AU600042B2 - A process for the production of moldings, more especially cushions, from at least two fluid reaction mixtures forming foams, more especially polyurethane foams, of different elasticity or hardness and the use of this process for the production of vehicle seat cushions having side webs - Google Patents

Description

1-P1187/GD/MP/3928T.6

AUSTRALIA

PATENTS ACT 1952 U COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE Application Number: Lodged: This document contains the amendments made under Section 49 and is correct for printing.

Complete Specification Lodged: Accepted: Published: 1 0 Priority: Related Art: *r TO BE COMPLETED BY APPLICANT Name of Applicant: Address of Applicant: Actual Inventor: BAYER AKTIENGESELLSCHAFT D-5090, Leverkusen, Bayerwerk, Germany Dr. Ralf Busch Dr. Winfried Schoberth Dr. Werner RaPhofer ARTHUR S. CAVE CO.

Patent Trade Mark Attorneys Goldfields House 1 Alfred Street SYDNEY N.S.W. 2000

AUSTRALIA

Address for Service: 1 Complete Specification for the invention entitled A PROCESS FOR THE PRODUCTION OF MOLDINGS, MORE ESPECIALLY CUSHIONS, FROM AT LEAST TWO FLUID REACTION MIXTURES FORMING FOAMS, MORE ESPECIALLY POLYURETHANE FOAMS, OF DIFFERENT ELASTICITY OR HARDNESS AND THE USE OF THIS PROCESS FOR THE PRODUCTION OF VEHICLE SEAT CUSHIONS HAVING SIDE WEBS.

The following statement is a full description of this invention including the best method of performing it known to me:- 1 ASC 49

I~YL

A PROCESS FOR THE PRODUCTION OF MOLDINGS, MORE ESPECIALLY CUSHIONS, FROM AT LEAST TWO FLUID REACTION MIXTURES FORMING FOAMS, MORE ESPECIALLY POLYURETHANE FOAMS, OF DIFFERENT ELASTICITY OR HARDNESS AND THE USE OF THIS PROCESS FOR THE PRODUCTION OF VEHICLE SEAT CUSHIONS HAVING SIDE WEBS 1 This invention relates to a process for the production of moldings, more especially cushions, from at least two fluid reaction mixtures forming foams, more especially polyurethane foams, of different elasticity or hardness, a first and at least a second reaction mixture being introduced into a mold cavity and left to react out to form a molding having zones of different elasticity or hardness before the molding is removed from the mold, and to the use of this process for the production of vehicle seat cushions having side webs.

The production of moldings, particularly cushions, by in-mold foaming is gaining in popularity over the hitherto standard method of cutting to size because it is efficient and involves virtually no losses. The cushions are either subsequently provided with a fabric covering or a covering placed in a vacuum mold is directly back-foamed.

Various processes have been proposed for the production of moldings having zones of different hardness: According to EP-B1-68 820, a second foam mixture is directly introduced onto a first foam mixture at a time corresponding to an expansion in volume of the first mixture of +100% to +2300%, so that one or more relatively hard zones are formed within a relatively soft flexible foam. In this process, the second reaction mixture cannot be introduced until the first reaction mixture has undergone the necessary expansion in volume. The cycle times of the in-mold foaming process are thus undesirably lengthened. In addition, the actual Le A 24 844 la 0 0) C, ;.0 oo 0 co 0000 0D'00 04 0r 0 04r) 0,00 I objective, namely covering relatively hard zones with a layer of softer flexible foam to increase comfort, is difficult to achieve because the expansion of the softer foam layer remains limited in certain zones to only narrow thicknesses which only inadequately impart the desired properties. In addition, difficulties also arise with regard to the adequate reproducibility of these coverings.

In another process (US-A-4,190,697), a mixture forming relatively harder flexible foam is first introduced into the mold where it is allowed to begin foaming, after which a second mixture forming softer flexible foam is introduced when the first mixture has reached 10 to 80% of its full foaming capacity, permeating the first mixture during introduction and causing it to swim up, after which both mixtures react out and form a polyurethane foam article having zones of different density.

The disadvantage of this process is that the permeation and underflow of the first reaction mixture introduced is irregular so that the properties, above all the indentation 20 hardness, of the moldings obtained are not sufficiently reproducible.

Accordingly, the object of the present invention is to provide a process of the type mentioned at the beginning which makes shorter cycle times possible for good reproducibility in the development of the zones of different hardness or elasticity.

According to the invention, this object is achieved in that, on introduction into the mold, the second reaction mixture is allowed to cream up to such an extent that, by the time it comes into contact with the first reaction mixture, it already has a lower density than the first reaction mixture, the second reaction mixture is introduced onto and/or next to the layer formed by the first reaction mixture.

In this way, any formulation may be used for the first 2

I

I IS lilt If S I S I lIt 1 reaction mixture which opens up new applications because, through the introduction of the second or further reaction mixture(s) with correspondingly lower density, the course of the process is made largely independent of the state of the first reaction mixture at the moment it is contacted by the second. Another effect of the creamy consistency is that, on contact with the first mixture by overflowing from the side or by direct application to the layer of the first mixture, no turbulence is generated providing the 10 force of impact is not too great. In other words, the introduction step has to be carried out with care. On the other hand, even the mixing units widely in use today guarantee sufficiently low discharge rates to avoid turbulence of the various reaction mixtures. Where a third or further reaction mixture(s) is/are introduced, this/these mixture(s) has/have to be balanced in regard to its/their creamy consistency in such a way that, at the moment of contact with one of the other reaction mixtures, it meets the lower density requirement.

The second or further reaction mixture(s) may be introduced at the same time as or after the first or other reaction mixture, depending on requirements. Simultaneous introduction is advisable in particular when the various reaction mixtures are introduced into various regions. In this connection, it is quite possible to charge two regions separated for example by a third region with the same reaction mixture while the region lying in between is charged with another reaction mixture. If it is desired to introduce another reaction mixture directly onto a first reaction mixture, it is best to do this after an appropriate time interval so that the mixture previously introduced has already spread out extensively over the region in question.

Where and when the softer or the harder foam-forming reaction mixture is introduced first or whether the two are introduced at the same time depends on various factors, but Le A 24 844 3 1 essentially on where in the mold cavity the corresponding zones of different hardness are to form.

In particular, it is possible by the new process to obtain harder zones covered on one side or all sides with layers of any thickness of flexible form or vice versa.

Since the second reaction mixture, through its creamy consistency, can have reached its maximal degree of foaming before the first reaction mixture providing appropriate activators are used, it is possible according to this degree of foaming for the still relatively liquid first reaction mixture to be laterally forced upwards at least to a certain level or even completely to surround the foam formed by the ,second reaction mixture. Such partial or complete coverage in any desired thickness may readily be de*ermined by tests and depends largely on the geometry of the molding or mold cavity and on the quantities involved.

Suitable raw materials for the production of the moldings in question are, in particular, any of the usual polyurethane foam systems (cf. also Kunststoff-Handbuch, Vol. II, "Polyurethanes", by Vieweg and Hbchtlen, Carl-Hanser-Verlag Munich, 1966, in particular pages 440 to 503 and 569 to 571), the differences in hardness of the foam resulting from the individual reaction mixtures being adjustable through index variation and/or through the formulations, for example through the filler content, crosslinker variation, gross density ratio, etc. The rapid creaming of the second mixture is obtained by adding to this formulation additives which, when the components are mixed, spontaneously evolve CO 2 or any other compound gaseous under the reaction conditions. The aminecarbon dioxide adducts described in EP-A-121 850 are preferably used. However, it is also possible to produce a froth foam. Alternatively, creaming may be obtained by high activation. The creaming can also be obtained or accelerated by loading one reaction component with gas, in particular inert gas, such as CO 2 or N 2 The component is charged with the gas at various gas pressures by means of a dissolving process and/or a dispersing process. Another Le A 24 844 4 m 1 possibility is to prepare the second reaction mixture correspondingly early, i.e. to introduce it with delay so that it has already acquired the necessary lower density by the time it comes into contact with the first mixture. In this sense, the second reaction mixture may be prepared even earlier than the first so that it may be introduced for example at the same time or immediately after the first mixture has spread out to form a layer.

The process according to the invention is particularly suitable for the production of vehicle seat cushions having side webs. The novel aspect of this particular application is that a first foam-forming reaction mixture is poured into those parts of the mold cavity corresponding to the webs and onto that part corresponding to the seat surface, followed by at least a second foam-forming reaction mixture so advanced in its expansion that, by the time it comes into contact with the layers of the first reaction mixture, it has already acquired a lower density than the first reaction mixture so that, at best, it sinks in but does not permeate the first layer.

In this way, it is possible to produce both uncovered seat cushions and also those having back-foamed coverings. Through the use of several mixing heads for preparing the same reaction mixture or different reaction mixtures, the new process may be varied very widely in its application.

The new process is illustrated by a practical example of its application for the production of a cushion for vehicle seats in conjunction with the accompanying drawings, wherein: Figures 1 and 2 illustrate the production of the seat cushion shown in Figure 3.

Figure 3 shows the finished seat cushion.

Figures 4 to 10 show further embodiments of seat cushions with side webs which can be produced by the new process.

Figure 11 is a longitudinal section through a seat cushion having foam zones of three different hardnesses.

The new process is to be used to produce a seat cushion of the type shown in Figure 3 with side webs 1, 2 and seat Le A 24 844 5 i section 3. The outer zones 4,5 of the side webs consist of a relatively hard foam having a density of 50 kg/dm 3 and a compression hardness according to DIN 53 577 of 7.3 kPa.

The seat section 3 is separated from the side webs 1,2 by grooves 6,7. A zone 8 of relatively soft foam having a 3 I density of 50 kg/dm and a compression hardness of 3.3 kPa extends over the seat section 3 beyond the grooves 6,7 into the side webs 1,2 and forms a firm, but clearly defined union with the zones 4,5. The total volume of the seat cushion is 32 dm 3 of which 25 dm 3 is occupied by the softer foam corresponding to the zone 8.

The seat cushion is produced as shown in Figures 1 and 2, the mold 11ii having a cavity 12 which represents the seat cushion upside down, as also shown in Figure 3. The regions 13,14 correspond to the side webs 1,2, the region to the seat section 3 and the dividers 16,17 to the grooves 6,7 of the seat cushion. By means of two mixing heads 18,19 (Figure the reaction mixture forming the softer foam is introduced into each of the two side web regions 13,14 in a quantity of 180 g. Thereafter (Figure the mixing heads 18,19 are placed over the seat region where the same reaction mixture is introduced in a quantity of 1150 g. The dividers 16,17 prevent the reaction mixture from flowing off into the side web regions 13,14.

By means of two mixing heads 20,21, the reaction mixture forming the harder foam is introduced onto the first reaction mixture already present in the side web regions 13, 14 at the same time as the seat region 15 is being filled by the Smixing heads 18,19. The density of the first reaction mixture at the moment of contact with the second reaction mixture is 0.8 kg/dm 3 while the second reaction mixture is introduced in such a creamed state that it has a density of 0.3 kg/dm 3 at the moment of contact with the first reaction mixture. The time delay between the beginning of introduction of the first reaction mixture and contact by the Le A 24 844 6 I, I 1 second is 7 seconds. After closure of the mold 11, the reaction mixtures foam completely to form the seat cushion shown in Figure 3.

The first reaction mixture forming the softer foam has the following formulation (pbw parts by weight): Component A 100 pbw polyether obtained by addition of propylene oxide .and then ethylene oxide to trimethylol propane and having a functionality of 3 and a primary OH content of approx. 80% by weight for an OH number of approx. 3.1 pbw water; 0.2 pbw bis-dimethylaminoethylether; 0.4 pbw commercial foam stabilizer consisting of a mixture of low molecular weight siloxanes (Stabilisator KS 43, a product of BAYER AG, Leverkusen, Fed. Rep. of Germany); I 4 0.8 pbw triethylenediamine (33% in dipropylene glycol).

Component B 45.3 pbw of an isocyanate of index 85 containing approx. by weight 4,4'-dimethylmethane diisocyanate and approx.

I 20 20% by weight 2,4'-diphenyl methane diisocyanate and approx. 15% by weight polymeric MDI; NCO content approx. 32.5%.

The second reaction mixture forming the harder foam has the following formulation: Component A 100 pbw polyether obtained by addition of propylene oxide and then ethylene oxide to trimethylol propane and having a functionality of 3 and a primary OH content of approx. 80% by weight for an OH number of approx. 3.1 pbw water; 0.2 pbw bis-dimethylaminoethylether; 0.4 pbw commercial foam stabiliser consisting of a mixture of low molecular weight siloxanes (Stabilisator KS 43, a product of Bayer AG, Leverkusen, Fed. Rep. of Germany); 0.8 pbw triethylenediamine (33% in dipropylene glycol); pbw of the adduct of CO 2 with N-methyl ethanolamine.

Le A 24 844 7

-S

1 Component B 70.6 pbw of an isocyanate of index 110 containing approx.

by weight 4,4'-diphenylmethane diisocyanate and approx. 20% by weight 2,4'-diphenylmethane diisocyanate and approx. 15% by weight polymeric MDI for an NCO content of approx. 32.5%.

In the other embodiments of seat cushions produced by the new process which are shown in Figures 4 to (in section in the normal position), the zones of softer foam are hatched at broad intervals while the zones of harder foam are hatched at narrow intervals.

In Figure 11, the seat section consists of a foam of medium hardness which is also at the back of the knees; on the underneath ofthe seat cushion, however, there is a very soft zone; the third zone is the hardest.

Aspects to be noted are the various embodiments of the side webs and the lining beneath seat sections and also combinations thereof.

Le A 24 844 8

Claims (4)

1. A process for the production of moldings, more especially cushions, from at least two fluid reaction mixtures forming foams, more especially polyurethane foams, of different elasticity or hardness, a first and at least a second reaction mixture being introduced into a mold cavity and left to react out to form a molding having zones of different elasticity or hardness before the molding is removed from the mold, characterized in that, on introduction into the mold, the second reaction mixture is allowed to cream up to such an extent that, by the time it comes into contact with the first reaction mixture, it already has a lower density than the first reaction mixture, wherein the second reaction mixture is o* introduced onto and/or next to the layer formed by the first 0o o reaction mixture. oo°

2. Process according to claim 1, characterized in that the second reaction mixture is introduced at the same time as the 0 04 S first reaction mixture.

3. The use of the process claimed in claim 1 or 2 for the production of vehicle seat cushions having side webs, S characterized in that a first reaction mixture is poured into 0 the regions of the mold cavity corresponding to the side webs o 0 and onto the region corresponding to the seat area and at least a second reaction mixture is introduced onto the layers of the first reaction mixture present in the regions corresponding to the side webs and/or in the region corresponding to the seat area, being so advanced in its expansion that, by the time it comes into contact with the first reaction mixture, it has a -9-RA 3g.' 0/RAP low<

4. ref DAT: 0 0 0 o 0 .00 0 0 0S 0 0 a at ©0T 0 0 0 0 0 00 0000 o ao 0 6 0 0 0 0 0f) 0 0 0 0 S0a 0 jif\ V ,027 Y^ lower density than the first reaction mi-xture. 4. A process-substantially as herein described with reference to the accompanying drawings. The invention as herein described. DATED this 3rd day of May, 1990. BAYER AKTIENGESELLSCHAFT By Its Patent Attorneys ARTHUR S. CAVE CO. 0'~000 0 0000 0.~00 O 00 00 0 0 00 00 0 0000 0000 0 0 0 00 0 00 *400 0 0 0000 04 00 0 0 04 00 0 0 0 0040 0. 27~ RAP 10