CA2027670A1 - Process for the preparation of molded polyurethane foams and the molded foams obtained by this process - Google Patents
Process for the preparation of molded polyurethane foams and the molded foams obtained by this processInfo
- Publication number
- CA2027670A1 CA2027670A1 CA002027670A CA2027670A CA2027670A1 CA 2027670 A1 CA2027670 A1 CA 2027670A1 CA 002027670 A CA002027670 A CA 002027670A CA 2027670 A CA2027670 A CA 2027670A CA 2027670 A1 CA2027670 A1 CA 2027670A1
- Authority
- CA
- Canada
- Prior art keywords
- carboxylic acid
- process according
- groups
- group
- organic carboxylic
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
- C08J9/06—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a chemical blowing agent
- C08J9/08—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a chemical blowing agent developing carbon dioxide
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
- C08G18/30—Low-molecular-weight compounds
- C08G18/32—Polyhydroxy compounds; Polyamines; Hydroxyamines
- C08G18/3225—Polyamines
- C08G18/3253—Polyamines being in latent form
- C08G18/3259—Reaction products of polyamines with inorganic or organic acids or derivatives thereof other than metallic salts
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
- C08G18/30—Low-molecular-weight compounds
- C08G18/32—Polyhydroxy compounds; Polyamines; Hydroxyamines
- C08G18/3271—Hydroxyamines
- C08G18/3296—Hydroxyamines being in latent form
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G2110/00—Foam properties
- C08G2110/0033—Foam properties having integral skins
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G2110/00—Foam properties
- C08G2110/0041—Foam properties having specified density
- C08G2110/0066—≥ 150kg/m3
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2375/00—Characterised by the use of polyureas or polyurethanes; Derivatives of such polymers
- C08J2375/04—Polyurethanes
Abstract
Mo-3464 LeA 27,266 A PROCESS FOR THE PREPARATION OF MOLDED POLYURETHANE
FOAMS AND THE MOLDED FOAMS OBTAINED BY THIS PROCESS
ABSTRACT OF THE DISCLOSURE
This invention relates to a process for the preparation of molded polyurethane foams having a compact skin and having a density of at least 250 kg/m3 comprising in-mold foaming at an isocyanate index of 75 to 1500 a reaction mixture of (a) a polyisocyanate component containing at least one aromatic polyisocyanate, (b) an isocyanate-reactive component containing at least one organic polyhydroxyl compound, (c) a blowing agent comprising a salt of (i) an organic carboxylic acid and (ii) a nitrogen base containing at least one N-H bond, with the proviso that the blowing agent (c) cannot be a compound formed in situ by interaction of the organic carboxylic acid with a difunctional or polyfunctional amine.
Mo-3464
FOAMS AND THE MOLDED FOAMS OBTAINED BY THIS PROCESS
ABSTRACT OF THE DISCLOSURE
This invention relates to a process for the preparation of molded polyurethane foams having a compact skin and having a density of at least 250 kg/m3 comprising in-mold foaming at an isocyanate index of 75 to 1500 a reaction mixture of (a) a polyisocyanate component containing at least one aromatic polyisocyanate, (b) an isocyanate-reactive component containing at least one organic polyhydroxyl compound, (c) a blowing agent comprising a salt of (i) an organic carboxylic acid and (ii) a nitrogen base containing at least one N-H bond, with the proviso that the blowing agent (c) cannot be a compound formed in situ by interaction of the organic carboxylic acid with a difunctional or polyfunctional amine.
Mo-3464
Description
2~2,~
Mo-3464 LeA 27,266 A PROCESS FOR THE PREPARATION OF MOLDED POLYURETHANE
FOAMS AND THE MOLDED FOAMS OBTAINED BY THIS PROCESS
BACKGROUND OF THE INVENTION
This invention relates to a new process for the preparation of molded polyurethane foams having a compact skin, in which salts of (i) organic carboxylic acids and (ii) nitrogen bases containing at least one NH bond are used as blowing agents, and to the moldings obtained by the process.
~he preparation of molded polyurethane foams having a o compact skin by foam molding is known. For example, German Auslegeschrift 1,196,864. It is carried out by the in-mold foaming of a reactive and foamable mixture of organic poly-isocyanates, compounds containing isocyanate-reactive groups, and the usual auxiliaries and additives. The reacted mixture iS introduced into the mold in a larger quantity than would be necessary to fill the interior of the mold by free foaming. By suitable choice of the starting components, particularly with respect to molecular weight and functionality, it is possible to produce both flexible, semi-rigid, and rigid moldings. The compact outer skin is obtained by introducing a foamable mixture into the mold in a larger quantity than would be necessary to fill the interior of the mold by free foaming and by using blowing agents (such as fluorochlorocarbons), which condense on the inner walls of the mold under the prevailing temperature and pressure conditions, so that the blowing reaction stops at the inner wall of the mold and a compact outer skin is formed.
In addition to physical blowing agents mentioned aboYe, water (which forms carbon dioxide by reaction with isocyanates) is also used as a chemical blowing agent in industrial polyurethane chemistry. Although free-foamed 2 ~ 2, ~
polyurethane foams of excellent quality can be prepared with this chemical blowing agent, it is not possible to prepare high-quality foam moldings having a compact skin (integral foams) because carbon dioxide dces not condense on the inner wall of the mold under the usual conditions. Consequently, the blowing effect is not stopped at the surface area. The same basic problem arises with other chemical or physical blowing agents, such as nitrogen-generating blowing agents such as azodicarbonamide and azo-bis(isobutyronitrile); blowing agents which eliminate carbon dioxide such as pyrocarbonic acid esters and anhydrides (U.S. Patent 4,070,310); and blowing agents such as air which are dissolved in the reaction components, particularly the component containing isocyanate-reactive groups. These other chemical blowing agents are, therefore, also unsuitable for the preparation of high-quality integral foams.
It has now surprisingly been found, however, that high quality molded polyurethane foams having a compact skin can be prepared from the usual starting materials using salts of (i) organic carboxylic acids and (ii) nitrogen bases containing at least one NH bond. The blowing effect of these materials is also based essentially on the release of carbon dioxide.
Although, according to German Offenlegungsschrift 3,041,58g, special mixed carboxylic/carbamic anhydrides of the type formed from carboxylic acids and aliphatic isocyanates are used as blowing agents for the preparation of polyurethane foams (particularly integral foams), this process is unsuitable for industrial application for the following reasons. Mixed anhydrides are often said to be stable in storage at temperatures of up to about 60-C even in solution, while, on the other hand, to develop the blowing effect with release of carbon dioxide at temperatures as low as about 80C.
Accordingly, the useful temperature range in which carbon dioxide is eliminated is very narrow. In addition, only Mo-3464 ~Q~ ~7i3 aliphatic isocyanates can be used for the preparation of mixed anhydrides. In contrast, the aromatic polyisocyanates typically used as polyisocyanate component are unsuitable for the preparation of the special blowing agents. To carry out s the process, the mixed anhydrides must first be prepared and isolated in a separate reaction and then carefully mixed with the polyol mixture. These additional process steps make the use of these compounds even more expensive and complicated.
Ready-to-use polyols containing the blowing agents mentioned above cannot be stored and transported safely because the danger of a dangerous pressure build-up cannot always be avoided in case of overheating which can occasionally occur despite careful handling.
According to German Patent Application P 3,840,~17.1 (believed to correspond to U.S. Patent Application Serial No.
07/440,6273, the free acids upon which the salts used acsording to the present invention are based, as described below, can be used as blowing agents. The present invention is not concerned with the use of the corresponding free acids as blowing agents.
SUMMARY OF THE INYENTION
The present invention relates to a process for the preparation of molded polyurethane foams having a compact skin and having a density of at least 250 kg/m3 comprising in-mold fsaming at an isocyanate index of about 75 to about 1500 a reaction mixture of (a) a polyisocyanate component comprising at least one aromatic polyisocyanate, (b) an isocyanate-reactive component comprising at least one organic polyhydroxyl compound, (C) a blowing agent comprising a salt of (i) an organic carboxylic acid and (ii) a nitrogen base containing at least one N-H bond, and, optionally, (d) other auxiliaries and additives, Mo-3464 ~2 i67~
with the proviso that the blowing agent (c) cannot be a compound formed in situ in component (b) by interac~on of organic carboxylic acid with a difunctional or polyfunctional amine.
The present invention also relates to molded polyurethane foams obta;ned by this process.
DETAILED DES~RIPTION OF THE INVENTION
Polyisocyanate component (a) may be any aromatic polyisocyanate having an NCO content of at least 20% by weight.
Examples of suitable aromatic polyisocyanates include 2,4-di-o isocyanatotoluene or technical mixtures thereof with 2,6-di-isocyanatotoluene or, preferably, known polyisocyanates or polyisocyanate mixtures of the diphenylmethane series of the type obtainable by phosgenation of aniline-formaldehyde condensates and, optionally, purification of the phosgenation products by distillation. These polyisocyanates or polyisocyanate mixtures, which are particularly suitable for the process according to the invention, generally contain from 50 to 100% by weight diisocyanatodiphenylmethane isomers, with the remainder being essentially higher homologs of thPse 20 diisocyanates. The preferred diisocyanates present in these mixtures consist essentially of 4,4'-diisocyanatodiphenyl-methane in admixture with up to 60% by weight, based on the total quantity of diisocyanates, of 2,4'-diisocyanatodiphenyl-methane and, optionally, small quantities of 2,2'-diisocyanato-25 diphenylmethane. Urethane-, carbodiimide-, or allophanate-modified derivatives of these polyisocyanates may also be used as the polyisocyanate component (a).
Isocyanate-reactive component (b) comprises at least one organic compound containing at least two isocyanate-30 reactive hydroxyl groups and generally consists of mixtures ofseveral such compounds. Isocyanate-reactive component (b) is Mo-3464 2 ~ ~ f ~ 7 ~
preferably an organic polyhydroxyl compound known from polyurethane chemistry.
Particularly suitable isocyanate-reactive compounds ~b) include known polyhydroxy polyethers having a molecular weight in the range from 400 to about 10,000 (preferably in the range from 1500 to 6000) and containing at least two (preferably two to six) hydroxyl groups per molecule. Such polyhydroxy polyethers can be obtained in known manner by alkoxylation of suitable starter molecules. Suitable starter o molecules include water, propylene glycol, glycerol, trimethylolpropane, sorbitol, cane sugar, amino alcohols such as ethanolamine or diethanolamine, aliphatic amines such as hexylamine or 1,5-diaminohexane, or mixtures of such starter molecules. Preferred alkoxylating agents include propylene oxide and, optionally, ethylene oxide, which may be used in admixture with propylene oxide or even separately in separate reaction steps during the alkoxylation reaction.
Other suitable isocyanate-reactive compounds (b) include known modification products of such polyether polyols, that is, known graft polyethers based on the simple polyether polyols mentioned above and known polyether polyols containing polyaddition products as fillers, such as polyether polyols containing polyhydrazocarbonamides as disperse fillers.
Also suitable as isocyanate-reactive compounds (b~ or as a part of component (b) are polyester polyols having a molecular weight in the range from 400 to about 10,~00 (preferably in the range from 1500 to 4000) and containing at least two (preferably two to six) hydroxyl groups per molecule.
Suitable polyester polyols include the known reaction products of excess quantities of polyhydric alcohols of the type mentioned above as starter molecules with polybasic acids such as succinic acid, adipic acid, phthalic acid, tetrahydro-phthalic acid, or mixtures of such acids.
Low molecular weight polyhydroxyl compounds, that is, those having a molecular weight in the range from 62 to 399, Mo-3464 ~ ~ 2 '~
are also suitable as component (b) or as a part of component (b). Suitable low molecular weight polyhydroxyl compounds include low molecular weight chain-extending agents or crosslinking agents containing hydroxyl groups known from polyurethane chemistry. Examples include alkane polyols of the type mentioned above as starter molecules, as well as low molecular weight polyether polyols of the type obtainable by alkoxylation of such starter molecules.
As mentioned above, component (b) preferably contains organic polyhydroxyl compounds or mixtures of organic polyhydroxyl compounds of the type mentioned above. Component (b) can be a mixture of the relatively high molecular weight polyhydroxyl compounds mentioned above with the low molecular weight polyhydroxyl compounds mentioned above or component (b) can be a low molecular weight polyhydroxyl compound of the type mentioned above used alone.
Salts of (i) organic carboxylic acids and (ii) nitrogen bases containing at least one N-H bond are used as the blowing agents (c) of the invention, optionally together with other known chemical or physical blowing agents.
Suitable carboxylic acids (i) for the preparation of the salts (c) include, preferably, aliphatic carboxylic acids having a molecular weight in the range from about 46 to about ~00 (preferably in the range from 60 to 300). For the purposes of the invention, cycloaliphatic compounds are regarded as aliphatic compounds. Particularly preferred carboxylic acids are those which contain, in addition to the carboxyl group always present in a carboxylic acid, additional carboxyl groups and/or at least one isocyanate-reactive group selected from the group consisting of primary alcoholic hydroxyl groups, secondary alcoholic hydroxyl groups, mercapto groups, primary amino groups, and secondary amino groups. Accordingly, suitable carboxylic acids can be simple monocarboxylic acids, such as acetic acid, propionic acid, pivalic acid, cyclohexane carboxylic acid, dodecanoic acid, stearic acid, oleic acid, or Mo-34~4 2~2~a mixtures of such acids, but are preferably aliphatic carboxylic acids which contain, in addition to the carboxyl group, other reactive groups of the type described above. Preferred aliphatic carboxylic acids containing other reactive groups include lactic acid (i.e., 2-hydroxypropanoic acid), glycolic acidS tartaric acid, 2-mercaptoacetic acid, 3-mercaptopropionic acid, hydroxypivalic acid, 6-aminohexanoic acid, 6-methyl-aminohexanoic acid, succinic acid, adipic acid, or hexahydro-phthalic acid. Lactic aid is a particularly preferred organic o carboxylic acid.
Suitable but less preferred organic carboxylic acids (i) include aromatic carboxylic acids, such as benzoic acid, 4-methylbenzoic acid, or phthalic acid.
Suitable nitrogen bases (ii) for the preparation of the salts (c) of the invention include basic nitrogen-containing compounds that contain at least one NH bond per molecule and that are capable of forming salts with the acids.
Particularly preferred nitrogen bases include amines corresponding to the formula H
Rl N - R2 wherein Rl represents hydrogen, a Cl 18 (preferably Cl 4) aliphatic hydrocarbon group, a Cl 1~ (preferably Cl 4) aliphatic hydrocarbon group containing further nitrogen atoms, a C2 4 hydroxyalkyl group, or a group of the formula -NHR
(wherein R is hydrogen or Cl 4 alkyl), and 30 R represents hydrogen, a Cl 18 (preferably Cl 4) aliphatic hydrocarbon group, a C2 4 hydroxyalkyl group, a C6 15 aromatic hydrocarbon group, a C6 15 aromatic hydroc~rbon group containing further amino groups, or the residue left by formal removal of an amino group from a polyamino poly~ther containing 2 to 4 primary aliphatic amino groups Mo-3464 ~2 ~&7~
and having a molecular weight in the range from 400 to about 12,000, with the proviso that Rl is hydrogen when R2 is the residue of said polyamino ether; or Rl and R2 together with the nitrogen atom form a preferably saturated heterocyclic 5- or 6-membered ring optionally containing further ring heteroatoms (preferably nitrogen, oxygen, or sulfur).
Examples of suitable amines for the preparation of the salts (c) of the invention include methylamine, propyl-amine, 2-ethylhexylamine, ethanolamine, oleylamine, dimethyl-amine, dibutylamine, diethanolamine, diisopropanolamine, 1,2-diaminoethane, 1,2- and 1,3-diaminopropane, 1,6-diamino-hexane, N,N-dimethyl ethylenediamine, piperazine, N-methyl-ethylenediamine, N-butyl-1,3-propylenediamine, diethylenetri-amine, triethylene tetraamine, aniline, 2,4- and ~,6-diamino-toluene, 2,4'- and 4,4'-diaminodiphenylmethane, ammonia, hydrazine, hydroxylamine, and N-methylhydrazine. Also suitable are amino polyethers containing aromatically or, preferably, aliphatically bound primary amino groups having a molecular weight in the range from 400 to about 12,000 (preferably in the range from 2000 to 8000). Amines containing tertiary amino groups and, in addition to the tertiary amino group, at least one primary or secondary amino group, such as N,N-dimethyl-1,3-propylene diamine, are also suitable.
The salts (c) are prepared by reaction of the carboxylic acids with the nitrogen bases using known methods.
~o prepare the preferred organic ammonium lactates, for example, it is possible initially to introduce the nitrogen base and gradually to add the calculated quant;ty of lactic acid, preferably at temperatures kept below 50C. When preparing the lactate salts, an aqueous solution of about 80 to about 99YO by wei~ht lactic acid and about 20 to about 1% by weight water (preferably commercial 90% aqueous lactic acid) is generally used. After the addition is completed, the ~ixture iS then heated at 80C for about 30 minutes to convert any Mo-3464 7 ~
condensation products of the lactic acid into the monomeric form. In the reaction with ammonia, the calculated quantity of ammonia can be introduced, for example, into 90% lactic acid through a gas inlet pipe at temperatures below 50C, with the resultant mixture then being stirred for about 30 minutes at 80C. It is, or course, possible to prepare salts of other carboxylic acids of the invention in like manner.
~hen using nitrogen bases that are not organic diamines or polyamines, it is even possible to prepare the salt in situ in the polyol component (b) by a simple mixing of the monofunctional amine and the carboxylic acid in the polyol component (b). The two salt components can be added in any order or even at the same time. The in-situ preparation of salts of difunctional and polyfunctional amines, on the other hand, falls within the scope of German Patent Application P 3,840,817.1 and is not the subject of the present invention.
When the salts are p~epared in situ in the component (b), or even when separately prepared, equivalent quantities of amine and carboxylic acid are generally used. The amine component, however, may also be used in an excess quantity, for example, in an equivalent ratio of amino groups (in the context of the invention, amino groups always include all amino groups neutralizable with the acids) to carboxyl groups of up to 4:1. It is also possible, although even less preferred, to use an excess of acid, for example, in an equivalent ratio of carboxyl groups to amino groups of up to 4:1. When an excess of either component is used, catalysis of the system must be adapted according to the particular excess.
The equivalent ratio of carboxyl groups to amino groups neutralizable with the carboxyl groups is from about 0.5:1 to about 2:1 (preferably 1:1).
In the practical application of the process according to the invention, the salts (c) of the invention discussed above may even be used in combination with small quantities of other known chemical or physical blowing agents, including water, gases physically dissolved in the starting components Mo-3464 2~67~
(such as air, carbon dioxide, or nitrogen), pyrocarbonic acid esters, nitrogen-generating compounds, volatile hydrocarbons, or halogenated hydrocarbons. Apart from the often unavoidable presence of stirred-in water and air, however, the use of these other blowing agents is not preferred. In general, such other blowing agents, if present at all, make up no more than 50% by weight (preferably no more than 25% by weight) of the total amount of blowing agents present in the reaction mixture.
~he use of water as an additional blowing agent often cannot be avoided because the starting components, particularly polyol component (b), often contain traces of water. Some of the carboxylic acids are commercially available as mixtures with water and are used as such. In general, the total quantity of water present in the reaction mixture is no more than 3 mole and generally no more than 1.5 mole of water per mole of carboxylate groups present in the salts. When lactic acid, the preferred acid component, is used, it is often used as an 80 to 99% by weight aqueous solution.
The total quantity of blowing agent (c) does, oF
course, depend on the particular density required for the molded products. In general, the weight of the acid component present in component (c) makes up from about 0.1 to about 10%
by weight (preferably from 0.4 to 4% by weight) of the reaction mixture of components (a), (b), (c~, and (d). The isocyanate-reactive groups of component (c) are included in the calculation of the isocyanate index.
The optionally used other auxiliaries and additives (d) include known catalysts that accelerate the isocyanate polyaddition reaction. Suitable catalysts include tertiary amines, such as triethylenediamine, N,N-d;methylbenzylamine, and N,N-dimethylcyclohexylamine, or organometallic compounds, particularly tin compounds such as tin(II) octoate or dibutyl tin dilaurate. I~ polyurethane foams containing isocyanurate groups are to be prepared by the process of the invention, it also possible to use trimerization catalysts, including alkali Mo-3464 ~ ~ 2 ~ ~ 7 ~
acetates such as sodium or potassium acetate, alkali phenolates such as sodium phenolate or sodium trichlorophenolate, or 2,4,6-tris(dimethylaminomethyl)phenol, or even lead naphthenate, lead benzoate, and lead octoate.
Other optional auxiliaries and additives (d) include known foam stabilizers, for example, those based on polyether-modified polysiloxanes. Other auxiliaries and additives (d) which may optionally be used include internal mold release agents, for example, those described in European o Patent Application 81,701; U.S. Patents 3,726,952, 4,098,731, 4,058,4g2, 4,033,912 4,024,090, and 4,098,731; British Patent 1,365,215; and German Offenlegungsschriften 2,319,648 and 2,427,273.
The process of the invention is generally carried out 15 by first mixing starting components (b), (c), and (d~ together and then combining the resulting mixture with polyisocy~nate component (a). Mixing is carried out, for example, using stirrer-type mixers or, preferably, using high-pressure mixing units of the type typically used in the preparation of 20 polyurethane foams. Immediately after preparation, the reaction mixture is introduced into the mold in a quantity adapted to the desired density of the molded product. In addition to this single-stage process, the process according to the invention may also be carried out on the semi-prepolymer 25 principle. In the semi-prepolymer method, the total quantity of polyisocyanate component (a~ is reacted with part of component (b), preferably while maintaining an NCO:OH
equivalent ratio of at least 3:1 (preferably at least 8:1), to form an NCO semi-prepolymer which is then reacted with a 30 mixture of the remaining components (b~, (c), and (d). Poly-hydroxyl compounds (b) that are different from the polyhydroxyl compounds (b) subsequently mixed with the NCO semi-prepolymers may, of course, be used for the preparation of the NCO
semi-prepolymers.
Mo-3464 2 ~
In all variants of the process of the invention, the quantities in which the individual components are used are selected so that the isocyanate index is from 75 to 1500, preferably from 80 to 150. By "isocyanate index" is meant the 5 quotient, multiplied by 100, of the number of isocyanate groups and the number of isocyanate-reactive groups. Isocyanate indexes far above 100 are appropriate when it is desired to prepare isocyanurate-modified polyurethane foams using trimer;~ation catalysts.
The molded products of the invention have densities of at least 250 (preferably from 4U0 to 800) kg/m3.
In ~eneral, the temperature of the molds used is at least 30C, preferably at least 50C. If necessary, the inner walls of the molds may be coated before filling with known 15 external mold release agents.
The salts used as blowing agents according to the invention may replace the fluorochlorocarbon blowing agents previously used in all of the usual formulations for the preparation of polyurethane foam moldings without any need for 20 significant changes in the catalysts used. The quantity of polyisocyanate must simply be adapted to the NC0-reactive components (i.e., carboxylic acid, nitrogen base, and, optionally, water) introduced along with the salts.
Accordingly, the process of the invention provides a 25 method for preparing high-quality polyurethane foam moldings having a compact, bubble-free skin without any need for the fluorocarbon blowing agents that have previously always been used. The process according to the invention is particularly suitable for the preparation of semi-rigid to rigid integral 30 foams having a compact skin of the type widely used in the automotive industry and furniture industry.
The following examples further illustrate details for the process of this invention. The invention, which is set forth in the foregoing disclosure, is not to be limited either 35 in spirit or scope by these examples. Those skilled in the art Mo-3464 ~276~
will readily understand that known variations of the conditions of the following procedures can be used. Unless otherwise noted, all temperatures are degrees Celsius and all parts and percentages are parts by weight and percentages by weight.
EXAMPLES
Examples 1 to 7 The formulations used in Examples 1-7 were prepared using the following starting materials according to the proportions (in parts by weight) shown in Table 1.
Startin~ materials:
Polvisocvanate com~onent (al): Polyisocyanate mixture of the diphenylmethane series having an NCO content of 31% by weight and a content of isomeric diisocyanatodiphenylmethanes of 60%
by weight (of which 55% by weight consists of 4,4'-diiso-cyanatodiphenylmethane and approximately 5% by weight of 2,4'-diisocyanatodiphenylmethane) PolYol component (bl): Propoxylation product (OH value 860) of trimethylolpropane Polvol component (b2!: Propoxylation product (OH value 42) of trimethylolpropane Blowinq aqent (cl): Salt of 2-hydroxypropanoic acid and diethanolamine (equivalence ratio of 1:1) Blowinq aqent (c2): Salt of 2-hydroxypropanoic acid and ammonia (equivalence ratio of 1:1) Blowinq aqent (c3): Salt of 2-hydroxypropanoic acid and ethylene diamine (equivalence ratio of ~
Blowinq aqent (c4): Salt of propanoic acid and diethanolamine ~equivalence ratio of 1:1) Blowing aqent ~c5): Salt of oleic acid and diethanolamine ~equivalence ratio of 1:1) Additive (dl~ (stabili2erl: Commercial polyetner siloxane (TE60STAB ~OS 50, a product of Goldschmidt AGs 4300 Essen 1, West Germany) Additive (d2) (Catalvst): ~,N-dimethylcyclohexylamine Mo-3464 202i~G~
Examples 1-5 are examples according to the invention.
Example 6 is Comparison Example using water as C02-forming blowing agent. Example 7 is a Comparison Example using monofluorotrichloromethane ("R 11") as blowing agent (conventional integral foam of high rigidity).
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_ ~) ~ l ~ o o~ C
C ~ r- C C C C C ~ ~ r~ v~ C
o o o~ 4 ~
~_ Cl. ~ 2 3 2 3 2 ~ tl~ ~ O :~
E ~-- r ~ ~ ns o -- ~
t-- ~ c~ > ~ 3 ~ C~ Z c~:
Mo-3464 7 ~
General_Observations on the Examples Sheet-form foam moldings having a density of 500 kg/m3 (see Table 2) were prepared using the formulations shown in Table 1. The mold used was a sheet mold measuring 10 x 200 X 200 mm, the inner walls of which had been coated with a commercial external wax-based mold release agent (ACMOSIL~ 180, a product of Acmos, D-2800 Bremen 1, West GermanyJ. Before processing, the polyol mixtures were charged with 10% by volume (based on atmospheric pressure) of finely dispersed air by brief stirring at high speed (5 minutes at 1000 r.p.m using a propeller stirrer).
The reaction mixtures were prepared from the polyol mixtures and the polyisocyanate component (a) using a typical stirrer-type mixer. The densities of the particular moldings were determined by the quantity of reaction mixture introduced into the mold. Table 2 shows the Shore D surface hardness of the individual foam moldings.
Table 2 - ~hore D surface hardness Density Examples (kg/~3) The surface hardness of each of Examples 1 to 5 according to the invention is distinctly greater than that of Comparison Example 6 at this density and only slightly below 30 the surface hardness of the integral foam produced without water using R 11 as blowing agent (Comparison Example 7).
Examples 8 to ll - Preparation of semi-rigid molded foams having a compact skin Mo- 3464 ~ ~r~
The formulations used in Examples 8-11 were prepared using the following starting materials according to the proportions (in parts by weight) shown in Table 3.
Starting materials:
PolYisocYanate (a2): Urethane-modified polyisocyanate mixture ha~ing an average NCO functionality of 2.2 and an NCO content of 28.5% by weight prepared by reaction of polypropylene glycol having an average molecular weight of 218 with a polyisocyanate mixture of the diphenylmethane series consisting of 75 parts by weight 4,4'-diisocyanatodiphenyl~ethane, 4 parts by weight 2,4'-diisocyanatodiphenylmethane, and 21 parts by weight of more highly nuclear polyisocyanates of the diphenyl methane series PolYol (b3): Polyether polyol (OH value 28) prepared by propoxylation of trimethylolpropane and subsequent ethoxylation of the propoxylation product (ratio by weight PO:E0 of 80:20) Polvol (b4): Polyether polyol (OH value 470) prepared by ethoxylation of N-ethyldiethanolamine Blowing aaent (c6~: Reaction product of 1 mole of ethylene diamine and 1 mole of aqueous 90% lactic acid Blowinq agent (c7): Reaction product of 1 mole of diethanolamine and 1 mole of aqueous 90% lactic acid CatalYst (d3): 30% Solution of triethylene diamine in dipropylene glycol Catalyst (d4): Dibutyltin dilaurate Stabilizer (d3): Commercial polyether polysiloxane stabilizer (Stabilizer DC 193, a product of Dow Corning) Sheet-form semi-rigid foam moldings having a density of 600 kg/m3 were prepared using the formulations shown in Table 3. The mold used was an aluminum sheet mold measuring 20 x 30 x 1 cm, the inner walls of which had been coated with a commercial external mold release agent (FLUORICON~ 36-134, a product of Acmos, D-2800 Bremen 1, West Germany). The mold temperature was kept at 45~C for each example.
Mo-3464 2 ~ 2 ~ ~ 7 1~
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r-~ O N N N O I I I O I O
r~
~ C~
~ n u~ l O
O O N C~l N O I I Lr~ O I C > el ~
-E
X ~ ~ r~ N
1~ o~ I N
0~ O N N N O I N I O O O O O C~
.~r) ~D ~ 3 r~ ~ r~ ~ cn u~ ~ >~
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r C
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, ~ ~ o E r ~_C ~ a~ r~
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o ^-- " E a~ a~ ~ ~> ~ ~ c ~ s_ ~) e~ c~ a v~ 0 ~ a ~ ra ~ O ~ ~ 0 a a O ~ ~ ~ ~ x E s ~
r ~ ~ c ~ ~ ~ ~ ._ o ~ ~ ~ ra c ~. ~ ~ c ~ ~,. vl c ~
a o ~. ~ ~ a~ 3 3 ~ ~a ra ~ r- _ E a~ cr E ~ r-- c 11~ ~ O C~ --O c~ O
~ ~ o o ~ O a ~ r-- o a Mo- 3464 7 ~
General Observat;ons on the Examples:
In Example 11, only water was used as blowing agent.
After demolding, the sheet expanded and had a higher surface hardness than the sheets of Examples 8 and 9.
Mo-3464 LeA 27,266 A PROCESS FOR THE PREPARATION OF MOLDED POLYURETHANE
FOAMS AND THE MOLDED FOAMS OBTAINED BY THIS PROCESS
BACKGROUND OF THE INVENTION
This invention relates to a new process for the preparation of molded polyurethane foams having a compact skin, in which salts of (i) organic carboxylic acids and (ii) nitrogen bases containing at least one NH bond are used as blowing agents, and to the moldings obtained by the process.
~he preparation of molded polyurethane foams having a o compact skin by foam molding is known. For example, German Auslegeschrift 1,196,864. It is carried out by the in-mold foaming of a reactive and foamable mixture of organic poly-isocyanates, compounds containing isocyanate-reactive groups, and the usual auxiliaries and additives. The reacted mixture iS introduced into the mold in a larger quantity than would be necessary to fill the interior of the mold by free foaming. By suitable choice of the starting components, particularly with respect to molecular weight and functionality, it is possible to produce both flexible, semi-rigid, and rigid moldings. The compact outer skin is obtained by introducing a foamable mixture into the mold in a larger quantity than would be necessary to fill the interior of the mold by free foaming and by using blowing agents (such as fluorochlorocarbons), which condense on the inner walls of the mold under the prevailing temperature and pressure conditions, so that the blowing reaction stops at the inner wall of the mold and a compact outer skin is formed.
In addition to physical blowing agents mentioned aboYe, water (which forms carbon dioxide by reaction with isocyanates) is also used as a chemical blowing agent in industrial polyurethane chemistry. Although free-foamed 2 ~ 2, ~
polyurethane foams of excellent quality can be prepared with this chemical blowing agent, it is not possible to prepare high-quality foam moldings having a compact skin (integral foams) because carbon dioxide dces not condense on the inner wall of the mold under the usual conditions. Consequently, the blowing effect is not stopped at the surface area. The same basic problem arises with other chemical or physical blowing agents, such as nitrogen-generating blowing agents such as azodicarbonamide and azo-bis(isobutyronitrile); blowing agents which eliminate carbon dioxide such as pyrocarbonic acid esters and anhydrides (U.S. Patent 4,070,310); and blowing agents such as air which are dissolved in the reaction components, particularly the component containing isocyanate-reactive groups. These other chemical blowing agents are, therefore, also unsuitable for the preparation of high-quality integral foams.
It has now surprisingly been found, however, that high quality molded polyurethane foams having a compact skin can be prepared from the usual starting materials using salts of (i) organic carboxylic acids and (ii) nitrogen bases containing at least one NH bond. The blowing effect of these materials is also based essentially on the release of carbon dioxide.
Although, according to German Offenlegungsschrift 3,041,58g, special mixed carboxylic/carbamic anhydrides of the type formed from carboxylic acids and aliphatic isocyanates are used as blowing agents for the preparation of polyurethane foams (particularly integral foams), this process is unsuitable for industrial application for the following reasons. Mixed anhydrides are often said to be stable in storage at temperatures of up to about 60-C even in solution, while, on the other hand, to develop the blowing effect with release of carbon dioxide at temperatures as low as about 80C.
Accordingly, the useful temperature range in which carbon dioxide is eliminated is very narrow. In addition, only Mo-3464 ~Q~ ~7i3 aliphatic isocyanates can be used for the preparation of mixed anhydrides. In contrast, the aromatic polyisocyanates typically used as polyisocyanate component are unsuitable for the preparation of the special blowing agents. To carry out s the process, the mixed anhydrides must first be prepared and isolated in a separate reaction and then carefully mixed with the polyol mixture. These additional process steps make the use of these compounds even more expensive and complicated.
Ready-to-use polyols containing the blowing agents mentioned above cannot be stored and transported safely because the danger of a dangerous pressure build-up cannot always be avoided in case of overheating which can occasionally occur despite careful handling.
According to German Patent Application P 3,840,~17.1 (believed to correspond to U.S. Patent Application Serial No.
07/440,6273, the free acids upon which the salts used acsording to the present invention are based, as described below, can be used as blowing agents. The present invention is not concerned with the use of the corresponding free acids as blowing agents.
SUMMARY OF THE INYENTION
The present invention relates to a process for the preparation of molded polyurethane foams having a compact skin and having a density of at least 250 kg/m3 comprising in-mold fsaming at an isocyanate index of about 75 to about 1500 a reaction mixture of (a) a polyisocyanate component comprising at least one aromatic polyisocyanate, (b) an isocyanate-reactive component comprising at least one organic polyhydroxyl compound, (C) a blowing agent comprising a salt of (i) an organic carboxylic acid and (ii) a nitrogen base containing at least one N-H bond, and, optionally, (d) other auxiliaries and additives, Mo-3464 ~2 i67~
with the proviso that the blowing agent (c) cannot be a compound formed in situ in component (b) by interac~on of organic carboxylic acid with a difunctional or polyfunctional amine.
The present invention also relates to molded polyurethane foams obta;ned by this process.
DETAILED DES~RIPTION OF THE INVENTION
Polyisocyanate component (a) may be any aromatic polyisocyanate having an NCO content of at least 20% by weight.
Examples of suitable aromatic polyisocyanates include 2,4-di-o isocyanatotoluene or technical mixtures thereof with 2,6-di-isocyanatotoluene or, preferably, known polyisocyanates or polyisocyanate mixtures of the diphenylmethane series of the type obtainable by phosgenation of aniline-formaldehyde condensates and, optionally, purification of the phosgenation products by distillation. These polyisocyanates or polyisocyanate mixtures, which are particularly suitable for the process according to the invention, generally contain from 50 to 100% by weight diisocyanatodiphenylmethane isomers, with the remainder being essentially higher homologs of thPse 20 diisocyanates. The preferred diisocyanates present in these mixtures consist essentially of 4,4'-diisocyanatodiphenyl-methane in admixture with up to 60% by weight, based on the total quantity of diisocyanates, of 2,4'-diisocyanatodiphenyl-methane and, optionally, small quantities of 2,2'-diisocyanato-25 diphenylmethane. Urethane-, carbodiimide-, or allophanate-modified derivatives of these polyisocyanates may also be used as the polyisocyanate component (a).
Isocyanate-reactive component (b) comprises at least one organic compound containing at least two isocyanate-30 reactive hydroxyl groups and generally consists of mixtures ofseveral such compounds. Isocyanate-reactive component (b) is Mo-3464 2 ~ ~ f ~ 7 ~
preferably an organic polyhydroxyl compound known from polyurethane chemistry.
Particularly suitable isocyanate-reactive compounds ~b) include known polyhydroxy polyethers having a molecular weight in the range from 400 to about 10,000 (preferably in the range from 1500 to 6000) and containing at least two (preferably two to six) hydroxyl groups per molecule. Such polyhydroxy polyethers can be obtained in known manner by alkoxylation of suitable starter molecules. Suitable starter o molecules include water, propylene glycol, glycerol, trimethylolpropane, sorbitol, cane sugar, amino alcohols such as ethanolamine or diethanolamine, aliphatic amines such as hexylamine or 1,5-diaminohexane, or mixtures of such starter molecules. Preferred alkoxylating agents include propylene oxide and, optionally, ethylene oxide, which may be used in admixture with propylene oxide or even separately in separate reaction steps during the alkoxylation reaction.
Other suitable isocyanate-reactive compounds (b) include known modification products of such polyether polyols, that is, known graft polyethers based on the simple polyether polyols mentioned above and known polyether polyols containing polyaddition products as fillers, such as polyether polyols containing polyhydrazocarbonamides as disperse fillers.
Also suitable as isocyanate-reactive compounds (b~ or as a part of component (b) are polyester polyols having a molecular weight in the range from 400 to about 10,~00 (preferably in the range from 1500 to 4000) and containing at least two (preferably two to six) hydroxyl groups per molecule.
Suitable polyester polyols include the known reaction products of excess quantities of polyhydric alcohols of the type mentioned above as starter molecules with polybasic acids such as succinic acid, adipic acid, phthalic acid, tetrahydro-phthalic acid, or mixtures of such acids.
Low molecular weight polyhydroxyl compounds, that is, those having a molecular weight in the range from 62 to 399, Mo-3464 ~ ~ 2 '~
are also suitable as component (b) or as a part of component (b). Suitable low molecular weight polyhydroxyl compounds include low molecular weight chain-extending agents or crosslinking agents containing hydroxyl groups known from polyurethane chemistry. Examples include alkane polyols of the type mentioned above as starter molecules, as well as low molecular weight polyether polyols of the type obtainable by alkoxylation of such starter molecules.
As mentioned above, component (b) preferably contains organic polyhydroxyl compounds or mixtures of organic polyhydroxyl compounds of the type mentioned above. Component (b) can be a mixture of the relatively high molecular weight polyhydroxyl compounds mentioned above with the low molecular weight polyhydroxyl compounds mentioned above or component (b) can be a low molecular weight polyhydroxyl compound of the type mentioned above used alone.
Salts of (i) organic carboxylic acids and (ii) nitrogen bases containing at least one N-H bond are used as the blowing agents (c) of the invention, optionally together with other known chemical or physical blowing agents.
Suitable carboxylic acids (i) for the preparation of the salts (c) include, preferably, aliphatic carboxylic acids having a molecular weight in the range from about 46 to about ~00 (preferably in the range from 60 to 300). For the purposes of the invention, cycloaliphatic compounds are regarded as aliphatic compounds. Particularly preferred carboxylic acids are those which contain, in addition to the carboxyl group always present in a carboxylic acid, additional carboxyl groups and/or at least one isocyanate-reactive group selected from the group consisting of primary alcoholic hydroxyl groups, secondary alcoholic hydroxyl groups, mercapto groups, primary amino groups, and secondary amino groups. Accordingly, suitable carboxylic acids can be simple monocarboxylic acids, such as acetic acid, propionic acid, pivalic acid, cyclohexane carboxylic acid, dodecanoic acid, stearic acid, oleic acid, or Mo-34~4 2~2~a mixtures of such acids, but are preferably aliphatic carboxylic acids which contain, in addition to the carboxyl group, other reactive groups of the type described above. Preferred aliphatic carboxylic acids containing other reactive groups include lactic acid (i.e., 2-hydroxypropanoic acid), glycolic acidS tartaric acid, 2-mercaptoacetic acid, 3-mercaptopropionic acid, hydroxypivalic acid, 6-aminohexanoic acid, 6-methyl-aminohexanoic acid, succinic acid, adipic acid, or hexahydro-phthalic acid. Lactic aid is a particularly preferred organic o carboxylic acid.
Suitable but less preferred organic carboxylic acids (i) include aromatic carboxylic acids, such as benzoic acid, 4-methylbenzoic acid, or phthalic acid.
Suitable nitrogen bases (ii) for the preparation of the salts (c) of the invention include basic nitrogen-containing compounds that contain at least one NH bond per molecule and that are capable of forming salts with the acids.
Particularly preferred nitrogen bases include amines corresponding to the formula H
Rl N - R2 wherein Rl represents hydrogen, a Cl 18 (preferably Cl 4) aliphatic hydrocarbon group, a Cl 1~ (preferably Cl 4) aliphatic hydrocarbon group containing further nitrogen atoms, a C2 4 hydroxyalkyl group, or a group of the formula -NHR
(wherein R is hydrogen or Cl 4 alkyl), and 30 R represents hydrogen, a Cl 18 (preferably Cl 4) aliphatic hydrocarbon group, a C2 4 hydroxyalkyl group, a C6 15 aromatic hydrocarbon group, a C6 15 aromatic hydroc~rbon group containing further amino groups, or the residue left by formal removal of an amino group from a polyamino poly~ther containing 2 to 4 primary aliphatic amino groups Mo-3464 ~2 ~&7~
and having a molecular weight in the range from 400 to about 12,000, with the proviso that Rl is hydrogen when R2 is the residue of said polyamino ether; or Rl and R2 together with the nitrogen atom form a preferably saturated heterocyclic 5- or 6-membered ring optionally containing further ring heteroatoms (preferably nitrogen, oxygen, or sulfur).
Examples of suitable amines for the preparation of the salts (c) of the invention include methylamine, propyl-amine, 2-ethylhexylamine, ethanolamine, oleylamine, dimethyl-amine, dibutylamine, diethanolamine, diisopropanolamine, 1,2-diaminoethane, 1,2- and 1,3-diaminopropane, 1,6-diamino-hexane, N,N-dimethyl ethylenediamine, piperazine, N-methyl-ethylenediamine, N-butyl-1,3-propylenediamine, diethylenetri-amine, triethylene tetraamine, aniline, 2,4- and ~,6-diamino-toluene, 2,4'- and 4,4'-diaminodiphenylmethane, ammonia, hydrazine, hydroxylamine, and N-methylhydrazine. Also suitable are amino polyethers containing aromatically or, preferably, aliphatically bound primary amino groups having a molecular weight in the range from 400 to about 12,000 (preferably in the range from 2000 to 8000). Amines containing tertiary amino groups and, in addition to the tertiary amino group, at least one primary or secondary amino group, such as N,N-dimethyl-1,3-propylene diamine, are also suitable.
The salts (c) are prepared by reaction of the carboxylic acids with the nitrogen bases using known methods.
~o prepare the preferred organic ammonium lactates, for example, it is possible initially to introduce the nitrogen base and gradually to add the calculated quant;ty of lactic acid, preferably at temperatures kept below 50C. When preparing the lactate salts, an aqueous solution of about 80 to about 99YO by wei~ht lactic acid and about 20 to about 1% by weight water (preferably commercial 90% aqueous lactic acid) is generally used. After the addition is completed, the ~ixture iS then heated at 80C for about 30 minutes to convert any Mo-3464 7 ~
condensation products of the lactic acid into the monomeric form. In the reaction with ammonia, the calculated quantity of ammonia can be introduced, for example, into 90% lactic acid through a gas inlet pipe at temperatures below 50C, with the resultant mixture then being stirred for about 30 minutes at 80C. It is, or course, possible to prepare salts of other carboxylic acids of the invention in like manner.
~hen using nitrogen bases that are not organic diamines or polyamines, it is even possible to prepare the salt in situ in the polyol component (b) by a simple mixing of the monofunctional amine and the carboxylic acid in the polyol component (b). The two salt components can be added in any order or even at the same time. The in-situ preparation of salts of difunctional and polyfunctional amines, on the other hand, falls within the scope of German Patent Application P 3,840,817.1 and is not the subject of the present invention.
When the salts are p~epared in situ in the component (b), or even when separately prepared, equivalent quantities of amine and carboxylic acid are generally used. The amine component, however, may also be used in an excess quantity, for example, in an equivalent ratio of amino groups (in the context of the invention, amino groups always include all amino groups neutralizable with the acids) to carboxyl groups of up to 4:1. It is also possible, although even less preferred, to use an excess of acid, for example, in an equivalent ratio of carboxyl groups to amino groups of up to 4:1. When an excess of either component is used, catalysis of the system must be adapted according to the particular excess.
The equivalent ratio of carboxyl groups to amino groups neutralizable with the carboxyl groups is from about 0.5:1 to about 2:1 (preferably 1:1).
In the practical application of the process according to the invention, the salts (c) of the invention discussed above may even be used in combination with small quantities of other known chemical or physical blowing agents, including water, gases physically dissolved in the starting components Mo-3464 2~67~
(such as air, carbon dioxide, or nitrogen), pyrocarbonic acid esters, nitrogen-generating compounds, volatile hydrocarbons, or halogenated hydrocarbons. Apart from the often unavoidable presence of stirred-in water and air, however, the use of these other blowing agents is not preferred. In general, such other blowing agents, if present at all, make up no more than 50% by weight (preferably no more than 25% by weight) of the total amount of blowing agents present in the reaction mixture.
~he use of water as an additional blowing agent often cannot be avoided because the starting components, particularly polyol component (b), often contain traces of water. Some of the carboxylic acids are commercially available as mixtures with water and are used as such. In general, the total quantity of water present in the reaction mixture is no more than 3 mole and generally no more than 1.5 mole of water per mole of carboxylate groups present in the salts. When lactic acid, the preferred acid component, is used, it is often used as an 80 to 99% by weight aqueous solution.
The total quantity of blowing agent (c) does, oF
course, depend on the particular density required for the molded products. In general, the weight of the acid component present in component (c) makes up from about 0.1 to about 10%
by weight (preferably from 0.4 to 4% by weight) of the reaction mixture of components (a), (b), (c~, and (d). The isocyanate-reactive groups of component (c) are included in the calculation of the isocyanate index.
The optionally used other auxiliaries and additives (d) include known catalysts that accelerate the isocyanate polyaddition reaction. Suitable catalysts include tertiary amines, such as triethylenediamine, N,N-d;methylbenzylamine, and N,N-dimethylcyclohexylamine, or organometallic compounds, particularly tin compounds such as tin(II) octoate or dibutyl tin dilaurate. I~ polyurethane foams containing isocyanurate groups are to be prepared by the process of the invention, it also possible to use trimerization catalysts, including alkali Mo-3464 ~ ~ 2 ~ ~ 7 ~
acetates such as sodium or potassium acetate, alkali phenolates such as sodium phenolate or sodium trichlorophenolate, or 2,4,6-tris(dimethylaminomethyl)phenol, or even lead naphthenate, lead benzoate, and lead octoate.
Other optional auxiliaries and additives (d) include known foam stabilizers, for example, those based on polyether-modified polysiloxanes. Other auxiliaries and additives (d) which may optionally be used include internal mold release agents, for example, those described in European o Patent Application 81,701; U.S. Patents 3,726,952, 4,098,731, 4,058,4g2, 4,033,912 4,024,090, and 4,098,731; British Patent 1,365,215; and German Offenlegungsschriften 2,319,648 and 2,427,273.
The process of the invention is generally carried out 15 by first mixing starting components (b), (c), and (d~ together and then combining the resulting mixture with polyisocy~nate component (a). Mixing is carried out, for example, using stirrer-type mixers or, preferably, using high-pressure mixing units of the type typically used in the preparation of 20 polyurethane foams. Immediately after preparation, the reaction mixture is introduced into the mold in a quantity adapted to the desired density of the molded product. In addition to this single-stage process, the process according to the invention may also be carried out on the semi-prepolymer 25 principle. In the semi-prepolymer method, the total quantity of polyisocyanate component (a~ is reacted with part of component (b), preferably while maintaining an NCO:OH
equivalent ratio of at least 3:1 (preferably at least 8:1), to form an NCO semi-prepolymer which is then reacted with a 30 mixture of the remaining components (b~, (c), and (d). Poly-hydroxyl compounds (b) that are different from the polyhydroxyl compounds (b) subsequently mixed with the NCO semi-prepolymers may, of course, be used for the preparation of the NCO
semi-prepolymers.
Mo-3464 2 ~
In all variants of the process of the invention, the quantities in which the individual components are used are selected so that the isocyanate index is from 75 to 1500, preferably from 80 to 150. By "isocyanate index" is meant the 5 quotient, multiplied by 100, of the number of isocyanate groups and the number of isocyanate-reactive groups. Isocyanate indexes far above 100 are appropriate when it is desired to prepare isocyanurate-modified polyurethane foams using trimer;~ation catalysts.
The molded products of the invention have densities of at least 250 (preferably from 4U0 to 800) kg/m3.
In ~eneral, the temperature of the molds used is at least 30C, preferably at least 50C. If necessary, the inner walls of the molds may be coated before filling with known 15 external mold release agents.
The salts used as blowing agents according to the invention may replace the fluorochlorocarbon blowing agents previously used in all of the usual formulations for the preparation of polyurethane foam moldings without any need for 20 significant changes in the catalysts used. The quantity of polyisocyanate must simply be adapted to the NC0-reactive components (i.e., carboxylic acid, nitrogen base, and, optionally, water) introduced along with the salts.
Accordingly, the process of the invention provides a 25 method for preparing high-quality polyurethane foam moldings having a compact, bubble-free skin without any need for the fluorocarbon blowing agents that have previously always been used. The process according to the invention is particularly suitable for the preparation of semi-rigid to rigid integral 30 foams having a compact skin of the type widely used in the automotive industry and furniture industry.
The following examples further illustrate details for the process of this invention. The invention, which is set forth in the foregoing disclosure, is not to be limited either 35 in spirit or scope by these examples. Those skilled in the art Mo-3464 ~276~
will readily understand that known variations of the conditions of the following procedures can be used. Unless otherwise noted, all temperatures are degrees Celsius and all parts and percentages are parts by weight and percentages by weight.
EXAMPLES
Examples 1 to 7 The formulations used in Examples 1-7 were prepared using the following starting materials according to the proportions (in parts by weight) shown in Table 1.
Startin~ materials:
Polvisocvanate com~onent (al): Polyisocyanate mixture of the diphenylmethane series having an NCO content of 31% by weight and a content of isomeric diisocyanatodiphenylmethanes of 60%
by weight (of which 55% by weight consists of 4,4'-diiso-cyanatodiphenylmethane and approximately 5% by weight of 2,4'-diisocyanatodiphenylmethane) PolYol component (bl): Propoxylation product (OH value 860) of trimethylolpropane Polvol component (b2!: Propoxylation product (OH value 42) of trimethylolpropane Blowinq aqent (cl): Salt of 2-hydroxypropanoic acid and diethanolamine (equivalence ratio of 1:1) Blowinq aqent (c2): Salt of 2-hydroxypropanoic acid and ammonia (equivalence ratio of 1:1) Blowinq aqent (c3): Salt of 2-hydroxypropanoic acid and ethylene diamine (equivalence ratio of ~
Blowinq aqent (c4): Salt of propanoic acid and diethanolamine ~equivalence ratio of 1:1) Blowing aqent ~c5): Salt of oleic acid and diethanolamine ~equivalence ratio of 1:1) Additive (dl~ (stabili2erl: Commercial polyetner siloxane (TE60STAB ~OS 50, a product of Goldschmidt AGs 4300 Essen 1, West Germany) Additive (d2) (Catalvst): ~,N-dimethylcyclohexylamine Mo-3464 202i~G~
Examples 1-5 are examples according to the invention.
Example 6 is Comparison Example using water as C02-forming blowing agent. Example 7 is a Comparison Example using monofluorotrichloromethane ("R 11") as blowing agent (conventional integral foam of high rigidity).
Mo-3464 2 ~ 2 6' 3 3 7 i~
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n _ C~ ~ ~D O C-E ~ ~ _ _ ~
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. l E o l _ ~ ~ ~ U~ O ~ 4_ _ o __~
I ~.~ .) al l CCCCC~ ~ _ LL ~ ~ ~> c ~
C~ O ~ _ ~ ~ ~ a ~ nl ~;1 ~ q~ ~ :~ X ~
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o o o~ 4 ~
~_ Cl. ~ 2 3 2 3 2 ~ tl~ ~ O :~
E ~-- r ~ ~ ns o -- ~
t-- ~ c~ > ~ 3 ~ C~ Z c~:
Mo-3464 7 ~
General_Observations on the Examples Sheet-form foam moldings having a density of 500 kg/m3 (see Table 2) were prepared using the formulations shown in Table 1. The mold used was a sheet mold measuring 10 x 200 X 200 mm, the inner walls of which had been coated with a commercial external wax-based mold release agent (ACMOSIL~ 180, a product of Acmos, D-2800 Bremen 1, West GermanyJ. Before processing, the polyol mixtures were charged with 10% by volume (based on atmospheric pressure) of finely dispersed air by brief stirring at high speed (5 minutes at 1000 r.p.m using a propeller stirrer).
The reaction mixtures were prepared from the polyol mixtures and the polyisocyanate component (a) using a typical stirrer-type mixer. The densities of the particular moldings were determined by the quantity of reaction mixture introduced into the mold. Table 2 shows the Shore D surface hardness of the individual foam moldings.
Table 2 - ~hore D surface hardness Density Examples (kg/~3) The surface hardness of each of Examples 1 to 5 according to the invention is distinctly greater than that of Comparison Example 6 at this density and only slightly below 30 the surface hardness of the integral foam produced without water using R 11 as blowing agent (Comparison Example 7).
Examples 8 to ll - Preparation of semi-rigid molded foams having a compact skin Mo- 3464 ~ ~r~
The formulations used in Examples 8-11 were prepared using the following starting materials according to the proportions (in parts by weight) shown in Table 3.
Starting materials:
PolYisocYanate (a2): Urethane-modified polyisocyanate mixture ha~ing an average NCO functionality of 2.2 and an NCO content of 28.5% by weight prepared by reaction of polypropylene glycol having an average molecular weight of 218 with a polyisocyanate mixture of the diphenylmethane series consisting of 75 parts by weight 4,4'-diisocyanatodiphenyl~ethane, 4 parts by weight 2,4'-diisocyanatodiphenylmethane, and 21 parts by weight of more highly nuclear polyisocyanates of the diphenyl methane series PolYol (b3): Polyether polyol (OH value 28) prepared by propoxylation of trimethylolpropane and subsequent ethoxylation of the propoxylation product (ratio by weight PO:E0 of 80:20) Polvol (b4): Polyether polyol (OH value 470) prepared by ethoxylation of N-ethyldiethanolamine Blowing aaent (c6~: Reaction product of 1 mole of ethylene diamine and 1 mole of aqueous 90% lactic acid Blowinq agent (c7): Reaction product of 1 mole of diethanolamine and 1 mole of aqueous 90% lactic acid CatalYst (d3): 30% Solution of triethylene diamine in dipropylene glycol Catalyst (d4): Dibutyltin dilaurate Stabilizer (d3): Commercial polyether polysiloxane stabilizer (Stabilizer DC 193, a product of Dow Corning) Sheet-form semi-rigid foam moldings having a density of 600 kg/m3 were prepared using the formulations shown in Table 3. The mold used was an aluminum sheet mold measuring 20 x 30 x 1 cm, the inner walls of which had been coated with a commercial external mold release agent (FLUORICON~ 36-134, a product of Acmos, D-2800 Bremen 1, West Germany). The mold temperature was kept at 45~C for each example.
Mo-3464 2 ~ 2 ~ ~ 7 1~
I~ lD u~
~o)~o~ c~J o~
r-~ O N N N O I I I O I O
r~
~ C~
~ n u~ l O
O O N C~l N O I I Lr~ O I C > el ~
-E
X ~ ~ r~ N
1~ o~ I N
0~ O N N N O I N I O O O O O C~
.~r) ~D ~ 3 r~ ~ r~ ~ cn u~ ~ >~
O 00 U~ . 0 0~ U~ O
r C
E a1 X V) a ~ c O ~ V~ Q
._ o S~ N E ~.
, ~ ~ o E r ~_C ~ a~ r~
~ ~ C ~ ~ _ ~~
o ^-- " E a~ a~ ~ ~> ~ ~ c ~ s_ ~) e~ c~ a v~ 0 ~ a ~ ra ~ O ~ ~ 0 a a O ~ ~ ~ ~ x E s ~
r ~ ~ c ~ ~ ~ ~ ._ o ~ ~ ~ ra c ~. ~ ~ c ~ ~,. vl c ~
a o ~. ~ ~ a~ 3 3 ~ ~a ra ~ r- _ E a~ cr E ~ r-- c 11~ ~ O C~ --O c~ O
~ ~ o o ~ O a ~ r-- o a Mo- 3464 7 ~
General Observat;ons on the Examples:
In Example 11, only water was used as blowing agent.
After demolding, the sheet expanded and had a higher surface hardness than the sheets of Examples 8 and 9.
Claims (12)
1. A process for the preparation of a molded polyurethane foam having a compact skin and having a density of at least 250 kg/m3 comprising in-mold foaming at an isocyanate index of 75 to 1500 a reaction mixture of (a) a polyisocyanate component comprising at least one aromatic polyisocyanate, (b) an isocyanate-reactive component comprising at least one organic polyhydroxyl compound, (c) a blowing agent comprising a salt of (i) an organic carboxylic acid and (ii) a nitrogen base containing at least one N-H bond, with the proviso that the blowing agent (c) cannot be a compound formed in situ in component (b) by interaction of the carboxylic acid with a difunctional or polyfunctional amine.
2. A process according to Claim 1 additionally comprising (d) auxiliaries and additives.
3. A process according to Claim 1 wherein the organic carboxylic acid (c)(i) is an aliphatic carboxylic acid having a molecular weight in the range from 60 to 300.
4. A process according to Claim 1 wherein the organic carboxylic acid (c)(i) contains one or more carboxyl groups and at least one isocyanate-reactive group selected from the group consisting of primary alcoholic hydroxyl groups, secondary alcoholic hydroxyl groups, mercapto groups, primary amino groups, and secondary amino groups.
5. A process according to Claim 1 wherein the organic carboxylic acid (c)(i) is an aliphatic carboxylic acid having a molecular weight in the range from 60 to 300 and containing one or more carboxyl groups and at least one isocyanate-reactive group selected from the group consisting of Mo-3464 primary alcoholic hydroxyl groups, secondary alcoholic hydroxyl groups, mercapto groups, primary amino groups, and secondary amino groups.
6. A process according to Claim 1 wherein the organic carboxylic acid (c)(i) is lactic acid.
7. A process according to Claim 6 wherein the lactic acid is used as an aqueous solution of 80 to 99% by weight lactic acid and 20 to 1% by weight water.
8. A process according to Claim 1 wherein the nitrogen base (c)(ii) is an amine corresponding to the formula wherein R1 represents hydrogen, a C1-18 aliphatic hydrocarbon group, a C1-18 aliphatic hydrocarbon group containing further nitrogen atoms, a C2-4 hydroxyalkyl group, or a group of the formula -NHR wherein R is hydrogen or C1-4 alkyl, and R2 represents hydrogen, a C1-18 aliphatic hydrocarbon group, a C2-4 hydroxyalkyl group, a C6-15 aromatic hydrocarbon group, a C6-15 aromatic hydrocarbon group containing further amino groups, or the residue left by formal removal of an amino group from a polyamino polyether containing 2 to 4 primary aliphatic amino groups and having a molecular weight in the range from 400 to about 12,000, with the proviso that R1 is hydrogen when R2 is the residue of said polyamino ether; or R1 and R2 together with the nitrogen atom form a heterocyclic 5- or 6-membered ring optionally containing further ring heteroatoms.
9. A process according to Claim 8 wherein R1 and R2 together with the nitrogen atom form a saturated heterocyclic 5- or 6-membered ring optionally containing further ring heteroatoms.
Mo-3464
Mo-3464
10. A process according to Claim 1 wherein the salt (c) is prepared beforehand in a separate reaction by reaction of the organic carboxylic acid (c)(i) with the nitrogen base (c)(ii) and is then added to the polyol component (b).
11. A process according to Claim 1 wherein the salt (c) is prepared in situ in polyol component (b) by mixing the nitrogen base (c)(ii) with the organic carboxylic acid (c)(i) in said polyol component (b), with the proviso that said nitrogen base (c)(ii) must be a monofunctional amine and not a diamine or polyamine.
12. A molded polyurethane foam prepared by the process according to Claim 1.
Mo-3464
Mo-3464
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3934955A DE3934955A1 (en) | 1989-10-20 | 1989-10-20 | METHOD FOR THE PRODUCTION OF FORM BODIES OF POLYURETHANE FOAMS AND THE FORMKOERPER OBTAINED BY THIS METHOD |
| DEP3934955.1 | 1989-10-20 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2027670A1 true CA2027670A1 (en) | 1991-04-21 |
Family
ID=6391835
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002027670A Abandoned CA2027670A1 (en) | 1989-10-20 | 1990-10-15 | Process for the preparation of molded polyurethane foams and the molded foams obtained by this process |
Country Status (9)
| Country | Link |
|---|---|
| EP (1) | EP0423594B1 (en) |
| JP (1) | JP2696426B2 (en) |
| KR (1) | KR910008020A (en) |
| AT (1) | ATE97681T1 (en) |
| CA (1) | CA2027670A1 (en) |
| DE (2) | DE3934955A1 (en) |
| DK (1) | DK0423594T3 (en) |
| ES (1) | ES2046646T3 (en) |
| FI (1) | FI905138A0 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20110263740A1 (en) * | 2009-06-02 | 2011-10-27 | Momentive Performance Materials Japan Llc. | Expandable polyurethane composition and manufacturing method of polyurethane foam |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5093382A (en) * | 1991-08-08 | 1992-03-03 | Texaco Chemical Company | Preparation of foams using polyfunctional organic acids |
| US5527876A (en) * | 1992-01-31 | 1996-06-18 | Henkel Kommanditgesellschaft Auf Aktien | Process for the production of plastics containing amide groups |
| DE9209776U1 (en) * | 1992-07-21 | 1992-09-17 | Dresdener Industrie Und Service Gmbh, O-8060 Dresden, De | |
| EP2700669A1 (en) | 2012-08-21 | 2014-02-26 | Basf Se | Plastic reformable polyurethane polyamide hard foam material |
| US9562131B2 (en) | 2012-08-21 | 2017-02-07 | Basf Se | Thermoformable rigid polyurethane-polyamide foam |
| US10023681B2 (en) | 2012-10-24 | 2018-07-17 | Evonik Degussa Gmbh | Delay action catalyst for improving the stability of polyurethane systems having halogen containing blowing agents |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5598218A (en) * | 1979-01-22 | 1980-07-26 | Sanyo Chem Ind Ltd | Production of polyol composition and foam |
| CA1189249A (en) * | 1981-07-09 | 1985-06-18 | Bernhard Liessem | Foam manufacture |
| GB8329628D0 (en) * | 1983-11-05 | 1983-12-07 | Rubber & Plastic Res Ass | Polyurethanes |
| US4818775A (en) * | 1987-05-21 | 1989-04-04 | Reeves Brothers, Inc. | Rapid cure of polyurethane foam with ammonium containing materials |
| DE3840817A1 (en) * | 1988-12-03 | 1990-06-07 | Bayer Ag | METHOD FOR THE PRODUCTION OF FORM BODIES OF POLYURETHANE FOAMS AND THE FORMKOERPER OBTAINED BY THIS METHOD |
-
1989
- 1989-10-20 DE DE3934955A patent/DE3934955A1/en not_active Withdrawn
-
1990
- 1990-10-09 DK DK90119315.1T patent/DK0423594T3/en active
- 1990-10-09 DE DE90119315T patent/DE59003599D1/en not_active Expired - Fee Related
- 1990-10-09 AT AT90119315T patent/ATE97681T1/en not_active IP Right Cessation
- 1990-10-09 ES ES199090119315T patent/ES2046646T3/en not_active Expired - Lifetime
- 1990-10-09 EP EP90119315A patent/EP0423594B1/en not_active Expired - Lifetime
- 1990-10-15 CA CA002027670A patent/CA2027670A1/en not_active Abandoned
- 1990-10-18 JP JP2277926A patent/JP2696426B2/en not_active Expired - Lifetime
- 1990-10-18 FI FI905138A patent/FI905138A0/en not_active Application Discontinuation
- 1990-10-20 KR KR1019900016762A patent/KR910008020A/en not_active Application Discontinuation
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20110263740A1 (en) * | 2009-06-02 | 2011-10-27 | Momentive Performance Materials Japan Llc. | Expandable polyurethane composition and manufacturing method of polyurethane foam |
| US9266994B2 (en) * | 2009-06-02 | 2016-02-23 | Momentive Performance Materials Japan Llc | Expandable polyurethane composition and manufacturing method of polyurethane foam |
Also Published As
| Publication number | Publication date |
|---|---|
| FI905138A0 (en) | 1990-10-18 |
| DK0423594T3 (en) | 1994-01-31 |
| JP2696426B2 (en) | 1998-01-14 |
| ES2046646T3 (en) | 1994-02-01 |
| DE3934955A1 (en) | 1991-04-25 |
| KR910008020A (en) | 1991-05-30 |
| EP0423594A3 (en) | 1991-07-24 |
| EP0423594B1 (en) | 1993-11-24 |
| DE59003599D1 (en) | 1994-01-05 |
| ATE97681T1 (en) | 1993-12-15 |
| EP0423594A2 (en) | 1991-04-24 |
| JPH03153721A (en) | 1991-07-01 |
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