CS232171B1 - Preparation method of stabilizing system for foam polystyrene production - Google Patents

Abstract

The invention relates to a method of preparation stabilization system for production foamable polystyrene suspension polymorphism. Stabilization system, ready by precipitation target. sodium phosphate water-soluble calcium salt, "The modulator reaches - water-soluble calcium salt of aliphatic or aromatic carboxylic acids. Use this stabilization system to produce expandable polystyrene with a very narrow particle distribution.

Description

The present invention relates to a process for preparing a stabilizing system for the production of foamable polystyrene by suspension polymerization using precipitated basic calcium phosphate as a suspension stabilizer.

For the production of expanded polystyrene fittings and thin-walled shells, foamable polystyrene beads of smaller mean diameter (<1mm) are used, while beads of larger mean diameter (χ * 1 mm) are applied to the production of blocks and insulating boards, whose proportion predominates by volume. The breadth of the moldings as well as the technological process of polystyrene foam production are significantly influenced by the width distribution of pearl sizes, the number of underlays, overlays and the presence of very small pearls (<ζ, 0.3 mm) ·

For this reason, expandable polystyrene for the production of high-quality individual moldings must correspond to the appropriate granulometry of the processed beads. It is therefore necessary to sort the expandable polystyrene beads obtained by suspension polymerisation (suspension product) into fractions of the desired properties. * The quality of these sorted fractions depends not only on the machine parameters, but also on the surface properties and granulometry of the suspension product. the width of the size distribution of the suspension product pearls increases the proportion of over-sieves and in particular sub-sieves in; sorted fraction of expandable polystyrene * quality of these commercial fractions is therefore determined by the polymerization suspension system used *

Polymerization systems using water-soluble suspension stabilizers in the production of foamable polystyrene, such as polyvinyl alcohol (c * pat * 134 330 »A0 175 556)» do not allow the formation of a suspension of pearls with a sufficiently narrow size distribution and are therefore disadvantageous in terms of sorting *

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When using precipitated calcium phosphate as the stabilizer of suspension styrene polymerization, a slurry product with a narrow bead size distribution can generally be obtained under suitable mixing conditions. However, the prior art stabilization systems on this basis did not allow reliable production of a bead product with an average bead size greater than about 1 mm.

Anionic surfactants, as the most common modulators of precipitated calcium phosphate _f, result in the suspension of pearls of extremely low mean diameter.

The use of precipitated calcium phosphate with or without a modulator in suspension polymerization of styrene leads to loss of suspension stability and / or insufficient technological safety of the polymerization process.

Improvement in the quality of the expandable polystyrene due to the slurry product having a larger medium diameter pearls and their narrow distribution can be achieved by using a stabilizing system for the production of expandable polystyrene prepared by the process of the invention.

A process for the preparation of a stabilizing system for the production of a foamable polystyrene by suspension polymerization by precipitation of a tertiary sodium phosphate in a water-soluble calcium salt in the presence of a modulator, comprising using at least one water-soluble aliphatic or aromatic acid calcium salt. 20% by weight, preferably 1 to 5% by weight, based on the amount of sodium terephosphate, the water-soluble calcium salt of aliphatic or aromatic cartonic acids preferably being calcium salt of stearic acid, palmitic acid or benzoic acid or a mixture thereof

The foamable polystyrene here is the atrium of polystyrene, which contains a foaming agent such as low boiling hydrocarbons, or other additives such as flame retardants to reduce the flammability of the foam material, or modifiers of processing properties.

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Almost insoluble calcium salts of alkyl or aryl-cristoxylic acids include, in particular, calcium salts of stearic palmitic acid or its salts. mixtures obtained from stearin or a calcium salt of the benzoic acid type.

According to the invention, it is possible to obtain a suspension product of foamable polystyrene which contains 75 to 95% by weight of beads of optimum size for each type of commercial fraction. Distribution of pearl sizes _! this material is very narrow and practically free of extremely small diameter beads * The properties of the suspension product make it possible to produce commercial fractions of granulometric quality higher than the purity requirements of the individual fractions, as they contain less pearls of undesirable diameter *

The following examples illustrate the process of the invention:

Example 1

In a polymerization reactor (80 L) with a 80 Pfaudler type stirrer, a phosphate slurry stabilizer was prepared with stirring as follows: distilled water (70 ° C) 10 L sodium phosphate <40 g sodium chloride 50 g

After dissolving the sodium phosphate in heated water, calcium phosphate was precipitated with the indicated amount of calcium chloride with stirring. After diluting the stabilizer suspension with 20 liters of distilled water, the following components of the polymerization system were metered into the aqueous phase:

styrene 30 1 dibenzoyl peroxide 110 g tert-butylperbonzoate 25 g ^{232 171}

The polymerization batch was heated to a polymerization temperature of 90 ° C · The polymerization proceeded in a relatively unstable suspension · After the first and second polymerization hours, the unmixed sample completely disrupts the colloid system within minutes · Approximately at the third polymerization hour (65 to 75) % conversion) there was a loss of stability of the polymer slurry in the reactor resulting in separation of the organic and aqueous phases ·

Styrene polymerization cannot be completed as a suspension using the prepared suspension stabilizer.

Example 2

In a similar manner to Example 1, the preparation and polymerization of styrene was carried out except that water-soluble sodium dodeoylbenzenesulfonate was added as a modulator to the suspension stabilizer in an amount of 0.2% by weight, based on the suspension stabilizer.

Polymerization of styrene was carried out in a stable suspension. Upon reaching 75% conversion (£ 3.5 hrs), the stability of the suspension was increased by adding 1% by weight of sodium dinaphthylmethanedisulfonic acid, based on the stabilizer of the suspension and in a closed reactor after pressurization to 0, 1 MPa with nitrogen, 2000 g of pentane was metered in. · After 6 h of total polymerization time at 90 ° C, polymerization temperature was raised to 125 ° C, at which polymerization was carried out for 3 h · After cooling, centrifuging and drying the suspension, foamable polystyrene beads were obtained having a size of less than 0,5 mm, with a foaming capacity (ČSl 64 3006) of 14 g / l and an unreacted styrene content of less than 0,1% by weight ·

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Example 3

The foamable polystyrene beads were prepared according to the procedure of Example 2 except that calcium stearate dissolved in styrene was used as a modulator. Foams of expandable polystyrene were obtained whose mean size was dependent on the amount of calcium stearate as shown in the following table.

Calcium stearate medium size variation (% by weight) pearls (mm) coefficient (%)

15 Dec 1.0 21 10 1,2 15 Dec 5 1.6 20 May 2 2.4 22nd

Note: the amount relative to the suspension stabilizer d. K-aig in * k g-r · 100% d. ^ - the mesh size (mm) of an imaginary sieve through which just 1% of the bead product would pass.

The coefficient of variation characterizes the width of the pearl size distribution, which is very narrow, as documented by the values.

Example 4

By the procedure of Example 2, beads of expandable polystyrene were prepared except that 3% by weight of stearin was used as a modulator per suspension stabilizer dissolved in styrene. The acids contained in the stearin form calcium salts due to the excess calcium ions in the aqueous phase. Beads with a mean diameter of 1.8 mm and a narrow distribution (coefficient of variation of about 25%) were obtained.

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Example 5

Suepensable foamable polystyrene was prepared according to Example 2 except that calcium benzoate, formed by dispensing 1% by weight of dissolved benzoic acid in styrene, was added to the polymerization batch suspension stabilizer. narrow distribution (coefficient of variation 20%) ·

Claims (1)

P IS D OF THE INVENTION Process for the preparation of a stabilizing system for the production of foamable polystyrene by suepensive polymerization by precipitation of tertiary sodium phosphate in water-soluble calcium salt in the presence of a modulator, characterized in that at least one water-soluble calcium salt of aliphatic or aromatic carfeexylic acid in 0.5 up to 20% by weight, preferably 1 to 5% by weight, based on the amount of sodium phosphate, the water-soluble calcium salt of aliphatic or aromatic kavboyylic acids preferably being calcium salt of stearic, palmitic and / or benzoic acid or a mixture thereof ·