DE1504888C - Polymeric, network-structured body and method for producing the same - Google Patents

Description

The invention relates to a polymeric, network-structured body made of a core structure of network-structured Polyurethane foam and thermoplastic material applied to it, as well as a method of making the same.

The new body produced according to the invention consists of a network-structured polyurethane polymer core, the completely and intimately from an outer shell made of polyolefin such as polyethylene or Is surrounded by polypropylene; the polyolefin is bonded to the polyurethane material in such a way that the polyurethane structure is first moistened with a liquid, preferably water, then in the moist structure distributed through and through a polyolefin resin powder and the latter then '5 melts together in a heat zone to form a shell. If desired, the polyurethane core can be used remove. The new bodies according to the invention are distinguished by the fact that they are practical are membrane-free.

The previously known foams with a perfect network structure were made practically from polyurethanes but more recently, polyvinyl chloride foams have also been made by Acceptable permeability in a network-structured form using a new type of explosion process receive.

The term "network-structured" is a well-known technical term in the field of foam technology and identifies a grid-like product of nodes and spaced point-like to one coherent structure connected ribs. In general you need as a preliminary stage for the Network structure training either an open-cell structure (with communicating cells), which one can give a network structure in an explosive or chemical way, or a structure in which by partial chemical attack the cell walls can be removed. But even in the latter case it is open-cell Structure appropriate, while it is mandatory for the formation of a network structure by means of an explosion is to allow the gas to penetrate inside the body.

Polyurethane structures have the disadvantage of low acid and alkali resistance and des unwanted swelling due to most organic solvents. Polyvinyl chloride foams on the other hand, it is difficult to manufacture in a controlled manner with regard to pore volume and uniformity.

Most polyolefin foams, i.e. those made of polyethylene or polypropylene, have closed Cells, so there are practically no internal passages. As a result, the closed-cell polyolefin foams do not structure the network in an explosive manner.

But since it is known that polyolefins are on the one hand highly acid and alkali resistant and on the other hand against Solvents are resistant to swelling, one has been looking for network-structured polyolefin structures for a long time acid and alkali filtration. Efforts have already been made in many ways to produce them. So one has Polyethylene in the form of chips or fibers has already been combined to form a filter element. Other attempts consisted in the sintering of polyethylene particles to form frit filters. Although you already have polyolefin foams has produced, the pore size control in their network structure could be in the areas required for filtration purposes practically do not perform, whereas this is the case with polyurethane foams is quite possible.

Process for coating and / or impregnating objects of various types, e.g. B. also of foam structures are known per se. For example, it is known from US Pat. No. 3,061,460 to use a foam structure made of a non-thermoplastic material, e.g. B. polyurethane, with a plasticizer-containing plastisol of a thermoplastic resin, e.g. B. polyvinyl chloride or polyvinyl acetate, by dipping, spraying or pressing, to impregnate or soak and to gel the plasticized thermoplastic resin located in the pores or interstices of the foam structure to increase the elasticity and the binding 'ability of the foam structure by heating . Foam structures coated through and through, in which the pore or network structure is retained after the coating process and which are to be used, for example, as filter media, cannot be produced by the known method, since gelling occurs in the pores or spaces in the foam structure plasticized thermoplastic resin located in a both overall and locally more or less strong pore closure cannot be avoided. An impregnated foam structure produced by the known method cannot be used as a filter medium.

It is also known to coat a preheated object with melted polyethylene. Since, however, at all temperatures at which there is still no risk of decomposition for polyethylene, its Viscosity is very high, it is uneconomical to dip polyethylene-coated objects produce, surprisingly, it has even been shown that network-structured polyurethane when immersed in melted polyethylene is clogged and filled with it through and through.

Other methods of coating objects with polyethylene are based on the relative Heat transfer and the heat content of a fluidized bed of polyethylene powder versus one in it introduced, heated object. It can be seen that metal objects are particularly suitable for this Well. In the case of thin-walled sections or those with insufficient heat storage capacity, this prepares more satisfactory coatings many difficulties. Apparently because of their low heat transfer capacity and their heat characteristics one has nothing yet about layering organopolymer foams in a fluidized bed of polyethylene powder heard.

Overlaying by electrostatic means is in the case of polyurethane foams because of their inadequacy Conductivity not feasible. In this way you can only cover comparatively flat metal sheets and even then only receives very thin layers.

The invention is based on the object of a porous, network-structured foam structure To coat polyurethane with a polyolefin while maintaining the network structure so that the finished polymeric body on the one hand the useful pore size characteristics of polyurethanes and on the other hand has the chemical resistance of polyolefins.

The invention thus relates to a polymeric, network-structured body made from a core structure

mesh-structured polyurethane foam and on it applied thermoplastic material, which is characterized in that the coating consists of melted polyolefin resin.

The invention also relates to a method for producing such a body, which thereby is characterized in that the network-structured core structure is moistened, in it through and distributed by polyolefin resin powder and the latter at temperatures below the decomposition points of Polyurethane and polyolefin melts onto the network-structured core structure and these work steps repeated if necessary.

In the manufacture of the polymeric, network-structured body according to the invention, neither are like this is absolutely necessary in the manufacture of the body known from US Pat. No. 3,061,460, Plasticizer additives and special measures for the preparation and incorporation of the plastisols (in the foam structure) required nor is there a risk of pore closure.

In general, there are network-structured polyurethane structures and composite structures produced accordingly, As already mentioned, from spaced ribs united at nodes, which means about Dodecahedra with approximately pentagonal surfaces that are practically free of membrane material are created. of course is this structural description is somewhat idealized, and the actual products have something from one another different dodecahedron units.

Although the individual cells are randomly oriented and therefore anisotropic to one another, this is the case Overall structure like an isotropic body. This foam property is desirable because of the pressure drop characteristic is cheaper than the known filter plates. Because of their uniform pore size and more isotropic nature compared to the known anisotropic filter and contact media, for example in the form of polyethylene mats, are consequently Structures made from the new composites especially for acid and alkali filtration purposes suitable.

In addition, the new composite structures show improved properties with regard to the load-deformation ratio. So is z. B. the energy required for compression in polyethylene-coated Polyurethane much higher than uncoated polyurethane. This property takes place Good application with self-supporting filter.

Correspondingly surprising results are obtained when the novel composite structures are thermally deformed to. any desired shaped articles. If you have the network-structured polyethylene-polyurethane structure heated, held in the desired shape and then cooled, you get a permanent shape A structure that, unlike polyurethane, does not return to its original shape on its own. This property of the new structure enables the production of various types of dimensionally stable articles with heavy moldable outlines.

In addition, the novel structure can easily be combined with various other materials, since molten polyethylene has good adhesive properties. For example, composite filters can be used with produce different pore sizes in such a way that one superficially with such a new structure the polyethylene melts and then merges with a second, narrow-pored structure of the new kind. There is no need to say that a wide variety of composite bodies can be produced in this way can. In a similar way, you can connect the new structure with any other surfaces that have sufficient binding capacity to melted polyethylene.

When normal polyurethane foams are deformed, there is a noticeable compression of the original structure and the associated noticeable impairment of the pressure drop characteristics of the molding. Everything has been tried to avoid this compression; certain very cumbersome methods have already provided a partial solution to this deformation problem, but the results have remained below what is desired. For example, a less than satisfactory attempt at a solution has been to cast polyurethane panels and them to be deformed and cured before a critical period of time has elapsed. All of these difficulties can can now be avoided by heat deformation of the novel polyethylene-polyurethane composite structure.

The new composite structures produced according to the invention are suitable for use in hot system filters, Humidifiers and Evaporative Cooling Plates (being-associated with surface modifiers such as glass, asbestos, feldspar or pumice stone can be used). So let yourself for example by using polyurethane as a carrier and an adhesive for the deposition various fine particulate material or powder on it, consisting of the materials already mentioned or others, such as alumina, carborundum and the like., produce novel, surface-modified structures.

It has now been found according to the invention that there are many problems of filtration occurring with polyurethane, Solve shaping and other types with the help of largely network-structured polyolefin structures can, which can be achieved by enveloping network-structured polymeric polyurethanes with this polyurethane structure similar polyolefin coating can win. Other products obtained from the new structures consist of compacted materials with good porosity and permeability with good structural strength. For example, compressions in a ratio of 2:15 to the initial volume were achieved.

As already stated, the invention is implemented in such a way that a polyurethane structure is used preferably moistened with water, in the moist structure powdery polyolefin, ζ. Β. Polyethylene or Polypropylene or their mixed polymers, distributed through and through and then the polyolefin powder melted in situ by the polyurethane structure moistened with water and covered with powder for example by placing in an oven or a heating zone using infrared, Radiant or transferred heat is subjected to a heat treatment and this sequence of steps from moistening, dusting and heating repeated if necessary. Depending on the pore size of the polyurethane structure and the particle size of the polyolefin powder can be determined through the first two steps apply additional amounts of polyolefin powder.

It is known that polyurethane foams tolerate considerably higher temperatures than the polyolefins ^{until they decompose (at about 230 0 C), and briefly}

even higher temperatures are permitted at times. The weight gain can be increased upon repetition of this Process · depending on the pore size of the polyurethane foam and the grain size of the polyolefin powder up to 700%.

This reference number will be explained in more detail later.

As noted, the polymeric bodies made in accordance with the present invention are generally the same Structural shape like the polyurethane foam; the end product therefore depends in its physical Appearance depends on the foam in question. In general, the pore size of the polyurethane foam is between 2 and 24, preferably between 2 and 18 pores / cm and in particular between 4 and 10 pores / cm.

In general, polyurethane foams are made from a polymeric polyol resin and a Polyisocyanate, whereby these components are produced in the presence of water with the release of blowing gas and / or a blowing agent activated by the heat of reaction, while the polymer has a a more solid, but still malleable state is achieved. Most common foams are made from either a polyester or a polyether resin. Such network-structured foams are available in the stores.

Polyolefins suitable for the process according to the invention are prepared in a known manner from precursors such as ethylene, propylene, 1-butene (and its isomers), or mixtures thereof. Their suitability depends on their melting point being below the decomposition temperature of the polyurethane. To certain advantageous properties, such as to obtain stress tolerance, in turn, the melting temperature of Uberzugsmaterials should not exceed 232 ⁰ C, depending on the heat resistance of the substrate. In the case of the present method, high temperatures above 232 ° C can also be tolerated if the exposure time is only short. However, the temperature should preferably be below 232 ° C and preferably below 215 ° C.

Polyolefin powder, e.g. B. polyethylene powder with grain sizes from 0.125 to 2 mm, densities between 0.912 and 0.950 and above and melt indices from 1 to 140, polyethylene and ethylene polymers with various densities up to the highest, polypropylene powder or any other fusible powder of polyethylene, polypropylene and their mixtures, Polybutene, polypentene, etc. as well as polyethylene powder with grain sizes from 0.080 to 2 mm and polyethylene with densities above 0.95, and preferably even higher densities, are commercially available. Using of the polyolefins listed above, it must be ensured that their melting and pouring points do not exceed the decomposition temperature of the polyurethanes used.

The following data shows the results of a pressure drop test on an uncoated or with Polyethylene coated polyurethane of 4 pores / cm. '-

The results show that the more rounded cross-sections of the coated ribs have less resistance than the concave triangular in the control sample. In general, the pressure drop increases with increasing amount of polyolefin only very little to, and structures with up to three times the amount of polyolefin with respect to polyurethane show only a slightly higher pressure drop.

Table I.

Pressure drop test with uncoated resp.
coated polyurethane

sample

Control attempt,
uncoated
Polyurethane foam, 10 pores / cm,
2.5 cm thick

According to the invention
Structure, 10 pores /
cm, 2.5 cm thick ....

coating compound
in percent by weight
Polyurethane foam
based

150

Pressure drop Δ P in centimeters of water column; Water at a flow rate of 106 m / min

1,875

Table II

Pressure drop values of compressed polyethylene-polyurethane foams with 6 pores / cm

Pressure drop / lPin cm water column from 1.27 to 0.45 cm Flow
speed a given water flow
speed compressed foam m / min 1.25 cm thicker material Polyethylene-poly 0.10 urethane foam 0.15 45.7 0.03 0.20 60.9 0.05 0.30 76.2 0.07 0.38 91.4 0.12 0.48 106.6 0.15 0.58 121.9 0.20 0.71 137.1 0.25 0.86 152.4 0.31 1.01 165.1 0.38 182.8 0.44

Other foams with different densities show different pressure drop values and apparently thus a special feature, namely the pressure drop control with the help of the compression of the structures according to the invention. As described above, the polyurethane body has after the polyolefin powder first was sintered and then had flowed around the polyurethane body, a core made of polyurethane and a polyolefin shell that closely envelops it. The ribs of the net-structured body have im generally have an elliptical cross-section and are not profiled in a concave manner, as is the case with polyurethane foam.

If you need a structure consisting essentially of polyolefin, you have to use the polyurethane core remove from the polyolefin. This can be achieved by making the foam, for example in the manner known from the German Auslegeschrift 1 036 515, simply with a hydrolyzing the polyurethane Solution soaks or its ribs or nodes in the desired firmness of the Finished product cuts appropriate distances, in a strongly hydrolyzing solution of z. B. strong acid or alkali, preferably at elevated temperature and high concentration, with

the polyurethane core comes off. In principle, any hydrolyzing agent is suitable for this purpose. whereby but acids such as sulfuric acid, hydrochloric acid or phosphoric acid are preferred. You can also go with weak acids work, but they take undesirably long treatment times. Instead of Acids are also strong bases, such as sodium, potassium or lithium hydroxide and their salts with weak ones Acids can be used. The same applies to the salts of weak bases with strong acids. In all cases the polyurethane is hydrolytically degraded, although other unknown factors, such as in the case of more concentrated Sulfuric acid maybe oxidation, come into consideration.

Polyurethane foams that are insufficiently cured or that are too low, i. H. below stoichiometric 100% lying polyisocyanate index can be hydrolyzed even more effectively. the The pore sizes of the polyurethanes are approximately the same as those given above for the polyolefin structures.

When using low-density foams, they offer correspondingly less due to the strong ones Hydrolyzing agent vulnerable mass.

In general, polyester-polyurethanes are the preferred starting material for the process according to FIG of the invention, but other polyol materials such as polyethers are acceptable if one longer treatment time can be accepted.

Instead of the polyurethane polyolefin structure for the purpose To facilitate the introduction of the hydrolyzing agent, one can also cut the polyolefin powder Heat until it becomes liquid and the ribs and nodes of the polyurethane structure only partially let cover. In this way, with correct treatment, only part of the polyurethane surface will be removed subject to hydrolytic degradation. A structure obtained in this way also falls under the idea of the invention, but is because of the tendency of polyethylene less firm for splitting into single cells, but on the other hand because of its considerably larger size Surface for special purposes of use.

Besides these two methods of incorporating the hydrolyzing agent into the polyurethane structure one can also start from cut material that has exposed edges (provided that it is not subsequently underwent a coating treatment), and long enough with an over-strength hydrolyzing agent, like sulfuric acid, treat; So where the treatment time does not matter, you can go to remove the polyurethane in this way. This procedure is generally suitable for small format Pieces. Wherever contamination of the filtrate stream is insignificant, the whole structure can be used use and then after some time retains the polyolefin framework.

If polyolefin powder has been added to the polyurethane-forming starting material, the after Treatment obtained polyolefin structure a considerably thinner core. In general, the hollow-core products used as such. However, if the hollow core is undesirable, one submits such a structure of an explosive flame front, but one has to do so for its protection against melting or Worry about burning.

Using the following examples and tables, the production process according to the invention for the network-structured, covered structures explained. The tables show the relationships between the process and product variables are shown, which reveal the various peculiarities of the invention.

^5baren Example 1

A 15 χ 15 χ 2.5 cm test specimen made from one Commercially available foam with 4 pores / cm was mixed with a polyethylene powder with a grain size of 0.30 mm mesh size, a melt index of 22 and a density of 0.9 IfT coated in such a way that the test specimen was first moistened with water, then dusted with the powder, dried and finally in an oven at 180 ° C for 10 minutes melted. The polyethylene coating was 229% of the weight of the polyurethane. Were in the same way Overlays with 190,269 and 310% polyethylene received.

Example 2

A polyethylene-coated polyester-polyurethane foam (with polyethylene glycol adipate as the ester component) with 4 pores / cm was on his Chemical resistance depending on the grain size of the polyethylene powder used a melt index of 22 and a density of 0.916. The powder with a grain size of 0.105 mm had a melt index of 5 and a density of 0.924. The results obtained are in given in the table below.

Table III

Effect of Particle Size
on the chemical resistance

Related
Olefin in Weight
loss on
Polyurethane
21% HCL 2 hours at 6O ⁰ C Standard size
in mm Weight
percent,
related to
Polyurethane 100 70%
H ₂ SO ₄ 10%
NaOH 0.84 406 42 100 39 0.50 343 28 93 21 0.30 281 2.5 49 5.4 0.177 210 41 83 0 0.105 180 72 2.8

The values show that despite the strong coating due to the coarser-grained resin substance, the highest Chemical resistance with this type of polyethylene in the grain size range between 0.30 and 0.177 mm ' Mesh size is achieved. Further 'experiments showed that variations in the melt index of the polyethylene have only a minor influence on the chemical resistance. Despite their above-proven acid resistance these structures can also be used for other purposes, such as shaping or profiling.

Example 3

The relationship between polyethylene resin coating and chemical resistance was based on one Mixture of 25% polyethylene powder with a grain size of 0.105 mm and a melt index of 5 and 75% polyethylene powder with a grain size of 0.30 mm and a melt index of 22 examined. The polyurethane foam coated in this way had the same properties as in Example 2. The in

209 627/63

The values given in Table IV below were obtained by immersing a cut sample in acid. Even better values than those given were obtained by additional covering of the cut edges for the purpose Covering the polyurethane core against the acid

^ö Table IV Weight loss des Effect of plastic uptake Polyurethane, 21% HCL, on the chemical resistance 2 hours at 60 ^° C Applied polyethylene resin 47 (in percent by weight 19th of polyurethane) 16 174 2.5 265 295 445

Example 4

Influence of water absorption and resin grain size
on resin uptake

Water absorption Resin absorption Grain size in percent by weight in percent by weight in mm of polyurethane of polyurethane 0.84 33 200 0.84 58 265 0.84 82 304 0.84 107 285 0.50 25th 195 0.50 50 254 0.50 75 273 0.50 100 278 0.30 25th 186 0.30 50 223 0.30 75 221 0.30 .100 250 0.177 25th 119 0.177 50 136 0.177 75 156 0.177, 100 197 0.105 25th 77 0.105 50 105 0.105 75 94 0.105 100 94

20th

The fine-grained (0.105mm) polyolefin has been found to always provide a perfect one Coating without visible "dry spots" under the microscope, but it is thinner than with coarser polyethylene particles. When using a mixture of 25% polyolefin powder of one grain size from 0.105 mm and 75% of a coarser polyolefin powder you not only get a better coating, but also an increased resin uptake.

30th

Foam with the properties given in Example 2 was made with that described in Example 3 Polyethylene coated, with polyethylene grain size and polyurethane water absorption varying became.

Table V

40

45 These figures show that resin uptake increases with increasing grain size. It should be noted, however, that when using coarse grain (e.g. 0.84 mm mesh size) the chemical resistance even with high resin absorption decreases, while the physical properties, such as Pressure load deformation, improve noticeably. Tests carried out in the same way with a fine-pored (10 pores / cm) polyurethane and a polyethylene with a grain size of 0.177 mm, a melt index of 22 and a density of 0.916 gave a resin pick-up of 217%; Attempts with coarser pores (4 pores / cm) polyurethane and melted polyethylene with a melt index of 9 and one A density of 0.950 gave a resin pick-up of 150%.

Example5

A polyurethane foam that structures a network through the explosive decomposition of an acetylene-oxygen mixture has a glassy-appearing surface that does not have the polyethylene applied cooperates. Rather, a stretching of the coated foam leads to loosening and in the case of a thin coating area, the resin may even become detached.

The physical properties of the new composite structures differ surprisingly from those of the polyurethane material. For example, the ribs of the coated, network-structured Structure an elliptical cross-section with z. B. a foam sample with 4 pores / cm and 267% Resin absorption on average 0.51 mm long and 0.47 mm short axis. With uncoated polyurethane foam on the other hand, the ribs have a cross-section of an approximately equilateral, concavely drawn-in Triangle.

The stiffness of the structures according to the invention is linearly related to the percentage resin uptake. An adipic acid polyester - polyurethane - foam (4 pores / cm), which is made with polyethylene (melt index: 22, grain size: 0.30mm, density: 0.916) is coated, shows the following stiffness values.

Table VI

Forming the stiffness factor of polyethylene-polyurethane composite sheets

50 Resin absorption
(%) Stiffness factor
(G) 0 20th 55 100 90 200 140 300 200 370 240

60 The stiffness factor is the weight required to bend a ^{piece of polyfoam with a cross-sectional area of 6.452 cm 2} that protrudes 19 cm above the edge of a 15 cm high block to the point where it makes an angle of 53 ° forms. All weights are placed on top of the block and within one inch of the free-standing end.

Table VII

Influence of resin uptake between 190 and 310 percent by weight on physical properties

the polyethylene-polyurethane composite structure at 24 ° C.

(The polyethylene starting material had a melt index of 22, a grain size of 0.30 mm

and a density of 0.916)

Adipic acid polyester
Polyurethane foam,
4 pores / cm '190% P.
Po polyethylene on net structure
polyurethane foam with 2.5
269% unertem
Pores / cm
310% 1.05 ± 30% 2.34 2.49 ± 29% 2.54 ± 5% 0.506 ± 25% 8.23 8.75 ± 24% 11.75 ± 9% 228 ± 28% 98 120 ± 31% 96 ± 12% 0.943 ± 28% 2,420 2.527 ± 24% 2.547 ± 15% 19.2 29.2 37.3 ± 10% 27.3 ± 3% 0.012 0.471 0.823 1.20 2.53 13.97 25.3 25.3

Tensile strength *) kg / cm ²

Modulus of elasticity under tensile load kg / cm ²

Elongation, kg / cm ²

Tear strength **) kg / cm ²

Remaining deformation at 70 ⁰ C,%

Compression energy absorption at a 20.3 / 25.4 mm deformation in kg / cm ² , calculated from the
Compressive load deformation curve

Shock absorption, cm

*) Value of the highest possible load in kg / cm ² before the material tears under tension. ♦ *) Load in kg / cm ² at which the material actually tears.

The height of fall of a 1.8 kg heavy foam is used as a measure of the shock absorption capacity of a foam Ball necessary to cope with the blow transmitted by a 2.5 cm thick foam sample just below Break 1.6 mm thick microscope slide glass. The ball consists of a 30 g Heavy hollow polyethylene body made from a material with a melt index of 3 and a density of 0.993 and a grain size of 0.30 mm, an outer diameter of 8.9 cm, made with Wood's alloy is filled to 1.8 kg final weight. A cemented into reinforced concrete serves as a base for the object glass Polyvinyl tile. The 7.5 χ 2.5 cm slides were commercially available Microscope slide.

Table IX

Effect of resin uptake on the
Compressive stress-deformation properties
a 2.5 cm thick sample of 4 pores / cm
exhibiting polyethylene-polyurethane composite structure at 24 ° C.
(The polyethylene feedstock possessed
Melt index 22, grain size corresponding to 0.30 mm mesh size and density 0.916)

Table VIII

45

Effect of resin absorption. on the compressive stress-deformation properties a 2.5 cm thick sample of 4 pores / cm having poly-

Ethylene-polyurethane composite structure at 24 ° C. (The polyethylene raw material had a melt index of 22, grain size corresponding to 0.30 mm mesh size and density 0.916)

55

0% Pressure applied i 267% η kg / cm ² 0.421 0.548 voltage 0.464 0.604 mm / mm 190% 310% 0.527 0.689 0.4 Polyethylene intake 0.632 0.843 2.54 0.4 0.274 0.733 0.984 5.08 0.42 0.288 1.054 1.265 7.62 0.45 0.316 1.476 2.109 10.16 0.5 0.365 - 3.093 12.70 0.6 0.435 3.163 - 15.24 0.8 0.562 17.78 - 0.805 19.50 1.52 - 20.32 1.406

Upset
Coating material,

based on the
Polyurethane weight

100
200
300

Applied pressure in kg / cm ²

25% deflection

0.028
0.140
0.323
0.632

50% deflection

Q, 042 0.210 0.492 0.975

75% deflection

0.098 0.527 1.165 2.39

65 Tear strength coated with 267% polyethylene polyester polyurethane foam with 4 pores / cm falls within a temperature range of 24 82 ° C each for 6 to ⁰ C. 0.141 kg / cm ^2.

With a load of the kind required for 25% deflection at room temperature, 170, 267 and 310% polyethylene coated polyurethane foams with 4 pores / cm up to about 99 ° C up powerful. The same composite material withstood 30 minutes in a 1.20 m high pile lingering in boiling water for a long time, with the 2.5 cm thick bottom piece shrinking less than 15% in thickness suffered. The above values show that

the composite structures have higher collapse temperatures than polyethylene. A network-structured polyester-polyurethane foam with 4 pores / cm and 332% coating made of polyethylene with melt index 3 and density 0.918 was compared with the same foam, but in which 70% of the polyurethane was leached. Samples of each 5 × 5 × 2.5 cm in size were ^{loaded with 0.35 kg / cm 2} and stored in an oven at 93 ^° C. for 15 minutes. The comparison results were: The deflection of the composite material was 25% at room temperature and 53.5% after heating, whereas the deflection of the leached material was 52 and 68%. However, this means that there is mutual reinforcement in the composite material, that is, the polyurethane structure would easily collapse with the same load. The higher load-bearing capacity at elevated temperatures also indicates the interaction of the two materials. Unless otherwise stated, all physical properties were evaluated according to ASTM specification D 1564-59-T.

Example 6

A 15 χ 15 χ 2.5 cm large commercial foam test specimen with 4 pores / cm was coated with commercial polyethylene powder with a grain size of 0.30 mm, a melt index of 22 and a density of 0.916 by first moistening it with water, then with the polyethylene powder dusted and dried and finally the powder was brought by heating to 18O ⁰ C lOminutiges for melting. The rather short oven dwell time of only 10 minutes was chosen on purpose so that the molten resin would definitely not completely cover the substrate and allow later acid attack. The powder application method can be varied depending on the type of coating desired. A polyethylene powder with a density of 0.95 was used in a similar manner. Instead of polyethylene, polypropylene powder can also be used.

Example 7

The sample produced in Example 6 was first immersed for 5 ¹ I ₂ hours in 60 ° C. and then for 6472 hours in 21% hydrochloric acid at normal temperature and then washed and dried. As a result, all of the polyurethane foam was converted into another substance. The polyethylene coating did not appear to have been attacked by the acid. The above-mentioned foam was also treated explosively with an explosive mixture of oxygen and acetylene, as a result of which changes in properties, such as melting of its ribs and nodes, were achieved.

Example 8

190 χ 56 χ 2.5 cm panels made from commercially available, mesh-structured panels Polyester-polyurethane foam with adipic acid polyethylene glycol ester as the ester component were moistened in an immersion tank and on passing through two squeeze rollers 45% water absorption - based on the weight of the polyurethane - adjusted. These damp plates were through and through with polyethylene powder with a grain size of 0.30 mm, a melt index of 22 and a density of 0.916 interspersed and then heated to 195 ° C for 15 minutes. This measure was repeated.

Polyethylene powder was made from the same foam under identical conditions with a Melt index of 3, a density of 0.918 and a Grain size of 0.50 mm melted, with the change in the melt index from 22 to 3 additional Melting time was required if the powder was applied in two stages.

Suitable samples were cut from this foam and according to the ASTM standard D 1564-59 T examined. The results are listed and discussed below.

Raising the melting point of the melted polyethylene causes, as the tablets show, a drastic increase in the load if you have polyurethane next to each other, polyurethane and polyethylene low density coated and compares low density polyethylene foam.

This increase in value shows that the structures according to the invention even after removal of about 95% of the polyurethane obtained highly desirable properties.

Z ₅ Table X

Compressive load-deformation relationships
for net-structured polyester-polyurethane foam with 10 pores / cm
30th

Pressure load deformation in kg / cm ² in mm / mm 35 0.0281 2.54 0.0284 5.08 0.0295 7.62 0.0323 10.16 40 0.0369 12.70 0.0435 15.24 0.0604 17.78 0.105 20.32

Table. XI

Compressive load-deformation relationships

with 4 pores / cm for the foam according to Table X.

but with a 300% coating of a polyethylene with a melting point of 22 and a density of 0.918

without acid leaching

load deformation in kg / cmr in mm / mm 0.464 2.54 0.478 5.08 0.492 7.62 0.548 10.16 0.632 12.70 0.880 15.24 1.546 . 17.78 3.515 20.32

Table XII

Compressive load-deformation relationships

in the case of foam according to Table X, but with a 331% coating of a polyethylene one Melt index of 3 and a density of 0.918

without acid leaching

load table XIII deformation in kg / cm ² in mm / mm 0.675 2.54 0.844 5.08 0.950 7.62 1.090 10.16 1,335 12.70 1,828 15.24 2.812 17.78 - 20.32

Compressive load-deformation relationships

for the coated foam according to Table XI, but after leaching of about 95% of the

Polyurethane with hydrochloric acid

load deformation in kg / cm ² in mm / mm 0.147 2.54 0.197 5.08 0.210 7.62 0.253 10.16 0.323 12.70 0.478 15.24 0.914 17.78 3.093 20.32

Table XIV

Compressive load-deformation relationships

for the coated foam according to Table XII, but after leaching of about 95% of the

Polyurethane with hydrochloric acid

load deformation in kg / cm in mm / mm 0.1898 2.54 0.323 5.08 0.449 7.62 0.548 10.16 0.740 12.70 1.054 15.24 1.757 17.78 4,218 · 20.32

The above values show that net-structured structures made of higher density polyethylene, from which about 95% of the polyurethane is removed, compared to a) lower with polyethylene Density coated polyurethane and b) a structure made of lower density polyethylene (from the 95% of the polyurethane has been removed) have excellent structural properties. The load-deformation values for polyurethane foam indicate a considerably less rigid structure.

As shown above, these constitute polyolefin structures self-supporting, net-structured bodies, which are particularly suitable for acid or alkali filtration or defog.

Higher density polyethylene from around 0.95 and above and polypropylene give stiffer and stronger Structure, while polyethylenes of lower density provide weaker structures. More solid structures, for example Polyethylene having a density of preferably about 0.935 to about 0.970 is preferred.

Polypropylene structures are generally more rigid than polyethylene because of their greater rigidity also very useful, but require a high temperature stabilizer or an antioxidant.

You can also first coat a polyurethane foam with polypropylene Remove polyurethane and recoat with polyethylene. But since the margin between the Melting of the polyethylene and the collapse of the foam structure is much closer than with When it comes to polyolefin-polyurethane combinations, precise temperature control is essential.

Claims (10)

Patent claims: 1. Polymeric, network-structured body consisting of a core structure of network-structured polyurethane foam and thermoplastic material applied to it, characterized in that the coating consists of melted polyolefin resin.
2. Body according to claim 1, characterized in that the coating material in at least the same amount by weight as the core material is present. 3. Body according to claim 1 or 2, characterized in that its pore size between about 2 and about 24, and preferably between about 2 and about 18 pores / cm. 4. Body according to one of claims 1 to 3, characterized in that the coating consists of Made of polyethylene or polypropylene. 5. Body according to one of claims 1 to 3, characterized in that the coating consists of a polyethylene-polypropylene composition. 6. Body according to one of claims 1 to 5, characterized in that the core material is made of polyurethane. 7. Process for the production of polymeric, network-structured bodies with the application of thermoplastic material on a core structure made of mesh-structured polyurethane foam, characterized in that the network-structured core structure is moistened, in it through and distributed by polyolefin resin powder and the latter at temperatures below the decomposition points of polyurethane and polyolefin on the network-structured core structure is melted and these work steps are repeated if necessary. 8. The method according to claim 7, characterized in that one polyolefin powder or mixtures of polyolefin powders of various grain sizes melts onto the network-structured core structure. 209 627/63 9. The method according to claim 7 and 8, characterized in that the polyurethane component of a network-structured core structure made of polyurethane foam with a melted polyolefin coating is dissolved in a manner known per se with a solution which has a hydrolyzing effect on polyurethane. ' 10. The method according to claim 9, characterized in that a net-structured core formed from polyurethane foam melts a first layer of a polyolefin powder, from the structure coated in this way, the polyurethane is released with a hydrolyzing solution, the remaining network-structured poly. Olefingebilde moistened and distributed in it thoroughly .. a \ another polyolefin having a lower melting point and melted on it.