US2773045A - Wax compositions and sheet materials coated therewith - Google Patents

Description

heat sealing properfties of waxes withoufj inpal 11 I-WAX comosmoNs SHEET MATERIALS r COATED Zililllnll E. Simerl, Menasha, Alfred 'M. Heald, 'Neenah,

.,1.zaud:iGe.orge "PLMueller, Appleton, Wis., assignors to Marathi!! 1C0rp0ration, Rothschild,'Wisa a corporation N Drawing- Ap n an nrehww 20. 51 Serial No. :2115968 Claims. '(Cl. 260-285) This invention relates to wax compositions and more l l arl to wet Cami-I sa nd he materials coated therewith.

Inthe manufacture of packaging materials it is the praeiijel toc'oat a basesheetsuch as paper, paperboard,"- cartons Hwy" a stie and foil sheets and the like'With-coating compositiopsto providea packaging material with pro- @QQYQPIQPQfties for the articlespackaged. Waxes, particularly petroleurnhydrocarbon waxes, i. e., parafiin and :rnicrocry stalline Wax, are widely used in-providing pro-, .tective coatings for food. packaging materia1s Tliese .waxes are often modified the addition of other materials which improve the coating for otherpurposes than :the protective function of the coating. For-example, in making bread wrappers, par-afiin Wax is generally used as a coatingtoprqvide aprotective water-vapor barrier. However, the wax coating alsois the medium whereby United Stew flteflt the 'wrapper ca n bejlmat-sealed and, hence,.the seal strength ofthe eoa tii g is'very'important. :Furthermore, n re d" Wra per 'be QmeS n advertising o i play m'edium, its gloss and gloss" retention, properties become an important consideration. Itis-importantthat the wax vshouldnot oon e. ofiin handling, i. e., s eu lf off; so as tobecome a nuisanee to purchasers{ 91 the bread.

' i' or e tthat the bread wr par h uld e low surface friction, i. e., low drag or "high slip, so as to function more readily'in automatic packaging equip- 'ment. It is also important that the coated sheets do not a block: or. .sticktdgether;particularly in rolls; "under any temperature .sconditi'onsflikely to be encountered in handling, In other types of packaging one or more of the above properties is usually necessary or desirable.

Additives} for waxes :whieh are presently available often improve-one property to the detriment of another. For example, polyisobutylene or rubber may be added to wax togirnprove its--heat-sealing properties; 'but'at 'the same timerthe blooking characteristic, i. e.,-the--tendency -tives result-in. anljincrease. ViSC'OSiEYL fliltliefiliscosityi is raised above that value at whichuit can be applied bythe usual commercial coating :egQipmntia 1d h at conventional rates of prqductiomthe increase in the cost of manufacture resulting'would discourage the use of the additive. lion example; a wax; composition 'for': making waxed papers gand paperboard ilca'r'tonsl by. conventional wet waxing rnethods should not be-more..than IOO-centipro i e uch compasit ns n. h chth se rep i ar film's, and the like @We have further ifoui d that small amounts within a critical range, produeje a peak value in the seal strengtlnthus makingour eomposition very qnq i T e id' j he isjw u r ik in character and-are sometimes referred to: as alcohol waxes. Prior toour inventionjthe unique cl feet onfthe seal strength of wax co1npo'sition's' eontaining alcohol- -waxes had never been appreciated, and particularly the critical rangeof amounts which ,we have discoveredto bemost eifectivehasnever, to our knowledge, heretofore been knownor-dise'losed. a

The alcohol-waxes which we use in our composition are in general solid aliphatic alcohols, particularly monohydric alcohols; 'having'a" melting pointabove' the melting point of the 'wax or waxes to" which they are added. They have a molecular weight in excess of about 500 and preferably 1500. Qurf preferred aleohol waxes have a melting point in'tl'ierangejof -about2l0 to about 1 240 Fil'A'. S. Ti MDS7Q4Z) foranfaverage moleeular 35" iveightin the raugeof a' bout 2000 to about 3 0QQ by the Staudinger, method 'These" preferred waxes are,fwe be-j lieve, solid tertiaryffalc'ohols, and morespeeifically dimethyl alkyl carbinol.-- Thesepreferred waxes are'fpjarticularly unique'in their effeet inpetroleurn waxes},

effect is most evidentineompositions"which are comprisedaof atleast 90% by we'ight of petroleum wax and notmore' than "5% by weight df alcohol-wax. Our .pre&

for the w'axed sheets to; stick to eagli 'other'gisadvefsely;

,, h e R sad e ferred'tertiary" .alcohol'-waXes" -are* described in United States Patent 2504,400 as the product o'f the polymerizai tion of ethylene in -the presence of isopropanol and a hydrogen'peroxide catalyst; They are believed to have the formula j RA.

a methyl groups. and R; *is a range of about @100. 5 An alcohol-wax prepared by* stokes 721L26 (A. s. T. M. D-4454-46T method B),

and' preferably should haveaviseosity of lessthan about SOoentistokes-at210 V v It'is an object of this invention to provide an improved wax eornposition'for producing 'waxedpackagijng'mate rials andxparticularly heat-sealablematerialsrwIt is 3.

aacritical minimum-amount of a wax add'tiv proveguoicik i-i *ing, gloss and slip properties and yet a further. object to such asethyl, propyl, butyl, etc. andfor-Rs, n has an};

' further object to provide a Wax composition moldifid liy V 1 "P fQ ?ISS f he abqve patent of this general formula.

1 and having an average molecular-weight oi -about 2100: a. is available 'on the market underthe trade name Alcowax, It is alproduct of the .Semet-Solvay-division----of Allied Chemical 8; Dye Corporation. Though. our in; vention shall jhe'reinafter be described by examples of' Alcowax as our'aleohol-wax, it is to'beunderstood that;

otheralcohol-waxes of the same generalformula are to' varyingdegrees applicable wherein {R1 and'Rz are alkyls;

average value greater than -about 12'0...10ur preferred aleoholsare symmetrical, that is, R1 andlRzare-the-same group.

combination 'offglds' s,- i if fvis'c'osity a i acteristies no t -heretof or'ei available vvith anyimix'tilre" of average'vaiue for n is in the;

1 Our improved compositions 'eoatedon' siieet'mm terials provide, in additiontosealjstrength an xeel 'nt' wax and wax additives. Furthermore, our compositions are economically desirable. We have found that in general the addition of not more than by weight and preferably about .25% to less than 5% of alcohol-wax, and, specifically Alcowax, to petroleum waxes, will yield a higher seal strength than greater or' lesser amounts. The addition of amounts in the range of about 1% to about 2% by weight will in addition provide considerably improved blocking, gloss, scuff and slip characteristics. These critical amounts, since they are small, mean that our compositions are not only low cost, but are also, due in part to the moderate molecular weight of the alcohol-waxes, of low viscosity which makes them well suited for conventional wet waxing methods.

thermore, in conventional wet waxing, as pointed out above, the lower the viscosity of the wax composition, the higher'theproduction rate, hence, a further cost savings. g

In the following tables are set forth the physical prophigh as 1 mm.) Each of the Examples 1-47 was prepared by melting the components together and then surface waxing a bleached sulfate-sulfite paper having a basis weight of per ream (2'x3--500 sheets) in the conventional manner to obtain about 4 to 6 pounds of surface wax composition per ream. The blocking temperature indicated is the minimum temperature at which coated sheets will block, i. e., stick together sufiiciently to prevent separation without disruptionof the coating, with the coating face to face when held for 16 hours under a pressure of 0.28 lb. per sq. in. The seal isvmeasured on a Socony-Vacuum Oil Company 'seal tester, which determines in grams per inch of width of the sheet tested the yield force at 73 F. of two sheets adhered in face to face relation. The fast value means that the test pieces were adhered by laminating the two sheets by wrapping them around a roll, steam heated to 210 F., at a speed of '50 ft. per minute andunder a' tension of about 2 lbs. per sq. in., and then passing the sample at the 'same speed through a water bath at 61 F. The fslow value means that the test pieces were cooled in a stream of air at room temperature while traveling at a speed of 10 feet per minute. These seal values bracket the values for seal strength obtainable under commercial sealingconditions, such as in wrapping machines;

From the above examples it will be seen that paraifin wax compositionsmodified with: up to about 5%, and more particularly with about 0.5% to about 2% Alco .wax, have the .best seal strength properties. It is fur.- ther seen that the blocking point sharply increases for Fur compositions having more than about 0.5% Alcowax. Compositions containing Alcowax in the range of about 1% to about 2% are excellent in respect of both seal strength and blocking. A sheet waxed with these compositions, e. g., Examples 5, 6, and 7, makes a very improved wrapping material, such as, a bread wrapper, plain waxed paper, food overwrap, etc., not only because of the improved blocking and seal characteristics but also because these advantages are obtained with an improvement in the gloss, scuff and slip characteristics. For example, we found the sheets of Examples 5, 6, and 7 show only slight scuff whereas that of Example 1 is great. V 7

Table II illustrates substantially the same results when Alcowax is added to a slightly higher melting point parafiin wax.

TABLE II Efiect of Alcowax on 135/37 F. paraflin wax Seal at 73 F., Alcowax, Blocking Grams/in. Example Percent By Point,

Weight F.

Fast Slow further found that there is no significant change in the gloss up to about 5% and the scufi characteristics are improved at' 25% and markedly at 1%.

Tables III, IV, V, and VI below illustrate the effect 7 ofsmall additions of Alcowax on various microcrystalline and paraflin hydrocarbon wax blends.

TABLE III Efiect of Alcowax on 20%:140/145 F. microclystalline wax 80% 135/37 F. paraffin wax Seal at 73 F., Alcowax, Blocking Grams/in.

Example Percent By Point,

- Weight F.

Fast Slow V 1 Producedand sold by Shell on Co. 7

'.TABLEIV;;.

' Efiect of A lc owax on 35% 140/ 145 F. microcrystqlline wax? 135/37 F. p arqfiin' wax Seal at 73 F., Alcowax, Blocking Grams/in. Example Percent By Point,

Weight 9F. Fast Slow 1 Produced and sold by Shell 011 Go.

TABLE v Efiectof Alcowax on Warc'o.155 F. microcrys- "talline wax '80% '135/37 F. 'purafiin Seal at 73 F., Alcowax, Blocking Grams/in.

Example Percent By Point,

' Weight F.

vFast; Slow 1 Produced and sold by Warwick=Wax 00.

TABLE VI Effect ofAlcowtzx on 20% 145/47 microcrystalline wax 80% 135/37" Fspiarafiin Seal at 73 F., Alcowax, Blocking Grams/in. Example Percent By, Point,

. Weight F.

1 Fast Slow 1 Produced and sold by Quaker State on Refining Corp.

7 With each difierent wax blend it is seen that with additions of Alcowax within the range from about .'5'% to about 3%, a peak seal is obtained. It further appears that in general a greater improvement is provided by less than 5% additions of Alcowax than by 1 larger amounts. It is further seen that in the range of about 11% toabout 2% the best results are obtained as was the case with paraffin wax. Alcowax wefound that the gloss, and scu'if characteristics were maintained or improved'and slip definitely improved. Microcrystalline wax has heretofore been blended with paraifin to improveseal strengthbutssuch compositions have considerably greater drag or poojrer slip than paraifin wax alone. Additives, known heretofore, that would improve the slip properties reduced'the seal strength, hence ofisetting the advantages ofthemicr'ocrystalline *wax: The compositions in Tables III and IV ar e,' therefore, particularly unique for their slip propewes and those offTables V' and VI-flare' particularly fdesirablejbecause of, slip andveryhigh seal strength. ""Table VII- illustrates the'eifectofAlcowax on a-' type of wax which is not strictly a fparaifin because it I has some characteristics of a microcrystalline 'waxyn'ame- 1y, smaller crystal structure, increased tack orstickiness,

andhi'gh surface 'friction. It resembles the blends'of V, the previous tables, which may be. considered as blends of 'n paraifinic, is'o-paraflinic and naphtheniclhydrocare boiis; but is distinct in that the iso-paraflinic and naphthenic'components are of lower average molecular weight than is foundin microcrystalline waxes. In 'thiswaxftl e .In-every example containing in the preceding tables.

lroduced and sold by Union Oif CoYof alifotnia. v

Fromtheaboveit is seen that as little as about .25

Alcowax improves the blocking and "seal characteristic ofthe'wax of Table VII when compared tothe control 'or theexarnple containing, 5% Alcowax. Here'the, range of about .75 to about 2% is'preferred 'which corresp'ond's closelytothe preferred range'for the compositions These compositions, we have found, also have good glossfscuif, and slip properties. Heretofore thepoor slip properties of compositions con-- taining this type of wax have limited its use.

Table VIII below illustrates the seal strength at two diflerent temperatures of compositions of Alcowax and the, microcrystalline wax used in the blend of Table 'VI which is a waxirom a Pennsylvania crude. The seal strengths shown are the fast values at. the temperatures indicated and the coated base sheet is #300 MAT-2 cellophane.

TABLE 'VIII Efiect of Alcowax 'on 145/47" F. microcrystalline wax 1 -Seal-,'Gran1s/in. Fast Example Percent Alcowax I 0 f "744 754 l .0425" 810 981 I 0. 5 840 1, 004 '0. 75 810. l, 017 1 310 1, 017 a .1. 5. l;051' l, 203 a 2. av 1,190; 1,203 3 .949 7 642 1 Produced and sold byQuakerStateRefining Corp.

At 73 F. and 45 F; the amounts of Alcowax for proved seal strength' arei'learly 'illustrated as being in the general range of .25 to 12%. Withfsoine'improvement even at 3%.. .It is clearly .evident frornthe results shown by each table above, and particularly, Tables II, VI, .and

VIII, that amounts of Alcowax in about "the same critical ranges inparaifin wax,'rnicrocry'stalline wax, and ablend of each, will in each case produce a composition having iniprov'edse'al' strength and blocking characteristics.-

Polyethylene, which is in, commercial use as a wax additive,"s erve s to improve blocking, gloss seufifresista eaand seal stability, thatjis, 'byour 'defin'itionthe ratio iso paraifinic and naphthenic materiaLWhich" comprises 7 about 30% by weight of the wax, has the' same'b'oiling us end point 'as' the n-parafiinic components. These waxes V are obtained from high, boiling lubricating .oil cuts produced' bythe vacuum distillation of crudeoil and have u a boiling range of from about 300 F. to about 700 at 1 'mm. 'Hgfpressure. These waxes in, general have 'meltingpointsofabout140 F..tojabout 17 0 F.

however, as Alcowax, within our critical concentration ranges, to improve the fast value as well as .the stability 7 V and also maintain or improve blockingf In facti'with microcrystalline wax, polyethylene reduces theseal strength." Furthermore, the characteristic or property :of slip-which we have used herein to define theldegree of friction between the coating and foreign surfacesysuch as wrapping machine surfaces, .is far superior with. Alco: wax-wax compositionsj than with polyethylene-wax compositions, Still a further important advantage of Alcowax'over polyethyleneas a wax 'additive is that. there' is httlesincrea se in viscosity in' the resulting wax composition'particular'ly within thecritical rangeof percentages special properties.

59 40%1'45 47 F. Microcr'ystalline we prefer. For example, the viscosity of compositions of Table ;I were lessv thanv 9 centistokes at 210? F. In the case of the microcrystalline wax compositions, the viscosities were not in excess of about 20 centistokes at 210 F.J Similar polyethylene wax compositions would have considerably higher viscosities.

Alcowax may be used along with other wax additives which may be added in small amounts to obtain certain Additives, such as rubber, polyisobutylene, polyethylene, rosin and rosin esters vegetable gums, metal stearates, and plasticizers, such as petrolatum, may be used. In general, however; our preterred compositions will contain at least about 75%, and preferably 90%, hydrocarbon wax and :will have a viscosity of less than.100 centistokes at 210. F. and preferably less than 50 centistokes at 210 F.

When polyethylene is used together with Alcowax in Wax compositions we have'found a totally'unexpected improvement in seal strength which indicates a synergistic effect." Table IX below illustrates this. Each example 'wa'sprepared by coating a papei' ba'se sheet to obtain about 4 to 6 pounds per ream of the described composi Ition on the surface as in the examples in the TablesI-Vll.

I nants. Excessive oil in parafl'in wax will affect its prop- Efiect of combining'Alcowax and polyethylene Block- Seal at 73 F., ing Grams/in. Example Composition Pgltent,

' Fast Slow a Polyethylene 1,000 M01. 50 35%145 4? F. Microcrystalllne 115 134 es ax. 01.5% l35l37 F. Parafiin Wax--- 3.5% Aleowam; 57 35.0% 145/47 F. Microcrystal- 115 126 50 line Wax. 61.5% l35l37 F. Parafiin Wax 1.75% Alcowax i ax. 51% 135/37 F. Paraflin Wax V 9% Alcowax V 60 40%,, 235/ 17 F. Microerystalllne 115 51% 135/37 F. Paraffin Wax 4.5% Aloowax 4.5V%t Polyethylene (7,000 M01.

40.0% i 47 F. Mlcroerystalline Wax. 51.0% 135/37" F. Paraffin Wax- A comparison of Examples '56 and 57 with 58 and of Exainples'5 9 and 60 with 61 shows that the combination ofpolyethylene. and Alcowax producesa greater seal strengththan thesame percentage of either additive alone. This unique result may in part be explained by the fact that in Examples 58 and 61 theamount of Alcowax is ducedwhich comprise from about .5% to less than about 5 5% 'byweight of Alcowax, about 1% to about 5% by weight of solid polyethylene, and the balance, orat least about75% .by weight, a mixture of a paraffin and micro: V crystalline wax- Compositions 'otAlcowax, inour critical amounts, and parafiin. wax, aloneor with microcrystalline wax, when coated on paper, paperboard,- regenerated cellulose and plastic films, result in materials extremely well suited for heatfsealing food-wraps 'andcontainers. Because of; the

erties, and the parafiin wax portion of our compositions is therefore of relatively low oilicontent, i. e., of less than about .75 and preferably about .5% when measured by A. S. T. M. method D-721-43T.

Many other modifications ofour improved composition other than those given herein by way of example will occur to those skilled in the art and no limitations are intended by the above examples except such as are contained in the following claims.

We claim: l. A heat-scalable sheet material comprising a fibrous paper base sheet having a superficial'coating comprising a solid polymer of ethylene and isopropanol having the CH3(C2H4)n group where the average value for n is in the range of about 60 to 100, said polymer being present in amounts from .25 to 5% by weight and having a molecular weight in the range of from 500 to about 3000 and having a melting point of from about 210 F. to about 240 F., 1% to 5% by weight of solid polyethylene, and to about 98.75% of petroleum wax having a melting point of fromabout 130 F. to about 170 F.

2. A heat-scalable sheet material comprising a fibrous paper base sheethaving a superficial coating comprising a solid polymer of ethylene and isopropanol having the formula.

Evil-R:

wherein R1 and Rz are methyl groups and R is a CH3' (C2H4)12. groupwhere the average value for n is in the range of aboutj60 to 100,'having a melting point in excess of 200 F. and a solid polyethylene in about equal proportions, from'about 20% to about 50% microjcrystalline wax, from about 40%- to about paraffin wax, having a melting point of from about F. to about 210 F said combined polymer and polyethylene having a ratio to the combined paraffin and microcrystalline wax of from 1:28 to about 1:10. 7

3. A wax composition'comprising paraffin wax containing from 0.5 to 10% by weight of a mixture of polyethylene and 40 to 60% byweight based on total polymer ,of polyethylenehaving a' terminal hydroxyl group, said hydroxylated polyethylene being produced by polymerizing ethylene under 42S475 atmospheres. at temperatures between and 200 C. in the presence of isopropanol and hydrogen peroxide, t. r -4. Composition --according to claim.3 ,in which the polyethylene has ,a molecular weight of 4,00 0-2 5,, 000 and the polyethylene havingia. terminal hydroxyl group'has ethylene under 2425-475 atmospheres at temperatures between 140 and 200? C. in the presence'of isopropanol and hydrogen peroxide. i 1 r 7 Composition according to claim 6 in which thepolyethylene has a molecularweight of 4,000-25,000 and the molecular weight of'about 500-10000.

0 r V a v 4 polyethylene';havinga terminal hydroxyl. grouphas a seal strength propertiesour. compositions, particularlythose containing micro'crystall nc wax, are excel en i- 9 r 10 ethylene has a molecular weight of 12,000 13,000 and the References Cited in the file of this patent polyethylene having a terminal hydroxyl group has UNITED STATES PATENTS molecular weight of about 2,000.

9. Composition according 'to claim 8 in which the 1,950,814 Pmgs et 1934 amount of the total polymers is about 2.5% by weight. 2,350,292 Sermattel May 30, 1944 10. A heat-sealable sheet material comprising a fibrous 2,361,582 Adams et a1 1944 paper base sheet having a superficial coating comprising gg f g 6 3: is rd 1 f d I l h th 1 r e a e 2 3 3 ymer o e ylene an lsopmpa"? avmg e 2,504,270 MacLaren et al Apr. 18, 1950 r l i 10 2,504,400 Erchak Apr. 18, 1950 i 2,551,087 Barnhart et a1. May 1, 1951 2,560,773 Lovell July 17, 1951 a 2,582,037 Hyde Jan. 8, 1952 wherein R1 and R2 are methyl groups and R: is a, 2712534 Erchak July 1955 CHs-(C2H4)n group where the average value for n is in t FOREIGN PATENTS the range of about 60 to 100, said polymer being present 621,923 7 Great Britain 22 1949 in amounts by weight from 0.25% to about 5%, from a about 1% to about 5% of solid polyethylene, from about OTHER REFERENCES to about 40% of microcrystalline wax, and from Th Chemistry a d Technology of w w i i about to about paraflin wax having a melting 20 bold Publishing Company, New York, New York, 1947.

point of from about to about 210 F.

Claims (1)

1. A HEAT-SEALABLE SHEET MATERIAL COMPRISING A FIBROUS PAPER BASE SHEET HAVING A SUPERFICIAL COATING COMPRISING A SOLID POLYMER OF ETHYLENE AND ISOPROPANOL HAVING THE FORMULA