Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
  • C08J9/12—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
  • C08J9/14—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent organic
  • C08J9/143—Halogen containing compounds
  • C08J9/144—Halogen containing compounds containing carbon, halogen and hydrogen only
  • C08J9/146—Halogen containing compounds containing carbon, halogen and hydrogen only only fluorine as halogen atoms
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
  • B29C44/34—Auxiliary operations
  • B29C44/3442—Mixing, kneading or conveying the foamable material
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2361/00—Characterised by the use of condensation polymers of aldehydes or ketones; Derivatives of such polymers
  • C08J2361/04—Condensation polymers of aldehydes or ketones with phenols only
  • C08J2361/06—Condensation polymers of aldehydes or ketones with phenols only of aldehydes with phenols

Definitions

• This invention relates to methods of forming foamed or expanded materials from synthetic polymers and resins and, more particularly, to methods of forming foamed or expanded materials from catalyst cured condensation polymers, particularly phenolic resins, such as phenol formaldehyde resins .
• the formation of expanded materials such as rigid foams involves combining a suitable polymer or resin with a blowing agent, surfactant or cell stabiliser and catalyst.
• the blowing agent creates voids in the polymer or resin which are stabilised by the surfactant, while the polymer or resin cross-links and thus hardens under the influence of the catalyst .
• phenolic resins such as phenol formaldehyde resins and conventionally used acid curing catalysts contain water which is released from solution during the foam-forming process. In addition, the catalyst initiated cross-linking process releases further water. It has been found that the more water present or formed, the more that is potentially trapped in the foam and, thus, the more likely water-related defects are to arise in the foam. The likelihood of water- related defects has been found to be exacerbated by the small cell size of many phenolic resin foams with the result that consistently achieving foam with defect-free cells, in a typical environment, has been virtually impossible.
• Preferred applications for expanded materials such as phenolic resin foams are those which require, or at least seek, good thermal insulating properties, low flammability, and low smoke generation and low toxicity when combusted.
• High thermal insulation or low thermal conductivity of expanded materials is achieved from a combination of : 1) fine cell size;
• Thermal conductivity will, however, generally increase with time as blowing gases, trapped within the closed cells during foam formation, diffuse through the cell walls.
• a further drawback of existing expanded foamed materials is that the processes for their formation do not provide adequate control over the structure of the finished material. It has been found that anisotropy arising from current processes typically leads to the formation of axes of minimum and maximum strength in cured phenolic resin foam. This must be borne in mind when specifying applications for such foam as, in many cases, because the axes of strength cannot be readily identified, application for the cured foam must be restricted to minimum observed strengths .
• Another significant characteristic of acid-cured resole phenolic resin foams is that they exhibit significant residual acidic activity. This acidity can limit their final application due to potential corrosive effects.
• EP-A-0 170 357 involve the use of strong mineral acids, such as sulphuric acid, as the catalyst and halogenated chlorofluorocarbons (CFCs) , in the form of freon, as the blowing agent.
• strong mineral acids such as sulphuric acid
• CFCs halogenated chlorofluorocarbons
• freon halogenated chlorofluorocarbons
• a further example of phenolic resin foam production is disclosed in EP-A-0 439 283.
• the processes disclosed in this document replace CFCs as blowing agents with materials which are a mixture of perfluorohydrocarbons and hydrogenated chlorofluorocarbons . Otherwise the processes disclosed are largely conventional.
• the catalysts specified in this disclosure again comprise strong mineral acids such as sulphuric or hydrochloric acids although mention is also made of using aryl sulphonic acids such as p-toluene or xylene sulphonic acids in the role of catalyst . However these forms of sulphonic acid, as described, contain significant amounts of water.
• GB-A-2 232 673 discloses a further acid-cured phenolic resin foam process in which the blowing agent incorporates non-CFC components. Also included within the disclosure is considerable background information on the mechanisms involved in phenolic resin foam formation and on various factors which can influence the process outcome . With this in mind the contents of this disclosure are incorporated herein by reference.
• the surfactant or cell stabiliser is premixed with the polymer or resin prior to the blowing agent and catalyst being added.
• This conventional premixing is considered by us to be responsible for certain types and degrees of cell defects typically found in expanded materials such as rigid phenolic resin foams .
• the surfactants used in expanded or foamed material are typically polar in nature and are often highly polar. More typically, one end of the surfactant molecule is hydrophilic while the other end is hydrophobic. We believe that the consequence of this is that, when premixed with a polymer resin to be expanded, the hydrophilic ends of many of the surfactant molecules are considered to attract water and retain that water in the system. Further, that the surfactant can stabilise air bubbles which form in the polymer or resin during the mixing process . The end result of both is that defects often arise in the cured foam.
• embodiments thereof can provide a novel process, and materials and apparatus for use therein, for producing, on a reproducible basis and under factory conditions, expanded or foamed materials, such as an acid-cured rigid phenolic resin foam, having one or more of the following: a) substantially defect-free cells both in struts and windows, b) controlled cell structure (open, partially open or closed) c) reduced residual acidity to effectively eliminate or at least substantially reduce corrosive behaviour in many applications, d) reduced surfactant requirement, e) in block foam, reduced anisotropy and therefore density for a given strength, f) controlled anisotropy in injection moulded product, and g) good and preferably stable thermal conductivity characteristics .
• expanded or foamed materials such as an acid-cured rigid phenolic resin foam
• Embodiments of the invention may at least provide a novel process, materials and apparatus which will provide a useful choice or overcome or mitigate the problems associated with known expanded or foamed materials and processes for their formation.
• a process which overcomes the problems involved in prior mixing the polymer or resin and surfactant.
• a process for the preparation of an expanded or foamed material which process comprises the expansion or foaming and subsequent hardening of a polymer or resin by the admixture of an expandable polymer or resin, a catalyst capable of causing hardening of the polymer or resin, a blowing agent capable of generating a gas within the polymer or resin so as to form cells therein and a surfactant capable of stabilising cells formed within the polymer or resin, the process being characterised in that the surfactant is substantially miscible with the blowing agent and the process involves the step of mixing the blowing agent with the surfactant prior to admixing those components with the resin and/or catalyst.
• the premixture of the surfactant and blowing agent not only mitigates or avoids the disadvantages given above for the premixture of resin and surfactant, but also provides an advantageous protective effect on acid or otherwise sensitive surfactants and an advantageous lubricating effect making it easier to control processing.
• the process includes the further step of admixing the resin and the blowing agent/surfactant pre-mixture, at least in part, prior to introducing, i.e. admixture with, the catalyst .
• Suitable polymers or resins for use in the present invention will be well known to the skilled man and include synthetic polymers and resins formed from the condensation or polymerisation of suitable condensation or polymerisation reagents.
• condensation polymers and resins include polyurethane resins and polystyrene, polyether and polyisocyanate polymers.
• Particularly suitable are phenolic resins formed from the condensation of a phenol with an aldehyde.
• the phenol may be a substituted phenol such as resorcinol, xylenol or a cresol, or preferably is phenol itself.
• the aldehyde may be acetaldehyde (ethanal) , benzaldehyde, furfuraldehyde, paraformaldehyde or preferable formaldehyde (methanal) .
• Condensation of the phenol and aldehyde may take place under any suitable conditions. It may take place using either an acid or preferably a base condensation catalyst such as sodium hydroxide. It is particularly preferred that the resin be a resole phenol formaldehyde resin.
• the polymer or resin is a low free formaldehyde resin having a formaldehyde to phenol mole ratio within the range 1.3 to 2.0:1 and, more preferably, within the range 1.5 to 1.6:1.
• Suitable catalysts for use in the process will be well known to the skilled man and will depend on the nature of the polymer or resin or other ingredients to be used. They include organic or inorganic acids, including mineral acids such as sulphuric or hydrochloric acid and aryl (aromatic) sulphonic acids such as p-toluene, xylene or cumene sulphonic acids or combinations thereof.
• the catalyst is an aryl (aromatic) sulphonic acid or a combination of such acids.
• Such sulphonic acids are selected preferentially so as to be low in water content.
• the water content of the catalyst is preferably close to or substantially zero. It is particularly preferred that the catalyst be a combination of benzene and xylene sulphonic acids.
• the combined acids are preferably mixed in ratios of benzene sulphonic acid to xylene sulphonic acid of 10 parts: 90 parts through to 90 parts: 10 parts. More preferred ranges are 30 parts: 70 parts through to 70 parts: 30 parts.
• the catalyst further includes a proportion of orthophosphoric acid or other phosphorus containing compound.
• Suitable blowing agents for use in the present invention will be well known to the skilled man and will depend on the nature of the polymer or resin and the other ingredients being used.
• Suitable blowing agents include halogenated, particularly fluorinated, methane or ethane derivatives such as hydrofluorocarbons (HFCs) such as 134a, -245, -356, -365 and hydrogenated chlorofluorocarbons (HCFCs) for example HCFC 141b.
• HFCs hydrofluorocarbons
• HCFCs hydrogenated chlorofluorocarbons
• Other options include dichloromethane, n-pentane and cyclopentane and may also include suitable hydrofluoroethers .
• Mixtures of blowing agents may also be used.
• a particularly preferred blowing agent comprises a blend of dichloromethane and one or more hydrofluoroethers .
• Suitable surfactants for use in the present invention will be well known to the skilled man and will depend on the nature of the polymer or resin and other ingredients being used.
• Suitable surfactants, or cell stabilisers include silicones and alkoxylates or glycerides and mixtures thereof .
• Suitable silicones include polymeric or modified silicones such as polysiloxane or organomodified silicone fluid.
• Suitable alkoxylates include castor oil and ethoxylated castor oils and phenol ethoxylates such as nanyl phenol ethoxylate .
• the surfactant comprises a mixture of modified polysiloxanes (such as a polysiloxane and polyether copolymer) and alkoxlylates .
• the alkoxlylates comprise ethoxylated castor oils.
• Admixture of the ingredients and their subsequent foaming and curing (hardening) can be carried out by any suitable method such as those currently employed in the art and may involve a batch wise or continuous process.
• the process further comprises the step of cooling the mixture of blowing agent and surfactant to below the temperature of the polymer or resin and/or catalyst, before admixture of the blowing agent/surfactant pre-mixture with the polymer or resin and/or catalyst .
• adjuvants may be added to the ingredients at any stage during the process.
• Adjuvants may be added for example to the individual ingredients prior to their admixture or to any combinations of the ingredients or to the combined admixture.
• Suitable adjuvants include solvents, viscosity modifiers, diluents, fillers, binders, reinforcing agents and reactivity control agents, e.g. for controlling the boiling point of the blowing agent.
• Alcohols and/or glycols may be added to the resin or polymer or to the catalyst so as to at least partially neutralise residual acidity of the foam mixture.
• the process preferably includes means for controlling the cell formation in the foam.
• Such means may include the step of reducing the vapour pressure of the blowing agent prior to combining the blowing agent/surfactant pre-mixture with the polymer or resin and/or the catalyst .
• the process may include the step of cooling the blowing agent/surfactant pre-mixture to below the temperature of the polymer or resin and/or the catalyst, prior to mixing or alternatively or in addition pressurising the blowing agent/surfactant pre-mixture.
• a process for the preparation of an expanded or foamed material which process comprises the expansion or foaming and subsequent hardening of a polymer or resin by the admixture of an expandable polymer or resin, a catalyst capable of causing hardening of the polymer or resin, a blowing agent capable of generating a gas within the polymer or resin so as to form cells therein and a surfactant capable of stabilising cells formed within the polymer or resin, the process being characterised in that the total water content of the polymer or resin and catalyst combined is no greater than 20% by total weight of those ingredients combined.
• the polymer or resin to be used should be chosen in a form having a minimum water content and aqueous ingredients, in particular solvents such as water, should be avoided so as to achieve the no greater than 20% water content.
• the polymer or resin, catalyst, blowing agent, surfactant and any adjuvants used and the process steps utilised may be substantially as described above for the first aspect of the invention.
• the catalyst water content of the polymer or resin/catalyst combination should not be greater than 20%, it is preferred that the catalyst water content will generally be less than 5% by weight of the catalyst and more preferably, will be closer to or substantially at zero per cent.
• an aromatic sulphonic acid or combinations of those acids be used as the catalyst. It is particularly preferred to use a combination of benzene and xylene sulphonic acids as mentioned above in relation to the first aspect of the invention.
• a process according to the second aspect of the present invention may be combined with a process according to the first aspect of the present invention as hereinbefore described.
• a process for the preparation of an expanded or foamed material, which process comprises the expansion or foaming and subsequent hardening of a polymer or resin by the admixture of an expandable polymer or resin, a catalyst capable of causing hardening of the polymer or resin, a blowing agent capable of generating a gas within the polymer or resin so as to form cells therein and a surfactant capable of stabilising cells formed within the polymer or resin, the process being characterised in that it includes the further step of the addition of a solvent to the polymer or resin, the solvent being dichloromethane.
• the solvent may be added to the polymer or resin before or after the admixture with the catalyst and/or any other ingredients .
• dichloromethane as a solvent is particularly advantageous where the polymer or resin is a phenolic resin such as a resole phenolic resin.
• the polymer or resin, catalyst, blowing agent, surfactant and any adjuvants used and the steps utilised may be substantially as described above for the first or second aspect of the invention.
• a process according to the third aspect of the invention may be combined with a process according to the first and/or second aspects hereinbefore described.
• the catalyst of choice is a strong acid such as an aqueous mineral acid with aqueous sulphuric acid being the most common.
• the conventional use of this acid is disadvantageous in several respects and in particular because the resultant products have significant residual acidic activity leading to corrosive behaviour.
• a process has now been found which overcomes or mitigates the problems associates with the prior art use of catalysts.
• a process for the preparation of an expanded or foamed material which process comprises the expansion or foaming and subsequent hardening of a polymer or resin by the admixture of an expandable polymer or resin, a catalyst capable of causing hardening of the polymer or resin, a blowing agent capable of generating a gas within the polymer or resin so as to form cells therein and a surfactant capable of stabilising cells formed within the polymer or resin, the process being characterised in that the catalyst used to harden the polymer or resin includes at least one aromatic sulphonic acid having substantially zero added mineral acid.
• the catalyst is an aromatic sulphonic acid such as p- toluene, xylene or cumene sulphonic acids or combinations thereof.
• aromatic sulphonic acids are selected preferentially so as to be low in water content. Indeed, the water content of the catalyst is preferably close to or substantially zero.
• the catalyst be a combination of benzene and xylene sulphonic acids.
• the combined acids are preferably mixed in ratios of benzene sulphonic acid to xylene sulphonic acid of 10 parts: 90 parts through to 90 parts: 10 parts. More preferred ranges are 30 parts: 70 parts through to 70 parts: 30 parts.
• the catalyst further includes a phosphorus containing compound, such as ortho-phosphoric acid.
• the ortho-phosphoric acid is preferably 85% food grade phosphoric acid and is mixed with the aromatic sulphonic acid(s) in the ratio of 20-50 parts ortho-phosphoric acid : 100 parts of sulphonic acid (e.g. benzene/xylene mix).
• the polymer or resin, blowing agent, surfactant and any adjuvants used and the process steps utilised may be substantially as described above for the first, second and/or third aspects .
• a process according to the fourth aspect may be combined with a process according to one or more of the first, second and third aspects hereinbefore described.
• a process for the preparation of an expanded or foamed material which process comprises the expansion or foaming and subsequent hardening of a polymer or resin by the admixture of an expandable polymer or resin, a catalyst capable of causing hardening of the polymer or resin, a blowing agent capable of generating a gas within the polymer or resin so as to form cells therein and a surfactant capable of stabilising cells formed within the polymer or resin, the process being characterised in that the blowing agent includes or comprises dichloromethane and a hydrofluoroether miscible therein.
• the hydrofluoroether comprises HFE-7100 or HFE- 301 Speciality Fluid as sold by 3M.
• the polymer or resin, catalyst, surfactant and any adjuvants used and process steps utilised may be substantially as described above for the first to fourth aspects .
• the process of the fifth aspect may be used in combination with one or more of the first, second, third and fourth aspects of the present invention.
• a method of reducing the residual acidity of an acid cured phenolic resin foam comprises the step of adding neutralising means to reduce residual acidity arising as a result of the resin-forming process or as a result of the foam-forming reaction.
• the method of the sixth aspect of the invention comprises the addition of one or more of : i) free phenol, ii) a low molecular weight condensation polymer, iii) an alcohol or glycol.
• the low molecular weight condensation polymer may comprise phenol formaldehyde, melamine formaldehyde or urea formaldehyde.
• the alcohol preferably comprises furfuryl alcohol.
• the method of the sixth aspect of the invention may be used in a process according to one or more of the first to fifth aspects of the invention when used to prepare a phenolic resin foam.
• blowing agent and surfactant for use in any of the processes or methods hereinbefore or hereinafter set forth.
• each of the said blowing agent and surfactant are as herein set forth.
• apparatus for producing an expanded or foamed material from the admixture of an expandable polymer or resin, a catalyst capable of causing hardening of the polymer or resin, a blowing agent capable of generating a gas within the polymer or resin so as to form cells therein and a surfactant capable of stabilising cells formed within the polymer or resin, which apparatus includes a mixing chamber; mixing means with the mixing chamber to effect intermixing of components supplied to the mixing chamber; first supply means constructed and arranged to supply polymer or resin into the mixing chamber; second supply means constructed and arranged to supply catalyst into the mixing chamber; and third supply means constructed and arranged to supply a mixture of blowing agent and surfactant to the mixing chamber.
• the first, second and third supply means include positive displacement pump means to enable metered quantities of each component to be supplied to the mixing chamber although, for foam applications in which the uncured foam mixture is dispensed in the absence of back-pressure, a variety of other pumps, such as gear/vane/lobe pumps, may be used.
• the preferred type of positive displacement pump is a piston pum .
• the third supply means further includes means to effect cooling of the blowing agent/surfactant mixture.
• the second supply means leads into the chamber at a position after there has been some mixing of the resin and the blowing agent/surfactant mixture.
• Figure 1 shows a process flow diagram for forming foam according to the invention:
• Figure 2 shows a schematic cross section of a typical mixing head useful in the performance of the invention.
• Figure 3 shows a view along the line A-A in Figure 2.
• the invention relates to a process for producing foam from synthetic polymer or resin hereinafter simply "resin".
• the formation of foam from synthetic resin involves combining the resin with a blowing agent to form cells, generally air-containing cells, within the resin whilst cross-linking the resin using a catalyst.
• a surfactant or cell stabiliser is also added to give stability to the cells during mixing formation and curing.
• the invention could have application to a number of resin/catalyst/blowing agent/surfactant systems, the invention has been developed particularly to allow the formation of stable, defect-free, rigid foam from acid-cured phenolic resins.
• Foam production from condensation polymers such as phenolic resins present particular problems, largely arising from the fact that the resins, and the catalysts typically used, contain significant amounts of water. Further water is produced as the cross-linking reaction proceeds. This water can become trapped during cell formation, often leading to defects in the windows and/or struts of the foam cells.
• the present invention at least in the preferred embodiment described herein, combines careful selection of low water content components, a novel order of combination of components, temperature control and mixing control to ensure the production of stable, consistent, defect-free foams.
• Typical resins used in the process according to the invention are low free formaldehyde resoles with a solids content in excess of 70%.
• Suitable resoles typically have a formaldehyde to phenol mole ratio in the range 1.3 to 2.0 and more preferably in the range 1.5 to 1.6.
• Suitable resins are available on a commercial basis from manufacturers such as Hepworths Minerals & Chemicals Limited, Borden, BP Chemicals, Cray Valley, Schenectady and Bitrez .
• viscosity and reaction controllers may be added to the resin. These are selected to balance with the chemistry of the intended catalyst .
• viscosity is a good measure of reactivity and may be adjusted using, for example, alcohols, particularly higher alcohols such as furfuryl alcohol; resorcinol and glycols. Furfuryl alcohol produces strong initial reactivity and is thus ideally suited to injection processes. Resorcinol is less reactive and has the added advantage that it provides a more controllable reactivity. Glycols are altogether less reactive and are thus ideally suited to block-forming processes.
• the viscosity modifiers may also be used to assist control of the density of the foam. It will be appreciated that, if mechanical strength is important, then a denser foam is required. If thermal resistance is important then a lower density foam is required. Viscosity modifiers can be added to lower the processing temperature and thus enable higher density foams to be reproducibly achieved.
• low water content we mean a total system (resin + catalyst) water content of not greater than 20% and preferably less than 15%. In many cases this water will be present totally, or almost totally, in the resin leaving a need to select a basic catalyst having a water content as near as possible to zero.
• Useful catalysts according to this invention preferably comprise a mixture of sulphonic acids and, optionally, a proportion of ortho-phosphoric acid or similar.
• the ortho- phosphoric acid enhances the fire performance of the resulting foam, serves as a diluent to reduce the tendency of the low water content sulphonic acids to commence to crystallise and also influences reactivity.
• ortho-phosphoric acid One feature of adding ortho-phosphoric acid is that a proportion of water is also added.
• ortho- phosphoric acids contain a minimum of 15% water and we select and use those which have the least water content .
• Suitable mixtures of sulphonic acids include benzene and xylene sulphonic acids in ratios falling in the range 10 parts : 90 parts though to 90 parts :10 parts. Preferred ranges are
• Ortho-Phosphoric acid (optionally) : 20 - 50 parts
• the strongest food grade ortho-phosphoric acid ie that having the lowest water content which we have been able to source is 85%.
• blowing agent and surfactant are extremely important.
• an essential feature is that the blowing agent and surfactant are pre-mixed prior to combination with the resin and catalyst. This is in contrast with prior art processes in which the surfactant is combined with the resin.
• blowing agent / surfactant mix is selected to balance with the resin and catalyst.
• Blowing agents used in performing the process according to the invention include hydro fluorocarbons, suitable examples of which are specified in the Montreal Protocol on Substances that Deplete the Ozone Layer. The Montreal Protocol specifically identifies HFCs -245, -356, -365.
• HCFC 141b can be replaced by dichloromethane, n-pentane or 25 cyclopentane .
• perfluoro alkanes such as perfluoro pentane or perfluoro hexane .
• Other possible additives include hydrofluoroethers such as HFEs -7100 or -301 and HFE B manufactured by 3M, or hydrofluorocarbons such as 134a.
• the additives act as cell refiners in that they decrease surface tension to enhance cell stability. They also ensure minimal ozone depletion potential of blowing agent systems.
• DCM dichloromethane
• DCM is at least partially soluble in the resole phenolic resins of the types used for foam production, and can thus also serve, to some extent, as a viscosity adjuster.
• DCM is at least partially soluble in the resole phenolic resins of the types used for foam production, and can thus also serve, to some extent, as a viscosity adjuster.
• DCM is at least partially soluble in the resole phenolic resins of the types used for foam production, and can thus also serve, to some extent, as a viscosity adjuster.
• DCM is at least partially soluble in the resole phenolic resins of the types used for foam production, and can thus also serve, to some extent, as a viscosity adjuster.
• the surfactant mixture must be able to: (i) Maintain stability of the blowing agent up to the maximum reaction temperature,
• Suitable polysiloxanes comprise those from the TEGOSTAB range of T H Goldschmidt whilst suitable alkoxlylates comprise ethoxylated castor oils from the ETHYLAN range of Akros. These are selected as they are substantially soluble in the blowing agent and effect the required control over cell formation under the full range of described conditions.
• the resin, catalyst, blowing agent and surfactant are combined as follows: Unlike prior art foam forming processes, the surfactant is not pre-mixed with the resin. It is our current belief that premixing a polar (often highly polar) surfactant with the resin is responsible for many of the defects which we have observed in foams formed using prior art processes. As a consequence, according to a first aspect of the invention we pre-mix the surfactant with the blowing agent and have observed a number of advantages in so doing.
• Pre-mixing surfactant with the resin also leads to wastage of the surfactant because, under the influence of the acidic catalyst, the surfactant reacts and becomes inactive. Obviously it is necessary to exceed a minimal concentration of surfactant throughout the resin, before the surfactant can perform its intended function.
• the surfactant By pre-mixing with the blowing agent, the surfactant is not only kept out of contact with the acid but also placed directly where it is needed. Thus, substantially more of the surfactant performs its intended function. In confirmation of this, we have found that defect free foams can be formed according to the invention using approximately half, or even less, of the quantity of surfactant used in prior art processes.
• defect free foams can be produced with a surfactant level of from less than 1 to about 1.5 parts per 100 parts of resin for low reactivity (block) systems and about 1.0 to 3 parts per 100 parts of resin for high reactivity (injection) systems.
• prior art methods in which the surfactant is pre-mixed with the resin typically require a surfactant content of 3 to 6% depending on the degree of reactivity required.
• the invention envisages reducing the vapour pressure of the blowing agent, by mixing the blowing agent with the surfactant. This objective may be further enhanced by increasing the external pressure i.e. by feeding the blowing agent/surfactant mixture from a pressurised source.
• the apparatus comprises a mixing chamber 10; mixing means 11 (fig 2) within said chamber 10 to effect mixing of materials placed within the chamber: first supply means, generally designated 12, to supply resin (hereinafter called Part A) into the chamber 10; second supply means, generally designated 14, to supply catalyst (hereinafter called Part B) into the chamber 10; and third supply means, generally designated 14, to supply a mixture of blowing agent and surfactant (hereinafter called Part C) into the chamber 10.
• first supply means generally designated 12, to supply resin (hereinafter called Part A) into the chamber 10
• second supply means generally designated 14, to supply catalyst (hereinafter called Part B) into the chamber 10
• third supply means generally designated 14, to supply a mixture of blowing agent and surfactant (hereinafter called Part C) into the chamber 10.
• each of the supply means 12, 13 and 14 include feed tanks 12a, 13a and 14a which are charged with Parts A, B and C respectively from suitable storage facilities (not shown) .
• Feed pumps 12b, 13b and 14b then convey their respective materials to metering pumps
• Pumps 12c, 13c and 14c are preferably of the positive displacement type so as to ensure metered amounts of Parts A, B and C are fed into the mixing chamber 10. However, if the foam mixture is dispensed at ambient pressure (there is no back pressure on the system) other pump types such as vane, lobe or gear pumps, may be used.
• the apparatus might include some other form of flow control system operating on the feed pumps to ensure precise amounts of each component are delivered into the mixing chamber 10.
• the metering pumps may, for example, comprise piston pumps operated by a common linkage to ensure simultaneous delivery of Parts A, B and C to the chamber 10.
• piston pumps or other forms of positive displacement pump, is that strict control can be maintained over component ratios and each component can be dispensed in accurately metered quantities even in the presence of back pressure.
• a recirculation valve 12d, 13d and 14d Interposed between each metering pump and the mixing head is a recirculation valve 12d, 13d and 14d to allow the components to be circulated through the system between mixing and injection steps and thus ensure consistent conditions are maintained at all times.
• Feed tanks may be provided with suitable heating/ cooling apparatus (not shown) to enable temperatures to be established and controlled.
• Suitable feed temperatures and pressures are as follows :
• the metering pumps 12c, 13c and 14c are set to deliver their respective materials to the mixing chamber in the following proportions although these ratios may vary according to the type of foam required:
• Part A 100 parts Part B 3 to 15 parts Part C 5 to 25 parts.
• Part C The precise amount of Part C will depend on the total resin content because, as stated above, we want the amount of surfactant to comprise about 2% or less by weight of the total weight of resin. Further, the amount of blowing agent controls the foam density.
• the mixing means 11 preferably comprise a combination of rotating and static tines. These tines mix Parts A, B and C as they enter, and pass down, the chamber 10 thereby forming a uniform flowable cream.
• the rotating tines are mounted on a central rotating shaft 15 whilst the static tines project radially inwardly from the wall defining the chamber 10.
• the static and rotating tines are arranged so as to impart a shearing action to the cream passing through the chamber 10.
• the parts A, B, and C are fed into a cavity 16 at the upper end of the chamber 10 through ports formed in the wall defining the cavity 16. Referring to Figure 3 , the Part A component is fed through port 17, Part C is fed through port 18 and Part B through port 19.
• the mixing chamber can be internally pressurised by providing a restricting nozzle 20 at the outlet thereof.
• the application of pressure prevents the formation of a vapour phase in the cream and therefore results in the formation of finer cells in the foam.
• the resulting cream is released through restricting nozzle 20 and thereafter flows into the mould cavity 21 which is at atmospheric pressure or slightly higher due to injection displacement effects.
• the cream is pumped into an insulated mould at ambient temperature. Before the mould is filled it is lined with polyethylene film and, after filling, the top of the foam is also covered with polyethylene film. This ensures water retention during initial curing.
• the foam is held in the mould for up to 24 hours or even longer, depending on the other curing parameters. This reduces anisotropy in the foam as can be shown by visual inspection of the cells and by mechanical testing. After release from the mould, the foam is subjected to further stabilisation for 7 days, held at ambient temperature or in an oven at about 40°C.
• the cream is injected into the panel cavity, the skins which define the cavity being in contact with platens held at a suitable temperature, typically in the range 30 to 50°C and more typically about
• the foam cures in less than 15 minutes, the differences from block arising because of the different foam component specifications and the typical differences in volume : surface area ratios of the end products.
• the process according to the invention was used to fill, by foam injection, the cavity of a building panel.
• a cassette system using aluminium box section faced with a suitable release system, to separate facing sheets of 8mm thick cement bonded particle board and fixed to a base of high performance birch ply (also coated with a release system), is placed between the heated platens of a press.
• the platens ensure that the facing sheets are maintained parallel to one another during injection, expansion and curing of the foam and are also used to control the temperature of the system, particularly at the interface thus controlling bond efficiency.
• Part A PA147 Resin (Borden) 100 parts ) Furfuryl alcohol 1 part ) Temp 16°C
• Part B Equal parts of low water content benzene & xylene sulphonic acids 100 parts )
• Resin Surfactant ratio of 100 : 2.7 or
• the loaded cassette is pre-heated to 40°C and held in the press at a pressure in the range 0.5 to 5 bar, preferably about 1 bar.
• Parts A, B and C are combined in a mixing chamber as above described to achieve a cream of uniform consistency.
• a cream volume equivalent to 55kg of Part A is injected.
• injection can be made through a hole provided in any edge, fine air bleed holes being positioned at the corners of the cassette.
• the cavity volume is 0.17 m 3 and thus requires 8.5kg of Part A and corresponding amounts of 20 Parts B and C.
• the cassette After filling, the cassette is held in the press for 10 to 15 minutes to allow the foam fully to cure.
• Part B Mixed xylene and benzene sulphonic acids (50/50) + 20% w/w 1.75 sg phosphoric acid.
• Part C Blowing agent (BA) 100 parts 141b and 5 parts PP1S (ex British Nuclear Fuels Limited)
• the end surfactant level is very low when compared with prior art foams.
• Foams produced according to the invention display increased pH and dramatically reduced leachable ionic species when compared with prior art foams .
• Samples yielding S04 ions at levels below lOppm were achieved by combining linear alcohol into a mixture of xylene sulphonic acid and food grade phosphoric acid together with DPG and Resorcinol in the resin.
• Samples itemised in Table 1 consisted of various ratios of HCFC : HFA blowing agents (not critical) and combinations of silicone surfactants B8473 and B8472 with C40AH
• Foams PA 1, PA 2 and PA 3 produced initial leachant values in the range 1.95 to 2.5 while those produced according to the invention yielded initial pH values in the less acidic range 2.5 to 3.4. After 6 hours these ranges had adjusted to 1.55 to 1.85 and 2.2 to 3.05 respectively, as can be seen from Table 1 .
• Samples Inv 2 and Inv 4 demonstrate the effect of sulphonic acid type. Although pH values are similar, Inv 4 (embodying phenol sulphonic acid) exhibits particularly high sulphate levels compared to the others .
• Inv 2 included the addition of an alcohol and gave a lower value than Inv 3 using similar sulphonic acids (predominantly xylene sulphonic acid) but Inv 3 having no alcohol addition.
• a block foam sample was prepared in accordance with the invention to test for particular leachant extractables. The results were compared with those derived from a commercially available (prior art) foam.
• the invention sample was prepared as follows
• Part A IR5306 [Hepworths) Resin + 5% dipropylene glycol +0.75% carbon black.
• Part B Benzene sulphonic acid 1 part Xylene sulphonic acid 7 parts 1.7sg ortho-phosphoric acid 4 parts
• Part A output 7.9 Kg/min Part B output: 395g/min Part C output: 948g/min
• Foam density was determined to be 37Kg/cubic metre
• cured foams display defect-free cells.
• process parameters have been selected to produce a closed cell foam, foams of low thermal conductivity can be achieved on a reliable and reproducible basis.
• foams formed using the process described herein show markedly reduced levels of acidity and leachant activity and thus can be used in a wider variety of applications where corrosion is a consideration.
• samples of foam produced as described herein show superior char stability and comply with a wide range of fire-related safe use requirements.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (2)

Family

ID=10809860

Family Applications (1)

Country Status (5)

Cited By (3)

Citations (4)

• 1997
  • 1997-03-24 GB GBGB9706219.4A patent/GB9706219D0/en active Pending
• 1998
  • 1998-03-24 AU AU67407/98A patent/AU6740798A/en not_active Abandoned
  • 1998-03-24 WO PCT/GB1998/000891 patent/WO1998042775A2/en not_active Application Discontinuation
  • 1998-03-24 EP EP98912627A patent/EP0971975A2/en not_active Withdrawn
• 1999
  • 1999-09-23 NO NO994632A patent/NO994632L/no unknown

Patent Citations (4)

Also Published As

Similar Documents

Legal Events