WO2010075089A1

WO2010075089A1 - Flame retarded latex foam compositions and their preparation

Info

Publication number: WO2010075089A1
Application number: PCT/US2009/068072
Authority: WO
Inventors: Dominique Fasbinder; Manon Loos; Jan Vijverman; Reza Fard-Aghaie
Original assignee: Albemarle Corporation
Priority date: 2008-12-23
Filing date: 2009-12-15
Publication date: 2010-07-01
Also published as: TW201033266A

Abstract

Flame retarded latex compositions, flame retarded latex foams, and process technology for producing such flame retarded compositions and foams are described, which compositions are formed by the incorporation therein of a flame retardant amount of melamine and at least one liquid chloroalkyl phosphate ester.

Description

FLAME RETARDED LATEX FOAM COMPOSITIONS AND THEIR

PREPARATION

TECHNICAL FIELD [0001] This invention relates to flame retarded latex foam compositions especially adapted for use in manufacture of upholstered furniture and pillows.

BACKGROUND

[0002] Latex foams, methods for their manufacture, and uses thereof are known and have been reported. Latex is generally defined as a suspension in water of rubber particles, which can be composed entirely of natural rubber or of a blend of natural and a synthetic rubber, e.g., SBR. Such suspensions can contain a soap or other dispersing agent. In general, there are two methods for producing latex foams, a.k.a., latex foam rubber. These are the Dunlop process and the Talalay process. Both processes produce the foam by a frothing procedure. This procedure involves dispersing a gas in a suitable latex, then causing the latex particles to coalesce and form a continuous rubber phase in the water phase. As a result of the deactivation of the soap in the water, the aqueous soap film breaks, which in turn results in breaking of the latex film. Thereafter, the expanded matrix is cured and dried to form the stabilized latex foam. In the Dunlop process, a chemical gelling agent such as sodium fluorosilicate is used to coagulate the rubber particles of the latex, while concurrently deactivating the soap. A major difference between the two processes relates to the processing of the latex froth prior to the curing step in a heated mold. In the Talalay process the volume of latex composition poured into the mold is small, leaving room for expansion. Air is extracted from the closed mold causing the latex to expand by the vacuum produced so that the mold is completely filled with the expanded latex. The foam is prevented from collapsing by rapidly cooling to -30⁰C to produce a frozen latex foam. At this point carbon dioxide gas is passed through the latex and the temperature is raised to about 115°C, which sets and vulcanizes the foam. The foam is then extracted from the mold. In the Dunlop process, the molds are filled to the rim. No vacuum is applied, nor is there any freezing technique utilized. Instead, the latex cell structure is cured in the mold at a suitable elevated temperature. For further details concerning the preparation of latex foams, reference may be had to the text entitled "Foamed Plastics" in the Kirk-Othmer Encyclopedia of Chemical Technology, copyright 1994, John Wiley & Sons, Inc., especially page 11, section 3.3.1. on "Frothing"; and E.W. Madge, Latex Foam Rubber, John Wiley & Sons, Inc., New York, 1962. See also the following online descriptions, copies of which are attached hereto and made a part hereof:

• http://www.dunloplatexfoam.com/latex.php • http://www.latexfoam.com/index.php?did=12

• http://ezinearticles.com/7The-Two-Main-Processes-Of-Latex-Mattress-Production- Explained— Dunlop-vs-Talalay&id=1053851

• http://irpec.lgm. gov.my/prd_latexfoam.html

[0003] In general latex foams formed principally or entirely from natural rubber(s) tend to be flexible. Latex foams formed from blends of synthetic latex tend to be more rigid. There is no apparent hard and fast line or demarcation between a flexible foam and a rigid foam. One convenient means of establishing classification between the two types of foams appears in ASTM Test Procedure D 1566-82 which appears in Volume 37 of ASTM, Philadelphia, PA, 1982. This classification indicates that a flexible foam is one that does not rupture when a 20 x 2.5 x 2.5 cm piece at 15 to 25°C is wrapped at a rate of 1 lap per 5 seconds around a 2.5 cm mandrel. A rigid foam ruptures under these test conditions. Latex foams can be distinguished from memory or viscoelastic foams in that the latter are derived from plastic materials, and the foams exhibit a relatively slow recovery from distortion by application of pressure. In contrast, latex foams are made from rubber (natural or blends of natural and man-made rubber) and the foams exhibit a relatively rapid recovery from distortion by application of pressure.

[0004] For many uses such as manufacture of upholstered furniture and pillows, it is essential that the latex foam be effectively flame retarded. For example, achieving the BS 5852 source 1&2 is a requirement which must be satisfied. [0005] Although many flame retardants for various polymeric compositions such as polyurethanes have been extensively studied in the prior art, the problem of effectively flame retarding latex compositions involves certain special inherent problems. For example, as pointed out in U.S. Pat. No. 4,239,670 at Column 3, lines 1-11:

Some flame-retardant compounds when added to latexes cause the latexes to become unstable. By unstable it is meant that the latex agglomerates and/or has a significant change in viscosity. In some instances, instability may be caused by adding particular types of flame retardant compounds to latexes which are extremely pH sensitive. Generally, such changes, agglomeration and/or rheological property changes, are undesirable because the latexes cannot be used for their intended purpose. For example, there are many latexes which are unstable to the addition of diammonium phosphate. [0006] In recent years, some concern has been expressed with respect to use of certain bromine flame retardants. It would thus be desirable if a way could be found for effectively flame retarding latex foams with a flame retardant composition devoid of any bromine component while at the same time avoiding the problems referred to in the foregoing U.S. patent. This invention is deemed to achieve this desirable result.

BRIEF SUMMARY OF THE INVENTION

[0007] Pursuant to this invention, flame retarded latex compositions, flame retarded latex foams, and process technology for producing such flame retarded compositions and foams are provided, which compositions are formed by the incorporation therein of a flame retardant amount of melamine and at least one liquid chloroalkyl phosphate ester. Thus, this invention provides, among other things, a flame retarded uncured latex composition with which has been blended, prior to curing, melamine and at least one liquid chloroalkyl phosphate ester. Also provided by this invention is, among other things, a process of producing a cured latex composition from a latex formulation comprising natural rubber or a mixture of natural rubber and a synthetic rubber (e.g., styrene-butadiene rubber) by curing the latex composition in a mold, said process being characterized by mixing with the latex composition, prior to processing the latex composition in the mold, melamine and at least one liquid chloroalkyl phosphate ester flame retardant to thereby produce a flame retarded cured latex composition. The resultant cured compositions, including cured foamed compositions, formed by a process of this invention are also provided by this invention.

[0008] The above and other features of this invention are encompassed by, included in, and will become still further apparent from the ensuing description and appended claims.

FURTHER DETAILED DESCRIPTION OF THE INVENTION [0009] This invention provides, among other things, a flame retarded uncured latex formulation formed from components comprising (a) a latex of natural rubber or a blend of natural rubber and a synthetic rubber, e.g., a styrene-butadiene rubber, (b) a flame retardant formed by introducing into the latex formulation (i) melamine and (ii) at least one liquid chloroalkyl phosphate ester. Typical of the formulations of this type are those in which the amount of liquid chloroalkyl phosphate ester introduced into the latex formulation is in the range of 10 to 25 parts per hundred parts by weight of the latex of (a) used in forming the formulation, and the amount of melamine introduced into the latex formulation is in the range of 10 to 30 parts per hundred parts by weight of the latex of (a) used in forming the latex formulation. Desirably, the amount of melamine introduced into the latex formulation exceeds the amount of liquid chloroalkyl phosphate ester introduced into the latex formulation. When using a latex formed from a blend or mixture of natural and synthetic rubbers, the particular rubbers used and the relative proportions thereof are selected in accordance with principles known to those of skill in the art to produce on curing a cured latex composition having the desired flexibility or rigidity.

[0010] Also provided by this invention are, among other things, cured flame retarded compositions formed by heat curing any of the formulations as described above. Desirably, the cured flame retarded compositions are in the form of a cured foam.

[0011] Provided by this invention is a preferred process of producing a cured flame retarded latex composition from a latex formulation comprising a latex of natural rubber or of natural rubber and a synthetic rubber, e.g., styrene-butadiene rubber, wherein the formulation under agitation (i. e. , while being physically converted into a froth) and while free of gel formation is introduced into a mold preheated at a temperature in the range of 70 to 100⁰C for a period of time causing said formulation to cure. This process is characterized by mixing with the latex composition prior to processing the composition in the mold of melamine and at least one liquid chloroalkyl phosphate ester flame retardant. [0012] This invention still further provides, among other things, a preferred process of producing a cured flame retarded composition, which process comprises:

• forming and frothing a latex formulation formed from components comprising (a) a latex of natural rubber or of natural rubber and synthetic rubber, e.g., a styrene-butadiene rubber, (b) melamine and (c) at least one liquid chloroalkyl phosphate ester flame retardant having a chlorine content of at least 30 wt% and a phosphorus content of at least 7 wt%, and introducing sodium silicofluoride into the formulation in an amount in the range of 5 to 10 parts by weight per hundred parts by weight of the amount of said latex of (a) used in forming the formulation; and

• introducing said formulation while free of gel formation into a mold preheated at a temperature in the range of about 70 to about 100⁰C for a period of time causing said formulation to cure.

In conducting this process, the amount of the at least one liquid chloroalkyl phosphate ester flame retardant composition introduced into the latex formulation is typically in the range of 10 to 25 parts per hundred parts by weight of latex used in forming the latex formulation and the amount of melamine introduced into the latex formulation is typically in the range of 10 to 30 parts per hundred parts by weight of latex used in forming the latex formulation. As noted above, it is desirable to have the amount of the melamine used in forming the flexible latex formulation larger than the amount of liquid chloroalkyl phosphate ester composition used in forming the latex formulation. [0013] Still another preferred process of this invention for producing a cured flame retarded composition, which process comprises:

• forming a latex formulation from components comprising (a) a latex of natural rubber or of natural rubber and synthetic rubber, e.g., a styrene-butadiene rubber, (b) melamine and (c) at least one liquid chloroalkyl phosphate ester flame retardant having a chlorine content of at least 30 wt% and a phosphorus content of at least 7 wt%; • partially filling a closable mold with said latex formulation and subjecting the formulation to vacuum conditions within the closed mold to produce a froth that fills the closed mold;

• rapidly cooling the contents of the mold to produce a frozen latex foam and then passing carbon dioxide gas through the latex and raising the temperature to a temperature at which the foam is cured; and • removing the cured foam from the mold.

The amount of vacuum applied can vary, depending upon the temperature and makeup of the formulation, but in any case is sufficient to convert the latex formulation into a frothed latex formulation that fills the closed mold. In any case where the magnitude of the vacuum has not been established, one or two few pilot experiments can be carried out in which the pressure within the closed mold is progressively reduced (i.e., where the vacuum is progressively increased) in order to determine the appropriate vacuum conditions for effecting formation of the desired froth. Likewise, the curing temperature can vary depending upon the makeup of the latex composition, but in any case it is sufficiently high as to cure (i.e., vulcanize) the foam. Typically, such temperatures are in the range of about 100⁰C to about 130⁰C, but in any case where the optimum temperature has not been established, this can be readily determined by the simple expediency of performing a few simple tests using the selected latex formulation.

[0014] As to the components or ingredients used in effecting the flame retardancy provided pursuant to this invention, melamine is known chemically as 2,4,6-triamino-s-triazine. It is preferable that melamine be pre-dispersed in a latex slurry. Moreover, latex formulations in liquid form can be effectively agitated to ensure uniformity of the formulation prior to curing. [0015] Chloroalkyl phosphate esters usable in the practice of this invention are those which are in the liquid state at temperatures as low as 20⁰C. Preferred are chloroalkyl phosphate esters which have a chlorine content of at least 30 wt% and a phosphorus content of at least 7 wt%. A number of such products are available in the marketplace. For example, and without in any way restricting the invention to only the following materials, effective use can be made of such commercially-available flame retardants as the following flame retardant compositions available from Albemarle Corporation: Antiblaze® V6 Flame Retardant (typical phosphorus content 10.50 wt%, typical chlorine content 36.50 wt%), Antiblaze® V66 Flame Retardant (typical phosphorus content 10.3 wt%, typical chlorine content 32.9 wt%), Antiblaze® TL-10-ST Flame Retardant (typical phosphorus content 10.6 wt%, typical chlorine content 36.5 wt%), and Antiblaze® WR-30-LV Flame Retardant (typical phosphorus content 7.2 wt%, typical chlorine content 35.9 wt%).

[0016] Other suitable liquid chloroalkyl phosphate esters are known and can be used. A few non-limiting examples include tris(chloromethyl)phosphate, tris(2-chloroethyl)phosphate, and tris(2-chloroisopropyl)phosphate.

[0017] As is well known in the art, rubber blends for making latices (a.k.a. latexes) and foamed latices are made from natural rubber latex or blends of natural and synthetic rubber latices, the natural rubber latex typically being based on suitable natural rubbers obtained from various worldwide rubber sources, and synthetic latices are typically based on styrene- butadiene rubbers (SBS). [0018] Flame retarded latices and flame retarded foamed latices formed in the practice of this invention formed from blends of natural and synthetic rubber typically contain in the range of 20 to 80 wt% of natural rubber latex and in the range of 85 to 15 wt% of synthetic rubber latex, typically a styrene butadiene rubber latex. Other flame retarded latices of this invention are made from 100% natural synthetic rubber(s).

[0019] The amounts of chloroalkyl phosphate ester and melamine utilized in forming the flame retarded latex blends, flame retarded latices and flame retarded foams of this invention are typically in the range of 10 to 25 parts by weight of liquid chloroalkyl phosphate ester composition and in the range of 10 to 30 parts by weight of melamine. Melamine can be added to the latex compounds in powder form or in a pre-dispersed form (slurry). The liquid flame retardant is added to the latex blend before processing the blend in the mold. In the case of a Dunlop-type process, it is preferred to add the liquid flame retardant to the latex blend after adding the sodium silicofluoride (NSF), and in any event, prior to processing the latex blend in the mold. In the Talalay process, the liquid FR must be mixed with the other components just before filling the mold.

[0020] In conducting a process of this invention for producing latex foam it is desirable to conduct the process utilizing either the procedure of the Talalay process or the Dunlop process. However, other process technology may be used, if desired. [0021] A suitable procedure for producing latex foam of this invention on a laboratory scale involves use of a bakery mixer, a mold in which foam is to be formed, the desired natural latex-styrene butadiene (SBS) latex blend, sodium silicofluoride, a liquid chloroalkyl phosphate ester flame retardant composition and melamine. The liquid chloroalkyl phosphate ester flame retardant composition and the melamine can be used as a preformed flame retardant blend or they can be used as separate flame retardant components. The laboratory procedure used involves the following steps:

• Preheat the mold so that its temperature is maintained at 70⁰C.

• Add 160 grams of the latex blend, 24 grams of a liquid chloroalkyl phosphate ester flame retardant composition and 40 grams of melamine to the mixer and mix these components for 4 minutes at full speed of the mixer, ranging from 50 up to 250 revolutions per minute (rpm). • While continuing the mixing, add 8.8 grams of sodium silicofluoride to the mixture during a period of 30 seconds and continue the mixing for one additional minute.

• Pour the mixture into the mold and place the mold in an oven maintained at 100⁰C for 35 minutes. • Allow the product and the mold to cool and then remove the cooled product from the mold and wash the product with water.

[0022] The following Examples are illustrative and are not intended to limit the invention to only the procedures used.

EXAMPLE 1

[0023] Using the above procedure, the following components are used: a commercially- available flexible 80/20 bedding latex compound, a chloroalkyl phosphate ester flame retardant (Antiblaze® TL-10-ST; Albemarle Corporation); melamine GPH from DSM, particle size < 300 microns, 18-20%, and a solution of sodium silicofluoride prepared from commercially-available powder. The resultant foam of this invention was then subjected to the standard BS 5852 (1990) Source 1 and Source 2 test procedure. The results of these tests are summarized in the Table.

EXAMPLE 2 [0024] For comparative purposes, a foam was made in the same manner as in Example 1, except that no flame retardant components were used. The resultant comparative foam was then subjected to the standard BS 5852 (1990) Source 1 and Source 2 test procedure. The results of these tests are also summarized in the Table, wherein except for the amount of latex used, the amounts are specified in terms of parts per hundred parts of latex (wt/wt), which term is abbreviated as pph. TABLE

[0025] Components referred to by chemical name or formula anywhere in the specification or claims hereof, whether referred to in the singular or plural, are identified as they exist prior to coming into contact with another substance referred to by chemical name or chemical type (e.g., another component, a solvent, or etc.). It matters not what chemical changes, transformations and/or reactions, if any, take place in the resulting mixture or solution as such changes, transformations, and/or reactions are the natural result of bringing the specified components together under the conditions called for pursuant to this disclosure. Thus the components are identified as ingredients to be brought together in connection with performing a desired operation or in forming a desired composition. Also, even though the claims hereinafter may refer to substances, components and/or ingredients in the present tense ("comprises", "is", etc.), the reference is to the substance, component or ingredient as it existed at the time just before it was first contacted, blended or mixed with one or more other substances, components and/or ingredients in accordance with the present disclosure.

[0026] Each and every patent, publication, or online reference referred to in any portion of this specification is incorporated in toto into this disclosure by reference, as if fully set forth herein.

[0027] Except as may be expressly otherwise indicated, the article "a" or "an" if and as used herein is not intended to limit, and should not be construed as limiting, a claim to a single element to which the article refers. Rather, the article "a" or "an" if and as used herein is intended to cover one or more such elements, unless the text taken in context clearly indicates otherwise. [0028] The invention may comprise, consist or consist essentially of the materials and/or procedures recited herein.

[0029] This invention is susceptible to considerable variation in its practice. Therefore the foregoing description is not intended to limit, and should not be construed as limiting, the invention to the particular exemplifications presented hereinabove.

Claims

CLAIMS:

1. A flame retarded uncured latex formulation formed from components comprising (a) a latex of natural rubber or of a mixture of natural and synthetic rubber in which the rubber components are in proportions to form a composition of selected flexibility or rigidity on curing, (b) a flame retardant formed by introducing into the latex formulation (i) melamine and (ii) at least one liquid chloroalkyl phosphate ester.

2. A formulation as in Claim 1 wherein the amount of liquid chloroalkyl phosphate ester introduced into the latex formulation is in the range of 10 to 25 parts per hundred parts by weight of the latex of (a) used in forming the formulation, and the amount of melamine introduced into the latex formulation is in the range of 10 to 30 parts per hundred parts by weight of the latex of (a) used in forming the latex formulation.

3. A formulation as in any of Claims 1-2 wherein the liquid chloroalkyl phosphate ester used has a chlorine content of at least 30 wt% and a phosphorus content of at least 7 wt%.

4. A formulation as in Claim 3 wherein the amount of melamine introduced into the latex formulation exceeds the amount of liquid chloroalkyl phosphate ester introduced into the latex formulation

5. A cured composition formed by heat curing a formulation of any of Claims 1-4.

6. A cured composition of Claim 5 wherein the cured composition is in the form of a cured foam.

7. A process of producing a cured latex composition from a latex formulation comprising natural rubber or a mixture of natural and synthetic rubber by curing the latex composition in a mold, said process being characterized by mixing with the latex composition, prior to processing the latex composition in the mold, melamine and at least one liquid chloroalkyl phosphate ester flame retardant to thereby produce a flame retarded cured latex.

8. A process as in Claim 7 wherein the amount of liquid chloroalkyl phosphate ester introduced into the latex formulation is in the range of 10 to 25 parts per hundred parts by weight of the latex used in forming the formulation, and the amount of melamine introduced into the latex formulation is in the range of 10 to 30 parts per hundred parts by weight of the latex used in forming the latex formulation.

9. A process as in any of Claims 7-8 wherein the liquid chloroalkyl phosphate ester prior to introduction into the latex formulation has a chlorine content of at least 30 wt% and a phosphorus content of at least 7 wt%.

10. A process as in any of Claims 7-9 wherein the amount of melamine introduced into the latex formulation exceeds the amount of liquid chloroalkyl phosphate ester introduced into the latex formulation.

11. A process of producing a cured latex composition from a latex formulation comprising natural rubber or a mixture of natural and synthetic rubber, which process comprises:

• forming a latex formulation from components comprising (a) a latex of natural rubber or of natural rubber and synthetic rubber, (b) melamine and (c) at least one liquid chloroalkyl phosphate ester flame retardant having a chlorine content of at least 30 wt% and a phosphorus content of at least 7 wt%;

• partially filling a closable mold with said latex formulation and subjecting the formulation to vacuum conditions within the closed mold to produce a froth that fills the closed mold;

• rapidly cooling the contents of the mold to produce a frozen latex foam and then passing carbon dioxide gas through the latex and raising the temperature to a temperature at which the foam is cured; and

• removing the cured foam from the mold.