DE1769096A1 - Finely divided, expandable styrene polymers - Google Patents

Description

Finely divided expandable styrene polymers The present invention relates to finely divided expandable styrene polymers with silicone and a Powdering agents are coated.

It is known that moldings made from foamable styrene polymers can be used obtained when finely divided styrene polymers, which are a gaseous or liquid Containing propellants in non-gastight forms at temperatures above the boiling point of the blowing agent and the softening point of the polymer. In technology, a way of working has been introduced in which the expandable Particles from a storage container are fed to an apparatus as required, in which they are made to foam with steam at around 100 ° C. This one The process is called "prefoaming". The pre-expanded particles are after a storage chain from a few minutes to several days in a non-gas-tight closing mold further heated (foamed), whereby they weld to form a molded body.

From US Pat. No. 3,086,885 it is known to use the expandable Particles before prefoaming with 0.0005 to 0.05% (Weight percent) a silicone of the composition R2SiO, where at least 75 ffi (mol percent) «er R radicals are methyl groups to be coated in order to prevent the thus treated expandable styrene polymers with little adhesion and free in the pre-expanded state to get trickling particles.

However, this method has the disadvantage that particles with for the For the desired effect, sufficient quantities of such silicones are coated, essential it is less difficult to weld together to form moldings than particles without this coating, what z. B. higher susceptibility to breakage and lower tightness of the molded bodies obtained in this way against liquids to the pole. The same applies to those in the UK Patent specification 953 759 claimed class of thermoplastics not as plasticizers acting silicone types too.

It has been found that finely divided expandable styrene polymers, which contain at least 50 percent by weight of styrene polymerized and with a Silicone of the composition X2SiO are coated when the silicone has a viscosity of at least 50 centistokes at 250C, in an amount of 0.005 to 0.05 percent by weight (based on the weight of the styrene polymer) is present and 35 to 60 mol percent of R radicals are phenyl radicals and 65 to 40 mole percent of R radicals are methyl the pre-expansion result in non-sticking and free-flowing particles, which in the later Foaming to form very well-welded moldings.

Silicones whose R radicals consist of less than 35% phenyl groups, cause with decreasing content of phenyl groups increasingly worse Welding of the pre-expanded particles when foaming to form molded bodies. the Silicones present as a coating according to the invention can be ring-shaped or chain-shaped Possess structure. In the case of a chain-like structure, the chain ends can next to Phenyl and methyl groups still contain hydroxyl groups. The viscosity of the silicone should be at least 50 centistokes at 25 0C, since the lower viscosity silicone greatly impair the foamability of the expandable styrene polymers. Another advantage of these silicones over the mainly methyl-substituted silicones is that with the help of organic protective colloids produced expandable Suspension styrene polymers which are inherently worse in the pre-expanded state trickle as suspension trol polymers produced with the help of organic pigments, have their full flow capacity immediately after leaving the pre-expansion unit, if the starting material with the silicone containing many phenyl radicals according to the invention is overdone. A coating of mainly methyl substituted Silicone is much less effective with such styrene polymers.

If one uses silicones as a coating agent for self-extinguishing adjusted expandable styrene polymers, one must with increasing amount Growing impairment of the flame resistance of the foamed ones due to the silicone coating Finished products are taken in Knauf, however, when using the inventive Silicone types have a much lower it than silicone, Q% essentially only methyl groups contain.

It is known as a powdering agent N, N'-distearoylethylenediamine or Use zinc stearate.

Have expandable styrene polymers coated in this way optimal processability on automatically working pre-expansion, sieving and foaming systems (Molded body machines) 'because they are not just individual, but all of the desired Meet requirements: good flowability of the unfoamed particles, low Adhesion tendency during pre-expansion of the particles, good flowability of the pre-expanded Particles and excellent welding of the particles during expansion into molded articles.

For the purposes of the present invention, styrene polymers are polystyrene and copolymers of styrene with at least 50 percent by weight of polymerized Styrene. The following are examples of mixed polymerisation components: methyl styrene. Nuclear halogenated styrenes, acrylonitrile, esters of acrylic or methacrylic acid, N-vinyl compounds such as Vinylcarbazole, or even small amounts of compounds that are two polymerizable Contain double bonds, such as butadiene, divinylbenzene or butanediol diacrylate.

The expandable styrene polymers contain blowing agents, d. H. gaseous or liquid hydrocarbons or halogenated hydrocarbons under normal conditions, which do not dissolve the styrene polymer and whose boiling points are below the softening point of the polymer lie. Suitable propellants are, for example. Propane, butane, pentane, Hexane, cyclohexane, dichlorodifluoromethane. The blowing agents can be in the foamable Masses, e.g. B. in amounts between 2 and 10 weight percent, based on the polymer, be included.

The expandable styrene polymers can also contain other components included, e.g. B. flame retardants, such as tris (dibromopropyl) phosphate or hexabromocyclododecane or organic or inorganic fillers, dyes, antistatic agents or plasticizers.

The finely divided expandable styrene polymers can be in the form of pearls or as. Granules are present.

Example 1 Each 10,000 parts by weight of expandable polystyrene particles were made by mixing in an intensive mixer with the substances listed below overdrawn. With these mixtures and with uncoated material as a comparison The following tests were carried out: A. Comparison of the flowability of the non-foamed Particle: A metal funnel with an opening angle of 450, an upper diameter of 25 cm and a 10 cm long outlet pipe with 2 cm clearance was closed with the Spout filled to the brim with the material to be tested. Then the spout was opened and determines the time required for the material to flow out. Fttr every setting the MLltelert of five individual measurements was given in column a of the table.

B. Comparison of the degrees of welding achieved during foaming: Each 100 g of the material to be tested was pre-expanded to around 20 g / l in flowing steam. After 24 hours of intermediate storage, the pre-foamed material was used to form a mold with the Dimensions 19 x 19 x 4 cm3 filled. By forcing in 0.8 atmospheres of steam for 10 seconds moldings were produced from the mold contents, which after 20 minutes were removed from the Form were taken. After one hour of storage, the plates were broken checked what proportion of the particles located on the fracture surface are not along separated from their surface, but was torn through. The one from each The mean values obtained from three experiments are listed in column B.

Table 1 Coating of the Particles Column A Column B Silicone Powdering Agent Flowability Welding of the non-foamed foam particle panels Seconds 4 parts by weight methylphenylpoly- - 30 80-90 siloxane a 4 parts by weight methyl- + 6 parts by weight N, N'-Di- 26 80-90 phenylpoly- staroylethylene-siloxane a diamine 6 parts by weight methylphenylpoly- - 44 90 siloxane a 6 pbw methyl + 12 pbw N, N'-diphenylpoly- stearoylethylene- 32 90 siloxane a diamine 20 parts by weight methylphenyl poly- - - 90-100 siloxane a 4 parts by weight methylphenyl poly- - 31 50 siloxane b 1 pbw dimethyl- - 28 40-50 polysiloxane 4 pbw dimethyl- - 31 20-30 polysiloxane 4 parts by weight dimethyl + 6 parts by weight N, N'-di- 26 20-30 polysiloxane stearoylethylenediamine uncoated particles 26 80-90 approximate numerical proportion of the phenyl groups methyl groups ii molecule methylphenylpolysiloxane a: 50% 50% Methylphenylpolysiloxane b: 20% 80 «Even with a relatively large amount of coating is not an impairment with methylphenylpolysiloxane a, but rather another one Determine improvement in the degree of fusion of the individual pre-expanded particles. In contrast, the degree of welding decreases even with the addition of minimal amounts of dimethylpolysiloxane sank. The methylphenylpolysiloxane b also gives unsatisfactory degrees of welding.

Example 2 Each 10,000 parts by weight of expandable polystyrene beads are in an intensive mixer with 4 parts by weight of a silicone and 6 parts by weight coated with a powdering agent.

Then the mixtures are fed into a pre-foaming device through a dosing system of the Rodman II type continuously feeds and itt flowing steam to a bulk weight of about 45 g / l pre-expanded. Shortly after leaving the pre-expander the particles in a sheet metal cylinder with a diameter of 30 cm and a height filled from 50 cm. The filled cylinder is at a speed of 20 cm / sec pulled up. The filling spreads to a cone of rubble, its Base width represents a measure of the flowability of the pre-expanded particles.

Table 2 Coating base-through-weight silicone powder knife of the percentage (each (cm 4 parts by weight - 6 parts by weight) parts) 1. - 102 5 siloxane a 2. methyl- N, N'-distearoyl- 110 0 phenylpoly- ethylenediamine siloxane a 3. Dimethyl- N, X'-distearoyl- 94 0 polysiloxane ethylenediamine 4. without 78 10 coating 7 The pre-expanded particles became even the smallest for complete separation Agglomerates passed through a rotary sieve with a mesh size of 3 mm. They turned out bad trickling mixtures 3 and 4 so much residue after a short time that the sieve to Cleaning had to be shut down, while the well-trickling mixes worked perfectly Allowed separation of the agglomerates.

The screened pre-foamed material was stored after 24 hours Molded parts are produced on a molding machine, where Fn is the degree of welding Similar differences appeared, as set out in Example 1.

Example 3 Per 10,000 parts by weight of expandable polystyrene. of Bead size range 0.8 to 2 am containing 2.5% hexabromocyclododecane each with 1 part by weight of one of the silicones listed below in one Intensive mixer coated. Then the pearls are poured in steam to a bulk weight of 20 g / l pre-expanded. After one day of intermediate storage, the samples are opened Usually processed into Scheumatoff blocks, which are 2 cm thick after 24 hours Plates are cut up.

The fracture weld is carried out according to Example 1 on some of the plates determined (column 2), the other part is freed from the edge zones and then 24 Degassed in vacuo at 600 hours.

After cooling, the panels are used to determine the afterburn time ignited in a draft-free space. The average value from 10 measurements is in column 3 specified.

For comparison, the tests are carried out with uncoated material executed.

Table 3 Coating fracture welding Afterburn time outside / inside Dimethylpolysiloxane 30 - 40% / 8.6 sec.

10 - 20% methylphenylpolysiloxane (methyl: phenyl groups number 80 - 90% / 2.5 sec. Moderately like 3: 2 70% without coating 80% / 70% 0.5 sec.

In contrast to the coating with dimethylpolysiloxane impaired Methylphenylpolysiloxane only slightly reduced the flame retardancy of the material samples the welding of the particles not at all.

Example 4 1000 parts by weight of expandable 5.8% pentane Polystyrene beads with diameters between 0.4 and 0.7 mm, made with the help of an organic Protective colloids are prepared in a mixer with the in Table 3 listed coating agents coated. Then the pearls are in a 1000C hot air stream with constant stirring to a bulk density of 80 g / l, which takes 3 minutes. Then coarser parts are made using a Sieves with a mesh size of 2 mm away. After one hour of intermediate storage the material is pneumatically filled into a shape that has a round, 90 mm high vessel with a diameter of 80 mm and a wall thickness of 2 mm results. The filled form is placed under a pressure of 2 atmospheres for 1.5 seconds Steam preheated. Then the contents of the mold are injected for 1.5 seconds welded by steam.

After cooling with water, the molded body is removed from the mold. After three days of storage, it is tested for breaking strength by the vessel wall long as it is pressed susavxen until the vessel wall ruptures. The distance is measured Opposite parts of the vessel wall where it begins to break (Mean value from 10 measurements).

Table 4 Coating distance (GT = parts by weight) (without deformation 76 mm) 1 part zinc stearate 53 mm brittle fracture 1 part zinc stearate + 61 mm brittle fracture 0.4 Part by weight of dinlethylpolysiloxane 1 part by weight of zinc stearate + less than 15 mm not brittle-0.4 part by weight of methylphenyl poly- break, but light siloxane with a phenyl group breaking portion of about 45 mole percent. 13. Dimethylpolysiloxane caused by zinc stearate Increased embrittlement due to its incompatibility with polystyrene, eliminated the higher phenylated methylphenylpolysiloxane due to its compatibility with Polystyrene completely this effect.

In the same way, beads are made with the help of inorganic suspending agents and brittle because of the residual content of suspension aid Shaped bodies produce elastic ones after coating with more highly phenylated silicones Molding received.

Claims (1)

Patent claim Finely divided expandable styrene polymers that contain at least 50 percent by weight of styrene polymerized and with a powdering agent and a silicone of the composition R2SiO are coated, characterized in that because * the silicone has a viscosity of at least 50 centistokes at 25 ° C, in one Amount from 0.005 to 0.05 percent by weight (based on the weight of the styrene polymer) and 55 to 60 mole percent of the R groups are phenyl groups and 65 to 40 mole percent the radicals R are methyl radicals.