Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D13/00—Pencil-leads; Crayon compositions; Chalk compositions
• • 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
  • B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
  • B29C44/20—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of indefinite length
  • B29C44/32—Incorporating or moulding on preformed parts, e.g. linings, inserts or reinforcements
  • B29C44/322—Incorporating or moulding on preformed parts, e.g. linings, inserts or reinforcements the preformed parts being elongated inserts, e.g. cables
• • 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
  • B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
  • B29C44/34—Auxiliary operations
  • B29C44/36—Feeding the material to be shaped
  • B29C44/46—Feeding the material to be shaped into an open space or onto moving surfaces, i.e. to make articles of indefinite length
  • B29C44/50—Feeding the material to be shaped into an open space or onto moving surfaces, i.e. to make articles of indefinite length using pressure difference, e.g. by extrusion or by spraying
  • B29C44/507—Feeding the material to be shaped into an open space or onto moving surfaces, i.e. to make articles of indefinite length using pressure difference, e.g. by extrusion or by spraying extruding the compound through an annular die
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B43—WRITING OR DRAWING IMPLEMENTS; BUREAU ACCESSORIES
  • B43K—IMPLEMENTS FOR WRITING OR DRAWING
  • B43K19/00—Non-propelling pencils; Styles; Crayons; Chalks
  • B43K19/16—Making non-propelling pencils
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/0061—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof characterized by the use of several polymeric components
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D151/00—Coating compositions based on graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Coating compositions based on derivatives of such polymers
• • 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
  • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
  • B29K2105/04—Condition, form or state of moulded material or of the material to be shaped cellular or porous
  • B29K2105/043—Skinned foam
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
  • B29L2031/00—Other particular articles
  • B29L2031/725—Drawing or writing equipment
  • B29L2031/7254—Pencils

Definitions

• This invention relates to a process for the production of pencils in which a lead, for example the lead of an ordinary pencil, a copying pencil or colored pencil, is surrounded in continuous process by a thermoplastic foam with a density of from 0.3 to 0.7 g/cc, and to the pencils obtained by this process.
• Pencils such as ordinary lead pencils or colored pencils, are conventionally manufactured by providing a suitable lead with a wooden sheath. This process, however, involves considerable work and many special conditions and individual operations. These may be summarized as follows:
• the wood Before it is processed, the wood has to be dried under suitable climatic conditions.
• the resin or essential oil content should neither exceed nor fall below certain limits.
• the prepared wood is cut up with special saws into thin boards which are subjected to the following operations: staining, grooving, inserting the leads, glueing together, coarse sanding, and cutting into crude pencils followed by further sanding to give the final form.
• German Patent specification No. 917,771 relates to a pencil comprising a tubular lead holder in the center of a pencil-like grip member with connections in the form of longitudinal strips between the lead holder and the grip member.
• the pencil is formed in one piece from a free-flowing injectable or extrudable, for example thermoplastic, plastics material.
• thermoplastic moulding compositions for example, polyethylene
• the pencils cannot be sharpened with a pencil sharpener of conventional design because the material cannot be cut like wood.
• moulding compositions of this kind are mixed with a suitable plasticizer in order thus to make them injectable, the problem of plasticizer migration occurs with the result that the quality of the leads in particular is detrimentally affected.
• foamable thermoplastic plastics are moulding compositions which contain expanding agents and which, under the processing conditions, give a porous strand of any desired cross section having the aforementioned density on issuing from a nozzle attached to a conventional type of extruder.
• thermoplastic plastics expandable polystyrene; expandable copolymers of styrene with other vinyl or vinylidene monomers, for example acrylonitrile or methyl methacrylate; expandable polymethyl methacrylate; expandable polyvinyl chloride; expandable polyvinyl chloride modified with monomeric or polymeric plasticizers; expandable cellulose esters modified with plasticizers; and expandable rubbermodified polystyrenes with a styrene content of at least about 50 percent by weight.
• the leads are sheathed in expandable thermoplastic moulding compositions comprising copolymer mixtures of polymers of acrylonitrile, butadiene and styrene (ABS- polymers) of the following composition:
• leads which contain as binder 99 to 0 parts by weight of the abovedescribed ABS-polymer and l to 100 parts by weight of a graft polymer of a. 25 to 85 percent by weight of an ethylene/vinyl acetate copolymer with a vinyl acetate content of from 20 to percent by weight and preferably from 30 to 55 percent by weight, and
• leads of any length and cross section which may be machine cut in any way, can be produced by a semi-continuous or fully continuous process.
• the operation of polishing and lacquering may finally be reduced to straightforward immersion in a conventional solvent.
• the pencils produced by the process according to the invention may also be lacquered by conventional processes and embossed after coloring.
• a conventional single-screw or twin-screw extruder is used to manufacturethe pencils according to the invention.
• An extruder head of the kind described for example in German Patent specification No. 940,492, may be used as the extrusion die for this purpose.
• the extruder head is designed in such a way that, providing a suitable heating or cooling medium is used, the temperature prevailing inside the die may be controlled as required.
• the process of expansion may be influenced in such a way that the density of the issuing foam varies from the outside towards the inside.
• the outer outlet opening (nozzle) of the extruder head is identical in shape with the shape of the pencil to be produced.
• a nozzle of round, hexagonal, triangular or oval cross section may be used.
• the diameter of the outlet is generally from to mm. and preferably around 7 mm.
• the cross section of the lead is governed by the shape of the die opening which can also be varied as desired. It is possible both to produce and to use leads-of any customary shape and diameter, for example round leads with diameters of from about 1.5 to about 3 mm., triangle or rectangular leads.
• thermoplastic plastics themselves are produced by known methods. Conventional thermoplastic plastics may be used to carry out the process according to the invention.
• British Patent specification No. 794,400 relates to the production of ABS- polymers, as does German Patent application F 44 156 lVd/39c.
• the expanding agents may be added by known methods.
• a granular thermoplast is used as the starting material, it has proved to be of advantage to add a small quantity of an adhesive promoter, for example 0.5 percent by weight (based on the mixture as a whole) of butyl stearate or of a higher alkyl sulphonic acid ester of phenol or of a substituted phenol.
• an adhesive promoter for example 0.5 percent by weight (based on the mixture as a whole) of butyl stearate or of a higher alkyl sulphonic acid ester of phenol or of a substituted phenol.
• the expanding agent may be worked in, for example, by means of a tumbler mixer in the case of a granulate, and by means of a high speed mixer in the case of a powder.
• the finished mixture should have a content of expanding agent of from about 0.7 to 1 percent by weight, although the density of the foam is also influenced by the particular processing conditions.
• Substances whose decomposition temperature lies in the processing range of the thermoplastic moulding compositions, may be used as the expanding agents, examples of such substances being azodicarbonamide and sulphohydrazide-based expanding agents.
• the moulding compositions containing the expanding agents may conveniently be processed in conventional single-screw or twin-screw extruders at temperatures in the range from 150 to 200C.
• Single-screw extruders are preferably used when an expandable thermoplast granulate is used for the foaming operation.
• Twin-screw extruders are used above all when an ex pandable thermoplast powder is used as the starting material.
• the granulate may already be colored, it is also possible to add appropriate pigments or dyes to the powder'during the process of mixing in the high speed mixer, and thus to obtain a colored foam.
• other additives for example, lubricants, anti-static agents, stabilizers and additional pigments may also be added.
• the leads are sheathed in the thermoplastic foam in a reversal-type extruder head attached to the extruder which contains two nozzles arranged one inside the other, the inner nozzle being used to guide the lead, whilst the outer nozzle is used to guide and form the surrounding, expandable thermoplastic composition.
• An extruder head which enables the temperature inside the die to be controlled is preferably used.
• the extruded length of pencil may be drawn off, fo example, by means of former sleeves and conveyor belts.
• the strand is passed through a suitable solvent, for example methyl ethyl ketone, as it is being drawn off.
• a suitable solvent for example methyl ethyl ketone
• the hitherto extremely complicated and, for the most part, batch-type production of lead pencils and colored pencils is simplified into a fully continuous and efficient extrusion process.
• the pencils produced have all the advantages of wooden pencils.
• the multi-layer lacquering and polishing are replaced by straightforward immersion in a solvent.
• the pencils thus obtained are eminently suitable for use as writing instruments and do not have any disadvantages at all when compared with conventional material, wood.
• EXAIWPLE l The following components are mixed in a high speed mixer: 1,000 parts by weight of an ABS-graft polymer of the following composition:
• this mixture is introduced into a twin-screw extruder equipped with a reversal-type extruder head.
• the outlet opening of this extruder head is atright-angles to its inlet opening.
• the head is designed in such a way that another material can be' introduced through an additional inlet at the bend between the inlet and outlet. This inlet which leads into the middle of the outlet opening of the die, is known as the mandrel.
• the outlet-opening of the extruder head itself is in this instance a regular hexagon with a diameter from corner to corner of 7 mm. It thus corresponds to the cross section of a normal hexagonal pencil. If the thermoplastic material is extruded through this extruder head at 150C.
• EXAMPLE 2 The following components are mixed together in a tumbler mixer: 1,000 parts by weight of polystyrene granulate,
• the expandable granulate is fed through a metering unit to a single-screw extruder to which an angled extruder head of the kind described in Example 1 is connected as the die.
• the temperature at which the material is processed is in the range from 120 to 150C. If ceramically bonded graphite leads are simultaneously introduced through the mandrel of the extruder head, followed by extrusion of the thermoplastic material, a continuous length of pencil with a silk-smooth surface is obtained. It is then cut up into pencils of standard length which are sufficiently rigid and which are easily sharpened.
• the foam has an average density of 0.4
• styrene/acrylonitrile copolymer weight ratio 70 1; 1.0 (as measured in dimethyl formamide at A rubber-modified polystyrene of the kindknown commercially as Polystyrene 475 (a registered trade mark of BASF).
• Weight ratio 70 1; 1.0 as measured in dimethyl formamide at A rubber-modified polystyrene of the kindknown commercially as Polystyrene 475 (a registered trade mark of BASF).
• Polymethyl methacrylate, 'n 0.8 (as measured in dimethyl formamide at 20c.).
• Example 2 the diphenyl sulphone- 3,3'-disulphohydrazide is replaced by azodicarbonamide in Examples 3 and 6 on account of the higher melt viscosity of the thermoplastic moulding compositions.
• EXAMPLE 7 The following components are mixed together in a high-speed mixer: Y 1,000 parts by weight of graft polymer of 20 percent by weight of polybutadiene,
• the mixture is further processed as described in Example 1..
• the resulting pencil withits graphite lead is easy to sharpen.
• a lead of the following'composition is extruded from a single-screw extruder attached to a 2 mm. extrusion die:' parts by weight of a graft polymer of 40 percent by weight of vinyl chloride, 23 percent by weight of vinyl acetate and 37 percent by weight of ethylene, 20 parts by weight of a graft polymer of a. 30 percent by weight of a graft polymer of 35 percent by weight of styrene and 15% by weight of acrylonitrile on 50 percent by weight of polybutadiene, and b.
• styrene/acrylonitrile copolymer weight ratio 70 30, 1; 0.60, 10 parts by weight of an alkyl sulphonic acid ester of phenol having an alkyl radical of 15 carbon atoms, 10 parts by weightof barium cadmium laurate, 40 parts by weight'of the bis-stearyl amide of ethylene diamine, and 750 parts by weight of graphite.
• the extrusion die attached to the extruder is designed in such a way that it simultaneously acts as the mandrel of an extruder head of the kind described in Example 1.
• the extruder head itself is connected to a second extruder (a twin-screw extruder) arranged perpendicularly of the first processing unit.
• An expandable. moulding composition is extruded through the 'outer nozzle of the extruder head.
• This moulding composition is identical with that described in Example 1, ex cept that the styrene/acrylonitrile copolymer' is replaced by an equivalent quantity of an a-methyl styrene/acrylonitrile copolymer with the same intrinsic viscosity.
• the procedure is as in Eitample 9.
• the lead composition used is made up as follows: 120 parts by weight of a graft polymer of 40 percent by weight of vinyl chloride, 23 percent by weight of vinyl acetate and 37 percent by weight of ethylene, 80 parts by weight of a graft co-polymer of 1. 30 percent by weight of a graft polymer of 35 percent lay-weight of styrene and 15% by weight of acrylonitrile on 50 percent by weight of a butadiene/styrene copolymcr in a weight ratio of 90 z l0, and b.
• styrene/acrylonitrile copolymer weight ratio '70 30, 1; 0.60, 10 parts by weight of an alkyl sulphonic acid ester of phenol having an alkyl radical of 15 carbon atoms, l parts by weight of barium cadmium laurate, 400 parts by weight of Cadmopurrot (registered trade mark of Wegriken Bayer AG), and 400 parts by weight of talc.
• a pencil having a sheath comprising a. foamed thermoplastic moulding composition of A. to 60 percent by weight of an elastomeric butadiene polymer with optionally up to 50 percent by weight of copolymerized styrene, isoprene, acrylonitrile or a lower alkyl ester of acrylic or .methacrylic acid; and
• a pencil comprising a central core of a graphitic or other coloring agent composition and a surrounding sheath, said sheath comprising a foamed thermoplastic moulding composition of a density of 0.3 to 0.7 g/cc and containing f A. 5 to 60 percent by weight of an elastomeric homopolymer of butadiene or a copolymer thereof with up to 50 percent by weight of copolymerized styrene, isoprene, acrylo'nitrile .or a lower alkyl ester of acrylic or methacrylic acid and B.
• sheath comprises a foamed thermoplastic moulding composition of 25 percent by weight of a graft polymer of 35 percent by weight of styrene and 15' percent by weight of acrylonitrile on 50 percent by weight of polybutadiene and 75% by weight of a styrene-acrylonitrile copolymer in a ratio by weight of :30.
• said central core comprises a graphite or other pencil coloring agent and, as a binder thereof, a mixture of C. l to 100 parts by weight of a graft polymer of a. 25 to 100 percent by weight of ethylene/vinyl acetate copolymer having a vinyl acetate content of from 20 to 70% by weight and b. to 0 percent by weight of grafted-on vinyl chloride and D. 99 to 0 parts by weight of a graft polymer of a.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Wood Science & Technology (AREA)
• Life Sciences & Earth Sciences (AREA)
• Health & Medical Sciences (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
• Extrusion Moulding Of Plastics Or The Like (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Inks, Pencil-Leads, Or Crayons (AREA)

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Cited By (34)

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Citations (5)

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• 1967
  • 1967-10-04 DE DE19671561767 patent/DE1561767B1/de active Pending
• 1968
  • 1968-08-28 US US755812A patent/US3704071A/en not_active Expired - Lifetime
  • 1968-09-24 NO NO683769A patent/NO134060C/no unknown
  • 1968-09-24 GB GB45223/68A patent/GB1240852A/en not_active Expired
  • 1968-09-24 AT AT930068A patent/AT296467B/de not_active IP Right Cessation
  • 1968-10-03 SE SE13381/68A patent/SE346086B/xx unknown
  • 1968-10-03 CH CH1479768A patent/CH523791A/de not_active IP Right Cessation
  • 1968-10-03 DK DK478968AA patent/DK131277B/da unknown
  • 1968-10-04 FR FR1588294D patent/FR1588294A/fr not_active Expired
  • 1968-10-04 NL NL6814263A patent/NL6814263A/xx not_active Application Discontinuation
  • 1968-10-04 JP JP43071949A patent/JPS4813368B1/ja active Pending
  • 1968-10-04 BE BE721839D patent/BE721839A/xx unknown

Patent Citations (5)

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