PL231699B1 - Elastic polyurethane foam with limited inflammability and method for producing it - Google Patents

Description

The subject of the invention is a flexible, flame-retardant polyurethane foam and a method of its production, the foam being modified to improve the performance and fire resistance of the porous polymer.

Foamed polyurethanes face more and more requirements regarding their functional, mechanical, fire-resistant and other properties. Therefore, the interest in obtaining and modifying polyurethane foams continues to grow. In recent years, great emphasis has been placed on the modification of polyurethanes and other polymers with environmentally friendly compounds - not containing halides, antimony oxide or melamine cyanurate. A very important aspect of the synthesis of polyurethane foam are its functional properties and, in many cases, fire resistance. One of the very important issues in limiting the flammability of polyurethane foam is to minimize the dripping phenomenon that causes the spread of fire. In order to improve the selected properties of the porous polyurethane, the polymer matrix is modified with additive and / or reactive additives of various kinds. In the last half-century, special attention has been paid to polymers with the addition of nanofillers. Silicon-containing compounds are very often used as nanoadditives. Properly carried out modification of polyurethane foams with such compounds may allow for the improvement of functional, mechanical and other properties. In addition, the accurate selection of a synergistically operating system of industrial flame retardants and modified silicate, as well as properly designed and prepared, modified polyurethane foam may have increased flame resistance.

In the publication of the article "Flammability reduction of flexible polyurethane foams via carbon nanofiber network formation" Polym. Adv. Technol. 2008, 19, 588-595 Zammarano M. et al., It was shown that the addition of carbon nanofibers to the industrial flame retardant system allows to reduce the dripping phenomenon during sample burning. A serious disadvantage of this modified polyurethane is the use of environmentally unfriendly compounds containing bromine as flame retardant.

In turn, the publication of the article "Heat release and structural collapse of flexible polyurethane foam" Polymer Degradation and Stability 2010, 95, 1115-1122 Kramer R. H. et al. Describes the preparation of a flexible polyurethane foam containing phosphate flame retardants. The obtained foam was characterized by a lower effective heat of combustion, worse ignitability and a lower rate of heat release during burning than the sample without flame retardants. A disadvantage of this known polyurethane foam is also the use of halogen flame retardants for its preparation.

Inventive publications WO 2015013226 A1 and US 2007221892 A1 disclose modified, flexible polyurethane foams characterized by increased flame resistance. The disadvantage of these known solutions is the addition of compounds containing halogen in their structure.

It is also known from the publication of the invention No. WO 2015050691 A1 shows a method of obtaining polyurethane foams with significantly increased resistance to fire. However, toxic melamine cyanurate is incorporated into the foam, and furthermore, these polyurethane foams are foamed with fluorine-containing compounds.

From the international publication of the invention publication no. WO 2009007715 A1, a flexible polyurethane foam with limited flammability is known, obtained from polyol, polyisocyanates and a nanofiller such as halloysite. On the other hand, from the US application description No. US 2004082697 A1 it is known to modify inorganic clays, including halloysite, with a melamine-formaldehyde resin. Modified clays are used as flame retardant additives in foams.

Flexible, flame-retardant polyurethane foam in the form of addition of at least one linear polyol with a diisocyanate, containing a nanofiller, the nanofiller containing organomodified halloysite with an organically modified melamine-formaldehyde adduct, and this modified halloysite is in the form of micrometric grains according to the invention in that it comprises a halogen-free flame retardant system with a different mechanism of action, said system containing said nanofiller and at least one additive ammonium phosphate and / or boric acid flame retardant.

A method of producing a flexible polyurethane foam with limited flammability, containing a nanofiller, and the foam is obtained by reacting a polyol premix of at least one linear polyol with a diisocyanate in the presence of an addition catalyst and in the presence of surface tension reducing agents and water as a blowing agent, and an organically modified filler is used and mechanically comminuted halloysite, the halloysite being previously modified

According to the invention, the melamine-formaldehyde adduct is characterized in that the melamine-formaldehyde adduct is obtained with a molar ratio of melamine to formaldehyde from 1: 1 to 1: 4, and a system of halogen-free flame retardants with a different composition is introduced into the premix of polyol foam. a mechanism of action, comprising said nanofiller and at least one additive ammonium phosphate and / or boric acid flame retardant.

Preferably, the melamine-formaldehyde adduct for the modification of halloysite is prepared by heating a mixture of melamine with formalin in a molar ratio of melamine to formaldehyde 1: 2 under reflux at a temperature close to the boiling point of the mixture, and the reaction is carried out to a tolerance of an aqueous resin of 1: 4, and furthermore at during the modification of halloysite, the melamine-formaldehyde adduct is introduced into the halloysite in the form of an aqueous solution and mixed with it at an elevated temperature until a homogeneous mixture is obtained, and then dried and ground into a product with micrometric grain sizes.

Further advantages are obtained when the foam polyol masterbatch is prepared by mixing 50 + 98% by weight of the polyol with a hydroxyl number Loh = 20 + 80 mg KOH / g, 2 + 10% by weight of the blowing agent, 0.5 + 8% by weight of the surface tension reducing agent. and 1 + 10% by weight of modified halloysite and 0.1 + 40% by weight of additive flame retardants, 1 + 40% by weight of ammonium phosphate and / or 0.1 + 10% of boric acid.

The polyol masterbatch is produced by the multi-stage homogenization of polyol, blowing agents, foam stabilizers and flame retardants. In turn, polyurethane foam is obtained by the reaction of a diisocyanate, a polyol masterbatch and an addition catalyst.

The subject of the invention is a flexible, flame-retarded polyurethane foam and a method of producing such a foam containing, as a nanofiller, developed within the scope of the invention, modified halloysite. Polyurethane foams with this nanofiller are characterized by a lower density than the foam without additives, and the addition of this nanofiller significantly eliminates dripping when applying the flame to the foam. In addition, foams containing a system of synergistically acting halogen-free flame retardants and the mentioned nanofillers are characterized by increased fire resistance.

The research conducted during the development of the invention was aimed at obtaining a flexible polyurethane foam, characterized by good operational properties and increased flame resistance. Work on improving flame resistance has focused primarily on minimizing dripping. During the research, special attention was paid to environmentally friendly commercial flame retardants, such as: ammonium polyphosphate, boric acid, triethyl pyrophosphate, tribytyl polyphosphate, zinc borate, expanding graphite, melamine and nanofillers. After numerous tests and modifications were carried out, a foam was obtained containing a new nano-additive - modified halloysite which inhibits dripping during material combustion. The porous polyurethane had this apparent density than the unmodified foam. Moreover, by adding a nanofiller to the polyurethane along with appropriately selected flame retardants, a significant increase in the flame resistance of the obtained foam was achieved. During the preparation of these foams, it turned out to be important to select the modifiers properly and to homogenize the composition.

The invention is explained in more detail in non-limiting examples.

Example 1 comparative

Preparation of modified halloysite

The melamine mixture with the formalin neutralized to pH 8.0 + 8.5 in the molar ratio of melamine to formaldehyde 1: 2 is heated under reflux at a temperature around the boiling point of the mixture. The reaction is carried out to a resin tolerance of 1: 4 in water. The modified halloysite is obtained by mixing the previously prepared melamine-formaldehyde adduct and unmodified halloysite in a mass ratio of 4: 1. The resulting mass is allowed to stand at room temperature for 24 hours. The mixture is then dried in an oven for 4 hours at 110 ° C. The dried halloysite is ground in a ball mill and then sieved through a sieve with a mesh size of 80 µm.

Preparation of polyol masterbatch

The polyol masterbatch is obtained by mixing the following components: 93% Rokopol 3600 polyol with a hydroxyl number Loh = 45 + 50 mg KOH / g; 1.9% silicone oil with a viscosity <50 mPas, 2.3% distilled water, 2.8% modified halloysite. The mixture is homogenized for 50 min in a high-speed mixer with a rotational speed of the turbine stirrer of 5000 min ^-1 . The premix is then grated for 5 minutes with a high-speed mixer of the type

PL231 699 Β1 cylinder-cylinder ensuring a shear rate of -1500 s ¹ . To 68.7 g of the thus homogenized polyol premix, 30.7 g of 4,4'-diphenylmethane diphenyl isocyanate under the trade name Isonate M 340 and 0.6 g of the catalyst 1,4 diazodicyclo [2.2.2.] Octane (DABCO) are added and mixed intensively for several seconds, and then poured into the mold. The foam growth time was 63 s, and the drying time 234 s. The polyurethane foam obtained in this way (A1 in Table 1) is characterized by a lower density than the foam (A0 in Table 1) which does not contain modifiers. During the combustion test of the obtained porous polyurethane, the phenomenon of dripping observed for the reference sample A0 was inhibited. The main application of this type of foam is the preparation of upholstery materials, especially for seats in public transport vehicles or passenger cars.

Table 1

Functional properties of the obtained A1 polyurethane foam and the reference porous polyurethane A0

Name of the foam Al A0 Apparent density, kg / m ³ 45.3 50.4 Temperature in the core during synthesis foams [° C] 132 Oxygen index [%] 18.7 17.4 Phenomena accompanying the burning of foam No dripping Intense dripping

Example 2

Preparation of modified halloysite

The modified halloysite is prepared according to the recipe given in Comparative Example 1.

Preparation of polyol masterbatch

The polyol masterbatch was obtained in several stages. In the first stage, 95.2% of Rokopol 3600 polyol with a hydroxyl number Loh = 45 + 50 mg KOH / g and 4.8% of the modified halloysite were mixed for 50 minutes in a high-speed mixer with a turbine stirrer speed of 5000 min ¹ . The mixture was then ground for 5 min with a high-speed cylinder-cylinder mixer providing a shear rate of 1500 sec. ¹ . 1.7% of a silicone surfactant, 2.2% of distilled water, 1.7% of boric acid and 4.3% of ammonium polyphosphate were added to the mixture thus obtained, constituting 90.1% of the polyol composition. The premix was ground for 5 min with a 1500 S ' ¹ high shear cylinder-cylinder mixer. To 70.4 g of the thus homogenized polyol premix, 29.0 g of 4,4'-diphenylmethane diphenyl isocyanate under the trade name Isonate M 340 and 0.6 g of the catalyst 1,4 diazodicyclo [2.2.2.] Octane (DABCO) were added and mixed intensively. for several seconds, and then poured into the mold. The foam growth time was 98 s, and the drying time was 440 s. The obtained polyurethane foam (A2 in Table 2) is characterized by a significant increase in the oxygen index compared to the unmodified polyurethane foam (A0). During the combustion of the obtained porous polyurethane, the dripping phenomenon was observed to be minimized compared to the reference sample A0. The main application of this type of foam is the preparation of upholstery materials, especially for seats in public transport vehicles or passenger cars.

PL231 699 Β1

Τ a b e I a 2

Functional properties of the obtained A2 polyurethane foam and the reference porous AO polyurethane

Name of the foam A2 A0 Apparent density, kg / m ³ 48.3 50.4 Temperature in the core during synthesis foam 114 126 Oxygen index [%] 22.5 17.4 Phenomena accompanying the burning of foam No dripping Intense dripping

The invention is particularly applicable to the production of polyurethane foams with reduced density, increased fire resistance and largely eliminated dripping of material when applying a flame to the foam.

Patent claims

Claims (5)

1. Flexible, flame-retardant polyurethane foam, in the form of addition of at least one linear polyol with a diisocyanate, containing a nanofiller, where the nanofiller is organically modified halloysite with melamine-formaldehyde adduct, and this modified halloysite is in the form of grains ground to micrometric sizes, characterized by in that it comprises a halogen-free flame retardant system with a different mechanism of action, the system comprising said nanofiller and at least one additive ammonium phosphate and / or boric acid flame retardant. The method of producing a flexible polyurethane foam with limited flammability, containing a nanofiller, and the foam is obtained by reacting a polyol premix of at least one linear polyol with a diisocyanate in the presence of an addition catalyst and in the presence of surface tension reducing agents and water as blowing agent, and the filler is used organically modified and mechanically comminuted halloysite, where halloysite is previously modified with a melamine-formaldehyde adduct, characterized in that the melamine-formaldehyde adduct is obtained with a molar ratio of melamine to formaldehyde from 1: 1 to 1: 4, and introduces the foam into the premix of the polyol foam there is a system of halogen-free flame retardants with a different mechanism of action, containing said nanofiller and at least one additive flame retardant in the form of ammonium phosphate and / or boric acid. 3. The method according to p. 2. The process of claim 2, characterized in that the melamine-formaldehyde adduct for the modification of halloysite is produced by heating the mixture of melamine with formalin in a molar ratio of melamine to formaldehyde 1: 2 under reflux at a temperature close to the boiling point of the mixture, and the reaction is carried out to achieve the tolerance of the aqueous resin 1: 4. 4. The method according to p. 2. The method of claim 2 or 3, characterized in that, during the modification of halloysite, the melamine-formaldehyde adduct is introduced into the halloysite in the form of an aqueous solution and mixed with it at an elevated temperature until a homogeneous mixture is obtained, and then dried and ground into a product with micrometric grain sizes . 5. The method according to p. A method according to claim 2, 3 or 4, characterized in that the foam polyol masterbatch is prepared by mixing 50% by weight of 98% by weight of a polyol with a hydroxyl number Loh 20 80 mg KOH / g, 2 -ί-10% by weight of the foaming agent. 0.5 to 8% by weight of surface tension reducing agent and 1 to 10% by weight of modified halloysite and 0.1 40 wt.% Of additive flame retardants, 1, 40 wt.% Ammonium phosphate, and or 0.1 to 10% boric acid.