Method of manufacturing articles from hot solid filler material coated with thermoplastic material

• US 3,897,527 A
• Filed: 03/28/1972
• Issued: 07/29/1975
• Est. Priority Date: 11/03/1969
• Status: Expired due to Term

• Current Assignee: Lars Ringdal
• Original Assignee: Lars Ringdal
• Inventors: Ringdal, Lars
• Primary Examiner(s): White, Robert F.
• Assistant Examiner(s): Hall, J. R.
• Application Number:
  US05/238,910
• Time in Patent Office: 1,218 Days
• Field of Search: 264/126,122,37
• US Class Current: 264/37.29
• CPC Class Codes: B29B 13/021 Heat treatment of powders
• CPC Class Codes: B29B 13/045 of powders or pellets
• CPC Class Codes: B29B 7/905 with means for pretreatment of the charges or fibres
• CPC Class Codes: B29B 9/16 Auxiliary treatment of granules

Abstract

A method of manufacturing articles such as a pipe section from particles of solid granular filler material and thermoplastic material is disclosed in which the particles of solid granular material are first heated to a temperature in excess of that required to melt the thermoplastic material and are then mixed with the thermoplastic material which is provided in the form of a powder. The thermoplastic material is melted and coats the solid granular material, the heat being supplied by the stored heat of the granular material itself. The coated granular material, still retaining considerable heat, is immediately then supplied to a suitable mold in which the coated particles adhere to each other to form the ultimate molded product bound together by the thermoplastic material.

Claims

1. THE METHOD OF MANUFACTURING ARTICLES FROM PARTICLES OF SOLID GRANULAR FILLER MATERIAL AND THERMOPLASTIC MATERIAL, IN WHICH THE PARTICLES OF SOLID GRANULAR MATERIAL ARE COATED WITH THERMOPLASTIC MATERIAL, THE METHOD COMPRISING THE STEPS OF CONDUCTING PARTICLES OF SOLID GRANULAR MATERIAL ADAPTED TO STORE HEAT THROUGH A HEATING ZONE AND THEREIN HEATING THE SOLID PARTICLES TO BE COATED TO A TEMPERATURE SUBSTANTIALLY IN EXCESS OF THAT REQUIRED TO MELT THE THERMOPLASTIC MATERIAL IN QUANTITIES SUFFICIENT TO COAT THE SOLID PARTICLES WITH THE STORED HEAT THEREIN, SAID PARTICLES OF SOLID GRANULAR MATERIAL GEING STABLE AND SUBSTANTIALLY RESISTANT TO DISINTEGRATION AT THE TEMPERATURE USED, CONDUCTING THE RESULTING SOLID PARTICLES INTO A MIXING ZONE SUBSEQUENT TO SAID HEATING, SUPPLYING POWDERED THERMOPLASTIC MATERIAL TO THE MIXING ZONE IN A PROPORTION SUFFICIENT TO COAT SAID SOLID PARTICLES, THOROUGHLY MINGLING THE SOLID PARTICLES WITH SAID PROPORTION OF POWDERED THERMOPLASTIC MATERIAL AND MELTING SAID THERMOPLASTIC MATERIAL ONTO THE SURFACES OF THE SOLID PARTICLES BY UTILIZING THE STORED HEAT OF SAID PARTICLES TO MELT SAID THERMOPLASTIC MATERIAL AND THUS COAT THE PARTICLES, PASSING THE RESULTING PLASTIC-COATED SOLID PARTICLES DIRECTLY AND CONTINUOUSLY INTO A MOLD HAVING A SHAPE OF THE ARTICLE TO BE PRODUCED UNTIL SAID MOLD IS FILLED, THE PLASTICCOATED SOLID PARTICLES AS DELIVERED INTO THE MOLD BEING AT SUCH A TEMPERATURE AND CONTAINING SUCH AN AMOUNT OF STORED HEAT AS A RESULT OF THE HEATING IN THE HEATING ZONE AS TO MAINTAIN THE PLASTIC COATING AT A TEMPERATURE SUCH THAT THE PARTICLES OF PLASTIC-COATED SOLID PARTICLES STICK TO EACH OTHER IN THE MOLD, AND COOLING THE PARTICLES IN THE MOLD SUFFICIENTLY TO PERMIT REMOVAL OF THE MOLDED ARTICLE FROM THE MOLD.

2. The method as claimed in claim 1, wherein the solid particles are heated in the heating zone to a centigrade temperature approximating twice that required to melt the powdered thermoplastic material sufficiently to provide a coating.

3. The method as claimed in claim 1, wherein said proportion of thermoplastic material is in excess of that necessary to coat the hot solid particles, passing the mingled hot coated solid particles and excess powdered thermoplastic into a separating zone and separating the hot coated solid particles from the excess thermoplastic material, and passing the separated hot coated solid particles directly into said mold.

4. The method as claimed in claim 1, wherein the particles of granular solid filler material are of gravel or expanded clay balls adapted to be heated to the required temperature without substantial alteration and having an average size of 7 to 8 mm.

5. The method as claimed in claim 3, including a collecting zone source for powdered thermoplastic material to be supplied to the mixing zone, and delivering the excess separated powdered thermoplastic material from the separating zone into the collecting zone.

6. The method of coating as claimed in claim 1, including the step of keeping the heated granular solid particles and powdered thermoplastic material in motion and in intimate mingled contact with each other until a coating of desired thickness is formed on said particles.

7. The method as claimed in claim 1, wherein a continuous operation is carried out in which a stream of heated solid granular particles is mingled with a stream of thermoplastic material in the mixing zone in excess of that required to coat said particles, conducting the resulting mingled materials through a separating zone in which the excess of thermoplastic material is separated from coated solid particles, and returning the separated excess of thermoplastic material to the mixing zone to be mingled with hot solid granular particles coming directly from the heating zone.

8. The method as claimed in claim 1, wherein the particles of solid granular material are stable and substantially resistant to disintegration when heated to temperatures of from 300* to 400* C.