Soft molded composites and a process for their production

Molded, soft composite articles such as seat cushions are made by (a) applying a composition which forms a soft elastomer to all interior walls of an open mold, (b) introducing a composition which will react to form a low density, high resiliency, flexible foam under molding conditions into the mold in a manner such that the foam-forming composition will be substantially completely within the elastomer-forming composition; (c) closing the mold (i) prior to introduction of the foam-forming composition or (ii) at some point during or subsequent to introduction of the foam-forming mixture but before foam formation is completed and (d) allowing the foam-forming mixture to form a foam. The composite articles produced by this simple one-step process are characterized by good cushioning characteristics, good abrasion resistance and good mold reproducibility. This molding process generates less waste and requires less labor and equipment than current commercial processes.

BACKGROUND OF THE INVENTION
 The present invention relates to soft molded composites such as seat
 cushions, particularly polyurethane and polyurethane/polyurea composites,
 and to a one-step process for the production of these composites.
 Soft composite materials are used in seating applications, exercise
 equipment pads, support pads in spas and jacuzzis, etc. These composite
 materials are typically made from a foam which is subsequently covered
 with a flexible material such as vinyl or fabric.
 Processes for the production of flexible foams covered with a soft material
 such as vinyl are known. In these known processes, the foam is generally
 molded into the desired form and then covered with a flexible membrane or
 a material such as vinyl or fabric. In addition to equipment for molding
 the foam, such processes also require equipment or significant manual
 labor to cover the foam. The foam covering operation is separate from the
 molding operation. These two separate operations increase the cycle time
 and effort necessary to produce the final composite article. Waste is
 generated in these processes due to inadequate coating, damaged foam,
 "fitting" the covering to the foam, etc. This waste has a significant
 effect upon the economy of the production process.
 SUMMARY OF THE INVENTION
 It is an object of the present invention to provide novel soft molded
 composites, particularly polyurethane and polyurethane/urea composites.
 It is also an object of the present invention to provide soft molded
 polyurethane and polyurethane/urea composites having complex shapes.
 It is another object of the present invention to provide a one-step process
 for molding soft polyurethane and polyurethane/urea composites.
 It is a further object of the present invention to provide a process for
 the production of molded soft polyurethane/urea composites in which cycle
 time and waste are substantially reduced.
 It is also an object of the present invention to provide a process for the
 production of molded soft composite polyurethane and polyurethane/urea
 composites characterized by improved foam/elastomer adhesion with reduced
 sag.
 It is a further object of the present invention to provide a process for
 building a seam in a composite article in which a foam-forming mixture
 acts as an adhesive bonding layer between two soft-elastomeric layers.
 These and other objects which will be apparent to those skilled in the art
 are accomplished by (1) applying (preferably by spraying) a composition
 which forms a soft, elastomeric layer after application to all of the
 interior walls of an open mold; (2) closing the mold; (3) introducing a
 composition which will form a low density, high resiliency, flexible foam
 under molding conditions to the mold in a manner such that the
 foam-forming composition will be substantially completely within the
 elastomer-forming composition; and (4) allowing the foam-forming
 composition introduced in (3) to complete foam formation. The foam-forming
 mixture may be introduced into the mold before the mold is closed but the
 mold must be closed prior to completion of foam formation. The resultant
 molded, composite article may then be removed from the mold. As can be
 seen from FIGS. 1 and 2, the foam-forming composition may act as an
 adhesive which bonds the "upper" and "lower" elastomeric layers present on
 the mold walls.

DETAILED DESCRIPTION OF THE INVENTION
 The present invention relates to molded, soft composite articles such as
 seat cushions and to a one-step process for the production of these
 composites.
 In the process of the present invention, the interior walls of the mold in
 which the composite material is to be produced are completely covered with
 a composition which forms a soft elastomer (preferably a polyurethane or
 polyurethane/urea elastomer) shortly (i.e., within from about 15 to about
 120 seconds, preferably within from about 15 to about 45 seconds) after it
 has been applied to the mold wall. A composition which forms a foam under
 the molding conditions is introduced into the mold which has walls treated
 with elastomer-forming material. The foam-forming composition must be
 introduced in a manner such that it is substantially completely within the
 elastomer "coating" of the mold walls. It is preferred that the mold be
 securely closed prior to introduction of the foam-forming composition but
 it is also possible to pour the foam-forming composition into the open
 mold. When the foam-forming composition is introduced into an open mold,
 the mold must, however, be closed prior to completion of the foam
 formation. Upon substantial completion of the foam formation, the molded
 composite article is removed from the mold.
 Any of the commercially available molds into which foamable materials may
 be introduced after the mold has been closed may be used in the practice
 of the present invention. The walls of the mold may, of course, be treated
 with a material that promotes release of a molded article from the mold
 (i.e., a mold release agent) prior to application of the elastomer-forming
 (preferably, polyurethanelpolyurea elastomer-forming) composition. Any of
 the commercially available solvent-based or water-based mold release
 agents may be used. Examples of suitable commercially available mold
 release agents include ChemTrend PRC-778, ChemTrend MR-515, ChemTrend
 RCTW-1151, ChemTrend RCTW-9011 and Chemlease 81W.
 The elastomeric composition which is applied to the mold walls may be
 applied by techniques such as spraying or reaction injection molding.
 Spraying is the preferred technique, particularly where the mold being
 used is for complex and intricate articles, because easy, even coverage of
 the mold wall is achieved. Either high pressure (i.e., 800-2,000 psi) or
 low pressure (i.e., 50-200 psi) metering units with static, impingement or
 dynamic mixing capability may be used to spray the elastomeric composition
 to the mold walls.
 The elastomer-forming composition is generally applied to the mold walls in
 an amount such that the elastomer layer which forms is at least about 30
 mils (i.e., at least about 0.030 inches) thick, preferably at least about
 40 mils (i.e., at least about 0.040 inches) thick. These thicknesses are
 used in order to achieve at least the minimum desired abrasion
 characteristics and to avoid bleed through of the foam.
 This elastomer-forming composition may be any material, preferably a
 polyurethane/polyurea material, which has (1) a sufficiently fast
 viscosity buildup or thixotropic effect that dripping and sagging are kept
 to a minimum and (2) a gel time such that bonding with the foam is
 achieved. Gel time is defined as the time it takes the reactive material
 to form a viscous gel such that no further visually observable flow
 occurs. The gel time is the amount of time which elapses between
 combination of the reactants and the point when no material is transferred
 onto an applicator stick when that stick is touched to the reaction
 product.
 Polyurethane and polyurethane/urea forming compositions are preferred
 elastomer compositions because in addition to these two required
 characteristics (i.e., gel time and fast viscosity buildup), they improve
 the flammability, electrical and physical properties of the elastomeric
 coating of the molded article. Particularly preferred polyurethane and
 polyurethane/urea elastomers are those which are soft (i.e., have a Shore
 A value of less than 90) and flexible (i.e., elongation &gt;50%, preferably
 &gt;80%, most preferably &gt;100%) because composites having such elastomeric
 coatings may be more readily demolded and recover their shape.
 Suitable elastomer-forming compositions include a polyisocyanate and at
 least one isocyanate-reactive material having at least two isocyanate
 reactive groups, preferably from about 2 to about 4 isocyanate reactive
 groups, and a molecular weight of at least 60, preferably from about 200
 to about 8000.
 Any of the known isocyanates may be used in the practice of the present
 invention to produce polyurethane and/or polyurea elastomers. Suitable
 isocyanates which may be used include aromatic, aliphatic, cycloaliphatic
 polyisocyanates and combinations thereof. Specific examples of suitable
 isocyanates include: diisocyanates such as m-phenylene diisocyanate,
 p-phenylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene
 diisocyanate, 1,6-hexamethylene diisocyanate, 1,4-hexamethylene
 diisocyanate, 1,4-cyclohexane diisocyanate, hexahydrotoluene diisocyanate
 and its isomers, 1,5-naphthylene diisocyanate, 1-methylphenyl-2,4-phenyl
 diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane
 diisocyanate, 4,4'-biphenylene diisocyanate,
 3,3'-dimethoxy-4,4'-biphenylene diisocyanate, and
 3,3'-dimethyl-diphenylpropane-4,4'-diisocyanate; triisocyanates such as
 2,4,6-toluene triisocyanate; and polyisocyanates such as
 4,4'-dimethyl-diphenylmethane-2,2',5,5'-tetraisocyanate and the
 poly-methylene polyphenylisocyanates.
 Crude polyisocyanates may also be used in the practice of the present
 invention. The crude toluene diisocyanate obtained by phosgenating a
 mixture of toluene diamines and the crude diphenylmethane diisocyanate
 obtained by phosgenating crude diphenylmethanediamine are examples of
 suitable crude polyisocyanates. Suitable undistilled or crude
 polyisocyanates are disclosed in U.S. Pat. No. 3,215,652.
 Isocyanate-terminated prepolymers having an NCO content of at least about
 8%, preferably from about 9 to about 30%, may be used to produce the
 elastomer-forming compositions of the present invention. Prepolymers of
 diphenylmethane diisocyanate having NCO contents of from about 8 to about
 17%, preferably about 10%, by weight, are particularly preferred. These
 preferred prepolymers are made by pre-reacting diphenylmethane
 diisocyanate (MDI) or an isomer mixture of MDI with an isocyanate-reactive
 compound such as a polyol or polyamine having a functionality of from
 about 1.9 to about 3.1, preferably about 2 in an amount such that the
 unreacted isocyanate group content is within the above-specified range.
 The isocyanate or isocyanate-terminated prepolymer may be reacted with any
 of the isocyanate-reactive compounds, particularly, polyols or polyamines,
 which are known to be useful in the production of polyurethane/polyurea
 elastomers. Suitable polyols include polyether polyols, polyester polyols,
 polyacetals, polycarbonates, polyester ethers, polythioethers, polyamides,
 polybutadienes and polylactones having a molecular weight of from about
 400 to about 10,000 (preferably from about 1,000 to about 8,000) and a
 functionality of at least about two, preferably from about 2 to about 4.
 Polyether polyols are preferred. Mixtures of polyether polyols in which
 from about 20 to about 55% by weight, preferably from about 40 to about
 45% by weight, is a difunctional polyether polyol and from about 30 to
 about 70% by weight, preferably from about 45 to about 65% by weight, is a
 trifunctional or higher functional polyether polyol are particularly
 preferred for the production of the elastomer-forming composition.
 A thixotropic agent which builds up the viscosity of the reactive mixture
 upon mixing is generally included in the isocyanate-reactive materials
 used. Any of the known thixotropic agents may be used but organic amines,
 particularly aromatic and aliphatic diamines having molecular weights of
 from about 60 to about 2,000 (preferably from about 100 to about 400) are
 preferred. Any of the known catalysts, surfactants, crosslinking agents
 and additives may also be included in the elastomer-forming mixture.
 The isocyanate and isocyanate-reactive material are used in amounts such
 that the equivalent ratio of isocyanate groups to isocyanate-reactive
 groups is from about 0.9:1 to about 1.2:1.0, preferably from about
 0.95:1.0 to about 1.1:1.0, most preferably about 1.05:1.
 Additives useful in the production of the elastomer-forming composition
 include: antioxidants, pigments, light stabilizers, heat stabilizers, UV
 stabilizers, crosslinking agents, moisture scavengers, defoamers, acid
 scavengers, inorganic fillers and organic fillers.
 A reaction promoter or catalyst may be included in the elastomer-forming
 composition to ensure that the elastomeric layer which forms on the mold
 walls is sufficiently set prior to introduction of the foam-forming
 mixture. Preferred catalysts include amines (particularly tertiary amines)
 and organo-metallic compounds of metals such as tin, bismuth and zinc.
 It is advantageous that the elastomer-forming composition have a gel time
 of from about 15 seconds to about 120 seconds, preferably from about 15 to
 about 75 seconds, most preferably from about 30 to about 50 seconds to
 ensure that the elastomeric coating which forms on the mold wall is
 sufficiently set that the foam-forming mixture will be substantially
 completely contained within that elastomeric coating.
 The foam-forming mixture may be introduced into the dosed mold by any of
 the known techniques such as pouring or injection. It is preferred,
 however, that the foam-forming mixture be injected into the mold with high
 or low pressure metering units.
 The foam forming mixture should be selected so that the product foam will
 have a density of from about 1.8 to about 4.5 pounds per cubic foot (from
 about 0.028 to about 0.075 gm/cm.sup.3), preferably from about 2.4 to
 about 3.6 pounds per cubic foot (from about 0.038 to about 0.057
 gm/cm.sup.3). It is preferred that the foam have high recovery (i.e., a
 recovery of at least 60%, as determined by ASTM D 3574), a sag factor of
 at least 2.5, preferably from about 2.5 to about 3.9 (as determined by
 ASTM D 3574 B1) and no yield point on the stress-strain tensile curve.
 Suitable foam-forming mixtures may be made by combining a diisocyanate, a
 polyisocyanate and or a modified isocyanate such as an
 isocyanate-terminated prepolymer with a polyisocyanate-reactive compound
 having a functionality of at least about two, preferably from about 2 to
 about 4, in quantities such that the equivalent ratio of isocyanate to
 isocyanate-reactive groups is from about 0.8:1.0 to about 1.2:1.0,
 preferably about 1:1.
 Any of the known diisocyanates, polyisocyanates, modified polyisocyanates
 (particularly, isocyanate-terminated prepolymers) and mixtures thereof may
 be used to produce the foam-forming mixture of the present invention.
 Specific examples of suitable isocyanates include those listed above as
 being suitable for the production of the polyurethane and/or polyurea
 elastomer. Mixtures of polyisocyanates, diisocyanates and modified
 polyisocyanates based on MDI and its isomers are preferred. Mixtures of
 diphenylmethane diisocyanates and/or polyisocyanates having an NCO content
 of from about 32.0 to about 32.8 are among the most preferred isocyanates.
 Modified polyisocyanates are obtained by chemical reaction of diisocyanates
 and/or polyisocyanates. Modified isocyanates useful in the practice of the
 present invention include isocyanates containing ester groups, urea
 groups, biuret groups, allophanate groups, carbodiimide groups,
 isocyanurate groups, uretdione groups and/or urethane groups. Preferred
 examples of modified isocyanates include prepolymers containing isocyanate
 groups and having an isocyanate group content of from about 25 to about
 42% by weight, preferably from about 28 to about 32% by weight,
 particularly those based on polyether polyols or polyester polyols and
 diphenylmethane diisocyanate. Processes for producing these modified
 polyisocyanates are known in the art.
 Any of the known isocyanate-reactive compounds having a molecular weight of
 at least about 400, preferably from about 1,000 to about 8,000, most
 preferably from about 2,000 to about 6,500 may be used to produce the
 foam-forming mixture of the present invention. Polyether polyols and
 mixtures of polyether polyols having an average functionality which is
 greater than or equal to 2 are particularly preferred.
 Any of the known blowing agents, catalysts, chain extenders, crosslinking
 agents, auxiliaries and additives may also be included in the foam-forming
 mixture. It is preferred that water, an HCFC, a hydrocarbon or mixtures of
 these known blowing agents be used as the blowing agent. An amine-based
 catalyst and/or a tin-based catalyst is preferably included in the
 foam-forming mixtures in an amount such that the foam formation takes
 place within a reasonable amount of time.
 Optional additives and auxiliaries which may be useful in the foam-forming
 compositions of the present invention include: cell openers such as
 polyether polyols based on sorbitol; surfactants, particularly silicone
 surfactants; crosslinking agents such as aliphatic amines and aromatic
 amines; antioxidants; UV stabilizers; and flame retardants such as
 melamine.
 The composite molded articles produced in accordance with the present
 invention may be removed from the mold after about 3 to about 10 minutes,
 preferably after from about 4 to about 5 minutes.
 These composite molded articles are characterized by good cushioning
 characteristics, good abrasion resistance, a dense flexible outer
 elastomer, good tear resistance and good mold reproducibility.
 Having thus described our invention, the following Examples are given as
 being illustrative thereof. All parts and percentages given in these
 Examples are parts by weight and percentages by weight, unless otherwise
 indicated.
 EXAMPLES
 The following materials were used in the Examples:
 POLYISOCYANATE A: A prepolymer of MDI having an NCO content of 10% which is
 commercially available from Miles Inc. under the name Mondur E-1437.
 POLYISOCYANATE B: MDI having an NCO content of 32.8% which is commercially
 available from Miles Inc. under the name Mondur MRS-20.
 POLYISOCYANATE C: A mixture of polyisocyanates made up of 90% polymeric MDI
 which is commercially available from Miles Inc. under the name Mondur
 MRS-2 and 10% monomeric MDI which is commercially available under the name
 Mondur ML which mixture has an NCO content of 32.5%.
 POLYOL A: A polyether polyol having a molecular weight of 6000 and a
 functionality of 3.0 which is commercially available from Miles Inc. under
 the name Multranol 3901.
 POLYOL B: A polyether polyol having a molecular weight of 3400 and a
 functionality of 6.0 which is commercially available from Miles Inc. under
 the name Multranol E-9185.
 POLYOL C: A polyether polyol having a molecular weight of 4800 and a
 functionality of 3.0 which is commercially available from Miles Inc. under
 the name Multranol E-9143.
 POLYOL D: A polyether polyol having a molecular weight of 4,000 and a
 functionality of 2 which is commercially available from Miles Inc. under
 the name Multranol E-9111.
 POLYOL E: A polyether polyol having a molecular weight of 6,000 and a
 functionality of 3.0 which is commercially available from Miles Inc. under
 the name Multranol E-9139.
 CATALYST A: An amine catalyst which is commercially available from OSI
 Specialties under the name Niax A-1.
 CATALYST B: An amine catalyst which is commercially available from OSI
 Specialties under the name Niax A-4.
 CATALYST C: An amine catalyst which is commercially available from Air
 Products under the name Dabco 33-LV.
 CROSSLINKING AGENT: Dytek A which is commercially available from DuPont.
 CHAIN EXTENDER: