NL1015271C2 - Thermosetting resin composition for manufacturing molded articles useful as, e.g. enclosure for electronics, comprises radically curable resin mixture, and shrink-resistant compound - Google Patents

Abstract

A thermosetting resin composition comprises a radically curable resin mixture comprising (parts by weight, pbw) radically curable resin containing a free monomer capable of copolymerizing with the resin (50-100), and shrink-resistant compound containing copolymerizable free monomer (0-50). A thermosetting resin composition comprises a radically curable resin mixture as matrix, in which 2-dimensional (2D)-randomly distributed, discontinuous carbon fibers and other additives are present; and optionally a filler. The radically curable resin mixture comprises (pbw) radically curable resin containing a free monomer capable of copolymerizing with the resin (50-100), and shrink-resistant compound containing copolymerizable free monomer (0-50). The discontinuously distributed carbon fibers are obtained by chopping split, continuous carbon fiber bundles. The bundles are provided with a sizing that is partially chemically bonded to the bundles, and a binder having solubility at room temperature in the copolymerizable free monomer of at least10 wt.%. The carbon fibers are 5-65 wt.%. An Independent claim is also included for a process of preparing the thermosetting resin composition comprising chopping fiber bundles to form packages of carbon filaments; adding sizing to a radically curable resin mixture; distributing the chopped, split, continuous carbon fibers by: (a) allowing the fibers to drop on a sheet molding compound line onto the resin mixture and covering the fibers with the resin mixture; or (b) adding the fibers to the resin mixture in a gap between two counter-rotating rolls followed by an impregnation step in a compacting unit or mixing apparatus.

Description

- 1 - .-.

THERMO-HARDENABLE RESIN COMPOSITION OF A RADICAL AIR CURABLE RESIN MIXTURE AND CARBON FIBER

The invention relates to a thermosetting resin composition containing a radically curable resin mixture as matrix, in which 10 2D randomly distributed discontinuous carbon fibers as well as other additives are present. Thermosetting resin compositions are also referred to as compounds. Such compounds can for instance be prepared and processed in the form of sheets (sheets) 15 and are therefore also referred to as Sheet Molding

Compounds (SMCs). It is also possible to prepare and process the compounds in bulk form. The invention also relates to a method for manufacturing a thermosetting resin composition, as well as to methods of manufacturing 3D moldings of this thermosetting resin composition and to 3D moldings made from a thermosetting resin composition.

Thermosetting resin compositions containing a radically curable resin mixture as matrix, 2D randomly distributed discontinuous carbon fibers as well as other additives are described in an article by N. Tsuchiyama, Progress in Science and Engineering of Composites, Proceedings of the ICCM-IV, 30 Tokyo, ( 1982), Volume 1, 497-503. This reference refers to thermosetting resin compositions mainly used in SMCs. The resin composition from the article of N. Tsuchiyama is obtained by using a radical curable resin mixture containing 100 wt. parts of a 1015271-2 polyester resin, 1.5 wt. parts of magnesium oxide and 1 wt. part t-butyl perbenzoate, add 20-55 vol.% cut carbon fiber bundles with a K value between 1-30. According to the author, SMCs are obtained which exhibit good mechanical properties when the volume% carbon fiber is between 40-45 and the K value of the carbon fiber bundle is 6. With cut carbon fiber bundles with a K-value greater than 6, products with much poorer mechanical properties are obtained.

The K value of a fiber bundle means the number of filaments present in the fiber bundle divided by a factor of 1000.

A major drawback of the resin compositions 15 of the prior art is that in the production of good SMCs relatively large numbers of fiber bundles introduced next to each other (or partly on top of each other) in a cutting device are required to make an SMC with a sufficiently homogeneous distribution and easily wettable fiber bed. The object of the present invention is to provide a thermosetting resin composition containing a radically curable resin mixture as matrix, 2D randomly distributed discontinuous carbon fibers and other additives, the above drawback not being applicable.

For the resin composition according to the invention, the radically curable resin mixture consists of: a) 50-95 wt. parts of a radically curable resin 30 which also contains a copolymerizable free monomer 1015271-3 b) 5-50 wt. parts of a shrink-resistant compound which may also contain an amount of copolymerizable free monomer, and that the 2D randomly distributed, discontinuous carbon fibers are obtained by cutting split continuous carbon fiber bundles, which carbon fiber bundles are provided with an at least partly chemically bonded adhesive (in English sizing) and of a binder (in English binder) which binder is at least 10% by weight soluble in copolymerizable free monomer present at room temperature, and that the weight percentage of carbon fibers relative to the resin composition is between 5 and 65% by weight and that a filler is also present in the resin composition.

Surprisingly, a resin composition has now been obtained in which the carbon fibers are well impregnated and completely 2D random and homogeneously distributed over the resin composition.

A 2D random distribution of fiber bundles is intended to mean a distribution in which the direction of the fiber bundles in the plane in which the fiber bundles are distributed is not regular.

The cut, split continuous carbon fiber bundles with the above-mentioned adhesives and binders exhibit excellent dropping behavior. As a result, it is now very possible to make compounds with a significantly more limited number of coils compared to the state of the art, for example SMCs, with a 2D randomly distributed and homogeneous and easily wettable fiber distribution. This is especially important for 1015271 - 4 - making SMCs with a large production width, eg wider than 70 cm, such as those that are important for making very large molded parts (eg car roofs, etc.) with a minimum of flow, through the use of 5 large inserts.

It is a further advantage of the invention that relatively low density resin compositions can be made. In addition, they are particularly suitable for EMI shielding and 10 parts can also be made with a Class-A surface.

Another important advantage of the resin compositions according to the invention is that they can also be used excellently in processing them in bulk form, for example via processing by extrusion compression (also referred to as "injection compression molding" or "transfer compression"). molding ").

In the radically curable resin mixture, the invention uses a radically curable resin (a). In general, resins containing an unsaturation are radically curable. Examples of such resins are: vinyl ester resins, unsaturated polyester resins and hybrid resins.

Suitable vinyl ester resins, also known under the name epoxy (meth) acrylates, which can be used in the resin composition according to the invention are addition products of polyepoxides and unsaturated carboxylic acids, preferably acrylic acid and methacrylic acid. Suitable polyepoxides are epoxy novolac resins and in particular polyepoxides based on bisphenol-A. A likewise suitable class I 01 5271-5 vinyl ester resins are the esterification products of alkoxylated bisphenol-A with (meth) acrylic acid. Examples include the ATLAC ™ resins from DSM Composite Resins, Zwolle, the Netherlands).

Suitable unsaturated polyester resins which can be used in the resin composition according to the invention are polyesters obtained by reaction of organic compounds containing carboxyl and / or alcohol groups. At least one of the 10 starting compounds herein contains unsaturated compounds. Examples include the PALATAL ™ resins from DSM Composite Resins.

Suitable hybrid resins that can be used in the resin composition of the invention are resins that form a polyester-urethane hybrid network by reacting low molecular weight starting compounds with one another in situ. Examples include the DARON ™ resins from DSM Composite Resins.

Preferably, the invention uses vinyl ester resins or unsaturated polyester resins.

The free monomer copolymerizable with the radically curable resin in the resin mixture contains one or more vinyl groups, and usually less than 50 carbon atoms. Suitable copolymerizable free monomers are, for example, of the type vinyl aromatic, vinyl ether, vinyl ester, acrylate and / or allyl. Preferably, the free monomer is vinyl aromatic. Suitable vinyl aromatic monomers are, for example, styrene, α-methylstyrene, o-, m-, p-methylstyrene, p-chlorostyrene, t-5271-6-butylstyrene, divinylbenzene, bromostyrene, vinylnaphthalene, α-chlorostyrene and divinylnaphthalene.

Styrene is preferably used.

The appropriate amount of radically curable resin and copolymerizable free monomer in the resin mixture of the invention is between 50 and 95 wt. parts relative to the total of (a) and (b).

Suitable shrink-resistant compounds (b) in the resin composition according to the invention are thermoplastic polymers such as, for example, polyvinyl acetate, ethylene vinyl acetate, polystyrene, polyacrylates, such as, for example, polymethyl methacrylate, saturated polyesters, polyethylene, polyurethane, and rubbers based on butadiene and styrene. Such shrink-resistant compounds are also referred to as "low profile additives" (LPA), or in other sources as "low shrink additives" (LSA). It is also possible to use a number of the above-mentioned polymers in carboxylated form, for example as a copolymer with ethylenically unsaturated carboxylic acids or the corresponding anhydride. Preferably the shrink-resistant compound is a thermoplastic polymer and / or a styrene butadiene rubber.

The amount of shrink-resistant compound (b) in the resin mixture according to the invention is between 5 and 50 wt. parts relative to the total of (a) and (b).

The amount of copolymerizable free monomer in (a) and (b) relative to the total of (a) and (b) will generally be less than 60 1015271 - 7% by weight, more particularly between 20- 50 wt%. Within the scope of the invention it is not critical whether use is made of one copolymerizable free monomer or of a mixture of copolymerizable free monomers. The free monomer (or mixture of free monomers) present in (a) and (b) may be different.

By continuous carbon fiber bundles is meant fibers with a length that is much greater than the width or thickness of the carbon fiber bundle.

For the purposes of this invention, split continuous carbon fiber bundles are understood to mean a composition of a number of packages of (continuous) carbon filaments. It is customary for those skilled in the art that the number of filaments of a fiber bundle or of the packages obtained therefrom is indicated in a K value, each K indicating a thousand filaments. Therefore, the split continuous output beam 20 used herein has a much greater K value overall than that of any of the carbon filament packages obtained at splitting. Those carbon filament packages preferably each have a K value between 1 and 12, particularly preferably between 3 and 12. The carbon filament packages present in the split continuous carbon fiber bundles can, in particular, in terms of K value differ by up to 30-40%. Preferably, the split continuous carbon fiber bundles have a total K value of £ 20, more preferably> 40.

Until now it has not been possible in practice to make suitable compounds, for example i Ü1 52 71 - 8 - SMCs, based on resin compositions containing carbon fiber bundles with a K value greater than 12. The distribution of the carbon fiber bundles is then in general, at a given width of the SMC and a given number of coils, insufficiently homogeneous and, if the width of the SMC - with the number of coils remaining the same - is reduced in order to improve the homogeneity of the fiber loading, SMCs obtained with a fiber bed that is already so thick at a relatively low fiber loading that no good wetting is possible. Incidentally, the same problem also arises in other embodiments in which the fiber loading of a resin mixture has to take place over a large width, for instance when adding fiber material to a resin mixture in a long, narrow gap between two counter-rotating rollers. The length of the gap approximately corresponds to the width of the rollers.

By using split continuous 20 carbon fiber bundles with adhesives and binders as further specified in this application (leading to a suitable drop behavior after cutting), it is now possible, using a more limited number of coils, to spread carbon fibers over a wide area of the fiber. resin mixture, without losing the homogeneity of the fiber bed with SMCs, or without losing the homogeneity of the fiber loading when using rollers.

The carbon fibers in the split continuous carbon fiber bundles used in the context of the present invention are provided with an adhesive (sizing) bound at least partly chemically thereto, from 5271-9, and with a binder (binder), which is at least 10% by weight is soluble in free monomer present.

Since the sizing is at least partially anchored to the carbon fibers via a chemical reaction, that part of the sizing can in no way dissolve in any copolymerizable free monomer present. The non-chemically bonded portion of the sizing may be partially or completely insoluble in the copolymerizable free monomer. As a rule, only a limited portion, for example less than 30% by weight, of the sizing will be chemically bonded to the carbon fibers.

Within the scope of this invention, binders are used which at room temperature are at least 10% by weight soluble in present copolymerisable free monomer. It is possible that the amount of binder used is completely soluble in the free monomer. Preferably, for the preparation of resin compositions intended for applications with Class-A properties (ie with very good surface properties), a binder will be used which is soluble in the copolymerizable free monomer for 10 to 30% by weight. For the preparation of resin compositions intended for applications in structural parts, it is preferred to use a binder which is more than 30% by weight, more particularly preferably 50 to 75% by weight, soluble in the copolymerizable free monomer. The amount of sizing plus binder used is usually between 0.2 and 5% by weight relative to the amount of fiber. The glue and 1015271 - 10 - the binder can be the same compound. More narrowly, in the context of this application, only the amount of the sizing chemically bound to the fiber bundles could also be referred to as sizing; The amount of the sizing which is not chemically bound to the fiber bundles can therefore in fact also be regarded as a binder. This has been taken into account in the percentages stated in this application.

The weight percentage of carbon fiber relative to the resin composition will generally be 5-65% by weight. Preferably, the weight percentage of carbon fiber is either between 5 and 30 wt% or between 40 and 60 wt%, more preferably in the range of 45-58 wt%. A fiber load below 30% by weight will generally be used. apply when one wants to obtain Class-A properties. On the other hand, a fiber loading above 40% by weight will be chosen when structural applications are pursued. When SMCs involve a combination of different loading types (eg, isotropic and unidirectional fiber loading), the total fiber loading may be slightly higher than the aforementioned limits. Within the scope of the invention it is then possible to replace part of the discontinuous fibers with continuous fibers.

Preferably, the cut spliced continuous carbon fiber bundles have an average length between 0.5 and 10 cm, preferably between 1 and 5 cm.

It may be advantageous here, for example for parts with very fine ribs and cams, if in the average length distribution of the cut split continuous carbon fiber bundles) 0 'i 52 71 - 11 - there is such a distribution that at least two avoid clear limits. A distribution with 2 maxima is also called a bimodal distribution.

For example, an average length of the cut spliced continuous carbon fiber bundles involving at least two clear maxima in the length distribution can be obtained by mixing (at least two) portions of each cut to a different different average length of spliced continuous carbon fiber bundles. Such different average lengths of cut carbon fiber bundles can be obtained, for example, by using at least 2 or 15 more cutting devices. Within the scope of this invention, however, 1 cutting device can also be used for this purpose, provided that at least some of the distances between successive cutting blades are different therein.

A cutting device is also understood to mean an assembly of two rollers that roll against each other and of which one roller is provided with cutting blades at fixed or selected distances from each other (equal or different) and the other (rubber) roller presses against the roller provided with knives. .

The cut carbon fiber bundles are generally introduced into the resin matrix in the preparation of SMCs by dropping them, on an SMC line, directly from one or more cutters on the surface of (a first layer of) the resin mixture and cover with the same resin mixture, after which the resin composition is passed between pressure rollers (compacting unit) for impregnation.

.015271 - 12 -

It is also possible to add the cut carbon fiber bundles to a resin mixture in the gap between two counter-rotating rollers. The resin composition discharged after the rollers have passed can be fed in the form of a sheet to a compacting unit of an SMC line, or it can be supplied in bulk form to a mixing device, in order to impregnate the fiber material well. When mixing in a mixing device, for example in a kneader or an extruder, the mixing must be controlled in such a way that the average length of the cut carbon fiber bundles does not become shorter than 0.5 cm. More particularly, it is recommended that the average length of the cut carbon fiber bundles not be less than 2 cm.

Those skilled in the art can easily determine which weight percentage of carbon fiber, depending on the chosen average length of the carbon fiber, as well as the chosen resin mixture, gives the best results.

In general, the resin composition contains a maximum of 75% by weight of filler.

In particular cases it may be advantageous to use lower filler contents, for example less than 40 wt%, preferably less than 20 wt%, and even more preferably less than 5 wt%. In a special embodiment of the invention less than 0.1 wt% filler is used, more in particular less than 0.01 wt%. As the amount of filler is selected lower, the skilled person will optionally use other additives such as thixotropic agents (viscosity modifiers) or other amounts of copolymerizable free monomer (styrene) to adjust the viscosity of the resin mixture to such an appropriate value. to state that with SMCs a good wetting of the fiber bed occurs and that the resin composition can be processed well after thickening. In bulk processing, the viscosity of the resin mixture is less critical and the skilled person generally has to make less use of the abovementioned additives.

Suitable fillers are, for example, calcium carbonate, kaolin, heavy spar, dolomite, quartz meal, slate meal, talc, aluminum trihydrate, glass beads, carbon black and sand. Fillers with a very low density can also be used, eg hollow glass spheres.

For the purposes of this invention, fillers do not include dyes, catalysts, accelerators, release agents, initiators and inhibitors which will, of course, also be present in the resin composition.

The resin composition will generally also contain a thickening agent, certainly in the case of the preparation of SMCs and often also when used in bulk form. Such thickeners are known to those skilled in the art, and include, for example, oxides and hydroxides of the metals of groups I, II and III of the Periodic Table. Examples of suitable thickeners are oxides or hydroxides of magnesium, lithium and / or calcium.

Preferably magnesium oxide is used.

The amount of magnesium oxide added according to the invention is preferably greater than 1.5 wt.

. ü 1 52 71 - 14 - parts relative to the resin mixture. Thickening can also be achieved via reaction of the resin with (di) isocyanate compounds present in the resin mixture. This is particularly suitable for thickening vinyl ester-5 and hybrid resins.

Suitable thixotropic agents are aerosils, colloidal silica, highly reactive silicas, bentones, calcium stearate and hydrogenated oils, for example castor oil.

The amounts of catalysts, accelerators, release agents, initiators and inhibitors, as well as thickeners and optional thixotropic agents, are the amounts customary for radically curable resins. They are 15 in general. in total about 5 to 20 parts (wt.) compared to 100 parts of radically curable resin mixture (i.e. the sum of of a) + b)). When isocyanate thickening is used, the number of parts by weight of (di-) isocyanate compound (s) is generally between 10 and 45 parts compared to 100 parts of radically curable resin mixture. The amount of the other additives does not change. As a rule, a small amount of a water trap, for example Baylith powder or another mole screen, is then added. All this can be properly determined by the skilled person.

In the context of this invention, it is also possible to add further reinforcing materials to the resin composition in addition to the cut split continuous carbon fiber bundles. Suitable reinforcing materials are, for example, shredded plate materials such as, for example, mica, or other fibers of natural or synthetic origin, eg aramid, polypropylene, polyethylene terephthalate (PET-P), glass fibers, etc. These additionally fibers to be added can, if desired, also be added unidirectionally in the preparation of SMCs.

The invention also relates to a method for the manufacture of a thermosetting resin composition, in which split continuous carbon fiber bundles are cut in a cutting device, the carbon fiber bundles being provided with an at least partly chemically bonded adhesive and with a binder before cutting and are added to a radically curable resin mixture consisting of: a) 50-95 wt. parts of a radically curable resin which also contains a copolymerizable free monomer b) 5-50 wt. parts of an anti-shrinkage compound which may also contain an amount of copolymerizable free monomer as well as an amount of filler, wherein the binder is soluble at room temperature at least 10% by weight in copolymerizable free monomer present and the cut split continuous carbon fiber bundles therein 2D random and homogeneously distributed by either dropping them on an SMC line onto the resin mixture and covering them with the same resin mixture or 2) in a gap between two counter-rotating rollers, adding to the resin mixture, followed by a 1015271 - 16 - impregnation step in a compacting unit or in a mixer.

The impregnation step in a mixer will in particular be used in the preparation of the compounds in bulk form.

The split continuous carbon fiber bundles are fed into the cutting device at intervals of a few centimeters.

The packages of continuous 10 carbon filaments used in the method according to the invention have a K value between 1 and 12, preferably between 3 and 12, and are obtained by unspliced continuous carbon fiber bundles with a total K value> 20, 15 preferably split> 40.

The resin composition thus obtained is suitable for use in the production of 3D molded parts. The molded parts have particularly good mechanical properties, good temperature resistance, excellent high temperature dimensional stability, as well as favorable fatigue properties. In a special embodiment of the invention, these good mechanical and other properties are associated with a low weight. The carbon fibers are also homogeneously distributed over special places in the 3D-shaped part, such as eg ribs and cams. According to the method of the invention, it appears quite possible to form moldings with high contents of filler (for example 60 to 75% by weight relative to the resin composition) and a shrink-resistant compound (for example 30 to 40% by weight of the resin mixture). Manufacture "Class -A" surface properties. In the event that ! In the split continuous carbon fiber bundles, a binder of which less than 30% by weight dissolves in the present copolymerizable free monomer and a fiber loading below 30% by weight will preferably be used.

The invention therefore also relates to the use of curable resin compositions according to the invention (or prepared according to the method thereof) for the production of molded parts.

The moldings according to the invention can be used as a housing for electronics with sufficient EMI shielding. In addition, the molded parts can be used as body panels for cars, as well as as inner and / or outer shell for shell parts and as (semi) structural parts in cars or other means of transport.

It is to be noted that JP-A-08-311242 describes electrically conductive thermosetting resin compositions (with short fibers - 0.1 to 1 cm-reinforced SMCs) which are mainly used as electronics housing with EMI shielding. The resin compositions according to the invention already give an even better or even better EMI shielding at a much lower carbon fiber loading than the products described in JP-A-08-311242.

The invention will now be further elucidated on the basis of a few examples, without however being limited to the compositions shown in the examples.

Example I

1015271 - 18 -

A vinyl ester (Atlac XP 810, DSM Composite Resins, Zwolle, The Netherlands) based resin mixture was prepared, with the following composition:

Atlac XP 810: 70 parts

5 Palapreg H814: 30 parts of LPA from DSM

Composite Resins calcium carbonate: 5 parts (filler)

Trigonox C: 1.5 parts initiator of

Akzo Nobel 10 p-benzoquinone (PBQ): 0.4 parts (of a 10% solution)

Zn stearate: 5 parts

MgO: 2.8 parts (thickener)

The amount of resin mixture was split into 2 parts, and using a doctor blade to a resin film spread on 2 polyethylene / polyamide carrier films.

The split continuous carbon fiber bundles with a styrene-soluble binder (K value 80, split into 10 packages averaging 8K) of 14 spools were introduced into the cutter at a distance of 4 cm above the bottom resin layer. The carbon fiber bundles were cut with rotary blades into packages of filaments about one inch long.

A 2D randomized and homogeneous fiber bed with a width of 50 cm was obtained on the bottom resin layer. The second resin layer was now applied to the fiber bed, after which the fiber material was impregnated with the resin mixture in a compacting unit.

The sheet-like resin composition thus obtained was then rolled up. A carbon fiber loading of 52% by weight was realized. The good 1015271 - 19 - wetting of the 8K packages to filament level with the resin mixture was clearly apparent.

Thickening of the obtained compound took place in 10 days, after which the resin composition was pressed into a flat sheet, using a 40% mold insert percentage. A homogeneous black colored plate was the result.

Test bars were sawn from the obtained flat sheet, which were then subjected to a bending test and an ILSS test.

Bending test results (ISO 178):

Flexural modulus 33 GPa Flexural strength 530 MPa 15

Results ILSS test (ASTM 2344): 68 MPa

The density of the obtained material 20 was 1.39 g / cm3.

Example II (EMI shielding)

Using the same resin mixture as in Example 1, as well as the same split continuous carbon fiber bundle, a compound was now made containing 25 wt% carbon fibers about 2.5 cm in length.

*

After 12 days of thickening, a number of flat plates 30 were pressed with a mold insert percentage of 40% with the following thicknesses: 1.4 mm, 2.8 mm and 5.8 mm.

1015271 - 20 -

Shielding efficiency was measured in accordance with ASTM 4935 in the frequency range between 30 MHz and 1 GHz.

The 5 shielding curves show a smooth course over a wide frequency range. A number of characteristic values of these curves are shown in the table.

Table 1: Shielding (EMI shielding) as a function of the 10 frequency at different plate thicknesses.

Frequency Shielding (dB) at different plate thicknesses 1.4 mm plate 2.8 mm plate 5.8 mm plate 30 Mhz 64 85 100 100 Mhz 65 89 105 300 Mhz 77 90 110 500 Mhz 87 93 108 700 Mhz 88 96 110 1 Ghz 87 98 110

Comparative example A

Using the resin mixture of Example I, 14-spool carbon fiber bundles were now cut with a non-spliced 24K carbon fiber bundle above the bottom resin bed to a length of about 2.5 cm.

The distance between the 20 fiber bundles, as in Example 1, was 4 cm. Instead of a homogeneous fiber bed over a width of 50 cm, 1015271-21 - 14 "ridges" of fiber material were now previously obtained, with in between areas where there were hardly any fiber bundles. A carbon fiber loading of 48% by weight was realized. To avoid such areas, the distance between the different bundles in the cutting device had to be reduced. Only at a mutual distance between the bundles of 1.5 cm could a homogeneous fiber distribution be achieved (width of the obtained SMC is then approximately 10-20 cm).

Impregnation of that 20 cm wide fiber bed, however, proved not to be possible, which was evident from the large proportion of dry fiber bundles still present after the compacting unit.

15

Comparative example B

Using the resin mixture of Example I, split continuous carbon fiber bundles with a non-styrene soluble binder (48K, split into 7 packages of 7K average) of 14 spools were cut to a length of about 2.5 cm.

Thus, under identical conditions as in Example 1, a 50 cm wide C-SMC was made, with a carbon fiber loading of 52% by weight.

After thickening the compound for 10 days, using a 40% mold insertion percentage, a flat sheet was pressed, from which a number of test bars were cut for a bending test. On the surface of the flat plate (and the test bars), areas were clearly visible where there were hardly any carbon fibers (light yellow in color).

1015271 - 22 -

The results of the bending test according to ISO

178 were:

Flexural strength: 200 MPa +40 MPa

Flexural modulus: 31 GPa.

The ILSS (ASTM 2344) was 59 MPa.

Example III

A maleate resin (Palapreg 0423-N-2, DSM Composite Resins) based resin mixture was prepared, with the following composition:

Palapreg 0423-N-2: 64 parts

Neulon LP40A: 33 parts of polyvinyl acetate LPA from Union Carbide Chemicals 15 Coathylene HA 1681: 3 parts of polyethylene from

Plast Labor SA

Styrene: 3 parts BYK W 996: 2 parts wetting agent from BYK Chemistry 20 calcium carbonate: 190 parts (filler)

Trigonox C: 1.6 parts initiator of AKZO Nobel

Trigonox 21 LS: 0.2 parts initiator of AKZO Nobel 25 p-benzoquinone (PBQ): 0.35 parts (of a 10% solution)

Ca stearate: 5 parts

MgO: 2.7 parts (thickener)

The amount of resin mixture was split into 2 parts, and using a squeegee to a resin film with a width of 30 cm spread on 2 rolls of a calender.

101 52 71 '- 23 -

The split continuous carbon fiber bundles with a styrene-soluble binder (K value 80, split into 10 packages of 8K average) of 8 spools were introduced 4 cm above the 5 slit space of the calender. The carbon fiber bundles were cut with rotary blades into packages of filaments about one inch long.

The cut fibers fell randomly onto the resin layers on the rollers, after which the fiber material together with the resin mixture passed the gap between the 2 rollers and was impregnated with the resin mixture. The belly-shaped resin composition thus obtained was then removed from the rollers by means of scrapers and packed.

A carbon fiber loading of 17% by weight was realized. The good wetting of the 8K packages to filament level with the resin mixture was clearly apparent.

Thickening of the obtained compound took place in 7 days, after which the resin composition was pressed into a flat plate. A homogeneous dark gray colored plate was the result.

Test rods were sawn from the flat sheet obtained, which were then subjected to a bending test.

Flexural Test Results (ISO 178): 30 Flexural Modulus 20 GPa

Flexural strength 200 MPa 101 52 71 - 24 -

The density of the obtained material was 1.79 g / cm3.

Comparative example C

Using the resin mixture of Example III, 8-spool carbon fiber bundles with an un-spliced 24K carbon fiber bundle were now cut above the calender to a length of about 2.5 cm. The distance between the 10 fiber bundles, as in Example III, was 4 cm. Instead of a homogeneous fiber distribution over a width of 30 cm, 8 "stripes" of fiber material have now been obtained, with in between regions where there were hardly any fiber bundles. A carbon fiber loading of 16% by weight was realized. To avoid the creation of such areas with and without fiber bundles, the distance between the different bundles in the cutting device had to be reduced. It is true that with a smaller mutual distance between the 20 bundles than 1.5 cm, a more homogeneous fiber distribution could be achieved. Impregnation of the fibers, however, proved not to be possible, which was evident from the large proportion of dry fiber bundles that were still present in the obtained bulk compound.

25 1 0 1 5271

Claims (17)

A thermosetting resin composition containing a radically curable resin mixture as matrix, containing 2D randomly distributed discontinuous carbon fibers as well as other additives, characterized in that the radically curable resin mixture consists of: 10 a) 50-95 wt. parts of a radically curable resin which also contains a copolymerizable free monomer b) 5-50 wt. parts of a shrink-resistant compound which may also contain an amount of copolymerizable free monomer and that the discontinuously distributed carbon fibers are obtained by cutting split continuous carbon fiber bundles, which carbon fiber bundles are provided with an adhesive bonded at least partly chemically thereto and with a binder which is room temperature is soluble for at least 10% by weight in the present copolymerizable free monomer of the radically curable resin mixture and that the weight percentage of carbon fibers with respect to the resin composition is between 5 and 65% by weight and that a filler is also present in the resin composition . A thermosetting resin composition according to claim 1, 1015271 - 26 - characterized in that the split continuous carbon fiber bundles have a total K value> 20, preferably> 40 and are composed of packages of 5 carbon filaments, each having a K value between 1 and 12, preferably between 3 and 12. A thermosetting resin composition according to claims 1-2, characterized in that the radically curable resin is a vinyl ester resin or an unsaturated polyester resin. A thermosetting resin composition according to claims 1-3, characterized in that the copolymerizable free monomer is styrene. A thermosetting resin composition according to any one of claims 1-4, characterized in that the shrink-resistant compound is selected from thermoplastic polymers and / or styrene butadiene rubbers. A thermosetting resin composition according to any one of claims 1 to 5, characterized in that the weight percentage of carbon fibers relative to the resin composition is either between 5 and 30% by weight or between 40 and 60% by weight. %, preferably between 45 and 58 wt. % lies. A thermosetting resin composition according to any one of claims 1-6, characterized in that the average length of the cut split continuous carbon fiber bundles is between 0.5 and 10 cm, preferably between 1 and 5 cm. A thermosetting resin composition according to claim 7, characterized in that the mean length of the cut split continuous carbon fiber bundles is not less than 2 cm. A thermosetting resin composition according to claim 7, characterized in that the average length distribution of the cut split continuous carbon fiber bundles involves at least two length distribution maxima. 10. A thermosetting resin composition according to any one of claims 1-9, characterized in that the amount of filler relative to the resin composition is a maximum of 75% by weight. A thermosetting resin composition according to claim 10, characterized in that in the resin composition there is less than 5 wt%, in particular less than 0.1 wt% and most preferably less than 0.01 wt% filler is present. 12. A thermosetting resin composition according to any one of claims 1-11, characterized in that the adhesive and the binder are the same compound. 13. A method of manufacturing a thermosetting resin composition containing a radically curable resin mixture as matrix, containing 2D randomly distributed discontinuous carbon fibers as well as other additives, characterized in that split continuous carbon fiber bundles are cut into 30 packages of carbon filaments in a cutting apparatus, the carbon fiber bundles provided before cutting 101 52 71 28 with an adhesive, at least partly chemically bound thereto, and with a binder, and added to a radically curable resin mixture consisting of: 5 a) 50-95 wt . parts of a radically curable resin which also contains a copolymerizable free monomer b) 5-50 wt. parts of an anti-shrinkage compound which may also contain an amount of copolymerizable free monomer as well as an amount of filler, wherein the binder is soluble at room temperature at least 10% by weight in copolymerizable free monomer present, and the 15 split continuous carbon fiber bundles therein 2D- are distributed randomly and homogeneously by either 1. dropping them onto an SMC line on the resin mixture and covering it with the same 20 resin mixture, or 2. adding them to the resin mixture in a gap between two counter-rotating rollers, followed by an impregnation step in a compacting unit or in a mixer. A method of manufacturing a thermosetting resin composition according to claim 13, characterized in that the packages of continuous carbon filaments each have a K value between 1 and 12, preferably between 3 and 12, and are obtained by unsplit • υ I 52 71> - 29 - split continuous carbon fiber bundles with a total K-value> 20, preferably> 40. 15. Method for manufacturing 3D molded parts, characterized in that a thermosetting resin composition as described in any one of claims 1-12 is used in its manufacture. Molded parts obtained according to claim 15, characterized in that the density of the thermosetting resin composition obtained is <1.8 g / cm3 and the molded part as material properties has a flexural modulus according to ISO 178 between 10 and 30 GPa, a flexural strength according to ISO 178 has between 100 and 500 MPa, and a 15 ILSS according to ASTM 2344 has between 50 and 75 MPa. Molded parts according to claim 15, characterized in that the density of the thermosetting resin composition obtained is <1.5 g / cm 3 and the molded part as material properties has a flexural modulus according to ISO 178 between 10 and 40 GPa, a flexural strength according to ISO 178 has between 100 and 600 MPa, and an ILSS according to ASTM 2344 has between 50 and 75MPa. 1015271 COOPERATION TREATY (PCT) REPORT ON NEWNESS RESEARCH OF INTERNATIONAL TYPE IDENTIFICATION OF THE NATIONAL APPLICATION FEATURE OF THE APPLICANT OR AUTHORIZED 4245 NL Dutch application no. Date of submission 1015271 23 May 2000 priority date Applicant NV an investigation by the International Research Authority (ISA) to international type the request for an investigation of international type toe9®k®ndnr · SN 35222 EN I. CLASSIFICATION OF THE SUBJECT (when using different classifications, indicate all badger marks) According to the International Classification (IPC) lnt.CI.7: C08J5 / 06 C08K9 / 04 II. FIELDS OF TECHNIQUE EXAMINED Minimum documentation examined Classification system Classification symbols ln.CI.7: C08J C08K C03C C08L Documentation examined other than minimum documentation, insofar as such documents are included in the areas examined III. □ NO EXAMINATION FOR CERTAIN CONCLUSIONS (comments on supplementary sheet) IV. LACK OF UNITY OF INVENTION (Comments on Supplementary Sheet) Form PCT / ISA201 a (11/2000)