CA2227346A1 - Low-viscosity polymer polyols, a process for their production and their use for producing polyurethane foams - Google Patents

Abstract

A process is disclosed for producing stable, agglomerate-free, low-viscosity graft copolymer dispersions by radical polymerization of ethylenically unsaturated monomers in a base polyol, wherein the polymerization is carried out in the presence of a free-radical catalyst, a macromer, and a chain transfer agent. Suitable chain transfer agents comprise aminocrotonic acid esters corresponding to the general formula below:

(see fig. I) in which R1 represents a monovalent or divalent aliphatic hydrocarbon radical containing from 1 to 6 carbon atoms, and which may additionally contain one or more ether bridges;

R2 represents a monovalent aliphatic, alicyclic, araliphatic or aromatic hydrocarbon radical containing from 1 to 12 carbon atoms, and which may additionally contain one or more ether bridges, and/or one or more hydroxyl groups and/or one or more tertiary amino groups;

and n represents one or two.

The use of these polymer polyols in the production of polyurethane foams is alsodescribed.

Description

t CA 02227346 1998-01-19 Le A 32 219-US/Pt/klu/S-P
~ - 1 -LOW-VISCOSITY POLYMER POLYOLS, A PROCESS
FOR T~IEIR PRODUCTION AND THEIR USE FOR
PRODUCING POLYURETHANE FOAMS

BACKGROUND OF THE INVENTION

According to the invention, polymer polyols (i.e., graft copolymer dispersions) are understood to be products which may be obtained by polymerization of ethyleni-cally unsaturated compounds in polyether polyols (i.e., "base polyols"). These polymer polyols may, for example, be used to produce polyurethane flexible 5 foams. Ethylenically unsaturated monomers which are typically used in the pre-paration of polymer polyols are the monomers styrene and acrylonitrile. These monomers are radically polymerized in polyether polyols as the base polyol.

The production of such polymer polyols is well known and is described in, for ex-ample, U.S. Patents 3,383,351 and 3,304,273, and in DE-A-1,152,536 and DE-A
1,152,537.

Ideally, the polymer polyols are relatively low-viscosity, fine-particle, non-sedi-menting dispersions of the polymer (preferably of an acrylonitrile/styrene graft co-polymer) in the substantially unchanged polyether polyol. Distinguishing features for the quality and processability of the polymer polyols are viscosity, storage15 stability (i.e., sedimentation resistance) and particle size. These properties are chiefly influenced by the nature and quantity ratios of the starting substances. In particular, the solids content (i.e., the monomer content in the batch) and the monomer ratio (e.g., styrene/acrylonitrile ratio) have considerable influence onquality of the polymer polyol produced.

20 In the production of graft copolymer dispersions (i.e., polymer polyols), the most important goals are to achieve a high solids content (i.e., at least 40% by weight solids), with the highest possible styrene content and the lowest possible viscosity, simultaneously accompanied by excellent product stability.

To achieve product stability, i.e., prevention of the formation of undesirable agglo-25 merated polymer particles arising from the continuous phase (i.e., the base polyol),the polymer particles must be stabilized during polymer polyol production. A cer-tain stabilization is achieved on the one hand by free-radical grafting of styrene and acrylonitrile onto the base polyol, wherein a part of the polyether molecules is Le A 32 219-US

incorporated into the polymer formed in .5'ilU. The effectiveness of this stabilization is promoted by a highest possible molar weight of the base polyol and a highest possible acrylonitrile content in the monomer mixture. The resulting drawbacks are that higher molecular weight base polyols increase the viscosity of the polymer S polyols, and a high acrylonitrile content increases the inherent color of the graft copolymer dispersions, and accordingly, their tendency to discolor on processing.
Both the increase in viscosity and increased color are undesirable.

A filrther possibility for stabilizing graft copolymer dispersions is the co-use of compounds which are compatible with the base polyol phase, and which contain 10 ethylenically unsaturated polymerizable groups. These so-called macromers co-polymerize with the vinyl monomers such that the polymer particles produced are sterically stabilized by polyether side chains and are thereby protected against ag-glomeration and sedimentation.

The production of graft copolymer dispersions with the co-use of macromers is desc,ribed in, for example, U.S. Patents 3,652,639, 3,823,201, 4,460,715, 4,390,645, 5,093,412, and 4,342,840. The ethylenically unsaturated double bonds can be introduced into polyether polyols, for example, by conversion with cyclicunsaturated carboxylic anhydrides such as, for example, maleic anhydride, and subsequent conversion with ethylene or propylene oxide; by esterification with 20 acrylic and/or methacrylic acid (derivatives); by conversion with allyl glycidyl ethers; by conversion with an unsaturated isocyanate such as isocya-natoalkyl-acryl ate and -methacrylate, I -( I -i socyanato- I -methylethyl)-3 -(1 -methyl -ethenyl )-benzene or NCO-functional adducts of a polyisocyanate and hydroxyethyl and/or hydroxypropyl acrylate.

25 The combination of macromers with chain transfer agents such as mercaptans oralcohols has already been described in, for example, DE-A 2,500,274, EP-A
0,190,769 and EP-A 0,091,036. Products produced with mercaptans have the dis-adv~mtage of having a more or less unpleasant smell. Such products also often donot have the desired low viscosity.

30 The co-use of enolethers as chain transfer agents, albeit without macromer addition, is described in, for example, DE 2,837,026 and EP-A 008~444. As the comparative examples show, however, this process is dependent on the use of base Le A 32 219-US

polyols with molecular weights of greater than 4,500 which result in higher vis-cosities of the resultant graft copolymer dispersions as mentioned above.

Even though the processes mentioned lead to graft copolymer dispersions which may in principle be used as the polyol component for the production of 5 polyurethane flexible foams, further improvements are, nevertheless, desirable. In particular, the viscosities of highly-filled graft copolymer dispersions as described in the literature are still very high, particularly those graft copolymer dispersions having higher styrene contents in the monomer mixture. It is also common to obse~rve smaller agglomerated polymer particles in the discharge, i.e., the fineness 10 of the particles in the graft copolymer dispersions is not adequate.

SUMMARY OF THE INVENTION

An object of the present invention was, therefore, to provide fine-particle graft copolymer dispersions of low viscosity and high sedimentation resistance.

Surprisingly, it has now been found that agglomerate-free graft copolymer dis-15 persions having high filler contents and low viscosities are obtained when the graftcopolymer dispersions are produced in the presence of a macromer having ethylenically unsaturated terminal groups, and a chain transfer agent. Suitable chain transfer agents comprise one or more aminocrotonic acid esters corre-sponding to the general formula:

O N

R' O
--n whereln:
Rl represents a monovalent or divalent aliphatic hydrocarbon radical containing from 1 to 6 carbon atoms, and which may additionally contain one or more ether bridges;

R2 represents a monovalent aliphatic, alicyclic, araliphatic or aromatic hydrocarbon radical containing from I to 12 carbon atoms, and Le A. 32 219-US

which may additionally contain one or more ether bridges, and/or one or more hydroxyl groups, and/or one or more tertiary amino groups;

and n represents one or two.

As is shown in the production examples, by the combination of one or more macromers with a chain transfer agent having the aminocrotonic acid ester structure as described above, stable, fine-particle polymer polyols are surprisingly obtained, which have lower viscosities, at given solids content and styrene content, 10 than corresponding polymer polyol products produced with other conventional chain transfer agent/macromer combinations. It is also possible that the polymerpolyols produced according to the present invention will have higher styrene contents and/or solids contents at a given viscosity, than corresponding polymerpolyol products produced with the other conventional chain transfer 15 agent/macromer combinations.

In comparison to polymer polyol products produced from mercaptans, the polymer polyols produced according to the invention are distinguished by their distinctly lower odor.

DETAILED DESCRIPTION OF THE INVENTION

20 The present invention provides a process for producing stable, agglomerate-free, low-viscosity graft copolymer dispersions by the free-radical polymerization of ethylenically unsaturated macromers in a base polyol, wherein the polymerizationis ca~rried out in the presence of a free-radical catalyst, a macromer (i.e., a polyol havi:ng ethylenically unsaturated terminal groups), and a chain transfer agent which 25 comprises an aminocrotonic acid ester corresponding to the general formula:

Le ~'~ 32 219-US

H~ ,R
,~, R' O
--n wherein:

Rl represents a monovalent or divalent aliphatic hydrocarbon radiGal containing from I to 6 carbon atoms, and which may additionally contain one or more ether bridges;

R2 represents a monovalent aliphatic, alicyclic, araliphatic or aromatic hydrocarbon radical containing from I to 12 carbon atoms, and which may additionally contain one or more ether bridges, and/or one or more hydroxyl groups, and/or one or more tertiary amino I 0 groups;

and n represents one or two.

It is also possible that an organic solvent is present for the free-radical polymeri-zation process of the present invention as described above.

15 Typically, the process according to the invention is carried out in such a way that ethylenically unsaturated monomers such as styrene and/or acrylonitrile are con-verted by radical polymerization in a base polyol which is a polyalkylene oxide having two to six hydroxyl groups and a molecular weight of less than 4,500, in the ~presence of a macromer (i.e., a polyol with ethylenically unsaturated terminal 20 grou.ps) and an aminocrotonic acid ester of the above specified formula.

In accordance with the present invention, it is preferred that:

i) the ethylenically unsaturated monomers are used in an amount of from 25 to 65% by wt., based on the total weight of the monomers, the base polyo and the macromer;

~ CA 02227346 1998-01-19 Le A 32 219-US

ii) the ethylenically unsaturated monomers comprise mixtures of styrene and acrylonitrile;

iii) the weight ratio of the mixtures of styrene and acrylonitrile used as theethylenically unsaturated monomers are from 20:80 to 100:07 particularly preferably 50:50 to 80:20;

iv) the base polyol is preferably a polyalkylene oxide having at least two and up to six hydroxyl groups and an OH number of 20 to 100, more preferably having an OH number of 30 to 70;

v) the base polyol has a molecular weight of 1,800 to 4,500, more preferably of from 2,000 to 4,000 g/mol;

vi) the macromer (polyol having ethylenically unsaturated terminal groups) isprepared from a polyol having a molecular weight of 3,000 to 15,000, more preferably 4,500 to 12,000 g/mol, and a functionality of 2 to 6, vii) the macromer has a statistical average of 0 1 to l S, more preferably 0 3 to IS I mols of double bonds per mol of polyol;

viii) the macromer is used in a quantity of 2 to 20% by weight, more preferably3 to 10% by weight, based on 100% by weight of the base polyol and the macromer;

ix) aminocrotonic acid esters prepared by reacting ethylacetoacetate with n-butylamine, cyclohexylamine or 3-N,N-dimethylpropylamine are used as aminocrotonic acid ester chain transfer agent;
x) the aminocrotonic acid ester is used in a quantity of from 0 1 to 5% by weight, based on 100% by weight of the monomer mixture.

The invention also provides stable, agglomerate-free, low-viscosity graft copoly-25 mer dispersions produced according to the process described above, and the use of the graft copolymer dispersions produced by this process as some or all of the polyol component in the production of flexible polyurethane foams accordin~~ to the isocyanate polyaddition process.

~ CA 02227346 1998-01-19 Le ~ 32 219-US

The polyols having at least two hydroxyl groups which are used as "base polyols"are preferably polyether polyols, such as the per se known addition products of cyclic ethers such as, for example, ethylene oxide, propylene oxide, styrene oxide, butyl.ene oxide on starter compounds such as, for example, polyhydroxy com-5 pounds such as, for example, alkylene glycols, glycerol, trimethylolpropane, penta-erythritol, sorbitol, amines such as ethylene diamine or toluylene diamines. Thepolyether polyols used as "base polyol" preferably have functionalities of 2 to 6 and OH numbers of 20 to 100. The polyether chains are preferably made up of prop~ylene oxide and ethylene oxide units. In principle, however, polyester polyols having functionalities of preferably 2 to 6 and an OH number of 20 to 100 may also be considered as suitable "base polyols".

The polymer polyols of the present invention are obtained by the free-radical poly-merization of ethylenically unsaturated monomers or mixtures of ethylenically unsaturated monomers in the base polyols (e.g., polyether polyols) described. Ex-15 amples of suitable monomers include compounds such as butadiene, styrene, o~-methylstyrene, methylstyrene, ethylstyrene, acrylonitrile, methacrylonitrile, methyl methacrylate, acrylates, etc. Styrene and acrylonitrile are preferably used as monomers. The quantity of ethylenically unsaturated monomers is from 25 to 65%
by weight, based on the total weight of the monomers, the base polyol and the 20 macromer. When styrene and acrylonitrile are used as the ethylenically unsaturated monomers, the weight ratio of styrene to acrylonitrile is preferably from 20:80 to 100:0, more preferably from 50:50 to 80:20.

The imitation of the radical polymerization takes place with conventional free-radical-forming initiators. Examples of such initiators include organic peroxides 25 such as, for example, benzoyl peroxide, tert.-butyl octoate, and dodecanoyl peroxide; azo compounds such as, for example, azoisobutyronitrile and 2,2'-azobis(2-methylbutyronitrile).

The polyol compounds used as starting material for the macromers (i.e., the polyol containing ethylenically unsaturated groups) are also preferably polyether polyols 30 such as the per se known addition products of cyclic ethers such as ethylene oxide, propylene oxide, styrene oxide, butylene oxide on starter compounds such as polyhydroxy compounds such as alkylene glycols, glycerol, trimethylolpropane,pentaerythritol, sorbitol, amines such as ethylene diamine or toluylene diamines.

Le A 32 219-US

The polyether polyols which serve as starting material for the macromer have functionalities of 2 to 6 and a molecular weight of 3,000 to 15,000 g/mol. The polyether chains are preferably made up of propylene oxide and ethylene oxide units.

5 The ethylenically unsaturated groups may be introduced into the polyether polyols to form macromers according to the processes known and described in the litera-ture. These include, for example, conversion of the polyols with maleic an-hydride, and subsequent alkoxylation with ethylene or propylene oxide; conversion with acrylic acid and/or its methyl or ethyl esters; and conversion with an un-saturated isocyanate such as 1-(1-isocyanato-1-methylethyl)-3-(1-methylethenyl)-kenzene or an NCO-functional adduct of a polyisocyanate and hydroxyethyl and/or hydroxy-propyl acrylate is preferred. To produce the latter type, polyisocyanates such as, for example, hexamethylene diisocyanate, isophorone diisocyanate, di-phenylmethane diisocyanate and more preferably toluene diisocyanate may be 1 5 used.

The macromers generally contain a statistical average of from 0.1 to 1.5, prefer-ably 0.3 to I mols of double bonds per mol of polyol.

The aminocrotonic acid esters to be used as chain transfer agents according to the present invention may be simply produced from, for example, acetoacetic acid 20 esters and primary amines with elimination of water according to the process de-scribed in, for example, Houben-Weyl, Methoden der Organischen Chemie, Vol.
Xl/l (1957) page 172 ff. After the water has been removed by distillation, the products are often already present in very pure form, such that further purification, such as by distillation, can be omitted.

25 Generally speaking, the aminocrotonic acid esters are used in an amount of from 0.1 to 5% by weight, based on 100% by weight of the monomer mixture.

Hydrocarbons such as, for example, toluene, ethylbenzene, isopropylbenzene, xylolls, ketones such as acetone or methylethylketone, alcohols such as methanol, ethanol, isopropanol or butanol may be used as solvents which are optionally used 30 in the present invention. Toluene and ethylbenzene are preferred.

Le A 32 219-US

The process according to the invention may be carried out either continuously ordiscontinuously. For example, a mixture which contains the ethylenically un-saturated monomers, the chain transfer agent (i.e., aminocrotonic acid ester), the initiator and optionally, solvent, and a portion of the base polyol to be used may 5 be metered into a mixing vessel which contains the pre-heated base polyether and the macromer. It is, however, also possible to meter in a portion of the macromer together with the ethylenically unsaturated monomers, the aminocrotonic acid ester, optionally the solvent, and a portion of the base polyether. As another possibility, the aminocrotonic acid ester may be placed in the reactor together with 10 the base polyether and/or the main quantity of the base polyether and the macro-mer, and the remaining components metered in.

Furthermore, a mixture of all reactants may be continuously metered into a reactor and lhe product removed in equal measure via an overflow.

The temperature at which polymerization is carried out is generally from about 80 to about 140~C, preferably 90 to 130~C.

When polymerization is complete, volatile components such as, for example, resi-dual monomers, solvent, etc., are removed from the product by vacuum distillation in the conventional manner.

The polymer polyols produced by the process according to the invention are particularly suitable for producing polyurethane plastics by the isocyanate poly-addit:ion process. These polymer polyols are free from polymer agglomerates of any kind, stable and low-viscosity. It is particularly surprising that the presently required combination of macromers with aminocrotonic acid esters as chain trans-fer agents, and using low-molecular weight base polyols having molecular weightsof between about 1,800 and about 4,500 produces polymer polyols with advan-tageously low viscosities. Since the present process allows the use of mercaptanchain transfer agents to be dispensed with, the products of the present invention are advantageously largely odorless.

The production of polyurethane plastics, preferably of soft, flexible polyurethane foams, is achieved by reacting Le A 32 219-US

a) one or more organic polyisocyanates, with b) one or more polymer polyols of the present invention, optionally, in the presence of 5 c) conventional higher-molecular weight and/or low-molecular weight organic compounds containing hydrogen atoms which are reactive with respect to isocyanate groups, d) one or more catalysts, e) blowing agents comprising water and/or one or more low-boiling hydro-I 0 carbons, and f) auxiliary substances and/or additives.

Suitable starting components for this aspect of the present invention include those compounds described below.

15 Suitable polyisocyanates for use as component a) in the process for the production of polyurethane plastics include, for example, aliphatic, cycloaliphatic, araliphatic, aromatic and heterocyclic polyisocyanates. Such polyisocyanates are as describedby, for example, W. Siefken in Justus Liebigs Annalen der Chemie, 362, pages 75 to 136. Some examples of such polyisocyanates include those corresponding to the20 gene:ral formula:

Q(NC~)n, wherein:

n represents 2 to 5, preferably 2 and 3, Le A. 32 219-US

and Q represents an aliphatic hydrocarbon group containing from 2 to 18carbon atoms, and preferably 6 to 10 carbon atoms, a cycloaliphatic hydrocarbon group containing from 4 to 15 carbon atoms, and preferably 5 to l0 carbon atoms, an aromatic hydrocarbon group containing from 6 to 15 carbon atoms, and preferably 6 to 13 carbon atoms.

Some examples of such polyisocyanates include those which are described on pages 10 to 11 of DE-OS 2,832,253.

In general, these polyisocyanates which are readily obtainable via industrial sources, such as, for example, 2,4- and 2,6-toluene diisocyanate, are particularly preferred, as well as any mixtures of these isomers ("TDI"), diphenylmethane diisocyanate ("MDI") and polyphenylpolymethylene polyisocyanates (PMDI), as are produced by aniline/formaldehyde condensation, and subsequent phosgenation.
Also suitable are those polyisocyanates having carbodiimide groups, urethane groups, allophanate groups, isocyanurate groups, urea groups or biuret groups ("mc,dified polyisocyanates"), and particularly those modified polyisocyanates which are derived from 2,4- and/or 2,6-toluylene diisocyanate and/or 4,4'- and/or 2,4-cliphenylmethane diisocyanate.

Suitable compounds to be used as component b) of the present invention include, for example the polymer polyols as described hereinabove.

In the process of producing polyurethane plastics, it is also possible that starting components include organic compounds which have at least two hydrogen atoms react:ive with respect to isocyanate groups and having a molecular weight of 40 to l0,000 g/mol. Such compounds are preferably polyether polyols, i.e., per se known addiltion products of cyclic ethers such as, for example, ethylene oxide, propylene oxide, styrene oxide, butylene oxide on suitable starter compounds such as poly-hydroxy compounds, such as alkylene glycols, glycerol, trimethylol-propane, pentaerythritol, sorbitol, amines such as ethylene diamine or toluene diamines, and, of course, the starlter compounds themselves.

Le A 32 219-US

According to the process of producing polyurethane plastics, it is, of course, possible to use conventional catalysts which are known per se to be suitable forthe area of polyurethane chemistry.

Blowing agents may also be used in the process of producing polyurethane plastics. Such blowing agents include, for example~ water and/or low-boiling hydrocarbons. These may be used alone or in combination with each other. Some exam.ples of low-boiling hydrocarbons include low-boiling alkanes such as, for exam ple, pentane, cycloalkanes such as, for example, cyclopentane, as well as alken,es and gases such as, for example, carbon dioxide, being introduced into the reaction mixture under pressure.

Suitable auxiliary substances and additives which are optionally used in the pro-duction of polyurethane plastics includes surface-active additives, reaction inhi-bitor,, cell regulators, pigments or dyes, flame-proofing agents, stabilizers, etc.
Some examples of suitable surface-active additives include emulsifiers and foam stabi]izers. Suitable cell regulators include the per se known type such as paraf-fins, fatty alcohols or dimethyl polysiloxanes; and also stabilizers which provide protection against the effects of ageing and the weather; and examples of plasticizers includes those substances with fungistatic and bacteriostatic action.

Specific examples of surface-active additives and foam stabilizers which are optionally to be used according to the invention, and reaction inhibitors, stabi lizers, flame-retardant substances, plasticizers, dyes and substances withfungistatic and bacteriostatic action, as well as details of the mode of use andaction of these additives are described at, for example, pages 104 to 127 of Kunst-stoff-Handbuch. Vol. VII, edited by G. Oertel, published by Carl Hanser Verlag, Munich, 1993.

Flexible polyurethane foams are produced in accordance with a per se known manner, as is described in, for example, pages 139 to 263 of Kunststoff-Handbuch.
Vol. VII, edited by G. Oertel, published by Carl Hanser Verlag, Munich, 1993.

The following examples further illustrate details for the process of this invention.
30 The invention, which is set forth in the foregoing disclosure, is not to be limited either in spirit or scope by these examples. Those skilled in the art will readily Le A 32 219-US

understand that known variations of the conditions of the following procedures can be used Unless otherwise noted, all temperatures are degrees Celsius and all per-centages are percentages by weight.

Le A 32 219-US

EXAMPLES:

The i.-'ollowing components were used in the working examples of the invention:

Polyol A: A polyether having a molecular weight of 3,000 and an OH
number of 56, based on glycerol, produced by addition of PO (30%), PO/EO (40/10%) and PO (20%).

Polyol B: A polyether having a molecular weight of 6,000 and an OH
number of 28; based on trimethylolpropane, produced by addition of PO (98%) and EO (2%).

Polyl)l C: A polyether having a molecular weight of 3,660 and an OH
number of 46; based on glycerol, produced by addition of PO (30%), PO/EO (40/10%) and PO (20%).

Polyol D: A polyether having a molecular weight of 5,430 and an OH
number of 31; based on trimethylolpropane, produced by addition of PO (17%), PO/EO (51/17%) and PO (15%).

Polymer Polyol A: A SAN polymer polyol, containing about 40% by weight solids and having a styrene to acrylonitrile wt. ratio of about 60 :40 .

Macromer: The reaction product of one mole of Polyol B with 1.2 moles of acrylic acid, produced by azeotropic esterification in the presence of 0.1% by wt. of p-toluene sulfonic acid related to Polyol B and toluene as solvent. After removal of the solvent, the resultant product had a double bond content of 139 meq/kg.

Aminocrotonic Acid Ester A: The reaction product of one mole of ethyl acetoacetate with one mole of i-propylamine, having a bp of 45 to 48~C at 0.2 mbars.

Le A 32 21'~-US

Aminocrotonic Acid Ester B: The reaction product of one mole of ethyl acetoacetate with one mole of n-butylamine, having a bp of 69 to 71~C at 0.2 mbars Aminocrotonic Acid Ester C: The reaction product of one mole of ethyl acetoacetate with one mole of cyclohexylamine, having a bp of 91 to 93~C at 0.2 mbars.

Aminocrotonic Acid Ester D: The reaction product of one mole of ethyl acetoacetate with one mole of benzylamine, having a bp of 119 to 120~C at 0.2 mbars.

Ami:nocrotonic Acid Ester E: The reaction product of one mole of ethyl acetoacetate with one mole of aniline, having a bp of 98 to 100~C at 0.2 mbars.

Ami nocrotonic Acid Ester F: The reaction product of one mole of ethyl acetoacetate with one mole of 3-N,N-dimethylamino-propylamine, having a bp of 84 to 87~C at 0.2 mbars.

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Aminocrotonic Acid Ester G: The reaction product of one mole of ethyl aceto-acetate with one mole of 2-aminoethanol. This undistilled product was 97% pure (based on GC analysis).

5 General process for producing the polymer polyols:

A mixture consisting of 267.8 g of polyol A, 271.1 g of styrene, 147.1 g of acrylonitrile, 8.4 g of an aminocrotonic acid ester (or other chain transfer agent), 5.5 ~, of 2,2'-azobis(2-methylbutyronitrile) and 158.8 g of toluene was uniformly added to a mixture of 307.5 g of polyol A and 31.9 g of macromer within 2 hours accompanied by stirring. Stirring was continued for another 30 minutes at 118~C.After quick addition of a solution of 0.92 g of 2,2'-azobis(2-methylbutyronitrile) in 25.4 g of toluene, stirring was continued for another hour at 118~C. Subsequently toluene and other volatile constituents were distilled off at 118~C, first for one hour in a waterjet vacuum (at 15 mbars), and then for 2 hours in an oil pump vacuum (at less than 2 mbars). After cooling to approx. 100~C, the product was filtered through a sieve with a mesh width of 100 llm.

Residue:

The residue is a means of evaluating the quality and eventually the storage stability of the polymer polyol. The test was performed by first wetting the inner wall of a 10 ml sample vial with 2-3 ml of polymer polyol. After 24 hours standling at room temperature, the glass wall was observed and evaluated based on the clarity of the film and the number of polymer particles or agglomerated polymer particles of about 5-30 ,~m in diameter.

Numerical Rating:
1: up to approx. 10 particles per cm2 2: approx. 10 to 30 particles per cm2 3: upwards of approx. 30 particles per cm2 Polymer polyols were produced according to the general process described above in w hich polyol A was used as the base polyol, and in which different chain Le A 32 219-US

transfer agents were used. In one example, the reaction was also conducted without a chain transfer agent for comparison purposes (see Example I below).

Table 1:

Pclymer Chain transfer agent Viscosity Residue Pc,lyol mPa s/25~C
- [ 1 ] 4,700 3 2 isopropanol [1] 4,120 3 3 2-butanol [ I ] 4,480 3 4 methylethylketone 4,410 3 dodecylmercaptan [2]

6 aminocrotonic acid 3,320 2 ester A

7 aminocrotonic acid 37380 2 ester B

8 aminocrotonic acid 3,600 2 ester C

9 aminocrotonic acid 3,810 9 ester D
aminocrotonic acid 3,540 ester E
11 aminocrotonic acid 3,480 2 ester F
12 aminocrotonic acid 3,490 2 ester G

[1]: product could not be filtered.
[2]: reaction had to be stopped since the batch could no longer be stirred because the viscosity was too high.

Le A. 32 219-US

The polymer polyols in accordance with the present invention were also used to produce flexible foams by following the general procedure below. General pro-cedure for producing a foam:

In the production of a laboratory foam, all components (except for Catalyst 3 and 5 the polyisocyanate) were intensively mixed together. Catalyst 3 was then added, mixed briefly, and the polyisocyanate then added, accompanied with stirring.
Then, the reaction mixture was poured into an open mold, in which it was allowedto foam to produce the flexible foam.

The results of the foam tests are summarized in the Tables which follow (quanti-10 ties are parts by weight in each case):

CatalLyst 1: Desmorapid~) DMEA, Rhein Chemie, Rheinau Catallyst 2: RC-PUR activator 108, Rhein Chemie, Rheinau Catalyst 3: Desmorapid(~ SO, Rhein Chemie, Rheinau Stabilizer: Stabilizer OS 22, Bayer AG
15 Isocyanate: Toluene Diisocyanate Le A. 32 219-US

Table 2: Resuits of foaming tests E~. l E~.2 E~.3 E~.4 E~.5 r~ 6 I'olyol A 50 50 63 63 50 63 Po!vmer polyol A 50 37 Po.vmer Polyol 8 50 37 Po.ymer Polyol ll 50 37 Water 2.5 2.5 4.5 4.5 2.5 4.5 ~tabilizer 0.7 0.7 1.0 1.0 0.7 1.0 Catalyst I 0 1 0.1 0 1 0 1 0 1 () 1 ~atalyst 2 0.05 0.05 0.05 0.05 ~.~S o.()s Catalyst 3 0.15 0.15 0.15 o 15 0.15 0 1~
Isocyanate 32.8 33.3 54.4 55.0 33.3 55.() [~o imability verv very very very ve~ elv good good good good good good Open cells 120 120 95 80 115 75 AFparent density 39 39 27 27 39 26 (l;g/m~3) Ten.iile strength 150 155 128 120 149 13() (kl'a) Elongation at break 136 147 136 128 143 147 (~/o ) 4()~/0 compressive 7.3 7.4 6.6 6.5 7.4 6 4 str~ngth (kPa) H~ndleme~ibility very very very very ver~ vel-y good good good good good good Le A. 32 219-US

The following properties were determined using the ASTM methods set forth below:
Apparent Density: D~N 53420 Tensile Strength: D~N 53571 Elongation at Break: D~N 53571 40% Compressive Strength: D~N 53577 Foaming Examples 1-6 above show that the fine-particle, low-viscosity polymer polyol dispersions according to the present invention produce foams having properties comparable to current commercial products of higher viscosity. Foam recipes based on the polymer polyols according to the invention may be processedmore easily due to their lower viscosity, at identical solids content. Furthermore, on the basis of an identical maximum processing viscosity? polymer polyols of higher solids content may be used to produce foams with correspondingly higher hardnesses.

Comparative Examples: 7 to 12:

For comparison purposes, polymer polyols without macromers were produced both with and without an aminocrotonic acid ester (i.e., chain transfer agent) by fol-lowing the procedure set forth below.

A nrlixture consisting of 375.3 g of polyol, 250 g of styrene, 166.8 g of acrylo-nitril.e, 8.34 g of aminocrotonic acid ester C, 5.2 g of 2,2'-azobis-(2-methylbutyro-nitrile) and 144 g of toluene was uniformly added to 250.2 g of polyol, ac-companied by stirring in a nitrogen atmosphere at 125~C, over the course of two hours. Stirring was continued for another 30 minutes at 125~C. After quick addition of a solution of 0.9 g of 2,2'-azobis(2-methylbutyronitrile) in 25.4 g of toluene, stirring was continued for another hour at 125~C. Subsequently toluene and other volatile constituents were distilled off at 125 ~C, first for one hour in a waterjet vacuum (at 15 mbars), and then for 2 hours in an oil pump vacuum (< 2 mbars). After cooling to approx. 100~C, the product was filtered through a sievewith a mesh width of 100 llm.

The results of the comparative tests are summarized in the Table below:

Table 3:

Cornparative Polyol Aminocrotonic Viscosity Residue Example acid ester (mPas/25~C) 7 Polyol A - lumpy [I]
8 Polyol A C lumpy [I]
9 Polyol C - lumpy Polyol C C high-viscosity [2]
Il Polyol D - 21,780 3 12 Polyol D C 7,180 3 [1] Dispersion not stable, reaction had to be discontinued.
[2] Reaction mixture became so viscous that the reaction had to be dis-continued.

The comparative examples show that without the addition of macromers, only un-desirable high-viscosity or clumpy polymer polyols are obtained.

Although the invention has been described in detail in the foregoing for the 5 purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without depalting from the spirit and scope of the invention except as it may be limited by the claims.

Claims (17)

1. A process for the production of stable, agglomerate-free, low-viscosity graft copolymer dispersions comprising polymerizing at least one ethylenically unsaturated monomer in a base polyol, in the presence of a free radical catalyst, at least one macromer, and a chain transfer agent, wherein said chain transfer agent comprises one or more aminocrotonic acid esters corresponding to the general formula:

wherein:

R1 represents a monovalent or divalent aliphatic hydrocarbon radical containing from 1 to 6 carbon atoms, and which may additionally contain one or more ether bridges;

R2 represents a monovalent aliphatic, alicyclic, araliphatic or aromatic hydrocarbon radical containing from 1 to 12 carbon atoms, and which may additionally contain one or more ether bridges, and/or one or more hydroxyl groups, and/or one or more tertiary amino groups;

and n represents one or two.

2. The process of Claim 1, wherein the polymerization additionally occurs in the presence of an organic solvent.

3. The process of Claim 1, wherein said ethylenically unsaturated monomers are present in an amount of 25 to 65% by weight, based on the total weight of the monomers, the base polyol and the macromer.

4. The process of Claim 1, wherein said ethylenically unsaturated monomers comprise a mixture of styrene and acrylonitrile in a weight ratio of 20:80 to 100:0.

5. The process of Claim 4, wherein the weight ratio of styrene and acrylonitrile is from 50:50 to 80:20.

6. The process of Claim 1, wherein said base polyol comprises a polyalkylene oxide having from two to six hydroxyl groups and an OH number of 20 to 100.

7. The process of Claim 6, wherein said polyalkylene oxide has an OH
number of 30 to 70.

8. The process of Claim 1, wherein said base polyol has a molecular weight of from 1,800 to 4,500.

9. The process of Claim 8, wherein said base polyol has a molecular weight of 2,000 to 4,000.

10. The process of Claim 1, wherein said macromer is prepared from a starting polyol having a molecular weight of 3,000 to 15,000, and a functionality of from 2 to 6.

11. The process of Claim 10, wherein said starting polyol has a molecular weight of 4,500 to 12,000.

12. The process of Claim 1, wherein said macromer is present in a quantity of 2 to 20% by weight, based on 100% by weight of base polyol and macromer present.

13. The process of Claim 12, wherein said macromer is present in a quantity of 3 to 10% by weight, based on 100% by weight of base polyol and macromer.

14. The process of Claim 1, wherein said aminocrotonic acid ester comprises the reaction product of i) ethyl acetate, with a compound selected from the group consisting of ii) isopropylamine, cyclohexylamine, and or 3-(N,N-di-methyl)propylamine.

15. The process of Claim 14, wherein said aminocrotonic acid ester is present in a quantity of 0.1 to 5 wt.%, based on 100% by weight of monomers.

16. The stable, agglomerate-free, low-viscosity graft copolymer dispersion produced by the process of Claim 1.

17. In a process for the production of flexible polyurethane foams comprising reacting a polyisocyanate with an isocyanate-reactive component, the improvement wherein said isocyanate-reactive component comprises the graft copolymer dispersion of Claim 16.