DE2132284A1 - Process for the production of fiber-reinforced rigid foam bodies and foam bodies produced by the process - Google Patents

Description

DIpI-I ... H. MITSCHERUCH 1ί ££ ϊϊ " Dipl.-Ing. K. GÜNSCHMANN Telephone: 10811} «2» i684

Dr. rer. near W. KDRBER 29 «June 1971

PATENTANWÄLTE Br.Kö / kq

COHTHAYBS AG

0H-8o52 Zurich / Switzerland
Schaffhauser Strasse 58o

Patent application

Process for producing fiber-reinforced rigid foam bodies and foam bodies produced by the process _c

The invention relates to a method of manufacture of fiber-reinforced, machinable and cutable rigid foam bodies by pouring a predetermined one Amount by weight of a liquid, for later foaming and solidifying binder resin mixture prepared in the foaming state in a cuboid, air-permeable mold cavity and foaming and allowing the contents of the mold to solidify to a predetermined final volume, as well as to a volume produced after the process Foam body

There are already known proposals for the production of specifically.light foam structures, for example, too based on polyurethane resin, in their cell walls for improvement the specific properties of the overall structure Fiber material, preferably glass fibers, embedded

are. 10988.2 / 1298

According to one of the previously known procedural principles, for example for the production of case lids or other prefabricated components, an air-permeable one in one operation The mold cavity is filled with a loose glass fiber mass, and it is inside this glass fiber mass a resin liquid prepared for foaming injected high pressure from one or more nozzles, so that the glass fibers from the inside with resin liquid to be soaked. However, this known method principle causes entrainment or displacement of the Fiber mass from the injection points against the mold walls, so that the fiber density in the outer walls of the Finished product becomes large and small inside the body. Provided that the danger is avoided by subtle fine-tuning of the injection quantity and the injection speed It can be the case that in individual areas the fiber density becomes too great for the fibers there to still be complete soaked in foam and glued together could be, a favorable distribution of strength is created for a prefabricated structure. The outer layers become denser and correspondingly more resistant than the inner parts. But it has been shown that way again and again at certain points the glass fibers are insufficiently embedded in the foam. In no case lets according to this, principle a homogeneous, glass fiber reinforced

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Foam body with the same good strength properties everywhere and the same specific weight everywhere produce so that you can use it to produce composite structures supporting bodies of selectable size and shape and of predetermined strength, such as from blocks of wood or planks.

According to another, previously known process principle, relatively thin, two-dimensional structures are made of meshed or glass fibers glued together from both sides with fibers prepared for foaming Polyurethane resin liquid impregnated and then moved between parallel conveyor belts. So that should can be achieved that in the subsequent foaming the resin mixture the two-dimensional fiber structure of both Penetrates from the outside so that a glass fiber reinforced foam structure is created after solidification. The air can only then be displaced from the interior of the fiber structure and replaced by foam if the whole structure remains relatively thin and an open-cell foam is used. Even through subsequent gluing of the foam-impregnated glass fiber layers does not result in favorable foam structures, because they tend to absorb moisture due to their open cells, which creates the desired specific

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Weight is greater and thus the heat insulation capacity is lower.

According to a further previously known process principle, homogeneous small-cell, glass fiber reinforced Lightweight structures in relatively thick panels achieved by using a liquid non-foamable Epoxy resin-glass fiber mixture so-called microballoons, i.e. a voluminous, loose mass of thin-walled, phenolic resin or glass hollow spheres with outside diameters of less than 0.5 mm, are mixed until a plastically deformable synthetic mass is formed with which a mold cavity can be filled and which is cured in the mold. The finished product can, however can only be made so easily with great difficulty that its specific volume corresponds to that of wood is similar. At least in comparison to the preferred direction of natural wood, they are in this way achievable strength properties of the end product mostly inadequate. According to this principle, namely only a relatively small proportion by weight of glass fibers are added to the epoxy resin, if afterwards the hollow spheres are to be mixed in.

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The aim of the present invention is to be seen in machining in a less labor-intensive manner machinable and cut planks or blocks with low specific weight and high tensile strength as a closed-cell plastic material that does not absorb moisture. The plastic material should represent a small-cell rigid foam structure and a As high a proportion of reinforcing glass fibers as possible, evenly distributed and individually complete glued into the plastic in order to achieve relatively high strength values in the end product. At best is a glass content of 50 percent by weight

of the end product.

¹ ι

Another object of the invention is to provide a method by which, while maintaining the relatively high glass content, the specific weight of the end product easily within wide limits can be predetermined fairly precisely, so that e.g. any liter weights in the range of 100 - 500 g depending on the Customer requirements can be achieved.

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The invention is based on a previously known, industrially proven method for producing Machinable and cuttable hard foam bodies by pouring in a predetermined amount of weight a liquid binder resin mixture prepared for later foaming and solidifying in the foamed state into a cuboid, air-permeable mold cavity and let it foam and solidify the shape content to a predetermined final volume. According to this well-known process, it is true that homogeneous and can be pre-set fairly precisely to a desired density in a range of approx. 50-300 kg / m Show body. The tensile strength of such foam structures is only small.

e.g. (- ^ with a volume weight of 60 kg / m ³ : 3-10 kg / cm ² ^ T with a volume weight of 300 kg / m ³ : 15-50 kg / cm ²

Also the flexural rigidity of such unreinforced rigid foam structures or the modulus of elasticity E is too low for many applications e.g.

3 2

E at a volume weight of 60 kg / m: 15 kg / mm

E at a volume weight of 300 kg / m ³ : 75 kg / mm ²

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In addition, e.g. rigid foam structures made of polyurethane resin become soft at temperatures of 60 - 80 ° C, and the rising internal pressure of the propellants contained in the closed cells inflates them Foam structures from the inside so that they lose their shape, e.g. when exposed to sunlight. To the Production of rigid foam bodies with fiber inserts in the resin significantly improved strength properties and, above all, improved dimensional stability At higher temperatures of the end product, the method according to the invention is characterized in that after pouring the foamable binder resin liquid

speed in the air-permeable mold cavity a pre-

Correct amount by weight of aerated fiber mass in more uniform Spread over the entire floor area and that before the onset of foam formation with the help of an air-permeable that fits and can be driven in from the open top of the mold in the mold cavity Press plunger the mold content is compressed to its minimum volume to displace air, that afterwards during onset and during foaming

of the binder under the foam pressure of the press

The punch gradually moved back to enlarge the mold cavity to a predetermined final volume

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and that after reaching this predetermined final volume, the mold contents until solidification in the shape is left.

The fact that the fiber mass with the press ram from above into the liquid binder mass in which the Foam formation should not have started yet, is pressed in and compressed in the process, the liquid penetrates with complete displacement of the air previously contained in the fiber mass by the press punch into the spaces between the fibers and completely envelops each fiber, whereby the three-dimensional everywhere 'guaranteed the same distribution density of the fibers remain.

When inserting and during the foam development, the press ram is gradually reached down to one a desired volume weight of the end product is gradually adjusted back to a predetermined "end volume care must be taken that the contents of the form are always kept under a certain excess pressure.

If the tensile strength and the modulus of elasticity may be slightly lower in the end product, possibly a certain elastic resilience is even desirable

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and only the dimensional stability of the end product up to temperatures above the softening point of the binder still has to be guaranteed, textile fibers can also serve well in place of glass fibers Afford.

As foamable and solidifiable in the foam state, Binder liquid are preferably urethane binder resins well known per se with polyether or polyester resins and a prepolymer with isocyanate used to ensure closed-cell foam formation.

To the consumer, the chemical composition is that of the manufacturers of the components or both The two liquids to be mixed by the consumer are practically never known but only one cipher designation. The urethane suppliers, on the other hand, meet practically all requirements set by the consumer of special properties. For the present invention, a relatively long duration of the liquid is particularly important Foam-free state of the mixture from pouring the two main components together until onset the foaming is desirable because during this time the loose fiber mass is filled into the mold cavity and the compression of the form content to its minimum

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volume must take place. Afterwards, however, the foaming and foam consolidation should take place relatively quickly. Until now downtimes of about 40-80 seconds are about a maximum, which is sufficient to create a mold cavity to a final thickness of the fiber-foam structure panels of about 10 cm and to press.

To quickly fill the required amount of air-containing fiber into the mold cavity after the When pouring in the binding resin liquid, it is advantageous to use a one-piece fiber block that fits into the Mold cavity and consisting of relatively long, un-

I.

straightened the fibers at their crossing points with a sizing agent soluble in the liquid resin mixture are glued.

It is also possible to have several rectangular mats stacked one on top of the other to form such a cuboid locally bonded fibers are used. The solubility of the binder, through which the long fibers are mutually glued at their crossing points,

i
in the resin liquid is important because otherwise the

Fiber mass is not sufficiently tightly compressible.

I.
I.

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With the use of powerful litter devices, however, relatively short fibers can also be poured into the mold cavity quickly enough in loose form. According to the method according to the invention, fiber-reinforced, closed-cell urethane rigid foam structures with a high fiber content (up to 50 percent by weight) and good homogeneity in thicknesses of up to about 10 cm can be produced, the density of which can be precisely preset in the range of about 100-300 kg / m ^. Such structures can be machined and cut and can therefore be used as a semi-finished product, or as raw material, for example natural wood for the production of support cores for composite structures instead of non-reinforced foam structures, natural wood, or honeycombs .

Because only relatively cheap materials are used and the production according to the invention requires little working time, the cost prices are favorable, which are for the time being even higher than for natural wood, but are small compared to honeycomb structures , for example.

When using known urethane rigid foam resin mixtures, for example, glass fiber reinforced rigid foam

x
structures with the following properties result:

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Glass proportion 50% of the total weight

Glass content 0%

a) density 100 kg / m ³ 100 kg / m ³ tensile strength (J * 50-100 kg / cm ² 15 kg / cm ² modulus of elasticity E 100 kg / cm ² 15 kg / cm ²

b) density 300 kg / m ³ tensile strength '(T 250 kg / cm ² modulus of elasticity E * 750 kg / cm ²

300 kg / m ³ 50 kg / cm "

E * 75 kg / cm *

The fiber-reinforced urethane rigid foam structures which are produced by the method according to the invention ' can be glued to other materials just as well as unreinforced hard foam structure doors. They also practically take up no water. If several layers of fiber mats are used as a fiberglass structure are layered on top of one another, layered end products result in which glass fiber reinforced foam layers are glued by fiberglass-free foam layers. This is transverse to the direction of the layer Poor tensile strength, but good in the direction of the layers.

Embodiments of the method according to the invention and fine structures in different manufacturing stages

ι
are shown schematically in the drawing.

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Show it:

Fig. 1 The first production stage, namely the introduction of a cuboid, air-containing Fiber structure la in a mold cavity Fl, in which the still foam-free resin liquid 2 has been poured.

FIG. 2 A fine structure image of the fiber structure 1 a according to FIG. 1.

Fig. 3 The compression of the mold contents to its minimum volume with the air-permeable press Stamp F2.

Fig. 4 The fine structure of the pressed mold contents Ib of Fig. 3.

Fig. 5 The final stage of the form content Ic after Return movement of the press ram and finished foaming of the resin liquid.

FIG. 6 The fine structure of the end product Ic according to FIG. 5.

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7 shows a drawing corresponding to FIG. 1 when several fiber mats ^{1 a 1 are introduced} into the mold cavity.

FIG. 8 A production stage corresponding to FIG. 3 with maximally compressed form content.

9 shows a representation of a layered end product corresponding to FIG. 5.

FIG. 10 A drawing corresponding to FIG. 1 when using short loose glass fibers la " the compression of the glass fibers.

In the drawings, Fl is part of a press mold with cuboid mold cavity and with F2 a drivable from the upper, open side into the mold cavity, air-permeable press stamp.

According to FIG. 1, a predetermined one is in the mold cavity F1 Amount by weight of a liquid urethane foam resin mixture 2 has been poured in such a way that in this resin liquid has not yet started foaming.

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If a glass fiber reinforced urethane foam board with a final volume of 10 dm ^ with a base area of the mold cavity of 100 cm χ 20 cm, corresponding to 2000 cm, and a final height of 5 cm, and with a glass fiber content of ^, 30% of the Total weight a volume weight of the end product of 200 g / dm * * is to be produced, 1500 g resin mixture and 500 g glass fibers are used for this. With a specific weight of 1000 g / dm * *, the non-foamed resin liquid will occupy a volume of 1000 cm ^ and cover the base of the mold at a height of about 7-8 mm.

To produce the end product, for example, the following liquid components, which were purchased from Reichhold Chemie AG, Hausen near Brugg (Switzerland) under the names Polylite 8666 or Polylite 8667 or Polylite 8667k, were mixed together:

a) 802 g "Polylite 8667"

b) 8g "Polylite 8667k"

c) 690 g "Polylite 8666"

The service life of this mixture in the liquid, not yet foaming state is at a temperature of

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20 ° C approx. 60 sec. Afterwards, the foam starts to form, which ends after another 5 minutes and changes to a solid state. If the weight of 1500 g resin mixture alone were foamed to a final volume of 7.5 dm with a density of 200 g / dm ^, a rigid polyurethane foam structure with a tensile strength 6 ** of <X 30 kg / cm ^{2 would result after total curing} .

But now according to the invention and FIG. 1 in the mold cavity Fl a relatively long (fiber length 5-30 cm fiber thickness 10 ^), undirected Fibers that fit into the mold cavity, i.e. that has a base area of 100 cm × 20 cm Glass fiber structure with a total weight of 500 g, immediately after pouring in the resin liquid brought in. The glass fibers 10 are at their crossing points with a soluble in the resin liquid Sizing agent 11 glued. A glass fiber cuboid of this type has a height given the assumed base area ha of about 3 cm.

Immediately after this air-containing glass fiber structure la has been introduced into the mold cavity, according to FIG. 3 by driving in the air-permeable press plunger F2

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from the upper, open porm side the entire form content Ib compressed to a height h ^ of about 8-10 mm, a structure according to FIG. 4 with closely compressed glass fibers 10b results. the Air is already there when it is compressed by the still non-foamed resin liquid penetrating from below been displaced from the fiberglass structure Ib, and the resin liquid now fills all remaining Gaps evenly between the glass fibers so that all glass fibers individually into Resin liquid. A small part of the resin mixture and the gases produced during foaming step out of the mold.

As soon as the foaming of the resin liquid then begins, the press plunger F2 is gradually moved back upwards during the foam development in the mass of the same, until a final height hc £ 50 mm of the mold contents _£ 1, ie the predetermined final volume of

6 '

10 dm "* has been reached. After about 6 minutes, calculated from the mixing of the resin components, the solidification of the mold contents 1 _c begins, which after a further 18 minutes has progressed so far that the glass fiber-reinforced foam body can be lifted out of the mold post-curing that takes 1 day

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should, the end product obtained can be further processed. Its glass fibers 10 are then complete according to FIG. 6 in a closed-cell hard urethane foam structure 20 embedded and glued in place.

Such a glass fiber reinforced urethane rigid foam structure then has the following properties:

Glass content 26% of the total weight

Density De 200 g / dm 3

Tensile strength (^ "^ 65 kg / cm ²

Modulus of elasticity E 2 300 kg / cm ²

Water consumption 1% by weight

c
Dimensional stability up to about 150 ° C.

The end product can be machined and cut like poplar or fir wood.

According to Fig. 7,8,9, instead of a single-stage glass fiber structure la a plurality of mats la ^{1 of the} same structure, but the smaller thickness (Da '1 mm) are used, which together also form a block of 3 cm thickness and the same glass weight of 500 g. The amount by weight of the resin liquid and its composition can also be the same.

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The compression of the mold contents according to FIG. 8 leads to the same minimum thickness hfc ¹ X.9 mm. On the other hand, it is planned to allow the mold content to rise to a final height h _c 'of 10 cm during the foaming of the resin, so that instead of just 10 dm ^{3, the} end product is 20 dm ³ , with an average density of ^{100 g / dm 3.}

This creates a layered end product with glass fiber reinforced urethane hard foam layers Ic which are glued to ^{one another by glass fiber-free hard urethane foam layers 2 1.} Such a layered glass fiber foam structure does not have a higher tensile strength than unreinforced foam when subjected to tensile stress transversely to the direction of the layer. On the other hand, the tensile strengths of this layer material are significantly higher when subjected to tensile loads parallel to the layer planes, for example according to the example mentioned ^ 50 kg / cm ^.

According to FIG. 10, after the predetermined weight of resin liquid has been poured into the mold cavity, an approximately equal weight amount of loose glass fibers la "(fiber length 3 mm, fiber thickness £ 10 M) is poured and first pressed to the minimum height h ^ with the press punch to a final height h _c

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set back. In this way, too, homogeneous structures according to FIG. 6 are produced with excellent Strength properties.

By choosing the weight amounts of resin and glass fibers or predetermining the final volume or the final height the content of the shape you have it in your hand, always with a selectable high fiber content of 25-50% the volume weight of the end product to predetermined values in the range of about 100 g / dm to 500 g / dm ^ in advance. The resin composition and the fiber material can can be varied within certain limits.

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Claims (1)

PATEJTiCAiISPEUCHB: j 1 ο jVerfaliren for the production of fiber-reinforced, machinable and cuttable hard foam bodies by pouring a predetermined weight by weight of a liquid, for later foaming and hardening in the foamed state, in a cuboid, air-permeable mold cavity and thereby foaming and solidifying the predetermined volume characterized that after pouring the foamable binding resin liquid (2) into the mold cavity (I ¹ I) a predetermined weight of air-containing paste (1) is poured in evenly distributed over the entire floor area and that before the onset of foam formation with the help of an air-permeable press plunger (F2) that fits and can be driven in from the open top of the mold to displace air to its minimum volume, so that afterwards when inserting and during the foaming of the Bi ndemittels (2) the Press-Stemper (Ρ2) to enlarge the lOrmhohlraumes (I ¹ I) to a predetermined final volume gradually aurtickveretellt and that after - 22 - 109882/1298 When this final volume is reached, the contents of the mold are left in the mold until solidification. ι ·
2. The method according to claim 1, characterized in that that as prepared for foaming and in the foam state solidifiable binder resin mixture a liquid polyurethane mixture containing a prepolymer with isocyanate, which after foaming turns into a closed-cell hard urethane ΐ ■ Solidified foam structure. r. ι 3. The method according to claim 1 or 2, characterized draws that on the poured binder resin liquid the predetermined, 25-100% of the binding resin weight (G2) amount of weight (Gl) \ - .
of aerated, undirected fiber mass (1) is introduced over the liquid binder resin mixture that by driving in the air-permeable Press punch (F2) the form content j to a minimum j '
volume, is compressed, whereby the glass J, ι: fiber material, displacing the ii
hold air evenly with resin liquid ¹ i is soaked and wetted, and that afterwards ! ^ jn onset and during the foaming of the resin liquid, through the gradual backwards I 1 . I. ■ 109882/129 8 movement of the press plunger under the foam pressure, the mold content is increased to a final volume corresponding to the desired specific weight of the end product (Ic) and remains enclosed in this state until it solidifies. 4. The method according to claim 3, characterized in that that a one-piece fiber guader (Ia) / fits into the Mold cavity (Fl) and consisting of relatively long, non-directional, at their crossing points (11) with a sizing agent (10) that is soluble in the liquid resin mixture (2) is used will. 5. The method according to claim 3, characterized in that the air-containing, non-directional glass fiber mass (la) is a plurality of rectangular mats (la ¹ ), each consisting of relatively long, non-directional and layered on one another to match a cuboid in the mold cavity (Fl) glass fibers (IQ) bonded with a sizing agent (11) that is detachable in the liquid resin mixture (2) is used at their crossing points » 109882/1298 6. The method according to claim 3, characterized in that ... that the predetermined weight of relatively short and loose glass fibers after the resin liquid is poured into the mold cavity (F2) as the air-containing, non-directional glass fiber mass. 7. By the method according to claim 1 or one of the Claims 2-6 produced cuboid, rigid polyurethane foam body, characterized in that the cell walls are distributed therein and individually glass fibers glued therein with a total weight, '■>: .ι at least 25% of the total body weight c
and that the specific weight of the total body does not exceed 500 g / liter. 8 «Glass fiber reinforced, closed-cell polyurethane rigid foam body according to claim 7, characterized in that it has a plurality of other by layers of unreinforced hard foam ti ^h structure of mutually glued glass ^ server-reinforced '' ι · ■ - '■ Contains foam layers, and that the 1
average specific weight of the total body is less than 250 g / liter. ι. ί 'The patent attorney 109882/1298 / ' li \ J ^{[lll [} ■■ ffSSffi Blank page