GB2119393A - Polyurethane foam - Google Patents

Abstract

A method of producing a dimensionally stable flexible polyester urethane foam comprises reacting a hydroxy terminated polyester polyol and diphenylmethane-4,4'- diisocyanate (MDI) together with a catalyst and a blowing agent, either in the absence of other constituents or with a silicone surfactant present in an amount of less than 1% by weight of the polyester or with a silicone surfactant and a silicone oil.

Description

SPECIFICATION Production of polyurethane foams This invention relates to the production of polyurethane foams and especially to the production of polyester urethane foams.

It is known that dimensionally stable flexible polyester urethane foams can be produced in slabstock form by reaction of toluene diisocyanate (generally on 80:20 or 65:35 blend of 2,4- and 2,6isomers) and hydroxyl terminated polyester polyols. Such polyesters are typically produced by the condensation polymerization of adipic acid and diethylene glycol, frequently in the presence of polyhydric species such as trimethylol propane, pentaerythritol, or glycerol to yield a functionality slightly in excess of 2, thereby facilitating light crosslinking in the subsequent reaction with the isocyanate. Such foams have been commercially available for over 20 years but increasingly stringent regulations apply to the handling of the highly volatile toluene diisocyanate (TDI) which are imposing economic penalties on both isocyanate manufacturers and users.

It is also known to produce both flexible and rigid polyether urethane foams based on hydroxy terminated polyether polyols and diphenylmethane-4,4'-diisocyanate (MDI). This eliminates the problems in handling toluene diisocyanate but hitherto it has not been possible to produce flexible polyester urethane foams from MDI.

Under standard established conditions the reaction of MDI and conventionally used polyester polyols yields dimensionally unstable closed cell foams which have no commercial value as slabstock as they cannot be converted to saleable items by fabrication. Efforts to produce a stable foam by modification of the gelling and blowing rates of conventional urethane foam catalysts have also proved unsuccessful.

According to one aspect of the present invention there is provided a method of producing a dimensionally stable, flexible, polyester urethane foam comprising reacting a hydroxy terminated polyester polyol and diphenylmethane-4,4'-diisocyanate (MDI) together with a silicone surfactant, a catalyst, a blowing agent and a silicone oil.

Preferably the silicone oil is present in an amount of between 0.005 and 0.05% by weight of the polyester. The polyester polyol preferably comprises an adipic acid/diethylene glycol polyester.

According to a further aspect of the invention there is provided a method of producing a dimensionally stable, flexible, polyester urethane foam comprising reacting a hydroxy terminated polyester polyol and diphenylmethane-4,4'-diisocyanate (MDI) together with a catalyst, a blowing agent and optionally a surfactant, the surfactant when present being a silicone surfactant and being present in an amount of less than 1% by weight of the polyester.

Preferably the surfactant when present is present in an amount of less than 0.6% by weight of the polyester. The polyester polyol preferably comprises an adipic acid/diethylene glycol polyester.

Incorporation of silicone oil in the formulation has been found to convert what would be a dimensionally unstable substantially closed cell foam into a dimensionally stable foam of very low porosity. The use of quantities of surfactant below 0.6% by weight of the polyol has been found to produce a dimensionally stable foam of very high porosity. In some cases the surfactant can be omitted altogether, thereby significantly reducing the cost of the basic formulation and hence the eventual foam.

Aspects of the invention will now be illustrated by reference to the following examples some of which relate to known or unsatisfactory foam forming formulations and are referred to for purposes of comparison and others of which relate to formulations according to the invention and are intended to be non-limitative and for purposes of illustration only.

EXAMPLE 1 This illustrates the production of conventional TDI based polyester foam with good dimensional stability and of commercial value in the production of laminated textiles or other products. The formulation comprises the following parts by weight: Fomrez50(1) 100 TDI (80:20) (2) 102 Index Water 4.0 NEM (3) 1.5 16D(4) 0.18 L532 (5) 1.2 Stannous octoate 0.02 Notes to Table (1) An adipic acid/diethylene glycol and polyester having an OH value of 50-55 mg KOH/g and a viscosity of approximately 25,000 cp at 250C.Manufactured by Witco Chemical Company (2) Toluene diisocyanate-80:20 blend of 2,4- and 2,6-isomers. "Index" refers to the isocyanate index which is well known within the polyurethane field and relates to the molar ratio of isocyanate to reactive hydroxyl groups in the water/polyol combination. An index of 100 is a perfect balance, a figure of less than 100 is indicative of a slight isocyanate deficiency, and one of greater than 100 is indicative of a slight isocyanate excess.

(3) N Ethyl Morpholine (catalyst) (4) Cetyl dimethylamine (catalyst) (5) Proprietary silicone surfactant manufactured by Union Carbide Corporation.

This system when reacted at 220C yielded an open celled foam of density 28 kg/m3. Cream and rise times were 8 and 70 seconds respectively.

EXAMPLES 2-9 These illustrate the problems encountered when TDI is replaced by MDI based isocyanates in conventional formulations and the ineffectiveness of catalyst modification (in particular gel catalyst reduction) as a means of producing greater dimensional stability. All of the foams displayed excessive shrinkage after their production and lacked commercial utility.The reactions took place at 220C.

Example 2 3 4 5 6 7 8 9 Fomrez 50(1) 100 100 100 100 100 100 100 100 Suprasec DND (6) 102 - 102 - 102 - 102 Index Index Index Index Suprasec VM30 (7) - 102 - 102 - 102 - 102 Index Index Index Index Water 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 NEM (3) 1.5 1.5 2.0 2.0 - - - 16D (4) 0.18 0.18 0.1 0.1 0.1 0.1 - L532 (5) 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 DMDE (8) - - - - 1.5 1.5 - DMEA (9) - - - - - - 1.0 1.0 Stannous octoate 0.02 0.02 - - - - - Rise Time (sec) 150 130 131 138 124 129 145 119 Foam Quality All foams were substantially closed cell and were dimensionally unstable on cooling

(6) Diisocyanato-diphenylmethane composition of isocyanate value 30.2-31.2% by weight supplied by Imperial Chemical Industries Functionality=2.8.

(7) Diisocyanato-diphenylmethane composition of isocyanate value 27.5-29.5% by weight supplied by Imperial Chemical Industries Functionality=2.3 (8) Dimorpholinodiethyl ether (9) Dimethylethanolamine EXAMPLES 10-16 These illustrate the production of low porosity dimensionally stable foams by the addition of a silicone oil.In all cases the reaction took place at 220C.

Example 10 11 12 13 14 15 16 Fomrez 50 (1) 100 100 100 100 100 100 100 Suprasec DND (6) - - - - - 102 102 Index Index Suprasec VM30 (7) 102 102 102 102 102 - Index Index Index Index Index Water 3.5 3.5 3.5 3.5 3.5 3.5 3.5 NEM(3) 1.5 1.5 1.5 1.5 1.5 1.5 1.5 L532 (5) 1.2 1.2 1.2 1.2 1.2 1.2 1.2 16D (4) 0.15 0.15 0.15 0.15 0.15 0.15 0.1 DC200 (10) - 0.005 0.01 0.02 0.04 0.05 0.05 Rise Time(sec) 121 119 115 116 110 Foam Quality Closed cell Fine celled, dimensionally stable, low porosity dimensionally unstable Density (kg/m ) - 36.0 35.6 34.9 35.2 34.9 36.2 (10) A polydimethyl siloxane oil supplied by Dow Corning.

EXAMPLES 17-20 These illustrate the production of dimensionally stable. very porous flexible foams by use of an abnormally low level of surfactant compared with the quantity normally used in the production of polyester-polyurethane foams from toluene diisocyanate. The reactions took place at 22 C.

Example 17 18 19 20 Fomrez 50 (1) 100 100 100 100 Suprasec DND (6) - - 102 102 Index Index Suprasec VM30 (7) | 102 index | - | Water 4.0 4.0 4.0 4.0 NEM (3) 1.5 1.5 1.5 1.5 L532 (5) 0.5 0.6 - 16D (4) 0.18 0.18 - 0.05 Rise Time (sec) 114 119 147 141 Foam Quality Fine celled, dimensionally stable, high porosity Density (kgIm3) 39.1 37.2 36.8 37.4 EXAMPLE 21 Foam was produced on a high pressure foaming machine according the formulation: Fomrez F50(1) 100 parts SuprasecVM30 (7) 102 Index Water 3.5 NEM (3) 0.75 16D (4) 0.25 NiaxA30(11) 0.175 NiaxA4(12) 0.125 L532 (5) 0.6 The foam had a rise time of 100 sec at 25 C and is described by the folowing physical properties:: Density - 36.4 kg/m3 Tensile strength - 1.4 kg/cm2 Elongation at Break - 160% Resiliency - 19% Indentation Hardness to BS3667 Part 1 - 18.0 kg Hardness to BS4443 Method 7B - 25% - 121 N - 40% -164N - 65% -325N -2.68 (11) Proprietary tertiary amine manufactured by Union Carbide Group (12) Proprietary tertiary amine manufactured by Union Carbide Group.

The foam was converted to rolls on a rotary peeling machine and flame laminated at a typical commercial speed of 25 metres/min.

By virtue of the invention dimensionally stable, commercially useable polyester-urethane foams can be produced in a range of densities from diphenylmethane-4,4'-diisocyanate thereby avoiding the problems associated with the use of toluene diisocyanate traditionally employed in the production of polyester based foams. Moreover in some cases the surface active agents normally employed may be substantially reduced or omitted entirely enabling a further saving in production cost.

Various modifications may be made without departing from the invention. Moreover whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to whether or not particular emphasis has been placed thereon.

Claims (9)

1. A method of producing a dimensionally stable, flexible, polyester urethane foam comprising reacting a hydroxy terminated polyester polyol and diphenylmethane-4,4'-diisocyanate (MDI) together with a catalyst and a blowing agent in the absence of other constituents.

2. A method of producing a dimensionally stable, flexible, polyester urethane foam comprising reacting a hydroxy terminated polyester polyol and diphenylmethane-4,4'-diisocyanate (MDI) together with a catalyst, a blowing agent and a silicone surfactant present in an amount of less than 1% by weight of the polyester.

3. A method according to claim 2 wherein said silicone surfactant is present in an amount of less than 0.6% by weight of the polyester.

4. A method of producing a dimensionally stable, flexible, polyester urethane foam comprising reacting a hydroxy terminated polyester polyol and diphenylmethane-4,4'-diisocyanate (MDI) together with a silicone surfactant, a catalyst, a blowing agent and a silicone oil.

5. A method according to claim 4 wherein the silicone oil is present in an amount of between 0.005 and 0.05% by weight of the polyester.

6. A method according to any preceding claim wherein the polyester polyol comprises an adipic acid/diethylene glycol polyester.

7. A method of producing a dimensionally stable, flexible, polyester urethane foam in accordance with any of Examples 10-16.

8. A method of producing a dimensionally stable, flexible, polyester urethane foam of high porosity in accordance with any of Examples 17-21.

9. Dimensionally stable, flexible, polyester urethane foam produced by the method according to any preceding claim.