WO2014037558A1

WO2014037558A1 - Process for the preparation of a polyol composition

Info

Publication number: WO2014037558A1
Application number: PCT/EP2013/068591
Authority: WO
Inventors: Nirupaplava METTA; Pranaya Man Singh PRADHAN; Ritika THAKUR
Original assignee: Shell Internationale Research Maatschappij B.V.; Shell Oil Company
Priority date: 2012-09-10
Filing date: 2013-09-09
Publication date: 2014-03-13

Abstract

The invention provides a process for the preparation of a polymer-modified polyol, wherein the polymer- modified polyol comprises a polyurethane polymer derived from the reaction of an olamine with an organic polyisocyanate and a polyol which comprises at least 50wt% secondary hydroxyl groups and wherein the process comprises the steps of: (a) mixing the olamine with an amount of the polyol in the range of from 30 to 80 wt% of the total polyol; (b) adding a catalyst and the polyisocyanate with mixing; (c) then adding the remaining portion of the polyol; and (d) mixing the reagents until the reaction is complete.

Description

PROCESS FOR THE PREPARATION OF A POLYOL COMPOSITION

Field of the Invention

The present invention relates to a process for the preparation of a polyol composition and to a process for preparing polyurethane foam with such a polyol

composition .

Background of the Invention

High hardness polyurethane foams are well known in the art. Although a wide range of different polyurethane foams are known, further foams are still being developed in order to obtain specific combinations of properties, to simplify production methods and to reduce cost.

Polyurethane foams are made by the polymerisations of polyols with isocyanates. A range of polyurethane foams having specific properties can be obtained using polymer-modified polyols (known as polymer polyols), which are made by the polymerisation, in situ, of monomers to form polymers dispersed in carrier or base polyols. Examples of polymer polyols include those made by (radical) polymerisation of ethylenically unsaturated monomers (e.g. styrene and acrylonitrile (SAN)) in carrier polyols, PHD (polyurea or polyharnstoff

dispersion) polymer polyols and PIPA (polyisocyanate addition) polymer polyols.

SAN polymer polyols are known in the production of high hardness polyurethane foams. However, the

production process of said foams is non-facile, see for example US 2008/0262119 Al, and is limited by the current worldwide availability of SAN polymer polyols.

PIPA polymer polyols are obtained by the in-situ reaction of an organic polyisocyanate and an olamine to produce a polyurethane dispersed in a liquid polyether polyol. This method inherently results in a mixture of products resulting from the reaction of the

polyisocyanate with (a) the olamine and (b) the base polyol. The ratio of these products must be controlled in order to produce a polyurethane foam with the desired properties .

Useful polyurethane foams have successfully been made from PIPA polymer polyols wherein the base polyol is an EO-tipped polyol (see, for example GB 2072204 and GB

2098229) . In an EO-tipped polyol, EO (ethylene oxide) is added at the end of the polyol production process such that the end of each polyol chain comprises a block of EO units and, thus, the polyol comprises a high proportion of primary hydroxyl groups . Such polyurethane foams are high value. Thus the foams made from them (usually high resilience foams), though valuable are expensive to produce .

It would be desirable to make PIPA polymer polyols and polyurethane foams therefrom, wherein the polyols are conventional polyols, that is manufactured using either only propylene oxide or a random mixture of ethylene oxide and propylene oxide, i.e. polyols comprising a high percentage of secondary hydroxyl groups. These polyols are cheaper and simpler to produce than EO-tipped polyols .

The known preparation of PIPA polymer polyols, wherein the polyol is an EO-tipped polyol, comprises the steps of (i) mixing the olamine into all of the base polyol, (ii) adding catalyst, (iii) then adding

polyisocyanate and (iv) continuing to mix until the desired product is formed. The present inventors have found that applying such a process to the preparation of PIPA polymer polyols comprising conventional polyols results in unstable polymer polyol mixtures and/or closed foams .

The present inventors have, therefore, sought to provide a process for the production of PIPA polymer polyols comprising conventional polyols that leads to a stable polymer polyol mixture suitable for the use in the production of polyurethane foams .

Summary of the Invention

Accordingly, the present invention provides a process for the preparation of a polymer-modified polyol, wherein the polymer-modified polyol comprises a

polyurethane polymer derived from the reaction of an olamine with an organic polyisocyanate and a polyol which comprises at least 50wt% secondary hydroxyl groups and wherein the process comprises the steps of:

(a) mixing the olamine with a portion of the polyol in the range of from 30 to 80 wt% of the total polyol;

(b) adding a catalyst and the polyisocyanate with mixing;

(c) then adding the remaining portion of the polyol; and

(d) mixing the reagents until the reaction is complete.

The present invention further provides a process for the preparation of polyurethane foam by reacting the product thus formed with organic polyisocyanate in the presence of a blowing agent, a polyurethane catalyst, optionally crosslinking agents and also optionally further usual auxiliaries .

Detailed Description of the Invention

The present inventors have surprisingly found that, a stable PIPA polymer polyol composition can be produced by a process which involves initial reaction of the olamine and the polyisocyanate in the presence of a limited amount of the polyol . Such a polymer polyol composition can be used to produce polyurethane foams with good hardness properties. Such foams may also exhibit a high degree of fire resistance

Organic polyisocyanates are organic isocyanates having two or more isocyanate groups . The organic polyisocyanates for polymerisation with olamine in the process for the preparation of the polymer-modified polyol can contain one or more different polyisocyanates. The polyisocyanate which can be used includes aliphatic, cycloaliphatic, aromatic and heterocyclic

polyisocyanates. Of particular interest are the aromatic polyisocyanates, for example toluene diisocyanate (TDI) and diphenylmethane diisocyanate (MDI) which are

commercially available in substantially pure and crude forms. More particularly these include 2,4 and 2,6- toluene diisocyanates and mixtures thereof;

diphenylmethane-2 , 4 ' , 2, 2', 4, 4 ' -diisocyanates and mixtures thereof (generally referred to as pure MDI) in crude, pure or polymeric form, for example, a mixture containing from 70 to 100%, especially 80%, by weight of the 4, 4 '-isomer and from 0 to 30%, especially 20%, by weight of the 2, 4 '-isomer; mixtures of MDI with

polyphenyl polymethane polyisocyanates made by

phosgenating a mixture of polyamines which is obtained by condensing aniline with formaldehyde (generally referred to as crude or polymeric MDI); and mixtures of TDI and MDI, pure or crude, for example, a mixture containing 60% by weight of TDI and 40% by weight of MDI. There may also be used diisocyanates which have been modified in known manner to introduce a significant isocyanurate, carbodiimide, uretonimine, buiret or allophanate content. Other polyisocyanates which may be used include isocyanate-ended prepolymers, for example, reaction products of a diisocyanate with a deficiency of one or more low molecular weight polyols such as

trimethylolpropane , dipropylene glycol or tripropylene glycol; and polyisothiocyanates , polyisoselenocyanates and mixtures thereof.

Olamines are defined as organic compounds having one or more hydroxyl groups and one or more amine groups, and may be any of those specified or described in GB 2072204. Suitable examples of olamines are: monoethanolamine , diethanolamine, triethanolamine, N-methylethanolamine, N- ethylethanolamine, N-butylethanolamine , N- methyldiethanolamine, N-ethyldiethanolamine , N- butyldiethanolamine, monoisopropanolamine,

diisopropanolamine, triisopropanolamine, N- methylisopropanolamine, N-ethylisopropanolamine, N- propylisopropanolamine . Substituted alkanolamines may also be used. A preferred alkanolamine is

triethanolamine .

The polymerisation of the olamine with the organic polyisocyanate may be catalysed using any of the

conventional catalysts for polyurethane chemistry. Such catalysts include tertiary amines such as, for example, triethylenediamine , N-methylmorpholine ,

diethylethanolamine, and dimethylbenzylamine ; tertiary phosphines such as trialkylphosphines, and

dialkylbenzylphosphines ; strong bases such as alkali and alkaline earth metal hydroxides, alkoxides and

phenoxides; salts or organic acids such as sodium acetate, stannous octoate, stannous oleate, lead octoate and zinc octoate; and organometallic derivatives such as disclosed in US 2846408. Preferably the catalyst is stannous octoate. In known methods for producing polymer polyols comprising EO-tipped polyols, the catalyst of choice is dibutyl-tin-dilaurate . However, said catalyst has known HSSE risks. An additional advantage of the present invention is that a less harmful catalyst, such as stannous octoate can be used effectively.

Further compounds known to be suitable to someone skilled in art, such as stabilizer, can be present during the polymerization.

A very much preferred polymer is the condensation product of triethanolamine and toluene diisocyanate (TDI) .

The polymer-modified polyol containing polymer formed by polymerising olamine with an organic

polyisocyanate, will usually contain from 5 to 50wt% of polymer in polyol, more preferably from 5 to 20wt.

The polyol which is present in the polymer-modified polyol can be any polyol prepared from hydroxyl

containing starting material compounds known to be suitable to one skilled in the art, with the proviso that the polyol contains at least 50wt% secondary hydroxyl groups. Preferably, the polyol contains at least 60wt%, more preferably 70wt%, even more preferably 80wt% and most preferably 85wt% secondary hydroxyl groups.

The polyol for use in the process of the present invention is a polyalkoxylated polyol prepared by reacting a hydroxyl containing starting material compound with propylene oxide, optionally also with one or more other alkylene oxides such as ethylene oxide, butylenes oxide and/or mixtures thereof. Preferably, the

polyalkoxylated polyol is prepared by reacting a hydroxyl containing starting material compound with propylene oxide either on its own or as a mixture with ethylene oxide in a ratio suitable to achieve the desired level of secondary hydroxyl groups .

Preferred hydroxyl containing starting material compounds for the polyol present in the polymer modified polyol, generally contain from 2 to 8 hydroxyl groups.

Examples of such alcohols comprise glycols, glycerol, pentaerythritol, trimethylolpropane, triethanolamine, sorbitol and mannitol. Usually a strong base like potassium hydroxide or a similar metal hydroxide salt is used as a catalyst in the reaction of the hydroxyl containing starting material compounds with the alkylene oxide (s) . However, catalysts such as double metal cyanide complex catalysts can also be used.

In the process of the present invention, the olamine is mixed in step (a) with a portion of the polyol. Said portion is suitably at least 30wt%, preferably at least 40wt%, more preferably at least 45wt% of the total polyol present in the desired polymer-modified polyol product. Said portion is suitably at most 80wt%, preferably at most 70wt%, more preferably at most 60wt%, most

preferably at most 55wt% of the total polyol present in the desired polymer-modified polyol product.

After the olamine is mixed with the polyol, catalyst and organic polyisocyanate are added. These may be added together or one at a time. In one preferred embodiment, the catalyst is added in its entirety before the organic isocyanate. That is, step b) involves the two steps of i) first adding the catalyst, with mixing and ii) then adding the organic isocyanate with mixing.

The reagents are mixed together before the remainder of the polyol is added. The remainder of the polyol comprises the 20 to 70wt% of the total polyol present in the desired polymer-modified polyol product which was not mixed with the olamine in step a) , such that the total polyol added in steps a) and c) is equal to 100wt% of the total polyol.

Further mixing is then carried out until the reaction is complete. The phrase 'the reaction is complete' as used herein refers to the reaction being substantially complete. That is at least 85wt%,

preferably at least 95wt%, more preferably at least 98wt%, most preferably at least 99wt% of the olamine added in step a) has reacted. This can be measured by known analytical methods and can also usually be judged qualitatively by the opaque appearance of the reaction mixture .

The present invention also relates to a process for the preparation of a polyurethane foam by reacting the polymer modified polyol with an organic polyisocyanate in the presence of a blowing agent, a polyurethane catalyst, optionally, crosslinking agents and, also optionally, further usual auxiliaries .

The organic polyisocyanate used in the process for the preparation of the polyurethane foam can be the same or different as the organic polyisocyanate used in the preparation of the polymer-modified polyol and can contain one or more different polyisocyanates . The polyisocyanate ( s ) which can be used includes aliphatic, cycloaliphatic, aromatic and heterocyclic

diphenylmethane-2 , 4 ' , 2,2', 4 , 4 ' -diisocyanates and mixtures thereof (generally referred to as pure MDI), in crude, pure or polymeric form for example, a mixture containing from 70 to 100%, especially 80%, by weight of the 4, 4 '-isomer and from 0 to 30%, especially 20%, by weight of the 2, 4 '-isomer; mixtures of MDI with

polyphenyl polymethane polyisocyanates made by

phosgenating a mixture of polyamines which is obtained by condensing aniline with formaldehyde (generally referred to as crude or polymeric MDI); and mixtures of TDI and MDI, pure or crude, for example, a mixture containing 60% by weight of TDI and 40% by weight of MDI. There may also be used diisocyanates which have been modified in known manner to introduce a significant isocyanurate, carbodiimide, uretonimine, buiret or allophanate content. Other polyisocyanates which may be used include

isocyanate-ended prepolymers, for example, reaction products of a diisocyanate with a deficiency of one or more low molecular weight polyols such as

trimethylolpropane , dipropylene glycol or tripropylene glycol; and polyisothiocyanates , polyisoselenocyantes and mixtures thereof.

Preferably, the organic polyisocyanate or

polyisocyanates used in the preparation of the

polyurethane foam is/are the same as used in the

preparation of the polymer-modified polyol. Most preferably that polyisocyanate is selected from MDI and TDI .

The use of water as a (chemical) blowing agent is well known. Water reacts with isocyanate groups

according to the well known NCO/H20 reaction, thereby releasing carbon dioxide which causes the blowing to occur. Other blowing agents, such as carbon dioxide and/or methylene chloride, can be used as well either per se or in combination with water. Preferably, water is the blowing agent in the formulation according to the present invention .

Typically at least one polyurethane catalyst is used in the process for the preparation of polyurethane foam.

Preferably more than one catalyst is used. Polyurethane catalysts are known in the art and include many different compounds. Such catalysts include those used for the preparation of the polymer-modified polyol. An extensive list of polyurethane catalysts is, for instance, given in

US-5, Oil, 908. A preferred catalyst is an amine,

especially a tertiary amine, catalyst. Preferred amine catalysts include an amine group substituted by at least two optionally-substituted, preferably unsubstituted, lower alkyl groups which may be the same or different, but are preferably the same. A lower alkyl group may have up to 8, preferably up to 6, more preferably up to 4, carbon atoms, with methyl and ethyl groups being especially preferred. A tertiary amine catalyst may be selected from bis ( 2 , 2 ' -dimethylamino ) ethyl ether, trimethylamine, triethylamine, triethylenediamine, dimethylethanolamine, N, ' , ' -dimethylaminopropylhexa- hydrotriazine and N, -dimethylcyclohexylamine . Examples of commercially available tertiary amine catalysts are those sold under the trade names NIAX, TEGOAMIN, JEFFCAT and DABCO (all trade names) .

Within the polyurethane catalysts and even within the tertiary amine catalysts a distinction can be made between gelation catalysts and blowing catalysts .

Gelation catalysts are catalysts which predominantly promote the gelation of the foaming mixture, i.e. which promote the reaction between polyols and polyisocyanate. Typical gelation catalysts are stannous octoate and dibutyltindilaurate . Blowing catalysts predominantly promote the CO/H2O reaction, whereby carbon dioxide is released which causes the blowing to occur. Typical blowing catalysts are dimethylaminoethylether and urea.

Other usual auxiliaries may include fillers, flame retardants, foam stabilisers (surfactants) and

colourants. The flame retardants can be liquid and/or solid flame retardants. Organosilicone surfactants are most conventionally applied as foam stabilisers in polyurethane production . A large variety of such organosilicone surfactants is commercially available. Preferred compounds include compound L2100, commercially available from Momentive, and compound B4900,

commercially available from Evonik. Usually, such foam stabiliser is used in an amount of up to 5% by weight based on the reaction mixture of polyol reactant and polyisocyanate reactant. The amount in which the usual auxiliaries can be present, can vary widely. Generally, the amount will be of from 0 to 50 parts by weight, based on amount of polyol, more specifically of from 0 to 40 parts by weight.

The present invention is further illustrated in the Examples .

Examples

Example 1 (PIPAl - Comparative)

A PIPA polyol was made using the constituent and amount listed in Table 1 in a method usually used in the preparation of EO-tipped PIPA polyols. At t=0seconds mixing of the polyol and triethanolamine (TEOA) was started. The catalyst (stannous octoate (Snoct) ) was added with mixing at t=2 minutes. The TDI was added after a further minute and the resulting mixture was stirred for a further 7 minutes . Example 2 (PIPA 2 - of the Invention)

A PIPA polyol was made according to the process of the present invention using the amounts listed in Table 1. At t=0sec mixing of 50wt% of the total polyol with the TEOA was started. After 1 minute the catalyst (Snoct) was added with mixing and after a further 1 minute the TDI was added. At t=2.3 minutes, the remaining 50wt% of the polyol was added and mixing was continued until t=10 minutes .

Table 1 - amounts used in PIPAl and PIPA2

SC48-08 is a glycerine-initiated polyol containing about 12.2% EO distributed randomly along the chain and having an approximate hydroxyl value of 48mg KOH/g polyol. It contains about 10% primary hydroxyl end- groups, the remainder of the hydroxyl-end groups are secondary .

Examples 3, 4 and 5

The polymer modified polyols made in Examples 1 and 2 were used to make polyurethane foams in Examples 3 and 4, respectively. In the reference example (Example 5), , SAN polyol, also containing 10wt% solids, was converted into a polyurethane foam using an equivalent process. The foam was made by mixing the polymer modified polyol with water, Al, A33, B4900 and Snoct in amounts according to Table 2. After mixing, TDI was added. TDI was then added and the foam processing was carried out under the conditions indicated in Table 3. Table 4 shows the physical properties of the resultant foams.

Table 2

* - Comparative example. SP30-45 is a SAN

containing polyol comprising 45% solids and with an OH value of 30mg KOH/g. PIPA refers to the polymer modified polyols made in Examples 1 and 2. Thus, in Example 3 it refers to PIPAl and in Example 4 it refers to PIPA2. Al is a blowing catalyst (Ex - Momentive) containing bis (2- dimethylaminoethyl ether. A33 is aminic catalyst (Ex - Momentive) containing 30% triethylene diamine and 60% DPG . B4900 is a silicone stabilizer for polyurethane foaming (Ex- Evonik) .

Table 3 - Foam Processing

Example 3* Example 4 Example 5*

(PIPA 1) (PIPA 2) (SAN)

Temp (°C) 20.5 20.5 21.2

RH (%) 79 79 84

Mixing speed 1760 1760 1760

( rpm)

Start of rise 21 21 22

( seconds )

End of rise 114 112 106

( seconds ) RH refers to relative humidity.

Table 4 - Physical Properties of the Foams

CLD refers to compression load density. Porosity is measured by taking a piece of foam, applying a pressure of 125 Pa across the foam, blowing air through the foam and measuring the air flow.

As can be seen from these examples, the process according to the present invention provides PIPA polymer- modified polyols, wherein the polyols contain a high proportion of secondary hydroxyl groups, which can be converted into foams having very similar properties, especially CLD and porosity, to foams created from SAN polyols. The foams prepared in this manner have an open structure (indicated by a high porosity and physical examination) . This is in comparison to foams made from PIPA polyols, wherein the polyols contain a high

proportion of secondary hydroxyl groups, which have been made using the known process for making PIPA polyols from EO-tipped polyols. Such foams have a much more closed structure than is desirable in high hardness foams.

The process of the present invention thus provides desirable high hardness foams by a facile method, avoiding the more complex preparation required and the limited availability issues involved in foams made from SAN polyols.

Claims

C L A I M S

1. A process for the preparation of a polymer-modified polyol, wherein the polymer-modified polyol comprises a polyurethane polymer derived from the reaction of an olamine with an organic polyisocyanate and a polyol which comprises at least 50wt% secondary hydroxyl groups and wherein the process comprises the steps of:

(a) mixing the olamine with an amount of the polyol in the range of from 30 to 80 wt% of the total polyol;

(b) adding a catalyst and the polyisocyanate with mixing;

(c) then adding the remaining portion of the polyol; and

(d) mixing the reagents until the reaction is complete.

2. A process according to claim 1, wherein the olamine is triethanolamine .

3. A process according to claim 1 or claim 2, wherein the organic polyisocyanate is selected from the group consisting of MDI and TDI .

4. A process according to any one of claims 1 to 3, wherein the polyol comprises at least 70wt% secondary hydroxyl groups.

5. A process according to any one of claims 1 to 4, wherein the catalyst is stannous octoate .

6. A process according to any one of claims 1 to 5, wherein the polyol comprises at least 60wt% secondary hydroxyl groups .

7. A process according to any one of claims 1 to 5, wherein the polyol comprises at least 80wt% secondary hydroxyl groups .

8. A process for the preparation of foam by reacting the product of the process of any one of claims 1 to 7 with an organic polyisocyanate in the presence of a blowing agent, a polyurethane catalyst, optionally, crosslinking agents and, also optionally, further usual auxiliaries .