Process for preparing prepregs from fibres that contain cellulose using aqueous resin compositions.

The present invention relates to a process for producing heat-curable prepregs from cellulose-containing fibers and to composites obtained by heat curing such prepregs.

Laminates made from thermosetting cellulosic prepregs are used industrially, for example in the production of base plates for printed circuits. These fiber-reinforced materials are generally made by impregnating cellulosic fibers with an aqueous solution of a phenol / formaldehyde resin, heating the fibers to dry them, re-impregnating them with a solution of an epoxy resin in an organic solvent, and then forming a thermosetting prepreg dries. Finally, the prepreg is heated under pressure (usually in the form of layers arranged one above the other) in order to harden the epoxy resin and thus form a composite.

The reason for the need for two separate impregnation and drying stages is that epoxy resins are generally too hydrophobic for direct impregnation of cellulosic fibers; the fibers must first be made less hydrophilic by treatment with an aqueous phenolic resin solution.

Because of the need for two stages of impregnation and two stages of drying, the process is relatively expensive, slow, and complicated. It also has the disadvantage that an organic solvent is required for the second impregnation, which creates possible dangers in terms of toxicity and flammability and costs for the recovery of the organic solvent.

It has now been found that these disadvantages can essentially be overcome by using a process which comprises a single impregnation step with an aqueous thermosetting formulation which contains an epoxy resin together with a certain photopolymerizable resin.

British Patent 1 006 587 describes adducts of diglyl ether with (meth) acrylic acid. Among the disclosed adducts are those of the FormeL<chemistry id="chem0001" num="0001"><img file="EP0091401A2_D0001.tif" /></chemistry>where R is a divalent aliphatic radical derived from an ALkandioL or PoLyaLkyLendiol and n is 0 to 20. The adducts are hot-polymerized and cured using peroxydimtiators.

British Patent 1,139,100 describes polymerizable, terminally unsaturated and unreacted epoxy groups-free products which are obtained by reacting (a) 1 MoL of a diepoxide, (b) 0.5 to 0.9 MoL of a dicarboxylic acid and (c) 1.0 to 0.2 MoL AcryL-, _Meth-acrylic or crotonic acid or a half ester of fumaric or maleic acid can be produced. The reaction sequence preferably comprises an initial reaction between (a) and (b) to form a pre-extended epoxy resin and thereafter its reaction with the unsaturated monocarboxylic acid. The epoxy resin (a) is a DigLycidy ether of a dihydric phenol or alcohol. The products are polymerized and hardened using peroxide initiators.

British Patent 1,362,906 describes adducts of (meth) acrylic acid with epoxy resins which are obtained by pre-elongating an epoxy resin with a polyester with carboxy end groups. A diglycidyl ether, a diglycidyl ester or an N-heterocyclic polyglycidyl compound such as an N, N-diglycidylhydantoin can be present as the starting epoxy resin. The adducts with (meth)_acry-Latend groups can be polymerized with radical initiators and can be used for the production of moldings.

British Patent 1,367,207 describes adducts of n mol (meth) acrylic acid with 1 mol of a polyglycidyl compound of the formula<chemistry id="chem0002" num="0002"><img file="EP0091401A2_D0002.tif" /></chemistry>in which A is a radical with at least one group of the FormeL<chemistry id="chem0003" num="0003"><img file="EP0091401A2_D0003.tif" /></chemistry>in which Z represents a divalent radical required to complement a 5- or 6-membered heterocyclic ring, X represents -H or -CH₃ stands and n is 2 or 3. The preferred polyglycidyl compounds include diglycidyl derivatives of hydantoins. In the examples, diacrylates are prepared by pre-elongating 1-glycidyl-3- (2'-glycidyloxy-n-propyl) -5,5-dimethylhydantoin with sebacic acid and reacting the pre-elongated resin with acrylic acid. The adducts can be polymerized using Radika initiators.

British Patent 1,399,135 discloses curing these adducts with ionizing radiation. This patent contains a generic disclosure with regard to the use of pre-extended epoxy resins, namely that polyglycidyl compounds containing more than two heterocyclic radicals can be prepared by reacting dicarboxylic acids with diglycidyl compounds in the corresponding molar ratio.

British Patent 1,400,286 describes the curing of the (meth) acrylate adducts from British Patent 1,362,906 with ionizing radiation.

British patent specification 1,456,486 discloses air-drying, light-curable coating compositions based on a product which can be obtained by reacting at least 60X of the epoxy groups of a polyoxyoxide with 0.01 to 0.5 NH equivalents of ammonia, an aliphatic or cycloaliphatic primary or secondary amine or a mixture of these compounds per epoxy equivalent and then with 0.99 to 0.5 carboxyl equivalent acrylic acid and / or methacrylic acid. Specially mentioned polyepoxides are the glycidyl ethers of polyhydric alcohols (including 1,4-butanediol) and phenols as well as polyglycidyl esters; aromatic polyepoxides are preferred. The epoxy / ammonia and epoxy / amine products should be 2-hydroxypropyl ethers containing free epoxy groups. It is said that the coating compositions cure very quickly, even in the presence of atmospheric oxygen, especially when using α-substituted benzoins as photoinitiators, and that they are particularly suitable for paper and cardboard coatings.

British Patent 1,489,425 discloses light curable resin compositions consisting of a modified epoxy resin and a photosensitizer. The modified epoxy resin has a molecular weight of 700 to 5000 and contains polymerizable unsaturated residues which are bonded to the main chain via ester bonds in order to give the resin a double bond equivalent weight of 200 to 3000, and also -COOH groups bonded to the main chain, so that Resin has an acid number in the range 30 to 150. One of the production routes given is the reaction of an epoxy resin with a dicarboxylic acid to produce a pre-extended resin, which is then reacted with (meth) acrylic acid to form a resin with (meth) acrylate end groups, which in turn (via its -OH groups) is reacted with a dicarboxylic acid anhydride. Various saturated and unsaturated aliphatic acids mentioned, inter alia, are mentioned for the pre-extension suitable dicarboxylic acids. In one example, a bisphenol A diglycidyl ether is pre-extended with adipic acid and the pre-extended resin is converted to an intermediate product with acrylic acid.

From the British patent 1,521,933, resins have become known which are water-soluble before exposure to actinic radiation, but which polymerize and become water-insoluble when exposed to actinic radiation, these resins having the general formula<chemistry id="chem0004" num="0004"><img file="EP0091401A2_D0004.tif" /></chemistry>where a is a whole number with an average value of at least 1, but preferably not more than 100, R and R¹ each for a group of FormeL<chemistry id="chem0005" num="0005"><img file="EP0091401A2_D0005.tif" /></chemistry>or -O- (OC)_c-R⁵- (CO)_c-O-, R² each for a hydrogen atom or a group of FormeL - (CH₂NH)_dCOC (R⁶) = CH₂with the proviso that at least 1 and preferably at least 25% of the 2a groups R are different from a hydrogen atom, R³ each for an ALkyL group with 1 to 4 carbon atoms or in pairs for a group of the FormeL -CH₂CH₂-, -C (R⁷R⁸) CO-,<chemistry id="chem0006" num="0006"><img file="EP0091401A2_D0006.tif" /></chemistry>-CH₂CH₂CH₂-, -COCO-, -COCOCO- or -COC (OH)₂CO and R⁴ represent a divalent aliphatic, cycloaliphatic or araliphatic radical with 1 to 8 carbon atoms, in particular an alkyl group with 1 to 6 carbon atoms, b, c and d are each zero or 1, R⁵ a straight-chain or branched aliphatic group with 2 to 20 atoms, such as one with 2 to 9 carbon atoms, in particular an alkylene group which may be interrupted by one or more carbonyloxy groups or one or more ether oxygen atoms, or, where appropriate, are also a group of the formulas<chemistry id="chem0007" num="0007"><img file="EP0091401A2_D0007.tif" /></chemistry>_R⁶a hydrogen atom or an ALkyL group with 1 to 4 carbon atoms and R⁷and R⁸ each represent a hydrogen atom or a methyl or ethyl group.

British Patent 1,537,909 describes UV-crosslinkable, vinyl and carboxy group-containing urethane resins, which are converted by converting an epoxy resin with (meth) acrylic acid so that 60X to 100% of the epoxy groups are converted into β-hydroxyester groups corresponding urethanes can be prepared by reaction with an isocyanate and reaction of the remaining hydroxy groups with a dicarboxylic acid anhydride. The epoxy resin can be pre-extended by reaction with, for example, aliphatic or aromatic diacids. In one example, a diglycidyl ether of bisphenol A is pre-extended with adipic acid and then converted to an intermediate product with acrylic acid.

A radiation-curable liquid coating composition based on (a) an epoxy resin containing at least one (meth) acryloyl group, (b) a photoinitiator and (c) a crosslinking agent for the epoxy groups in (a) is known from European Patent 0 008 837. The resin (a) is obtained by reacting an epoxy resin with a deficit of (i) (meth) acrylic acid or (ii) a half ester of a hydroxy-substituted (meth) acrylate and a polycarboxylic acid or -anhydride available. A hydantoin-based resin may be present as the epoxy resin. Numerous types of crosslinking agents (c) are indicated, preference being given to those which are active at room temperature. In a special embodiment, an emulsifier is added to the resin (a) so that it can be diluted with water after mixing with a suitable crosslinking agent such as a polyamine. The composition is cured in two stages: in the first stage it is irradiated with UV light, and in the second stage it is cured by reaction of the epoxy groups with (c).

European patent specification 0 030 213 describes a photo-crosslinkable layer which can be developed after exposure to water and which consists of a crosslinkable unsaturated monomer or oligomer based on (meth) acrylic acid-modified epoxy resins with an acid number of less than 0.2 and a photoinitiator . In one example, an adduct of acrylic acid with an epoxy resin obtained by pre-elongating neopentyl glycol diglycidyl ether with bisphenol A is used there.

US Pat. No. 4,309,529 discloses water-dispersible, energy-curable polyesters with hydantoin groups and α-methylene groups (= CH₂) on the "main chain". These Polyesters contain recurring units of the FormeL:<chemistry id="chem0008" num="0008"><img file="EP0091401A2_D0008.tif" /></chemistry>where R⁹ represents a single bond or an ALkyLengruppe optionally with a chain oxygen atom, R¹⁰_For -_H, -_COR¹² or -CONHR¹³, _R¹¹ for -H or -CH₃, where R¹² ALkyL or optionally substituted by PhenyL or CarboxyL ALkenyL and R¹³ an aliphatic or aromatic hydrocarbon radical, W for a divalent group required to supplement a 5- or 6-membered ring, Q for the divalent or trivalent radical with up to 40 carbon atoms and possibly chain oxygen atoms containing hydrocarbon di- or tricarboxylic acids after removal of the active hydrogens from the -COOH groups and Z stand for -COOH and a is 0 or 1, but can only be 1 for no more than 20 mol% of the acids.

In the description essential to the invention it was stated that at least 10 mol% of the acids from which Q is derived. α-methylene groups should. The polyesters are generally made by reacting a heterocyclic diepoxide with a dicarboxylic acid; If an excess of diepoxide is used, polyesters with epoxy end groups are obtained which can be reacted with (meth) acrylic acid. Numerous diglycidyl derivatives of hydantoins are proposed for use as a heterocyclic diepoxide. Numerous saturated and unsaturated aliphatic and aromatic acids are mentioned as dicarboxylic acids. In order for the polyester to contain α-methylene groups, at least a part of the dicarboxylic acid component must be an α-methylene acid. The polyesters produced in the examples partially carry acrylic latend groups.

A process has now been found for the production of prepregs in which cellulose-containing fibers are impregnated with an aqueous composition consisting of (a) a photopolymerizable resin and (b) an epoxy resin, preferably in the presence of a photosensitizer for (a) and a heat-activatable hardener for (b), and then exposing the impregnated fibers to actinic radiation so that (a) is photopolymerized, with (a) the form<chemistry id="chem0009" num="0009"><img file="EP0091401A2_D0009.tif" /></chemistry>where b is zero or 1 and e is an integer of at least 1, R¹⁴ each for a hydrogen atom or a methyl group, R¹⁵ each for the divalent radical of a compound with two GLycidyL groups bonded directly to an oxygen, nitrogen or sulfur atom or atoms after removal of these two GLycidyL groups, _R¹⁶ in each case for the divalent radical of a dihydric alcohol, a divalent phenol, a dicarboxylic acid or a compound containing two groups selected from amide and imide groups after removal of two terminal hydrogen atoms bonded to an oxygen or nitrogen atom or atoms, R¹⁷ each for an ALkyLengruppe with 1 to 6 carbon atoms, an ALkenyLengruppe with 2 to 10 carbon atoms, an arylene group with 6 to 10 carbon atoms or a CycLoaLkyLen or CycLoaLkenylengruppe with 5 to 8 carbon atoms and R¹⁸ each represent a divalent aliphatic, cycloaliphatic or araliphatic group with 2 to 8 carbon atoms, with the proviso that at least 25% of the sum of the (e + 1) _R^15- and _{e R}^16-Groups one group of the FormeL<chemistry id="chem0010" num="0010"><img file="EP0091401A2_D0010.tif" /></chemistry>or a group of the formula<chemistry id="chem0011" num="0011"><img file="EP0091401A2_D0011.tif" /></chemistry>represent where R⁴ has the meaning given above, c and _d j_e zero or ₁ are, _R¹⁹ each an ALkyL group with 1 to 4 carbon atoms or pairs R¹⁹ together a group of FormeL -CH₂CH₂-, -C (R²¹R²²) CO-,<chemistry id="chem0012" num="0012"><img file="EP0091401A2_D0012.tif" /></chemistry>-CH₂CH₂CH₂- or -COCO- mean R²⁰ a straight-chain or branched aliphatic group with 2 to 20 carbon atoms or, if all d are 1, optionally also a group of the formula<chemistry id="chem0013" num="0013"><img file="EP0091401A2_D0013.tif" /></chemistry>represents and R²¹ and R²² either represent a hydrogen atom or a straight-chain or branched alkyl group with up to 9 carbon atoms or together represent a tetramethylene, pentamethylene, methylpentamethylene or hexamethylene group.

The resins of Form VIII VIII are not necessarily completely soluble in water, but they are miscible with them and thus promote the impregnation of the fibers with the epoxy resin.

Resins of formula VIII in which e is an integer of at most 10, in particular from 1 to 5, are preferred. Preferably at most 75% of the sum of the (e + 1) R^15- and e R¹⁶Groups represent a group of formulas IX or X, in which d is 1, and at least 25% of the sum of the groups R¹⁵ and R¹⁶ mean either (i) an oxyaLkyLenoxy group with 2 to 40 carbon atoms optionally interrupted in the chain by one or more ether oxygen atoms, ie a group of the formula X, where d is zero, or an oxyalkyLenoxy group with 21 to 40 carbon atoms which does not correspond to the formula IX or X. or in particular (ii) an oxyarylenoxy group having 6 to 18 carbon atoms.

Compounds of formula VIII are preferred in which at least 25% of the groups R¹⁵ and R¹⁶ j_e an oxyalkyleneoxy group, the alkylene component of which is a chain having 3 to 6 successive carbon atoms or a chain of 4 to 28 carbon atoms interrupted by one or more ether oxygen atoms, an oxyphenyleneoxy group or a group of the formula<chemistry id="chem0014" num="0014"><img file="EP0091401A2_D0014.tif" /></chemistry>where R²³ represents a carbon-carbon bond, an ether oxygen atom, a carbonyl group, a siliconyl group, a methyl group or an isopropylidene group.

If b is 1, then both R¹⁷_as also R¹⁸ preferably ALkyLengruppen with 2 to 6 carbon atoms.

R²⁰ preferably represents an alkylene group with up to 9 carbon atoms which may be interrupted by one or more carbonyloxy groups or one or more ether oxygen atoms.

Resins containing groups of the formula IX in which each pair of R¹⁹ a group of FormeL -C (R²¹R²²) Means CO-, where R²¹ for a methyl, ethyl, n-propyl, n-pentyl, neopentyl, sec.amyl or 2-ethylhexyl group and R²² represent a methyl group or R²¹ and R²² together represent pentamethylene or hexamethylene.

SPECIAL EXAMPLES FOR AS R¹⁵ and R¹⁶ suitable groups, if they also conform to FormeL IX<chemistry id="chem0015" num="0015"><img file="EP0091401A2_D0015.tif" /></chemistry><chemistry id="chem0016" num="0016"><img file="EP0091401A2_D0016.tif" /></chemistry><chemistry id="chem0017" num="0017"><img file="EP0091401A2_D0017.tif" /></chemistry><chemistry id="chem0018" num="0018"><img file="EP0091401A2_D0018.tif" /></chemistry><chemistry id="chem0019" num="0019"><img file="EP0091401A2_D0019.tif" /></chemistry>as well as, if they also conform to FormeL X,<chemistry id="chem0020" num="0020"><img file="EP0091401A2_D0020.tif" /></chemistry>where g is 2, 3 or 4.

The groups of formulas XIII to XXI represent the rest of the 5,5-dimethyLhydantoin, 5-AethyL-5-methyLhydantoin, imidazolidin-2-ones, 1,3-dimethylurea, hexahydro-2H-pyrimidin-2-ones, 5 -Methyl-5- (2-ethylhexyl) hydantoins, 5,5-pentamethylene hydantoins, 4-methylimidazolidin-2-ones or 1,1'-methylene-bis- (5,5-dimethylhydantoins), while the groups of Formula XXII are the residues of succinic, GLutaric and adipic acids.

Further examples of suitable groups R¹⁵ and R¹⁶, if these also correspond to FormeL X, are those of FormeLn<chemistry id="chem0021" num="0021"><img file="EP0091401A2_D0021.tif" /></chemistry><chemistry id="chem0022" num="0022"><img file="EP0091401A2_D0022.tif" /></chemistry>

SPECIAL EXAMPLES FOR SUITABLE GROUPS _R¹⁵ and R¹⁶, if these do not also comply with FormeL IX or X, they are with FormeL<chemistry id="chem0023" num="0023"><img file="EP0091401A2_D0023.tif" /></chemistry>where f is an integer from the average 7.3, and<chemistry id="chem0024" num="0024"><img file="EP0091401A2_D0024.tif" /></chemistry>

The groups of formulas XXIII to XXVI represent the residues of AethyLengLykoL, butane-1,4-diol, a PoLy-Coxypropylene) glycol with an average molecular weight of 425 or 2,2-bis (4-hydroxyphenyL) propane.

The resins of formula VIII, in which b is zero, can be produced in two stages.

The first is the implementation of a diepoxide from FormeL<chemistry id="chem0025" num="0025"><img file="EP0091401A2_D0025.tif" /></chemistry>with a dihydric alcohol, a dihydric phenol, a dicarboxylic acid or an amide or amide-imide of the formula<chemistry id="chem0026" num="0026"><img file="EP0091401A2_D0026.tif" /></chemistry>to a pre-extended, linear diepoxide of the formula<chemistry id="chem0027" num="0027"><img file="EP0091401A2_D0027.tif" /></chemistry>where e, _R¹⁵ and R¹⁶ have the meanings given above.

The diepoxide of the formula XXVII is usually heated to a temperature in the range of 120 with the compound of the formula XXVIII^0-210 ° C and especially 140 ° -190 ° C. The reaction can be accelerated by adding suitable catalysts. Such catalysts are, for example, ALkaLihydroxydes such as sodium hydroxide, ALkaLihaLogenide such as lithium chloride, potassium chloride and sodium chloride, bromide or fluoride, tertiary amines such as triethylamine, tri-n-propylamine, N-BenzyLdimethyLaminate, N, N'-ammonium ammonium, N, N'-n-aminium-dimethylamine, N, N'-ammonium-dimethylamine, N, N'-ammonium-dimethylamine, N, N'-n-aminium-dimethylamine, quaternary ammonium salts such as tetramethylammonium chloride, tetraethylammonium chloride, benzyltrimethylammonium chloride, benzyltrimethylammonium acetate, and methyltrithylammonium chloride, and hydrazines with a tertiary nitrogen atom, such as 1,1-dimethylhydrazine, which can also be used in its quaternized form. Depending on the choice of starting materials, the reaction sometimes proceeds quantitatively and so quickly that no additional catalyst is required. While the starting materials are generally mixed with one another at room temperature and then brought to the reaction temperature, it is advantageous in the case of components which are very reactive with one another if the diepoxide of formula XXVII is first heated to the required reaction temperature and then the remaining reactive components are gradually added small portions. The progress of the reaction up to the formation of the end product with a defined, essentially constant epoxy group content can be followed by titration of the epoxy groups in samples taken during the reaction.

Such pre-elongation reactions are known (see for example British Patent No. 1,521,933 mentioned above).

In the second stage, the water-thinnable resin of formula VIII is obtained from the pre-extended diepoxide of formula XXIX by opening the terminal epoxy groups by reaction with acrylic acid or methacrylic acid.

This reaction generally takes place at a temperature of 60 ° to 150 ° C., in particular at 100 ° to 130 ° C., in the presence of an inert polar solvent such as chloroform. The molar ratio of the pre-extended diepoxide of formula XXIX to acrylic acid or methacrylic acid preferably has a value such that essentially all of the GLycidyL groups specified are converted into (meth) acryLoyL-2-hydroxypropyl groups.

A catalytic converter for the ring opening reaction is expediently present. This catalyst can be sodium acetate or preferably a tertiary amine such as one of the above, a quaternary ammonium salt such as one of the above or a salt of the trivalent chromium with an alkanoic acid such as octanoic acid and 2-ethylhexanoic acid or an alkenoic acid such as acrylic acid.

If desired, a radical inhibitor such as hydroquinone or 2,6-di-tert-butyl-4-methylphenol can be used to counteract the occurrence of side reactions. Such inhibitors do not need to be removed after the reaction has taken place, since they do not prevent the polymerisation of the product when exposed to actinic radiation.

The resins of formula VIII, in which b is 1, can be obtained from the pre-extended linear diepoxides of the formula XXIX by opening the terminal epoxy groups in the reaction with a dicarboxylic acid of the formula<chemistry id="chem0028" num="0028"><img file="EP0091401A2_D0028.tif" /></chemistry>where R¹⁷ has the meaning given above, or the anhydride of a diacid of formula XXX and subsequent esterification of the terminal carboxylic acid groups thus formed with a hydroxyl group-containing ester of acrylic or methacrylic acid of formula<chemistry id="chem0029" num="0029"><img file="EP0091401A2_D0029.tif" /></chemistry>wherein _R¹⁴ and _R¹⁸ have the meanings given above.

The ring opening of the epoxy groups generally takes place under the same conditions as described above for the ring opening of the diepoxides of FormeL XXIX with acrylic or methacrylic acid, ie at a temperature of 60-150⁰C in the presence of a catalyst and optionally a radical inhibitor.

The esterification with a hydroxyester of formula XXXI can be carried out under customary esterification conditions, in particular by heating at 60 ° to 150 ° C., especially at 100 ° to 130 ° C., optionally in an inert solvent, preferably water-immiscible, and optionally in the presence of a Perform dehydrating agents. Desired CASES These two steps can be carried out as a single reaction by mixing and heating the reactants in a single vessel.

The epoxy resins suitable for use as component (b) in the process according to the invention include the diglycidyl ethers of polyvalent phenols such as bisphenol A (2,2-bis (4-hydroxyphenyL) propane) and tetrabromobisphenol A (2,2-bis (3, 5-dibromo-4-hydroxyphenyl) propane) and epoxy resins obtained by pre-extension of these diglycidyl ethers. The use of water-soluble N, N-diglycidyl compounds, in particular N, N'-diglycidylhydantoins, as the epoxy resin component is particularly preferred.

The cellulose-containing fibers can be loose, as a woven sheet or as a non-woven fabric and preferably consist of cotton or paper.

The weight ratio of component (a), ie the resin of formula VIII, to component (b), ie the epoxy resin, can vary within wide limits, but is preferably in the range 1: 0.5-4.

The fibers can be impregnated in the usual way. In general, the water content is not of critical importance, but it should be limited, for example, to about 2 to 30% by weight, calculated on the aqueous composition, in order to avoid the need for drying. The absorption of the composition is usually 50 to 300% by weight, preferably 50 to 150% by weight, calculated on the fiber weight.

The impregnation mixture can also contain conventional additives such as flame retardants.

In the method according to the invention, actinic radiation with a wavelength of 200 to 600 nm is preferably used.

As already indicated, the impregnated fibers are preferably exposed to actinic radiation in the presence of a photosensitizer. The photosensitizer is expediently introduced into the impregnation composition. Suitable sensitizers include quinones, diphenylcarbinols, 5-nitroacenaphthene, 2-substituted thioxanthones, diphenyl methanes and α-haloacetophenones such as p-tert-butylphenyl-trichloromethyl ketone, photoredox catalysts such as a mixture of a phenothiazine dye (e.g. Methylene blue) or a substituted quinoxaline with an electron donor (such as a sulfinic acid or its SaLz, a phosphine, arsine or thiourea), benzophenones, benzil dialkyl ketals such as benzil dimethyl ketal (ie .alpha.-methoxybenzoin methyl ether), benzoins, benzoin alkoxymethyl ether and o-benzyl alkoxyl ether -Phenylpropane-1,2-dions such as benzil- (O-ethoxycarbonyl) -α-monoxime and 1-phenylpropane-1,2-dione-2- (O-ethoxycarbonyl) oxime. Preferred sensitizers are MichLers ketone (ie 4,4'-bis (dimethylamino) benzophenone), benzoin-n-butyl ether and mixtures of these two, mixed with a metal salt of the ToLuoL-p-suLfic acid, metal salts of 2- (m- or p -Methoxyphenyl) -quinoxaline-6'- or -7'-sulfonic acid, 1-phenylpropane-1,2-dione-2- (O-ethoxycarbonyl) oxime, BenziLdimethyLketaL and mixtures of these two, and 2-chlorothioxanthone and its mixtures with BenziLdimethyLketal. Usually 0.1 to 20 and preferably 0.5 to 15% by weight of sensitizer are used, calculated on the weight of component (a).

Suitable actinic radiation sources include carbon arcs, mercury vapor arcs, fluorescent lamps with fluorescent light emitting uLtravioLettes, argon and xenon glow lamps, tungsten lamps and photographic flood lamps. Among them, mercury vapor arcs, especially sunlamps, fluorescent sunlamps and metal halide lamps, are the most suitable. The time required to expose the impregnated fibers depends on various factors, including, for example, the component (a) used, the type of light source and its distance from the fibers, and can easily be determined by series tests.

The invention further relates to a process for producing a composite article, which is characterized in that a prepreg produced by the process according to the invention is hot-hardened.

As also already indicated, the cellulose-containing fibers are preferably also impregnated with a heat-curing amount of a latent heat hardener for the epoxy resin (b). Such means are well known and include dicyandiamide (alone or as a mixture with an N, N-dimethyl-N'-arylurea such as bis- (N, N-dimethylureido) toluene or N, N-dimethyL-N '- (4-chlorophenyl) ) -urea), imidazole and amine complexes of boron trichloride or boron trifluoride. These agents are expediently incorporated into the aqueous composition containing (a) and (b).

The person skilled in the epoxy resin technology can easily determine the suitable heat and pressure conditions to be used in the formation of the thermoset composite, which is generally in the form of a laminated laminate, by conventional methods.

The following examples serve to explain the invention.

The epoxy resins and photopolymerizable resins used in the examples are made as follows. The epoxy contents are determined by titration with 0.1 n-overchloric acid solution in glacial acetic acid in the presence of excess tetraethylammonium bromide with crystal violet as an indicator. Parts and percentages are always parts by weight and percentages by weight.

Epoxy resin A

Stir N, N'-DigLycidyL-5,5'-dimethyLhydantoin (epoxide content 8.04 val / kg, 100 g), bisphenol A diglycidyl ether (epoxide content 5.30 val / kg, 100 g), 1.4- Butanediol (37.2 g) and N-phenylimidazole (0.2 g) for 5 hours at 120 ° C. A further portion of 2-phenylimidazole (0.2 g) is added and the mixture is heated for a further 5 hours at 120 ° C. and then for 6 1/2 hours at 140 ° C., after which the epoxy content of the mixture is 2.44 vaL / kg.

Epoxy resin B

N, N'-Diglycidyl-5,5-dimethylhydantoin (epoxide content 8.04 vaL / kg, 100 g), the diglycidyl ether of a polyoxypropylene glycol with an average molecular weight of 425 (epoxide content 3.07 val / kg, 200 g), bisphenol-A are stirred -diglycidyl ether (epoxy content 5.30 vaL / kg, 100 g), bisphenol-A (100 g) and N-phenylimidazole (0.4 g) for 3 1/2 hours at 120 ° C, after which the epoxy content of the mixture 2.67 val / kg.

Epoxy resin C

N, N'-Diglycidyl-5,5-pentamethylene hydantoin (epoxy content 6.23 eq / kg, 200 g), 1,4-butanediol (36 g) and N-phenylimidazole (0.4 g) 12 1/4 are stirred Hours at 140 ° C and then 3 3/4 hours at 160 ° C, after which the epoxy content has dropped to 2.35 eq / kg.

Epoxy resin D

Adipic acid (73 g) is added in portions with stirring to N, N'-diglycidyL-5,5-dimethyLhydantoin (epoxy content 8.04 eq / kg, 200 g) containing N-PhenyLimidazoL (0.4 g), while maintaining the temperature holds at 100 ° C and the addition is carried out over the course of 40 minutes. The mixture is heated for a further 4 1/3 hours at 100 ° C., after which the epoxy content has dropped to 2.35 vaL / kg.

Photopolymerizable resin I

5.5-DimethyLhydantoin (77.4 g) are added in portions with stirring to a mixture of 1,4-butanediol diglycidyl ether (epoxy content 8.6 vaL / kg, 200 g), the tetramethylammonium chloride (0.25 g) as a pre-extension catalyst contains. The mixture is heated to 120 ° C, whereby an exothermic reaction sets in, which raises the temperature to 230 ° C. Then you cool to 100 ° C; the epoxy content is now 2.2 vaL / kg. 2,6-Di-t-butyl-4-methylphenol (0.44 g) is used as a polymerization inhibitor and then methacrylic acid (54.6 g) and 2,6-di-tert-butyl-4-methylphenol over an hour (0.88 g). The mixture is heated to 100 ° C. for 3 1/2 hours, after which its epoxy content has dropped to a low value (0.6 val / kg).

This product corresponds essentially to the formula VIII, in which b is nuLL and R¹⁴ each for a methyl group, R¹⁵ each for a group of FormeL _XXIV and _R¹⁶ each represent a group of formula XIII.

Photopolymerizable resin II

N, N'-DigLycidyL-5,5-dimethyLhydantoin (epoxy content 7.88 vaL / kg, 50 g) is heated, which contains 2 drops of a 5X solution of chromium-III-trisoctanoate in PetroLäther as a catalyst for the subsequent reaction with acrylic acid , to 100 ° C and add adipic acid (14 g) over 1 hour. When the addition is complete, the mixture is heated at 100 ° C. for a further 1 3/4 hours, after which the epoxy content is 3.96 eq / kg. Acrylic acid (8.1 g), 0.1 g of 2,6-di-t-butyl-4-methylphenol and a further 2 drops of chromium III trisoctanoate are added to the resin at 100 ° C. in the course of 30 minutes Solution contains, and heated for another 6 1/2 hours at 100 ° C. The epoxy content of the product is 0.46 vaL / kg.

This product corresponds essentially to Formula VIII, where b is zero and R¹⁴ each for a hydrogen atom, R¹⁵ each for a group of the formula XIII and R¹⁶ each stand for a group of FormeL XXII with g = 4.

Photopolymerizable resin III

Acrylic acid (20.8 g), 2,6-di-t-butyl-4-methylphenol (0.2 g) and a 5X solution of chromium III trisoctanoate in petroleum ether (0.1 g) are added in the course of 1/2 hour with stirring at 100 ° C. to epoxy resin A (118.6 g). After the addition is complete, the mixture is heated at 100 ° C. for a further 5 1/2 hours, after which the epoxy content has fallen to a negligible value (0.07 vaL / kg). Then water (23.1 g) is added.

The product essentially corresponds to the FormeL _VIII, in which _b is zero, some of the groups R¹⁵ Form XIII and the rest of Form XXVI correspond to the groups _R¹⁶_Oxyb_utyLeno_xare y groups and R¹⁴ means a hydrogen atom.

Photopolymerizable resin IV

Acrylic acid (50.3 g), 2,6-di-t-butyl-4-methylphenol (0.6 g) and a 5X solution of chromium III trisoctanoate in petroleum ether (0.3 g) are added over 1/2 hour with stirring at 100 ° C to epoxy resin B (261.5 g). The mixture is heated for a further 4 1/2 hours at 100 ° C., after which the epoxy content has fallen to a negligibly small value (0.08 val / kg).

The product corresponds essentially to the formula VIII, in which b is zero, some of the groups R¹⁵ FormeL XIII, some of FormeL XXV and the rest of FormeL XXVI and groups R¹⁶ also correspond to the formula XXVI and R¹⁴ means a hydrogen atom.

Photopolymerizable resin V

Epoxy resin C (118 g) is stirred at 100 ° C. and methacrylic acid (23.8 g), 2,6-di-t-butyl-4-methylphenol (0.4 g) and a 5X solution of chromium III are added -Trisoctanoate in PetroLäther (0.1 g) containing solution over 1/2 hour. The mixture is heated for a further 4 1/3 hours at 100 ° C., after which the epoxy content has fallen to a negligible value (0.28 vaL / kg). Then water (45 g) is added.

The product corresponds essentially to Form VIII, where b is zero, R¹⁴ each for a methyl group, _R¹⁵ each for a group of FormeL XIX and R¹⁶ each represent a group of formula XXIV.

Photopolymerizable resin VI

Epoxy resin D (273 g) is stirred at 100 ° C. and an acrylic acid (46.2 g), 2,6-di-t-butyl-4-methylphenol (0.6 g) and a 5X solution of chromium III are added -solution containing trisoctanoate in petroleum ether (0.3 g) over the course of 1/2 hour. The mixture is heated for a further 2 hours, after which the epoxy content has fallen to a negligible value (0.34 vaL / kg). Then water (30 g) is added.

The product corresponds essentially to the formula VIII, in which b is nuLL, R¹⁴ each for a hydrogen atom, R¹⁵ for a group of FormeL XIII and R¹⁶ each represent a group of FormeL XXII.

Photopolymerizable resin VII

Diglycidyl hexahydrophthalate (epoxy content 6.4 vaL / kg, 41.2 g) containing tetramethylammonium chloride (0.1 g) and heated to 100 ° C. is added in portions over the course of 1 hour with 5,5-dimethylhydantoin (10.2 g). The mixture is then stirred for 4 hours at 100 ° C., after which the epoxy content has dropped to 2.45 vaL / kg.

Succinic anhydride (30 g), 2-hydroxyethyl acrylate (34.2 g), tetramethylammonium chloride (0.2 g) and 2,6-di-t-butyl-4-methylphenol (0.15 g) 3 are stirred in a separate vessel Hours at 90 ° C and then cools down. The product, ie 3- (2- (Acryloyloxy) -ethoxycarbonyl) propionic acid (27.2 g) is then mixed with 2,6-di-t-butyl-4-methylphenol (0.1 g) and over one hour at 100 ° C added to the pre-elongated resin; the mixture is stirred for 4 1/2 hours at 100 ° C, after which its epoxy content is negligible. The product is diluted with 33% water.

The product corresponds essentially to the formula VIII, in which b is 1, round R¹⁸ each for -CH₂CH₂-, R¹⁴ for a hydrogen atom, R15 for hexahydrophthaloyl and R¹⁶ represent a group of formula XIII.

EXAMPLE 1

Photopolymerizable resin I (10 parts) is mixed with 40 parts of an epoxy resin, namely N, N'-diglycidyl-5,5-dimethylhydantoin (epoxy content 7.88 val / kg), 2 parts of water, 0.5 part of benzyl dimethyl methyl and 1 part Boron trichloride / trimethylamine complex.

The clear solution obtained is used to impregnate electrical quality kraft paper with a basis weight of 60 g / m² used, the absorption is 100%, calculated on the weight of the paper. The impregnated paper is irradiated for 30 seconds on both sides with an 80 W / cm medium-pressure mercury lamp at a distance of 25 cm, which results in a somewhat sticky prepreg. Four layers of these are arranged one above the other, heat-cured in a press for 1 hour at 120 ° C. under 7 MPa pressure and then post-cured by heating at 140 ° C. for 2 hours. The laminate is hard and stiff and is not damaged by the puncture test specified in British Standard No. 5102: 1974, Appendix R.

EXAMPLE 2

Photopolymerizable resin I (15 parts) is mixed with 20 parts each of the two epoxy resins N, N'-diglycidyl-5,5-dimethylhydantoin (epoxy content 7.88 val / kg) and with tetrabromobisphenol A to an epoxy content of 2.0 val / kg of pre-extended N, N'-diglycidyl-5,5-dimethylhydantoin, 2.0 parts water, 0.5 parts 2-chlorothioxanthone, 2.0 parts dicyandiamide and 0.5 parts N- (4-chlorophenyl) -N, N '-dimethylurea.

This mixture is used to impregnate kraft paper as described in Example 1 and is irradiated for 10 seconds on both sides with an 80 W / cm medium-pressure mercury lamp at a distance of 25 cm, which results in a somewhat sticky prepreg. Four layers of it are placed one above the other and heat-cured in a press at 120 ° C for 1 hour under 7 MPa pressure. The resulting, hardened laminate is hard and stiff and is not damaged by the puncture test specified above.

EXAMPLE 3

Photopolymerizable resin II (20 parts) is mixed with 20 parts of an epoxy resin, ie N, N'-diglycidyL-5,5-dimethyLhydantoin, 10 parts of water, 0.2 parts each of BenziLdimethyLketaL and 1-phenyL-1,2-propanedione. 2- (0-ethoxycarbonyl) oxime, 2.6 parts of a mixture of 2,4- and 2,6-bis (N, N-dimethylureido) toluene and 0.65 parts of dicyandiamide. When the mixture is heated to 60 ° C, a clear solution is formed. With this, kraft paper weighing 350 g / m² impregnated, the absorption is 100%, calculated on the weight of the paper. The impregnated paper is irradiated on both sides for 5 seconds with the lamp used in Example 1, a non-stick prepreg being obtained. Four layers of the prepreg are placed one above the other and then heated for 5 minutes at 120 ° C only under nominal pressure and then at 120 ° C, while the laminate is pressed for 3 courses of 2 minutes at 7 MPa, applying the pressure for 30 seconds relaxed between the courses. Finally, the laminate is heated for 1 hour under 7 MPa pressure, giving a well-solidified product in which holes can be punched easily without deformation; the resin content is 41%.

EXAMPLE 4

Photopolymerizable resin VII (60 parts) is mixed with 45 parts of epoxy resin C, 5 parts of water, 0.6 part of benzil dimethyl ketal and 2 parts of boron trichloride / octyldimethylamine complex.

The clear solution obtained is used to impregnate electrical quality kraft paper with a basis weight of 75 g /_m² used, the absorption is 100%, calculated on the weight of the paper. The impregnated paper is irradiated for 3 seconds on both sides with an 80 W / cm medium-pressure mercury lamp at a distance of 25 cm, which results in a non-adhesive prepreg. Six layers of this are placed one above the other and heated in a press at 120 ° C for 1 hour under 7 MPa pressure. The resulting laminate is hard and stiff and is not damaged by the puncture test specified above.

EXAMPLE 5

Photopolymerizable resin III (50 parts) is mixed with 25 parts of epoxy resin A, 5 parts of water, 0.5 part of benzyl dimethyl methyl and 1 part of boron trifluoride / monoethylamine complex.

The clear solution obtained is used to impregnate electrical quality kraft paper with a basis weight of 75 g / m² used, the absorption is 150%, calculated on the weight of the paper. The impregnated paper is irradiated for 5 seconds on both sides with an 80 W / cm medium-pressure mercury lamp at a distance of 25 cm, which results in a tack-free prepreg. Eight layers of it are placed one above the other and heat-cured in a press at 120 ° C for 1 hour under 7 MPa pressure. The resulting laminate is well consolidated and is not damaged by the puncture test specified above.

EXAMPLE 6

Photopolymerizable resin IV (40 parts) is mixed with 25 parts of epoxy resin B, 5 parts of water, 0.5 part of benzaldimethylketal and 0.5 part of N-phenylimidazole.

The clear solution obtained is used to impregnate electrical quality kraft paper with a basis weight of 75 g / m² used, the absorption is 200%, calculated on the weight of the paper. The impregnated paper is irradiated for 8 seconds on both sides with an 80 W / cm medium pressure mercury lamp at a distance of 25 cm, which results in a somewhat sticky prepreg. Six layers of these are arranged one above the other and heat-cured in a press for 1 hour at 120 ° C. under 7 MPa pressure. The resulting laminate is hard and stiff and is not damaged by the puncture test specified above.

EXAMPLE 7

Photopolymerizable resin V (30 parts) is mixed with 25 parts of epoxy resin B, 0.3 part of benzaldimethyl ketal and 0.3 part of boron trichloride / trimethylamine complex.

The mixture is heated to 60 ° C to obtain a clear solution which is used to make a woven cotton cloth with a basis weight of 120 g / m² to be impregnated, the absorption being 275%, calculated on the weight of the cotton. The impregnated cotton is irradiated for 2 seconds on both sides with an 80 W / cm medium pressure mercury lamp at a distance of 25 cm, which results in a tack-free prepreg. Six layers of these are arranged one above the other and heat-cured in a press for 1 hour at 120 ° C. under 7 MPa pressure. The resulting laminate is hard and flexible and is not damaged by the puncture test specified above.

EXAMPLE 8

Photopolymerizable resin VI (30 parts) is mixed with 25 parts of epoxy resin B, 5 parts of water, 0.5 part of benzyl dimethyl methacrylate and 0.5 part of boron trichloride / trimethylamine complex.

The clear solution obtained is used to impregnate a woven cotton cloth with a basis weight of 120 g / m² used, the absorption is 50%, calculated on the weight of the cotton. The impregnated cotton is irradiated for 5 seconds on both sides with an 80 W / cm medium pressure mercury lamp at a distance of 25 cm, which results in a tack-free prepreg. Four layers of it are arranged one above the other and heat-cured in a press for 1 hour at 120 ° C under 7 MPa pressure. The resulting laminate is hard and flexible and is not damaged by the puncture test specified above.