CS268871B1 - Method of self-extinguishing foamingpolystyrene by means of radical polymerization in suspension - Google Patents

Abstract

A method for producing a flame retardant foam organic polystyrene based brominated compounds by polymerization in auapenzl in which it is polymerized the dispersion stabilized with precipitated phosphate calcium, based on that the size of the suspension product is controlled by the moment of dosing organic brominated compounds to polymerization and is within the range of styrene conversion 5 to 75% by weight.

Description

The present invention relates to a process for the production of flame retardant polystyrene to base-organically precipitated compounds containing at least 40% bound bromine by slurinating in which the polymerization dispersion is stabilized by the calcium phosphate. This manufacturing process makes it possible to prepare a high-content suspension product of the desired bead size, in particular a 1.0-2.5 mm fraction.

Individual areas of application of flame retardant polystyrene require a suspension product at a certain * and for a given size range of the pearl.

For the production of large-scale blocks or thickening plates, a foamable polystyrene of bead size from about 0.5 to about 2.5 is suitable, and a bead size of 0.5 to 1.0 * or 0.5 is used to produce shaped articles. - 0,7 mm in the case of thin-walled articles. The influx of beads smaller and larger than the optimum bead size range affects the negative process of foamable polystyrene processing and product quality. for this reason, the suspension product from polyseration is classified into fractions according to size - commercial types of expandable polystyrene.

The quality of these types of foamable polystyrene does not only depend on the machine parameters in terms of the sharpness of the screening, but also on the granular-tetriisuspension product. With the spreading size distribution of the suspension product, the size of the beads in the sorted fractions is increasing. In addition, the suspension products with a wide bead size distribution provide an increased amount of secondary polystyrene-based foamable applications. For these reasons, it is necessary that the polymerization suspension product has as close a distribution as possible to the bead size with a maximum pearl frequency of the desired diameter. In flame retardant expandable polystyrene, the most widely used application area is the production of large volume blocks for which a 1.0 - 2.5 mm bead fraction is used. The polymerization suspension system used largely determines the granulometry of the suspension polymerization product and hence the quality of the flame retardant polystyrene flame retardant grades.

Polymerization systems employing water-soluble suspension stabilizers such as polyvinyl alcohol (Nos. 134-330) do not allow the formation of a pearl suspension with a sufficiently narrow distribution and are therefore unsatisfactory in terms of sorting quality and main yield fraction. The slurry products of the flame retardant foamable polystyrene with narrow bead size distribution can generally be obtained by stabilizing the calcium phosphate precipitated suspension in conjunction with modulators such as persulfate, sodium salts of alkylaryl sulfonic acids, water-soluble calcium salts of aliphatic or aromatic carboxylic acids and the like. AO 232 171, CSO AO 1756). However, these processes do not allow the production of flame retardant polystyrene having a mean bead size of more than 1 mm, since the use of organic flame retardants reduces the diameter of the bead formed before or at the start of the polymerization. By attempting to increase the diameter of the bead, it reduces the concentration of stabilizer or modulators, deteriorating the stability of the polymerizing system, which is accompanied by a bead of irregular shape and widening of the distribution curve. The dosing of the suspension stabilizer during the polymerization (00S 26 38.839) also appears to be unfavorable since a product with an expanded bead size distribution is produced and, in addition, in the field of conversion where stabilization is required to obtain a product of the size of the beads is less than 1 mm, the mean size of the beads is strongly dependent on the time of dosing of the phosphate stabilizer.

A suspension product of flame retardant expandable polystyrene with a narrow bead size distribution with a bead diameter greater than 1 mm can be prepared by the process of the invention. It is a process for the production of flame retardant polystyrene based on organic pelleted compounds containing at least 40% bound bromine by sus-retarding polymerization in which the polymerization dispersion is stabilized by precipitated calcium phosphate * CS 268871 B1, with one or more modulators added to the polymerization system. one or the wolf doses at the beginning or during the polyaeration, at the latest at the conversion rate of 85%, characterized in that the size of the slurry product bead is controlled by the moment the organic compound is added to the polymerization mixture in the monomer conversion range of 5 - 75%, preferably 5 - 50%. % by weight. The basic mono-styrene component of styrene may be used alone or in admixture with other woolly monomers such as n-methylstyrene, acrylonitrile or divinylbenzene, the styrene content being the! than 50% of respondents. Conventional radical initiators may be used to initiate polyaeration, for example organic peroxides or azo compounds. As the flame retardant, an organic bromine compound with a bound broau content of over 40% is used. Suitable retarders are, for example, 1, 2, 5, 6, 9, 10-hexabroacyclododecane, 1,2,3,4,5-pentabroa-6. chlorocyclohexane, 1,2,5,6-tetrabroacyclooctane, dibromoethyl dibromocyclohexane, dosed in an amount of 0.2-20% by weight, the effectiveness of the flame retardant is enhanced by the addition of conventional synergists such as organic peroxides with a half-life and at least 2 hours at 100 ° C .

The suspension-precipitated calcium phosphate stabilizer is used in conjunction with modulators such as potassium persulfate, anioactive surfactants with sulfo or sulphate, i.e., alkali metal salts of alkyl and alkylaryl sulfonic acids, alkyl with alkali metal alkylaryl sulfates. Another suitable modulator is calcium saliphatic or aroaatic acids. These nodulators can be used either alone or in combination with each other in a total amount of 0.01-2.0% by weight, based on the amount of suspension stabilizer.

Low boiling and aliphatic hydrocarbons, preferably a mixture of n - and isopentane, are used as blowing agents in the process of the invention. The polymerization system may further comprise various modifiers of physical, mechanical or processing properties.

According to the present invention, a method for producing a flame retardable expandable polystyrene according to the present invention is to produce a slurry product comprising 94-98% of the major commercial fractions and of which 75-90% of the preferred type. The narrow pearl size distribution of the slurry product makes it possible to produce commercial types of foamable polystyrene with high screening sharpness, that is to say with minimal bead content of undesirable size. The advantages of this method of production are documented in the following examples. Example i. (Comparative) Phosphate suspension stabilizer was prepared under stirring in a Pfaudler-type reactor (8011) as follows: To 10 L of distilled water submitted to 60-70 ° C was added. 40 g of phosphate sodium and, after dissolution, 50 g of calcium chloride. The stabilizer slurry was diluted with 20 l of distilled water and additional components of the polymerization system were added to the aqueous phase: styrene 30 1-benzoyl peroxide 110 gter. butyl perbenzoate 20 ghexabromeyclododecane 160 gdicylyl peroxide 80 g and a potassium persulfate modulator of 0.06 g, ie 0.15% by weight based on dicalcium phosphate.

The polymerization batch was heated to a polymerization temperature of 90 ° C. polyaeration was stable. At a conversion of 75% by weight, 0.4 g of dinaphthalate-ethanedisulfonic acid sodium salt was added, and 2000 g of pentane was charged into the closed reactor after nitrogen pressure was 0.1 MPa.

After 6 hours of total polymerization time at 90 ° C, the temperature was raised to 120 ° C and polymerized for 3 hours at this temperature. After cooling and isolation, a CS 268871 81 3 slurry was obtained with an average size of 0.51 mm with a yield of only 49% of the major fractions and from this only 3% of the most significant fraction.

Granulometry Refer to Table 1. Example 2 (Comparative)

The procedure of Example 1 was repeated with the difference that the potassium persulfate modulator was reduced to 0.011 g to 0.03% by weight (based on the stabilizer). The resulting product had a mean bead size of more than 1 mm, but contained an increased amount of deformed beads and, as a result of the Sirius distribution, the bead size 1 increased the amount of minor fractions. Granulometry See Table 1. Example 3 (comparative)

The procedure of Example 1 was repeated with the difference that the potassium persulphate modulator was not fed to the polynerization feed. The suspension product had a higher mean size than the desired optimum and contained a significant proportion of deformed beads. The yield of the main fractions was only 75% by weight (65% for the production of blocks and 10% for the production of tubes). Granulometry is shown in Table 1. Examples 4 to 7 of Example 1 were repeated with the difference that the bromine compound hexabromocyclododecane was fed to the polymerization system at styrene conversions of 15% (Example 4) 30% (Example 5), 40 % (Example 6) and 50% by weight (Example 7). Suspension products were prepared with a yield of the main fractions of 94-97%, of which 75% of the fraction for the fittings (0.5-1 ··) in the procedure of Example 4 and 77-90% by weight of the fraction for the production of blocks (1, 0 - 2.5 mm) for the procedures of Examples 5-7. Granulometry is shown in Table 1.

The quality of flame retardant polystyrene has not been influenced in terms of flammability. Example 8

The procedure of Example 1 was repeated, with the difference that the accumulated compound hexabromocyclododecane was fed to the polymerization system at a styrene conversion of 30% by weight and the potassium persulphate modulator was added in two portions: 0.04 g at the start of the polymerization and 0.04 g at the conversion styrene 50%. The suspension product had a 98% yield of the main fractions, of which 78% was a fraction for the production of blocks. 4 CS 268871 B1

Table 1 Effect of Conversion in Dosing of Organic Brominated Compound and Modulator on Bead Size and Recovery of Major Types of Foamable Polystyrene * Example HBCD Additive Conversion (% by weight, Perforated Potassium /% w / w) Medium Sphere / mm / v.k. ✓V Main types yield /% weight / 1 0 0.15 0.51 25 49 2 0.03 1.30 43 88 3 0 0.00 1.95 36 75 4 15 0.15 0.88 25 96 5 30 0.15 1.30 27 97 6 40 0.15 1.40 28 94 7 50 0.15 1.60 25 94 8 30 0.10 at the beginning + 0.10 at 50% no conversion i 1.28 20 98

Remarks: HBCD hexabroncyclododecane

The amount of potassium Iranian pen is based on the suspension stabilizer 84 "d16 v.k. coefficient of variation - 100 (d / size / mm / imaginary sewn, which was even 1% pearl product). The coefficient of variation characterizes the sulfur pearl distribution.

Claims (1)

SUMMARY OF THE INVENTION A process for the production of flame retardant polystyrene based on organic brominated compounds containing at least 40% bound bromine by suspension polymerization, wherein the polymerization dispersion is stabilized with precipitated calcium phosphate in the presence of one or more modulators added to the polymerization system in one or more at the beginning or during the polymerization at the latest at a styrene conversion of 85%, characterized in that the bead size of the slurry product is controlled by the moment the organic pelleted compound is metered into the polymerization mixture at a styrene version of 5 to 75%, preferably 10%. up to 50% by weight »