DE2148338A1 - - Google Patents

Description

September 24, 1971 R / Fi

Applicant: Specialty Converters, Inc. South Chapel and Dawson Drive

Newark, Delaware

UNITED STATES.

A 13 840 A 13 841

Polyurethane foam and process for its manufacture

The invention relates to cellular polyurethane which is used for many purposes, including where a high level of abrasion resistance is required. Many of these uses are not just about high levels of abrasion resistance but also "breathability" (easy permeability for air and water vapor) is in great demand. Combined abrasion resistance and permeability are among other things in cover fabrics for outerwear, furniture cover " fabric, upper leather for shoes, acoustic wall cladding and

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porous conveyor belt systems are very desirable.

Numerous methods of making an abrasion-resistant, non-porous skin on cellular polyurethane have been proposed been. In this process, a thin layer of hardened urethane foam is placed under a hot one, among other things Knife or a hot roller passed through to cause melting and solidification of the surface, or the urethane foam compositions (which contain a volatile blowing agent) are placed in a mold poured with cooled surfaces, which avoids evaporation of the blowing agent on the cooled surface and consequently molded articles with a surface skin comes. In all cases, however, the skins obtained are not porous and respiration is not achieved.

The object of the invention is to provide a cellular urether * with To create a skin that is both abrasion-resistant and very is porous. Another object is to provide an inexpensive and simple method of manufacturing these products create.

It has now been found that it is possible to use foamed polyurethane systems with a dense but gas-permeable structure on one side continuously. The structure with high density advantageously has the shape of a distinct skin that with the foam core with lower Density forms a whole. These layers of structural or integral foam can have very different thicknesses, very different ones Have elasticity, strength, elongation and tear resistance, whereas the surface skin is extremely thin (5 Milliinch or less) or 50 or even 100 Mill :.

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inch thick. In addition, the skin surface can be permeable be extremely dense, i.e. with a pore volume of only 10 to 20% per unit volume of skin foam, or they may have a lower density up to a pore volume of 75 to 85%, but generally the skin layer has at least twice the density of the foam core.

The invention seeks to provide an improved method of making integrated gas permeable foamed polyurethane systems or sheets, the density of which is significantly greater on one side than the density of the foam core, which is characterized in that a) a foamable liquid ITrethane resin mixture in the form of a thin layer pours, b) at least one side of the layer is heated while the core of the layer is kept at a relatively cool temperature is until the layer is substantially foamed and partially cured, c) the partially cured foamed layer is compressed, while it is heated differently to cause the foam to collapse on its heated side,

d) releases the location from compression, and

e) the hardening of the layer then leads to the end.

The sheet is preferably heated on one side while it is kept relatively cool on the opposite side will. In this way, a layer can be obtained with a distinctly integrated, high-density skin on one side behind which there is a core layer of low foam density that separates it from the opposite Side of the situation. That way you can

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also a layer with an increasing density from one side to the other, but without any special skin will. If both sides of the sheet are heated while the center piece is kept relatively cool, one can Make the layer with high density on both sides and relatively low density in the middle.

The invention also relates to an integrated gas-permeable foamed polyurethane system or sheet, the density of which is significantly greater than that on at least one side The density of the core is (the core can be the middle piece be between the two surfaces or delimit such a surface). Such a situation is characterized by predominantly very small cells (or pores) of generally elongated shape on the high density side and predominantly relatively large essentially isometric cells in the core, with the density of the layer on their side being higher Density is at least about twice that of the core.

A preferred product according to the invention is a gas permeable one foamed polyurethane plant or »-bahn with a skin layer of considerable thickness on one side, which with a foamed main body layer forms a whole, wherein the skin layer is a foam whose density is at least twice is as high as that of the core layer and the skin layer is characterized in that its cells become flattened Shape are deformed so that the cell dimension in the vertical plane of the location is much smaller (generally considerably less than half) than the average size of the cell, in the layer plane

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measured, and the cells of the foam body layer are substantially isometric.

Further features and advantages of the invention result from the following description in conjunction with the claims and the drawing.

Show in the drawing

Fig. 1 is a view, partially in section, showing the individual process stages, and

Fig. 2 shows a cross section of a foamed layer or Web material according to the invention.

Any of the materials and compositions normally used to make flexible polyurethane foams can be used in the process be used. The composition used in each case can, depending on the desired density, tensile strength, Extensibility, tear resistance, solvent resistance, flexibility, cell dimension and other desired properties be very different. The choice of certain ingredients to achieve desired end properties is in literature references and earlier patents.

Polyurethane foams are made by determining a substance with at least two active hydrogen atoms ( according to the Zerewitinoff method) in the presence of small amounts of water with an organic polyisocyanate. That Carbon dioxide formed by the reaction between isocyanate and water causes foam formation, while the simultaneous Conversion between isocyanate and the active water

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Substance containing atoms of matter leads to chain extension and polymerization. In practically applied foam systems are catalysts, foam stabilizers, pigments, fillers and volatile liquids as expansion aids often also present in a foamable urethane mixture

In FIG. 1, a composition 10 explained in more detail above is distributed on a carrier web or conveyor belt 11 in a conventional manner. The composition 10 passes through measuring rollers 12 which serve to spread the composition _{β into a uniform layer of the desired thickness}

The composition emerging from the rollers, which is now enclosed between the conveyor belt 11 and the upper cover layer or bar 13, is guided behind the rollers 12 in an area A. In this area, the upper surface of the composition is heated by heating the top layer 13 by infrared radiation from lamps 14. The lower outer surface of the composition is kept at its lower temperature as desired by passing cooling air of a suitable temperature through the Fan 15 feeds *

During this process stage, the entire foam mass expands to a low density foam «The upper outer surface» Chen portion 10a of the foam composition 10 is because of the combined effect of the heating lamps and the exothermic foaming and polymerisation reaction released heat very hot * The lower portion 10b of the foam composition, on the other hand, becomes at a lower temperature held as the air flows past the surface of the lower conveyor belt 11 and exothermic heat from the Composition takes away.

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BATH ORIGINAL

The sustained the composition during the different heating of opposite sides temperature difference should be at least about "40 ⁰ C (75 ° F). · That is the highest temperature of the foam composition should be based on the heated side of the liner at least about 40 ⁰ C (75 ° F.) and preferably 56 ° C (100 ⁰ F) are above the lowest temperature of the foam composition on the cooled side under the conveyor belt when the conveyor belts have resulted in the composition at the end of the treatment zone A. However, if you want a foam with a density that is graduated from one side to the other,

but which should not have a special skin layer, then the temperature difference can be significantly less than 40 ⁰ C (75 ° F.); in such a case it can be between approximately 14 and 40 ° C (25 to 75 ° F.). In order to produce a foam with a particular skin, it is generally desirable to heat the composition on the top (heated) side to a temperature in the range of about 50 to about 120 ° C (125 to 250 ° F.) While the temperature (bottom) on the cooled side below 50 ° C (120 ⁰ F) hälto the heated side is brought to a temperature of preferably about 80 to about 95 ° C (175-200 ⁰ F _0), while the opposite side in the range of about 25 to about "49 ° C is maintained (80 to 120 ⁰ F.).

After the foaming reaction is essentially complete is, the partially polymerized and differentially heated foamed composition 10 is sandwiched between compression rolls 16 passed, which the composition on a Compress a fraction of their previous thickness. The hot, soft, plastic foamed topsheet 10a of the composition collapses into a forever when compressed

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High density skin that is porous, whereas the cooler elastic underlayer 10b of the foamed composition is only temporarily deformed by the compression treatment and essentially re-expanded to a low density foam structure.

When leaving the compression stage, the composition is held between the carrier layers for a sufficiently long time so that the polymerization can proceed to a point where the composition is easy to handle is strong enough. The conveyor belt 11 and the top layer 13 are then guided away from the foamed layer via rollers 18, and the foamed hardened layer, which has a porous skin surface on top, is removed in the usual manner from the treatment zone, e.g., by a take-up roller (not shown).

Rather than removing the backing and cover layers from the foam layer, one or both layers can be a sheet of any suitable material to be coated on one or both surfaces of the foam layer. Such web then passes because of the adhesive property of the polyurethane adhesive bonding with the foam layer a _o

The foam product produced by the process of the invention is shown in FIG. A typical cross-section of a foamed sheet having a porous skin is shown 21 of high density and uniformly connected to it has a foam body 22 of relatively low density. The cells of the Skin 21 are strongly flattened so that their dimensions on the X and Y axes (along and across the foam web, parallel to the plane of the path) is larger and the one on the Z-axis (perpendicular to the plane of the path) is much smaller compared to the im essential isometric cells of the foam body 22

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are. On average, the greatest extent on the Z-axis of the skin cells is considerably smaller than half the average diameter of the core layer cells *

The density of the skin layer is noticeably greater than that of the core layer. In general the skin density is at least twice the density of the core layer, and it can be much higher, up to twenty times as much the pore volume of the skin layer is relatively small in relation to that of the foam layer. For example, the skin pore volume make up only 10 to 20% or even 75% or more of the total skin volume. In contrast, there is the pore volume The core layer typically ranges from 90 to 97% of the total volume, although it can also be above or below it can lie.

The thickness of the skin layer is generally considerable. Usually it is in the range of about 0.075mm (0.003 in.) up to 1.9 mm (o «075 in.) or more. The skin generally makes up 10 to 60% of the total thickness of the foamed layer. It is however, it is possible to manufacture products whose skins are thinner or considerably thicker, or smaller or larger Share in the total thickness of the layer than the areas mentioned.

The phenomenon exhibited when a foamable urethane mixture is expanded under various heating conditions is amazing and unexpected. It is well known that high temperatures accelerate organic reactions, and this is known to occur in the reaction of an isocyanate with a substance containing an active hydrogen

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Case. One would therefore expect "that the hot upper surface of a foam composition is more polymerized _β than the cooler lower surface It must be even §o; one should therefore assume that the upper outer surface shows properties that tend towards a fully hardened product (e.g. elasticity) than the lower, less hardened outer surface «

It should here no binding statement be issued to the phenomenon, but it is believed 'that the surprising shrinkage of the hot _c 1st due stronger hardened upper layer of a foam collapse-reduction in this method that partially cured polyurethanes are thermoplastic = So is the hot upper outer surface, although it is more completely polymerized than the lower outer surface, made soft and plastic by the high temperature, whereas the cooler lower outer surface is more or less elastic because of the lower temperature despite the lower degree of polymerization.

The operating conditions can be very different, depending. according to the foam composition used and the thickness and density of the desired skin. It is well known in the art that the rate of foaming and polymerization reaction in the production of a polyurethane foam by the choice and concentration of the catalytic converter or the catalytic converters used can be changed to a large extent «, one can apply general rules but the best conditions for a particular formulation must be determined through experimentation *

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Thick, dense skins are produced if there is a temperature difference during the foaming stage of the reaction of at least 40 ° C (75 ° F.) and preferably 56 ° C (100 ° F ·) or more between the surfaces of the upper and the lower broadside is maintained at the end of the foam rise and the heat during the entire foaming time is applied more or less uniformly.

Thin, dense skins are produced when the heat suddenly picks up in the final stages of the foam rise stage applied to the selected surface and a temperature differential of at least 40 ° C (75 ° F.) and preferably 56 ° C (100 ° P.) Or more is reached by the completion of the foam rise.

At lower temperature differences (14 ° C to 40 ° C, typically 28 ° C, (25 to 75 ° F., Typically 50 ⁰ F ₀ )), products with a density gradient through the thickness of the layer are more likely to be obtained, with the density at the heated side is twice as high or even higher than on the opposite side; but the density gradient from one side of the sheet to the other is more or less uniform, and no special skin is made.

The following examples serve to further illustrate the invention

EXAMPLE 1

This example shows the production of a polymeric polyester-polyurethane foam sheet with a thick dense Skin described *

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In a closed container with a stirrer and a device to maintain a nitrogen purge at room temperature 50 parts by weight of an approximately 80/20 mixture of isomers from toluene-2,4-diisocyanate and toluene ~ 2,6-diisocyanate and 50 parts by weight of an adipate polyester resin with a Given a hydroxyl number of 53, an acid number less than 1, and a viscosity of 23,000 cps at 25 ° C (77 ° F.) »

The above mixture is stirred in an atmosphere of nitrogen, over a period of six hours is allowed them to ca _c 30 ° C (85 ° P.) Heating and cooled to 21 ° C (70 ⁰ P .. '). The product is called component A.

There are 100 parts by weight of the above-mentioned polyester resin, 3.0 parts of water, 1.0 part of n-ethylmorpholine at room temperature and 3.0 parts of a commercially available foam stabilizer mixed " This product is called Component B.

Using a conventional urethane foam measuring and dispensing device, Ingredients A and B were continuously measured, mixed, and placed on a moving conveyor belt in a ratio of 112/100 parts by weight. The foamable mixture was applied using rollers and a top cover sheet to form a uniform layer 0.5 mm ( 20 mils) thick. layers. After passing through the measuring rollers, the conveyor belt V was kept cool (about 80 ° to 90 ° F _e, ⁽⁰ to 30 C) about 25), while the top sheet was heated by many heaters. After five minutes the foam had risen to a height of 10mm (400 rails) and the top layer had a surface temperature of 82 to 93 ° C (180 to 200 ° F.). The carrier webs were placed together with the foam mass between heavy compression

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rollers passed through to bring the foam to a thickness before Irr- (40 mils). The compressed product, always held between the carrier webs, was then transferred to a Heated to a temperature of about 105 to 121 ° C (about 225 to 25C ° F.) For a period of 10 minutes to complete the cure. It was then peeled off between the conveyor belt and the top cover sheet

The product was tested and found to be a foam product approximately 1.9 mm (75 mils) thick, having an approximately 1.27 mm (50 mils) thick, fine cell, low density foam layer and approximately a dense skin layer 0.63mm (25 mils). The skin was extremely porous; tested in a Gurley permeometer, it released 100ml of air in three seconds
happen. The skin was scratched repeatedly with a small wire and showed good abrasion resistance.

EXAMPLE 2

This example also shows the production of a polymeric polyester-polyurethane foam layer with a thick, dense one Skin described.

The procedure of Example 1 was repeated except
that the measuring rollers were opened to a 0.76mm (30 mils)
allow a foamable mixture to spread thickly.
The foam height after 5 minutes without prior compression was 16.5mm (650 mils). After compression and curing, after the compression rollers had meanwhile been set to an opening of 1.5 mm (60 mils), the product was approximately 4.45 mm (175 mils) thick and consisted of a foam

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low density layer approximately 3.7 nm (145 mils) thick and a dense skin layer approximately 0.75 mm (30 mils) thick. As in Example 1, the skin layer was very porous.,

EXAMPLE 3

In this example, the production of a polymeric polyester-polyurethane foam layer with a thickness of a dsi "is graded Density without skin described

The procedure of Example 1 was repeated, except that the lower conveyor belt (Pc 140 ⁰⁾ yurde erwirnvi with the aid of steam pipes gradually to a temperature of about 60 ⁰ C. After 3 minutes, the foam had a height of about 11.5 to _c 12,2mm (450-475 mils) increased * After 6 minutes, the foam was gepraßt between compression rollers, the set (60 mils) at a gap of 1.5mm wareru After curing according to Example 1, the product was tested. No skin of significant thickness was visible; the foam structure ranged from an isometric cellular structure of low density on the lower level to a compacted foam structure with many relatively small elongated cells on the upper level., The permeability was extremely high

EXAMPLE 4

This example shows the production of a polymeric polyester-polyurethane foam layer with a thick skin

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using the so-called "Einufi? * - procedure for Foam production described.

Using a conventional urethane foam measurement and The dispenser was made up of a foamable composition composed of a mixture of the following output streams on itself moving conveyor belt applied:

Component A: 100 parts of adipate polyester; Ingredient B: 37.5 parts of an 80/20 isomer mixture

of toluene-2,4-diisocyanate and toluene-2,6-

diisocyanate.
Ingredient C: A mixture of 2.8 parts water, 0.3

Parts of n-ethylmorpholine, 0.15 parts of tri-

ethylenediamine and 2.0 parts conventional

Foam stabilizer.

The foamable mixture was measured with rollers and a topcoat to form a uniform 0.25mm (10 mils) layer. Spread thick. After the conveyor belt passed the metering rollers, it was for a period of two minutes heated to a temperature of 54 to 60 ° C (130 to 140 ° F.). During the same period of time, the top cover layer gradually to a temperature of 105 to 121 ° C (225 to 25O ° F.S. warmed up. After the three minute period during which the foam had completely risen to a height of approximately 6.6 mm (260 mils) was, the carrier and cover layers were passed together with the expanded foam mass between heavy compression rollers, which were set so that they Compressed foam to a thickness of 0.64 mm (25 mils). The compressed one still held between the carrier webs

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Product was held at a temperature of 121 to 135 ° C (250 to 275 ° F.) For five minutes to complete the cure. The product was then removed from the conveyor belt and the cover sheet.

The product was tested and found to be a foam product about 1.1mm (42 mils) thick with a thickness of about 0.76mm (30 mils) thick, thin layer of foam and a dense skin layer 0.25 to 0.3mm (10 to 12 mils) thick. The skin was porous and resistant to abrasion.

EXAMPLE 5

In this example, the production of a polymeric polyester-polyurethane foam layer with a dense porous Skin described.

Using a conventional urethane foam measuring and dispensing device became a foamable composition from a mixture of the following output streams onto a moving one Conveyor belt applied.

Component A: 100 parts of a toluene diisocyanate polyoxy

propylene polyol prepolymer with a content of 9.4% free NCO.

Ingredient B: A mixture of 2.0 parts water, 0.2

Parts of tetramethylbutanediamine, 0.2 part of triethylenediamine and 0.5 part of silicone oil.

The foamable mixture was with the help of measuring rollers between a carrier and a top cover layer to form a

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uniform layer 0.5mm (20 mils) thick. After the conveyor belt was passed through the measuring rollers, there was a period of time 90 seconds gradually to a temperature of 50 ° C (120 ° F.) Heated "In the same period, the upper cover sheet to a temperature of 105 ⁰ C (22O ° F.) "After the period of 90 seconds, during which the foam had completely risen to a height of approx. 9.5 mm (375 mils), the carrier and top layers together with the expanded foam mass were passed between heavy compression rollers, adjusted to compress the foam to a thickness of 0.9 mm (35 mils). The compressed product, still held between the backing and liner, was held at a temperature of 121 to 135 ° C (250 to 275 ° F.) For a period of five minutes to complete cure, after which the backing and liner was removed became. The product was tested to be about 1.5 to 1.68 mm (60 to 65 mils) thick with a low density foam layer about 0.76 mm (30 mils) thick and a porous skin about 0, 76 to 0.9 mm (30 to 35 mils) thick. The skin was not as abrasion-resistant as the products made from the adipate polyester, but it was still abrasion-resistant enough for many areas of application.

From the foregoing it can be seen that many embodiments of the procedure are possible. Radiant heat was used to explain the device in more detail for carrying out the process, but other types of heat are also possible, e.g. compressed

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Hot air can be used very well. When the heat is applied to the lower outer surface of a layer of foamable urethane mixture instead of wanting to apply it to the upper outer surface, products with a skin surface on the can also be used Easily produce a relatively high density underside.

From the above discussion it should be clear that it can be done by establishing a temperature differential during the foaming step on both broad sides of a foamable composition based on the temperature in the middle of the Composition is possible to produce embodiments of the product that have a permeable density on each side Have skin and a lower density foam core.

By using an embossed backing on the surface side that is to be compressed into the dense skin Products with embossed or relief-like breathable skins getting produced.

There are also embodiments provided that have composite structures in which the Prodiakte according to the invention on a Are stapled to the substrate. A material suitable for upholstery fabric or upper leather for shoes can thus be produced by the products according to the invention are layered on felt or fabric. Such compositions can be produced by subsequently applying a product according to the invention to a suitable substrate. The foamable mixture can can also be cast directly onto the substrate and, using the method of the invention, a composite material can be made from substrate / foam / porous skin in one step. Depending on the intended use, it is the polyurethane foam is a more or less soft material.

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Claims (14)

Expectations 1. Process for the production of a gas-permeable polyurethane integral Foam sheet or layer, the density of which is significantly greater than the density on at least one side of the layer core is characterized in that a foamable liquid urethane resin mixture is poured into a thin layer is, at least one side of the cast layer is heated, while the layer core is at a relatively cool temperature is held until the layer is substantially foamed and partially cured, the partially cured foamed layer is compressed while it is heated differently in order to put the foam on the heated Side to collapse, and then the location out of the Compression is released, after which the curing of the layer is completed. 2. The method according to claim 1, characterized in that the layer is heated on one side, while the other side is kept relatively cool. 3. The method according to claim 1, characterized in that both sides of the layer are heated, while the center piece of the Location is kept relatively cool. 4. The method according to any one of the preceding claims, characterized in that at least one before compressing The side of the sheet is heated to a temperature at least 40 ° C (75 ° F.) Higher than the temperature of the relatively cool part of the location. 209815/1660 A 13 840/41 - 20 - 5. The method according to any one of the preceding claims, characterized in that at least one side of the sheet to a temperature in the range from about "50 is heated to 120 ⁰ C, while the relatively cool part of the layer is maintained at a temperature below 49 ° C . 6. The method according to claim 5, characterized in that at least one side of the layer is heated to a temperature in the range from about 80 to 95 ° C, while the relatively the cool part of the layer is kept at a temperature in the range of approx. 15 to 32 ° C. 7. The method according to any one of claims 1, 2, 4, 5 and 6 for producing a gas-permeable foamed polyurethane system with an integrated skin layer on one side of considerable thickness with a density which is at least twice as high as the density in the foam core of the layer , characterized in that a thin layer of a foamable liquid urethane resin mixture is formed between continuously running carrier and cover layers, one side of the layer is heated by one of the layers while the other layer and the other side of the layer are kept at a relatively cool temperature, as long as the layer develops into a substantially foamed, partially cured sheet and to a temperature difference of at least about 40 ⁰ C (70 ° F.) of the layer is reached between the two opposite sides, and the partially cured foamed sheet section between the carrier and cover sheet is compressed while it is heated differently to to collapse the foam on the heated side. 209815 / 1B60 8 · The method according to claim 7, characterized in that at least one of the carrier and cover layers of the foamed Layer is removed after the web is compressed and substantially hardened. 9. The method according to any one of the preceding claims, characterized in that the foamable liquid urethane resin mixture from a prepolymer of toluene diisocyanate and a hydroxyl-containing compound, one by polyester resin foamable liquid or a polyether resin. 10. Gas-permeable sheet or layer made of integral polyurethane foam, characterized in that it has an integral skin layer on at least one side of which Density is much greater than the density of the core of the layer that the skin layer has cells that are related to their axes perpendicular to the layer plane are strongly flattened, while the core of the layer is relatively large isometric Cells, and the density of the skin layer is at least twice the density of the core of the layer. 11. polyurethane foam layer according to claim 10, characterized in that that the cell volume in the skin is about 25 to about 75% per unit volume of foam and the cell volume is greater than 90% foam per unit volume in the low density layer core. 12. Polyurethane foam layer according to claim 10, characterized in that that the skin is a single layer on one surface of the ply and the low density core is a single Layer forms on the opposite surface of the ply. 209815/1660 13. Gas-permeable foamed polyurethane foam layer according to one of claims 10 to 12, characterized in that that each skin layer has a thickness in the range of 0.075 to 2mm (0.003 inch to 0/075 inch). 14. Gas-permeable foamed polyurethane foam layer according to one of claims 10 to 13, characterized in that the skin layer or layers 10 to 60% of the total thickness make out the location. 209815/1660