DE2542281C2 - Finely divided, expandable styrene polymers for the production of foam bodies - Google Patents

Description

Tetrabromodibenzalacetone, fl-chloro-2,2,2-tribromo] ethyl acrylate, bis- [1-chloro-2,2,2-tribromo] ethyl fumarate, fi

[1 -Chlor-2,2,2-tribromo] ethyl-2,3-dibromopropionate, 1,2-dibromo-2-methylbutane-4-acrylate, ":

[1-chloro-2,2,2-tribromo] ethyl-2-chloro-propionate, [1-bromo-2 ^ -tribromo] ethyl-2-bromo-propionate, 1,3- and i-j

1,4-bis [1,2-dibromoisopropyl] benzene etc. i ·}

The bromine compounds to be used according to the invention are preferably those which are used in are soluble in organic solvents. y

For the purposes of the invention, styrene polymers are polystyrene and copolymers of styrene which contain at least _; v-

Contains 50 percent by weight of styrene polymerized. As copolymerization components come, for. Am Question-methylstyrene, nuclear halogenated styrenes, nucleus alkylated styrenes, acrylonitrile, methacrylonitrile, esters of Acrylic and methacrylic acid with alcohols with 1 to 8 carbon atoms, N-vinylcarbazole, maleic anhydride or also small amounts of compounds that contain two polymerizable double bonds, such as butadiene,;.

Divinylbenzene, butanediol diacrylate, etc. The styrene polymers contain one or more homogeneously distributed several propellants. Suitable propellants are, for. B. gaseous or liquid under normal conditions Hydrocarbons or halogenated hydrocarbons which do not dissolve the styrene polymer and whose boiling i

points below the softening point of the polymer. Suitable propellants are e.g. B. propane, butane, Pentane, cyclopentane, hexane, cyclohexane, dichlorodifluoromethane and trifluorochloromethane. The propellants are in the styrene polymers generally in amounts between 3 and 15 percent by weight, based on the Polymer, present.

The polymer can also contain additives such as plasticizers, stabilizers, dyes, fillers or Contains flame retardants. The expandable polystyrenes according to the invention can also be used in a known manner

Be coated on the surface with substances to achieve severe flammability against Clumping during prefoaming, against static charging, to further shorten the minimum mold dwell time, etc.

The expandable polystyrenes are produced by the methods customary in the art. You can in Pearl form or in any other form, the particles advantageously having a diameter of 0.1 to 6, in particular from 03 to 3 mm.

In the finely divided, expandable styrene polymers, the bromine compounds should be present in as homogeneous a distribution as possible, or at least initially should have been present. This is achieved, for example, by adding monomeric styrene, optionally together with other monomers, in the presence of the organic bromine compound and polymerized by blowing agent in aqueous suspension. However, it is too possible to impregnate styrene polymers in aqueous suspension at elevated temperature with the organic bromine compounds, optionally also at the same time with blowing agent.

example 1

A mixture of 150 parts of drinking water, 0.1 part of sodium pyrophosphate, 100 parts of styrene, 0.45 part of benzoyl peroxide, 0.15 part of tert-butyl perbenzoate, 7 parts of pentane and those in Table 1 were each placed in a pressure-resistant stirred tank made of corrosion-free steel mentioned additives in the amounts stated there heated ^{to 90 ° C. with stirring.} After 2 hours at 90 ° C., 4 parts of a ten percent aqueous solution of polyvinylpyrrolidone were added. After 6 hours at 90 ⁰ C for 2 hours at 100 ⁰ C and 2 hours was heated to 120 ° C

After the end of the polymerization cycle, the mixture was cooled. The bead polymer formed was from separated from the aqueous phase, dried and sieved.

The bead fraction between 1.0 and 23 mm in diameter was prefoamed in a continuous stirring pre-expander type Rauscher with flowing steam to a bulk density of 15 g / l for 24 hours temporarily stored and then in a 5001 block mold type Rauscher by steaming with a pressure welded at 13 bar for 20 seconds to form a block. The measured minimum mold retention periods are compiled in table 1

The minimum dwell times in the mold are determined by the following method: The prefoamed styrene polymer particles are welded into a mold by vapor deposition with water vapor in a mold, in the center of which is a pressure probe. It will be the time from the start of cooling to the Determined point in time at which the pressure in the interior of the molding has dropped to 1.05 bar. Experience has shown that the molding can be removed from the mold without risk at this pressure.

Table 1

additive additive Saponification Minimum shape lot speed dwell time (%) of addition (min) (Mol%)

Without

Hexabromocyclododecane Hexabromocyclododecane Tetrabromoethane Tetrabromoethane Tetrabromodibenzalacetone Tetrabromodibenzalacetone

[1 -Chlor-2Z2-tribromo] ethyl acrylate

Bis [t-chloro-2,2,2-tribromo] ethyl fumarate

Table 1 clearly shows that the organic bromine compounds according to the invention are extremely effective, so that you can manage with additional amounts that are more than an order of magnitude lower than in the past used nucleating agents.

- - 103 0.0015 0.95 101 0.017 0.95 13th 0.0015 1.0 102 0.017 1.0 9 0.0015 2.2 30th 0.003 2.2 11th 0.0015 6.6 13th 0.0008 10.2 12th

Claims (1)

Claim: Finely divided expandable styrene polymer, characterized in that this 0.0001 to 0.01 based on the styrene polymer, an organic bromine compound containing that contained at 100 ⁰ C within 3 Stunder in double distilled water per equivalent of bromine in the molecule, 2.2 to 30 mole percent hydrogen bromide anspaltet . The invention relates to expandable styrene polymers, which are more favorable through a combination Characteristic features. The procedures for processing expandable styrene polymers are known and are for example in the book by H. L v. Cube and K. E. Pohl, "The technology of foamable polystyrene", Dr. A. Hüthig Verlag GmbH, Heidelberg 1965, described. Only the term "minimum mold residence time" is intended here again explained. This is understood to be the time that a shaped body takes after steaming or heating must remain in the pressure-resistant form for the purpose of cooling before it can be safely removed from the mold. It It goes without saying that the processors of expandable polystyrene for economic reasons short minimum mold residence times are interested. It is already known that fine-celled polystyrene foams with cell counts of 10 to 25 cells / mm are short Have minimum mold residence times. It is also known that such fine-cell polystyrene foams by Addition of certain bromine compounds can be obtained. For example, DE-B-12 56 888 and AT-A-2 79 183 recommended, organic compounds with aliphatically or cycloaliphatically bound bromine atoms, such as tetrabromoethane and hexabromocyclododecane to be added in amounts of 0.005 to 0.1% by weight. A disadvantage of the bromine compounds recommended up to now for the production of fine-cell foams is however, that relatively high concentrations of bromine-containing compounds are required to be sufficient short cooling times. However, such additives already lead to an unfavorable influence on the mechanical properties of the foam and especially the heat resistance - bromine-containing Compounds are also very often harmful to health. The object of the invention was to avoid the described disadvantages of the prior art. The invention relates to finely divided, expandable styrene polymers characterized in that they are characterized are that they are 0.0001 to 0.01 and preferably 0.0005 to 0.005 percent by weight, based on the styrene polymer, contain an organic bromine compound, which is distilled at 100 ° C within 3 hours Water splits off 2.2 to 30 mol percent of hydrogen bromide per equivalent of bromine contained in the molecule. It has been shown, surprisingly, that such finely divided styrene polymers, despite the applied- * ■ / The low concentrations of bromine compounds can advantageously be used to produce fine foams. Since ti the bromine compounds largely decompose during the manufacturing process, they are in the finished ^ Foam is practically no longer available and therefore cannot adversely affect it. Egg- The hydrolytic saponification rate of the organic bromine compounds is determined as follows. f. 1 g of the substance in question is poured into a pressure-tight vessel together with 100 g of double-distilled water; 'ΐ Stainless steel heated to 100 ° C for 3 hours with stirring. After cooling to room temperature, the f.} resulting amount of HBr determined by potentiometric titration. In this test, bromine compounds suitable according to the invention develop 2.2 to 30 mol percent HBr per equivalent of bromine in the nucleating agent molecule. _^ί:; According to the invention suitable bromine compounds, which under the above test conditions 2.2 to 30? Eliminating mol percent of HBr per equivalent of bromine in the molecule are, for example, i |