CA1106992A - Reinforced composites containing a friedel-crafts resin - Google Patents
Reinforced composites containing a friedel-crafts resinInfo
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- CA1106992A CA1106992A CA307,031A CA307031A CA1106992A CA 1106992 A CA1106992 A CA 1106992A CA 307031 A CA307031 A CA 307031A CA 1106992 A CA1106992 A CA 1106992A
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Abstract
Abstract of the Disclosure Fibrous-reinforced composites, such as prepregs and sheet moulding compounds, are made with a thermosettable Friedel-Crafts resin, a heat-curing agent therefor, and a photopolymerisable compound. The Friedel-Crafts resins employed are those obtainable by a Friedel-Crafts reaction of certain aralkyl alkyl ethers and/or certain aralkyl halides with phenolic compounds. The heat-curing agents employed are those used to cure novolac resins, and include formaldehyde in various forms, sources of formaldehyde, and also epoxide resins. Fibers may be impregnated with a liquid mixture of the resin, heat-curing agent, and the photopolymerisable compound, and exposed to actinic radiation to cause the mixture to solidify through photopolymerisation. Alternatively, the liquid mixture is exposed to actinic radiation to form a solid film into which the fibers are pressed. The product, when desired, e.g., after stacking to form a multilayer laminate, or after shaping, is heated to cure the resin.
Description
9~2 Background of the Invention This invention relates to reinforced composites containing photopolymerisable and thermosettable compositions and fibrous reinforcing materials, and to methods for their production.
Composite stractures are commonly made by impregnating fibrous materials, such as fibers of paper, glass, aromatic polya~ide, or carbon, metal filaments, and whiskers, usually in the form of layers, with a solution, in a volatile solvent, of a solid thermosettable resin and a heat-activated curing agent for the resin, causing the resin to solidify by evaporation of the solvent, and, when desired, curing the resin composition in the resultant so-called "prepreg" by the action of heat. Frequently, the prepregs are stacked before heat-curing, so that a multilayer laminate is formed.
Sheet moulding compositions are made by impregnating chopped fibrous reinforcement with a liquid thersettable resin composition, and then causing the resin to thicken by chemical means such as by reaction of carboxyl groups in the resin with magnesium oxide. The resin is subsequently heat-cured when the moulding is in the desired shape.
Composite structures may also be prepared from films of a thermosettable resin composition by laying a film of the composition containing the resin and the curing`agent on a fibrous reinforcement and applying heat and pressure so that the resin composition flows about the fibers but remains curable, and then heating further when desired so that the resin is cured by the heat-activated curing agent.
Both these methods suffer from certain drawbacks. Some thermosettable resin compositions are solid, and if a solvent is ~ ' , used it is not always possible to eliminate all traces of it before the final curing takes place, and in consequence the final composite may contain voids caused by evaporation of such residual solvent.
Solvents may cause difficulties due to their toxicity or flammability or to pollution. If a film adhesive is used, it is usually cast from a liquid thermosettable resin and this is then advanced to the solid state; such a process adds considerably to the cost of the composite. The methods also require a considerable expenditure of heat energy, either to evaporate the solvent or to advance the resin.
Recently, certain resins have become of considerable technical interest because the crosslinked products obtained therefrom have high glass transition temperatures. These resins, which are cured by reaction with substances employed as curing agents for novolac resins, are obtained by a Friedel-Crafts reaction of certain aralkyl halides and/or aralkyl ethers with a phenolic compound. They are called herein a "Friedel-Crafts resin" for brevity.
Detailed Disclosure ~ e have now developed procedures whereby fiber-reinforced composites containing a thermosettable resin composition as a matrix material may be obtained using these Friedel-Crafts resins and without the need to incur the disadvantages just mentioned.
In one procedure, the reinforcement is impregnated with the Friedel-Crafts resin and with a liquid photopolymerisable compound, then the impregnated fibers are irradiated with actinic radiation such that the photopolymerisable compound solidifies, the Friedel-Crafts resin, however, remaining thermosettable.
In another procedure, a mixture of the Friedel-Crafts resin and a liquid photopolymerisable compound is similarly irradiated, to form a solid film, and this is used to impregnate the fibres.
It is not necessary to convert immediately the Friedel-Crafts resin in the photopolymerised composition distributed on the fibres into the fully cured, insoluble, and infusible C-stage; often, it can be changed into the still fusible B-stage, or remain in the A-stage, and, when desired, e.g., after stacking, and/or after the prepreg has been formed into some desired configuration, fully cured by heating. For example, if a hollow shaped article is required, it is convenient to impregnate a continuous tow of fibrous reinforcement and wind the tow around a former while, at the same time, exposing the winding to actinic radiation. Such windings still have a certain degree of flexibility, permitting the former to be removed more easily than when a rigid winding is formed in one step. ~hen required, the filament winding is heated to complete the cure.
~ccordingly, this invention provides composites comprising (a) a fibrous reinforcing material, (b) a Friedel-Crafts resin, as herein defined, (c) a heat-activated curing agent for novolac resins, and (d) a photopolymerised compound.
Also included in this invention are a method of making a reinforced composite which comprises heat-curing a photopolymerised, but still thermosettable, composite of this invention, and heat~cured reinforced composites made thereby.
A convenient method of preparing the composites of this invention comprises i) impregnating a fibrous reinforcing material (a) with a liquid composition comprising (b) a Friedel-Crafts resin, as herein defined, (c) a heat-activated curing agent for novolac resins, (e) a photopolymerisable compound ( other than a Friedel-Crafts resin) and, if required, (f) a photopolymerisation catalyst for the compound (e), and ii) in the absence of a substance which gives rise to a substantial degree of photoinduced polymerisation of the Friedel-Crafts resin, exposing the impregnated material to actinic radiation such that the composition solidifies due to photopolymerisation of the photopolymerisable compound (e) while the Friedel-Crafts resin remains substantially in the thermosettable state.
This method is particularly useful for the production of filament ~indings and~when chopped strand reinforcing material is used, of sheet moulding compounds. --Another method of preparing the composites of this invention from fibro~us reinforcing material (a) comprises --i) in the absence of a substance which gives rise to a substantial degree of photoinduced polymerisation of a Friedel-Craf~s resin ( as herein defined), exposing to actinic radiation ~69~2 a layer of a liquid compositon comprising (b) a Friedel-Crafts resin, (c) a heat-activated curing agent for novolac resins, (e) a photopolymerisable compound (other than a Friedel-Crafts S resin) and, if requiredJ
(f) a photopolymersation catalyst for the compound (e), until the said composition solidifies to form an essentially solid, continuous film due to photopolymerisation of the photopolymerisable compound (e) while the Friedel-Crafts resin remains substantially in the thermosettable state, and ii) bringing together the film so formed and the fibrous reinforcing material (a) under conditions such that the solid film flows about the fibres, and the components of the film and the fibres form a coherent structure but the Friedel-Crafts resin remains substantially in the lS thermosettable state.
Usually, the film and fibrous reinforcing material are brought together with the application of heat and/or pressure. The period of heating can be very short, as there need be no solvent to evaporate and the film need not be thick. The latter procedure is particularly convenient when unidirectional fibrous reinforcement is to be used, especially if the fibres are short and/or light, because there is less tendency for the fibres to become displaced and the reinforcing effect ehereby become irregularly distributed.
The reinforcement may be in the form of a woven or non-~oven cloth, unidirectional lengths, or chopped strands, and may be of natural or synthetic fibres, including strands and filaments, especially of glass, boron, stainless steel, tungsten, alumina, silicon carbide, asbestos, an aromatic polyamide such as poly(m-phenylene isophthalamide) or poly(p-phenylene terephthalamide), or carbon, and whiskers of, e.g., potassium titanate.
Compositions used to prepare the thermosettable composites of the present invention must be liquid under the conditions used in making the films or in impregnating the reinforcing material before irradiation, but are preferably solvent-free.
The Friedel-Crafts resins concerned in this invention, which may be used in the form of prepolymers if wished, are those obtainable by a Friedel-Crafts reaction of (i) an aralkyl ether of formula R(CH20R )a and/or an aralkyl halide of formula R (CH2X)a IA
where R is a divalent or trivalent aromatic hydrocarbon or hydrocarbonoxy radical, preferably a mononuclear, fused dinuclear, or bridged dinuclear benzenoid group, optionally containing one or more inert substituents, such as a methyl group or a chlorine or fluorine atom, on the aromatic nucleus or nuclei, each Rl is an alkyl radical of up to 5, but preferably not more than 3, carbon atoms, R2 is a divalent or trivalent aromatic hydrocarbon radical, preferably a mononuclear, fused dinuclear, or bridged dinuclear benzenoid group, optionally containing one or more inert substituents on the aromatic nucleus or nuclei, 69~
each X is a chlorine, bromine, or iodine atom, and a is 2 or 3, with a molar excess of (ii) a phenolic compound, or a mixture of a phenolic compound with a non-phenolic compound which contains one of more aromatic nuclei and which is capable of condensation with the aralkyl ether or aralkyl halide (i) under the reaction conditions employed to form the Friedel-Crafts resin, the said phenolic compound and, if used, the said non-phenolic compound, having at least two free nuclear hydrogen atoms per molecule, the phenolic compound being a benzenoid compound, or mixture of benzenoid compounds, containing from 1 to 3 hydroxyl groups directly attached to a benzene nucleus, there being a total of not more than 3 substituents attached to carbon atoms in that benzene nucleus.
Such resins and their production in the presence of Friedel-Crafts catalysts such as stannic chloride and diethyl sulphate are described in, e.g. British Patent Specifications Nos. 1 150 203, 1 305 551, and 1 365 936. Preferably, 1.3 to 3.0 and more particularly 1.4 to 2.5, and especially 1.4 to 2.0, moles of (ii) are used per mole of (i).
The resins eontain a repeating unit of formula (CH2R OH)a-2 and/or a repeating unit of formula -CH2 - R - CH2 ~ ~H~ IIA
(CH2R30H)a 2 where R, R , and a each have the meaning previously assigned and R is the residue of a phenolic compound after removal of a phenolic hydroxyl group and 2 nuclear hydrogen atoms.
.?~
69~;~
Examples of suitable phenolic compounds are phenol, p-cresol, resorcinol, catechol, bis(p-hydroxyphenyl)methane, 2,2-bis(p-hydroxy-phenyl)propane, 2,2-bis(p-hydroxyphenyl)sulphone, p-ethylphenol, p-tert.-butylphenol, _-tert.octy].phenol, o-phenylphenol, p-phenylphenol, pyrogallol, phloroglucinol, and 2-naphthol.
In formula I, R preferably denots a group of any of formulae III
to VII
III IV
~~ ' '~
V VI
and .' ~
VII
and in formula IA, R preferably denotes a group of any of . formulae III, IV, and VII.
Particularly preferred specific examples of compounds of formula I or IA are p-xylylene glycol dimethyl ether and p-xylylene dichloride, and their 2,2,5,6-tetrachloro derivati~es.
Suitable non-phenolic compounds containing one or more aromatic ..~
~6~2 nuclei, which may be employed with the phenolic compound as component (ii) to modify the properties of the Friedel-Crafts resin, are those capable of - condensation with the aralkyl ether or aralkyl halide (i) under the reaction conditions employed to form the Friedel-Crafts resin and are preferably aromatic hydrocarbons or aromatic ethers (including thioethers). Specific examples of such compounds containing aromatlc nuclei are diphenyl ether, dibenzyl ether, terphenyl, diphenyl sulphide, diphenyl, anthracene, and naph~halene. Diphenyl sulphone and triphenyl phosphate are examples of other compounds which may be used.
10 When a non-phenolic compound containing one or more aromatic nuclei is employed, it is not then essential that the phenolic compound should itself be in molar excess over the aralkyl halide and/or aralkyl ether, provided that the total of the phenolic compound and the compound containing aromatic nuclei taken together represents the required molar excess.
The heat-activated curing agent (c) for the Friedel-Crafts resin is any agent suitable for curing novolac resins, although it must, of course, have negligible curing effect on the resin at the temperature at which photopolymerisation is carried out. These agents are usually some form of formaldehyde or a formaldehyde donor, or else a compound containing more than one 1,2-epoxide group on average per molecule.
Hexamethylenetetramine is strongly preferred among formaldehyde donors but, e.g., p-benzoquinone~ chloranil, anhydroformaldehyde-aniline (i.e., hexahydro-1,3,5-triphenyltriazine, ethylenediamine-formaldehyde (i.e., 1,4,6,9-tetrazatricyclo L4.4.1.14'9~ dodecane), and N-methylol derivatives of urea or of melamine may also be used.
As already indicated, epoxide resins, i.e., compounds containing more than one 1,2-epoxide group per molecule on average, may be used as heat-curing agents, they reacting with phenolic hydroxyl groups of ~6C~2 the Friedel-Crafts resin.
In the usual methods of manufacturing epoxide resins, mixtures of compounds of differing molecular weight are obtained, these mixtures ordinarily containing a proportion of compounds whose epoxide groups 5 have undergone partial hydrolysis. The average number of 1,2-epoxide r groups per molecule of the resin need not be an integer of at least 2;
it is generally a fractional number but must in any case be greater than 1Ø
Examples of epoxide resins which may be used are polyglycidyl and 10 poly(~-methylglycidyl) esters obtainable by reaction of a substance containing two or more carboxylic acid groups with epichlorohydrin, glycerol dichlorohydrin, or ~-methylepichlorohydrin in the presence of alakali. Such esters may be derived from aliphatic carboxylic acids, e.g., oxalic acid, succinic acid, adipic acid, sebacic acid, and dimerised 15 and trimerised linoleic acid, from cycloaliphatic carboxylic acids such as hexahydrophthalic acid, 4-methylhexahydrophthalic acid, tetrahydrophthalic acid, and 4-methyltetrahydrophthalic acid, and from aromatic carboxylic acids such as phthalic acid, isophthalic acid, and terephthalic acid.
Other epoxide resins which may be used include polyglycidyl and 20 poly(~-methylglycidyl) ethers, such as those obtainable by reaction of a substance containing at least two alcoholic hydroxyl groups or at least two phenolic hydroxyl groups with the appropriate epichlorohydrin or glycerol dichlorohydrin under alkaline conditions or, alternatively, in the presence of an acidic catalyst with subsequent treatment with 25 alkali. Such ethers may be derived from aliphatic alcohols, for example, ethylene glycol, diethylene glycol, triethylene glycol, and higher poly(oxyethylene) glycols, propylene glycol and poly(oxypropylene) glycols, propane-1,3-diol, butane-1,4-diol, pentane-1,5-diol, hexane-l, 6-diol, hexane-1,2,6-triol, glycerol, l,l,l-trimethylolpropane, and z pentaerythritol; from cycloaliphatic alcohols such as quinitol, 1,1-bis(hydroxymethyl)cyclohex-3-ene, bis(4-hydroxycyclohexyl)methane, and 2,2-bis(4-hydroxycyclohexyl)propane; and from alcohols containing aromatic nuclei, such as N,N-bis(2-hydroxyethyl)aniline and 4,4-bis(2-hydroxyethylamino)diphenylmethane. Preferably the ethers are polyglycidylethers of an at least dihydric phenol, for example, resorcinol, catechol, hydroquinone, bis(4-hydroxyphenyl)methane, 1,1,2,2-tetrakis(4-hydroxy-phenyl)ethane, 4,4'-dihydroxydiphenyl, bis(4-hydroxyphenyl) sulphone, and phenol-formaldehyde, alkylphenol-formaldehyde and chlorophenol-formaldehyde novolac resins, 2,2-bis(4-hydroxyphenyl)propane (otherwise known as bisphenol A), and 2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane.
There may further be employed poly(N-glycidyl) and poly(N-B-methyl-glycidyl compounds, for example, those obtained by dehydrochlorination of the reaction products of the epichlorohydrin and amines containing at least two hydrogen atoms directly attached to nitrogen, such as aniline, n-butylamine, bis(4-aminophenyl)methane, bis(4-aminophenyl) sulphone, and bis(4-methylaminophenyl)methane. Other poly(N-glycidyl) compounds that may be used include triglycidyl isocyanurate, N,N'-diglycidyl derivatives of cyclic alkylene ureas such as ethyleneurea and l,3-propyleneurea, and N,N'-diglycidyl derivatives of hydantoins such as 5,5-dimethylhydantoin.
Other epoxide resins which may be used include bis(2,3-epoxycyclopentyl) ether, 2,3-epoxycyclopentyl glycidyl ether, and 1,2-bis(2',3'-epoxy-cyclopentyloxy)ethane.
Especially suitable .poxide resins are polyglycidyl ethers ofpolyhydric phenols such as 2,2-bis(4-hydroxyphenyl)propane, bis(4-hydroxyphenyl~methane, or of a novolac from phenol ( which may be substituted in-the ring by chlorine or a hydrocarbon alkyl group of from 1 to 4 carbon atoms) and form-aldehyde, having an epoxide content of at least l.O epoxide equivalent per kilogram.
Ordinarily, from 1 to 20, and especially 5 to 15, parts by weight of the heat-activated curing agent is employed per 100 parts by weight of the Friedel-Crafts resin. It is convenient to dissolve or suspend the curing agent in the liquid composition before impregnation or irradiation.
The curing effect of hexamine may be accelerated by incorporating zinc borate, salicylic acid, benzilic acid, benzoic acid, cinnamic acid, hydrocinnamic acid, p-hydroxybenzoic acid, ~-naphthoic acid, phenylacetic acid, p-toluic acid, or toluene-p-sulphonic acid.
The curing effect of epoxide resins may be accelerated by incorporating amino compounds, especially tertiary amines.
The photopolymerisable compound (e) used in the processes of the present invention may be of any chemical type known to polymerise under influence of actinic radiation. Such materials are described in, for example, Kosar, "Light-sensitive Systems: Chemistry and Applications of Non-Silver Halide Photographic Processes", ~iley, New York, 1965. As is well known, ,hese materials fall into two main classes -(i) those which are polymerised through a free-radical chain reaction (photoinitiated polymerisation) and (ii) those in which polymerisation is effected by reaction of an excited molecule of the monomer with an unexcited lecule of the monomer.
The first type require only one photopolymerisable group per molecule to form long chains on polymerisation, while the second type must have at least two photopolymerisable groups per molecule, since if they have only one such group per lecule they will dimerise, but not polymerise, on irradiation.
- 13 ~
Z
Photopolymerisable substances of the first type preferred for use in this invention have one ethylenic linkage, or more than one providing they are unconjugated. Examples of these substances are styrene and crotonic acid and, preferably, acrylic esters containing at least one group or the general formula VIII, IX, or X
CH2 = C(R )COO - VIII
CH2 = C(R )CO~H ~ CHCOO- IX
CH2 = C(R )CONHCH(OH)CH2COO- X
where R is a hydrogen, chlorine, or bromine atom, or an alkyl hydrocarbon group of 1 to 4 carbon atoms, especially a hydrogen atom or a methyl group. More specific examples of preferred acrylates are neopentyl glycol diacrylate and those given below under formulae XXIII, XXIV, and XXVI to XXVIII.
Photopolymerisable materials of the second type include those having at least two, and preferably three or more, groups which are azido, coumarin, stilbene, maleimide, pyridinone, chalcone, propenone, or pentadienone groups, or acrylic acid groups which are substituted in their 3- position by groups having ethylenic unsaturation or aromaticity in conjugation with the ethylenic double bond of the acrylic group.
Examples of suitable a~ides are those containing at least two groups of the formula or ~6~
where R5 denotes a mononuclear or dinuclear divalent aromatic radical containing from 6 to 12 carbon atoms, especially a phenylene or naphthylene group.
Examples of suitable coumarins are those containing groups of the formula CO~o ~ R6 XIII
where R is an oxygen atom, a carbonyloxy group (-C00-), a sulphonyl group, or a sulphonyloxy group.
Examples of photopolymerisable materials containing stilbene groups are those having groups of the formula R? ~ CH=CH ~ XIV
where R is the residue, containing up to 8 carbon atoms in all, of a five or six-membered, nitrogen-containing heterocyclic ring, fused to a benzene or naphthalene nucleus, and linked through a carbon atom of the said heterocyclic ring adjacent to a nitrogen hetero atom thereof to the indicated benzene nucleus, such as a benzimidazolyl, benzoxazolyl, benzotriazolyl, benzothiazolyl, or a naphthotriazolyl residue.
Examples of photopolymerisable substances containing maleimide units are those having groups of the formula " - ~
69~2 lc~
directly attached to carbon atoms, where each R is an alkyl group of 1 to 4 carbon atoms, a chlorine atom, or a phenyl group, especially a methyl group.
Examples of photopolymerisable substances containing pyridinone units are those having, directly attached to carbon atoms, groups of the formula .
b ~ O XVI
where R is an aliphat;c or cycloaliphatic radical of 1 to 8 carbon atoms and b is zero or an integer of 1 to 4.
Examples of compounds containing chalcone, propenone, or pentadienone groups are those containing structures of formula ~ ~ 12 or ,~ Rll~;~Rl2 RVIII
where each R is a halogen atom, or an alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkoxy, cycloalkoxy, alkenoxy, cycloalkenoxy, carbalkoxy, carbocycloalkoxy, carbalkenoxy, or carbocycloalkenoxy group, such organic S groups containing 1 to 9 carbon atoms, or a nitro group, or a carboxyl, sulphonic, or phosphoric acid group in the form of a salt, b has the meaning previously assigned, R represents a grouping of formula ~ Cd = C ~ C ~ C - CH ~ XIX
or I CH = C - C - XX
c f = CH ~ Rl7 or R16 o -CH = C - C ~ R17 XXI
where R and R are each individually a hydrogen atom, an alkyl group, e.g., of l to 4 carbon atoms, or an aryl group, e.g., of up to 12 carbon atoms, preferably a mononuclear group such as a phenyl group, or conjointly denote a polymethylene chain of 2 to 4 methylene groups, R 6 and R 7 are each a hydrogen atom, an alkyl group, e.g., of l to 4 carbon atoms, or an aryl group, e.g., of up to 12 carbon atoms, - 17 ~
-3~ .
preferably a mononuclear group such as a phenyl group, c and d are each zero, 1, or 2, with the proviso that they are not both zero, R represents a valency bond or a hydrogen atom, and R represents an oxygen or sulphur atom.
Suitable 3- substituted acrylates contain groups of the general formula R13cH=c(R4)coo- XXII
where R 8 is an aliphatic or mononuclear aromatic, araliphatic, or heterocyclic group, preferably of not more than 12 carbon atoms, which, as already indicated, has ethylenic unsaturation or aromaticity in conjugation with the ethylenic double bond shown, such as a phenyl, 2-furyl, 2- or 3-pyridyl, prop-2-enyl, or styryl group, and R has the meaning previously assigned.
Specific examples are disorbates and bis(2-furylacrylates) of polytoxyethylene) glycols and poly(oxypropylene) glycols.
If desired, a mixture of photopolymerisable compounds may be used.
Especially preferred photopolymerisable compounds used in processes of this invention are neopentyl glycol diacrylate and esters of acrylic acid which are of any of the following general formulae XXIII, XXIV, and X~VI to XXVIII.
~ormula XXIII is CH 2 = CHCOO ~ (CH2)f - (CHRl9) - CHO ~ OCCH = CH2 R g . -:
~' ~
9~Z
where e is zero or 1, f is an integer of 1 to 8, g is an integer of 1 to 20, S R denotes -H, -OH, or -OOCCH=CH2, and R denotes -H, -CH3, -C2H5, -CH20H, or -CH200CCH=CH2.
Examples of compounds of formula XXIII are triethylene glycol diacrylate and tetraethylene glycol diacrylate.
Formula XXIV is Ch2 = CUCOO ~ (C~2)h L ~ ~ ~ R
where e, g, and R have the meanings assigned above, h is zero or a positive integer, preferably of not more than 8, provided that e and h are not both zero, i is an integer of from 1 to 4, R21 denotes -H -Cl -CH3, or -C2H , and R22 denotes an organic radical of valency i, linked through a carbon atom or carbon atoms thereof to the indicated i terminal oxygen atoms, preferably the hydrocarbon residue of an aliphatic alcohol containing from 1 to 6 carbon atoms, such as -CH3 or
Composite stractures are commonly made by impregnating fibrous materials, such as fibers of paper, glass, aromatic polya~ide, or carbon, metal filaments, and whiskers, usually in the form of layers, with a solution, in a volatile solvent, of a solid thermosettable resin and a heat-activated curing agent for the resin, causing the resin to solidify by evaporation of the solvent, and, when desired, curing the resin composition in the resultant so-called "prepreg" by the action of heat. Frequently, the prepregs are stacked before heat-curing, so that a multilayer laminate is formed.
Sheet moulding compositions are made by impregnating chopped fibrous reinforcement with a liquid thersettable resin composition, and then causing the resin to thicken by chemical means such as by reaction of carboxyl groups in the resin with magnesium oxide. The resin is subsequently heat-cured when the moulding is in the desired shape.
Composite structures may also be prepared from films of a thermosettable resin composition by laying a film of the composition containing the resin and the curing`agent on a fibrous reinforcement and applying heat and pressure so that the resin composition flows about the fibers but remains curable, and then heating further when desired so that the resin is cured by the heat-activated curing agent.
Both these methods suffer from certain drawbacks. Some thermosettable resin compositions are solid, and if a solvent is ~ ' , used it is not always possible to eliminate all traces of it before the final curing takes place, and in consequence the final composite may contain voids caused by evaporation of such residual solvent.
Solvents may cause difficulties due to their toxicity or flammability or to pollution. If a film adhesive is used, it is usually cast from a liquid thermosettable resin and this is then advanced to the solid state; such a process adds considerably to the cost of the composite. The methods also require a considerable expenditure of heat energy, either to evaporate the solvent or to advance the resin.
Recently, certain resins have become of considerable technical interest because the crosslinked products obtained therefrom have high glass transition temperatures. These resins, which are cured by reaction with substances employed as curing agents for novolac resins, are obtained by a Friedel-Crafts reaction of certain aralkyl halides and/or aralkyl ethers with a phenolic compound. They are called herein a "Friedel-Crafts resin" for brevity.
Detailed Disclosure ~ e have now developed procedures whereby fiber-reinforced composites containing a thermosettable resin composition as a matrix material may be obtained using these Friedel-Crafts resins and without the need to incur the disadvantages just mentioned.
In one procedure, the reinforcement is impregnated with the Friedel-Crafts resin and with a liquid photopolymerisable compound, then the impregnated fibers are irradiated with actinic radiation such that the photopolymerisable compound solidifies, the Friedel-Crafts resin, however, remaining thermosettable.
In another procedure, a mixture of the Friedel-Crafts resin and a liquid photopolymerisable compound is similarly irradiated, to form a solid film, and this is used to impregnate the fibres.
It is not necessary to convert immediately the Friedel-Crafts resin in the photopolymerised composition distributed on the fibres into the fully cured, insoluble, and infusible C-stage; often, it can be changed into the still fusible B-stage, or remain in the A-stage, and, when desired, e.g., after stacking, and/or after the prepreg has been formed into some desired configuration, fully cured by heating. For example, if a hollow shaped article is required, it is convenient to impregnate a continuous tow of fibrous reinforcement and wind the tow around a former while, at the same time, exposing the winding to actinic radiation. Such windings still have a certain degree of flexibility, permitting the former to be removed more easily than when a rigid winding is formed in one step. ~hen required, the filament winding is heated to complete the cure.
~ccordingly, this invention provides composites comprising (a) a fibrous reinforcing material, (b) a Friedel-Crafts resin, as herein defined, (c) a heat-activated curing agent for novolac resins, and (d) a photopolymerised compound.
Also included in this invention are a method of making a reinforced composite which comprises heat-curing a photopolymerised, but still thermosettable, composite of this invention, and heat~cured reinforced composites made thereby.
A convenient method of preparing the composites of this invention comprises i) impregnating a fibrous reinforcing material (a) with a liquid composition comprising (b) a Friedel-Crafts resin, as herein defined, (c) a heat-activated curing agent for novolac resins, (e) a photopolymerisable compound ( other than a Friedel-Crafts resin) and, if required, (f) a photopolymerisation catalyst for the compound (e), and ii) in the absence of a substance which gives rise to a substantial degree of photoinduced polymerisation of the Friedel-Crafts resin, exposing the impregnated material to actinic radiation such that the composition solidifies due to photopolymerisation of the photopolymerisable compound (e) while the Friedel-Crafts resin remains substantially in the thermosettable state.
This method is particularly useful for the production of filament ~indings and~when chopped strand reinforcing material is used, of sheet moulding compounds. --Another method of preparing the composites of this invention from fibro~us reinforcing material (a) comprises --i) in the absence of a substance which gives rise to a substantial degree of photoinduced polymerisation of a Friedel-Craf~s resin ( as herein defined), exposing to actinic radiation ~69~2 a layer of a liquid compositon comprising (b) a Friedel-Crafts resin, (c) a heat-activated curing agent for novolac resins, (e) a photopolymerisable compound (other than a Friedel-Crafts S resin) and, if requiredJ
(f) a photopolymersation catalyst for the compound (e), until the said composition solidifies to form an essentially solid, continuous film due to photopolymerisation of the photopolymerisable compound (e) while the Friedel-Crafts resin remains substantially in the thermosettable state, and ii) bringing together the film so formed and the fibrous reinforcing material (a) under conditions such that the solid film flows about the fibres, and the components of the film and the fibres form a coherent structure but the Friedel-Crafts resin remains substantially in the lS thermosettable state.
Usually, the film and fibrous reinforcing material are brought together with the application of heat and/or pressure. The period of heating can be very short, as there need be no solvent to evaporate and the film need not be thick. The latter procedure is particularly convenient when unidirectional fibrous reinforcement is to be used, especially if the fibres are short and/or light, because there is less tendency for the fibres to become displaced and the reinforcing effect ehereby become irregularly distributed.
The reinforcement may be in the form of a woven or non-~oven cloth, unidirectional lengths, or chopped strands, and may be of natural or synthetic fibres, including strands and filaments, especially of glass, boron, stainless steel, tungsten, alumina, silicon carbide, asbestos, an aromatic polyamide such as poly(m-phenylene isophthalamide) or poly(p-phenylene terephthalamide), or carbon, and whiskers of, e.g., potassium titanate.
Compositions used to prepare the thermosettable composites of the present invention must be liquid under the conditions used in making the films or in impregnating the reinforcing material before irradiation, but are preferably solvent-free.
The Friedel-Crafts resins concerned in this invention, which may be used in the form of prepolymers if wished, are those obtainable by a Friedel-Crafts reaction of (i) an aralkyl ether of formula R(CH20R )a and/or an aralkyl halide of formula R (CH2X)a IA
where R is a divalent or trivalent aromatic hydrocarbon or hydrocarbonoxy radical, preferably a mononuclear, fused dinuclear, or bridged dinuclear benzenoid group, optionally containing one or more inert substituents, such as a methyl group or a chlorine or fluorine atom, on the aromatic nucleus or nuclei, each Rl is an alkyl radical of up to 5, but preferably not more than 3, carbon atoms, R2 is a divalent or trivalent aromatic hydrocarbon radical, preferably a mononuclear, fused dinuclear, or bridged dinuclear benzenoid group, optionally containing one or more inert substituents on the aromatic nucleus or nuclei, 69~
each X is a chlorine, bromine, or iodine atom, and a is 2 or 3, with a molar excess of (ii) a phenolic compound, or a mixture of a phenolic compound with a non-phenolic compound which contains one of more aromatic nuclei and which is capable of condensation with the aralkyl ether or aralkyl halide (i) under the reaction conditions employed to form the Friedel-Crafts resin, the said phenolic compound and, if used, the said non-phenolic compound, having at least two free nuclear hydrogen atoms per molecule, the phenolic compound being a benzenoid compound, or mixture of benzenoid compounds, containing from 1 to 3 hydroxyl groups directly attached to a benzene nucleus, there being a total of not more than 3 substituents attached to carbon atoms in that benzene nucleus.
Such resins and their production in the presence of Friedel-Crafts catalysts such as stannic chloride and diethyl sulphate are described in, e.g. British Patent Specifications Nos. 1 150 203, 1 305 551, and 1 365 936. Preferably, 1.3 to 3.0 and more particularly 1.4 to 2.5, and especially 1.4 to 2.0, moles of (ii) are used per mole of (i).
The resins eontain a repeating unit of formula (CH2R OH)a-2 and/or a repeating unit of formula -CH2 - R - CH2 ~ ~H~ IIA
(CH2R30H)a 2 where R, R , and a each have the meaning previously assigned and R is the residue of a phenolic compound after removal of a phenolic hydroxyl group and 2 nuclear hydrogen atoms.
.?~
69~;~
Examples of suitable phenolic compounds are phenol, p-cresol, resorcinol, catechol, bis(p-hydroxyphenyl)methane, 2,2-bis(p-hydroxy-phenyl)propane, 2,2-bis(p-hydroxyphenyl)sulphone, p-ethylphenol, p-tert.-butylphenol, _-tert.octy].phenol, o-phenylphenol, p-phenylphenol, pyrogallol, phloroglucinol, and 2-naphthol.
In formula I, R preferably denots a group of any of formulae III
to VII
III IV
~~ ' '~
V VI
and .' ~
VII
and in formula IA, R preferably denotes a group of any of . formulae III, IV, and VII.
Particularly preferred specific examples of compounds of formula I or IA are p-xylylene glycol dimethyl ether and p-xylylene dichloride, and their 2,2,5,6-tetrachloro derivati~es.
Suitable non-phenolic compounds containing one or more aromatic ..~
~6~2 nuclei, which may be employed with the phenolic compound as component (ii) to modify the properties of the Friedel-Crafts resin, are those capable of - condensation with the aralkyl ether or aralkyl halide (i) under the reaction conditions employed to form the Friedel-Crafts resin and are preferably aromatic hydrocarbons or aromatic ethers (including thioethers). Specific examples of such compounds containing aromatlc nuclei are diphenyl ether, dibenzyl ether, terphenyl, diphenyl sulphide, diphenyl, anthracene, and naph~halene. Diphenyl sulphone and triphenyl phosphate are examples of other compounds which may be used.
10 When a non-phenolic compound containing one or more aromatic nuclei is employed, it is not then essential that the phenolic compound should itself be in molar excess over the aralkyl halide and/or aralkyl ether, provided that the total of the phenolic compound and the compound containing aromatic nuclei taken together represents the required molar excess.
The heat-activated curing agent (c) for the Friedel-Crafts resin is any agent suitable for curing novolac resins, although it must, of course, have negligible curing effect on the resin at the temperature at which photopolymerisation is carried out. These agents are usually some form of formaldehyde or a formaldehyde donor, or else a compound containing more than one 1,2-epoxide group on average per molecule.
Hexamethylenetetramine is strongly preferred among formaldehyde donors but, e.g., p-benzoquinone~ chloranil, anhydroformaldehyde-aniline (i.e., hexahydro-1,3,5-triphenyltriazine, ethylenediamine-formaldehyde (i.e., 1,4,6,9-tetrazatricyclo L4.4.1.14'9~ dodecane), and N-methylol derivatives of urea or of melamine may also be used.
As already indicated, epoxide resins, i.e., compounds containing more than one 1,2-epoxide group per molecule on average, may be used as heat-curing agents, they reacting with phenolic hydroxyl groups of ~6C~2 the Friedel-Crafts resin.
In the usual methods of manufacturing epoxide resins, mixtures of compounds of differing molecular weight are obtained, these mixtures ordinarily containing a proportion of compounds whose epoxide groups 5 have undergone partial hydrolysis. The average number of 1,2-epoxide r groups per molecule of the resin need not be an integer of at least 2;
it is generally a fractional number but must in any case be greater than 1Ø
Examples of epoxide resins which may be used are polyglycidyl and 10 poly(~-methylglycidyl) esters obtainable by reaction of a substance containing two or more carboxylic acid groups with epichlorohydrin, glycerol dichlorohydrin, or ~-methylepichlorohydrin in the presence of alakali. Such esters may be derived from aliphatic carboxylic acids, e.g., oxalic acid, succinic acid, adipic acid, sebacic acid, and dimerised 15 and trimerised linoleic acid, from cycloaliphatic carboxylic acids such as hexahydrophthalic acid, 4-methylhexahydrophthalic acid, tetrahydrophthalic acid, and 4-methyltetrahydrophthalic acid, and from aromatic carboxylic acids such as phthalic acid, isophthalic acid, and terephthalic acid.
Other epoxide resins which may be used include polyglycidyl and 20 poly(~-methylglycidyl) ethers, such as those obtainable by reaction of a substance containing at least two alcoholic hydroxyl groups or at least two phenolic hydroxyl groups with the appropriate epichlorohydrin or glycerol dichlorohydrin under alkaline conditions or, alternatively, in the presence of an acidic catalyst with subsequent treatment with 25 alkali. Such ethers may be derived from aliphatic alcohols, for example, ethylene glycol, diethylene glycol, triethylene glycol, and higher poly(oxyethylene) glycols, propylene glycol and poly(oxypropylene) glycols, propane-1,3-diol, butane-1,4-diol, pentane-1,5-diol, hexane-l, 6-diol, hexane-1,2,6-triol, glycerol, l,l,l-trimethylolpropane, and z pentaerythritol; from cycloaliphatic alcohols such as quinitol, 1,1-bis(hydroxymethyl)cyclohex-3-ene, bis(4-hydroxycyclohexyl)methane, and 2,2-bis(4-hydroxycyclohexyl)propane; and from alcohols containing aromatic nuclei, such as N,N-bis(2-hydroxyethyl)aniline and 4,4-bis(2-hydroxyethylamino)diphenylmethane. Preferably the ethers are polyglycidylethers of an at least dihydric phenol, for example, resorcinol, catechol, hydroquinone, bis(4-hydroxyphenyl)methane, 1,1,2,2-tetrakis(4-hydroxy-phenyl)ethane, 4,4'-dihydroxydiphenyl, bis(4-hydroxyphenyl) sulphone, and phenol-formaldehyde, alkylphenol-formaldehyde and chlorophenol-formaldehyde novolac resins, 2,2-bis(4-hydroxyphenyl)propane (otherwise known as bisphenol A), and 2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane.
There may further be employed poly(N-glycidyl) and poly(N-B-methyl-glycidyl compounds, for example, those obtained by dehydrochlorination of the reaction products of the epichlorohydrin and amines containing at least two hydrogen atoms directly attached to nitrogen, such as aniline, n-butylamine, bis(4-aminophenyl)methane, bis(4-aminophenyl) sulphone, and bis(4-methylaminophenyl)methane. Other poly(N-glycidyl) compounds that may be used include triglycidyl isocyanurate, N,N'-diglycidyl derivatives of cyclic alkylene ureas such as ethyleneurea and l,3-propyleneurea, and N,N'-diglycidyl derivatives of hydantoins such as 5,5-dimethylhydantoin.
Other epoxide resins which may be used include bis(2,3-epoxycyclopentyl) ether, 2,3-epoxycyclopentyl glycidyl ether, and 1,2-bis(2',3'-epoxy-cyclopentyloxy)ethane.
Especially suitable .poxide resins are polyglycidyl ethers ofpolyhydric phenols such as 2,2-bis(4-hydroxyphenyl)propane, bis(4-hydroxyphenyl~methane, or of a novolac from phenol ( which may be substituted in-the ring by chlorine or a hydrocarbon alkyl group of from 1 to 4 carbon atoms) and form-aldehyde, having an epoxide content of at least l.O epoxide equivalent per kilogram.
Ordinarily, from 1 to 20, and especially 5 to 15, parts by weight of the heat-activated curing agent is employed per 100 parts by weight of the Friedel-Crafts resin. It is convenient to dissolve or suspend the curing agent in the liquid composition before impregnation or irradiation.
The curing effect of hexamine may be accelerated by incorporating zinc borate, salicylic acid, benzilic acid, benzoic acid, cinnamic acid, hydrocinnamic acid, p-hydroxybenzoic acid, ~-naphthoic acid, phenylacetic acid, p-toluic acid, or toluene-p-sulphonic acid.
The curing effect of epoxide resins may be accelerated by incorporating amino compounds, especially tertiary amines.
The photopolymerisable compound (e) used in the processes of the present invention may be of any chemical type known to polymerise under influence of actinic radiation. Such materials are described in, for example, Kosar, "Light-sensitive Systems: Chemistry and Applications of Non-Silver Halide Photographic Processes", ~iley, New York, 1965. As is well known, ,hese materials fall into two main classes -(i) those which are polymerised through a free-radical chain reaction (photoinitiated polymerisation) and (ii) those in which polymerisation is effected by reaction of an excited molecule of the monomer with an unexcited lecule of the monomer.
The first type require only one photopolymerisable group per molecule to form long chains on polymerisation, while the second type must have at least two photopolymerisable groups per molecule, since if they have only one such group per lecule they will dimerise, but not polymerise, on irradiation.
- 13 ~
Z
Photopolymerisable substances of the first type preferred for use in this invention have one ethylenic linkage, or more than one providing they are unconjugated. Examples of these substances are styrene and crotonic acid and, preferably, acrylic esters containing at least one group or the general formula VIII, IX, or X
CH2 = C(R )COO - VIII
CH2 = C(R )CO~H ~ CHCOO- IX
CH2 = C(R )CONHCH(OH)CH2COO- X
where R is a hydrogen, chlorine, or bromine atom, or an alkyl hydrocarbon group of 1 to 4 carbon atoms, especially a hydrogen atom or a methyl group. More specific examples of preferred acrylates are neopentyl glycol diacrylate and those given below under formulae XXIII, XXIV, and XXVI to XXVIII.
Photopolymerisable materials of the second type include those having at least two, and preferably three or more, groups which are azido, coumarin, stilbene, maleimide, pyridinone, chalcone, propenone, or pentadienone groups, or acrylic acid groups which are substituted in their 3- position by groups having ethylenic unsaturation or aromaticity in conjugation with the ethylenic double bond of the acrylic group.
Examples of suitable a~ides are those containing at least two groups of the formula or ~6~
where R5 denotes a mononuclear or dinuclear divalent aromatic radical containing from 6 to 12 carbon atoms, especially a phenylene or naphthylene group.
Examples of suitable coumarins are those containing groups of the formula CO~o ~ R6 XIII
where R is an oxygen atom, a carbonyloxy group (-C00-), a sulphonyl group, or a sulphonyloxy group.
Examples of photopolymerisable materials containing stilbene groups are those having groups of the formula R? ~ CH=CH ~ XIV
where R is the residue, containing up to 8 carbon atoms in all, of a five or six-membered, nitrogen-containing heterocyclic ring, fused to a benzene or naphthalene nucleus, and linked through a carbon atom of the said heterocyclic ring adjacent to a nitrogen hetero atom thereof to the indicated benzene nucleus, such as a benzimidazolyl, benzoxazolyl, benzotriazolyl, benzothiazolyl, or a naphthotriazolyl residue.
Examples of photopolymerisable substances containing maleimide units are those having groups of the formula " - ~
69~2 lc~
directly attached to carbon atoms, where each R is an alkyl group of 1 to 4 carbon atoms, a chlorine atom, or a phenyl group, especially a methyl group.
Examples of photopolymerisable substances containing pyridinone units are those having, directly attached to carbon atoms, groups of the formula .
b ~ O XVI
where R is an aliphat;c or cycloaliphatic radical of 1 to 8 carbon atoms and b is zero or an integer of 1 to 4.
Examples of compounds containing chalcone, propenone, or pentadienone groups are those containing structures of formula ~ ~ 12 or ,~ Rll~;~Rl2 RVIII
where each R is a halogen atom, or an alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkoxy, cycloalkoxy, alkenoxy, cycloalkenoxy, carbalkoxy, carbocycloalkoxy, carbalkenoxy, or carbocycloalkenoxy group, such organic S groups containing 1 to 9 carbon atoms, or a nitro group, or a carboxyl, sulphonic, or phosphoric acid group in the form of a salt, b has the meaning previously assigned, R represents a grouping of formula ~ Cd = C ~ C ~ C - CH ~ XIX
or I CH = C - C - XX
c f = CH ~ Rl7 or R16 o -CH = C - C ~ R17 XXI
where R and R are each individually a hydrogen atom, an alkyl group, e.g., of l to 4 carbon atoms, or an aryl group, e.g., of up to 12 carbon atoms, preferably a mononuclear group such as a phenyl group, or conjointly denote a polymethylene chain of 2 to 4 methylene groups, R 6 and R 7 are each a hydrogen atom, an alkyl group, e.g., of l to 4 carbon atoms, or an aryl group, e.g., of up to 12 carbon atoms, - 17 ~
-3~ .
preferably a mononuclear group such as a phenyl group, c and d are each zero, 1, or 2, with the proviso that they are not both zero, R represents a valency bond or a hydrogen atom, and R represents an oxygen or sulphur atom.
Suitable 3- substituted acrylates contain groups of the general formula R13cH=c(R4)coo- XXII
where R 8 is an aliphatic or mononuclear aromatic, araliphatic, or heterocyclic group, preferably of not more than 12 carbon atoms, which, as already indicated, has ethylenic unsaturation or aromaticity in conjugation with the ethylenic double bond shown, such as a phenyl, 2-furyl, 2- or 3-pyridyl, prop-2-enyl, or styryl group, and R has the meaning previously assigned.
Specific examples are disorbates and bis(2-furylacrylates) of polytoxyethylene) glycols and poly(oxypropylene) glycols.
If desired, a mixture of photopolymerisable compounds may be used.
Especially preferred photopolymerisable compounds used in processes of this invention are neopentyl glycol diacrylate and esters of acrylic acid which are of any of the following general formulae XXIII, XXIV, and X~VI to XXVIII.
~ormula XXIII is CH 2 = CHCOO ~ (CH2)f - (CHRl9) - CHO ~ OCCH = CH2 R g . -:
~' ~
9~Z
where e is zero or 1, f is an integer of 1 to 8, g is an integer of 1 to 20, S R denotes -H, -OH, or -OOCCH=CH2, and R denotes -H, -CH3, -C2H5, -CH20H, or -CH200CCH=CH2.
Examples of compounds of formula XXIII are triethylene glycol diacrylate and tetraethylene glycol diacrylate.
Formula XXIV is Ch2 = CUCOO ~ (C~2)h L ~ ~ ~ R
where e, g, and R have the meanings assigned above, h is zero or a positive integer, preferably of not more than 8, provided that e and h are not both zero, i is an integer of from 1 to 4, R21 denotes -H -Cl -CH3, or -C2H , and R22 denotes an organic radical of valency i, linked through a carbon atom or carbon atoms thereof to the indicated i terminal oxygen atoms, preferably the hydrocarbon residue of an aliphatic alcohol containing from 1 to 6 carbon atoms, such as -CH3 or
2 ~ / 2 / C XXV
~69{~2 A specific example of a compound of formula XXIV is 2-methoxyethyl acrylate.
Formula XXVI is [ CH2 = CHCO-~-CH2CHCH2-0(cO)e ~ R
OH
where e and i have the meanings previously assigned and R 3 denotes an organic radical of valency J, linked through a carbon atom thereof, other than the carbon atom of a carbonyl group.
More particularly, when e is zero, R 3 may denote the residue, ~ containing from 1 to 18 carbon atoms, of an alcohol or phenol having i hydroxyl groups.
R may thus represent, for example an aromatic group (which may be substituted in the ring by alkyl groups), an araliphatic, cycloaliphatic, heterocyclic, or heterocyclo-aliphatic group, such as an aromatic group containing only one benzenering, optionally substituted by a chlorine atom or atoms or by one or more alkyl groups each of from 1 to 9 carbon atoms, or an aromatic group comprising a chain of two benzene rings, optionally interrupted by an ether oxygen atom, an aliphatic hydrocarbon group of 1 to 4 carbon atoms, or a sulphone group, each benzene ring being optionally substituted by a chlorine atom or atoms or by one or more alkyl groups, each of from 1 to 6 carbon atoms, or, preferably, a saturated or ethylenically unsaturated, straight or branched-chain aliphatic group, which may contain one or more ether oxygen linkages and which may be substituted by one or re hydroxyl groups, especially a saturated or monoethylenically-unsaturated straight chain aliphatic hydrocarbon group of from 1 to 8 carbon atoms.
Specific examples of such groups are the aro7~atic groups of the formulae -C6H5 and -C6H4CH3, in which case ~ is 1, -C6H4C(CH3)2 C6H4- and C6H4CH2C6H4~, in which case J is 2, and -C6H4(CH2C6H3~kCH2C6H4-, where _ is 1 or 2, in which case i is 3 or 4, and the aliphatic groups of formula -CH2CHCH2- or -CH2CH(CH2)3CH2-, in which case i is 3, or -(CH2)4, -CH2CH=CHCH2-, -CH2CH20CH2CH2-, or -(CH20CH20)2CH2CH2-, in which case i is 2, or -(CH2)3CH3, -(CH2)40H, -CH2CH=CH2, -(CH2)20H, -CH2CH(CH3)0H, in which case J is 1.
When e is 1, R23 may represent the residue, containing from 1 to 60 carbon atoms, of an acid having ~ carboxyl groups, preferably a saturated or ethylenically-unsaturated straight chain or branched aliphatic hydrocarbon group of from 1 to 20 carbon atoms, which may be substituted by one or more chlorine atoms and which may be interrupted by one or more ether oxygen atoms and/or by one or more carbonyloxy groups, or a saturated or ethylenically-unsaturated cycloaliphatic or aliphatic-cycloaliphatic hydrocarbon group of at least 4 carbon atoms, or an aromatic hydrocarbon group of from 6 to -12 carbon atoms, which may be substituted by one or more chlorine atoms.
Further preferred are such compounds in which R represents a saturated or ethylenically-unsaturated straight chain or branched aliphatic hydrocarbon group of from l to 8 carbon atoms, optionally substituted by a hydroxyl group, or a saturated or ethylenically-unsaturated straight chain or branched aliphatic hydrocarbon group of from 4 to 50 carbon atoms and interrupted in the chain by one or more carbonyloxy groups, or a satuFated or ethylenically-unsaturated monocyclic or dicyclic - 21 ~
cycloaliphatic hydrocarbon group of 6 to 8 carbon atoms, or an ethylenically-unsaturated cycloaliphatic-aliphatic hydrocarbon group of from 10 to 51 carbon atoms, or a mononuclear aromatic hydrocarbon group of from 6 to 8 carbon atoms.
Specific examples of these residues of carboxylic acids are those
~69{~2 A specific example of a compound of formula XXIV is 2-methoxyethyl acrylate.
Formula XXVI is [ CH2 = CHCO-~-CH2CHCH2-0(cO)e ~ R
OH
where e and i have the meanings previously assigned and R 3 denotes an organic radical of valency J, linked through a carbon atom thereof, other than the carbon atom of a carbonyl group.
More particularly, when e is zero, R 3 may denote the residue, ~ containing from 1 to 18 carbon atoms, of an alcohol or phenol having i hydroxyl groups.
R may thus represent, for example an aromatic group (which may be substituted in the ring by alkyl groups), an araliphatic, cycloaliphatic, heterocyclic, or heterocyclo-aliphatic group, such as an aromatic group containing only one benzenering, optionally substituted by a chlorine atom or atoms or by one or more alkyl groups each of from 1 to 9 carbon atoms, or an aromatic group comprising a chain of two benzene rings, optionally interrupted by an ether oxygen atom, an aliphatic hydrocarbon group of 1 to 4 carbon atoms, or a sulphone group, each benzene ring being optionally substituted by a chlorine atom or atoms or by one or more alkyl groups, each of from 1 to 6 carbon atoms, or, preferably, a saturated or ethylenically unsaturated, straight or branched-chain aliphatic group, which may contain one or more ether oxygen linkages and which may be substituted by one or re hydroxyl groups, especially a saturated or monoethylenically-unsaturated straight chain aliphatic hydrocarbon group of from 1 to 8 carbon atoms.
Specific examples of such groups are the aro7~atic groups of the formulae -C6H5 and -C6H4CH3, in which case ~ is 1, -C6H4C(CH3)2 C6H4- and C6H4CH2C6H4~, in which case J is 2, and -C6H4(CH2C6H3~kCH2C6H4-, where _ is 1 or 2, in which case i is 3 or 4, and the aliphatic groups of formula -CH2CHCH2- or -CH2CH(CH2)3CH2-, in which case i is 3, or -(CH2)4, -CH2CH=CHCH2-, -CH2CH20CH2CH2-, or -(CH20CH20)2CH2CH2-, in which case i is 2, or -(CH2)3CH3, -(CH2)40H, -CH2CH=CH2, -(CH2)20H, -CH2CH(CH3)0H, in which case J is 1.
When e is 1, R23 may represent the residue, containing from 1 to 60 carbon atoms, of an acid having ~ carboxyl groups, preferably a saturated or ethylenically-unsaturated straight chain or branched aliphatic hydrocarbon group of from 1 to 20 carbon atoms, which may be substituted by one or more chlorine atoms and which may be interrupted by one or more ether oxygen atoms and/or by one or more carbonyloxy groups, or a saturated or ethylenically-unsaturated cycloaliphatic or aliphatic-cycloaliphatic hydrocarbon group of at least 4 carbon atoms, or an aromatic hydrocarbon group of from 6 to -12 carbon atoms, which may be substituted by one or more chlorine atoms.
Further preferred are such compounds in which R represents a saturated or ethylenically-unsaturated straight chain or branched aliphatic hydrocarbon group of from l to 8 carbon atoms, optionally substituted by a hydroxyl group, or a saturated or ethylenically-unsaturated straight chain or branched aliphatic hydrocarbon group of from 4 to 50 carbon atoms and interrupted in the chain by one or more carbonyloxy groups, or a satuFated or ethylenically-unsaturated monocyclic or dicyclic - 21 ~
cycloaliphatic hydrocarbon group of 6 to 8 carbon atoms, or an ethylenically-unsaturated cycloaliphatic-aliphatic hydrocarbon group of from 10 to 51 carbon atoms, or a mononuclear aromatic hydrocarbon group of from 6 to 8 carbon atoms.
Specific examples of these residues of carboxylic acids are those
3,~ CH2CH3, -CH2CH(OH)CH3, -CH Cl a d C H
which case i is 1, and -CH2CH2-, -CH=CH-, and -C6H4-, in which case J is 2.
Specific examples of suitable compounds of formula XXVI are 1,4-bis(2-hydroxy-3-(acryloxy)propoxy)butane, a poly(2-hydroxy-3-(acryloxy)propyl) ether of a phenol-formaldehyde novola~, 1-(2-hydroxy-3-(acryloxy)propoxy)-butane, -n-octane, and -n-decane, bis(2-hydroxy-3-(acryloxy)propyl) adipate, 2-hydroxy-3-(acryloxy)propyl propionate, and 3-phenoxy-2-hydroxypropyl acrylate.
Formula XXVII is R C ~ CH200CCH=CH2~
vhere R denotes CH3-, C2H5-, or CH2=CHCOOCH2-.
Examples of such acrylates are pentaerythritol tetra-acrylate and l,l,l-trimethylolpropane triacrylate.
Formula XXVIII is CH2 = CHCOOR
where R25 denotes either an alkyl group of 1 to 6 carbon atoms, optionally substituted by one hydroxyl group, such as an ethyl, n-propyl, n-butyl, 2-hydroxyethyl, or 2-hydroxypropyl group~ or a dialkylaminoalkyl 69~2 group containing in all 3 to 12 carbon atoms, such as a diethylaminoethyl - group.
The lar ratio of the Friedel-Crafts resin to photopolymerisable compound is such that there is sufficient of each present to form both a satisfactory heat-curable composite and a satisfactory heat-cured composite.
Usually the molar ratio is from 10:1 to 1:10, and especially from 5:1 to 1:5.
Preferably the photopDlymerisable compound is irradiated in the presence of a photopolymerisation catalyst. Suitable catalyst are well known and are described in, for example, the book by Kosar cited above.
Like the photopolymerisable compounds, the catalysts fall into two main classes -(i) those which, on irradiation, give an excited state that leadsto formation of free radicals which then initiate polymerisation of the monomer (photoinitiators) and (ii) those which, on irradiation, give an excited state which in turn transfers its excitation energy to a molecule of the monomer, giving rise to an excited molecule of the monomer which then crosslinks with an unexcited molecule of the monomer (photosensitisers).
The first class includes organic peroxides and hydroperoxides, ~-halogen-substituted acetophenones such as trichloromethyl 4'-tert.
butylphenyl ketone, benzoin and its alkyl ethers, e.g., the n-butyl ether, ~-methylbenzoin, benzophenones, 0-alkoxycarbonyl derivatives of an oxime of benzil or of l-phenylpropane-1,2-dione, such as benzil (0-ethoxycarbonyl)-~-monoxime and 1-phenylpropane-1,2-dione-2-(0-ethoxycarbonyl)oxime, benzil acetals, e g., its dimethyl acetal, substituted thioxanthones, e.g., 2-chlorothioxanthone, anthraquinones, and mixtures of a phenothiazine dye (e.g., methylene blue) or a quinoxaline (e.g., metal salts of 2-(m or p-11~69~2 methoxyphenyl)quinoxaline-6'- or 7'-sulphonic acids) with an electron donor such as benzenesulphinic acid, toluenesulphinic acid, or other sulphinic acid or salt thereof such as the sodium salt, an arsine, a phosphine, or thiourea (photoredox systems), these initiators being used with unsaturated esters, especially acrylates and methacrylates and also acrylamides.
The second class includes 5-nitroacenaphthene, 4-nitroaniline, 2,4,7-trinitro-9-fluorenone, 3-methyl-1,3-diaza-1,9-benzanthrone, and bis(dialkylamino)benzophenones, especially Michler's ketone, i.e., bis(p-dimethylamino)benzophenone.
Suitable photopolymerisation catalysts are readily found by routine experimentation. The catalyst must not, of course, give rise to a substantial degree of photoinduced polymerisation of the Friedel-Crafts - resin, neither should any other substance present: further, they mustnot cause curing of the Friedel-Crafts resin such that the resin does not remain substantially ther settable.
Generally, 0.1 to 20%, and preferably 0.5 to 10%, by weight of the photopolymerisation catalyst is incorporated, based on the weight of the photopolymerisable compound.
In the photopolymerising step actinic radiation of wavelength 200-600 nm is preferably used. Suitable sources of actinic radiation include -carbon arcs, mercury vapour arcs, fluorescent lamps with phosphors emitting ultraviolet light, argon and xenon glow lamps, tungsten lamps, and photographic flood lamps. Of these, mercury vapour arcs, particularly sun lamps, fluorescent sun lamps, and metal halide lamps are most suitable. The time required for the exposure of the photopolymerisable compound will depend upon a variety of factors which include, for example, the individual i9~;~
compound used, the amount of that compound on the reinforce~ent, the type of light source, and its distance from the impregnated material.
Suitable times may be readily determined by those familiar with photopolymerisation techniques, but in all cases the product after photopolymerisation must still be curable by heating: for this reason, photopolymerisation is carried out at temperatures below those at which curing of the Friedel-Crafts resin becomes substantial.
The temperature and duration of heating required for the thermal curing are readily found by routine experimentation and easily derivable from what is readily well known concerning the heat-curing of novolac resins.
The Friedel-Crafts resin, the photopolymerisable compound, the heat-curing catalyst, and, if used, the catalyst for the photopolymerisation, are preferably applied so that the composite contains a total of from 20 to 80% by weight of the said components and, correspondingly, 80 to 20% by weight of the reinforcement. More preferably, a total of 30 to 50% by weight of these components and 70 to 50% by weight of the reinforcement are employed.
As already indicated, when the Friedel-Crafts resin and the photopolymerisable compound are applied as a film, the components are caused to flow about the fibrous material by applying heat and/or pressure.
Heated platens or pairs of rollers may be used, for example, and in the latter case, when unidirectional fibres are used, a rolling pressure may be applied in the direction of the fibre alignment. In place of pairs of rollers, the assembly may be passed under tension around part of the periphery of a single roller.
The film may be provided with a strippable backing sheet, e.g., of a polyolefin or a polyester, or of cellulosic paper having a coating of a silicone release agent, on the face opposite to that brought into contact . - 25 ~
69~2 with the fibrous reinforcement. Manipulation of the assembly is often easier if the film has a tacky surface. This may be produced by coating the film with a substance which is tacky at room temperature but which cures to a hard, insoluble, infusible resin under the conditions of heat S employed to cure the Friedel-Crafts resin component of the film. However, an adequate degree of tackiness often exists without additional treatment.
Prepregs may be made by a batch process, the fibrous reinforcing material being laid on the film of the photopolymerised composition which is advantageously under slight tension, when a second such film may, if desired, be laid on top and then the assembly is pressed while being heated.
Prepregs may also be made continuously, such as by contacting the fibrous reinforcing material with the film of the photopolymerised composition, then, if desired, placing a second such film on the reverse face of the fibrous reinforcing material, and then applying heat and pressure.
More conveniently, two such films, preferably supported on the reverse side by belts or strippable sheets, are applied simultaneously to the fibrous reinforcing material so as to contact each exposed face.
When two such films are applied, they may be the same or different.
Multilayer prepregs may be made by heating under pressure interleaved films and layers of one or re fibrous reinforcing materials.
When unidirectional fibres are the reinforcement material, successive layers of them may be oriented to form cross-ply prepregs. With the fibrous reinforcing material there may be used additional, non-fibrous, types of reinforcement, such as a foil of a metal (e.g., aluminium, steel, or titanium), or a sheet of a plastics material (e.g., an aromatic or aliphatic polyamide, a polyimide, a polysulphone, or a polycarbonate) or of a rubber (e.g., a neoprene or acrylonitrile rubber).
~ 26 -9~2 In the production of sheet moulding compositions a mixture of the Friedel-Crafts resin, the heat-activated curing agent for novolac resins, the photopolymerisable compound, and, if used, the photopolymerisation catalyst, together with the chopped strand reinforcing material and any other components, are exposed to irradiation in layers through supporting sheets.
The following Examples illustrate the invention. Temperatures are in degrees Celsius and, unless otherwise indicated, parts are by weight.
Epoxide contents were determined by titration against a O.LN solution of perchloric acid in glacial acetic acid in the presence of excess of tetraethylammonium bromide, crystal violet being used as the indicator.
Flexural strengths are the mean of three results and were determined according to BS 27~2, Method 304B.
Materials used in the Examples were obtained as follows:
9~
Acrylate A
This, which is substantially l-phenoxy-2-hydroxypropyl acrylate, was prepared in the following manner.
To 500 g of phenyl glycidyl ether of epoxide content 6.16 equiv./
kg containing tetramethylammonium chloride (1.5 g) and 2,6-di-tert.
butyl-p-cresol ( 1 g) at 100 was added with stirring over 1 hour 222 g of acrylic acid. The mixture was stirred for a further 4 hours at 100 , by which time its epoxide content had fallen to 0.~2 equiv./kg, affording the desired acrylate.
10` Friedel-Crafts Resin A
This denotes a com~ercially-available solid resin which is substantially of the formula OH OH OH
~3CH2~ CH2~CH~}'~ CH2 ~
k XXIX
where k is zero or a positive integer of value up to 6 or more, and has an average value of 1.6.
Sorbate A
- To a stirred solu~ion of 100 g of polyoxyethylene glycol ( having an aYerage molecular weight of 200), 110 g of triethylamine,and 500 ml of toluene at room temperature was added 130.5 g of sorboyl chloride over 30 minutes. The mixture was then stirred at 80 for 1 hour, cooled, and filtered. Removal of the solvent under reduced pressure gave the desired polyoxyethylene disorbate.
9~Z
EX~PLE I
Friedel-Crafts Resin A (S0 parts), 6 parts of hexamethylenetetramine, and 1 part of benzil dimethyl acetal were dissolved in 50 parts of Acrylate A. This liquid composition was used to make a glass cloth prepreg S in the following manner.
Glass cloth (epoxysilane treated, plain weave, weighing 200 g/m2) was impregnated with the composition and then exposed on both sides for three minutes to 400 W high pressure metal halide quartz arc lamps emitting pre-dominantly in the 365 waveband to give a prepreg.
A six-ply laminate was then prepared by pressing six 10 cm-square pieces of the prepreg for 1 hour at 170 at a pressure of 1.4 MN/m2. The laminate, which consisted of 51.9% of glass, had a flexural strength of - 199 MN/m2 25 lS Friedel-Crafts Resin A (S0 parts), 6 parts of hexamethylene-tetramine, and 2 parts of benzoin-n-butyl ether were dissolved in 50 parts of neopentyl glycol diacrylate. A unidirectional carbon fibre prepreg was made with this liquid composition by applying a layer of the composition 36 ~m thick on siliconised paper, irradiating for 4 minutes with a 400W metal halide quartz arc lamp, and pressing the film so obtained onto both sides of unidirectional carbon fibre tl.8 tows/cm; weight per tow 0.2 g/m) for 10 minutes at 100 under an applied pressure of 0.07 MN/m .
A six-ply laminate was prepared from this prepreg by pressing six 25 10 cm-square pieces for 1 hour at 170 at a pressure of 1.4 MN/m . The laminate" which consisted of 49.1% of carbon fibres, had a flexural strength of 405 MN/m2 at 25.
- 29 ~
6~Z
.
Six 10 cm-square pieces of a cloth composed of fibres of poly(_-phenylene terephthalamide) were impregnated with a composition comprising 10 parts of Sorbate A, 10 parts of Friedel-Crafts Resin A, 10 parts of a polyglycidyl ether (epoxide content 5.48 equiv~/kg) of a novolac of number average lecular weight 420 formed from phenol and formaldehyde (1:0.75 moles), and 0.3 part of Michler's ketone. The impregnated sheets were exposed for 4 minutes to irradiation from a lamp as used in Example 1 to obtain tack-free prepregs. A six-ply laminate was then made from the sheets by heating for 1 hour at 170 , a pressure of l.4 MN/m2 being applied after a dwell time of 3 minutes. The laminate was then post-cured by heating for 2 hours at 200 ; its fibre content was 64.9%, and its flexural strength at 25 was 164 MN/m2.
which case i is 1, and -CH2CH2-, -CH=CH-, and -C6H4-, in which case J is 2.
Specific examples of suitable compounds of formula XXVI are 1,4-bis(2-hydroxy-3-(acryloxy)propoxy)butane, a poly(2-hydroxy-3-(acryloxy)propyl) ether of a phenol-formaldehyde novola~, 1-(2-hydroxy-3-(acryloxy)propoxy)-butane, -n-octane, and -n-decane, bis(2-hydroxy-3-(acryloxy)propyl) adipate, 2-hydroxy-3-(acryloxy)propyl propionate, and 3-phenoxy-2-hydroxypropyl acrylate.
Formula XXVII is R C ~ CH200CCH=CH2~
vhere R denotes CH3-, C2H5-, or CH2=CHCOOCH2-.
Examples of such acrylates are pentaerythritol tetra-acrylate and l,l,l-trimethylolpropane triacrylate.
Formula XXVIII is CH2 = CHCOOR
where R25 denotes either an alkyl group of 1 to 6 carbon atoms, optionally substituted by one hydroxyl group, such as an ethyl, n-propyl, n-butyl, 2-hydroxyethyl, or 2-hydroxypropyl group~ or a dialkylaminoalkyl 69~2 group containing in all 3 to 12 carbon atoms, such as a diethylaminoethyl - group.
The lar ratio of the Friedel-Crafts resin to photopolymerisable compound is such that there is sufficient of each present to form both a satisfactory heat-curable composite and a satisfactory heat-cured composite.
Usually the molar ratio is from 10:1 to 1:10, and especially from 5:1 to 1:5.
Preferably the photopDlymerisable compound is irradiated in the presence of a photopolymerisation catalyst. Suitable catalyst are well known and are described in, for example, the book by Kosar cited above.
Like the photopolymerisable compounds, the catalysts fall into two main classes -(i) those which, on irradiation, give an excited state that leadsto formation of free radicals which then initiate polymerisation of the monomer (photoinitiators) and (ii) those which, on irradiation, give an excited state which in turn transfers its excitation energy to a molecule of the monomer, giving rise to an excited molecule of the monomer which then crosslinks with an unexcited molecule of the monomer (photosensitisers).
The first class includes organic peroxides and hydroperoxides, ~-halogen-substituted acetophenones such as trichloromethyl 4'-tert.
butylphenyl ketone, benzoin and its alkyl ethers, e.g., the n-butyl ether, ~-methylbenzoin, benzophenones, 0-alkoxycarbonyl derivatives of an oxime of benzil or of l-phenylpropane-1,2-dione, such as benzil (0-ethoxycarbonyl)-~-monoxime and 1-phenylpropane-1,2-dione-2-(0-ethoxycarbonyl)oxime, benzil acetals, e g., its dimethyl acetal, substituted thioxanthones, e.g., 2-chlorothioxanthone, anthraquinones, and mixtures of a phenothiazine dye (e.g., methylene blue) or a quinoxaline (e.g., metal salts of 2-(m or p-11~69~2 methoxyphenyl)quinoxaline-6'- or 7'-sulphonic acids) with an electron donor such as benzenesulphinic acid, toluenesulphinic acid, or other sulphinic acid or salt thereof such as the sodium salt, an arsine, a phosphine, or thiourea (photoredox systems), these initiators being used with unsaturated esters, especially acrylates and methacrylates and also acrylamides.
The second class includes 5-nitroacenaphthene, 4-nitroaniline, 2,4,7-trinitro-9-fluorenone, 3-methyl-1,3-diaza-1,9-benzanthrone, and bis(dialkylamino)benzophenones, especially Michler's ketone, i.e., bis(p-dimethylamino)benzophenone.
Suitable photopolymerisation catalysts are readily found by routine experimentation. The catalyst must not, of course, give rise to a substantial degree of photoinduced polymerisation of the Friedel-Crafts - resin, neither should any other substance present: further, they mustnot cause curing of the Friedel-Crafts resin such that the resin does not remain substantially ther settable.
Generally, 0.1 to 20%, and preferably 0.5 to 10%, by weight of the photopolymerisation catalyst is incorporated, based on the weight of the photopolymerisable compound.
In the photopolymerising step actinic radiation of wavelength 200-600 nm is preferably used. Suitable sources of actinic radiation include -carbon arcs, mercury vapour arcs, fluorescent lamps with phosphors emitting ultraviolet light, argon and xenon glow lamps, tungsten lamps, and photographic flood lamps. Of these, mercury vapour arcs, particularly sun lamps, fluorescent sun lamps, and metal halide lamps are most suitable. The time required for the exposure of the photopolymerisable compound will depend upon a variety of factors which include, for example, the individual i9~;~
compound used, the amount of that compound on the reinforce~ent, the type of light source, and its distance from the impregnated material.
Suitable times may be readily determined by those familiar with photopolymerisation techniques, but in all cases the product after photopolymerisation must still be curable by heating: for this reason, photopolymerisation is carried out at temperatures below those at which curing of the Friedel-Crafts resin becomes substantial.
The temperature and duration of heating required for the thermal curing are readily found by routine experimentation and easily derivable from what is readily well known concerning the heat-curing of novolac resins.
The Friedel-Crafts resin, the photopolymerisable compound, the heat-curing catalyst, and, if used, the catalyst for the photopolymerisation, are preferably applied so that the composite contains a total of from 20 to 80% by weight of the said components and, correspondingly, 80 to 20% by weight of the reinforcement. More preferably, a total of 30 to 50% by weight of these components and 70 to 50% by weight of the reinforcement are employed.
As already indicated, when the Friedel-Crafts resin and the photopolymerisable compound are applied as a film, the components are caused to flow about the fibrous material by applying heat and/or pressure.
Heated platens or pairs of rollers may be used, for example, and in the latter case, when unidirectional fibres are used, a rolling pressure may be applied in the direction of the fibre alignment. In place of pairs of rollers, the assembly may be passed under tension around part of the periphery of a single roller.
The film may be provided with a strippable backing sheet, e.g., of a polyolefin or a polyester, or of cellulosic paper having a coating of a silicone release agent, on the face opposite to that brought into contact . - 25 ~
69~2 with the fibrous reinforcement. Manipulation of the assembly is often easier if the film has a tacky surface. This may be produced by coating the film with a substance which is tacky at room temperature but which cures to a hard, insoluble, infusible resin under the conditions of heat S employed to cure the Friedel-Crafts resin component of the film. However, an adequate degree of tackiness often exists without additional treatment.
Prepregs may be made by a batch process, the fibrous reinforcing material being laid on the film of the photopolymerised composition which is advantageously under slight tension, when a second such film may, if desired, be laid on top and then the assembly is pressed while being heated.
Prepregs may also be made continuously, such as by contacting the fibrous reinforcing material with the film of the photopolymerised composition, then, if desired, placing a second such film on the reverse face of the fibrous reinforcing material, and then applying heat and pressure.
More conveniently, two such films, preferably supported on the reverse side by belts or strippable sheets, are applied simultaneously to the fibrous reinforcing material so as to contact each exposed face.
When two such films are applied, they may be the same or different.
Multilayer prepregs may be made by heating under pressure interleaved films and layers of one or re fibrous reinforcing materials.
When unidirectional fibres are the reinforcement material, successive layers of them may be oriented to form cross-ply prepregs. With the fibrous reinforcing material there may be used additional, non-fibrous, types of reinforcement, such as a foil of a metal (e.g., aluminium, steel, or titanium), or a sheet of a plastics material (e.g., an aromatic or aliphatic polyamide, a polyimide, a polysulphone, or a polycarbonate) or of a rubber (e.g., a neoprene or acrylonitrile rubber).
~ 26 -9~2 In the production of sheet moulding compositions a mixture of the Friedel-Crafts resin, the heat-activated curing agent for novolac resins, the photopolymerisable compound, and, if used, the photopolymerisation catalyst, together with the chopped strand reinforcing material and any other components, are exposed to irradiation in layers through supporting sheets.
The following Examples illustrate the invention. Temperatures are in degrees Celsius and, unless otherwise indicated, parts are by weight.
Epoxide contents were determined by titration against a O.LN solution of perchloric acid in glacial acetic acid in the presence of excess of tetraethylammonium bromide, crystal violet being used as the indicator.
Flexural strengths are the mean of three results and were determined according to BS 27~2, Method 304B.
Materials used in the Examples were obtained as follows:
9~
Acrylate A
This, which is substantially l-phenoxy-2-hydroxypropyl acrylate, was prepared in the following manner.
To 500 g of phenyl glycidyl ether of epoxide content 6.16 equiv./
kg containing tetramethylammonium chloride (1.5 g) and 2,6-di-tert.
butyl-p-cresol ( 1 g) at 100 was added with stirring over 1 hour 222 g of acrylic acid. The mixture was stirred for a further 4 hours at 100 , by which time its epoxide content had fallen to 0.~2 equiv./kg, affording the desired acrylate.
10` Friedel-Crafts Resin A
This denotes a com~ercially-available solid resin which is substantially of the formula OH OH OH
~3CH2~ CH2~CH~}'~ CH2 ~
k XXIX
where k is zero or a positive integer of value up to 6 or more, and has an average value of 1.6.
Sorbate A
- To a stirred solu~ion of 100 g of polyoxyethylene glycol ( having an aYerage molecular weight of 200), 110 g of triethylamine,and 500 ml of toluene at room temperature was added 130.5 g of sorboyl chloride over 30 minutes. The mixture was then stirred at 80 for 1 hour, cooled, and filtered. Removal of the solvent under reduced pressure gave the desired polyoxyethylene disorbate.
9~Z
EX~PLE I
Friedel-Crafts Resin A (S0 parts), 6 parts of hexamethylenetetramine, and 1 part of benzil dimethyl acetal were dissolved in 50 parts of Acrylate A. This liquid composition was used to make a glass cloth prepreg S in the following manner.
Glass cloth (epoxysilane treated, plain weave, weighing 200 g/m2) was impregnated with the composition and then exposed on both sides for three minutes to 400 W high pressure metal halide quartz arc lamps emitting pre-dominantly in the 365 waveband to give a prepreg.
A six-ply laminate was then prepared by pressing six 10 cm-square pieces of the prepreg for 1 hour at 170 at a pressure of 1.4 MN/m2. The laminate, which consisted of 51.9% of glass, had a flexural strength of - 199 MN/m2 25 lS Friedel-Crafts Resin A (S0 parts), 6 parts of hexamethylene-tetramine, and 2 parts of benzoin-n-butyl ether were dissolved in 50 parts of neopentyl glycol diacrylate. A unidirectional carbon fibre prepreg was made with this liquid composition by applying a layer of the composition 36 ~m thick on siliconised paper, irradiating for 4 minutes with a 400W metal halide quartz arc lamp, and pressing the film so obtained onto both sides of unidirectional carbon fibre tl.8 tows/cm; weight per tow 0.2 g/m) for 10 minutes at 100 under an applied pressure of 0.07 MN/m .
A six-ply laminate was prepared from this prepreg by pressing six 25 10 cm-square pieces for 1 hour at 170 at a pressure of 1.4 MN/m . The laminate" which consisted of 49.1% of carbon fibres, had a flexural strength of 405 MN/m2 at 25.
- 29 ~
6~Z
.
Six 10 cm-square pieces of a cloth composed of fibres of poly(_-phenylene terephthalamide) were impregnated with a composition comprising 10 parts of Sorbate A, 10 parts of Friedel-Crafts Resin A, 10 parts of a polyglycidyl ether (epoxide content 5.48 equiv~/kg) of a novolac of number average lecular weight 420 formed from phenol and formaldehyde (1:0.75 moles), and 0.3 part of Michler's ketone. The impregnated sheets were exposed for 4 minutes to irradiation from a lamp as used in Example 1 to obtain tack-free prepregs. A six-ply laminate was then made from the sheets by heating for 1 hour at 170 , a pressure of l.4 MN/m2 being applied after a dwell time of 3 minutes. The laminate was then post-cured by heating for 2 hours at 200 ; its fibre content was 64.9%, and its flexural strength at 25 was 164 MN/m2.
Claims (10)
1. Composites comprising (a) a fibrous reinforcing material, (b) a Friedel-Crafts resin, (c) a heat-activated curing agent for novolac resins, and (d) a photopolymerised compound, the resin (b) being one obtainable by a Friedel-Crafts reaction of (i) an aralkyl ether of the formula R(CH2OR1)a I
and/or an aralkyl halide of the formula R2(CH2X)a IA
where R is a divalent or trivalent aromatic hydrocarbon or hydrocarbonoxy radical, optionally containing one or more inert substituents on the aromatic nucleus or nuclei, each R1 is an alkyl radical of up to 5 carbon atoms, R2 is a divalent or trivalent aromatic hydrocarbon radical, optionally containing one or more inert substituents on the aromatic nucleus or nuclei, each X is a chlorine, bromine, or iodine atom, and a is 2 or 3, with a molar excess of (ii) a phenolic compound, or a mixture of a phenolic compound with a non-phenolic compound which contains one of more aromatic nuclei and which is capable of condensation with the aralkyl ether or aralkyl halide (i) under the reaction conditions employed to form the Friedel-Crafts resin, the said phenolic compound and, if used, the said non-phenolic compound, having at least two free nuclear hydrogen atoms per molecule, the phenolic compound being a benzenoid compound, or mixture of benzenoid compounds, containing from 1 to 3 hydroxyl groups directly attached to a benzene nucleus, there being a total of not more than 3 substituents attached to carbon atoms in that benzene nucleus.
and/or an aralkyl halide of the formula R2(CH2X)a IA
where R is a divalent or trivalent aromatic hydrocarbon or hydrocarbonoxy radical, optionally containing one or more inert substituents on the aromatic nucleus or nuclei, each R1 is an alkyl radical of up to 5 carbon atoms, R2 is a divalent or trivalent aromatic hydrocarbon radical, optionally containing one or more inert substituents on the aromatic nucleus or nuclei, each X is a chlorine, bromine, or iodine atom, and a is 2 or 3, with a molar excess of (ii) a phenolic compound, or a mixture of a phenolic compound with a non-phenolic compound which contains one of more aromatic nuclei and which is capable of condensation with the aralkyl ether or aralkyl halide (i) under the reaction conditions employed to form the Friedel-Crafts resin, the said phenolic compound and, if used, the said non-phenolic compound, having at least two free nuclear hydrogen atoms per molecule, the phenolic compound being a benzenoid compound, or mixture of benzenoid compounds, containing from 1 to 3 hydroxyl groups directly attached to a benzene nucleus, there being a total of not more than 3 substituents attached to carbon atoms in that benzene nucleus.
2. The composites of claim 1, in which R is a mononuclear, or fused dinuclear, or bridged dinuclear, benzenoid group.
3. The composites of claim 1, in which R2 is a mononuclear, or fused dinuclear, or bridged dinuclear, benzenoid group.
4. `The composites of claim 1, in which the curing agent (c) is formaldehyde, a formaldehyde donor, or a compound containing more than one 1,2-epoxide group on average per molecule.
5. The composites of claim 1, in which the component (d) has been photopolymerised through a free-radical chain reaction.
6. The composites of claim 1, in which the component (d) is produced by photopolymerisation of a compound hàving one ethylenic linkage, or more than one provided they are unconjugated.
7. The composites of claim 1, in which the component (d) has been obtained by photopolymerisation of an acrylate ester containing at least one group of any of the general formulae VIII, IX, and X
CH2 = C(R4)COO- VIII
IX
CH2 = C(R4)CONHCH(OH)CH2COO X
where R4 is a hydrogen, chlorine, or bromine atom, or an alkyl hydrocarbon group of 1 to 4 carbon atoms.
CH2 = C(R4)COO- VIII
IX
CH2 = C(R4)CONHCH(OH)CH2COO X
where R4 is a hydrogen, chlorine, or bromine atom, or an alkyl hydrocarbon group of 1 to 4 carbon atoms.
8. The composites of claim 1, in which the component (d) has been photopolymerised by reaction of an excited molecule of the monomer with an unexcited molecule of the monomer.
9. The composites of claim 1, in which the compound which has been photopolymerised to furnish component (d) contains at least two azido, coumarin, stilbene, maleimide, pyridinone, chalcone, propenone, or pentadienone groups, or at least two acrylic acid groups which are substituted in their 3- position by groups having ethylenic unsaturation or aromaticity in conjugation with the ethylenic double bond of the acrylic group.
10. The composites of claim 1, in which the compound which has been photopolymerised to furnish component (d) contains at least two groups of the formula R18CH = C(R4)COO XII
where R18 is an aliphatic or a mononuclear aromatic, araliphatic, or heterocyclic group which has ethylenic unsaturation or aromaticity in conjugation with the ethylenic double bond shown and R4 is a hydrogen, chlorine, or bromine atom, or an alkyl group of 1 to 4 carbon atoms.
where R18 is an aliphatic or a mononuclear aromatic, araliphatic, or heterocyclic group which has ethylenic unsaturation or aromaticity in conjugation with the ethylenic double bond shown and R4 is a hydrogen, chlorine, or bromine atom, or an alkyl group of 1 to 4 carbon atoms.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB2894877 | 1977-07-11 | ||
| GB28948/77 | 1977-07-11 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1106992A true CA1106992A (en) | 1981-08-11 |
Family
ID=10283783
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA307,031A Expired CA1106992A (en) | 1977-07-11 | 1978-07-07 | Reinforced composites containing a friedel-crafts resin |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1106992A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115141305A (en) * | 2022-07-06 | 2022-10-04 | 中国科学院赣江创新研究院 | Functional polymer, preparation method thereof and method for preparing ion imprinted polymer by using functional polymer |
-
1978
- 1978-07-07 CA CA307,031A patent/CA1106992A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115141305A (en) * | 2022-07-06 | 2022-10-04 | 中国科学院赣江创新研究院 | Functional polymer, preparation method thereof and method for preparing ion imprinted polymer by using functional polymer |
| CN115141305B (en) * | 2022-07-06 | 2023-09-19 | 中国科学院赣江创新研究院 | Functional polymer, preparation method thereof and method for preparing ion imprinting polymer by using functional polymer |
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