US3808091A - Method for producing synthetic paper - Google Patents

Abstract

Synthetic paper is produced by adding a dispersion medium to a polyolefin slurry to prepare an emulsion, jetting said emulsion under an autogenous or higher pressure, and collecting and compressing the jetted fibrous paper material. The product is homogeneous and smooth and well adapted for printing and writing.

Description

United States Patent [191 Aoki et al.

[ METHOD FOR PRODUCING SYNTHETIC PAPER [75] Inventors: Kazuharu Aoki, Kyoto; Tadami Kamaishi, Otsu, both of Japan [73] Assignee: Toray Industries, Inc., Tokyo, Japan [22] Filed: Apr. 28, 1971 [21] App]. No.: 138,067

[30] Foreign Application Priority Data May 4, 1970 Japan 45-37483 June 23, 1970 Japan 45-54014 [52] US. Cl. 162/157 R, 264/13 [51] Int. Cl D2111 5/00 [58] Field of Search 162/146, 157 R; 161/247; 264/13, 14, 91

[56] References Cited UNITED STATES PATENTS 2,999,788 9/1961 Morgan 162/157 R [451 Apr. 30, 1974 3,561,003 2/1971 I Lanham et al 264/13 3,342,921 9/1967 Brundige et 3.1....

3,617,438 11/1971 Nakao 162/157 C OTHER PUBLICATIONS Reich, Polymerization by Organometallic C0mpounds, (1966), p. 243.

Primary Examiner-S. Leon Bashore Assistant Examiner-Peter Chin 57 ABSTRACT 18 Claims, 6 Drawing Figures PRIOR ART PRIOR ART INVENTORS. KAZUHARU AOKI TADAMI KAMAISHI ATTORNEYS.

METHOD FOR PRODUCING SYNTHETIC PAPER The present invention relates to a method for producing synthetic paper, more particularly a special fibrous paper material containing a polyolefin.

Heretofore, various synthetic papers have been made. One is a film paper obtained by making the surface of a film microporous with capacity for absorbing ink but, at the same time, opaque by means such as pressing with an uneven surface, foaming, treating with chemicals, swelling, introducing an inorganic compound therein and extracting one component of the blend. The foregoing combination was disclosed in published German Pat. No. 1,954,477.

According to another disclosure of the prior art,

. paper may be obtained from staple synthetic fibers in a manner similar to making paper from pulp (British Pat. No. 1,188,322).

According to another prior art disclosure, split fiber paper is prepared using a material obtained by slitting a film into the fibrous state (French Pat. No. 1,548,246). Further, a spun bond paper may be obtained by directly collecting a melt spun fiber in a sheetlike manner [W. Hearle, Skinners Rec, 39, 647 (1965)].

According to other disclosures of the prior art, a plexifilament paper may be obtained by jetting a polymer solution directly in a filamentary state and collecting it in a sheetlike form [W. l-learle, Skinners Rec., 39, 647 (1965)], and a fibrid paper may be obtained by making a paper from fibers produced by extruding a polymer solution while shearing into a coagulating bath of said solution (U. S. Pat. No. 3,382,305).

Of these synthetic papers, the film paper, the synthetic fiber paper and the split fiber paper have shortcomings in that their thicknesses are not uniform, their surfaces are uneven and their basis weight or fiber distribution over the whole sheet are not uniform. Accordingly, because of localized differences, deviations of appearance, luster and ink absorbability are brought about. The spun bon'd'paper and the plexifilament paper have shortcomings in that patterns due to the presence of continuous filaments appear on the surface; when said patterns are flattened, the corresponding portions of the surface are compressed in the flat state and look lustrous; these papers lack uniformity. Further, in the case of the'fibrid paper, because the constituting fibrid is produced by shearing of a liquid, it is not possible to obtain sufficient molecular orientation for purposes of strength, and a paper high in tenacity cannot be obtained.

Japanese Pat. application Ser. No. 7728/1969 proposes the idea of shearing a polymer solution by means of a high speed gas stream to convert the solution into fibers, collecting the fibrious matter and using it as a filter. However, according to this method, although the resulting fiber is not branched, it is suitable when used as a filter. However, the non-branched fibers are not intertwined enough for use, and the paper product lacks uniformity.

Again, Japanese Pat. application Ser. No. 4471/1963 discloses spraying a resin emulsion to obtain a powder;

however, this method does not produce a paper material having fiber intertwining properties.

An object of the present invention is to provide a synthetic paper which is free of the shortcomings of the aforementioned conventional synthetic papers and excellent in mechanical properties, intertwining characteristics, uniformity and smoothness.

Another object of the present invention is to provide a method for producing a synthetic paper which is free of surface patterns, rich in printability and excellent in luster, appearance and hand.

Other objects of the present invention will be made clear from the following description.

According to the present invention,'the aforementioned objects are attained by:

1. preparing an emulsion from (A) a slurry consisting of a polyolefin and a solvent from said polyolefin, and (B) a dispersion medium having a boiling point at a pressure less than 1 atm. which is lower than the melting point (at a pressure less than 1 atm.) of said polyolefin and which is insoluble or nearly insoluble in said solvent and preferably not reactive with said solvent, wherein the volume of said dispersion medium (B) present in the emulsion is larger than the volume of the slurry (A),

2. jetting said emulsion under at least an autogenous pressure obtained by heating said emulsion from a nozzle to thereby make a fibrous paper material, and

3. collecting said fibrous paper material and compressing the same.

In the practice of the present invention, use of a slurry obtained by solution polymerizing an olefin monomer is advantageous because of the continuity of its steps; it is preferable for purposes of sheet formation in a later step that the solvent for the polyolefin in this case should have a boiling point which is lower than the melting point of said polyolefin.

In the present invention, a specified dispersion me dium is added to such a slurry to prepare an emulsion. It is preferable for obtaining a paper material having good intertwining properties that the particle size of the slurry in the emulsion be about 3 400 microns. And by jetting such an emulsion from a nozzle at a high temperature under a high pressure, a branched paper material having good intertwining properties is obtained.

Hereinbelow, specific details of the present invention will be described.

Polyolefins as used in the practice of the present invention have a fiber-forming capacity, are obtained by polymerizing olefin monomers and may be straight chain or branched polymers.

As examples of the olefin monomers, there are infor example, ethylene, propylene, butene-l 3- methylbutene-l, 4-methylpentane-l, hexen e l s tyrefiejoctene-l and decaTefielihowever, said monomers are not limited thereto. It goes without saying that these olefins may be copolymerized with hitherto known copolymerizable monomers. However, in this case it is necessary that an olefin should be present in an amount of at least 50 percent by weight.

Various polymerization catalysts may be used. Generally a Ziegler-Natta type catalyst is used; however, when the monomer is ethylene, a compound having a radical, a transition metal oxide, a transition metal and a halogen compound are used as catalyst.

The Ziegler-Natta type catalysts used are generally transition metal compounds, metals of Groups 1 TV of the Periodic Table, organometallic compounds of such metals or hydrides of such metals. However, for increasing the crystallinity of the polymer produced, an

electron donor compound, a proper halide or a metal salt may be added as a third component.

The olefin may be.present alone or as a mixture of at least two components. However, in the case of copolymerization of at least two components, in order that the composition of the polymer produced may be constant, the components may be equally randomly copolymerized or the monomer components may be supplied with each other and block copolymerized. Again, homopolymerization, random copolymerization or block copolymerization may be combined in one polymerization step. The polymer produced is generally crystalline and the catalyst is selected accordingly.

In the practice of the present invention, polyethylene, polypropylene or a copolymer of the two is especially preferable. Further preferable is polypropylene or a blend or graft copolymer of polypropylene and polyvinyl alcohol, polyvinyl acetate or polyacrylic acid in an amount not exceeding 30 percent of the polypropylene.

The slurry used in the practice of the present invention may be prepared by dissolving or swelling a polyolefin in a solvent. However, it is preferable from the procedural viewpoint to prepare the slurry by polymerizing an olefin monomer in a solvent which is capable of dissolving or swelling the polyolefin at a jetting temperature.

As examples, the following solvents may be used alone or in admixture:

(I) water; (2) hydrocarbons including saturated hydrocarbons having five l 1 carbon atoms such as, for example, hexene, heptane, acetone, nonane, decane, cyclohexane, methyl cyclohexane, decalin and petroleum ether; as aromatic hydrocarbons benzene, toluene, xylene and p-cymeme; as unsaturated alicyclic hydrocarbons tetralin, a -pinene and turpentine oil; (3) as halogenated hydrocarbons: aliphatic halogenated hydrocarbons such as, for example, methylene chloride, chloroform, bromoform, carbon tetrachloride, ethyl bromide, dichloroethane, ethylidene dichloride, tetrachloroethane, pentachloroethane, dichloroethane, trichloroethylene, tetrachloroethylene, isobutyl chloride and isoamyl chloride; as aromatic halogenated hydrocarbons chlorobenzene, bromobenzene and odichlorobenzene; (4) as monohydric alcohols aliphatic alcohols such as methanol, ethanol, isopropanol, butanol and amyl alcohol; aromatic and alicyclic alcohols such as, for example, cyclohexanol and methyl cyclohexanol; (5) as ethers aliphatic ethers such as, for example, isopropylether and butylether; aromatic and alicyclic ethers such as, for example, anisole, dioxane and furfuryl alcohol; (6 as ketones aliphatic ketones such as, for example, acetone, acetone oil and methylethyl ketone; aromatic ketones such as, for example, cyclohexanone; (7) as esters, fatty acid esters and monobasic aromatic carboxylic acid esters such as, for example, methyl acetate, ethyle acetate, propyl acetate, butyl acetate, amyl acetate, ethyl propionate, butyl propionate, isoamyl propionate, ethyl butyrate and butyl butyrate; dibasic acid and tribasic acid esters such as, for example, diethyl carbonate; hydroxy acid esters such as, for example, ethyl lactate and ethyl oxyisobutyrate; and (8) polyhidric alcohols and derivatives thereof such as, for example, a -butylene glycol.

In terms of boiling point, solvents having a boiling point from about 38 C to about 192 C are used in many cases. In the present invention, hexane, heptane and methylene chloride are preferably used.

In the practice of the present invention, a solvent which is capable of substantially uniformly dissolving a polyolefin at a temperature higher than the boiling point under atmospheric pressure of the solvent, under an autogenous vapor pressure or a higher pressure than that may be selected. In a step to be mentioned later, it is preferable that the boiling point of the solvent be lower than the melting point of the polyolefin.

The concentration of the polyolefin based on the solvent is preferably 5 percent by weight (although it may vary depending upon the specific gravity, it corresponds to about 38 percent by volume). For example, in case the concentration is smaller than five percent, the amount of the product is small and its production is not efficient; on the contrary, when the concentration is higher than 70 percent, due to the high viscosity the fiber is unlikely to be transformed at the time of being jetted from the nozzle. In addition, the emulsion is apt to be condensed, and this is not preferable. The condensation of the emulsion results in making the jetted fiber continuous, in which case it becomes similar to the so-called plexifilament. This is because the higher the concentration of the polyolefin based on solvent, the higher the viscosity of the polymer. The more highly viscous the polymer, the more the polymer becomes apt to condense.

An emulsion used in the practice of the present invention is obtained by adding a dispersion medium to a slurry prepared in such a manner as is mentioned above. The dispersion medium is insoluble or hardly soluble in the solvent (preferably not reacting with the solvent) and the boiling point of said medium is lower than the melting point of the polyolefin.

As examples of the dispersion medium, water and alcohols having one 10 carbon atoms as well as mutually insoluble solvents selected from the list provided in this specification may be cited. A mixed dispersion medium may be used; especially water or a mixed liquid consisting predominantly of water is advantageous.

It is preferable to add the dispersion medium in an amount of 30 2,000 percent by volume to the slurry; an amount not less than 200 percent by volume is preferable.

Unless a dispersion medium in an amount of at least 100 percent by volume of the slurry is added to the slurry, a so-called continuous fiber is apt to be formed. This is because the slurry becomes a dispersion medium on the contrary or condensed. In any event this is not preferable. When expressed in terms of percentage by weight, 10 percent by weight of the slurry is preferable (in percentage by volume, the figure may vary depending upon the combination of the respective specific gravity values; however, it is about 7 percent by volume).

In case the ratio of the dispersion medium to, the slurry is excessive, the jetted material assumes the form of finely divided particles and this results in the production of fibers which are very short and have poor intertwining properties when formed into paper. Moreover, the proportion of polymer in the resulting jetted material is too small and the fiber production rate is too low.

If desired, it is possible to add pigments, stabilizers, antistatic agents, binders, sizing agents or other substances to the slurry provided the added amount is in a proper proportion and does not interfere with the proper functioning of the present invention. They may be added to the liquid in advance, to the slurry, to the emulsion, or in other ways.

The emulsion is thermodynamically unstable and always shows an inclination to condense to reduce the surface free energy. Accordingly, formation of an emulsion is a competitive reaction between condensation and redivision of the dispersed phase. Accordingly, in the present invention also, it is beneficial to cover the surface of the dispersed phase with a dispersion stabilizer, for example, a surface active agent, preferably a polymer of the olefin series and a surface active agent for the emulsion to stabilize the dispersion.

As specific examples of suitable surface active agents, there are (l) anionic surface active agents, for example, carboxylic acid salts, sulfuric acid esters, sulfonic acid salts and phosphoric acid esters; (2) cationic surface active'agents, for example, amine salt types and quaternary ammonium salt types: (3) anionic and cationic surface active agents, for example, amino acid salts and betaine types; and (4) non-ionic surface ac-. tive agents, for example, polyethylene glycol types and polyhydric alcohol types. As percentage to be added, 0.01 percent by weight based on the slurry is preferable.

However, at high temperature, the performance of the dispersion stabilizer added to the emulsion is reduced in many cases. Accordingly, it is preferable to facilitate redivision even when the dispersed phase is condensed, and always to include'a redividing operation for the dispersed phase, such as stirring. Generally, because a polymer melt has a high viscosity, being viscous, especially in case the dispersed phase is a polymer only, particles of the dispersed phase tend to condense due to contact with other particles of the dispersed phase.

In practice of the present invention, it is possible to produce a fibrous paper material by jetting the soprepared emulsion or an emulsion while forming the same from a nozzle of a proper shape at a temperature higher than the boiling point of the solvent and preferably lower than the melting point of the polymer under an autogenous pressure or higher pressure.

If the emulsion is jetted at a temperature lower than the boiling point of the solvent, then upon being jetted from the nozzle the solvent is not gasified and is not removed from the polymer. Therefore the molecular orientation of the polymer is not fixed, but the polymer tends to be saturated. The reason why it is preferable that the jetting temperature be lower than the melting point of the polymer is the same. Namely, in the emulsion before it is caused to be jetted, the polymer is dissolved or swollen in the solvent. When it is caused to be projected through the jet nozzle, the molecules are oriented due to a shearing type action in the nozzle. However, when the emulsion is set free from the nozz'le, the jetted stream expands, losing its kinetic energy and tends not to receive the shearing action. When the boiling point of the solvent and the melting point of the polymer are lower than the jetting temperature, the oriented state of the polymer received in the nozzle is fixed because the solvent is gasified upon being jetted from the nozzle. However, when the boiling point of the solvent is higher than the jetting temperature, the polymer is naturally cooled as a solution or a swollen mixture in the solvent. Because the speed of this cooling is lower than the relaxing speed of the molecular orientation, the molecular orientation naturally becomes relaxed. Even when the melting point of the polymer is lower than the jetting temperature, when the solvent is gasified at the time of jetting, the solvent is cooled to a temperature below its melting point due to the heat of evaporation; therefore, it does not matter in many cases.

Heating of the emulsion may be carried out inside a sealed container having a nozzle or spinneret (i.e., autoclave) and it is normally carried out at a temperature in the range from the dissolving temperature of the polymer in the solvent (normally above 100 C) to 280 C. A temperature at least 30 C higher than the boiling point of the solvent is preferable.

At a temperature lower than 30 C above the boiling point of the solvent, it becomes difficult to obtain a fibrous structure having a fibrillated inner structure as in the present invention. A fiber having a filled crosssection, and densely packed withpolymer only, is apt to be produced.

(The dissolving temperature of the polymer may conveniently be measured as follows: 15 cc of the polymer solution containing 10 percent by weight of the polymer is prepared, which is sealed in an ampoule, heated and cooled inside an autoclave and the dissolving temperature is measured according to whether the polymer has been dissolved or not).

Jetting of the emulsion from the nozzle is carried out under an autogenous pressure brought about by heating or a higher pressure.

Because a satisfactory jetting temperature of the emulsion is obtained as above, the nozzle need not be positively heated.

In the present invention, it is not preferable to perform the emulsion jetting step by utilizing the principle of a so-called sprayer, blowing a high speed gas such as air upon an opening for flowing out the polymer emulsion and jetting the emulsion using, for example, a spray gun. At the time of jetting, even when the molecules are oriented by shearing action inside the nozzle, the jetted stream expands, losing kinetic energy and not receiving the desired shearing strength. Because the solidifying speed of the polymer is lower than the relaxing speed of the molecular orientation, naturally the molecular orientation is relaxed and the resulting material is unsatisfactorily weak.

, However, these means may be used together provided conditions are controlled in a manner not to obstruct the effect of the present invention.

When a fibrous paper material is produced by the foregoing method, the shape and type of nozzle are not important because the size and length of the paper fibers produced are determined by the particle size of the dispersed phase of the emulsion. In contrast, in a method involving releasing a solution or a melted solution, since the form, size and length of the resulting to blockage by dust, while when the diameter is larger than 2 mm, the jetted materials tend to become intertwined with each other causing collection deviation. A

ratio of length to diameter of the nozzle of 0.5 200 is often used; however, in the present invention there is no such limitation.

In order to produce a fibrous paper material according to the present invention, it is preferable to adjust the particle size of the emulsion to 3 400 microns. If the particle size is smaller than 3 microns, the jetted material is similar to powder because the particle size is too small. When the particle size is larger than 400 microns, the jetted material tends to be continuous and becomes a plexifilament.

The atmosphere into which the emulsion is jetted is not particularly critical, but conditions are preferred under which at least the solvent or the dispersion medium evaporates and solidification of the polymer can be carried out promptly. Normally, the emulsion is jetted into air at room temperature under atmospheric pressure. However, it may be jetted under a reduced pressure. If the solidification of the polymer is not carried out promptly, the orientation of the fibrous paper material jetted from the nozzle is relaxed.

Specifically, according to the present invention, when the dispersion medium and/or the solvent is gasified and at the same time the polymer is solidified because of the attendant reduction of the temperature, the polymer expands when the dispersion medium and- /or the solvent is gasified, stretching the polymer which is going to be solidified, thus making a fibrous paper material in which the molecules are oriented.

The majority of the fibrous paper material so obtained consists of fibers having a size of 10 1,000 microns and a length of 50 25,000 microns, the inside of the respective fiber is a structure in which fibrils, ribbons or films whose diameter or thickness is not more than 10 microns are assembled or dispersed integrally in three dimensions, and which may be compressed to produce a flat cross-section.

If the size of the paper material of the present invention is less than 10 microns and the length of said material is less than 50 microns, this is not preferable because the tenacity of the synthetic paper produced as a result is weak. In fibrid or natural pulp, microfibrils having diameters of less than 10 microns stretch outwardly from the center and the microfibrils have a plurality of branches (diverging structures). In contrast, the paper material of the present invention has a plurality of fibrils inside; however, the number of fibrils projecting outwardly is small (converging structures). When shown schematically, a typical example of the former appears in FIG. 1 and of the latter in FIG. 2.

In the diverging structure of FIG. 1, divergent microfibrils are mutually intertwined, and the paper strength is developed accordingly. In contrast, in the converging structure of the present invention, the paper strength is developed by inter-twining of the paper as a whole in a three-dimensional manner and by contact with the surfaces of the paper material. Accordingly, a length and a width greater than some dimensions of the paper material are necessary. Next, because conventional paper materials other than plexifilament have filled crosssections, in order to increase the areas of the surfaces that come into contact with each other and develop the strength of the paper as well as obtain a paper having a smooth surface, it has been necessary to provide a thin fiber having a diameter of less than 10 microns. Because the cross-section of the paper material of the present invention consists of a bundle of fibrils, ribbons or films, the cross-section may be freely transformed by an outer force. Accordingly, a paper is produced whose surface is smooth and in which the mutually contacted surfaces are large. When shown schematically, these become FIGS. 3 and 4. FIG. 3(a) is a cross-section of conventional paper material other than a plexifilament and FIG. 3(b) shows a product obtained by pressing the same. FIG. 4(a) is a cross-section of the paper material of the present invention, and FIG. 4(b) shows a product obtained by pressing the same.

When the size of the paper material of the present invention exceeds 1,000 microns, even when the material is pressed, it cannot become completely flat and it is very difficult to produce a paper whose surface is smooth. Also, because the paper material does not tend to be soft and tends not to be freely intertwined, the paper tenacity becomes low. Again, the appearance of the paper becomes similar to that of a natural paper wherein fibers are bundled, namely, a Japanese paper. Next, it is not desired if the length of the paper materials exceeds 25,400 microns, because of behavior substantially similar to that of a continuous fiber, viz. a plexifilament. In case of length of the paper material is less than 50 microns, there is less intertwining and the paper tenacity is reduced.

In case the thickness of fibrils, ribbons or films constituting the inside of the paper material exceeds microns, the surface unevenness of the resulting paper increases, the feel of the resulting paper is rough and undesirable. Again, the paper material is not desirably soft and not intertwined.

The process for producing paper material of the present invention may use a coarse screen when the material is made into paper, and as compared with fibrid and pulp, said material is superior in terms of the paper making efficiency and conservation of the screen.

As will be seen from these explanations, a threedimensionally intertwined paper may be made from the paper material of the present invention. Accordingly, the material becomes a paper having a tenacity of at least 0.2 kg/cm by such means as pressing without using an adhesive. The reason why the paper material of the present invention tends to be threedimensionally intertwined as compared with other paper materials is because the cross-section is not a filled one, because the paper material is soft and because a coarse screen such as 10 mesh may be used for making a paper; the stream of liquid and gas used in making the paper flows in a direction penetrating the screen (i.e., in the direction of the thickness of the paper).

In the practice of the present invention, it is possible to make a paper from the paper material obtained by the aforementioned method in the same manner as from pulp. However, it is also possible to blow the jetted paper material directly on a porous collecting surface such as a wire netting, collect the material and compress the same to make a synthetic paper.

A very simple method is to make a paper from fibrous sheets collected on wire transfer netting (e.g., on a conveyor belt) on a normal paper making net. However, the paper material may be jetted not only on the wire netting, but also directly on or in a fluid like water; thereafter the jetted paper material may be hit and smashed, or another component may be added and then a paper may be made therefrom. Again, the paper material may be blown on a film to make a laminated paper or collected on another flat plate. As occasion demands, a natural pulp or a synthetic fiber may be properly blended in.

The pressure for compressing the collected paper To the so-obtained slurry, water in varied amounts as shown in Table 1 was added, further, 1 percent by weight, based on the polypropylene, of sodium dodecylbenzene sulfonate was added to prepare an emulun isotactic polypropylene having a viscosity of 4.0. The percentage of this polypropylene in the slurry was 30 percent by weight.

The weight and area of a test piece was measured and it was expressed as the weight per unit area so determined.

material is normally lO g/cm 100 kg/cm and the 5 sion. paper material may be heated at 50 200 C concur- This emulsion was heated to 160 C with stirring inrently with or before this compression. side a steel autoclave having an internal diameter of 18 Besides, in the present invention, it is possible to mm and an internal depth of 100 mm (the particle size c y Out Calender p g, h treatment, embOSS- being about 5 microns). Subsequently, when a nozzle ing treatment, surface coating, re-compression, colorhaving a diameter of 0.8 mm was left open, a fibrous ation, g, heat Sealing and p g on t a paper material having a diameter of about 100 microns resin liquid. and a length of 10,000 microns was jetted under an au- The paper produced by using the paper material of togenous pressure (about 16 atmospheres). the present invention has the following characteristics 1 Thi fib s paper material was soft like a sponge and as compared with the conventional synthetic papers: h i was b d d r a mi r s o it was found 1. The surface is smooth and free from the fiber patthat a plurality of fine fibers having a size of about 8 miterns as seen in a Japanese paper or a plexifilament pacrons was asse -nbjedin a re tjgulatgdatate M1 per. This fibrous paper material was collected on a 100 2. The thickness is uniform. imesh stainless steel wire netting at a distance of 30 cm 3. The surface tenacity of the paper is high due to 20 *in sheet form. three-dimensional intertwining. The tear feeling when Thereafter, when compressed air was blown from the the paper is torn is like that of a fibrid paper which is 1 back surface of the wire netting, a sheet-like paper maless resistant and not like the tear feeling of a film, but terial was peeled off from the wire netting. because the fiber is thick and tenacious, the resistance This paper material was inserted between two sheets at the time of tearing'is large and felt discontinuously. of filter paper, lightly squeezed and dried; thereafter it Accordingly, when the paper is torn up a vibrating feelwas pressed (40 glcm by an iron at 115 C for 5 mining is imparted to the hand and the feel is similar to that utes. of a natural paper. When the cross-section of a synthetic paper obtained 4. The fibrous paper material is lower in sieve passing by said ironing treatment was observed under a micro property than a fibrid. Accordingly, because a more scope, it was recognized that not all fine fibers were coarse screen may be used upon making a paper, effiparallel to the paper surface, but some fine fibers faced ciency is realized from the viewpoint of removingwain the direction of the thickness and they were interter, and the screen is free from blocking and conservatwined three-dimensionally. The characteristics of the tion of the screen is achieved. synthetic, papers obtained were shown in Table 1. In 5. The paper may be made by a dry method, and at- Table 1,Comparative Examples wherein the amount of tentive control of the fiber form is unnecessary (in case the dispersion medium was small and large were shown of a fibrid, the permissible range of the form is narrow). at the Same time.

TABLE 1 Percentage of the cantidispersion medium lever hang I Basis Apparent Elonga- (by (by length weight density Tenacity tion Example volume) weight) Jetted state (cm) (flm) (glee) (kglcm (percent) Cements Comparative 0 0 Contmuousffiber was dis- 7.8 270 0.48 3.6 218 Lon fibers were embossed, reexample 1. su ting in non-uniform luster. Comparative 10 8.4 260 .42 3.3 232 Do.

example 2.

200 8.0 270 .54 3.2 7 Texture uniform. 500 5.2 270 .68 2.8 4 Do. 1.000 1.430 ..do.. 4.6 200 .72 1.3 3 Do. Comparative 6,000 8,580 Finely divided particles 200 .L Intertwining property lacking. example 3. were discharged. Even when paper-making was attempted, the material could not be peeled off the papermaking net.

The fo llowing examples more specifically illustrate The following measuring methods were used in conthe present invention; however, the present invention nection with the examples: is not limited by these examples. 1. 45 cantilever hang length (Pierce tester method):

lkAMPLES 1 3 if 160 A 1.5 cm wide and 15 cm long test piece was made H v v to project from a, horizontal surface toward a 45 ln 2,500 parts of an industrial heptane having a boilinclined surface and the measured length was the ing point of 95 C, 1,500 parts of propylene were polylength of the test piece when the free end thereof conmerized using titanium trichloride and diethyl alumitacted said inclined surface. num chloride as catalysts to prepare a heptane slurry of 2. Basis weight:

3. Apparent density:

The weight per unit volume calculated from the thickness measured by a micrometer and the area weight.

EXAMPLE 9 An ethylene block copolypropylene powder having a viscosity of 2.69 and a residue after extraction with 4. Tenacity and elongation: boiling n-heptane of 87.3 percent, containing 9.0 per- These were measured on a 1.5 cm wide and cm cent of ethylene (melting point 165 C), was prepared. long text piece by using an lnstron tensile tester at a This powder was added to methylene chloride (boiling tensile speed of 0.5 cm/min. point 39.8 C) to prepare a slurry, which was dispersed 5. For of the paper material (dimension, etc.): in water to prepare an emulsion. The composition of The test piece was enlarged by using an optical mi- 10 the emulsion by volume was polymer l2/methylene croscope or a projector and the dimension was mea- C e 8/wate 200- sured. Besides, 1 percent, based on the weight of the poly- 6. Particle size of the emulsion: mer, of sodium dodecylbenzene sulfonate was added to Measuring the particle size at a high temperature, the emulsion as a surface active agent. The resulting higher than the boiling points of the dispersion medium emulsion was heated to 140 C inside an autoclave simand the dispersed phase, under a high pressure, is diffillar to that 1n Example 1, J dfrqm a HOZZleltaV- cult. Accordingly, the particle size of the emulsion in ing a diameter of 0.8 mm (the pressure being 18 atmoa system of the solvent, nonsolvent (and surface active spheres). From the nozzle, a fibrous paper material agent) not added with the polymer was measured by having a diameter of about 120 microns and a length means of an optical microscope to make it a parameter 20 vof 3,000 microns was jetted. This fibrous paper mateof the dispersed state. rial was soft like a sponge and when observed under a The synthetic papers obta ine d in Exarnp les l 3 microscope, it was found that a plurality of fine fibers were white and lent themselves well to writing with a having a thickness of about 8 microns was assembled fountain pen and also with a ball point pen. in a reticulated state.

This jetted fibrous paper material was collected on a EXAMELE-SATQ 60-mesh wire netting at a distance of cm from the Example 1 was repeated except the pressu a d nozzle and made into a sheet. This sheet was peeled off temperature of the emulsEn inside the autoclave were the wire netting (by jetting compressed air from the varied as shown in Table 2. The results appear in back surface of the wire netting, the sheet could be Table 2. W. R' w 30 peeled off easily), passed between a pair of chromium- TABLE 2 8 Pressure canti- T p inside lever l re of the auto Particle hang Basis Apparent Elongathe em clave size length weight density Tenacity tion amp e sion C) (kg/cm) (rnicrons) Jetted state (cm) (g/cm) (glcc) (kg/cm) (percent) Comments Comparative 34 5 Could not be disexample 4. charged. Comparative 4 5 Discharged only inter- 240 Could not be made example 5. mittently. into a sheet. Example4 8 5 Good 8.3 260 0.68 2.9 4 Example 5. 11 s 8.7 270 .71 3.4 6 Example 6 34 5 do 7.8 280 .69 2.7 5 Comparative 300 80 5 Colored by thermal 6.3 280 .73 .8 3 Became a colored example 6. degradation. I paper.

Note: The pressure inside the autoclave was a pressure when the inside was pressed by nitrogen gas (N,).

The synthetic papers obtained in Examples 4 6 4; -plated nip rollers at room temperature to smooth the cellently accepted writing with a fountain pen and also with a ball point pen.

surface, and further ironed at 115 C. The sheet obtained was in the form of a paper, having a basis weight of 86 glcm an apparent density of 0.54 g/cc, a tenacity of 0.31 kg/cm and an elongation of 11 percent.

EXAMPLES 7 8 0 Example w s ated at bsmt 292f EXAMPLE the slurry in the emulsion inside the autoclave was var- Polypropylene Noblen FB (trade name, manufacied as shown n Table 3. Theresultsappear in Table 3. tured by Mitsui Toatsu Chemical Co., Ltd., melting TABLE 3 45 canti- Size of the paper lever Particle Means for changmaterial (micron) han Basis Ap arent Elongasize ing the particle lengt weight ensity Tenacity tion Example (micron) size Jetted state Size Length (cm) (glcm') (glee) (kg/cm) (percent) Other forms Comparative 1 10% of glycerol Good 100 50 280 Lacked interexample 7. was added. twining property. Example 7 20 0.001% of CaO was ..do 100 10,000 8.8 260 0.78 3.3 4 Texture uniadded as a conform. densing agent. Example 8 100 The solvent was ..do 100 20,000 8.4 270 .69 2.9 5 Texture unichanged to triform. chloroethylene. Comparative 750 0.1% of acidic Became a con- S00 l fi ig 81 260 .28 4,3 251 Texture uniexample 8. bentonite was tinuous fiber. form. Nonadded as a conuniform densing agent luster due to long fiber.

Note: infinity is used as meaning a continuous fiber.

13 point 165C) was added to methylene chloride (boiling point 39.8 C) to prepare a slurry, which was dispersed.

in water to prepare an emulsion. The composition of the emulsion by volume was polymer l2/methylene chloride 88/water 200. Besides, 1 percent, based on the weight of the polymer, of sodium dodecylbanzene sulfonate was added to the emulsion as a surface active agent. The resulting emulsion was heated to 140 C inside an autoclave and jetted from a nozzle having a diameter of 0.8 mm. From the nozzle, a fibrous paper material having a diameter of 100 300 microns and a length of about 3 mm was jetted. This fibrous paper material was soft like a sponge and when observed under a microscope, it was found that a plurality of fine fibers having a thickness of below 8 microns was assemshown m Table 4. The results are shown in Table 4.

bled in a reticulated state to form a fibrous paper material. This jetted fibrous paper material was collected on 60-mesh wire netting at a distance of about cm from the nozzle and made into a sheet. By jetting compressed air from the back surface, this sheet was peeled off the wire netting and ironed at 1 15 C. The sheet obtained was in the form of a paper, having a basis weight of 44 glm an apparent density of 0.37 g/cc, a

.of 0.21 kg/mm and an elongation of 8 percent.

EXAMPLES 11 32 Twas repeated solvent, dispersion medium and heating temperature as TABLE 4 canti- Size of paper lever v Tempermaterial (1;) hang Basis Apparent Elonga- Dispersion ature Particle length weight density Tenacity tion Example Polymer Solvent medium C) size Size Length (cm) (glm') (glcc) (kg/cm) (percent) Comments 11 Polypropylene Methyl- Water 5 1. 1000 10,000 8.9 180 0.82 3.2 4 Paper like ([17] 1.8). ene matter of chlouniform 'n'de. texture. 12 Low pressure Trichlo- ..-...do 180 100 1000 10,000 6.8 126 .41 .6 7 Do. method polyroethethylene ylene. (manufactured by Mitsui Petrochemical Co., Ltd. 13 High pressure Methyl- .....do '140 5 1000 10,000 4.3 .62 .5 7 Do.

method polyene ethylene chlm (manufactured ride. by Mitsubishi Petrochemical Co. Ltd. 14 10% polyethylene .....do ..do 140 5 1000 20,000 9.3 98 .78 1.3 4 Do.

block copoly- Y propylene (M 15 7% vinyl acetate .....do "do 5 1000 20,000 9.2 88 .81 1.3 4 Do.

block copolypropylene (1 0 16 Saponified vinyl .....-do ..do 140 5 1000 20,000 9.8 85 .82 1.9 4 Do.

7 acetate graft polypropylene. 17 ..'6% acrylic acid .....do ..do 140 5 1000 20,000 9.2 93 .78 1.2 5 Do.

graft polypropylene 1 1.8). 18 Polybutene-l .....do ..'do 140 5 1000 5,000 3.2 .65 3 9 Do.

1] 19 Poly-3 methyl- .....do ..do 5 1000 5,000 3.8 98 .71 4 8 Do.

butene'l ([nl 3.4). Poly-4 methyl- .....do "do. 140 5 1000 10,000 6.9 97 .78 2.8 4 Do.

'pentene-l (1 111.4)- Polyhexene-l .....do ..do 140 .5 1000 10,000 5.8 105 .68 1.2 6 Do.

([1 2.8). Polypropylene Hexane ..do 140 5 1000 20,000 8.2 250 .52 3.2 4 Do Polypropylene Cyclo- .....do 170 5 1000 15,000 7.8 125 .61 1.5 4 Do.

([1 1.8). hexane Polypropylene Cyclo- .....do 200 20 1000 20,000 6.9 111 .63 1.3 5 Do.

([11] 1.8). pentane. 25 Polypropylene Benzene ..do 10 600 10,000 5.8 113 .71 1.2 3 Do.

7] 1.8)- 26 Polypropylene Xylene ..do 190 10 1000 20,000 6.2 108 .68 11 4 Do.

(1 1 1.8). 27 Poly propylene Butyln- .....do 1 90 50 1000 24,000 6.6 106 .70 1.2 5 Do.

([1 1.8). acetate 28 ..Polypropylene Carbon .....do 10 1000 20,000 5.8 98 .52 9 3 Do.

([1 1.8). tetrach10 ride. 29 Polypropylene Trichlo- .....do 140 100 1000 20,000 6.1 100 61 .8 4 Do.

([1 1.8). roethylene. 30 Polypropylene Toluene ..do 10 1000 20,000 6.3 110 .72 1.3 3 Do.

1 1.8). 31 Pl y propylene To1uene.. oz-bptyll 200 10 1000 20,000 6.2 108 .69 1.0 3 Do.

]1.8). g yco. Mixing 50% of Methyl- Water 140 5 1000 10,000 9.9 101 .88 9 4 Do.

the polymer of ene example 11 and chlo- 50% of the ride. polymerof examp1e12.

All the compositions were a-ratio of polymer 1-1glso1vent Slice/dispersion medium 200cc.

tenacity The following is claimed:

1. A method for producing a synthetic paper from a polyolefin comprising the steps of:

l. preparing a dispersion from (A) a mixture consisting of 5-70 percent by weight of a polyolefin and a solvent for said polyolefin wherein the boiling point of said solvent is from about 30 C to about 192 C, and (B) in an amount of about 30 2,000 percent by volume based on said mixture (A), a dispersion medium having a boiling point which is below the melting point of said polyolefin, said dispersion medium being substantially insoluble in said solvent,

2. jetting said dispersion under at least an autogenous pressure obtained by heating said dispersion at a temperature in the range from at least 30 C higher than the boiling point of said solvent to 280 C. from a nozzle to make a paper-making fibrous material, and

3. collecting said fibrous material and compressing the same.

2. The method according to claim 1 wherein said dispersion medium is present in an amount of about 200 2,000 percent by volume based on said mixture.

3. The method according to claim 1 wherein said dispersion medium is present in an amount of about three times the volume of said mixture.

4. The method according to claim 1 wherein the particle size of said mixture (A) in said dispersion is about 3 400 microns.

5. The'method according to claim 1 wherein said polyolefin is selected from the group consisting of polypropylene and a polypropylene graft polymerized with a water-soluble monomer.

6. The method according to claim 1 wherein said dispersion medium is water and said solvent for the polyolefin is a member selected from the group consisting of hexane, heptane and methylene chloride.

7. The method according to claim 1 wherein said dispersion is heated to a temperature in a range between the dissolving temperature of said polyolefin to about aiidsaidfdispers'iori Ts'jeiied fr'dfiiZiTrdZil under at least an autogenous pressure obtained thereby.

8. The method according to claim 7 wherein the jetting pressure is 5 70 kglcm polyolefin comprising the steps of:

l. polymerizing an olefin monomer in the presence of a solvent for the polyolefin to prepare a slurry containing 5-70 percent by weight based on said solvent of the polyolefin wherein the boiling point of said solvent is from about 30 C to about 192 C,

2. preparing an emulsion from said slurry and, in an amount of about 30-2,000 percent by volume based on said slurry, a dispersion medium having a boiling point lower than the melting point of said polyolefin and being substantially insoluble in said solvent,

3. heating said emulsion to a temperature from at least 30 C higher than the boiling point of said solvent to 280 C.,

4. jetting said emulsion under at least an autogenous pressure obtained by said heating to make a fibrous paper material, and

5. collecting said fibrous paper material and compressing the same.

10. The method according to claim 9 wherein said polyolefin is a member selected from the group consisting of polyethylene, polypropylene and copolymers thereof.

11. The method according to claim 9 wherein said dispersion medium is present in an amount of about 200 2,000 percent by volume on said slurry.

12. The method according to claim 9 wherein said dispersing medium is used in an amount of at least two times by volume based on saidslurry.

13. The method according to claim 9 wherein the concentration of said polyolefin based on said solvent is about 5 percent by weight and the amount of said slurry is about 10 percent by weight based on said dispersion medium.

14. The method according to claim 9 wherein said solvent is selected from the group consisting of hexane, heptane and methylene chloride.

15. The method according to claim 9 wherein said dispersion medium is water.

16. The method according to claim 9 wherein the particle size of said slurry in said emulsion is about 3 400 microns.

17. The method according to claim 9 wherein the jetting pressure of said emulsion is about 5 70 kglcm slurry and stabilizes the dispersion, is added.

Claims (23)

1. 2. The method according to claim 1 wherein said dispersion medium is present in an amount of about 200 - 2,000 percent by volume based on said mixture.
2. 2. jetting said dispersion under at least an autogenous pressure obtained by heating said dispersion at a temperature in the range from at least 30* C higher than the boiling point of said solvent to 280* C. from a nozzle to make a paper-making fibrous material, and
3. 2. preparing an emulsion from said slurry and, in an amount of about 30-2,000 percent by volume based on said slurry, a dispersion medium having a boiling point lower than the melting point of said polyolefin and being substantially insoluble in said solvent,
4. 3. heating said emulsion to a temperature from at least 30* C higher than the boiling point of said solvent to 280* C.,
5. 3. collecting said fibrous material and compressing the same.
6. 3. The method according to claim 1 wherein said dispersion medium is present in an amount of about three times the volume of said mixture.
7. 4. The method according to claim 1 wherein the particle size of said mixture (A) in said dispersion is about 3 - 400 microns.
8. 4. jetting said emulsion under at least an autogenous pressure obtained by said heating to make a fibrous paper material, and
9. 5. collecting said fibrous paper material and compressing the same.
10. 5. The method according to claim 1 wherein said polyolefin is selected from the group consisting of polypropylene and a polypropylene graft polymerized with a water-soluble monomer.
11. 6. The method according to claim 1 wherein said dispersion medium is water and said solvent for the polyolefin is a member selected from the group consisting of hexane, heptane and methylene chloride.
12. 7. The method according to claim 1 wherein said dispersion is heated to a temperature in a range between the dissolving temperature of said polyolefin to about 280* C, and said dispersion is jetted from a nozzle under at least an autogenous pressure obtained thereby.
13. 8. The method according to claim 7 wherein the jetting pressure is 5 - 70 kg/cm2.
14. 9. A method for producing a synthetic paper from a polyolefin comprising the steps of:
15. 10. The method according to claim 9 wherein said polyolefin is a member selected from the group consisting of polyethylene, polypropylene and copolymers thereof.
16. 11. The method according to claim 9 wherein said dispersion medium is present in an amount of about 200 - 2,000 percent by volume on said slurry.
17. 12. The method according to claim 9 wherein said dispersing medium is used in an amount of at least two times by volume based on said slurry.
18. 13. The method according to claim 9 wherein the concentration of said polyolefin based on said solvent is about 5 - 70 percent by weight and the amount of said slurry is about 10 - 120 percent by weight based on said dispersion medium.
19. 14. The method according to claim 9 wherein said solvent is selected from the group consisting of hexane, heptane and methylene chloride.
20. 15. The method according to claim 9 wherein said dispersion medium is water.
21. 16. The method according to claim 9 wherein the particle size of said slurry in said emulsion is about 3 - 400 microns.
22. 17. The method according to claim 9 wherein the jetting pressure of said emulsion is about 5 - 70 kg/cm2.
23. 18. The method according to claim 9 wherein to said emulsion a surface active agent which coveres said slurry and stabilizes thE dispersion, is added.

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