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(11) | EP 1 079 282 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
| published in accordance with Art. 158(3) EPC |
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| (54) | MELT EXTRUDED MATERIAL SUITABLE FOR FORMING TRANSFER LAYER OF PHOTOSENSITIVE UNIT OF IMAGE FORMING DEVICE |
| (57) To provide the melt-extrudable material suitable for forming a transfer layer of
photosensitive part of image forming device, particularly the melt-extrudable material
comprising a fluorine-containing resin which is excellent in non-sticking property,
smoothness and strength and is easy in controlling of volume resistivity, and a transfer
belt produced by using the melt-extrudable material. The melt-extrudable material
is suitable for forming a transfer layer of photosensitive part of image forming device
and comprises a composition comprising (A) a filler and (B) a fluorine-containing
thermoplastic resin; at least a part of the filler being fluorinated and the composition
giving a coating film having a surface volume resistivity of from 108 to 1013 Ω·cm, a water contact angle of not less than 96 degrees, a surface roughness Ra of
not more than 0.5 µm and a tensile strength of not less than 400 kgf/cm2 at 25°C. |
TECHNICAL FIELD
[0001] The present invention relates to a melt-extrudable material suitable for forming a transfer layer of photosensitive part of image forming device and to a transfer belt of photosensitive part formed by using the same.
BACKGROUND ART
[0002] Fluorine-containing resins are excellent in chemical and thermal stability and in addition, surface lubricity, electrical properties, mechanical properties and abrasion resistance, and are widely used for a carrier of transfer material and an image forming part in the field of electrophotographic copying machine.
[0003] A fluorine-containing resin composition is an electrically insulating material having a volume resistivity exceeding 1016 Ω·cm, and in a pressure roll and paper feeding roll inside an electrophotographic copying machine, causes troubles such as adherence of paper pieces thereto and adherence or scattering of toner due to static electricity.
[0004] For that reason, addition of an electrically conductive substance to the fluorine-containing resin composition has been tried. Examples of the electrically conductive substance are carbon materials such as carbon black, graphite powder and carbon fiber, metal powder, and the like.
[0005] However if a carbon black is added in an amount enough for obtaining electric conductivity, there is a problem that a viscosity of the resin becomes high due to a structure of the carbon black, which lowers moldability significantly. If a powder having an anisotropic form such as graphite powder and carbon fiber is added, there is a problem with an increase in surface roughness of the resin. When the surface roughness increases, a non-uniform contact arises between a drum and a paper, which results in an inaccurate image. When a metal powder is added, there is a problem with lowering of excellent chemical resistance inherent to fluorine-containing resins.
[0006] Also an electrically conductive belt is used widely in an intermediate transfer device, transfer separation device, carrying device, charging device and developing device of electrophotographic copying machine, printer or facsimile machine. A usual electrically conductive belt is, for example, one produced by adding an electrically conductive carbon black to a thermoplastic resin. The resin is molded into films and the films are connected to make a belt. Also the resin is extrusion-molded into a tubular film, and this tubular film is cut crosswise in a horizontal direction. The resulting product is known as a seamless belt (JP-A-2-233765, JP-A-3-89357, JP-A-64-26439, etc.).
[0007] For the electrically conductive belt, various thermoplastic resins are used depending on requirements. Particularly a fluorine-containing polymer has flame resistance, durability arid anti-filming property (toner-releasing property) which are more excellent than those of other thermoplastic resins, and therefore is widely used. However in case of copying machine, printer and facsimile machine provided with an electrically conductive belt of fluorine-containing polymer, there was a problem that a resistance of the electrically conductive belt is lowered with a lapse of time and an image is deteriorated. For example, when the electrically conductive belt is used as an intermediate transfer belt of a copying machine, etc., the belt is required to be electrically charged in order to electrostatically attract a toner onto a surface of the belt, and therefore high voltage is applied repeatedly to the belt by corona discharging. A resistance of the fluorine-containing polymer belt is lowered gradually by the applied high voltage and for that reason, an amount of toner transfer to the belt decreases, which has an adverse effect on an image. It is assumed that the reason why such a phenomenon occurs on the fluorine-containing polymer belt is that the resistance of the belt is lowered in a space-charge-limited-current state due to trapping of electrically conductive carrier which is caused by interface separation between the electrically conductive filler and the fluorine-containing polymer and by crystal defect in the polymer.
[0008] Further a specific range of conductivity is demanded in so-called semi-conductive rolls and belts such as a charge roll and belt, transfer roll and developing roll in an electrophotographic copying machine. In the roil and belt, a volume resistivity is required to be controlled in the range of from 108 to 1013 Ω·cm.
[0009] In those applications, in order to use a fluorine-containing resin composition containing a usual conductive substance, a precise control of an adding amount of such a substance and sufficient kneading are required. This is because it is difficult to control the volume resistivity in a narrow range of from 108 to 1013 Ω·cm since when an adding amount of usual conductive substance to a fluorine-containing resin is increased, a resistance is lowered drastically in a certain adding amount. Therefore there is demanded a fluorine-containing resin composition having electric conductivity and non-sticking property which does not cause a drastic change in a resistance by an adding amount of the conductive substance, does not lower excellent properties inherent to the fluorine-containing resin such as chemical resistance and can minimize changes in mechanical properties such as an increase in a viscosity, surface roughness and non-sticking property.
[0010] It is an object of the present invention to provide the melt-extrudable material suitable for forming a transfer layer of a photosensitive part of image forming device, particularly the melt-extrudable material comprising a fluorine-containing resin which is excellent in non-sticking property, smoothness and strength and easy in controlling volume resistivity, and a transfer belt produced by using the melt-extrudable material.
DISCLOSURE OF INVENTION
[0011] The present invention relates to the melt-extrudable material which is suitable for forming a transfer layer of a photosensitive part of image forming device and comprises a composition comprising (A) a filler and (B) a fluorine-containing thermoplastic resin and to the transfer belt produced by molding the melt-extrudable material; at least a part of the filler being fluorinated, and the composition giving a coating film having a surface volume resistivity of from 108 to 1013 Ω·cm, a water contact angle of not less than 96 degrees and a tensile strength of not less than 400 kgf/cm2 at 25°C.
BEST MODE FOR CARRYING OUT THE INVENTION
[0012] The melt-extrudable material of the present invention comprises (A) a filler, at least a part of which is fluorinated and (B) a fluorine-containing thermoplastic resin.
[0013] Examples of the preferred filler as the component (A), at least a part of which is fluorinated, are fluorinated carbon materials such as carbon black, carbon fiber, petroleum coke and graphite powder.
[0014] Among them, a fluorinated carbon black obtained by fluorinating a carbon black, particularly a fluorinated carbon black having a fluorine atom/carbon atom ratio F/C of not less than 0.1 and less than 1.0, particularly not less than 0.1 and less than 0.5 is preferred.
[0015] When F/C of the fluorinated carbon black of the component (A) is less than 0.1, an effect of fluorination is insufficient and the problems inherent to carbon material before fluorination remain unsolved, that is, controlling of conductivity is difficult because a rate of change in a resistance for an adding amount thereof is very big, a dispersion of the fluorinated carbon black becomes non-uniform due to growth of structure, and the obtained composition gets hard. When F/C is not less than 1.0, a desired conductivity cannot be imparted to the composition.
[0016] In the present invention, F/C is measured in the manner mentioned below. A fluorinated carbon black is wrapped together with a combustion improver Na2O2 and a polyethylene film in a filter paper, followed by firing in a closed flask filled with oxygen. An amount of generated hydrogen fluoride is measured through usual method by using a fluoride ion meter (ION ANALYZER 901 available from Orion Corporation). A fluorine content is calculated from the obtained value. F/C is calculated from the obtained fluorine content.
[0017] A major component of the fluorinated carbon black (A) is poly(carbon monofluoride). Preferred is a fluorinated carbon black obtained by fluorinating a carbon black having an average particle size of from 0.01 to 50 µm, preferably 0.01 to 1 µm with a fluorine gas. In case of a fluorinated carbon black obtained by using a carbon material having an average particle size exceeding 50 µm, for example, petroleum coke, graphite powder or carbon fiber, an amount thereof for imparting conductivity and non-sticking property to the resin must be increased and there is a tendency that there arise problems on the obtained composition such as an increase in a surface roughness, lowering of mechanical strength and non-uniform resistivity.
[0018] A carbon material suitable for the fluorinated carbon black (A) is a carbon black having the above-mentioned average particle size. Examples of the usable carbon black are, for instance, commercially available ones such as a furnace black for rubber (for example, ASAHI #55 available from Asahi Carbon Co., Ltd., etc.), a channel black for coloration (for example, LEBEN 7000 available from Columbia Carbon Co., Ltd.), thermal black (SEVACARBON MT-C1 available from Columbia Carbon Co., Ltd.), and the like.
[0019] Among carbon blacks, particularly preferred are those commonly called conductive carbon blacks. The conductive carbon black is defined by the factors such as a small average particle size (average particle size: not more than 0.1 µm), a large surface area (N2 surface area: not less than 50 m2/g), a developed structure (oil absorption: not less than 100 cc/g), a small content of impurities (ash content: less than 0.1 %) and an advanced graphitization. The conductive carbon black is widely used because conductivity can be imparted to the material with a relatively small amount thereof. Examples thereof are commercially available carbon blacks, for instance, KETJEN BLACK EC and KETJEN BLACK EC-600JD (The foregoing are available from Ketjen Black International, Inc.), BLACK PEARLS 2000, VULCAN XC-72 and CSX-99 (The foregoing are available from Cablack Co., Ltd.), DENKA BLACK (Denid Kagaku Kogyo Kabushiki Kaisha), CONDUCTEX 950 (Columbia Carbon Co., Ltd.), and the like.
[0020] The fluorinated carbon black (A) used in the present invention is obtained by bringing those carbon materials into contact with fluorine gas at a temperature in a range of from 200° to 600°C, more preferably 300° to 500°C. When a reaction temperature is lower than the above-mentioned range, there occur problems such that a fluorination reaction is slow, it is difficult to increase a degree of fluorination, thermal stability is not sufficient and properties inherent to the fluorinated carbon black such as non-sticking property and lubricity are not exhibited. On the contrary, when the reaction temperature is higher than the above-mentioned range, a thermal decomposition reaction easily arises and yield of the obtained fluorinated carbon black is lowered. Also in some cases, a drastic thermal decomposition reaction may occur and result in an explosion. Therefore full attention must be paid to that.
[0021] The fluorine gas used in the reaction may be diluted with an inert gas such as nitrogen, argon, helium or carbon tetrafluoride and may contain hydrogen fluoride. Though the reaction can be carried out at normal pressure, there is no problem even if the reaction is carried out under reduced pressure or under pressure.
[0022] Besides the above-mentioned conditions, a reaction time and an amount of fluorine gas flow may be optionally adjusted depending on a reactivity of a starting carbon material with fluorine and a desired F/C (fluorine content).
[0024] A feature of the present invention is to provide a fluorine-containing thermoplastic resin material capable of melt-extrusion molding. In that field, hitherto rubber materials such as a fluorine-containing rubber and silicone rubber have been used. However materials mainly comprising those rubbers cannot be extrusion-molded.
[0025] Examples of the fluorine-containing thermoplastic resin are copolymers of tetrafluoroethylene (TFE) with at least one ethylenically unsaturated monomer copolymerizable therewith (for example, olefins such as ethylene and propylene, halogenated olefins such as hexafluoropropylene, vinylidene fluoride, chlorotrifluoroethylene and vinyl fluoride, perfluoro(alkyl vinyl ethers), and the like), polychlorotrifluoroethylene, polyvinylidene fluoride, and the like. A particularly preferred fluorine-containing thermoplastic resin is a fluorine-containing thermoplastic resin having hydrogen atom from the point that a high strength can be obtained and processability is excellent. Examples thereof are ethylene (ET)-tetrafluoroethylene (TFE) copolymer (ET/TFE=40/60 to 60/40, in mole ratio), vinylidene fluoride polymers (for example, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer), and the like. Particularly ethylene-tetrafluoroethylene copolymer (ETFE), polyvinylidene fluoride (PVdF) and vinylidene fluoride-hexafluoropropylene copolymer are preferred from the viewpoint of high strength and processability. When those fluorine-containing thermoplastic resins are used, an effect of obtaining a composition having excellent heat resistance, non-sticking property, water- and oil-repellency, lubricity and chemical resistance is exhibited as compared with usual resins. Examples of such a usual resin are, for instance, non-fluorine-containing thermoplastic resins such as polyether ether ketone, thermoplastic polyimide, polyethylene naphthalate, polybutylene naphthalate, polyether sulfone, polysulfone, polycarbonate, polyarylate, polybutylene terephthalate and polyether nitrile.
[0026] A proportion of the component (A) to the component (B) is 1/99 to 20/80 (weight ratio, hereinafter the same). If the amount of the component (A) decreases, there is a tendency that an effect of adding the fluorinated carbon black is not obtained sufficiently, and if the amount is too much, there is a tendency that a mechanical strength such as a tensile strength is lowered. In addition to the component (B), the above-mentioned non-fluorine-containing thermoplastic resin may be blended in a range not lowering the effect of the present invention.
[0027] A feature of the melt-extrudable material of the present invention is such that a good extrusion-moldability can be obtained even without adding a plasticizer and a stable semi-conductivity can be obtained even without adding a surfactant. Therefore it is possible to eliminate an addition of a fluorine-containing surfactant and ester type plasticizer having a low electric resistance which have caused a problem with contamination because of bleeding thereof.
[0028] The composition of the present invention can be prepared, for example, by the following mixing methods.
[0029] The resin, fluorinated carbon black and if necessary, a minimum of additives are mixed with a mixer such as V-blender, tumbler or Henschel mixer and then further mixed with a melt-kneader such as a two screw extruder to give pellets. The so-obtained pellets are molded into a desired form, for example, belt, plate, film, and the like by using an extrusion-molding machine.
[0030] The melt-extrudable material of the present invention has properties suitable as a molding material for a transfer layer of photosensitive part of image forming device.
[0031] Namely a tube or film obtained by melt-extrusion molding of the material of the present invention has the following properties.
(1) A surface volume resistivity is from 108 to 1013 Ω·cm, preferably 1010 to 1013 Ω·cm. When the volume resistivity is in that range, excellent toner transfer is exhibited. Also a ratio of maximum volume resistivity/minimum volume resistivity on a surface of the same tube or film is not more than 10, and so semi-conductivity is uniform and dielectric breakdown is difficult to arise.
(2) A water contact angle is not less than 96 degrees, preferably not less than 98 degrees. When the water contact angle is large, non-sticking property is good.
(3) A tensile strength (25°C) is not less than 350 kgf/cm2, preferably from 360 to 600 kgf/cm2.
[0032] Also (4) it is preferable that a surface roughness (Ra) is not more than 5 µm, especially not more than 0.5 µm. A smooth surface having a small surface roughness (Ra) is excellent from the viewpoint of a small amount of remaining toner and image forming property.
[0033] A transfer belt which the present invention is directed to is subject to a large tension when rotated at high speed. Hitherto there was no transfer belt not only satisfying the above-mentioned properties (1), (2) and (4) but also giving a large tensile strength. Such a transfer belt is obtained only by the present invention.
[0034] The material of the present invention can provide molded articles of various forms by melt-extrusion molding method, for example, molded articles in the form of film, tube, plate, belt, etc. A uniform and homogeneous melt-extrusion-molded article cannot be obtained unless a material therefor has excellent melt-moldability. In case where a carbon black which is not fluorinated is blended, as mentioned above, a melt viscosity is increased significantly due to its structure and thus melt-kneading becomes insufficient and dispersion becomes non-uniform. In case of the material of the present invention, a melt flow rate (MFR) thereof which is one of indices for melt-moldability is in an allowable range (not less than 0.5 g/10 min, preferably not less than 0.7 g/ 10 min, ETFE: 297°C, PVdF: 230°C, load: 5 kg) and dispersibility (kneading property) as well as melt-moldability are good.
[0035] The present invention also relates to the transfer belt of a photosensitive part of film forming device.
[0036] Examples of the film forming device in the present invention are electrophotographic copying machine, facsimile machine, laser printer, and the like. The film forming device is not limited to them and encompasses a device for transferring a toner according to electrostatic copying.
[0037] On a photosensitive part of a fun forming device, for example, art electrophotographic copying machine are usually used semi-conductive rolls such as a charge roll, developing roll and transfer belt (or roll).
[0038] A transfer belt functions to transfer a toner image on a photosensitive drum to a transfer paper usually in such a manner that the endless transfer belt presses the transfer paper onto the photosensitive drum with three rolls.
[0039] Such a transfer belt is a single endless belt (thickness: usually from 50 to 250 µm) or an endless belt comprising a heat resistant resin fabric and a transfer layer (thickness: from about 10 µm to about 50 µm) provided thereon. The transfer belt of the present invention can be applied to those conventional structures.
[0040] The melt-extrudable material of the present invention is also useful for a resistive layer such as a transfer roll, charge roll or developing roll in addition to the use for the transfer belt.
[0041] Such rolls are obtained by forming a conductive elastic layer on a conductive substrate. A material for the conductive elastic layer is not limited particularly. The layer is formed by using a composition prepared by mixing a conductive powder, conductive fiber (carbon black, metal powder, carbon fiber, etc.), or the like to a synthetic rubber such as silicone rubber, ethylene propylene rubber, epichlorohydrin rubber, nitrile rubber or urethane rubber. The material to be used is one having a volume resistivity of not more than 105 Ω·cm, preferably not more than 103 Ω·cm and a rubber hardness (JIS A) in the range of 20 to 50 degrees, preferably 25 to 40 degrees. It is not preferable to use a plasticizer and surfactant for the purpose to adjust a resistivity and rubber hardness when mixing a conductive powder, etc. This is because bleeding of those chemicals arises with a lapse of time, which causes contamination of a surface of photosensitive and toner filming on a surface of the roll.
[0042] A material of the conductive substrate is not limited particularly, and aluminum, an alloy mainly comprising aluminum or stainless steel can be used.
[0043] Then the melt-extrudable material of the present invention is made into a tubular form through usual melt-extrusion molding. If necessary, the tube may be stretched or may have thermal shrinkability, but usually may have neither stretchability nor thermal shrinkability. A wall thickness of the tube need be in the range of from 0.01 to 0.15 mm. If the wall thickness is beyond the range, a preferred roll for photosensitive part cannot be obtained.
[0044] Then a method for producing the roll for photosensitive part of the present invention is explained below. Namely the roll for photosensitive part of the present invention can be produced by a method of firstly putting the metallic core roll and the tube produced from the melt-extrudable material of the present invention in a cylindrical molded article so that a space is provided between the roll and the tube and the inner surface of the cylindrical molded article comes into contact with the outer surface of the tube, and then pouring a material for the conductive elastic layer into the above-mentioned space, and if necessary, carrying out vulcanizing. It is a matter of course that the roll covered with the tube has to be taken out of the cylindrical molded article at a necessary time. In that case, the inner surface of the tube may be subjected previously to etching treatment or primer treatment so that it is easily contacted to the rubber portion. Also the roll may be produced by previously making the conductive elastic layer and then covering the tube of the present invention on the surface of the conductive elastic layer. In that case, it is better to use a tube having thermal shrinkability. Thus there is no restriction in the production method of the roll.
[0045] As mentioned above, the melt-extrudable material of the present invention is suitable for various rolls and belts of a photosensitive part of film forming device, particularly for a transfer belt which is required to have high strength.
EXAMPLE 1
[0047] Carbon black (DENKA BLACK available from Denki Kagaku Kogyo Kabushiki Kaisha, average particle size: 0.04 µm) was fluorinated to give a fluorinated carbon black having F/C of 0.1.
[0048] 10 Parts of the fluorinated carbon black and 90 parts of ETFE (ethylene/tetrafluoroethylene=48/52 in mole ratio) were mixed at 30°C in Henschel mixer, and then melt-kneaded at 300°C in a two screw extruder (LABOPLASTOMILL available from Toyo Seiki Kabushild Kaisha) and extruded to give pellets. The pellets were melt-extruded (300°C) into a film of 150 µm thick with an extrusion molding machine (30 diameter single screw extruder available from Tanabe Plastic Kabushild Kaisha).
[0049] The following physical properties of the obtained film were measured. The results are shown in Table 1.
(Volume resistivity)
[0050] A volume resistivity is measured with a resistance measuring cell (Resistivity Chamber R12702A) and a resistance meter (Digital Ultra-high Resistance Meter R8340A) which are available from ADVANTEST CORPORATION) according to JIS K 6911.
(Water contact angle)
[0051] A water contact angle is measured with a contact angle meter available from Kyowa Kaimen Kagaku Kabushiki Kaisha.
(Tensile strength)
(Surface roughness)
[0053] Measurement is made automatically on 2.5 mm surface of a sample at a pick-up speed of 0.3 mm/sec with a diamond pick-up having a needle end of 2 µmR by using a surface roughness meter (Surfcom 470A) available from Tokyo Seimitsu Kabushild Kaisha. The surface roughness Ra is a center line average height prescribed in JIS B 0601-1982.
[0054] A melt flow rate (MFR)(ETFE: 297°C, PVdF: 230°C, load: 5 kg) is measured according to ASTM D 3307 to examine melt-moldability of the melt-extrudable material of the present invention. The results are shown in Table 1.
EXAMPLES 2 to 6
[0055] Pellets were obtained in the same manner as in Example 1 except that a fluorinated carbon black having F/C shown in Table 1 was used in an amount shown in Table 1, and then melt-extrusion-molded to give a film. Physical properties of the film were measured. The results are shown in Table 1.
EXAMPLE 7
[0056] Pellets were obtained in the same manner as in Example 1 except that polyvinylidene fluoride (PVdF) was used instead of ETFE, and then melt-extrusion-molded to give a film. Physical properties of the film were measured. The results are shown in Table 1.
COMPARATIVE EXAMPLE 1
[0057] A film was produced in the same manner as in Example 1 except that only ETFE was melt-extrusion-molded without blending a fluorinated carbon black. Physical properties of the film were measured. The results are shown in Table 1.
COMPARATIVE EXAMPLES 2 to 3
[0058] Melt-extrusion molding was carried out in the same manner as in Example 1 except that a non-fluorinated carbon black (DENKA BLACK available from Denki Kagaku Kogyo Kabushiki Kaisha, average particle size: 0.04 µm) was used instead of a fluorinated carbon black in an amount shown in Table 1, to give a film. Physical properties of the film were measured. The results are shown in Table 1.
COMPARATIVE EXAMPLE 4
[0059] Melt-extrusion molding was carried out in the same manner as in Example 1 except that a completely fluorinated carbon black (F/C=1.1) was used instead of a fluorinated carbon black in an amount shown in Table 1, to give a film. Physical properties of the film were measured. The results are shown in Table 1.
INDUSTRIAL APPLICABILITY
[0060] As it is clear from Table 1, the melt-extrudable material of the present invention is excellent in melt-moldability (MFR), and a variation of a volume resistivity is small even if an adding amount of fluorinated carbon black is changed (comparison between Example 1 and 2, 3 and 4, and 5 and 6, respectively). The melt-extrudable material gives a molded article which is suitable for a transfer belt or roll of photosensitive part, has enough strength and is excellent in non-sticking property (water contact angle) and smoothness (surface roughness).
1. A melt-extrudable material which is suitable for forming a transfer layer of photosensitive
part of image forming device and is characterized in that the melt-extrudable material
comprises a composition comprising (A) a filler and (B) a fluorine-containing thermoplastic
resin; at least a part of said filler being fluorinated, and said composition giving
a coating film having a surface volume resistivity of from 108 to 1013 Ω·cm, a water contact angle of not less than 96 degrees and a tensile strength of
not less than 400 kgf/cm2 at 25°C.
2. The melt-extrudable material of Claim 1, wherein a surface roughness Ra of a coating
film obtained from said composition is not more than 0.5 µm.
3. The melt-extrudable material of Claim 1, wherein the filler (A) is a fluorinated carbon
black having a fluorine atom to carbon atom ratio F/C of not less than 0.1 and less
than 1.0.
4. The melt-extrudable material of Claim 1, wherein the filler (A) is a fluorinated carbon
black having a fluorine atom to carbon atom ratio F/C of not less than 0.1 and less
than 0.5.
5. The melt-extrudable material of Claim 1, wherein a content of the filler (A) is from
1 to 20 % by weight.
6. The melt-extrudable material of Claim 1, wherein the resin (B) is a fluorine-containing
thermoplastic resin having hydrogen atom.
7. The melt-extrudable material of Claim 1, wherein the resin (B) is an ethylene/tetrafluoroethylene
copolymer or a vinylidene fluoride polymer.
8. A transfer belt of photosensitive part of film forming device which is obtained by
molding the melt-extrudable material of Claim 1.