WO1990015833A1

WO1990015833A1 - Polyurethane compositions exhibiting reduced smoke density and method of preparing same

Info

Publication number: WO1990015833A1
Application number: PCT/US1990/003370
Authority: WO
Inventors: John W. Miller
Original assignee: Basf Corporation
Priority date: 1989-06-13
Filing date: 1990-06-12
Publication date: 1990-12-27
Also published as: CA2018823A1; EP0435981A1; EP0435981A4; GB9011742D0; GB2232676A

Abstract

A high density polyurethane foam composition which exhibits low smoke upon combustion is the reaction product of a reaction of a resin blend and an isocyanate in the presence of reduced levels of melamine as a flame retardant.

Description

POLYURETHANE COMPOSITIONS EXHIBITING REDUCED SMOKE DENSITY

AND METHOD OF PREPARING SAME

Background of the Invention

1. Field of the Invention

The present invention relates to polyurethane compositions which exhibit low smoke density when combusted and to methods of preparing such compositions. More particularly, the present invention relates to polyurethane compositions utilizing a combination of polyols and in which melamine is used as an additive to impart smoke-resistance to the finished product.

2. Prior Art

In the more than fifty years since Professor Otto Bayer discovered the addition polymerization reaction leading to polyurethanes (1937), the field of polyurethane polymers has become a well established, mature technology. While the first uses of

polyurethanes were in the field of fibers, rigid foams were developed in 1947 and flexible foams in 1952. In the year 1981, world production of polyurethanes

exceeded 3 million metric tons.

By the term "polyurethane" is meant a polymer whose structure contains predominantly urethane

linkages between repeating units. Such linkages are formed by the addition reaction between an organic isocyanate group R - NCO and an organic hydroxyl group [HO ] R. In order to form a polymer, the organic isocyanate and hydroxyl group-containing compounds must be at least difunctional. However, as presently

understood, the term "polyurethane" is not limited to those polymers containing only urethane linkages, but includes polymers containing allophanate, biuret, carbodiimide, oxazolinyl, isocyanurate, uretidinedione, and urea linkages in addition to urethane. The

reactions of isocyanates which lead to these types of linkages are summarized in the Polyurethane Handbook.

Gunter Vertei, Ed. Hanser Publishers, Munich, §1985, in Chapter 2, pages 7-41; and in Polyurethanes; Chemistry and Technology. J. H. Saunders and K. C. Frisch,

Interscience Publishers, New York, 1963, Chapter III, pages 63-118. In addition to polyols (polyhydroxylcontaining monomers), the most common isocyanatereactive monomers are amines and alkanolamines. In these cases, reaction of the amino group leads to urea linkages interspersed within the polyurethane structure.

Within this broad class of compounds, the art has developed specific polyols, isocyanurates, fire retardants and the like to tailor the properties of the products to the attendant needs. One of the more rapidly growing types of polyurethane products is high density polyurethane foam. Such products enjoy

widespread usage such as in vehicles, furniture, decorative trim, etc. While the art has developed suitable flame retardants and blowing agents for these high density foams, the same cannot be said of reducing smoke generation which occurs upon combustion.

For example, in U.S. Patent #4,221,875 there is disclosed the use of melamine as a flame-resistant additive in a polyurethane foam. However, the invention thereof produces excessive amounts of smoke, and does not address the issue of low smoke generation on

combustion. Thus a need exists for high density

polyurethane foams which will exhibit low smoke generation on combustion for use in manufacturing consumer products. The present invention, as will be subsequently detailed, addresses smoke generation in high density and other polyurethane foams.

SUMMARY OF THE INVENTION

The present invention provides a high density polyurethane foam which exhibits reduced smoke

generation on combustion and which employs melamine, in specific quantities as a low smoke generating additive. The foams hereof are prepared by reacting a polyol, preferably, a sucrose-based polyol, and an organic polyisocyanate in the presence of catalyst and in the presence of a specific quantity of malamine.

The present invention, also, provides a method of producing a high density polyurethane foam which exhibits reduced smoke generation on combustion. The method hereof, generally comprises the steps of:

(a) admixing together, at high speed, a polyol or a mixture of polyols and a catalyst.

(b) adding a low smoke-generating component which comprises malamine, in a range of from about 8 to 14%, by weight, of the total composition, while

continuing to agitate the mixture;

(c) adding a blowing agent thereto;

(d) adding a polyisocyanate to the mixture; and,

(e) reacting the components to form a

polyurethrane foam.

As noted, the present invention is

particularly applicable to the preparation of high density rigid polyurethane foams which exhibit low smoke generation on combustion.

For a more complete understanding of the present invention, reference is made to the following detailed description and accompanying examples.

DETAILED DESCRIPTION

As hereinabove notes, and in accordance with the present invention high density rigid polyurethane foams having reduced smoke values, when combusted, are prepared by reacting together;

(a) a polyol or a mixture of polyols;

(b) a polymeric isocyanate;

(c) a catalyst;

(d) melamine in a range of 8-14 weight % as a flame retardant and smoke inhibitor; and

(e) a blowing agent;

the ingredients being mixed together at high speed.

In the preparation of the foams thereof, the isocyanate is, generally, reacted with the polyol (s) in an isocyanate to active hydrogen equivalent ratio of from about 0.5 to 1 to about 10 to 1. The "index" of the composition is defined as the -NCO/active hydrogen ratio multiplied by 100. While an extremely large range may be utilized, most polyurethane processes have indices of from 90 to about 120 or 130, and more

preferably from 95 to about 110. In the case of

polyurethanes which also contain significant quantities of isocyanurate groups, indices of greater than 200 and preferably greater than 300 may be used in conjunction with a trimerization catalyst in addition to the usual polyurethane catalysts. In calculating the quantity of active hydrogens present, in general all active hydrogen containing compounds other then non-dissolving solids are taken into account. Thus the total is inclusive of polyols, chain extenders, functional plasticizers, etc.

As noted, the major components involved in the preparations of the foams hereof are:

(a) a polyol(s),

(b) an isocyanate(s)

(c) a catalyst

(d) a blowing agent, and

(e) melamine, in a range of 8-14 wt. % as a smoke inhibitor. POLYOLS

Hydroxyl group-containing compounds (polyols) useful in the preparation of polyurethanes are described in the Polyurethane Handbook in chapter 3, 3.1 pages 42-611; and in Polyurethanes: Chemistry and Technology in Chapter II, III and IV, pages 32-47. Many hydroxylgroup containing compounds may be used, including simple aliphatic glycols, dihydroxy aromatics, bisphenols, and hydroxyl-terminated polyethers, polyesters, and

polyacetals, among others. Extensive lists of suitable polyols may be found in the above references and in many patents, for example in columns 2 and 3 of U.S. Patent 3,652,639; columns 2-6 of U.S. Patent 4,421,872; and columns 4-6 of U.S. Patent 4,310,632; these three patents being hereby incorporated by reference. A sucrose-based polyol such as that known in the art as Pluracol Polyol 975 may be used to practice the present invention, either, alone or in combination with another polyol such as, e.g., a triol or other glycerine-based polyol, and the like, as well as mixtures thereof.

Also useful in preparing polyurethanes are monomers containing other functional groups which are reactive with isocyanates. Examples of these are preferably the amines, for example the substituted and unsubstituted toluenediamines and methylenedianilines; the alkanolamines; the amino-terminated polyoxyalkylene polyethers; and sulfhydryl terminated polymers, to name but a few. The alkanolamines and amines, particularly diamines, are particularly useful, as the amino group reacts faster than the hydroxyl group and thus these molecules can act as isocyanate chain extenders in situ without the need to prepare prepolymers. Examples of hindered, alkyl substituted aromatic diamines which are particularly useful are disclosed in U.S. Patent

#4,218,543.

In the practice of the present invention, it is preferred to employ sucrose, alone, or in a admixture with other polyols as the polyol. It should be noted in this regard that in its commercially available form, a sucrose polyol is ordinarily dissolved in glycerine or the like. Generally, sucrose, where used in admixture, with glycerine or any other polyol, will be present in amounts sufficient to provide the requisite NCO/OH ratio.

ISOCYANATES

Many isocyanates are useful in the preparation of the polyurethane foams hereof. Examples of such isocyanates may be found in columns 8 and 9 of U.S.

Patent #4,690,956, herein incorporated by reference. The preferred isocyanates are the commercial

isocyanates, such as toluene diisocyanate (TDI)

methylenediphenylene diisocyanate (MDI), and crude or polymeric MDI. Other isocyanates which may be useful include isophoronediisocyanate and

tetramethylxylylidenediisocyanate. Other isocyanates may be found in the Polyurethane Handbook, Chapter 3, 3.2 pages 62-73 and Polyurethanes: Chemistry and

Technology Chapter II, II, pages 17-31.

Modified isocyanates are also useful. Such isocyanates are generally prepared through the reaction of a commercial isocyanate, for example TDI or MDI, with a low molecular weight diol or amine, or alkanolamine, or by the reaction of the isocyanates with themselves. In the former case the isocyanates containing urethane, biuret, or urea linkages are prepared, while in the latter case isocyanates containing allophanate,

carbodiimide, or isocyanurate linkages are formed.

In practicing the present invention the preferred isocyanate is polymethylene polyphenylene polyisocyanate. Such isocyanate is well known and commercially available.

CATALYSTS

The urethane forming reaction is generally catalysed. Useful catalysts useful are well known to those skilled in the art, and many examples may be found, for example, in the Polyurethane Handbook.

Chapter 3, 3.4.1 on pages 90-95; and in Polyurethanes: Chemistry and Technology in Chapter IV, pages 129-217. Most commonly utilized catalysts are teritary amines and organotin compounds, particularly dibutyltin diacetate and dibutyltin dilaurate. Combinations of catalysts are often useful also. Ordinarily, the catalyst is present in an amount ranging from about 0.5 to 1.5 percent, by weight, based on the total weight and, preferably, from about 0.9 to 1.1 percent, by weight, based on the total weight of the composition.

BLOWING AGENTS

Polyurethanes may be prepared in the form of films and coatings, fibers, extruded forms, castings and foams. Non-cellular or microcellular polyurethanes are prepared in substantial absence of blowing agents, while polyurethane foams contain an amount of blowing agent which is inversely proportional to the desired foam density. Blowing agents may be physical (inert) or reactive (chemical) blowing agents. Physical blowing agents are well known to those in the art and include a variety of saturated and unsaturated hydrocarbons having relatively low molecular weights and boiling points.

Examples are butane, isobutane, pentane, isopentane, hexane, and heptane. Generally the boiling point is chosen such that the heat of the polyurethane-forming reaction will promote volatilization.

The most commonly used physical blowing agents, however, are currently the halocarbons,

particularly the cholorofluorocarbons. Examples are methyl chloride, methylene chloride,

trichlorofluoromethane, dichlorodifluoromethane,

chlorotrifluoromethane, chlorodifluouromethane, the chlorinated and fluorinated ethanes, and the like.

Brominated hydrocarbons may also be useful. Blowing agents are listed in the Polyurethane Handbook on page 101. Current research is directed to lowering or eliminating the use of chlorofluorocarbons in

polyurethane foams.

Chemical blowing agents are generally low molecular weight species which react with isocyanates to generate carbon dioxide. Water is the only practical chemical blowing agent, producing carbon dioxide in a one to one mole ratio based on water added to the foam formulation. Unfortunately, completely water-blown foams have not proven successful in many applications, and thus it is common to use water in conjunction with a physical blowing agent.

Blowing agents which are solids or liquids which decompose to produce gaseous byproducts at

elevated temperatures can in theory be useful, but have not achieved commercial success. Air, nitrogen, argon, and carbon dioxide under pressure can also be used in theory, but have not proven commercially viable.

Research in such areas continues, particularly in view of the trend away from chlorofluorocarbons.

In preparing high density foams the blowing agent is generally present in an amount ranging from about 0.5 to 3.0 percent, by weight, and, preferably, from about 1.0 to 2.0 percent, by weight, based on the total weight of the composition.

ADDITIVES

Chain extenders may also be useful in the preparation of polyurethanes. Chain extenders are generally considered to be low molecular weight

polyfunctional compounds or oligomers reactive with the isocyanate group. Aliphatic glycol chain extenders commonly used include ethylene glycol, propylene glycol, 1,4-butanediol, and 1,6-hexanediol. Amine chain

extenders include aliphatic monoamines but especially diamines such as ethylenediamine and in particular the aromatic diamines such as the toluenediamines and the alkysubstituted (hindered) toluenediamines. Other additives and auxiliaries are commonly used in polyurethanes. These additives include

plasticizers, flow control agents, fillers,

antioxidants, flame retardants, pigments, dyes, mold release agents, and the like. Many such additives and auxiliary materials are discussed in the Polyurethane Handbook in Chapter 3, 3.4, pages 90-109; and in

Polyurethanes: Chemistry and Technology. Part II, Technology.

SURFACTANTS

Polyurethane foams generally require a

surfactant to promote uniform cell sizes and prevent foam collapse. Such surfactants are well known to those skilled in the art, and are generally polysiloxanes or polyoxyalkylene polysiloxanes. Such surfactants are described, for example, in the Polyurethane Handbook on pages 98-101. Commercial surfactants for these purposes are available from a number of sources, for example from Wacker Chemie, the Union Carbide corporation, and the Dow-Corning Corporation.

FLAME RETARDANT

Although numerous flame retardants have been taught in the prior art, the present invention. It has now surprisingly been found that by using the reduced levels hereof not only is adequate flame retardancy achieved but low smoke generation is achieved, as well. In the practice hereof, melamine is preferably used, alone, as the smoke reducing agent flame retardant.

However, the melamine may be combined with other smoke reducing agents and/or flame retardants.

PROCESSES

Numerous processes for the preparation of polyurethane foams and the equipment used therefor are known to those in the art, and are described, for example in the Polyurethane Handbook in Chapter 4, pages 117-160 and in Polyurethanes: Chemistry and

Techonology. Part II, Technology, in Chapter VII, III and IV on pages 7 - 116 and Chapter VIII, III and IV on pages 201-238. A preferred process in accordance with the present invention comprises the steps of:

(a) providing admixing together, at high speed, a polyol (s); and

(b) adding the melamine thereto, with

agitation,

(c) adding a blowing agent thereto;

(d) adding a polyisocyanate to the mixture, and

(e) reacting the components to form a

polyurethane foam.

The foams hereof are, preferably, high density foams ranging in density from about 8 to 30pcf.

For a more complete understanding of the present invention reference is made to the following examples. In the examples, which are to be construed as illustrative, rather than limitative, all parts are by weight, absent indications to the contrary.

EXAMPLES 1-10

To illustrate the efficacy of the present invention, a series of polyurethane foams were prepared by the following procedure at room temperature.

Into a suitable reaction vessel equipped with agitation means was charged a polyol mixture.

Thereafter, a catalyst, fire retardant and blowing agent were added thereto, agitation being maintained

throughout at about 1750 rpm. Then, an organic

polyisocyanate was added thereto in about 8 to 10 second with stirring at 1750 rpm whereupon foam formation occurred. The only variable in Examples 1-10 was the melamine concentration, which was increased by 2% in each new sample.

A sample of each of the resulting foams was, then, tested for smoke generation by performing the NBS Smoke Chamber ASTM E 662-79 smoke test.

The following table. Table I, sets forth the ingredients, their amounts, and the resulting smoke density. It is to be seen from the data that the utilization of melamine, at low levels, with a sucrosebased polyol provides a low smoke generating high density polyurethane foam.

The data in Table I shows that an improvement in smoke inhibition was obtained using melamine in a preferred range of 8-14% by weight of the total

composition. An unexpected and dramatic improvement in smoke inhibition was obtained using melamine in a range of 10-12% by weight of the total composition. Samples prepared using melamine concentrations outside of the preferred range exhibited unacceptably high smoke densities when combusted.

TABLE I

SMOKE DENSITY DATA

Example 1 2 3 4 5 6 7 8 9 10

Polyol A ¹ 70.0 70.0 70.0 70.0 70.0 70.0 70.0 70.0 70.0 70.0

Polyol B² 70.0 70.0 70.0 70.0 70.0 70.0 70.0 70.0 70.0 70.0

Catalyst A³ 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0

Surfactant A⁴ 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0

Melamine 0 6.0 12.0 18.5 25.0 32.5 39.5 47.0 55.0 63.0

H2O 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0

Isocyanate A⁵ 143.0 143.0 143.0 143.0 143.0 143.0 143.0 143.0 143.0 143.0 Molded Density, lb/ft³ 14.0 14.0 14.0 14.0 14.0 14.0 14.0 14.0 14.0 14.0 Smoke Density, NBS ⁶ 348.0 242.0 251.0 233.0 437.0 124.0 183.0 363.0 481.0 577.0 % Melamine in Resin 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0

1 A commercially available sucrose-based polyol sold by BASF Corp. under the name PLURACOL 975 2 A commercially available glycerine-based polyol sold under the trade name LHT-240

3 A commercially available catalyst sold by Air Products as Daboo 33LV, which is a 33% solution of is a 33% solution of triethylene diamine in dipropylene glycol.

4 A commercially available polysilcxane surfactant sold by Dow Corning as DC 193

5 A commercially available polymethylene polyphenylene polyisocyanate sold by BASF as Lupranate

M200

NBS Smoke Chamber ASTM E 662-79

EXAMPLES 11-14

A second series of high-density polyurethane foams was prepared by a procedure essentially as described for the preparation of examples 1-10. In examples 11-14, the formula of Examples 1-10 was varied by increasing the molded density.

Additionally, in Examples 13 and 14, the melamine concentration was approximately doubled from that of Examples 10 and 11. These foams were tested for smoke of combustion by performing the NBS Smoke Chamber ASTM E 662-79 smoke test.

The following table. Table II, sets forth the ingredients, their amounts, and the resulting smoke density.

It is apparent from the data in Table II that a surprisingly beneficial reduction in smoke of combustion is obtained by using melamine in an amount between 10 and 12% by weight of the total composition.

TABLE II SMOKE DENSITY DATA

Example 11 12 13 14

Polyol A 70.0 70.0 70.0 70.0

Polyol B 70.0 70.0 70.0 70.0

Catalyst A 2.0 2.0 2.0 2.0

Surfactant B ⁽¹⁾ 1.0 1.0 1.0 1.0

Melamine 32.0 32.0 64.0 64.0

H2O 1.0 1.0 1.0 1.0

Isocyanate A 119.6 119.6 119.6 119.6

Molded Density, pcf 24.0 30.0 24.0 30.0 Smoke Density, ASTM E

662-79 138.0 232.0 503.0 503.034

% Melamine in Polymer 10.8 10.8 19.5 19.5

¹⁾ A surfactant sold by GOLDSCHMIDT under the name B 8435.

EXAMPLES 15-18

A third series of high-density polyurethane foams was prepared using the same procedure as

outlined for Examples 1-10. These foams had densities ranging from 14-30 pcf, and were tested for smoke of combustion using the ASTM E-84 Steiner tunnel test.

Model Building Codes for residential applications (Class II) require a flame spread of less than 75 and a smoke density of less than 450 based on the ASTM E-84 Steiner tunnel test.

The following table. Table III, sets for the ingredients, their amounts, and the resulting smoke density.

Table III shows that the polymer systems of the present invention, containing a sucrose-based polyol and melamine within the preferred range, meet the requirements of the Model Building Code for a class II rated foam, and are thus suitable for use in residential building materials.

TABLE III

E-84 STEINER TUNNEL DATA

Example 15 16 17 18

Polyol A 70.0 70.0 70.0 70.0

Polyol B 70.0 70.0 70.0 70.0

Surfactant A 1.0 1.0 1.0 1.0

Catalyst A 2.0 2.0 2.0 2.0

Melamine 32.0 32.0 32.0 32.0

H2O 2.0 2.0 2.0 2.0

Isocyanate A 143.0 143.0 143.0 143.0

Molded Density , pcf 14.0 18.0 24.0 30.0

Flame Density, NBS 48.0 38.0 44.0 77.0

Smoke Density, 117.0 197.0 249.0 235.0

Having, thus, described the invention, what is claimed is:

Claims

C L A I M S

1. A low smoke generating polyurethane foam

comprising the reaction product of:

(a) a polyol;

(b) a catalyst;

(c) melamine in a range of 8-14% by weight of the total mixture as a smoke reducing agent,

(d) a blowing agent, and

(e) an organic polyisocyanate.

2. The polyurethane of claim 1, wherein melamine is present in a range of 10-12% by weight of the total mixture.

3. The foam of claim 1, wherein the polyol comprises a sucrose-based polyol.

4. The polyurethane foam of claim 3, wherein the polyisocyanate is a polymethylene polyphenylene

polyisocyanate.

5. The polyurethane foam of claim 4, wherein the foam has a density of from about 8 to about 30 pcf.

6. The polyurethane foam of claim 1, wherein:

(a) the polyol is a sucrose polyol;

(b) the polyisocyanate is a polymethylene

polyphenylene polyisocyanate, and

(c) the foam has a density of foam about 8 to about 30 pcf.

7. A method of preparing a low smoke generating polyurethane foam composition, comprising the steps of:

(a) admixing together, at high speed agitation, a polyol;

(b) adding a smoke retardant component thereto which comprises melamine in a range of 8-14% by weight of the total composition while continuing to agitate the mixture;

(c) adding water thereto; and

(d) adding a polyisocyanate to the mixture, and reacting the components to form a high-density foam.

8. The method of claim 7, wherein the polyisocyanate is a polymethylene polyphenylene polyisocyanate.

9. The method of claim 7, wherein the foam has a density of from about 8 to about 30 pcf.

10. The method of claim 7, wherein:

(a) the polyol is a sucrose polyol;

(b) the polyisocyanate is a polymethylene polyphenylene polyisocyanate, and

(c) the foam has a density of foam about 8 to about 30 pcf.