US2425501A - Prevention of crazing of flash heated shapes of polystyrene - Google Patents

Prevention of crazing of flash heated shapes of polystyrene Download PDF

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Publication number
US2425501A
US2425501A US485650A US48565043A US2425501A US 2425501 A US2425501 A US 2425501A US 485650 A US485650 A US 485650A US 48565043 A US48565043 A US 48565043A US 2425501 A US2425501 A US 2425501A
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United States
Prior art keywords
shape
temperature
polystyrene
heating
flash
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Expired - Lifetime
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US485650A
Inventor
Fred E Wiley
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Plax Corp
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Plax Corp
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Priority to US485650A priority Critical patent/US2425501A/en
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Publication of US2425501A publication Critical patent/US2425501A/en
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    • 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
    • C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
    • C08J7/08—Heat treatment
    • 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
    • B29C71/00—After-treatment of articles without altering their shape; Apparatus therefor
    • B29C71/02—Thermal after-treatment
    • 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
    • B29C71/00—After-treatment of articles without altering their shape; Apparatus therefor
    • B29C71/02—Thermal after-treatment
    • B29C2071/025—Quenching, i.e. rapid cooling of an object
    • 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
    • B29C71/00—After-treatment of articles without altering their shape; Apparatus therefor
    • B29C71/02—Thermal after-treatment
    • B29C2071/027—Tempering, i.e. heating an object to a high temperature and quenching it
    • 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
    • B29C2791/00—Shaping characteristics in general
    • B29C2791/001—Shaping in several steps
    • 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
    • B29K2025/00—Use of polymers of vinyl-aromatic compounds or derivatives thereof as moulding material
    • 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
    • C08J2325/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring; Derivatives of such polymers
    • C08J2325/02—Homopolymers or copolymers of hydrocarbons
    • C08J2325/04—Homopolymers or copolymers of styrene
    • C08J2325/06—Polystyrene

Definitions

  • Thi invention relates to the production of articles of polystyrene by processes which involve "flash heating which term as used herein means an operation in which the surface of the polystyrene is rapidly heated to or above, usually substantially above, the transition temperature of the material which is about 180 F. Flash heating may occur in bufllng, polishing or machining operations or in die drawing shapes of polystyrene in a highly heated die which may be heated to 580-600 F. Die drawing may be used to. obtain articles of accurate shapes and dimensions and having a high polish.
  • Flash heating of shapes of polystyrene causes crazing or cracking upon cooling of the shapes.
  • crazing or cracking resulting from flash heating of polystyrene shapes may be prevented by a certain heat treatment.
  • This treatment involves heating a shape in a temperature range above the transition temperature, preferably 194-221 F., for a certain period of time before flash heating, then immediately flash heating the shape, then immediately quenching the shape in a cold bath, preferably a bath at a temperature below room temperature, for example, 4050 F., and holding the shape in the quenching bath for a certain minimum time.
  • the initial heating of the shape is eflected in a a certain minimum time to soften the sub-surface material but for an insuflicient time to soften the core of the shape to such an extent that the shape can be permanently deformed, or in the case of a rod, permanently stretched until it'has become undersized as might occur in die drawing.
  • This treatment prevents surface crazing and cracking of the shape during and after flash heating as well as preventing deformation or stretching of the shape which might occur if the heating should be conducted at a higher temperature and/or longer time.
  • the shape may be further treated to mechanically stabilize it, as by heating the shape to or above the transition temperature, and then cooling it at a rate predetermined to produce in the shape-a selected maximum stress which will permit machining the shape or will permit it to be used without cracking or failure, as a result of internal mechanical stress.
  • Example A rod of polystyrene is heated to a temperature of approximately 194-221 F., preferably in a bath of ethylene glycol, for a period of time not less than about one-quarter of the time necessary to obtain uniformity of temperature throughout the shape within 1 F.
  • the length of the heating period is less than the time required to heat the core of the rod to such an extent that when the rod is subjected to flash heating in a drawing die and is drawn therethrough it would stretch permanently and become undersized.
  • the shape is immediately flash heated as by die drawing it through a die heated to 580-600 F.
  • the rod is quenched in a cold water bath which may be maintained at a temperature of 40-50 F.
  • the rod is held in the quenching bath for a minimum period of time, preferably not less than one-half the approximate time necessary to obtain uniform temperature throughout the rod within 1 F. Following this treatment, the rod may be removed from the bath.
  • the rod or other shape should not be allowed to remain out of the heating medium and the quenching bath any longer than necessary before and after flash heating and usually this period of time is not over 1 minutes.

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  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Treatments Of Macromolecular Shaped Articles (AREA)

Description

Patented Aug. 12, 1947 PREVENTION or caazma F FLASH HEATED SHAPES OF POLYSTYRENE Fred E. Wiley, Hartford, Conn., assignor to Plax Corporation, Hartford, Conn., a corporation of Delaware No Drawing. Application May 4, 1943,
Serial No.
8 Claims.
Thi invention relates to the production of articles of polystyrene by processes which involve "flash heating which term as used herein means an operation in which the surface of the polystyrene is rapidly heated to or above, usually substantially above, the transition temperature of the material which is about 180 F. Flash heating may occur in bufllng, polishing or machining operations or in die drawing shapes of polystyrene in a highly heated die which may be heated to 580-600 F. Die drawing may be used to. obtain articles of accurate shapes and dimensions and having a high polish.
Flash heating of shapes of polystyrene causes crazing or cracking upon cooling of the shapes.
I have discovered that crazing or cracking resulting from flash heating of polystyrene shapes may be prevented by a certain heat treatment. This treatment involves heating a shape in a temperature range above the transition temperature, preferably 194-221 F., for a certain period of time before flash heating, then immediately flash heating the shape, then immediately quenching the shape in a cold bath, preferably a bath at a temperature below room temperature, for example, 4050 F., and holding the shape in the quenching bath for a certain minimum time. The initial heating of the shape is eflected in a a certain minimum time to soften the sub-surface material but for an insuflicient time to soften the core of the shape to such an extent that the shape can be permanently deformed, or in the case of a rod, permanently stretched until it'has become undersized as might occur in die drawing.
This treatment prevents surface crazing and cracking of the shape during and after flash heating as well as preventing deformation or stretching of the shape which might occur if the heating should be conducted at a higher temperature and/or longer time.
Subsequent to the above steps the shape may be further treated to mechanically stabilize it, as by heating the shape to or above the transition temperature, and then cooling it at a rate predetermined to produce in the shape-a selected maximum stress which will permit machining the shape or will permit it to be used without cracking or failure, as a result of internal mechanical stress.
Example A rod of polystyrene is heated to a temperature of approximately 194-221 F., preferably in a bath of ethylene glycol, for a period of time not less than about one-quarter of the time necessary to obtain uniformity of temperature throughout the shape within 1 F. The length of the heating period is less than the time required to heat the core of the rod to such an extent that when the rod is subjected to flash heating in a drawing die and is drawn therethrough it would stretch permanently and become undersized. After heating the rod within the limits of time above stated, the shape is immediately flash heated as by die drawing it through a die heated to 580-600 F. Immediately after the flash heating, the rod is quenched in a cold water bath which may be maintained at a temperature of 40-50 F. The rod is held in the quenching bath for a minimum period of time, preferably not less than one-half the approximate time necessary to obtain uniform temperature throughout the rod within 1 F. Following this treatment, the rod may be removed from the bath. The rod or other shape should not be allowed to remain out of the heating medium and the quenching bath any longer than necessary before and after flash heating and usually this period of time is not over 1 minutes.
It will be understood that changes may be made in the above described procedure and my novel process may housed in treating various materials containing polystyrene or the like, without departing from the scope of the appended claims.
Having thus described my invention, what I claim is:
1. The process of preventing crazing of a flash heated shape of polystyrene which comprises first heating the shape at a temperature of approximately 194-221 F., flash heating the shape at a temperature substantially above said flrst named temperature, and quenching the shape.
2. The process of preventing the crazing of a flash heated shape of polystyrene which comprises heating the shape to a temperature of approximately l94-221 F. for a period of time not less than approximately one-fourth of the time required to obtain uniformity of temperature throughout the shape within 1 F., flash heating the shape at a temperature substantially above said first-named temperature, and immediately quenching the shape.
3. The process of preventing the crazing of a flash heated shape of polystyrene which comprises initially heating the shape at a temperature of approximately 19422l F., flash heating the shape at a temperature substantially above said first-named temperature, and quenching the shape in a bath maintained at a temperature of approximately 4050 F. a
4. The process of preventing the crazing of a flash heated shape of polystyrene which comprises initially heating said shape at a temperature of approximately 194-221 F. for not less than about one-fourth of the time necessary to obtain uniformity of temperature throughout the shape within 1 F. and for an insufficient period of time to heat the core of the shape enough to permit permanent deformation of stretching of the shape, flash heating the shape at a temperature substantially above said first named temperature, and immediately quenching the shape.
5. The process of preventing the crazing of a flash heated shape of polystyrene which comprises heating said shape in a. liquid bath at a temperature of approximately 194-221 F. for not less than about one-quarter of the time necessary to obtain uniformity of temperature in the shape within 1 F. and for a period of time less than that in which the core of the shape would be heated sufliciently to permit permanent deformation or stretching, immediately flash heating the shape at a temperature substantially above said first-named temperature, and immediately thereafter quenching the shape in a bath having a temperature not higher than approximately 50 F.
6. The process of preventing the crazing of a flash heated shape of polystyrene which comprises initially heating said shape at a temperature of approximately 194-221 F. for not less than about one-fourth of the time necessary to obtain unifprmity of temperature within 1 F. for an insuflicient time for the core of the shape to be heated enough to permit permanent deformation or stretching of the shape, immediately flash heating the shape at a temperature substantially above said first-named temperature, immediately quenching the shape in a bath maintained at a temperature not higher than approximately F. and holding the shape in the quenching bath for not less than approximately one-half the time necessary to obtain uniform temperature throughout the shape within 1 F.
7. The process of preventing the crazlng of a flash heated shape of polystyrene which comprises first heating the shape to a temperature of approximately 194-221 F., immediately flash heating the shape at a temperature of approximately 580-600 F., and immediately quenching the shape 8. The process of preventing crazing of a flash heated shape of polystyrene which comprises first heating the shape at a temperature of approximately 194-221 F., immediately flash heating the shape by drawing it through a die heated to a temperature of approximately 580-600 F., and thereafter immediately quenching the shape.
FRED E. WILEY.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS OTHER REFERENCES Ind. & Eng. Chem., Sept. 1942, pages 1052 to 1056.
US485650A 1943-05-04 1943-05-04 Prevention of crazing of flash heated shapes of polystyrene Expired - Lifetime US2425501A (en)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2514088A (en) * 1948-07-23 1950-07-04 Plax Corp Heat-treatment for plastic articles
US2661499A (en) * 1950-07-22 1953-12-08 Polymer Corp Method for sizing nylon shapes
US2813089A (en) * 1955-07-21 1957-11-12 Standard Oil Co Direct production of polystyrene from petroleum by-product ethylbenzene
US3200182A (en) * 1961-01-07 1965-08-10 Bayer Ag Production of a stress-free polycarbonate shaped article
EP0700773A3 (en) * 1994-08-08 1996-10-23 Gen Electric Process for annealing thermoplastics

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1683402A (en) * 1924-07-12 1928-09-04 Naugatuck Chem Co Polymerized styrol and its homologues and process for the polymerization of styrol and its homologues
US2145119A (en) * 1935-04-17 1939-01-24 Corning Glass Works Tempering glass articles
US2166215A (en) * 1936-12-28 1939-07-18 Ernest G Lloyd Method of and means for forming unbreakable lenses
US2177633A (en) * 1937-02-25 1939-10-31 Eastman Kodak Co Method and apparatus for making thermoplastic sheeting
US2194313A (en) * 1937-06-26 1940-03-19 Evarts G Loomis Method and apparatus for shaping thermoplastic rods, tubes, and the like
US2205449A (en) * 1938-03-04 1940-06-25 Dow Chemical Co Treating vinylidene chloride polymers
US2239780A (en) * 1937-05-19 1941-04-29 Gen Aniline & Film Corp Process for improving the properties of thermoplastic, film-forming, organic substances
US2311818A (en) * 1940-09-06 1943-02-23 Prophylactic Brush Co Method of making brushes

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1683402A (en) * 1924-07-12 1928-09-04 Naugatuck Chem Co Polymerized styrol and its homologues and process for the polymerization of styrol and its homologues
US2145119A (en) * 1935-04-17 1939-01-24 Corning Glass Works Tempering glass articles
US2166215A (en) * 1936-12-28 1939-07-18 Ernest G Lloyd Method of and means for forming unbreakable lenses
US2177633A (en) * 1937-02-25 1939-10-31 Eastman Kodak Co Method and apparatus for making thermoplastic sheeting
US2239780A (en) * 1937-05-19 1941-04-29 Gen Aniline & Film Corp Process for improving the properties of thermoplastic, film-forming, organic substances
US2194313A (en) * 1937-06-26 1940-03-19 Evarts G Loomis Method and apparatus for shaping thermoplastic rods, tubes, and the like
US2205449A (en) * 1938-03-04 1940-06-25 Dow Chemical Co Treating vinylidene chloride polymers
US2311818A (en) * 1940-09-06 1943-02-23 Prophylactic Brush Co Method of making brushes

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2514088A (en) * 1948-07-23 1950-07-04 Plax Corp Heat-treatment for plastic articles
US2661499A (en) * 1950-07-22 1953-12-08 Polymer Corp Method for sizing nylon shapes
US2813089A (en) * 1955-07-21 1957-11-12 Standard Oil Co Direct production of polystyrene from petroleum by-product ethylbenzene
US3200182A (en) * 1961-01-07 1965-08-10 Bayer Ag Production of a stress-free polycarbonate shaped article
EP0700773A3 (en) * 1994-08-08 1996-10-23 Gen Electric Process for annealing thermoplastics

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