GB2226030A - Blowing agent - Google Patents

Abstract

Blowing agent consists essentially of 10-80 mol % of trichlorofluoromethane and 20-90 mol % a normally-liquid organic compound of boiling point below 120 DEG C (especially 1,1, 1-trichloroethane or 1,1-dichloro-1-fluoroethane). The blowing agent is useful for making polyurethane foams.

Description

BLOWING CE:NT This invention relates to blowing agents useful in the production of polyurethane and polyisocyanurate foams.

The manufacture of polymeric foams by processes involving the vaporisation of a low boiling point liquid in the presence of a polymeric material or precursors thereof is well established.

As examples of such processes, there may be mentioned the production of expanded polystyrene by heating polystyrene beads containing entrapped blowing agent and the production of polyurethane foams by causing polyurethane precursors to interact in the presence of a blowing agent, vaporisation in this case being brought about by the exothermic reaction.

The foams made by these processes can, depending upon the amount of blowing agent used, vary in density from about 20 kg/m3 to about lOOO.kg/m3. Similarly, depending upon the starting components, the foams can vary in texture from very soft types useful in upholstery applications to rigid foams useful as structural materials.

A number of blowing agents have been proposed but the one most commonly used for some thirty years has been trichlorofluoromethane having a boiling point of 23.8 C at atmospheric pressure. In recent years it has been determined that the amount of trichlorofluoromethane used as a blowing agent in the manufacture of foams should be reduced. As a result much effort has been devoted by industry to the discovery of alternative blowing agents in order to replace trichlorofluoromethane partially.

The present invention is concerned with a blowing agent consisting essentially of 10-80 mol % of trichlorofluoromethane and 20-90 mol % of a normally-liquid organic compound of boiling point below 120 C. Preferably the amounts are 25-75 mol % of trichlorofluoromethane and 25-75 mol % of the normally-liquid organic compound.

By the term "normally-liquid organic compound" there is meant an organic compbund which has a boiling point above 25 C, preferably above 30" C and more preferably above 50 C.

The normally-liquid organic compound may be selected fron the hydrocarbons wherein at least one hydrogen has been replaced by C1, F or Br. Preference is given to chlorofluorohydrocarbons, chlorohydrocarbons, chlorofluorocarbons, chlorocarbons and fluorohydrocarbons like 1,2,2-trichloro-l,l-difluoroethane, 1, 2-dichloro-l, 1-difluoroethane, 1, l-dichloro-l-fluoroethane, 1,1,1,2-tetrachlorodifluoroethane, 1,1,2,2-tetrachlorodifluoroethane, 1,2-dichloro-1,2,2-trifluoroethane, 1, 1-dichloro-2, 2 ,2-tri fluoroethane, 1,1,2-trichloro,1,2,2-trifluoroethane, hexachloroethane, 1,2-difluoroethane, fluorobenzene, perchloroethylene, trichloroethylene, 1,1, 1-trichioroethane, methylene chloride, 1,2,2-trichloroethane, 1,2-dichloroethane, l,l-dichloroethane, ethylene dichloride, carbon tetrachloride and chloroform.

Combinations of two or more normally-liquid organic compounds may be used as well. Most preference is given to chlorofluorohydrocarbons and chlorohydrocarbons and in particular to l,l,l-trichloroethane and l,l-dichloro-l-fluoroethane.

The blowing agent is prepared by combining the ingredients and stirring such combination of ingredients at ambient temperature.

The blowing agent may contain stabilizers in order to protect the blowing agent against alteration, like degradation. Such stabilizers are generally known.

The blowing agent is used in the manufacture of foams. In such manufacture of foams, the blowing agent is incorporated in the foam-forming material or a precursor mixture thereof. In one aspect, the invention provides a foamable polymer or a precursor of a foamable polymer containing a blowing agent as hereinbefore defined.

As examples of foamable polymers which may contain the blowing agents described herein, there may be mentioned polyolefins, for example polystyrene, poly(vinyl chloride) and polyethylene.' As examples of precursors of foamable polymers, there may be mentioned precursors of phenolic resin foams, epoxy resin foams, silicon resin foams and especially isocyanate-based foams such as polyurethane, polyurea, polycarbodiimide and polyimide foams.

In general, the amount of blowing agent present in the foamable polymer or polymer precursor will be an amount sufficient to provide a foamed polymer of the desired density. Amounts of from 5 to 40 % by weight of the foam forming ingredients are typical.

The invention is of particular relevance to the production of isocyanate-based foams by processes involving the polymerisation, for example trimerisation, of an organic polyisocyanate or the reaction thereof with one or more compounds containing a plurality of isocyanate-reactive groups.

The production of such foams has been fully described in the literature and the methods conventionally used may be readily adapted to the use of the blowing agents described herein.

In particular, the blowing agents may be used in the production of polyurethane and isocyanate-modified polyurethane foams by processes comprising reacting an organic polyisocyanate with an organic polyol, optionally in the presence of cross-linking agents, chain extenders, foam-stabilising agents, surfactants, catalysts for urethane formation, trimerisation catalysts, fire retardants, fillers, pigments, antioxidants and the like.

Thus, in a further aspect, the invention provides a polyurethane precursor containing a blowing agent as hereinbefore defined.

The polyurethane precursor containing the blowing agent will be an organic polyisocyanate or an organic polyol. As examples of polyisocyanates there may be mentioned any of the polyisocyanates proposed in the literature for use in the production of foams. Of particular importance are aromatic diisocyanates such as tolylene and diphenylmethane diisocyanates in pure, modified or crude forms. Special mention may be made of the so-called MDI variants (diphenylmethane diisocyanate modified by the introduction of urethane, allophanate, urea, biuret, carbodiimide, urethoniamine or isocyanurate residues) and crude MDI (polymethylene polyphenylene polyisocyanates).

Usually however, the blowing agent will be incorporated in the polyol precursor. The nature of the organic polyol which may contain the blowing agent will depend on the type of foam being produced. In general, the polyols can have hydroxyl numbers of from 20 to 1830 but for the production of flexible foams typical values are from 20 to 100, especially from 25 to 75 and functionalities of 2 to 4, especially 2 or 3. For rigid foam production, the polyols typically have hydroxyl numbers of from 200 to 800, especially from 300 to 600 and functionalities of 2 to 8, especially 3 to 8.

No other blowing agents are employed. However, since polyols contain small amounts of water and since this small amount of water may act as a blowing agent as well, the presence of small amounts of water (up to 3 mol % calculated on the total amount of trichlorofluoromethane and normally-liquid organic compoundj in the composition according to the present invention is encompassed.

Suitable organic polyols for polyurethane foam production are polymeric polyols such as hydroxyl-terminated polyethers, polyesters, polyesteramides, polythioethers, polyzarbonates, polyacetals and polyolefins.

Suitable polyether polyols include products obtained by the polymerisation of a cyclic oxide, for example ethylene oxide, propylene oxide or tetrahydrofurane or by the addition of one or more such oxides to polyfunctional initiators, for example water, ethylene glycol, propylene glycol, diethylene glycol, glycerol, trimethylolpropane, sorbitol, sucrose, triethanolamine, ethylene diamine, tolylene diamine, diaminodiphenylmethane, polymethylene polyphenylene polyamines and mixtures thereof. Of particular importance are the polyoxypropylene polyols and poly(oxyethylene-oxypropylene) polyols obtained by the simultaneous or sequential addition of ethylene and propylene oxides to appropriate initiators.

Suitable polyester polyols include hydroxyl-terminated reaction products of polyhydric alcohols such as ethylene glycol, diethylene glycol, neopentyl glycol, hexamethylene glycol, glycerol, trimethylolpropane or pentaerythritol or mixtures thereof with polycarboxylic acids, especially dicarboxylic acids or their ester-forming derivatives, for example succinic, glutaric and adipic acids or their dimethyl esters, phthalic anhydride or dimethyl terephthalate. Polyesters obtained by the polymerisation of lactones, for example caprolactam, in conjunction with a polyol, may also be used. Polyesteramides may be obtained by the inclusion of amino-alcohols or polytmLnes in polyesterification mixtures.

Polythioether polyols which may be used include products obtained by condensing thiodiglycol either alone or with other glycols, dicarboxylic acids, formaldehyde, aminoalcohols or aminocarboxylic acids.

Polycarbonate polyols which may be used include products obtained by reacting diols such as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol or tetraethylene glycol with diaryl carbonates, for example diphenyl carbonate, or with phosgene.

Polyacetal polyols which may be used include those prepared by reacting glycols such as diethylene glycol, thriethylene glycol and hexanediol with formaldehyde. Suitable polyacetals may also be prepared by polymerising cyclic acetals.

Suitable polyolefin polyols include hydroxyl-terminated butadiene homo- and copolymers.

Thus, in a further embodiment of the invention there is provided a polymeric polyol, especially a rigid foam polyol, containing a blowing agent as hereinbefore defined, and optionally one or more other components (other than polyisocyanates) of foam formulation.

Other components of foam formulations which may be present in the polyol compositions include non-polymeric polyols useful as cross-linking or chain-extending agents, for example butanediol or triethanolamine, foam-stabilising agents or surfactants, for example siloxane-oxyalkylene copolymers, urethane catalysts, for example tin compounds such as stanuous octate or dibutyltin dilaurate or tertiary amines such as dimethylcyclohexylamine or triethylene diamine, trimerisation catalysts, for example potassium acetate or lead octoate, and fire-retardants, for example tris chloropropyl phosphate.

The invention also covers foam-forming systems suitable for performing the foaming method according to the invention. The expression "system" as used herein refers to a set of individual components which are produced and/or marketed with the obvious purpose to be suitable for use in combination with each other to perform a specific process or to achieve specific performances. Hence, the present invention is further concerned with a system for preparing a foam comprising a foamable polymer or the precursors of a foamable polymer, a blowing agent according to the present invention and, optionally, one or more of the auxiliaries and additives mentioned before. Such auxiliaries and additives may be present in the system separately from or together with the polymer, one of the precursors or the blowing agent.In particular the invention is concerned with a system for preparing a foam comprising a) an organic polyisocyanate b) an organic polyol c) a blowing agent according to the present invention ; and d) optionally one or more of the auxiliaries and additives mentioned before.

The ingredients constituting the blowing agent according to the present invention could be provided separately from each other in the above systems.

The invention also provides a method for the preparation of polyurethane foams, and in particular of rigid polyurethane and polyisocyanurate foams, which comprises reacting an organic polyisocyanate with a polymeric polyol in the presence of a blowing agent as hereinbefore defined.

In preparing the foams, which may be flexible, semi-rigid or rigid depending upon the components used, conventional techniques and mixing methods may be used and the foams may be produced in the form of mouldings or slabstock or in the form of laminates with other materials such as hardboard, plaster board, paper or metals.

A still further embodiment of the invention resides in a foam, in particular a rigid polyurehtane or polyisocyanurate foam, made using a blowing agent as hereinbefore defined and containing the residues and reactants of the blowing agent.

Such rigid foams show beneficial insulating and ageing properties.

The invention is illustrated by the following example.

Example Three blowing agents were prepared by combining trichlorofluoromethane and trichloroethane in molar ratios 3:1, 1:1 and 1:3 respectively.

Subsequently these blowing agents were combined with P18C (a polyol), P2lO (a polyol), SFC (a catalyst), PMDET (a catalyst) and B8404 (a surfactant). These compositions were reacted with a MDI-type polyisocyanate. Rigid polyurethane foams were obtained.

Claims (9)

1. Blowing agent consisting essentially of 10-80 mol % of trichlorofluoromethane and 20-90 mol % of a normally-liquid organic compound of boiling point below 120" C.

2. The blowing agent according to claim 1, characterised in that the normally-liquid compound is selected from the hydrocarbons wherein at least one hydrogen atom has been replaced by C1, F or Br,

3. The blowing agent according to claim 1 or 2, characterised in that the normally-liquid compound is selected from chlorofluorohydrocarbons and chlorohydrocarbons.

4. The blowing agent according to claims 1-3, characterised in that the normally-liquid compound is selected from 1,1, l-trichloroethane and 1, l-dichloro-l-fluoroethane.

5. Composition comprising a foamable polymer or a precursor of a foamable polymer and a blowing agent according to claims 1-4.

6. Composition according to claim 5, characterised in that the precursor is an organic polyisocyanate or an organic polyisocyanate-reactive compound.

7. Composition according to claim 6, characterised in that the organic polyisocyanate-reactive compound is a polyol.

8. Process for preparing a foam by contacting a foamable polymer and a blowing agent according to claims 1-4 under foam-forming conditions or by reacting the precursors of a foamable polymer in the presence of a blowing agent according to claims 1-4 under foam-forming conditions.

9. Process according to claim 8, characterised in that an organic polyisocyanate and an organic polyisocyanate reactive compound are reacted.