Classifications

• • 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
  • C08J3/00—Processes of treating or compounding macromolecular substances
  • C08J3/02—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques
  • C08J3/03—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques in aqueous media
• • 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
  • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
  • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
  • C08J2323/04—Homopolymers or copolymers of ethene
  • C08J2323/06—Polyethene

Definitions

• dispersions of normally solid polyethylene by a process which, comprises passing moltennormally solid polyethylene with water, at a temperature above 115 C. and at sufficient pressure to keep the water in "the liquid'state, through an emulsifying device, and then releasin'g'the pressure.
• Convenient emulsifying devices are any machines which provide high rates; of shear and keep a substantial pressure on' the materials besure casing.
• the rate of shear is one of the factors which determines the particle size of the dispersed norm'allysolid polyethylene, but a suitable rate is provided by either of these types of emulsifying device.
• Colloid mills have two surfaces situated within. about one-hundredth of a centimetre moving at high speed'relative'to each other, and the rate of shear is-determined by the speed and the gap. They canbe adapted so that the mixture is under pressure. Suitable conditions for a 10 centimetre diameter mill, for example, are that the gap shall be between and thousandths of a centimetre.
• the temperature of operation must be above 115 (3., which is the melting point of normally solid polyethylene, and as normally solid polyethylene does not produce a free-flowing liquid 2 when melted, it is preferably at least 130
• The'top temperature is limited both by the critical temperature above which water cannot be a liquid and by the'decomposition of normallysolid polyethylene, and preferably does not exceed'2 '50 0;; when emulsifying agents are present it is limited by the temperature at'which'they become inactive, which is generally about 160 C.
• the minimum pressure needed exceeds the vapour pressure of water at the operating temperature, and is thereforeat least2 atmospheres absolute and generally at least 3-6' atmospheres. For convenience, however, we prefer to use rather high pressures between 20 and atmospheres.
• the amount of water used is between 1 and 5 parts by weight per part of normally solid polyethylene, preferably between 2 and 5 parts by weight per part of normally solid polyethylene. It. is not commercially attractive to make dispersions which contain as little as 15% of normally solid polyethylene, and technical difiiculties arise in making dispersions containing as much as 35% of solid ethylene polymers.
• an emulsifying agent inorder to assist in preparing the dispersion and to increase its stability. Agents which are not decomposed at 'the'emulsiflcation temperature are effective, and of these we prefer the fatty acid compounds known broadly as soaps, for example the potassium and sodium salts of stearic, palmitic, and other long chain carboxylic acids, as-
• the water and normally solidip'ol'yethylene can within about 10 seconds of leaving the emulsifying device, in order to avoid coalescence of the particles. This is done by making the connecting space between the blow-off valve where the pressure is released and the outlet of the emulsifying device as small as possible. The releasing of the pressure can be done into the air so as to allow steam to flash oil and thus cool the emulsion to 100 C., but we prefer to cool further than this by blowing off the dispersion direct into some cooled dispersion at 3060
• the normally solid polythene particles in the dispersions obtained by this process can readily be made as small as 5-20 microns.
• the invention is illustrated by the following example.
• Example A colloid mill with a gap of .01 cm. and a cm. diameter rotor in a steel casing to withstand pressures up to 100 atm. was fitted with a pressure release valve for delivering the dispersion, a pressure tight gland for the drive, and a steam jacket. It was also fitted with two feed pipes, one of which led from a water heater fed by a pump from a stock tank while the other led from a heater for the normally solid poly ethylene fed by a screw extrusion pump. 300 kgm. of water with 6.6 kgm. of triethanolamine were mixed in the stock tank. 100 kgm.
• normally solid polythene (Alkathene brand of polythene, Grade 70, Alkathene being a registered trade-mark) were mixed with 10 kgm. of stearic acid on steam-heated rubber milling rolls and fed into the hopper of the screw extrusion pump.
• the aqueous phase was fed into the mill at a rate of 20 kgm./hr. and the pressure release valve adjusted to maintain a pressure of 40 atm. in the mill.
• the steam was then turned on to the steam jacket of the mill, and the electric heaters for the water and the normally solid polythene switched on. When the water, normally solid polyethylene and mill temperatures had reached 150 C. the mill was started and run at 7500 R. P. M.
• the average particle size of the dispersed normally solid polyethylene was 10 microns Dispersions made according to the process of this invention are of most value in coating paper in order to waterproof it, and in impregnating fabrics to stiffen them.
• the normally solid polythene retains its well known toughness, which is such an important factor in its use for coating and impregnating materials.
• a process for the manufacture of polyethylene dispersions which comprise subjecting a mixture of molten, normally solid polyethylene and one to five parts by weight of water per part of polyethylene at a temperature above 115 C. and at a suflicient pressure to keep the water in the liquid state, to a high rate of shear such that the dispersed particles of said polyethylene have an average particle size of from about 5 to 20 microns, and then releasing the pressure.
• a process as claimed in claim 1 carried out at a temperature between 130 and 250 C. and at a pressure between 20 and atmospheres.
• a process as claimed in claim 1 carried out in the presence of a soap as an emulsifying agent, the soap being made in situ by having a higher fatty acid dissolved in the normally solid polyethylene and a base dissolved in the aqueous phase.
• a process as claimed in claim 1 in which an emulsifying agent is employed and in which the amount of emulsifying agent is between 1 and 10 parts by weight per parts of normally solid polyethylene.
• a process as claimed in claim 1 carried out in the presence of an emulsifying agent and at a temperature between and C.

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• Chemical & Material Sciences (AREA)
• Dispersion Chemistry (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Processes Of Treating Macromolecular Substances (AREA)
• Colloid Chemistry (AREA)
• Treatments For Attaching Organic Compounds To Fibrous Goods (AREA)

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Cited By (27)

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Citations (3)

• 0
  • BE BE498124D patent/BE498124A/xx unknown
• 1949
  • 1949-09-28 GB GB24921/49A patent/GB671968A/en not_active Expired
• 1950
  • 1950-09-06 US US183475A patent/US2653919A/en not_active Expired - Lifetime
  • 1950-09-22 FR FR1024822D patent/FR1024822A/fr not_active Expired
  • 1950-09-29 DE DEI2243A patent/DE862513C/de not_active Expired

Patent Citations (3)

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