DE2506599A1 - FLAME RETARDANT FOR POLYURETHANE FOAM - Google Patents

Description

CIBA-GEIGY AG, BASEL (SWITZERLAND)

DR. ERLEND DINNE PATE MTANWALT 28 BREMEN

Case 3-9290 uhlandstrasse 25

Germany

Flame retardants for polyurethane foams

The invention relates to new phosphonate mixtures obtained by reacting pentaerythritol with dimethyl methane ^ phosphonate are obtained, and their use as flame retardants for polyurethane foams.

The flame retardancy of plastics is particularly important for plastics that are used as construction materials be used. Foam plastics are particularly at risk because they are particularly vulnerable because of their increased surface area burn easily. To reduce the risk of fire, such engineering plastics are often flame retardant Mistake. While with most plastics

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only a physical addition of the flame retardant is possible, one has the option of a chemical one with the polyurethanes and the foams made from them Reaction of the flame retardant if the flame retardant has groups that react with isocyanates, such as hydroxyl or amino groups. The chemical incorporation of a flame retardant has the advantage over the physical admixture, that a gradual loss of effectiveness through migration, extraction or sublimation is not possible.

There have therefore already been phosphorus compounds containing hydroxyl groups, such as those produced by the reaction of polyols with trialkyl or triaryl phosphites, proposed in US Pat. No. 3,263,002 as flame retardants for polyurethanes. These polyol phosphites are not very suitable as flame retardants because of their hydrolytic sensitivity, they can, however, be converted into phosphonates by an Arbuzow reaction with organic halogen compounds, which are relatively stable to hydrolysis. Such phosphonates of polyols, which by Arbuzow reaction of the corresponding Polyol-phosphites are formed, are described, for example, in U.S. Patents 3,263,003, 3,265,681, 3,330,888 and 3,511,857. In these Patent specifications are also mentioned that as a polyol, inter alia, pentaerythritol in various molar ratios reacted with trialkyl or triaryl phosphites and the resulting phosphite ester by subsequent reaction with an organic halogen compound into a hydroxyl-containing one Phosphonate or phosphonate mixture converted. These products can be used as flame retardants for polyurethanes are used, but they have the disadvantage of high manufacturing costs, mainly due to the relatively high Cost of the trialkyl phosphite and the halogen compound are based.

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It has now been found that novel phosphonate mixtures, which are useful as flame retardants for polyurethanes can be prepared by that one pentaerythritol with 2 to 4 moles of dimethyl phosphonate at temperatures of 50-200 ⁰ C, and optionally post-treated the reaction mixture with alkylene oxides. Compared to the known polyol phosphonates, these new phosphonate mixtures have the advantage of being more economical to manufacture, since the dimethyl methanephosphonate used as the starting material is obtained as a by-product in the manufacture of other technical products. Compared to trialkyl phosphites, this substance also has the advantage of physiological harmlessness, odorlessness and storability. Furthermore, the new phosphonate mixtures can be produced in one step compared to the two-step production process of the known phosphonate flame retardants. Another advantage of the new phosphonate mixtures is their usability. While similar phosphonates of polyols are suitable for the production of rigid polyurethane foams, they are only suitable to a limited extent for the flame protection of flexible polyurethane foams, since they noticeably impair their compression set behavior. This is less the case with the new phosphonate mixtures, even if they are used in the crude state without further purification or separation operations, as occur in the aforementioned reaction. Compared to halogen-containing flame retardants, the phosphonates according to the invention have the advantage that, in the event of a fire, no hydrogen halide vapors can form, which are dangerous both because of their physiological effect and because of their corrosive effect.

The invention therefore relates to novel phosphonate mixtures, the phosphonate dimethyl-by reaction of pentaerythritol with 2 to 4 moles at 50-200 ⁰ C and, where

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if aftertreatment with an alkylene oxide are available. The conversion can be accelerated by using catalysts. Known transesterification catalysts are suitable for this, preferably alkali or alkaline earth metals, oxides or alcoholates. Examples are Na, K. Ca, MgO, CaO, NaOCH ₃ , NaOC ₂ H ₅ , Mg (OC ₂ Hc) ₂ , Ca (OCHo) ₂ or KOC (CH ₃ ) O.

The temperature required for transesterification also depends on the type of catalyst in question. The course of the transesterification can be determined from the amount of split off • methanol, which is why the reaction is appropriate executes so that the split off methanol is constantly distilled off. Execution of the reaction under a massive A vacuum, for example at 100 torr, facilitates the distilling off of the methanol and accelerates the reaction. Included of this reaction the pentaerythritol is functionally tetravalent and the phosphonate used is functionally divalent A large number of reaction products are formed, the composition of which can be influenced by the reaction conditions is. For example, at a molar ratio of pentaerythritol: phosphonate of 1: 2, a relatively large amount of non-cyclic diphosphonate is formed the formula

0
Il CH ₀ OH
ι 2 0
π CH ₃ -PO-CH ₂ - -C-CH ₂ - -0 — P — CH "
I. OCH CH ₂ OH OCH

In addition, cyclic diphosphonates are also formed, e.g. the link

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-D-

II OO — CH ₀ CEL — O — P — CH-

ρ ρ ι

y \ / \ och

CH ₃ Q-CH ₂ CH ₂ OH ^

Such a reaction mixture also contains monophosphonates and triphosphonates of pentaerythritol, as well as oligomeric polyphosphonates, for example those of the formula

OH, —P — O—

CH ₀ OH 0

I Il

CH ₀ —C — CH ₀ —0 — Ρ — 0—

² I ² I

CIUOH CH.

OCH

OH CH

—CH -C (CH ₀ OH) "

With a molar ratio of the starting components of 1: 3 or 1: 4, correspondingly more tri- and tetraphosphonates are formed. Most of these phosphonates have hydroxyl groups, which are important for incorporation into polyurethanes. Their content in the phosphonate mixture can be determined by determining the hydroxyl number using known methods. The mixtures according to the invention can also contain small amounts of substances which are not phosphonates, for example unchanged pentaerythritol or substances with free phosphonic acid groups. The latter arise above all when the reaction is carried out at relatively high temperatures, for example above 150 ^° C. The content of such acidic groups in the reaction mixture can be determined by determining the acid number (neutralization number). Since these acidic groups can interfere with the use of the phosphonate mixtures for the flame protection of polyurethane foams, it is advisable in these cases to eliminate them. This can be done by post-treating the reaction mixture with an alkylene oxide

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at temperatures of 40-100 ⁰ C, preferably by treatment with propylene oxide at 70-80 ⁰ C. At this after-treatment, esterification of the acid groups occurs. Which can be controlled by tracking the acid number.

The phosphonate mixtures obtainable according to the invention are odorless and almost colorless products that are liquid to viscous. The more dimethyl methanephosphonate per Mol pentaerythritol is used for the reaction, the lower the viscosity of the products and the higher their viscosity Phosphorus content. One can therefore assess the properties of the phosphonate mixtures vary greatly due to the reaction conditions.

The incorporation of the hydroxyl-containing phosphonate mixtures can be added to the polyurethanes by mixing them with the starting components before or during the formation of the polyurethanes happen. In the simplest case, the phosphonate mixtures are mixed with the hydroxyl-containing component (polyester or polyether) before it reacts with the polyisocyanate component. But you can also use a phosphonate mixture with a polyisocyanate to form a phosphorus-containing one Implement adduct which, depending on the selected molar ratio, can have predominantly hydroxyl or isocyanate end groups and then with further polyisocyanate or polyhydroxyl component or both components to form the finished foam is implemented. Such step-by-step processes are well known in polyurethane foam production their implementation is not impaired by the addition of the phosphonate mixtures. Likewise, everyone can do the production additives commonly used in polyurethane foams such as catalysts, accelerators, dispersants, blowing agents, Silicones, antistatic agents etc. can be used.

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The amount of phosphonate mixture required to achieve adequate flame protection depends on the phosphorus content of the same, of the chemical structure of the polyurethane components and of the physical structure of the foam away. In general, additions of 2-8% by weight of phosphonate mixture, based on the foam, or about 3-10% by weight are sufficient % By weight based on the hydroxyl component.

The horizontal test according to ASTM D 1692 is suitable for assessing the burning behavior of foams. Here, samples of 15 cm x 5 cm x 1.25 cm are placed horizontally on a sieve and on the outer edge through a burner flame ignited. The length of the burning distance until the fire is extinguished and the burning speed are measured.

Since foams often require a long service life, apart from the flame retardant effect itself its resistance to prolonged storage is also of great importance. Many potential flame retardants lose their effectiveness when the foam is stored for a long period of time or when it is exposed to moisture, and this can in the event of a fire a surprising failure of the flame retardant, although the foam immediately after its production was not flammable. The simulation of long-term storage takes place in the test by storage at elevated temperature, in a dry or humid atmosphere. The toughest resistance test is storage in superheated steam. The inventive flame retardants show under very good storage and hydrolysis stability under these test conditions.

It is also important for the flame retardancy of foams that the addition of the flame retardant means that the The speed of foam formation and curing is not significantly influenced, so that the shaping processing

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processing (foaming) can take place on the same machines as with the non-flame-retardant foams. After all, it is important that the technological properties of the foams as little as possible altered by the addition of the flame retardant. This applies above all to the hardness or elasticity and the porosity of the foams, and these properties should also be retained in the event of prolonged storage or the influence of moisture. The flame retardants according to the invention are completely satisfactory in this respect, while, for example, when using a flame retardant based on 1,3-bis [di- (ß-chloroethyl) phosphato] -2,2-di- (chloromethyl) propane, both the Flame resistance as well as the elasticity of polyurethane foams decreases significantly with prolonged storage or moist storage.

The following examples describe the preparation of the phosphonate mixtures according to the invention and their preparation Use as a flame retardant for polyurethane foams.

Parts are parts by weight and% are percentages by weight to understand, the temperatures are given in degrees Celsius.

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_ 9 -

example 1

0.1 mol of sodium methylate as a 30% methanolic solution is added dropwise to two moles of dimethyl methanephosphonate and 1 mole of pentaerythritol with stirring and under a weak vacuum. About 3 mol of methanol distill off with slow heating to 130 ° and at 100 Torr vacuum. The resulting viscous, odorless product has an acidity below 0.1 meq / g and an OH number of 350.

Example 2

0.2 mol of sodium methylate is added to 4 mol of dimethyl methanephosphonate and 1 mol of pentaerythritol with stirring and under a slight vacuum added dropwise as a 30% methanolic solution. Distilled while slowly heating up to 130 ° and at 100 Torr vacuum about 3 moles of methanol.

The resulting product is liquid and odorless. The acidity is below 0.1 meq / g and the OH number approx. 140.

Example 3

2 moles of dimethyl methanephosphonate, 1 mole of pentaerythritol and 0.1 mole of calcium oxide are heated to 150 ° under a vacuum of 400 mm. Methanol is distilled off in the process. As soon as about 2 mol of methanol 64 g (80 ml) have distilled off, the reaction is terminated. The acidity of the product is approx. 2.0 meq / g. At 70 ° and normal pressure, 1 mol of propylene oxide (58 g =

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68 ml) are added dropwise with stirring within 6 hours until the product is obtained no longer absorbs propylene oxide. (This can be seen from the no longer decreasing reflux of propylene oxide). The thus obtained vi-skoce product now has an acidity of 0.03 meq / g and a hydroxyl number of 350.

Example 4

The procedure is as in Example 3, but instead of the aftertreatment with propylene oxide, 1 mole of ethylene oxide is used initiated in gaseous form at 40-50 °. The phosphonate mixture obtained in this way shows a somewhat lower viscosity, but is in its other properties the same as the product from example 3. Its hydroxyl number is 300.

Example 5

To 4 moles of dimethyl methanephosphonate and 1 mole of pentaerythritol is added with stirring and a weak vacuum (100 torr) 0.2 mol of calcium methylate was added dropwise as a methanolic solution. 3.7 mol of methanol are distilled off while heating to 130 °.

The resulting product is filtered and 283 g of liquid, odorless filtrate are obtained. The characteristics are: OH number 60, acidity 0.01 meq / g.

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Example 6

Production of flexible polyurethane foams with the addition of phosphonate mixtures.

Basic recipe parts by weight

Desmophen ^ - ^ 7100 (polyether polyol with hydroxyl 100.0 49 of the paint factories Bayer AG, Leverkusen)

Solution of triethylenediamine in 2 parts 0.35

Dipropylene glycol

Silcon DC 190 (surface-active polysiloxane 1.0 from Dow Corning Corp., Midland)

Water 3.5

Phosphonate mixture of Examples 1 to 5 6.0

Desmodur®T 80 (mixture of 80% 2,4- and 20% 2,6-toluene diisocyanate from paint factories

Bayer AG, Leverkusen) 43.0 to 47.0

Tin octoate 0.06 to 0.16

The above components are in a high speed mixer (2000 rpm) mixed at room temperature, the isocyanate being added last. The time of the encore of the isocyanate until the mixture has a cream-like consistency is reported as the "cream time". the The time it takes for the foam to reach its maximum height is specified as the "rise time". The time until the foam doesn't is more tacky is referred to as "tack free". After the freedom from tack has been achieved, the foam will cure completed by heating at 140 ° for one hour.

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After a storage time of 24 hours, the test specimens are cut out of the foam. The results of the exams are shown in the table below. As a comparison, the same foam was produced without flame retardants.

Test results

a) Flame retardant used: Experiment no.

Acidity in mVal / g hydroxyl number Viscosity in cst Phosphorus content% 0.02 0.01 0.03 0.02 0.01 348 140 350 349 60 20,000 300 3000 2100 1260 19.3 22.5 15.5 15.5 22.5

without

b) Foam production: Desmodur® T 80 tin octoate g / 100 g polyol cream time, sec rise time, sec tack-free time, min 47.0 45.0 "47.0 47.0 44.3 43.7

0.04 0.16 0.08 0.08 0.12 0.16 10 10 20th 15th 10 10 125 130 115 125 115 90 3 3 3 3 3 3

c) Physical properties of the foam

Compression set

2)

Compression hardness

Air permeability

3)

in %

70 hours storage 22 ° C 22 hours storage 70 ° C 4)

ml / min 3 3

14th
10

4th
11

1 5

1.08 1.3 2.5 2.0 2.9 2.7 2.7 6.2 18.8 19.0 19.0 18.5

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d) Burning behavior ASTM D 1692 ¹ ^ 1 day 50 65 55 65 110 burns Horizontal test mm 2 days 75 65 75 100 105 It Burning distance 4 days 70 70 50 105 60 It Storage 140 ⁰ C 7 days 75 60 45 120 95 Il dry 1 day 55 60 70 75 45 It 2 days 55 70 65 55 burns ti 4 days 60 60 70 65 110 ti Storage 90 ⁰ C 7 TaKe 45 60 65 60 115 It wet 70 55 55 60 70 Il

Saturated steam at 120 ^° C

5 hours

95

70 burns 105 burns

Burning speed mm / min 10 10 9 8th 9 27 Storage 140 ° ( 8th 10 11 9 9 12th 10 10 9 8th 9 19th 9 12th 9 12th 9 11 9 9 9 9 9 15th Storage 90 ⁰ C 10 11 9 9 10 - wet 10 11 9 10 10 - 10 10 7th 5 10 - 10 9 6th 9 10 - Saturated steam 120 ^c 9 10 4th 6th 9 - Z 1 day 2 days 4 days 7 days 1 day 2 days 4 days 7 days ¹ C / 5 hours

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Remarks:

1) The specified values for burning length and burning rate are mean values from 3 measurement samples. The result is referred to as "burns" (br) if 2 out of 3 samples completely burned out (150 mm).

2) - The samples are stored for 3 days under normal conditions before the test. They are then compressed to 50% and so for 22 hours at 70 ⁰ C, respectively. Stored for 70 hours at 22 ° C. The value given is the relative residual deformation 30 minutes after relaxation. (Mean of 3 samples).

3) The air permeability is measured on 8 cm thick samples tested with a pressure difference of 10 mm. The specified value is ml air per minute and 28 cm ^ area.

4) Deformation force in kg measured on unaged samples at 50% compression. (DIN 53 577).

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Claims (8)

DR. ERLEND DlNNi Claims UHLANDSTRASSE A process for preparing a composition suitable as a flame retardant for polyurethane foams Phosphonatgemiscb.es, characterized in that pentaerythritol containing from 2 to 4 moles of dimethyl phosphonate at 50 to 200 ⁰ C and reacting · the reaction mixture, if appropriate, at 40 to 100 ⁰ C with an alkylene oxide post-treated. 2. The method according to claim 1, characterized in that the reaction is carried out in the presence of transesterification catalysts performs. 3. The method according to claim 2, characterized in that the catalyst used is alkali metal or alkaline earth metal Ie, oxides or alcoholates are used. 4. The method according to claim 1, characterized in that the reaction product at 40 to 100 ⁰ C with the content of acid groups in the reaction mixture equivalent or slightly excess amount of an alkylene oxide post-treated. 5. The method according to claim 4, characterized in that there is used as alkylene oxide propylene oxide, and the after-treatment is carried out at 70 to 80 ⁰ C. 6. A method for flame protection of polyurethane foams by the incorporation of hydroxyl group-containing phosphonates, characterized in that one uses a Phosphonatgemisch, the phosphonate dimethyl-by reaction of pentaerythritol with 2 to 4 moles at 50 to 200 ⁰ C and optionally an aftertreatment with an alkylene oxide is made. 09834/1026 7. The method according to claim 6, characterized in that that the phosphonate mixture before or during the polyurethane formation is added to the starting components. 8. A flame-retardant polyurethane foams, -the as flame-protective component 2 to 10 wt .-% of a phosphonate · mixture, as by reaction of pentaerythritol with 2 to 4 moles of dimethyl phosphonate at 50 to 200 ⁰ C, and optionally a post-treatment with a Alkylene oxide is formed, contained built-in. 509834/1026