HK1023580A - Rigid polyurethane foams - Google Patents

Description

Rigid polyurethane foams

The present invention relates to rigid polyurethane or urethane-modified polyisocyanurate foams, to a process for their preparation and to polyol blends for use in the process.

Rigid polyurethane and urethane-modified polyisocyanurate foams are generally prepared by reacting a stoichiometric excess of a polyisocyanate with an isocyanate-reactive compound in the presence of a blowing agent, a surfactant and a catalyst. One use of such foams is as a thermal insulation medium, for example in buildings.

Polyether polyols or polyester polyols are generally used as isocyanate-reactive compounds. Polyester polyols impart excellent flame retardant characteristics to the resulting polyurethane foams and in some cases even lower cost than polyether polyols.

There are problems with the stability of polyol blends containing polyester polyols and tertiary amine catalysts. It has been proposed to solve this problem by adding organic carboxylic acids (e.g. formic acid, acetic acid, 2-ethylhexanoic acid) to polyol blends (see USP4,758,605). In order to maintain reactivity after long-term storage, the amount of catalyst needs to be increased. However, this instability problem can be successfully solved in this way, but the processing of this system is still not controllable, which is reflected in the expansion profile of the expanded foam when the polyol blend is reacted with the polyisocyanate composition.

It is therefore an object of the present invention to provide a polyol blend comprising a polyester polyol and a tertiary amine catalyst which does not exhibit the above-mentioned disadvantages.

According to the present invention, there is provided a polyol blend comprising a polyester polyol, a tertiary amine catalyst and an organic carboxylic acid, wherein the organic carboxylic acid contains at least one of OH, SH, NH₂Or a NHR functional group, wherein R is alkyl, cycloalkyl or aryl.

The polyol blends of the present invention are stable for several weeks. Improved reaction profiles are obtained when rigid polyurethane foams are made using the polyol blends; the expansion of the foam at the drawing time (stretching time) can be almost completed while the cream time is reduced.

The carboxylic acids to be used according to the invention have the general formula X_n-R′-(COOH)_mWherein X is OH, SH, NH₂Or NHR, R' is an at least divalent hydrocarbon group, typically an at least divalent linear or branched aliphatic hydrocarbon group and/or an at least divalent cycloaliphatic or aromatic hydrocarbon group, n is an integer of at least 1 and is available for mono-and polyfunctional substitution on the hydrocarbon group, m is an integer of at least 1 and is available for mono-and polycarboxylic substitution on the hydrocarbon group.

The "at least divalent hydrocarbon group" may be a saturated or unsaturated group containing 1 to 20 carbon atoms, including a straight-chain aliphatic group, a branched aliphatic group, an alicyclic group or an aromatic group. Unless otherwise specified, R' may be, for example, a straight or branched alkylene group having 1 to 10 carbon atoms, a cyclic alkylene group having 4 to 10 carbon atoms, or an arylene, alkarylene, or aralkylene group having 6 to 20 carbon atoms. Specific non-limiting examples of suitable hydrocarbyl groups are methylene, ethylene, n-propylene, isopropylene, n-butylene, isobutylene, n-pentylene, n-decylene, 2-ethylhexylene, o-, m-or p-phenylene, ethyl-p-phenylene, 2, 5-naphthylene, p' -biphenylene, cyclopentylene, cycloheptylene, xylylene, 1, 4-dimethylenephenylene and the like, although the above groups have two available substitution positions, at least one for carboxyl and one for OH, SH, NH, OH₂Or NHR groups, but it will be appreciated that further hydrogens on the hydrocarbon may be replaced by further carboxyl groups and/or OH, SH, NH₂Or NHR group substitution.

Useful such carboxylic acids of the present invention typically have a molecular weight of less than about 250.

The following carboxylic acids are particularly suitable as compounds for carrying out the invention: citric acid, dimethylolpropionic acid, bis (hydroxymethyl) propionic acid, bishydroxypropionic acid, salicylic acid, m-hydroxybenzoic acid, p-hydroxybenzoic acid, dihydroxybenzoic acid, glycolic acid, beta-hydroxybutyric acid, methylsalicylic acid, 3-hydroxy-2-naphthoic acid, lactic acid, tartaric acid, malic acid, dihydroxybenzoic acid, hydrocerulic acid, glycine, alanine, thioglycolic acid, and the like.

Preferably X is OH, n is 1, R' is a straight or branched aliphatic hydrocarbon containing 1 to 5 carbon atoms and m is 1,2 or 3. Polycarboxylic acids are preferred. The hydroxyl group is preferably located at the alpha or beta position relative to the carboxyl group.

The most preferred carboxylic acids are lactic acid, glycolic acid, malic acid and citric acid.

At least one of the above carboxylic acids may be used; mixtures of two or more of these acids may also be used.

Particularly preferred carboxylic acids for use in the present invention are malic acid or a combination of malic acid and citric acid, preferably in a weight ratio of from 75: 25 to 25: 75, most preferably in a weight ratio of about 1: 1. Further improvement of the reaction profile can be observed. The combination of malic acid and citric acid also improves other physical properties of the resulting foam such as compressive strength and tack; and the density distribution is less variable.

The carboxylic acid is generally used in an amount of from 0.1 to 5% by weight, preferably from about 1 to 3% by weight of the isocyanate-reactive composition.

As used herein, "polyester polyol" is meant to encompass any polyester polyol having at least two hydroxyl functionalities, wherein the primary repeat unit contains an ester linkage and has a molecular weight of at least 400.

The polyester polyols useful in the present invention preferably have an average functionality of from about 1.8 to 8, more preferably from about 2 to 6 and most preferably from about 2 to 2.5. The hydroxyl number is generally in the range of about 15 to 750, preferably about 30 to 550, more preferably about 70 to 550 and most preferably about 200 to 550mg KOH/g. The molecular weight of the polyester polyol is generally in the range of about 400 to about 10000, preferably about 1000 to about 6000. Preferably, the polyester polyol has an acid value of between 0.1 and 20mg KOH/g; the acid number can generally be up to 90mg KOH/g.

The polyester polyols of the present invention can be prepared by known procedures from polycarboxylic acids or acid derivatives such as anhydrides or esters of polycarboxylic acids, and any polyols. The polyacid and/or polyol component may be used in the preparation of the polyester polyol as a mixture of two or more compounds.

The polyols may be aliphatic, cycloaliphatic, aromatic and/or heterocyclic. Low molecular weight lipidsGroup polyols such as aliphatic diols containing no more than about 20 carbon atoms are highly desirable. The polyols may optionally contain substituents that are inert in the reaction, such as chlorine and bromine substituents, and/or may be unsaturated. Suitable amine alcohols such as monoethanolamine, diethanolamine, triethanolamine, and the like may also be used. The preferred polyol component is a glycol. The glycol may contain heteroatoms (e.g., thiodiglycol) or may be composed exclusively of carbon, hydrogen and oxygen. Preferably of the formula C_nH_2n(OH)₂Are distinguished by simple glycols or by insertion of ether linkages in the hydrocarbon chain and are of the formula C_nH_2nO_x(OH)₂The polyglycols are shown. Examples of suitable polyols include: ethylene glycol, propylene glycol- (1,2) and- (1,3), butylene glycol- (1,4) and- (2,3), hexylene glycol- (1,6), octylene glycol- (1,8), neopentyl glycol, 1, 4-bis (hydroxymethyl) cyclohexane, 2-methyl-1, 3-propanediol, glycerol, trimethylolethane, hexanetriol- (1,2,6), butanetriol- (1,2,4), quinolones, methyl glycosides, triethylene glycols, tetraethylene glycols and higher polyethylene glycols, dipropylene glycols and higher polypropylene glycols, diethylene glycols, glycerol, pentaerythritol, trimethylolpropane, sorbitol, mannitol, dibutylene glycols and higher polybutylene glycols. Particularly suitable polyols are alkylene glycols and oxyalkylene glycols, such as ethylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, tetraethylene glycol, tetrapropylene glycol, trimethylene glycol, tetramethylene glycol and 1, 4-cyclohexanedimethanol (1, 4-bis-hydroxymethylcyclohexane).

The polycarboxylic acid component may be aliphatic, cycloaliphatic, aromatic and/or heterocyclic and may optionally be substituted, for example by halogen atoms, and/or may be unsaturated. Examples of suitable carboxylic acids and derivatives thereof for preparing polyester polyols include: oxalic acid, malonic acid, adipic acid, glutaric acid, succinic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic anhydride, terephthalic anhydride, isophthalic acid, terephthalic acid, trimellitic acid, tetrahydrophthalic anhydride, pyromellitic dianhydride, hexahydrophthalic anhydride, tetrachlorophthalic anhydride, nadic anhydride, glutaric anhydride, maleic acid, maleic anhydride, dimethyl terephthalate, terephthalic acid-bis (ethylene glycol) esters, fumaric acid, and di-and tri-unsaturated fatty acids optionally mixed with a mono-unsaturated fatty acid such as oleic acid.

While the polyester polyols can be prepared from substantially pure reaction materials, more complex ingredients, such as side streams, waste materials or scale residues from the manufacture of terephthalic acid, dimethyl terephthalate, polyethylene terephthalate, and the like, can be used. The compositions can be converted to polyester polyols by reaction with polyols through conventional transesterification or esterification procedures.

The production of the polyester polyols can be carried out in a known manner by simply reacting the polycarboxylic acids or acid derivatives with the polyol component until the hydroxyl and acid values of the reaction mixture fall within the desired ranges. After transesterification or esterification, the reaction product may optionally be reacted with an alkylene oxide.

As used herein, "polyester polyol" includes a minor amount of unreacted polyol remaining after the preparation of the polyester polyol and/or unesterified polyol (e.g., ethylene glycol) added after preparation. The polyester polyol preferably contains up to about 40% by weight free ethylene glycol. Preferably, the free ethylene glycol content is from 2 to 30, more preferably from 2 to 15% by weight of the total polyester polyol content.

Aliphatic and/or aromatic polyester polyols may be used in the present invention. Mixtures of two or more different polyester polyols may be used.

According to the invention, the polyester polyols described above may constitute the entire reaction mixture reacted with the polyisocyanate; it is to be understood that the polyols may also be mixed with other isocyanate-reactive compounds conventionally used in the art; preferably at least 10% by weight, more preferably at least 20% by weight of the total isocyanate-reactive compounds are the polyester polyols described above.

The isocyanate-reactive compounds that may be used in combination with the polyester polyols in the preparation of the rigid polyurethane foams of the present invention include any compounds known in the art for this purpose. Of particular importance in the preparation of rigid foams are polyols and polyol mixtures having an average hydroxyl number of from 300 to 1000, in particular from 300 to 700mg KOH/g, and a hydroxyl functionality of from 2 to 8, in particular from 3 to 8. Suitable polyols have been fully described in the prior art and comprise the reaction product of alkylene oxides, such as ethylene oxide and/or propylene oxide, with initiators containing from 2 to 8 active hydrogen atoms per molecule. Suitable initiators include polyols such as glycerol, trimethylolpropane, triethanolamine, pentaerythritol, sorbitol and sucrose: polyamines such as ethylenediamine, methylenephenylenediamine, diaminodiphenylmethane, and polymethylene polyphenylene polyamine; and amine alcohols such as ethanolamine and diethanolamine; and mixtures of such initiators. Further suitable polymeric polyols include hydroxyl terminated polythioethers, polyamides, polyesteramides, polycarbonates, polyacetals, polyolefins and polysiloxanes.

Any organic compound containing at least one nitrogen atom, preferably a tertiary nitrogen atom, and which catalyzes the hydroxyl/isocyanate reaction may be used in the blends of the present invention.

The general class of tertiary amine catalysts comprises N-alkyl morpholines, N-alkyl alkanolamines, N, N-dialkyl cyclohexylamines and alkylamines, wherein the alkyl is methyl, ethyl, propyl, butyl, and the like, and isomers thereof; and heterocyclic amines. Typical, but non-limiting, examples are triethylenediamine, tetramethylethylenediamine, bis (2-dimethylaminoethyl) ether, triethylamine, tripropylamine, tributylamine, tripentylamine, pyridine, quinoline, dimethylhexahydropyrazine, hexahydropyrazine, N-dimethylcyclohexylamine, N-ethylmorpholine, 2-methylhexahydropyrazine, N-dimethylethanolamine, tetramethylpropylenediamine, methyltriethylenediamine, 2,4, 6-tris (dimethylaminomethyl) phenol, N', N "-tris (dimethylaminopropyl) -s-hexahydrotriazine, and the like, and mixtures thereof. Amines containing isocyanate-reactive groups, such as aminoalcohols; examples thereof include 2- (2-dimethylaminoethoxy) ethanol, trimethylaminoethylethanolamine and dimethylethylethanolamine. Preferred tertiary amine catalysts include triazines, dimethylbenzylamine, bis (dimethylaminoethyl) ether, and dimethylcyclohexylamine. Particularly preferred are dimorpholinodiethyl ether, N-methylimidazole and dimethylaminopyridine; which can further improve the response profile.

The tertiary amine catalyst is typically present in a proportion of from about 0.01 to about 10pbw per 100pbw of polyol. Preferably the amount of amine is from about 0.1 to about 5pbw, more preferably from about 0.2 to about 3pbw, per 100pbw of polyol.

The blends of the present invention may also contain any of the blowing agents known in the art for preparing rigid polyurethane or urethane-modified polyisocyanurate foams. Such blowing agents comprise water or other carbon dioxide evolving compounds or inert low boiling compounds having a boiling point above-70 ℃ at atmospheric pressure.

When water is used as blowing agent, the amount may be selected in a known manner to provide the desired density of the foam, typically in the range of from 0.05 to 5% by weight of the total reaction system.

Suitable inert blowing agents include those well known and described in the art, such as hydrocarbons, dialkyl ethers, alkyl alkanoates, aliphatic and cycloaliphatic hydrofluorocarbons, hydrochlorofluorocarbons, chlorofluorocarbons, hydrochlorocarbons and fluorine-containing ethers.

Examples of preferred foams include isobutane, n-pentane, isopentane, cyclopentane or mixtures thereof, 1, 1-dichloro-2-fluoroethane (HCFC141b),1,1, 1-trifluoro-2-fluoroethane (HFC134a), chlorodifluoromethane (HCFC22),1, 1-difluoro-3, 3, 3-trifluoropropane (HFC245fa) and mixtures thereof. In particular, the blowing agent mixture described in PCT patent publication No. 96/12758 can be mentioned for the production of low-density, dimensionally stable rigid foams. These blowing agent mixtures generally comprise at least 3 and preferably at least 4 components, preferably at least one component being a (cyclo) alkane (preferably having 5 or 6 carbon atoms) and/or acetone.

The blowing agent is used in an amount sufficient to give the resulting foam the desired bulk density (which is typically in the range of from 15 to 70 kg/m³Preferably 20 to 50 kg/m³Preferably 25 to 40 kg/m³Range of (d). The amount of blowing agent is generally from 2 to 25% by weight of the total reaction system.

When the blowing agent has a boiling point at or below ambient temperature, it is maintained under pressure until mixed with the other ingredients. Or it may be maintained below ambient temperature until mixed with the other ingredients.

Other optional additives for the polyol blends of the present invention include crosslinking agents, for example low molecular weight polyols such as triethanolamine, processing aids, viscosity reducers, dispersants, plasticizers, mold release agents, antioxidants, fillers (e.g. carbon black), cell size regulators such as insoluble fluorinated compounds (as described in US4981879, US5034424, US4972002, EP0508649, EP0498628, WO95/18176), non-amine polyurethane catalysts (e.g. stannous salts of carboxylic acids), trimerisation catalysts (e.g. alkali metal carboxylates), surfactants such as polydimethylsiloxane-polyoxyalkylene block copolymers and non-reactive and reactive flame retardants, for example halogenated alkyl phosphates such as trichloropropyl phosphate, triethyl phosphate, diethyl ethyl phosphonate and dimethyl methyl phosphonate. The use of such additives is well known to those skilled in the art.

Suitable organic polyisocyanates to be reacted with the polyol blends of the present invention to form rigid polyurethane or urethane-modified polyisocyanurate foams include any of those known in the art for preparing rigid polyurethane or urethane-modified polyisocyanurate foams, and especially aromatic polyisocyanates such as diphenylmethane diisocyanate in the form of its 2,4 ' -2,2 ' -and 4,4 ' -isomers and mixtures thereof, mixtures of diphenylmethane diisocyanate (MDI) and its oligomers known in the art as "crude" or polymeric MDI (polymethylene polyphenylene polyisocyanates) having an isocyanate functionality of greater than 2, toluene diisocyanate in the form of its 2, 4-and 2, 6-isomers and mixtures thereof, 1, 5-naphthylene diisocyanate and 1, 4-diisocyanatobenzene. Other organic polyisocyanates which may be mentioned include aliphatic diisocyanates such as isophorone diisocyanate, 1, 6-diisocyanatohexane and 4, 4' -diisocyanatodicyclohexylmethane. Other suitable polyisocyanates suitable for use in the process of the present invention are described in EP-A-0320134.

Modified polyisocyanates such as carbodiimide or uretonimine modified polyisocyanates may also be used. Still other useful organic polyisocyanates are isocyanate-terminated prepolymers prepared by reacting an excess of organic polyisocyanate with a minor amount of an active hydrogen-containing compound. Preferred polyisocyanates to be used in the present invention are polymeric MDI's.

The amounts of polyisocyanate composition and polyfunctional isocyanate-reactive composition to be reacted can be readily determined by those skilled in the art. In general, the NCO: OH ratio falls within the range of 0.85 to 1.40, preferably about 0.95 to 1.20. Higher NCO: OH ratios (e.g., up to 3.0) are also within the scope of the invention.

In carrying out the process of the invention for producing rigid foams, the known one-shot, prepolymer or semi-prepolymer techniques can be used in combination with known mixing methods, and the rigid foams can be in the form of slabs, moldings, cavity fillers, spray foams, foamed foams or laminates with other materials, such as hardboards, plastic boards, plastics, paper or metals.

According to one embodiment of the present invention, the polyol blend described above is reacted with a polyisocyanate composition to prepare a rigid polyurethane foam.

According to another embodiment of the invention, the components (polyester polyol, amine catalyst and carboxylic acid) are not added in admixture but are added separately to the reaction mixture.

The foams of the present invention can advantageously be used to make laminates whereby the foam is provided with a sheet on one or both sides. The laminate is preferably made in a continuous or discontinuous manner by depositing the foam-forming mixture on the facing sheet and preferably placing the other facing sheet on top of the deposited mixture. Any of the end sheets described above for making building panels may be used and may be of a rigid or flexible nature.

The invention will be illustrated in various aspects but not limited thereto by the following examples in which the following ingredients are used:

polyol A sorbitol initiated polyether polyol having an OH value of 460mg KOH/g.

The polyol B is aliphatic polyester polyol with an OH value of 356mg KOH/g and an acid value of 0.5mg KOH/g.

Polyol C-polyether polyol initiated with aromatic amine having an OH value of 495mg KOH/g.

Polyol D brominated polyether polyol having an OH number of 310mg KOH/g.

Polyol E aromatic polyester polyol with OH value of 240mg KOH/g.

Polyol F is an aromatic polyester polyol having an OH value of 350mg KOH/g.

Flame retardant A: a chlorinated flame retardant.

And (3) a flame retardant B: phosphorous based flame retardants.

Surfactant (b): a silicone surfactant.

DMBA: dimethylbenzylamine catalyst from Protex.

DMDEE: dimorpholinodiethyl ether catalyst from Nitroil.

DMAP Aldrich dimethylaminopyridine catalyst.

NMI was obtained from BASF as N-methylimidazole catalyst.

Polycat 41: tris (dimethylaminopropyl) hexahydrotriazine catalyst from Air products.

Niax A1: bis (dimethylaminoethyl) ether catalyst from OSi.

Texacat DP 914: catalyst from Texaco.

DMCHA: dimethylcyclohexylamine catalyst from BASF.

SUPRASEC DNR: polymeric MDI available from Imperial chemical industries, inc.

SUPRASEC is a trademark of Imperial chemical industries. Example 1

Rigid polyurethane foams were prepared from a polyol composition and a polyisocyanate composition containing the ingredients listed in Table 1 below at an NCO index of 1.15.

The reaction profile was followed by cream time (the time it took for the reaction mixture to begin foaming) and string time (the time it took for the reaction mixture to reach the transition point from the fluid to the cross-linked mass). Measuring the expansion height at the drawing time and also at the end of the expansion of the foam; from these two numbers, the expansion factor (drawing height/height at the end of expansion) of the drawing time was determined. The results are also shown in Table 1.

The inflation profile is also tracked by dynamic flow data analysis. The results are shown in FIGS. 1,2 and 3, which show the height of the expanded foam versus the reaction time.

These results show that the addition of a functionalized carboxylic acid according to the invention improves the reaction profile (foam No. 3) due to the delayed catalysis by acetic acid (foam No. 2) (see fig. 1). The addition of a selected class of catalysts (e.g. DMDEE, DMAP, NMI, Texacat DP914) (foam numbers 4, 5, 6, 7, 9) can further improve the reaction profile (see fig. 2).

In terms of improvement of the reaction profile, glycolic acid (foam No. 9) was superior in efficiency to lactic acid (foam No. 4) (see fig. 3).

TABLE 1

Foam number		1	2	3	4	5	6	7	8	9
											Polyhydric alcohols
Polyol A	pbw	20.5	20.5	20.5	20.5	20.5	20.5	20.5	20.5	20.5
											Polyol B	pbw	23.0	23.0	23.0	23.0	23.0	23.0	23.0	23.0	23.0
Polyol C	pbw	10.0	10.0	10.0	10.0	10.0	10.0	10.0	10.0	10.0
											Polyol D	pbw	21.0	21.0	21.0	21.0	21.0	21.0	21.0	21.0	21.0
Acetic acid	pbw		1.0
											Glycolic acid	pbw									1.0
Lactic acid	pbw			1.1	1.1	1.1	1.1	1.1	1.1
											Flame retardant A	pbw	8.3	8.3	8.3	8.3	8.3	8.3	8.3	8.3	8.3
Flame retardant B	pbw	8.3	8.3	8.3	8.3	8.3	8.3	8.3	8.3	8.3
											Surface active agent	pbw	2.0	2.0	2.0	2.0	2.0	2.0	2.0	2.0	2.0
DMBA	pbw	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0
											DMDEE	pbw				1.5					1.5
DMAP	pbw							0.3
											NMI	pbw					0.3

TABLE 1 continuation

Foam number		1	2	3	4	5	6	7	8	9
											Polycat 41Niax AlTexacat DP914DMCHA HydroHCFC 141b	pbw								0.7
pbw	0.15
										pbw							0.5
pbw	0.80	0.80	0.80
										pbw		3.3	3.3	3.3	3.3	3.3	3.3	3.3	3.3	3.3
pbw	4.2	4.2	4.2	4.2	4.2	4.2	4.2	4.2	4.2
										Polyisocyanate
SUPRASEC DNR	pbw	139	139	139	139	139	139	139	139		139
										Expansion factor at the time of wire drawing at the milk white stage		Second of	17	18	16	17	20	16	17	18	13
Second of	154	162	128	120	134	131	141	137	127
											％	93	56	79	89	90	86	90	84	95

Example 2

The stability of the polyol blends of foam numbers 1 and 3 (as described in Table 1) was determined by measuring the cream time, the stringiness time, and the density of the foam just prepared and the density of the foam prepared after storage of the polyol blend at 40 ℃ for 3 days, 1 week, and 3 weeks, respectively. The results of foam No. 1 are shown in Table 2 and the results of foam No. 3 are shown in Table 3.

TABLE 2

Foam No. 1	Milk white period (seconds)	Drawing time (seconds)	Density (g/L)
				Initially, the process is started	17	154	27.6
After 3 days	18	185	28.0
				After 1 week	20	245	29.0
After 3 weeks	24	267	29.6

TABLE 3

Foam No. 1	Milk white period (seconds)	Drawing time (seconds)	Density (g/L)
				Initially, the process is started	23	152	27.8
After 3 days	24	155	28.2
				After 1 week	23	160	28.3
After 3 weeks	24	161	28.1

The results show that foam No. 1 has considerable variation in cream time, drawing time and density, and that the difference is only minimal for foam No. 3. Thus the stability of the polyol blend containing the functionalized carboxylic acid of the present invention is improved over polyol blends not containing the acid. Example 3

Rigid polyurethane foams were prepared from a polyol composition and a polyisocyanate composition containing the ingredients listed in Table 4 below at an NCO index of 1.15.

The reaction profile was followed by cream time (the time it took for the reaction mixture to begin foaming) and string time (the time it took for the reaction mixture to reach the transition point from the fluid to the cross-linked mass). Measuring the expansion height at the drawing time and also at the end of the expansion of the foam; from these two numbers, the expansion factor (drawing height/height at the end of expansion) of the drawing time was determined. The results are also shown in Table 4.

It can be seen that the use of citric acid or malic acid results in a lowest density foam. Example 4

Rigid polyurethane foams were prepared from a polyol composition and a polyisocyanate composition containing the ingredients listed in Table 5 below at an NCO index of 1.15.

The reaction profile was followed by cream time (the time it took for the reaction mixture to begin foaming) and string time (the time it took for the reaction mixture to reach the transition point from the fluid to the cross-linked mass). Measuring the expansion height at the drawing time and also at the end of the expansion of the foam; from these two numbers, the expansion factor (drawing height/height at the end of expansion) of the drawing time was determined. The results are also shown in Table 5.

The inflation profile was followed by dynamic flow data analysis. The results are shown in FIG. 4, which shows the height of the expanded foams of foam numbers 18,19 and 20 versus the reaction time.

These results show that when malic acid (foam No. 19) or a combination of malic acid and citric acid (foam No. 20) was used instead of lactic acid (foam No. 18), the reaction profile can be further improved.

TABLE 4

Foam number		10	11	12	13	14	15	16	17
										Polyhydric alcohols
Polyol A	pbw	20.5	20.5	20.5	20.5	20.5	20.5	20.5	20.5
										Polyol B	pbw	23.0	23.0	23.0	23.0	23.0	23.0	23.0	23.0
Polyol C	pbw	10.0	10.0	10.0	10.0	10.0	10.0	10.0	10.0
										Polyol D	pbw	21.0	21.0	21.0	21.0	21.0	21.0	21.0	21.0
Lactic acid	pbw	1.1
										Tartaric acid	pbw		1.1
4-hydroxybenzoic acid	pbw			1.1
										Citric acid	pbw				1.1
Salicylic acid	pbw					1.1
										Malic acid	pbw						1.1
Glycolic acid	pbw							1.1
										Bis (hydroxymethyl) propionic acid	pbw								1.1
Flame retardant A	pbw	8.3	8.3	8.3	8.3	8.3	8.3	8.3	8.3
										Flame retardant B	pbw	8.3	8.3	8.3	8.3	8.3	8.3	8.3	8.3

TABLE 4 continuation

Foam number		10	11	12	13	14	15	16	17
										Surface active agent	pbw	2.0	2.0	2.0	20	2.0	2.0	2.0	2.0
DMBADMDEE Water HCFC141b	pbw	1.0	1.1	0.5	1.0	1.25	0.6	0.8	0.5
										pbw	1.5	1.5	1.5	1.5	1.5	1.5	1.5	1.5
	pbw	3.3	3.3	3.3	3.3	3.3	3.3	3.3	3.3
										pbw	4.2	4.2	4.2	4.2	4.2	4.2	4.2	4.2
	Polyisocyanate
SUPRASEC DNR											pbw	139	139	139	139	139	139	139	139
	Density of	kg/m3	30.9	32.6	33.1	30.5	32.1	30.8	31.8	32.5
Expansion factor at the time of wire drawing at the milk white stage											Second of	20	16	19	20	23	17	34	21
	Second of	110	113	107	103	107	110	125	110
										％	92	88	92	92	92	92	84	89

TABLE 5

Foam number		18	19	20	21	22
							Polyhydric alcohols
Polyol A	pbw	20.5	20.5	20.5	20.5	20.5
							Polyol B	pbw	23.0	23.0	23.0	23.0	23.0
Polyol C	pbw	10.0	10.0	10.0	10.0	10.0
							Polyol D	pbw	21.0	21.0	21.0	21.0	21.0
Lactic acid	pbw	1.1
							Malic acid	pbw		1.0	0.5	0.25	0.75
Citric acid	pbw			0.5	0.75	0.25
							Flame retardant A	pbw	8.3	8.3	8.3	8.3	8.3
Flame retardant B	pbw	8.3	8.3	8.3	8.3	8.3
							Surface active agent	pbw	2.0	2.0	2.0	2.0	2.0
DMBA	pbw	1.0	0.6	0.7	0.66	0.79
							DMDEE	pbw	1.5	1.5	1.5	1.5	1.5
Water (W)	pbw	3.3	33	3.3	3.3	3.3
							HCFC 141b	pbw	4.2	4.2	4.2	4.2	4.2
Polyisocyanate
							SUPRASEC DNR	pbw	139	139	139	139	139
Milk white period	Second of	20	13	13	17	13
							Time of wire drawing	Second of	108	108	104	102	104
Expansion factor at drawing time	％	91.4	90.1	92.4	92.2	91.7

Example 5

The stability of the polyol blends of foam numbers 19 and 20 (as shown in Table 5 above) was determined by measuring the cream time, the stringiness time, and the density of the foam as prepared and the density of the foam made after storage of the polyol blend at 40 ℃ for 1 day, 4 days, 1 week, and 2,3, 4, and 5 weeks, respectively.

The results of foam No. 19 are shown in Table 6 and the results of foam No. 20 are shown in Table 7.

TABLE 6

Foam No. 19	Milk white period (seconds)	Drawing time (seconds)	Density (g/L)
				Initially, the process is started	12	107	30.4
After 1 day	15	111	30.3
				After 4 days	15	115	31.3
After 1 week	15	113	31.6
				After 2 weeks	15	112	31.4
After 3 weeks	15	117	31.7
				After 4 weeks	14	115	31.1
After 5 weeks	15	118	30.8

TABLE 7

Foam number 20	Milk white period (seconds)	Drawing time (seconds)	Density (g/L)
				Initially, the process is started	15	106	30.8
After 1 week	15	106	30.3
				After 2 weeks	15	108	30.3
After 4 weeks	15	110	31.2
				After 5 weeks	15	108	30.1

Example 6

Rigid polyurethane foams were prepared from a polyol composition and a polyisocyanate composition containing the ingredients listed in Table 8 below at an NCO index of 1.

The reaction profile was followed by cream time (the time it took for the reaction mixture to begin foaming) and string time (the time it took for the reaction mixture to reach the transition point from the fluid to the cross-linked mass). The free swell density was also determined.

The results are shown in Table 8.

TABLE 8

Foam number		23	24	25
					Polyhydric alcohols
Polyol A	pbw	21.4	21.4	21.4
					Polyol B	pbw	34.0
Polyol C	pbw	11.7	11.7	11.7
					Polyol D	pbw	11.0	11.0	11.0
Polyol E	pbw		34.0
					Polyol F	pbw			34.0
Lactic acid	pbw	1.1	1.1	1.1
					Flame retardant B	pbw	13.5	13.5	13.5
Surface active agent	pbw	1.8	1.8	1.8
					DMBA	pbw	1.2	1.1	1.0
DMDEE	pbw	0.9	0.8	0.9
					Water (W)	pbw	3.4	3.4	3.4
HFC 134a	pbw	4.0	4.0	4.0
					Polyisocyanate
SUPRASEC DNR	pbw	140	126	140
					Milk white period	Second of	7	7	6
Time of wire drawing	Second of	95	91	95
					Free expansion density	kd/m3	27.6	27.3	28.0

Claims (15)

1. An isocyanate-reactive composition comprising a polyester polyol, an amine catalyst and a carboxylic acid, characterised in that the carboxylic acid contains at least one OH, SH, NH group₂Or a NHR functional group, wherein R is alkyl, cycloalkyl or aryl.

2. The isocyanate-reactive composition according to claim 1 wherein the carboxylic acid corresponds to the formula X_n-R′-(COOH)_mWherein X is OH, SH, NH₂Or NHR, R' is an at least divalent hydrocarbon radical, n is an integer of at least 1 and m is up toAn integer less than 1.

3. The isocyanate reactive composition according to claim 2 wherein X is OH, R' is a straight or branched aliphatic hydrocarbon containing 1 to 5 carbon atoms, n is 1 and m is 1,2 or 3.

4. The isocyanate reactive composition according to claim 3 wherein the carboxylic acid is selected from the group consisting of lactic acid, glycolic acid, malic acid and citric acid.

5. The isocyanate reactive composition according to claim 4 wherein a mixture of citric acid and malic acid in a weight ratio of about 1: 1 is used as the carboxylic acid.

6. The isocyanate reactive composition according to any one of the preceding claims wherein the carboxylic acid is used in an amount ranging from 0.1 to 5% by weight of the isocyanate reactive composition.

7. The isocyanate reactive composition according to any one of the preceding claims wherein the polyester polyol has an average functionality of 1.8 to 8, a hydroxyl number of 15 to 750mg KOH/g and a molecular weight of 400 to 10000.

8. The isocyanate reactive composition according to any preceding claim wherein the polyester polyol comprises at least 10 weight percent of the total isocyanate reactive compounds.

9. The isocyanate reactive composition according to any preceding claim wherein the amine catalyst is a tertiary amine selected from the group consisting of N-alkyl morpholines, N-alkyl alkanolamines, N-dialkyl cyclohexanes, alkylamines, heterocyclic amines.

10. The isocyanate reactive composition according to any preceding claim wherein the amine catalyst is dimorpholinodiethylether or N-methylimidazole or dimethylaminopyridine or triazine.

11. The isocyanate reactive composition according to any one of the preceding claims wherein the amine catalyst is used in an amount of 0.1 to 5% by weight of the isocyanate reactive composition.

12. The isocyanate reactive composition according to any preceding claim further comprising a blowing agent.

13. A process for making rigid polyurethane or urethane-modified polyisocyanurate foams comprising the step of reacting an organic polyisocyanate composition with an isocyanate-reactive composition characterized in that the isocyanate-reactive composition is as defined in any one of the preceding claims.

14. A process for the manufacture of rigid polyurethane or urethane-modified polyisocyanurate foams comprising the step of reacting an organic polyisocyanate composition with an isocyanate-reactive composition comprising a polyester polyol in the presence of an amine catalyst and a carboxylic acid, characterized in that the carboxylic acid is as defined in any one of claims 1 to 6.

15. A rigid polyurethane or urethane-modified polyisocyanurate foam prepared by the process of claim 13 or 14.