US1982024A - Treatment of fibrous material - Google Patents

Description

Patented Nov. 27, 1934 UNITED STATES PATENT OFFICE 7 TREATMENT OF FIBROUS MATERIAL No Drawing. Application April 7, 1930, Serial No. 442,464

8 Claims. (01. 18-50) This invention relates to processes for the production of combinations of rubber and fibrous materials such as wood pulp, hemp, cotton, leather, asbestos and other fibres of animal, vegetable or mineral origin and particularly to such combinations where the rubber is in the form of a dispersion or emulsion either naturally occurring or artificially prepared. The present method is also concerned with an improved method for 10 combining rubber and fibres of any sort.

The principal object of the invention is to Drepare a plastic material from natural or artificial dispersions of rubber and fibres which can be formed into sheets without the use of ordina y paper making machinery such-as the so-called Fourdrinier machine, cylinder machines and wet machines but to substitute for these machines calenders or other devices for obtaining relatively thin sheets, and tubing machines, pug mills and molding devices for forming the plastic material into continuous ribbons of anydesired shape, or

molded article such as valves or cups for pumps,

shims for use in the automotive industry, soles and heels for the leather shoe industry and the like.

The invention also includes among its objects the preparation of fibre and rubber combinations by combining latex, either natural or artificially prepared with fibres of any desired length, as

such,.0r fibres that have been hydrated to any degree in an ordinary beating engine and also fibres very much longer than can be handled with the usual paper making equipment and approaching the ordinary length of naturally oocurring fibrous materials such as cotton, asbestos,

etc.

The invention comprises mixing fibrous materials in any type of mixing apparatus such as a Werner and Pfieiderer mixer or the like with either natural or artificially prepared latex in the presence of added protective colloids which tend to stabilizethe latex and to permit of severe mechanical and heat treatment without coagulation of the rubber. In some cases the protective colloids may not be necessary. The fibres used f r the mixture may be either specially prepared by beating in an ordinary beating engine to any desired degree or may be separated in their dry condition by carding, picking or shredding by 0 means of any suitable type of impact grinder or shredding machine and may be fed to the mixing apparatus in either a moistened or dry condition. The type of protective colloid where it is used in the process of this invention depends to a large extent on the end product which is desired and the extent of the mechanical and heat treatment to which the mass is to be subjected during the process and the degree of plasticity required in the resulting mass to permit of sufficient sheeting or molding. In general, there may be added proteins such as glue, casein, vegetable and animal albumens, or a mixture of the proteinous constituents of blood, modified albumens such as protalbinic and lysalbinic acids, protective colloids derived from vegetable sources such as starches, either in the naturally occurring or modified form, such as acetylated starches, saponin and the like, also protective colloids derived from in organic sources such as silicic acid and the freshly precipitated hydroxides of iron and aluminum and the colloidal silicates of iron, aluminum, magnesium, etc., also the soluble or partially soluble compounds of saponifiable organic acids such as oleic, stearic, palmitic, as such, or in the form of natural oils or fats, the resin acids and the like, or any suitable mixtures of the foregoing. It has also been found advantageous in order to promote the mixing of the fibrous materials with the latex and particularly where relatively long fibres are used, to use wetting agents common to the industry such as the sulphonated oils, triethanolamine, sulphonated diphenyl, either as such .or in combination with alkalies or the above mentioned protective colloids.

Heretofore it has been proposed to make combinations of fibrous materials with either natural or artificially prepared latex by incorporating the latex and fibrous ,pulpwith or without the addition of protective colloids in an ordinary paper making beating engine and then to add coagulants in such form as to precipitate the rubber upon the fibres and cause the substantially complete separation of the aqueous portion of the latex from the rubber and the latex.

The preferred method of carrying out the invention is as follows:

The fibrous material such as cotton is placed in a beating engine with water in the usual way and beaten to the desired condition. The beaten fibre is then removed from the beater by any suitable means and placed in a drainer so as to remove the excess water. Any further quantity of water may, if desired, be removed by centrifuging in any of the standard type basket centrifuges or by pressing at low pressures between the platens of a mechanical or-hydraulic press or by any other suitable method. The removal of the water may also be accomplished by running the pulp over a so-called wet machine where the'resulting sheet built up on the pick-up 1 or making roll will contain from to 70% moisture and this sheet may be further dehydrated by pressing as above. Enough moisture should be retained in the sheet to permit ready breaking up of the fibres in the mixer. The wet mass resulting from this operation may then be placed in a W & P mixer or any suitable type of mixing or kneading machine or it may be placed in a Banbury mixer, well known in the rubber industry, or in any special type of beating engine designed to handle pulp of high fibre content. After the wet mass of fibre has been disintegrated in the above mentioned mixing or kneading machine, alkali, preferably in concentrated solution so as not to unduly increase the water content of the fibrous mass, may be added to aid in preserving the stability of the later added dispersion of rubber. Any alkali such as ammonia, caustic soda or caustic potash may be used. The resulting mixture should have an alkalinity corresponding to pH 8 to pH 12 and preferably between pH 10 and pH 12. Any of the above mentioned protective colloids may then be added to the mass in the mixer or may be added to the latex before it has been added to the mixer. The amount of protective colloid required depends on the nature of the fibre used, the nature of the protective colloid itself and the properties desired in the finished product. If animal glue is used as the protective colloid and the desired finished product is to be flexible, the proportion of glue on the weight of the finished batch should be between the limits of approximately 5 and approximately 15% depending on the grade of glue used, it being recognized that the higher grades of glue are more flexible than the cheap- 61' grades. After the protective colloid has been added to the mass in the mixer the latex is added in a proportion to give the desired rubber content in the finished product. As stated above the protective colloid may be mixed with the latex before placing in the mixing machine. Either before or after the latex is added any desired compounding materials may be added such as pigments to give color, stiffness, or density to the finished product, or softeners to give plasticity or moldability either to the mass before sheeting or molding or in the finished product. The materials should be thoroughly mixed. The softeners may be of two classes-first, softeners such as glycerine, triethanolamine, diethylene glycol which tend to soften and render more flexible the glue used as protective colloid, and sec- 0nd, softeners such as asphalt, oils, pine tar,

pitches, waxes and the like which have a softening action on the rubber contained in the mixture. If it is desired to have the finished product waterproof, compounding materials of the heavy metal soap type such as aluminum stearate, oleate, palmitate and resinate may be added. Also some of the above mentioned rubber softeners such as asphalt have been found to be beneficial in this condition.

The mixing or agitation is carried on for a sufficient length of time to give a uniform mixing of all the ingredients. Owing to the fact that an appreciable amount of water has been added to the batch with the addition of the protective colloid and the latex, the mass at this stage would have a comparatively high fluidity and if passed between the rolls of a calender for sheeting or through a tubing machine or other molding device an appreciable amount of water would separate from the mass, carrying with it a portion of the protective colloid and latex and other added materials desired in the finished product. In order to increase the viscosity of the mass and to prevent separation of water and the consequent loss of the desired compounding ingredients, it is preferred to thicken the mass to a stage where it has a dough or putty-like consistency and can be calendered into a smooth and homogeneous sheet or tubed and molded into various shapes. The viscosity of the mass may be increased to the desired point in one of several general ways depending on the nature and amount of protective colloid used. In the case of the glue used in the above example, increase in viscosity or thickening may if desired be brought about by the evaporation of part of the water in the mixture by means of applying heat in any desired manner to the mixing apparatus. The application of heat, however, is less preferred on account of its depolymerizing and coagulating effect on the rubber contained in the batch and also because ordinary protective colloids, particularly of the proteinous type, coagulate at relatively low temperature. For example, most proteins can be coagulated from solution on simply heating to approximately 65 C. The use of temperatures below this necessitates extremely long periods of time to carry out the required evaporation. In lieu of heat, or with the use of only a slight amount of heat evaporation, it is preferred to increase the viscosity by chemical means such as the addition of gel-forming agents of the inorganic type or the formation of these gel-forming agents in situ. The addition of from about 2 to about 8% of silicic acid formed in situ by adding a solution of sodium silicate and boric acid to the mixture has been found to give thickened masses which may be readily formed into sheets by calenders or any other shapes by tubing or molding. The freshly precipitated hydroxide of aluminum and iron have also been found effective in this connection. These gelforming agents may be used with or without the use of the other protective colloids.

Another method of thickening the mass or obtaining gel formation without the evaporation of appreciable amounts of the water used in preparingthe mixture involves the use of protein precipitants or gelling agents, such as formaldehyde, polyhydric phenols, organic color bases and such inorganic compounds as ferric chloride and acetate, mercuric chloride, basic lead acetate, basic aluminum acetate, phospho tungstic acid. It has also been found that the use of zinc acetate and in some cases zinc oxide in finely divided condition promotes the formation of gels containing comparatively large amounts of water when used in connection with proteinous protective colloids. These protein-precipitating gelling agents, if desired, may be used in connection with any of the above mentioned processes. It is necessary to use considerable care in adding these protein-precipitating gelling agents, since under ordinary circumstances they would cause precipitation or coagulation of the protective colloid and rubber from the latex. However, by adding them very slowly, thoroughly mixing each portion before the addition of more of the agent, it has been found that a very definite thickening action results and that the mass in the mixer attains the consistency of heavy dough or putty which can be easily calendered in sheet form or molded as described above. It has also been found advantageous to heat the mass in the mixer to a temperature not exceeding 45 to 50 C. in order to promote the thickening action of the above agents. As stated above, however, care must be taken not to carry the temperature appreciably above 50 C. because there is danger of irreversibly coagulating both the protective colloid and the rubber.

The plasticmass resulting from the above procedure may be of almost any viscosity desired ranging from a material which will easily flow and may be spread out by means of rollers or knives on endless metallic belts, screens and the like to form sheets which may be subsequently dried and finished by calendering or pressing, if desired, to products with a very high viscosity which are well adapted to forming into sheets by means of calendering or tubing or forming into ribbons or other shapes by means of the ordinary tubers of the rubber industry or pug mills such as are used in the ceramic industry, or can be formed into any desired shape by specially constructed mold. Thus the thickened mass may be shaped into any desired form, as by a sheeting, calendering, tubing, or molding operation or the like, and dried to the final product. The products resulting from this process are different from those obtained'by the ordinary milling of compounding materials and crude rubber because it is possible to incorporate much higher percentages of fibrous materials in the compound and to use fibres of much greater length than it is possible to accomplish by the regulation milling operation. Also the effect of the various compounding ingredients used together with the vulcanizing agents is much more pronounced in these compounds because the process gives a much more uniform distribution and dispersion of these compounds throughout the mass.

While the invention has been described with particularity by way of illustration it is not intended so to limit the invention inasmuch as many variations in the details thereof may be made without departing from the principles and spirit of this invention, the scope of which is set forth in the following claims.

Having thus described our invention, what we claim and desire to protect by Letters Patent is:

l. A process for the manufacture of fibre and rubber combinations for molding, sheeting, tubing and like operations which comprises introducing an aqueous dispersion of rubber and fibrous material into a mixer and uniformly mixing the same, and evaporating water from the same to thicken the mixture without substantial coagulation of the rubber therein.

2. A process for the manufacture of fibre and rubber combinations for molding, sheeting, tubing and like operations which comprises introducing an aqueous dispersion of rubber and fibrous material into a mixer and uniformly mixing the same, and thickening the mixture by the addition of an inorganic gelling agent without substantial coagulation of the rubber therein.

3. A process for the manufacture of fibre and rubber combinations for molding, sheeting, tubing and like operations which comprises introducing an aqueous dispersion of rubber and fibrous material into a mixer and uniformly mixing the same, and thickening the mixture by the addition of an inorganic gelling agent and evaporation of water from the mixture without sub stantial coagulation of the rubber therein.

4. A process for the manufacture of fibre and rubber combinations for molding, sheeting, tubing and like operations which comprises introducing an aqueous dispersion of rubber and fibrous material into a mixer and uniformly mixing the same, and thickening the mixture withthe aid of chemical means and heat evaporation without substantial coagulation of the rubber therein.

5. A process for the manufacture of fibre and rubber combinations for molding, sheeting, tubing and like operations which comprises introducing an aqueous dispersion of rubber, fibrous material, and a protective colloid into a mixer and uniformly mixing the same, and thickening the mixture by the addition ofv an inorganic gelling agent without substantial coagulation of the rubber therein.

6. A process for the manufacture of fibre and rubber combinations for molding, sheeting, tubing and like operations which comprises introducing an aqueous dispersion of rubber, fibrous material, and a protective colloid into a mixer and uniformly mixing the same, and thickening the mixture by evaporating water from the same without substantial coagulation of the rubber therein.

7. A process for the manufacture of fibre and rubber combinations for molding, sheeting, tubing and like operations which comprises introducing an aqueous dispersion of rubber, fibrous material, and protein material into a mixer and uniformly mixing the same, and thickening the mixture with the aid of chemical means and heat evaporation without substantial coagulation of the rubber therein.

8. A process for the manufacture of fibre and rubber combinations for molding, sheeting, tubing and like operations which comprises introducing an aqueous dispersion of rubber, fibrous material, and protein material into a mixer and uniformly mixing the same, and thickeningthe mixture by the addition of an inorganic gelling agent and evaporation of water from the mixture without substantial coagulation of the rubber therein.

REED P. ROSE. ALLEN F. OWEN.