DE1569162C - Foamable molding compounds - Google Patents

Description

than 5 cP at 25 ⁰ C. Purified petroleum fractions of a test gasoline similar manner, but which are odorless, can be also used.

The amount of the liquid hydrocarbon additive is not more than 5%, e.g. B. up to 3 ° / ₀ , based on the weight of the polymer, for example 0.1 to 2 ⁰ I ₀ , or 0.2 to 1.5 percent by weight. Good results have been obtained at amounts of about 0.5 or 1 percent by weight.

The liquid hydrocarbon additive can be added in any suitable manner. For example the particles of a foamable polymer can be mixed with the appropriate amount of additive shaken or immersed in the additive until it is sufficiently absorbed. at Another possible way of working ensures that the hydrocarbon additive is present at least during the last stages of a suspension process in which the foamable Polymer is formed so that the additive is incorporated into the polymer particles.

It has been found that when the hydrocarbon additive is added to the foamable polymer particles, for example by shaking, excellent results are obtained when the particles also contain a small amount, e.g. B. 0.1 to 1.5 percent by weight, in particular 0.2 to 1 percent by weight, based on the polymer, of a finely divided inert solid, in the form of a surface coating of the particles. The preferred inert solid is silica (silica); other solids that can be used are e.g. B. aluminum oxide, zinc stearate, chalk, titanium dioxide, talc, calcined tori or a wax. The inert solid preferably has a particle size of less than 25 μm and is applied, for example, to the particles by a drum method after the hydrocarbon additive has been added. The foamable particles of polystyrene, a volatile blowing agent from 0.1 to 3 percent by weight, based on the weight of the polystyrene, liquid aliphatic hydrocarbon additive and from 0.1 to 1.5 ° included / ₀ silica, are particularly useful.

The foaming and molding processes can be carried out in a conventional manner. The foamable ones Particles can e.g. B. by steam, hot water, hot air or by the action of a Infrared radiator are heated. The foamed beads obtained are preferably thereby conditioned to be exposed to ambient air for a day or two before a compression molding process be subjected. For this purpose, a suitable shape is wholly or partially foamed with the Beads filled and sealed and then through .openings in the mold walls Steam initiated. After foaming has ended, the supply of steam is turned off and it is left in the Let the mold cool before opening the mold. The object obtained, e.g. B. a block becomes so strong cooled so that there is no "bulge" when the mold is opened.

The cooling time of the compression molded article made from foamable particles according to the invention is significantly less than the cooling time required when otherwise identical foamable polymer particles are used which do not contain a liquid aliphatic hydrocarbon additive according to the invention. Although 'the cooling time of a compression molded article depends to some extent on its size, it has been found in numerous cases that the cooling time e.g. B. is between 30 and 80 per cent of the "normal" cooling time; 40 to 70 ° / ₀ , e.g. B. 50 or 60 ° / _{0 of} the normal cooling time are often sufficient.

The invention is illustrated by the following example:

example

The example describes foamable polystyrenes according to the invention and the production of a foamed one Polystyrene molded body. It also shows the improvement in cool down time obtained in accordance with the present invention was obtained.

Foamable .Polystyrene particles which contain a pentane blowing agent were first mixed in a double-cone drum mixer with 1 percent by weight, based on polystyrene, of white spirit having a boiling range from 150 to 200 ^° C. and then with 0.5 percent by weight of finely divided silicon dioxide.

a ₅ Another batch of particles was treated in the same manner using only ¹ J ₂ percent by weight of mineral spirits and in a similar manner using Va weight percent n-decane instead of mineral spirit as an additive. In all cases, after treatment with the hydrocarbon, the particles were treated with 0.5 percent by weight silicon dioxide in a coating drum.

Each batch was foamed in a steam atmosphere for 4 minutes and then left to dry in an open drying cabinet for a day. A control sample of beads that had not been treated with a liquid hydrocarbon additive was foamed and dried in the same manner. A certain amount of each batch of the foamed beads was placed in a mold and formed into a block with a volume of 0.02832 m ³ by introducing steam through several holes in the walls of the mold, so that a pressure of about 0. 98 kg / cm ^{3 was} produced. The block was allowed to cool and removed from the mold as soon as the mold could be opened without the block bulging. Several compression molding procedures were used to determine the minimum cool down time for each batch. The minimum cooling time and the density of the molded block are each listed below.

Liquid
Hydrocarbon
Additive crowd
Weight
percent Density of
Blocks
(g / ccm) Cooling
time
(Minutes) (Comparative
. attempt)
no 1
0.5
0.5 0.012
0.016
0.015
0.015 20th
4th
5
12th Mineral spirits
White spirit ■
n-decane

All of the compression molded blocks had good physical properties. These results show that after Invention, significant improvements in cool-down time could be achieved.

Claims (1)

1 2 Additions are all above 150 ⁰ C. This means Claim: that the subject matter of the invention contains the special additions at the usual foaming temperatures Foamable molding compounds made from hydrocarbons or resins remain essentially liquid, while those containing vinylaromatic foaming agents are foamed through the volatilization of the polymers for this purpose, the customary foaming agents identified thereby,
η et that they are additionally 0.1 to 5 percent by weight. This means that the hydrocarbons with 9 to 11 carbon added to the resins according to the invention, based on the polymer weight, aliphatic hydrocarbons with 9 to 11 carbon additives have a completely different function than atoms and boiling points at atmospheric io the additions of Belgian patent 555 654.
Pressure between 150 and 200 ⁰ C, or an aliphatic From USA. Patent 2,989,782 it is already included diagram petroleum fraction which exceeds known, to avoid the risk of breakage during Entwiegend a mixture of these hydrocarbons assume the foamed moldings of the shape of the fabric. the foamable masses means with plasticizer ■■ 15 effect to be added. Besides that this Additives have a completely different function such additives, especially diethylbenzene or mineral oil, have the significant disadvantage that they The invention relates to foamable molding compositions which make foamable compositions sticky and thereby from vinyl containing hydrocarbon propellants make handling difficult in an annoying manner, aromatic polymers. A note that by using others, there A foamed vinylaromatic polymer, substances not mentioned, those provided according to the invention such as foamed polystyrene, is a task in a surprisingly simple and effective Article of industrial importance especially in the full way can be solved, is this counter In the form of blocks that cannot be removed in plates or other form-keeping. pieces can be cut. Foamed poly- Particularly valuable results are obtained Styrene blocks are usually made by a process if the vinylaromatic polymer is polystyrene Manufactured with the foamable particles that is in itself. However, it can also be, for example, a be essentially made of polystyrene and a volatile toughened polystyrene, a polymer of a Propellants consist, by exposure to heat, 30 substituted styrene, such as alpha-methylstyrene or be expanded in this way to create a »prepolymer of a styrene with a smaller one foam «of foamed beads. This ge proportion, z. B. 10 or 20 weight percent, one foamed beads are converted into a suitable form of ethylenically unsaturated monomers, e.g. B. one brought and by means of steam in a molding acrylate such as methyl methacrylate, acrylonitrile. or drive heated, with an expansion and co-35 butadiene. Closure of the pearls takes place and a block corresponding to the shape of the volatile propellant is produced. This substance propellant. Under normal conditions, the process can work well in principle, but a hydrocarbon propellant is gaseous or an improvement in some respects is possible; so would be liquid, and for example butane, or it may be advantageous, for example, the time, which is sometimes 40 pentane. Preferably, it is essentially one needed for the block to cool before the butane or pentane fraction. Typically, up to this can be safely removed from the mold, about 10 ° / ₀ of the blowing agent to shorten based on the weight (Mindestformverweilzeit). It has now been found that the polymer is present, for example 3 to 10% more, that an improvement in this additional layer can be achieved if the foamable, one of the components of the foamable bare Polymer is also certain hydrocarbon resin according to the invention, is of course contains substances. significantly less volatile than the propellant used The subject of the invention are therefore foamable agents. Molding compounds made from hydrocarbon propellants, however, are by no means non-volatile, as the liquid aliphatic hydrocarbon additives-containing vinylaromatic polymers, which are characterized by the fact that they additionally show 0.1 to 5 weight properties given above. The liquid percent, based on the polymer weight, of aliphatic aliphatic hydrocarbon additive has, for example, in table hydrocarbons with 9 to 11 carbon atoms, generally a viscosity of not more than 12 cP atoms and boiling points at 25 ° C at atmospheric. Mixtures of hydrocarbon pressures between 150 and 200 ^° C. or an aliphatic substance can be used. A particularly useful fraction of petroleum which is predominantly a mixture is the aliphatic petroleum fraction which is a mixture of these hydrocarbons. as paint or white spirit is known and largest-off Belgian Patent 555,694 are comparable partly contains Cj-Cn-paraffin hydrocarbons, welschäumbare molding compositions made from styrene polymers before substantially in the range of 150 known to 200 ⁰ C, a volatile blowing agent and a 60 boil. However, this gasoline can also contain components of hydrocarbons with 7 carbon atoms and one that has a boiling point above 95 ^° C. outside this boiling point. With those in the area. For example, 98 weight Belgian Patent additives mentioned is percent of a suitable mineral spirit at above it is typical blowing agent whose boiling point is 135 ° C, 95% above 150 ⁰ C, _85/0 lie ° below 200 ⁰ C below 100 ⁰ C. In contrast, it is 65 and 97 ° / ₀ below 220 ⁰ C boil. A viscosity of about 1 cP at 25 ° C. for the additives according to the invention is normal for such a paint or tive which is added to white spirit in addition to conventional propellants. Preferably its viscosity will be. The boiling points of these according to the invention are not greater than 10 cP and in particular not more