FI59623C - FOER FARING FRAMSTAELLNING AV POLYOLEFINFIBRER - Google Patents

Description

rBl M1v ANNOUNCEMENT CQ ^ 7 IBJ <11) UTLÄGGNINGSSKRIPT

C ^ Pator.Vtl ay knotty 10 09 1901 ^ T ^ (51) Kv.ik? /Int.ci.3 D 01 F 6/04, D 21 H 5/20 # D 01 D 5/04 FINLAND —FINLAND ( 21) P »t« nttlhtktmu.-P «.nttn.elci.lnf 2688/73 (22) H« k * ml * ptlvt - Anaeknlngtdag 29 · 08.73 '(23) Alkupiivi — Glltlghutidag 29 · 08.73 (41) Interpreters swept - Bllvlt offuntllg 01.03 · 7 ^. ,. . . (44) Date of issue of the letter. - _ n.

Patent · och registeratyrelaen 'Aiwdktn utlagd och utl. «Krtft * n puMkurad 29.05.8l (32) (33) (31) Pjryduttjr« uotkuu »—Begird prlorltut 30.08.72 usa (us) 285386 (71) Crown Zellerbach International Inc. , Delaware, US; One Bush Street,

San Francisco, California 9 ^ 119, USA (72) John Henry Kozlowski, Vancouver, Washington, Paul Clyde Litzinger,

Camas, Washington, Frank John Steffes, Camas, Washington, USA (US) (7 * 0 Berggren Oy Ab (54) Method for the production of polyolefin fibers - Förfarande för framställning av polyolefinfibrer

The present invention relates to the production of fibers of suitable quality for the production of paper or similar nonwoven webs.

Various methods have been proposed in the past for preparing such fibers by rapid evaporation of a mixture of a synthetic fiber-forming polymer in a volatile liquid. Upon rapid evaporation of the mixture, it is expanded by expansion using a nozzle operating at elevated pressure, from which the feed takes place to a zone having a lower pressure, whereby the temperature of the liquid before rapid evaporation is such that during evaporation the liquid boils, i. at least a portion of the liquid evaporates at a lower pressure. Methods in which the polymer solution in solution is rapidly evaporated to form fibers are disclosed in U.S. Patent 3,081,519> British Patent 1,262,531 and German Patent Application No. 19,580,609. · Methods in which an aqueous dispersion of molten polymer is rapidly evaporated are disclosed in U.S. Patent 3,402,231 in patent 1,350,931.

2,59623

In order to obtain a fiber of better quality than the fibers obtained from the above methods, it has been proposed to rapidly evaporate an emulsion containing a polymer, a solvent of this polymer and water. Such proposals have been made in British Patent 1,323,174, German Application No. 21,440,409 and Finnish Patent No. 55,379. · In these prior emulsion-flash evaporation methods, the rapidly evaporated liquid contains water as a continuous dispersed dispersed solvent. phase.

The object of the present invention is to provide a process for the production of polyolefin fibers, in particular polyethylene and polypropylene fibers, by means of which fibers are obtained which are either superior in terms of ease of papermaking or from which considerably better paper can be produced. It has been found that the fibers obtained by rapid evaporation of the polymer emulsion, solvent and water are better when the solvent forms a continuous phase and the water a dispersed phase than when the water forms a continuous phase and the solvent a dispersed phase.

An inverse (in water-in-oil) emulsion in which water forms a dispersed phase is generally more difficult to form than those emulsions most commonly found in emulsion technology which are oil-in-water emulsions, and we have found that it is possible to form and evaporate water-in-oil emulsions containing polymer and that rapid evaporation of the reverse emulsion produces very good fibers.

A surprising effect of the rapid evaporation of an emulsion containing a polymer in aqueous oil is that the product is obtained as relatively discrete fibers rather than as a continuous fiber. Most of the prior art methods have been designed to form continuous filaments, which is not desirable for a fibrous product intended for use in the manufacture of nonwoven webs.

Accordingly, the present invention relates to a process for producing polyolefin fibers, especially polyethylene and polypropylene fibers (1) by forming a mixture containing water and a solution of polyolefin in an organic liquid, (2) by expansion evaporation of the mixture at a temperature of 120-160 ° C from an elevated pressure zone. , to a lower pressure zone where the organic liquid evaporates and the polyolefin precipitates as fibers, after which the fibers are refined.

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The process according to the invention is characterized in that water is mixed with a polyolefin solution in order to disperse the water as droplets in the continuous phase formed by the solution. In the process of the invention, the polyolefin precipitates in the form of fibers which can be comminuted relatively easily and formed into paper webs in a conventional manner.

The polymer is preferably dissolved in the liquid so that the mixture formed in the first step of the treatment, which is rapidly evaporated in the second step of the treatment, comprises an emulsion in which water is in the dispersed phase and the solution in the continuous phase.

The polymer is preferably a thermoplastic polymer and the greatest utility of the invention is in the manufacture of fibers from a polyolefin.

For a reason that is not fully understood at present, it has been found that the fibers produced by the process of the invention are superior in properties to those produced by the rapid evaporation of a corresponding mixture in which the polymer solution is a dispersed phase in water.

A detailed comparison of the properties is given below, but in short, when comparing fibers made by rapid evaporation of the corresponding mixture with water in the continuous phase, the fibers obtained by the process of the invention have a larger surface area, dry faster, are stronger and provide such sheets of paper with generally superior properties. These improved properties of the fibers are not only surprising but also very important, because such properties of the fibers are very important in order to obtain the right papermaking pulp! The larger surface area gives greater whiteness and shine to the fibers and better adsorption properties. Better strength properties such as breaking strength, puncture strength, breaking strength, etc. also make these fibers more competitive with naturally occurring cellulosic pulps.

In addition, the process according to the invention makes it possible to obtain such improved fibers which also have a relatively low concentration of polymer bundles and fiber agglomerates. The small number of polymer bundles and fiber agglomerates is very important for the fibers to be used in various grades of paper, for example in printing papers, because the roll pressures during these papermaking processes cause these agglomerates and bundles to form transparent spots on the paper.

* 11 59623

The polymer used in the process of the invention is preferably a thermoplastic fiber-forming polymer. (By fiber-forming we mean a polymer capable of forming fibers using conventional spinning methods). It is preferred to use crystalline or partially crystalline polyolefins such as low pressure (Ziegler-Natta) polyethylene, isotactic or partially isotactic polypropylene and ethylene-propylene copolymers. Polybutenes and polymethylpentenes are other examples of polyolefins that can be used in the practice of the invention. .

'* you. Crystalline or partially crystalline polyamides and polyesters can also be used. Also useful are non-crystalline polymers such as polycarbonates, polysulfones, polyvinyl chloride, polymethyl methacrylate, polyacrylonitrile and polystyrene. Mixtures of the above polymers with each other (or with other polymers are also useful).

The most preferred useful polyolefins are those having an intrinsic viscosity in excess of about 0.7 dl / g, which in the case of polyethylene corresponds to an average molecular weight of about 30,000 to 40,000.

f The polymers used in the process according to the invention (when taken, may be in the form of a dried powder or spheres, ai are preferably in the form of a wet cake, slurry or polyolefin solution in a reaction solvent, such products are obtained after polymerization.

In general, any substituted or unsubstituted aliphatic or aromatic or cyclic hydrocarbon which is a solvent for the polymer at elevated temperature and pressure and which is relatively inert under processing conditions, and which preferably has a boiling point lower at atmospheric pressure than the main softening point of the polymer to be treated, with or to form a polymer solution that is substantially water-immiscible is used as an organic liquid in the process of the invention. This solvent may be liquid or gaseous at room temperature and atmospheric pressure. It is preferred that it be liquid under normal conditions, as otherwise the system may need to be kept under overpressure after the rapid evaporation zone. Typical solvents that can be used include aromatic hydrocarbons (e.g., benzene and toluene), aliphatic hydrocarbons (e.g., butane, pentane, hexane, heptane, octane and their isomers and homologues), alicyclic hydrocarbons (e.g., cyclohexane), chlorinated hydrocarbons (e.g., methylene chloride, carbon tetrachloride, chloroform, ethyl chloride, and methyl chloride), higher alcohols, esters, ethers, ketones, nitriles, amides, fluorinated compounds (e.g., fluorocarbons, nitromethane), and mixtures of the aforementioned solvents and other solvents.

The polymer-solvent-water mixture according to the invention, depending on its water content, can be formed by several different methods. Thus, a solution in a polymer solvent obtained from a solution polymerization process can be used either using the same concentration in the polymer solvent or diluted or concentrated, and water can then be added to the solution or vice versa. Such a method generally uses hot water to prevent polymer precipitation. Alternatively, a slurry in the solvent of the polymer particles, such as that prepared by the slurry polymerization process, may be used, and a suitable amount of water is added to this slurry or vice versa. A further possibility is to start with a dry polymer powder or granules or a wet polymer cake prepared in a polymer manufacturing plant at some stage of solvent removal, and the appropriate amount of solvent jar is then mixed with the dry polymer in any order.

As discussed below, it is preferred that the solvent be present prior to the addition of water, since the addition of water to the solvent and not the other way around helps to ensure that the solvent or polymer solution forms a continuous phase of the mixture to be formed. This latter point is important when using an amount of water close to the limit of the reverse reaction, i. close to the point where the amount of water is such that it can form a continuous phase. The amount of water is kept substantially below the limit value of such an inverse reaction, especially below 30% by volume. mixture, in which case any suitable mixing method or order of addition of materials can be used.

The concentration of the polymer relative to the solvent is not critical and the amount of solvent present must exceed 100% by weight. based on the polymer and be sufficient to provide a viscosity at the solution temperature used such that the resulting product can be easily processed, i. the viscosity should be less than about 500 poise. The polymer concentration generally ranges from about 2 to 30 weight percent. based on the amount of solvent plus polymer and is preferably in the range of about 5-15?.

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One function of water is to reduce the temperature of the pulp in the zone immediately following the nozzle. Adding water increases the total vapor pressure of the system, thus reducing its boiling point. In practice, however, water must be used for at least about 1 S? and preferably more than 10% by volume based on the mixture of solvent and water. Thus, by lowering the boiling point of the mixture, the temperature of the pulp formed after rapid evaporation decreases and the properties of the obtained fibers are improved, taking into account the papermaking purposes.

Another effect of water is that it acts as a carrier for a hydrophilic water dispersant to form fibers.

It has been found that it is highly preferred that the water dispersant be present during the flash evaporation and that the fibrous polymer be used. during manufacture. Although the presence of a water dispersant in the fibers prepared by this method is preferred, the best of these are those that could be considered detrimental to the water oil from the point of view of emulsion. Nevertheless, the presence of hydrophilic water dispersants in the mixture prior to flash evaporation is preferred. An equivalent amount of the same substance added to the fibers already formed at a later stage does not provide the same degree of fiber purity. As a result, a sufficient amount of water should be present relative to the amount of hydrophilic material used to impart the desired dispersibility to the fibrous polymer in water, preferably as a solution thereof. A larger amount of water compared to this minimum amount of water required to receive the hydrophilic substance can be used to impart a suitable viscosity to the aqueous solution or dispersant, i. the aqueous solution of the water dispersant must not be so viscous that there are difficulties in handling or adding it to the polymer solution as a dispersed phase. In addition, water can help reduce the viscosity of the blend to a value lower than the viscosity of the polymer solution alone, allowing for higher polymer concentrations. In general, the viscosity of the aqueous solution and / or mixture should be less than about 500 poise at the temperature used.

An additional function of water is to provide energy (enthalpy) to promote solvent evaporation during rapid evaporation, as it is not desirable for the temperature to be so high that sufficient energy is applied to the solvent alone to achieve complete evaporation. However, the amount of water must not be so large that it requires the use of heat from the demand towers to achieve the desired 7 59623 rapid evaporation temperature, i. once the amount of water to obtain the appropriate viscosity has been determined, more water can be used in a limited amount as it helps to lower the viscosity of the mixture and also helps to evaporate the solvent, but this additional amount should not be too large.

The amount of water required to perform the above tasks is always less than the amount at which the reverse reaction takes place, i. wherein water forms a continuous phase of the mixture. One condition necessary to ensure that the organic liquid or solution forms a continuous phase is that the amount of water in the mixture is sufficiently low. If the amount of water is greater than 70 #, it is very difficult to form an emulsion in water oil by any means. Even when using somewhat lower amounts of water, say more than 60 #, all conventional mixing methods tend to form emulsions in oil water. As the amount of water decreases, it becomes easier to form emulsions in water oil. In mixtures where water tends to be more stable as a continuous phase, it is desirable to utilize special mixing methods in order to provide water as a less permanent discontinuous phase. Such suitable methods are known to those skilled in the art and are described, for example, in Kirk-Othmer's Encyclopaedia of Chemical Technology, Volume 8, Second Revised Edition.

One preferred method of ensuring an emulsion in an aqueous oil when the amount of water is sufficient to cause either water or an organic liquid to form a continuous phase is to add water to the liquid slowly, i. slowly enough so that there is no local excess of water in addition to the organic liquid and the emulsion already formed, while the mixture is stirred so that the water disintegrates into small droplets as it is added. The addition of water can be considered slow enough by measuring the electrical conductivity of the organic liquid and then adjusting this electrical conductivity to ensure that the rate of addition under certain mixing conditions is such that the electrical conductivity remains less than twice the original electrical conductivity.

As a useful guide, it can be said that it is preferable to use such special mixing methods if the amount of water is about 30% by volume or more based on the mixture. In particular, when the amount of water used is about 30% by volume or more, it is desirable to first form a solution of the polymer and the solvent and then add 8,59623 water to this solution while stirring vigorously. In this regard, "polymer solution" means a swollen or dissolved mixture obtained by mixing a solvent with a polymer, usually at an elevated temperature. It is further desirable that the entire mass of the mixture be continuously subjected to such agitation both during and after the addition of water. The mixing tank or equipment can be designed to provide such uniform and vigorous mixing, for example, by using a suitable tank structure, midsoles, and proper mixing techniques. In this way, areas of very slow mixing that can cause a phase change can be avoided.

It is preferred to carry out this blending treatment when both the water and the polymer solution are relatively hot. The polymer solution should preferably be at a temperature above the dissolution temperature of the melt, and the temperature of the added water should be high enough so that the mixture remains above the dissolution temperature of this melt during and after the addition of water. Such treatment helps to prevent phase changes during the addition of water.

If the aqueous and polymer solution phases are allowed to separate during or after the addition of water, a phase change may occur. As a result, it is desirable to add water at a rate that avoids phase separation, and to maintain vigorous agitation during and after the addition of water for the same purpose. As mentioned above, water is preferably added gradually at such a rate that it mixes rapidly with the homogeneous polymer solution. In other words, water must not be added faster than what is dispersed in small droplets in the continuous polymer solvent phase.

When the mixture contains about 30% or less water, an emulsion is preferably formed in the aqueous oil, and it is also not necessary to add water to the organic liquids. When low concentrations of water are used, the two liquids can also be mixed with each other and then mixed together, or a solution (or slurry of polymer particles in an organic liquid) can be added to the water.

Thus, in the following Examples 1-6, with a water concentration of only 16%, no special mixing treatments were used. In Experiment No. 1 according to Example 7, in which the water concentration was 40%, water was gradually added to the solution. Water concentrations of the order of 40-50% are in fact most advantageous in the process according to the invention, although in this case more attention must be paid to 9,596,23 in order to ensure that the water is in a discontinuous phase.

In a continuous flash evaporation treatment, when a portion of the mixture thus formed is flash evaporated through a nozzle, additional amounts of polymer solution and water can be added continuously while stirring the remaining mixture at suitable dosages as previously described to keep water in a continuous phase in the mixture.

One feature of the invention is that it has been found that it is not necessary to form a permanent "emulsion", thus eliminating the need for emulsifiers. However, the invention also encompasses the use of such substances in a mixture for the purpose of promoting the dispersion of the fibrous polymer formed after rapid evaporation in water. These substances are preferably water-soluble or partially water-soluble high molecular weight substances. However, they can also be substances which are soluble or only partially soluble in the solvent. Some of these substances can be technically classified as "emulsifiers", but are not only used in sufficient amounts to achieve the desired degree of dispersion, nor in the amounts generally required to form stable emulsions. In reality, since water dispersants are to some extent hydrophilic, they are not of the type commonly used to form emulsions of the water type, i. a hydrophobic (lipophilic) emulsifier with a relatively low HLB (hydrophilic-lipophilic balance) in aqueous oil is usually used to form an emulsion. The amount of water dispersant used may range from about 0.1 to 15% by weight of the polymer, preferably from about 0.1 to 5% by weight. The most preferred water dispersant is polyvinyl alcohol having a degree of hydrolysis greater than about 77% and preferably greater than about 85%, and having a viscosity (as a 4% aqueous solution at 20 ° C) of greater than about 2 centipoise. The polyvinyl alcohol is preferably added with water at the time of mixture formation. Other typical water dispersants that can be used include cationic guar, cationic starch, potato starch, methylcellulose, and "Lytron 820" (styrene-maleic acid copolymer).

The ingredients of the mixture can be placed in any suitable vessel that can be heated to elevated temperature and pressure. An autoclave is usually used. However, it is important that the vessel used be equipped with a mixing device capable of keeping the mixture in a continuous stirred state, otherwise 10 59623 no permanent emulsion is formed and the mixture separates rapidly into two separate phases when standing.

The ingredients are then heated to a suitable temperature and mixed to form a mixture in which water is present as a discontinuous or dispersed phase in the continuous phase of the polymer solution. The temperature used is preferably above the dissolution temperature of the polymer melt in the solvent used. The dissolution temperature of a given polymer melt in a solvent is determined by adding small amounts of polymer (e.g., 0.1 and 1.0 wt.%) To the solvent in an ampoule, which is then sealed and placed in an oil bath. the temperature of the oil bath is raised slowly (e.g. 10 ° C / hour) until the last waste of the polymer disappears. This temperature is the melt dissolution temperature. In a few cases, it may be advantageous to operate using a temperature below the melt dissolution temperature, in which case, however, the polymer must be present at least in a swollen state.

The maximum temperature used should be lower than the critical temperature of the solvent and / or the Decomposition temperature of the polymer.

However, it is preferred to use somewhat lower temperatures. When polyethylene and polypropylene are used, it is preferred to operate at a temperature between about 120 and 180 ° C, and most preferably at a temperature between about 130 and 160 ° C.

The pressure used in the vessel containing the heated mixture is preferably substantially autogenic. Pressures that substantially exceed the autogenous pressure are not required, and when a certain type of nozzle structure is used, this can result in poor fiber formation. It may be advantageous to use an inert gas, such as nitrogen, during the flash evaporation treatment to keep the rate of the mixture through the nozzle constant.

Rapid evaporation is preferably performed through a nozzle (having elongate dimensions) rather than using a sharp-edged opening (which cannot be considered to have longitudinal dimensions) because it has been found highly desirable to provide shear forces in the mixture (especially its polymer component) immediately before rapid evaporation. Such a shear effect promotes the formation of fibers and improves the properties of the fibers for papermaking purposes. The nozzle may be round or non-circular in cross-section and may also be annular.

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Rapid evaporation is performed by passing a mixture of polymer, solvent and water through a nozzle into a zone of lower pressure. The pressure in the lower pressure zone is preferably substantially the same as or below atmospheric pressure, because the higher the pressure, the higher the temperature of the fibrous product after it is made. Generally, the pressure of the emulsion should be less than about 3.5 kp / cm, preferably less than about 1.0 kp / cm, prior to its rapid evaporation to atmospheric pressure.

Rapid evaporation is performed primarily adiabatically, although this may vary to some extent.

During rapid evaporation, the polymer precipitates as a "fiber rope," a loose arrangement of fibers that is sometimes in a continuous form.

According to a preferred embodiment of the present invention, low pressure steam (pressure less than about 1.4 kp / cm) is added to the fiber rope after rapid evaporation in the coming zone to remove residual solvent from the fibers. This can be done in a tank or preferably in a passage located immediately after the nozzle.

The fibrous rope is recovered in a suitable receiving vessel, which is preferably one which allows the evaporated solvent to be separated therefrom.

In a factory scale treatment, water is added to the fiber rope to a suitable dilution of less than about 5% and preferably less than 2% by weight, and then passed as an aqueous slurry through a disc mill to bring the fibers into a form optimal for papermaking. The comminution of the fiber rope separates the fibers from each other and can also be used to adjust the lengths of the fibers. More passage through the grinder is generally desirable. However, it is not necessary to grind the fiber rope with discs.

After comminution, the fibers can be diluted to a suitable concentration and formed into synthetic paper webs, either alone or mixed with conventional cellulosic papermaking fibers. Alternatively, the fibers can be dewatered, baled, stored and transported to the site of use.

Although a batch process has been described above in which a mixture of polymer, solvent and water is prepared in a suitable vessel, it is also possible to prepare the mixture by a continuous process by continuously mixing the polymer solution with superheated water in a suitable mixer just before rapid evaporation through a nozzle.

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Determining whether water is present as a discontinuous phase or as a continuous phase can be performed as follows.

The mixture is formed using the appropriate temperature and pressure and the amount of mixing generally used. Electrodes made of two electrically conductive metal parts with a spacing of about 1 cm or more are immersed in a liquid mixture. The electrodes are connected to the terminals of the battery and the signal obtained is recorded by means of a measuring device connected in series with the electrodes. The signal obtained is directly proportional to the electrical conductivity of the mixture. A very small amount of an ionizable substance such as sodium chloride can be used in water to improve its electrical conductivity. When water is a discontinuous phase, a very low value of electrical conductivity or zero value is obtained, i.e. about the same electricity! conductivity than the polymer-solvent phase of the mixture.

Thus, it can be seen that in forming the desired water-discontinuous mixture, the mixing speed of the mixture is high enough to keep the electrical conductivity of the mixture approximately equal to the electrical conductivity of the polymer solution phase. Similarly, when forming such blends in which the water concentration is preferably so high that a continuous aqueous phase is possible, water must be added to the polymer solution slowly enough to maintain the electrical conductivity of the mixture approximately equal to the electrical conductivity of the polymer solution phase.

Other suitable methods for determining whether an oil-in-water or water-in-oil type emulsion is obtained are described in Kirk-Othmer, Encyclopedia of Chemical Technology, Volume 8, pages 146-147, second revised edition, 1965 ·

Example 1 The dissolution vessel used in this example is a 3600 L glass lined tank with midsoles with a centrally arranged 7.5 horsepower mixing device comprising two 4-vane turbine type agitators. The diameter of the lower turbine was 68 cm and that of the upper turbine 48 cm. The stirrer was used throughout the treatment. 270 l of water containing 1 weight of 5 t of polyvinyl alcohol ("Monsanto Gelvatol", viscosity 4-6 CP and hydrolyzed 87.7-89%), based on the weight of polyethylene used, was added to the tank and then 45.4 kg of large density polyethylene having an intrinsic viscosity of 1.4 dl / g and a melt index of 5.5 ("Mitsui 2200P"). The tank was sealed and 1350 L of n-hexane was added.

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The volume ratio of water to hexane in the mixture was 1: 5 and the polyethylene concentration was 40 g per liter of hexane. The contents of the tank were heated to a temperature of 130-135 ° C and a pressure of 8.5 kp / cm 2. The valve at the bottom of the tank was then opened and the mixture was passed through a 12.5 cm long pipe with a diameter of 7.5 cm to a "Valtek" angle type control valve with an orifice diameter of 9.5 mm and a length of 7 mm. A nipple-shaped plug formed a ring in the opening of the ring with the wall of the opening. The valve was operated so that it was about 1/4 open. The mixture flowed through a ring which formed a rapid evaporation nozzle at a rate of 180 g of polyethylene per minute. The mixture was flash evaporated to a line 2.5 cm in diameter. At a distance of about 15 cm after the nozzle, low pressure steam (0.7 kp / cm) was introduced into a 2.5 cm line to remove solvent that had not previously evaporated from the pulp. At a distance of approximately 5> 4 m from the nozzle, this 2.5 cm line opened into a steam separation vessel and the vapors were removed from the top of this vessel. Hot dilution water at 185 ° C was passed to the top of the steam separation tank at a rate of about 22.6 in 1 minute. Water and pulp fell to the bottom of the steam separation tank and were passed at a temperature of 80-90 ° C and a concentration of about 1% to a Jones double disc separator (disc diameter 30 cm) equipped with crushing-type plates (Jones species 1, 1, 1 , 5 + 10 °). The plates were rotated at 2117 rpm with a clearance of 0.1 to 0.1 mm. A total of four fibers were passed through a comminuter and a second to fourth treatment was performed at a pulp temperature of 40-50 ° C. In addition, 1% by weight of 5 '' Gelvatol 20-30 "polyvinyl alcohol (based on the weight of polyethylene) was added to the pulp tank and the pulp was subjected to a Fifth Disintegration Treatment with a plate clearance of 0.25 to 0.1 mm. TAPPI Standard T233 with 64:

Table IA

Mesh Weight

With sieve No. 20 10.3 "" 35 33.8 "" 65 23.8 "" 150 17.4 "" 270 5.0 Through No. 270 9.7

The flow value of the fibers was 0.24 seconds / g.

m 59623

Some of the obtained fibers were formed into sheets by hand using the method TAPPI Standard T-205 m-58 and a modified wet compression (28 kp / cnr) and thermal bonding step (121 ° C at minimum pressure). The other part of the fibers was mixed with a 50:50 bleached alder force pulp with a Canadian Standard Freeness value of 410 ml and formed into sheets by hand using the same method.

The resulting handmade sheets were tested and the results were as follows:

Table IB

Feature 100% 50% alloy -

Base weight, g / m 61.2 6l, 2

Density, g / ml 0.36 0.48

Opacity,% 83.4 78.9

Whiteness,% (Elrepho No. 8) 88.9 84.4

Breaking length, m 139 24l6 TEA, kg-cm / cm2 0.06 34.3

Internal commitment,

Scott units 14 90

Tear strength, g / sheet 6 28 TEA = Tensile energy absorption (= toughness)

A second batch of polyethylene fibers was blended with a bleached alder pulp with a Canadian Standard Preeness value of 410 ml to produce a pulp containing 40 wt%? polyethylene fibers and 60 weight? kraft pulp fibers. The resulting mixture was comminuted in a Jordan mill to produce a pulp having a Canadian Standard Preeness value of 250 mm and formed into paper on a paper machine. The paper machine was used to provide thermal bonding at two different temperatures (107 ° and 135 ° C, sheet temperature). The resulting sheets of paper had the following characteristics:! 5 59623

Table 1C

Feature Heat setting temperature

107 ° C 135 ° C

2

Base weight, g / m 66.6 63.3

Caliber, mm 0.132 0.11

Density, g / ml 0.504 0.573

Tear strength, g / sheet MD 23 24 XD 26 27

Tensile strength, kg / 15 mm MD 2.93 3.11 XD 1.49 1.70

Elongation,% MD 1.6 1.7 XD 3.5 3.8 TEA, kg-cm / cm2 MD 0.019 0.020 XD 0 ', 025 0.032

Double Refractive Index (MIT) MD 3 7 XD 2 3 Stiffness, g / cm (Taber) MD 1.17 0.96 XD 0.46 0.45

Internal binding (Scott) kg-cm / crn x 10 ”“ 2,152,285

Smoothness, ml / min (Sheffield) WS 328 327 PS 352 293

Porosity, ml / min (Sheffield) 249 278 Oil absorption,% 45 32

Sugar color, sec. WS 0 2.1 PS 0 1.6

Whiteness,% (Elrepho No. 8) 85.4 80.9

Opacity,% 80.4 69.1

Coefficient of determination 408 253

Breaking length, m MD 2931 3271 XD 1492 1786

Note.

WS = wire side MD = machine direction PS = felt side XD = perpendicular direction to machine direction

Caliber = thickness determined at a given pressure using a specified type of device.

In the above example and the following examples, the basis weight, caliber, tear strength, double fold number, and density of handmade sheets were determined using the TAPPI Standard T-220 method. For sheets made on a paper machine, the basis weight was determined by the TAPPI Standard T-410 method, the caliber 16,59623 by the TAPPI Standard T-411 method, the tear strength by the TAPPI Standard T-410 method, and the double refractive index by the TAPPI-5H method and the density by the TAPPI Standard method. Tensile strength, elongation, TEA (tensile energy absorption) and breaking length for both manual and paper machine sheets were determined using the TAPPI Standard T- method. Stiffness for both sheets was determined using the method TAPPI Standard T-489-70. "Elrepho" whiteness No. 8 was determined for both sheets using TAPPI Standard T-525 · The smoothness of both sheets was determined by TAPPI Routine Control Method No. 285. oil absorption was determined for both sheets using TAPPI Routine Control Method No. 26 ( 1966). Opacity and light scattering coefficient were determined for each sheet using the method TAPPI Standard T- ^ 25. The manner in which the other tests were performed is indicated by the equipment used to perform these tests, all of which are well known in the paper industry. The drying value, which corresponds relatively closely to the hydrodynamic surface area of the fibers and is more closely related to the drying properties of the fibers used in papermaking than the gas adsorption surface area, was determined mainly by TAPPI test T221 OS-63 with a small modification of the calculation method. Briefly, about 10 g of fiber sample was weighed and dispersed in water. The slurry is then added to a conventional sheet forming machine and water is added up to the mark. The slurry is mixed using four up and down movements of a conventional mixing device, and the mixing device is then removed. The water temperature in the mold is measured and the drain valve is opened. The time between the opening of the valve and the first detection of the detected suction is recorded. The method is repeated using only water (no fibers) in the sheet machine and the temperature and run-off time are recorded. The drying or run-off value in seconds per gram is then calculated from the following formula DF = / D + 0,3 (h - 1) (D - i »27 - / d + 0,3 (i - 1) (d - * 07” iji * rp w where DF = flow factor, seconds / gram D = flow time of the mass in the apparatus, seconds d = flow time without mass, seconds

VT = viscosity of water at temperature T

W = weight of fiber used in the test, grams 17 59623

Quantity - 1) is tabulated with the TAPPI Test T221-OS-63 avS of the above experiment. This quantity is multiplied by 0.3, which is determined empirically by the fibers.

Example 2

The treatment according to Example 1 was repeated except for the following: a) the polyethylene concentration was 80 g / l b) the mixture was passed through a nozzle at a rate of 250 g per minute, and c) the grinding conditions were as follows: 1) the first treatment was carried out at 80-90 ° C using with a clearance of 0.1 mm; 2) from the second to the sixth treatments were performed at a temperature of 40-50 ° C with a clearance between the plates of 0.1 mm.

No addition of polyvinyl alcohol was performed.

The fibers obtained had the following fiber fractionation:

Table 2A

Mesh Weight - / &

With a No. 20 sieve 6.4 "" 35 33.5 "" 65 29.2 "" 150 17.4, f "270 6.3 Through No. 270 7.2 The flow coefficient of these fibers was 0.46 seconds / g.

The sheets were made by hand in the same manner as in Example 1, with 1 group containing 100% polyethylene fibers and the other group being made of a 50/50 blend with the bleached alder pulp described in Example 1. The features were as follows:

Table 2B

Property 100% 50% alloy 2

Base weight, g / m 63.5 63.4

Density, g / mm 0.36 0.44

Opacity,% 90.3 84.7

Whiteness,% ("Elrepho" No. 8) 92.2 86.0

Breaking length, m 145 2036 TEA, g-cm / cm 2 0.06 29.8

Internal Commitment, Scott Units 25 82

Tear strength, g / sheet 3 30 18 59623

Some of these fibers were mixed with the bleached alder pulp described in Example 1 (40 wt.% Polyethylene fibers, 60 wt.% Pulp) and formed into a paper web on a paper machine using two different heat bonding treatments in the same manner as in Example 1. The resulting web had the following characteristics:

Table 2C

Feature Binding temperature

107 ° C 135 ° C

2

Base weight, g / m 66.6 63.3

Caliber, mm 0.132 0.11

Density, g / ml 0.504 0.573

Tear strength, g / sheet MD 23 24 i XD 26 27

Tensile strength, kg / 15 mm MD 2.93 3.11 XD 1.49 1.70

Elongation, # MD 1.6 1.7 XD 3.5 3.8 TEA, kg-cm / cm 2 MD 0.019 0.020 XD 0.025 0.032

Double Refractive Index (MIT) MD 3 7 XD 2 3 Stiffness, g / cm (Taber) MD 1.17 0.96 XD 0.46 0.45

Internal binding strength (Scott), kg-cm / cm x 10 "^ 152 285

Smoothness, ml / min (Sheffield) WS 328 327 PS 352 293

Porosity, ml / min (Sheffield) 249 278 oil absorption, # 45 32

Sugar color, sec. WS 0 2.1 PS 0 1.6

Whiteness ("Elrepho" No. 8) 85.4 80.9

Opacity, # 80.4 69.1

Breaking length, m MD 3155 3714 XD 1553 1900

Example 3

The treatment according to Example 1 was repeated except for the following: 19 59623 a) the polyethylene concentration was 80 g / l b) the mixture was passed through a nozzle at 150 g / min and c) the purification conditions were as follows: 1) the first treatment was carried out at 80-90 ° C and plates with a clearance of 0.05 to 0.1 mm 2) Treatments 2 to 6 were performed at 20 ° C with a plate clearance of 0.05 to 0.1 mm. No addition of polyvinyl alcohol was performed.

The fibers obtained had the following fiber fraction properties:

Table 3A

Mesh Weight

With sieve No. 20 2.3 "" 35 21.2 "65 32.7" "150 26.2" "270 9.0 Through No. 270 8.6

The flow value of the fibers was 1.10 seconds / g.

\

Test sheets were prepared in the same manner as in Example 1, with one group containing 100% polyethylene fibers and the other group being prepared from a 50/50 blend with the bleached pulp described in Example 1. The properties were as follows:

Table 3B

Property 100% 50/50 mixture p

Base weight, g / m 62.2 62.3

Density, g / mm 0.4l 0.50

Opacity,% 93.7 88.2

Whiteness,% ("Elrepho" No. 8) 93.7 88.4

Breaking length, m 305 2534 TEA, g-cm / cm -1 2.4 47.6

Internal Commitment, Scott Units 20 82

Tear strength, g / sheet 5 29

Some of the fibers were mixed with the bleached alder pulp described in Example 1 (40 wt.% Polyethylene fibers, 60% pulp) and formed into a paper web on a paper machine using two different thermal bond values as in Example 1. The resulting web had the following characteristics:

Table 3C

Feature Binding temperature

1000 ° C 135 ° C

2

Base weight, g / m 60.3 59.9

Caliber, mm 0.130 0.118

Density, g / ml 0.461 0.504

Tear strength, g / sheet MD 31 31 XD 33 36

Tensile strength, kg / 15 mm MD 2.83 3.65 XD 1.39 1.80

Elongation,% MD 1.6 1.7 XD 3.8 3.5 TEA, kg-cm / cm 2 MD 0.019 0.025 XD 0.027 0.034

Double refractive index (MIT) MD 5 12 XD 2 7 Stiffness, g / cm (Taber) MD 1.2 1.1 XD 0.51 0.56

Internal bond strength (Scott), kg-cm / cm ^ x 10 "3 147 466

Smoothness, ml / min (Sheffield) WS 329 363 PS 325 3 ^ 6

Porosity, ml / min (Sheffield) 265,400 oil absorption,% 53 35

Sugar color, sec. WS 0 14.6 PS 0 16.9

Whiteness (“Elrepho” No. 8) 87.4 79.5

Opacity,% 85.9 65.4

Breaking length, m MD 3152 4068 XD 1543 2108

Example 4 In this example, the tank used to prepare the flash evaporation mixture was a 4.54 L "Benco Model o 575" reaction vessel equipped with a 10.5 kg / cm steam jacket, a nitrogen inlet and outlet line, and a centrally located air -driven mixing shaft with mechanical seal. A 10 cm diameter 6-vane turbine (Bench Scale Equipment Co.) was fitted at a distance of no3n] 2.5 cm from the bottom of the tank to the shaft, and a rapidly rotating propeller was fitted about 9 cm below the turbine. The tank was equipped with four vertical partitions at the same distance 21,596,223. The container was provided with an electrode formed by a piece of metal wire tightly fitted through one end of a short glass tube. The other end of the metal wire was inserted through a 30 cm long stainless steel tube (outer diameter 6.3 mm) and the glass tube and the metal tube were connected by means of a "Swagelok" connection device. The electrode was arranged in the vessel so that the metal wire was located above the surface of the water in the mixture described below. The metal wire was attached to one end of the resistance meter in series with the battery. A stainless steel sheath, separated from the metal wire by insulation along its entire length, with an opening between them of about 15 mm, was connected to the other pole. It was found that the value given by brine alone was about 140 millivolts, while the value given by n-hexane alone was about 0-1.0 millivolts. A 19 mm pipe with a ball valve 5 cm below the bottom of the tank left the bottom of the tank. There was a nozzle right next to the ball valve. This nozzle consisted of a 10 * 1 mm long bronze plug with a centrally fitted housing 3.5 mm in diameter. The nozzle plug was fitted to this 19 mm tube, which extended approximately 60 cm to the other side of the nozzle and ended in the outside air. 500 ml of water, 2500 ml of n-hexane, 100 g of polyethylene ("Mitsui 2200P", described in Example 1), 2 g of "Gelvatol 20-30" polyvinyl alcohol and 20 drops of 25% aqueous sodium chloride solution were introduced into the tank. The tank was sealed, purged with nitrogen and the contents heated to 1 * J5-150 ° C while the stirrer was running at 650 rpm. The contents of the container were maintained at 1-5-150 ° C for about 1 1/2 hours to ensure complete dissolution of the polymer. The conductivity of the mixture was about 0.1 x 1.2 millivolts, indicating that water formed a discontinuous phase. The ball valve was then opened and the mixture was passed through a nozzle while maintaining the pressure in the tank constant by the addition of nitrogen. The fibrous product was recovered by causing it to collide with a wire mesh. The fibers were purified by passing them at room temperature through a simple "Sprout Waldron" plate shredder with 60 cm plates ("Sprout Waldron", Fig. C-29-78-B) operating at 2800 rpm, between the plates. with a clearance of 0.005 mm, and a total of four treatments were performed.

The distribution of the fibers obtained was as follows: 22 59623

Table 4A

Mesh Weight%

With a sieve No. 20 2.2 "" 35 18.8 "" 65 35.3 "" 150 24.6 "" 270 9.5 Through a sieve No. 270 9.6

The flow value of the fibers was 4.3 seconds / g.

Test sheets were prepared in the same manner as in Example 1, with one group containing 100% polyethylene fibers and the other prepared from a 50/50 blend with the bleached alder pulp described in Example 1. The features were as follows:

Table 4B

Property 100% 50/50 mixture p

Base weight, g / m 58.6 63.3

Density, g / ml 0.35 0.55

Opacity,% 95.3 89.5

Whiteness,% (Elrepho No. 8) 95.3 88.4 TEA, g-cm / cm ^ 0.009 0.06

Internal? Binding (Scott), kg-cm / cnr x 10 “5 76.7 271, p

Tear strength, g / sheet 8.8 29.6

Tensile strength, kg / 15 mm 0.54 3.4

Elongation,% 3.4 3.7

Example 5

Example 4 was repeated except that polyvinyl alcohol was omitted from the mixture. The electrical conductivity of the mixture was the same as in Example 4. Stirring was stopped for a short time to check the electrodes, and the electrical conductivity rapidly increased to about 100 millivolts, indicating phase separation. After stirring was resumed, the electrical conductivity quickly returned to 0.4-1.2 millivolts. The mixture was kept at 140 ° C for half an hour and then passed through a nozzle at a constant pressure of 11.5 2 kp / cm. The prepared fibers could not be comminuted or hand-made into sheets until they had been treated with 1 weight - ?: 11a of fibers based on "Gelvatol 20-30" polyvinyl alcohol by mixing it with the fibers in an aqueous slurry. fractionation: 23 5 9 6 2 3

Table 5A

Mesh Weight%

With sieve No. 20 0.8 "No. 35 11.7" No. 65 3 ^, 1 "No. 150 31, ^" No. 270 14.0 Through sieve No. 270 8.0

The flow value of the fibers was 16.5 seconds / g.

The test sheets were prepared by the method of Example 1, with one group made of 100 Arista polyethylene fibers and the other a 50/50 blend with the bleached alder pulp described in Example 1. The features were as follows:

Table 5B

Feature 100% 50/50 mixture

Caliber, mm 5.1 »l», l. 2

Base base, g / m 59.0 58.8

Density, g / ml 0.1 * 3 0.57

Opacity,% 9 ^, 8 89.1 *

Whiteness,% ("Elrepho" No. 8) 9 ^, 3 89.0 TEA, cm-g / cm2 27.2 1 * 1 », 5

Internal Commitment, Scott Units 60 102

Tear strength, g / sheet 16.0 33.0

Tensile strength, kg / cm 0.57 1.91

Elongation,% 6.0 3.1 »

Breaking length, m 955 3255

Example 6

The treatment according to Example 1 * was repeated using polypropylene having an intrinsic viscosity of 1.7 dl / g ("Hercules Profax" 6301). In one treatment, the mixture contained 500 ml of water, 2500 ml of n-hexane, 200 g of polypropylene and 2 g of "Gelvatol 20-30" polyvinyl alcohol. This mixture was heated to 11 ° C and maintained at this temperature for 1 hour before flash evaporation. The second treatment was identical to the first treatment except that 100 g of polypropylene was used. The third treatment was identical to the second treatment, except that the temperature of the mixture was raised to 175-180 ° C before rapid evaporation. In all cases, a fibrous product was obtained.

2 "59623

Example 7 Comparative example

Two experiments were performed to compare the fiber products prepared according to the invention (Experiment No. 1) with a fiber product prepared under equivalent fiber production conditions, but using a flash evaporation mixture in which water formed a continuous phase (Experiment n: o 2).

In both of these experiments, a 10-liter steam-jacketed tank with a nitrogen inlet and outlet pipe, an electrode for measuring electrical conductivity, and a central vertical mixing shaft equipped with a mechanical seal were used. A 10 cm diameter upward pumping vane turbine was fitted to the shaft 5 cm from the bottom of the tank.

Two 10 cm diameter straight wing propellers were fitted to the shaft 15 cm and 25 cm above the bottom of the tank. A 10 cm diameter downward pumping turbine and a 7.5 cm diameter downward pumping turbine were fitted to the shaft 35 * 6 cm and 45.7 cm above the bottom of the tank, respectively. The three vertical partitions were arranged at equal distances radially from each other as they extended inwardly from the vessel wall.

This structure ensures that the whole mixture is mixed and avoids areas where only slight mixing occurs which could result in the formation of a continuous aqueous phase.

A 19 mm diameter pipe was fitted to the bottom of the tank with a 19 mm ball valve fitted to the pipe 5 cm below the bottom of the tank. Immediately adjacent to the ball valve was a nozzle with a bronze plug 28 mm long and a hole 1.78 mm in diameter drilled in the center. The nozzle plug was fitted to a tube with an inner diameter of 19 mm and a length of 2.4 mm and terminated in a quick-evaporating tank maintained at ambient pressure.

In both experiments, the materials used to form the flash evaporation mixture were the same, namely 4800 ml of n-hexane, 384 g of polyethylene (Mitsui Hyzex 5000P, intrinsic viscosity 2.0), 3200 ml of water and 7.7 g of Gelvatol 20- 30 ”polyvinyl alcohol (88% hydrolyzed, molecular weight 10,000) .However, the formation of this flash evaporation mixture from these materials was different in the two experiments.

25 59623

In Experiment No. 1 (an example of the invention), the solvent and polymer were first introduced into the tank, the tank was then sealed and purged with nitrogen, and the contents were heated to about 144 ° C and maintained at that temperature with the stirrer running at 1000 rpm for about 2 hours. to ensure dissolution. The PVA was then dissolved in water in a separate tank and this solution was heated to about 144 ° C. The heated solution was then introduced under pressure into a container containing the heated polymer solution at a rate of about 500 ml / minute. This slow and gradual rate of addition caused the water to form and remain as a dispersed phase in the mixture. During the addition of the aqueous PVA, the mixing device rotates in the tank containing the polymer solution at a speed of 100 rpm. Stirring of this mixture was continued for 15 minutes and then the conductivity of the mixture was measured and found to be substantially zero millivolts, indicating that water was a discontinuous phase in the mixture.

In Experiment No. 2 (Comparative Example), the preparation of a flash evaporation mixture was performed using the method of Example 4, i. all the material was introduced into the tank used in Experiment No. 1 at room temperature, and the mixture was heated and then stirred at the same rate as in Experiment No. 1 to effect dissolution of the polymer and dispersion of water containing PVA. After stirring at 110 to 140 ° C for 2 hours, the conductivity of this mixture was measured and found to exceed 100 millivolts, indicating that water was in the continuous phase and the polymer solution in the discontinuous phase.

In each of Experiments 1 and 2, the mixture was formed as described and then heated to 144 ° C and flash evaporated at this temperature and pressure of 11.2 kp / cm using the procedure of Example M, and the flash evaporated material was comminuted using the apparatus described in Example 4, except that the chopping discs used were those with the '' Sprout Waldron '' pattern P-29-76-B. The comminution was performed in water with a consistency of approximately 3%. · The clearances between the plates were as follows: First treatment 6.4 mm, second treatment 0.6 mm, third treatment 0.3 mm, fourth and additional treatments 0.05 mm. The rapidly evaporated material from each treatment was comminuted in this manner until the fibrous product had a classified fiber length (CPL) of approximately 1.2 mm. A portion of the products from each experiment were then comminuted using further processing by this process to produce a fibrous product having a rated fiber length (CPL) of about 0.8 mm. The properties of these fibrous products and the sheets made from them (as described in Example 1) were determined and compared with each other to give the following results: 27 59623

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Comparing the fiber properties of the fiber products obtained from Experiments 1 and 2 and the properties of the test sheets which were comminuted to substantially the same classified fiber length, it can be easily seen that the fiber products made according to the invention (Experiment 1) are completely superior to those produced by flash evaporation. a corresponding mixture in which water occurs as a continuous phase (Experiment 2). The flow value of the fibrous products made according to the invention is considerably higher, as are the strength properties of the sheets made by hand from such fibrous products. These products were also found to contain very small amounts of fiber bundles and polymer agglomerates.

Claims (5)

30 59623 A process for producing polyolefin fibers, especially polyethylene and polypropylene fibers (1) by forming a mixture containing water and a solution of polyolefin in an organic liquid, (2) by expansion evaporation of the mixture at a temperature of 120-160 ° C from a zone of elevated pressure, under reduced pressure to the zone where the organic liquid evaporates and the polyolefin precipitates as fibers, after which the fibers are refined, characterized in that the water is mixed with the polyolefin solution to disperse the water as droplets in the continuous phase formed by the solution. Process according to Claim 1, characterized in that less than 30% by volume of water is added to the mixture. Process according to Claim 1 or 2, characterized in that the polyolefin is present in an amount of about 2 to 30% by weight of solvent plus polyolefin. The method of claim 1, wherein the polyolefin is polyethylene or polypropylene having an intrinsic viscosity of greater than about 0.7 dl / g and is present in an amount of about 5-15 weight percent solvent plus polyolefin. Process according to any one of the preceding claims, characterized in that A. a solution is formed which contains: (1) at least partially crystalline polyolefin, and (2) a substantially water-immiscible organic solvent of polyolefin in an amount of 70 to 98% by volume of polyolefin and solvent. B. water is added to this solution at a temperature above the melting point of the polyolefin and in an amount of 30 to 70% by volume of the mixture, while the solution is sufficiently agitated to disperse water into the dispersed phase, C. the mixture thus formed is kept at said temperature, at the melt dissolution temperature and autogenous pressure or higher, and D. the mixture is passed through a nozzle to a lower pressure zone.