CA1178757A - Polyoxymethylene fibrids, a process for their preparation, and their use - Google Patents
Polyoxymethylene fibrids, a process for their preparation, and their useInfo
- Publication number
- CA1178757A CA1178757A CA000415335A CA415335A CA1178757A CA 1178757 A CA1178757 A CA 1178757A CA 000415335 A CA000415335 A CA 000415335A CA 415335 A CA415335 A CA 415335A CA 1178757 A CA1178757 A CA 1178757A
- Authority
- CA
- Canada
- Prior art keywords
- fibrids
- polyoxymethylene
- weight
- fibrid
- polymer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B16/00—Use of organic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of organic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
- C04B16/04—Macromolecular compounds
- C04B16/06—Macromolecular compounds fibrous
- C04B16/0608—Fibrilles, e.g. fibrillated films
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
- D01D5/00—Formation of filaments, threads, or the like
- D01D5/06—Wet spinning methods
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
- D01D5/00—Formation of filaments, threads, or the like
- D01D5/26—Formation of staple fibres
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
- D01F6/58—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products
- D01F6/66—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products from polyethers
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H5/00—Special paper or cardboard not otherwise provided for
- D21H5/12—Special paper or cardboard not otherwise provided for characterised by the use of special fibrous materials
- D21H5/20—Special paper or cardboard not otherwise provided for characterised by the use of special fibrous materials of organic non-cellulosic fibres too short for spinning, with or without cellulose fibres
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Textile Engineering (AREA)
- Ceramic Engineering (AREA)
- Mechanical Engineering (AREA)
- Organic Chemistry (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- General Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Compositions Of Macromolecular Compounds (AREA)
- Artificial Filaments (AREA)
- Preparation Of Compounds By Using Micro-Organisms (AREA)
- Paper (AREA)
- Polyoxymethylene Polymers And Polymers With Carbon-To-Carbon Bonds (AREA)
- Manufacture Of Macromolecular Shaped Articles (AREA)
Abstract
Abstract of the disclosure:
The invention relates to polyoxymethylene fibrids having a reduced specific viscosity of 0.5 to 2.0 dl/g-1 and a specific surface area of 30 to 200 m2/g, which are comprised of at least 95% of fiber-like particles the mean length of which is between 0.2 and 5 mm and have a bulk density which does not exceed 150 g/liter.
According to the invention, the fibrids are pre-pared by forcing a solution of polyoxymethylene in a solvent mixture of lower alcohols and water through a nozzle into a moving precipitation bath, the solvent mixture being comprised of a mixture of lower alcohol and 3-25% by weight of water and the temperature of the precipitation bath being 0 to 100°C. The fibrids thus obtained are suitable for preparing paper and as an addi-tive for building materials.
The invention relates to polyoxymethylene fibrids having a reduced specific viscosity of 0.5 to 2.0 dl/g-1 and a specific surface area of 30 to 200 m2/g, which are comprised of at least 95% of fiber-like particles the mean length of which is between 0.2 and 5 mm and have a bulk density which does not exceed 150 g/liter.
According to the invention, the fibrids are pre-pared by forcing a solution of polyoxymethylene in a solvent mixture of lower alcohols and water through a nozzle into a moving precipitation bath, the solvent mixture being comprised of a mixture of lower alcohol and 3-25% by weight of water and the temperature of the precipitation bath being 0 to 100°C. The fibrids thus obtained are suitable for preparing paper and as an addi-tive for building materials.
Description
1 ~7875~ `
- 2 - HOE 81/F 308 Fibrids are understood as meaning small fibers ~hich are oriented in longitudinal direction and have a cellulose-like structure, i.e. which have a finite but non-uniform length, ;rregular thickness, fissured surface and a high degree of twinning.
The preparation of such fibrids is known, for example from German Patent 1,290,040. In this patent, the first step is to prepare plexus filaments, which are then cut into staple lengths, the staple fiber particles are suspended in a l;quid, and the particles present in the suspension are fibr;llated in a way which is in itself known. The term plexus filament is used here to describe a filamentous product which is made from a crystalline plastic and has a three-dimensional network which is virtually free of tunnel-like channels and voids and con-sists of a large number of molecularly oriented film- or tape-l;ke fibrids which have a th;ckness of less than 2 ~m and wh;ch co~b;ne w;th and separate from one another at irregular intervals along their length and are preferably 2û oriented in the direction of the longitud;nal axis.
These plexus filaments, and their preparation, are described in more detail in 8elgian Patent 568,524. In this patent, a solution which is under its autogenous pres-sure or under an elevated pressure of a synthetic polymer 25 tS ex~ruded at a temperature which ;s above the atmos-pher;cally measured bo;ling point of the solvent through an orifice into a space under a low pressure, to prcpare l 178757 the plexus filaments. This preparation of plexus filaments is also called flash spinning or relaxation spinning.
Polyoxymethylene can also be used to prepare plexus filaments in this way and then to fibrillate them to give fibrids. The solvents used in Belgian Patent 568,524, to prepare the plexus filaments, are aprotic solvents, namely methylene chloride, ethylene chloride, acetonitrile and methyl ethyl ketone. As experiments have shown, the process does not produce fibrids, but only plexus filaments, even at extremely low polymer concen-trations of, for example, 1X by weight in methyl ethyl ketone. However, since plexus filaments are unsuitable for producing paper and for use as an additive for build-ing materials, they must be processed in a second process step in accordance with German Patent 1,290,~40 above to g;ve fibrids, the process becoming more involved as a result. The polyoxymethylene fibrids thus obtained have, in particular, a relatively small specific surface area and a low degree of beating, and papers made therefrom have relatively low strengths.
In contrast, U.S. Patent 2,988,782 proposes the preparation of fibrids by precipitatin~ polymers under certain precipitation conditions. Fibrids of this type are suitable for preparir)g sheet-like structures on a paper machine~ Ho~lever, in this patent fibrids are understood as meanin~ particles which are fiber-like or film-like~ ~he film-like constituents are troublesome in industrial paper manufacture, since some of ~hem pass throuyh the sieve. They also render the resulting paper 1 1~87~7 to be of low quality, since on printing film-like con-stituents are picked out and white defects form. In building materials, film-(ike constituents contribute virtually nothing to the thickening action desired and are therefore quality-reduc;ng.
Further, German Auslegeschrift 1,241,116 describes the formation of long- or short-fibrous polyoxymethylene by precipitating polyoxymethylene from its solutions (cf.
Examples). The products characterized as short-fibrous are, however, those which are severely contaminated uith film-like constituents. The long-fibrous product is found to be unsuitable for making paper and for use as a thicken-ing agent in building materials due to its excessive length of 10 to 50 cm and its thickness of more than 1 mm.
Neither can the products described be dried without des-troying their fibrid structure.
Finally, German Offenlegungsschrift 2,947,490 has for the first time disclosed a one-stage process for pre-paring polyoxymethylene fibrids using the flash spinning 2D method and which is characterized by a specific choice of solvent mixture. However, this process has the disadvan tage that the mixture claimed, of a low alcohol and water, changes its composition during the evaporation step and that expensive measuring and control devices therefore become necessary for the continuous recycling of the evaporated solvent mixture in order to maintain the sol-vent composition at a constant value. The fibrids obtained in this process also tend to stick together on drying with substantial loss of their fibrid structure; their 1 1787~
bulk density is also relatively high.
The object of the present invention, then, was to provide polyoxymethylene fibr;ds and a process for their preparation which are free, or at least largely free, of the disadvantages of the state of the art and, in par-ticular, the abovementioned disadvantages.
Accordingly, the invention relates to polyoxy-methylene fibrids which have a reduced specific viscosity of 0.5 and 2.0 dl . 9-1, preferably 0.6 to 1.20 dl . 9-1 (measured in butyrolactone which contains 2% by weight of diphenylamine, at 140C in a concentration of 0.5 9/100 ml) and a specific surface area (by BET with argon) of 30 to 200 m2/g, preferably 50 to 120 m2/g, which are comprised of at least 95% of fiber-like particles the average length of which is between 0.2 and 5 mm and have a bulk density which does not exceed 150 g/liter (air-dispersed s~ate).
The invention also relates to a process for pre-paring polyoxymethylene fibrids by extruding a solution of the polymer in a solvent mixture of lower alcohol and water through a nozzle into a Drecipitation bath which is kept in motion, wherein the temperature in the precipi-tation bath is 0-100C and the solvent mixture contains
The preparation of such fibrids is known, for example from German Patent 1,290,040. In this patent, the first step is to prepare plexus filaments, which are then cut into staple lengths, the staple fiber particles are suspended in a l;quid, and the particles present in the suspension are fibr;llated in a way which is in itself known. The term plexus filament is used here to describe a filamentous product which is made from a crystalline plastic and has a three-dimensional network which is virtually free of tunnel-like channels and voids and con-sists of a large number of molecularly oriented film- or tape-l;ke fibrids which have a th;ckness of less than 2 ~m and wh;ch co~b;ne w;th and separate from one another at irregular intervals along their length and are preferably 2û oriented in the direction of the longitud;nal axis.
These plexus filaments, and their preparation, are described in more detail in 8elgian Patent 568,524. In this patent, a solution which is under its autogenous pres-sure or under an elevated pressure of a synthetic polymer 25 tS ex~ruded at a temperature which ;s above the atmos-pher;cally measured bo;ling point of the solvent through an orifice into a space under a low pressure, to prcpare l 178757 the plexus filaments. This preparation of plexus filaments is also called flash spinning or relaxation spinning.
Polyoxymethylene can also be used to prepare plexus filaments in this way and then to fibrillate them to give fibrids. The solvents used in Belgian Patent 568,524, to prepare the plexus filaments, are aprotic solvents, namely methylene chloride, ethylene chloride, acetonitrile and methyl ethyl ketone. As experiments have shown, the process does not produce fibrids, but only plexus filaments, even at extremely low polymer concen-trations of, for example, 1X by weight in methyl ethyl ketone. However, since plexus filaments are unsuitable for producing paper and for use as an additive for build-ing materials, they must be processed in a second process step in accordance with German Patent 1,290,~40 above to g;ve fibrids, the process becoming more involved as a result. The polyoxymethylene fibrids thus obtained have, in particular, a relatively small specific surface area and a low degree of beating, and papers made therefrom have relatively low strengths.
In contrast, U.S. Patent 2,988,782 proposes the preparation of fibrids by precipitatin~ polymers under certain precipitation conditions. Fibrids of this type are suitable for preparir)g sheet-like structures on a paper machine~ Ho~lever, in this patent fibrids are understood as meanin~ particles which are fiber-like or film-like~ ~he film-like constituents are troublesome in industrial paper manufacture, since some of ~hem pass throuyh the sieve. They also render the resulting paper 1 1~87~7 to be of low quality, since on printing film-like con-stituents are picked out and white defects form. In building materials, film-(ike constituents contribute virtually nothing to the thickening action desired and are therefore quality-reduc;ng.
Further, German Auslegeschrift 1,241,116 describes the formation of long- or short-fibrous polyoxymethylene by precipitating polyoxymethylene from its solutions (cf.
Examples). The products characterized as short-fibrous are, however, those which are severely contaminated uith film-like constituents. The long-fibrous product is found to be unsuitable for making paper and for use as a thicken-ing agent in building materials due to its excessive length of 10 to 50 cm and its thickness of more than 1 mm.
Neither can the products described be dried without des-troying their fibrid structure.
Finally, German Offenlegungsschrift 2,947,490 has for the first time disclosed a one-stage process for pre-paring polyoxymethylene fibrids using the flash spinning 2D method and which is characterized by a specific choice of solvent mixture. However, this process has the disadvan tage that the mixture claimed, of a low alcohol and water, changes its composition during the evaporation step and that expensive measuring and control devices therefore become necessary for the continuous recycling of the evaporated solvent mixture in order to maintain the sol-vent composition at a constant value. The fibrids obtained in this process also tend to stick together on drying with substantial loss of their fibrid structure; their 1 1787~
bulk density is also relatively high.
The object of the present invention, then, was to provide polyoxymethylene fibr;ds and a process for their preparation which are free, or at least largely free, of the disadvantages of the state of the art and, in par-ticular, the abovementioned disadvantages.
Accordingly, the invention relates to polyoxy-methylene fibrids which have a reduced specific viscosity of 0.5 and 2.0 dl . 9-1, preferably 0.6 to 1.20 dl . 9-1 (measured in butyrolactone which contains 2% by weight of diphenylamine, at 140C in a concentration of 0.5 9/100 ml) and a specific surface area (by BET with argon) of 30 to 200 m2/g, preferably 50 to 120 m2/g, which are comprised of at least 95% of fiber-like particles the average length of which is between 0.2 and 5 mm and have a bulk density which does not exceed 150 g/liter (air-dispersed s~ate).
The invention also relates to a process for pre-paring polyoxymethylene fibrids by extruding a solution of the polymer in a solvent mixture of lower alcohol and water through a nozzle into a Drecipitation bath which is kept in motion, wherein the temperature in the precipi-tation bath is 0-100C and the solvent mixture contains
3-25X by weight of water, relative to the total mixture.
Known polyoxymethylenes are a suitable material for preparing fibrids according to the invention. These polyoxymethyLenes may be understood as incLuding homo-polymers of formaldel7yde or of a cyclic oligomer of form-aldehydef for example trioxane, the terminal hydro>yl groups of which are stabilized against degradation in a l 178757 kno~n ~ay by chemical means, for example by etherification or esterification.
Furthermore, according to the invention, the term polyoxymethylenes also embraces copolymers of formaldehyde or of a cyclic oligomer of formaldehyde, preferably trioxane, the copolymers having, in addition to oxymethylene units, oxyalkylene un;ts in the primary valency chain which have at least two, preferably two to eight, and specifically two to four, adjacent carbon atoms and possess terminal primary alcohol groups. The comonomer content in the copolymers is advantageously 0.1 - 20, preferably 0.5-10, % by weight and, in particular, 0.7 - 5X by ~eight.
Compounds which are suitable for copolymerizing with formaldehyde or cyclic oligomers of formaldehyde, preferably trioxane, are in particular cyclic ethers pre-ferably having 3, 4 or 5 ring members and/or cyclic acetals which differ from trioxane, namely preferably formals having 5 - 11, preferably 5, 6, 7 or 8, ring members and/
or l;near polyacetals, preferably polyformals.
Suitable comonomers for trioxane are in particular compounds of the formula C~2 ~ ~CR1H]X - tO - (CR2~) ] -0 L z y in which (A) R1 and R2 are identical or different and each deno.es a hydrogen atom, an aliphatic alkyl radical having 1 - 6, preferably 1, 2, 3 or 4, carbon atoms or a phenyl radical and ~a) x is equal to 1, 2 or 3 and y is equal to zero or (b) x is equal to zero, y is equal to 1, 2 or 3 and z is equal to 2 or (c) x is equal to zero, y is equal to 1 ar,d z is equal ~o 3, 4, 5 or 6, or ~e) R1 l 178757 denotes an alkoxymethyl radical having 2 - 6, preferably 2, 3 or 4, carbon atoms or a phenoxymethyl radical, and x is equal to 1 and y is equal to zero or y and z are equal to 1 and R2 has the abovementioned meaning.
Epoxides, for example ethylene oxide, propylene oxide, styrene oxide, cyclohexene oxide, oxacyclobutane and phenyl glycidyl ether, in particular, are used as cyclic ethers.
Suitable cyclic acetals are in particular cyclic formals of aliphatic or cycloaliphatic a,~ -diols having 2 - 8, preferably 2, 3 or 4 carbon atoms and the carbon chain of ~hich can be interrupted by an oxygen atom at intervals of 2 carbon atoms, for example glycol formal (1,3-dioxolane), propanediol formal (1,3-dioxane), butane-diol formal ~1,3-d;oxepane) and diglycol formal (1,3,6-trioxocane) and 4-chloromethyl-1,3-dioxolane and hexane-diol formal ~1,3-dioxonane). Unsaturated formals, such as butenediol formal (1,3-dioxacyclohept-5-ene), are also possible.
Not only homopolymers but also copolymers of the cyclic acetals defined above and also linear condensates of aliphatic or cycloaliphatic a ,~ -diols ~ith aliphatic aldehydes or thioaldehydes, preferably formaldehyde, can be used as linear polyacetals. In particular, homopoly-mers of l;near formals of aliphatic a,~ -diols having 2 -8, preferably 2 - 4, carbon atoms, for example poly(1,3-dioxolane), poly(1,3-dio%ane) and poly(1~3-dioxepane), are used.
Conlpoul1ds having several polymeri~able qroups in the 1 17875~
molecule, for example alkylglycidyl formals, polyglycol diglycidyl ethers, alkanediol diglycidyl ethers or bis-(alkanetriol) triformals, may also be used as addit;onal comonomers for trioxane, in an amount of O.OS - 5, pre-ferably 0.1 - 2, X by weight, relative to the total amount of monomer. Such additional comonomers have been des-cr;bed, for example, in German Auslegeschrift 2,101,817.
The values for the reduced specific viscosity (RSV values~ of polyoxymethylenes used according to the invention, and hence also of fibrids obtained therefrom, are in general between 0.5 and 2.0 dl.g 1, preferably between 0.7 and 1.20 dl.g 1 (measured in butyrolactone which contains 2X by weight of diphenylamine, at 140C in a concentration of 0.5 9/100 ml).
The crystallite melting points of the polyoxy-methylenes are within a range of 140 - 180C, preferably 150C - 170C, and their densities are between 1.38 and 1.45 g.ml 1, preferably 1.40 and 1.43 g.ml~1 (measured ;n accordance with DIN 53,479).
lf polymers are used which have an RSV value which is lower than those indicated above, fibrids are admittedly also formed; but they are relatively short and mixed ~o an increasing extent with non-fibrous fractions. By means of the RSV value of the polymer it is thus possible to control the fiber length, the degree of slenderness and the degree of branching of the fibrids, so that preferable ranges depend on where the fibrids are to be used. At higher RSV values, in particular dissolving the polymer proves increasingly troublesome and therefore nore expensive.
l 1787~7 The preferably binary or ternary oxymethylene co-polymers used according to the invention are prepared in a known ~ay by polymerizing the monomers in the presence of cationically active catalysts at temperatures between 0 and 100C, preferably between 50 and 90C (cf. for example U.S~ Patent 3,027,352). Examples of catalysts used here are Lewis acids, for example boron trifluoride and antimony pentafluoride, and complex compounds of Lewis acids, preferably etherates, for example boron trifluoride diethyl etherate and boron trifLuoride di-tert.-butyl etherate. Protonic acids, for example perchloric acid, and salt-like compounds, for example triphenylmethyl hexa-f luorophosphate, triethyloxonium tetrafluoroborate or acetyl perchLorate, are also suitable. The polymerization can be ~arried out in water~ a suspension or a solution.
To remove unstable fractions, the copolymers are advan-tageously subjected to partial controlled thermal or hydrolytic degradation down to terminal primary alcohol groups (cf. U.S. Patents 3,103,499 and 3,119,623).
2U Homopolymers of formaldehyde or of trioxane which are used according to the invention are also prepared in a known manner by catalytically polymerizing the r,onomer (c~. for example U.S. Patents 2,768,994 and 2,989,505).
Fibrids according to the invention are comprised of at least 95%, preferably o, at least 97% and in par-ticular of 98 to 100% of fiber-like particles. They thus contain either no or only an extremely small fraction of film-like consti uents. The content of film-like con-stituents is determined microscopically on moist, r,ot yet I ~87~7 -- ~o --dried, product. Their content is defined as the number of film-like constituents in proportion to the total number of par~icles in an area of the microscope slide.
Particles are called film-like if their ratio of length to diameter is belo~ 5 : 1. The measurement area, and also the concentration of particles in this measurement area, must of course be chosen in such a way that an adequate number of particles can be seen and hence the accuracy of measurement is correspondingly high.
Since the content of fiber-like particles is high, the bulk density is low and is at most 150 g/liter, pre-ferably between 10 and 100 g/liter and in particular ' between 20 to 80 g/liter. To measure the bulk density ~;thin the meaning of the ;nvention, 10-50 9 of fibrids dried at room temperature are whipped up at level II
~about 1,000 rpm) in a kitchen mixer, for example "Starmix"
from Messrs. Elektrostar Schottle GmbH and Co., Reichenbach, with 1 liter capacity, until all fibrids are freely mobile;
this usually takes about 10 seconds. They are then dis-charged by means of an earthed wire to eliminate theinfluence of an electrostatic charge which may be present.
The ~eight of the loose material is determined in a 250 ml graduated rylinder, ~hich, before the reading is taken, is repeatedly tapped firmly until the volume of the loose material remains constant.
Fibrids according to the invention also have a non-uniform length the mean of which is between 0.2 and 5 mm, preferably 0~2 to 2 mm and in particular betweon 0.5 and 1.5 mm. 1'he cross-sec~ion is also non-uniform in ~ vt~s tr~
shape and size; the thickness ~the apparent diameter) is predominantly about 1 - 2ûO ym~ preferably 2 - 50 ,um. The mean length of the fibrids is determined as CFL (classi-fied fiber length) in accordance with the TAPPI method T 233, and the thickness of the fibrids is determined in accordance with TAPPI method T 234 (coarseness). A method which is suitable for rapidly determining th;s mean length and the thickness of the fibrids is a measurement by ~ microscope, in which the most frequently occurring lengths and thicknesses are visually determined. Only the longest fibrils (branches) on the fibrids enter into this measure-ment of len~th.
Since fibrids according to the invention are highly branched, they have a large specific surface area (by 8ET using ar~on) of usually 30 - 200 m2/g, prefer-ably 50 - 120 m2/g.
The degree of beating is also correspondingly high and amounts to 20 to 80 SR, preferably 25 to 50 SR. The degree of beating is determined as the Schoppcr-Riegler value in accordance with leaflet V/7/61 (old version 107) of the Verein der Zellstoff- und Papier-Chemiker und Ingenieure CAssociation of Cellulose and Paper Chemists and ~ngineers] (issued on 1st July 1961).
Polyoxymethylene fibrids according to the invcntion have hydrophilic surface properties and are therefore readily dispersible in ~ater - usually even without a wetting agent. Filters prepared therefrom have improvcd adsorptive properties. In spccial cases it can even be advisable to produce hydrophobic surface properties by l 178757 adding suitable hydrophobing agents.
Fibrids according to the invention can contain the additives described below, namely functional additives, for example nucLeating agents, colored pigments, stabil~
izers, antistatic flame retardants, lubricants, optical brighteners and the like as well as fillers. This can affect the properties of the fibrids, for example in res-pect of the morphology, the degree of beating or the bulk density. Thus, certain heavy fillers will correspond-ingly raise the bulk density; if such fillers are presentin high percentages, the limit specified above, of 150 g/liter, can be exceeded. However, the range accord-ing to .he invention, of the bulk density, is maintained if the dens;ty difference between filler and polymer ;s allowed ~for.
The additives content is generally up to 75X by weight, in the case of functional additives, preferably 0.1 to 10X by weight, relative to the total mixture; for fil-lers the preferable range extends from 30 to 65% by weight.
Owing to their branched morphology, fibrids accord-ing to the ;nvention can be very readily processed in a known way, for example as described in German Patent 1,290,040, to give paper having good properties.
Excellent papers, which can be glazed, coated, laminated and printed in a customary way, can be prepared from these fibrids even when mixed w;th other fiber materials, such as cellulose, cellulose fibers and synthetic fibers.
Fibrids according to the invention can also be used, for example, for wallpapers, filters, labels, metallic papers and other special papers and the like.
Polyoxymethylene fibrids can also be processed on board machines, the resulting cardboards having an excellent resistance to water. Polyoxymethylene fibrids according to the invention can also be used in non-wovens and as a thickening agent in rapid-curing asphalt, paints, renders, adhesives, sealing compositions and coating materials based on unsaturated polyesters, epoxide resins, bitumen pastes and PVC plastisols. Finally, they are also highly suitable as an additive to building materials, such as cement, if appropriate together with other fiber-forming materials, for example for manufacturing cement-fiber boards and the like.
In the process according to the invention for pre-paring polyoxymethylene fibrids, a solution of the polymer is forced through one or more nozzles into a moving precipitation bath. To carry out this process, first a preferably homogeneous solution of the polymer is prepared, starting from a dry or solvent-moist powder or granules, depending on the method of preparation of the polymer, and mixing the polymer ~ith the solvent and heating the mixture, for example in pressure autoclaves with stirring, for example by steam jacket heating or by blowing in steam.
~f in the polymer;zation or the subsequent stabilizing and working-up processes the polyoxymethylenes are obtaincd as a solution or suspension in an alcoholtwater mixture of the composi' ion according to the invention, it is possible to use this solut-ion or susper~sion d;rectly in 1 17875~
the process according to the invent;on.
According to the invention - as already mentioned -~he solvent used is a mixture of 75 - 97X by weight of a lower alcohol having 1 - 4 carbon atoms and 3 - 25X
by weight of water, each relative to the total solvent mixture. Examples of lower alcohols which are possible for this purpose are methanol, ethanol, isopropanol, n-propanol, n-butanol and i-butanol and mixtures of these alcohols. If higher alcohols, of more than 4 carbon atoms, for example n-hexanol, are used fibrids are admittedly also formed, but ;n this case the temperature which is neces-sary for preparing the solution is relatively high.
Methanol and isopropanol are preferably used.
The mixing rat;o of alcohol and water is of con-siderable importance for the preparation of the fibrids.If, for example, less than about 75% by ~eight of the lower alcohol and more than about 25X by weight of water are used, fibrids are obtained which, on drying not only at room temperature, but also at elevated temperatures, 2~ stick together to form a more or less granular product and lose their fibrid structure. The fibrid structure can no longer be recovered by means of dispersing equip-ment using customary mechanical forces. The tendency to stick together can be monitored by measuring the bulk Z5 density in the manner described above. A further disad-vanta~e if the a~cohol content in the solvent mixture is too low is that in this case the fibrids end up rela-tively short.
~ f, on the other hand, a solvent mixture is used ~ 1787~7 which contains a relatively large amount of alcohol and a relatively loh amount of water, the result is increasing difficulties in dissolving the polymer. The range of 85 - ~SX by veight of the lo~er alcohol and 5 - 15X by weight of water is preferable, since at these values the dissolution properties of the polymer and the stability of the fibrid morphology on drying and the producible length of the fibrids are particularly well balanced.
The concentration of .he polymer in the solvent mixture is as a rule between 10 and 300 9 per liter of soLution, preferably bet~een 50 and 200 9 per liter.
Lower concentrations are usually uneconomicaL, since they require a large amount of circulating solvent; higher concentrations frequently harbour the risk that two-1~ dimensional film-like constituents are formed. The upper limit of the polymer concentration also depends to a certain extent on the molecular weight; the h;gher the molecular weight, the lower is the concentration permissible in this process. If the process is carried out in a continuous manner, the polymer concentration used must also be har-monized with the amount of solvent in the precipitation bath ;n order for the resulting fiber suspension to remain pumpable, which requires a fibrid concentration of less than 5% by weight. Depending on the length of the fibrids, a final concentration of 1 - 3% by weight is as a rule desirable. The longer the fibrids the more the suspension has to be diluted.
There i a relationship between the polymer con-centration and the fiber length, so that an expert can l 1787~7 ~ 16 -use the polymer concentration (and - as mentioned - the amount of alcohol) to set the desired fiber dimensions.
Thus, the fibrids become shorter the lower the polymer concentration (and the lower the amount of alcohol).
The temperature of the solutiGn of the polyoxy-methylene depends on the molecular weight of the polymer, the nature and amount of the comonomer and the composition of the solvent. If homogeneous solutions are used the temperature necessary for d;ssolution must be considered the lower temperature limit, while the upper temperature limit is essentially only restricted by economic consider-ations. The dissolution temperature is known for many examples and can otherwise be easily experimentally determined or interpolated from known data by an expert.
This temperature range ;s between 150 and 190C for the preferred alcohols in their preferred mixing ratios with ~ater. The solution is as a rule under the autogenous Yapor pressure of the solvent mixture at this temperature, but the pressure can be considerably increased by inert gas pressure or by means of a pump. The pressure is in general between 20 and 60 bar, preferabLy between ZO and 30 bar.
In addition to the polymer, the solution can also contain auxiliaries from the polymerization, for example decomposition products of the catalys~s for the cationic polymerizat;on, which products are described in 8ritish Patent 1,i46,649~ ~erman Offenlegungsschriften 1,595,7U5 and 1,595,668 and German Ausle~eschriften 1,199,504 and 1,175,~2. These auxiliaries also include compounds which I ~ 787~7 have a basic reaction and are used for removing unstable fractions down to the terminal pr;mary aLcohol group, for example lo~er tertiary aliphatic amires, such as tri-ethylamine or triethanolamine, or a secondary alkali metal phosphate, such as disodium hydrogenphosphate (cf. U.S.
Patents 3,174,948, 3,219,6Z3 and 3,666,714), and the resulting reaction products, for example methylal, tri-oxanc, tetroxane, formic acid and methyl formate.
The polymer solution can also contain a very wide variety of known additives. Examples of such additives are customary nucleating agents, which accelerate the crystallization and by means of which the morphology of the fibrids can be influenced, such as, for example, branched or crosslinked polyoxymethylenes, taLc or boron nitride (cf. German Patent 2,101,817 and German Offen-legungsschrift 1,940,132).
Fillers can also be suspended ;n the solution.
Suitable fillers are all naturally occurring or synthetic-ally prepared inorganic materials in unmodified or surface-modified form, in particular metal powders, antimony tri-oxide, carbon black, graphite, ground rock, quartz powder, mica, slate po~der, feldspath powder, diatomaceous earth, finely d;vided asbestos, sparingly soluble oxides, hy-drated oxides, hydroxides, silicates, aluminates, borates, 2~ ferrites, sulfates, carbonates, basic salts and double salts~ preferably containing aluminum and/or magnesium, calcium, sodium, titaniuM or iron as the metal component.
Particularly prefer2ble fillers are t;tanium dioxide, alumina, calcium carbonate, talc, dolornite, wollastor,ite, 1 1787~
silica, hydrated aluminum oxide and calcium sulfate. Of these clay, calcium carbonate, talc and silica are par-ticularly preferable.
These fillers can have been treated in a known manner, for example ~ith silanes, and generally have a mean particle size between 0.1 and 50 ~m, preferably between 0.5 and 10 ~m.
The amount of additive in the polymer solution depends on the field of application and on the nature of the additive and is sufficiently high for the abovementioned contents in the fibrids to be obtained. In general, the amount ;s thus up to 80X, in the case of functional additives preferably between 0.1 and 10X by weight, rela-tive to the total solids comprised of polymer and additive.
In the case of a filler, a concentration of 30 - 70X by ~eight, relative to total sol;ds, is advantageously used in most fields of applicat;on.
Further additives to be mentioned are kno~n stabil-;zers against the influence of heat, oxygen and/or air, as described, inter alia, in German Offenlegungsschrift 2,043,498. Compounds particularly suitable for this pur-pose are bisphenol compounds, alkaline earth metal salts of carboxylic acids and guanidine compounds. The bis-phenol compounds used are chiefly esters of monobasic 4-hydroxyphenylalkanoic ac;ds which conta;n 7 - 13, prefer-ably 7, ~ or 9, carbon atoms and are mono- or di-ring-substituted by an alkyl radical containing 1 - 4 carbon atoms. The alcohol components in these esters are ali-phatic dihydric, trihydric or tetrahydric alcohols which ~ ~787~7 _ 19 _ contain 2 - 6, preferably Z, 3 or 4, carbon atoms. Examples uhich may be mentioned of such esters are esters of ~-(3-tert.-butyl-4-hydroxyphenyl)-pentanoic acid, ~-(3-methyl-5-5-tert.-butyl-4-hydroxyphenyl)-propionic acid, ~3,5-di-tert.-bu.yl 4-hydroxyphenyl)-acetic acid, ~-(3,4-di-tert.-butyl-4-hydroxyphenyl)-propionic acid or ~3,5-di-isopropyl-
Known polyoxymethylenes are a suitable material for preparing fibrids according to the invention. These polyoxymethyLenes may be understood as incLuding homo-polymers of formaldel7yde or of a cyclic oligomer of form-aldehydef for example trioxane, the terminal hydro>yl groups of which are stabilized against degradation in a l 178757 kno~n ~ay by chemical means, for example by etherification or esterification.
Furthermore, according to the invention, the term polyoxymethylenes also embraces copolymers of formaldehyde or of a cyclic oligomer of formaldehyde, preferably trioxane, the copolymers having, in addition to oxymethylene units, oxyalkylene un;ts in the primary valency chain which have at least two, preferably two to eight, and specifically two to four, adjacent carbon atoms and possess terminal primary alcohol groups. The comonomer content in the copolymers is advantageously 0.1 - 20, preferably 0.5-10, % by weight and, in particular, 0.7 - 5X by ~eight.
Compounds which are suitable for copolymerizing with formaldehyde or cyclic oligomers of formaldehyde, preferably trioxane, are in particular cyclic ethers pre-ferably having 3, 4 or 5 ring members and/or cyclic acetals which differ from trioxane, namely preferably formals having 5 - 11, preferably 5, 6, 7 or 8, ring members and/
or l;near polyacetals, preferably polyformals.
Suitable comonomers for trioxane are in particular compounds of the formula C~2 ~ ~CR1H]X - tO - (CR2~) ] -0 L z y in which (A) R1 and R2 are identical or different and each deno.es a hydrogen atom, an aliphatic alkyl radical having 1 - 6, preferably 1, 2, 3 or 4, carbon atoms or a phenyl radical and ~a) x is equal to 1, 2 or 3 and y is equal to zero or (b) x is equal to zero, y is equal to 1, 2 or 3 and z is equal to 2 or (c) x is equal to zero, y is equal to 1 ar,d z is equal ~o 3, 4, 5 or 6, or ~e) R1 l 178757 denotes an alkoxymethyl radical having 2 - 6, preferably 2, 3 or 4, carbon atoms or a phenoxymethyl radical, and x is equal to 1 and y is equal to zero or y and z are equal to 1 and R2 has the abovementioned meaning.
Epoxides, for example ethylene oxide, propylene oxide, styrene oxide, cyclohexene oxide, oxacyclobutane and phenyl glycidyl ether, in particular, are used as cyclic ethers.
Suitable cyclic acetals are in particular cyclic formals of aliphatic or cycloaliphatic a,~ -diols having 2 - 8, preferably 2, 3 or 4 carbon atoms and the carbon chain of ~hich can be interrupted by an oxygen atom at intervals of 2 carbon atoms, for example glycol formal (1,3-dioxolane), propanediol formal (1,3-dioxane), butane-diol formal ~1,3-d;oxepane) and diglycol formal (1,3,6-trioxocane) and 4-chloromethyl-1,3-dioxolane and hexane-diol formal ~1,3-dioxonane). Unsaturated formals, such as butenediol formal (1,3-dioxacyclohept-5-ene), are also possible.
Not only homopolymers but also copolymers of the cyclic acetals defined above and also linear condensates of aliphatic or cycloaliphatic a ,~ -diols ~ith aliphatic aldehydes or thioaldehydes, preferably formaldehyde, can be used as linear polyacetals. In particular, homopoly-mers of l;near formals of aliphatic a,~ -diols having 2 -8, preferably 2 - 4, carbon atoms, for example poly(1,3-dioxolane), poly(1,3-dio%ane) and poly(1~3-dioxepane), are used.
Conlpoul1ds having several polymeri~able qroups in the 1 17875~
molecule, for example alkylglycidyl formals, polyglycol diglycidyl ethers, alkanediol diglycidyl ethers or bis-(alkanetriol) triformals, may also be used as addit;onal comonomers for trioxane, in an amount of O.OS - 5, pre-ferably 0.1 - 2, X by weight, relative to the total amount of monomer. Such additional comonomers have been des-cr;bed, for example, in German Auslegeschrift 2,101,817.
The values for the reduced specific viscosity (RSV values~ of polyoxymethylenes used according to the invention, and hence also of fibrids obtained therefrom, are in general between 0.5 and 2.0 dl.g 1, preferably between 0.7 and 1.20 dl.g 1 (measured in butyrolactone which contains 2X by weight of diphenylamine, at 140C in a concentration of 0.5 9/100 ml).
The crystallite melting points of the polyoxy-methylenes are within a range of 140 - 180C, preferably 150C - 170C, and their densities are between 1.38 and 1.45 g.ml 1, preferably 1.40 and 1.43 g.ml~1 (measured ;n accordance with DIN 53,479).
lf polymers are used which have an RSV value which is lower than those indicated above, fibrids are admittedly also formed; but they are relatively short and mixed ~o an increasing extent with non-fibrous fractions. By means of the RSV value of the polymer it is thus possible to control the fiber length, the degree of slenderness and the degree of branching of the fibrids, so that preferable ranges depend on where the fibrids are to be used. At higher RSV values, in particular dissolving the polymer proves increasingly troublesome and therefore nore expensive.
l 1787~7 The preferably binary or ternary oxymethylene co-polymers used according to the invention are prepared in a known ~ay by polymerizing the monomers in the presence of cationically active catalysts at temperatures between 0 and 100C, preferably between 50 and 90C (cf. for example U.S~ Patent 3,027,352). Examples of catalysts used here are Lewis acids, for example boron trifluoride and antimony pentafluoride, and complex compounds of Lewis acids, preferably etherates, for example boron trifluoride diethyl etherate and boron trifLuoride di-tert.-butyl etherate. Protonic acids, for example perchloric acid, and salt-like compounds, for example triphenylmethyl hexa-f luorophosphate, triethyloxonium tetrafluoroborate or acetyl perchLorate, are also suitable. The polymerization can be ~arried out in water~ a suspension or a solution.
To remove unstable fractions, the copolymers are advan-tageously subjected to partial controlled thermal or hydrolytic degradation down to terminal primary alcohol groups (cf. U.S. Patents 3,103,499 and 3,119,623).
2U Homopolymers of formaldehyde or of trioxane which are used according to the invention are also prepared in a known manner by catalytically polymerizing the r,onomer (c~. for example U.S. Patents 2,768,994 and 2,989,505).
Fibrids according to the invention are comprised of at least 95%, preferably o, at least 97% and in par-ticular of 98 to 100% of fiber-like particles. They thus contain either no or only an extremely small fraction of film-like consti uents. The content of film-like con-stituents is determined microscopically on moist, r,ot yet I ~87~7 -- ~o --dried, product. Their content is defined as the number of film-like constituents in proportion to the total number of par~icles in an area of the microscope slide.
Particles are called film-like if their ratio of length to diameter is belo~ 5 : 1. The measurement area, and also the concentration of particles in this measurement area, must of course be chosen in such a way that an adequate number of particles can be seen and hence the accuracy of measurement is correspondingly high.
Since the content of fiber-like particles is high, the bulk density is low and is at most 150 g/liter, pre-ferably between 10 and 100 g/liter and in particular ' between 20 to 80 g/liter. To measure the bulk density ~;thin the meaning of the ;nvention, 10-50 9 of fibrids dried at room temperature are whipped up at level II
~about 1,000 rpm) in a kitchen mixer, for example "Starmix"
from Messrs. Elektrostar Schottle GmbH and Co., Reichenbach, with 1 liter capacity, until all fibrids are freely mobile;
this usually takes about 10 seconds. They are then dis-charged by means of an earthed wire to eliminate theinfluence of an electrostatic charge which may be present.
The ~eight of the loose material is determined in a 250 ml graduated rylinder, ~hich, before the reading is taken, is repeatedly tapped firmly until the volume of the loose material remains constant.
Fibrids according to the invention also have a non-uniform length the mean of which is between 0.2 and 5 mm, preferably 0~2 to 2 mm and in particular betweon 0.5 and 1.5 mm. 1'he cross-sec~ion is also non-uniform in ~ vt~s tr~
shape and size; the thickness ~the apparent diameter) is predominantly about 1 - 2ûO ym~ preferably 2 - 50 ,um. The mean length of the fibrids is determined as CFL (classi-fied fiber length) in accordance with the TAPPI method T 233, and the thickness of the fibrids is determined in accordance with TAPPI method T 234 (coarseness). A method which is suitable for rapidly determining th;s mean length and the thickness of the fibrids is a measurement by ~ microscope, in which the most frequently occurring lengths and thicknesses are visually determined. Only the longest fibrils (branches) on the fibrids enter into this measure-ment of len~th.
Since fibrids according to the invention are highly branched, they have a large specific surface area (by 8ET using ar~on) of usually 30 - 200 m2/g, prefer-ably 50 - 120 m2/g.
The degree of beating is also correspondingly high and amounts to 20 to 80 SR, preferably 25 to 50 SR. The degree of beating is determined as the Schoppcr-Riegler value in accordance with leaflet V/7/61 (old version 107) of the Verein der Zellstoff- und Papier-Chemiker und Ingenieure CAssociation of Cellulose and Paper Chemists and ~ngineers] (issued on 1st July 1961).
Polyoxymethylene fibrids according to the invcntion have hydrophilic surface properties and are therefore readily dispersible in ~ater - usually even without a wetting agent. Filters prepared therefrom have improvcd adsorptive properties. In spccial cases it can even be advisable to produce hydrophobic surface properties by l 178757 adding suitable hydrophobing agents.
Fibrids according to the invention can contain the additives described below, namely functional additives, for example nucLeating agents, colored pigments, stabil~
izers, antistatic flame retardants, lubricants, optical brighteners and the like as well as fillers. This can affect the properties of the fibrids, for example in res-pect of the morphology, the degree of beating or the bulk density. Thus, certain heavy fillers will correspond-ingly raise the bulk density; if such fillers are presentin high percentages, the limit specified above, of 150 g/liter, can be exceeded. However, the range accord-ing to .he invention, of the bulk density, is maintained if the dens;ty difference between filler and polymer ;s allowed ~for.
The additives content is generally up to 75X by weight, in the case of functional additives, preferably 0.1 to 10X by weight, relative to the total mixture; for fil-lers the preferable range extends from 30 to 65% by weight.
Owing to their branched morphology, fibrids accord-ing to the ;nvention can be very readily processed in a known way, for example as described in German Patent 1,290,040, to give paper having good properties.
Excellent papers, which can be glazed, coated, laminated and printed in a customary way, can be prepared from these fibrids even when mixed w;th other fiber materials, such as cellulose, cellulose fibers and synthetic fibers.
Fibrids according to the invention can also be used, for example, for wallpapers, filters, labels, metallic papers and other special papers and the like.
Polyoxymethylene fibrids can also be processed on board machines, the resulting cardboards having an excellent resistance to water. Polyoxymethylene fibrids according to the invention can also be used in non-wovens and as a thickening agent in rapid-curing asphalt, paints, renders, adhesives, sealing compositions and coating materials based on unsaturated polyesters, epoxide resins, bitumen pastes and PVC plastisols. Finally, they are also highly suitable as an additive to building materials, such as cement, if appropriate together with other fiber-forming materials, for example for manufacturing cement-fiber boards and the like.
In the process according to the invention for pre-paring polyoxymethylene fibrids, a solution of the polymer is forced through one or more nozzles into a moving precipitation bath. To carry out this process, first a preferably homogeneous solution of the polymer is prepared, starting from a dry or solvent-moist powder or granules, depending on the method of preparation of the polymer, and mixing the polymer ~ith the solvent and heating the mixture, for example in pressure autoclaves with stirring, for example by steam jacket heating or by blowing in steam.
~f in the polymer;zation or the subsequent stabilizing and working-up processes the polyoxymethylenes are obtaincd as a solution or suspension in an alcoholtwater mixture of the composi' ion according to the invention, it is possible to use this solut-ion or susper~sion d;rectly in 1 17875~
the process according to the invent;on.
According to the invention - as already mentioned -~he solvent used is a mixture of 75 - 97X by weight of a lower alcohol having 1 - 4 carbon atoms and 3 - 25X
by weight of water, each relative to the total solvent mixture. Examples of lower alcohols which are possible for this purpose are methanol, ethanol, isopropanol, n-propanol, n-butanol and i-butanol and mixtures of these alcohols. If higher alcohols, of more than 4 carbon atoms, for example n-hexanol, are used fibrids are admittedly also formed, but ;n this case the temperature which is neces-sary for preparing the solution is relatively high.
Methanol and isopropanol are preferably used.
The mixing rat;o of alcohol and water is of con-siderable importance for the preparation of the fibrids.If, for example, less than about 75% by ~eight of the lower alcohol and more than about 25X by weight of water are used, fibrids are obtained which, on drying not only at room temperature, but also at elevated temperatures, 2~ stick together to form a more or less granular product and lose their fibrid structure. The fibrid structure can no longer be recovered by means of dispersing equip-ment using customary mechanical forces. The tendency to stick together can be monitored by measuring the bulk Z5 density in the manner described above. A further disad-vanta~e if the a~cohol content in the solvent mixture is too low is that in this case the fibrids end up rela-tively short.
~ f, on the other hand, a solvent mixture is used ~ 1787~7 which contains a relatively large amount of alcohol and a relatively loh amount of water, the result is increasing difficulties in dissolving the polymer. The range of 85 - ~SX by veight of the lo~er alcohol and 5 - 15X by weight of water is preferable, since at these values the dissolution properties of the polymer and the stability of the fibrid morphology on drying and the producible length of the fibrids are particularly well balanced.
The concentration of .he polymer in the solvent mixture is as a rule between 10 and 300 9 per liter of soLution, preferably bet~een 50 and 200 9 per liter.
Lower concentrations are usually uneconomicaL, since they require a large amount of circulating solvent; higher concentrations frequently harbour the risk that two-1~ dimensional film-like constituents are formed. The upper limit of the polymer concentration also depends to a certain extent on the molecular weight; the h;gher the molecular weight, the lower is the concentration permissible in this process. If the process is carried out in a continuous manner, the polymer concentration used must also be har-monized with the amount of solvent in the precipitation bath ;n order for the resulting fiber suspension to remain pumpable, which requires a fibrid concentration of less than 5% by weight. Depending on the length of the fibrids, a final concentration of 1 - 3% by weight is as a rule desirable. The longer the fibrids the more the suspension has to be diluted.
There i a relationship between the polymer con-centration and the fiber length, so that an expert can l 1787~7 ~ 16 -use the polymer concentration (and - as mentioned - the amount of alcohol) to set the desired fiber dimensions.
Thus, the fibrids become shorter the lower the polymer concentration (and the lower the amount of alcohol).
The temperature of the solutiGn of the polyoxy-methylene depends on the molecular weight of the polymer, the nature and amount of the comonomer and the composition of the solvent. If homogeneous solutions are used the temperature necessary for d;ssolution must be considered the lower temperature limit, while the upper temperature limit is essentially only restricted by economic consider-ations. The dissolution temperature is known for many examples and can otherwise be easily experimentally determined or interpolated from known data by an expert.
This temperature range ;s between 150 and 190C for the preferred alcohols in their preferred mixing ratios with ~ater. The solution is as a rule under the autogenous Yapor pressure of the solvent mixture at this temperature, but the pressure can be considerably increased by inert gas pressure or by means of a pump. The pressure is in general between 20 and 60 bar, preferabLy between ZO and 30 bar.
In addition to the polymer, the solution can also contain auxiliaries from the polymerization, for example decomposition products of the catalys~s for the cationic polymerizat;on, which products are described in 8ritish Patent 1,i46,649~ ~erman Offenlegungsschriften 1,595,7U5 and 1,595,668 and German Ausle~eschriften 1,199,504 and 1,175,~2. These auxiliaries also include compounds which I ~ 787~7 have a basic reaction and are used for removing unstable fractions down to the terminal pr;mary aLcohol group, for example lo~er tertiary aliphatic amires, such as tri-ethylamine or triethanolamine, or a secondary alkali metal phosphate, such as disodium hydrogenphosphate (cf. U.S.
Patents 3,174,948, 3,219,6Z3 and 3,666,714), and the resulting reaction products, for example methylal, tri-oxanc, tetroxane, formic acid and methyl formate.
The polymer solution can also contain a very wide variety of known additives. Examples of such additives are customary nucleating agents, which accelerate the crystallization and by means of which the morphology of the fibrids can be influenced, such as, for example, branched or crosslinked polyoxymethylenes, taLc or boron nitride (cf. German Patent 2,101,817 and German Offen-legungsschrift 1,940,132).
Fillers can also be suspended ;n the solution.
Suitable fillers are all naturally occurring or synthetic-ally prepared inorganic materials in unmodified or surface-modified form, in particular metal powders, antimony tri-oxide, carbon black, graphite, ground rock, quartz powder, mica, slate po~der, feldspath powder, diatomaceous earth, finely d;vided asbestos, sparingly soluble oxides, hy-drated oxides, hydroxides, silicates, aluminates, borates, 2~ ferrites, sulfates, carbonates, basic salts and double salts~ preferably containing aluminum and/or magnesium, calcium, sodium, titaniuM or iron as the metal component.
Particularly prefer2ble fillers are t;tanium dioxide, alumina, calcium carbonate, talc, dolornite, wollastor,ite, 1 1787~
silica, hydrated aluminum oxide and calcium sulfate. Of these clay, calcium carbonate, talc and silica are par-ticularly preferable.
These fillers can have been treated in a known manner, for example ~ith silanes, and generally have a mean particle size between 0.1 and 50 ~m, preferably between 0.5 and 10 ~m.
The amount of additive in the polymer solution depends on the field of application and on the nature of the additive and is sufficiently high for the abovementioned contents in the fibrids to be obtained. In general, the amount ;s thus up to 80X, in the case of functional additives preferably between 0.1 and 10X by weight, rela-tive to the total solids comprised of polymer and additive.
In the case of a filler, a concentration of 30 - 70X by ~eight, relative to total sol;ds, is advantageously used in most fields of applicat;on.
Further additives to be mentioned are kno~n stabil-;zers against the influence of heat, oxygen and/or air, as described, inter alia, in German Offenlegungsschrift 2,043,498. Compounds particularly suitable for this pur-pose are bisphenol compounds, alkaline earth metal salts of carboxylic acids and guanidine compounds. The bis-phenol compounds used are chiefly esters of monobasic 4-hydroxyphenylalkanoic ac;ds which conta;n 7 - 13, prefer-ably 7, ~ or 9, carbon atoms and are mono- or di-ring-substituted by an alkyl radical containing 1 - 4 carbon atoms. The alcohol components in these esters are ali-phatic dihydric, trihydric or tetrahydric alcohols which ~ ~787~7 _ 19 _ contain 2 - 6, preferably Z, 3 or 4, carbon atoms. Examples uhich may be mentioned of such esters are esters of ~-(3-tert.-butyl-4-hydroxyphenyl)-pentanoic acid, ~-(3-methyl-5-5-tert.-butyl-4-hydroxyphenyl)-propionic acid, ~3,5-di-tert.-bu.yl 4-hydroxyphenyl)-acetic acid, ~-(3,4-di-tert.-butyl-4-hydroxyphenyl)-propionic acid or ~3,5-di-isopropyl-
4-hydroxyphenyl)-acetic acid with ethylene glycol, propane-1,2-d;ol, propane-1,3-diol, butane-1,4-dioL, hexane-1,6-d;ol, 1,1,1-trimethylolethane or pentaerythritol.
The alkaline earth metal salts of carboxylic acids which are used are in particular alkaline earth metal sa;ts of aliphatic, preferably hydroxyl-containing mono-bas;c, dibac;c or tribasic carboxylic acids having 2 - 20, preferably 3 ~ 9, carbon atoms, for example the calcium or magnesium salts of stearic acid, ricinoleic acid, lactic acid, mandelic acid, malic acid or citric acid.
Suitable guanidine compounds are compounds of the formula NC - NH - C - NH - R
NH
in which R denotes a hydrogen atom, a cyano group or an alkyl radical having 1 - 6 carbon atoms, for e~ample cyanoguanidine, N-cyano-N'-methylguanidine, N-cyano-N'-ethylguanidine, N-cyano-N'-isopropylguanidine, N-cyano-N'-tert.-butylg~anidine or N,N'-dicyanoguanidine. The guan-idine compound, if used, is used in an amount ~f 0.01 -1, preferably 0~02 - 0.5, X by weight, relative to the total weight.
The solution can also contain other additives, 1 1787~
such as known antistatic agents, flame-retardants or lubri-cants and the like.
Colored polyoxymethylene fibrids can be obtained by dissolving or dispersing dyestuffs in the polymer solution. The addition of optical brighteners is also interestin~ for some applications.
To improve the dispersibility of the polyoxy-methylene fibrids, surface-active agents, such as ethoxyl-ated alcohols, carboxylic acids or amines, alkanesulfonates or hydroxyl-bearing polymers such as polyvinyl alcohol or carboxymethylcellulose, can also be added to the solution.
The polymer solution is then forced through one or more nozzles which, although their design (size, shape and length) affects the dimensions of the resulting fib-rids, are not essential to the invention. Suitablenozzles have been described, for example in Belgian Patent 568,52~. Examples which may be mentioned here are simple ho'e nozzles having a diameter of, for example, 0.5 - 5 mm, tubes having a diameter of 1 - 10 mm and a length of 1 -1,000 cm and conical nozzles having an annular gap witha width of ~.02 - 5 mm, preferably 0.05 - 0.5 mrn~ Valves w;th an adjustable circle-shaped annular gap, where the fiber dimensions can be affected by varying the annular gap, are part;cularly preferable. A valve of this type is shown in the attached Figure. In this Figure (1) denotes a pipe through which the precipitation bath flows.
The valve (2), through which the polymer solution is added, is mounted at right angles to the pipe; (3) represents the valve housing and (4) represen~s the valve cone, ~ith ~ ~787~7 ~hich the circle-shaped annular gap can be variably adjusted. (a), (b), (c) and (d) indicate the valve cone position actually used in the present IlLustrative Embodi-ment 1.
The narrower the gap or the orifice of the nozzle, the shorter and more slender are the resulting fibrids.
The linear speed at the narrowest point of the nozzle is in general between 1 and 200 m/s, preferably 5 - 30 m/sec The polymerization product passes through the nozzle and then into a cold moving precipitation bath, where the polymer prec;pitates with the formation of fibrids. The precipitation bath is preferably comprised of the same solvent mixture as that of the polymer solution, s;nce if the process is carried out in a continuous manner t~is enables solvent recycling to take place without expensive measuring and control equipment. However, in principle the process according to the invention can also be operated without this advantage, using mixtures of a lo~er alcohol and ~later of a different composition. Also, other solvents which are not acidic, for example ketones, esters, ethers and the like, can also be used in principle as the precipitation bath.
The temperature of the precipitation bath is, according to the invention, advantageously between 0 and 100C, preferably between 30 and 70C. The temperature of the precipitation bath is measured downstream of the nozzle, after complete and thoroucJh mixing of solvent and pr~cipitating medium. Although the polymer also precipi-tates a~ eleva~ed ~emperatures, very short fibrids or l ~78757 two-dimensional film-like structures are increasingly produced - according to the other process conditions.
This tendency can be opposed to a certain extent by using ~ solvent mixture with a correspondingly higher alcohol
The alkaline earth metal salts of carboxylic acids which are used are in particular alkaline earth metal sa;ts of aliphatic, preferably hydroxyl-containing mono-bas;c, dibac;c or tribasic carboxylic acids having 2 - 20, preferably 3 ~ 9, carbon atoms, for example the calcium or magnesium salts of stearic acid, ricinoleic acid, lactic acid, mandelic acid, malic acid or citric acid.
Suitable guanidine compounds are compounds of the formula NC - NH - C - NH - R
NH
in which R denotes a hydrogen atom, a cyano group or an alkyl radical having 1 - 6 carbon atoms, for e~ample cyanoguanidine, N-cyano-N'-methylguanidine, N-cyano-N'-ethylguanidine, N-cyano-N'-isopropylguanidine, N-cyano-N'-tert.-butylg~anidine or N,N'-dicyanoguanidine. The guan-idine compound, if used, is used in an amount ~f 0.01 -1, preferably 0~02 - 0.5, X by weight, relative to the total weight.
The solution can also contain other additives, 1 1787~
such as known antistatic agents, flame-retardants or lubri-cants and the like.
Colored polyoxymethylene fibrids can be obtained by dissolving or dispersing dyestuffs in the polymer solution. The addition of optical brighteners is also interestin~ for some applications.
To improve the dispersibility of the polyoxy-methylene fibrids, surface-active agents, such as ethoxyl-ated alcohols, carboxylic acids or amines, alkanesulfonates or hydroxyl-bearing polymers such as polyvinyl alcohol or carboxymethylcellulose, can also be added to the solution.
The polymer solution is then forced through one or more nozzles which, although their design (size, shape and length) affects the dimensions of the resulting fib-rids, are not essential to the invention. Suitablenozzles have been described, for example in Belgian Patent 568,52~. Examples which may be mentioned here are simple ho'e nozzles having a diameter of, for example, 0.5 - 5 mm, tubes having a diameter of 1 - 10 mm and a length of 1 -1,000 cm and conical nozzles having an annular gap witha width of ~.02 - 5 mm, preferably 0.05 - 0.5 mrn~ Valves w;th an adjustable circle-shaped annular gap, where the fiber dimensions can be affected by varying the annular gap, are part;cularly preferable. A valve of this type is shown in the attached Figure. In this Figure (1) denotes a pipe through which the precipitation bath flows.
The valve (2), through which the polymer solution is added, is mounted at right angles to the pipe; (3) represents the valve housing and (4) represen~s the valve cone, ~ith ~ ~787~7 ~hich the circle-shaped annular gap can be variably adjusted. (a), (b), (c) and (d) indicate the valve cone position actually used in the present IlLustrative Embodi-ment 1.
The narrower the gap or the orifice of the nozzle, the shorter and more slender are the resulting fibrids.
The linear speed at the narrowest point of the nozzle is in general between 1 and 200 m/s, preferably 5 - 30 m/sec The polymerization product passes through the nozzle and then into a cold moving precipitation bath, where the polymer prec;pitates with the formation of fibrids. The precipitation bath is preferably comprised of the same solvent mixture as that of the polymer solution, s;nce if the process is carried out in a continuous manner t~is enables solvent recycling to take place without expensive measuring and control equipment. However, in principle the process according to the invention can also be operated without this advantage, using mixtures of a lo~er alcohol and ~later of a different composition. Also, other solvents which are not acidic, for example ketones, esters, ethers and the like, can also be used in principle as the precipitation bath.
The temperature of the precipitation bath is, according to the invention, advantageously between 0 and 100C, preferably between 30 and 70C. The temperature of the precipitation bath is measured downstream of the nozzle, after complete and thoroucJh mixing of solvent and pr~cipitating medium. Although the polymer also precipi-tates a~ eleva~ed ~emperatures, very short fibrids or l ~78757 two-dimensional film-like structures are increasingly produced - according to the other process conditions.
This tendency can be opposed to a certain extent by using ~ solvent mixture with a correspondingly higher alcohol
5- content. The use of relatively low temperatures is tech-nically more involved, since this requires using expensive refrigerants, without the quality of the resulting fibrids being significantly improved. To obtain the preferred ranges of the precipitation temperature, the temperature of the precipitating so(vent before the nozzle, depending on the intensity of agitation, the temperature of the solution and the throughput speed is between 20 and 60C.
If the process is carried out in a continuous manner, this solvent is obtained by cooling down the filtrate after the fibrids have been separated off or by cooling the fib-rid suspension and subsequently separating off the fibrids, cooling ~ater be;ng normally used for the cooling down.
According to the invention, the precipitation bath must be adequately agitated to enable the formation of the fibrids aimed at according to the invention. The exact extent of this necessary agitation can be readily determined by a small number of experiments, but, naturally, the intensity of agi.at,on must be chosen to be hi~her the greater the throughput through the nozzle in order to avoid damming in front of the nozzle and to generate rapid mi~;ng. It can also be stated in general that a low degree of agitation favors the formation of film-like constituents. If, thus, there ;s the risk of forming such short-fibered film~like cons~ituents even due to the other l 1787$~
process conditions, such as low alcohol content, high concentration of the dissolved polymer or high temperature of the precipitation bath, then th;s risk can be opposed, to a certain extent, by more thorough agitation of the 5- prec;pitation bath. In general, this agitation should be such that the linear speed is at least 0.1 m/s, preferably 0.1 - 30 m/s and part;cularly preferably 0.3 - 10 m/s.
Lower speeds can produce sheet-shaped constituents with-out fibrid characteristics or continuous filament-like 1~ structures. In contrast, speeds higher than 30 m/s re-quire an unnecessarily high mechanical energy. To obtain this linear speed, the precipitation bath, if contained in a cylindrical vessel, can be stirred or, if contained in a closed tube, circulated. It is essentially ;mmater;al for the formation of dryable fibrids without f;lm-l;ke constituents whether the flow ;s l;near or turbulent.
The angle between the direction of motion of the solut;on in the nozzle and of the cold solvent has no sign;ficant influence on the properties of the product.
An angle between 30 and 90 ;s preferable for technical reasons. In particular in the case of conical nozzles, th;s angle may not be the same for all parts of the nozzle.
If necessary, the fibrids can be ground and/or Z5 classified by known methods to affect the degree of fibril-lation, the fiber length or the distribution of fiber lengths. However, grindiny is in principle not necessary in order to set free discrete particles.
The fibrids are then rernoved frorn the precipitation l 1~87S~
bath by freeing them from a large proportion of non-evaporated solvent, by known mechanical methods, for example by filtering with suction, squeezing oft, centri-fuging and the like, and, if necessary, washed with water and dried. The fibrids can be loosened up mechanically by means of suitable mills, a bulk density of 10 -150 g/liter being obtained.
A significant advantage of the process according to the invention, over known methods of preparing fibers by precipitating, is that highly branched fibrids which are almost or completely free of sheet-shaped film-like constituents are solely formed. The process according to the invention, by the choice of suitable parameters such as polymer concentration in the solution, size of the nozzle orifice and speed of the solution and of the pre-cipitation bath, also produces fibrids which ~hile having a high degree of slenderness have a mean length within the millimeter range. Fibrids prepared according to the invention do not stick together on drying, unlike polyoxymethylene fibrids prepared by flash evaporation, so that the fibrid structure is fully retained on drying.
This feature makes these fibrids very highly suitable even for dry mixtures of building materials, into which the filler-containing fibrids can be mixed particularly ~ell owing to their higher specific density. The process according to the invention is also technically less involved, since the condensation of the vapors and the correction of the solvent composit;on by dis~illation and the associated-measurin~ and con~rolling effort are ~ 1787~
eliminated.
The examples which follow illustrate in more detail the fibrids according to the invention and the process for their preparation:
Example 1 A solution of 3.8X by weight of a copolymer of 98X by weight of trioxane and 2X by weight of ethylene oxide and which had an RSV value of 1.0 dl/g and 0.1% by weight of triethylamine in a mixture of 95-~ by weight of methanol and 5% by weight of water was prepared with st;rring at 180C in a pressurized storage vessel. The solution, under a pressure of 27 b2r, was forced through an annular nozzle as in the Figure. In th;s nozzle, the valve cone had a position which was such that a = 7 mm, b = 0.15 mm, c = 0.07 mm and d = 7.2 mm. the diameter of the valve housing was 12.4 mm. A throughput of 280 liter~h was obtained under the above conditions.
After passing through the nozzle this solution then flowed immediately into a pipe which was located at right-angles to the nozzle and had a diameter of 40 mm and inwhich the above solvent mixture flowed by with a speed of 0.35 m/s. The temperature of the precipitation bath was 40C
in front of the nozzle and 59C after mixing had been effected. The resulting fibrids were filtered off with suction on a drum filter, washed with water until methanol-free, dried at room temperature and mechanically loosened up by stirring for 5 minutes in a Henschel mixer. Micro-scopic inspection in polarized light showed that the fibrids were free of film-like constituents. The data 1 ~787~
measured are listed in Table 1.
3.0 g of the fibrids obtained in accordance with this example were used, together with 10 liters of water, to form a sheet of paper on the Rapid-Kothen manual sheet S former; no losses occurred.
50 g of these fibrids were also used to prepare a t~ ~(tile) adhesive comprising 40 parts of cement, 6~
, . . . .. . . . . . .
parts of sand, 5 parts of an ethylene/vinyl acetate co-polymer powder prepared ~ith po~yvinyl alcohol as a pro-tective colloid (88% by weight of vinyl acetate, and 12Xby weight of ethylene), 0.5 part of methylhydroxyethyl-cellulose (viscosity of 2% strength solution in water at 20C: 6,000 mPa.s) and 0.4 part of polyoxymethylene fibrids. After stirring with 33 parts of water the mix-ture produced a thin-bed adhesive which had a creamy con-sistency and which could be smoothly spread out by means of a doctor blade.
10 9 of these fibrids were also used to prepare a fiber-cement board, by being dispersed in 800 ml of water in a kitchen mixer and the dispersion being stirred into 200 9 of Portland cement. The evenly dispersed suspension was then used, this time together with 6 liters of water, to form a fiber-cement board on the Rapid-Kothen manual sheet former. This board was com-25 pressed overnight under a pressure of 200 kp/cm2 C2,850 psi~ at room temperature using wire screens. After stor-age for four weeks, the board had a weight of 201~ 9 and a density of 1.63 g/cm3.
1 1 787~7 - 2~ -Example 2 Corresponding to Example 1, a solution of 3.0X
by weight of a copolymer of ~7.94% by weight of trioxane, 2X by weight of ethylene oxide and 0.06% by weight of butanediol diglycidyl ether and which had an RSV value of 0.99 dl/g and 0.1% by weight of triethylamine was pre-pared at 180C in a mixture of 90X by weight of iso-propanol and 10% by weight of water and forced through a nozzle as in the ~igure, but the valve was adjusted so as to produce a throughput of 250 liter~h. The precipi-tation bath of 90X by weight of isopropanol and 10X by ~le;ght of water ;n this case flowed with a speed of 0.55 m/s at rightangles past the mouth of the nozzle. The precipitation bath had a temperature of 42C in front of the nozzle and a temperature of 55C after rixing had been effected. In isolating the fiber the vater wash of Example 1 was dispensed with. The data measured are summarized in Table 1.
A filter sheet of 3 mm thickness was prepa ed from the fibrids obtained, bleached fir sulfite pulp with 40 SR and kieselguhr in a weight ratio of 40~0/20 in a Rapid-Kothen manual sheet former. This sheet was in-serted into a laboratory pressure filter. On filtering turbid cider, all materials responsible for this turbid-ity were retained. The filtrate was clear.Example 3 Corresponding to Example 1, a solution of 4.3'~
by weigh~ of a homopolymer of trioxane and the .erminal groups of which had been blocked wi~h acetate groups and l 178757 She RSV value of which was 0.81 dl/g was used. The flow rate of the prec;p;tation bath was in th;s case 0.60 m/s and the precipitation temperature was 50C. The data measured are summarized in Table 1.
If the process is carried out in a continuous manner, this solvent is obtained by cooling down the filtrate after the fibrids have been separated off or by cooling the fib-rid suspension and subsequently separating off the fibrids, cooling ~ater be;ng normally used for the cooling down.
According to the invention, the precipitation bath must be adequately agitated to enable the formation of the fibrids aimed at according to the invention. The exact extent of this necessary agitation can be readily determined by a small number of experiments, but, naturally, the intensity of agi.at,on must be chosen to be hi~her the greater the throughput through the nozzle in order to avoid damming in front of the nozzle and to generate rapid mi~;ng. It can also be stated in general that a low degree of agitation favors the formation of film-like constituents. If, thus, there ;s the risk of forming such short-fibered film~like cons~ituents even due to the other l 1787$~
process conditions, such as low alcohol content, high concentration of the dissolved polymer or high temperature of the precipitation bath, then th;s risk can be opposed, to a certain extent, by more thorough agitation of the 5- prec;pitation bath. In general, this agitation should be such that the linear speed is at least 0.1 m/s, preferably 0.1 - 30 m/s and part;cularly preferably 0.3 - 10 m/s.
Lower speeds can produce sheet-shaped constituents with-out fibrid characteristics or continuous filament-like 1~ structures. In contrast, speeds higher than 30 m/s re-quire an unnecessarily high mechanical energy. To obtain this linear speed, the precipitation bath, if contained in a cylindrical vessel, can be stirred or, if contained in a closed tube, circulated. It is essentially ;mmater;al for the formation of dryable fibrids without f;lm-l;ke constituents whether the flow ;s l;near or turbulent.
The angle between the direction of motion of the solut;on in the nozzle and of the cold solvent has no sign;ficant influence on the properties of the product.
An angle between 30 and 90 ;s preferable for technical reasons. In particular in the case of conical nozzles, th;s angle may not be the same for all parts of the nozzle.
If necessary, the fibrids can be ground and/or Z5 classified by known methods to affect the degree of fibril-lation, the fiber length or the distribution of fiber lengths. However, grindiny is in principle not necessary in order to set free discrete particles.
The fibrids are then rernoved frorn the precipitation l 1~87S~
bath by freeing them from a large proportion of non-evaporated solvent, by known mechanical methods, for example by filtering with suction, squeezing oft, centri-fuging and the like, and, if necessary, washed with water and dried. The fibrids can be loosened up mechanically by means of suitable mills, a bulk density of 10 -150 g/liter being obtained.
A significant advantage of the process according to the invention, over known methods of preparing fibers by precipitating, is that highly branched fibrids which are almost or completely free of sheet-shaped film-like constituents are solely formed. The process according to the invention, by the choice of suitable parameters such as polymer concentration in the solution, size of the nozzle orifice and speed of the solution and of the pre-cipitation bath, also produces fibrids which ~hile having a high degree of slenderness have a mean length within the millimeter range. Fibrids prepared according to the invention do not stick together on drying, unlike polyoxymethylene fibrids prepared by flash evaporation, so that the fibrid structure is fully retained on drying.
This feature makes these fibrids very highly suitable even for dry mixtures of building materials, into which the filler-containing fibrids can be mixed particularly ~ell owing to their higher specific density. The process according to the invention is also technically less involved, since the condensation of the vapors and the correction of the solvent composit;on by dis~illation and the associated-measurin~ and con~rolling effort are ~ 1787~
eliminated.
The examples which follow illustrate in more detail the fibrids according to the invention and the process for their preparation:
Example 1 A solution of 3.8X by weight of a copolymer of 98X by weight of trioxane and 2X by weight of ethylene oxide and which had an RSV value of 1.0 dl/g and 0.1% by weight of triethylamine in a mixture of 95-~ by weight of methanol and 5% by weight of water was prepared with st;rring at 180C in a pressurized storage vessel. The solution, under a pressure of 27 b2r, was forced through an annular nozzle as in the Figure. In th;s nozzle, the valve cone had a position which was such that a = 7 mm, b = 0.15 mm, c = 0.07 mm and d = 7.2 mm. the diameter of the valve housing was 12.4 mm. A throughput of 280 liter~h was obtained under the above conditions.
After passing through the nozzle this solution then flowed immediately into a pipe which was located at right-angles to the nozzle and had a diameter of 40 mm and inwhich the above solvent mixture flowed by with a speed of 0.35 m/s. The temperature of the precipitation bath was 40C
in front of the nozzle and 59C after mixing had been effected. The resulting fibrids were filtered off with suction on a drum filter, washed with water until methanol-free, dried at room temperature and mechanically loosened up by stirring for 5 minutes in a Henschel mixer. Micro-scopic inspection in polarized light showed that the fibrids were free of film-like constituents. The data 1 ~787~
measured are listed in Table 1.
3.0 g of the fibrids obtained in accordance with this example were used, together with 10 liters of water, to form a sheet of paper on the Rapid-Kothen manual sheet S former; no losses occurred.
50 g of these fibrids were also used to prepare a t~ ~(tile) adhesive comprising 40 parts of cement, 6~
, . . . .. . . . . . .
parts of sand, 5 parts of an ethylene/vinyl acetate co-polymer powder prepared ~ith po~yvinyl alcohol as a pro-tective colloid (88% by weight of vinyl acetate, and 12Xby weight of ethylene), 0.5 part of methylhydroxyethyl-cellulose (viscosity of 2% strength solution in water at 20C: 6,000 mPa.s) and 0.4 part of polyoxymethylene fibrids. After stirring with 33 parts of water the mix-ture produced a thin-bed adhesive which had a creamy con-sistency and which could be smoothly spread out by means of a doctor blade.
10 9 of these fibrids were also used to prepare a fiber-cement board, by being dispersed in 800 ml of water in a kitchen mixer and the dispersion being stirred into 200 9 of Portland cement. The evenly dispersed suspension was then used, this time together with 6 liters of water, to form a fiber-cement board on the Rapid-Kothen manual sheet former. This board was com-25 pressed overnight under a pressure of 200 kp/cm2 C2,850 psi~ at room temperature using wire screens. After stor-age for four weeks, the board had a weight of 201~ 9 and a density of 1.63 g/cm3.
1 1 787~7 - 2~ -Example 2 Corresponding to Example 1, a solution of 3.0X
by weight of a copolymer of ~7.94% by weight of trioxane, 2X by weight of ethylene oxide and 0.06% by weight of butanediol diglycidyl ether and which had an RSV value of 0.99 dl/g and 0.1% by weight of triethylamine was pre-pared at 180C in a mixture of 90X by weight of iso-propanol and 10% by weight of water and forced through a nozzle as in the ~igure, but the valve was adjusted so as to produce a throughput of 250 liter~h. The precipi-tation bath of 90X by weight of isopropanol and 10X by ~le;ght of water ;n this case flowed with a speed of 0.55 m/s at rightangles past the mouth of the nozzle. The precipitation bath had a temperature of 42C in front of the nozzle and a temperature of 55C after rixing had been effected. In isolating the fiber the vater wash of Example 1 was dispensed with. The data measured are summarized in Table 1.
A filter sheet of 3 mm thickness was prepa ed from the fibrids obtained, bleached fir sulfite pulp with 40 SR and kieselguhr in a weight ratio of 40~0/20 in a Rapid-Kothen manual sheet former. This sheet was in-serted into a laboratory pressure filter. On filtering turbid cider, all materials responsible for this turbid-ity were retained. The filtrate was clear.Example 3 Corresponding to Example 1, a solution of 4.3'~
by weigh~ of a homopolymer of trioxane and the .erminal groups of which had been blocked wi~h acetate groups and l 178757 She RSV value of which was 0.81 dl/g was used. The flow rate of the prec;p;tation bath was in th;s case 0.60 m/s and the precipitation temperature was 50C. The data measured are summarized in Table 1.
6 Example 4 Corresponding to Example 1, a mixture of 97X by weight of a solvent mixture comprising 85X by ~eight of methanol and 15X by weight of water and 3% by weight of solids compr;sing 33 1/3% by weight of alumina (English china clay with a mean particle size of 3 ~m and the analysis of which produces 46.2X of SiO2, 3~.7X of - Al2G3 and 13.1% of loss on ignition) and 66 2/3X by we;ght of the copolymer in accordance with Example 2 was prepared at 182C, and the copolymer dissolved. As for the rest, Example 1 was followed, but the water wash was dispensed with. The fibrids contained 31.2X of alumina, uhich corresponds to a pigment incorporation rate of 93X.
The remaining data are listed in Table 1.
Example 5 Example 4 was repeated using a solvent mixture of ~0% by weight of methanol and 10X by weight of water and as sol;ds a mixture of 70X by weight of calcium car-bonate with an orthorhombohedral particle shape and a mean particle size of 0.6 ~m and 30% by weight of the copolymer used in Example 2. The resulting fibrids con-tained 63.6% of calcium carbonate, which corresponds to a pîgment incorporation rate of 91% by weight~ The remaining data are listed in Table 1.
~ ~787~
Example 6 Corresponding to Example 2, a solution ~as prepared of 10.0X by weight of the copolymer specified there in a m;xture of 90X by weight of methanol and 10X by weight of water, at 182C and, as described in Example 2, forced through a nozzle into a precipitation bath. The product was ~orked up as described in Example 1. The data measured are shown in Table 1.
~ Morphology moist fibrids dry f;brids Specific surface area 53 m2/g Fraction of fiber-like particles ~9.5 %
Bulk density 25 g/liter Mean fiber length 1.4 mm Example 7 Example 1 was modified in such a way that the precipitation bath was not a methanol/water mixture but pure water. The data measured are shown in Table 1.
Morphology moist fibrids dry fibrids Specific surface area 61 m2/g Fraction of fiber-like particles 99.5 X
8ulk density 44 g/liter Mean fiber length 0.6 mm Example 8 Example 1 was modified in such a way ~hat the copolymer used comprised 96.6X of trioxane and 3.4X of dioxolane and was emplGyed in a concentration of 2.0% by weight, relative to the poly~er solu~ion. ~he data ~ 178~
measured can be seen ,ro~ Table 1.
Morphology moist fibrids dry fibrids Specific surface area 79 m2/g Fraction of fiber-like particles 99.5 X
Bul~ density 31 g/liter Mean fiber length 0.3 mm A coating composition was prepared from 3.0X by weight of the dried fibrids and 98% by weight of an un-saturated polyester having a viscosity of 1,000 mPa.s,by dispersing the mixture in a toothed disk disperser.
Applied in a thickness of 1 mm, this composition did not run off from a glass plate mounted so as to be vcrtical.
Comparative Example 1 Corresponding to Example 1, a solvent mixture co~prising 6~X by weight of methanol and 40% by weight of water was used. The resulting fibrids were extremely short and severely contaminated with film-like material.
On drying at room temperature, the fibrids stuck to-gether to form a crumbly product. If the moist product ;s used to prepare paper as in Example 1, 16% by weight of the product pass through the sieve.
If the dried product is used to prepare a thin-bed adhesive in accordance with Examplc 1, the adhesive, after having been made up with water and applied with a doctor blade, does not have a hold-out (it flows without the action of shear forces) and its sur,ace is not smooth due to grainy constituents. Thin-bed adhesives contain-ing dried f;~rids produced by the flash process in ~ 178757 accordance with German Offenlegungsschrift 2,947,490 behave in the same way. The data measured are listed in Table 1. The fibers were classified before the drying step.
Comparative Example 2 ~ xample 1 was followed, but the precipitation temperature was adjusted to 132C. Th;s did not pro-duce any fibrids but only a grainy product having a mean particle size of about 0.45 mm.
Comparative Example 3 Example 1 of German Offenlegungsschrift 2,947,490 was repeated. The fibrids formed were filtered off and dr;ed at room temperature. In this step, fibr;ds became stuck together with the formation of an essentially crumbly and grainy product having a bulk density of 190 g/liter.
1 1787~7 V~
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1~ C ~ ~ E . . . . . . . . . ~.
O ~ ~ ~ O ~ O ~ O O O ~ E
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X ~ ~ CJ~ ~ ~ oo~ .C , LL, m~ ~ ~
aJ ~
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.,_ ~ ~ ~ ~ oo ~o ~o ~~ ~1 ~ o~ 1/~ I t~') cn u~ v~ ~ O
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~ ~ ~C r c c Q L ~n .. L ~ L - L L ~ O~ _ ~ S ~ ~ ~ ~ -- ~ ~ ~~ ~ ~ ~ ~ ~ ~ ~1 ~' C
~0 L r E a~ r rL Q~
O ~ ' O~ c , O L = ~ -- ~ Q ~ ~C ~;~ L ~ C O
E .~ ~ ~ ~ ~ C2. al ~ ~~ O
E __ _ _ _ cJ QJ Ql v~ ~ N r~ ~ ~ ~ r~ E E L o a~ CJ a) aJ Q~ Q ~ r~l ________ _ . _ _ c,c~v~
O~ Q Q Q Q Q Q Q Q~ Q ~ Q Q ~ ~~ ~
_ E E EE~ E E E EQ E Q E Q E Q ~~ O
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x x x x X >~ x O x O x O x LL.I W 111 W WLU ~U W ~ W ' I ~ ILI ~) l~l ~ ~1 r~
The remaining data are listed in Table 1.
Example 5 Example 4 was repeated using a solvent mixture of ~0% by weight of methanol and 10X by weight of water and as sol;ds a mixture of 70X by weight of calcium car-bonate with an orthorhombohedral particle shape and a mean particle size of 0.6 ~m and 30% by weight of the copolymer used in Example 2. The resulting fibrids con-tained 63.6% of calcium carbonate, which corresponds to a pîgment incorporation rate of 91% by weight~ The remaining data are listed in Table 1.
~ ~787~
Example 6 Corresponding to Example 2, a solution ~as prepared of 10.0X by weight of the copolymer specified there in a m;xture of 90X by weight of methanol and 10X by weight of water, at 182C and, as described in Example 2, forced through a nozzle into a precipitation bath. The product was ~orked up as described in Example 1. The data measured are shown in Table 1.
~ Morphology moist fibrids dry f;brids Specific surface area 53 m2/g Fraction of fiber-like particles ~9.5 %
Bulk density 25 g/liter Mean fiber length 1.4 mm Example 7 Example 1 was modified in such a way that the precipitation bath was not a methanol/water mixture but pure water. The data measured are shown in Table 1.
Morphology moist fibrids dry fibrids Specific surface area 61 m2/g Fraction of fiber-like particles 99.5 X
8ulk density 44 g/liter Mean fiber length 0.6 mm Example 8 Example 1 was modified in such a way ~hat the copolymer used comprised 96.6X of trioxane and 3.4X of dioxolane and was emplGyed in a concentration of 2.0% by weight, relative to the poly~er solu~ion. ~he data ~ 178~
measured can be seen ,ro~ Table 1.
Morphology moist fibrids dry fibrids Specific surface area 79 m2/g Fraction of fiber-like particles 99.5 X
Bul~ density 31 g/liter Mean fiber length 0.3 mm A coating composition was prepared from 3.0X by weight of the dried fibrids and 98% by weight of an un-saturated polyester having a viscosity of 1,000 mPa.s,by dispersing the mixture in a toothed disk disperser.
Applied in a thickness of 1 mm, this composition did not run off from a glass plate mounted so as to be vcrtical.
Comparative Example 1 Corresponding to Example 1, a solvent mixture co~prising 6~X by weight of methanol and 40% by weight of water was used. The resulting fibrids were extremely short and severely contaminated with film-like material.
On drying at room temperature, the fibrids stuck to-gether to form a crumbly product. If the moist product ;s used to prepare paper as in Example 1, 16% by weight of the product pass through the sieve.
If the dried product is used to prepare a thin-bed adhesive in accordance with Examplc 1, the adhesive, after having been made up with water and applied with a doctor blade, does not have a hold-out (it flows without the action of shear forces) and its sur,ace is not smooth due to grainy constituents. Thin-bed adhesives contain-ing dried f;~rids produced by the flash process in ~ 178757 accordance with German Offenlegungsschrift 2,947,490 behave in the same way. The data measured are listed in Table 1. The fibers were classified before the drying step.
Comparative Example 2 ~ xample 1 was followed, but the precipitation temperature was adjusted to 132C. Th;s did not pro-duce any fibrids but only a grainy product having a mean particle size of about 0.45 mm.
Comparative Example 3 Example 1 of German Offenlegungsschrift 2,947,490 was repeated. The fibrids formed were filtered off and dr;ed at room temperature. In this step, fibr;ds became stuck together with the formation of an essentially crumbly and grainy product having a bulk density of 190 g/liter.
1 1787~7 V~
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x x x x X >~ x O x O x O x LL.I W 111 W WLU ~U W ~ W ' I ~ ILI ~) l~l ~ ~1 r~
Claims (12)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A polyoxymethylene fibrid which has a reduced specific viscosity of 0.5 and 2.0 dl/g-1 and a specific surface area of 30 to 200 m2/g, which comprises at least 95% of fiber-like particles the average length of which is between 0.2 and 5 mm and which has a bulk density which does not exceed 150 g/liter.
2. A polyoxymethylene fibrid as claimed in claim 1, which is comprised of at least 97% of fiber-like particles.
3. A polyoxymethylene fibrid as claimed in claim 1, wherein the average length of the particles is 0.2 to 2 mm.
4. A polyoxymethylene fibrid as claimed in claim 1, claim 2 or claim 3, wherein the bulk density is at most 100 g/liter.
5. A polyoxymethylene fibrid as claimed in claim 1, claim 2 or claim 3, which contains up to 75% of additives.
6. A process for the preparation of a polyoxymethylene fibrid in which a solution of the polymer in a solvent mixture of lower alcohol and water is forced through a nozzle into a precipitation bath which is kept in motion, the temperature in the precipitation bath being 0-100°C and the solvent mixture containing 3-25% by weight of water, relative to the total mixture.
7. A process as claimed in claim 6 in which the precipi-tation bath is moved with a linear speed of at least 0.1 m/s.
8. A process as claimed in claim 6 in which the solvent mixture for the polymer and the solvent mixture in the precipi-tation bath have the same composition.
9. A process as claimed in claim 6, claim 7 or claim 8 in which the solvent used is a mixture of 85 to 95% by weight of a lower alcohol having 1-4 carbon atoms and 5 to 15% by weight of water.
10. A process as claimed in claim 6, claim 7 or claim 8 in which the polymer solution is forced through nozzles having an adjustable annular gap into a pipe through which the precipitation bath flows.
11. Paper formed from polyoxymethylene fibrids as claimed in claim 1, claim 2 or claim 3.
12. Building material containing polyoxymethylene fibrids as claimed in claim 1, claim 2 or claim 3 in admixture with other materials.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP3144916.6 | 1981-11-12 | ||
| DE19813144916 DE3144916A1 (en) | 1981-11-12 | 1981-11-12 | POLYOXYMETHYLENE FIBRIDE, METHOD FOR THE PRODUCTION THEREOF AND THEIR USE |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1178757A true CA1178757A (en) | 1984-12-04 |
Family
ID=6146206
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000415335A Expired CA1178757A (en) | 1981-11-12 | 1982-11-10 | Polyoxymethylene fibrids, a process for their preparation, and their use |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0079554B1 (en) |
| JP (1) | JPS5891814A (en) |
| AT (1) | ATE24743T1 (en) |
| CA (1) | CA1178757A (en) |
| DE (2) | DE3144916A1 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2547285Y2 (en) * | 1991-07-25 | 1997-09-10 | 松下電工株式会社 | Electric razor |
| US5993537A (en) | 1998-03-11 | 1999-11-30 | Dalhousie University | Fiber reinforced building materials |
| US8785526B2 (en) | 2010-12-16 | 2014-07-22 | Ticona Llc | Polyoxymethylene fibers in concrete |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2988782A (en) * | 1958-12-09 | 1961-06-20 | Du Pont | Process for producing fibrids by precipitation and violent agitation |
| GB1053119A (en) * | 1963-04-24 | |||
| GB1050858A (en) * | 1963-06-07 | |||
| DE2947490A1 (en) * | 1979-11-24 | 1981-06-04 | Hoechst Ag, 6000 Frankfurt | POLYOXYMETHYLENE FIBRIDE AND METHOD FOR THE PRODUCTION THEREOF |
-
1981
- 1981-11-12 DE DE19813144916 patent/DE3144916A1/en not_active Withdrawn
-
1982
- 1982-11-08 EP EP82110274A patent/EP0079554B1/en not_active Expired
- 1982-11-08 DE DE8282110274T patent/DE3274995D1/en not_active Expired
- 1982-11-08 AT AT82110274T patent/ATE24743T1/en not_active IP Right Cessation
- 1982-11-10 CA CA000415335A patent/CA1178757A/en not_active Expired
- 1982-11-11 JP JP57196851A patent/JPS5891814A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| EP0079554A3 (en) | 1984-12-27 |
| DE3274995D1 (en) | 1987-02-12 |
| EP0079554B1 (en) | 1987-01-07 |
| DE3144916A1 (en) | 1983-05-19 |
| ATE24743T1 (en) | 1987-01-15 |
| EP0079554A2 (en) | 1983-05-25 |
| JPS5891814A (en) | 1983-05-31 |
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