WO1990003997A1

WO1990003997A1 - Effect of using chemical modifiers in the curing of polyurethane foams

Info

Publication number: WO1990003997A1
Application number: PCT/AU1989/000426
Authority: WO
Inventors: Allen Wood; Michael David Joubert
Original assignee: Pacific Dunlop Ltd
Current assignee: Dunlop Olympic Ltd
Priority date: 1988-10-07
Filing date: 1989-10-02
Publication date: 1990-04-19
Anticipated expiration: 1991-04-07
Also published as: CA2000208A1; NZ230878A

Abstract

An improved method and process for making a foam material, preferably a polyurethane foam material, more preferably a flexible foam material in which an additional additive is incorporated into the liquid foamable mixture. The additive is capable of undergoing or entering into an endothermic reaction or is capable of forming or decomposing into one or more gaseous products at a preselected temperature or over a preselected range of temperatures. The endothermic reaction or decomposition or production of gaseous product beneficially influences the properties of the foamed material when forming or when formed. The properties of the foam material produced by the improved method and process are more uniform, reproducible and controllable than the corresponding properties of foams produced by conventional formulations.

Description

EFFECT OF USING CHEMICAL MODIFIERS IN THE CURING OF

POLYURETHANE FOAMS

The present invention relates in general to polyurethane foams including both flexible foams and rigid foams and to methods for their manufacture- In particular, the present invention relates to improvements in the foaming and/or curing step of the method used in the manufacture of foamed material.

In particular, the present invention finds application in the formulation of a foamable mixture for making foam material by including in the formulation an additive which undergoes a chemical and/or physical change to produce a gaseous and/or vaporous material so that foam material with more controllable, reproducible and/or uniform properties can be manufactured. Another aspect of the present invention relates to the incorporation of additives that undergo an endothermic change during the foaming and/or curing step so that less heat may be produced during the exotherm.

Although the present invention will be described with particular reference to improvements in the curing step of the method of making flexible polyurethane slabstock, it is to be noted that the present invention is not limited to this application and is more extensive in scope so as to include modifications of other steps in the overall process and to other processes useful in other applications.

In general polyurethane flexible or rigid foams are produced by reacting a suitable polyol or mixture of polyols with di- or polyisocyanates in the presence of stabilizers, eell control agents, blowing agents, catalysts and the like. The reaction is of a polyaddition type and is strongly

exothermic.

The polyols used in flexible foam production are generally diols or triols having a molecular weight of about 1000 to 7000. It is to be noted that the present invention may be used in the manufacture of both polyether polyurethanes and polyester polyurethanes.

The isocyanates used in flexible foam production are mostly based on toluene-diisocyanates and/or on

raethyl-diphenyl-diisocyanates in their various monomeric or polymeric forms or may be based or other aliphatic or aromatic isocyanates.

The stabilizer/cell control agent/surfactant

compounds are generally various types of organo-siloxanes added in suitable amounts depending on the precise end

properties required by the polyurethanes.

The blowing agents are included so as to expand during the foaming and/or expansion stage of the reaction to fill the pores in the foam structure to make the product a cellular plastic. Water which is one example of the blowing agent is generally present in formulations at a concentration of from about 0.06 to 4.0 parts by weight based upon 100 p.b.w. of the polyol or polyols. However, it is to be noted that higher amounts of water may be used. The water/isocyanate reaction will liberate carbon dioxide gas in a strongly exothermic reaction. This reaction contributes to the exotherm produced during the manufacture of the flexible polyurethane.

Low boiling halo-carbons such as

monofluoro-trichloro methane and/or methylene chloride or other similar substances may act as auxiliary blowing agents.

These will expand at relatively low temperatures, e.g. 25°C to

75°C, into vapours to fill the cells or pores of the foam structure which are produced due to the heat developed as a result of the reaction exotherm.

Air may also be used as a nucleating agent and may be added by injecting it into the reaction mix to facilitate the formation of the cellular structure. The reactant

chemicals used in the formulation such as the actual

reactants, catalysts, additives and the like are mixed in a pre-determined ratio.

The density of the foam produced in a given polyol/isocyanate system is typically from aoout 12 to 70 kg/m³ or more - and is determined by the amount of blowing agent or agents present in the reaction mixture.

Other ingredients in a foam mix or system may include solid or liquid fillers, modifiers, cross linkers andother reactive or non-reactive components aimed at modifying the physical properties, combustion performance, weldability or other characteristics of the end product.

In general, the final physical properties of the resulting cellular plastic are determined by the nature and amounts of reacting and non-reacting components present in the initial mixture. The final physical properties are generally reached after full cure which may last 1 to 2 days after manufacture of the foam. In particular, the density of the cellular plastic is determined by the ratio and concentration of the chemical and/or physical blowing agents present in the reaction mix as well as by the presence or absence of inert or reactive fillers, which may be present as either solids or liquids.

In particular, the final hardness of the resulting cellular plastic is determined by the nature of the polyols, the stoichioraetric ratio of the isocyanates to the polyol or polyols, the nature of the cross linking agent or agents if more than a single agent is present, whether other reactive components and water are present as well as whether liquid extenders or solid fillers are present in the reaction mix, including their quantity and in the case of solids their particle size distribution.

In addition to the effects indicated above due to the nature and amount of the various ingredients which are in essence chemical effects on the cellular plastic there is at any particular point within the cellular plastic produced the effects which result from essentially physical effects. In particular the ultimate physical properties at any particular point within the foamed block are influenced by the precise position and location of that particular point within the moulding or block, the size of the moulding or block, the conditions under which the block was cured, such as for example, the temperature and humidity of the atmosphere surrounding the block during the period of curing.

Briefly, there are two basic techniques for producing polyurethane foam: The first technique is

(a) Slabstock Production

Large blocks of foam can be produced by either, a batch process or continuously.

In a typical continuous process 100 to 500 kg/min of a liquid foam reaction mixture is laid on to a paper former on a moving conveyor and allowed to expand into a continuous block of - say for example - 2m width and lm in height, defined within two side walls and a base surface. Further along the conveyor the continuous block of foam is cut into individual, suitably sized blocks, say typically, of the order of from 1.5 to 2m in length or more, and sometimes as long as 50m.

These 2ra wide by lm high by 1.5 to 2m or more long individual blocks require storage for a minimum of 16 to 24 hours to allow the heat generated by the exotherm during curing to be safely dissipated and for the curing process to reach completion before the blocks can be warehoused or processed into slabs, sheets, furniture components or

whatever.

During the initial 16 to 24 hours of storage all of the foam blocks are laid down individually in an attempt to allow the exotherm which develops within each sufficient time to dissipate uniformly. Temperatures of up to about 100° to 175°C are reached within the inside core of these blocks as a result of exothermic reactions during this post curing period. However, the heat developed by the exothermic reactions is not uniformly distributed throughout the block since the central portions of the block which are relatively more insulated by the bulk of the block develop a much higher temperature than the peripheral portions which are less well insulated by being surrounded with less foam material and accordingly, the dissipation of heat is uneven. The other technique is

(b) Moulding

In this technique, the liquid foam reaction mixture is injected into a suitably constructed enclosure - the mould - where the liquid is allowed to expand by foaming such that on expansion and solidification the polyurethane foam takes on the shape of the mould to form a solid block of foam of the desired shape. After demoulding, the final curing process takes place either at room temperature or in temperature controllable ovens or tunnels at temperatures above ambient. However, with some sizes and shapes of moulded foam

post-curing is required. It is to be noted that the present invention is more suitable in the process of slabstock production rather than in the process of producing shaped foamed articles by the

moulding process. However, the present invention can be useful and also find, application in treating moulded pieces as well.

The post curing of slabstock foams takes place traditionally at the ambient temperature of the storage area. The blocks are set apart from each other by a minimum

distance (say of the order of a minimum of 50mm) and during this initial period of 16 - 24 hours they are not, under usual circumstances, stacked on top of each other but rather are placed side by side in slightly spaced apart relationship.

The blocks are stored spaced apart from each other so as to allow air to circulate between to provide more uniform cooling and to prevent heat build up and thus, reduce the danger of auto-ignition of the freshly produced foam.

Typically, the cure or post-cure of the freshly manufactured and cut blocks from the slabstock production line takes place in a fresh foam or "hot block storage" room, where the inner core or inner portion of each block reaches a temperature of about 100° to 175°C in from up to 200 seconds after formation, maintains this temperature for a further period of up to several hours and then gradually cools down to ambient temperature. This process is slow, taking about 10 to 36 hours, because the foam by its nature is an excellent insulator of heat.

During this cure or post cure period, secondary chemical reactions take place in the polyurethane structure such as for example residual isocyanate and amine/or urethane groups can react to form biuret and/or allophanate linkages or the like, all of which contribute to determining the final physical properties of the material.

The nature of these reactions, including the nature and amount of any byproducts produced, and their reaction rates including the formation of reaction products which are incorporated into the polymer chains are each dependent on the temperature and humidity conditions in the fresh foam storage room but more particularly on the temperature and humidity conditions existing within the foam block itself. The current practice in slabstock manufacture is to allow the block to cure by itself thus creating a situation whereby the inner core of the foam block cures at a higher temperature than the portions near the outer walls of the block where heat is lost to the surrounding atmosphere.

The variation in the conditions and temperature of cure referred to above is in part responsible for the

variation in hardness and related properties within a single block of foam, such as for example tensile strength, or the like.

As a result of the high inner core temperature some types of foam tend to discolour in the inner core due to the effect of heat degradation.

More often than not, the ambient temperature and humidity conditions within the fresh foam or hot block storage area at this stage of the curing process are not totally predictable or at least are not accurately controllable which leads to further variations in properties of the cured

polyurethane.

Even changes in atmospheric humidity within the fresh foam or "hot block" storage area are known to cause changes in foam properties e.g. a block of foam produced and cured under conditions of high humidity can exhibit softer properties (i.e. lower in IFD hardness) than a foam made under identical conditions from the same ingredients but cured under conditions of lower absolute humidity.

Therefore, it is an aim of the present invention to provide a method which attempts to produce a more

controllable, uniform and/or reproducible foam material, particularly a polyurethane foam, by chemically modifying the environment around and within the cells of the foamed

material. Typically, the properties which are more controlled are hardness, density, tensile strength, elongation,

compression set and the like. According to one aspect of the present invention there is provided a method for the production of a foam material, preferably a polyurethane foam material, comprising including in the foamable liquid reaction mixture an additive which is capable of undergoing an endothermic reaction or is capable of forming a vapour and/or decomposing into one or more gaseous materials at a known preselected temperature or over a known preselected range of temperatures said vapour or gaseous material beneficially influencing the properties of the foamed material when forming and/or when formed.

According to another aspect of the present invention there is provided a foamable reaction mixture for forming a polyurethane flexible foam that is capable of expanding and polymerizing to form a shaped piece or block of foam wherein at least one additional additive which is capable of

undergoing an endothermic reaction or is capable of forming a vapour and/or decomposing into one or more gaseous materials at a known preselected temperature or over a known preselected range of temperatures so as to influence the final physical properties of the foam is incorporated into the reaction mixture.

Typically the decomposition occurs endothermically. Typically the properties of the foamed material are beneficially influenced by reducing the maximum temperature reacted during the curing process.

The additive material that is additionally added typically includes materials which decompose or give up their water of crystallization or breakdown endothermically when heated. Examples of such additive materials typically decompose or give up their water of crystallization at temperatures between 10°C and 200°C preferably at a

temperature of at least about 80°. Typical examples of such materials include the following:

Ammonium carbonate which decomposes to ammonia and carbon dioxide at a temperature of 58°C.

Aluminium sulphate Al₂ (SO₄)₃.18H₂O at 86.5°C; Calcium phosphate, (monobasic) CaH₄ (PO₄)₂.H₂O at 100°C;

Calcium sulphate CaSO₄.2H₂O losing 1% H₂O at

128°C,the balance (½H₂O) at 163°C;

Ferrous ammonium sulphate Fe(NH₄ )₂ (SO₄)₂.6H₂O at 100 to 110°C;

Potassium sodium tartate KNaC₄H₄O₆.4H₂O, melting range 70-80°C, liberating water of crystallization at 140°C;

Sodium borate Na₂B₄O₇.10H₂O at 75°C to 320°C;

Sodium carbonate, raonohydrate Na₂CO₃.H₂O at 109°C;

Sodium phosphate Na₃PO₄.12H₂O at 100°C (melting point 75°C).

Aluminium ammonium sulphate Al₂ (NH₄)₂ (SO₄)₄-24H₂O, loses 20 H₂O at 120°C.

Aluminium potassium sulphate Al₂K₂(SO₄)₄ . 24H₂O, loses 18H₂O at 64.5°C.

Calcium acetate Ca(C₂H₃O₂)₂-H₂O, decomposes on heating to produce gaseous products.

Calcium acetyl salicylate Ca(CH₃COO.C₆H₄COO)₂ .2H₂O, aquepus solution unstable and decomposes to give off gaseous products.

Calcium chloride CaCl₂, CaCl₂.2H₂O, CaCl₂.6H₂O, loses 4H₂O at 30°C, 6H₂O at 200°C.

Calcium citrate Ca₃(C₆H₅O₇)₂.4H₂O, loses water at 100-120°C.

Calcium salicylate Ca(C₇H₅O₃)₂.2H₂O, loses water at

120°C.

Silica gel when heated gives off its absorbed water. Sodium sulphate decahydrate Na₂SO₄.10H₂O, at 100°C (melting point 33°C).

Other additive materials typically include the following: gas saturated adsorptive carbons, zeolites, molecular sieves, and the like, polypropylene, polyethylene, and other plastics, calcium stearate, and similar materials which are endothermic due to their melting properties in the required temperature range. Typically, the additional material is included in the reaction mixture at the time of formulation of the liquid mixture in addition to the usual, typical or conventional materials that are incorporated in the reaction mixture.

Typically, the products of the decomposition of the additional material include a gas or mixture of gases or a vapour or mixture of vapours. The gaseous decomposition products influence the curing step of the solid urethane polymeric structure.

Typically, the selective influence of the vapour or gases may be localised. The inner core of a freshly produced block will stay for longer periods of time at higher exotherm temperatures, say at from 120° to 165°C. Peripheral areas of the same block will stay for shorter periods at the high exotherm level or will be at lower exotherm levels.

Therefore, the rate and amount of decomposition of the

additional material and the decomposition processes will take place to different degrees and varying amounts depending upon precisely where inside the block the additive material is located and whether the additive material is located

internally within the cell or in the polymeric materials forming the matrix in which the cells are located i.e. whether the location is intra or intercellular.

Alternatively, the block may be insulated all around so that the heat distribution is more uniform, and accordingly so is the cooling-down process which allows the decomposition products to develop as fully as possible, because variation in the cooling rate of different parts of the block will not oe as great and the rate overall will be slowed down compared to the situation where the block is uninsulated.

Typically, the additional material is a hydrated mineral salt, giving up its water of crystallisation at elevated temperatures. The developing water vapour from the decomposition of, say for example, hydrated calcium sulphate CaSO₄.2H₂O, would occupy the cells of the freshly produced cellular polyurethane thereby providing a controlled humidity condition for curing. In certain instances such endothermic chemical reaction, i.e. the loss of water of crystallisation, will reduce the maximum exotherm temperature of the foaming

material, thus reducing the danger of auto-ignition of the freshly produced foam block in some cases which is another advantage of the present invention.

Typically the additional material is a compound like the ammonium salts, such as for example ammonium carbonate or the ammonium acetates. Typically, the additional material is any such compound which decomposes at about 60° to 180°C, typically 100° to 170°C, more typically 120° to 165°C, often giving up vapours or gases which can influence the secondary chemical reactions which take place during the curing period immediately following the foam formation.

Typically, the additional material can be organic or inorganic and may be a solid or liquid at ambient or room temperature. If the additional material is a solid, it may sublime at an elevated temperature to give off a gas.

Alternatively, the solid material may undergo a change from solid to liquid to gas. If the additional material is a liquid, it may undergo a change from liquid to vapour.

Therefore, the final physical properties of the polyurethane foam polymer as well as the temperatures developed during the foaming and/or curing step, such as from the time the exotherm begins and thereafter, can be directly influenced by the presence of the vapour or gas from the additive material when inside the cells of the foamed blocks, or can be influenced by the endothermic nature of the change in phase, e.g. melting of the additive.

Although not wishing to be bound by the following theory, it is thought that in some cases the advantages of the present invention may be brought about by free isocyanate groups present in the foaming material or in the freshly produced foam reacting with the additive material,

particularly the water vapour given off by any decomposition or loss of water of crystallization. The foamed material may then cool down faster because there are no or very little free isocyanate groups left unreacted to enter into further

reactions which conventionally prolong the curing of the foamed material to produce heat.

Also, it is thought that the water vapour resulting from the loss of water of crystallization contributes to reducing the hardness of the foamed material in the centre of the foam, which balances the effect of atmospheric moisture in the outer portions of the block. This effect can be utilized to reduce or eliminate the use of chlorofluorocarbon or methylene chloride to achieve a given type of foam which will be described by way of example later in this specification.

The amount of the additives included in the reaction mixture may vary widely depending on the particular additive chosen and the end result sought. Typical ranges are from .05 pph to 170 pph expressed as parts per hundred based on the total amount of polyol present in the reaction mixture. More typically, the amounts range from .2 to 100 pph, even more typically 2 to 30 pph.

Typical materials useful as additives in the present invention include mineral hydrates, organo metallic hydrates and dessicant materials also adsorptive carbons, molecular sieves, zeolites, polyethylene, polypropylene, calcium

stearate etc. which are useful due to being endothermic because of their melting properties rather than due to their chemical breakdown and the attendant production of gaseous products. Although these materials do not decompose under heating the can give off water vapour or other gases at elevated temperatures. A particularly preferred material is gypsum G75 which is supplied by Commercial Minerals Limited of Camberwell, Victoria and which has the following

specifications. Typical Chemical An talysis

Calcium Sulphate CaSO₄2H₂O 97 .5%

Calcium Carbonate CaCO₃ 0 .3%

Combined Iron and

Aluminium Oxides 0 .37%

Sodium Chloride NaCl 0.03%

Acid Insolubles 1.46%

Sizing Analysis

Residue at 7 Microns: Less than 5.0%

Mean Particle Diameter: 3.3 Microns Surface Area 7,900 cm²/gm.

Typical Physical Properties

Brightness 84%

Oil Absorption 31 ml/100gm Specific Gravity 2.3

pH 8.3

Bulk Density (Tapped) 1.08 gm/cc

Bulk Density (Loose) 0.64 gm/cc

Another aspect of the present invention relates to the incorporation of additive materials which may either enter into endothermic reactions with other materials already present in the formulation or may undergo a change which is endothermic. Any material added to the foaming mixture which undergoes or enters into an endothermic reaction will reduce the amount of exotherm since heat will be taken away from the exotherm to drive the endothermic reaction.

The present invention will now be described by way of example with reference to the accompanying drawings in which;

Figure 1 is a schematic representation of a foam block showing the position of representative test samples taken from the block upon which performance tests were conducted; Figure 2 is a plot of hardness as a function of vertical position of the selected test sample within the block;

Figure 3 is a plot of hardness as a function of horizontal position of the selected test sample within the block;

Figure 4 is a plot of exotherm temperature as a function of time for various locations of the test samples within the block;

Figure 5 is a plot of the internal foam temperature developed within the block as a function of time for varying quantities of additives;

Figure 6 is a plot of the internal foam temperature developed within the block as a function of time for different additives;

Figure 7 is a plot of density as a function of vertical position of the test sample within the block; and

Figure 8 is a plot of hardness as a function of vertical position of the test sample within the block.

In Figure 1 there is shown schematically a block of foam generally denoted by A, from which representative test samples are taken generally denoted by b, and tested for various properties such as hardness, density and the like.

The location of the test samples are denoted by one of the reference numerals 1 to 9 in a horizontal plane or grid and by one of the reference numerals 1 to 14 in a vertical plane or column. It is to be noted that none of the samples tested are taken from the extreme edges of the block but rather the block is skinned by removing one or more layers from the block prior to subdividing the block into the test samples. The block is skinned to remove the extreme outer layers because the

properties possessed by the extreme outer layer are very atypical of the block as a whole and are hence discarded so as not to produce spurious results in any of the tests conducted on the samples. Generally, as shown in Figure 1, the vertical

positions are broadly divided into 3 main areas which are denoted as top, middle, or bottom of the block. Although each of the 9 horizontal positions is associated with 14 vertical positions, in practice each horizontal position is usually only associated with 3 vertical positions, making a choice of 27 different samples. By selectively taking the samples from the choice of 27 positions it is possible to gain an overall picture of the block. If more detailed information is

required because each of the 9 horizontal positions can be subdivided into the 14 vertical samples a more detailed picture of any one area can be obtained. In practice however, it is usual to select only 3 vertical samples for each

horizontal positions.

In Figure 2 there is shown a plot of hardness expressed in newtons as a function of the 14 vertical

positions for a column located at each of two horizontal positions, both with and without additives; one of the

horizontal positions being located at or towards an edge whilst the other is located at the centre. The abbreviations "EXP" refers to an experimental batch of foam having the additive , in this case 4.0 pph of G75, whereas the

abbreviation "REF" refers to a standard foam block formulation for producing a conventional foam block without additive.

Clearly from Figure 2 both of the experimental foam blocks containing 4.0 pph additive are considerably softer than the corresponding blocks made to the conventional formulation.

The hardness of the EXP blocks being of the order of 85 to 105N whereas the hardness of the REF blocks is from 125 to 145N. Additionally, the EXP blocks exhibit more homogeneous properties with less variation than do the REF blocks. The test samples at vertical positions 6 to 10 of the REF blocks, particularly the REF block at the centre exhibits a greater variation from about 130N to about 145N when compared to the more even hardness obtained in the EXP blocks of about 94±1 N. Thus, in this example it can be readily seen that the

inclusion of the additive produces a foam with more uniform properties than is achieved without the inclusion of the additive and thus the final properties of the foam are more controllable. It also reduces the foam hardness relative to the REF block.

Figure 3 illustrates the difference in hardness obtained between the experimental foam, EXP, containing additive and the reference foam, REF, not containing the additive for each of the 9 horizontal positions at the same vertical level. From the top vertical position, a test sample was taken from each of the 9 horizontal positions which are number 1 through to 9 as per the positions illustrated in Figure 1. Similarly, 9 test samples were taken from the middle vertical level and tested. Also, 9 test samples were taken from the bottom vertical position and tested. The 27 test samples in all were tested for hardness and the results plotted in Figure 3 in groups of threes. The results from the EXP block were compared to the results from the REF block.

Clearly, the variation of hardness within a single vertical level of 9 test samples, was greater for the REF block than for the EXP block. The variation of the REF block being generally of the order of between about 10 and 15N whereas the variation of the EXP block was about 5N. In addition, the EXP block was. appreciably softer. Moreover, the variation between adjacent positions of the REF block, particularly between edge locations and centre locations, was considerably greater than the variation between corresponding adjacent positions in the EXP block. This is particularly illustrated in the values of hardness obtained at positions 4, 5 and 6 of the block for the middle and bottom test samples of the REF block which vary by about 13N when compared to the values obtained at the

corresponding positions of the EXP block which vary only by about 3N. Additionally, it can be seen that the variation between samples taken at the same horizontal position but at different vertical positions of the one block was considerably greater for the REF block than for the EXP block. Thus, again the inclusion of the additive clearly produces a foam block having less variation in hardness through both its thickness and length or width.

Figure 4 illustrates a temperature-time profile of the cooling of the foam block during post cure for two samples of each of the REF block and EXP block in which a first sample was taken at the edge of the block while the other sample was taken at the centre of the block. The temperature-time profile clearly indicates that the inclusion of the additive results in a lower maximum temperature being attained during the exotherm, about 150°C for the REF block at the edge as compared to about 125°C for the EXP block at the edge, and faster rate of cooling as in the case of the centre test sample where both initial temperatures were about 150°C but the REF block took 600 minutes to cool to 120°C whereas the EXP block took about 400 minutes to cool to 120°C.

Figure 5 is a time-temperature profile for the exotherm during the manufacture of the foam block for

different formulations containing differing amounts of

additives: The additive was G75 and was added in amounts of 0 pph (corresponding to a conventional formulation) 5, 10, 20, 40, 60 pph. With the exception of the formulation containing 50 pph G75, the exotherm temperature in all other cases was less than the exotherm of the conventional formulation. This clearly indicates that once the additive has been added above a critical threshold the heat generated by the exotherm is somehow modified so as not to reach such a high level.

Typically, it is thought that the modification is probably caused by the endothermic nature of the breakdown of the additive. The reduction in maximum exotherm temperature clearly aids in providing a foam of more uniform properties as was illustrated in Figure 3.

It also provides the opportunity to use formulations which would otherwise generate unsafe exotherms, with the danger of auto-ignition. This concept can be used to modify formulations for the given density foam, so that no auxiliary blowing agent (CFC methylene chloride) is required. An example illustrating the effect of incorporating an additive and omitting the auxiliary blowing agent will be described later in more detail.

This is particularly so when the rate of cooling of the block with the formulation containing 20, 40 and 60 pph is considered since their rate of cooling is greater than the rate of cooling of blocks having an amount of additive less than 20 pph. (e.g. 0, 5 and 10 pph).

Figure 6 illustrates the modifying effect or the maximum temperature of exotherm of additives other than G75. The other additives used are magnesium sulphate, sodium tetraborate and sodium orthophosphate as indicated. All three of these other additives reduce the maximum temperature of exotherm at 5.0 pph levels of addition. Clearly, the observed beneficial effect of the present invention is apparent with a range of additives.

Figure 7 illustrates the difference in density of each of the test samples at position 1 through to 14 of one column of test samples similar to that of Figure 2 in relation to hardness for a different overall formulation than that used in Figure 2. Although the variation of density between the test samples of the EXP block is about the same as that of the REF block, the REF block is somewhat less dense and

accordingly, shows a flattening of the density profile.

Figure 8 illustrate a hardness profile for a

different formulation as a function of vertical position within a column of test samples.

Examples

Improvement in the desired properties of the foam, such as a more uniform distribution of density and/or hardness from the top to the bottom of the foam block has been achieved in a number of cases.

Such improvements of the gradients is claimed to be due to the release of water vapour from the additives on reaching exotherm temperatures corresponding to the liberation of the water of crystallization whereby this takes place in the centre, higher temperature sections of the block, and balances a similar process taking place in the outer portions of the block which are subject to reaction with atmospheric moisture, and which do not reach the dehydration temperature of the additives.

Example 1

Foam Grade: A30-120

Nominal Density (kg/m³) : 30

Nominal Hardness, IF₄₀(Newtons) 120

Additive: Gypsum G75 *Supplied by Commercial

Minerals

Concentration: 0.2 parts per 100 polyol

Method of Processing: Laboratory hand batch in 38cm² box No. of Samples : 3 each.

Results

Reference Sample

(untreated foam) (treated foam)

Density in kg/m³

Range 30.6-34.1(3.5) 30.4-32.2(1.8)

Average 32.03 31.07

Std. Deviation 1.834 0.987

IF₄₀ Hardness in Newtons

Range 127-148(21) 122-132(10) Average 137.3 126.7

Std. Deviation 10.50 5.03

Comment: Hardness deviation reduced.

Example 2

Foam Grade: HR36-130 High Resilience Type Foam Nominal Density (kg/m³): 36

Nominal Hardness, IF₄₀(Newtons): 130

Additive: Gypsum G75

Concentration: 0.15 pphp

Method of Processing: Laboratory handraix

No. of Samples: 3 each. Results

Reference Sample

(untreated foam) (treated foam) Density in kg/m³

Range 37.2-38.6(1.4) 36.7-38.1(1.4) Average 37.80 37.23

Std. Deviation 0.721 0.757

IF₄₀ Hardness in Newtons

Range 150-155(5) 146-148(2)

Average 152.00 147.33 Std. Deviation 2.646 1.155

Comment: Hardness deviation reduced.

Example 3

Foam Grade: A27-150

Nominal Density (kg/m³): 27

Nominal Hardness, IF₄₀ (Newtons): 150

Additive: Gypsum G75

Concentration: 0.2 pphp

Method of Processing: Laboratory handmix

No. of Samples: 3 each.

Results

Reference Sample

(untreated foam) (treated foam) Density in kg/m³

Range 27.3-31.5(4.2) 27.4-30.5(3.1) Average 28.93 28.60

Std. Deviation 2.250 1.664

IF₄₀ Hardness in Newtons

Range 152-182(30) 157-182(25)

Average 163.67 170.33 Std. Deviation 16.073 12.583

Comment: Density and hardness deviation reduced.

Example 4

Foam Grade: A24-150

Nominal Density (kg/m³): 24

Nominal Hardness, IF₄₀(Newtons): 150

Additive: Gypsum G75

Concentration: 0.5 pphp

Method of Processing: Laboratory handmix

No. of Samples: 5 each. Results

Reference Sample

(untreated foam) (treated foam)

Density in kg/m³

Range 24.5-27.0(2.5) 24.4-27.0(2.6) Average 25.44 25.38

Std. Deviation 0.96 1.01

IF₄₀ Hardness in Newtons

Range 168-190(22) 167-188(21)

Average 176.8 177.4 Std. Deviation 10.13 8.38

Comment: Hardness deviation reduced.

Example 5

Foam Grade: A30-120 (repeat tests)

Nominal Density (kg/m³) : 30

Nominal Hardness, IF₄₀ (Newtons ) : 120

Additive: Gypsum G75

Concentration: 0.2 , 1. 0 , 3.0 pphp

Method of Processing: Handmix

No. of Samples : 4 of each set

Results

Reference Sample

(untreated foam) (treated foam)

Density in kg/m³ 0.2 pphp Range 30.4-32.9(2.5) 30.1-31.8(1.7) Average 31.18 30.78 Std. Deviation 1.184 0.741

Density in kg/m³ 1.0 pphp Range 30.4-32.9(2.5) 30.6-32.6(2.0) Average 31.18 31.38 Std. Deviation 1.184 0.866

Density in kg/m³ 3.0 pphp Range 30.4-32.9(2.5) 30.4-32.1(1.7) Average 31.18 31.03 Std. Deviation 1.184 0.759

IF₄₀ Hardness in Newtons 0.2 pphp Range 123-161(38) 123-136(13)

Average 135.5 131.8

Std. Deviation 17.3 .5.97

IF₄₀ Hardness in Newtons 1.0 pphp Range 123-161(38) 127-133(6)

Average 135.5 131.0

Std. Deviation 17.3 2.7

IF₄₀ Hardness in Newtons 3.0 pphp

Range 123-161(38) 102-115(13)

Average 135.5 107.0

Std. Deviation 17.3 5.72

Comment: Reduced deviation in hardness and density Example 6

Foam Grade: A27-150

Nominal Density (kg/m³): 27

Nominal Hardness, IF₄₀ (Newtons) : 150

Additive : Gypsum G75

Concentration: 0.5 pphp and 1.0 pphp

Method of Processing: Laboratory handmix

No . of Samples: 4 each.

Results

Reference Sample

(untreated foam) (treated foam)

Density in kg/m³ 0.5 pphp G75 Range 27.4-29.0(1:6) 27.3-28.6(1.3) Average 27.95 27.85 Std. Deviation 0.755 0.580

Density in kg/m³ 1.0 pphp G75 Range 27.4-29.0(1.6) 27.3-29.0(1.7) Average 27.95 27.95 Std. Deviation 0.755 0.742

IF₄₀ Hardness in Newtons 0.5 pphp G75

Range 152-167(15) 157-170(13)

Average 160.3 162.5

Std. Deviation 6.652 6.137

IF₄₀ Hardness in Newtons 1.0 pphp G75

Range 152-167(15) 160-171(11)

Average 160.3 166.0

Std. Deviation 6.652 4.546

Comment: Deviation reduced. Example 7

Foam Grade: A27-150

Nominal Density (kg/m³): 27

Nominal Hardness, IF₄₀(Newtons): 150

Additive: Gypsum G75

Concentration: 0 .2 pphp and 2.0 pphp

Method of Processing: Hand mix 45cm²x58cm high

No. of Samples: 8 each. Results

Reference Sample

(untreated foam) (treated foam)

Density in kg/m³ 0.2 pphp G75

Range 27.8-28.6(0.8) 27.4-29.1(1.7)

Average 28.2 27.9

Std. Deviation 0.26 0.57

Density in kg/m³ 2.0 pphp G75

Range 27.8-28.6(0.8) 28.0-29.2(1.2)

Average 28.2 28.4

Std. Deviation 0.26 0.39

IF₄₀ Hardness in Newtons 0.2 pphp G75

Range 178-192(14) 174-185(11)

Average 189 180

Std. Deviation 5.3 4.3

Example 8

Foam Grade: H35-160

Nominal Density (kg/m³): 35-37

Nominal Hardness, IF₄₀ (Newtons): 150-180

Additive: Sodium phosphate, Na₃PO₄.12H₂O

Concentration: 0.3 pphp

Method of Processing: 45cm² handbatch, 60-65 cm high

No. of Samples: 8 each. Results

Reference Sample

(untreated foam) (treated foam) Density in kg/m³

Range 36.3-37.8(1.5) 35.9-36.9(1.0) Average 36.8 36.4

Std. Deviation 0.40 0.31

IF₄₀ Hardness in Newtons

Range 164-181(17) 157-175(18)

Average 173 167.4

Std. Deviation 7.5 6.0

Example 9

Foam Graαe : A27-150

Nominal Density (kg/m³) : 27

Nominal Hardness , IF₄₀ ( Newtons ) 150

Additive : Gypsum G75

Concentration: 1.0 pphp

Method of Processing: Maxfoam machine, full size blocks

(2.08ra wide, 1.06m high, 1.52m long) No. of Samples: 20 each.

Results

Reference Sample

(untreated foam) (treated foam)

Density in kg/m³ All 20 Samples 20 Samples Range 26.2-28.6(2.4) 26.3-28.4(2.1) Average 27.6 27.3

Std. Deviation 0.700 0.567

Density in kg/m³ 18 Samples Without 18 Samples

Top & Bottom

Range 26.2-28.2(2.6) 26.3-27.8(1.5)

Average 27.5 27.2

Std. Deviation 0.674 0.489

IF₄₀ Hardness in Newtons

All 20 Samples 20 Samples

Range 126-172(46) 133-168(35)

Average 157 156

Std. Deviation 11.75 10.18 lF₄₀ Hardness in Newtons 18 Samples Without 18 Samples

Top & Bottom

Range 136-172(36) 139-168(29)

Average 160 -159

Std. Deviation 8.86 7.82

Example 10

Foam Grade: A17-80

Nominal Density (kg/m³) : 17

Nominal Hardness , IF₄₀ (Newtons): 80

Additive: Gypsum G75

Concentration: 0.5 pphp

Method of Processing: Maxfoam block machine

No. of Samples : 20 each

Results

Reference Sample

(untreated foam) (treated foam) Density in kg/m³

Range 16.5-17:4 (0.9) 16.5-17.1(0.6 ) Average 17.0 16.8

St'd. Deviation 0.25 0.20

IF₄₀ Hardness in Newtons

Range 75-94(9) 76-92(6)

Average 87.5 86.7

Std. Deviation 5.26 4.44

Comments: Two graphs attached to this example (see Figures 7 and 8).

Example 11

ELIMINATION OF CFC 11 IN A LOW DENSITY FOAM

Formulation using Gypsum G -75 Laboratory Handmixes

1 2 3

Reference Gypsum G-75 Same as 2

No. CFC but without

G-75 (a)

Polyol Niax 16-56 100.00 100.00 100.00

OMU 56, Mwt. 3000

(b)

Silicone BF.2370 1.20 1.50 1.50 Total water 4.55 6.00 6.00

Stannous octoate 0.22 0.40 0.25

*Amine Catalyst 0.19 0.05 0.05

CFC 11 5.00

Gypsum G-75 0 30.00 T;D.I. 80:20 60.8 68.00 68.-00

Density Kg/m³ 20.1 21.3 17.3

Hardness IF₄₀ Newtons 135 132 153

Exotherm Temperature C 162 142 175 * Araine Catalyst - 3 Parts (33% triethylene diamine,

67% dipropylene glycol)

- 2 Parts (70% Bis-dimethylaminoethyl-ether, 30% dipropylene glycol) (a) Supplied by Union Carbide Australia Ltd.

(b) Supplied by Th. Goldschmidt AG.

In Example 11, is shown a comparison of 3 batches of foam denoted as Batches 1, 2 and 3. Batch 1 corresponds to a standard reference formulation which includes the auxiliary blowing agent but no additive. The auxiliary agent is CFCll which is a chlorofluorohydrocarbon. Batch 2 corresponds to a formulation falling within the scope of the present invention and has an additive material incorporated but no auxiliary blowing agent. Batch 3 contains no additive and no auxiliary agent.

As can be seen from the properties obtained for Batches

1 and 2, particularly the properties relating to density and hardness which are indicator properties giving an indication of the overall properties of the foam, the properties of Batch

2 corresponds closely to the properties of Batch 1. Thus, the incorporation of the additive contributes to the final

properties which are more reproducible and controllable even when the auxiliary agent is omitted from the formulation.

Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is understood that the invention includes all such variations and modifications which fall within its spirit and scope.

Claims

CLAIMS :

1. A method for the production of a foam material,

preferably a polyurethane foam material, comprising

incorporating into the foamable liquid reaction mixture an additive which is capable of entering into or undergoing an endothermic reaction or is capable of forming a vapour and/or decomposing into one or more gaseous materials at a known preselected temperature or over a known preselected range of temperatures, said vapour or gaseous materials so produced or said endothermic reaction beneficially influencing the

properties of the foamed material when forming or when formed.

2. A foamable reaction mixture for forming a foam

material, preferably a polyurethane foam material, said mixture capable of expanding and polymerizing to form a shaped piece or block of foam wherein at lest one additional additive which is capable of entering into or undergoing an endothermic reaction or is capable of forming or decomposing into one or more gaseous or vapourous materials at a known preselected temperature or over a known preselected range of temperatures so as to beneficially influence the properties of the foam is incorporated into the foamable mixture.

3. A method or mixture according to Claims 1 or 2, in which the decomposition occurs endothermically so as to reduce the amount of exotherm during the manufacturing process.

4. A method or mixture according to any preceding claim in which the properties are beneficially influenced by reducing the maximum temperature attained by the foam during the manufacturing process, preferably the temperature of exotherm.

5. A method or mixture according to any preceding claim in which the additive material decomposes by giving up its water of crystallization.

6. A metlhod or mixture according to any preceding claim in which the additive material decomposes to yield carbon dioxide.

7. A method or mixture according to Claim 5 in which the water of crystallization is given up at temperatures of between 10°C and 200°C, preferably at least about 80°C.

8. A method or mixture according to any preceding claim in which the additive material is one or more of the following:

ammonium carbonate, aluminium sulphate, calcium

phosphate, calcium sulphate, ferrous ammonium sulphate, potassium sodium tartate, sodium borate, sodium carbonate, sodium phosphate, aluminium ammonium sulphate, aluminium potassium sulphate, calcium acetate, calcium acetyl,

salicylate, calcium chloride, calcium citrate, calcium

salicylate, silica gel, sodium sulphate and the like.

9. A method or mixture according to any preceding claim in which the polyurethane foam is rigid or flexible.

10. A method or mixture according to any preceding claim in which the properties that are beneficially influenced are physical properties of the foam.

11. A method or mixture according to any preceding claim in which the physical properties are hardness, density, tensile strength, resilience, elongate, compression set, and the like.

12. A method or mixture according to any preceding claim in which the additive material includes one or more of the following gas saturated adsorptive carbons, zeolites,

molecular sieves, polyethylene, polypropylene, and calcium stearate.

13. A method or mixture according to any preceding claim in which the additive material decomposes in the range from about 60°C to 180°C, typically from about 100°C to 170°C, preferably from about 120°C to 165°C.

14. A method or mixture according to any preceding claim in which the additive material is incorporated in an amount in the range from about 0.05 pph to 170 pph based on the total amount of polyol present in the reaction mixture, typically 0.2 to 100 pph, and preferably 2 to 30 pph.

15. A method or mixture according to any preceding claim in which the additive is gypsum G75 which is supplied by

Commercial Minerals Limited of Camberwell.

16. A method or mixture according to any preceding claim in which the properties of the foam produced by formulation and/or method of the present invention is closely related to the properties produced by a corresponding conventional formulation.

17. A method or mixture substantially as hereinbefore described with reference to any one of the foregoing examples and/or accompanying drawings.