NO129910B - - Google Patents

Description

Process for the production of porous, shaped objects from expanded polystyrene.

The invention relates to a method for the production of porous, shaped objects (foam plastic) which are produced by extruding expandable polystyrene.

Expandable polystyrene is a polymer of styrene, which contains homogeneously dispersed 2-20% by weight of a propellant which is normally a liquid or gaseous hydrocarbon, insoluble in polystyrene, or a halogenated hydrocarbon, which is soluble or insoluble in polystyrene.

When conventionally producing thin plates (sheets)

of expanded polystyrene (foamed polystyrene) from expandable polystyrene, the sheets become inhomogeneous due to the stresses produced during extrusion. During the extrusion, the change also takes place that the propellant, which is initially dispersed inside the polymer, collects in relatively large bubbles which are elongated in the direction of the extrusion. These give the material a high degree of stiffness and a low degree of isotropy.

In order to avoid these disadvantages, it has been proposed to incorporate "nucleating agents", i.e. substances which interact with the propellants and promote the development of microbubbles of gas from the propellants, which bubbles remain homogeneously distributed. The plastic thereby gains better properties, such as e.g. absence of tensions,

an extremely low volume weight, high flexibility and high elasticity.

The best-known nucleating agents that have previously been used are silicon dioxide, silicates, boric acid and organic acids, such as citric acid, in combination with substances that can release carbon dioxide (see e.g. NO-PS 96 081). However, these known nucleating agents have the disadvantage that they do not enable a setting or regulation of the volume weight of the expanded product. The addition of a large amount of citric acid, e.g. from 0.5 to 1.5 percent by weight, together with a corresponding amount of NaHCO-j, does not, as expected, reduce the volume weight of the foam plastic. On the contrary, an increase in the amount of citric acid in certain cases leads to an increase in the volumetric weight. It is therefore difficult, if not impossible, to obtain an expanded material with a specific volumetric weight, when starting from a material to which one of the above-mentioned nucleating agents has been added.

From GB-PS 986035, nucleating agents of another type are known, namely copolymers containing acid groups. These are produced by copolymerizing aromatic monomers, especially styrene, with monomers containing acid groups such as acrylic acid. Optionally, the copolymer can be neutralized with NH3 (claim 2). According to this patent, however, COj-releasing substances are not added, and it is recommended to introduce the propellant into the mass in the actual

the extruder^cia^mHl? thus relates to a method for the production of semi-synthetic 6-acylaminopenicillanic acid, the method is characterized by the raw material reacting. 6-,im.ino!>eni cillan-The present invention is thus directed at a forward acid with.N-acylsaccharins.with.the.general form!

feed for the production of structures from foamed polystyrene, whereby expandable polystyrene beads are extruded after til-CO

mixture of a ✓nucleating-,^ acid group-containing copolymer, and the method is characterized by extruding a mixture containing<1>^

hv<ai)i ''ø}:2l -b(5t:d'érer^tffror<tTi'rmsv.i5sal05l5itudT?i5 délétojyaty. a copolymer

of acrylic- étLlert metak^lSyrtet ©gs«madkyA&^^^ einrom e n 'me&afcr-yl syr;él f <ir ih v.M'kene copolymerl rsyr.emohomerehs mt g j &rn mir^stt enlSolVektpYoTaen^aroiger for these groups in other compound has already been synthesized and described in the literature _/~Ber. 19, 1400f-i b)c\0,-2/Tm 5c-,deler7 of, .a carbonateT or, hydrogen carbonate of, (lirdb)yj".Km.^u^. -jj,7tH\xy}z>) 3Journal chemrDOC. i9^y, t>ide Ua sodium, potassium or ammonium, all parts being parts by weight per

lOO weight deaefc^lyfcst^r1eria.acyl derivatives are compounds with 3 acyl residues at the nitrogen atom. In the turnover with 6-APS, only deÆ^jSJ^as^^^ is transferred

opPos/^lervln^^ is that they- Fepj& Mfc& e Bp^ nnehpl^ Brgrm^ lome£ kog3rl0£ $ £& ?F???& r*^&k^JM^^J^^^^etlC^n^^ ^,^ due to their bacterial spectrum with authentic comparison preparations. The reaction of the alkali metal carbonates or hydrogen carbonates or the active acyl derivatives with 6-APS takes place using ammonium carbonate or hydrogen carbonate preferably at room temperature or under ice cooling. As ;in a small excess in relation to the acid groups 1 nucleating solvent, anhydrous ones can be used, such as e.g. methylene-klcmi&l^^ ;nite<g>jie<t>tetrahydrofuran. The penicillins formed below are recovered in the usual way. ;It polym^«^i«%S^&t><e\4^ dare ^rfeA^^ntmneit Anende aktsAandeti^y<i>^A<g>^Æ^ ^^Klft^^eM^t^s^ ^e^^i^e^n^ avWI^&Mfl&WlSfcMil^\^^^%^^^ PaXi^ rhAte Ek^l^ajb^en, either fttr or during the extrusion operation. ;a) Fj^tJf-ijH^°9the nucleating agent, as well as the substance 2eom is ;and ±<cf ©sveien teiStnt^Éfe of 18 g of a-phenoxy-propionyl chloride and 15 ml of acetone. It was then boiled £ hour. The porous, shaped objects of expanded polystyrene which are produced according to the invention have a low volume weight and a homogeneous distribution of the cells, which are all small and of practically the same diameter. This gives the expanded material great flexibility and elasticity. "Polystyrene" in this connection means a homopolymer of styrene, or a copolymer of styrene and other copolymerisable monomers, which copolymer contains at least 50% by weight of styrene. The propellants can be incorporated into the polystyrene in different ways, during or after the polymerization of the styrene, and they can be liquid or gaseous. ;As liquid propellants, it is preferred to use hydrocarbons or halogen-substituted hydrocarbons, alone or in a mixture with each other, whereby the boiling points at atmospheric pressure are between 20 and 100°C. These propellants are usually not solvents for the polystyrene, but can possibly cause it to swell. Propane or butane, or chlorofluorohydrocarbons, derived from methane or ethane are preferred as gaseous propellant. Some of these gaseous agents are capable of dissolving the polystyrene. The preferred propellants are pentane or a petroleum ether with a boiling point of between 30 and 60°C. '. ;i;.«■•• ;The polystyrene can be extruded through a conventional extruder, i.e. one of the extruders that are usually used for extruding such polymers. ^ ;The invention will now be illustrated by an example.

In the following table, the volume weight at 25°C of expanded polystyrene has been compiled which has been obtained by extrusion at 14o°C of 100 parts expandable polystyrene in the form of beads with diameters between o, 5 and 1.5 mm and containing 5% petroleum ether ( boiling point between 30 and 56°C), previously mixed. The polystyrene was also mixed with one or more nucleating agents:

Experiments 1 to 3 ....... citric acid (comparative experiment) Experiments 4 to 6 ....... citric acid + NaHCO^ (comparative experiment) Experiments 7 to 9 ....... potassium metasilicate (comparative experiment) Experiment 10 to 12 ..... copolymer of 89 parts by weight acrylic acid and 11 parts by weight 2-ethylhexyl acrylate Experiment 13 to 15 copolymer as indicated above + NaHCOj.

Experiments 1 to 9 deal with known nucleating agents and are included as a basis for comparison, while experiments 10 to 15 make use of nucleating agents according to the invention.

In all the experiments, a laboratory extruder of the NRM type (National Rubber Machines, USA) is used, which has a diameter of 2.54 cm, a ratio between the length and the diameter of 8, and a cross section of the main nozzle of 2 x 15 mm.

For each of the resulting expanded polystyrenes, a wet photograph was taken using a RECHERT MF microscope, using transmitted light under normal illumination, with a magnification of 20 times and on a cross-section with a thickness of 0.5 mm. From the results obtained with the known nucleating agents (experiments 4 to 9), it can be seen that in one case there is a decrease in the volume weight of the expanded polystyrene when the amount of the agent is increased (experiments 4 to 6), while in a other case (experiments 7 to 9) is no effect. When the nucleating agents according to the invention are used, on the other hand, a reduction in the volumetric weight is obtained when the amount of the agent is reduced (experiments 13 to 15).

When the known nucleating agents are added in an amount greater than 0.5 parts per 100 parts polystyrene, it is assumed on the basis of the above results that they behave like a mineral filler and thus lead to an increase in the bulk weight (ie they are not able to promote and regulate the propellant). The nucleating agents according to the invention have the opposite effect, in that in amounts above 0.5 parts per 100 parts polystyrene act as real nucleating agents, whereby they regulate the expansion of the propellant.

The internal structure of the product corresponding to tests 1 to 15 is shown in the photographs taken, on the basis of these photographs it is possible to get a close understanding of the structure and uniformity of the cells formed inside the material. One can thus deduce the following from the photographs:

a) Experiment with citric acid alone (experiments 1 to 3)

The presence of citric acid causes a more regular distribution of

the bubbles in the mass, but it is in no way sufficient to produce a regular three-dimensional structure.

b) Experiment with citric acid and bicarbonate (experiments 4 to 6)

The distribution of the bubbles inside the mass is more limited and

regular than with citric acid alone.

c) Experiment with metasilicate alone (experiments 7 to 9)

In this case the structure is more regular than the structure

of expanded polystyrene produced without a nucleating agent»However, it is still inhomogeneous and very similar to those products,

which is produced using citric acid alone.

d) ■ Experiment with a copolymer of acrylic acid and ethylhexyl

, acrylate (forsbk 10 to 12)

• In this case the structure appears to be regular, but forward

brought by cells with a relatively high rate of movement. In this case, the bulk density, although high, decreases with increasing amounts of nucleating agent.

e) Experiment with a copolymer of acrylic acid mixed with NaHCO, (experiments 13 to 15)

The cell structure is regular as in case b, but in this

trap decreases both the cell size and the volumetric weight when the amount of nucleating agent increases.

Claims (1)

Process for the production of structures from foamed polystyrene, whereby expandable polystyrene beads are extruded after the addition of a nucleating, acid group-containing copolymer, characterized by extruding a mixture containing a) 0.2-5 parts*, preferably 0.5 - 1.3 parts, of a copolymer of acrylic or methacrylic acid with an alkyl effect of acrylic or methacrylic acid, $ of which the copolymeric acid monomer constitutes at least 50% by weight late ,\ and b) 0.2-5 parts of a carbonate or bicarbonate of sodium, potassium or ammonium, all parts being parts by weight. 100 parts by weight polystyrene.