AU3896493A

AU3896493A - Filled polymer compositions

Info

Publication number: AU3896493A
Application number: AU38964/93A
Authority: AU
Inventors: Geraldine Anne Moorman
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Imperial Chemical Industries Ltd
Priority date: 1992-04-01
Filing date: 1993-03-31
Publication date: 1993-11-08
Also published as: FI935352A0; NO934343D0; WO1993020136A1; FI935352A; BR9305459A; NO934343L; JPH07505427A; GB9207097D0; EP0593704A1

Description

Filled Polymer Compositions

This invention relates to curable compositions containing high volume concentrations of finely divided particulate fillers having improved rheology characteristics, particularly when used in combination with fibrous reinforcement.

Interest in highly filled materials in which high

concentrations of particulate and/or fibrous reinforcement are present within a polymeric matrix has grown rapidly over the past 10 to 15 years. In one aspect of these materials the matrix of the material is obtained from a curable composition. The filled, curable composition can be cured in a mould to a desired shape. Alternatively, the curable compositions can be used in a continuous process, such as pultrusion, in which a curable composition is used to impregnate a continuous fibre structure, such as a roving, the impregnated material subsequently being formed into profile of a desired shape and thereafter cured.

In these processes the fabricator requires materials which can be used with a minimum of running problems (particularly in a continuous process), are easy to use and as a consequence give high productivity. The materials themselves should give optimum properties at minimum expense. In addition, the resulting products must have desirable physical properties, such as mechanical strength and stiffness, excellent burning performance such as smoke emission and have good surface finish.

Compositions have now been developed which have attractive rheology characteristics enabling products to be readily fabricated, such products having excellent fire and smoke properties, good surface finish and high levels of mechanical properties.

According to the invention there is provided a fluid, highly filled, curable composition comprising

(A) a curable unsaturated polyester composition,

(B) from 35 to 85% by weight, preferably 50 to 80% by

weight of a finely divided inorganic filler having a weight average particle size of between 0.5 and 7 microns, preferably between 3.0 and 5.0 microns, and a surface area measured by the BET nitrogen absorption method of less than 5m².g^-1

and

(C) a carboxylic acid ester or amide carrying a terminal acid group selected from sulphate, sulphonate, phosphate and phosphonate.

The curable unsaturated polyester composition comprises polyesters based on unsaturated acids or acid anhydrides and diols in admixture with unsaturated aromatic monomers. When initiated with peroxides these compositions give cross-linked polymers.

Unsaturated polyesters useful in preparing the compositions of the invention are polyesters of a dicarboxylic acid and a diol having a major amount of olefinic unsaturation, preferably 10 to 75 olefin groups per ester groups. The olefinic unsaturation is preferably derived from the carboxylic acid although the diol may be unsaturated. Typical diols are ethylene glycol and propylene glycol. Typical unsaturated acids include maleic acid, fumaric acid as well as anhydrides of these acids. Such polyesters are made by conventional techniques of esterification as is well known in the art. Generally, polyesters having molecular weights of from about 400 to 10,000 and acid numbers in the range of from 35 to 45 mg KOH per gram of resin are useful for preparing thixotropic polyester compositions. Additionally,

di-cyclopentadiene or isophthalic acid based polyester resins may also be used.

The unsaturated aromatic monomers are aromatic compounds to which is bonded one or more ethylenically unsaturated groups such _{as a} vinyl group, substituted vinyl group or an allylic group. Suitable monomers include styrene, alpha-methyl styrene, divinyl benzene, and allyl benzene. Styrene is preferred due to its effectiveness, wide use and availability. Such monomers are used in cross-linking the polyesters and also act as diluents to reduce viscosity. In a typical procedure for preparing unsaturated polyester compositions, the liquid unsaturated polyester resin is mixed in a conventional apparatus with unsaturated aromatic monomer to prepare a solution having a solids content between about 40 and 95% by weight polyester. Additional descriptions of polyester compositions exist in US Patent Nos. 3 974 125, 4 216 135 and 4 240 951.

It is preferred that the viscosity of the unsaturated polyester composition is less than 1000 centipoise and preferably less than 200 centipoise measured at ambient temperature.

Component (B) is a particulate inorganic filler having a mean particle size by weight of between 0.5 and 7 microns, preferably between 3 and 5 microns. Suitable filler materials include forms of alumina, particularly alumina trihydrate, forms of silica such as quartz, cristobalite and tridymite, kaolin and its calcination products, magnesium hydroxides, dolomite, gypsum and other metal silicates, aluminates, aluminosilicates, phosphates, sulphates, carbonates and oxides.

The filler will be chosen with a view to the properties required of the final composite, for example, products with a high level of fire retardancy will include an appropriate filler such as alumina trihydrate, magnesium hydroxides, dimagnesium phosphate trihydrate, trimagnesium phosphate octahydrate, magnesium hydroxide, hydrated magnesium carbonates and sulphates and other fillers which show an endothermic decomposition.

In general the particles in a given filler cannot be regarded as spherical in shape. The particle sizes quoted in this specification take this into account, averaging the dimensions of a given particle as seen through a microscope or taken from a photographic record.

The filler particle size distribution, surface area and other surface chemistry/morphology aspects have a profound effect on the processability of the described compositions. This is particularly in evidence when high levels of particulate filler are used in the composition, typically 50 to 80% by weight, in order to achieve good fire and smoke properties.

The particle size distribution of the filler must be carefully chosen such that less than 25% by wt but most

preferably less than 10% by wt of the particles have an average diameter of greater than 10 microns. The presence of higher concentrations of particles greater than 10 microns in average diameter can result in poor processability when used in resin transfer moulding (RTM), cold press moulding (CP) and pultrusion.

The surface area (BET method) of the filler must also be carefully controlled to enable a composition of suitable

viscosity to be achieved. The surface area should be less than 5 m²g^-1 but preferred fillers have surface areas of less than 3 _m2g-1 and in particular less than 2 m²g^-1. In order to achieve such low surface areas with particle size distributions as previously described, it is preferred that the particle shape is approximately spherical and that the particle size distribution is such that optimum particle packing can occur.

Component (C) is a carboxylic acid ester or amide carrying a terminal acid group. Compounds of this general type are disclosed in EP 0164817 A.

A preferred compound which can be used as component (C) is one having the general formula:

A - (O - B - CO)_m - D I wherein A and D are end groups, one of which is or carries a terminal acid group selected from sulphate, sulphonate, phosphate and phosphonate and the other is a terminal group which does not render the compound hydrophilic; B is a divalent hydrocarbon group; and m is from 1 to 100.

in the compound of Formula I, when D carries the acid group, A is preferably the residue (A¹-CO-) of an esterifiable

carboxylic acid of the formula A-¹-COOH, in which A¹ is H, a hydrocarbon or a substituted hydrocarbon. Although A¹ is conveniently an optionally substituted alkyl, alkenyl, cycloalkyl or polycycloalkyl group containing up to 50, more preferably up to 35, carbon atoms, it can be any convenient monovalent group. In this case D preferably includes a polyvalent, more preferably di- or tri-valent, bridging group which links the acid group to the ester chain, A¹CO(O-B-CO)_m-, for example a group such as D² defined hereafter. Where D has a valency greater than 2 it may link two or more acid groups to a single ester or two or more esters chain to a single acid group. Where the acid group has more than one valency it may be linked to two more more esters through two bridging groups.

In the compound qf Formula I, when A carries the acid group, D is preferably the residue of an alcohol, a thiol or a primary or secondary amine, D¹-XH, in which D¹ is an aliphatic or alicyclic group as described for A¹; X is -O-, -S- or -NR-; and R is H, alkyl, alkenyl, cycloalkyl, or phenyl, in which the alkyl and alkenyl groups contain up to 20 carbon atoms and the

cycloalkyl groups from 4 to 8 carbon atoms. In this case A is preferably the acid group itself and where the acid group has more than one valency it may be linked to two or more polyester chains, although A may also include a polyvalent linking group, like D above, which links the acid group to the polyester chain.

The hydrocarbon group represented by B, which is preferably an optionally substituted divalent alkyl, alkenyl, cycloalkyl or polycycloalkyl group, preferably contains up to 50, more preferably from 3 to 24, carbon atoms, with at least 3 carbon atoms separating the -O- and -CO- groups. Optional substituents for A¹, D¹ and B include halo, especially chloro, hydroxy, amino, alkoxy and other non-ionic species in so far as they do not make the ester/amide chain hydrophilic in character.

It is preferred that m is from 2 to 75, more preferably 3 to 30, so that the compound of Formula I is an oligo- or poly-ester. Where m = 1, it is preferred that the group represented by A or D which is remote from the acid group contains at least 6 carbon atoms and that the surfactant contains at least 12 carbon atoms and more preferably at least 20 carbon atoms. It is also generally preferred that B is a pentamethylene group. One preferred compound which can be used as component (c) is a compound conforming to the formula:

[A¹ - CO -(O - B¹ - CO)_m - D²]k - L M II

wherein

cl-CO is the residue of an esterifiable carboxylic acid of the formula, A¹-COOH;

B¹ is selected from alkylene, alkenylene,

cycloalkylene, polycycloalkylene and halo

derivatives thereof;

D² is a bridging group of the formula - X - G - Y

-wherein X is -O-, -S- or -NR- and Y is -O-, -NR-or a direct link, in which each R independently is as hereinbefore defined or, where X and Y are both -NR-, the two groups, R, may form a single alkylene or alkenylene group linking the two nitrogens to which they are attached, and G is alkylene, alkenylene, cycloalkylene or arylene; L is phosphonate or sulphonate;

M is a cation;

k is 1 or 2; and

m is as hereinbefore defined.

An especially preferred compound which can be used as component (c) is a compound conforming to the formula:

[D¹ - X -(CO - B¹ - O)_m]k - L M III wherein D¹ is an aliphatic or alicyclic group and B¹, L, M, X, m and k are all as hereinbefore defined.

The residue of the esterifiable carboxylic acid represented by A¹CO in Formula II may be any convenient terminal hydrophobic group for the ester chain, -(O - B¹ - CO)_m, although it is preferably an optionally substituted alkyl, alkenyl, cycloalkyl or polycycloalkyl group containing up to 50 carbon atoms and more preferably from 1 to 35 carbon atoms. The optional substituents are preferably selected from hydroxy, amino, halogen and alkoxy provided A¹ does not render the compound hydrophilic in

character. The aliphatic or alicyclic group represented by D¹ in

Formula III is preferably an optionally substituted alkyl, alkenyl, cycloalkyl or polycycloalkyl group containing up to 35 carbon atoms , the optional substituents being preferably selected from halogen , tertiary amino and alkoxy.

The alkylene , alkenylene, cycloalkylene and

polycycloalkylene groups represented by B¹ preferably contain from 3 to 35 carbon atoms, more preferably from 4 to 20 carbon atoms, with at least 3 and more preferably at least 4 carbon atoms separating the -O- and -CO- groups, and are preferably unsubstituted. It is especially preferred that B¹ is a

pentamethylene group. The alkylene and alkenylene groups represented by G preferably contain up to 10 carbon atoms and more preferably from 2 to 6 carbon atoms. The cycloalkylene group represented by G preferably contains from 4 to 8 carbon atoms and especially preferably is 1,4-cyclohexylene. The arylene group represented by G is preferably monocyclic and especially 1,4-phenylene.

The alkyl and alkenyl groups represented by R may contain up to 25 carbon atoms and preferably contain up to 5 carbon atoms.

Where two groups, R, form a single group this preferably contains up to 10 carbon atoms.

In the compound of Formula II, when Y is -O-, the acid group, L, is attached to the ester/amide chain through an oxygen atom so that phosphonate and -O- form phosphate and sulphonate and -O- form sulphate. Similarly, in the compound of Formula II, when Y is -NR-, phosphonate and -NR- form phosphoramide and sulphonate and -NR- form sulphonamide. In the compound of

Formula III, the group L is attached to the ester chain through an oxygen atom and the phosphonate and sulphonate groups then form phosphate and sulphate groups respectively.

The cation represented by M is preferably H⁺, a metal ion, an ammonium ion or a substituted ammonium ion and examples of suitable cations are Na⁺, K⁺, Ca²⁺, NH₄ ⁺, NH(CH₂CH₂OH)₃+,

NH(CH₃)₃+ and N(CH₃)₄ ⁺. Specific examples of the bridging group represented by D² are - NHC₂H₄ -, - OC₂H₄ -, - OC₂H₄O -, - OC₂H₄NH -,

- NH(CH2)_nNH -, wherein n is from 2 to 5, piperazin-1,4-ylene and phen-l,4-ylene- diamino.

Examples of the groups represented by A¹ and A² are methyl, ethyl, CH₃(CH₂)₄ -, CH₃(CH₂)₁₀ -, CH₃(CH₂)₁₄ -,CH₃(CH₂)₁₆ -, HO(CH₂)₅ -, CH₃(CH₂)₇CH=CH(CH₂)₇ -, CH₃(CH₂)₂₈ -,

CH₃(CH₂)₅CH(OH)(CH₂)₁₀ -, CH₃(CH₂)₄CH=CHCH₂CH=CH(CH₂)₇ -,

CH₃(CH₂)₅CH(OH)CH₂CH=CH(CH₂)₇ - and CH₃OCH₂ -.

Examples of the group represented by D¹ are methyl, ethyl,

CH₃(CH₂)₉ -, CH₃(CH₂)₁₁ -, CH₃(CH₂)₁₅ -, CH₃(CH₂)₁₇ -,

CH₃(CH₂)₂₉ -, CH₃(CH₂)₇CH=CH(CH₂)₇ -, CH₃OCH₂ - and

CH₃ (CH₂)₄CH=CHCH₂CH=CH(CH₂)₇ - .

Examples of the groups represented by B and B¹ are:

and preferably - (CH₂)₅ -.

Component C may be present at a concentration of between 0.5 and 5.0% by weight of the filler component (B), and is preferably used within the range 1.5 to 2.5% by weight.

The compositions of the invention find particular use when used in conjunction with continuous fibre reinforcement, particularly glass fibre. By 'continuous fibre' is meant fibre of length at least 20 mm, although the fibre is preferably continuous through the major dimensions of the article formed by curing the compositions. This enhances impact and stiffness properties resulting in a high strength to weight ratio article. The compositions can be used to impregnate fibe structures such as mats prepared from woven fibre or random fibres at least 20 mm long, or continuous fibre filament in the form of rovings. The compositions are particularly appropriate for impregnating fibre reinforcement using the processing technologies of resin transfer moulding (RTM), cold pressing moulding (CP) and pultrusion.

The concentration of fibre reinforcement present in the final article will depend on the properties required. With higher levels of fibre, the mechanical properties are greater.

Fire and smoke properties are also improved if the overall resin content of the article is reduced by incorporation of high fibre levels. The fibre content may range from 10 to 702 by volume of the final article. For RTM and CP processing methods, it is preferred that the fibre content is 15 to 40% by volume. For pultrusion processing, it is preferred that the fibre content is 25 to 50% by volume.

The particulate filled, compositions of the invention are ideally suited for preparing reinforced articles in which a fibrous structure such as a chopped fibre mat or woven fibre mat is impregnated with the composition and subsequently cured. For RTM and CP processes the mat is normally located in a mould prior to filling the mould with the curable composition and curing in the mould. Prior art compositions which have a suitably low viscosity have a marked tendency for the filler to be at least partially filtered out by the fibre mat.

The low viscosity of the compositions provided by the combination of low viscosity resin, particular filler surface area and dispersant enables the mould to be filled quickly and with even distribution of filler and resin throughout the glass reinforcement.

For RTM processing, compositions of viscosity less than 25 Poise, preferably less than 15 Poise (measured on a Brookfield viscometer) are preferred to enable quick mould filling. For CP processing, compositions of viscosity less than 100 Poise, preferably less than 60 Poise, are preferred.

The excellent processability of the compositions of the invention make them ideally suited for use in continuous pultrusion processes in which continuous fibres are impregnated with a material for example by pulling the fibres through a bath of material, and subsequently curing the composite. For

pultrusion processing compositions having a viscosity of less than 100 Poise, preferably less than 60 Poise are preferred. The low viscosity and good rheological properties enable the fibres to be impregnated easily, even though the rate of pull through of the fibre roving is high. The ease of impregnation provides a uniformity of filler and resin distribution which gives a continuously running process which is seldom interrupted by breakages caused by build up of fluid material filtered out on the surface of the impregnated roving, which are particularly prone to occur as the roving passes into the profiling die to produce a profiled article.

Pultrusion processes give rise to products of very high strength and stiffness because parallel alignment of fibres enables a very high volume of fibres to be incorporated in an article through close packing of the parallel fibres. The resin content may consequently be reduced to the minimum necessary to wet the fibres and the dispersed filler and fill the interstices between the parallel fibres. Provided that the matrix resin is well bonded to the fibres, very high levels of mechanical properties can be achieved through these high fibre levels.

Although the bonding between the inorganic materials and the matrix resin may be sufficient for most purposes, the particulate filled compositions of the invention may also include coupling additives to ensure that the inorganic materials are even more strongly bonded to the matrix polymer after curing. Coupling agents fulfilling this function are well known in the art.

Fibres are normally provided by the fibre manufacturer with a size to enable the fibre to withstand the fibre manufacturing process without undue damage to the fibre surface. In the case of glass fibres the size normally includes a silane coupling agent to help achieve optimum properties in the application for which the glass fibre is intended to be used. Glass fibre manufacturers will normally be able to recommend a fibre carrying a coupling agent most suited to the application. The strength properties contributed by the continuous fibres dominate the strength of the cured composite. Shaped articles formed from the compositions of the invention, whether fibre reinforced or not, exhibit remarkably good burning performance in respect of both fire retardancy and smoke emission.

Claims

1. A fluid, highly filled, curable composition comprising

(A) a curable unsaturated polyester composition,

(B) from 35 to 85% by weight of a finely divided inorganic filler having a weight average particle size of between 0.5 and 7 microns and a surface area measured by the BET nitrogen absorption method of less than 5m².g^-1 and

2. A fluid, highly filled, curable composition as claimed in claim 1 comprising 50 to 80% by weight of the finely divided inorganic filler.

3. A fluid, highly filled, curable composition as claimed in either claim 1 or claim 2 wherein the finely divided inorganic filler has a weight average particle size of between 3.0 and 5.0 microns.

4. A curable composition as claimed in any one of claims 1 to 3 comprising from 50 to 80% by weight of a finely divided inorganic filler having a weight average particle size of between 0.5 and 7 microns.

5. A curable composition as claimed in any one of claims 1 to 4 wherein the finely divided inorganic filler has a weight average particle size of between preferably between 3.0 and 5.0 microns.

6. A curable composition as claimed in any one of claims 1 to 5 wherein the finely divided inorganic filler is one which shows an endothermic decomposition.

7. A curable composition as claimed in any one of claims 1 to 6 wherein component (C) is one having the general formula:

A - (O - B - CO)_m - D I wherein

A and D are end groups, one of which is or carries a terminal acid group selected from sulphate, sulphonate, phosphate and phosphonate and the other is a terminal group which does not render the compound hydrophilic;

B is a divalent hydrocarbon group; and

m is from 1 to 100.

8. A curable composition as claimed in any one of claims 1 to 6 wherein component (C) is one having the general formula:

[A¹ - CO -(O - B¹ - CO)_m - D²]_k - L M II wherein

A¹-CO is the residue of an esterifiable carboxylic acid

of the formula, A¹-COOH;

B¹ is selected from alkylene, alkenylene, cycloalkylene, polycycloalkylene and halo derivatives thereof;

D² is a bridging group of the formula - X - G - Y - wherein X is -O- , -S- or -NR- and Y is -I-, -NR- or a direct link, in which each R independently is as hereinbefore defined or, where X and Y are both -NR-, the two groups, R, may form a single alkylene or alkenylene group linking the two nitrogens to which they are attached, and G is alkylene, alkenylene, cycloalkylene or arylene;

L is phosphonate or sulphonate;

M is a cation;

k is 1 or 2; and

m is from 1 to 100.

9. A curable composition as claimed in any one of claims 1 to 6 wherein component (C) is one having the general formula:

[D¹ - X -(CO - B¹ - O)_m]k - L M III wherein D¹ is an aliphatic or alicyclic group and

L is phosphonate or sulphonate;

M is a cation;

k is 1 or 2; and

m is from 1 to 100.

10. A curable composition as claimed in any one of claims 1 to 9 comprising continuous fibre reinforcement formed from glass fibre.

11. A shaped article formed by curing a curable composition as claimed in any one of claims 1 to 10.