JPS6246567B2 - - Google Patents

Description

[Detailed description of the invention]

This application is filed by CLKehr, LLWood and JL
U.S. Patent Application No. 728464 (Title of the Invention: Low Residue Urethanes and Process for Producing the Same) filed on September 29, 1976 by Guthrie, a continuation-in-part of U.S. Patent Application No. 728464 filed on September 29, 1976; US Patent Application No.
No. 831,628 (the title of the invention is the same as above), and the gist of the invention of the US parent application is incorporated herein for reference. This application also relates to the Wood et al.
Also relevant is U.S. Patent Application No. 805,458, filed June 10, 1977. Recently, it has been discovered that polyurethane foams contain aromatic amines, possibly resulting from hydrolysis in the finished foam or during its manufacture. It has also been found that aromatic amines can leach out of foams; for example, in certain applications such as sponges, aromatic amines can leach out during use. Evidence has also recently emerged that certain aromatic amines tend to represent a potential health risk. The inventor is aware of certain prior art that is considered appropriate. In particular, British patent no.
No. 1,368,625 describes a method for making polyurethane foams using 1 to 20% by weight of aliphatic polyisocyanates in combination with conventional polyurethane foam reagents. The role of aliphatic polyisocyanates appears to be to enhance the formation of a dense skin layer during molding of polyurethane foams. It is also said that aliphatic isocyanates greatly contribute to preventing yellowing of foams. The specification of U.S. Patent No. 3790508 (Japanese Unexamined Patent Publication No. 49-47493) describes polyols, aliphatic isocyanates,
Light-stable polyurethane foams prepared by reacting aromatic isocyanates, blowing agents, and catalysts are described. The index of the aliphatic isocyanates used is from about 5 to about 40. British Patent No. 1323955 (JP 47-33198) also describes a formulation containing a mixture of aromatic and aliphatic isocyanates, water and a catalyst to cause trimerization of the aromatic isocyanates. things are listed. The resulting foam is said to have good physical properties as well as flame resistance. As far as the present inventor is aware, there are further patents listed below. U.S. Patent No. 3839491 U.S. Patent No. 3554962 Id. 3925319 French Patent No. 2000741 Id. 3590002 German Patent No. 2234507 Id. 3919173 Republic of South Africa Patent Application Publication No. 68/00476 Id. No. 3706710 The present invention comprises: We have found that polyurethane foams contain residual aromatic amines believed to be derived from hydrolysis during and following the foaming process, and possibly due to hydrolysis of the foam during storage. This was done based on the fact that For example, both one-shot and prepolymer foams using toluene diisocyanate can be prepared using the corresponding amines such as toluene diamine (TDA).
was found to contain. It is believed that foams using other aromatic polyisocyanates also contain the corresponding polyamines and that the present invention is equally applicable to these foams. In explaining the present invention, the term "aromatic amine" will mainly be used.
Although referring to TDA, the term also encompasses other aromatic amines derived from the corresponding polyisocyanates. Scavengers are added prior to foaming to reduce the amount of aromatic amines. The scavenger is a substance capable of reacting with aromatic amines generated after the foaming reaction, trapping the amines, and allowing the foaming reaction to continue. The most effective scavengers have been found to be aliphatic diisocyanates such as bis(cyclohexyl isocyanate) methane, isophorone diisocyanate, and the like. The aliphatic isocyanate is mixed with the urethane prepolymer or the components of the one-shot foam system. The amount of TDA or other aromatic amines leached from the foam in the resulting polyurethane foam is reduced compared to a foam without scavenger. It has also been found that the resulting foam contains small amounts of aliphatic amines, which are hydrolysis products of aliphatic isocyanates. However, it is believed that aliphatic amines do not pose the potential health problems caused by aromatic amines. Although the theory of aromatic amine formation and scavenger action is not clearly understood, aromatic isocyanates containing urea and urethane linkages and possibly their reaction products are hydrolyzed to free aromatic amines. This is considered to occur. This free aromatic amine can be leached from the polyurethane foam. It is believed that aliphatic diisocyanates do not successfully compete with aromatic isocyanates for functional groups during the polymerization reaction. It is therefore believed that the aliphatic isocyanate continues to undergo polymerization and forms a urea adduct with the aromatic amine as it forms. These adducts are difficult to leach from polyurethane foams and are not believed to pose a potential health hazard. Many factors are important in reducing TDA levels and optimizing scavenger effectiveness. For example, foams that are stored while still wet may have higher levels of foam than comparable foams that are stored after drying.
It tends to show TDA. It has also been found that the use of certain catalysts is harmful. That is, any catalyst used is preferably a "mild" catalyst, such as: That is, it promotes the reaction of the aromatic isocyanate with the hydroxyl groups of the polyol and allows the foaming reaction to proceed at a reasonable rate, but without involving either the aromatic or aliphatic isocyanate, such as biuret formation or trimerization. A catalyst that does not cause undesirable side reactions or incorporate aliphatic isocyanates into the polymer. If conventional strong catalysts (eg tin salts) are used, the amount of catalyst must be reduced. In addition to aliphatic isocyanates, there are other classes of compounds that are believed to be useful as aromatic amine binders. For example, as follows. i.e., organic oxirane compounds such as epoxidized soybean oil, epichlorohydrin, propylene oxide, etc.; epoxy resins derived from bisphenol A, such as that manufactured and sold by Shell Oil Company as EPON 828; organic anhydrides; Examples include phthalic anhydride, trimellitic anhydride, pyromellitic dianhydride, α-olefin/maleic anhydride copolymer, poly(maleic anhydride) and its oligomers, styrene/maleic anhydride copolymer , alkyl vinyl ether/maleic anhydride copolymer, etc.; benzoyl chloride, octanoyl chloride, sebacoyl chloride and the same effects; organic sulfonyl halides such as benzenesulfonyl chloride, etc., Isonate 143 (manufactured and sold by Upjohn), Staboxol (bis( 2,6-diiso-
Propylphenyl) carbodiimide]
(manufactured and sold by Naftone, Inc.) and their equivalents. The above-mentioned compounds can of course be used in admixture or combination with each other if desired. The desire is for the initial polymerization reaction to survive with slow or no reaction with water, polyols or isocyanate groups, but then to form an elastomeric, foamy or resinous polyurethane. The goal is to select compounds that react rather rapidly with by-product organic amine moieties during drying and/or storage of the product. It is a further possibility, if desired, to attach the organic amine moiety in a post-treatment step. Thus, the polyurethane product can be prepared in a conventional manner and then subjected to the influence of an organic amine binder in a subsequent operation. This can be done either by absorbing the binder into the polyurethane product using a liquid vehicle (water, organic solvent, etc.) or by absorbing the binder into the polyurethane product in the form of a gaseous vapor or aerated spray. This can be done by exposure to a binder. From the above discussion it is clear that the scavenger should react with water slower than the aromatic isocyanate. Suitable scavengers for use with certain aromatic isocyanates include the corresponding amine (e.g. TDA in the case of toluene diisocyanate) and a stoichiometric equivalent (or more) of the scavenger in a conventional inert It can be determined by dissolving it in a solvent. That is, 1 of each NH ₂ group with sufficient scavenger
React with hydrogen atoms. At ambient temperature, within 16 hours, the scavenger and amine should undergo a reaction that is essentially irreversible and complete in 16 hours. Additionally, when dispersed in water, the scavenger should exhibit a reaction rate for water of no more than about 10 ^-2 times the reaction rate of aromatic isocyanate and water, preferably from 10 ^-3 to ^{10 -5} . In conducting the tests, separate aqueous solutions or dispersions of aromatic isocyanate and scavenger can be prepared at a concentration of about 10 ^-2 mol/ml. Reaction rates are measured at approximately 25°C.
Once either the scavenger or the aromatic isocyanate is insoluble in water, the test is carried out using a suitable surfactant with constant stirring. Suitable co-solvents that are miscible with water may also be used. The above test method is believed to be a useful guide or "rough sieve" in selecting useful scavengers. However, due to the complexity of the foaming process, the decision to use a particular scavenger should be based on actual operations. The low aromatic amine retention foams produced in accordance with the present invention can be rigid, semi-rigid or flexible. Foams generally have a fluid permeable skin. "Fluid permeable" means that a piece of foam (0.254 cm thick) cut parallel to the surface and embodying said surface is
At least using a pressure difference of about 0.002 atm
It refers to permeability to air of 0.25ft ³ /min/ft ² . Similar test conditions are described in ASTM D-737 for measuring the permeability of textiles. In contrast, a foam with a very dense skin should exhibit about 10 ^-3 ft ³ /min/ft ² using the test method described above. Prepolymer Foam System A preferred embodiment of the present invention can be illustrated by the following method for producing polyurethane foam. That is, the method involves foaming (under conventional conditions) a mixture comprising (a) a urethane polymer having a polyether backbone portion terminated with an aromatic isocyanate and (b) an aliphatic isocyanate. and in this method the aliphatic isocyanate is present in an amount up to or equal to about 8% by weight of the prepolymer. Preferably, the amount of aliphatic isocyanate is less than or equal to about 4% by weight of the prepolymer. The lower limit for the amount of aliphatic isocyanate present is not critical, but is determined by the desired activity as a scavenger and also by the nature of the aliphatic isocyanate. Generally an amount of 0.01% by weight or more should be used. Suitable aliphatic isocyanates include cycloaliphatic isocyanates or aralkyl polyisocyanates. For example, xylene-α-diisocyanate, n-dodecyl isocyanate, ethylene diisocyanate, n-butyl isocyanate, cyclohexyl isocyanate, trimethylene diisocyanate, dicyclohexylmethane-4.
4'-diisocyanate, isophorone diisocyanate, 1,6-hexamethylene diisocyanate, 2,2,4-trimethyl-1,6-hexane diisocyanate, bis(3-methyl-4-isocyanatocyclohexyl) ) methane, etc.
The above list of compounds is illustrative and not all-inclusive or limiting. Any one type or a mixture of two or more of the above aliphatic or cycloaliphatic isocyanates or polyisocyanates may be used as desired. When producing foams by the prepolymer process, the prepolymer is generally combined with a suitable blowing agent (e.g. water), a catalyst (optional), and other additives depending on the final properties desired for the foam (e.g. Flame retardants)
mixed with. The amount of water used as a blowing agent is
Approximately 0.4 mole of H ₂ O to 1 NCO group per mole of NCO group
It can range from about 1000 moles of _H2O per mole. In determining the amount of water, "moles of NCO groups" refers to the aliphatic NCO groups of the scavenger, as well as the NCO groups generated from the prepolymer or aromatic isocyanate in the one-shot reaction mixture.
group, but does not include NCO groups, which are theoretically required to react with all the hydroxyl groups of the polyol used in the one-shot method embodiment of the present invention. For one-shot foams, the amount of water used depends on the amount of NCO groups (required for reaction with the polyol).
Approximately 0.40 to approximately 0.55 H ₂ O per mole (excluding NCO group)
Moles are preferred. The urethane prepolymers used generally consist of a polyether backbone terminated with an aromatic isocyanate (eg, TDI). Suitable aromatic isocyanates are listed below. Suitable polyether prepolymers include, for example, polyalkylene oxide ethers. Examples of these ethers include ethylene oxide, propylene oxide, butylene oxide, styrene oxide,
picoline oxide or methyl glucoside,
Such as reaction products with compounds having two or more reactive hydrogens such as water, resorcinol, glycerol, trimethylolpropane, pentaerythritol, ethylene glycol, diethylene glycol, triethylene glycol, etc. Further examples of the ethers include compounds such as polyoxypropylene glycol, polyoxyethylene glycol, polyoxybutylene glycol, polyoxyethylene oxypropylene glycol, polyoxyethylene oxybutylene glycol, and polyoxypropylene oxybutylene glycol. I can list them. The polyether urethane prepolymer used is preferably hydrophilic. That is, it is preferred that at least 40 mol% of the oxyalkylene units in the prepolymer main chain are oxyethylene units, with the remainder being oxypropylene, oxybutylene, or other oxyalkylene units.
In the resulting polyurethane foam, the branching points of the polymeric chain are essentially linear polyoxyalkylene containing at least 40 mole % oxyethylene units (excluding the initiator at the branching point), as described above. connected by chains. Oxyethylene content is approximately 60~
Preferably it is 75 mol%. At levels of 40 to 60 mole percent oxyethylene, it may be desirable to use surfactants, such as those described above, to facilitate dispersion of the prepolymer in the water prior to foaming. Suitable prepolymers are prepared by adding an excess of polyisocyanate (eg toluene diisocyanate) to the ends of a polyoxyalkylene polyol (ie polyether). Before adding to the end, the polyol is about 200 to about
It should have a molecular weight of 20,000, preferably from about 600 to about 6,000. The hydroxy functionality and corresponding isocyanate functionality of the polyol after terminal addition is from 2 to about 8. When the foam is made from a prepolymer having an isocyanate functionality of about 2, the resulting foam is essentially linear;
It does not have the tensile strength of cross-linked foam. Thus, although linear uncrosslinked foams can be used in the present invention if the isocyanate functionality is about 2, crosslinking agents can be used. To minimize adverse reactions involving aliphatic isocyanates, the crosslinkers used should be based on aliphatic polyols (e.g.
TMOP, glycerol or pentaerythritol). Examples of suitable polyols to which polyisocyanates are added at their ends include (A) essentially linear polyols obtained, for example, by reacting ethylene oxide with water, ethylene glycol or high molecular weight glycols as an initiator; Includes types. As mentioned above, mixtures of ethylene oxide and other alkylene oxides can be used as long as the mole percent of ethylene oxide is at least 40%. Also as previously mentioned, it is desirable to use a crosslinking agent in these systems if it can be included in the water in which the prepolymer is dispersed. If the linear polyether is a mixture of ethylene oxide and, for example, propylene oxide, the polymer will be either a random or block copolymer and the terminal units can be either oxyethylene or oxypropylene. The second type of polyols (B) has a hydroxy functionality of 3
or more. Such polyols are usually prepared by reacting alkylene oxides with polyfunctional initiators such as trimethylolpropane, pentaerythritol, and the like. The alkylene oxide used in producing polyol B may be ethylene oxide or a mixture of ethylene oxide and other alkylene oxides as described above. Useful polyols include examples of linear or branched polyfunctional polyols (C) as shown in A and B above, further accompanied by an initiator or crosslinking agent. Particular examples of C include mixtures of polyethylene glycol (molecular weight approximately 1000) with trimethylolpropane, trimethylolethane or glycerin. The prepolymers useful in this invention can be obtained by subsequent reaction of this mixture with excess polyisocyanate. Alternatively, linear or branched polyols (eg polyethylene glycol) may be reacted separately with excess polyisocyanate. Initiators such as trimethylolpropane can also be reacted separately with the polyisocyanate. Two isocyanate-terminated materials can be combined to produce a prepolymer. Suitable polyisocyanates useful in making prepolymers include the compounds described below. That is, toluene-2,4-diisocyanate,
Toluene-2,6-diisocyanate, commercially available mixture of toluene-2,4- and 2,6-diisocyanates, m-phenylene diisocyanate, 3,3'-diphenyl-4,4' -bisphenylene diisocyanate, 4,4'-biphenylene diisocyanate, 3,3'-dichloro-4,4'-biphenylene diisocyanate, 1,5-naphthalene diisocyanate, cumene-2. 4-diisocyanate, 4-methoxy-1,3-phenylene diisocyanate, 4-chloro-1,3-phenylene diisocyanate, 4-bromo-1,3-phenylene diisocyanate, 4- Ethoxy-1・3
-phenylene diisocyanate, 2,4'-diisocyanate diphenyl ether, 4,4'-diisocyanate diphenyl ether, and 4,6-dimethyl-1,3-phenylene diisocyanate. One shot method urethane foam mixture In order to clarify the differences from the present invention, a method for producing a polyurethane foam using the one shot method will be described. The one-shot method uses a mixture containing (a) an aliphatic isocyanate, (b) an aromatic isocyanate, (c) a polymeric polyol, and a catalyst system for promoting the reaction of the aromatic isocyanate with the hydroxyl groups of the polyol. (using conventional methods)
This includes foaming. The index of the aliphatic isocyanate in the mixture is preferably from about 0.01 to about 4.
0.2 to 4, and the aromatic isocyanate index is from about 110 to about 96, preferably from 99.8 to 96. The expression "index" is an art-recognized term that refers to the amount of aromatic or aliphatic isocyanate in the reaction mixture relative to the theoretical amount of isocyanate required to react with all active hydrogen compounds present in the reaction mixture. It is expressed by multiplying the actual amount of Nato by 100. Conventional catalyst systems can be used in the production of this one-shot foam. The method of using the catalyst is also conventional. However, many catalysts have been found to increase the amount of aromatic amines in the foam, and therefore the amount of catalyst used can be kept to a minimum to achieve the desired rate in the blowing reaction as well as the desired rate in the final foam. characteristics should be ensured.
As mentioned above, a suitable catalyst should promote the reaction between the polyol and the NCO groups of the aromatic isocyanate and reduce deleterious side reactions (e.g. trimerization, dimerization and biuret formation). Must be used under certain conditions. A list of conventional catalysts for promoting NCO/alcohol reactions is Polyurethanes by Saunders and Frisch:
Part 1 of Chemistry and Technology [John
Published by Wiley & Sons in 1962] Table LXX
(page 212). In one-shot foam manufacturing, all ingredients, such as polyether or polyester polyols, aromatic isocyanates, aliphatic isocyanates, blowing agents, catalysts, and any other ingredients such as UV absorbers, surfactants, fuel additives,
The fillers are mixed together and poured onto or into a mold where they are foamed. General techniques for making one-shot foams are known to those skilled in the art. See, for example, US Pat. No. 3,790,508 and British Patent No. 1,368,625. These patents are incorporated herein by reference to the extent that they teach the manufacture of foams by conventional one-shot methods. Suitable aromatic and aliphatic isocyanates as well as polyols are also described in said patents. Examples 1 to 8 Examples of the use of various aliphatic diisocyanates to reduce the amount of toluenediamine (TDA) in polyurethane foams Using the prepolymer method, prepolymers A, B, or C (described below) were added to 4 g of surfactant. including water 200
A polyurethane foam was produced by reacting with g. With the exception of Examples 6-8, the surfactant used was Pluronic L-62 (BASF-Wyandotte), a nonionic polyether-based surfactant. In Examples 6-8, the stearate surfactant Brij72 (Atlas Chemical
Division of ICI, America, Inc.). Also for control foams using prepolymers B and C.
Brij stearate surfactant was used. Control foam with Prepolymer C and Example 1:
The amount of Brij surfactant used was approximately 0.5% by weight based on the weight of the prepolymer. Prepolymer A consists of trimethylolpropane (TMOP) and Carbowax 1000 (Union Carbide
and Chemicals Corp. (polyoxyethylene glycol)) with toluene diisocyanate (TDI).
Sufficient amount of the mixture was used to give a TDI/TMOP/glycol ratio of 7.1/1/2 based on molar equivalents. Analysis of the prepolymer for free TDI showed that the prepolymer contained 3% by weight. During the production of the prepolymer, TDI was added in two steps. Enough TDI was added initially to react with 95% of the hydroxyl groups, followed by the remaining TDI. A gap of several hours between the two addition steps promotes chain elongation within the prepolymer. Prepolymer B was made using the same reactants as Prepolymer A, except that the TDI/TMOP/glycol ratio was 6.7/1/2. The prepolymer contained 1% free TDI by weight. Prepolymer C followed the method used to make Prepolymer A, but used ethylene glycol as the other reactant. The ratio of reactants used was
TDI/TMOP/polymer glycol/ethylene glycol was 8.6/1/2/1. Each foam produced as described above was
TDA was analyzed by extracting 20 g seven times with hot water followed by evaporation of the water. The extraction method is to add 20 g of foam to 150 ml of deionized water at 38°C in a beaker.
This consisted of soaking for a minute, during which time the foam was compressed several times using a spatula. This process was repeated seven times using fresh water, keeping the foam as dry as possible between extractions. The combined extracts were filtered to remove solid particles of foam and concentrated on a rotary evaporator to approximately 50 ml.
The concentrate was evaporated to dryness in a beaker placed on a hot plate to obtain about 0.134 to about 0.330 g of dry extract. The temperature was kept constantly below 60°C. Table 1 shows the results of measuring the TDA content in the extract.

Table 1 From Table 1 above, it is clear that for the isocyanate foam of Example 1, as the amount of aliphatic isocyanate used increases, the initial amount of diamine, calculated at 36 ppm, decreases significantly. Comparing Examples 2, 3 and 7 shows a steady decrease from 27 to 14 and completely undetectable. A similar comparison for methylene bis(cyclohexyl isocyanate) in Examples 4 and 5 shows a similar reduction. This decrease is surprising since each aliphatic diisocyanate is difunctional and one would expect some polymerization reaction to be involved. However, we showed that despite the exothermic polymerization conditions, the presence of aliphatic isocyanates still has a significant effect on the amount of residual total extractables and free tolylene diamine in the foam. . Examples 9-15 Utilization of bis(3-methyl-4-isocyanato)methane as a scavenger for aromatic amines.
-isocyanate) methane into two different hydrophilic urethane prepolymers (prepolymers F and G)
mixed with. Foaming was carried out by mixing prepolymer (100 parts), water (100 parts) and surfactant (2 parts). The surfactant used was
It was Pluronic L-62 (BASF/Wyandts). The resulting foams were analyzed for residual aromatic amines according to the method described in Examples 9-18.
The results are shown in Table 3. Prepolymer F was prepared by mixing polyethylene glycol (molecular weight 1000) with TMOP. Add enough TDI to terminate 95% of the hydroxyl groups present, followed by 10% more than the theoretical amount.
TDI was added in % excess. After the initial addition of TDI, the mixture was allowed to react for several hours before the final addition of 15% TDI.
The molar ratio of PEG1000/TMOP was 2/1. Prepolymer G was prepared in the same general manner as Prepolymer F, but the ratio of PEG1000/TMOP was 2/0.66. Also, during the first addition
Added only 92% TDI. After the reaction time has passed,
Added an additional 13% TDI. Control 1 and Examples 9-12 used Prepolymer F. Control 2 and Examples 13-15 used Prepolymer G.

【table】

Claims (1)

[Scope of Claims] 1 (a) A hydrophilic urethane prepolymer consisting of a polyol or polyol mixture having an aromatic polyisocyanate at its end, provided that at least one of the isocyanate-terminated polyols has a hydroxyl group at its end. hydrophilic ethylene oxide homopolymer or copolymer whose ethylene oxide content is at least
(b) an aliphatic isocyanate present in an amount up to about 8% by weight of the prepolymer; (c) 6.5 for each mole of -NCO in the prepolymer
of a fluid-permeable hydrophilic polyurethane foam with a reduced amount of free aromatic amines, consisting of foaming a mixture of (a), (b) and (c) with ~390 moles of water; Manufacturing method. 2 The urethane prepolymer is obtained by the reaction between the -OH groups contained in monomeric alcohols and polyoxyethylene polyols having at least three hydroxyl groups per molecule and -NCO of aromatic isocyanates. a reaction product that is
The method according to claim 1, which has an aromatic isocyanate added to its terminal end. 3 -OH groups contained in the aliphatic alcohol and polyoxyethylene glycol in which the prepolymer has three hydroxyl groups per molecule;
3. The method according to claim 2, which is a reaction product obtained by the reaction between an aromatic isocyanate and -NCO, which has an aromatic isocyanate added to its terminal end. 4. The method according to claim 1, wherein the aliphatic isocyanate is 4,4'-methylenebiscyclohexyl diisocyanate. 5. The method according to claim 1, wherein the aliphatic isocyanate is isophorone diisocyanate. 6 Aliphatic isocyanate is bis(3-methyl-
4-Isocyanatocyclohexyl)methane. 7. The method according to claim 1, wherein the aliphatic isocyanate is tris(6-isocyanatohexamethylene)biuret. 8. The method according to claim 1, which comprises a step of drying the foam after producing the foam.