Moulded bodies of cellular polyurethane and a process for their preparation

The invention relates to a molding made of polyurethane, in particular a seat cushion, and a method for its production. The process for the production of the molded article comprises several alternatives as part of a molding process.

Polyurethanes are used in various morphologies, each of which has found its applications. The use of polyurethane foam is known, for example, for upholstered furniture parts, seats, in particular car seats, and for seat cushions. This material, when used in the seating area, is used as a molded part or cut from blocks.

In the automotive sector, for example, more than 80% of all vehicles are currently equipped with polyurethane foam seat cushions. The comfort behavior of these seat cushions is sometimes rated negatively.

Likewise, gels of polyurethane are known for use as a seat cushion.

The patent EP 57838 claims gels for the prevention of bedsores, which are characterized by a low characteristic, ie by so-called sub-crosslinking. They are prepared by the reaction of a polyisocyanate with long-chain polyols which are said to be free of short chain fractions. These dimensionally stable gels made of polyurethane raw materials can be used as mattresses, mattress inserts, automobile seats and upholstered furniture.

Patent EP 511570 protects improved gels from low-index polyols and polyisocyanates made from mixtures of long-chain and short-chain polyethers. Possible applications include upholstery in shoes, on bicycle saddles and on seats, pads for preventing and preventing injuries, face masks and padding under horse saddles.

The high weight and the high heat capacity of seat cushions made of pure gel are disadvantageous. The high heat capacity can lead to a cold seat feeling as body heat is noticeably removed to heat a complete pad of gel.

The object of the invention is therefore to overcome the aforementioned disadvantages of the prior art and in particular to combine good spring and damping properties of the molded part in the loading direction with a comfortable seating comfort.

To solve this problem, the invention provides a molding made of polyurethane, which is composed of at least two different polyurethane materials, namely at least one polyurethane gel and at least one polyurethane foam, which are arranged in at least two different spatial areas of the molding, wherein the Materials are associated by the implicit adhesive properties during the production of urethane.

The molded article can be produced in a molding process in a conventional form, as it is also used in foam production. The summarized in the molding according to the invention composite material optimally connects the spring or Damping properties of the individual materials, so that there is a significant progress in terms of seating comfort. Various, eg Also multilayer arrangements of the different materials are possible. Also partially different arrangements, wherein, for example, the one material is arranged only in the region of the seat, can be advantageously selected and applied depending on the desired properties.

Preferably, the molded article comprises an outer cover layer, which is impermeable to the polyurethane gel, in particular.

The cover layer may consist of a film, in particular a polyurethane film, a polyvinyl chloride film or leather or a textile material, such as a microfiber material. In principle, different elastic materials are suitable as the film material.

In a preferred embodiment of the invention, the polyurethane foam and the polyurethane gel are superimposed in at least two layers, so that the foam and the gel stacked on top of each other act as a spring or damping element against a load in the transverse direction.

In some embodiments, a gel layer may be at least partially enclosed by foam or a foam block may be at least partially enclosed by a gel.

In a further development of the invention, the molded body is designed as a seat cushion, wherein preferably at least on the seat mirror side side additionally a textile cover layer is present. This is especially true when a film was used in the foaming. In this case, the pillow is usually covered later.

Be used in this embodiment of the invention outside textiles, they should be closed vacuum-tight to the gel side. The use of a textile cover material directly as a cover layer is therefore not possible with simple, coarser textiles, since penetration of the still liquid gel material into the textile should be prevented. To deposit a textile cover material, for example, films of thermoplastic polyurethane or closed-cell, cut polyurethane foam can be used.

To prepare the polyurethane foam, the customary polyols and polyisocyanates are reacted with one another. The processing technique and the typical raw materials can be found for example in the "Polyurethane Handbook", edited by G. Oertel.

Raw materials can be used to prepare the gels, as described in European patents EP 57838 and EP 511570.

The inventive method for producing a molded body made of polyurethane is characterized in that in a molding process, a molded article of a polyurethane gel mass and a foamable polyurethane reaction mixture is prepared, wherein the two masses connect with each other during foaming and curing.

The fact that the sandwich construction of two different polyurethanes optimally utilizes the adhesive properties of this material has a particularly advantageous effect on the molded body produced.

The materials are preferably poured onto a cover layer which has been inserted into the mold or the cover layer is placed on the finished composite material.

If desired, the moldings produced can subsequently be covered with another material.

In one embodiment, the process may be conducted so that in a lined with a cover layer form a freshly prepared mixture of polyol and polyisocyanate is introduced as a gel mass, that then a polyurethane raw material mixture for foam production is applied to the gel layer and that conditions for the Foaming and hardening of the masses are kept in shape.

According to a further embodiment of the method, a prefabricated gel layer can be introduced into the mold, preferably with a covering layer, after which a polyurethane raw material mixture is applied for foam production and subsequently conditions for foaming and curing the shaped body in the usual way - dheine certain residence time at a certain temperature profiles are maintained.

The prefabricated gel layer can be placed for example either on the mold bottom or attached to the mold cover.

In a further alternative embodiment, a prefabricated foam block can be inserted into the mold, after which the mold is filled with a gel mass and the reaction conditions for the production of the polyurethane gel from the gel mass are maintained.

Preferably, the polyurethane gel is made from raw materials having an isocyanate functionality and a functionality of the polyol component of at least 5.2, preferably at least 6.5, more preferably at least 7.5.

In preferred embodiments, the polyol component for the preparation of the gel consists of a mixture of<ul id="ul0001" list-style="none" compact="compact"><li>a) one or more polyols having hydroxyl numbers below 112 and</li><li>b) one or more polyols having hydroxyl numbers in the range 112 to 600, wherein the weight ratio of component a) to component b) is between 90:10 and 10:90, the isocyanate index of the reaction mixture in the range of 15 to 59.81 and the product of isocyanate functionality and functionality of the polyol component is at least 6.15.</li></ul>

In a further specific embodiment, the raw materials for the production of the gel consist of<ul id="ul0002" list-style="none" compact="compact"><li>a) one or more polyisocyanates and</li><li>b) a polyol component consisting of<ul id="ul0003" list-style="dash" compact="compact"><li>one or more polyols (b₁) with hydroxyl numbers below 112 and</li><li>one or more polyols (b₂) having hydroxyl numbers in the range of 112 to 600 and</li></ul></li><li>c) optionally a catalyst for the reaction between isocyanate and hydroxyl groups and</li><li>d) optionally from polyurethane chemistry known fillers and / or additives,</li></ul> wherein the weight ratio of the component (b₁) to component (b₂) is between 90:10 and 10:90, the isocyanate index of the reaction mixture is in the range of 15 to 59.81 and the product of isocyanate functionality of the polyol component is at least 6.15.

Preferably, the polyol component for the preparation of the gel consists of one or more polyols having a molecular weight between 1,000 and 12,000 and an OH number between 20 and 112, wherein the product of the functionalities of the polyuret-hanbildenden components is at least 5.2 and the isocyanate index between 15 and 60 is.

As isocyanates, it is possible to use for gel production preferably those of the formula Q (NCO)_n where n is 2 to 4 and Q is an aliphatic hydrocarbon radical having 8 to 18 carbon atoms, a cycloaliphatic hydrocarbon radical having 4 to 15 carbon atoms, an aromatic hydrocarbon radical having 8 to 15 carbon atoms. The isocyanates can be used in pure form or in the form of the customary isocyanate modifications, such as urethanization, allophantization or biuretization.

The invention will be described in more detail below with reference to exemplary embodiments, which are intended to better illustrate the possible embodiments.

In one embodiment of the invention, a film or textile provided with a vacuum-tight film is deep-drawn into a seat mold. The underside of the shape later represents the seat mirror of the pillow. Thereafter, a freshly prepared mixture of polyol and polyisocyanate is introduced liquid in this form. These gel starting materials completely or partially cover the seat mirror after filling. After this mixture has reacted completely or partially to a polyurethane gel, in the next step, a liquid or prefoamed mixture of polyurethane raw materials for foam-molded production is introduced into the mold. The mixture foams, the lid of the mold is enclosed and after the curing time of usually between one to 10 minutes, the complete seat cushion is removed from the mold.

In a further embodiment of the invention, the polyurethane gel is prepared separately and placed as a dimensionally stable gel in one piece or in sections in the mold. The gel is positioned on the foil or on the laminated textile. After foaming in the mold, the gel is fixed at defined positions of the seat mirror by the polyurethane foam. This allows the gel to specifically improve comfort. In this embodiment, it is also possible to position a gel pad on the mold lid. As a result, it is below after foaming. In this case, the seated feeling in a foam can be advantageously combined with the pressure-distributing properties of the polyurethane gel.

In a third embodiment of this invention, a cut polyurethane foam is associated with the gel by the governing gel. This happens, for example, in that the gel is poured onto a thermoformed film or a vacuum-tight textile and is then placed on the not fully reacted gel of the foam. Upon reaction, the intimate combination of gel and foam is created.