NL9401907A - Method for processing and preparing microcellular, elastomeric polyurethane, and products fabricated using microcellular, elastomeric polyurethane - Google Patents

Abstract

The invention relates to a method for processing microcellular, elastomeric polyurethane containing ester compounds by solvolysis with an alcohol in the presence of a base, to form a mixture of polyols, the solvolysis being carried out in the absence of oxygen and water in an enclosed apparatus. The invention also relates to a product, wholly or partially fabricated from microcellular, elastomeric polyurethane that has been prepared using a mixture of polyols.

Description

Process for the processing and preparation of microcellular elastomeric polyurethane, as well as product manufactured using microcellular elastomeric polyurethane.

This invention relates to a process for processing microcellular elastomeric polyurethanes containing ester bonds, and in particular residues and trimmings thereof, by solvolysis with an alcohol in the presence of a base to form a mixture of polyols.

In the description of the present invention, "scraps and trimmings" means scraps and trimmings released during the manufacture of polyurethane-containing products. Products containing polyurethane which do not meet the stated specifications are also included in these residues and trimmings.

A method of processing polyurethanes by solvolysis is known from U.S. Patent 4,316,992, which describes solvolysis with water as a solvolysis reagent to diamines, diols and carbon dioxide as a discontinuous process. This solvolysis with water as a solvolysis reagent can also be carried out continuously by means of an extruder, as described, for example, in the article by E. Gigat, Kunststoffe, 68 (1978) 281. However, these processes have the drawback that the diols they can be returned to the process, separate from the diamines. In addition, the diamines must first be converted into the corresponding diisocyanates before they can be used again for the preparation of polyurethanes.

Such a method is also known from the article by G. Bauer in Kunststoffe, 81 (1991) 301 *, in which an alcohol is used as solvolysis reagent in the presence of a catalyst, which catalyses saponification reactions. In this way, a mixture of mainly diols and low molecular weight polyurethanes is obtained from polyurethanes. If a diol is used instead of an alcohol, polyurethanes are formed which, in addition to a low molecular weight, have terminal hydroxyl groups. This chemical conversion of polyurethane containing ester bonds is shown schematically in Figure 1. Here R 1 represents a polyol residue, R 2 represents a polyester residue and R 3 represents the rest of the diol used as a solvolysis reagent.

[ Figure 1]

In particular, high-boiling diols obtained from ethylene oxide and propylene oxide are used as solvolysis reagent in such processes. However, these methods have the drawback that, sometimes carcinogenic, diamines are formed to a considerable extent as by-products, as described in the article by M. Kugler, Urethanes Technology, February / March 1994, p. 49 ·

When polyurethanes derived from bis (4-isocyanatophenyl) methane are subjected to solvolysis according to a prior art method, the solvolysis product contains 1,000 to 5,000 ppm of the carcinogenic bis (4-aminophenyl) methane, such as is described in the article by G. Bauer, Kunststoffe, 81 (1991) 301. Since the target value is 50 ppm, the solvolysis product can only be used in amounts of 1-5 wt. % are mixed with the polyol normally used for the production of polyurethanes.

Another drawback of the above-mentioned methods is that a solvolysis product is obtained, which can only be recycled in the preparation of hard PUR foams, as described in the Poly-urethane Handbook, G. Oertel (ed.), Carl Hanser Verlag , 1994, p. 664.

The object of the present invention is to find a solution to the above-mentioned problems. This object is achieved by a method as mentioned in the preamble, characterized in that the solvolysis is carried out in the absence of oxygen and water in a closed device.

In the description of the present invention, "in the absence of oxygen and water" is understood to mean a state where oxygen and water are each present in an amount of generally less than 10,000 ppm. Preferably, oxygen and water are each present in an amount of less than 1000 ppm, for example in an amount of 1 - 400 ppm.

In the description of the present invention, a "sealed device" is understood to mean a device in which reactants can be added, reacted, and from which the formed products can be removed, without the reactants, reaction mixture or products coming into contact with undesirable compounds, such as oxygen and water, which can give rise to undesired side reactions and / or by-products.

More particularly, the invention relates to a method for processing polyurethane rubber (PUR soft foam) soft foam residues and trimmings used in the manufacture of boots, soles, cushions and the like into a product, comprising a mixture of polyols. It has surprisingly been found that this product can be used in the preparation of polyurethanes, in particular soft PUR foam.

The hardness of PUR foams is determined by the ratio of polyol containing a short diol. Herein, the short diol component is considered as the hard part and the polyol component as the soft part. In the description of the present invention, soft PUR foams are understood to be polyurethanes in which the soft: hard ratio is less than or equal to 1: 2. Another feature of the PUR soft foam is that it was prepared from bis (4-isocyanatophenyl) methane, a polyester polyol of molecular weight over 2000, and 1,4-butane diol.

Previously, residues and trimmings were disposed of as chemical waste. Because the cost price of polyurethanes is high and, especially nowadays, the costs associated with the removal of chemical waste are increasing, a method has been sought to convert these residues and trimmings into a product that can be recycled in the preparation of polyurethanes.

The present invention provides a method of preparing a solvolysis product containing less than 1000 ppm, preferably less than 400 ppm, bis (4-aminophenyl) methane and which, mixed with the normally used polyol, can be used for the preparation made of soft PUR foam.

The presence of oxygen and water should not be too high, at least not more than 10,000 ppm, because oxygen gives rise to an unusable product, which is believed to be caused by oxidation and subsequent decomposition of the carbamate groups of the polyurethane. The presence of water gives rise to the formation of undesirably large amounts of bis (4-aminophenyl) methane. Therefore, the solvolysis is preferably in the presence of less than. 1000 ppm oxygen and less than 1000 ppm water, and in particular less than 400 ppm oxygen and less than 400 ppm water.

The solvolysis is preferably carried out in a closed device, such as an extruder, in the absence of oxygen and water.

The solvolysis is carried out at a temperature of 100-200 ° C, preferably 120-160 ° C, because higher temperatures lead to the formation of excessive amounts of bis (4-aminophenyl) methane.

The solvolysis is carried out under a pressure of 10-300 bar, preferably 40-80 bar, in order to prevent the formation of large amounts of bis (4-aminophenyl) methane.

The lead time in the extruder is 1-20 minutes, preferably $ -10 minutes, in order to prevent the formation of bis (4-aminophenylmethane) as much as possible. A short lead time is beneficial here, although for a full conversion the lead time must be sufficiently long. It is therefore preferable to carry out the solvolysis at a lower temperature and a longer run time than at a higher temperature and a shorter run time.

Solvolysis is performed in the presence of a diol, which has a molecular weight of less than * 100. For this, C2-C10 alkane diols, for example 1,4-butanediol, but also polyols, for example oligomers and polymers of ethylene oxide and propylene oxide such as diethylene glycol, triethylene glycol, dipropylene glycol, polypropylene glycol and the like, can be used. It is also possible to use triols, such as glycerol, or compounds containing four hydroxyl groups, such as pentaeritritol. Especially when cross-linked polyurethanes are desired, these triols and compounds containing four hydroxyl groups are very suitable.

A catalyst catalyzing saponification reactions can be added to accelerate solvolysis. However, this is not necessary because polyurethanes already contain a small amount of this. In principle, all bases, both inorganic and organic, can be used as catalyst. However, it is preferred to use bases that are homogeneously miscible or soluble in the reaction mixture, such as amines. The amines can contain 1-3 alkyl, alkaryl, arylalkyl or aryl groups. Tertiary amines are preferred. Examples are trialkylamines such as trimethylamine and triethylamine, trialkarylamines such as tri (4-tolyl) amine, triarylalkylamines such as tribenzylamine, triarylamines such as triphenylamines, but also tertiary amines such as diphenylmethylamine, dimethylphenylamine, dibenzylmethyl. The tertiary amines can also be mono- and dicyclic compounds containing one or more tertiary nitrogen atoms. Examples of such compounds are monocyclic compounds such as N-alkylpiperidines such as N-methylpiperidine, N-alkylpyrollidines such as N-methylpyrollidine, N-alkylindolines such as N-methylindoline, N, N-dialkylpiperazines such as N, N-dimethylpiperazine, Ν, Ν, Ν-triazacycloalkanes such as 1,4,7 "triazacyclononane, and the like. Examples of bicyclic compounds are 1,8-diazabicyclo [5 * - 0] undec-7-ene, 1,4-diazabi-cyclo [2.2.2 ] octane and 1,5-diazabicyclo [4.3 * 0] non-5-one In particular, 1,4-diazabicyclo [2.2.2] octane is used because polyurethanes already contain this tertiary amine in a small amount. therefore, it is not necessary to add an additional amount of this amine, although it is advantageous to do so, because then the reaction proceeds faster.

If desired, the solvolysis can be carried out in the presence of additives, solvents, agents that improve the rheology of the polyurethane, and the like, as are known in the art.

The product obtained by the process of the present invention is a mixture comprising polyols containing ester groups and polyols containing carbamate groups. This mixture can therefore be used without further purification, chemical treatment and or conversion for the preparation of polyurethanes (Figure 1).

The invention will be illustrated by the following examples.

Example I

Residues and trimmings, which may contain impurities such as steel, from boots made of polyurethane, which had been prepared from bis (4-isocyanatophenyl) methane and a polyester polyol of about 2500 molecular weight, were milled into particles using a granulator with a diameter of less than 5 mm. When present, the inorganic impurities, such as steel, were removed. After this, the material was mixed with 0.5 wt. Using a high-speed mixer (Papenmeyer). % 1,4-diazabicyclo [2.2.2] octane and 5 wt. % 1,4-butanediol, whereby a product with a molecular weight of about 2000 is obtained, to a physical solution, which is a dry free-flowing granulate, at a temperature of 50 ° C for 150 seconds. Then, the liquid was extruded at a temperature of 160 ° C and a pressure of 60 bar in a Boy type extruder having a fill volume of 25 cm 3 for 5 minutes. The pressure was maintained at the desired value by varying the size of the outflow opening and the speed of the screw. The solvolysis product was analyzed for the content of bis (4-aminophenyl) methane and 2-aminophenyl-4-aminophenyl methane as described below. It was found to contain 362 ppm of bis (4-aminophenyl) methane and 20 ppm of 2-aminophenyl-4-aminophenyl methane.

Determination of the content of bis (4-aminophenyl) methane and 2-aminophenyl-4-aminophenylmethane

The bis (4-aminophenyl) methane and 2-aminophenyl-4-aminophenyl methane content was determined using a Hewlett Packard HP 1090 liquid chromatograph equipped with a UV spectrophotometric detector, an injector of the type Rheodyne 7l6l and an integrator of the type Hewlett Packard 3392, or with a liquid chromatograph of the type Hewlett Packard HP 1050, which is equipped with a quaternary pumping system, an automatic system that exchanges and injects samples, a UV detector, which is a multiple wavelength can detect, and an HP 1 Chemstation. The analysis was performed with a Nucleosil Cl8 column (250 x 2 mm), which has a 5 µm particle size at either room temperature (HP 1090) or at 25 ° C (HP 1050). The column was protected by a 2 µm filter. The response factor of 2-aminophenyl-4-aminophenylmethane was believed to be that of bis (4-aminophenyl) methane.

For the analysis, a solution of the obtained polyol (solution A) and a reference solution (solution B) containing bis (4-amino-phenyl) methane were prepared. Solution A was obtained as follows: 1 g of the resulting solvolysis product was placed in a 20 ml volumetric flask and this was made up to the mark with a buffer solution, 1 composed of 55 parts by volume of methanol and 45 parts by volume of 0.002 M ammonium carbamate. The solution was then filtered using a syringe equipped with a PTFE filter with a pore diameter of 0.45 µm. Solution B was obtained as follows: 0.1 g of bis (4-aminophenyl) methane was placed in a 100 ml volumetric flask and made up to the mark with a buffer solution composed of 55 parts by volume of methanol and 45 parts by volume of 0.002 M ammonium carbamate. Then 1 ml of this solution was placed in a 100 ml volumetric flask and made up to the mark with the aforementioned buffer solution. Solution B was used to determine the response factor 1 of bis (4-aminophenyl) methane.

The eluent consisted of two solutions C and D. Solution C is composed of 55 parts by volume of 0.002 M ammonium carbamate, 45 parts by volume of methanol and three drops of triethylamine. Solution B is methanol and was fed to the liquid chromatograph according to the following gradient profile:

Samples of solutions A and B were inserted either manually with a 5 μΐ HPLC microinjection syringe (HP 1090) or automatically (HP 1050).

The absorption of UV light was measured at a wavelength of 230 nm using the UV detector.

The HP 3392 integrator was set as follows:

The HP Chemstation was set up as follows:

Example II

The experiment of Example I was repeated, except that 10 wt. % 1,4-butanediol was used to prepare a product with a molecular weight of about 1000. The solvolysis product contained 308 ppm of bis (4-aminophenyl) methane and 13 ppm of 2-aminophenyl-il-aminophenyl methane.

Example III

The solvolysis product was mixed with the polyol normally used in amounts such as those shown in Tables 1 and 2, after which polyurethane boots were made. The curing time and a number of physical properties were determined thereof; all values were corrected for density and are shown as relative values in Tables 1 and 2.

Table 1. Curing time

Table 2. Improvement of a number of physical properties

a Comply with specifications in accordance with NEN-EN No. 3 ^ 4 (NL standard 1993).

Regarding the curing time (Table 1), the best result is obtained when 10% by weight of the mixture of polyols obtained by the process of the invention is incorporated in the polyurethane.

With regard to the physical properties, without deterioration, even up to 15 wt. % of the polyol obtained by the process of the invention are incorporated in the polyurethane.

Claims (8)

A method of processing microcellular elastomeric polyurethane containing ester bonds by solvolysis with an alcohol in the presence of a base to form a mixture of polyols, characterized in that the solvolysis is carried out in the absence of oxygen and water in a closed establishment. Process according to claim 1 for the processing of polyurethanes containing bis (4-aminophenyl) methane, characterized in that a product is prepared which does not exceed 1000 ppm, preferably not more than 400 ppm bis (4 -aminophenyl) methane. Method according to claim 1 or 2, characterized in that the solvolysis in an extruder is carried out under conditions, wherein (a) the temperature is 100-200 ° C, (b) the pressure is 10-300 bar and (c) the lead time is 1-20 minutes. Method according to any one of claims 1-3. characterized in that (a) the temperature is 120-160®C, (b) the pressure is 40-80 bar and (c) the lead time is 5-10 minutes. Process according to any one of claims 1 to 4, characterized in that the base is a tertiary amine and the alcohol is a 2-26 alkanediol or polyol with a molecular weight of less than 400. Process according to claim 5, characterized in that the tertiary amine is 1,4-diaminobicyclo [2.2.2] octane and the alcohol is 1,4-butanediol. A process for the preparation of microcellular, elastomeric polyurethane from bis (4-isocyanatophenyl) methane and a mixture of polyols, characterized in that the mixture of polyols is the product obtained according to the process of any one of claims 1-6 in quantities up to 25% by weight, preferably up to 15% by weight! 8. Product wholly or partly manufactured from microcellular elastomeric polyurethane, prepared using a mixture of polyols obtained by the process of any one of claims 1-6.