DE1427587A1 - Process for the production of objects from foamed elastomers - Google Patents

Description

Dip '. In * ^ ί ¹ - "· -« :. puW.

DIETRICH IiWiNCKY

PAlENi'NWALT MiBthen-Pasini.Ajrc Brt '? IiM-S! RaSe202

1 ti 59

Pvnl

ühe Osbom Manufacturing Company,

54Dl, Hamilton Avenue, Cleveland 14, Ohio, V. St. A.

Process for the production of objects from foamed

Elastomers

EtLe invention relates to the manufacture of objects from foamed elastomers and in particular the manufacture such items by Fonaungsverfahren. öbw> hl die Invention does not relate to the use of polyurethane as foam is limited, the use of this material has particular advantages. This is the case in particular, W) foamed polyurethane as porous or cellular it Binder of more or less rigid nature for abrasive grains or similar elements with grinding, polishing or Brush effect used -szLrd. For example, there is a

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wide possible field of application of the current Invention in the molding of rotary grinding and brushing tools and generally in the production of slices zellfÖKnigaa elastomeric »material in which the formation and distribution of the to produce the porous or cell structure necessary gas bubbles controlled accordingly can be.

So-called ^ foams have been an important one for years Stage in the advancement of plastics and in particular of synthetic resins. These plastics can be divided into closed-cell and open-cell types. Also, depending on the plastic used, the End product can be described as flexible, semi-flexible or rigid. As is well known, the Foams, u.zw. both the open-cell and the closed s single cell types, in the manufacture of upholstery for cushions and the like, and the semi-flexible and rigid types are used for insulation and other building materials.

When developing such foams one uses im There are two foaming processes, namely either one mechanical or chaotic process. In the former case, the resin is in the liquid or semi-liquid state with a pressurized gas, e.g. carbon dioxide, is and the foaming takes place as a result of the pressure relief. In the case of the ch sni process, the synthetic resin is combined with a chanic Provide additive, e.g. with nitrogen or carbon dioxide,

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which causes the desired vision. In addition to the aforementioned and of particular interest is the case of the polyurethane, in which carbon dioxide is split off by reaction of the isocyanate with Viasser to form the composition which leads to the formation of the vesicles. These were originally perceived as a power rush, but this move, when used correctly, has made use of these polyurethanes ils important foams are more flexible, semi-rigid and ctarrer Nature led.

If the foam or elastomer make closed-cell Should be nature and not open-cell nature, must the formation of the gas bubbles, regardless of the process used to form them, are controlled in such a way that they are not excessively into another or merge. It is therefore It is desirable that their size be relatively small should and that they are present in large numbers, since this the tendency to overlap is limited. On the other hand can be a foam with a variety of small or even tiny gas vesicles may be suitable for various purposes, while for other purposes a closed-cell product with less, but larger gas bubbles are preferable.

As is well known, the development of polyurethane began in an attempt to manufacture a plastic of the illylon type. ELnes is the one selected in the manufacture of this plastic from the reaction components, e.g. a polyester or polyether and Disozyanat occurring Pro bee

P. n

was that the reaction takes place by splitting off carbon dioxide, which forms bubbles in the mixture. D to accordingly attempts were made to also prevent this blister formation in that it held the carbon dioxide escape Hess, or the carbon dioxide achieved by the application of pressure in the mixture, or, me in US ArP at ent. No. 2,729,618 from J .January 1956 proposed by adding a so-called "vulcanizing agent" to the mixture.

Around the same time this was found to be, originally for the industrial use of the polyurethane as an afterthought Perceived blistering is used to advantage for the production of cellular elastomers of a soft, semi-hard and rigid nature and foamed polyurethane has been used to make a wide variety of sponge-like objects, comprising a range of soft sponges, suitable as cleaning agents or upholstery, up to aircraft striving and Lightweight panels for the construction industry and other purposes. Among these is also (in accordance with the U.S. Ar patent

* 2,885,276 dated May 5, 1959) made polishing wheels.

a mixture of polyurethane and a granular abrasive material.

In the production of such a fo img eg the stand was off foamed polyurethane by means of conventional molding processes, and especially if the object contains other, heavier substances, there is a problem of regulation the formation of bubbles or foaming, so that not only the.

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desired cell structure -is achieved, but also the Desired distribution of the granular or other material which is to be embedded in the polyurethane.

It has now been found that such a scheme is very useful satisfactory WÜse by centrifugal effect instead the conventional foaming methods can be carried out, yjodurch Fo mg eg is made of foamed polyurethane or from have other gellable, foamable, resin compositions produced. In the special case of polyurethane this knowledge at the correct stage of the formation of the polyurethane or by other regulation of the reaction used between the components forming the polyurethane.

It is a main purpose of the invention to produce articles made of a shameable plastic or such a combination to be produced in such a way that the formation of the gas bubbles is controlled in such a way that their size is more or less uniform increases while maintaining their desired distribution.

Another purpose of the invention is to provide a method of making film articles from one another gesch'Äiaaten elastomer, with centrifugal force as a control factor in the formation of cells and for the creation of the cellular structure the object is used after it has hardened.

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Other features of the invention include choosing the correct level for applying centrifugal force.

Other features of the invention include proper tuning the addition of abrasives or other fillers to the foamed elastomer and especially to the polyurethane.

Other objects and advantages of the invention can be seen in US Pat following description.

To achieve the vorgaiannt.eö and similar purposes the invention includes the following in detail features described and shown in the claims, the description and the accompanying drawings, which certain details, for example execution sfo im en represent the invention. However, these! Show only a few the various possibilities of the application forms principles according to the invention.

In the accompanying drawings shows:

KLg. 1 is a fine sharia of a centrifugal film and shows a Method for introducing a foamable elastomer according to the invention to produce a disk or a disc-shaped object made of pure Can consist of elastomer or of elastomer with the addition of a granular abrasive;

FIG. 2 is a side elevational view of the process of FIG manufactured item;

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Fig. 5 is an enlarged Scottish cross-section of a such article along line 3-5 in Figure 2;

Fig. 4 is a view similar to that of Fig. 3 of one Object during a creation stage;

Fig. 5 is a view similar to that in Fig. 3 and shows a Article in which a granular abrasive or other material is molded with the elastomer was mingled;

Fig. 6 is a view similar to Fig.l and shows another Process for the production of the article according to Fig.l and 2;

Fig. 7 j 8 and 9 are views similar to Fig.l, and showing another method of manufacturing a plate-like object, the s a ring-shaped brush part with radially projecting bristles or elements corresponding burst contains;

Fig.10 is a Schenati shear cross-section of one using the llethode item produced according to Figure 7-9;

Fig.11 is a view similar to Fig.l and shows another Process shape for the production of a round, disc-shaped Subject;

Figure 12 is a view similar to Figure 11 and shows the formation such an annular object and a central, disc-shaped core, and

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14 and 14 show enlarged cross-sections through one Object and in particular by a grinding wheel during a generation stage and through the finished one Grinding wheel.

For the sake of simplicity, and because the improved invention Method is particularly suitable for the production of objects made of foam polyurethane, "the method is only discussed in connection with this particular elastomer.

As already mentioned, foamed polyurethane is obtained by ■ reaction of toluene diisocyanate with his chosen one Polyester or polyether resin or / a mixture thereof, which contain an excess of active hydroxyl groups, under certain conditions and usually in the presence of a catalyst. The presence of the active hydrogen in the Hydroxyl groups lead to additional polymerisation with evolution of carbon dioxide, which was originally considered undesirable. This reaction starts the resulting polyurethane immediately starts to gel or solidify, and this gelation must be both on the progressive Reaction, as well as any treatment of the resulting product.

One method of making foamed polyurethane is by Mixing of the ingredients, i.e. isocyanates, polyols, Kalaysatoren, Emulsifier, us ?, in a certain ratio. A Another and better method is the use of the so-called.

"Vorpolymeiisierungssystoiis", where ioluoldii so cyanate with Polyol are reacted and a liquid prepolymer form which free toluene diisocyanate im Contains excess, so after adding water and catalyst this free I reacts so cyanate and now the desired Foaming effect.

The speed of this Schäuiimngsvorgangs is very quickly and without correct regulation of the process can lead to a thirty-fold increase in volume. One The simple method of using the resulting polyurethane foam is to form simple blocks, which then become objects of the desired size and shape, e.g. to seat cushions or the like. be tailored. On the other hand the material can also be poured into corresponding molds, which correspond to the final product. In the formation of these products, be it soft, semi-rigid or rigid liatur, Therefore, the only regulation of the expanding polyurethane is to limit the expanding mass, being in addition to the pressure caused by the reaction an externally applied pressure can also be used.

This latter method is in the aforementioned U.S. Patent No. 2,885,276 for the manufacture of grinding wheels described, although the application of pressure, especially in the case of mixtures of polyurethane with abrasives, is an obstacle, Firstly, the blistering characteristic of the foaming is more or less imprecise, especially where the polyurethane is

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look free to expand into a soft porous or spongy mass. Second, if fillers, vde granular Abrasives are used, this material is difficult to keep in a uniform distribution in the mass, since it is subject to gravity and becomes unevenly distributed during foaming.

In comparison with the preceding and other methods for Fozsiung of sehaumbaren elastomers and particularly of polyurethane, it has been found that when the article during foaming to a centrifugal force, and in particular an induced relatively buckle Botation centrifugal force is subjected ^, so \ iöhl The size of the bubbles and thus also of the cells can be controlled, as well as the more uniform distribution of them. In particular, it has been found that if the foaming process is such that a large number of tiny bubbles are formed in the plastic body, the result is such that the bubble size is enlarged by the coincidence of the bubbles with a radial distance from the axis of rotation. At the same time, the structure in between becomes thicker in the outer parts of the rotating body.

At the same time, additives such as granular abrasives, under the influence of centrifugal force in equal distribution in the circumference of the body, e.g. the polishing or Grinding wheel on, and then remain, after completion of the foaming and provided that the gelation of her has reached the correct stage, in a loose position in the cell body.

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This means that the grains of the thicker structural or Structural parts are borne while the intermediate ones Parts of more or less spherical cells ingested which disfigure from the enlarged gas bubbles, this product is sharply different from the conventional ones Resin or ceramic discs differentiate between those used for surface treatment used v / earth, tmd in which it It has appeared desirable to densify the grains and the binder, i.e., the resin or ceramic material, serves here Exclusively as a binding agent, without the elbow movement of the Allow grains like this in building the present Invention is possible.

Eventually the outer periphery and that of the same develop parts lying first, probably as a result of the centrifugal force, form a "skin". (Fig. 4 and 5 ^ which is almost completely free of bubbles, and therefore has a higher density than the adjacent inner parts of the object. By Proper regulation of the process can reduce the thickness of this skin adjusted so that they have a solid surface material corresponds, such as sheet metal or another solid Building material, y / like many other types of grinding wheels or polls must be incorporated to this the to give necessary rigidity. This is the case with this Skin that naturally forms this process is of great importance as stiffening the side walls of the pane; she will immediately removed from the periphery when the disk is used, or it can also be removed beforehand by trimming will.

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The best results were achieved with a polyurethane which was produced by esterifying a polyhydric alcohol and a dicarboxylic acid. Examples of suitable acids are adipic, phthalic, succinic, malonic, and maleic anhydride. Examples of suitable alcohols are propanetriol, ethyl englycol, diethyl englycol, butyl englycol and Tiimethylpropane. These polyesters preferably have an acid number of less than 1 to 40 and are in the range of the following ratios between hydroxyl and carbonoxy groups in the resin reagents: from Ά hydroxyl per 1 carboxyl to 1j hydroxyl per 1 carboxyl.

The polyester reacts with an organic diisocyanate or polyisocyanate to form polyurethane. Suitable Diisocyanates include hetatoluene diisocyanate, para-phenylene diisocyanate, Naphtha! en-l, 5-Dii so zy an at and 4 ^ 4-diphenylmetyldiisozyanat, However, metatoluene diisocyanate is preferable.

Examples of suitable polyester T-cylinder sections. are :

1. Trimethylolpropane 4 moles Adipic acid. 1 mole of phthalic anhydride ± d2 i mole of dimers ί mole

2. Glycerol. 4 moles of adipic acid. 1 mole of phthalic anhydride -J mole

^. Trimethylpropane 4 moles

Adipic acid. 2j mol

Phthalic anhydride i mol

Dimers t moles

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Suitable polyurethane is obtained by mixing 50 parts by weight of one of the examples below listed resins with 25 to 75 G era. cht st eil en metatoluene di-isocyanate with an ethyl cellulose content of 1-25 grams.

: The heat resistance of the above formulation can be improved by adding polymethylolphenyls to the reaction mixtures for the production of cellular plastics. A suitable cellular polyurethane can be produced by adding 0.5-5 wt .- ^ water to the reaction mixture to generate the CO ₂ ^ ¹¹ ^ - ^ er foaming. A metal soap, such as zinc stearate, can also be added to the above mixture in order to obtain a more uniform cell joint.

As already mentioned, resins and elastomers other than polyurethane are also suitable for use in accordance with the invention. A corresponding example would be an epoxy resin mixture following formulation:

Epoxy resin (EPON 828 from Shell Chemical CO) 100 grams Tween 20 (polyoxyethylene sorbitan

Mbnolaurate) 5 drops

Lied (foam concentrate) 2 grams

DETA (EÖLäthylenetriamine). 6 grams

Celogen has the following composition: Ρ, Ρ ^ -öxybis (benzenesulfonylhydrazide). Another foaming agent that can be used is BL-555 with the composition K, M ¹ -Dimetiiyl-N, N ¹ -DLnitrosote'rephthalamide. The above mixture has a compressive strength of 7> 9 & 5 kg / cm ² , which can be increased even further by centrifugation.

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As already mentioned, it is suitable for use with the

or according to the invention method any elastomer - ^ - plastic, in which air or gas was trapped while mingling provided that this elastomer or plastic with its air or gas bubbles is sufficiently free-flowing, to be poured into a mold and before gelling or solidification of the effects of centrifugal force.

The following are some improved methods of manufacture of articles made of foamed elastomer, without concern, looks at the composition of the plastic, and with reference to the drawings.

The device according to FIG. ₅ I comprises an annular shape 1, the base plate of which is preferably removably attached to a turntable T , which by means of RL, tendon or the like. can rotate around its © vertical axis »The mold has a detachable desk 2 and a central opening 5 in this cover, which fits with a screw pin through which the cover can be firmly attached to the mold by means of a nut 5. In this simple device, with the lid removed, a metered amount of a foamable, gellable resin is added, preferably as layer F, which fills the bottom of the mold, but leaves part of the space of the mold above it when the lid is reattached.

If the material introduced is foamable polyurethane, the material is preferably immediately before the start of the

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Foaming introduced into the fona, which is then applied to the correct Temperature and under the correct conditions following the bringing together of the reactants. In case of a Compilation, such as the aforementioned epoxy resins or the like., which comprises a foaming agent which is active by heating tcLrd, the foaming takes place naturally only after the application of Warmth. Here the shape is turned into a brought to a suitable oven, or heat to another suitable one Applied in this way, with the result that the material in the mold is simultaneously liquefied and foamed.

In all cases, the shape after the closure and Filling in the foamable, not yet gelled material, set in rotation about its axis, and so on, preferably with relatively high speed, r..B. up to 5OOO U / T & n, if the radius is between I52 and 178 mm. With smaller or larger radius vdrd the speed of course varies to to generate a comparable centrifugal force, and un the degree of fluidity the material, the type of gas bubble formation and the gelation time. These factors also affect the length of the centrifuge enxng, but above usually a few minutes are enough to get what you want Get result.

In any case, the amount of material in the mold before it is foamed should be smaller than that required for complete filling the form would be necessary. Whether the material is introduced as a layer on the bottom of the form, or in the early stages

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located along its axis, me shown in Fig. 6, that is The result of the centrifuge ensures that the material moves radially is thrown from the outside, so in the Foim of an ELngs accumulates, which is more limited to the outside, however can expand freely radially inwards when its yolumen enlarged by the formation of gas pockets, he Ibtation the form yard continued until the material gelled sufficiently is to at least in its outer ring part which is made up to maintain the cell structure resulting from the centrifugal effect unchanged,

If a polyurethane is used, it is enough to simply shape the shape let stand until the reaction forming the composition is perfected to be flexible, semi-rigid or rigid Make make. In the case of a plastic or elastomer that must be heated after placing in the mold, let one cools until the material has gelled on a stable fora

The end product is a cell-shaped disk A, as in FIG. The radial section shown in FIG Part of the body merge into one another and thus form larger gas bubbles or cells a ¹ , which, however, are also closed and evenly distributed over the cross-section of this zone. At the same time, the material structure a ^ between the cells is thicker here a central part in which the gas bubbles are small and very numerous and one from seres or edge part of which

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radial depth can be varied so that the cells gradually enlarge and the intervening material structure gradually thicker vdrd. This edge part also has a higher density than the middle part, i.e., its weight depending Cubic centimeters can be two or three times the size of Vienna a foamable polyurethane is used.

ELneider-type manufactured disc has for various purposes of application better coating than a disc with more even Consistency, i.e., a slice with evenly distributed Bubbles or cells. This is particularly the case when the polishing or grinding effect of the disc is achieved by adding a granular abrasives to the plastic mixture before their Bringing it into the mold was increased. Fig. 5 shows schematically the radial section of such a disk, which, as far as the foamed structure is concerned, corresponds to FIG. 4, but additionally this contains abrasive grains g embedded in the thickened part of the structure. At the same time they are grounded through the intermediate cells or bubbles end at a distance from one another held, but thanks to the elastic resilience of the structure, they also have the option of one restricted mobility.

Such a grinding wheel becomes the grinding material Adapt in type and size to the nature of the grinding process, probe its volume accordingly to adjust. ELne such grinding wheel for general use sz purposes, with a diameter of 178 mm and a thickness

from 12 _? 7 ffim. includes. E.g. 55O grams of sanding agent, consisting of Al-undim (Aluminum © 22yd) _S 46 sanding dust and 300 grams of the foamable, rigid, pol yur e than type described above Outer ring of approx. 25 mm radial die accumulated vdrd. On the other hand, to produce a disc of the same dimensions and grain size, with low micro-inch machining, but not suitable for sanding or long life, comprises 150 grams of the same plastic mixed with 160 grams of the same abrasive.

In the following, the production of such a grinding wheel with a polyurethane bonding agent as the wheel body is described, for example. The prescribed quantities of the chemical components, ie a polyester blend and a diisosyanate? / Ground together _o This leads to a reduction in viscosity; when this is reached after about JO seconds, the granular abrasive is added

and / Eehren 40 seconds! long continued. To. by this time the sting has already burned and a considerable amount. Your amount of arm released billion. The mixture νά.τά is now attached to the Foim and (after 5 ° seconds have elapsed) one begins immediately with the potation, which as quickly as possible

brought to its maximum value värd. Since the first curing yon

stuf erhy polyurethane is exothermic, it has been found that Temperattirregelung can be used to make the grinding wheel relatively bulky "hard" or "soft". If a hard disk is to be created (i.e., a disk,

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in which the abrasive is particularly stuck) the FoTm and disk can immediately be removed from the centrifuge and placed in an oven at a relatively high temperature of up to ¹⁴ 3 ° ^C for 20-50 minutes; for the preparation einefweichen disc (ie, a disc in which the abrasive grains sit less solid) -is the shape and disc only for 6 minutes in water at 15.6 ⁰ C and then dipped 2O-5O lower minutes in an oven at Hardened temperature of approx. 79j4 ° C. Solutions lying between these borderline cases can of course also be set. The foregoing obviously relates to rigid grinding wheels, regardless of whether their effect on the workpiece is "hard" or "soft", and not to resilient finishing wheels.

The botation speed is high enough to keep the Ensure distribution of the abrasive over the circumference and to prevent it from precipitating, w> in the case of foaming of the chemical constituents helps in the latter effect. The chemical reaction continues during spinning leads to a gradual thickening (increase in viscosity) of the plastic binder; at the same time worried the evoked Centrifugal force causes the bubbles to collapse in the periphery of the body, passing these bubbles through the pressure acting on them are compressed. the Centrifugation vd.rd now continued until the plastic is sufficient is gelled to prevent setting of the same, and vdLrd interrupted before the plastic solidifies to a point is in which expansion of the compressed bubbles is prevented

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will. As a result of expansion and possible further Gas formation, these compressed bubbles expand, i.e., they enlarge - and so do the distance between the individual soles eifkö mein, those in between lying thicker structure are held.

The result of this expansion of the compressed bubbles is of course, an increase in the total volume of the disc. Accordingly, and in contrast to the previous practice of shaping grinding and polishing wheels, the shape must be so designed to allow the body to expand before it finally solidifies. In different, läsr For example, the fens shown are the body against one secured radially from the axis outward expansion, as well as in the transverse direction to this, can. but expand freely radially inwards. Alternatively, you can allow the body to move laterally instead of radially expand inward by making the FoimdeckaL axially movable arranged and not secured by a nut 5. In no case should the lid sit so tightly that the excess gas the reaction gases or the additional gases present are prevented from escaping.

The effect of this simultaneous application of centrifugal force and foaming on a body made of foamable plastic with elnffiK Celil eifmitt el additive is further illustrated by Fig. 15 and 14 illustrates which enlarged cross-sections of the outer parts of the Y / piece according to FIG. 5 in a plane parallel to represent the side surfaces, me is shown in Fig.lJ,

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The centrifugal force once causes the accumulation of the Abrasive grain in the outer parts of the disc in one Foaming stage, while soft «? a variety of small Gas bubbles are formed. 14 then shows the state after further foaming and adjustment of the flow force effect. As you can see that here the abrasive grains are further apart stored, and preferably have a spacing that is proportionate to size corresponds to its diameter; the grains are in the thicker parts to be joined, which are caused by the Enlargement of the cells come about and in them External parts arise in the course of gelation and hardening.

The modified method according to Fig. 6 basically exists in how the foamable plastic or elastomer is put into the mold. The latter generally has the same Construction like the Foim in Fig.l; also the potentiometer, which is not shown here., is the same. However, the way in which the mass is brought into the Foxm differs through a funnel-like vessel 6, which contains a metered amount F »of the low-foam elastomer in question brings in next to the pin 4, which is preferably done with slowly rotating mold. Then vdlrd the Deekel 2 attached and the botation speed is increased to the desired maximum, so that the mass is thrown outwards and the Fona completely fills the periphery, here by the outer ring wall and the side walls is held., itself but can expand freely inwards. As can be seen from the description of the following figures, this method is suitable especially for the production of certain objects with a disk shape

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The modified method according to FIG. 9 shows the use of this improved method when embedding a brush body B in a body A made of foamed elastomer, as described above. After the brush part is inserted into the open poim 1, the amount F ^{1 of} the viscous elastomer in question is introduced into liquid foam from the funnel β eL & e, u.zw. in the opening zm. see the brush and the pin 4, me in Fig. ¹ J * Then vdrd the Deekel 2 attached, the FoBn rotates quickly, whereupon the material after. After a certain period of time, the Fo in and the state according to Fig. 8 and Q gradually assumes.

Here the material is only thrown outwards through and around the bristles of the brush and takes on the position. Fig * 8 eirio BIe formation of gas bubbles, however, causes its radial inward expansion, until the body practically collapses. Pb us ei auafüllt space, me _c shown in Fig. 9 WLe above, sucii here the size of the gas bubbles iron on the axis of rotation outwardly on ¥, so that after the completion of the gelation of the shark between the bristles of the brush γοη an elastomeric body is filled, the cell structure of which corresponds to that of a body without Brush subject to this procedure. YJi e shown in Fig. 10, the cells a- of the foamed plastic body or elastomer between the bristles are larger and the cell structure thicker (see a) in the circumference of the structure than in its inner parts.

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Fig.ll shows a further application of the current one Invention, namely for the manufacture of an article in Foinn a ring C. "For this purpose the Fo33a forms the wreath or the rim of a ribbed disc or wheel W with a relatively large diameter compared to the drawings discussed earlier; this wheel is rotatably mounted on a shaft w. This shown in Fig. 11, left RLngfonn comprises a bottom plate 10, which is the rim part of a wheel, a removable inner wall 11, a fixed one Outer wall 12 and an annular cover plate I3, which here is in one piece with the outer wall and is different from it extends inward, but can also be constructed to be removable. A locking ring holds the inner wall in place solid and has a sloping outer wall, the purpose of which is still will be explained. The appropriate amount of the mass is poured into the ring-shaped channel, the removable one Wall is removed and the outer, sloping ¥ / and of the locking ring controls the material flow, as shown in Fig. 11, left. After reinserting the removable inner wall 11, the mold is rotated rapidly and the formation of gas bubbles already described takes place. After sufficient gelation or curing of the plastic or elastomer body in the mold, this can be removed, or the other Treatment is done in the form itself.

The shaped piece C produced in this way can of course be of the radial and transverse dimensions of the illustration differ. For example, the object can correspond to the pane according to FIG. 2, Only the central opening has a larger diameter.

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On the other hand, the object can also be the foisa of a band with a round surface which, depending on the application, is flat or can also be curved laterally. One such Eundband can also be used, for example, as a vehicle tire or Part of such can be used. In all cases the centrifugal force causes the size and during the molding Distribution of the bubbles and cells representing those already described Mark objects.

FIG. 12 shows a further modification * of the method, iso with an annular, wheel-open object C of the described Type on the periphery of a center disk D is chamfered, which may have a different composition and in this case

ff

consists of a cheaper building material, so that the foamable assembly only forms the outer ring. The periphery this disc thus forms the inner wall of the elongated shape of the im The embodiment described above with the difference, that, because of the centrifugal force formed bing on it remains attached, the annular cover plate 15 is removable.

Obviously, any form of one can be, on one Apparatus according to Figures 11 and 12, any granular abrasive or other material desired be added in exactly the same way as already in connection with the manufacture of discs has been described. A brush body can also be such, for example on a Apparatus according to FIGS. 11 and 12 produced annular article are incorporated.

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The method according to the invention allows extraordinarily good results to be obtained, especially when producing grinding disks in which the granular grinding material is embedded in a body made of rigid, foamed polyurethane. For example, when using two molds with inner diameters of 178 mm and a thickness of 12.7 ™ & for forming 250 grams of polyurethane each, - one Fo was centrifuged and the other was not, the density in the The centrifuged disk fluctuates, while it is practically the same everywhere in the non-centrifuged disk. In this example, when polyurethane is centrifuged at 300 rpm, the disc in an I-ring 12.7 mm thick has a density of 17.5 grams per cubic centimeter, while the innermost ring, 12.7 w® thick, has a density of has only 636 grams per cubic centimeter. In contrast, the non-centrifuged disc has an average density of ea 1467 grams per cubic centimeter.

It has also been found that the strength is made of foamable Polyurethane of the composition described, centrifuged disk is twice as high, vde the tensile strength of a "similar but not centrif ugi inherit Disc. In addition, the sides of the centrifugation have a disc a significantly higher «tensile strength than the adjacent ones Inner parts of the disc.

There is also a fundamental difference in the size and thickness of the parts lying between the cells, depending on the distance from the center of the disc. Not only is ¹ Ie

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Strength of the structure in the Saheibe thereby regulated, rather the centrifugal effect also strengthens the "outside of the wheel, and this sojohl on the periphery as well as on the side walls. This is an important factor when adding to the washer of Sehleifkornern has the shape of a grinding wheel, as such Discs are often guided sideways over the workpiece must and the weaknesses of the edges cause the frequent trimming of the panes. EtLe leading edge of an inventive Floating disc is durable for a long time than a conventional grinding wheel and cuts parallel Slots better and more reliable.

It has also been proposed to use centrifugal force to produce conventional resin and ceramic grinding wheels. As far as is known, however, the effect of centrifugal force has only been used to collect the granular abrasive in a compact form, initially around the periphery of the foil, and to fill the existing viewing rooms with a liquid but non-foaming binder, even if There are pores, the grains are as close together as possible and are held in place after the binder has solidified. In contrast, according to the invention, the granular material is accumulated in the outer longitudinal part of the mold and is kept at a distance from one another by the cells that are being formed, so that this material can have a restricted movement of the skeleton as a result of its storage. This not only prevents the workpiece from being scratched by protruding particles, but also significantly reduces their premature falling out of the working surface of the disc. _; . · ·

BATH ORIGINAL.

8098 10/0370

In the previous description and the following Claims "means the term" disc-shaped body " any means of the process according to the invention which can be produced Object. The term gellable resin includes all commercially available resins in addition to those cited as an example, which are checked under Conditions can develop a cell structure, quite regardless of whether this structure is chemical or mechanical, and in the former case by adding a separate foaming agent or by reacting the constituents comes about.

The terms "foamable" and "foamed" relate liier on the plastic composition during or after centrifugation and affect such plastics without Take into account vd.e the gas bubbles formed in them will.

BATH

809810 / 037C

Claims (1)

Claims 1. A process for preparing Foinngegenständen from a gelable, sehaumbaren plastic composition, characterized in that it -umfasst the ELnsehliessen a plastic body during foaming but _f not during gelling against radially from a central axis outward movement, the Botieren this body about its Axis at a speed and for a time that is sufficient to form gas bubbles in order to increase its volume, to thicken the structure in the outer part of this body, and finally to allow the composition to gel. 2. Hn process for the production of moldings from a gellable, foamable plastic composition, thereby characterized in that it comprises a foaming agent, TJomit in elnB ^ daggers plastic body a multitude of small gas bubbles can be generated under controlled conditions, and comprising the connection of this plastic body during the foaming and the non-gelation stage against the radial of Outward movement directed towards its central axis, the botany this body rotates around its axis at a speed and for a time sufficient to increase the volume of gas bubbles form and thicken the structure in the outer part of the body, and finally the gelation of the composition. BAD ORIGINAL / 'Ο3Γ7 O 3 · ELn Process for the production of molded objects from a Applicable, writable plastic together position, thereby characterized in that it comprises a foaming agent, iromit in such a plastic body and controlled conditions en a large number of small gas bubbles can be generated, and including the connection of this plastic body during the effervescence but not the gelation stage radially outward movement from its central axis, the Rotation of this body around its axis at a speed and for a time that is sufficient to enlarge the gas bubbles and to thicken the structure progressively from the central axis outwards, and finally the gelation of the composition. 4. A method for the production of molded objects from a gellable, foamable plastic composition, characterized by the connection of a body made of plastic during the foaming but not gelling stage against outward movement radially from the central axis, wobbling the body also sideways is included, but can expand freely inwards, the botching of this body around its axes at a speed and for a time that is necessary to enlarge the gas bubbles and thicken the structure in the outer part of the body, and gelation the crowd. 5. ELn process for the production of molded articles from a Ii gellable, foamable plastic composition, marked by connecting the plastic body during of the foaming but not the gelation stage against radial from outward movement directed towards its central axis, rotation of the Body around this axis with a speed and for a time, 009910/0370 which is sufficient to enlarge the gas bubbles and to thicken the structure in the outer part of the body, and that Gelation of the mass containing a granular material, which is simultaneously accumulated in the outer part of the body and held here by the thickened structure will" · β. ΕΙη Process for the production of fo! »Objects from a gellable, breathable plastic compound, marked duxeh the connection of the plastic body during the Edging but not gelling stage against radial from outward movement on its central axis, moving the body around its axis at a speed and for a time, soft is enough «, eat the gas bubbles and enlarge the structure to thicken in the outer part of the body, and that Gelation of the mass containing a granular abrasive material, which at the same time accumulated in the outer part of the body and is held here by the thickened microstructure. 7 “A process for the production of fo img eg objects from one gellable, sohanobar en plastic mass, characterized by the insertion of such a plastic body during the seaming in a rapidly rotating film with a round one Outer wall and flat side walls, through the gas bubbles in the outer part of the body is enlarged and the intervening structure is thickened, and gelling of the mass. BAD ORIGiMAU 809810/0378 8. ELn method of making disc-shaped articles made of a gellable, foamable plastic compound, characterized by the insertion of such a plastic body During the foaming in a rapidly rotating mold with a round outer wall and flat side walls, but which are radial is open inwards, due to the gas bubbles in the outer Parts of the body enlarge and those in between The microstructure thickens and the mass gels. 9. ELn method of making disc-shaped articles made of a foamable polyurethane mass, marked with the use of such a plastic body during the Foaming in a rapidly rotating mold with a round outer edge and flat side walls, which, however, move radially is open on the inside, or through the gas bubbles in the outer part of the body enlarge and the intervening authority structure thickened and the mass gelled. 10. A method of making disc-shaped articles made of a foamable polyurethane compound, characterized by the Inserting the body into a rapidly rotating mold with a round outer edge and flat side land during foaming, which is open radially inward, through the gas bubbles in the outer parts of the body enlarge and the intervening tissue structure thickens as the body grows can expand freely inwards, and gelation of the mass. 11. A method of making disc-shaped articles I ' made of a gellable, foamable plastic compound by inserting such a plastic body during BATH ORIGINAL A Π Q ft 1 Π / Π 3 7 P, the foaming in a fast rotating Foim with a round one Outer wall and flat side walls, which, however, move radially is open on the inside, through which the gas bubbles in the outside Parts of the body enlarge and the intervening structure thickens, and the mass that gels contains an additive of a granular abrasive which at the same time accumulates in the parts of the body outside of it and is held here by the thickened structure. 12. ELn methods of making disc-like objects ) made of a foamable polyurethane mass, characterized by the insertion of such a plastic body during the Foaming in a fast rotating Foim with a round one Aussenv / and and flat side walls, which, however, radially open inside 3: st, causing the gas bubbles in the outer parts of the body and the other lying Microstructure thickens, and gelling of the mass that rush addition of a granular abrasive contains which accumulates in the outer parts of the body at the same time and is retained here by the thickened microstructure. I. 13. ELn disc-shaped body, characterized by a gelled, foamed plastic mass, in which the during the Sehäutaung cells formed by gas bubbles around the body larger and the structures in between are thicker than in the rest of the body. 14. A disc-shaped body, marked by a gelled, foamed plastic mass, in which the during foaming cells formed by gas bubbles are generally icugeo-shaped, and are closed, and that these cells are steep in extent of the 809810/037 The body is larger and the structure lying between it
is thicker than the rest of the body. 15. A disk-shaped body, characterized by a gelled, foamed plastic compound, the cells formed during foaming being larger and the structural
t & Le are thicker in the "circumference of the body than in the rest of the part, and small abrasive grains in the thickened texture
are embedded. 16. Hn disc-shaped body, characterized by a gelled, foamed polyurethane, -wherein the cells formed by gas bubbles during foaming in the peripheral part of the body and the intervening structure is thinner than in the
Rest of the body. VJ. A disk-shaped body, characterized by a gelled, foamed polyurethane, vjobei the cells formed by gas bubbles during the foaming are generally round and closed and are larger in the peripheral part of the body, and the underlying structure is thinner than in the rest of the body
Body. 18. ELn disk-shaped body, characterized by a rigid, foamed polyurethane, TObei the cells formed by gas bubbles during foaming in the peripheral part of the body are larger and the structural parts in between are thinner than in the rest of the body and small grains of sand in the
thickened microstructure are embedded. BATH 809810/0370 19- A disc-shaped body characterized by a gelled, Foamed plastic compound, with the -währoid of foaming cells formed by gas bubbles in the trap part of the body are larger and the intervening structure is thicker is as in the rest of the body, and the side faces This ISaf fear rushes through an integral layer of a thickened, No plastic can be limited. 20. ELn disc-shaped body, characterized by a rigid, foamed polyurethane, -which during the foaming through Gas bubbles formed larger cells in the trap part of the body are and the intervening structure is thicker than in the rest of the body, and small "loaf grains" in the thickened microstructure are embedded, and the side surfaces this IM catching parts of the body by an integral layer a thickened ^ non-cellular plastic are bordered. 21. ELn disc-shaped body, characterized by a gelled, foamed plastic compound, during foaming formed cells circumference sgen§.ss are exposed, the sides of the Body but be framed by an integral layer of a thickened, non-cellular plastic. ■ 22. ELn disc-shaped body, characterized by a rigid, foamed polyurethane mass, the during foaming formed cells are exposed circumferentially, but the sides of the body are covered by an integral layer of a thickened, non-cellular plastic are edged, and with small particles of an abrasive embedded in the body. iAÖ 809810/03? 2Y. A process for the production of moldings consisted of one gellable, foamable plastic compound, characterized by the inclusion of such a plastic body during the Schavan en s, but not during the GeI er ens jinn a radial from to prevent outward movement of its axis while allowing the body to freely expand inward rapid movement of the body along its axis during the Hemorrhage, and the gelling of the ilasse. 24. A process for the production of moldings of a gellable, foamable plastic mass, characterized by the connection of such a plastic body during foaming, but not gelation, to both a radially outward and a sideways downward movement to prevent, while the body can expand freely inward, the rapid to animals of this body around its axis, and the gelling of the mass. 25. The manufacture of a grinding wheel with a foamed Polyurethane body and abrasive embedded in it, characterized in that a liquid polyurethane mixed rr.with a granular abrasive during the foaming of the Polyurethane is subjected to centrifugal force, so that the Enlarge display bubbles in the outer part of the body while the intervening structure thickens, in which the abrasive grains are embedded and that exothermic dyeing is applied during the initial curing stage - followed by thorough cooling of the disc and their final hardening in a medium. ORIGINAL 809810 / 037C 26. The method according to claim 25, characterized in that the disc is cooled in a liquid bath. 27. The method according to claim 2, characterized in that the disc is cooled in a liquid bath and then cured at 79.4 ° C. 28. The manufacture of a grinding wheel with a body foamed polyurethane and abrasives embedded in it, characterized in that it is a liquid polyurethane and granular abrasive during the foaming of a strong Centrifugal force is subjected, -yso through the foam bubbles enlarge the outer part of the body and the one in between Microstructure thickens in which the abrasive grains are embedded, and that during the initial stage of the Curing exothermic heat is applied and that the Disc is then immediately heated to a temperature which is higher than that applied by the essothemic "heat, and kept vdrd at this temperature for the purpose of hardening. 29. The method of claim 28 _5, characterized in that the disc is heated to about 145.5 ⁰ C. 50. The generation. a grinding wheel with a Polsrur ethan body and abrasives, characterized in that a mixture is foamed from liquid polyurethane and soap that ExD thermal heats during the initial curing stage is applied that the disc is then immediately cooled and finally cured in a low temperature oven will. BAD OftlGlNAl / R η Q P 1 η-Xfr-Q 7: 0V =: -