine in the treatment chamber, and the time of treatment indicated in the table. The fluorination procedure otherwise was substantially the same as hereinabove described in connection with Example IV.
TABLE 4 OXYGEN PERMEABILITY Percent by Vol- Percent time Fluorine Permea- Permea- Reducand Diluent Duration bility of bility of tion in Film Thick- Concentration of Treat- Film Film Permeaness, Mils in Treatment ment in Before After bility Chamber Hours Treat- Treat- Efiected ment ment by Treatment F Diluent 85 15 air 2 116 23 78.5 85 15 air-- 1 167 39 76.4 50 50 Na... it 256 44 82.7 50 50 Na... it 303 46 84.8
CARBON DIOXIDE PERMEABILITY 85 15 air 1 600 136 77.2 50 50 N2 92 995 148 85.2 50 50 Namit 814 122 85.0 90 Air-.- 1 406 161 60.2
FREON 114 PERMEABILI TY 2.0 50 50 Air-.. /1 13s 25 21.9
1 Air in all examples was dried air.
In all of the above examples, the fluorinated polyethylene retained its original tensile strength, clarity, heatsealing ability, and its property of transmitting ultraviolet light. The percentage transmittance of the treated and untreated polyethylene film for wave lengths of from 230 to 280 millimicrons (the ultra-violet range) shows little or no difference for film fluorinated in accordance with this invention and for the untreated film. In one comparative test the fluorinated film showed a percentage transmittance of about 28% for radiation having a wave length of 230 millimicrons, the percentage transmittance gradually increasing with increase in the wave length to approximately 70% in the case of radiation having a wave length of about 380 millimicrons. The untreated film showed a transmittance in this same range of wave lengths of only 1% or 2% greater than the treated film.
The treated film takes print much better than the un-' treated film. Thus, for example, when untreated film was printed using inks specially prepared for printing on polyethylene and scotch tape applied over the printed area, it was found that the printing could readily be removed with the scotch tape, in the case of untreated film, but the scotch tape remained clear, i. e., would not remove the printing in the case of the treated film.
The impermeable containers embodying this invention have all the desirable properties of the polyethylene; in the case of flexible bottles, such as squeeze bottles, the fluorination treatment does not deleteriously affect the flexibility of the polyethylene.
In the case of the more rigid type of polyethylene bottles, the treatment of this invention does not have any deleterious effect on the desirable properties of the polyethylene, i. e., does not cause substantial rigidification or otherwise deleteriously affect the polyethylene.
Bottles treated in accordance with this invention will be found eminently satisfactory for the packaging and storage of toilet waters, cosmetic lotions, colognes, liquid deodorants, etc.
The present invention provides polyethylene film and containers which are substantially impermeable to gases, such as oxygen, air, nitrogen, nitrous oxide, carbon dioxide, the Freons, sulfur dioxide, ethylene, other preserving or pressurizing gases or fluids, and to the vaporizable constituents, including the light and medium notes l0 of perfume compositions, and this without sacrifice to the flexibility, heat scalability and ultra-violet light transmitting properties of the polyethylene.
Films embodying this invention provide an excellent wrapping material for foodstufis and other perishable materials deleteriously aitected by atmospheric gases.
Films embodying this invention may be formed into a bag to provide a membrane in an aerosol package, separating Freon, nitrous oxide or other gaseous propellants from the foodstuff or other material placed in the bag within the aerosol package. For example, anchovy paste, mayonnaise, jams, etc., may be packaged in such fluorinated polyethylene bags disposed in a suitable container,
such as a metal container having a Freon or other gaseous I propellant, the polyethylene bag serving to maintain the foodstuff out of contact with the gaseous propellant, while the foodstuff is within the container. In this way, the foodstufi may be dispensed in the form of a ribbon or controlled stream from the container by releasing the pressure, and this without intermingling of the foodstuff with the propellant.
Moreover, the present invention provides a substantially impermeable container which may be'used in storing or packaging toluene, other aromatic solvents, mineral oils, including'refined petroleum oils, vegetable oils, such as corn oil, peanut oil, cottonseed oil, and emulsions in which oil is the continuous phase, providing an unbreakable container in which the flexible properties of the polyethylene may be utilized, e. g., a squeeze bottle for storing and dispensing such oils, emulsions, etc. Hence, polyethylene bottles embodying this invention may be used as squeeze bottles for storing and dispensing as a spray such oils and oil emulsions.
' In this specification, unless otherwise indicated, pere centages are on a weight basis. The pressures hereinabove given are in' terms of inches of mercury. T he expression polyethylene, it will be understood, includes the polymethylenes which are produced by the polymeriza tion of ethylene. e r p j This application is a continuation-impart of copending application Serial No. 492,030, filed March 3, 1955, which application (but not the invention thereof) has been abandoned in favor of this application.
Since certain changes in carrying out the process and in the containers embodying this invention may be made without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense. Thus, instead of using gaseous fluorine for the fluorination treatment, a solution of fluorine in a suitable solvent may be employed.
What is claimed is:
1. A polyethylene film having at least one surface fluorinated, to contain not more than about 3.5% by weight of fluorine and enough fluorine so that said surface is substantially impermeable to the passage of atmospheric gases therethrough.
2. A polyethylene film containing from 0.03% to 1.5% by weight of fluorine.
3. A polyethylene container having its walls fluorinated, to contain not more than about 3.5% by weight of fluorine and enough fluorine so that the walls of said container are substantially impermeable to the passage therethrough of the light notes of perfume compositions.
4. A polyethylene container having its walls fluorinated to contain less than about 3.5% by weight of fluorine and enough fluorine to render the walls substantially impermeable to the passage therethrough of the light notes of a perfume composition.
5. Apolyethylene container having fluorinated polyethylene walls containing from 0.03% to 3.5% by Weight of fluorine.
6. A polyethylene container having a wall thickness of from 0.25 to 250 mils and having fluorinated polyamass 11 ethylene walls containing from 0.03% to 3.5% by weight 'offluorinep" 'j 7,. A polyethylene container having a. wall thickness of from 0.25 to mils and having fluorinated polyethylene walls containing from 0.05% to 1.5 by weight of fluorine. i I l 8. A'polyethylene container constitute'd of polyethylene having a molecular weight of from 14,000 to 60,000, a 'wall'thickness of from 0.25 to 250 mils and having fluorinated polyethylenewalls containing from 0.03% to 3.5% by Weight of fluorine. i V 9. A container of polyethylene having a molecular weight of from 14,000 to 60,000, -a'wall thickness of from 0.25 *to 250 mils and having thewalls' 'fluorinated to contain'from 0.03 to 3.5 by weight of fluorine based on'the' weight of the polyethylene. I p
10. A process of fluorinating 'a wall constituted of polyethylene -to render it substantially? impermeable to the passage therethrough' of aromatic flavor constituents which comprises fluorinating the said wallto'contaiiinot more than about 3.5 by weight of fluorineto render the polyethylene substantially impermeable to the passage therethrough of said aromatic flavor constituents.
11. A process of fluorinating a polyethylene surface adapted to form a container which comprises contacting said polyethylene surface with fluorine to form a fluorinated polyethylene surface containing from 0.03% to 3.5 by weight of fluorine.
12. A process of fluorinating polyethylene film which comprises cleaning the film to remove grease and foreign matter therefrom, subjecting the cleaned polyethylene film to contact with fluorine gas for from 5 minutes to 3 hours to fluorinate said polyethylene to a maximum of 3.5% by weight of fluorine, and flushing said polyethylene with a gas to remove residual fluorine therefrom.
13. A process of treating polyethylene containers which process comprises fluorinating the walls of said containers to introduce from 0.03% to 3.5% of fluorine based on the weight of the polyethylene walls.
14. A process of treating polyethylene containers which 12 7 process comprises cleaning the containers to remove lint and oil therefrom, passing fluorine into contact with the walls of said containers while maintaining said walls at a'temperature below C. and continuing said passage of fluorine into contact with the Walls of said containers until the polyethylene Walls contain from 0.03% to 3.5 by Weight of fluorine based on the weight of the polyethylene, discontinuing passage of the fluorine into contact with the Walls of said polyethylene containers and flushing the walls with an inert gas to remove unreacted fluorine therefrom.
. 15. A process of treating polyethylene containers,
which process comprises cleaning the interior and exterior walls of the container to remove lint and oil therefrom, introducing the clean container into a chamber,
evacuating said chamber, introducing fluorine into said chamber into contact with the interior and exterior walls of said container, maintaining said container in contact with the fluorine until the polyethylene walls of the container contain from 0.03% to 3.5 by weight of fluorine, removing the container from the chamber and flushing the walls of the container with an inert gas to remove unreacted fluorine.
16. The process as defined in claim 15, in which the temperature of the container while in contact with the fluorine is maintained below 50 C.
References Cited in the file of this patent UNITED STATES PATENTS 2,129,289 S011 Sept. 6, 1938 2,450,408 Baymiller Oct. 5, 1948 2,502,841 Henderson Apr. 4, 1950 FOREIGN PATENTS 710,523 Great Britain June 16, 1954 OTHER REFERENCES Modern Plastics, vol. 25, No. 6, February 1948, page 76; 117118.