US2985546A

US2985546A - Method of rendering cellulosic material non-adherent and article produced thereby

Info

Publication number: US2985546A
Authority: US
Inventors: Herbert J Leavitt
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1958-03-26
Filing date: 1958-03-26
Publication date: 1961-05-23
Anticipated expiration: 1978-05-23

Description

United States Patent IVIETHOD OF RENDERING CELLULOSIC MATE- RIAL NON-ADHERENT AND ARTICLE PRO- DUCED THEREBY Herbert J. Leavitt, Schenectady, N.Y., assignor to General Electric Company, a corporation of New York No Drawing. Filed Mar. 26, 1958, Ser. No. 723,965

7 Claims. (Cl. 117-143 This invention is concerned with rendering cellulosic materials non-adherent to various organic solids. More particularly, the invention is concerned with a process for rendering paper or paperboard non-adherent to normally adherent materials such as, for instance, asphalts, bitumen, tars, waxes, paraffin solids, flour-containing pastes and frozen foodstuffs, and other high molecular weight polymers which process comprises treating the said cellulosic material with a mixture of ingredients comprising (1) a linear polydimethylsiloxane containing a terminal silicon-bonded hydroxy group, (2) a polyalkyl silicate, and (3) a metallic salt selected from the class consisting of dibutyl tin dilaurate and dibutyl tin diacetate.

Cellulosic fibers in the form of cel'lulosic papers and paperboard are used extensively as confining and shipping means for various highly adhesive materials including such organic compositions as asphalt or pitch, tar, various unvulcanized rubbers, particularly synthetic rubbers, other high molecular weight organic polymers used as adhesives, etc. For optimum use of these cellulosic containers, it is essential that they be capable of being readily separated or stripped from the cargo contained therein. Thus, in the transportation and shipment of asphalt used for roofing purposes, the asphalt is generally poured while still hot into a container, such as a carton, bag or drum whose sides are cellulosic in nature. After cooling, the asphalt becomes quite hard and can be readily transported with little difficulty. At its destination of use, it is essential that this paper in Whatever form be capable of being readily stripped from the asphalt so as to permit easy access to the latter without any extraneous portions of the paper or fibers thereof adhering to the asphalt so as to undesirably affect the constitution of the asphalt.

Various treatments have been accorded these types of papers which are often referred to as anti-blocking paper or release paper). One method for treating the paper to render it anti-blocking comprises treating the paper in a three-coat operation with (1) finely divided clay and casein, (2) finely divided clay, and (3) polyvinyl acetate. Such paper provides release by fracture of the clay coating, but the polyvinyl acetate remains on the adhesive material. Another method commonly employed in the art involves applying several thicknesses of polyethylene to the paper, usually by treating the latter with solutions of the polyethylene. A still further method for treating cellulosic material to render it non-adherent, particularly to asphalt and to permit it to be readily removed from direct contact with the latter, involves depositing a double coating of cellulosic materials, the first coating being ofclay and the second coating being of methyl cellulose and starch.

ice

However, all the foregoing methods have been exceedingly expensive and in many respects have not been too satisfactory since too often it has been found that these adhesive materials, particularly asphalt, which apparently has a high affinity for cellulosic fibers, stick to the anti-blocking paper so that great difficulty is encountered in attempting to separate the latter from the asphalt.

U.S. Patent 2,588,367 describes the use of methyl hydrogen polysiloxanes in combination with water-soluble cellulose ethers for the purpose of treating anti-blocking paper to render it less adherent to ordinarily adhesive organic compositions. Although such combinations of ingredients are ordinarily helpful in reducing the adhesive properties of the paper, nevertheless much is left to be desired from such treatment of the paper. Often, the release properties are unreliable and the release characteristics are not uniform throughout the surface of the paper. In addition, it is essential that, in order to obtain optimum release properties, the treated paper be aged for extended periods of time, e.g., by storage before it is useful for release purposes; this is necessary because accelerated aging by high-temperature treatment is not usually available commercially in paper-treating establishments. Furthermore, paper such as parchment paper cannot be heated above 1125" C. without deleteriously affecting the paper. Moreover, after treatment of paper with the methyl hydrogen polysiloxane, the abhesive characteristics (i.e., the release properties) tend to decrease with time so that after long term storage, such treated paper no longer shows abhesive characteristics.

In addition to the difficulties described above, particularly when using methylpolysiloxanes for anti-adhesion (abhesive) purposes, and even when using the more currently employed methyl hydrogen polysiloxanes for this purpose, it has been found that although release properties are improved, nevertheless, there is an undesirable tendency of the silicone in the abhesive paper to migrate to the surface of the paper thereby coming in contact with the material which it is desired to release. Often the abhesive paper is in contact with compositions which are destined to be used for adhesion applications, and the tack or the adhesion is undesirably reduced as a result of this migration of the organopolysiloxane from the treated release paper to the adhesive.

Unexpectedly, I have discovered that a certain mixture of ingredients can be used to treat release paper whereby the various difficulties recited above are obviated. In addition, release paper treated with these compositions shows no evidence of migration of the organopolysiloxane therein to the surface so as to con taminate any material with which the release paper may come in contact. The compositions which I have found to be so eminently suitable in the practice of the present invention comprise (l) a linear polydimethylsiloxane having a terminal silicon-bonded hydroxyl group, (2) a polyalkyl silicate, e. g., polyethyl silicate, etc., and (3) a tin salt, selected from the class of dibutyl tin dilaurate and dibutyl tin diacetate.

The polydimethylsiloxanes employed in the practice of the present invention are those having the general formula zls'iiol where n is an integer greater than 1, for instance, from 25 to 100,000, and Z is a radical selected from the class consisting of the --OH and CH radicals. These polydimethyl-siloxanes containing the terminal silicon-bonded hydroxyl group or groups (hereinafter referred to as polydimethylsiloxane), are soluble in organic solvents such as xylene, toluene, trichloroethylene, etc., and are preferably of a fluid nature-which may range in viscosity from highly fluid materials to difficultly flowable compositions; the viscosities of such polydimethylsiloxanes may range from about 50 to 2,000,000 centipoises when measured at 25 C. The presence of up to 0.5 mol percent of trimethylsiloxy units [(CH SiO in the linearmethylpolysiloxane will furnish the terminal CH group so as to have a chain-stopping (CH SiO group, in addition to an -OH group, in the linear polydimethylsiloxane.

These polydimethylsiloxanes may be prepared by any one of several well-known methods. Thus, the high viscosity polydimethylsiloxanes may be obtained by condensing the hydrolysis product of dimethyldichlorosilane with either acidic or alkaline catalysts such as hydrochloric acid, sulfuric acid, potassium hydroxide, etc. Alternatively, one can heat cyclic polymers of the formula where m is an integer equal to from 3 to 6, for instance, octamethylcyclotetrasiloxane, with an alkaline catalyst such as potassium hydroxide, cesium hydroxide, etc. (in an amount equal, by weight, to from about 0.001 to 0.1% based on the weight of the octamethylcyclotetrasiloxane) at temperatures of from 125 to 175 C. for times ranging from about 15 minutes to 2 hours or more and thereafter, if desired, removing the alkaline catalyst to yield a polydimethylsiloxane of Formula I having a viscosity of from about 700,000 to 2,000,000 centipoises when measured at 25 C. By incorporating during this polymerization, small amounts of sources of the CH chain-stopping radical, e.g., from 0.01 to 0.1%, by weight, based on the weight of the octamethylcyclotetrasiloxane, of hexamethyldisiloxane, decamethylpolysiloxane, etc., one can obtain linear olydimethylsiloxanes having one terminal hydroxyl group and one terminal CH group (see Formula I). Also present will be polydimethylsiloxanes containing two terminal hydroxyl groups randomly distributed with the monohydroxy substituted polydimethylsiloxane.

When lower viscosity polydimethylsiloxanes containing terminal silicon-bonded hydroxyl groups are desired, one can treat the high molecular weight products ob tained above with water to reduce the viscosity of the polymer to within the range from about 50 to 100,000 centipoises at 25 C. This can be accomplished by blowing steam across the surface of the high molecular weight product or through the polymer for 'a sufficient time to give the lower viscosity material having the desired silanol content. Such compositions and various methods for preparing the same are more particularly described in U.S. Patent 2,607,792. The use of steam in this fashion will cause a decrease in the viscosity of the polymer while at the same time the formed linear polysiloxane will have terminal silicon-bonded hydroxy groups. 7

An alternative method for making the linear organopolysiloxane containing terminal silicon-bonded hydroxy groups comprises adding water to the high molecu lar weight polymer described above in such amount that when heated at elevated temperatures, for instance, 150 to 170 C., the viscosity is reduced to the desired level of 1,000 to 50,000 centipoises. The amount of water used will vary depending upon such factors as the molecular weight of the polymer being treated, the time and temperature at which the mixture of high molecular weight organopolysiloxane and water will be heated, the ultimate viscosity desired, etc.

The amount of water used to reduce the molecular weight can be readily determined. For instance, one can obtain a linear fluid methylpolysiloxane containing terminal silicon-bonded hydroxy groups and having a viscosity of from 1,000 to 2,000 centipoises at 25 C. by heating a high molecular weight methylpolysiloxane (prepared in accordance with the directions above) of about 2,000,000 centipoise viscosity, with only 0.5 percent, by weight, thereof water for about 2 hours at 150 to 170 C.

The polyalkyl silicate employed in the practice of the present invention can be obtained by efiecting partial hydrolysis in water of monomeric organosilicates having the forinula (RO) Si where R is a lower alkyl radical containing from 1 to 5 carbon atoms, for instance, methyl, ethyl, propyl, butyl, amyl, etc., radicals. Such hydrolysis products are generally obtained by effecting partial hydrolysis in water of the particular monomeric organosilicate in the presence of small amounts of acid to a point where it is still water-insoluble and it is still possible to isolate a liquid, partially hydrolyzed organosilicon compound. Thus, taking as a specific example the controlled partial hydrolysis of ethyl silicate having the formula (C H O) Si, the hydrolysis of the latter may be carried out by adding acids or acid-forming metal salts to the liquid monomeric organosilicate, for instance, FeCl CuCl AlCl SnCl.,, etc., and thereafter efiecting suitable hydrolysis of this mixture of ingredients in water to obtain the two-phase composition from which the water-insoluble, partially hydrolyzed organosilicate can readily be separated from the aqueous phase and catalyst.

I have unexpectedly found that contrary to what might be expected, dibutyl tin dilaurate and dibutyl tin diacetate gave minimum migration of the methylpolysiloxane and were able to be used in lower concentrations than when one employed metallic soaps even tin soaps, such as tin octoate, tin naphthenate, tin oleate, and even such a metallic salt as butyl tin trioctoate, which is closely akin to dibutyl tin dilaurate and dibutyl tin diacetate.

The above essential ingredients used for treating cellulosic materials to render them abhesive in the form of a coating material which is non-migratory as far as the methylpolysiloxane contained therein is concerned, are advantageously dissolved in a solvent such as, for instance, xylene, toluene, mineral spirits, trichloroethylene, perchloroethylene, etc. The above-described mixture of essential ingredients composed of the polydimethylsiloxane, the polyalkyl silicate, and the specific dibutyl tin salt in combination with a solvent can be used as treating baths for cellulosic materials such as cellulosic sheet material, parchment paper, kraft paper, linen rag paper, rice paper, glassine, cellophane, sulfite cellulose paper and the like; as well as sheeting or boxing materials such as paperboard, cardboard, pulpboard,

and pasteboard.

A formulation comprising a solution of the above inbasis as specified above, an alternative means for calculating the proportion of the dibutyl tin salt comprises basing it on the amount of tin contained therein; on such a basis one advantageously employs at least 0.1%, preferably from 0.5 t 2 by weight, tin either in the form of dibutyl tin dilaurate or dibutyl tin diacetate, based on the weight of the polydimethylsiloxane. The amount of dibutyl tin salt employed will depend upon such factors as, for instance, the particular metal salt used, its efiect on the stability of emulsions, where emulsions are used; the type of organopolysiloxane employed, the type of paper to which the treating composition will be applied,

the solubility of the tin salt, as well as the medium in which the tin salt will be used, the treating conditions including temperature and time of treatment, etc.

Following treatment of the cellulosic material with the solution of the above described ingredients, the cellulosic material is advantageously dried by passing the treated paper over heated rolls (or cans) maintained at temperatures of about 50 to 90 C., for from 2 to 20 minutes or more. The use of circulating hot air at temperatures of from 50 to 125 C. may also be used for times of from 15 seconds to 3 minutes to effect curing of the treated paper. 7 This drying step .will bring out the optimum re.- lease properties of the paper Without further heat treatment, and such optimum release properties are immediately available without requiring aging or storage of the treated paper.

In order that those skilled in the art may better understand how the present invention may be practiced, the following examples are given by way of illustration and not by way of limitation. All parts are by weight.

The polyethyl silicate employed in the following examples is sold by Carbide and Carbon Chemicals Corporation of New York, N.Y., under the name of Ethyl Silicate 40 and is a mixture of ethyl polysilicates having about 40 percent available silica and is derived from the controlled hydrolysis of tetraethyl silicate, the formula for said polyethyl silicate being described as follows:

where Et represents the C H group. [Additional information for making the partial hydrolysis products of the monomeric organosilicon compounds described above maybe foundin the article by H. D. Hogan and C. A. Setterstrom entitled EthyLSilicates, in Industrial and Engineering Chemistry, volume 39, page 1364, No. 11 (1947).]

The high viscosity polydimethylsiloxane containing a terminal silicon-bonded hydroxyl group (hereinafter referred to as methylpolysiloxane No. 1) used in the following examples had a viscosity of around 3,000,000

centipoises when measured at 25 C. and had a ratio of approximately two methyl groups per silicon atom. This high viscosity composition was obtained by heating octamethylcyclotetrasiloxane with about 0.001%; by weight thereof, potassium hydroxide and with about 0.05%, by weight, thereof, decamethylpolysilox ane for about 2 to 4 hours at about C. until a benzenesoluble product was obtained.

The low molecular weight polydimethylsiloxane containing two terminal silicon-bonded hydroxyl groups (hereinafter referred to as methylpolysiloxaneNo. 2). employed in the following examples was obtained by mixing with the high molecular weight polydimethylsiloxane about 0.5% weight thereof water, and the mixture of ingredients heated with stirring for about 2 hours at to C. until a product having a viscosity of about 3,700 centipoises (when measured at about 25 C.) was obtained.

In the following tests, therelease characteristics of the treated paper (parchment paper was used) were determined by pressing "'(byhand) a strip of surgical adhesive tapeon the surface of the treated paper and lifting'the tape from the paper; evaluation of the release was determined by assigning numerical values as follows:

0-No lifting of paper whatever 1--One edge of paper lifted up to A 2-One edge of paper lifted A" to 1" 3One edge of paper lifted l to 2" 4-Paper falls off after being lifted by tape 5Paper shakes off after being lifted by tape 6Paper will not shake off Migration of the silicone from the treated paper to the surface with which. it came in contact was determined by observing the detackification of a surgical adhesive tape (loss of tack of the adhesive) caused by migration of the silicone from the surface of the paper to the adhesive on the tape. This was accomplished by pressing (by hand) a strip of adhesive tape onto the surface of the treated paper five times in five different areas. This technique greatly accelerated determination of migration because the adhesive would be expected to pull off silicone which, if given suflicient time, might migrate of its own accord to the material with which it came in contact. Surgical adhesive tape was used because a major application of release paper is its use as interleaving sheets where the treated paper is in intimate contact with adhesives and no loss of tack can be tolerated in such an application. A strip of the adhesive tape was then lifted from the paper and folded over so that the adhesive surface (which had been in contact with the release paper) was brought into contact with itself. The pull required to separate the adhesive surface from itself (evaluated subjectively as to poor, fair, fair-good, and good tack) compared with tape which had not been in contact with release paper was used as a measure of detackification of the tape and thus as a measure of migration of the silicone material. The methylpolysiloxane pickup was within the range from about A to 1%%, by weight, based on the weight of the parchment paper used.

EXAMPLE 1 In this example a solution was prepared composed of methylpolysiloxane No. 1, ethyl silicate 40, and toluene. The percent toluene in the solutionwas held substantially constant so that it represented about 70 percent of the total weight of the aforesaid three ingredients, while the ethyl silicate 40 and the methylpolysiloxane No. l were varied. Catalyst solutions were also prepared from various metallo-organic salts in which the metallic salt in the catalyst solution comprised, by weight, about 33 percent, and the solvent (toluene) used to make the solution comprised about 67 percent, by weight. Various treating solutions were prepared by mixing together the methylpolysilox anepolyethyl silicate solution with the catalyst solution. The bath life of the mixture of the catalysts and the methylpolysiloxane solutions was determined by noting the time within which gelling of the active ingredients in the treating solution occurred.

Parchment paper was treatedwith the various treating baths by immersing the paper. in the bath, removing the treated paper and'pa'ssing it between squeeze rolls, and heating the treated paperat a temperature of about 65 C. for about 3 minutes. This method for treatment of parchment paper was followed in all the following examples as well. The following Table I shows the percent methylpolysiloxanelNo. .1, and the percent polyethyl silicate 40 in each of the treating baths, as well as the particular metallo-organic salt used and theperce'nt of such salt expressed as percent metal. All percents are on a weight basis based on the total weight of the active r ingredients and the toluene solvent, the toluene comprising the difference between the weight of the active ingredients and 100 percent. In the following tests, the bath: life of the treating solutions ranged from 2 to 15 hours with the exception of Test No. 14 where the treatingzba-th'gelled after .15 hours.- 1 i Table 1 Percent Percent Percent Methyl- Ethyl Catalyst 4 Test po1y-S11- Silicate Catalyst (Expressed Release Tack N0. oxane 40 as the No. 1 Metal) '4 0.12 Dlbutyl tin dllaurate 0.08 Good. 4 0.12 Dibutyl tin diacetate 0. 08 0 Do.

10 1.0 Dibutyl tin dilaurate... 4. 4 0 Do.

10 1. 0 Dibutyl tin diacetat 4. 4 0 Do. 4 0.12 Lead tetra octoate... 0.08 0 Fair. 4 0.12 0. 08 0 Do. 4 0.12 0.08 0 Do. 4 0. 12 0. 08 0 Do. 4 0.12 0.08 0 D0. 4 0.12 0.08 0 D0.

10 1.0 Tin naphthenate 4. 4 0 Do.

10 1. 0 Tin octoate 4. 4 0 Do.

10 1.0 Tin oleate 4. 4 0 Do.

It will be noted from the above Table I that although various organo-metallic salts can be used to catalyze the mixture of the polydimethylsilox-ane and the polyethyl silicate, for retention of maximum tack, that is, minimum migration of the methylpolysiloxane, dibutyl tin dilaurate and dibutyl tin diacetate showed better performances at both low and high concentrations of catalyst, methylpolysiloxane, and polyethyl silicate concentrations'.

EXAMPLE 2 This example illustrates the importance of including the polyalkyl silicate with the methylpolysiloxane and the organo-metallic catalyst in order to obtain a treated paper which shows good release without migration as shown by full retention of tack by the adhesive tape. More particularly, toluene solutions were prepared of methylpolysiloxane No.1, ethyl silicate 40 and various organometallic salts including the dibutyl tin dilaurate and dibutyl tin diacetate found to give the improved performance more particularly recited above. The method for preparing the catalyzed solutions was the same as that used to prepare the solutions described in Example 1. The following Table II shows the proportions and ingredients used as well as the test results on the treated paper. In all instances the bath life was satisfactory for 8 hours. The paper used was again parchment paper and was tested in the same manner as recited in Example l.

the ethyl silicate 40, and within the range of at least 0.16 to 4.4 percent for the dibutyl tin dilaurate (which was the only catalyst used in this example), each based on the total weight of the treating bath, good results were obtained regardless of the proportions used.

1 Bath life in each instance was satisfactory for at least 2 hours.

EXAMPLE 4 This example illustrates that in addition to toluene, one can also employ other diluents or solvents for the treating bath. More particularly, various solvents, such Table II Percent Percent Percent Methyl- Ethyl Catalyst Test poly-Sil- Silicate Catalyst (Expressed Release Tack No oxane 40 as the No. 1 Metal) 4 None... Dibutyl tin dilaurate..- 0.16 0 Poor. 6 Nonedo 0. 2 0 Poor-fair. 5 None do 1.1 0 Poor. 5 None. Dlbutyl tin diacetatc 0. 2 0 Poor-fair. 10 None do 0. 4 0 Fair. 10 Nonedo 0.4 0 'Poor. 5 0.15 Dibutyl tin dilaurate-.. 0. 2 0 Good 5 0. 15 Dlbutyl tin dlacetate---- 0. 2 0 Fair. 10 0. 15 Dibutyl tin d1laurate 0. 4 0 Good. 10 l. 0 Dibutyl tin diaeetate 4. 4 0 D0. 10 1. 0 Dibutyl tin dilaurate 4. 4 0 Do.

EXAMPLE 3 This example illustrates that the concentration of polyethyl silicate can be varied widely without adversely affecting the bath life of the treating solution or the properties of the treated paper. The treating solutions were prepared similarly as in Example 1. Table HI which" follows shows the ingredients and proportions used as well as the test results on'the paper treated with these solutions. It will be noted that Table III shows that within the range of from 0.15 percent to 9.0 percentof as xylene, trichloroethylene, perchloroethylene, and mineral spirits present in the same proportions as the toluene used in Example 1 were employed as solvents for a mixture of methylpolysiloxane No. 1, ethyl silicate 40 and dibutyl tin dilaurate as the catalyst. The method for making the solution was the same as that described in Example-l and the percentages of the ingredients are found recited in the following Table IV which also gives the results on the paper treated in such baths. In each instance the bath life was satisfactory for at least 6 hours.

Table IV Percent Percent Percent Methyl- Ethyl Catalyst Test No. poly- Silicate (Expressed Diluent Release Tack siloxane 40 as the No. 1 Metal) 10 l 4.4 Xylene 0 Good. l 0 4.4 Trichloroethylene... 0 3 Do. 10 1 0 4.4 Perchloroethylene-- 0 D0. 10 1 O 4. 4 Mineral spirits 0 D0.

EXAMPLE 5 This example illustrates the preparation of toluene solution-treating baths employing methylpolysiloxane No. 2 as the silicone composition. The ethyl silicate 40, as well as the catalysts described in this example, are the same as those employed in Example 1. The method for making the treating baths was identical with the procedure recited in Example 1.

Table V shows the percentages of methylpolysiloxane No. 2, the ethyl silicate 40, the particular catalyst used, the percent catalyst, as well as the bath life of the various solutions and the properties of the paper treated with the various baths. The treatment of the paper was the same as that described in Example No. 1.

for the above specified purposes are manifold. By means of my invention, it is possible to obtain high quality release characteristics for highly adherent materials such as uncured synthetic rubbers, pitch, asphalt, tar, many adhesives and other type of materials. The anti-blocking properties are effective even at low concentrations of organopolysiloxane pickup; the paper treated can be- Table V Percent Percent Percent Test Methyl- Ethyl Catalyst No. poly- Silicate Catalyst (Expressed Bath Life Release Tack siloxane as the No. 2 Metal) 40.... 4 0.12 Bibutyl tin dilaurate.--. Q. 08 OK 0 Good. 41...- 4 0. l2 Dibutyl tin diacetate 0. 08 Viscous after 3 hrs...-- 0 D0. 42.... 4 0. 12 Lead tetra octoate 0. 08 OK 0 Poor. 43...- 4 0.12 Lead octoate 0.08 0 Do. 44..-- 4 0.12 Tin octoate 0.08 0 "Do. 4 0. l2 Tin naphthenate-- 0. 08 0 Do. 46..-- 4 0.12 Tin oleate 0. 08 0 D0. 47.--. 4 0.12 Dibutyl tin dioctoate. 0. 08 0 Do.

It will, of course, be apparent to those skilled 1n the for its anti-release purposes with realization of essentially art that in addition to the methylpolysiloxanes of viscosity recited above,'other 'methylpolysiloxanes containing terminal silicon-bonded hydroxy groups of other viscosities within the range of to 2 million centipoises, when measured at 25 C. can be employed without departing from the scope of the invention. The concentration of the polydimethylsiloxane, as well as of the catalyst and emulsifying agent (where employed), may be varied within the ranges previously recited, again within the scope of the present invention. The concentration of the dibutyl tin dilaurate or the dibutyl tin diacetate (or mixtures of such tin salts) may also be varied within wide limits depending on the factors recited previously.

The amount of organopolysiloxane which is picked up by the cellulosic material as a result of the treatment with the emulsion or solution of the organopolysiloxane depends upon such factors as the absorbency of the cellulosic material, the method of application, the concentration of organopolysiloxane solution or emulsion, etc. Generally, the amount of organopolysiloxane pickup ranges from about 0.2 to about 5%, or more, based on the dry weight of the cellulosic material; the preferred pickup being within the range of about 0.5 to about 2% organopolysiloxane pickup. Obviously, larger amounts of organopolysiloxane pickup may be employed, but generally this is not necessary and usually serves merely to increase the cost of the treatment. The ability to obtain maximum pickup with minimum amounts of organepolysiloxane and to realize the maximum release properties is one of the unexpected and unobvious advantages of employing the particular combination of ingredients herein described for release purposes.

Advantages of using the compositions herein described optimum properties. Heretofore, organopolysilolxanes previously available on the market for the same purpose required aging, that is, storing of the treated paper for times as long as six weeks, in order to bring out the optimum release characteristics of the treated paper. Of considerable importance is the fact that eve-n at high temperatures, the release characteristics are maintained at optimum levels and elevated temperatures do not destroy the release film. The compositions for treating cellulosic materials herein described are readily amenable to a single step procedure and are easily regulated and controlled for adjustable organopolysiloxane pickup by minor variations in formulations. Standard paper making or paper converting equipment is readily employed in connection with the treating operations and no precautions need be taken for any toxic materials which may be contained in the treating emulsions.

Cellulosic materials treated as described above have a wide range of usefulness. Thus, asphalt or high molecular weight organic polymers, such as various synthetic rubbers, can be poured hot into containers fashioned from the treated paper or paperboard, and after cooling it will be found that solidified asphalt or polymer is readily and cleanly separated from container Walls.

My invention permits paper treated in accordance 'With my process to be substituted for various fabrics which have heretofore been used in contact with adhesive surfaces of electricians pressure-sensitive tape, adhesive tapes used for surgical purposes, and regenerated cellulose tapes carrying a permanent adhesive upon one surface. Vulcanized or unvulcanized sheets of rubber can be prevented from adhering to each other despite the fact that these sheets of rubber are quite sticky and cohesive when in direct contact with each other. Paper treated in accordance with the instant invention is also useful in lining various boxes of partially prebaked goods such as buns, rolls and the like, and advantage can be taken of the outstanding release properties at elevated temperatures by completing the baking cycle in the origi-' (1) from 1 to 20 parts of a linear polydimethyl-siloxane containing a terminal silicon-bonded hydroxy group,

(2) from 0.1 to 40 parts of a polyalkyl silicate,

(3) from 0.01 to parts of a metallic salt selected from the class consisting of dibutyl t-in dilaurate and dibutyl tin diacetate, and

(4) from 75 to 97 parts of an organic solvent, and thereafter drying the treated material.

2. The method for rendering cellulosic fibrous sheet material non-adherent to surfaces which normally adhere thereto, which process comprises treating the cellulosic fibrous sheet material with a treating bath containing, by weight, the following sole active ingredients:

(1) from 1 to 20 parts of a linear polydimethyl-siloxane containing terminal silicon-bonded hydroxy groups,

(2) from 0.1 to 40 parts of a polyethyl silicate,

(3) from 0.01 to 5 parts dibutyl tin dilaurate, and

3. The method for rendering cellulosic fibrous 'sheet'" material non-adherent to surfaces which normally adhere thereto, which process comprises treating the cellulosic fibrous sheet material with a treating bath containing, by weight, the following sole active ingredients:

(1) from 1 to 20 parts of a linear polyclimethyl-siloxane containing terminal silicon-bonded hydroxy groups,

(2) from 0.1 to 40 parts of a polyalkyl silicate,

-( 3) from 0.01 to 5 parts dibutyl tin diacetate, and

(4) from to 97 parts of an organic solvent, and thereafter drying the treated material.

4. The method for rendering cellulosic fibrous sheet material non-adherent to surfaces which normally adhere thereto, Which process comprises coating the said fibrous sheet material with an aqueous emulsion containing as the sole' active ingredient, by weight, (1) from 1 to 20 parts of a linear polydimethyl-siloxane containing terminal silicon-bonded hydroxy groups, (2) from 0.1 to 40 parts of polyalkyl silicate, and (3) from 0.01 to 5 parts of a metallic salt selected from the class consisting of dibutyl rtin dilaurate and dibutyl tin diacetate, and thereafter drying the coated material.

5. The method for rendering cellulosic fibrous sheet material non-adherent to surfaces which normally adhere thereto, which process comprises coating the said fibrous sheet material with an organic solution consisting essentially of, by weight, the following essential ingredients: (1) from 1 to 20 parts of a linear polydimethylsiloxane containing terminal silicon-bonded hydroxy groups, (2) from 0.1to' 40 parts of polyethyl silicate and (3) from 0.01 to 5 parts of dibutyl tin dilaurate, and thereafter drying the coated material.

6. The method for rendering cellulosic fibrous sheet material non-adherent to surfaceswhich normally adhere thereto, which process comprises coating the said fibrous sheet material with an organic solution consisting essentially of, by weight, the following essential ingredients: (1) from 1 to 20 parts of a linear polydimethylsiloxane containing terminal silicon-bonded hydroxy groups, (2) from 0.1 to 40 parts of polyethyl silicate and (3) from 0.01 to 5 parts of dibutyl tin diacetate, and thereafter drying the coated material.

7. Cellulosic sheet material treated in accordance with the method described in claim 1.

References Cited in the file of this patent UNITED STATES PATENTS ,2,504,388-- Braley Apr. 18, 1950 2,588,367 Dennett Mar. 11, 1952 2,814,601 Currie et a1. Nov. 26, 1957 2,843,555. Berridge July 15, 1958

Claims

1. THE METHOD FOR RENDERING CELLULOSIC FIBROUS SHEET MATERIAL NON-ADHERENT TO SURFACES WHICH NORMALLY ADHERE THERETO, WHICH PROCESS COMPRISES TREATING THE CELLULOSIC FIBROUS SHEET MATERIAL WITH A TREATING BATH CONSISTING ESSENTIALLY OF, BY WEIGHT, THE FOLLOWING ACTIVE INGREDIENTS: (1) FROM 1 TO 20 PARTS OF A LINEAR POLYDIMETHYL-SILOXANE CONTAINING A TERMINAL SILICON-BONDED HYDROXY GROUP, (2) FROM 0.1 TO 40 PARTS OF A POLYALKYL SILICATE, (3) FROM 0.01 TO 5 PARTS OF A METALLIC SALT SELECTED FROM THE CLASS CONSISTING OF DIBUTYL TIN DILAURATE AND DIBUTYL TIN DIACETATE, AND (4) FROM 75 TO 97 PARTS OF AN ORGANIC SOLVENT, AND THERE AFTER DRYING THE TREATED MATERIAL.