DE2945856A1 - Sheets prodn. from highly exothermically foaming polymers - where foamed mix is immediately cut hot and sheets are rapidly cooled - Google Patents

Abstract

Foamed plastics sheets are produced by cutting while still hot and then cooling, both processes being carried out within two hrs. of the start of the polymerisation reaction; the sheets are stored with air gap between. Suitable process even for reaction mixes which develop high temps. (e.g. polyols with high OH number), prods. have good mechanical strength and flame resistance.

Description

Process and plant for the production of foam

blocks of material Processes used technically today on a large scale for the production of foams, especially polyurethane foams, are the continuous and discontinuous block production.

Processes of this type are, for example, in the Kunststoffhandbuch, Band VII, Vieweg-Höchtlen, Carl Hanser Verlag, Munich, 1966, e.g. on pages 458 -463. As in the production in these foams due to the high Heat of reaction occurs in the interior of the block, high temperatures are allowed in all the usual Process completely cool the blocks over a period of several days, before they are further processed.

This cooling is necessary because cutting too early will cause major dimensional changes, such as swelling or warpage or even severe discoloration - probably caused by the addition of atmospheric oxygen -, caused.

But even the slow cooling over several days only reduces this Problems without picking them up. Depending on the recipe, core embrittlement is observed, strong differences in density between the core and the edge area as well as core discoloration or cracks.

These phenomena appear all the more pronounced, the higher the internal temperature of the block is.

This value in turn depends primarily on the OH number of the polyol, provided that the NCO content of the isocyanate does not change. That explains itself from a simple thermodynamic consideration, according to which per mole of isocyanate at the same heat of reaction always arises when the reaction is complete. The maximum temperature is therefore dependent on the amount of reaction mixture from this amount of heat must be heated. For this amount, the OH number is a linear measure, so that one can say that the maximum temperature increases with increasing OH number.

The foam defects are correspondingly greater with higher OH numbers; If the OH numbers are very high, foaming is no longer possible if one does not makes serious compromises on the foam quality.

For this reason, the use of large amounts of polyols with high OH number in block systems has not been possible up to now, although such products can improve very important foam properties, especially mechanical ones Properties like Temperature stability and compressive strength, however Resistance to chemical attack and fire behavior are also positive influenced.

The object of the present invention is therefore to provide a method and a To create a system, which means that even with the development of high reaction temperatures, e.g.

if polyols with very high OH numbers are to be used, foams can be achieved with good mechanical and flame-retardant values.

The inventive method consists in that one the foam blocks slices open while still hot and that of the foam pieces obtained Heat of reaction dissipates by cooling.

The foams obtained in this way are in terms of their mechanical properties and the freedom from warping of excellent quality, as well as the differences in raw density between the core and edge zones are extremely small.

Because the inside of the foam block is almost adiabatic prevail, the once reached maximum temperature remains unchanged for many hours. During this time, there can be many changes in the polymer structure, especially too Decompositions occur which not only depend on the temperature but also on the time. It is therefore advantageous according to a preferred embodiment of the method, cutting open within two hours at the latest, which is particularly advantageous Way within thirty minutes after the foaming reaction started to undertake.

The blocks are cut open using band, chain or circular saws or knives, by rotating wires, filaments or similar known devices. It is not critical which option is chosen, if only afterwards rapid cooling of the cut panels is ensured.

This cooling is in the simplest case, preferably by storing the Cut open foam pieces with air gaps achieved, with the circulation The air between the foam pieces may be reinforced by fans can be.

Furthermore, it is also possible to cut the foam pieces contact with cooling plates by using the discontinuous process Stacking cold plates and foam pieces alternately; in the continuous process the foam pieces over and / or under the cooling elements.

The cooling plates in turn can absorb the heat of reaction directly to the air through protruding cooling fins or to one of the cooling plates Cooling medium flowing through completely or at the edge.

Direct cooling of the cutting element, e.g. of the saw blade or knife.

The cooling plates used can of course also be wedge-shaped be formed so that the cut pieces of foam while cooling at the same time be distanced from each other. This is particularly beneficial to cover greater distances to win if the plates are made thicker for the flow of a cooling medium must be or if the plates are followed by cooling rollers, how to proceed is listed below.

Alternatively, additional or sole cooling of the cut Foam pieces through one or more chill rolls connected in series be effected.

This can be particularly advantageous for the continuous process Use at least one cooling gap through which the cut pieces of foam be guided. Roller gaps, plate gaps and a combination are suitable gap formed by roller and plate.

It is particularly advantageous to provide several cooling gaps and they to be adjusted slightly closer one after the other, which on the one hand ensures safe guidance, in particular with driven chill rolls, is guaranteed and on the other hand a Equalizing effect is achieved, whereby particularly flat pieces of foam with small manufacturing tolerances can be produced. By using structured Rolling can also structure the surface of the cut pieces at the same time so that a later labeling or marking process is saved can be. Via the cooling roller, turning one to it pressed additional color-bearing roller also has a colored structure or labeling can be applied.

Due to the successive cooling gaps that are set ever closer is also a compaction of the surface with the resultant better mechanical Load capacity possible. In these cases it can also be beneficial to do the first or not to cool the first pairs of rollers but even to heat them up and only in the to cool the following calibration process.

Of course, according to the present procedure, this does not necessarily have to be the case evenly limited pieces can be produced, but it is also a shaping element Design possible, with either air cooling afterwards or, if metallic cooling surfaces are used, the cooling elements of the contour to be touched Foam pieces must be adapted.

Although it is the aim of the present invention, the foam produced If possible, cool it as soon as possible after breaking it into smaller pieces certain reaction mixtures may be advantageous between the cutting and cooling devices to arrange an additional heating unit. This can be uniform over the entire width Giving off heat in order to accelerate a post-reaction, or even more intensely act on the edge zones in order to achieve that over the whole cross-section a uniform temperature profile is built up.

The type of heating can be very different, but is above all with larger thicknesses of the cut pieces a radiant heating, which not only the surface but also the inside of the foam pieces is heated, advantageous. Microwaves, UV, IR, short or radio wave heating can also be used for this such as X-rays, electrons, ultrasound or g # radiation.

Since the resulting Heat of reaction is very large, it is advantageous in many cases for cooling Amount of heat released into the air or the cooling medium directly or via heat pumps to be reused for heating purposes, thereby reducing the total energy consumption of the system to restrict significantly.

The method can then be used particularly advantageously if very small amounts of polyol are used as reactants of the isocyanate, because in this case very high internal block temperatures are reached. In particular this case will occur when the ratio of mass of NCO mass of reaction mixture is particularly high, since then the heat of reaction generated by each mass unit of NCO focus on only a few mass units of reaction mixture distributed.

Foams in which this ratio is greater than or equal to 1: 6, can therefore preferably be produced by this method while they are after with conventional storage methods, very severe core defects in the form of discoloration, Show embrittlement or strong differences in gross density and therefore technically worthless are. The foams that are produced according to this ratio can both predominantly urethane bonds or predominantly polyisocyanurate bonds or mixtures both included.

As starting components for the production of polyurethane foams are used: 1. Aliphatic, cycloaliphatic, araliphatic, aromatic and heterocyclic polyisocyanates such as are used, for. B. von W. Siefken in "Justus Liebigs Annalen der Chemie ', 562, pages 75 to 136, for example those of the formula Q (NCO) n in which n = 2-4, preferably 2, and Q is aliphatic Hydrocarbon radical with 2-18, preferably 6-10, carbon atoms, a cycloaliphatic Hydrogen radical with 4-15, preferably 5-10 carbon atoms, a aromatic hydrocarbon radical with 6-15, preferably 6-13 carbon atoms, or one araliphatic hydrocarbon radical with 8-15, preferably 8-13 carbon atoms, z. B. those as described in DE-OS 2737951, pages 24-26.

Preferred polyisocyanates are aromatic polyisocyanates.

As a rule, those that are technically easily accessible are particularly preferred Polyisocyanates, e.g. B. the 2,4- and 2,6-tolylene diisocyanate and any mixtures of these isomers ("TDI"), Pol # rphenyl-polymethylene-polyisocya nate, as defined by Aniline-formaldehyde condensation and subsequent phosgenation are produced ("raw MDI") and carbodiimide groups, urethane groups, allophanate groups, isocyanurate groups, Polyisocyanates containing urea groups or biuret groups ("modified polyisocyanates"), in particular those modified polyisocyanates which are derived from 2,4- and / or 2,6-tolylene diisocyanate or derived from 4,4'- and / or 2,4'-diphenylmethane diisocyanate.

2. As starting components also connections with at least two isocyanate-reactive hydrogen atoms of a molecular weight usually from 400 to 10,000. This includes amino groups and thiol groups or compounds containing carboxyl groups, preferably hydroxyl groups Compounds, in particular compounds containing two to eight hydroxyl groups, special those with a molecular weight of 1000 to 6000, preferably 2000 to 4000, e.g. B. at least z #: ej, # usually 2 to 8, but preferably 2 to 4 polyesters, polyethers, polythioethers, polyacetals containing hydroxyl groups, Polycarbonates and polyester amides, such as those used for the production of homogeneous and of cellular polyurethanes are known per se.

The connections in question are z. B. in DE-OS 2737951, Pages 26-29.

The polyhydroxyl compounds in question can prior to their use modified in the most varied of ways in the polyisocyanate polyaddition process be: According to DE-Offenlegungsschrift 2 210 839 (US patent specification 3,849,515) and 2,544,195 a mixture of different polyhydroxyl compounds (e.g. from a polyether and a polyester polyol) by etherification in the presence condense a strong acid to a higher molecular weight polyol, which consists of Ether bridges connected to different segments is constructed. It is also possible, z. B. according to DE-Offenlegungsschrift 2,559,372 into the polyhydroxyl compounds amide groups or according to DE-Offenlegungsschrift 2 620 487 by reaction with polyfunctional ones Introduce cyanic acid esters triazine groups. By reacting a polyol with a less than equivalent amount of a diisocyanatocarbodiimide and then Reaction of the carbodiimide group with an amine, amide, phosphite or a carboxylic acid one obtains guanidine, phosphonformamidine or acylurea groups Polyhydroxyl compounds (DE-Offenlegungsschrift 2 714 289, 2 714 292 and 2 714 293). Of particular interest in some cases is the higher molecular weight polyhydroxyl compounds by reaction with isatoic anhydride to completely or partially convert into the corresponding anthranilic acid esters, as in DE-Offenlegungsschriften 2,019,432 and 2,619,840 and US patents 3,808,250, 3,975,428 and 4,016,143. In this way, higher molecular weight is obtained Compounds with terminal aromatic amino groups.

By reacting NCO prepolymers with hydroxyl groups Enamines, aldimines or ketimines and subsequent hydrolysis are obtained according to DE-Offenlegungsschrift 2,546,536 and US Patent 3,865,791 higher molecular weight, terminal amino groups containing compounds. Other manufacturing processes for higher molecular compounds with terminal amino groups or hydrazide groups are described in German Offenlegungsschrift 1,694,152 (US Pat. No. 3,625,871).

If necessary, polyhydroxyl compounds can also be used, in which high molecular weight polyadducts or polycondensates or polymers in finely dispersed or dissolved form are contained (cf. z. B. DE-OS 2737951, page 31).

Also polyhydroxyl compounds modified by vinyl polymers, how they z. B by polymerizing styrene and acrylonitrile in the presence of polyethers (U.S. Patents 3,383,351, 3,304,273, 3,523,093, 3,110,695; DE Auslegeschrift 1 152 536) or poly carbonate polyols (DE patent specification 1,769 795; US Pat. No. 3,637,909) are for the invention Procedure suitable. When using polyether polyols, which according to DE-Offenlegungsschriften 2,442,101, 2,644,922 and 2,646,141 by graft polymerization with vinyl phosphonic acid esters and optionally (meth) acrylonitrile, (meth) acrylamide or OH-functional (meth) acrylic acid esters have been modified, plastics are obtained that are particularly resistant to flaking. Polyhydroxyl compounds, in which by radical graft polymerization using unsaturated carboxylic acids and optionally other olefinically unsaturated monomers carboxyl groups were introduced (DE-Offenlegungsschriften 2 714 291, 2 739 620 and 2 654 746) can be used with particular advantage in combination with mineral fillers will.

Representatives of the compounds to be used are, for. 3. in High Polymers, Vol. XVI, "Polyurethanes, Chemistry and Technology" written by Saunders-Frisch, Interscience Publishers, New York, London, Volume I, 1962, pages 32-42 and pages 44-54 and Volume II, 1964, pages 5-6 and 198-199, as well as in the Kunststoff-Handbuch, Volume VII, Vieweg-Höchtlen, Carl-Hanser-Verlag, Munich, 1966, e.g. B. on the sides 45-71. Mixtures of the abovementioned compounds can of course be used with at least two isocyanate-reactive hydrogen atoms with a molecular weight of 400-10,000, e.g. B.

Mixtures of polyethers and polyesters are used.

From. In some cases it is of particular advantage to have low-melting points and to combine high-melting polyhydroxyl compounds with one another (DE-Offenlegungsschrift 2 706 297).

If necessary, connections with at least were used as outgoing components two hydrogen atoms which are reactive towards isocyanates are of a single weight from 32 to 400 in question. In this case too, this is understood to mean hydroxyl groups and / or amino groups and / or thiol groups and / or carboxyl groups Compounds, preferably compounds containing hydroxyl groups and / or amino groups, which serve as chain extenders or crosslinking agents. These connections generally have 2 to 8, preferably 2 to 4, isocyanate-reactive Hydrogen atoms.

In this case too, mixtures of different compounds can be used with at least two isocyanate-reactive hydrogen atoms with molecular weights of 32 to 400 can be used.

Examples of such compounds are those in DE-OS 2737951 on page 30 are in question.

The mixtures of hydroxyaldehydes are also used as low molecular weight polyols and hydroxyketones ("formose") or the polyvalent ones obtained therefrom by reduction Alcohols ("formite") in question, as they occur in the self-condensation of formaldehyde hydrate in the presence of metal compounds as cata- lysator and from to Compounds capable of forming enediol are formed as cocatalysts (DE-Offenlegungsschriften 2 639 084, 2 714 084, 2 714 104, 2 721 186, 2 738 154 and 2 738 512). About plastics To obtain with improved flame retardancy, these formoses are used with advantage in combination with aminoplast images and / or phosphites (DE-Offenlegungsschriften 2 738 513 and 2 738 532). Also solutions of polyisocyanate polyaddition products, in particular of polyurethane ureas containing ionic groups and / or of Polyhydrazodicarbonamides, come in low molecular weight, polyhydric alcohols as Polyol component into consideration (DE-Offenlegungsschrift 2,638,759).

Compounds such as 1-mercapto-3-aminopropane, optionally substituted amino acids, e.g. B. glycine, alanine, valine, serine and Lysine and optionally substituted dicarboxylic acids, for example succinic acid, Adipic acid, phthalic acid, 4-hydroxyphthalic acid and 4-aminophthalic acid are used will.

Compounds which are monofunctional with respect to isocyanates can also be used in proportions of 0.01 to 10% by weight, based on the polyurethane solids, as so-called Chain terminators can also be used. Such monofunctional compounds are z. B. monoamines such as butyl and dibutylamine, octylamine, stearylamine, N-methylstearylamine, Pyrrolidine, Piperidine and cyclohexylamine, monoalcohols such as butanol, 2-ethylhexanol, octanol, Dodecanol, the various amyl alcohols, cyclohexanol, ethylene glycol monoethyl ether.

As auxiliaries and additives: water and / or volatile inorganic substances or organic substances as propellants, as described in DE-OS 2737951 (page 32) and, if appropriate, catalysts of those known per se Kind, e.g. B. those as described in DE-OS 2737951 (pages 32 and 33).

The reaction between NCO groups and Zerewitinoff-active hydrogen atoms is also greatly accelerated by lactams and azalactams, with a first Associate between the lactam and the compound with acidic hydrogen forms. Associates of this type and their catalytic effect are described in the German Offenlegungsschriften 2,062,288, 2,062,289, 2,117,576 (U.S. Patent 3,758,444), 2,129,198, 2,330,175 and 2,330,211.

It goes without saying that all catalysts can be used as mixtures will. Combinations of organic metal compounds are of particular interest and amidines, aminopyridines or hydrazine pyridines (DE-Offenlegungsschriften 2 434 185, 2 601 082 and 2 603 834).

Further representatives of catalysts to be used and details about the mode of operation of the catalytic converters can be found in the plastics manual, tape VII, published by Vieweg and Höchtlen, Carl-Hanser-Verlag, Munich 1966, z. B. on pages 96-102 described.

The catalysts are usually used in an amount between about 0.001 and 10% by weight, based on the total amount of compounds with at least two isocyanate-reactive hydrogen atoms are used.

Surface-active additives, such as emulsifiers and foam stabilizers, Reaction retarders and other additives (see for all these additives DE-OS 2737951, page 34) can also be used.

Further examples of surface-active substances which may also be used Additives and foam stabilizers as well as cell regulators, reaction retarders, Stabilizers, flame retardants, plasticizers, dyes and fillers as well as fungistatic and bacteriostatic substances and details about the use and mode of action of these additives can be found in the plastics manual, Volume VII, edited by Vieweg and Höchtlen, Carl-Hanser-Verlag, Munich 1966, z. 3. Described on pages 103 to 113.

Example 1 In a box with a base area of 1 x 1 m, a floating lid a block 0.7 m high from a reaction mixture following Recipe made: Propylene Glycol 23 GT Ethylene Glycol 23 GT Trifunctional, Polyether started on trimethylolpropane with OHN = 35 (Desmophen ~ 3900) * 20 GT Desmorapid® DB * 1 part by weight triethylamine 1 part by weight stabilizer VP OS 720 * 1 part by weight diphenyl cresyl phosphate 20 pbw trichlorofluoromethane 37 pbw Desmodur # 44V150 * 200 pbw (* commercial products of Bayer AG Leverkusen, Federal Republic of Germany).

37 kg of this mixture were intensively used with a propeller stirrer 1000 rpm mixed. A slabstock foam was obtained with the following reaction data: Mixing time tR = 30 sec lying time tL = 53 sec setting time tA = 94 sec rising time tS = 100 sec The block was cut open after 48 hours and showed one complete charred dark brown core that was totally brittle.

Example 2 In a box as in Example 1, the same recipe and using the same process, an identical slabstock foam is produced.

After about 15 minutes this block became plate-like in 10 cm thick Cut pieces of foam, which are still at a temperature of approx. 1800C and not yet fully cured. The foam Pieces were stacked on top of each other immediately after being cut open and in this Leave the mold for 48 hours at room temperature. After this time the foam showed pieces a narrow usable edge zone, while the vast majority of all central ones Foam pieces were brown and brittle. The top and bottom pieces showed lesser ones Embrittlement.

Example 3 Analogously to Examples 1 and 2, a block was foamed and cut open after 15 minutes. The cut foam pieces were made placed between 2 mm thick aluminum plates, the edge lengths of which were 20 cm longer than the outer edges of the foam pieces. After about 3 hours the foam pieces were cooled to room temperature and showed a uniform, not discolored and tough foam structure.

Example 4 Analogously to Examples 1 to 3, another was block foamed and cut. The sheet-like foam pieces were between Water-cooled metal surfaces are placed and so within 10 minutes to room temperature cooled down. The quality of the foam pieces was just as good as in the example 3.

Example 5 A polyisocyanurate foam was produced on a continuous block foaming plant manufactured according to the following recipe: 45 GT Baymer 4500 y * 21 GT trichlorofluoromethane 1 GT Baymer e Aktivator 1118 * 100 GT Desmodur ~ 44V20 * (* commercial products from the company. Bayer AG Leverkusen, Federal Republic of Germany).

The response dates are.

Laying time tL = 25 sec. Setting time tA = 110 sec. The foam showed after 48 hours of storage an embrittled core zone and density differences of 8 kg / m3 between the core and the outside area.

Example 6 Analogously to Example 5, a continuous block was made manufactured. A piece of this block was converted into 10.2 cm thick sheet-like foam pieces after 10 minutes cut and then passed through 5 roller gaps, one after the other a width of 10.20 cm, 10.15 cm, 10.10 cm, 10.05 cm and 10.00 cm were set. The plates no longer showed any brittleness and had raw density differences of 3 kg / m3.

To carry out a batch process can be in Obviously, use a cooling rack in which the foam pieces with Intermediate space can be individually stored on support arms or cooling plates, so that air, optionally with the aid of a fan, can flow through between them; or you put the foam pieces by hand into a pair of rollers, Cooling device forming cooling gaps, in which it is cooled during the passage will.

A continuous system for the implementation of the process goes out from a conveyor trough which has a mixture application device on the inlet side and at the outlet end of which a cutting device is arranged.

The novelty is to be seen in the fact that the cutting device has a cooling device assigned.

This preferably has cooling gaps.

This ensures that the block is foamed in a single pass, cut and the resulting foam pieces can be cooled. Possibly can the pieces are simultaneously calibrated and / or marked in the manner described above will.

The drawing shows a continuously operating block foaming system shown purely schematically and described in more detail below. They show: FIG. 1 the system in the side view and FIG. 2 the system in the plan view with section according to line A - B in Fig. 1.

In Fig. 1, 2 forms an endless belt 1, assigned to the side walls 2 are, a conveyor trough, the inlet side via a mixing head 3 with one on one Bottom and side sheet 4 abandoned reaction mixture is fed. The educated Block 5 is passed through a cutting device 6 at the exit of the conveyor trough and thereby split into plate-like foam pieces 7. The cutting knives 8 are chilled. A cooling device 9 is arranged behind the cutting device 6. In the edge zone sections 10, it is even heated to over the block width To even out temperature. In section 11 there is only cooling. The sections 10, 11 consist of wedge-like cooling plates 12 through which temperature control media flows, which form between them cooling gaps 13 through which the cut foam pieces 7 slide. Downstream of the cooling plates 12 are cooling rollers 14 or an upper one and a lower cooling plate 15, between which cooling gaps 13 are also formed. Seen in the conveying direction, the cooling gaps 13 are narrower, so that the Foam pieces are calibrated at the same time during the run. The laterally mounted cooling rollers 14 are charged with coolant via mechanical seals 16.

Claims (10)

Claims 1. Process for continuous or discontinuous Production of foam blocks, characterized in that the foam blocks cuts open while it is still hot and the pieces of foam obtained inside Heat of reaction dissipates by cooling. 2. The method according to claim 1, characterized in that the cutting open and cooling the block carried out within two hours of the start of the reaction will. 3. The method according to claims 1 and 2, characterized in that that the cut foam pieces are stored with an air gap. 4. The method according to claims 1 to 3, characterized in that that the cut pieces of foam are brought into contact with cooling plates. 5. Process according to claims 1 to 4, characterized in that that the cut pieces of foam are brought into contact with cooling rollers. 6. The method according to claims 4 and / or 5, characterized in that that the cut pieces of foam passed through at least one cooling gap will. 7. The method according to claim 6, characterized in that in the conveying direction seen, the cut foam pieces go through several narrowing cooling gaps. 8. The method according to claims 1 to 7, characterized in that that the ratio of unit mass of NCO unit mass of reaction mixture is greater or equals 1: 6. 9. Plant for carrying out the continuous process, consisting from a conveyor trough which has a mixture application device on the inlet side and at the outlet end of which a cutting device is arranged, characterized in that that the cutting device (6) is followed by a cooling device (9). 10. Plant according to claim 9, characterized in that the cooling device (9) has cooling gaps (13).