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
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/16—Making expandable particles
  • C08J9/20—Making expandable particles by suspension polymerisation in the presence of the blowing agent
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F257/00—Macromolecular compounds obtained by polymerising monomers on to polymers of aromatic monomers as defined in group C08F12/00
  • C08F257/02—Macromolecular compounds obtained by polymerising monomers on to polymers of aromatic monomers as defined in group C08F12/00 on to polymers of styrene or alkyl-substituted styrenes
• • 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

Definitions

• the invention relates to a process for the preparation of spherical, expandable styrene polymers with a narrow bead size distribution by polymerizing styrene which is absorbed in particulate styrene polymers.
• Spherical, expandable styrene polymers are usually prepared by polymerizing styrene in aqueous suspension in the presence of a blowing agent. This creates a pearl size distribution that corresponds to a Gaussian distribution. From this spectrum of pearls, only selected fractions can usually be sold on the market, while others cannot be used directly for processing reasons. This is especially true for those particles whose size is less than about 0.4 to 0.5 mm. Attempts are being made to feed these inevitable fractions back into suspension polymerization by redissolving them in monomeric styrene. However, this generally results in products of poor quality.
• Expandable styrene polymers can also be used in an Ex Melt the truder under pressure at elevated temperatures, press out through nozzles and cool the resulting Pc.Lystyrene strands in a water bath and transfer them into cylindrical expandable granules of uniform size in a granulator. These extruder granules can then be converted into an essentially uniform, spherical bead material in aqueous suspension at temperatures above their softening point and elevated pressures (DT-OS 25 34 833). However, one has to work at relatively high temperatures of around 125 ° C., which means that the styrene polymer particles obtained have a relatively high internal water content.
• a process oil is described in DT-OS 23 38 132, in which selected sieve fractions are suspended in aqueous phase before styrene polymers, for this suspension with him.
• dropwise monomeric styrofoam] is added at high temperature and this is polymerized in the presence of an organic peroxide and a polymerization retarder.
• an organic peroxide and a polymerization retarder At the. sem time-consuming procedure is achieved that the added styrene is absorbed in the polymer particles and polymerized there, depending on the proportions differently enlarged telchen would be obtained with a substantially uniform size.
• the task of the polymerization retarder is to reduce the polymerization of the monomeric styrene for the purpose of diffusion into the polymeric particles.
• the invention was based on the object, a simple method for manufacturing spherical expandable sty. rolpolymerisaten to develop essentially uniform particle size It should be assumed that Particulate styrene polymers which are enlarged by polymerizing monomeric styrene, the shape of the particles being converted into a spherical shape, unless it is spherical from the outset.
• Styrene polymers are to be understood as homopolymers or copolymers of styrene which can contain up to 50% by weight of comonomers in copolymerized form.
• Possible comonomers are: ⁇ -methylstyrene, halogenated or alkylated styrenes, acrylonitrile, methacrylonitrile, esters of acrylic and methacrylic acid with alcohols having 1 to 8 carbon atoms, male acidic anhydride or also small amounts of compounds containing two polymerizable double bonds, such as butadiene, divinylbenzene or butanediol acrylate.
• the styrene polymers can contain conventional additives, such as e.g. Dyes, especially lightfast pigment dyes, also plasticizers, stabilizers, other plastics, e.g. Polyethylene or polyisobutylene, fillers, cell regulators or flame retardants.
• Dyes especially lightfast pigment dyes
• plasticizers especially lightfast pigment dyes
• stabilizers e.g. Polyethylene or polyisobutylene
• other plastics e.g. Polyethylene or polyisobutylene, fillers, cell regulators or flame retardants.
• the particle size of the styrene polymer used can vary within wide limits between 0.1 and 5 mm.
• unsaleable or hard-to-sell fractions from a styrene suspension polymer with an average particle diameter between 0.2 and 0.5 mm. They are expediently separated into partial fractions with a substantially uniform particle size by sieving. You can also use regrind that was produced by grinding edge fractions with too large a particle diameter. This regrind is also expediently broken down into partial fractions with a uniform particle size by sieving.
• extruder granules can be used which were obtained from edge fractions by melting, extruding through perforated nozzles and granulating. Due to the method of manufacture, these granules have essentially uniform particle sizes.
• cylinders are preferred shaped particles with a diameter between 0.2 and 2 mm and a length between 0.3 and 3 mm.
• the blowing agent-containing styrene polymer particles are suspended in water, preferably with the addition of an inorganic or organic suspension stabilizer, with stirring.
• stabilizers e.g. in question: water-soluble or water-dispersible homo- or copolymers of vinyl pyrrolidone and acrylic acid, polyvinyl alcohols and cellulose ethers; also poorly soluble alkaline earth metal phosphates, carbonates or sulfates, optionally together with emulsifiers or surfactants. They are preferably used in amounts of 0.01 to 4% by weight, based on the styrene polymer.
• 10 to 100, preferably 50 to 90% by weight (based on the blowing agent-containing styrene polymer) of monomeric styrene are added to this suspension.
• the styrene can again be replaced by up to 50% of its weight by the above-mentioned comonomers.
• the suspension is preferably from 1 to 3 hours then maintained 0.5 to 5 hours, at temperatures below 100 o C, preferably between 0 and 75 ° C and in particular between 20 and 50 ° C.
• the styrene should not yet polymerize, even in the presence of conventional organic peroxides. However, it diffuses into the styrene polymer, so that it is impregnated with monomers.
• the diffusion of the monomers into the polymer particles is particularly complete and uniform if the impregnation takes place under pressure up to 20 bar, preferably between 3 and 10 bar; and if the suspension is kept in motion, for example by vigorous stirring.
• the absorbed styrene is polymerized in a polymerization step B by increasing the temperature to 90 to 140 ° C., preferably to 100 to 125 ° C.
• This polymerization is done for the purpose moderately directly in the suspension obtained in impregnation step A in the presence of the same suspension stabilizers and under the same pressure, also with stirring.
• the polymerization is triggered by organic peroxides in amounts of 0.01 to 1% by weight (based on the monomers) . These peroxides can either only be added to the suspension in the polymerization stage, but they are preferably already present in the suspension during the impregnation step.
• the volume of the styrene polymer particles increases in accordance with the ratio of polymer to monomer, and cylindrical or otherwise irregularly shaped particles are converted into spherical ones.
• the process according to the invention makes it easy to enlarge the particles in such a way that they can be used in practice for the production of foam moldings. You can also repeat process steps A + B two or more times if you want to achieve a correspondingly large increase in particle size.
• the process according to the invention also has the advantage that the treatment temperature can be reduced by about 10 to 15 ° C. because of the softening effect of the absorbed monomers on the polymer. As a result, the internal water content of the styrene polymer beads drops and they no longer need as much or at all can no longer be dried.
• soluble auxiliaries such as amines or bromine compounds
• the expandable styrene polymers prepared in accordance with the invention can be converted into foams in a customary manner by treatment with hot gases with liberation of the blowing agents,
• Example 1 is repeated, but the expandable polystyrene beads are colored dark blue with a pigment. A product with an even color distribution in the pearl is obtained. White, uncolored polystyrene particles that would result from separate polymerization of the styrene are not formed.
• Example 1 is repeated, using 100% monomeric styrene, based on expandable polystyrene, in. the 0.36% tert-butyl perbenzoate is dissolved. 1.5 l of pentane are also added. The correspondingly reclaimed end product has a blowing agent content of 6.8% and be - sits an average bead diameter of 0.6 mm. The very fine-celled material with 12 cells / mm shows the same foaming behavior as described in Example 1.
• Example 2 17 liters of water are filled in, in which 110 g of trisodium phosphate are dissolved. 6.5 kg of a polystyrene granulate with a length of 0.5 mm and a diameter of 0.8 mm, which contains 5% pentane, are added. Then 330 ml of a 35% calcium chloride solution are added, then 15 ml of an emulsifier and 680 ml of a 10% aqueous solution of polyvinylpyrrolidone and finally 6.5 kg of styrene, in which 0.36% of tert-butyl perbenzoate are dissolved. The mixture is stirred at 20 ° C.
• the round beads obtained after working up have an average diameter of 1.0 mm with a narrow distribution width.
• the product coated with 0.04% zinc stearate produces foam beads with a bulk density of less than 12 g / l and a cell count of 10 to 12 cells / mm when pre-foaming.
• Example 5 is repeated, but using a blowing agent term polystyrene extruder granules is used, to which 1% hexabromocyclododecane and 1,000 ppm n-hexylamine were added during extrusion.
• the result is a pearl-shaped material with an average diameter of 1.0 mm and the narrow distribution width.
• pre-foaming a coarse-celled product with 6 to 8 cells / mm is obtained.

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)

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Cited By (7)

Citations (3)

• 1977
  • 1977-08-01 DE DE19772734607 patent/DE2734607A1/de not_active Withdrawn
• 1978
  • 1978-07-21 IT IT50422/78A patent/IT1107662B/it active
  • 1978-07-24 EP EP78100482A patent/EP0000572B1/fr not_active Expired
  • 1978-07-24 DE DE7878100482T patent/DE2860065D1/de not_active Expired

Patent Citations (3)

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