EP2956501A1

EP2956501A1 - Foamable composition, polymeric foam composite and method of making poltmeric foam composite

Info

Publication number: EP2956501A1
Application number: EP14751379.0A
Authority: EP
Inventors: Dorte Bartnik JOHANSSON; Peter Farkas Binderup Hansen; Anders Bach
Original assignee: Rockwool International AS
Current assignee: Rockwool AS
Priority date: 2013-02-18
Filing date: 2014-02-18
Publication date: 2015-12-23
Also published as: WO2014125367A1

Abstract

A foamable composition comprising: a foam precursor; from 40 to 98 % by weight, based on the total fibre weight, first fibres, defined as those fibres having a length less than 150μm; and from 2 to 60 % by weight, based on the total fibre weight, second fibres, defined as those fibres having a length of at least 150μm; wherein at least 50 % of the first fibres by weight are discontinuous man- made vitreous fibres, and wherein at least 60 % of the first fibres by weight have a length less than 65pm and at least 30% of the second fibres by weight have a length of at least 250μm.

Description

Foamable Composition, Polymeric Foam Composite and Method of Making

Polymeric Foam Composite

The invention relates to insulating products for use in buildings in circumstances where a high compressive strength, high compression modulus of elasticity, good dimensional stability and fire resistance are required.

Background to the Invention Traditionally, where building insulation materials were required to have both a high compressive strength and modulus of elasticity and a high level of fire- resistance, such as for roofing boards, the natural solution has been to use mineral fibre boards of very high density. Whilst such roofing boards have the advantage of a very high compressive strength and point load compressive resistance, and are non-combustible, it would be desirable to reduce the density and cost of production of such products, whilst maintaining or increasing their compressive strength and compression modulus of elasticity.

Roofing boards have also been manufactured in the past in the form of foam boards. Whilst these are less dense than high-density mineral fibre boards, most have the inherent disadvantage of being much more combustible than mineral fibres so must usually be coated or otherwise treated with a suitable thermal barrier. Even when treated, the foam boards still tend to be more combustible than mineral fibre-based boards.

Foam boards are also prone to deterioration over time. In particular, dimensional stability can be a problem, because foam materials tend to shrink over time, in particular in hot or humid conditions. Composite foam materials comprising fibres are known for use in the building industry.

For example DE1991351 1 A1 describes a method of making synthetic resin polyurethane foam comprising graphite and incombustible fibres. In one example there is a mixture of two-component polyurethane foam with an equal amount of graphite and 70% by weight glass fibres, based on the weight of graphite. The fibres have a length of 5mm. GB 882296 states that the addition of a fibrous material to liquid foamable materials causes an increase in viscosity of the foamable materials with the result that it is very difficult to stir in more than about 10% by weight of fibres, based on the weight of the foamable material. The inventors of GB 882296 use a special process involving associating a foamable material with a mass of intermeshed mineral fibres, at least partially enclosing a zone around the mass, foaming the material to fill the zone and setting the foamable material. The fibres used are at least about 0.5 inches long.

US 2003/0068485 A1 describes the use of chopped or milled fibre glass in foam as a termite repellent. The fibres preferably range in length from 0.396mm to 12.7mm.

DE 10 2005 060 744 A1 describes a polymeric foam composite material based on fibrous material and a mixture of a curable resin with unexpanded thermoplastic particles, the particles being expanded after being impregnated in the fibrous material. The proportion of fibres in the finished foam composite material is between 15 and 50 wt/%.

WO 94/29375 describes a fire resistant product based on an expanded polymeric foam material comprising a mixture of a foam-forming agent, a resin, fibrous material and an exfoliating material. The fibrous material can comprise man-made mineral fibres and/or inorganic fibres. The total content of exfoliating agent and/or made man mineral fibres is between 1 % and 90% of the total mix of materials.

US 4839393 describes polyurethane foams based on reactive pol ols and polyisocyanate containing a filler and modified with an organofunctional silane containing a hydrolysable group and an ethylenically unsaturated linkage. The filler can be glass fibres and the production method involves producing T IB2014/000176

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polyurethane foam chips, which are subsequently admixed with the filler material. The fibre length is from about 0.25 inches to about 1.5 inches.

US 4,082,702 discloses a rigid polyurethane foam obtained by mixing an organic polyol, a polyisocyanate, a catalyst, microballoons and a flame retardant. The mixture can also contain flexible fibres such as glass fibres which gan be chopped, preferably to about 6mm in length. There is no disclosure of fibres shorter than 150pm.

CN101781395 relates to a hard polyurethane adiabatic heat insulation foam material. The material contains chopped glass fibre powder having a length of 100-500pm.

EP1878663 describes a thermal insulation panel for a thin-walled cryogenic tank. The panel is formed from a polyurethane foam that is reinforced with glass fibres. The fibres have an average length greater than 10mm.

CN2856234 describes a panel formed by combining polyurethane with glass fibres having a length of 15-150mm. JPH 62210 describes a urethane foam resin embedded with carbon and glass fibres of length 13-50mm.

In the article "Anwendung zerkleinerter Glasfasem als modifizierender Zusatz fur Polyurethanhartschaumstoffe" (Plaste und Kautschuk, vol. 26 no.1 , pg 23-25), the characteristics of polyurethane composites comprising continuous E type AIBSi glass fibres of length less than 0.5mm are investigated.

Generally, there has been little focus on the role that the length distribution of fibres plays in determining the properties of a foam composite.

There remains a need for a foam composite having a high fire resistance, high compressive strength, a high compression modulus of elasticity, and a high level of dimensional stability, but with a low density as compared with high-density mineral fibre boards. Furthermore, there remains a need for a foam composite having this combination of properties that can be produced by mixing fibres into a foamable composition without complex .mixing processes to provide a homogeneous distribution of fibres within the composite.

Summary of the Invention

Therefore, the invention provides a foamable composition comprising:

a foam precursor;

from 40 to 98% by weight, based on the total fibre weight, first fibres, defined as those fibres having a length less than 150pm; and

from 2 to 60% by weight, based on the total fibre weight, second fibres, defined as those fibres having a length of at least 150pm;

wherein at least 50% of the first fibres by weight are discontinuous man- made vitreous fibres, and wherein at least 60% of the first fibres by weight have a length less than 65pm and at least 30% of the second fibres by weight have a length of at least 250pm.

In a second aspect, the invention provides a polymeric foam composite comprising:

a polymeric foam;

In a first method aspect, the invention provides a method for producing a polymeric foam composite according to the invention comprising:

(i) providing a foam precursor; (ii) providing from 40 to 98% by weight, based on the total fibre weight first fibres, defined as those fibres having a length less than 150μπι and from 2 to 60% by weight, based on the total fibre weight, second fibres, defined as those fibres having a length of at least 150pm;

(iii) providing a further component suitable for inducing foam formation; and

(iv) mixing the foam precursor, the first fibres, the second fibres and the further component to induce foam formation;

wherein at least 50% of the first fibres by weight are discontinuous man- made vitreous fibres, and wherein at least 60% of the first fibres by weight have a length less than 65 m and at least 30% of the second fibres by weight have a length of at least 250μηι.

In a second method aspect, the invention provides a method for producing a polymeric foam composite according to the invention comprising:

(i) providing a foam precursor;

(ii) providing from 40 to 98% by weight, based on the total fibre weight first fibres, defined as those fibres having a length less than 150pm and from 2 to 60% by weight, based on the total fibre weight, second fibres, defined as those fibres having a length of at least 150μιη;

(iii) mixing the foam precursor, the first fibres and the second fibres; and

(iv) inducing foam formation by carrying out a further processing step, wherein at least 50% of the first fibres by weight are discontinuous man- made vitreous fibres, and wherein at least 60% of the first fibres by weight have a length less than 65μιτι and at least 30% of the second fibres by weight have a length of at least 250μηι.

The inventors have found that the length distribution and the types of fibres used plays an important role in providing a composite with a desirable combination of properties. In particular, the inventors have found that providing both very short man-made vitreous fibres and a portion of much longer fibres, of any suitable type, provides a foam composite which highly fire resistant, has high compressive strength and a high compression modulus of elasticity. The polymeric foam composite that is produced also has a high level of dimensional stability and can be produced with simple mixing methods.

It has also been found that including a significant quantity of short fibres ensures that the thermal conductivity of the polymeric foam composite remains low for a long period of time. In conventional polymeric foams, the cell walls of the foam tend to break over time, which opens the cells and releases the blowing gas that often has a lower thermal conductivity than air. The resulting open cells therefore lead to the foam providing a reduced level of insulation and an increased level of water permeability. It is believed that the short first fibres used in the invention strengthen the cell walls of the foam, reducing breakage of the cell wall, which in turn reduces degradation in the insulating properties and water impermeability of the foam composite over time. Detailed Description of the Invention

According to the present invention, the weight percentage of fibres above or below a given fibre length is measured with a sieving method. A representative sample of the man-made vitreous fibres is placed on a wire mesh screen of a suitable mesh size (the mesh size being the length and width of a square mesh) in a vibrating apparatus. The mesh size can be tested with a scanning electron microscope according to DIN ISO 3310. The upper end of the apparatus is sealed with a lid and vibration is carried out until essentially no further fibres fall through the mesh (approximately 30 mins). If the percentage of fibres above and below a number of different lengths needs to be established, it is possible to place screens with incrementally increasing mesh sizes on top of one another. The fibres remaining on each screen are then weighed.

In order to measure the length of fibres present in a polymeric foam composite of the invention, it is possible to, burn off the foam from a representative sample of the foam composite by placing it in a 590°C furnace for 20 min. This method is according to ASTM C612-93. The remaining fibres can then be analysed using a wire mesh screen as set out above. The present invention uses first fibres and second fibres. The first fibres are defined as those fibres having a length of less than 150μιτι. The second fibres are defined as those fibres having a length of at least 150pm. Of the fibres present in the foamable composition and in the polymeric foam composite of the invention, from 40 to 98% by weight, based on the total fibre weight, are first fibres (i.e. fibres having a length less than 150pm). The remaining fibres, i.e. from 2 to 60% by weight of the fibres, based on the total fibre weight, are second fibres (i.e. fibres having a length of at least 150μιη). Preferably, of the fibres present in the foamable composition and in the polymeric foam composite, from 50 to 95% by weight, more preferably from 60 to 90% by weight and most preferably from 70 to 85% by weight, based on the total fibre weight, are first fibres. Preferably, of the fibres present in the foamable composition and in the polymeric foam composite, from 5 to 50% by weight, more preferably from 10 to 40% by weight and most preferably from 15 to 30% by weight, based on the total fibre weight, are second fibres.

Often, the length distribution of the first and second fibres, means that the overall combined length distribution of first and second fibres present in the foamable composition and in the polymeric foam composite is at least bimodal, having a mode below 65μιτι and another mode above 250pm. The modes can be determined by separating fractions of the combined first and second fibres by length, at 5pm intervals for example, and weighing each fraction. A mode exists where a fraction contains more fibres by weight than either of the neighbouring length fractions. The possibility of there being more than two modes is not excluded by the phrase "at least bimodal".

Within the first fibres present in the foamable composition and in the polymeric foam composite, at least 60% by weight of the first fibres, based on the total weight of first fibres, have a length less than 65pm. Preferably, the length distribution of the first fibres is such that at least 80% or even 85% or 90% of the first fibres have a length less than 125 micrometres.

The greatest compressive strength can be achieved when at least 90% by weight of the first fibres, based on the total weight of first fibres, have a length less than 100 micrometers and at least 75% by weight of the first fibres, based on the total weight of first fibres, have a length less than 65 micrometers.

The present inventors have discovered that the first fibres can be included in a foamable composition at a relatively high level without processing difficulties being encountered. Therefore relatively large quantity of first fibres can be included in the foamable composition and, as a result, the compressive strength, fire resistance, and in particular the compression modulus of elasticity of the resulting foam can be improved. Previously, it had been thought that ground fibres having such a low length would simply act as a filler, increasing the density of the foam. The inventors have surprisingly found that by using first fibres having the length distribution described above, high levels of fibres can be incorporated into the foam precursor and the resulting foam. The result of this is that significant increases can be achieved in the compressive strength and, in particular, the compression modulus of elasticity of the foam. The first fibres are also able to strengthen the cell walls of the foam, reducing breakage of the cell walls, which in turn reduces degradation in the insulating properties and water impermeability of the foam composite over time. Preferably, at least 0.5%, more preferably at least 1 % of the first fibres by weight, based on the total weight of first fibres, have a length less than 10pm. Including a significant level of very short fibres is believed to assist with the foam formation process as a nucleating agent. Within the first fibres, at least 50% by weight, based on the total weight of first fibres, are discontinuous man-made vitreous fibres. Preferably at least 60%, more preferably at least 70%, even more preferably at least 90% and most preferably substantially all of the first fibres, based on the total weight of first fibres, are man-made vitreous fibres.

The term "discontinuous man-made vitreous fibres" is well understood by those skilled in the art. Discontinuous man-made vitreous fibres are, for example, those produced by internal or external centrifugation, for example with a cascade spinner or a spinning cup. Preferably, in the foamable composition and in the polymeric foam composite, at least 60%, more preferably at least 70%, even more preferably at least 90% and most preferably substantially all of the fibres having a length less than 65 m, based on the total weight of those fibres having a length less than 65pm, are discontinuous man-made vitreous fibres.

The use of a high level of short man-made vitreous fibres results in a polymeric foam composite with a high level of compressive strength, fire resistance, compression modulus of elasticity. It also results in a reduced degree of degradation in insulation properties and water impermeability over time.

The discontinuous man-made vitreous fibres are preferably stone fibres. In general, stone fibres have a content of oxides as follows:

Si0₂ 25 to 50%, preferably 38 to 48%

Al₂0₃ 12 to 30%, preferably 15 to 28%, more preferably 17 to 23%

Ti0₂ up to 2%

Fe₂0₃ 2 to 12%

CaO 5 to 30%, preferably 5 to 18%

MgO up to 5%, preferably 1 to 8% or 4 to 10%

Na₂O up to 15%

K₂0 up to 15%

P₂0₅ up to 3%

MnO up to 3%

B₂0₃ up to 3%.

These values are all quoted as weight % oxides, with iron expressed as Fe₂0₃, as is conventional. An advantage of using fibres of this composition, especially in the context of polyurethane foams, is that the significant level of iron and alumina in the fibres can act as a catalyst in formation of the foam. This effect is particularly relevant when at least some of the iron in the fibres is present as ferric iron, as is usual and/or when the level of Al₂0₃ is particularly high such as 15 to 28% or 18 to 23%.

Composites including stone fibres of the above composition have also been found to have improved fire resistance as compared with composites in which the filler used does not contain a significant level of iron.

An alternative stone wool composition useful in the invention has oxide contents in the following ranges:

Si0₂ 37 to 42%

Al₂0₃ 18 to 23%

CaO + MgO 34 to 39%

Fe₂0₃ up to 1 %

Na₂0 + K₂0 up to 3%

Again, the high level of alumina in fibres of this composition can act as a catalyst in the formation of a polyurethane foam. Whilst stone fibres are preferred, the use of discontinuous glass fibres and slag fibres as first fibres in the foamable composition and polymeric foam composite of the invention is also possible.

The man-made vitreous fibres that must make up at least 50% by weight of the first fibres in the present invention are discontinuous fibres that are preferably produced with a cascade spinner or a spinning cup. Preferably, the methods of the invention include the step of producing the man-made vitreous fibres with a cascade spinner or a spinning cup. Traditionally, fibres produced by these methods have been used for insulation, whilst continuous glass fibres have been used for reinforcement in composites. Continuous fibres (e.g. continuous E glass fibres) are known to be stronger than discontinuous fibres produced by cascade spinning or with a spinning cup (see "Impact of Drawing Stress on the Tensile Strength of Oxide Glass Fibres", J. Am. Ceram. Soc, 93 [10] 3236-3243 (2010)). Nevertheless, the present inventors have surprisingly found that foam composites comprising short, discontinuous fibres have a compressive strength that is at least comparable with foam composites comprising continuous glass fibres of a similar length. This unexpected level of strength is combined with good fire resistance, a high level of thermal insulation and cost efficient production.

In order to achieve the required length distribution of the first fibres, it will usually be necessary for the discontinuous man-made vitreous fibres to be processed further after the standard production. The further processing will usually involve grinding or milling of the man-made vitreous fibres for a sufficient time for the required length distribution to be achieved. Usually, the first fibres have an average diameter of from 1.5 to 7 micrometres, preferably from 2 to 6 or from 3 to 6 micrometers. Thin first fibres as preferred in the invention are believed to provide a higher level of thermal insulation to the composite than thicker fibres, but without a significant reduction in strength as compared with thicker fibres as might be expected. According to the present invention, the average fibre diameter is determined for a representative sample by measuring the diameter of at least 200 individual fibres by means of the intercept method and scanning electron microscope or optical microscope (1000x magnification). Any first fibres that are not man-made vitreous fibres can be any other type of suitable fibres. Suitable fibres include cellulose fibres, for example in the form of cellulose pulp, carbon fibres, synthetic fibres such as aramid fibres (e.g. Kevlar), polyester fibres, polyamide fibres, PAN fibres or pre-oxidised PAN fibres, for example in the form of PAN pulp and mixtures thereof. The fibres can be fibrillated fibres. The amount of first fibres that are not man-made vitreous fibres is preferably kept low, however.

Within the second fibres, in the foamable composition and in the foam composite of the invention, at least 30%, preferably at least 50% by weight, based on the total weight of second fibres, have a length of at least 250pm. Preferably, at least 95%, preferably at least 97%, more preferably at least 99% of the second fibres by weight have a length of less than 6000pm. Second fibres having these length distributions have been found to provide an excellent level of dimensional stability to the polymeric foam composite of the invention, even when the second fibres are included at a relatively low level. Fibres longer than 6000pm have been found to destroy bubbles during foam formation resulting in an increase in viscosity that hinders foam formation.

The second fibres can be any type or types of fibre that can withstand the foaming process. Generally, a certain level of heat resistance and a relatively high melting point are advantageous. For polyurethane foams, for example, it is preferred that the second fibres are stable (i.e. do not melt or degrade) up to at least 150°C.

Preferably, in the foamable composition, and in the foam composite, at least 80%, more preferably at least 90% and most preferably substantially all of the second fibres by weight, based on the total weight of second fibres, are man- made vitreous fibres, cellulose fibres, for example in the form of cellulose pulp, carbon fibres, synthetic fibres such as aramid fibres (e.g. Kevlar), polyester fibres, polyamide fibres, PAN fibres or pre-oxidised PAN fibres, for example in the form of PAN pulp or a mixture thereof. The fibres can be fibrillated fibres. Most preferred are man-made vitreous fibres, in particular stone fibres.

The stone fibres preferably have the composition set out above in relation to the first fibres.

Where man-made vitreous fibres are present as second fibres, they are preferably discontinuous man-made vitreous fibres, more preferably produced by internal or external centrifugation, especially with a cascade spinner or a spinning cup.

The second fibres preferably have an average diameter of 3 to 15pm. Second fibres of this average diameter have been found to be advantageous, because thicker fibres can destroy the struts in the foam.

Whatever the type of fibres included in the second fibres, it is preferred that these fibres have a high tensile strength and a high tensile modulus. Preferably the tensile modulus of the second fibres is at least 5GPa. Preferably, at least 80%, more preferably at least 90%, most preferably essentially all of the second fibres by weight, based on the total weight of second fibres, have this property. Preferably, the foamable composition comprises a combined total of first and second fibres of at least 15%, more preferably at least 20%, most preferably at least 35% by weight, based on the total weight of the composition. Preferably, the foamable composition comprises a combined total of first and second fibres of less than 85%, preferably less than 80%, more preferably less than 75% by weight, based on the total weight of the composition.

The foamable composition comprises a foam precursor. The foam precursor is a material that either polymerises (often with another material) to form a polymeric foam or is a polymer that can be expanded with a blowing agent to form a polymeric foam. The composition can be any composition capable of producing a foam on addition of a further component or upon a further processing step being carried out.

Preferred foamable compositions are those capable of producing polyurethane foams. Polyurethane foams are produced by the reaction of a polyol with an isocyanate in the presence of a blowing agent. Therefore, in one embodiment, the foamable composition comprises a polyol as the foam precursor. In another embodiment, the foamable composition comprises an isocyanate as the foam precursor. In another embodiment, the composition comprises a mixture of an isocyanate and a polyol as the foam precursor.

If the foam precursor is a polyol, then foaming can be induced by adding a further component comprising an isocyanate. If the foam precursor is an isocyanate, foam formation can be induced by the addition of a further component comprising a polyol.

Suitable polyols for use either as the foam precursor or to be added as a further component to the foamable composition to induce foam formation are commercially available polyol mixtures from, for example, Bayer Material Science, BASF or DOW Chemicals. Commercially available polyol compositions are often supplied as a pre-mixed component that comprises polyol and any or all of catalyst(s), flame retardant(s), surfactants and water, the latter which can act as a chemical blowing agent in the foam formation process. Generally it comprises all of these. Such a pre-formed blend of polyol with additives is commonly known as a pre-polyol.

The isocyanate for use either as the foam precursor or to be added as a further component to the foamable composition to induce foam formation is selected on the basis of the density and strength required in the foam composite as well as on the basis of toxicity. It can, for example, be selected from methylene polymethylene polyphenol isocyanates (PMDI), methylene diphenyl diisocyanate (MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI), PMDI or MDI being preferred. One particularly suitable example is diphenylmethane-4,4'-diisocyanate. Other suitable isocyanates are commercially available from, for example, Bayer Material Science, BASF or DOW Chemicals.

In order to form a foam composite, a blowing agent is required. The blowing agent can be a chemical blowing agent or a physical blowing agent. In some embodiments, the foamable composition comprises a blowing agent. Alternatively, the blowing agent can be added to the foamable composition together with a further component that induces foam formation. In the context of polyurethane foam composites, in a preferred embodiment, the blowing agent is water. Water acts as a chemical blowing agent, reacting with the isocyanate to form CO₂, which acts as the blowing gas.

When the foam precursor is a polyol, in one embodiment, the foamable composition comprises water as a blowing agent. The water is usually present in such a foamable composition in an amount from 0.3 to 2 % by weight of the foamable composition. As an alternative, or in addition, a physical blowing agent, such as liquid C0₂ or liquid nitrogen could be included in the foamable composition or added to the foamable composition as part of the further component that induces foam formation.

The foamable composition, in an alternative embodiment, is suitable for forming a phenolic foam. Phenolic foams are formed by a reaction between a phenol and an aldehyde in the presence of an acid or a base. A surfactant and a blowing agent are generally also present to form the foam. Therefore, the foamable composition of the invention could comprise, in addition to the man- made vitreous fibres, a phenol and an aldehyde (the foam precursor), a blowing agent and a surfactant. Alternatively, the foamable composition could comprise as the foam precursor, a phenol but no aldehyde, or an aldehyde but no phenol. Whilst foamable compositions suitable for forming polyurethane or phenolic foams are preferred, the invention also encompasses foamable compositions suitable for forming polyisocyanurate, expanded polystyrene and extruded polystyrene foams. In an alternative embodiment, the foam composite is especially a polyisocyanurate foam composite, where the blowing agent is preferably pentane. Pentane has the advantage over other blowing agents that it is more environmentally friendly and cost effective than for instance HFC blowing agents.

Pentane can be c-pentane, i-pentane, or n-pentane or a mixture of two or more of these. The choice between c-pentane, i-pentane and n-pentane is dependent on the production method. They are quite different in boiling point, initial thermal conductivity, aged thermal conductivity and price. The preferred pentane in this invention is n-pentane based on the price and aged thermal conductivity.

The foamable composition and the foam composite of the invention can contain additives in addition to the foam precursor and the first and second fibres. When it is desired to include additives in the foam composite, as an alternative to including the additives in the foamable composition, the additive can be included with a further component that is added to the foamable composition to induce foam formation. As an additive, it is possible for the foam precursor or the polymeric foam composite to comprise a fire retardant such as expandable powdered graphite, aluminium trihydrate or magnesium hydroxide. The amount of fire retardant in the foam precursor is preferably from 3 to 20% by weight, more preferably from 5 to 15% by weight and most preferably from 8 to 12 % by weight. The total quantity of fire retardant present in the foam composite is preferably from 1 to 10%, more preferably from 2 to 8% and most preferably from 3 to 7 % by weight.

Alternatively, or in addition, the foamable composition or polymeric foam composite can comprise a flame retardant such as nitrogen- or phosphorus- containing polymers.

The first and/or second fibres used in the present invention can be treated with binder, which, as a result, can be included in the composition as an additive if it is chemically compatible with the composition. The binder is usually present in the foamable composition at a level less than 5% based on the total weight of the foamable composition. The foam composite usually contains less than 5% binder, more usually less than 2.5% binder. In a preferred embodiment, the first and second fibres used are not treated with binder. In some circumstances, it is advantageous, before mixing the first and/or second fibres into the foamable composition, to treat the fibres with a surfactant, usually a cationic surfactant. The surfactant could, alternatively, be added to the composition as a separate component. The presence of a surfactant, in particular a cationic surfactant, in the composition and as a result in the foam composite has been found to provide easier mixing and, therefore, a more homogeneous distribution of fibres within the foamable composition and the resulting foam. The polymeric foam composite of the invention comprises a polymeric foam and first and second fibres as defined above. The polymeric foam composite can be formed from the foamable composition of the invention. It is also possible to form the polymeric foam composite of the invention without using a foamable composition according to the invention, in particular when a foamable composition is used that contains only some of first and second fibres, so that the distribution of fibres is not as required in the foamable composition of the invention. In such a case, the required distribution can be achieved by addition of further fibres as part of a further component that induces foam formation or by the addition of further fibres in a separate stream.

It is preferred that the polymeric foam is a polyurethane foam or a phenolic foam. Polyurethane foams are most preferred due to their low curing time. Preferably, the polymeric foam composite comprises a combined total of first and second fibres of at least 5%, preferably at least 10%, more preferably at least 15% by weight, based on the total weight of the polymeric foam composite.

Preferably, the polymeric foam composite comprises a combined total of first and second fibres of less than 85%, more preferably less than 70%, even more preferably less than 55% by weight, based on the total weight of the polymeric foam composite.

There are two alternative methods for producing the polymeric foam composite of the invention.

In both method aspects of the invention, the method comprises (i) providing a foam precursor, and (ii) providing from 40 to 98% by weight, based on the total fibre weight, first fibres, defined as those fibres having a length less than 150pm and from 2 to 60% by weight, based on the total fibre weight, second fibres, defined as those fibres having a length of at least 150μηι. The foam precursor and first and second fibres are as discussed above. In the first method aspect of the invention, it is required to provide a further component suitable for inducing foam formation. The first fibres, second fibres, foam precursor and further component are then mixed, which induces foam formation.

Thus, in the first method aspect, the invention provides a method for producing a polymeric foam composite according to the invention comprising:

(i) providing a foam precursor;

(iii) providing a further component suitable for inducing foam formation; and

There are a number of options for the mixing step (iv) in the first method aspect of the invention. In one embodiment, step (iv) comprises mixing the first fibres and the second fibres into the foam precursor and subsequently mixing the further component with the foam precursor. In this embodiment, a foamable composition according to the invention is produced as an intermediate product. For example, in the case of a polyurethane foam, the first and second fibres can be mixed with a polyol as the foam precursor, which forms a foamable composition according to the invention. The foamable composition usually also comprises water as a chemical blowing agent. Then foaming can be induced by the addition of an isocyanate. In an alternative embodiment, step (iv) comprises mixing a first portion of the fibres provided in step (ii) with the foam precursor, mixing a second portion of the fibres provided in step (ii) with the further component and subsequently mixing the foam precursor with the further component. The first and second portions of the fibres can contain any selection of the first and second fibres. However, preferably, the first portion of the fibres provided in step (ii) comprises at least 70%, more preferably at least 85%, most preferably at least 95% by weight first fibres, based on the weight of the first portion of fibres. Preferably, the second portion of the fibres provided in step (ii) comprises at least 70%, more preferably at least 85%, most preferably at least 95% by weight second fibres, based on the weight of the second portion of fibres.

In a further alternative embodiment step (iv) comprises mixing a first portion of the fibres provided in step (ii) with the foam precursor to provide a stream comprising foam precursor and fibres, then mixing, in a single step, the stream comprising foam precursor and fibres, a stream comprising the further component and a stream comprising a second portion of the fibres provided in step (ii), wherein the second portion of fibres is metered directly into a mixing chamber of a mixing head by axial injection. This can be achieved using a SPL/3 mixing head from Cannon. In this embodiment also, the first and second portions of the fibres can contain any selection of the first and second fibres. However, preferably, the first portion of the fibres provided in step (ii) comprises at least 70%, more preferably at least 85%, most preferably at least 95% by weight first fibres, based on the weight of the first portion of fibres. Preferably, the second portion of the fibres provided in step (ii) comprises at least 70%, more preferably at least 85%, most preferably at least 95% by weight second fibres, based on the weight of the second portion of fibres. In a further alternative embodiment, the foam precursor is provided in a first stream of foam precursor and a second stream of foam precursor and step (iv) comprises:

mixing a first portion of the fibres provided in step (ii) into the first stream of foam precursor; mixing a second portion of the fibres provided in step (ii) into the second stream of foam precursor; and

subsequently mixing the first stream of foam precursor, the second stream of foam precursor and the further component.

In this embodiment also, the first and second portions of the fibres can contain any selection of the first and second fibres. However, preferably, the first portion of the fibres provided in step (ii) comprises at least 70%, more preferably at least 85%, most preferably at least 95% by weight first fibres, based on the weight of the first portion of fibres. Preferably, the second portion of the fibres provided in step (ii) comprises at least 70%, more preferably at least 85%, most preferably at least 95% by weight second fibres, based on the weight of the second portion of fibres. At least part of the mixing step (iv) can be carried out with a mechanical mixing method such as use of a rotary mixer or simply by stirring. In a preferred embodiment, the mixing step (iv) is carried out at least in part using a visco jet agitator. These method are particularly advantageously used to mix the fibres with either the foam precursor, the further component, or both.

Mixing the fibres into the foam precursor or further component has been found to be simplified by the presence of a surfactant, preferably a cationic surfactant. The surfactant can be applied to the fibres themselves or be added to the foam precursor or to the further component. Therefore, the method preferably further comprises providing a surfactant and mixing the surfactant with at least one of: the foam precursor;

the fibres provided in step (ii); and

the further component;

before the fibres provided in step (ii) are mixed with the foam precursor or the further component.

In the first method aspect of the invention, often, the foam precursor and the further component are mixed using a high pressure mixing head as commercially available. Additives as discussed above can be added to any of the components or added separately in step (iv). In the second method aspect of the invention, surfactant has also been found to be useful for facilitating mixing of the fibres into the foam precursor. Therefore, the method preferably further comprises providing a surfactant and mixing the surfactant with at least one of the foam precursor and the fibres provided in step (ii), before the mixing step (iii).

In the second method aspect of the invention, foam formation is induced by carrying out a further processing step. The further processing step depends on the type of foam precursor being used, but could, for example be applying a reduced pressure to the mixture of foam precursor and first and second fibres.

In both method aspects, the precise manner in which the foam is formed depends on the type of foam to be formed and is known to the person skilled in the art for each type of polymeric foam. In this respect, reference is made to "Handbook of Polymeric Foams and Foam Technology" by Klempner et al.

Example 1 (comparative)

A foamable composition was produced by mixing 240g of a commercially available polyol formulation with 60g of mineral wool fibres having an average length determined by the sieving method described herein of 500pm. Mixing was performed in a beaker with slow addition of the fibres and mixing by propellers. The mixing was increasingly difficult as fibers were added, limiting the amount of fibres that could be added. To this mixture, 340 g of a commercially available composition of diphenylmethane-4,4'-diisocyanate and isomers and homologues of higher functionality, were mixed by propellers for 20 seconds at 3000 rpm. The material was then transferred into a mold and allowed to foam. The total amount of inorganic, non-combustible, fibers in the foam was 9% of the total mass. Example 2

A foamable composition was produced by mixing 240g of a commercially available polyol formulation with 90g ground discontinuous stone wool fibres with over 50% having a length less than 64 m. Mixing was easy and a homogeneous suspension was easily obtained. To the mixture, 30g of mineral wool fibres having an average length determined by the sieving method described herein of 50 μιη. Mixing was performed in a beaker with slow addition of the fibers and mixing by propellers. Mixing was less difficult than in example 1. The overall distribution of fibres was such that from 40 to 98% by weight of the fibres, based on the total fibre weight, had a length less than 150pm and at least 50% of these fibres had a length less than 65pm and such that from 2 to 60% by weight of the fibres, based on the total fibre weight, had a length of at least 150 m and at least 30% of these fibres had a length of at least 250μιη. To this mixture, 340 g of a commercially available composition of diphenylmethane-4,4'-diisocyanate and isomers and homologues of higher functionality, were mixed by propellers for 20 seconds at 3000 rpm. The material was then transferred into a mold and allowed to foam.

The total amount of inorganic, non-combustible, fibers in the foam was 17% of the total mass or twice as high as the amount of fibers that could be added in Example 1.

Claims

23

Claims

1. A foamable composition comprising:

a foam precursor;

from 40 to 98% by weight, based on the total fibre weight, first fibres, defined as those fibres having a length less than 150μιη; and

from 2 to 60% by weight, based on the total fibre weight, second fibres, defined as those fibres having a length of at least 150μιη;

wherein at least 50% of the first fibres by weight are discontinuous man- made vitreous fibres, and wherein at least 60% of the first fibres by weight have a length less than 65μιη and at least 30% of the second fibres by weight have a length of at least 250pm.

2. A foamable composition according to claim 1 , wherein at least 70%, preferably at least 80%, more preferably at least 90% of the first fibres by weight are discontinuous man-made vitreous fibres.

3. A foamable composition according to claim 1 or claim 2, wherein at least 75% of the first fibres by weight have a length less than 65gm and at least 95% of the first fibres by weight have a length less than 1 ΟΟμιτι.

4. A foamable composition according to any preceding claim, wherein at least 0.5%, preferably at least 1 % of the first fibres by weight have a length less than 10pm.

5. A foamable composition according to any preceding claim, wherein the first fibres have an average diameter of from 1.5 to 7μιη, preferably from 2 to 6μηι, more preferably from 3 to 6μηι. 6. A foamable composition according to any preceding claim, wherein at least 95%, preferably at least 97%, more preferably at least 99% of the second fibres by weight have a length of less than 6000μιη.

7. A foamable composition according to any preceding claim, wherein the second fibres have an average diameter of 3 to 15μηι.

8. A foamable composition according to any preceding claim, wherein at least 80%, preferably at least 90% of the second fibres by weight are, man-made vitreous fibres, cellulose fibres, for example in the form of cellulose pulp, carbon fibres, synthetic fibres such as aramid fibres (e.g. Kevlar), polyester fibres, polyamide fibres, PAN fibres, pre-oxidised PAN fibres, for example in the form of PAN pulp and mixtures thereof.

9. A foamable composition according to any preceding claim, wherein composition comprises a combined total of first and second fibres of at least 15%, preferably at least 20%, more preferably at least 35% by weight, based on the total weight of the composition.

10. A foamable composition according to any preceding claim that is suitable for forming a polyurethane foam or a phenolic foam composite.

1 1. A foamable composition according to any preceding claim, wherein the composition is suitable for forming a polyurethane foam and the foam precursor is a polyol.

12. A foamable composition according to any preceding claim, wherein the composition is suitable for forming a polyurethane foam and the foam precursor is an isocyanate.

13. A foamable composition according to any preceding claim, wherein the composition further comprises a blowing agent.

14. A foamable composition according to any preceding claim, wherein the composition further comprises a flame retardant.

15. A polymeric foam composite comprising:

a polymeric foam; 25

from 40 to 98% by weight, based on the total fibre weight, first fibres, defined as those fibres having a length less than 50pm; and

wherein at least 50% of the first fibres by weight are discontinuous man- made vitreous fibres, and wherein at least 60% of the first fibres by weight have a length less than 65 m and at least 30% of the second fibres by weight have a length of at least 250pm. 16. A polymeric foam composite according to claim 15, wherein the polymeric foam is polyurethane foam or phenolic foam. 7. A polymeric foam composite according to claim 15 or claim 16, wherein the first and second fibres are as defined in any of claims 2 to 9.

18. A polymeric foam composite according to any of claims 15 to 17, wherein the polymeric foam composite comprises a combined total of first and second fibres of at least 5%, preferably at least 10%, more preferably at least 15% by weight, based on the total weight of the polymeric foam composite. 9. A polymeric foam composite according to any of claims 15 to 18, wherein the polymeric foam composite comprises a combined total of first and second fibres of less than 85%, preferably less than 70%, more preferably less than 55% by weight, based on the total weight of the polymeric foam composite.

20. A polymeric foam composite according to any of claims 15 to 19, further comprising a flame retardant.

21. A method for producing a polymeric foam composite according to any of claims 5 to 20 comprising:

(i) providing a foam precursor;

(ii) providing from 40 to 98% by weight, based on the total fibre weight first fibres, defined as those fibres having a length less than 150pm and from 2 to 60% by weight, based on the total fibre weight, second fibres, defined as those fibres having a length of at least 150μηι;

(iii) providing a further component suitable for inducing foam formation; and

22. A method according to claim 21 , wherein step (iv) comprises mixing the first fibres and the second fibres into the foam precursor and subsequently mixing the further component with the foam precursor.

23. A method according to claim 21 , wherein step (iv) comprises mixing a first portion of the fibres provided in step (ii) with the foam precursor, mixing a second portion of the fibres provided in step (ii) with the further component and subsequently mixing the foam precursor with the further component.

24. A method according to claim 21 , wherein step (iv) comprises mixing a first portion of the fibres provided in step (ii) with the foam precursor to provide a stream comprising foam precursor and fibres, then mixing, in a single step, the stream comprising foam precursor and fibres, a stream comprising the further component and a stream comprising at a second portion of the fibres provided in step (ii) wherein the second portion of fibres is metered directly into a mixing chamber of a mixing head by axial injection.

25. A method according to claim 21 , wherein the foam precursor is provided in a first stream of foam precursor and a second stream of foam precursor and step (iv) comprises:

26. A method according to any of claims 23 to claim 25, wherein the first portion of the fibres provided in step (ii) comprises at least 70% by weight first fibres, based on the total weight of the first portion of fibres and the second portion of the fibres provided in step (ii) comprises at least 70% by weight second fibres, based on the total weight of the second portion of fibres.

27. A method according to any of claims 21 to 26, further comprising providing a surfactant and mixing the surfactant with at least one of:

the foam precursor;

the fibres provided in step (ii); and

the further component;

before the fibres provided in step (ii) are mixed with the foam precursor or the further component. 28. A method according to any of claim 21 to 27, wherein the foam precursor is a polyol and the further component comprises an isocyanate.

29. A method according to any of claims 21 to 27, wherein the foam precursor is an isocyanate and the further component comprises a polyol.

30. A method for producing a polymeric foam composite according to any of claims 15 to 20 comprising:

(i) providing a foam precursor;

(ii) providing from 40 to 98% by weight, based on the total fibre weight first fibres, defined as those fibres having a length less than 150μιτι and from 2 to 60% by weight, based on the total fibre weight, second fibres, defined as those fibres having a length of at least 150 m;

(iii) mixing the foam precursor, the first fibres and the second fibres; and

(iv) inducing foam formation by carrying out a further processing step, wherein at least 50% of the first fibres by weight are discontinuous man- made vitreous fibres, and wherein at least 60% of the first fibres by weight have a length less than 65um and at least 30% of the second fibres by weight have a length of at least 250μηι.

31. A method according to claim 30, further comprising providing a surfactant and mixing the surfactant with at least one of the foam precursor and the fibres provided in step (ii), before the mixing step (iii).