The invention relates to a composition comprising a curable pre-polymer, to the use of a polymer having a polymer main chain comprising repeating units of polymerized di-unsaturated hydrocarbons and which polymer main chain is grafted with monomers having one ethylenically unsaturated group as de-foaming agent and for reducing shrinkage, and to a process of improving the de-foaming characteristics of a curable pre-polymer.

In many industrial processes, foaming is an important problem. De-foaming or anti-foaming agents are known. A defoamer or an anti-foaming agent is a chemical additive that reduces and hinders the formation of foam in industrial process liquids. The terms de-foaming agent and anti-foaming agents are often used interchangeably. Commonly used de-foaming agents are insoluble oils, polydimethylsiloxanes and other silicones, certain alcohols, stearates and glycols. De-foaming agents based on small scale particles like ureas are known as well. The additives are generally used to prevent formation of foam, or they are added to break a foam already formed.

US 8309648 B2 relates to a silicone free defoamer for solvent-based coatings. The defoamer formulation comprises a graft copolymer having a polymer main chain consisting of repeating units of polymerized mono-functional ethylenically unsaturated monomers. The polymer main chain is grafted with monomers selected from (meth)acrylates, styrene, and vinyl acetate.

EP 0221755 B1 relates to a process for producing a polyamide. The process comprises polymerizing a polyamide monomer in the presence of a low amount of a modified hydrocarbon polymer bearing at least one type of group selected from carboxyl, carboxylic acid derivative, amino- and hydroxyl group. The hydrocarbon polymer is a homopolymer or copolymer of an alphaolefin, or a hydrogenated homopolymer or copolymer of a diene.

The production of de-foaming agents and compositions is often costly, and the use of de-foaming agents contributes to the overall costs of curable pre-polymer compositions. The inclusion of defoaming agents also increases the complexity of the overall recipe of curable pre-polymer compositions and the risk of unpredictable interactions between components.

There is an ongoing need for further de-foaming agents for curable pre-polymer compositions which address the above-mentioned problems. In particular, the agents should provide good defoaming properties or prevent the formation of foam, while not detracting from other desirable properties, such as the clarity or absence of turbidity of the compositions. The de-foaming agents should also be suitable for different types of pre-polymer compositions, in particular for pre- polymer compositions comprising dicyclopentadiene resin, which so far have been found difficult to provide with acceptable de-foaming properties. Furthermore, it is desirable that the de-foaming agent provides other desirable properties, such as reduced shrinkage of the curable pre-polymer compositions upon curing.

The invention provides a composition comprising a) a curable pre-polymer (A), and b) a polymer (B) having a polymer main chain comprising or consisting of repeating units of polymerized di-unsaturated hydrocarbons and which polymer main chain is grafted with monomers having one ethylenically unsaturated group, wherein polymer (B) is a liquid at a temperature of 23 °C.

The composition of the invention has good de-foaming properties or prevent the formation of foam, while not detracting from other desirable properties, such as the clarity or absence of turbidity of the compositions. These properties are attainable with a large variety of different types of prepolymers. Furthermore, it has been found that in some embodiments the compositions of the invention exhibit reduced shrinkage of the curable pre-polymer compositions upon curing.

Curable pre-polymer compositions are applied in different areas, for example as casting resins, in the manufacture of composite materials, such as fiber reinforced materials, and in the manufacture of laminates. The curable pre-polymer composition is a liquid or viscous composition comprising monomeric or oligomeric molecules having functional groups. The functional groups are capable of chemical reactions to increase the molecular weight of the monomeric or oligomeric molecules. These reactions thus lead to a cured polymer which generally is solid. The cured polymer may be crosslinked or non-crosslinked. The chemical reaction of the functional groups may be triggered in various ways.

In some embodiments, the curable pre-polymer composition is provided as a two- or more component composition, wherein the components comprise mutually reactive functional groups which are mixed prior to use. Examples include epoxide groups, which are reactive with amine groups, hydroxyl groups, or carboxylic acid groups; isocyanate groups which are reactive with amine, hydroxyl, or thiol groups; and electron deficient ethylenically unsaturated groups which are reactive with amine groups or thiol groups. In a further embodiment, the functional groups are radically polymerizable functional groups. In that case, the curing reaction is a radical polymerization reaction which can triggered by radical generating initiators, such as peroxides, or by actinic radiation, such as UV radiation or electron beam radiation, or by combinations thereof. In a specific embodiment, the curable pre-polymer composition comprises an unsaturated polyester base and a polymerizable monomer diluent, such as styrene or an acrylic or methacrylic monomer. In a further embodiment, the curable pre-polymer composition comprises a dicyclopentadiene resin. In still further embodiments, the curable pre-polymer composition comprises a curable silicone or a curable phenolic resin, epoxy(meth)acrylate resin, and urethane (meth)acrylate resin.

In preferred embodiments, the curable pre-polymer (A) comprises at least one of epoxy resin, unsaturated polyester resin, and dicyclopentadiene modified unsaturated polyester resin.

Examples of suitable epoxide resins include diepoxides. Suitable diepoxides are compounds having two epoxide groups. Preferred diepoxides are diglcidylethers of aliphatic and aromatic alcohols. Such diglycidylethers are commercially available. They are suitably formed by reacting reactive phenols or alcohols with epichlorohydrin. Alternatively, diepoxides can be prepared by epoxidation reaction of compounds having two olefinic double bonds. Preferably the diepoxides used in the present invention are selected from the group consisting of glycidyl ethers, like bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, hydrogenated bisphenol F diglycidyl ether, oligomeric and polymeric diglycidylethers based on bisphenol A and/or Bisphenol F and/or hydrogenated bisphenol A and/or hydrogenated Bisphenol F, 1 ,3-propane-, 1 ,4-butane- or 1 ,6-hexanediol -diglycidyl ether and polyalkylenoxide glycidyl ether; glycidyl esters, like hexahydrophthalic acid diglycidyl ester; cycloaliphatic epoxides, like 3,4-epoxycyclohexyl-epoxyethane or 3,4-epoxycyclohexylmethyl-3,4-epoxy-cyclohexane carboxylate.

Examples of suitable monoepoxides include epoxidized olefins, glycidylethers of monoalcohols, and glycidylesters. Specific compounds include aliphatic, cycloaliphatic, aromatic and/or araliphatic glycidyl ether, glycidyl ester and olefin oxides like C1 -C20- alkyl glycidyl ether, phenyl glycidyl ether, cresyl glycidyl ether, naphthyl glycidyl ether, butyl glycidyl ether, p-tert.-butyl-phenyl glycidyl ether, 2-ethyl-hexyl glycidyl ether, C12-C14-glycidyl ether, allyl glycidyl ether, 2,3- epoxypropylneodecanoate (Cardura® E 10, Resolution Performance Products), C4-C20-olefine oxides like 1 ,2-octene oxide, 1 ,2-nonene oxide, 1 ,2-undecene oxide, 1 ,2-dodecene oxide, 1 ,2- octadecene oxide, 4-methyl-1 ,2-pentene oxide, 1 ,2-butene oxide, propene oxide, ethylene oxide, styrene oxide, butadiene monoxide, isoprene monoxide, cyclopentene oxide and/or 2-ethyl-1 ,2- butene oxide.

Examples of suitable curing agents for epoxide resins are polyamines, more particularly (hetero)aliphatic, (hetero)aromatic, and (hetero)cycloaliphatic polyamines, polyamidoamines, polyaminoamides, and also polycarboxylic acids and their anhydrides.

As mentioned above, the curable pre-polymer composition comprises an unsaturated polyester resin in some preferred embodiments. Typically, these unsaturated polyesters are the reaction product of unsaturated mono- or dibasic acids with difunctional alcohols used in the manufacture of the aforementioned unsaturated polyester. Suitable examples of a,[3-unsaturated dibasic acids are maleic acid, maleic anhydride, fumaric acid, itaconic acid and itaconic anhydride.

Suitable dibasic acids are phthalic acid, phthalic anhydride, halogenated phthalic anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, hexahydroterephthalic acid, hexahydroisophthalic acid, succinic acid, malonic acid, glutaric acid, adipic acid, sebacic acid, 1 ,12-dodecane dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, 2,7-naphthalene dicarboxylic acid, 2,3-naphthalene dicarboxylic acid, 2,3-naphthalene dicarboxylic acid anhydride, 4,4'- biphenyldicarboxylic acid, as well as dialkylesters of the aforementioned, and the like.

Suitable monobasic acids include benzoic acid, stearic acid, oleic acid, linolenic acid, linoleic acid, palmitic acid and the like, including combinations thereof.

Examples for suitable multifunctional alcohols are polyhydric alcohols which include, for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, 2-methyl-1 ,3-propane diol, 1 ,3-butane diol, neopentylglycol, bisphenol A hydroxide, 1 ,4-butane diol, adduct of bisphenol A and propylene oxide or ethylene oxide, 1 ,2,3,4-tetrahydroxybutane, glycerin, trimethylol propane, 1 ,3-propane diol, 1 ,2-cyclohexane glycol, 1 ,3-cyclohexane glycol, 1 ,4-cyclohexane glycol, 1 ,4-cyclohexane dimethanol, paraxylene glycol, dicyclohexyl-4, 4'-diol, 2,6-decalin glycol, 2,7-decalin glycol, and mixtures thereof. Monohydric alcohols include benzyl alcohol, hydroxy(dicyclopentadiene), cyclohexyl alcohol, 2-ethylhexyl alcohol, lauryl alcohol, stearyl alcohol, and mixtures thereof. In addition to the monomeric or oligomeric molecules having functional groups, the curable prepolymer composition may comprise other ingredients which are typically present in such compositions. Examples of such ingredients include organic or inorganic particulate fillers, pigments, dispersants or dispersing aids, stabilizers, such as UV stabilizers, and fibers.

Unsaturated polyester resins are typically used in combination or admixture with ethylenically unsaturated polymerizable monomers, it is possible to use any ethylenically unsaturated monomer and ethylenically unsaturated oligomer conventionally used in unsaturated polyester resins, which can crosslink with an unsaturated polyester. The ethylenically unsaturated polymerizable monomer is preferably a monomer containing a vinyl group. Preferably, one of a (meth)acrylate group, styryl group, allyl group and vinylether group.

Examples of the aforementioned vinyl monomer include alpha-methylstyrene, chlorostyrene, dichlorostyrene, divinylbenzene, t-butylstyrene, vinyltoluene, vinyl acetate, diallylphthalate, triallylcyanurate, acrylic esters, (meth)acrylic esters, methyl (meth) acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth) acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth) acrylate, stearyl (meth)acrylate, tridecyl (meth)acrylate, dicyclopentenyloxyethyl (meth) acrylate, ethylene glycol monomethylether (meth)acrylate, ethylene glycol monoethylether (meth)acrylate, ethylene glycol monobutylether (meth) acrylate, ethylene glycol monohexylether (meth)acrylate, ethylene glycol mono-2- ethylhexylether (meth)acrylate, propylene glycol monomethylether (meth)acrylate, propylene glycol monoethylether, propylene glycol monobutylether (meth)acrylate, (meth) acrylate, propylene glycol monohexylether (meth)acrylate, propylene glycol mono-2-ethylhexylether (meth)acrylate, ethylene glycol di(meth) acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth) acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth) acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth) acrylate, dipentaerythritol hexa(meth)acrylate, N-vinylpyrolidone and the like. These aforementioned monomers may be used alone or in combination.

In a preferred embodiment, the curable pre-polymer (A) comprises or consists of dicyclopentadiene modified unsaturated polyester resin.

Dicyclopentadiene, abbreviated DCPD, is a chemical compound with formula C10H12. The IUPAC name is Tricyclo[5.2.1.0 ²ⁱ⁶ ]deca-3,8-diene. At room temperature, it is a white brittle wax, although lower purity samples can be straw-colored liquids. Dicyclopentadiene is co-produced in large quantities in the steam cracking of naphtha and gas oils to ethylene. The major use is in resins.

Dicyclopentadiene modified unsaturated polyester resins are unsaturated polyester resins which have been modified with DCPD.

In a first embodiment, dicyclopentadiene modified unsaturated polyester resins are unsaturated polyester resins as described above, and which are mixed with DCPD. In this case, the DCPD serves as a reactive diluent for the unsaturated polyester resin. DCDP can partly or entirely replace styrene or other vinyl monomers as reactive diluent. In this case, the DCPD modified unsaturated polyester resin generally comprises DCPD in a range of 2 to 15 % by weight, preferably 3 to 10 % by weight, calculated on the weight of the unsaturated polyester resin without DCPD. In this embodiment, DCPD participates in the radical curing reaction of the unsaturated polyester resin upon curing.

In a second embodiment, dicyclopentadiene modified unsaturated polyester resins are unsaturated polyester resins, wherein DCPD is chemically linked to the unsaturated polyester resin. The following methods for incorporating dicyclopentadiene into an unsaturated polyester are mentioned by way of example. The anhydride method has been known wherein the pre-formed Diels-Alder adduct of dicyclopentadiene and maleic anhydride is reacted with further amounts of maleic anhydride, optionally other di- or polycarboxylic acids, and a glycol in a polyesterification reaction. Another method involves reacting a mixture of maleic anhydride, dicyclopentadiene and a glycol, followed by polyesterifying. Yet another known method consists of pre-reacting maleic anhydride and glycol to obtain an esteracid prior to reaction with dicyclopentadiene, followed by polyesterification. A further known method involves polyesterification of maleic anhydride and a glycol, followed by subsequent reaction with dicyclopentadiene. A still further method involves the formation of maleic acid half ester of dicyclopentyl alcohol by reaction of maleic acid, formed for example by hydrolysis of maleic anhydride by water, and DCPD. The intermediate is then reacted with further alcohols and carboxylic acids to form an unsaturated polyester. The methods relating to the second embodiment are described in US 4233432.

In a third embodiment, dicyclopentadiene modified unsaturated polyester resins are unsaturated polyester resins according to the second embodiment, which are mixed with DCPD and wherein DCPD serves as a reactive diluent for the unsaturated polyester resin, as described for the first embodiment. The composition of the invention further comprises a polymer (B) having a polymer main chain comprising or consisting of repeating units of polymerized di-unsaturated hydrocarbons and which polymer main chain is grafted with monomers having one ethylenically unsaturated group.

Polymer (B) of the composition is a liquid at a temperature of 23 °C. This facilitates the mixing of polymer (B) with the curable pre-polymer. In typical embodiments, polymer (B) is dissolved in the curable pre-polymer or forms a homogeneous mixture with it.

Polymer (B) being a liquid at a temperature of 23 °C further eliminates the need to use volatile organic solvents to dissolve polymer (B). However, if so desired polymer (B) may also be dissolved in a suitable organic solvent prior to mixing it with the curable pre-polymer. Alternatively, polymer (B) may also be dissolved in a reactive diluent, which cures together with the curable pre-polymer.

As mentioned above, polymer (B) is a graft polymer having a polymer main chain. The polymer main chain comprises repeating units of polymerized di-unsaturated hydrocarbon monomers. The polymer main chain generally is a linear polymer chain or is essentially linear.

In some embodiments, the polymer main chain further comprises repeating units of polymerized units of mono-unsaturated hydrocarbon monomers. Such repeating units may be present in the polymer main chain in an amount of 0 to 30 mol-%, preferably 0 to 20 mol-%, calculated on the total number of repeating units. In other embodiments, the polymer main chain of polymer (B) consists of repeating units of polymerized di-unsaturated hydrocarbon monomers.

Said di-unsaturated hydrocarbon monomers may be conjugated dienes or unconjugated dienes. Examples of suitable dienes include isoprene (2-methyl-1 ,3-butadiene), butadiene (1 ,3-butadiene), 1 ,5-cyclooctadiene, piperylene, dimethylbutadiene, 2-methylpentadiene, 2-ethylhexadiene, and norbornadiene. It is preferred, that polymer (B) has a polymer main chain comprising repeating units of polymerized units of butadiene or isoprene or mixtures thereof.

The preparation of polymers for the polymer main chain is known from the state of the art. US 6437205 B describes a process for the preparation of low molecular weight high cis-1 ,4 polybutadienes using specific catalysts. The catalyst system comprises: (a) a neodymium- containing compound; (b) an aluminoxane; (c) an organoaluminum hydride compound; and (d) a halide source. US 3312752 describes a process for producing liquid polydienes from the polymerization of a conjugated 1 ,3-diene monomer in an inert solvent in the presence of a vinyl cycloolefin and catalytic quantities of a nickel compound and an aluminum halide compound.

Depending on the polymerization process, a polybutadiene polymer consists of a typical distribution between different stereounits: 1 ,4-cis configuration, 1 ,4-trans configuration and 1 ,2- vinyl configuration. Preferred polymers have a high content of 1 ,4-cis double bonds and a low content of 1 ,2-vinyl double bonds.

Suitable polymers for the polymer main chain are commercially available from various sources, such as from Kuraray under the trade designations LBR-302, LBR-305, LBR-307, LIR-30, LIR-50, LIR-390, from Synthomer under the trade designation Lithene™, from Evonik under the trade designation Polyvest®, from Nippon Soda company under the trade designation NISSO-PB, and from Cray Valley under the trade designation Ricon®.

The polymer main chain of polymer (B) is grafted with monomers having one ethylenically unsaturated group. Suitable monomers for grafting are all ethylenically unsaturated monomers capable of undergoing a grafting reaction under the influence of free radicals.

In preferred embodiments, polymer (B) is grafted with monomers comprising at least one of maleic anhydride, maleic acid, hydroxyalkyl (meth)acrylate, such as hydroxy ethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 4- hydroxybutyl methacrylate, (meth)acrylic acid, ethylenically unsaturated monoamine, such a oleylamine (1-Amino-9-octadecen), mono-ethylenically unsaturated hydrocarbon having 4 to 24 carbon atoms, such as vinylaromatic compounds, in particular styrene, alpha-olefins, di-C ₂ to C ₈ alkyl fumarate, and di-C ₂ to C ₈ alkyl maleate, mono-C ₂ to C ₈ alkyl fumarate, and mono-C ₂ to C ₈ alkyl maleate. Other suitable grafting monomers are allylethers, in particular mono allylethers of diols, for example ethyleneglycol monoallylether, and monoallylether of polyethylene glycol or polypropylene glycol. Also suitable are vinyl-functional heterocyclic compounds, such as 5-Methyl- 3-vinyl-2-oxazolidinone.

Polymer (B) can suitably be obtained by using commercially available polymers comprising or consisting of repeating units of polymerized di-unsaturated hydrocarbons, and grafting these polymers with monomers having one ethylenically unsaturated group. The polymers comprising or consisting of repeating units of polymerized di-unsaturated hydrocarbons suitably have a weight average molecular weight Mw in the range of 5000 to 25000 g/mol. It is preferred, that these polymers are liquid at a temperature of 23 °C. The grafting process is suitably carried out in the presence of a radical generating agent and the above-mentioned monomers having one ethylenically unsaturated group. Examples of suitable radical generating agents are peroxides and diazo compounds. The temperature during the grafting process is suitably controlled within a range that ensures generation of radicals from the radical generating agent. In some embodiments, the grafting process is carried out in a suitable organic solvent.

The amount of grafted monomers in polymer (B) can varied in wide ranges. Generally, polymer (B) comprises grafted monomers in the range of 0.5 to 60.0 % by weight, calculated on the total weight of polymer (B). If the content of grafted monomers is outside this range, the technical advantages of the composition of the invention, such a de-foaming property, may not be fully achieved. In preferred embodiments, polymer (B) comprises grafted monomers in the range of 1.0 to 55.0 % by weight, more preferred 2 to 40 % by weight, calculated on the total weight of polymer (B).

Polymer (B) generally has a number average molecular weight Mn in the range of 2000 g/mol to 50000 g/mol, preferably 2000 to 40000 g/mol, most preferably in the range of 3000 to 25000 g/mol. The number average molecular weight is suitably determined by gel-permeation chromatography using tetrahydrofuran as eluent and polystyrene as calibration standard. When the number average molecular weight of polymer (B) exceeds the above-mentioned values, it may be a solid, which detracts from dissolving it in the curable pre-polymer. When the number average molecular weight of polymer (B) is below the above-mentioned values, the technical advantages, such a defoaming property, may not be fully achieved.

In the composition of the invention polymer (B) is generally present in an amount of 0.005 to 1 .000 % by weight, calculated on the weight of the curable pre-polymer (A). When polymer is present in the above-mentioned about, satisfactory anti-foaming properties of the composition are generally obtained. When polymer (B) is used in lower amounts, the anti-foaming properties may be less than sufficient. Higher amounts of polymer (B) can be used. However, a further improvement of anti-foaming properties is not generally obtained by higher amounts of polymer (B). In preferred embodiments of the composition of the invention polymer (B) is present in an amount of 0.050 to 0.800 % by weight, more preferred 0.0800 to 0.700 % by weight, calculated on the weight of the curable pre-polymer (A).

The terms “anti-foaming” and “defoaming” relate to the prevention of foam formation, as well as to improved release of foam in a composition.

In some embodiments the composition of the invention also exhibits decreased shrinkage upon curing of the curable pre-polymer. Shrinkage during curing of a pre-polymer is undesirable, as it can cause surface defects of the cured objects, as well as dimensional inaccuracy of shaped parts, and reduced mechanical properties due to internal in the cured material.

Reduced shrinkage has been observed in particular for embodiments wherein the curable prepolymer is an unsaturated polyester resin or a dicyclopentadiene resin, or a combination thereof. For anti-shrinking properties, polymer (B) is generally applied in higher amounts than required for de-foaming properties. Therefore, in some preferred embodiments of the composition of the invention, the curable pre-polymer (A) comprises at least one of unsaturated polyester resin and dicyclopentadiene modified unsaturated polyester resin, and polymer (B) is present in an amount of 5.000 to 30.000 % by weight, preferably 7.000 to 25.000 % by weight, calculated on the weight of the curable pre-polymer (A).

It is generally preferred that the composition of the invention comprises a low amount of volatile organic solvents. Volatile organic solvents are organic compounds having an initial boiling point less than or equal to 250 °C measured at a standard atmospheric pressure of 101.3 kPa.

Volatile organic solvents can evaporate during handling and curing of the composition and generally can pose environmental and safety hazards.

The composition of the invention preferably comprises volatile organic solvents in an amount of 0.0 to 8.0 % by weight, preferably 0.0 to 5.0 % by weight, more preferably 0.0 to 3.0 % by weight, calculated on the weight of the composition.

The invention is based on the finding that a polymer (B) having a polymer main chain comprising repeating units of polymerized di-unsaturated hydrocarbons and which polymer main chain is grafted with monomers having one ethylenically unsaturated group reduces foam formation in curable pre-polymer compositions and/or increases the decomposition of foam in curable prepolymer compositions. Therefore, the invention further relates to the use of a polymer (B) having a polymer main chain comprising repeating units of polymerized di-unsaturated hydrocarbons and which polymer main chain is grafted with monomers having one ethylenically unsaturated group as de-foaming agent for a curable pre-polymer (A); wherein polymer (B) is a liquid at a temperature of 23 °C.

It has further been found that a polymer (B) having a polymer main chain comprising repeating units of polymerized di-unsaturated hydrocarbons and which polymer main chain is grafted with monomers having one ethylenically unsaturated group reduces shrinkage upon curing of curable pre-polymer compositions. Therefore, in a further embodiment the invention relates to the use of a polymer (B) having a polymer main chain comprising repeating units of polymerized di- unsaturated hydrocarbons and which polymer main chain is grafted with monomers having one ethylenically unsaturated group for reducing shrinkage during curing of a curable pre-polymer, wherein polymer (B) is a liquid at a temperature of 23 °C.

In such embodiments, it is preferred that the curable pre-polymer (A) comprises or consists of at least one of unsaturated polyester resin and dicyclopentadiene resin. It is further preferred, that in such embodiments polymer (B) is present in an amount of 5.000 to 30.000 % by weight, preferably 7.000 to 25.000 % by weight, calculated on the weight of the curable pre-polymer (A).

The invention further relates to a process of improving the de-foaming characteristics of a curable pre-polymer (A), comprising adding to the curable pre-polymer (A) a polymer (B) having a polymer main chain comprising repeating units of polymerized di-unsaturated hydrocarbons and which polymer main chain is grafted with monomers having one ethylenically unsaturated group.

Examples

Raw Materials General procedure for the grafting of liguid polymers

The detailed amounts for each component are summarized in Table 1. For all reactions, butyl acetate was used as solvent, tert-butyl peroxy-2-ethylhexanoate was used as initiator and 2,6-di- tert-butyl-4-methylphenol as stabilizer. General grafting procedure: A four-necked round bottom flask equipped with a condenser, an inert gas inlet, a dropping funnel and a thermo-couple was charged with the liquid polymer and 90 % by weight of the total solvent amount. The mixture was heated to 120°C with a heating mantle. 19.5% by weight of the total initiator amount were added and a mixture of 10 % by weight of the total solvent amount, 61 .0% by weight of the total initiator amount and the complete monomer amount were metered into the reaction mixture over a period of 3h. The reaction temperature was held for 0.5h. Further 19.5% by weight of the total initiator amount were added and the mixture stirred at 120°C for 1 h. The stabilizer was added. The volatiles were removed under reduced pressure at elevated temperatures (130°C, 30 mbar) to yield the final product.

GPC-analysis of the prepared polymers:

The determination of the molecular weight distribution, molecular weight averages Mw; Mn; Mp and polydispersity (Mw/Mn) _G pc were done by GPC according to DIN 55672 part 1 :

The number-average and weight-average molecular weights and the molecular weight distribution were determined according to DIN 55672-1 :2007-08 at 40°C using a high-pressure liquid chromatography pump (WATERS 600 HPLC pump) and a refractive index detector (Waters 410). A combination of 3 Styragel columns from WATERS with a size of 300 mm x 7.8 mm ID/column, a particle size of 5 pm and pore sizes HR4, HR2 and HR1 was used as separating columns. The eluent used for the copolymers was Tetrahydrofuran p.A. filtered through a 0.2pm membrane filter with an elution rate of 1 ml/min. The conventional calibration was carried out using Polystyrene standards. Molecular weights reported and referred to in this document always have the unit g/mol.

Table 1 Experimental details for the sample preparation. The amounts are indicated in parts by weight.

The effectiveness of polymer main chain grafted with monomers A1 to A19 summarized above as de-foaming agents was tested in different pre-polymer systems. The raw materials used for testing are mentioned in Table 2 below:

Table 2

Test System for Air release / Turbidity

Test System 1 :

To 100 g of Araldite GY 784 CH x% of the test substance (amount and description: see Table 3) was added. The mixture was stirred by hand until the mixture was homogeneous. Afterwards, 58.65 g of Hardener ARADUR 43-1 BD. This mixture was stirred using a dissolver (Pendraulik TD 100, Dissolver plate diameter: 40 ± 10 mm) for 30 seconds ± 10 seconds with a speed of 930 rpm ± 50 rpm to create foam. 50 g ± 1g of the final mixture was transferred to a round PE mould (d=115mm, h=7,5mm). After complete curing, the samples were rated with marks from 1 (very good defoaming properties, no air bubbles) to 5 (poor defoaming properties, massive amount of air bubbles). Also haze was rated with marks from 1 (very good haze properties, clear) to 5 (poor haze properties, cloudy). Table 3

It can be inferred from Table 3 that polymer main chain grafted with monomers used according to the invention in Examples 1 to 42 exhibit very useful de-foaming properties. Comparative examples 43* to 46* demonstrate that the test system is severely or to a certain extent hampered by foam formation when no additive or other additives than those according to the invention are included.

Test System 2: One foil with the dimensions 40cm*30cm and a smaller one 40cm*27cm was prepared for each sample. To 49 g of Resin Palatal P4-010 0,5g Accelerator NL-49P (Cobalt 1%) was added stirred by hand until the mixture was homogeneous. Afterwards x% of the test substance (amount and description: see Table 4) was added as well. The mixture was stirred by hand until the mixture was homogeneous. Afterwards, 1 g of Butanox M50 was added. This mixture was stirred using a dissolver (Pendraulik TD 100, Dissolver plate diameter: 40 ± 10 mm) for 30 seconds ± 10 seconds with a speed of 4660 rpm ± 50 rpm to create foam. 50 g ± 1g of the final mixture was transferred to the prepared foil (40cm*30cm). After 30 s of self-de-aeration the sample was covered with the smaller foil (40cm*27cm)

After 30 min, the samples were cut into sheets of 10cm*10cm. Afterwards they are rated with marks from 1 (very good defoaming properties, no air bubbles) to 5 (poor defoaming properties, massive amount of air bubbles). Also, transparency was rated with marks from 1 (very good haze properties, clear) to 5 (poor haze properties, cloudy).

Table 4

It can be inferred from Table 4 that polymer main chain grafted with monomers used according to the invention in Examples 47 to 63 exhibit very useful de-foaming properties. Comparative examples 64* to 66* demonstrate that the test system is severely or to a certain extent hampered by foam formation when no additive or other additives than those according to the invention are included.

Test System 3:

One foil with the dimensions 40cm*30cm and a smaller one 40cm*27cm was prepared for each sample. To 49 g of Resin COR208-824E 0,9g Accelerator NL-49P was added stirred by hand until the mixture was homogeneous. Afterwards x% of the test substance (amount and description: see Table 4) was added as well. The mixture was stirred by hand until the mixture was homogeneous. Afterwards, 0,625 g of Butanox M50 was added. This mixture was stirred using a dissolver (Pendraulik TD 100, Dissolver plate diameter: 40 ± 10 mm) for 30 seconds ± 10 seconds with a speed of 4660 rpm ± 50 rpm to create foam. 50 g ± 1g of the final mixture was transferred to the prepared foil (40cm*30cm). After 30 s of self-de-aeration the sample was covered with the smaller foil (40cm*27cm)

After 30 min, the samples were cut into sheets of 10cm*10cm. Afterwards they are rated with marks from 1 (very good defoaming properties, no air bubbles) to 5 (poor defoaming properties, massive amount of air bubbles). Also, transparency was rated with marks from 1 (very good haze properties, clear) to 5 (poor haze properties, cloudy).

Table 5

It can be inferred from Table 5 that polymer main chain grafted with monomers used according to the invention in Examples 67 to 78 exhibit very useful de-foaming properties. Comparative examples 79* to 82* demonstrate that the test system is severely hampered by foam formation when no additive or other additives than those according to the invention are included.

Test of Anti-shrink properties

Test System 4:

To 198 g of Resin Palatal P4-0102,0g Accelerator NL-49P (Cobalt 1%) was added stirred by hand until the mixture was homogeneous. Afterwards x% of the test substance (amount and description: see Table 6) was added as well. The mixture was stirred by hand until the mixture was homogeneous. Afterwards, 4,0 g of Butanox M50 was added. This mixture was stirred using a dissolver (Pendraulik TD 100, Dissolver plate diameter: 40 ± 10 mm) for 5 min ± 10 seconds with a speed of 500 rpm ± 50 rpm to create foam. 180 g ± 1 g of the final mixture was transferred to the prepared mold.

Test System 5:

To 200 g of Resin COR208-824E 3,6g Accelerator NL-49P was added stirred by hand until the mixture was homogeneous. Afterwards x% of the test substance (amount and description: see Table 6) was added as well. The mixture was stirred by hand until the mixture was homogeneous. Afterwards, 2,5 g of Butanox M50 was added. This mixture was stirred using a dissolver (Pendraulik TD 100, Dissolver plate diameter: 40 ± 10 mm) for 30 5 min. ± 10 seconds with a speed of 500 rpm ± 50 rpm to create foam. 180g ± 1g of the final mixture was transferred to the prepared mold.

Test of Anti Shrink:

As casting mold a 18,5 mm x 18,5 mm X 1000,0 mm, Angle 90° was used. Inside the L-shaped aluminum profiles (1) was coated with the release agent Chemiease 41-90 EZ. The open ends were sealed with PP-tape to ensure that the resin does not leak but also does not stick, so that any shrinkage that may occur is not hindered. The cured mixture was poured into the mold. The total difference in length between cast and cured sample is measured with calipers. Afterwards they are rated with marks from 1 (very good anti shrink properties) to 5 (poor anti shrink properties).

Table 6

It can be inferred from Table 6 that polymer main chain grafted with monomers used according to the invention in examples 83 to 88 and examples 90 to 93 exhibit very useful anti shrink properties in unsaturated polyester and dicyclopentadiene resins. Comparative examples 89* and 94* demonstrate that the test system shows a large degree of shrinkage when no additive is included.