NO134665B - - Google Patents

Description

Process for the production of polymeric materials.

The present invention relates to a

method for the production of polymeric materials, and more particularly foamed polymeric materials from polymers with hydroxyl end groups and organic polyisocyanates.

It has already been proposed to prepare polymeric materials by reaction of organic polyisocyanates with hydroxyl-containing materials, e.g. polyesters, polyesteramides and polyethers, and to modify the reaction e.g. by adding water in order to produce inflated, cell-shaped polyurethane materials.

In the production of foamed polyurethane materials in this way, an available method involves allowing hydroxyl-containing materials in a single-step process to react with organic polyisocyanates and water, if necessary in the presence of catalysts, surface-active agents or other aids, whereby it takes place a simultaneous reaction between the isocyanate, water or the hydroxyl-containing material so that a foamy product is obtained. Alternatively, the hydroxyl-containing material can be reacted with sufficient polyisocyanate to give an intermediate reaction product containing isocyanate groups, and this product can then be reacted with water, if desired in the presence of catalysts, surfactants or other auxiliaries to produce the finished foamed product.

Although a single-step process is more

desirable from both technical and economic considerations, it has so far been shown that the production of satisfactory foam

mete products by this method is difficult and in some cases impossible, especially when the hydroxyl-containing materials used are polyethers, e.g. polypropylene glycol. These difficulties seem, at least in part, to be explained by the lower reactivity towards polyisocyanates of secondary hydroxyl end groups, which are present in such polyethers, in contrast to the higher reactivity of the primary hydroxyl-containing end groups which are usually present in the polyesters used for preparation of elastic foam. The addition to the reaction mixture of tertiary amines, e.g. dimethylcyclohexylamine and dimethylbenzylamine, which are used to a large extent in the technique as catalysts in the production of foamed polyurethane products, do not, however, act in such a way that they accelerate the reaction of polyethers containing many secondary hydroxyl end groups to a sufficient extent to enable the production of satisfactory foams.

We have now found that it is possible to carry out this simultaneous reaction of polymers with hydroxyl end groups, polyisocyanate and water very easily, and to produce a satisfactory foam when a substituted 4-aminopyridine is present as a catalyst. The new catalysts are remarkably efficient, and their use produces foams of excellent physical properties in an expedient and economical manner. Similar results cannot be obtained when using even larger quantities of the tertiary amines, such as e.g. dimethylcyclohexylamine and dimethylbenzylamine, which are usually used as catalysts in the previously known methods.

In accordance with the foregoing, the invention concerns a method for the production of polyurethane materials by reaction of an organic polyisocyanate and a hydroxyl-containing material, and the method is characterized in that the reaction is carried out in the presence of a catalyst consisting of pyridine, which in the 4-position is substituted with a nitrogen atom, to which two radicals are attached, which may optionally be members of a heterocyclic ring.

Thus, N-substituents can be substituted or unsubstituted radicals, which can be hydrocarbon radicals or radicals containing a hetero atom in a carbon chain. The nitrogen in 4-aminopyridine can form a ring in association with a difunctional substituent radical.

The N-substituents can e.g. be alkyl groups, especially lower alkyl groups, e.g. methyl, ethyl, propyl and butyl groups, cycloalkyl groups, e.g. cyclopentyl and cyclohexyl groups, aralkyl groups, e.g. benzyl and phenylethyl, unsaturated aliphatic radicals, e.g. alkyl and pentenyl and difunctional radicals, e.g. alkylene radicals such as tetramethylene and pentamethylene, or difunctional radicals comprising fully saturated chains having as members at least 4 carbon atoms together with a hetero atom such as oxygen or nitrogen atom, e.g. the difunctional radicals which, in union with the nitrogen atom in the 4-aminopyridine, form morpholine and piperazine rings.

The N-substituents can themselves carry substituting radicals, e.g. alkyl and dialkyl amino groups, where the alkyl groups e.g. can be methyl, ethyl, propyl and butyl groups.

As examples of fully N-substituted 4-aminopyridines that can be used in the method according to the invention, mention should be made of N:N-dimethyl-4-aminopyridine, N:N-diethyl-4-aminopyridine, N-ethyl-N-methyl-4- aminopyridine, N-allyl-N-methyl-4-aminopyridine, N-pentenyl-N-methyl-4-aminopyridine, N-allyl-N-cyclohexyl-4-aminopyridine, N:N-di-n-hexyl-4- aminopyridine, N:N-dicyclohexylaminopyridine, 4-(N-pipe-ridino)-pyridine, 4-(N-pyrrolidine)-pyridine, 4-(N-morpholine)-pyridine, N:N-bis ((5- dimethylaminoethyl)-4-aminopyridine, N-((3-dimethylaminoethyl)-N-ethyl-4-aminopyridine and N-(|3-N'-pyrrolidineethyl)-N-methyl-4-aminopyridine.

It is also possible to use completely N-substituted 4-aminopyridines which contain substituents in the 3- and/or 5-positions of the pyridine ring, e.g. short chain alkyl groups, or amino groups which are fully substituted with short chain alkyl groups containing 1 to 6 carbon atoms, with cyclic alkylene groups or with piperidine or morpholine groups. If desired, compounds containing more than one completely N-substituted 4-aminopyridine residue can also be used, e.g. N:N'-bis(4-pyridyl)-N:N'-dimethyl-propylenediamine, N:N'-bis(4-pyridyl)-N:N'-dimethylethylenediamine, N :N'-bis (4-pyridyl ) -N:N'-dimethylhexamethylenediamine, N:N'-bis-(4-pyridyl)-N:N'-dimethyl-(3 :p'-diaminodiethylether, N:N'-bis(4-pyridyl) -N: N'-dimethyl-1:4-diaminocyclohexane, N-(4-pyridyl)-jN'-methylpiperazine and N:N'-bis(4i-pyridyl)-piperazine.

The fully N-substituted 4-aminopyridines which are specifically mentioned above are examples of types of a compound which can be used in the method according to the invention. Other examples thus include 4-aminopyridines which carry different pairs of N-substituents selected from the already mentioned N-substituents.

Particularly advantageous results are obtained by the method according to the invention, if N:N-dimethyl-4-aminopyridine and 4-(N-pyrrolidine)-pyridine are used as catalyst.

The amounts of the fully N-substituted 4-aminopyridine to be used may be between 0.01 and 5%, and preferably between 0.5 and 2.5% by weight of the hydroxyl-containing material. Larger or smaller quantities can be used if desired, but larger quantities need not lead to any further benefit and smaller quantities will be able to produce an effect that is unsatisfactory for most technical requirements. However, the optimal amounts will necessarily depend to a significant extent on the particular reaction components and the conditions used.

The method according to the invention can be used for the production of any kind of polyurethane products, whether these are solid or elastic, cellular or homogeneous, and in the form of coatings, shaped articles and the like, but it is particularly advantageous for use in the production of foamed polyurethane products by the simultaneous reaction of the hydroxyl-containing material, isocyanate and water, especially when the hydroxyl-containing material is a polyether.

The starting materials to be used in the method according to the invention are those which are described to a large extent in the known literature regarding the production of polyurethane products.

In particular, suitable polyisocyanates include aliphatic diisocyanates such as hexamethylene diisocyanate, aromatic diisocyanates such as tolylene diisocyanates, diphenylmethane-4:4'-diisocyanate, 3-methyldiphenylmethane-4:4'-diisocyanate, m- and p-phenylenediisocyanate, chlorophenyl-2:4 '-diisocyanate and cycloaliphatic diisocyanates such as dicyclohexylmethane diisocyanate. Triisocyanates that can be used include aromatic triisocyanates such as, for example 2:4:6-triisocyanate toluene and 2:4:4'-triisocyanate diphenyl ether. Other polyisocyanates that can be used include polymers of tolylene-2:4-diisocyanate and polyisocyanate preparations containing diarylmethane diisocyanate as the main component and at least 5% by weight of polyisocyanate with a functionality greater than two, produced e.g. by phosgenation of the corresponding diamines or depolyamine products obtained by condensing formaldehyde with aromatic amines. Mixtures of polyisocyanates can be used.

Any hydroxyl-containing material containing at least two hydroxyl groups per molecule, can be used, in particular polyester, polyether or polyesteramide.

The polyesters or polyesteramides are prepared essentially from dicarboxylic acids and glycols and, if necessary, diamines or amino alcohols. Suitable dicarboxylic acids include succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid and sebacic acids as well as aromatic acids such as phthalic acid, isophthalic acid and terephthalic acid. Mixtures of acids may be used. Examples of glycols are ethylene glycol, 1:2-propylene glycol, >1:3-butylene glycol, diethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, decamethylene glycol and 2:2-dimethyltrimethylene glycol. Mixtures of glycols can be used and polyhydric alcohols such as trimethylolpropane, pentaerylthritol or glycerol can be introduced in varying amounts according to the desired firmness or stiffness of the products. Examples of diamines and amino alcohols include ethylenediamine, hexamethylenediamine, monoethanolamine, phenylenediamines and benzidine.

Examples of polyethers for use in the method according to the invention include polymers and copolymers, with hydroxyl end groups, of cyclic ethers and in particular of ethylene oxide, epichlorohydrin, 1:2-propylene oxide, 1:2-butylene oxide or other alkylene oxides, oxacyclobutane and substituted oxacyclobutanes , and tetrahydrofuran. Such polyethers can be linear polyethers, which are produced e.g. by polymerization of an alkylene oxide in the presence of a glycol initiator. Alternatively, branched polyethers produced, for example, can be used. in the polymerization of an alkylene oxide in the presence of a substance with more than two active hydrogen atoms, e.g. glycerol, pentaerythritol and ethylenediamine. Mixtures of linear and branched polyethers or mixtures of polyesters and polyethers can be used if desired.

Particularly useful are polyethers which are polymers of 1:2-propylene and 1:2-butylene oxides.

It is preferable to use a hydroxyl-containing material, where the hydroxyl groups are predominantly secondary hydroxyl groups, as this achieves the most valuable and surprising technical results, namely the extraordinary ease with which satisfactory foaming takes place. The method according to the invention can also be used to advantage with hydroxyl-containing materials that contain predominantly primary hydroxyl groups, the specified amines are, however, much more effective, less basic and less volatile than ordinary tertiary amines, and therefore exhibit no odor at normal temperatures, and favors the catalysis of the polyisocyanate/hydroxyl group reaction. Examples of compounds containing predominantly secondary hydroxyl groups are polypropylene diols with a molecular weight of 500 to 2,000, which are obtained by polymerizing propylene oxide using a basic catalyst and either water or a simple glycol as initiator. The polypropylene triols and polyols are obtained in a similar way using as initiators either simple triols such as glycol or triethanolamine, or compounds with higher functionality such as ethylenediamine, mannitol or sucrose.

The reaction between the polyisocyanate, the hydroxyl-containing material and any water used can be carried out in a continuous or discontinuous manner using previously known methods for the production of polyurethane products. The reaction can be modified if desired by introducing other ingredients and known aids including other catalysts for the urethane-forming reaction either of a basic nature (e.g. other tertiary amines such as dimethylcyclohexylamine and basic inorganic compounds such as potassium carbonate, potassium acetate and potassium naphthenate) or non-basic metal catalysts, e.g. mangano- and manganese-acetyl-acetonates and dialkyltin compounds, e.g. di-n-butyltin dilaurate, non-ionic surfactants, salts of sulfuric acid derivatives, of high molecular weight, of organic compounds, silicone oils, foam stabilizers, e.g. ethylcellulose, low-molecular polyhydroxy compounds such as e.g. trimethylolpropane, pigments, dyes, plating agents, e.g. dialkyl phthalates and flame retardants, e.g. tri-((3-chloroethyl)-phosphate or antimony compounds, "blowing agents" such as volatile haloalkanes, e.g. fluorotrichloromethane or mixtures thereof.

The catalysts used in the invention are generally low-melting solids, which are easily soluble either in water or the hydroxyl-containing material, and which do not possess any malodorous or other undesirable properties.

The invention shall be clarified by a number of examples, where parts and percentages are by weight.

Example 1:

30 parts linear polypropylene glycol of molecular weight 1930, 17.5 parts 80:20 mixture of tolylene 2:4 and 2:6 diisocyanates, 0.50 parts 4-dimethylaminopyridine, 0.5 parts of the condensation product of octylphenol with 10 molecular parts of ethylene oxide, 0.37 parts of the sodium salt of sulfated methyloleate and 1.2 parts of water are vigorously mixed together. The foaming and still liquid reaction mixture is poured into a mold, where it is allowed to remain without the addition of heat from the outside.

The product is an elastic foam of low density and with good physical properties.

Repetition of the procedure according to the above-mentioned example, except that the 0.5 parts of 4-dimethylaminopyridine are replaced by an equal amount of dimethylbenzylamine, dimethylcyclohexylamine, N-methylmorpholine or N-ethylpiperidine gave no foamy product. Unusable results were also obtained when the amount of these amines was increased. In each case a vigorous reaction took place, but the foam either did not rise or collapsed.

Example 2: The procedure according to example 1 is repeated, except that the 4-dimethylamino-pyridine is replaced by an equal weight of 4-(N-piperidine)-pyridine. The results obtained are the same as described in example 1.

Example 3: The procedure according to example 1 again taken, except that 4-dimethylaminopyridi- net is replaced by an equal weight of 4-(N-morpholine)-pyridine. The results obtained are the same as described in example 1.

Example 4: The procedure according to example 1 is repeated, except that the 4-dimethylaminopyridine is replaced with a mixture of 0.25 parts of di-n-butyltin dilaurate and 0.25 parts of 4-dimethylaminopyridine. The results obtained are the same as described in example 1.

Example 5: The procedure according to example 1 is repeated, except that the 4-dimethylaminopyridine is replaced by an equal weight of 4-(N-morpholine)-pyridine. The results obtained are the same as those described in Example 1.

Example 6:

A solution of 1.4 parts of 4-dimethylaminopyridine in 3 parts of water and 1.2 parts of an alkyl-silane-polyoxyalkylene copolymer is stirred gently in 100 parts of a linear polypropylene glycol of approximate molecular weight 2,000 until a clear solution is obtained. 40 parts of an 80:20 mixture of tolylene-2:4-diisocyanate and tolylene-2:6-diisocyanate are added and the mixture is stirred vigorously for 5 seconds, and poured into a mold. An elastic foam of fine structure and a specific gravity of 0.04 g/ml is obtained.

Example 7:

0.2 parts of 4-dimethylaminopyridine and 0.5 parts of dimethylbenzylamine are dissolved in 4.7 parts of a solution obtained from 50 parts of the reaction product of 1 mol of octylphenol with 8 mol of ethylene oxide, 34 parts of the sodium salt of sulphated methyloleate and 151 parts of water. The resulting mixture is stirred into 100 parts of a linear polypropylene glycol of approximate molecular weight 2,000, and a solution of 1 part of a methyl-phenylpolysiloxane containing 3 methyl groups to each phenyl group and having a viscosity of 120 centistokes at 25° C., in 42.5 parts of an 80:20 mixture of tolylene-2:4-diisocyanate and tolylene-2:6-diisocyanate. At the beginning of the foaming, the mixture is poured into a mold. A foam is obtained with a specific gravity of 0.030 g/ml and a compression modulus of 25.7 g/ml at 40% compression. When heated to 125° C for 2 hours, the compression modulus increases slightly to 27.3 g/ml.

Example 8: The preparation described in example 7 is repeated, with the 4-dimethylaminopyridine being replaced with 0.2 parts of 4-piperidine-pyridine, the dimethylbenzylamine being replaced with 0.7 parts of N-methylmorpholine and the polypropylene glycol being replaced with 100 parts of a glycerol/propylene oxide reaction product of approximate molecular weight 3,000. An elastic foam of a specific gravity of 0.033 g/ml with a compression modulus of 33.5 g/ml and 40% compression is obtained. The compression hardening after heating for 22 hours at 70° C under 50% compression is 5.9%.

Example 9: The preparation described in Example 7 is repeated, with the 4-dimethylaminopyridine being replaced by 0.2 parts of 4-diethylaminopyridine and the polypropylene glycol being replaced by 100 parts of a glycerol/propylene oxide reaction product of approximate molecular weight 3,000 An elastic foam of specific gravity 0.034 g/ml with a compression modulus of 20.3 g/ml at 40% compression is obtained.

Example 10:

1 part of 4-dimethylaminopyridine and 0.2 parts of 1-dimethylamino-Æ-ethoxypropane are dissolved in a solution of 1.5 parts of alkyl-silane-polyoxyalkylene copolymer in 3.7 parts of water. This solution is carefully stirred into a mixture of 71 parts of a linear polypropylene glycol of approximate molecular weight 2,000 and 71 parts of a triol of approximate molecular weight 3,000, which is obtained by the reaction of glycerol and propylene oxide. 51.2 parts of an 80:20 mixture of tolylene-2:4-diisocyanate and tolylene-2:6-diisocyanate are added to this mixture with vigorous stirring. When the foam begins to form, the mixture is poured into a mold. An elastic foam of specific gravity 0.043 g/ml is obtained.

Example 11:

The high catalytic activity of the catalyst which forms the object of the present invention shall be clarified by their use in the following varnish preparation. A mixture of cyclohexanone and methyl ethyl ketone (1:4 by volume) is prepared and 124 parts of this mixture is stirred with 52 parts of a polyester (made from a mixture of glycerol, ethylene glycol and adipic acid in the molar ratio 1:3:3), until a clear solution is obtained. To this solution are added 20.8 parts of tolylene-2:4-diisocyanate in 20 parts of a cyclohexanone/methyl ethyl ketone mixture of the same composition, and the resulting clear solution is allowed to stand for 21 hours. A solution of 0.04 parts of each of the following tertiary amines in 2 parts of the same cyclohexanone/methyl ethyl ketone mixture is added with stirring to 42 parts of a polyester/polyisocyanate/solvent mixture, prepared as described above. The time taken by the mixture to form a gel is listed for comparison in the following table.

The lacquer system gelatinizes after approx. 200

hours in the absence of a catalyst.

The 4-N-pyrrolidinepyridine used in this example is prepared by the action of 12.4 parts of pyrrolidine hydrochloride on 10 parts of 4-phenoxypyridine at 210 to 220°C

for 3 hours. The product is obtained by making the mixture basic with eth-alkali liquid followed by steam distillation and extraction of the distillate with petroleum ether (boiling point 40 to 60° C). Recrystallization of the 5.2 parts of the white solid extract from petroleum ether (boiling point 30 to 40° C) gives colorless flakes which melt at 62 to 63° C, and which contain 73.2% carbon, 8.2% hydrogen and 18.9% nitrogen (C9H12N2 requires C = 73%, H = 8.1%, and N = 18.9%).

The picrate of this product melts at 149 to 150°C and contains 47.7% carbon, 4.1% hydrogen and 18.7% nitrogen. (C15H15 N5O7 requires C = 47.8%, H = 4.0%, N = 18.6%).

Example 12:

100 parts of liquid polyester prepared from 1460 parts of diethylene glycol, 68 parts of pentaerythritol and 1898 parts of adipic acid and having a viscosity at 25°C of 145 poise, a hydroxyl value of 65 mg KOH/g and an acid value of 4.5 mg KOH/ g is mixed with 46.7

portions of a 65:35 mixture of tolylene-2:4-

diisocyanate and tolylene-2:6-diisocyanate until a clear solution is obtained. Add immediately under vigorous stirring and the mixture is poured into a mould. An elastic foam with a fine structure and a low specific gravity is quickly obtained.

Example 13: To 100 parts by weight of a polyester prepared from 0.66 parts of pentaerythritol, 2.44 parts of butane-1:3-diol, 2.0 parts of adipic acid and 0.33 parts of phthalic anhydride are added 4 parts of water, 2 parts of an alkyl -silane-polyoxy-alkylene copolymer, 15 parts (3-trichloro-ethyl phosphate and 6 parts of a solution containing 2 parts of 4-dimethylaminopyridine in 4 parts of water. The components are mixed thoroughly. 180 parts of a diphenylmethane diisocyanate preparation are added and the whole is mixed for 1 min with a high-speed stirrer. The mixture is poured into a mould, where the foaming takes place, so that a solid cellular structure with an exceedingly fine structure and a specific weight of about 0.04 kg is obtained / liter.

The diphenylmethane diisocyanate preparation used in this example is prepared by phosgenerating a crude diaminodiphenylmethane containing approx. 15% polyamines (mainly triamines) obtained by condensing formaldehyde with aniline in the presence of hydrochloric acid.

Example 14: To 100 parts by weight of a branched propylene oxide polymer produced by reaction of propylene oxide with a trihydric alcohol and with an approximate molecular weight of 450, 1.5 parts of 4-dimethylaminopyridine are added and the mixture is heated at 80°C for 1 hour. The resulting solution is cooled, 0.75 parts of an alkyl-silane-polyoxyalkylene copolymer is added and 50 parts of monofluorotrichloromethane is mixed with the mixture. 110 parts of the diphenylmethane diisocyanate preparation used in example 13 are added and the mixture is stirred rapidly using an efficient stirrer for 30 seconds. The mixture is poured into a mold and foamed so that a fine firm cell-shaped structure with a specific gravity of 0.024 kg/litre is obtained.

Claims (4)

1. Process for the production of polyurethane materials by reaction of an organic polyisocyanate and a polymeric hydroxyl-containing material, characterized in that the reaction is carried out in the presence of a catalyst consisting of pyridine which is substituted in the 4-position with a nitrogen atom to which two radicals are attached, which optionally may be members of a heterocyclic ring. 2. Process for the production of polyurethane materials as stated in claim 1, characterized in that the reaction is carried out in the presence of N:N-dimethyl-4-aminopyridine or 4-(N-pyrrolidine)-pyridine as catalyst. 3. Process for the production of polyurethane materials as stated in claim 1 or 2, characterized in that the amount of the completely N-substituted 4-aminopyridine used is between 0.01 and 5% by weight, preferably between 0.05 and 2.5% by weight of the hydroxyl-containing material. 4. Process for the production of polyurethane materials as stated in one of the preceding claims, characterized in that the -hydroxylinne-containing material is a polymer of hydroxyl group-containing 1:2-propylene oxide or 1:2-butylene oxide.