Патент USA US2404422код для вставки
Patented July 23, 1946' 2,404,422 UNITED STATES a PATE NT‘ 2,403,422 7 ' OFFICE ‘ TRANSPARENT PLASTIC MATERiAL Bjorn Andersen, Maplewood, N. .L, assignor_to_ Celanese Corporation of America, a corporation ' ‘of Delaware No Drawing. ‘Original application January 28, 1939, Serial No. 253,251. Divided and this ap plication February 12, 194,2, Serial No. 430,618‘ ‘ 6 Claims. (Cl. 2.29--3~.5) ‘ 1 This invention relates to the production of tate, or other certain synthetic resins, such- as. transparent plastic materials of improved prop erties, and relates more particularly to the'pro polymerized vinyl resins, polymerized. acrylic acid and methacrylic acid esters, urea formaldehyde, duction of a non-foggingv type of transparent ma terial. etc. were used as or in the container, it was. 5 found that these plastic materials also failed to resist fogging or sweating._ Thisv lack of resist ance of a transparent plastic material to fogging or sweating was due to thefact-that such plastic ,This invention is a division of the invention described in my co-pending application S. No. 253,251, ?led January 28, 1939. An object of‘ this invention is to provide a transparent plastic- material which is not sus ceptible to fogging or sweating when exposed to moisture-laden atmosphere, or at low: tempera tures conducive to moisture condensation. Another object of this invention is the provi sion of 1a transparent plastic material suitable 16 vent clear’ visibility therethrough but would also for use as or in packages for moisture-containing permit air to pass therethrough which, in. the substances. case of some foods, would cause deterioration. > Other objects of this invention will appear from the following detailed description. materials were all made more or less Water-in soluble to minimized‘ moisture absorption. These‘ plastic materials could; of course, be made more porous, and sponge-like and. thus absorb‘ mois ture, but there is‘ always the danger that the. plastic material ‘being porous would not only pre In‘ac'cordanc'e with my invention, I produce a , transparent plastic material having non-fogging In recent years certain plastic. materials have 20 and non-sweating characteristics, which trans been utilized in the manufacture of cartons for foods or other moisture-containing materials. parent plastic material retains its non-porous character, bytreating one or both surfaces of a However, the plastic materials suffered from the disadvantage of fogging or sweating when mois derivative of cellulose sheet leaving'the inner por tion or- core thereof in a'substantially unaffected ture-containing foods or other substances were 25 condition. Such a sheet is substantially impervi sealed up or enclosed in containers made of the plastic material or having windows thereof. To ous to both moisture and gas and has a. layer, on one‘ or both surfaces thereof, which. is water' overcome in some measure the fogging orsweat absorptive. The treatment comprises super?cial. ly saponifying, hydrolyzing ‘or de-est'eri-fying made to utilize a thin sheet of gelatin orother 30 sheet material comprising esters-of cellulose, such‘ moisture absorptive transparent medium on the as cellulose nitrate, cellulose propionate, cellu inside of the plastic material, 1. e. between the lose acetopropionate, cellulose butyrate, cellulose plastic material and the moisture-containing sub aceto-butyrate; and-'particuarly cellulose acetate. stances. These gelatin inserts or linings suffered As stated above, either one orboth surfaces may from a number of disadvantages. For example, 35 :be saponi?ed. In order to obtain sheets which under certain conditions, the gelatin swells, be are perfectly ?at and free from distortion, “knife comingsticky, wrinkled and pu-trescent. Fur lines” etc. it is preferable to heat press and polish thermore, the gelatin coatings when exposed. to an thesheets before and after treatment with the extremely dry warm atmosphere tend to shrink and crack and, therefore, do not afford a clear 40 Super?cial saponi?cation of the‘cellulose ester vision through the transparent container. sheet material may be effected in any convenient ing that takes place, attempts have hitherto been saponifying The inherent disadvantages of gelatin as a ' r ' ' manner such as by treatment in an alkaline ‘bath or by padding or otherwise mechanically impreg coating have led investigators to try other ex pedients to prevent the fogging or sweating. For nating the sheet‘ material with the requisite quan instance, attempts have been made to use on the plastic material chemical compositions found on tity of saponifying agent. ~ 7 ‘ ' V The alkaline bath used for super?cially sapon; ifying the cellulose ester sheet material may be the market for spraying onto glass Windshields to prevent frosting, water condensation or sweat, etc. agent. either of low concentration or high concentration These chemical compositions were often not depending on the temperature and duration'of satisfactory for use, particularly where food came 50 treatment. “If an alkaline solution of low con; in contact therewith. Another objection is that centration is used higher temperatures-may be their water-solubility resulted in the eventual removal thereof from the plastic material. employed in theprocess, whereasv if alkaline ‘so lutions of high concentrations are employed low 7 Where transparent plastic materials made from cellulose derivatives,’ such as cellulose ace 65 temperatures of treatment are used. If' a solu tion of intermediate concentration is employed, _ 32,404,422 3 bing. The surfaces of the sheets are then dried intermediate temperatures of treatment should thoroughly by Wiping with Chamois and by stor be used. The saponifying bath may contain any suitable alkali or alkaline salt for producing hy droxyl ions in aqueous .solution. The alkalies ing the sheets at room temperature between tis sue-lined “falulah” boards for a period of 3 to 4 hours to 3 days depending on the thickness of ‘ which may be used are sodium hydroxide, po the sheet employed. For example, sheets of a' tassium hydroxide ‘or ammonia. Examples of thickness of}. 0.005 to 0.010 of an inch are dried at’ room‘temerature for 3 to'4 hours, whereas alkaline salts are sodium or potassium carbon-v ates, sodium potassium or ammonium sulphide. sheets having a thickness of 0.060 of an inch are or hydrosulphide, sodium or potassium silicate‘and I tri-sodium phosphate. In order to promote in 10 preferably dried for 24 hours at room temper ' ature vbetween the boards, then are transferred tense surface’saponi?cation of the cellulose -es to dry pads and further dried for 24 hours at‘ ter sheet material, salts or modifying agents such 120° F. and then 24 hours at 140° F. When the sheets are thoroughly dried they are flattened ‘ anates, boraX, alcohol, glycol and polyglycol or their derivatives such as methyl glycol, etc. may 15 between polishing plates in a pre-heated press for 7 about 20 minutes at 50 to 150, preferably 125, be addedto the saponifying bath. The sheet materials usedin accordance with‘ pounds of steam under from 500 to 1500, prefer this invention may contain, besides the cellulose viably 1250, pounds of hydraulic pressure per as soap, sodium acetate, sodium “oleate', thiocy-f ' square inch. vThis removes any surface irreg ester, effect materials for modifying the prop- _, erties of said sheet materials, such as plasticizers, 20 ularities, distortions, knife lines, etac. The pol ished sheets are then ready for use. ?llers, dyes ,or lakes, ?re retardants, etc. For Aswill appear from theyfollowing tables, the ‘ instance, the sheet material may contain about cellulose ester sheets treated in accordance with 5to~30or more parts of plasticizer which may this invention have physical characteristics which be any suitable one for the particular cellulose ester employed. vThe plasticizers maybe any of 25 are quite different from those of the untreated the high boiling solvents or softening agents as, The chemical formula of the sheets‘ tested is for example, the aryl sulphonamides such as sheet. _ ' " ' cellulose aceate 1007 parts by weight and dim'eth para ethyl toluol sulphonamide, the alkyl phthal oxy ethyl phthalate (plasticizer) 30 parts by ates such as dimethyl phthalate, the 'dialkyl tar trates such asdibutyl tartrate, the alkoxy es 30 Weight.’ This composition is, however, only illus ters of polybasic organic acids such as dimeth ‘ trative. . . 1 (A) Untreated sheet, oxy ethyl phthalate, the polybasic acid esters of the mono alkyl ethers of polyhydricalcohols such (thousandth; of Thickness V" as diethylene glycol ethyl ether ester of phthalic inch) ______ __1_-__‘__" _____ _~_ *5 acid, the alkyl esters of ‘phosphoric acid such as 35 Fog resistance (in seconds)___ ' 2 triethyl glycol phosphate, tricresyl phosphate, the Tensile strength, in pounds mixed alkyl and aryl phosphatesgand camphor. A mixture of, any of the foregoing plasticizers may beemployed if desired. The ?re retardants vwhich- may be, employed in the cellulose ester sheet material may be tricresyl phosphate, tri persq.in.: A. Yield 10 2 20 V 2 " ' p0int____'___'____ _ _ _ 6160 "4825 _ ‘5260" ' VB. Break point __I__-____-__ 7730;- 6150 15860 Elongation (percentage) _v_;__ 38.7‘ 35.5‘ 32.1 phenyl phosphate, chlorinated naphthalenes,‘ chlorinated. diphenyls, compounds containing Hardness __________ __' _____ __ 6.66 6.34‘ Moistureabsorption;1 _____ __ 3.94 4.05v 4.50 ‘6.74 bromine and other like ?re retardants known to be compatible, with the cellulose ester employed. The ?re retardants may be added to the sheet y *(B) . Treated; sheet v(Inon-f0.997mg) material in a quantity of about 15 or more'parts by weight. If desired, water-soluble plasticizers Thickness inch) ___v_' ‘_ (thousandths. ____ __~__>__~__'____ "of "5 "710 - - Y‘ ‘20 and/or ?re retardants may be used to some ex tent as, for example, to secure a greater depth 50 Fog resistance (in seconds) _-_“ 4' 90 140 >120‘ of porosity. . , -' . yWhile any of the vforegoing saponifrying agents’ Tensile ..persq_in_-: A. Yield strength, ‘point>.. ____ in pounds __,__'___' 9850',I 8850 7.; l7300 may be used in making the sheet material of my invention, I prefer to use ‘an aqueous solution B. Break point '___-i ____ ___ 9850 2‘8850 - 7560 of ammonia. In the preferred process of treat ing the cellulose acetate sheet material the sheets which may vary in thickness from about 0.001 to 0.100 of van inchpor more are ?rst cleaned and Elongation (percentage) ‘___"__~'_l10.2’ 20.6 ' '30 Hardness l___;_-___~ _____ _"__;_1_' 10.6 Moisture absorption__-_,__-_;__ 8.83 10.6 "9.13 "7.73 " 5.96 then polished in the usual manner between heat- ' Water age)‘ ______ shrinkage _. ___________ (percent_-__- - 074' - 1; .125 ' ~~ i209 ' ' ed ; polishing , plates. These sheets are then im mersed for a period of from 2 to 6 hours, de pending on the thickness, in a saponifying bath containing ammonia in a concentration of about 15 to 20%, at a temperature between 60 to 75° F., preferably 65° F. If the temperature exceeds '75"v F.- an undesirable distortion of the sheet ma terial- may‘ take place. After the sheets are‘ taken from the bath they are washed in running Water at a temperature of 60 to ‘75° F., prefer ably 65° F., for from 20 to 300_hours depending upon the thickness of the sheet being treated. In order to. prevent discoloration of thesheet. material it is preferable, to exclude air from the sheets until all of‘ the ammoniayand degraded Heat 1055 ____ __4..'__'____~_._"__’_I_'. .329v .258 .211’ In the tables the ?gures _for_ “fog resistance" were obtained by ?rst preconditioning the sampleof the sheet to be tested for one hour at 80° F. and 5.0% relative humidity. The sheet was then placed ?at over the mouth of a one quart; Mason jar containing onepintof water at 140?,F.,-_ the jar being in turn placed'over- a newspaper..~'i‘he~ time in seconds was noted-when fogging ?rst be: gan to. appear and the newsprint became illegible; 730 By this test, treated’ ornon-fvogging plastic sheet: ‘ing is fog resistant for. not less‘ than goseconqsl. usually from 90' to >150seconds, whereasuntreated, plastic Sheeting and glass Wil1...fQg in-~.twb.eeqéeiis' PKQQQCWPW? been removed by ‘57.351.11.119. 91' .5339: 7.5 0r.- .less-1Tha?guréstori/hardness ae-eaesa . . 5‘ 6 I ciably'minimi‘zed. This quality is alsoiofmate as Brinell hardness in kilograms per’ square‘mil; rial aid when it is“ desired to ‘make antifog'ging, , limeter with a 3.5 ‘millimeter ball; liliikilogram shatterproof glass lenses, Windshields,‘ et'c'.,;wliere load, 1 minute; Thei'moistur'e absorption figures one or both ‘sides of-theglassh'a's'a- treated sheet were obtained by‘ conditioning the sheet material of cellulose'es'ter laminated thereto. "The'toughl for 24 hours at'zeropercentage relative-humide ity, and noting the gain in weightafter 48’hours at 90% relative ‘humidity. To obtain the ?gures for water shrinkage, the sheet material was ?rst ness and resiliency of the treated plastic sheet ing, compared with an untreated sheet‘, make for added safety. ' ' - If desired, a roll of cellulose acetate ?lmrmay ity. “The sheet material was then immersed'in 10 have one or both‘ sides saponi?ed or de-esterified su?icieritly so that a thin coating or substratum water‘ for?» hours'and then conditioned: again of gelatin may be effectively applied; After the for 24 hours at 50% relative humidity. [ The ?g ?lm is thus “subbed” say in continuous lengths, ures' given in the tables represent the percentage a thicker adhesive layer of glue, gelatin,' gum shrinkage in length. The ?gures for‘ heat ‘loss conditionedfor 24 hours at 50% relativehumid; arable, casein, sodium silicate‘, egg albumin, ‘dex trin, glyceryl or glycolbo'ri-borate resins, etc, may be subsequently appliedso"v that the ?nal, represent the percentage of loss‘in weight after heating thesheet material'for 3 days at ‘70° C. > From the above tables itwill beseen that the treated sheet material of plasticized cellulose ace tate is remarkably stronger than the untreated plasticized cellulose acetate although the percent dried coated ?lmt orlsheeti’n‘g may ‘be‘stuck to a . variety of surfaces-‘suchv as glass, wood, metal, paper, etc, by the-mere application'of water as . in the'sticking of ‘a postage stamp. In thepast it has been quite difficult to apply gelatin coat ings, even though extremely thin, directly to plas ticized cellulose acetate materials, for example, in motion picture and X-ray ?lm, where a heavier vcoating of light sensitive ‘gelatin emulsions is usually applied over the thingelatin substratum. This‘ di?iculty in securing proper anchorage of age of elongation is less. ’ The latter, however, in creases with the thickness of the sheet material whereas in the untreated plasticized- cellulose ace tate sheet material it decreases as the‘ thickness increases. The treated material is moreover-‘de cidedly harder and more scratch-resisting than the untreated sheet material. This is probably due to the case hardening e?ect oflthe sapohify ing treatment and the absence on the surface ‘of any substance such as a plasticizer. Indeed, celé lulose acetate sheets treated in this manner ap the gelatin to the surface’ of the ?lm is generally attributed to the incompatibility of the oily, Water-insoluble or hydrophobic plasticizer in or pear to approximate the good mechanical prop erties of the well known product, Celluloid, such as resiliency and stiffness Without brittleness, gelatin. The saponi?cation of the cellulose ester and plasticizer results in a porous, water absorp on the ?lm with a hydrophilic colloid such as try. The light transmission of the treated'sheet tive layer making possible more e?ective gelatin substrating. Ordinary glued paper labels‘ may material is over 90% of white light which is prac tically unalfected by long exposure to sun or ultra violet light. For example, one hundred hours ex— fogging sheet by mere application of‘ moisture. This feature is also quite desirable for packaging which are so‘much ‘desired in the plastics indus posure in a standard “Fadeometer” testing ma chine caused only a slight bleaching of color with no apparent e?ect on light transmission. i4. also be readily stuck to the surface of the non 40 material. While this invention thus ?nds exceedingly useful applications in many ?elds, the physical properties of the sheet material treated in ac The tables also show that the moisture absorp cordance with this invention makes the same emi .tion is very high in the treated plasticized cellu lose acetate sheet material as_ compared with the ;- nently suitable for use where non-fogging, trans parent sheet material is desired. For example, untreated plasticized cellulose acetate sheet ma when sheet material of this invention is used as terial, while the water shrinkage is less. A containers or as windows in food cartons, the marked difference will also be noted in the Weight said material will not fog or sweat due to the loss at elevated temperatures, the untreated plas ticized cellulose acetate sheet material losing ap 50 condensation moisture thereon, such as may be induced by exposure to low outside temperatures preciably after 3 days at 70° C. The case-harden or by conditions obtaining within the food car ing saponi?ed layer in the treated sheet mate ton. This feature, as indicated above, is due to rial acts as a seal and prevents further volatility the porous and moisture absorptive character of of the plasticizer from the core of the sheet ma terial. This is a very signi?cant ?nding. Its 55 the surface of the sheet material. No droplets of the moisture (fog) Will appear on the surface bene?ts are appreciated in the case of printing of the sheet to mar the transparency thereof. cellulose acetate sheets and subsequently polish Moreover, the treated material will not Wrinkle ing same. The dii‘?culties of ink transfer as or become sticky and distorted in use due to brought out in U. S. Patent No. 1,931,485 are con siderably diminished. Due to the porous surface 60 shrinkage or swelling, but will remain strong, ?exible, non-tacky, non-moldy, clear and durable. the ink is more readily absorbed. In polishing Treated material will also exhibit less “static” the sheet any tendency of the plasticizer to exude than untreated material which is highly desir is offset by this super?cial absorption. Indeed, able in the case of packaging material. The the treated sheets may be readily marked with ordinary ink and pen, and for this reason are very 65 treated surface is also more resistant to spotting by solvents such as acetone, alcohol, etc. suitable for tracing cloth purposes. This ease of printing is utilized to advantage in marking or If desired, the treated sheets or ?lms may be printing the non-fogging material, particularly suitably composited or laminated to one or both sides of other plastic materials, such as those when it is used for packaging purposes. The saponi?ed, porous surface also renders pos 70 made of cellulose derivatives, synthetic resins such as Vinyloid, Lucite, Styrol, condensation prod sible an easier lamination of the material to glass uts of urea-formaldehyde, phenol-formaldehyde, with cements such as gelatin, etc. The exuda glycerol-phthalic anhydride, etc. tion of plasticizer on the surface of the sheet forming an oily skin interfering with proper ad _While this invention has been described pri hesion to the glass or gelatin coating is appre 75 marily with reference to the treatment of sheets, BEST AVAILABLE copr ‘an. '7 _. . ~ S ' containing an ester of cellulose, said sheet ma? terial being saponi?ed so that at least’ its inner or unexposed surfaceis; capable of absorbing itis obvious vthat the cellulose es‘ er;w material being treated may be in any otherioi‘m such- as a'molded article of irregular shape and thick ness. For example, threaded lens tops for?/ash lights are generally made by the so-called injec moisture and the sheet material'as a'whole being resistant to‘the penetration of water and gases. 4. A container for holding food and other tion Jmolding of cellulose acetate. 'Such a ?n ished molded article may be subjected‘ ‘to a .saponi?cation treatment to render the lens non products yielding moi'sturetending to condense Within the container, said' container having a window comprising transparent sheet material It is to be understood, therefore, that the fore 10 containing cellulose acetate, said sheet 'mate rial being saponi?ed so that at least ‘its inner 'or going detailed description is givenrmerely by way unexposed surface is capable of absorbing mois of illustration and that many variations may be fogsing. . r n _ V ‘ made therein without departing ,from the spirit ture and the sheet material as a whole being of my invention. resistant to the penetration of water and gases. 5. A container for holding food and other i Having described my invention, what I desire 15 to secure by Letters Patent is:, I Y‘ r products yielding moisture tending to condense p within the container, said container having a l. A container for holding food and other prod_ window comprising transparent sheet material ucts yielding moisture tending to’ condense with in the container, comprising substantially im§ pervious transparent sheet material containing an ester of cellulose; 'said sheet material being saponi?ed so that at least its inner or unexposed containing cellulose ester sheet material sap'onie ?ed at least on one surface thereof, which sheet material is characterized by being hard, resistant’ to the penetration of water and gases, of low water shrinkage and heat loss, of high tensile surface is capable of absorbing moisture and said sheet material is free from the tendency to fog strength and having a fog resistance of 50 to15‘0 orsweat.v seconds. .‘ » ‘ - ‘ =76. A container for holding food and other 2.'A ‘container for holding food and other products'yielding moisture tending to condense products yielding moisture tending to condense Within the container», comprising. substantially impervious transparent sheetlmaterial contain ing cellulose acetate, said sheet material being within the container, said container having a window comprising transparent sheet material 30 containing cellulose ‘ acetate sheet material said sheet material is free from the tendency to saponi?ed at least on one surface thereof, which sheet material is characterized by being hard, re sistant to the penetration of water and gases; of fog or sweat. ' low water shrinkage and heat loss, of high ten saponi?ed so that ‘at least its inner or unexposed surface is capable of absorbing moisture and ' ' 3. A container for holding food and other , products yielding moisture tending to condense Within the container, said container having a window comprising transparent sheet material sile strength and having a fog' resistance of‘ 50 ‘ to 150 seconds. 7 V BJORN ANDERSEN. .