GB2213094A - Method for making foamed articles having a laminated structure - Google Patents

Abstract

In order to make a foamed article use is made of a mold (31) so disposed that at least part of a cavity face (35) is inclined. A first foamable composition 32 is poured into the cavity 34, and, when this starts to foam, but before completion of the foaming, a second foamable composition 33 is poured onto the inclined face (35) at a position above the surface of the first foamable composition 32, so that it slips under the first foamable composition 32. The mold may then be adjusted in position (e.g. levelled if previously tilted) and the two foamable compositions complete their foaming to give the desired article. <IMAGE>

Description

METHOD FOR MAKING FOAMED ARTICLES HAVING A LAMINATED STRUCTURE This invention relates to a method for making foamed articles having a laminated structure and in which foamed layers of different physical properties are integrally combined. Examples of such articles are cushions for automobile seats.

In order to increase the comfort of seated travellers in automobiles, there has been proposed a seat cushion having a soft foamed layer on one side which contacts the human body and a rigid foamed layer on the opposite side. A seat using this type of cushion is soft to the surface touch and becomes hard as one sits down, ensuring a comfortable and stable posture.

Such cushions have been made by various methods including a method in which a soft foam and a rigid foam are separately formed or cut and are bonded together by means of an adhesive, and a method in which a separately formed first layer is set in a mold and a second layer is superposed on the first layer. However, these methods are disadvantageous in that the productivity is low, thus increasing production costs, and that, when an adhesive is used, the bonded portion becomes hard, so that one will feel a dishomogeneity on sitting.

Japanese Patent Application Laid-open Nos. 5596195 and 59-138423 have proposed methods to cope with the above problems. These methods comprise, as shown in Figs. 12 to 14 , pouring into a mold 1 a first foamable liquid composition 2 (hereinafter referred to simply as first composition) and then a second foamable liquid composition 3 (hereinafter referred to simply as second composition) on the first composition 2 at the time when the first composition 2 is foaming. In this method, the second composition 3 passes through the first composition 2, which is in the course of foaming and has thus a lowered specific density, to the bottom of the mold where it foams.

Since, however, the second composition 3 is poured over the first composition 2 which is foaming, the second composition 3 entrains and mixes with the foaming first composition 2 at the pouring position A. Accordingly, the resultant product has a mixed layer of a foamed layer 2'of the first composition 2 and a foamed layer 31 of the second composition 3 at the pouring position A as particularly shown in Fig. 15 . The cushion obtained by the method inconveniently gives, more or less, a feeling of dishomogeneity because the resiliency at the pouring position A is different from that at the other positions.

Moreover, the second composition 3 poured through the first composition 2 being foamed cannot spread easily at the bottom of the mold 1, so that the foamed layer formed from the second composition tends to become thick at the pouring position A and thinner at a more distant place, resulting in a non-uniform thickness, as shown in Fig.15 . Thus, there is a demand for a cushion which is more comfortable in use.

In the above method, the second composition is compressed by application of the foaming pressure of the first composition, so that the foamed layer of the second composition is liable to become harder than desired.

An object of the invention is to provide a method for making a foamed article having a laminated structure in which the respective foamed layers are smooth and flexible and are integrally bonded together at the boundary thereof.

According to the invention, there is provided a method for making a foamed article having a laminated structure which comprises setting a mold in such a way that at least part of a cavity face is inclined, pouring 2 first foamable liquid composition into the cavity of the mold, and further pouring a second foamable liquid composition from a position, which is above the surface of the first foamable liquid composition, onto the inclined cavity face during a time between the commencement of foaming of the first foamable liquid composition and the completion of the foaming whereby the second foamable liquid composition is permitted to slip under the first foamable liquid composition and is foamed.

In performing this method, the second composition which has been poured from the position above the surface of the first composition onto the inclined cavity face passes along the cavity face below the first composition and foams below the first composition. The second composition is not mixed with the first composition and the foamed layers of these two compositions establish a clear interface therebetween.

Since the method utilizes flow along an inclined face, the second composition smoothly spreads out at the lower portion of or below the first composition where it foams. Thus, the final foamed article obtained according to this embodiment has a good laminated structure and is usable as a cushion which is comfortable in use.

The objects, features and advantages of the present invention will be more clearly understood by the following description with reference to the accompanying drawings in which: Figs. 1 to 3 are sectional views illustrating one example for making a foamed article having a laminated structure according to the method of the invention; Fig. 4 is a sectional view of the foamed article made by the method of Figs. 1 to 3; Fig. 5 is a sectional view illustrating another example according to the method of the invention; Fig. 6 is a sectional view of a foamed article obtained by the method of Fig. 5; Figs. 7 to 9 are, respectively, graphs of a compression characteristic of the foamed articles determined in Example 1; Fig. 10 is a sectional view illustrating a conventional method used in Comparative Example 1;; Fig. 11 is a sectional view of a foamed article obtained in Comparative Example 2; Figs. 12 to 14 are, respectively, sectional views illustrating a conventional method of making a foamed article; and Fig. 15 is a sectional view illustrating the foamed articles obtained according to the method of Figs. 12 to 14.

Reference is now made to the accompanying drawings in order to describe a method for making foamed articles having a laminated structure according to the invention.

Figs. 1 to 3 show an example for making a foamed article according to the invention, in which reference numeral 31 indicates a mold. The mold 31 has a cavity 34 of a rectangular parallelpiped form. The cavity 34 is closed with a cover not shown in the figures. The cavity 34 has a flat bottom face which is a part of the inner faces of the cavity 34.

In the procedure of this example, the mold 31 is set such that the bottom face 35 is inclined as shown in Fig. 1. In this condition, a first composition 32 is poured to a lower portion of the cavity 34 where it starts to foam.

Subsequently, a second composition 33 is poured from a position above a surface 32a of the first composition 32 on to the inclined bottom surface 35 as shown in Fig. 2. The second composition 33 may be poured at the time between commencement of foaming of the first composition 32 and completion of the foaming and is preferably at the time when the first composition foams to an extent of from 5 to 90 t of a final degree of foaming of the first composition 32.

The thus poured second composition 33 flows down along the bottom 35 under the first composition 32 which is foaming. Because the foaming first composition 32 lowers in apparent specific gravity, the first composition 32 floats on the inserted second composition.

In some cases, it is possible to increase the difference in specific gravity between the first and second compositions 32 and 33 by adding an inorganic filler to the second compssition 33. When the specific gravity of the second composition increaseS the second composition 33 can pass below the first composition 32 more smoothly.

After the pouring of the second composition, the mold 31 may be made horizontal, if necessary, as shown in Fig. 3. The compositions 32, 33 become horizontal by their fluidity to uniform thicknesses under which they foam.

The foamed article obtained by the above procedure is, as shown in Fig. 4, a laminate of a foamed layer 32' of the first composition 32 and a foamed layer of 33' of the second composition 33 with a boundary B.

Fig. 5 shows another example according to the invention in which like reference numerals indicate like parts as in Figs. 1 to 4.

In this method, the bottom face 35 which is part of the inner faces of the cavity of a mold 36 is formed of a higher central portion 35a and side portions 35b, 35b gradually descending from the central portion 35a.

Slot-forming ribs 37, 37 are formed at boundaries between the central portion 35a and the side portions 35b, 35b.

For the fabrication of a foamed article having a laminated structure by the use of the mold 36, the mold 36 is placed horizontally since the side portions 35b, 35b are both inclined at the bottom 35 of the mold 36.

In this embodiment, the first composition 32 is first poured into side portions 34a, 34a of the cavity 34 of the mold 36 set horizontally. After the first composition has. started to foam, the second composition 33 is poured into the central portion 35a in amounts sufficient to overflow the ribs 37, 37, so that the poured second composition 33 passes along the inclined side portions 35b, 35b and is allowed to slip under the first composition 32 at the opposite sides.

The resultant foamed article has, as shown in Fig. 6, foamed layers 32', 32' of the first composition 32 substantially in the form a triangle in section at opposite sides thereof and a foamed layer 33' of the second composition 33 ranging from the surfaces of the foamed layers 32',32' to the central portion.

The present invention is more particularly described by way of examples, which should not be construed as limiting the present invention. Comparative examples are also shown.

Example 1 The mold 31 of Fig. 1 having the flat bottom 35 was made. The cavity 34 has a depth of 70 mm, a width of 350 mm and a length of 350 mm. The mold 31 was set in such a way that the bottom face was inclined at 15 with respect to the horizontal face. Thereafter, 300 g of the first composition 32 was poured into the lower portion of the cavity 34. The first composition 32 had a formation indicated below. The poured first composition 32 became cream in about 10 seconds and commenced to foam. Ten seconds after the commencement of the foaming, 200 g of the second composition 33 was poured from a portion which was higher than the surface 32a of the first composition on to the bottom 35.The second composition had a formulation indicated below After confirmationthatthe second composition had slipped along the bottom 35 under the first composition, the mold 31 was hermetically closed. Subsequently, the mold 31 was turned horizontal and allowed to stand for 10 minutes at room temperature. The resultant molding was a foamed article having a laminated structure of the foamed layer 32' of the first composition and the foamed layer 33' of the second composition 33.

First Composition (high density foam): Polyether polyol [ V-4702 (Daw Co., Ltd.) ] 80 parts by weight Polyether polyol tPOP-31-28 (Mitsui-Nisso Co., Ltd.) ] 20 parts by weight Amine catalyst [ DABCO 33LV (Sankyo Aero Products Co., ltd.) ] 2.7 parts by weight Silicone [ L-5305 (Nippon Unicar Co., 1.2 parts by weight Ltd) ] HO 2.5 parts by weight Tolylene diisocyanate [TDI-80 (Nippon Polyurethane Co., Ltd.) ] 39 parts by weight Second Composition (low density foam):: Polyether polyol 80 parts by weight [ V-4702 (Daw Co., Ltd.) ] Polyether polyol 20 parts by weight [ POP-31-28 (Mitsui-Nisso Co., Ltd.) ] Amine catalyst [ DABCO 33LV (Sankyo 2.6 parts by weight Aero Products Co., Ltd.) ] Silicone [ L-5305 (Nippon Unicar Co., 1.1 parts by weight Ltd) ] HO 3.0 parts by weight Tolylene diisocyanate [ TDI-80 (Nippon 42 parts by weight Polyurethane Co., Ltd.) ] The foamed article was cut for checking, revealing that the foamed layer 32' of the first composition 32 and the foamed layer 33' of the second composition had, respectively, uniform thicknesses and that the boundary B between the foamed layer 32' and the foamed layer 33' was formed as smooth.Thus, it was found that according to the method of the invention, the second composition 33 could be smoothly spread below the first composition, ensuring a foamed article having a good quality.

The foamed article obtained above (foam VI) was subjected to measurement of a compression characteristic. For comparison, 500 g of the first composition 32 was poured into the mold 31 to obtain a foams and 500 g of the second composition 33 was poured into the mold 31 to obtain a foam V. These foams were also subjected to measurement of the compression characteristic. The compression characteristic was determined by compressing the respective foams with a compression disk having a diameter of 200 mm andcheckingthe relation betweenthedegree of deformation of the foam andthecompression force. The compression characteristic of the foam VI was determined such that the compression disk was contacted against the foamed layer 33' of the second composition. The characteristic of the foam VI obtained according to the method of the invention is shown in Fig. 7 , that of the foam IVis shown in Fig. 8 and that of the foam V is shown in Fig. 9.

From the results of the compression characteristic, an initial compression hardness (25 % compression hardness), a final compression hardness (65 % compression hardness) and a sag factor were determined. The results are summarized in Table 1 below.

Table 1 Density 25 Compression 65% Compression Sag g/cm2 Hardness Hardness factor keg/200 keg/200 Foam IV 0.0590 30 85 2.8 Foam V 0.0432 14.5 46 3.2 Foam VI - 15 57 3.8 As will be clear from the above results, the method of the invention is effective in making a cushion which has a large sag factor and is thus comfortable to sit in.

Example 2 The general procedure of Example 1 was repeated except that 50 parts by weight of barium sulfate was added to 200 parts by weight of the second composition to increase the specific gravity, thereby making a foam.

The foam had a sag factor of 4.5 which was larger than 3.8 of the foam VI obtained in Examplel . The second composition 33 in this example could smoothly slip under the first composition and the resulting foam had a better laminated structure.

Comparative Example 1 A mold of the same type as used in Example 1 and the first and second composition used in Example 1 were subjected to molding of a foam according to the known method described in Japanese Patent Application Laid-open No. 55-96195. More particularly, the mold was placed horizontally and the first composition was first poured into the cavity of the mold and then the second composition was further charged over the first composition which was foaming. The time when the second composition was charged was similar to the case of Example 1.

The resultant foam was divided into two pieces to check the section, revealing that, as shown in Fig.15 a foamed layer 3' of the second composition 3 was formed below a foamed layer 2' of the first composition 2 in the form of a dome. At the position A at which the second composition 3 had been poured, there was observed a mixture of the first and second compositions 2, 3.

Comparative Example 2 The mold 36 shown in Fig. 5 was used to make a foam according to the known method described in Japanese Patent Application Laid-open No. 55-96195. The first composition 32 was charged into the opposite side portions 34a, 34a of the cavity 34, after which, as shown in Fig. 10 , the second composition 33 was poured over the first composition 32 at the side portions 34a, 34a and was also poured at the central portion 35a in amounts not overflowing from the ribs 37, 37.

The resultant foam was comprised of the foamed layers 32', 32' of the first composition 32 substantially in the form of a rectangular parallelpiped form in section at opposite sides of the foam and the foamed layer 33', 33' of the second composition 33 as projections 38, 38 at opposite sides. Thus, the foam had not a good laminated structure.

Claims (8)

1. A method for making a-foamed article having a laminated structure which comprises setting a mold in such a way that at least part of a cavity face is inclined, pouring a first foamable liquid composition into the cavity of the mold, and further pouring a second foamable liquid composition from a position, which is above the surface of the first foamable liquid composition, onto the inclined cavity face during a time between the commencement of foaming of the first foamable liquid composition and the completion of the foaming whereby the second foamable liquid composition is permitted to slip under the first foamable liquid composition and is foamed.

2. A method according to claim 1, wherein said mold has, in section, a flat central portion having a rib to form a first block and inclined side portions descending from the central portion to form a second block with surrounding wall faces of the mold, and the second liquid composition is poured into the first block as overflowing the rib and slips under the first liquid composition in the second block along the inclined portions.

3. A method according to claim 1 or claim 2, wherein said second composition has an inorganic filler to increase the specific gravity of the composition.

4. A method according to any preceding claim, wherein the cavity of the mold has a flat bottom face, the mold is set such that the bottom face is inclined to pour the first and second foamable liquid composition and the mold is held such that the bottom face becomes horizontal after completion of the pouring of the second liquid composition.

5. A method according to any preceding claim wherein the first foamable liquid composition forms a higher density polyurethane foam than the second foamable composition.

6. A method according to claim 5 wherein the resulting foam has a laminated structure in which the entire upper surface of the lower density polyurethane foam is covered with the higher density polyurethane foam.

7. A method for making a foamed article substantially as described with reference to Figs. 1 to 4 or Figs. 5 and 6 of the accompanying drawings.

8. A method for making a foamed article substantially as described in either of Examp#es 1 or 2.