权利要求：
1.-14. (canceled)
15. A filament comprising a core material (CM) coated with a layer of shell material (SM), wherein
the core material (CM) comprises the components a) to c)
a) 30 to 80% by volume, based on the total volume of the core material (CM) of at least one inorganic powder (IP),
b) 20 to 70% by volume, based on the total volume of the core material (CM) of at least one binder (B) comprising component b1)
b1) at least one polymer (P)
c) 0 to 20% by volume, based on the total volume of the core material (CM) of at least one additive (A),
wherein the at least one polymer (P) is a polyoxymethylene (POM) homopolymer, a polyoxymethylene (POM) copolymer or polyoxymethylene (POM) terpolymer and wherein at least some of the OH-end groups of the polyoxymethylene (POM) homopolymer are capped,
and the shell material (SM) comprises the components d) to f)
d) 75 to 100% by volume, based on the total volume of the shell material (SM) of at least one thermoplastic polymer (TP)
e) 0 to 20% by volume, based on the total volume of the shell material (SM) of the at least one inorganic powder (IP),
f) 0 to 25% by volume, based on the total weight of the shell material (SM) of the at least one additive (A), wherein the thickness of the layer of shell material is 0.05 to 0.5 mm.
16. The filament according to claim 15, wherein the binder (B))
i) comprises from 50 to 96% by weight or the at least one polymer (P), based on the total weight of the binder.
17. The filament according to claim 15, wherein the binder (B) in the core material (CM) further comprises components b2) or b3)
b2) at least one polyolefin (PO),
b3) at least one further polymer (FP), in case component b) is a polyoxymethylene (POM).
18. The filament according to claim 17, wherein the binder (13) comprises 2 to 35% by weight of component b2), based on the total weight of the binder (B), or from 2 to 40% by weight of component b3), based on the total weight of the binder (B).
19. The filament according to claim 15, wherein
i) the diameter of the filament is 1.5 to 3.5 mm, or
ii) the diameter of the core material is 1.5 to 3.0 mm, or
iii) the thickness of the layer of shell material (SM) is 0.09 to 0.3 mm, or
iv) the particle size of the inorganic powder (IP) is from 0.1 to 80 μm, or
v) the inorganic powder (IP) is a powder of at least one inorganic material selected from the group consisting of a metal, a metal alloy and a ceramic material, or
vi) the at least one thermoplastic polymer (TP) of the shell material (SM) is selected from the group of polyoxymethylene (POM), polyolefins (PE) such as polypropylene or polyethylene, polyurethanes (PU), polyamides (PA), polyethers (PETH), polycarbonates (PC), or polyesters (PES) such as polylactic acid and blends thereof.
20. The filament according to claim 15, wherein the polymer (P) in component (b1) is a polyoxymethylene (POM) copolymer which is prepared by polymerization of
from at least 50 mol-% of a formaldehyde source (b1a),
from 0.01 to 20 mol-% of at least one first comonomer (b1b) of the general formula (II)
wherein
R1 to R4 are each independently of one another selected from the group consisting of H, C1-C4-alkyl and halogen-substituted C1-C4-alkyl;
R5 is selected from the group consisting of a chemical bond, a (—CR5aR5b—) group and a (—CR5aR5bO—) group,
wherein
R5a and R5b are each independently of one another selected from the group consisting of H and unsubstituted or at least monosubstituted C1-C4-alkyl,
wherein the substituents are selected from the group consisting of F, Cl, Br, OH and C1-C4-alkyl;
n is 0, 1, 2 or 3;
and
from 0 to 20 mol-% of at least one second comonomer (b1c) selected from the group consisting of a compound of formula (III) and a compound of formula (IV)
wherein
Z is selected from the group consisting of a chemical bond, an (—O—) group and an (—O—R6—O) group,
wherein
R6 is selected from the group consisting of unsubstituted C1-C8-alkylene and C3-C8-cycloalkylene.
21. The filament according to claim 17, wherein the further polymer (FP) is at least one further polymer (FP) selected from the group consisting of a polyether, a polyurethane, a polyepoxide, a polyamide, a vinyl aromatic polymer, a poly(vinyl ester), a poly(vinyl ether), a poly(alkyl (meth)acrylate) and copolymers thereof.
22. A process for the preparation of a filament according to claim 15, wherein a core material (CM) is coated with a layer of a shell material (SM) by co-extrusion of the core material (CM) with the shell material (SM).
23. A process for preparation of a three-dimensional green body, by a fused filament fabrication process, comprising at least the steps a), b), c),
a) providing the filament according to claim 15 on a spool to a noozle,
b) heating the filament to a temperature (TM),
c) depositing of the heated filament obtained in step b) in a build chamber using a layer based additive technique in order to form the three dimensional green-body.
24. The process according to claim 23, wherein the temperature (TM) in step b) is 140 to 240° C.
25. The process according to claim 23, wherein step c) is followed by a step d) in which at least a part of the binder (B) or at least a part of the shell material (SM) is removed from the three-dimensional green body in order to form a three-dimensional brown body.
26. The process according to claim 25, wherein in step d)
i) the binder (B) or the shell material (SM) is removed by acidic treatment or
ii) the binder (B) or the shell material (SM) is removed at a temperature below the melting point of the binder (B) or the shell material (SM).
27. The process according to claim 25, wherein step d) is followed by a step e), in which the three-dimensional brown body is sintered to form a three-dimensional sintered body.
28. A three-dimensional green-body, prepared by the process according to claim 23.
29. The filament according to claim 15, wherein
i) the diameter of the filament is 2.0 to 3.1 mm, or
ii) the diameter of the core material is 1.9 to 2.7 mm, or
iii) the thickness of the layer of shell material (SM) is 0.1 to 0.25 mm, or
iv) the particle size of the inorganic powder (IP) is from 0.5 to 50 μm.
发明内容：
[0001]The invention relates to a filament comprising a core material (CM) comprising an inorganic powder (IP) and the core material (CM) is coated with a layer of shell material (SM) comprising a thermoplastic polymer. Further, the invention relates to a process for the preparation of said filament, as well as to three-dimensional objects and a process for the preparation thereof.
[0002]One of the most used 3D printing technologies or additive manufacturing technology is the fused deposition modeling (FDM), also known as fused filament fabrication process (FFF). For the production of three-dimensional objects, usually filaments of thermoplastic materials, provided on a spool, are deposited layer-by-layer through a heated nozzle on a base. Therefore, the thermoplastic material is heated to a temperature past its melting and/or glass transition temperature. The thermoplastic material and the temperature gradient are selected in order enable its solidification essentially immediately upon contacting the base or a preceding layer of thermoplastic material extruded.
[0003]In order to form each layer, drive motors are provided to move the base and/or the extrusion nozzle (dispending head) relative to each other in a predetermined pattern along the x-, y- and z-axis. Fused deposition modeling (FDM) was first described in U.S. Pat. No. 5,121,329. Typical materials for the production of three-dimensional objects are thermoplastic materials. The production of three-dimensional metallic or ceramic objects by fused filament fabrication is only possible if the metal or ceramic material has a low melting point so that it can be heated and melted by the nozzle. If the metal or ceramic material has a high melting point, it is necessary to provide the metal or ceramic material in a binder composition to the extrusion nozzle. The binder composition usually comprises a thermoplastic material. When depositing the mixture of a metal or ceramic material in a binder on a base, the formed three-dimensional object is a so called “green body” which comprises the metal or ceramic material in a binder. To receive the desired metallic or ceramic object, the binder has to be removed and finally the object has to be sintered. However, the use of filaments comprising an inorganic powder and a binder coated with a shell material (SM) comprising a thermoplastic polymer is not mentioned.
[0004]U.S. Pat. No. 5,738,817 and U.S. Pat. No. 5,900,207 describe a fused deposition modeling process for making a three-dimensional article by using a mixture of a particulate composition dispersed in a binder. The particulate composition comprises ceramic materials, elemental metals, metal alloys and/or steels. The binder consists of a polymer, a wax, an elastomer, a tackifier and a plasticizer. The binder is removed from the article by a burnout cycle during which the article is slowly heated to cause some of the components of the binder system to melt and flow out of the article. After these components are removed from the article, the temperature is increased and the other components of the binder are thermally decomposed and are removed from the article by diffusion and evaporation. This step d) process is very time consuming. Furthermore, the melting of the binder before evaporation leads to distortion of the article and moreover, the high temperatures may lead to blistering on the surface or internal cracking and/or delamination of the article. The application of filaments comprising an inorganic powder and a binder coated with a shell material (SM) comprising a thermoplastic polymer is not disclosed.
[0005]US 2012/0033002 describes a process for the preparation of three-dimensional thermomagnetic objects by fused filament fabrication using a mixture of a thermomagnetic powder and a binder system. This binder system comprises polymers like polyesters, polysulfones, poly(ether sulfones) and styrene copolymers. After the printing of the three-dimensional object, the binder has to be removed. For this step d) step, very high temperatures are necessary. The high temperatures that are necessary for the step d) step may, as stated above, lead to blistering on the surface of the three-dimensional object, internal cracking and/or delamination of the article. Filaments comprising a core material (CM) coated with a layer of shell material (SM) are not mentioned.
[0006]US 2012/0231225 discloses filaments for use in an extrusion-based additive manufacturing system. These filaments comprise a core portion of a first thermoplastic polymer and a shell portion of a second thermoplastic polymer that is compositionally different from the first thermoplastic material. In some embodiments of the filaments disclosed in US 2012/0231225, the material of the core portion and the shell portion exhibit different crystallization temperatures. This difference in crystallization temperatures is desired, since it “reduces distortions, internal stresses, and sagging of the semi-crystalline polymeric materials when deposited as extruded roads to form layers of 3D models.” Inorganic materials are not involved in any of the filaments mentioned.
[0007]EP 15 152 349.5 describes the use of a mixture comprising an inorganic powder and a binder in a fused filament process and to a process for producing three-dimensional objects by a fused filament fabrication process. However, a filament comprising a core material and an additional shell material is not disclosed.
[0008]WO 2015/077262 A1 discloses filaments as 3D printer inputs comprising separated layers or sections. These layers may comprise different materials, such as polymers, carbon fiber, fiber glass, wood fiber, nanocellulose fiber or carbon nanotubes. But WO 2015/077262 A1 does not disclose the combination of an inorganic powder and at least one binder as core material and at least one thermoplastic polymer as shell material.
[0009]The object underlying the present invention is to provide new filaments for an application in an extrusion-based additive manufacturing system.
[0010]This object is achieved by a filament comprising a core material (CM) coated with a layer of shell material (SM), wherein the core material (CM) comprises the components a) to c)[0011]a) 30 to 80% by volume, based on the total volume of the core material (CM) of at least one inorganic powder (IP),[0012]b) 20 to 70% by volume, based on the total volume of the core material (CM) of the at least one binder b) comprising component b1)[0013]b1) at least one polymer (P)[0014]c) 0 to 20% by volume, based on the total volume of the core material (CM) of the at least one additive (A), and the shell material (SM) comprises the components d) to f)[0015]d) 75 to 100% by volume, based on the total weight of the shell material (SM) of at least one thermoplastic polymer (TP)[0016]e) 0 to 20% by volume, based on the total volume of the shell material (SM) of the at least one inorganic powder (IP),[0017]f) 0 to 25% by volume, based on the total volume of the shell material (SM) of the at least one additive (A), wherein the thickness of the layer of shell material (SM) is 0.05 to 0.5 mm.
[0018]One advantage of the inventive filaments is their higher mechanical stability compared to filaments prepared from the same core material (CM) but without the shell material (SM). In particular, the inventive filaments can be rolled on a spool, while filaments without shell material (SM) are usually too brittle and therefore are not suited to be spooled.
[0019]Since the mechanical properties and therefore the processability of the inventive filaments in a conventional machine for a fused filament fabrication process (FFF) are mainly determined by the shell material (SM), there is more freedom of variation in regard to the composition of the core material (CM) compared to filaments without a shell material (SM). For example, the inventive shell material (SM)-core material (CM) configuration allows for the use of significantly higher loads of inorganic powder in the core material (CM) or ultra-low viscosity binders and/or additives in the core material (CM) that could result in a more brittle core. Without a layer of shell material (SM) according to the invention it was not possible to consistently feed highly brittle material in the conventional machines used in the fused filament fabrication process (FFF). Furthermore, it is also possible that the inventive filaments exhibit a tacky or extremely tacky core material (CM), which would without the presence of the shell material (SM) block the feeder mechanism. Consequently, by the inventive process filaments for the application in a fused filament fabrication process (FFF) can be realized, which obtain a core material (CM) of ultra-low viscosity or of extreme tackiness.
[0020]The core material (CM) shows a good flowability at the processing temperatures and at the shear rates used in a conventional Fused Deposition Modeling (FDM) process. Moreover, no demixing of the inorganic powder (IP) and the binder (B) of the core material (CM) occurs and usually no stress cracks arise during the hardening. Another advantage of the present invention is that the binder (B) can easily be removed at temperatures below the melting point of the binder (B), resulting in only little or even no deformation of the three-dimensional object.
[0021]In one embodiment of the invention Polyoxymethylene (POM) is present in the binder (B). Polyoxymethylene (POM) as component of the binder (B) exhibits a high crystallization rate and hardens quickly. Furthermore, polyoxymethylene (POM) is not known to be a sticky polymer as it has a low coefficient of friction.
[0022]Consequently, it is surprising that layers of the filament comprising an inorganic powder (IP) and a binder (B), which comprises polyoxymethylene (POM), adhere to each other, although polyoxymethylene (POM) has a low coefficient of friction and that as a consequence of this adherence the filament can be used in a fused deposition modeling (FDM) process using a layer-based additive technique.
[0023]The invention is specified in more detail as follows.
[0024]The filament comprises a core material (CM) coated with a layer of shell material (SM).
[0025]The filament may exhibit any length and/or diameter as deemed appropriate by the person skilled in the art.
[0026]Preferably, the diameter of the filament is 1.5 to 3.5 mm, more preferably 2.0 to 3.1 mm, most preferably 2.6 to 3.0 mm.
[0027]The layer of shell material (CM) may have any thickness as deemed appropriate by the person skilled in the art.
[0028]Preferably, the thickness of the layer of shell material (SM) is 0.05 to 0.5 mm, more preferably 0.09 to 0.3 mm, most preferably 0.1 to 0.25 mm.
[0029]The core material (CM) may have diameter as deemed appropriate by the person skilled in the art.
[0030]Preferably the diameter of the core material is 1.5 to 3.0 mm, more preferably 1.9 to 2.7 mm, most preferably 2.2 to 2.7 mm.
[0031]The core material (CM) comprises the components a) to c).
[0032]The core material (CM) comprises as component a) 30 to 80% by volume, preferably 40 to 68% by volume, more preferably 50 to 65% by volume, based on the total volume of the core material (CM), of at least one inorganic powder (IP).
[0033]The terms “component (a)” and “inorganic powder (IP)” for the purpose of the present invention are synonymous and are used interchangeably throughout the present invention.
[0034]As component a), any known inorganic powder (IP) can be used. Preferably, a sinterable inorganic powder (IP) is used as component a). More preferably, the inorganic powder (IP) is a powder of at least one inorganic material selected from the group consisting of a metal, a metal alloy and a ceramic material, most preferably the at least inorganic powder is a metal or a metal alloy, particularly preferably, the at least inorganic powder is a metal.
[0035]Another subject of the present invention is therefore a filament, wherein the inorganic powder (IP) is a powder of at least one inorganic material selected from the group consisting of a metal, a metal alloy and a ceramic material, preferably the at least inorganic powder is a metal or a metal alloy, particularly preferably, the at least inorganic powder is a metal.
[0036]“An inorganic powder (IP)” means precisely one inorganic powder (IP) as well as a mixture of two or more inorganic powders (IP). The same holds true for the term “an inorganic material”. “An inorganic material” means precisely one inorganic material as well as mixtures of two or more inorganic materials.
[0037]“A metal” means precisely one metal as well as mixtures of two or more metals. A metal within the present invention can be selected from any metal of the periodic table of the elements which is stable under the conditions of a fused filament fabrication process and which can form three-dimensional objects. Preferably, the metal is selected from the group consisting of aluminium, yttrium, titanium, zirconium, vanadium, niobium, chromium, molybdenum, tungsten, manganese, iron, carbonyl iron powder (CIP), cobalt, nickel, copper, silver, zinc and cadmium, more preferably, the metal is selected from the group consisting of titanium, niobium, chromium, molybdenum, tungsten, manganese, iron, carbonyl iron powder (CIP), nickel and copper. With particular preference, the metal is selected from the group consisting of titanium, iron and carbonyl iron powder (CIP).
[0038]Carbonyl iron powder (CIP) is highly pure iron powder, prepared by chemical decomposition of purified iron pentacarbonyl.
[0039]“A metal alloy” means precisely one metal alloy as well as mixtures of two or more metal alloys. Within the context of the present invention, the term “metal alloy” means a solid solution or a partial solid solution, which exhibits metallic properties and comprises a metal and another element. “A metal” means, as stated above precisely one metal and also mixtures of two or more metals. The same applies to “another element”. “Another element” means precisely one other element and also mixtures of two or more other elements.
[0040]Solid solution metal alloys exhibit a single solid phase microstructure while partial solid solution metal alloys exhibit two or more solid phases. These two or more solid phases can be homogeneous distributed in the metal alloy, but they can also be heterogeneous distributed in the metal alloy.
[0041]The metal alloys can be prepared according to any process known to the person skilled in the art. For example, the metal can be melted and the other element can be added to the molten metal. However, it is also possible, to add the metal and the other element directly to the core material (CM) without the preparation of a metal alloy before. The metal alloy will then be formed during the process of the preparation of the three-dimensional object.
[0042]Concerning the metal, the above-stated embodiments and preferences for the metal apply.
[0043]The other element can be selected from the metals described above. However, the other element differs from the metal comprised in the metal alloy.
[0044]The other element can be selected from any element of the periodic table, which forms a metal alloy that is stable under the conditions of a fused filament fabrication process or, which is stable or forms stable alloys with the metal under the conditions of a fused filament process. In a preferred embodiment of the present invention the other element is selected from the group consisting of the aforementioned metals, boron, carbon, silicon, phosphorous, sulfur, selenium and tellurium. Particularly preferably, the at least one other element is selected from the group consisting of the aforementioned metals, boron, carbon, silicon, phosphorous and sulfur.
[0045]Preferably, the metal alloy according to the present invention comprises steel.
[0046]“A ceramic material” means precisely one ceramic material as well as mixtures of two or more ceramic materials. In the context of the present invention, the term “ceramic material” means a non-metallic compound of a metal or a first metalloid, and a non-metal or a second metalloid.
[0047]“A metal” means precisely one metal and also mixtures of two or more metals. The same relies to “a non-metal” and “a first metalloid”, as well as “a second metalloid”. “A non-metal” means precisely one non-metal and also mixtures of two or more non-metals. “A first metalloid” means precisely one first metalloid and also mixtures of two or more first metalloids. “A second metalloid” means precisely one second metalloid and also mixtures of two or more second metalloids.
[0048]Non-metals are known per se to the person skilled in the art. The non-metal according to the present invention can be selected from any non-metal of the periodic table. Preferably, the at least one non-metal is selected from the group consisting of carbon, nitrogen, oxygen, phosphorus and sulfur.
[0049]Metalloids are as well known per se to the skilled person. The first metalloid and the 30 second metalloid can be selected from any metalloid of the periodic table. Preferably, the first metalloid and/or the second metalloid are selected from the group consisting of boron and silicon. It should be clear that the first metalloid and the second metalloid differ from each other. For example, if the first metalloid is boron, then the second metalloid is selected from any other metalloid of the periodic table of the elements besides boron.
[0050]In one embodiment of the present invention, the ceramic material is selected from the group consisting of oxides, carbides, borides, nitrides and silicides. In a preferred embodiment the ceramic material is selected from the group consisting of MgO, CaO, SiO2, Na2O, Al2O3, ZrO2, Y2O3, SiC, Si3N4, TiB and AlN. Particularly preferred, the ceramic material is selected from the group consisting of Al2O3, ZrO2 and Y2O3.]
[0051]For the preparation of the inorganic powder (IP), the inorganic material has to be pulverized. To pulverize the inorganic material, any method known to the person skilled in the art can be used. For example, the inorganic material can be ground. The grinding for example can take place in a classifier mill, in a hammer mill or in a ball bill.
[0052]The carbonyl iron powder (CIP) is prepared by chemical decomposition of purified iron pentacarbonyl.
[0053]The particle sizes of the inorganic powders (IP) used as component a) are preferably from 0.1 to 80 μm, particularly preferably from 0.5 to 50 μm, more preferably from 0.1 to 30 μm, measured by laser diffraction.
[0054]Another subject of the present invention is therefore a filament, wherein the particle size of the inorganic powder (IP) is from 0.1 to 80 μm.
[0055]The core material comprises (CM) comprises as component b) 20 to 70% by volume, preferably 20 to 60% by volume, more preferably 20 to 50% by volume, based on the total volume of the core material (CM), of at least one binder (B).
[0056]The terms “component b)” and “binder (B)” for the purpose of the present invention are synonymous and are used interchangeably throughout the present invention.
[0057]The binder (B) comprises a component b1) which is at least one polymer (P).
[0058]Preferably, the binder (B) comprises 50 to 96% by weight, more preferably 60 to 90% by weight, most preferably 70 to 85% by weight of the at least one polymer (P), based on the total weight of the binder (B), as component b1).
[0059]Preferably, the at least one polymer (P) is a polyoxymethylene (POM).
[0060]As component b1), at least one polyoxymethylene (POM) may be used. “At least one polyoxymethylene (POM)” within the present invention means precisely one polyoxymethylene (POM) and also mixtures of two or more polyoxymethylenes (POM).
[0061]For the purpose of the present invention, the term “polyoxymethylene (POM)” encompasses both, polyoxymethylene (POM) itself, i. e. polyoxymethylene (POM) homopolymers, and also polyoxymethylene (POM) copolymers and polyoxymethylene (POM) terpolymers.
[0062]Polyoxymethylene (POM) homopolymers usually are prepared by polymerization of a monomer selected from a formaldehyde source (b1a).
[0063]The term “formaldehyde source b1a) relates to substances which can liberate formaldehyde under the reaction conditions of the preparation of polyoxymethylene (POM).
[0064]The formaldehyde sources b1a) are advantageously selected from the group of cyclic or linear formals, in particular from the group consisting of formaldehyde and 1,3,5-trioxane. 1,3,5-trioxane is particularly preferred.
[0065]Polyoxymethylene (POM) copolymers are known per se and are commercially available. They are usually prepared by polymerization of trioxane as main monomer.
[0066]In addition, comonomers are concomitantly used. The main monomers are preferably selected from among trioxane and other cyclic or linear formals or other formaldehyde sources b1a).
[0067]The expression “main monomers” is intended to indicate that the proportion of these monomers in the total amount of monomers, i. e. the sum of main monomers and comonomers, is greater than the proportion of the comonomers in the total amount of monomers.
[0068]Quite generally, polyoxymethylene (POM) according to the present invention has at least 50 mol-% of repeating units —CH2O— in the main polymer chain. Suitable polyoxymethylene (POM) copolymers are in particular those which comprise the repeating units —CH2O— and from 0.01 to 20 mol-%, in particular from 0.1 to 10 mol-% and very particularly preferably from 0.5 to 6 mol-% of repeating units of the formula (I),
wherein[0069]R1 to R4 are each independently of one another selected from the group consisting of H, C1-C4-alkyl and halogen-substituted C1-C4-alkyl;[0070]R5 is selected from the group consisting of a chemical bond, a (—CR5aR5b—) group and a (—CR5aR5bO—) group,
wherein[0071]R5a and R5b are each independently of one another selected from the group consisting of H and unsubstituted or at least monosubstituted C1-C4-alkyl,[0072]wherein the substituents are selected from the group consisting of F, Cl, Br, OH and C1-C4-alkyl;[0073]n is 0, 1, 2 or 3.
[0074]If n is 0, then R5 is a chemical bond between the adjacent carbon atom and the oxygen atom. If R5 is a (—CR5aR5bO—) group, then the oxygen atom (0) of the (—CR5aR5bO—) group is bound to another carbon atom (C) of formula (I) and not to the oxygen atom (O) of formula (I). In other words, formula (I) does not comprise peroxide compounds. The same holds true for formula (II).
[0075]Within the context of the present invention, definitions such as C1-C4-alkyl, as for example defined above for the radicals R1 to R4 in formula (I), mean that this substituent (radical) is an alkyl radical with a carbon atom number from 1 to 4. The alkyl radical may be linear or branched and also optionally cyclic. Alkyl radicals which have both a cyclic component and also a linear component likewise fall under this definition. Examples of alkyl radicals are methyl, ethyl, n-propyl, iso-propyl, butyl, iso-butyl, sec-butyl and tert-butyl.
[0076]In the context of the present invention, definitions, such as halogen-substituted C1-C4-alkyls, as for example defined above for the radicals R1 to R4 in formula (I), mean that the C1-C4-alkyl is substituted by at least one halogen. Halogens are F (fluorine), Cl (chlorine), Br (bromine) and I (iodine).
[0077]The repeating units of formula (I) can advantageously be introduced into the polyoxymethylene (POM) copolymers by ring-opening of cyclic ethers as first comonomers (b1b). Preference is given to first comonomers (b1b) of the general formula (II),
wherein[0078]R1 to R5 and n have the meanings as defined above for the general formula (I).
[0079]As first comonomers b1b) mention may be made for example of ethylene oxide, 1,2-propylene oxide, 1,2-butylene oxide, 1,3-butylene oxide, 1,3-dioxane, 1,3-dioxolane and 1,3-dioxepane (=butanediol formal, BUFO) as cyclic ethers and also linear oligoformals or polyformals such as polydioxolane or polydioxepane. 1,3-dioxolane and 1,3-dioxepane are particularly preferred first comonomers (b1b), very particular preferred is 1,3-dioxepane as first comonomer b1b).
[0080]Polyoxymethylene (POM) polymers which can be obtained by reaction of a formaldehyde source together with the first comonomer (b1b) and a second comonomer (b1c) are likewise suitable. The addition of the second comonomer (b1c) makes it possible to prepare, in particular, polyoxymethylene (POM) terpolymers.
[0081]The second comonomer (b1c) is preferably selected from the group consisting of a compound of formula (III) and a compound of formula (IV),
wherein[0082]Z is selected from the group consisting of a chemical bond, an (—O—) group and an (—O—R6—O—) group,
wherein[0083]R6 is selected from the group consisting of unsubstituted C1-C8-alkylene and C3-C8-cycloalkylene.
[0084]Within the context of the present invention, definitions such as C1-C8-alkylene means C1-C8-alkanediyle. The C1-C8-alkylene is a hydrocarbon having two free valences and a carbon atom number of from 1 to 8. The C1-C8-alkylene according to the present invention can be branched or unbranched.
[0085]Within the context of the present invention, definitions such as C1-C8-cycloalkylene means C1-C8-cycloalkanediyle. A C3-C8-cycloalkylene is a cyclic hydrocarbon having two free valences and a carbon atom number of from 3 to 8. Hydrocarbons having two free valences, a cyclic and also a linear component, and a carbon atom number of from 3 to 8 likewise fall under this definition.
[0086]Preferred examples of the second comonomer (b1c) are ethylene diglycidyl, diglycidyl ether and diethers prepared from glycidyl compounds and formaldehyde, dioxane or trioxane in a molar ratio of 2:1 and likewise diethers prepared from 2 mol of a glycidyl compound and 1 mol of an aliphatic diol having from 2 to 8 carbon atoms, for example the diglycidyl ether of ethylene glycol, 1,4-butanediol, 1,3-butanediol, 1,3-cyclobutanediol, 1,2-propanediol and 1,4-cyclohexanediol.
[0087]In a preferred embodiment component b1) is a polyoxymethylene (POM) copolymer which is prepared by polymerization of from at least 50 mol-% of a formaldehyde source, from 0.01 to 20 mol-% of at least one first comonomer (b1 b) and from 0 to 20 mol-% of at least one second comonomer (b1c).
[0088]In a particularly preferred embodiment component (b1) is a polyoxymethylene (POM) copolymer which is prepared by polymerization of from 80 to 99.98 mol-%, preferably from 88 to 99 mol-% of a formaldehyde source, from 0.1 to 10 mol-%, preferably from 0.5 to 6 mol-% of at least one first comonomer (b1b) and from 0.1 to 10 mol-%, preferably from 0.5 to 6 mol-% of at least one second comonomer (b1c).
[0089]In a further preferred embodiment component b1) is a polyoxymethylene (POM) copolymer which is prepared by polymerization of from at least 50 mol-% of a formaldehyde source, from 0.01 to 20 mol-% of at least one first comonomer (b1 b) of the general formula (II) and from 0 to 20 mol-% of at least one second comonomer (b1c) selected from the group consisting of a compound of formula (III) and a compound of formula (IV).
[0090]Another subject of the present invention is therefore a filament, wherein component b1) is a polyoxymethylene (POM) copolymer which is prepared by polymerization of[0091]from at least 50 mol-% of a formaldehyde source (b1a),[0092]from 0.01 to 20 mol-% of at least one first comonomer (b1b) of the general formula (II)
[0093]wherein[0094]R1 to R4 are each independently of one another selected from the group consisting of H, C1-C4-alkyl and halogen-substituted C1-C4-alkyl;[0095]R5 is selected from the group consisting of a chemical bond, a (—CR5aR5b—) group and a (—CR5aR5bO—) group,[0096]wherein[0097]R5a and R5b are each independently of one another selected from the group consisting of H and unsubstituted or at least monosubstituted C1-C4-alkyl,[0098]wherein the substituents are selected from the group consisting of F, Cl, Br, OH and C1-C4-alkyl;[0099]n is 0, 1, 2 or 3;[0100]and[0101]from 0 to 20 mol-% of at least one second comonomer (b1c) selected from the group consisting of a compound of formula (III) and a compound of formula (IV)
[0102]wherein[0103]Z is selected from the group consisting of a chemical bond, an (—O—) group and an (—O—R6—O—) group,[0104]wherein[0105]R6 is selected from the group consisting of unsubstituted C1-C8-alkylene and C1-C8-cycloalkylene.
[0106]In a preferred embodiment of the present invention at least some of the OH-end groups of the polyoxymethylene (POM) are capped. Methods for capping OH-end groups are known to the skilled person. For example, the OH-end groups can be capped by etherification or esterification.
[0107]Preferred polyoxymethylene (POM) copolymers have melting points of at least 150° C. and weight average molecular weights MW in the range from 5 000 g/mol to 300 000 g/mol, preferably from 6 000 g/mol to 150 000 g/mol, particularly preferably in the range from 7 000 g/mol to 100 000 g/mol.
[0108]Particular preference is given to polyoxymethylene (POM) copolymers having a polydispersity (Mw/Mn) of from 2 to 15, preferably from 2.5 to 12, particularly preferably from 3 to 9.
[0109]The measurement of the weight average molecular weight (Mw) and the number average molecular weight (Mn) is generally carried out by gel permeation chromatography (GPC). GPC is also known as sized exclusion chromatography (SEC).
[0110]Methods for the preparation of polyoxymethylene (POM) are known to those skilled in the art.
[0111]Further, the binder (B) may comprise a component b2).
[0112]Preferably, the binder (B) comprises from 2 to 35% by weight, more preferably 3 to 20% by weight, most preferably 4 to 15% by weight of component b2).
[0113]Preferably component b2) is at least one polyolefin (PO). “At least one polyolefin (PO)” within the present invention means precisely one polyolefin (PO) and also mixtures of two or more polyolefins (PO).
[0114]Polyolefins (PO) are known per se and are commercially available. They are usually prepared by polymerization of C2-C8-alkene monomers, preferably by polymerization of C2-C4-alkene monomers.
[0115]5 Within the context of the present invention, C2-C8-alkene means unsubstituted or at least monosubstituted hydrocarbons having 2 to 8 carbon atoms and at least one carbon-carbon double bond (C—C-double bond). “At least one carbon-carbon double bond” means precisely one carbon-carbon double bond and also two or more carbon-carbon double bonds.
[0116]In other words, C2-C8-alkene means that the hydrocarbons having 2 to 8 carbon atoms are unsaturated. The hydrocarbons may be branched or unbranched. Examples for C2-C8-alkenes with one C—C-double bond are ethene, propene, 1-butene, 2-butene, 2-methyl-propene (=isobutylene), 1-pentene, 2-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, 2-hexene, 3-hexene and 4-methyl-1-pentene. Examples for C2-C8-alkenes having two or more C—C-double bonds are allene, 1,3-butadiene, 1,4-pentadiene, 1,3-pentadiene, 2-methyl-1,3-butadiene (=isoprene).
[0117]If the C2-C8-alkenes have one C—C-double bond, the polyolefins (PO) prepared from those monomers are linear. If more than one double bond is present in the C2-C8-alkenes, the polyolefins (PO) prepared from those monomers can be crosslinked. Linear polyolefins (PO) are preferred.
[0118]It is also possible to use polyolefin (PO) copolymers, which are prepared by using different C2-C8-alkene monomers during the preparation of the polyolefins (PO).
[0119]Preferably, the polyolefins (PO) are selected from the group consisting of polymethylpentene, poly-1-butene, polyisobutylene, polyethylene and polypropylene. Particular preference is given to polyethylene and polypropylene and also their copolymers as are known to those skilled in the art and are commercially available.
[0120]The polyolefins (PO) can be prepared by any polymerization process known to the skilled person, preferably by free radical polymerization, for example by emulsion, bead, solution or bulk polymerization. Possible initiators are, depending on the monomers and the type of polymerization, free radical initiators such as peroxy compounds and azo compounds with the amounts of initiator generally being in the range from 0.001 to 0.5% by weight, based on the monomers.
[0121]The binder (B) may comprise a further polymer (FP) as component b3).
[0122]The terms “component b3)” and “further polymer (FP)” for the purpose of the present inventio