PL248565B1 - Method for obtaining a flexible and foamed polyurethane-rubber composite and a flexible and foamed polyurethane-rubber composite - Google Patents

Description

The invention is a flexible, foamed polyurethane-rubber composite with desirable properties, containing rubber crumb from post-consumer car tires, and a method for obtaining a flexible, foamed polyurethane-rubber composite containing rubber crumb from post-consumer car tires. The invention finds particular application in the production of construction materials, carpet underlays, damping mats, and other products designed to dampen acoustic and mechanical vibrations. In the description of the invention, the word "foamed" describes the material's structure, as opposed to the word "solid," indicating the presence of pores in the material's structure. The word "elastic" refers to the material's mechanical properties and is consistent with the commonly accepted classification of foamed polyurethanes into flexible and rigid.

Tires are typically a consumable part of a car, so regular replacement is necessary, which, for relatively economical driving, occurs on average every three years. According to literature data from the Europe Tire Recycling Market Analysis Report \ 2021 Edition \ 2019-2035 \ Industry Insights, available at https://www.goldsteinresearch.com/report/europe-tire-recycling-market-industry-analysis-growth-outlook, nearly 3.3 million tons of car tires are retired annually in Europe. Due to their quantity and durability (their degradation time in the natural environment is estimated at over 100 years), used car tires are a nuisance and should be used industrially. Due to the global problems with the management of post-consumer tires, their recycling has been a very popular research topic for many years. Due to their chemical composition and cross-linked structure, tire recycling is significantly more difficult than recycling thermoplastics, which constitute the primary waste product of the packaging industry. Used tires are generally divided into three main groups: partially used (with tread depths exceeding the minimum), used tires suitable for retreading, and worn-out tires. It is the latter group that should be recycled. Currently, landfilling used car tires is prohibited, so their recovery and recycling is mandatory. Tire recycling can be divided into two types based on the specific technology: material recycling and energy recovery. Material recycling is the most preferred form and involves processing tires into products with useful value. Proper selection of the composition, processing method, and processing parameters allows for high-yield, high-quality secondary materials. One of the main methods of material recycling is granulation, which shreds tires into granulate, commonly known as rubber crumb. Energy recovery involves incinerating rubber waste and partially recovering the energy used to produce it. However, it only recovers up to 40% of the energy used to produce new tires, making it not the preferred method of managing this waste. In European Union countries, material recycling is the primary method for managing used car tires. Although literature data from the aforementioned report indicate that approximately 75% of used car tires in Europe are granulated, effectively managing the resulting rubber crumb remains a challenge.

Currently, recycled car tire materials are used as fillers in the construction of tunnels, road surface layers, sports surfaces, as well as for the production of car mats, doormats, cattle mats, and as asphalt modifiers, as described in Formela, K. (2021). Sustainable development of waste tire recycling technologies - recent advances, challenges, and future trends. Advanced Industrial and Engineering Polymer Research, 4(3), 209-222. However, these applications still do not guarantee sufficient demand for processed rubber waste. Therefore, a great deal of research is currently being conducted to identify potential applications for rubber crumb, including in the plastics industry. The production of composite materials seems to be the most promising research direction due to the multitude of potential applications for polymer-rubber products. To date, rubber crumb has been used as a filler in composites based on polyolefins, acrylic polymers, vinyl polymers, polyesters, and rubber. Methods for incorporating rubber crumb into these matrices are known.

Patent descriptions US6558773 and US6703440 describe products obtained by mixing rubber waste with a polymer binder such as poly(ethylene-co-vinyl acetate), low density polyethylene or high density polyethylene, and extruding the obtained compositions and then compression molding them into the desired form.

Patent description EP2868453 describes a method of utilizing rubber waste, including that from post-consumer car tires, in the process of producing polymer composites containing from 26 to 80% of rubber waste and from 1 to 8% of a compatibilizer aimed at improving the adhesion between the rubber waste and the polymer matrix, which is polypropylene, polyethylene, thermoplastic elastomer or polyester.

Patent EP2143755 describes a method for producing materials containing waste thermosetting materials, preferably rubber crumb, and waste in the form of acrylic or vinyl polymer emulsions. By adding polymer emulsions, the material can be processed as a thermoplastic material.

Methods for obtaining polyurethane-rubber composites based on a solid, non-foamed polyurethane matrix are also known.

Patent description WO2009013598 describes a method for the simultaneous recycling of rubber waste, including waste from post-consumer car tires, and polyurethane waste in the form of granulates through a pressing process at a temperature in the range of 100-280°C and under pressure of 5-80 atm. A disadvantage of this solution is the non-foamed structure of the resulting materials, which significantly limits their use as thermal or acoustic insulation materials.

Patent descriptions US6896964 and US6821623 describe products obtained by recycling rubber waste, including waste from used car tires, in the form of granules by combining it with a single- or two-component polyurethane resin and cross-linking the prepared mixture. The process of obtaining the materials according to this method consists of two stages. The first stage involves treating the rubber waste with polyurethane resin, added at a rate of 1-2%. The second stage involves mixing the modified rubber waste obtained in the first stage with polyurethane resin, added at a rate of 1-20%, and pressing it under pressure. A disadvantage of this solution is the non-foamed structure of the resulting materials, which significantly limits their potential use as thermal or acoustic insulation materials.

Patent description CN101629025 describes products obtained by recycling plastic and rubber waste, including waste foamed thermosetting plastics, rubber waste, and powdered waste from epoxy resin grinding. A disadvantage of this solution is the non-foamed structure of the resulting materials, which significantly limits their potential use as thermal or acoustic insulation materials.

The known patents mentioned above do not concern polyurethane foams, but other materials. Rubber waste, including rubber dust, can be used as a filler for various plastics, and such solutions are known, but no literature was found concerning polyurethane foams, but for other materials.

Polyurethane foams are a very broad group of materials that can be most simply divided into rigid and flexible foams. The first group comprises foams primarily used as thermal insulation materials. The most important aspect is achieving the appropriate cellular structure, which ensures the lowest possible thermal conductivity coefficient. Adding rubber powder to rigid polyurethane foams could positively impact the thermal insulation properties of the final product due to the lower thermal conductivity coefficient of rubber compared to solid polyurethane (-160 and -220 mWZ(m-K)). However, achieving this effect would require appropriate adjustment of the cellular structure, which is not simple and is not known.

Solutions for obtaining foamed flexible polyurethane-rubber composites with rubber powder based on a flexible polyurethane foam matrix have been published so far in the form of scientific articles.

From the work - Hejna, A., Olszewski, A., Zedler, Ł., Kosmela, P., Formela, K. (2021). The Impact of Ground Tire Rubber Oxidation with H2O2 and KMnO4 on the Structure and Performance of Flexible Polyurethane/Ground Tire Rubber Composite Foams. Materials, 14, 499, a method for obtaining foamed polyurethane-rubber composites based on a flexible polyurethane foam matrix is known. According to the method, composites produced by the single-stage method contain 20% by weight of modified rubber powder. The disadvantage of this solution is the use of previously chemically modified rubber powder and the resulting disturbances in the cellular structure of the flexible polyurethane foam matrix, which is unfavorable, as well as a reduction in thermal stability compared to the flexible polyurethane foam matrix resulting from the introduction of chemically modified rubber powder.

From the work - Kosmela, P., Olszewski, A., Zedler, Ł., Burger, P., Piasecki, A., Formela, K., Hejna, A. (2021). Ground Tire Rubber Filled Flexible Polyurethane Foam - Effect of Waste Rubber Treatment on Composite Performance. Materials, 14, 3807, a method for obtaining foamed polyurethane-rubber composites based on a flexible polyurethane foam matrix is known. According to the method, composites produced by the single-stage method contain 20% by weight of rubber powder. A disadvantage of this solution is the use of rubber powder previously thermomechanically modified in a twin-screw extruder with or without the addition of vegetable oils, which leads to worse parameters of the resulting composite.

From the work of Zhang, X., Lu, Z., Tian, D., Li, H., Lu, C. (2012). Mechanochemical devulcanization of ground tire rubber and its application in acoustic absorbent polyurethane foamed composites. Journal of Applied Polymer Science, 127(5), 4006-4014, a method for obtaining foamed polyurethane-rubber composites based on a flexible polyurethane foam matrix is known. According to the method, composites produced by the single-stage method contain from 10 to 30% by weight of modified rubber powder. A disadvantage of this solution is the use of thermomechanically modified rubber powder. Another disadvantage of this solution is the disruption of the cellular structure of the flexible polyurethane foam matrix, leading to an increased average pore size observed when using rubber powder. A larger pore diameter leads to a deterioration of thermal insulation properties, which is a well-known relationship.

From the work of Shan, C.M., Idris, M., Ghazali, M.I. (2012). Study of Flexible Polyurethane Foams Reinforced with Coir Fibers and Tire Particles. International Journal of Applied Physics and Mathematics, 2(2), 123-130, a method for obtaining foamed polyurethane-rubber composites based on a flexible polyurethane foam matrix is known. According to this method, foamed polyurethane-rubber composites based on a flexible polyurethane foam matrix are produced using a single-stage method. A disadvantage of this method is the very low content of rubber powder in the composite, amounting to only 2.5% by weight, which is associated with the need to use at least 97.5% by weight of the flexible polyurethane foam matrix and does not allow for a noticeable reduction in material costs resulting from the use of waste rubber powder as a filler.

From the work of Gayathri, R., Vasanthakumari, R., Padmanabhan, C. (2013). Sound Absorption, Thermal, and Mechanical Behavior of Polyurethane Foam Modified with Nano Silica, Nano Clay, and Crumb Rubber Fillers. International Journal of Scientific & Engineering Research, 4(5), 301-308, a method for obtaining foamed polyurethane-rubber composites based on a flexible polyurethane foam matrix is known. According to this method, foamed polyurethane-rubber composites based on a flexible polyurethane foam matrix are produced in a single-stage method. A disadvantage of this method is the very low content of rubber crumb in the composite, amounting to only 2% by weight, which is associated with the need to use at least 98% by weight of the flexible polyurethane foam matrix and does not allow for a noticeable reduction in material costs resulting from the use of waste rubber crumb as a filler. Another drawback of this solution is the disruption of the cellular structure of the flexible polyurethane foam matrix, which leads to an increase in the average pore size due to the introduction of rubber powder into the flexible polyurethane foam matrix. This effect may be related to the insufficient viscosity of the reaction mixture, resulting from the polyol components used or from the low rubber powder content.

In summary, composites based on rigid and flexible polyurethane foams, including a foamed, flexible polyurethane matrix, can be obtained by a single-step or two-step method (i.e., a prepolymer method, which involves prepolymer preparation). The production of foamed, flexible polyurethane-rubber composites using a single-step method is known, as described in the aforementioned scientific articles. The described foamed polyurethane-rubber composites are only obtained by a single-step method, which, as noted during the development of the invention, has certain disadvantages. According to available literature data, the prepolymer method is used and advantageous in the case of increased viscosity of the reaction mixture, which may result from the chemical structure of the components used or the introduction of particulate filler into the matrix. The aforementioned works on the preparation of foamed, flexible polyurethane-rubber composites based on a flexible polyurethane foam matrix indicated a significant increase in the viscosity of the reaction mixture resulting from the introduction of rubber particles. As a result, disruptions in the cellular structure of the flexible polyurethane foam matrix were observed, leading to deterioration of the material's mechanical and thermal insulation properties. An additional drawback of the solutions described in the cited scientific publications was the use of a modified rubber component.

Therefore, the search continues for methods for obtaining polyurethane composites based on polyurethane foam and rubber material, particularly post-waste rubber, with improved and more desirable properties, as indicated above and described below. Methods for obtaining such materials are also sought, leading to composites with better properties than those found in known materials of this type, such as reduced composite pore size, which translates into improved thermal and acoustic insulation properties. The aim is for composites to have a reduced thermal conductivity coefficient, increased thermal stability, and increased sound absorption coefficient, which offers good application potential.

This was the goal of the invention. The invention therefore concerns improving the properties of polyurethane-rubber composites and the use of flexible foams in the composite, primarily due to their multitude of applications. Flexible polyurethane foams are widely used in the furniture, automotive, construction, and packaging industries. They are used in products where material cost is often a key consideration, so using relatively inexpensive rubber powder could reduce the material's cost and significantly increase its attractiveness to potential buyers.

According to the invention, it was intended to introduce rubber powder into flexible polyurethane foams, among other things, to improve the cellular structure, improve thermal insulation properties, and improve damping properties towards acoustic vibrations.

Considering the above-described drawbacks of using known methods, particularly the single-step method for producing flexible, foamed polyurethane-rubber composites, and their drawbacks. Furthermore, due to the lack of a recipe or description of a method for producing flexible, foamed polyurethane-rubber composites containing rubber crumb from post-consumer car tires in the available literature, including a two-step method, research was undertaken in this area. The focus was, among other things, on developing a prepolymer method tailored to the specific conditions and substrate. Unexpectedly, it turned out that producing composites from polyurethane foam and rubber crumb according to the invention using the two-step method offers significant benefits. This resulted in a reduction in pore size, which positively impacted the thermal insulation properties and acoustic vibration damping properties of polyurethane-rubber composites based on a foamed, flexible polyurethane matrix. Unlike known solutions in this field of composites, foamed polyurethane-rubber composites with the features of the invention are not known. The indicated publications/articles describe other polyurethane-rubber composites and other methods for producing such composites.

The flexible and foamed polyurethane-rubber composite containing rubber powder from post-consumer tires, especially car tires, and polyurethane foam is characterized according to the invention in that it contains an elastic matrix in the form of flexible polyurethane foam in the amount of 83.50-95.50% by weight in relation to the entire polyurethane-rubber composite and rubber powder with an average particle size of less than 0.7 mm from post-consumer tires in the amount of 4.50-16.50% by weight in relation to the entire composite. The matrix of flexible polyurethane foam itself is a reaction product of the following components: poly(tetrahydrofuran), glycerin, dibutyltin dilaurate, a surfactant which is a polyether-polydimethylsiloxane copolymer, water and 2,4-diisocyanate-toluene, a catalyst which is a solution of 1,4-diazabicyclo[2.2.2]octane in dipropylene glycol in the amount of 0.20-0.50% by weight.

Preferably, the flexible polyurethane foam used is, in particular, a molded flexible foam obtained by the prepolymer method using 2,4-diisocyanate toluene.

Preferably, the matrix of the flexible polyurethane foam itself is a product obtained from such components as poly(tetrahydrofuran) in the amount of 58.00-69.00% by weight, glycerin in the amount of 3.95-6.30% by weight, dibutyltin dilaurate in the amount of 0.18-0.61% by weight, a surfactant being a polyether-polydimethylsiloxane copolymer in the amount of 0.05-0.55% by weight, water in the amount of 0.02-1.10% by weight and 2,4-diisocyanate-toluene in the amount of 21.90-37.60% by weight.

Preferably, the composite comprises rubber fines derived from post-consumer tires in an amount of 4.50-16.50% by weight, preferably in an amount of at least 13.00% by weight, and a foam matrix obtained from the following components: poly(tetrahydrofuran) in an amount of 53.00-61.00% by weight, glycerin in an amount of 4.00-5.50% by weight, dibutyltin dilaurate in an amount of 0.20-0.30% by weight, a polyether-polydimethylsiloxane copolymer surfactant in an amount of 0.15-0.20% by weight, water in an amount of 0.15-0.20% by weight, 2,4-diisocyanate-toluene in an amount of 25.00-29.00% by weight of the composite.

Preferably, the composite has a pore size below 190 micrometers and thermal stability exceeding 240°C.

The method of obtaining a flexible, foamed polyurethane-rubber composite consisting in combining rubber powder from post-consumer tires, especially car tires, is characterized in that it is obtained by a two-stage, prepolymer method, where the first stage is the preparation of a prepolymer containing poly(tetrahydrofuran) and 2,4-diisocyanate-toluene in a weight ratio defined by the intended content of free, unbound isocyanate groups in the prepolymer in the range of 12-23%, wherein the weight ratio of poly(tetrahydrofuran) and 2,4-diisocyanate-toluene is in the range of 7.6:10.0 to 10.9:10.0. In order to prepare the prepolymer, poly(tetrahydrofuran) is dried in an amount of 43.18 to 52.15% by weight of the prepolymer at a temperature of at least 90°C, but not higher than 110°C, then an amount of 2,4-diisocyanate toluene appropriate to the amount of poly(tetrahydrofuran) is added, constituting from 47.85 to 56.82% by weight of the prepolymer being a mixture of poly(tetrahydrofuran) and 2,4-diisocyanate toluene, and the reactions are carried out at a temperature of at least 50°C, but not higher than 90°C, until the functional groups react. In the second stage, the obtained prepolymer is mixed with a polyol mixture, where in order to prepare the polyol mixture, the rubber fines in the amount of 9.87-31.59% by weight in relation to the weight of the polyol mixture, corresponding to 4.50-16.50% by weight of the final composite, are mixed with a polyol component in the amount of 58.59-77.19% by weight in relation to the weight of the polyol mixture, corresponding to 30.60-35.20% by weight of the final composite, and glycerin in the amount of 7.66-12.06% by weight in relation to the weight of the polyol mixture, corresponding to 4.00-5.50% by weight of the final composite, until a homogeneous mixture is obtained, then a catalyst is added, which is a solution of 1,4-diazabicyclo[2.2.2]octane in dipropylene glycol in the amount of 0.48-0.77% by weight based on the weight of the polyol mixture, corresponding to 0.25-0.35% by weight of the final composite, dibutyltin dilaurate in an amount of 0.38-0.66% by weight based on the weight of the polyol mixture, corresponding to 0.20-0.30% by weight of the final composite, a polyether-polydimethylsiloxane copolymer surfactant in an amount of 0.29-0.44% by weight based on the weight of the polyol mixture, corresponding to 0.15-0.20% by weight of the final composite, and distilled water in an amount of 0.29-0.44% by weight based on the weight of the polyol mixture, corresponding to 0.15-0.20% by weight of the final composite. The polyol mixture thus prepared is mixed with the prepolymer until a uniform mixture is obtained.

As indicated in the examples and shown in the tables, the composites according to the invention are superior to those known in the art. For example, they are characterized by smaller pores or a higher sound absorption coefficient. Therefore, the resulting cellular structure of the foamed composite is crucial to the invention. Importantly, rubber powder serves as a filler for polyurethane foams. According to the invention, rubber powder is a filler in composites based on a foamed polyurethane matrix – flexible foam. This feature and process leads to a significant reduction in material costs due to the significant differences in the prices of polyurethane systems and rubber powder. Depending on the particle size of the rubber powder, rubber powder can be up to 15 times cheaper than polyurethane systems used to produce flexible polyurethane foams. Furthermore, the use of rubber powder as a filler in composites based on a foamed polyurethane matrix – flexible foam – leads to improved thermal insulation properties of the material, expressed by a lower thermal conductivity coefficient due to the lower thermal conductivity coefficient of rubber compared to solid polyurethane (-160 and -220 mWZ(m-K)). Furthermore, the use of rubber powder as a filler in composites based on a foamed polyurethane matrix – flexible foam, according to the developed method, leads to an increase in the sound absorption coefficient, which indicates improved damping properties of the material against acoustic vibrations. Furthermore, the use of the method and rubber powder as a filler in composites based on a foamed polyurethane matrix – flexible foam leads to increased thermal stability of the material.

The described weight % of flexible foam and rubber powder refer to the weight % of the entire flexible and foamed polyurethane-rubber composite, wherein the given weight % of rubber powder corresponds to the amount of 5 to 20 parts by weight of rubber powder from post-consumer car tires in relation to 100 parts by weight of the flexible polyurethane foam matrix - i.e. these are the proportions in weight parts of both components of the composite - rubber powder in relation to 100 parts by weight of the flexible polyurethane foam.

The invention concerns the use of rubber powder as a filler in polyurethane foams. The invention therefore provides a flexible, foamed polyurethane-rubber composite containing rubber powder derived from post-consumer car tires, and a method for obtaining a flexible, foamed polyurethane-rubber composite containing rubber powder derived from post-consumer car tires.

According to the invention, the composites have a small pore size of less than 190 micrometers, a reduced thermal conductivity coefficient of less than 62.3 mW/m-K, and increased thermal stability exceeding 240°C. The invention is characterized by a high sound absorption coefficient compared to a flexible polyurethane foam matrix. Compared to the prior art, the invention is based on a different use of unmodified substrates and allows for the introduction of a significantly larger amount of unmodified fines than in the solutions described. At the same time, the composite materials obtained according to the invention are characterized by better properties than those previously described. Furthermore, the method used to obtain polyurethane composites is a two-stage method, which allows for obtaining materials with better properties than those previously described.

The invention is described in the following examples and in Figure 1 as spectroscopic spectra for flexible, foamed polyurethane-rubber composites obtained using Fourier transform infrared spectroscopy. The figure therefore confirms the invention, showing all the bands characteristic of polyurethanes. The properties of the invention in the example are given in the tables below.

Example I

Description of how to receive

A flexible, foamed polyurethane-rubber composite containing rubber crumb from post-consumer car tires was obtained according to the example using a two-stage prepolymer method. The first step involved preparing a prepolymer containing poly(tetrahydrofuran) and 2,4-diisocyanate toluene in a 1:1:1 ratio. For this purpose, 40.55 g of poly(tetrahydrofuran) was dried for 90 minutes at 90°C under a reduced pressure of 20 mm Hg. Next, 45.14 g of 2,4-diisocyanate toluene was added and the reaction was carried out at 60°C for 120 minutes. The given masses in grams correspond to the weight percentage of the prepolymer, 47.37% by weight of poly(tetrahydrofuran) and 52.63% by weight of 2,4-diisocyanate toluene, respectively. Furthermore, the given weights in grams correspond to the weight percentage of the resulting composite, 25.74% by weight of poly(tetrahydrofuran) and 28.66% by weight of 2,4-diisocyanate toluene, respectively. In the next, second step, the obtained prepolymer was mixed with the polyol mixture. To prepare the polyol mixture, 7.54 g of crushed rubber from post-consumer car tires with a particle size below 0.7 mm was mechanically mixed using a high-speed mixer with 55.21 g of the polyol component, poly(tetrahydrofuran), and 7.64 g of glycerin for 30 seconds at a rotational speed of 500 rpm, in order to improve the dispersion of crushed rubber from post-consumer car tires in the polyol mixture. You can add different sizes of fines, but within the specified range - when preparing it, it is often not possible to have one specific size, i.e. with fillers, the coarse fraction above a certain size is usually sieved out and particles below a certain threshold remain - as specified.

Then, the remaining components of the polyol mixture were added, i.e. 0.46 g of a catalyst being a 33% solution of 1,4-diazabicyclo[2.2.2]octane in dipropylene glycol, 0.40 g of dibutyltin dilaurate, 0.30 g of a surfactant being a polyether-polydimethylsiloxane copolymer, and 0.29 g of distilled water. The given masses in grams correspond to the weight percentages of the obtained composite, respectively 4.79 wt% rubber crumb from post-consumer car tires, 35.05 wt% poly(tetrahydrofuran), 7.85 wt% glycerin, 0.29 wt% catalyst being a 33% solution of 1,4-diazabicyclo[2.2.2]octane in dipropylene glycol, 0.25 wt% dibutyltin dilaurate, 0.19 wt% surfactant being a polyether-polydimethylsiloxane copolymer, and 0.18 wt% distilled water. The polyol mixture thus prepared was mechanically mixed with the prepolymer using a high-speed mixer at 900 rpm for 10 seconds. The resulting mixture was then poured into a sealed mold at 60°C. After 20 minutes, the flexible, foamed polyurethane-rubber composite containing rubber crumb from used car tires was removed from the mold. The flexible, foamed polyurethane-rubber composite containing rubber crumb from used car tires was cured at 60°C for 24 hours. The obtained composite has a reduced pore size compared to the unmodified flexible polyurethane foam matrix, i.e. 188.5 micrometers, compared to 263.1 micrometers for the unmodified flexible polyurethane foam matrix, a reduced thermal conductivity coefficient compared to the unmodified flexible polyurethane foam matrix, amounting to 61.22 mWZ(m-K), compared to 62.90 mWZ(m^K) for the unmodified flexible polyurethane foam matrix, an increased thermal stability, defined as the temperature of 2% mass loss, compared to the unmodified flexible polyurethane foam matrix, i.e. 240.4°C, compared to 232.5°C for the unmodified flexible polyurethane foam matrix, and an increased sound absorption coefficient, compared to the unmodified flexible polyurethane foam matrix, amounting to 0.04, 0.06, 0.07, 0.08, respectively. 0.10 and 0.12 for frequencies of 630 Hz, 800 Hz, 1000 Hz, 1250 Hz, 5000 Hz and 6300 Hz, compared to values of 0.03, 0.01, 0.02, 0.03, 0.08 and 0.07 for the unmodified flexible polyurethane foam matrix.

The confirmation of obtaining a flexible, foamed polyurethane-rubber composite containing rubber dust from post-consumer car tires is the spectroscopic spectrum obtained using Fourier transform infrared spectroscopy presented in Fig. 1.

Description of the final product - composite composition

The flexible, foamed polyurethane-rubber composite containing rubber powder derived from post-consumer car tires obtained according to the example contained 60.79% poly(tetrahydrofuran), 4.85% glycerin, 4.79% rubber powder derived from post-consumer car tires, 0.29% catalyst being a 33% solution of 1,4-diazabicyclo[2.2.2]octane in dipropylene glycol, 0.25% dibutyltin dilaurate, 0.19% surfactant being a polyether-polydimethylsiloxane copolymer, 0.18% distilled water, and 28.66% 2,4-diisocyanate-toluene. The amount of rubber powder from post-consumer car tires in the flexible, foamed polyurethane-rubber composite containing rubber powder from post-consumer car tires obtained according to the example corresponded to an amount of 5 parts by weight per 100 parts by weight of the flexible polyurethane foam matrix.

Example II

Description of the method of obtaining a composite with a higher content of rubber powder.

A flexible, foamed polyurethane-rubber composite containing rubber crumb from post-consumer car tires was obtained using a two-stage prepolymer method. The first step involved preparing a prepolymer containing poly(tetrahydrofuran) and 2,4-diisocyanate toluene in a 1:1:1 ratio. For this purpose, 40.59 g of poly(tetrahydrofuran) was dried for 90 minutes at 90°C under a reduced pressure of 20 mm Hg. Next, 45.18 g of 2,4-diisocyanate toluene was added and the reaction was conducted at 60°C for 120 minutes. The given masses in grams correspond to the weight percentage of the prepolymer, 47.37% by weight of poly(tetrahydrofuran) and 52.63% by weight of 2,4-diisocyanate toluene, respectively. Furthermore, the given weights in grams correspond to the weight percentage of the resulting composite, 24.57% by weight of poly(tetrahydrofuran) and 27.36% by weight of 2,4-diisocyanate toluene, respectively. In the next step, the obtained prepolymer was mixed with the polyol mixture. To prepare the polyol mixture, 15.02 g of crushed rubber from post-consumer car tires with a particle size below 0.7 mm was mechanically mixed using a high-speed mixer with 55.23 g of the polyol component, poly(tetrahydrofuran), and 7.64 g of glycerin for 40 seconds at a rotational speed of 750 rpm, in order to improve the dispersion of crushed rubber from post-consumer car tires in the polyol mixture. Then, the remaining components of the polyol mixture were added, i.e. 0.46 g of a catalyst being a 33% solution of 1,4-diazabicyclo[2.2.2]octane in dipropylene glycol, 0.40 g of dibutyltin dilaurate, 0.30 g of a surfactant being a polyether-polydimethylsiloxane copolymer, and 0.29 g of distilled water. The given masses in grams correspond to the weight percentages of the obtained composite, respectively 9.10 wt% rubber crumb from post-consumer car tires, 33.46 wt% poly(tetrahydrofuran), 4.63 wt% glycerin, 0.28 wt% catalyst being a 33% solution of 1,4-diazabicyclo[2.2.2]octane in dipropylene glycol, 0.24 wt% dibutyltin dilaurate, 0.18 wt% surfactant being a polyether-polydimethylsiloxane copolymer, and 0.18 wt% distilled water. The polyol mixture thus prepared was mechanically mixed with the prepolymer using a high-speed mixer at 800 rpm for 8 seconds. The resulting mixture was then poured into a sealed mold at 60°C. After 20 minutes, the flexible, foamed polyurethane-rubber composite containing rubber crumb from used car tires was removed from the mold. The flexible, foamed polyurethane-rubber composite containing rubber crumb from used car tires was cured at 60°C for 24 hours. The obtained composite has a reduced pore size compared to the unmodified flexible polyurethane foam matrix, i.e. 144.8 micrometers, compared to 263.1 micrometers for the unmodified flexible polyurethane foam matrix, a reduced thermal conductivity coefficient compared to the unmodified flexible polyurethane foam matrix of 62.23 mW/(m K), compared to 62.90 mWZ(m^K) for the unmodified flexible polyurethane foam matrix, an increased thermal stability, defined as the temperature of 2% mass loss, compared to the unmodified flexible polyurethane foam matrix, i.e. 242.2°C, compared to 232.5°C for the unmodified flexible polyurethane foam matrix, and an increased sound absorption coefficient, compared to the unmodified flexible polyurethane foam matrix of 0.04, 0.06, 0.08, 0.09, respectively. and 0.09 for frequencies of 800 Hz, 1000 Hz, 1250 Hz, 5000 Hz and 6300 Hz, compared to values of 0.01, 0.02, 0.03, 0.08 and 0.07 for the unmodified flexible polyurethane foam matrix.

The confirmation of obtaining a flexible, foamed polyurethane-rubber composite containing rubber dust from post-consumer car tires is the spectroscopic spectrum obtained using Fourier transform infrared spectroscopy presented in Fig. 1.

Description of the final product - composite composition with a higher content of rubber powder.

The flexible, foamed polyurethane-rubber composite containing rubber powder from post-consumer car tires obtained according to the example contained 58.03% poly(tetrahydrofuran), 4.63% glycerin, 9.10% rubber powder from post-consumer car tires, 0.28% catalyst being a 33% solution of 1,4-diazabicyclo[2.2.2]octane in dipropylene glycol, 0.24% dibutyltin dilaurate, 0.18% surfactant being a polyether-polydimethylsiloxane copolymer, 0.18% distilled water, and 27.37% 2,4-diisocyanate-toluene. The amount of rubber powder from post-consumer car tires in the flexible, foamed polyurethane-rubber composite containing rubber powder from post-consumer car tires obtained according to the example corresponded to an amount of 10 parts by weight per 100 parts by weight of the flexible polyurethane foam matrix.

Example III.

Description of the method of obtaining a composite with a higher content of rubber powder.

A flexible, foamed polyurethane-rubber composite containing rubber crumb from post-consumer car tires was obtained using a two-stage prepolymer method. The first step involved preparing a prepolymer containing poly(tetrahydrofuran) and 2,4-diisocyanate toluene in a 1:1:1 ratio. For this purpose, 40.55 g of poly(tetrahydrofuran) was dried for 90 minutes at 90°C under a reduced pressure of 20 mm Hg. Next, 45.15 g of 2,4-diisocyanate toluene was added and the reaction was conducted at 60°C for 120 minutes. The given masses in grams correspond to the weight percentage of the prepolymer, 47.37% by weight of poly(tetrahydrofuran) and 52.63% by weight of 2,4-diisocyanate toluene, respectively. Furthermore, the given weights in grams correspond to the weight percentage of the resulting composite, 23.50% by weight of poly(tetrahydrofuran) and 26.17% by weight of 2,4-diisocyanate toluene, respectively. In the next step, the obtained prepolymer was mixed with the polyol mixture. To prepare the polyol mixture, 22.53 g of crushed rubber from post-consumer car tires with a particle size below 0.7 mm was mechanically mixed using a high-speed mixer with 55.21 g of the polyol component, poly(tetrahydrofuran), and 7.66 g of glycerin for 60 seconds at a rotational speed of 250 rpm, to improve the dispersion of crushed rubber from post-consumer car tires in the polyol mixture. Then, the remaining components of the polyol mixture were added, i.e. 0.46 g of a catalyst being a 33% solution of 1,4-diazabicyclo[2.2.2]octane in dipropylene glycol, 0.39 g of dibutyltin dilaurate, 0.0 g of a surfactant being a polyether-polydimethylsiloxane copolymer, and 0.30 g of distilled water. The given weights in grams correspond to the weight percentages of the obtained composite, respectively 13.06 wt% rubber crumb derived from post-consumer car tires, 32.00 wt% poly(tetrahydrofuran), 4.43 wt% glycerin, 0.27 wt% catalyst being a 33% solution of 1,4-diazabicyclo[2.2.2]octane in dipropylene glycol, 0.23 wt% dibutyltin dilaurate, 0.17 wt% surfactant being a polyether-polydimethylsiloxane copolymer, and 0.17 wt% distilled water. The polyol mixture thus prepared was mechanically mixed with the prepolymer using a high-speed mixer at 1000 rpm for 10 seconds. The resulting mixture was then poured into a sealed mold at 58°C. After 20 minutes, the flexible, foamed polyurethane-rubber composite containing rubber crumb from used car tires was removed from the mold. The flexible, foamed polyurethane-rubber composite containing rubber crumb from used car tires was cured at 60°C for 24 hours. The obtained composite has a reduced pore size in comparison to the unmodified flexible polyurethane foam matrix, i.e. 170.2 micrometers, compared to 263.1 micrometers for the unmodified flexible polyurethane foam matrix, a reduced thermal conductivity coefficient in comparison to the unmodified flexible polyurethane foam matrix of 62.27 mW/(m K), compared to 62.90 mW/(m-K) for the unmodified flexible polyurethane foam matrix, increased thermal stability, The obtained composite has a reduced pore size in comparison to the unmodified flexible polyurethane foam matrix, i.e. 170.2 micrometers, compared to 263.1 micrometers for the unmodified flexible polyurethane foam matrix, a reduced thermal conductivity coefficient in comparison to the unmodified flexible polyurethane foam matrix of 62.27 mW/(m K), compared to 62.90 mW/(m K) for the unmodified flexible polyurethane foam matrix, increased thermal stability, defined as the temperature of 2% mass loss, compared to the unmodified flexible polyurethane foam matrix, i.e. 240.9°C, compared to 232.5 °C for the unmodified flexible polyurethane foam matrix, and an increased sound absorption coefficient, compared to the unmodified flexible polyurethane foam matrix, amounting to 0.09, 0.12, 0.15, 0.10, 0.12, 0.09 and 0.10 for the frequencies of 630 Hz, 800 Hz, 1000 Hz, 1250 Hz, 3150 Hz, 5000 Hz and 6300 Hz, compared to the values of 0.03, 0.01, 0.02, 0.03, 0.06, 0.08 and 0.07 for unmodified flexible polyurethane foam matrix.

The confirmation of obtaining a flexible, foamed polyurethane-rubber composite containing rubber dust from post-consumer car tires is the spectroscopic spectrum obtained using Fourier transform infrared spectroscopy presented in Fig. 1.

Description of the final product - composite composition with a higher content of rubber powder.

The flexible, foamed polyurethane-rubber composite containing rubber powder derived from post-consumer car tires obtained according to the example contained 55.50% poly(tetrahydrofuran), 4.43% glycerin, 13.06% rubber powder derived from post-consumer car tires, 0.27% catalyst being a 33% solution of 1,4-diazabicyclo[2.2.2]octane in dipropylene glycol, 0.23% dibutyltin dilaurate, 0.17% surfactant being a polyether-polydimethylsiloxane copolymer, polydimethylsiloxane, 0.17% distilled water, and 26.16% 2,4-diisocyanate-toluene. The amount of rubber powder from post-consumer car tires in the flexible, foamed polyurethane-rubber composite containing rubber powder from post-consumer car tires obtained according to the example corresponded to an amount of 15 parts by weight per 100 parts by weight of the flexible polyurethane foam matrix.

Example IV

Description of the method of obtaining a composite with a higher content of rubber powder.

A flexible, foamed polyurethane-rubber composite containing rubber crumb from post-consumer car tires was obtained using a two-stage prepolymer method. The first step involved preparing a prepolymer containing poly(tetrahydrofuran) and 2,4-diisocyanate toluene in a 1:1:1 ratio. For this purpose, 40.54 g of poly(tetrahydrofuran) was dried for 90 minutes at 90°C under a reduced pressure of 20 mm Hg. Next, 45.14 g of 2,4-diisocyanate toluene was added and the reaction was conducted at 60°C for 120 minutes. The given masses in grams correspond to the weight percentage of the prepolymer, 47.37% by weight of poly(tetrahydrofuran) and 52.63% by weight of 2,4-diisocyanate toluene, respectively. Furthermore, the given weights in grams correspond to the weight percentage of the resulting composite, 22.61% by weight of poly(tetrahydrofuran) and 25.17% by weight of 2,4-diisocyanate toluene, respectively. In the next step, the obtained prepolymer was mixed with the polyol mixture. To prepare the polyol mixture, 29.37 g of crushed rubber from post-consumer car tires with a particle size below 0.7 mm was mechanically mixed using a high-speed mixer with 55.21 g of the polyol component, poly(tetrahydrofuran), and 7.66 g of glycerin for 30 seconds at a rotational speed of 600 rpm, in order to improve the dispersion of crushed rubber from post-consumer car tires in the polyol mixture. Then, the remaining components of the polyol mixture were added, i.e. 0.46 g of a catalyst being a 33% solution of 1,4-diazabicyclo[2.2.2]octane in dipropylene glycol, 0.40 g of dibutyltin dilaurate, 0.29 g of a surfactant being a polyether-polydimethylsiloxane copolymer, and 0.29 g of distilled water. The given masses in grams correspond to the weight percentages of the obtained composite, respectively 16.37 wt% rubber crumb from post-consumer car tires, 30.78 wt% poly(tetrahydrofuran), 4.27 wt% glycerin, 0.26 wt% catalyst being a 33% solution of 1,4-diazabicyclo[2.2.2]octane in dipropylene glycol, 0.22 wt% dibutyltin dilaurate, 0.16 wt% surfactant being a polyether-polydimethylsiloxane copolymer, and 0.16 wt% distilled water. The polyol mixture thus prepared was mechanically mixed with the prepolymer using a high-speed mixer at 1000 rpm for 10 seconds. The resulting mixture was then poured into a sealed mold at 55°C. After 20 minutes, the flexible, foamed polyurethane-rubber composite containing rubber crumb from used car tires was removed from the mold. The flexible, foamed polyurethane-rubber composite containing rubber crumb from used car tires was cured at 60°C for 24 hours. The obtained composite has a reduced pore size compared to the unmodified flexible polyurethane foam matrix, i.e. 178.3 micrometers, compared to 263.1 micrometers for the unmodified flexible polyurethane foam matrix, a reduced thermal conductivity coefficient compared to the unmodified flexible polyurethane foam matrix of 60.20 mWŻ (m-K), compared to 62.90 mW/(m-K) for the unmodified flexible polyurethane foam matrix, an increased thermal stability, defined as the temperature of 2% mass loss, compared to the unmodified flexible polyurethane foam matrix, i.e. 243.6°C, compared to 232.5°C for the unmodified flexible polyurethane foam matrix, and an increased sound absorption coefficient, compared to the unmodified flexible polyurethane foam matrix, of 0.04, 0.06, 0.10, 0.17 and 0.18, respectively. 0.06 for frequencies of 630 Hz, 800 Hz, 1000 Hz, 1250 Hz and 3150 Hz, compared to values of 0.03, 0.01, 0.02, 0.03 and 0.06 for the unmodified flexible polyurethane foam matrix.

The confirmation of obtaining a flexible, foamed polyurethane-rubber composite containing rubber dust from post-consumer car tires is the spectroscopic spectrum obtained using Fourier transform infrared spectroscopy presented in Fig. 1.

Description of the final product - composite composition with a higher content of rubber powder.

The flexible, foamed polyurethane-rubber composite containing rubber powder derived from post-consumer car tires obtained according to the example contained 53.39% poly(tetrahydrofuran), 4.27% glycerin, 16.37% rubber powder derived from post-consumer car tires, 0.26% catalyst being a 33% solution of 1,4-diazabicyclo[2.2.2]octane in dipropylene glycol, 0.22% dibutyltin dilaurate, 0.16% surfactant being a polyether-polydimethylsiloxane copolymer, 0.16% distilled water, and 25.17% 2,4-diisocyanate-toluene. The amount of rubber powder from post-consumer car tires in the flexible, foamed polyurethane-rubber composite containing rubber powder from post-consumer car tires obtained according to the example corresponded to an amount of 20 parts by weight per 100 parts by weight of the flexible polyurethane foam matrix.

The flexible, foamed polyurethane-rubber composites produced as described in Examples 1-4, containing rubber crumb from post-consumer car tires, were subjected to Fourier transform infrared spectroscopy to investigate their chemical structure and confirm the production of polyurethane materials. The results of the analysis are presented in Figure 1, which also includes the spectroscopic spectrum obtained for the matrix, a flexible polyurethane foam, free of rubber crumb from post-consumer car tires.

Flexible, foamed polyurethane-rubber composites prepared as described in Examples 1-4, containing rubber crumb from post-consumer car tires, were tested using scanning electron microscopy to determine the average pore size. The analysis results are summarized in Table 1, which also includes the properties obtained for the matrix, a flexible polyurethane foam, free of rubber crumb from post-consumer car tires.

Flexible, foamed polyurethane-rubber composites, prepared as described in Examples 1-4, containing rubber crumb from post-consumer car tires, were subjected to thermal conductivity tests using a plate-type apparatus. The analysis results are summarized in Table 2, which also includes the properties obtained for the matrix, a flexible polyurethane foam, free of rubber crumb from post-consumer car tires.

Flexible, foamed polyurethane-rubber composites prepared as described in Examples 1-4, containing rubber crumb from post-consumer car tires, were subjected to thermogravimetric analysis to determine their thermal stability. The analysis results are summarized in Table 3, which also includes the properties obtained for the matrix, a flexible polyurethane foam, free of rubber crumb from post-consumer car tires.

Flexible, foamed polyurethane-rubber composites, prepared as described in Examples 1-4, containing rubber crumb from post-consumer car tires were subjected to acoustic attenuation testing. The analysis results are summarized in Table 4, which also includes the properties obtained for the matrix, a flexible polyurethane foam, free of rubber crumb from post-consumer car tires.

Description of samples:

• PO - matrix of flexible polyurethane foam, not containing rubber dust from used car tires;

• P5 - flexible, foamed polyurethane-rubber composite containing rubber powder from post-consumer car tires obtained according to example 1, containing rubber powder from post-consumer car tires in the amount of 5 parts by weight per 100 parts by weight of the flexible polyurethane foam matrix;

• P10 - flexible, foamed polyurethane-rubber composite containing rubber powder from post-consumer car tires obtained according to example 2, containing rubber powder from post-consumer car tires in the amount of 10 parts by weight per 100 parts by weight of the flexible polyurethane foam matrix;

• P15 - flexible, foamed polyurethane-rubber composite containing rubber powder from post-consumer car tires obtained according to example 3, containing rubber powder from post-consumer car tires in the amount of 15 parts by weight per 100 parts by weight of the flexible polyurethane foam matrix;

• P20 - flexible, foamed polyurethane-rubber composite containing rubber powder from post-consumer car tires obtained according to example 4, containing rubber powder from post-consumer car tires in the amount of 20 parts by weight per 100 parts by weight of the flexible polyurethane foam matrix.

Figure 1 presents spectroscopic spectra for flexible, foamed polyurethane-rubber composites and a flexible polyurethane foam matrix, indicating the most important signals confirming the presence of urethane groups in the material and thus confirming that the desired chemical structure has been obtained. Individual signals, numbered 1-5, indicate vibrations of the chemical bonds comprising the urethane groups:

- stretching vibrations of single nitrogen-hydrogen (N-H) bonds,

- stretching vibrations of carbon-oxygen double bonds (C=O),

- stretching vibrations of single carbon-nitrogen (C-N) bonds,

- bending vibrations of single nitrogen-hydrogen (N-H) bonds,

- stretching vibrations of single carbon-oxygen (C-O) bonds.

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The presence of individual signals in the spectroscopic spectra of flexible, foamed polyurethane-rubber composites and the flexible polyurethane foam matrix confirms the presence of urethane groups.

Table 1

Average pore size determined for flexible, foamed polyurethane-rubber composites containing rubber dust from post-consumer car tires

Sample AFTER P5 PIO P15 P20 Average pore size, μηι 263.1 ±64.9 188.5 ±49.7 144.8 ±87.8 170.2 ±78.6 178.3 ± 109.0

The resulting flexible, foamed polyurethane-rubber composites containing rubber crumb from post-consumer car tires are characterized by a smaller average pore size compared to the matrix, a flexible polyurethane foam that does not contain rubber crumb from post-consumer car tires. This effect positively affects the insulating and mechanical properties of porous materials, as repeatedly demonstrated in the scientific literature.

A similar effect was observed in the literature:

• Kosmela, P., Olszewski, A., Zedler, Ł., Burger, P., Piasecki, A., Formela, K., Hejna, A. (2021). Ground Tire Rubber Filled Flexible Polyurethane Foam-Effect of Waste Rubber Treatment on Composite Performance. Materials, 14, 3807, • Kosmela, P., Olszewski, A., Zedler, Ł., Burger, P., Formela, K., Hejna, A. (2021). Structural Changes and Their Implications in Foamed Flexible Polyurethane Composites Filled with Rapeseed Oil-Treated Ground Tire Rubber. Journal of Composites Science, 5, 90.

This effect, however, was related to the introduction of rubber crumb from post-consumer car tires into the flexible polyurethane foam matrix, which was additionally thermomechanically modified using raw and waste rapeseed oil. In the case of flexible, foamed polyurethane-rubber composites containing rubber crumb from post-consumer car tires, which are the subject of the invention, additional modifications to the rubber crumb from post-consumer car tires are not necessary.

In the case of the work - Kosmela, P., Olszewski, A., Zedler, Ł., Burger, P., Formela, K., Hejna, A. (2021). Structural Changes and Their Implications in Foamed Flexible Polyurethane Composites Filled with Rapeseed Oil-Treated Ground Tire Rubber. Journal of Composites Science, 5, 90, the effect was also observed for foam containing unmodified rubber powder from post-consumer car tires, however, the addition of rubber powder from post-consumer car tires allowed only a 20% reduction in the average pore size, and in the case of flexible, foamed polyurethane-rubber composites containing rubber powder from post-consumer car tires obtained as the subject of the invention, the average pore size was reduced by at least 28%, regardless of the percentage of rubber powder from post-consumer car tires in the composite. Furthermore, the materials described in the work - Kosmela, P., Olszewski, A., Zedler, Ł., Burger, P., Formela, K., Hejna, A. (2021). Structural Changes and Their Implications in Foamed Flexible Polyurethane Composites Filled with Rapeseed Oil-Treated Ground Tire Rubber. Journal of Composites Science, 5, 90, were obtained by a one-step method.

A reduction in the average pore size of the flexible polyurethane foam matrix resulting from the introduction of rubber crumb from post-consumer car tires was also observed in the work of Shan, C.M., Idris, M., Ghazali, M.l. (2012). Study of Flexible Polyurethane Foams Reinforced with Coir Fibers and Tyre Particles. International Journal of Applied Physics and Mathematics, 2(2), 123-130. However, this effect was associated with the introduction of rubber crumb from post-consumer car tires in an amount of only 2.50% by weight of the final composite. In the case of flexible, foamed polyurethane-rubber composites containing rubber crumb from post-consumer car tires being the subject of the invention, the rubber crumb from post-consumer car tires is introduced in an amount of at least 4.50% by weight of the final composite.

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Table 2

Thermal conductivity coefficient determined for flexible, foamed polyurethane-rubber composites containing rubber dust from post-consumer car tires

Sample AFTER P5 P10 P15 P20 Thermal conductivity coefficient, mW/(mK) 62.90 61.22 62.23 62.27 60.20

The obtained flexible, foamed polyurethane-rubber composites containing rubber powder from post-consumer car tires are characterized by a reduced thermal conductivity coefficient compared to the matrix, flexible polyurethane foam, not containing rubber powder from post-consumer car tires, which indicates improved thermal insulation properties.

Table 3

Thermal stability determined for flexible, foamed polyurethane-rubber composites containing rubber dust from post-consumer car tires

Sample AFTER P5 P10 P15 P20 Thermal stability, °C 232.5 240.4 242.2 240.9 243.6

The obtained flexible, foamed polyurethane-rubber composites containing rubber powder from post-consumer car tires are characterized by increased thermal stability, defined as the temperature of 2% mass loss, in relation to the matrix, flexible polyurethane foam, not containing rubber powder from post-consumer car tires.

In the case of the work - Kosmela, P., Olszewski, A., Zedler, Ł., Burger, P., Formela, K., Hejna, A. (2021). Structural Changes and Their Implications in Foamed Flexible Polyurethane Composites Filled with Rapeseed Oil-Treated Ground Tire Rubber. Journal of Composites Science, 5, 90, an increase in the thermal stability of polyurethane-rubber composites was also observed compared to the matrix, flexible polyurethane foam, however, this effect was related to the use of rubber powder derived from post-consumer car tires additionally subjected to thermomechanical modification using raw and waste rapeseed oil. In the case of flexible, foamed polyurethane-rubber composites containing rubber powder derived from post-consumer car tires being the subject of the invention, additional modifications of the rubber powder derived from post-consumer car tires are not necessary. The effect was also observed for foam containing unmodified rubber crumb from post-consumer car tires, however, the materials described in the work - Kosmela, P., Olszewski, A., Zedler, Ł., Burger, P., Formela, K., Hejna, A. (2021). Structural Changes and Their Implications in Foamed Flexible Polyurethane Composites Filled with Rapeseed Oil-Treated Ground Tire Rubber. Journal of Composites Science, 5, 90, were obtained by a one-step method.

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Table 4

Sound absorption coefficient determined for flexible, foamed polyurethane-rubber composites containing rubber dust from used car tires

Frequency, Hz Sample AFTER P5 PIO P15 P20 Sound absorption coefficient 630 0.03 0.04 0.03 0.09 0.04 800 0.01 0.06 0.04 0.12 0.06 1000 0.02 0.07 0.06 0.15 0.10 1250 0.03 0.08 0.08 0.10 0.17 3150 0.06 0.00 0.00 0.12 0.07 5000 0.08 0.10 0.09 0.09 0.07 6300 0.07 0.12 0.09 0.10 0.08

The obtained flexible, foamed polyurethane-rubber composites containing rubber powder from post-consumer car tires are characterized by an increased sound absorption coefficient compared to the matrix of flexible polyurethane foam not containing rubber powder from post-consumer car tires at frequencies exceeding 630 Hz.

A beneficial effect associated with an increase in the sound absorption coefficient resulting from the introduction of crushed rubber from post-consumer car tires into the flexible polyurethane foam matrix was also observed in the work - Gayathri, R., Vasanthakumari, R., Padmanabhan, C. (2013). Sound absorption, thermal and mechanical behavior of polyurethane foam modified with nano silica, nano clay and crumb rubber fillers. International Journal of Scientific & Engineering Research, 4(5), 301-308, however, this effect was observed in the frequency range of 100-200 Hz. Furthermore, this effect was associated with the introduction of crushed rubber from post-consumer car tires only in the amount of 2.00% by weight of the final composite. In the case of flexible, foamed polyurethane-rubber composites containing crumb rubber derived from post-consumer car tires, which are the subject of the invention, crumb rubber derived from post-consumer car tires is incorporated in an amount of at least 4.50% by weight of the final composite. Furthermore, the materials described in the work - Gayathri, R., Vasanthakumari, R., Padmanabhan, C. (2013). Sound absorption, thermal and mechanical behavior of polyurethane foam modified with nano silica, nano clay and crumb rubber fillers. International Journal of Scientific & Engineering Research, 4(5), 301-308, were obtained by a single-step method.

Claims (6)

1. Flexible and foamed polyurethane-rubber composite containing rubber powder from post-consumer tires, especially car tires, and polyurethane foam, characterized in that it contains an elastic matrix in the form of flexible polyurethane foam in the amount of 83.50-95.50% by weight in relation to the entire polyurethane-rubber composite and rubber powder with an average particle size below 0.7 mm from post-consumer tires in the amount of 4.50-16.50% by weight in relation to the entire composite, wherein the flexible polyurethane foam matrix itself is a reaction product of the following components: poly(tetrahydrofuran), glycerin, dibutyltin dilaurate, a surfactant being a polyether-polydimethylsiloxane copolymer, water and 2,4-diisocyanate-toluene, a catalyst being a solution of 1,4-diazabicyclo[2.2.2]octane in glycol dipropylene in the amount of 0.20-0.50% by weight. 2. A composite according to claim 1, characterized in that the flexible polyurethane foam used is, in particular, a molded flexible foam obtained by the prepolymer method using 2,4-diisocyanate-toluene. 3. A composite according to claim 1-2, characterized in that the matrix of the flexible polyurethane foam itself is a product obtained from the following components: poly(tetrahydrofuran) in the amount of 58.00-69.00% by weight, glycerin in the amount of 3.95-6.30% by weight, dibutyltin dilaurate in the amount of 0.18-0.61% by weight, a surfactant being a polyetherpolydimethylsiloxane copolymer in the amount of 0.05-0.55% by weight, water in the amount of 0.02-1.10% by weight and 2,4-diisocyanate-toluene in the amount of 21.90-37.60% by weight. 4. Composite according to claim 1. The method of claim 1, wherein the composite comprises rubber powder from post-consumer tires in an amount of 4.50-16.50% by weight, preferably at least 13.00% by weight, and a foam matrix obtained from the following components: poly(tetrahydrofuran) in an amount of 53.00-61.00% by weight, glycerin in an amount of 4.00-5.50% by weight, dibutyltin dilaurate in an amount of 0.20-0.30% by weight, a surfactant being a polyether-polydimethylsiloxane copolymer in an amount of 0.15-0.20% by weight, water in an amount of 0.15-0.20% by weight, 2,4-diisocyanate-toluene in an amount of 25.00-29.00% by weight of the composite. 5. The composite according to claims 1-4, characterized in that it has a pore size below 190 micrometers and thermal stability exceeding 240°C. 6. A method for obtaining a flexible, foamed polyurethane-rubber composite consisting in combining rubber powder from used tires, especially car tires, characterized in that it is obtained by a two-stage prepolymer method, wherein the first stage is the preparation of a prepolymer containing poly(tetrahydrofuran) and 2,4-diisocyanate-toluene in a weight ratio defined by the intended content of free, unbound isocyanate groups in the prepolymer in the range of 12-23%, wherein the weight ratio of poly(tetrahydrofuran) and 2,4-diisocyanate-toluene is in the range of 7.6:10.0 to 10.9:10.0, and in order to prepare the prepolymer, poly(tetrahydrofuran) is dried in an amount of 43.18 to 52.15% by weight in relation to the weight of the prepolymer at a temperature of at least 90°C, but not higher than 110°C, then an amount of 2,4-diisocyanate toluene appropriate to the amount of poly(tetrahydrofuran) constituting from 47.85 to 56.82% of the mass of the prepolymer being a mixture of poly(tetrahydrofuran) and 2,4-diisocyanate toluene is added and the reactions are carried out at a temperature of at least 50°C, but not higher than 90°C, until the functional groups react, and in the second stage the obtained prepolymer is mixed with a polyol mixture, where in order to prepare a polyol mixture, rubber powder in the amount of 9.87-31.59% by weight in relation to the mass of the polyol mixture, corresponding to 4.50-16.50% by weight of the mass of the final composite, is mixed with a polyol component in the amount of 58.59-77.19% by weight in relation to the mass of the mixture polyol, corresponding to 30.60-35.20% by weight of the final composite and glycerine in the amount of 7.66-12.06% by weight of the polyol mixture, corresponding to 4.00-5.50% by weight of the final composite to obtain a homogeneous mixture, then, a catalyst is added which is a solution of 1,4-diazabicyclo[2.2.2]octane in dipropylene glycol in the amount of 0.48-0.77% by weight of the polyol mixture, corresponding to 0.25-0.35% by weight of the final composite, dibutyltin dilaurate in the amount of 0.38-0.66% by weight of the polyol mixture, corresponding to 0.20-0.30% by weight of the final composite, a surfactant which is a copolymer polyether-polydimethylsiloxane, in an amount of 0.29-0.44% by weight of the polyol mixture, corresponding to 0.15-0.20% by weight of the final composite, and distilled water in an amount of 0.29-0.44% by weight of the polyol mixture, corresponding to 0.15-0.20% by weight of the final composite, and the polyol mixture thus prepared is mixed with the prepolymer until a uniform mixture is obtained.