Abstract: In an aspect, a biaxially oriented pipe has a thickened end portion. The end portion has the same inner diameter as the biaxially oriented pipe and has a larger thickness than the biaxially oriented pipe. The end portion is made of the same thermoplastic polymer composition as the biaxially oriented pipe.

Abstract: A resin composition is disclosed that includes a thermosetting base resin; a curing agent; an inorganic filler; and at least one fluorine resin powder selected from polyvinylidene fluoride, polychlorotrifluoroethylene, and a tetrafluoroethylene/perfluoro(alkyl vinyl ether)/chlorotrifluoroethylene copolymer, and a semiconductor device which is fabricated by being sealed using a sealant formed of the resin composition.

Abstract: The present invention relates to a method of manufacturing a hydrophilized hollow fiber membrane by a continuous process using an extruder. According to the method of the present invention, thermal curing agent in the form of a monomer or a oligomer is added to a polymer solution, and in the melt state before a separation membrane is manufactured, thermal polymerization occurs due to an initial reaction of a thermal initiator at the appropriate temperature within a cylinder of the extruder. Thus, a hydrophilic component is evenly distributed into the membrane at the micro-level, and the hydrophilic component is not washed out, resulting in very high stability. Another advantage is high economic value and efficiency because the process for hydrophilizing the membrane as well as the process for manufacturing the membrane is carried out by the continuous process using the extruder without using conventional extrusion equipment in the form of an agitator.

Abstract: A method of preparing a green tire innerliner, the method comprising mixing one or more vulcanizable rubbery polymers, less than 0.75 parts by weight zinc oxide, less than 0.75 parts by weight magnesium oxide, and less than 0.75 parts by weight sulfur, per 100 parts by weight rubber, to form a vulcanizable mixture and extruding the mixture to form a green tire innerliner.

Abstract: A process to produce a laminate comprising coextruding a dynamically vulcanized alloy (DVA) film with an adhesive layer comprising a vulcanizable elastomeric composition through a die to produce the laminate. The process provides a residence time of the vulcanizable elastomeric composition in the melt to partially scorch the vulcanizable elastomeric composition. A melt of the DVA is in contact with the melt of the vulcanizable elastomeric composition in the die for at least 5 seconds, optionally also with a change in the area of the contact between the DVA film and the adhesive layer as it passes through the die, to increase the adhesion between the adhesive layer and the DVA layer relative to a shorter co-residence time. A laminate and a pneumatic tire comprising the laminate are also disclosed.

Abstract: A method for producing a high strength, flexible crosslinked polyethylene (PEX) material is provided wherein the base polymer is intermixed with a polymer modifier which affects the amorphous region of the polymer, leaving the crystalline portion of the base polymer virtually unaffected. Consequently, the amorphous region's density is lowered, resulting in a more flexible final product, while the crosslinked molecular structure and/or crystalline portion of the polymer, which controls the strength of the base polymer, remains strong. The polymer modifier can comprise a hydrocarbon fluid such as PAO, Group III basestocks, or a gas-to-liquid hydrocarbon. The plastic material has particular utility in the production of tubing, piping, and conduits for transporting gases, liquids, and the like, as well as wire and cable coatings such as jacketing and insulation.

Abstract: The present invention relates to an automatic elastomer extrusion apparatus and method. An apparatus 400 for in-situ extrusion of an elastomeric coating 410 on a profiled helical surface 450 can include a template (100, 200) forming a gap between the profiled helical surface 450 and an adjacent profiled helical surface (102, 202) of a template (100, 200) itself to extrude an elastomer therethrough. A tracking mechanism 302 and/or carriage 300 can allow a template to follow the contours of the profiled helical surface 350. The apparatus can include means for providing relative movement between the profiled helical surface and the template. The apparatus (500, 600) can include a cleaning module (502, 602), an adhesive application module (504, 604), an elastomer deposition module (506, 606), and/or a curing module (508, 608). Each module can further include a template (100, 200) and/or a tracking mechanism 302.

Abstract: A process for producing moldings with condensing-up of a polyamide molding composition whose polyamide component contains, as a result of the method of preparation, at least 5 ppm of phosphorus in the form of an acidic compound by means of a compound having at least two carbonate units, wherein a) from 0.001 to 10% by weight, based on the polyamide, of a salt of a weak acid is added to the polyamide molding composition prior to compounding or during compounding, b) a mixture of the finished composition and the compound having at least two carbonate units is prepared, c) the mixture is, if appropriate, stored and/or transported and d) the mixture is subsequently processed to produce the molding, with the condensing-up occurring only in this step, effects a significant increase in the melt stiffness combined with moderate processing pressures, which considerably simplifies, in particular, the production of hollow bodies and hollow profiles having large diameters.

Abstract: A method and extrusion line for producing peroxide-cross-linked polyethylene pipes in an extrusion line having an extruder, a cross-linking furnace and a flue. The extruded tube is subjected to a stretching process, and the cross-linking furnace has a first heating section that extends from its inlet to an actuated deflection roller and a second heating section from the deflection roller to its outlet. The stretching process in the first heating section and the stretching process in the second heating section are monitored and regulated in such a manner that the necessary stretching of the pipe takes place primarily in the first heating section, and the stretching of the pipe in the second heating section is subjected to zero adjustment. In this case, the height of the deflection roller(s) of the cross-linking furnace and the angle of the heating sections to the horizontal plane can be height-adjustable.

Abstract: A single site catalysed ethylene polymer including ethylene and optionally at least one comonomer having a Mw/Mn of less than 5 and wherein the total amount of unsaturations of the ethylene polymer is at least 0.8.

Abstract: Disclosed herein is a method of manufacturing inorganic hollow yarns, such as cermets, oxide-non oxide composites, poorly sinterable non-oxides, and the like, at low costs. The method includes preparing a composition comprising a self-propagating high temperature reactant, a polymer and a dispersant, wet-spinning the composition through a spinneret to form wet-spun yarns, washing and drying the wet-spun yarns to form polymer-self propagating high temperature reactant hollow yarns, and heat-treating the polymer-self propagating high temperature reactant hollow yarns to remove a polymeric component from the polymer-self propagating high temperature reactant hollow yarns while inducing self-propagating high temperature reaction of the self-propagating high temperature reactant to form inorganic hollow yarns. The composition comprises 45˜60 wt % of the self-propagating high temperature reactant, 6˜17 wt % of the polymer, 0.1˜4 wt % of the dispersant, and the balance of an organic solvent.

Abstract: A fuel line comprising a thermoplastic composition is described. The thermoplastic compositions exhibit high strength and flexibility and can be used to form one or more layers of single layer or multi-layer fuel lines. Methods for forming the thermoplastic compositions are also described. Formation methods include dynamic vulcanization of a composition that includes an impact modifier dispersed throughout a polyarylene sulfide. A crosslinking agent is combined with the other components of the composition following dispersal of the impact modifier. The crosslinking agent reacts with the impact modifier to form crosslinks within and among the polymer chains of the impact modifier. The compositions can exhibit excellent physical characteristics at extreme temperatures.

Abstract: A family of functionalized polymers is provided capable of forming membranes having exceptional OH? ionic conductivity as well as advantageous mechanical properties, which may be applied to membranes including such polymers for use in, e.g., AEMFC/HEMFC fuel cells. Preferred functional groups include a quaternary phosphonium, and the polymer may specifically be (tris(2,4,6-trimethoxyphenyl) phosphine)3 functionalized phosphonium polysulfone hydroxide, ECL-PVBC-QPOH, or QPOH based on any of the commercial polumers including polycarbonate (PC), poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), polyetherimine (PEI), poly(ether sulfone) (PES), poly(phenylene sulfoxide) PPS, poly(ether ether ketone) (PEEK), or polybenzimidazole (PBI), polyvinyl chloride (PVC). An ionomer membrane may include polysulfone based TPQPOH, ECL-PVBC-QPOH, and/or PPO.

Abstract: The present invention relates to a method for producing an annular belt made of polyimide comprising; a) joining both ends of a sheet made of a polyimide precursor to form an annular belt; and b) performing an imidizing reaction of the polyimide precursor.

Abstract: A closed-section beam element is provided, especially in a form of a tubular beam, manufactured of composite material containing comminuted and/or broken-up filing material, mainly wooden chips and particles, and thermosetting resin, wherein said beam element (10) has generally of longitudinal shape and having cross section of its external contour of any polygonal shape, or a circular or oval shape and/or of any irregular shape, preferably provided with projections and/or recesses arranged over the external surface of said beam element, and additionally said beam element has a central through opening (20) forming an internal through channel, preferably of a circular cross section, wherein surface of the internal through channel is provided with a continuous contour of at least one screw or spiral line (40) in relation to a centre axis of said beam element and extending, preferably, along full length of the internal channel along its central axis.

Abstract: The present disclosure provides a method for preparing polylactic acid and its products using a twin-screw extruder, comprising the step of mixing carbon dioxide adducts of carbene and lactide, and obtaining polylactic acid and its products via reactive extrusion using a twin-screw extruder.

Abstract: A method for extruding transparent and/or translucent article is provided. In one embodiment, the method comprises providing a propylene-based polymer comprising propylene derived units and one or more dienes, the propylene-based polymer having a triad tacticity of from 50% to 99% and a heat of fusion of less than 80 J/g, extruding the propylene-based polymer in the absence of processing oil into an article; and then crosslinking the extruded article.

Abstract: A hose has at least the following layer structure: an inner layer made of an amine-bonded rubber mixture having media-resistance properties and an adhesion layer of a peroxide-bonded rubber mixture lying on the external side of the inner layer. The inner layer and the adhesion layer form an adhesive bond. The inner layer includes a rubber mixture based on unblended AEM or an AEM blend or on unblended ACM or an ACM blend and the adhesion layer includes a rubber mixture based on EPM or EPDM, each of which are unblended. The hose often includes a strengthening support layer and an external layer of a rubber mixture having resistance to external influences. The external layer preferably includes a peroxide-bonded rubber mixture based on unblended EPM or an EPM blend or on unblended EPDM or an EPDM blend.

Abstract: The process for the preparation of articles from polymer materials having a medicamentous depot effect is performed by mixing the starting materials, shaping the mixture, cross-linking the polymer material at least until a sufficient dimensional stability is reached, performing all the necessary processing work, introducing the article into a protective package, sterilizing the packaged article, optionally with further cross-linking of the polymer material.

Abstract: A hydrophobic molecular sieve having a pore size of about 5 ? can be blended into a silane grafted crosslinkable polyethylene to reduce the level of extractable methanol present in articles made with such polymeric compositions after crosslinking. The molecular sieve apparently acts to “lock-up” the methanol generated as a by-product of the crosslinking reaction without compromising the desirable chemical or physical properties of articles that are manufactured with the crosslinked polyethylene.

Abstract: Disclosed herein is a method for preparing a crosslinked hollow fiber membrane. The method involves spinning a one phase solution comprising a monoesterified polyimide polymer, acetone as a volatile solvent, a spinning solvent, a spinning non-solvent, and optionally an organic and/or inorganic additive, wherein the volatile solvent is present in an amount of greater than 25 wt. % to about 50 wt. %, based on the total weight of the solution.

Abstract: The invention relates to the use of silane-modified polyvinyl alcohols for producing membranes, characterized in that the silane-modified polyvinyl alcohols can be obtained by a) radically initiated copolymerization of one or more vinyl esters from unbranched or branched carboxylic acids having 1 to 15 C-atoms and one or more ethylenically unsaturated silane compounds selected from the group comprising compounds of the general formulae CR2?CR—B—Si(OR?)3-n(R?)n (1), or CR2?CRC (?0)-D-B—Si(OR?)3-n(R?)n (2), wherein B is an aryl, heteroaryl or (CR2)m residue, wherein one or more non-neighboring CR2 groups can be replaced by heteroatoms as applicable, D is a heteroatom, R is a hydrogen atom, an alkyl or aryl residue or a heteroatom that is substituted as applicable by a hydrogen atom or an alkyl, aryl residue, OR? is an alkoxy, alkylcarboxy or arylcarboxy residue, R? is an alkyl or aryl residue and n 0, 1 or 2 and in 0 to 15, and b) subsequent saponification of the silane-modified vinyl ester copolymerisate obtai

Abstract: This invention relates to a chemically-modified polybenzimidazole porous tube. The tube has an outer diameter of 100-1000 microns, a wall thickness of 20-100 microns, and a pore size of 0.1-0.5 nm.

Abstract: A mandrel having an integral heat pipe is employed in the manufacture of filament wound pipe segments and vessels to provide even heating of the interior of the pipe or vessel during the heating and curing process. Heating or cooling can be provided using the thermal transfer characteristics of the heat pipe.

Abstract: [Problem] To provide a method for producing a polyol-crosslinking, crosslinked fluororubber product which exhibits low tack properties and significantly increased rubber hardness. [Means for Solving the Problem] The method comprises pressurizing, heating, and vulcanizing a fluororubber composition to mold a vulcanized product; the fluororubber composition comprising a polyol-crosslinkable fluororubber, a crosslinking accelerator including a quarternary phosphonium salt or a quarternary ammonium salt, and a polyol crosslinking agent, the weight ratio X of the crosslinking accelerator to the polyol crosslinking agent (crosslinking accelerator/polyol crosslinking agent) being from 0.90 to 3.00 for a quarternary phosphonium salt, and being from 0.4 to 0.

Abstract: The present invention refers to medical devices comprising cross-linked modified polyamides especially to stent carrying balloon catheters, for use in angioplasty and other procedures of vessel repair.

Abstract: The invention relates to a process for the production of a polymer layer of a flexible unbonded offshore pipe. The process comprises the steps of shaping a polymer material by extrusion into or onto a supporting unit in an extrusion station and cross-linking said extruded polymer material, said polymer material comprising a polyethylene and a peroxide for providing a cross-linking of the polymer material. The peroxide has an activation temperature substantially above the temperature of the polymer material during the extrusion thereof. The cross-linking of the extruded polymer material is carried out by exposing the extruded polymer material to electromagnetic waves, selected from the group consisting of infrared radiation and microwave. The invention also relates to a flexible unbonded offshore pipe comprising such polymer layer.

Abstract: A rubber member for tires is formed by spirally winding an unvulcanized rubber strip. The rubber strip has a first longitudinal end portion for serving as a starting side of winding of the rubber strip and a second longitudinal end portion for serving as an end side of the winding. The end surface of at least one of the first end portion and the second end portion is an inclined surface inclining to the longitudinal direction line of the rubber strip.

Abstract: A process for the extrusion of peroxide crosslinked polymer parts, mainly tubes, in which the crosslinkable polymer is heated in an extruder in a controlled manner to a value above the crystallite melting point of the polymer, but below the crosslinking temperature, and fed continuously to an extrusion die to create the part and in which at least a partial crosslinking of the polymer is achieved in the extrusion die by heating of the polymer above a crosslinking temperature provision.

Abstract: Disclosed herein are a polyamic acid dope solution composition, a method for preparing a hollow fiber using the composition and a hollow fiber prepared by the method. More specifically, disclosed are a method for preparing a hollow fiber, comprising preparing a polyamic acid dope solution composition comprising polyhydroxyamic acid, polythiolamic acid or polyaminoamic acid, spinning the composition to prepare a hollow fiber, and imidizing and thermally rearranging the hollow fiber, and the hollow fiber prepared by the method. In accordance with the method, a hollow fiber made of a high free volume polymer membrane can be prepared by spinning the dope solution composition to prepare a hollow fiber and thermally rearranging the hollow fiber via thermal treatment. The hollow fiber thus prepared exhibits excellent gas permeability and selectivity, thus being suitable for use as a gas separation membrane.

Abstract: The present invention generally relates to wireless flexible hose articles and methods. Some embodiments include low-mass hoses. Furthermore, some embodiments can comprise methods for making and/or using such hose articles.

Abstract: A process produces a conductive rubber roller having small aspect ratios of inner and outer diameters, having a stable measure of its inner diameter, having uniform cell distribution and being free from non uniformity of hardness and electrical resistance in the peripheral direction. The process has a step of continuously extruding a tube composed of a specific unvulcanized rubber composition from a rubber extruder in a microwave vulcanizing unit, and a step of foaming and vulcanizing the tube by using a microwave irradiator having a microwave irradiation zone 4 m or less in length while being transported at given speed. The foamed rubber tube has an inner diameter 20 to 35% smaller than the outer diameter of the conductive core material over the whole region in the lengthwise direction, and the conductive core material is press fitted into the foamed rubber tube without using any adhesive.

Abstract: The invention refers to a charge air hose for motor vehicles, comprising: a hose-shaped base member and a textile reinforcement. In a conventional charge air hose the textile reinforcement is embedded into the base member or it is arranged between two layers of the base member. A continuing dynamic load of the conventional charge air hose leads to delamination of the composite. To solve the problems known from the prior art, the invention provides a charge air hose for motor vehicles, comprising: a hose-shaped base member, a textile reinforcement arranged on the surface of the base member, wherein the hose-shaped base member is a vulcanized, elastomer-containing hose.

Abstract: The disclosure is directed to a flex endurant tube including a blend of a silicone polymeric matrix material and a migrating component. The disclosure is further directed to methods for making the aforementioned tube.

Abstract: A carbon black monolith comprising a matrix comprising ceramic material and carbon black dispersed throughout the matrix and a method for making a carbon black monolith comprising extruding an extrudable mixture including a carbon black, a ceramic forming material, water, an extrusion aid, and a flux material. A carbon black monolith catalyst comprising a finished self-supporting carbon black monolith having at least one passage therethrough, and comprising a supporting matrix and carbon black dispersed throughout the supporting matrix and at least one catalyst precursor on the finished self-supporting carbon black monolith. A method for making and a method for use of such a carbon black monolith catalyst in catalytic chemical reactions are also disclosed.

Abstract: A flexible hose is disclosed, e.g., a charge-air hose for the automobile industry. A charge-air hose has rigid and flexible sections, which can be manufactured at lower costs and is less prone to material failure during permanent use than is a conventional hose. An exemplary flexible hose comprises at least one crosslinkable material, wherein the hose has crosslinking degrees differing in portions.

Abstract: A process produces cling-fastener parts with a large number of interlocking members (24) from a formulation encompassing radiation-crosslinkable prepolymers. The prepolymer is molded, cast, and/or compression molded into the shape of a large number of interlocking members (24) together with a cling-fastener base (21), and is then radiation-cured. The apparatus producing the cling fasteners encompasses a feed (32, 10) for the formulation (14) of radiation-crosslinkable, in particular acrylic, prepolymers, at least one shaping roll (11) and one backing roll (12). The shaping roll (11) has a large number of radial cutouts (17). A source of UV radiation (19), or an electron-beam source, provides radiation curing of the molded radiation-curable formulation.

Abstract: A thin walled microtube is formed by providing a continuous elongated member having an outer surface. The member is at least partially formed of a water soluble material. A coating material is provided. The coating material may be a silicone compound that is curable such that the coating material cures into a substantial non-porous silicone. The outer surface of the elongated member is coated with a coating material so as to form a substantially uniform and continuous layer of coating material on the outer surface. The layer of coating material is cured so as to form a substantial uniform and continuous layer of substantially non-porous silicone on the outer surface. The elongated member is at least partially dissolved using water and purged from the silicone layer, such that an elongated tube of substantially non-porous silicone is formed.

Abstract: The invention concerns a method which consists in: a) forming by extrusion an extruded thermoplastic tube (20) having, when coming out of the extruder, a diameter D1; b) then subjecting said extruded tube of diameter D1 to a radiation treatment, so as to produced a cross-linked tube (21); c) after bringing said cross-linked tube (21) to a temperature not less than a temperature substantially equal to the melting point of its crystalline phase, subjecting it, in displacement, to a radial monoaxial expansion for form an expanded tube (22) of diameter D2, then cooling it down to a temperature, typically room temperature, at which it can be cut into tube portions (23) with length substantially equal to the height of said caps (1); and e) assembling or forming a head (10, 100, 101, 102, 103) on said tube portion (23), so as to obtain a cap or top (1), with heat-shrinkable skirt, economical and having a homogeneous skirt (11, 12) free of axial connection line.

Abstract: A paper-feeding roller (1) formed by cylindrically molding a thermoplastic elastomer composition containing a thermoplastic resin or a thermoplastic elastomer in which a rubber or a thermoplastic elastomer that can be crosslinked is dispersed by dynamic crosslinking. A surface layer of the paper-feeding roller (1) contains titanium oxide at not less than 1.5% nor more than 50% in a volume fraction.

Abstract: A high performance thermoplastic hose useful as a power steering hose, the high performance thermoplastic hose comprising a high performance engineering thermoplastic such as polyurethane and a chlorine-containing polyolefin such as chlorinated polyethylene, chlorinated polypropylene, chlorinated copolymers containing ethylene and propylene, chlorosulfonated polyethylene, chlorosulfonated polypropylene, chlorosulfonated copolymers of ethylene and propylene or mixture thereof, is disclosed. Also disclosed are a method for manufacturing the high performance thermoplastic hose, and a thermoplastic vulcanizate capable of resisting chemical attack and withstanding temperatures up to about 300° F.

Abstract: The present invention relates to apparatus for extruding mouldings from cross-linkable polymer material. The apparatus includes a first part to which the polymer material is delivered from a material container, and a second part which forms a moulding tool for moulding and cross-linking said article. The first part of the apparatus includes a feed zone (2) that has an inlet (8), a generally tubular outlet (7) and a rotatable feed screw (10) that functions to compress and feed the polymer material in a unmelted or solid state from said inlet (8) to said outlet (7), wherein the length of the feed screw (10) does not exceed the length of the feed zone (2).

Abstract: A high performance thermoplastic hose useful as a power steering hose, the high performance thermoplastic hose comprising a high performance engineering thermoplastic such as polyurethane and a chlorine-containing polyolefin such as chlorinated polyethylene, chlorinated polypropylene, chlorinated copolymers containing ethylene and propylene, chlorosulfonated polyethylene, chlorosulfonated polypropylene, chlorosulfonated copolymers of ethylene and propylene or mixture thereof, is disclosed. Also disclosed are a method for manufacturing the high performance thermoplastic hose, and a thermoplastic vulcanizate capable of resisting chemical attack and withstanding temperatures up to about 300° F.

Abstract: An efficient process is described for making rubber tube segments, such as lathe-cut gaskets or conveyor roller covers, by cross-head extrusion of uncured rubber onto an axially aligned string of mandrels. Each mandrel in the string is separated from its two neighbors by respective spacers. The outer diameter of the extruded tube is kept within precise tolerances by making a non-contact measurement of the outer diameter at the output from the extruder and using the measured diameter to control the extrusion process. The extruded tube is cut into segments by a cutter that acts responsive to a spacer sensor and that makes the cuts between the mandrels. In one version, the extruded tube is conveyed through a curing oven by apparatus that only contacts and supports the tube adjacent ones of the spacers.

Abstract: A method for providing improved absorbency against pressure characteristics to non-surface crosslinked superabsorbent polymer fibers.

Abstract: The present invention relates to a method for making a silicon balloon catheter in which a first tube having its outer diameter slightly smaller than that of a desired catheter is formed by an extruding method, mold lubricant is coated at a portion of a balloon injection opening, a thin film type second tube is formed at the coated outer surface of the first tube by a second extruding, and then the catheter is vulcanized and cut. As a result, when liquid is injected to an expansion tube, the second tube is separated from the first tube, thereby performing a function as a balloon.

Abstract: A method of producing reformed crosslinked polymer articles provides reformed crosslinked articles free of visible and objectionable folds, seams and interfaces on reformed surfaces thereof. In a preferred embodiment, a product is produced by a method including the steps of extruding a silane-grafted polyethylene tube, heating an end of the tube, reforming the end of the tube to produce a radially enlarged sealing surface thereon, cooling the reformed tube, and curing the reformed tube to produce an increase in the degree of crosslinking of the polyethylene material.

Abstract: Use of at least partly cross-linked polyolefin plastic, which is oriented biaxially, as material for pressure pipes, is described. The pressure pipe is produced by extrusion with subsequent axial and peripheral orientation of the pipe, the pipe being at least partly cross-linked before the biaxial orientation. Preferably, the pipe is cross-linked to about 20-50% before orientation. By the at least partial cross-linking before orientation, this can be carried out at temperatures above the crystalline melting point of the plastic material.

Abstract: PET with low gas permeability and good mechanical properties is produced utilizing strain-induced crystallization. This strain-induced crystallization process is utilized to produce PET films and sheets, among other products.

Abstract: An injection hose intended for sealing expansion joint in concrete structures. The hose is in the form a continuous hollow extrusion (12), made of elastic, flexible material, with a continuous longitudinal bore (10) and at least one longitudinal groove (16). The groove (16) is connected to the bore (10) by means of apertures (22) in the wall of the extrusion and is fitted with a sealing strip (24), made of compressible, elastic material, which extends over the apertures (22). Production of the hose is made particularly simple and inexpensive by virtue of the fact that the width of the groove openings (26) is less than the diameter of the sealing strip (24) and that the means of holding the sealing strip (24) in place are formed by making undercuts in the side (30) of the groove (16).