WO1995011944A1 - Coating composition for direct adhesion to thermosetting materials and laminates using such a composition - Google Patents

Abstract

Composition useful as a gel layer for coating laminates or as a thermosetting resin composite material layer. The composition comprises, for 100 parts by weight of the composition: 80 to 95 parts by weight of unsaturated polyester resin or vinylester resin and 5 to 20 parts by weight of an oligomer polyunsaturated ether. The composition is useful for direct adhesion of thermosetting materials without using an adhesion primer.

Description

COATING COMPOSITION FOR DIRECT ATTACHMENT TO THERMOSETTING AND LAMINATE MATERIALS USING SUCH COMPOSITION.

The present invention relates to the manufacture of laminates coated with a gelled layer called "gel-coat" and of composite materials of thermosetting resin.

Usually a laminate of thermosetting resin, such as for example a phenolic resin, coated with a gelled layer is produced according to a process comprising the following steps: - coating the mold with cold wax,

- deposition of a gelled layer, most often based on unsaturated polyester resin or vinyl ester resin and, where appropriate, a pigment, subjected to cooking for approximately 1 hour at approximately 60 ° C., - spraying onto the gelled layer , a bonding primer (for example based on furan resin added with a catalyst) at room temperature (around 20 ° C),

- steaming for around 30 minutes at around 60 ° C,

- cooling down to room temperature, - stratification of the thermosetting resin in the mold,

- steaming for approximately 90 minutes at approximately 75 ° C, then

- cooling to a temperature not exceeding approximately 35 ° C and demolding.

As can easily be understood, the figures for temperature and duration at each stage are only examples of embodiments around which the person skilled in the art can envisage variants while obtaining a satisfactory result.

At least in the case where the thermosetting resin is a phenolic resin, the presence of a bonding primer has hitherto been considered necessary to guarantee the integrity of the phenolic structure. However, it is obvious that the application of the primer is a problem both by increasing the number of steps in the laminate manufacturing process and by lengthening the overall duration of this process, it that is, by decreasing productivity.

Those skilled in the art are therefore looking for, in the field of manufacturing laminates coated with a gelled layer called "gel- coat ", of a solution making it possible to eliminate the application of a bonding primer between said thermosetting resin and said gelled layer without harming the properties of the laminates, among which the most important to take into account are:

- the resistance to tearing of the gelled layer, before and after aging (natural or accelerated) of the laminate, that is to say before and after having subjected the laminate to temperature and climate variations. - resistance of the laminate to fire and ignition.

In the same way, the manufacture of composite materials associating two layers of thermosetting resins of different natures is often made difficult without the application of a bonding primer between the two layers, unless this affects the properties of the material.

The present invention is based on the fact that the problem thus exposed can be solved by modifying the constitution of the gelled layer covering a laminate or of a layer of a composite material by the incorporation of particular additives in carefully chosen proportions. . Thus conceived, the present invention has been found to be applicable to laminates and composite materials in which the thermosetting resin can be a phenolic resin or else an unsaturated polyester resin.

A first object of the present invention therefore consists of a composition, useful as a gelled layer for coating laminates or else as a layer of a composite material of thermosetting resin, comprising per 100 parts by weight of composition:

- from 80 to 95 parts approximately by weight of unsaturated polyester resin, or of vinyl ester resin, and

- from 5 to 20 parts approximately by weight of an oligomeric polyunsaturated ether.

This composition can also comprise, when it is intended for coating laminates with thermosetting resin (in as a "gel-coat"), at least one white or colored, mineral or organic pigment, such as those usually used in the constitution of this kind of gelled layers. The proportions of pigment to be used in this case are well known to those skilled in the art depending on the intensity of the shade to be obtained.

The oligomeric polyunsaturated ether used to modify the gelled layer applied to the laminate or else the unsaturated polyester layer of a thermosetting composite material constitutes the characteristic element of the present invention. Its proportion in the composition according to the invention is a function of the result to be achieved concerning the direct bonding of the composition (that is to say without the use of a primer layer known in the prior art) on the laminate or on the second layer of the thermosetting composite material. It has thus been found that a proportion of less than about 5 parts by weight per 100 parts of composition generally does not achieve the desired goal while a proportion of more than about 20 parts by weight per 100 parts of composition is generally superfluous to achieve this goal and, given the high cost price of the oligomer compared to the unsaturated polyester resin, would harm the economic efficiency of the invention.

It is very important that the polyunsaturated ether present in the composition according to the invention is an oligomer as defined below, that is to say that it comprises a number of reactive functions, in particular in the presence of oxygen , sufficiently large to allow a chemical bond with the polyester or vinyl ester resin.

Indeed, it has been observed that a monomeric polyunsaturated ether such as trimethylolpropane diallylether, used in the same proportion, does not make it possible to solve the abovementioned technical problem, probably because it contains too few reactive functions with polyester resin or vinylester.

By oligomer within the meaning of the present invention is meant a polymer (that is to say according to commonly accepted international definitions such as that of the Organization for Economic Cooperation and Development, a molecule comprising at least 4 recurring units) low weight molecular, that is to say comprising a small number, for example from 4 to 20, of recurring ether units.

As polyunsaturated ether oligomer, it is preferred to use a polyallylic ether such as those of general formula.

dans laquelle n est un nombre entier allant de 2 à 10. De tels oligomères sont disponibles commercialement auprès de la société MONSANTO et se présentent sous la forme de liquides incolores..

in which n is an integer ranging from 2 to 10. Such oligomers are commercially available from the company MONSANTO and are presented in the form of colorless liquids.

It is well known that atmospheric oxygen can react with the allyloxy groups of this oligomeric ether to form a polyhydroperoxide capable itself of decomposing into an oligomeric free radical, in particular in the presence of certain promoters such as mineral or organic salts of transition metals. such as vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, molybdenum or lead.

The term “unsaturated polyester resin” within the meaning of the present invention means the polycondensation product of α, β- ethylenically unsaturated polycarboxylic acids or anhydrides, optionally mixed with saturated polycarboxylic acids or anhydrides, and poly- water or alkylene oxides.

The molecular weight of the unsaturated polyester resin is not critical and can vary over a wide range, generally between 250 and 5000 approximately and more particularly between 350 and 2500. Its functionality as a hydroxyl group, expressed by the ratio / OH = ² IOH / IA + IOH in which IA and IOH are respectively the acid and hydroxyl numbers, must be greater than 1, and preferably at least equal to 1.5. Its water content should not be more than about 3000 ppm, preferably not more than about 1000 ppm. Unsaturated polycarboxylic acids or anhydrides which can be used include in particular maleic acids. fumai, chloromaleic, citraconic, metaconic, itaconic, tetraconic or the like or, where they exist, the corresponding anhydrides. Saturated polycarboxylic acids or anhydrides which can be used to partially replace, for example up to around 95 mol%, and preferably up to around 45 mol%, the unsaturated acids or anhydrides, in particular include orthophthalic, isophthalic, tere- phthalic, succinic, methylsuccinic, adipic, sebacic, tetrabromo-phthalic, tetrachlorophthalic, glutaric, pimelic or similar or, where they exist, the corresponding anhydrides. Among the polyhydric alcohols which can be used, saturated aliphatic diols are generally preferred such as ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, 1, 3-butanediol , 1,4-butanediol, tripropylene glycol, pentanediol, hexanediol and neopentylglycol. Bisphenol A and its alkoxylated derivatives, as well as other aromatic polyols can also be used. Ethylene and propylene oxides can also be used.

When the unsaturated polyester resin is prepared from maleic anhydride, it is advantageous to carry out their preparation in the presence of morpholine in order to increase the rate of isomerization of the maleate functions into fumarate functions. The amount of morpholine used in this case can reach up to 1% by weight, and is preferably between 0.1% and 0.5% by weight of the polyester.

Preferably, in order to facilitate a covalent bond with the oligomeric polyunsaturated ether or its oxidation or decomposition products, the unsaturated polyester resin is preformulated by the incorporation in a proportion preferably of between 0.3% and 1.5 % by weight, of certain promoters such as mineral or organic salts of transition metals such as vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, molybdenum or lead.

By vinylester resin within the meaning of the present invention means a resin comprising a polymer chain with a terminal reactive double bond, such as an acrylate or methacrylate termination, obtained for example by reaction of acrylic acid or methacrylic with an epoxy resin such as a bisphenol A resin, a phenolic-novolak-epoxy resin or a tetrabromo bisphenol A resin. Examples of such resins are described in more detail by Matthew B. LAUNITIKIS in Handbook of Composites, pages 38 to 49.

The unsaturated polyester resin or vinyl ester resin used in the composition according to the invention are most often in solution in at least one ethylenically unsaturated monomer with which they can copolymerize in order to generate a crosslinked structure. This monomer can be chosen from styrene, substituted styrenes such as vinyltoluene, tert-butylstyrene, alphamethylstyrene, chlorostyrene, dichlorostryrene, lower alkyl esters (Ci to Ce) of acrylic acid and d methacrylic acid, cyclic acrylates and methacrylates, such as those of cyclohexyl and benzyl, bi-cyclic methacrylates and acrylates such as isobornyl, diallyl phthalate, diallyl maleate, diallyl fumarate, triallyl cyanurate , vinyl acetate, crotonate and propionate, divinylether, conjugated dienes such as butadiene-1, 3, isoprene, 1,3-pentadiene, 1,4-pentadiene, 1,4 -hexadiene, 1,5-hexadiene, 1-9-decadiene, 5-methylene-2-norbornene, 5-vinyl-2-norbornene, 2-alkyl-2,5-norbor-nadienes, 5 -ethylidene-2-norbornene, 5- (2-propenyl) -2-norbornene, 5- (5-hexenyl) -2-norbornene, 1,5-cyclooctadiene, bicyclo [2,2,2] octa-2,5-diene, cyclopentadiene, 4,7,8,9-tetrahydroindene and isopropylidene tetra-hydroindene, and unsaturated nitriles such as acrylonitrile and methacrylonitrile as well as polyol (meth) acrylates such as the diacrylates and dimethacrylates of ethylene glycol, propylene glycol, 1, 3-butanediol, 1, 4-butanediol, 1, 6-hexane diol, neopentyl glycol, 1 , 4-cyclo-hexane-diol, 1, 4-cyclo-hexane-dimethanol, 2,2,4-trimé-thyl-l, 3-pentanédiol, 2-ethyl-2-methyl-l, 3- propanediol, 2,2-diethyl-1,3-propanediol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, tetraethylene glycol, tetrapropylene glycol, trimethylolethane, trimethylopropane, glycerol, pentaerythritol , the triacrylates and trimethacrylates of trimethylolethane, trimetylolpropane, glycerol, pentaerythritol, pentaerythritol tetraacrylates and tetramethacrylates, hexa (meth) acrylates of dipentaerythritol di (meth) acrylates, polyols (meth) acrylates of mono- or polyethoxylated or mono- or polyproxylates such as triacrylate and trimethacrylate triethoxylated, tripropoxylated trimethylolpropane, tripropylylated glycerol triacrylate and trimethacrylate, triacrylate, trimethacrylate, pentaerythritol tetraethoxylated tetraacrylate and their mixtures in all proportions. The amount of ethylenically unsaturated monomer used is preferably between 10 and 50 parts by weight approximately per 100 parts by weight of unsaturated polyester resin.

A second object of the present invention consists of a thermosetting resin laminate coated with a gelled layer based on unsaturated polyester resin and optionally with pigment, characterized in that said gelled layer is obtained from a composition such as described above, comprising per 100 parts by weight of composition:

- from 80 to 95 parts approximately by weight of unsaturated polyester resin or of vinylester resin and,

- from 5 to 20 parts approximately by weight of an oligomeric polyunsaturated ether.

The laminate according to the invention is preferably made of a thermosetting resin which is difficult to coat without bonding primer while maintaining good properties for the laminate. Examples of such resins include, on the one hand, phenolic resins of the resol or novolak type and, on the other hand, certain qualities of unsaturated polyester resins known as having low volatile matter emissions. Among the latter, there may be mentioned in particular those in accordance with patent application EP-A-369,683 or patent application WO 93/08235.

As previously, these unsaturated polyester resins are preferably preformulated by the incorporation of promoters such as transition metal salts. In the laminates according to the invention, the thermosetting resin can be mechanically reinforced by the addition of approximately 20% to 80% of its own weight of fibers. glass (varying in length from 5 to 50 mm approximately), asbestos, carbon or polyamide.

Another object of the present invention consists of a composite material comprising at least one layer of a first thermosetting resin and at least one layer of a second thermosetting resin, characterized in that it comprises, disposed between the two said layers, a layer obtained from a composition as described above, comprising per 100 parts by weight of composition: - from 80 to 95 parts approximately by weight of unsaturated polyester resin or vinylester resin, and - from 5 to 20 parts approximately by weight of an oligomeric polyunsaturated ether.

In the composite material according to the invention, at least one of the two layers of thermosetting resin is preferably made up of a thermosetting resin that is difficult to coat without bonding primer while maintaining good properties for the composite material. Examples of such resins have been provided above. In the composite material according to the invention, the first thermosetting resin and the second thermosetting resin can be identical but preferably they will be chosen from different natures in two adjacent layers linked by the intermediate layer of composition according to the invention. For example, it could be a material associating a layer of phenolic resin with a layer of unsaturated polyester resin.

In this way, the present invention makes it possible to solve the problem known as resumption of stratification, which is encountered in particular in the manufacture of boat hulls in composite materials, that is to say the difficulty of making a layer of phenolic resin on a layer of unsaturated polyester resin already polymerized unless applying a primer.

An example of a process for obtaining a laminate according to the invention comprises the following steps: coating the mold (in metal or in composite material) with cold wax, - Application to the mold, for example by spraying with a spray gun, of a layer of composition according to the invention further comprising a polymerization catalyst and, where appropriate, a pigment and / or a release agent, - polymerization of the layer of composition according to the invention at a temperature between 15 ° C and 70 ° C approximately for a period of between 3 and 75 minutes approximately,

application, on the polymerized layer of the composition according to the invention, of at least one thermosetting resin optionally reinforced with fibers and containing at least one polymerization catalyst,

- Polymerization of said thermosetting resin at a temperature between 40 ° C and 80 ° C approximately for a period between 1 and 5 hours approximately, and - cooling to a temperature not exceeding approximately 35 ° C and demolding.

As is easily understood, the characteristic element of the process according to the invention resides in the choice, as composition based on unsaturated polyester resin or vinyl ester resin usable for direct application to the mold and before direct attachment of the thermosetting resin, of a composition as described above, comprising a selected proportion of oligomeric polyunsaturated ether.

The polymerization catalyst added to the composition according to the invention is an agent capable of forming free radicals at the polymerization temperature (15 ° to 70 ° C approximately) in the subsequent step. As suitable agents, there may be mentioned, inter alia, organic peroxides, peroxydicarbonates and peroxyesters such as benzoyl peroxide, tertiary butyl hydroperoxide, tertiary butyl peroxide, dicumyl peroxide, 2,2 bis (ter-butylperoxy ) butane, paracetal, 1, 1 -bis (t-butylperoxy) 3,3,5-trimethyl cyclohexane, tertiary butyl perbenzoate, tertiary butyl peroxyoctoate, tert-butyl peroxy isopropylcarbonate, tertiary butyl perisononanoate , tertiary butyl permaleinate, cyclic peracetal, 2,5-dimethyl-2,5-bis (2-ethylhexolperoxy) hexane, methyl ethyl ketone peroxide, tertioamyl peroxyoctoate, 2,5-diperoxy- octoate, or alternatively 2,4-pentanedione peroxide. An effective amount of this polymerization catalyst is preferably between 0.5% and 5% approximately by weight of the weight of the composition to be polymerized. The application, after polymerization-gelation of the composition according to the invention, of the thermosetting resin optionally reinforced with fibers and of its polymerization catalyst can be carried out by any known technique such as: - contact stratification, most often manual ,

- simultaneous projection,

- continuous hot molding (used in particular in the manufacture of plates),

- resin transfer molding, - pultrusion,

- filament winding.

The polymerization catalyst for the thermosetting resin is of course chosen according to the nature of this resin. In the case of a phenolic resin, it may be either a basic catalyst or an acid catalyst, generally a strong organic mineral acid.

Thanks to its main characteristic, the method according to the invention allows an appreciable saving of time, and therefore an improvement in productivity, by eliminating the intermediate step of spraying a bonding primer.

An example of a process for obtaining a composite material according to the invention comprises, before the stratification of at least one layer of a thermosetting resin, the application of a layer of composition according to the invention further comprising a polymerization catalyst and optionally reinforcing fibers, then polymerization of said layer at a temperature between 15 ° C and 40 ° C for a period of between 3 and 10 minutes approximately. As in the previous case (obtaining a laminate), the method according to the invention most often comprises coating the mold (in metal or in composite material) with a release agent such as wax. As is well known to those skilled in the art, the layer of the thermosetting resin contains, at least one polymerization catalyst for its stratification and can also be reinforced by glass fibers (of variable length from 5 to 50 mm approximately), asbestos, carbon or polyamide. The polymerization of this layer takes place under conditions of temperature and duration well known to those skilled in the art, depending on the nature of the thermosetting resin concerned and on the thickness of the layer which it is desired to obtain.

This process makes it possible to obtain composite materials associating thermosetting resins between which adhesion is very poor in the absence of bonding primer without significantly lengthening the manufacturing process.

As is easily understood, obtaining laminates coated with a gelled layer and obtaining composite materials are two aspects of the same concept of the invention consisting in applying the composition according to the invention, as a coating, to at least one layer of thermosetting material.

The examples below are provided purely by way of non-limiting illustration of the present invention. EXAMPLE 1 In a mold coated with cold wax, a layer of thickness approximately 400 μm of a composition is applied with a gun comprising a composition comprising (per 100 parts by weight):

- 78.4 parts by weight of a polyester gel-coat sold by the company NESTE OY under the name SKIN COAT 793 V 6, and preformulated by the addition of a cobalt salt.

- 19.6 parts by weight of a polyallyl ether sold by the company MONSANTO under the name SANTOLINK XI 100, and

- 2 parts by weight of a methyl ethyl ketone peroxide sold by the company AKZO under the name BUTANOX M 50.

This layer is polymerized at room temperature (20 ° C) for one hour and then a mixture is applied to this polymerized layer comprising (per 100 parts by weight):

- 30 parts by weight of glass fibers, - 65.5 parts by weight of a phenolic resin of the resol type sold by the company CRAY VALLEY SA under the name NORSOPHEN N 1205, and - 4.5 parts by weight of a catalyst consisting of 65% paratoluenesulfonic acid in water.

This mixture is polymerized at 80 ° C for 90 minutes, then cooled to 30 ° C before demolding the laminate. The gel-coated surface of the phenolic laminate thus obtained is subjected to a tear-off test consisting of sticking a metal patch on the gel-coat using a polyurethane adhesive and then, 24 hours after the adhesive has dried, to be measured the breakout force using a DYNATEST device. In the present case, the breakout force is equal to 2100 N. EXAMPLE 2

The operating process of example 1 is reproduced with the exception of the composition of the layer applied with a spray gun, which is now (per 100 parts by weight): - 88.2 parts by weight of the gel coat SKIN COAT 793 V 6,

- 9.8 parts by weight of SANTOLINK XI 100, and

- 2 parts by weight of BUTANOX M 50.

Under these conditions, the breakout force, measured as in Example 1, is equal to 1500 N. EXAMPLE 3

In a mold coated with cold wax, a layer is first applied comprising (per 100 parts by weight):

- 98 parts by weight of an unsaturated polyester resin sold by the company CRAY VALLEY SA under the name NORSODYNE S 49021 TAIE, containing 1500 ppm of paraffin as an agent for reducing volatile matter emissions and preformulated by adding a salt cobalt.

- 2 parts by weight of BUTANOX M 50.

After polymerization at room temperature (20 ° C) of this first layer, a second layer is applied comprising (per 100 parts by weight):

- 88.2 parts by weight of the NORSODYNE S 49021 TAIE resin,

- 9.8 parts by weight of SANTOLINK XI 100, and

- 2 parts by weight of BUTANOX M 50. After polymerization at room temperature (20 ° C) of this second layer, the composite material obtained can be removed from the mold. By carrying out tensile shear tests of test pieces of this composite material, it is verified that there is good adhesion between the two layers of the material. Indeed, failure during the tensile test always occurs at one or the other of the two layers, but never at their interface.

Claims

1. Composition, useful as a gelled layer for coating laminates or else as a layer of a composite material of thermosetting resin, comprising per 100 parts by weight of composition: - from 80 to 95 parts by weight of unsaturated polyester resin, and - from 5 to 20 parts by weight of an oligomeric polyunsaturated ether. 2. Composition according to claim 1, characterized in that it further comprises at least one pigment, white or colored, mineral or organic. 3. Composition according to one of claims 1 and 2, characterized in that the "polyunsaturated oligomeric ether is a polyallylic ether of general formula

where n is an integer ranging from 2 to 10. 4. Composition according to one of claims 1 to 3, characterized in that the unsaturated polyester resin is in solution in at least one ethylenically unsaturated monomer with which it can copolymerize. 5. Composition according to claim 4, characterized in that the amount of ethylenically unsaturated monomer is between 10 and 50 parts by weight per 100 parts by weight of unsaturated polyester resin. 6. A thermosetting resin laminate coated with a gelled layer based on unsaturated polyester resin and optionally with pigment, characterized in that said gelled layer is obtained from a composition according to one of claims 1 to 5. 7. Composite material comprising at least a first layer of a thermosetting resin and at least a second layer comprising an unsaturated polyester resin, characterized in that said second layer is obtained from a composition according to one of claims 1 to 5.