CA1142724A - Extruded, surface-textured, synthetic resin strands of hollow cross-section - Google Patents
Extruded, surface-textured, synthetic resin strands of hollow cross-sectionInfo
- Publication number
- CA1142724A CA1142724A CA000346165A CA346165A CA1142724A CA 1142724 A CA1142724 A CA 1142724A CA 000346165 A CA000346165 A CA 000346165A CA 346165 A CA346165 A CA 346165A CA 1142724 A CA1142724 A CA 1142724A
- Authority
- CA
- Canada
- Prior art keywords
- strand
- band
- synthetic resin
- textured
- hollow
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 229920003002 synthetic resin Polymers 0.000 title claims abstract description 25
- 239000000057 synthetic resin Substances 0.000 title claims abstract description 25
- 238000001125 extrusion Methods 0.000 claims abstract description 22
- 229920001169 thermoplastic Polymers 0.000 claims abstract description 13
- 239000004416 thermosoftening plastic Substances 0.000 claims abstract description 13
- 238000000034 method Methods 0.000 claims abstract description 7
- 238000001816 cooling Methods 0.000 claims abstract description 5
- 229920005989 resin Polymers 0.000 claims description 4
- 239000011347 resin Substances 0.000 claims description 4
- 229920003229 poly(methyl methacrylate) Polymers 0.000 abstract description 6
- 239000004926 polymethyl methacrylate Substances 0.000 abstract description 6
- 238000002360 preparation method Methods 0.000 abstract description 2
- 239000000463 material Substances 0.000 description 6
- -1 polyethylene Polymers 0.000 description 3
- 229920000915 polyvinyl chloride Polymers 0.000 description 3
- 239000004800 polyvinyl chloride Substances 0.000 description 3
- 239000004698 Polyethylene Substances 0.000 description 2
- PPBRXRYQALVLMV-UHFFFAOYSA-N Styrene Chemical compound C=CC1=CC=CC=C1 PPBRXRYQALVLMV-UHFFFAOYSA-N 0.000 description 2
- 239000000853 adhesive Substances 0.000 description 2
- 230000001070 adhesive effect Effects 0.000 description 2
- 229920001577 copolymer Polymers 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000004049 embossing Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 238000000465 moulding Methods 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 229920000573 polyethylene Polymers 0.000 description 2
- 229920002689 polyvinyl acetate Polymers 0.000 description 2
- 239000011118 polyvinyl acetate Substances 0.000 description 2
- 229920005992 thermoplastic resin Polymers 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- VVQNEPGJFQJSBK-UHFFFAOYSA-N Methyl methacrylate Chemical compound COC(=O)C(C)=C VVQNEPGJFQJSBK-UHFFFAOYSA-N 0.000 description 1
- 239000004952 Polyamide Substances 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 239000004793 Polystyrene Substances 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000004873 anchoring Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 229920001971 elastomer Polymers 0.000 description 1
- 239000006260 foam Substances 0.000 description 1
- 238000007373 indentation Methods 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 229920002647 polyamide Polymers 0.000 description 1
- 229920000515 polycarbonate Polymers 0.000 description 1
- 239000004417 polycarbonate Substances 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 229920002223 polystyrene Polymers 0.000 description 1
- 239000011253 protective coating Substances 0.000 description 1
- 239000005060 rubber Substances 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 238000010104 thermoplastic forming Methods 0.000 description 1
- 238000009827 uniform distribution Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C59/00—Surface shaping of articles, e.g. embossing; Apparatus therefor
- B29C59/02—Surface shaping of articles, e.g. embossing; Apparatus therefor by mechanical means, e.g. pressing
- B29C59/021—Surface shaping of articles, e.g. embossing; Apparatus therefor by mechanical means, e.g. pressing of profiled articles, e.g. hollow or tubular articles, beams
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C43/00—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
- B29C43/22—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor of articles of indefinite length
- B29C43/222—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor of articles of indefinite length characterised by the shape of the surface
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/001—Combinations of extrusion moulding with other shaping operations
- B29C48/002—Combinations of extrusion moulding with other shaping operations combined with surface shaping
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/022—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the choice of material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
- B29C48/09—Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/25—Component parts, details or accessories; Auxiliary operations
- B29C48/30—Extrusion nozzles or dies
- B29C48/32—Extrusion nozzles or dies with annular openings, e.g. for forming tubular articles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/25—Component parts, details or accessories; Auxiliary operations
- B29C48/88—Thermal treatment of the stream of extruded material, e.g. cooling
- B29C48/90—Thermal treatment of the stream of extruded material, e.g. cooling with calibration or sizing, i.e. combined with fixing or setting of the final dimensions of the extruded article
- B29C48/901—Thermal treatment of the stream of extruded material, e.g. cooling with calibration or sizing, i.e. combined with fixing or setting of the final dimensions of the extruded article of hollow bodies
- B29C48/903—Thermal treatment of the stream of extruded material, e.g. cooling with calibration or sizing, i.e. combined with fixing or setting of the final dimensions of the extruded article of hollow bodies externally
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/25—Component parts, details or accessories; Auxiliary operations
- B29C48/88—Thermal treatment of the stream of extruded material, e.g. cooling
- B29C48/90—Thermal treatment of the stream of extruded material, e.g. cooling with calibration or sizing, i.e. combined with fixing or setting of the final dimensions of the extruded article
- B29C48/908—Thermal treatment of the stream of extruded material, e.g. cooling with calibration or sizing, i.e. combined with fixing or setting of the final dimensions of the extruded article characterised by calibrator surface, e.g. structure or holes for lubrication, cooling or venting
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2033/00—Use of polymers of unsaturated acids or derivatives thereof as moulding material
- B29K2033/04—Polymers of esters
- B29K2033/12—Polymers of methacrylic acid esters, e.g. PMMA, i.e. polymethylmethacrylate
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2995/00—Properties of moulding materials, reinforcements, fillers, preformed parts or moulds
- B29K2995/0037—Other properties
- B29K2995/0088—Molecular weight
Abstract
ABSTRACT OF THE DISCLOSURE
What is disclosed are an extruded hollow strand of thermoplastic synthetic resin, particularly an acrylic glass, provided with a textured surface which is variable in the direction of extrusion, as well as a method for the preparation of such a textured strand by extruding a thermoplastic synthetic resin through an extrusion nozzle provided with one or more core pieces, introducing the extruded hollow strand into a calibration or forming apparatus together with a flexible band provided with a negative surface structure, cooling the hollow strand --in contact with the flexible band-- beneath the softening point of the synthetic resin within the calibration apparatus, and then separating the band and strand upon exiting from the calibration apparatus.
What is disclosed are an extruded hollow strand of thermoplastic synthetic resin, particularly an acrylic glass, provided with a textured surface which is variable in the direction of extrusion, as well as a method for the preparation of such a textured strand by extruding a thermoplastic synthetic resin through an extrusion nozzle provided with one or more core pieces, introducing the extruded hollow strand into a calibration or forming apparatus together with a flexible band provided with a negative surface structure, cooling the hollow strand --in contact with the flexible band-- beneath the softening point of the synthetic resin within the calibration apparatus, and then separating the band and strand upon exiting from the calibration apparatus.
Description
~ ~42724 `EXTRUDED, SURFACE-TEXTURED, SYNTHETIC RESIN
STRANDS OF HOLLOW CROSS-SECTION
The present invention relates to extruded strands of thermoplastic resin, which strands have a hollow cross-section.
Hollow strands of this type for the most part have a smooth surface. Such strands can also be prepared with a textured surface which is uniform in the direction of extrusion if a correspondingly formed extrusion tool or a shaping arrangement (calibration arrangement) having a corresponding structure on its inner surface is employed.
However, it is often desired to prepare hollow strands of this type with a surface structure which varies in the extrusion direction, for example in order to effect a more uniform distribution of light passing therethrough or to impart a more pleasing appearance.
It is known to prepare hollow strands having a granular surface structure by the extrusion of a partially thermoplastic forming mass which contains finely-divided synthetic resin particles which are difficultly fusible and therefore not thermoplastic. After leaving the extrusion nozzle or the calibrating arrangement, the included particles produce a granular surface structure as a result of their thermoelastic restoring forces. The inhomogeneous forming masses suitable for such a purpose 114Z7~4 are only processed reluctantly because waste material, particularly the useless extrudate which is produced when an installation is started up, cannot be used again together with waste material from a homogeneous forming mass.
Extruded strands of a thermoplastic synthetic resin which have a solid cross section can be readily provided with a textured surface varying in the extrusion direction by running them through an embossing calender.
However, this process cannot be used for strands having a hollow cross section, since such strands would be pressed together between the calender roll. The present invention solves the problem of providing extruded strands of a thermoplastic synthetic resin, which strands have a hollow cross section and a textured surface varying in the extrusion direction. By such a textured surface is to be understood every structure not showing the same cross section on every section of surface taken across the extrusion direction.
According to the invention, thermoplastic synthetic resins are such resins which completely melt under the conditions of extrusion or --as in the case of pigmented synthetic resins-- permit an exact reproduction, by molding, of a tool surface. Forming masses containing portions which do not melt or which melt only with difficulty and which have an influence on the surface structure of shaped bodies produced therefrom are unsuitable.
11427z4 Summary of the Invention The invention is a method for making an extruded hollow strand of a thermoplastic synthetic resin having at least one textured surface with a surfaced texture variable in the extrusion direction. The method comprises extruding a thermoplastic synthetic resin through an extrusion nozzle having one or more core pieces to form a hollow stand, introducing the extruded hollow strand into a vacuum calibra-tion apparatus together with at least one air-impermeable flexible band having a negative textured surface, said band covering the surface of the strand which is to be textured thereby. The band and strand adhere to each other with a force of at least 0.1 N/cm , so that the band supports the strand adhering thereto within the vacuum calibration apparatus.
The strand and band are passed together through the vacuum calibration apparatus while maintaining the strand and band in contact with the apparatus by the application of a vacuum to the band and while cooling the resin of the strand to a temperature below its softening point. The strand and band are then separated as they leave the calibration apparatus.
Detailed Description of the Invention For preparing the hollow strands according to the invention, a hollow strand is prepared by the extrusion of a thermoplastic synthetic resin through an extrusion nozzle having one or more core pieces, which strand is then cooled beneath the softening temperature of the synthetic resin in a forming apparatus or calibration apparatus. According to the invention, a flexible band provided with a "negative textured surface" is introduced into the calibration arrange-ment together with the synthetic resin strand and is separated 1~42~24 from the strand after exit from the calibration arrangement.
The "negative textured surface" describes that form, complementary to the texture to be imparted to the synthetic resin strand, against which the textured surface of the synthetic resin strand is molded. Since the textured surface can have any desired form, the form of the "negative textured surface" is also widely variable according to choice.
The depth of the structure, i.e. the difference between the highest ridges and the deepest indentations within the structure, can vary between fractions of a millimeter up to several millimeters. In order tG be moldable from the surface of the flexible band, the textured surface of the hollow strand must be largely free of undercutting, which is not however necessarily true of the negative structure of the band. For example, a structured surface can be molded on a sieve mesh without the forming mass penetrating through the sieve openings and in this way -3a-'" ~1~724 inextricably anchoring itself therein by the formation of undercuts. Within the aforementioned limits, there is a great degree of freedom of design. Irregular or geometrically regular or ornamental structures, letters and characters, pictorial representations, or structures with particular technical effects can be made use of, whereby even broader limits pertain for the extent of the area of the structural elements than apply for their depth.
A variety of textured surfaces can be formed directly from planar textured materials, i.e. from rough papers, graded or woven structures formed from metal threads or strips, sandpaper, open-pored foams, crackled lacquered surfaces, and the like. Other structures, for example surfaces decorated with ornamental forms, can be imparted to the hollow strand by molding the structured surface as a negative structure on a band and then texturing the hollow strand on such a band according to the present invention.
The material of the band provided with a negative surface structure is so chosen that the band can be removed from the hollow strand after the latter has been cooled off. The band should at least be flexible enough so that it can be applied to and removed from the surface of the hollow strand with a short radius of curvature, for example on a guide roll. An adhesive force of at least 0.1 N/cm2 is required between the band and the hollow strand when working with a band impermeable to air and ~;142~24 vacuum calibration apparatus. In this case, the vacuum acts then only on the band and supports the hollow strand adhering thereto. If the adhesive force is too small, the hollow strand separates from the band and collapses.
When using a air-permeable band, for example a woven band, the vacuum can act through the band directly on the surface of the hollow synthetic resin strand and maintain its cross section. In this case, the adhesion value can also be below the aforementioned value. This is also true in all cases not employing a vacuum calibration apparatus, but an apparatus employing an excess gas pressure in the cavity of the strand.
Surprisingly, by a proper choice of the band material, a sufficient adhesion arises immediately upon the mutual entry of the textured band and the thermoplastic hollow strand into the mouth of the calibration apparatus, particularly if the hollow strand is minimally compressed thereby. An adhesion of sufficient magnitude is present between most of the synthetic resins which come into consideration for use in the process and metals such as steel, aluminum, and copper. The hollow strand adheres to a textured band of synthetic resin if there is a sufficient difference in polarity between the materials.
Thus, the adhesion of polymethyl methacrylate or polyvinyl chloride on a corona-treated polyethylene, cross-linked polyvinyl acetate, polyamides, and rubber is over 0.1 N/cm2, but is generally beneath this value on non-pretreated polyethylene or polypropylene.
The adhesion between polymethyl methacrylate and polyvinyl chloride or non-cross-linked polyvinyl acetate is usually so strong that these materials cannot be separated from one another after cooling. A certain adhesion of the band is also desired, for example, if the band is to remain as a protective coating on the surface of the hollow strand until the latter is used, for example a paper band or strip.
Bands or strips of paper, cardboard, and synthetic resin can be provided in a known fashion with the desired negative textured surface by means of embossing rolls. If the structured band is itself made of a thermoplastic synthetic resin, then it is sufficient that its surface structure not soften plastically so long as it is in contact with the hot hollow strand and until the surface of the latter has been conformed to the structure.
Therefore, if the band is to be used several times, it is advantageous to employ a material which will not soften plastically under the operating conditions: in the case of synthetic resins, then, such bands should be used which are crossed-linked or hardened after impartation thereto of the negative textured surface.
~427Z4 On passage through the calibration apparatus, the hollow strand is pressed against the inner surface of the calibration apparatus by an excess gas pressure in the hollow or cavity of the strand or by a reduced pressure acting in the forming channel of the calibration apparatus.
An excess pressure in the cavity can be maintained in a known fashion by means of a stopper attached to the extrusion nozzle core and which slips through the hollow strand, or by a periodic melt-sealing of the end of the strand, if a pressurizing gas can find access to the cavity by way of a gas conduit in the extrusion nozzle core.
Preferably, calibration apparatus employing a vacuum is used since in this case a gas-tight seal of the cavity is dispensable.
Forming masses suitable for the preparation of strands having a hollow cross-section according to the present invention are, for example, acrylic glass, polyvinyl chloride, polycarbonate~ polystyrene, or impact-resistant copolymers of styrene. Acrylic glass is particularly preferred. By this term is to be understood polymethyl methacrylate and copolymers predominantly comprising methyl methacrylate and having molecular weights between 100,000 and 250,000. As needed, the forming masses can be optically clear, opacified, or colored as desired.
A preferred embodiment of the invention involves double-walled planar structures having two parallel outer walls and a plurality of supports, arranged between the outer walls and bonding the outer walls. These structures can be textured on one or on both of the parallel exterior walls.
A better understanding of the present invention will be had by referring to the accompanying drawings, wherein Fig. 1 is a side view, in section, of an - extrusion train and calibration chamber for texturing a hollow synthetic resin strand according to the invention and Fig. 2 is an end view of a preferred strand embodiment.
More in particular, Fig. 1 shows extrusion nozzle 10 having nozzle core 11 from which issues hollow strand 12 of a thermoplastic resin. Strand 12 enters calibration apparatus 13 together with flexible band 14, such as of wire mesh, having negative textured surface 15 which can vary in the extrusion direction. Within apparatus 13, a vacuum is applied to strand 12 and/or band 14 through passages 16. Cooling tubes 17 present within apparatus 13 ultimately cool strand 12 to a temperature below the softening temperature of the resin.
On leaving apparatus 13, band 14 is separated from solidified strand 12 at guide roll 18, leaving strand 12 with textured surface 19 thereon. Band 14 may run through apparatus 13 continuously or may be taken off a supply roll and rewound after separation. These variations are not shown.
Fig. 2 is an end view of a preferred embodiment of a hollow extruded structure 20 comprising parallel outer ~14~:724 walls 21, one or both of which can be provided with textured surface 22 according to the invention. Walls 21 are separated by plurality of supports 23 running the length of the structure and defining a plurality of cavities 24 within the structure.
_9_
STRANDS OF HOLLOW CROSS-SECTION
The present invention relates to extruded strands of thermoplastic resin, which strands have a hollow cross-section.
Hollow strands of this type for the most part have a smooth surface. Such strands can also be prepared with a textured surface which is uniform in the direction of extrusion if a correspondingly formed extrusion tool or a shaping arrangement (calibration arrangement) having a corresponding structure on its inner surface is employed.
However, it is often desired to prepare hollow strands of this type with a surface structure which varies in the extrusion direction, for example in order to effect a more uniform distribution of light passing therethrough or to impart a more pleasing appearance.
It is known to prepare hollow strands having a granular surface structure by the extrusion of a partially thermoplastic forming mass which contains finely-divided synthetic resin particles which are difficultly fusible and therefore not thermoplastic. After leaving the extrusion nozzle or the calibrating arrangement, the included particles produce a granular surface structure as a result of their thermoelastic restoring forces. The inhomogeneous forming masses suitable for such a purpose 114Z7~4 are only processed reluctantly because waste material, particularly the useless extrudate which is produced when an installation is started up, cannot be used again together with waste material from a homogeneous forming mass.
Extruded strands of a thermoplastic synthetic resin which have a solid cross section can be readily provided with a textured surface varying in the extrusion direction by running them through an embossing calender.
However, this process cannot be used for strands having a hollow cross section, since such strands would be pressed together between the calender roll. The present invention solves the problem of providing extruded strands of a thermoplastic synthetic resin, which strands have a hollow cross section and a textured surface varying in the extrusion direction. By such a textured surface is to be understood every structure not showing the same cross section on every section of surface taken across the extrusion direction.
According to the invention, thermoplastic synthetic resins are such resins which completely melt under the conditions of extrusion or --as in the case of pigmented synthetic resins-- permit an exact reproduction, by molding, of a tool surface. Forming masses containing portions which do not melt or which melt only with difficulty and which have an influence on the surface structure of shaped bodies produced therefrom are unsuitable.
11427z4 Summary of the Invention The invention is a method for making an extruded hollow strand of a thermoplastic synthetic resin having at least one textured surface with a surfaced texture variable in the extrusion direction. The method comprises extruding a thermoplastic synthetic resin through an extrusion nozzle having one or more core pieces to form a hollow stand, introducing the extruded hollow strand into a vacuum calibra-tion apparatus together with at least one air-impermeable flexible band having a negative textured surface, said band covering the surface of the strand which is to be textured thereby. The band and strand adhere to each other with a force of at least 0.1 N/cm , so that the band supports the strand adhering thereto within the vacuum calibration apparatus.
The strand and band are passed together through the vacuum calibration apparatus while maintaining the strand and band in contact with the apparatus by the application of a vacuum to the band and while cooling the resin of the strand to a temperature below its softening point. The strand and band are then separated as they leave the calibration apparatus.
Detailed Description of the Invention For preparing the hollow strands according to the invention, a hollow strand is prepared by the extrusion of a thermoplastic synthetic resin through an extrusion nozzle having one or more core pieces, which strand is then cooled beneath the softening temperature of the synthetic resin in a forming apparatus or calibration apparatus. According to the invention, a flexible band provided with a "negative textured surface" is introduced into the calibration arrange-ment together with the synthetic resin strand and is separated 1~42~24 from the strand after exit from the calibration arrangement.
The "negative textured surface" describes that form, complementary to the texture to be imparted to the synthetic resin strand, against which the textured surface of the synthetic resin strand is molded. Since the textured surface can have any desired form, the form of the "negative textured surface" is also widely variable according to choice.
The depth of the structure, i.e. the difference between the highest ridges and the deepest indentations within the structure, can vary between fractions of a millimeter up to several millimeters. In order tG be moldable from the surface of the flexible band, the textured surface of the hollow strand must be largely free of undercutting, which is not however necessarily true of the negative structure of the band. For example, a structured surface can be molded on a sieve mesh without the forming mass penetrating through the sieve openings and in this way -3a-'" ~1~724 inextricably anchoring itself therein by the formation of undercuts. Within the aforementioned limits, there is a great degree of freedom of design. Irregular or geometrically regular or ornamental structures, letters and characters, pictorial representations, or structures with particular technical effects can be made use of, whereby even broader limits pertain for the extent of the area of the structural elements than apply for their depth.
A variety of textured surfaces can be formed directly from planar textured materials, i.e. from rough papers, graded or woven structures formed from metal threads or strips, sandpaper, open-pored foams, crackled lacquered surfaces, and the like. Other structures, for example surfaces decorated with ornamental forms, can be imparted to the hollow strand by molding the structured surface as a negative structure on a band and then texturing the hollow strand on such a band according to the present invention.
The material of the band provided with a negative surface structure is so chosen that the band can be removed from the hollow strand after the latter has been cooled off. The band should at least be flexible enough so that it can be applied to and removed from the surface of the hollow strand with a short radius of curvature, for example on a guide roll. An adhesive force of at least 0.1 N/cm2 is required between the band and the hollow strand when working with a band impermeable to air and ~;142~24 vacuum calibration apparatus. In this case, the vacuum acts then only on the band and supports the hollow strand adhering thereto. If the adhesive force is too small, the hollow strand separates from the band and collapses.
When using a air-permeable band, for example a woven band, the vacuum can act through the band directly on the surface of the hollow synthetic resin strand and maintain its cross section. In this case, the adhesion value can also be below the aforementioned value. This is also true in all cases not employing a vacuum calibration apparatus, but an apparatus employing an excess gas pressure in the cavity of the strand.
Surprisingly, by a proper choice of the band material, a sufficient adhesion arises immediately upon the mutual entry of the textured band and the thermoplastic hollow strand into the mouth of the calibration apparatus, particularly if the hollow strand is minimally compressed thereby. An adhesion of sufficient magnitude is present between most of the synthetic resins which come into consideration for use in the process and metals such as steel, aluminum, and copper. The hollow strand adheres to a textured band of synthetic resin if there is a sufficient difference in polarity between the materials.
Thus, the adhesion of polymethyl methacrylate or polyvinyl chloride on a corona-treated polyethylene, cross-linked polyvinyl acetate, polyamides, and rubber is over 0.1 N/cm2, but is generally beneath this value on non-pretreated polyethylene or polypropylene.
The adhesion between polymethyl methacrylate and polyvinyl chloride or non-cross-linked polyvinyl acetate is usually so strong that these materials cannot be separated from one another after cooling. A certain adhesion of the band is also desired, for example, if the band is to remain as a protective coating on the surface of the hollow strand until the latter is used, for example a paper band or strip.
Bands or strips of paper, cardboard, and synthetic resin can be provided in a known fashion with the desired negative textured surface by means of embossing rolls. If the structured band is itself made of a thermoplastic synthetic resin, then it is sufficient that its surface structure not soften plastically so long as it is in contact with the hot hollow strand and until the surface of the latter has been conformed to the structure.
Therefore, if the band is to be used several times, it is advantageous to employ a material which will not soften plastically under the operating conditions: in the case of synthetic resins, then, such bands should be used which are crossed-linked or hardened after impartation thereto of the negative textured surface.
~427Z4 On passage through the calibration apparatus, the hollow strand is pressed against the inner surface of the calibration apparatus by an excess gas pressure in the hollow or cavity of the strand or by a reduced pressure acting in the forming channel of the calibration apparatus.
An excess pressure in the cavity can be maintained in a known fashion by means of a stopper attached to the extrusion nozzle core and which slips through the hollow strand, or by a periodic melt-sealing of the end of the strand, if a pressurizing gas can find access to the cavity by way of a gas conduit in the extrusion nozzle core.
Preferably, calibration apparatus employing a vacuum is used since in this case a gas-tight seal of the cavity is dispensable.
Forming masses suitable for the preparation of strands having a hollow cross-section according to the present invention are, for example, acrylic glass, polyvinyl chloride, polycarbonate~ polystyrene, or impact-resistant copolymers of styrene. Acrylic glass is particularly preferred. By this term is to be understood polymethyl methacrylate and copolymers predominantly comprising methyl methacrylate and having molecular weights between 100,000 and 250,000. As needed, the forming masses can be optically clear, opacified, or colored as desired.
A preferred embodiment of the invention involves double-walled planar structures having two parallel outer walls and a plurality of supports, arranged between the outer walls and bonding the outer walls. These structures can be textured on one or on both of the parallel exterior walls.
A better understanding of the present invention will be had by referring to the accompanying drawings, wherein Fig. 1 is a side view, in section, of an - extrusion train and calibration chamber for texturing a hollow synthetic resin strand according to the invention and Fig. 2 is an end view of a preferred strand embodiment.
More in particular, Fig. 1 shows extrusion nozzle 10 having nozzle core 11 from which issues hollow strand 12 of a thermoplastic resin. Strand 12 enters calibration apparatus 13 together with flexible band 14, such as of wire mesh, having negative textured surface 15 which can vary in the extrusion direction. Within apparatus 13, a vacuum is applied to strand 12 and/or band 14 through passages 16. Cooling tubes 17 present within apparatus 13 ultimately cool strand 12 to a temperature below the softening temperature of the resin.
On leaving apparatus 13, band 14 is separated from solidified strand 12 at guide roll 18, leaving strand 12 with textured surface 19 thereon. Band 14 may run through apparatus 13 continuously or may be taken off a supply roll and rewound after separation. These variations are not shown.
Fig. 2 is an end view of a preferred embodiment of a hollow extruded structure 20 comprising parallel outer ~14~:724 walls 21, one or both of which can be provided with textured surface 22 according to the invention. Walls 21 are separated by plurality of supports 23 running the length of the structure and defining a plurality of cavities 24 within the structure.
_9_
Claims
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for making an extruded hollow strand of a thermoplastic synthetic resin having at least one textured surface having a surface texture variable in the extrusion direction, which method comprises extruding a thermoplastic synthetic resin through an extrusion nozzle having one or more core pieces to form a hollow strand, introducing said extruded hollow strand into a vacuum calibration apparatus together with at least one air-impermeable flexible band having a negative textured surface, said band covering the surface of said strand which is to be textured thereby and said band and strand adhering to each other with a force of at least 0.1 N/cm2 whereby said band supports said strand adhered thereto within said vacuum calibration apparatus, passing said strand and band through said vacuum calibration apparatus while maintaining said strand and band in contact with the calibration apparatus by applying a vacuum to said band and while cooling the resin of said strand to a temper-ature below its softening point, and then separating said strand and band as they leave the calibration apparatus.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP2908487 | 1979-03-05 | ||
| DE19792908487 DE2908487A1 (en) | 1979-03-05 | 1979-03-05 | EXTRUDED HOLLOW PROFILE ROD MADE OF THERMOPLASTIC PLASTIC WITH SURFACE STRUCTURE |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1142724A true CA1142724A (en) | 1983-03-15 |
Family
ID=6064501
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000346165A Expired CA1142724A (en) | 1979-03-05 | 1980-02-21 | Extruded, surface-textured, synthetic resin strands of hollow cross-section |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0015312B1 (en) |
| CA (1) | CA1142724A (en) |
| DE (2) | DE2908487A1 (en) |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3215175C2 (en) * | 1982-04-23 | 1985-05-02 | Gebrüder Kömmerling Kunststoffwerke GmbH, 6780 Pirmasens | Device for embossing the surfaces of rod material made of thermoplastic material in a warm plastic state |
| DE3240454A1 (en) * | 1982-11-02 | 1984-05-03 | kabelmetal electro GmbH, 3000 Hannover | Process for continuous manufacture of shrink articles |
| US4849045A (en) * | 1988-05-05 | 1989-07-18 | General Motors Corporation | Extrusion casting method |
| JPH0745168B2 (en) * | 1990-03-09 | 1995-05-17 | テルモ株式会社 | Method and device for manufacturing annular thermoplastic resin film having rough inner surface |
| US6132200A (en) * | 1998-08-28 | 2000-10-17 | General Electric Co. | Apparatus and process for texturing a thermoplastic extrusion |
| US9016221B2 (en) | 2004-02-17 | 2015-04-28 | University Of Florida Research Foundation, Inc. | Surface topographies for non-toxic bioadhesion control |
| US7650848B2 (en) | 2004-02-17 | 2010-01-26 | University Of Florida Research Foundation, Inc. | Surface topographies for non-toxic bioadhesion control |
| DE102007003511A1 (en) * | 2007-01-24 | 2008-08-14 | Konrad Lehrhuber | Plastic construction profile strip with a surface anchoring structure for plaster |
| WO2010056824A2 (en) | 2008-11-11 | 2010-05-20 | University Of Florida Research Foundation, Inc. | Method of patterning a surface and articles comprising the same |
| US9937655B2 (en) | 2011-06-15 | 2018-04-10 | University Of Florida Research Foundation, Inc. | Method of manufacturing catheter for antimicrobial control |
| DE102015211086B4 (en) | 2015-06-17 | 2023-11-02 | Samvardhana Motherson Innovative Autosystems B.V. & Co. KG | Plastic element, manufacturing device and method for producing the plastic element |
| WO2018057582A1 (en) * | 2016-09-20 | 2018-03-29 | Sharklet Technologies, Inc. | Die for continuously manufacturing textured surfaces and methods of manufacture thereof |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1191550B (en) * | 1959-03-13 | 1965-04-22 | Heinz Faigle | Process for the production of finned tubes from plastic material |
| DE2209895A1 (en) * | 1971-03-05 | 1972-09-14 | Amut Spa | Method and apparatus for the continuous production of hollow extrusions |
| US4173607A (en) * | 1977-06-09 | 1979-11-06 | Textron Inc. | Method for texturing the surface of non-woven fabric films |
-
1979
- 1979-03-05 DE DE19792908487 patent/DE2908487A1/en not_active Withdrawn
- 1979-11-21 EP EP79104629A patent/EP0015312B1/en not_active Expired
- 1979-11-21 DE DE7979104629T patent/DE2967457D1/en not_active Expired
-
1980
- 1980-02-21 CA CA000346165A patent/CA1142724A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE2908487A1 (en) | 1980-09-11 |
| DE2967457D1 (en) | 1985-07-04 |
| EP0015312B1 (en) | 1985-05-29 |
| EP0015312A1 (en) | 1980-09-17 |
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