Use of metal salts of ricinoleic acid in producing polyurethane

Details Use of metal salts of ricinoleic acid in producing polyurethane Use of metal salts of ricinoleic acid in producing polyurethane

1999-12-16

2001-02-27

Sergent, Rabon (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Cellular products or processes of preparing a cellular...

C521S055000, C521S114000, C521S116000, C521S118000, C521S124000, C521S125000, C521S126000, C521S127000, C521S129000, C521S130000, C521S906000

Reexamination Certificate

active

06194475

ABSTRACT:

RELATED APPLICATIONS
This application claims priority to German application No. 198 59 099.7, filed on Dec. 21, 1998, herein incorporated by reference
BACKGROUND OF THE INVENTION
The invention relates to the use of metal salts of ricinoleic acid and solutions thereof in producing polyurethane foams (PU foams).
1. Field of the Invention
The excellent mechanical and physical properties of polyurethane foams lead to their use in a very wide variety of sectors. The automotive industry is a very important market for a great variety of PU foam grades, such as conventional flexible foams based on ether polyol or on ester polyol, cold-cure foams (also frequently termed HR foams) and rigid foams, and also foams whose properties lie between these classifications, e.g. semirigid systems. Examples are the use of rigid foams as headliners, ester foams for internal door trims and also for die-cut sun visors, and cold-cure foams and flexible foams for seat systems.
2. Description of the Related Art
In recent years there has been a marked tightening of the requirements placed by automotive manufacturers on their foam suppliers, in particular in relation to an emission specification. Whereas previously the sole emphasis was the permanent fogging performance of the foams (DIN 75 201, Determination of the windscreen fogging characteristics of trim materials in motor vehicles), nowadays the content of volatile organic constituents (VOC=volatile organic compounds) is also analyzed (Volkswagen central standard 55 031 and Daimler Benz PB VWT 709). The Daimler Benz method requires classification of the individual chemical compounds in the emissions as well as quantitative determination of the VOC value and fogging value.
A conventional flexible foam with a density of 25 kg/m
3
typically has the following VOC emissions: overall value 800 ppm, comprising 550 ppm of BHT (bis-2,6-tert-butyl-4-hydroxytoluene), 200 ppm of 2-ethylhexanoic acid, 20 ppm of tertiary amines, 10 ppm of siloxanes and 20 ppm of unidentified compounds. The emissions are, of course, highly dependent on the particular mixing specification used, but BHT and 2-ethylhexanoic acid are always the main components. BHT typically derives from the polyol and isocyanate. The manufacturers of these raw materials have recently begun to supply their products also as BHT-free grades. Using these raw materials it is possible to produce foams with a VOC value of about 250 ppm. 2-ethylhexanoic acid is a decomposition product of the stannous octoate which acts as catalyst for the polyurethane reaction. Since there is no industrially available alternative to stannous octoate which fully covers its application profile, the VOC value cannot be significantly reduced in the prior art, and certainly not to a value<100 ppm.
Since automotive manufacturers have now specified a guideline VOC value of 100 ppm to be achieved in the coming years, there is an urgent requirement in the industry to reduce the emission of 2-ethylhexanoic acid.
Related to the problem of emissions, the automotive industry is attempting to reduce the odor from PU foams. One sign of this is the implementation of tests on PU foam products received, using what is known as an “electronic nose” (Aroma Scan, UK), automating the work of panels of odor testers.
The substances responsible for odor in foams have not yet been clearly identified. It is certain that a wide variety of classes of substance is involved, and these may be necessary constituents of the formulation (e.g. tertiary amines), contaminants in the raw materials (e.g. aldehydes in the polyetherol) or products of side reactions during foam production.
There is currently no industrial solution for meeting this requirement. In the automotive industry, and in particular in aircraft construction, specifically flame-retardant foam qualities are needed. To this end, flame retardants are added to PU foams. The chemicals used here are in most cases halogenated phosphoric esters. In 1986 in the U.S. alone, 13,000 metric tons of flame retardant were mixed into PU foams (J. Troitzsch, International Plastics Flammability Handbook, 1990). It is known that specifically these flame retardants contribute considerably to the emissions from foams. Foams produced with the widely used flame retardant TDCPP (tris(1, 3-dichloroisopropyl) phosphate) give off a large number of volatile compounds, the majority of which are chlorinated propyl alcohols. There is therefore a requirement to comply with flame-retardancy specifications while reducing, or eliminating, the use of flame-retardants.
SUMMARY OF THE INVENTION
Surprisingly, there has now been found a group of compounds whose use in polyurethane foam solves the abovementioned industrial problems.
This involves the use of metal salts of ricinoleic acid or solutions thereof in water or in organic solvents during the production of polyurethane foams. For the purposes of the present invention, the term “production” covers either addition prior to the actual foaming, or posttreatment of the finished foam, for example by spray-application or by saturating with a solution of the metal salt. For the purposes of the present invention, polyurethane foams are either flexible foams based on ether polyols or on ester polyols or else rigid foams, or else foams whose properties lie between these classifications, e.g. semi-rigid systems.
Adding the metal salts of ricinoleic acid allows foams to be produced with lower emission values, better flame-retardancy properties and less odor. In addition, the hardening of the foam surface is accelerated. These advantages can be achieved without changing the other physical properties, e.g. density, hardness, rebound resilience or compressive strength.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Particularly suitable ricinoleates are those of the metals of the 1st, 2nd or 4th main group, or also the 1st, 2nd or 8th transition group, of the periodic table.
The metal salt of ricinoleic acid here may be dissolved in advance in what is known as the activator solution, composed of water, tertiary amine, silicone stabilizer and, if desired, emulsifier. Direct feeding of the solid ricinoleate into the components for the foaming gives a foam with non-uniform cell structure. Since many foamers only have direct-feed equipment, a product in which the metal salt of ricinoleic acid is present in dissolved form represents a considerable improvement. Anhydrous solutions are preferable here, since otherwise the water from the solvent reacts with the isocyanates and must therefore be taken account of in the formulation. Some transition metal salts moreover have only limited resistance to hydrolysis.
Suitable anhydrous solvents for the metal salt of ricinoleic acid are in principle combinations of from about 5 to about 50% by weight, based on the weight of solvent and salt, of an ethoxylated fatty alcohol with a straight or branched alkyl chain and with from 10 to 18 carbon atoms and with less than 30 ethylene oxide units and from about 5 to about 30% by weight of a tertiary amine. Up to about 60% by weight of the metal salt of ricinoleic acid can be dissolved in solvents of this description to give a clear solution.
Preference is given to a combination of from 5 to 35% by weight of a fatty alcohol with a straight or branched alkyl chain and with from 10 to 18 carbon atoms and with less than 20 ethylene oxide units and from 5 to 30% by weight of a tertiary amino alcohol.
The amino alcohol used is particularly preferably N,N,N′,N′-tetrakis(2-hydroxypropyl)ethylenediamine.
Among the preferred cations, particular preference is given to zinc, and in particular in bivalent form.
A solution of this type has been described, for example, in DE-A-40 14 055 as an agent with a deodorizing action. Applications described are cosmetics, washing and cleaning, and odor absorption in industrial applications. The use according to the invention in PU foam differs from these applications in three fundamental points.
Firstly, the metal salt of ricinoleic acid is exposed to highly reactive reaction

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