PL242558B1 - Flexible flame-retardant polyurethane foam and method of obtaining flexible flame-retardant polyurethane foam - Google Patents

Abstract

The foam contains a matrix in the form of a mixture of polyol and isocyanate and a flame retardant additive in the form of a mixture of shredded sheep wool and graphite in the amount of 5 - 30% by weight in the foam, with the weight percentage of powdered wool and graphite in the mixture of flame retardants being 50 - 75% and 25 - 25%, respectively. 50% by weight.

Description

Description of the invention

The subject of the invention is a flexible flame retardant polyurethane foam. The subject of the invention is also a method of obtaining flexible polyurethane foam with reduced flammability. The invention finds application especially in the production of mattresses for beds, carpet underlays, furniture, other polymer matrices, e.g. in rigid polyurethane foam, which is an insulating material.

The most important components of polyurethane foams are polyols and isocyanates. The production of polyurethanes is mainly based on the use of toluene diisocyanate (TDI), which is considered a key ingredient in the production of flexible foams. The main disadvantage of using polyurethane is its low fire resistance and high smoke density during a fire, as well as the high consumption of isocyanate (TDI), which is considered a toxic substance.

For this reason, the use of flame retardant materials, i.e. flame retardants, is very important.

Various flame retardants are known to be used for polymers.

Halogen flame retardants are known. Nevertheless, a significant disadvantage of the combustion reaction of polymers with halogens and antimony trioxide is the release of toxic substances and greater emission of fumes. In addition, halogen compounds can cause corrosion and increase the cost of foam production.

Halogen-free flame retardants used to increase fire resistance and are mainly phosphorus and nitrogen compounds, graphite, aluminum, magnesium, molybdenum, silicon and boron.

The US4698369 patent describes a method of producing fire-resistant flexible polyurethane foam using a mixture of polyol, organic polyisocyanate and expanded graphite.

Compositions of fire-resistant, polymeric materials are known from the patent US4871477. The composition includes polymeric materials and inorganic fillers containing one or more (A) microparticles containing an inner phase, i.e. alumina hydrates, and an outer phase, e.g. sodium silicate, (B) finely divided, expanded alkali metal silicate, (C) finely divided inorganic salts such as ammonium salts of phosphate or polyphosphate.

The US4746682 patent describes a liquid substance used as an agent increasing the fire resistance of polyurethane foams and a process for the production of polyurethane foam. The liquid flame retardant composition used for the polyurethane foam is a mixture of polybrominated diphenyl oxide, alkylated triaryl phosphate ester, brominated diphenyl oxide and triaryl phosphate used in various proportions.

However, better methods of reducing the flammability of important materials such as flexible foams with a wide range of applications are still being sought.

The invention concerns the development of a new method of obtaining polyurethane foam by reducing the amount of isocyanate in the foam formulation by using selected flame retardants.

The inventors of the present invention have become interested in replacing commercial flame retardants with compounds from renewable sources - recycling. For this purpose, agents were selected that contain fire-resistant elements such as nitrogen and sulfur in a product that fulfilled its role in this particular application. The main objectives of the invention include: reducing the flammability of flexible polyurethane foams, reducing the use of chemical compounds and managing sheep wool waste.

The polyurethane foams according to the invention are the reaction product of a mixture of a polyol, such as a polyether or polyester, an organic polyisocyanate and an environmentally friendly and economically advantageous flame retardant selected for the amount and type. To increase the resistance to fire, crushed e.g. powdered sheep wool waste and expanded graphite are used, which are a mixture of flame retardants. According to the invention, suitable proportions of the individual components in the foam have been developed in order to meet the desired purpose.

According to the invention, the method of obtaining polyurethane foam consists in carrying out two main stages.

In the first stage, a mixture of flame retardants is obtained by mixing powdered sheep wool and graphite in the form of expanded graphite flakes with a share of 50-75% by weight - wool and 25-50% by weight - graphite, e.g. using a mechanical mixer.

In the second stage, a mixture of flame retardants is added to the polyol used in the production of polyurethane foam. The mixture is stirred, e.g. with a mechanical stirrer, and the isocyanate used is added. The percentage ratio between polyol and polyisocyanate in the polyurethane matrix is 50-70% by weight of polyol and 50-30% by weight, respectively, preferably 60% to 40%, respectively. The following weight percentages of the mixture of flame retardants and the polyurethane matrix, i.e. a mixture of polyol and isocyanate, of 5-30% and 70-95% by weight, respectively, are selected. The reaction proceeds at room temperature and the final product is annealed until the final foam is obtained, e.g. for 24 hours at an elevated temperature, e.g. 70°C.

The final product of the invention, i.e. polyurethane foam, contains a flexible polyurethane foam matrix, i.e. polyol and isocyanate, from 70 to 95% by weight in the final product, and a flame retardant in the form of a mixture of crushed, powdered sheep wool and graphite in the range of 5-30% by weight in the final product. product. The weight percentage of powdered wool and graphite in the flame retardant mixture, constituting the filler in the foam, is 50-75% and 25-50% by weight of the mixture in the final product, respectively. The percentage ratio between polyol and polyisocyanate in the polyurethane matrix is 50-70% by weight of polyol and 50-30% by weight, respectively, preferably 60% to 40%, respectively.

The method of obtaining modified polyurethane foam is carried out in two stages: a polyol such as polyether or polyester is added to a mixture of powdered sheep wool and graphite, then polyisocyanate is added to the mixture at a room temperature of, for example, 25°C and the whole thing is mixed for a few seconds at speeds ranging from 500 rpm (revolutions per minute) to 3000 rpm. The resulting mixture is poured into a mold and heated at 70-80°C. As a result of the procedure, flame-retardant, flexible polyurethane foams are obtained, containing 70-95% by weight of a polyurethane matrix and from 5% to 30% by weight of a mixture of flame retardants, i.e. powdered sheep wool and expanded graphite in appropriate proportions. The mass fraction of powdered sheep wool and expanded graphite in the flame retardant mixture is 50-75% and 25-50% each, respectively. The temperature during the mixing process to obtain the flame retardant blend is preferably 25 ± 1.5°C. The mixing speed in the reactor is preferably between 500-3000 rpm.

The addition of sheep wool fibers and graphite reduces the flammability of the flexible polyurethane foam and increases the quality of the product. The process is carried out to evenly disperse the mixture of flame retardants in the polyurethane matrix, namely sheep wool and graphite fibers. Modification of flexible polyurethane foam with a mixture of sheep wool and expanded graphite also results in the creation of a product with good physical properties. In particular, powdered sheep wool with a thickness of less than 0.2 mm, obtained by physical action, is used. Wool is mixed with graphite. A mixture of flame retardants - graphite and powdered sheep wool is mixed with polyurethane foam components. A uniform dispersion of ingredients in the polyurethane matrix should be obtained. The use of the developed mixture of flame retardants increases the fire resistance of the final product.

Sheep wool contains a large amount of nitrogen (17-20%) and sulfur (4-6%), which make the wool a good flame retardant compound with excellent mechanical properties. Due to its unique properties, wool has many uses. It can be used for cleaning up oil and chemical spills, sewage treatment and water treatment, as well as insulating material. Sheep wool fibers are used in the textile industry. Due to the increase in the population, the consumption rate of textile products has increased sharply, hence the amount of waste has increased accordingly, which can be excellently used in the method of the invention. Wool waste generated during the production and processing of textile fibers and/or sheep shearing has been effectively used in a mixture of flame retardants, thus increasing the fire resistance of products made of polyurethane foams. The use of waste sheep wool additionally contributes to reducing the level of environmental pollution. Wool is a biodegradable and environmentally friendly material. Sheep wool fibers are resilient and flexible. They can be bent thousands of times without the risk of breakage or damage. Wool is more plastic than black plastic. Foam with wool fibers, due to its fire resistance, can be successfully used, for example, in airplane seats. In addition, it is characterized by excellent mechanical properties. The main advantage of the invention is the application of the principles of green chemistry, which relate to the reduction of the use of harmful or dangerous chemical compounds. The process of modifying polyurethane foams with waste sheep wool and graphite fibers does not require prior chemical or physical treatment - powdered sheep wool and graphite are used. The presented method does not pose a threat to the environment, does not generate secondary waste and allows for the reuse of waste wool fibres. The use of ecological flame retardants according to the invention reduces the mass concentration of isocyanate in the foam to 30%, which is environmentally friendly. The use of powdered sheep wool as an ecological filler reduces the degree of corrosion of materials, toxicity and the amount of emission products of the polyurethane foam combustion reaction.

The modified polyurethane foams of the invention can be effectively used in furniture, carpet pads, beds and sofas. The modified polymers presented in the present invention can also be used in the seats of cars, trains and airplanes. In addition, the final product can be used to insulate buildings.

The invention is presented in detail in an embodiment and in the drawing, in which Fig. 1 shows a block diagram of the process of increasing the fire resistance of polyurethane foam,

Fig. 2 shows photos of the fire resistance test of the foams modified according to the invention in comparison with unmodified flexible polyurethane foam,

Fig. 3 shows the mechanical properties, i.e. the tensile strength of the foam modified according to the invention in relation to the polyurethane foam not modified according to the invention.

In Figure 3, A denotes an unmodified foam, B a foam containing 15 wt. sheep wool, C - foam containing a mixture of flame retardants in the amount of 10% by weight. sheep wool and 5% expanded graphite in the foam.

From the diagram in Fig. 1, it can be seen that the method according to the invention can be carried out in a mobile system.

In the description, the terms flame retardant mixture and filler are used interchangeably. The term "ecological filler" means a mixture of flame retardants, i.e. sheep wool fibers and expanded graphite, similarly "mix of materials" - sheep wool and graphite, "final product" - modified polyurethane foam.

In Fig. 1, the number 1 denotes powdered wool fibers; 2 - graphite; 3 - polyol; 4 - polyisocyanate; 5 - chemical reactor; 6 - casting of the mixture; 7 - final product.

In Figures 2 and 3, the letter A indicates unmodified polyurethane foam; B - polyurethane modified with powdered wool in an amount of 15% by weight in relation to polyurethane; C - polyurethane modified with a mixture of flame retardants, i.e. fillers in the amount of 15% by weight in relation to the polyurethane matrix, in which the share of powdered wool is 10% and graphite 5% by weight; Y - burner set to a temperature above 300°C, S1 - modified and unmodified samples prepared for combustion; S2 - start of combustion of samples; S3 - modified and unmodified samples at the end of the combustion reaction; S4 - samples after the combustion reaction.

To obtain the modified foam, an ecological mixture of flame retardants was used - powdered wool 1 obtained from wool waste, which was previously washed, dried, ground to a particle size between 0.05-0.4 mm at a powder density of 0.48 g/ml; untreated graphite powder 2 with a powder density of 0.60 g/ml and a particle size between 0.12-0.4 mm.

In the first stage, wool and graphite were mixed with a share of 50-75% and 25-50% by weight, using a mechanical mixer. The filler mixture was then added to the polyol, mixed with a mechanical stirrer, and the isocyanate was added. The mass fraction of fillers and polyurethane matrix was 5-30% and 70-95%, respectively. The mass fraction of powdered wool and graphite in the mixture of fillers was 50-75% and 25-50%, respectively.

According to the invention, a method of modifying flexible polyurethane foam using powdered wool and expanded graphite in a proportion of 50-75% by weight. and 25-50% by weight, suitably takes place in two steps. The first stage consists in mixing the appropriate amount of powdered wool 1 and expanded graphite 2 in the proportion of 50-75% by weight. and 25-50% by weight, respectively, with polyol 3. The second step consists in mixing the polyol masterbatch obtained in step 1 with polyisocyanate 4 using a mechanical stirrer 5 at a speed of 3000 rpm for several seconds. The finished mixture is then poured 6 to obtain the final product 7.

The final product of the invention consists of a matrix of flexible polyurethane foam up to 95% by weight, powdered wool and graphite in the range of 5-30% by weight. The weight percentage of powdered wool and graphite in the filler is 50-75% and 25-50%, respectively. The percentage ratio between polyol and polyisocyanin is 60% to 40%, respectively. The reaction proceeds at room temperature and the final product is annealed for e.g. 24 hours at 70°C.

Polyurethane foam can be modified at different temperatures and mixing speeds. Room temperature 25 ± 1.5°C is described in the examples. The ratio of the ingredients used, the type of fillers and their percentage in the mixture, in accordance with the above-mentioned ranges, have a significant impact on the properties of the final product.

PL 242558 B1

Example 1

Materials used in the example:

The components of the polyether matrix, i.e. a mixture of polyol and isocyanate, are known in the art. Commercially available polyol mixture and isocyanate mixture are the main ingredients used in the production of polyurethane foams.

An example of the composition of the mixtures used is presented in Table 1.

Table 1. Compositions of mixtures used for the synthesis of flexible polyurethane foams

Component Contents [%] Polyol mixture polyether polyol >80.0 polymeric polyol (poly(styrene-co-acrylonitrile)) 5.0-10.0 2,2'-iminodiethanol 0.1-0.5 Isocyanate mixture 4,4'- diisocyanate -methylenediphenyl (MDI) 40.0-60.0 diphenylmethane diisocyanate (isomers) 15.0-25.0 2,4'- diisocyanate -methylenediphenyl 10.0-20.0 prepolymer (MDI+polyol) 5.0-15.0

The mixture of flame retardants was used:

- waste wool fibers in the form of powder with a particle size between 0.05-0.2 mm,

- commercially available powdered expanded graphite with a particle size not exceeding 0.4 mm.

The production method of flexible polyurethane foam modified with a mixture of flame retardants, i.e. fillers in the foam - powdered wool 1 and graphite 2 consists of two stages. First, a filler mixture of 25% (25 g) by weight to final product was combined with 45% (45 g) of polyol mixture 3 at room temperature. Then, at room temperature (about 25 ± 1.5°C), a 30% (30 g) polyisocyanin mixture 4 was added to the obtained mixture and mixed at 3000 rpm for several seconds in a reactor equipped with a mechanical stirrer 5. The final mixture was placed in a mold and were heated in an oven at 70°C for 24 hours. The final product 7 contained a flexible polyurethane foam (consisting of the polyol mixture and the polyisocyanate mixture shown in Table 1) in an amount of 75% by weight and a blend of fillers (powdered wool, graphite) in an amount of 25% by weight. The weight percentage of the powdered wool and graphite content was 50% (12.5 g) and 50% (12.5 g), respectively. The weight percent of polymeric polyol and polyisocyanate was 60% and 40%, respectively.

Table 2. Composition and density of final products for example 1

i. Ingredients mass, g Flexible, unmodified polyurethane foam Flexible modified polyurethane foam Powdered wool 1 0.0 12.5 Expanded graphite 2 0.0 12.5 Polyol mixture 3 60.0 45.0 Polyisocyanate mixture 4 40.0 30.0 ii. Density, kg/m ³ 100.5 108

PL 242558 B1

Example 2

The procedure is carried out similarly as described in Example 1 using the raw materials shown in Table 1 except that 20% by weight (20 g) of wool powder 1 was mixed with 48% (48 g) of polyol mixture 3 at room temperature and then 32% (32 g) of polyisocyanate mixture 4 was added to the obtained mixture and mixed at room temperature at 3000 rpm for several seconds. The final blend was placed in mold 6 and baked in an oven at 70°C for 24 hours. The final product obtained by method 7 contained a flexible polyurethane foam (consisting of the polyol mixture and the polyisocyanate mixture shown in Table 1) in an amount of 80% by weight and one filler - powdered wool - in an amount of 20% by weight.

Table 3. Composition and density of final products for example 2

i. Ingredients mass, g Unit measure Flexible polyurethane foam Flexible modified polyurethane foam Powdered wool 1 g 0.0 20 Expanded graphite 2 g 0.0 0.0 Polyol mixture 3 g 60.0 48 Polyisocyanate mixture 4 g 40.0 32 ii. Density, kg/m ³ kg/ ^m3 100.5 102.5

Unmodified polyurethane foam was prepared similarly to examples 1 and 2, using the raw materials shown in Table 1. The same conditions were maintained for the preparation of the foam according to the invention and the comparative - unmodified.

The production process was as follows: 120 g of polyurethane foam - 60% by weight of polyol mixture (72 g) and 40% by weight of polyisocyanate mixture (48 g) - were stirred for several seconds in the reactor with a mechanical stirrer at 3000 rpm. The final mix was poured into a mold and baked in an oven at 70°C for 24 hours. The final product was a flexible, unmodified polyurethane foam consisting of 60% by weight polyol mixture (72 g) and 40% by weight polyisocyanate mixture (48 g).

Example 3

The procedure is carried out similarly as described in Example 1, using the raw materials shown in Table 1. The percentage (based on the total weight of the polyurethane foam blend) of powdered wool (15% by weight, equal to 15 g) and all other conditions are left unchanged, i.e. which were used in Example 1-2. The total weight of the polyurethane foam components was reduced from 100 g to 85 g, the density of the mixture was 105.5 kg/m ³ . Example 4

The procedure is carried out similarly as described in Example 1, using the raw materials shown in Table 1. The percentage (based on the total weight of the polyurethane foam blend) of powdered wool (10% by weight, equal to 10 g) and all other conditions are left unchanged, i.e. which were used in Example 1-2. The total weight of the polyurethane foam components was reduced from 100 g to 90 g, the density of the mixture was 105.5 kg/m ³ . Example 5

The method of obtaining the foam is consistent with the method presented in Example 1, using the raw materials shown in Table 1. Percentage (relative to the total weight of the polyurethane foam mixture) of flame retardants (15% by weight, equal to 15 g, with 10 g being sheep wool, and 5 g expanded graphite) and all other conditions were left unchanged, i.e

PL 242558 B1 as used in Example 1-2. The total weight of the polyurethane foam components was reduced from 100 g to 85 g, the density of the mixture was 105.5 kg/m ³ .

Table 4. Summary of substrate consumption for the production of the final product in examples 1-5 and unmodified polyurethane foam.

Final product Filler content, % by weight Reduction of polyisocyanate, % by weight Unmodified foam polyurethane 0.0% 0.0% Flexible polyurethane foam modified with a mixture of powdered wool and graphite, example 1 25.0 25.0 Flexible polyurethane foam modified with powdered wool, example 2 20.0 20.0 Flexible polyurethane foam modified with powdered wool, example 3 15.0 15.0 Flexible polyurethane foam modified with powdered wool, example 4 10.0 10.0 Flexible polyurethane foam modified with a mixture of powdered wool and graphite, example 5 15.0 15.0

PL 242558 B1

Table 5. Mechanical properties of modified and unmodified polyurethane foam

Foam symbol in Fig. 3 A sample deformation, % 10 20 thirty 40 50 Compressive stress, kPa AND 0.0% filler (unmodified flexible polyurethane foam) Example 1 8.6 10.6 12.4 14.8 18.3 b Flexible polyurethane foam modified with powdered wool in the amount of 15% by weight Example 3 7.9 10.6 13.7 18 24.9 c Flexible polyurethane foam modified with a mixture of flame retardants in the amount of 15% by weight (powdered wool 10% by weight, graphite 5% by weight) Example 5 8.6 10.7 13.3 16.9 22.7

According to the results presented in examples 1-5, it can be stated that the amount of components containing polymeric polyol and polyisocyanate in the case of modified, flexible polyurethane foam modified with a mixture of fillers (wool, graphite) was reduced, in particular, the amount of isocyanate is significantly reduced compared to the unmodified foam. . This reduction depends on the level of fillers content. An interesting fact from the comparison of the samples is that the modified and unmodified products had similar densities, which is reflected in their application.

During the mixing process, there is no interaction between the polyurethane matrix and fillers, which resulted in good dispersion and the possibility of adding up to 30% by weight of fillers.

According to the flammability results shown in Fig. 2, it is found that the best flame retardant effects of the polyurethane material are obtained only with the foam modified with a mixture of fillers.

The results shown in Fig. 2 indicate that the modified polyurethane foam with powdered wool in a mixture of fillers is characterized by a lower amount of fumes and the lack of liquid combustion products during the air test with the use of a heater (temp. 300°C) compared to the unmodified foam and modified only with wool. .

Analyzing the results, it can be concluded that powdered wool in the filler mix has a large impact on the density of the final product. The reason for this is the elasticity of the wool fiber and its viscosity during mixing, especially at high filler contents. The final test product, consisting of modified, flexible polyurethane foam, with a share of about 5-30% by weight of filler, especially 10-25%, is characterized by higher fire resistance.

The modification of polyurethane foam with a renewable material such as sheep wool fiber and inexpensive graphite is an economical, environmentally friendly way of production. The transformation of this technology in the conditions of a mobile system is also possible due to the light weight of wool and graphite fibers, moreover, the modification does not require high energy inputs and takes place at room temperature.

PL 242558 B1

The final product of the invention, a flexible polyurethane foam modified with powdered wool and expanded graphite, has good mechanical properties, such as compressive and tensile strength. The mechanical properties were tested using a Zwick/Roell 1000N testing machine in two modes: compression and tension. The samples were compressed in accordance with the PN-EN ISO 604:2006 standard, at a compression speed of 10%/min. The results presented in Table 5 show that the addition of a mixture of flame retardants in the form of sheep wool and expanded graphite does not significantly affect the compressive strength. A slight increase in compressive stress as a function of deformation is observed with the addition of a mixture of flame retardants to the polyurethane matrix. The tensile test was performed in accordance with the PN-EN ISO 527-1:2012 standard, at a tensile speed of 50 mm/min. The obtained results, presented in Fig. 3, prove that the addition of a mixture of flame retardants to the polyurethane matrix causes an increase in stiffness and a slight deterioration in the tensile strength of flexible polyurethane foams. Comparing both tests, it can be concluded that the addition of a mixture of flame retardants to the polyurethane matrix does not deteriorate the mechanical properties, which is an advantage of the proposed solution.

Claims (6)

1. Polyurethane foam containing a matrix in the form of a mixture of polyol and isocyanate and a flame retardant additive, characterized in that as a flame retardant it contains a mixture of ground sheep wool and graphite in the amount of 5-30% by weight in the foam, the weight percentage of powdered wool and graphite in the mixture of flame retardants is 50-75% and 25-50% by weight, respectively. 2. The foam of claim The composition of claim 1, wherein the matrix is present in an amount of 70 to 95% by weight. 3. The foam of claim 1 or 2, characterized in that the percentage ratio between the polyol and the isocyanate in the matrix is 50-70% by weight and 50-30% by weight, respectively. 4. A method of obtaining polyurethane foam consisting in mixing a matrix with a flame retardant, characterized in that the mixture of flame retardants is obtained by mixing crushed sheep wool and graphite with a share of 50-75% by weight of wool and 25-50% by weight of graphite, and the mixture of flame retardants is added to the matrix in an amount of 5-30% by weight. 5. The method of claim 4, characterized in that the mixture of flame retardants is mixed with the matrix in an amount of 70 to 95% by weight. 6. The method of claim 4 or 5, characterized in that the percentage ratio between the polyol and the isocyanate in the matrix is 50-70% by weight and 50-30% by weight, respectively.