Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Patent
1993-06-15
1994-11-01
Welsh, Maurice J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
427373, 4284231, 521133, 521155, 521170, C08G 1800, C08G 1808
Patent
active
053608313
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the preparation of all types of flexible or semi-flexible polyurethane foam-in-fabric articles useful in various furniture and automotive vehicle seating applications.
Most furniture and automotive vehicle seats, arm-rests and head-rests have traditionally been produced from moulded polyurethane foam cushions or parts wrapped subsequently in pre-cut and pre-sewn fabric covers. This "pre-cut and sew" method has drawbacks in that it is very labor intensive and the seats produced by this method tend to deteriorate rapidly or pockets form after repeated use. It is also difficult to achieve a consistently perfect shape from seat to seat and to produce concave contours.
To overcome deficiencies of the "pre-cut and sew" method, the so called "pour-in-place" method has been developed in the 1970's. The pour-in-place method involves pouring polyurethane foam reactants in a liquid form onto a pre-shaped cover and then allowing the foam to expand and cure to form an in-situ foamed moulded part. In the 1970's the pour-in-placmethod was applied for the production of office furniture and other simple-shaped articles such as tractor seating using impermeable PVC sheet covers. The pour-in-place method using fabric covers was introduced subsequently and is now referred to as foam-in-fabric method.
Initially, foam-in-fabric articles were produced using so called "barrier" techniques in which textile composites with or without foam interliners were laminated with a nonpermeable film backing, placed in a mould and shaped to fit the contoures of the mould by applying vacuum (see ICI Polyurethane Newsletter, 1990, Vol.4, No. 6; L. Deno, 1990, U. Tech, pp. 142-144; 33rd Annual Polyurethane Technical/Marketing Conference, Sep. 30-Oct. 3, 1990, D. Murphy et al, p. 172 and F. W. Schneider et al, p. 32; as well as EP-A-0 210 587; EP-A-1 901 828 and EP-A-0 181 604). The non-permeable film serves two purposes: (a) when vacuum is applied between the mould surface and the laminate, no air is sucked through the laminate and the laminate is pressed upon the mould surface and (b) the foam formulation which is poured in a liquid state on top of the laminate cannot penetrate or strike-through the non-permeable layer, thus avoiding uncomfortable stiffening and staining of the fabric. However, since the laminate is non-permeable to any fluid or gas, there is a definite drop in thermal comfort of the seats produced with this technique. This is a clear disadvantage for car seats because lack of "breathability" makes car seats particularly uncomfortable to use for an extended period of time.
To overcome the "breathability" problem, a so called "non-barrier" foam-in-fabric technique has recently been developed. According to the non-barrier technique, the fabric is laminated with a polyurethane slabstock foam layer of about 2 to 5 mm thickness but without the non-permeable film. The slabstock foam layer can be of two types, having virtually zero, or alternatively low air breathability, usually less than 1.0 cfm (cubic foot per minute) of air going through a foam sample (5.times.5.times.2.5 cm) as described in ASTM Method D-3574 p. 9 Ref.: Air Flow Test.
When a slabstock foam layer is used which has virtually zero air breathability it protects the fabric against liquid polyurethane foam reactants to almost the same extent that is achieved by using the nonpermeable film. However, the low porosity of the foam layer produces little improvement to thermal comfort of a car seat compared to the one produced by the barrier technique.
On the other hand, when a slabstock foam backing is used which has some air breathability, it is obvious that polyurethane reactants cannot be poured in liquid form since they would penetrate the foam layer creating a hardening effect and staining the fabric.
In order to avoid penetration of the foam layer two techniques are being currently used:
(1) Use of foam formulations which have a very fast cream time (cream foams) as described in FR-A-2,470,566. Such cream foams, however,
REFERENCES:
patent: 4304872 (1981-12-01), Tenhagen
Casati Francois M.
Gatouillat Gerard
Lidy Werner A.
Dodson Shelley A.
Polyol International B.V.
Welsh Maurice J.
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