US2939814A - Treatment of fibrous materials with coating or impregnating agents - Google Patents

Description

being rendered substantially insoluble in water.

United States Patent TREATMENT on FIBROUS MATERIALS WITH COATING 0R IMIVREGNATING AGENTS Philip H. Amphlett, James Dundas, and Geoffrey L. H.

woodthorpe, all of Lincoln, England, assignors to Jointme Products Company Limited, Lincoln, England, a British company a No Drawing. FiledJan. 31, 1956, Ser. No. 562,584

Claims priority, application Great Britain Jan. 31, 1955 5 Claims. (Cl. 162-182) This invention relates to the treatment of fibrous substances with the object of coating or surrounding the into a sheet or board on the normal paper making or 3 board making equipment or can be separated from the water and compressedari'd moulded by pressure.

Within the term Water insoluble fibre-coating substance in the present invention are included all those fibre-coating substances insoluble in water or capable of being rendered insoluble in water which are in the form of an aqueous dispersion or emulsion in the natural state or are capable of being made into a dispersion or emulsion in water. Within the term aqueous dispersion or emulsion are included systems in water containing particles of solid or liquid stabilised by. any of the known protective agents stable under both acid and alkaline conditions and in the presence of metallic salts, but exclude'those systems stabilised by cationic soaps to give dispersions or emulsions having particles possessing a positive charge of electricity. Typical examples of known protective agents are the fatty alcohol ethylene oxide condensate known as Lubrol W and the sodium salt of alkylated naphthalene sulphonic acid known as Perminal BX. t

Since however coagulation occurs in the aqueous phase; considerable. agglomeration takes place before deposi tion on the fibre with the result that the Water insoluble fibre-coating substance may be deposited on the fibres in relatively largelumps, or may not adhere to the fibres at all. It has also been found difiicult to achieve wil form coating of the fibres by the means just described. Another known method is to add to the fibres, suspended in Water a coagulant such as alum and then run this mixture into the aqueous dispersion or emulsion as previously described. In both methods coagulation occurs before deposition on the fibre. By the process .of' the present invention coagulation of. the dispersion of water insoluble fibre-coating substance is effected at the surfac {if the fibre and. there is a progressive build up of coagulum on the'fibre until the dispersion is completely exhausted of water insoluble fibre-coating substance. In this Way the fibres are evenly and uniformly coated.

Of the known coagulants for aqueous dispersions some are effective immediatelyon coming into contact with the aqueous dispersion, for example acids and certain salts. Others have a delayed action whereby intimate mixing of the delayed action coagulant and aqueous dispersion can be effected and the coagulation follows after an interval of time; while a third type known as heat sensitive coagulant can be mixed into the aqueous A wide variety of water insoluble fibre-coating substances may be used dispersed oremulsified in water and the following types of aqueous dispersion are given as illustrative of but not limitative of the scope of the invention:

Rubber latex either naturally occurring or made by redispersing solid rubber, vulcanised and unvulcanised and latices of the following substances:

Polyvinyl chloride, polyvinylidene chloride, co-polymers of vinyl chloride and vinylidene chloride polyvinyl acetate, co-polymers of vinyl acetate and vinyl chloride, polyacrylates, polymethacrylates and co-polymers thereof; poly-isoprene, polychloroprene, co-polymers of butadiene and styrene, co-polymers of butadiene and acrylonitn'le, polystyrene, linseed oil, rosin, alkyd resins, ester gum, paraffin wax, petroleum jelly,.carnauba wax, microcrystalline Waxes, asphalt, tar, pitch, bitumen and terpene resins, phenol formaldehyde, urea formaldehyde, melamine formaldehyde, resins and polyester resins.

Mixtures of various latices may also be used, for exampledispersions of vinyl polymers or co-polymers with dispersions of butadiene acrylonitrile co-polymers.

In the normal paper making processes, it is usual to suspend fibres by beating for example and to add thereto aqueous dispersions or emulsions of water insoluble fibrecoating substances or fibre-coating substances capable of A coagulant such as alum is then stirred in with the object of breaking the dispersion or emulsion so that the pardispersion and coagulation will not occur until the mixture is heated, for example above 15 C. r

Some of these heat sensitive coagulants decompose on heating to liberate acid and thereby bring about coagulation. Some, very sparingly soluble at room temperature, may be added as a dispersion and then on heatingdissolve and cause coagulation. Some quite solubleat room temperature, becomeless soluble at elevated temperatures. This last mentioned class of heat'sensitive coagulants is particularly suited to the process [of the present invention. This class is referred to herein as a polymeric heat sensitive coagulant and is herein defined as an organic compound containing an ether linkage R-O--R in which R is a polymeric group and R an alkyl or aryl group and is characterised in that it is soluble in Water at a given temperature and becomesinsoluble at an elevated temperature. By the term 5e16- vated temperature is meant that temperature atwhich the solubility in Water of the polymeric heat sensitive coagulant becomes so low that precipitation occursi lA typical example of such a coagulant is polyvinyl methyl other, which is soluble in Water at 20- C. but becomes much less soluble within the temperature range from 30 to 40 C. and is precipitated. a

From one aspect the present invention may. be considered as consisting in adding to a suspension of fibres in water a polymeric heat sensitive coagulant of the kind herein defined and heating the suspension toan elevated temperature whereby the fibres. are conditioned for the subsequent deposition thereon of a water insoluble fibre-coating substance from an' aqueous dispersion of the substance.

From another aspect the invention may be considered as comprising the coating of fibres suspended in water with a polymeric heat sensitive coagulant as herein defined and adding thereto an aqueous dispersionoremulsion of a Water insoluble fibre-coating substance in the presence of an acid or acidic substance or salts of trior polyvalent metal and a protective soap in such proportions and under such conditions of temperature that fthe water insoluble fibre-coating substance is deposited on the fibre in a uniform manner.

The mixture of fibrous material, acid, acidic substance or a salt of a trior polyvalent metal and the tides agglomerate and become deposited on the fibres. heat sensitive'coagulant is howeverheated, then cooled Patented June 7, 1960 V prior to the addition of the aqueous dispersion of water insoluble substance, and re-heated after the addition.

Tho essential feature of the process is the addition of a polymeric heat sensitive coagulant to the suspension of fibres in water and heating to an elevated temperature betore the addition of the aqueous dispersion of water insoluble fibre-coating substance. This is to ensure that coagulation occurs at the fibre and the water insoluble fibre-coating substance is deposited thereon:

. Various fibres both natural and synthetic such as cellulose, wood, jute, hemp, sisal, manila, wool, rayon, nylon, leather, asbestos, glass and mixtures thereof may be treated by the process according to the present inven tion.

A preferred mode of carrying out the process of the invention is as follows:

The fibre .is beaten with water to give a uniform suspension ,which is then treated with acids or acidic Lsubstance or a salt of a trior polyvalent metal such as aluminum sulfate, hereinafter referred to as alum. A polymeric heat sensitive coagulant having the property of becoming insoluble in water at temperatures above 30 .C. for example, polyvinyl methyl ether, is then mixed into the suspension of fibre in water and the whole mixture heated to a temperature above 30 C. with the object of depositing the polymeric heat sensitive coagulant on the fibre. The mixture is then cooled below 30 C. and an aqueous dispersion or emulsion of water insoluble fibre-coating substance containing a suitable protective agent such as anionic or non-ionic soaps stable under alkaline and acid conditions and in the presence of metallic salts, is added. No coagulation of the dispersion takes place under these conditions but on subsequent re-heating above 30 C. the water insoluble fibrecoating substance is deposited on the fibre in a uniform manner.

We havefound that this procedure may be varied in the following ways:

vThe process as previously described can be carried out up 'to the point where the mixture of water, fibre polymeric heat sensitive coagulant is heated to a temperature above 30 C. at which point the particular aqueous dispersion of Water-insoluble fibre-coating substance is added and partial coagulation occurs. It has however been found necessary to cool the mixture and re-heat to a temperature above 30 C. to effect complete deposition.

The process may be further modified by adding the acids, acidic substance or salt of trior polyvalent metal with the aqueous dispersion of water insoluble fibrecoatingsubstance suitably protected by soap instead of adding it to the fibre in the first step of the process.

Although the preferred method results in a more uniform deposition of water insoluble substance on the fibre,

. and is easier to control, the other methods give a'product from which it is possible to form a sheet or mass having latices are readily coagulated by small amounts of acid ized by sodium, potassium or ammonium hydroxides are stable under acid conditlfil s'nnd therefore can be used with acid hutth y are n 'suitabl for. use wit s lts of trior polyvalent metals.

Non-ionic soaps can be used with acids or salts of trior polyvalent metals. A typical example is a fattyalcohol ethylene oxide condensate knownas Lubrol W.

The amount of acid or acids,-acidic substance or trior polyvalent metal used in any of the methods just described can be varied between wide limits. more the amount so used affects the quantity of protective soapto be used and inturn controls the amount of polymeric heat sensitive coagulant required,

The following table shows the range of proportions of these ingredients that can be used with wood fibre, all

7 .parts being dry weight:

whereas some synthetic .dispersions contain considerable amounts of protective agent, included during manufacture, and are not readily coagulated by acid but can be coagulated by metallic salts such as alum.

Again the type of protective soap to be used is influ- "enced by the choice of acid or metallic salt. Anionic soaps derived fromfatty acidsby neutralisation with sodium or potassium or ammonium hydroxide are notsuit- TABLE 1 Wood fibre 100 100 Aqueous Dispersion of Rubber or Resin 5O 50 Alum--. 100 2 Polymeric Heat Sensitive Ooagulant 15 3 Non-ionic Soap (Lubrol W) 10 1 Columns A and B represent the broad limits within which these ingredients may be varied. Furthermore the type of fibre and the particular aqueous dispersion of water-insoluble fibre-coating substance used influences the amounts of the various ingredients required and it is necessary to carry out a series of experiments to determine the preferred amounts. It is found that the best procedure is to startwith a largeamount of alum and use the Example I 5 parts of Wood fibre are beaten into a suspension with 1000 parts of water. This suspension is then acidified to a pH of 3.5 with 20 parts of alum solution containing 20 parts of aluminum sulfate in parts of water. 5- parts of a solution containing 15 parts of polyvinyl methyl ether in parts of water are added to the acidified suspension and the whole is heated to 36 C. with gentle agitation. When this temperature is attained the suspension is cooled down and the following mixture added:

8 parts of an aqueous dispersion consisting of 40 parts of butadiene acrylonitrile co-polymer and. .60 parts of water, 7 V 5 parts of a solution of a non-ionic soap such as Lubrol W containing 10 parts of soap in parts of Water. parts of water.

The suspension is then re-heated to 35 C. with gentle by removal of the supernatant liquor.

Example II 5 parts of ground leather is beaten into a suspension with 1000 parts ofwater. The fibre is detanned by adding .5 part .of ammonia S.G. 880 such that thesuspension acquires a pH 0f7.5. The suspension is fltli l fid i LP Further- 3.5 with a solution of alum containing 20 parts of aluminum sulfate in 80 parts of water.

5 parts of a solution containing 15 parts of polyvinyl methyl ether in 85 parts of water are added to the acidified suspension and the whole is heated to 35 C. with gentle agitation. When this temperature is attained the suspension is cooled down and the following mixture added:

8 parts of an aqueous dispersion consisting of 40 parts of butadiene acrylonitrile co-polymer and 60 parts of water, i

5 parts of a solution of a non-ionic soap such as Lubrol W containing parts of soap in 90 parts of water.

100 parts of water.

The suspension is then re-heated to 35 C. with gentle agitation and the resulting treated fibre formed into a sheet by removal of the supernatant liquor.

Example Ill 5 parts of wood fibre are beaten into a suspension with 1000 parts of water. This suspension is then acidified with 10 parts of alum solution containing 10 parts of aluminum sulfate in 90 parts of water. 2 parts of a solution containing 10 parts of polyvinyl methyl ether in 90 parts of cold water are added to the acidified suspension and the whole is heated to 35 C. with gentle agitation. When this temperature is attained the suspension is cooled down and the following mixture added:

5 parts of natural rubber latex consisting of 60 parts of Hevea rubber and 40 parts of water,

1 part of a 4% solution of formaldehyde in water,

6 parts of a solution of a non-ionic soap, a fatty alcohol ethylene oxide condensate known as Lubrol W containing 1 part of Lubrol W in 99 parts of water,

100 parts water.

The suspension is then reheated to 35 C. with gentle agitation and the resulting treated fibre formed into a sheet by removal of the supernatant liquor.

. Example IV 5 parts of long fibre asbestos is beaten into a suspension with 1000 parts ofwater. This suspension is then acidified to a pH of 3.5 with 20 parts of alum solution consisting of 20 parts of aluminum sulfate and 80 parts of water. 5 parts of a solution containing parts of polyvinyl methyl ether in 85 parts of cold water are added to the acidified suspension and the whole is heated :to 35 C. with gentle agitation. When this temperature is attained the suspension is cooled down and the following mixture added:

6 parts of an aqueous dispersion consisting of 40 parts of butadiene acrylonitrile co-polymer and 60 parts of water. r a 6 parts of solution containing 1 part of Lubrol Win 99 parts of water. 100 parts of water.

I The suspension is then re-heated to 35 C. with gentle agitation and the resulting treated fibre formed into a sheet by removal of the supernatant liquor.

Example V 5 parts of natural rubber latex consisting of 60 parts of Hevea rubber and 40 parts of water,

1 part of a 4% solution of formaldehyde in water,

5 parts of a solution of an anionic soap containing 5 parts of Perminal BX in 95 parts of water,

100 parts of water.

The suspension is then re-heated to 35 C. with gentle agitation and the resulting treated fibre formed into a sheet by removal of the supernatant liquor.

The phrase water-insoluble fibre-coating substance" as used in the specification and claims is intended to include fibre-coating materials of the types and kinds listed in the specification as well as other materials used for coating fibres in aqueous suspension, particularly where the resulting coated fibres are subsequently formed into a bonded material, such as a sheet or board.

We claim:

1. In the method of coating fibres in which a waterinsoluble fibre-coating substance is deposited on the fibres from an aqueous dispersion thereof, the steps which comprise forming an aqueousdispersion of the fibres to be coated and a polymeric heat-sensitive coagulant for the fibre-coating substance comprising a polyvinyl alkyl ether, said polyvinyl alkyl ether being decreasingly soluble in water as the temperature of the water is raised, heating said dispersion to a temperature sufiiciently high to precipitate polyvinyl alkyl ether therefrom with resultant deposition of said polyvinyl alkyl ether on said fibres, and thereafter adding to the resultant dispersion of fibres an aqueous dispersion of the water-insoluble fibre-coating substance.

2. In the method of coating fibres as set forth in claim 1 in which the suspension, after being heated to precipitate polyvinyl alkyl ether with resultant deposition thereof on the fibres, is cooled to a temperature below that at which polyvinyl alkyl ether was precipitated therefrom, and the aqueous dispersion of the water-insoluble fibrecoating substance is added to the cooled. dispersion, and the dispersion thereafter is reheated to said temperature at which polyvinyl alkyl ether was precipitated therefrom.

3. In the method of coating fibres as set forth in claim 1 in which the aqueous dispersion of the fibres is acidified and the aqueous dispersion of the water-insoluble fibre-coating substance which is added to the aqueous dispersion of fibres contains a protective soap.

4. In the method of coating fibres as set forth in claim 1 in which the polyvinyl alkyl ether is polyvinyl methyl ether.

5. In the method of coating fibres as set forth in claim 4 in which the aqueous dispersion containing the fibres and the polyvinyl methyl ether is heated to a temperature of about 35 C. to precipitate polyvinyl methyl ether therefrom.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Yost et al.: TAPPI, vol. 34, No. 1, January 1951, pages 30-38, particularly page 36.

Disselhoif: (Badische Anilinand Soda-Fabrik A.G., Ludwingshafen (Rhine), Germany); Farbe u. Lack 61, 3603 (1955), Chemical Abstracts, vol. 49, 1955;

Claims (1)

1. IN THE METHOD OF COATING FIBRES IN WHICH A WATERINSOLUBLE FIBRE-COATING SUBSTANCE IS DEPOSITED ON THE FIBERS FROM AN AQUEOUS DISPERSION THEREOF, THE STEPS WHICH COMPRISES FORMING AN AQUEOUS DISPERSION OF THE FIBRES TO BE COATED AND A POLYMERIC HEAT-SENSITIVE COAGULANT FOR THE FIBRE-COATING SUBSTANCE COMPRISING A POLYVINYL ALKYL ETHER, SAID POLYVINYL ALKYL ETHER BEING DECREASINGLY SOLUBLE IN WATER AS THE TEMPERATURE OF THE WATER IS RAISED, HEATING SAID DISPERSION TO A TEMPERATURE SUFFICIENTLY HIGH TO PRECIPITATE POLYVINYL ALKYL ETHER THEREFROM WITH RESULTANT DEPOSITION OF SAID POLYVINYL ALKYL ETHER ON SAID FIBRES, AND THEREAFTER ADDING TO THE RESULTANT DISPERSION OF FIBRES AN AQUEOUS DISPERSION OF THE WATER-INSOLUBLE FIBRE-COATING SUBSTANCE.