MXPA99007558A - Resins and compounds containing mis - Google Patents

Abstract

The present invention relates to curable compositions for making structural composites with fiber reinforcement such as GRP comprising an unsaturated polyester resin base, a copolymerizable monomer and, preferably, one or more performance enhancing additives. Thixotropy is obtained by 5 weight percent or less of an organic amide

Description

"RESINS AND COMPOUNDS CONTAINING THE SAME" The present invention relates to polyester resins of the kind used to produce fiber reinforced structural compounds, preferably even if not exclusively, of the laminated type, such as fiberglass reinforced plastic (GRP) or resin reinforced composites with polymer fibers. Although it is not usual to use polyester resins for carbon fiber reinforced resin components, this is also theoretically possible. These polyester resins are conventionally based on an unsaturated polyester resin and a copolymerizable unsaturated monomer, such as styrene. These compounds are used extensively in building construction sectors, automotive / transport sectors for chemical resistant applications and in sports and luxury applications notably boat building. The conversion of the polyester resin and reinforcing fibers to form the required structure constitutes the molding process. In Europe, a significant part of the structural composite sector uses open molds and application by spraying or by hand, such as the molding process. In general, the parts required are three-dimensional which requires the application of resin to the vertical mold surfaces. Polyester resins should not be excessively high in viscosity for spray application / cylinder. In contrast, the low viscosity resin will result in extensive drainage of the vertical mold / part surfaces. A satisfactory solution is achieved by modifying the rheology of the liquid resins, by incorporating thixotropic structuring agents. The thixotropic agent predominantly used in polyester resins is fuming silica. Even when the fuming silica confers the properties to impart the required structure, it suffers from a number of limitations. One of these disadvantages is due to the nature of the fine dust of the material, which makes handling unpleasant and dangerous. Another inconvenience is the requirement for high shear dispersion equipment, of intense capital for satisfactory incorporation. Finally, the smoky silica tends to settle in the resin during storage, with the consequent loss in structure and thixotropic functioning. The last problem (sedimentation or separation) is particularly limiting of operation and is worsened by the use of low viscosity resins that are now popular in manual spraying / placement. This sedimentation effect is often determinative of the system for designating shelf life. Correction procedures before resin use involve re-dispersion, which may not be practical in bulk storage or transport trays of 1 cubic meter. The use of the sedimented resin can result in the generation of defective parts and scrap. A number of additives can be used along with the silica which can slow down sedimentation, but none of them completely solves the problem. Consequently, improved thixotropic solutions have been sought for many years. It is a reflection of the difficulty of the challenge, that in spite of the dedicated efforts, the smoky silica remains as the predominant thixotropic agent. Other products have reached the market that counteract the sedimentation problem, but they impart inconveniences in other parameters. These products include clays and organ-modified clays that need a "pre-gelling" stage for their incorporation. However, with these alternative materials, color, entrapment of air, gelling time stability and mechanical properties can be detrimentally affected. Therefore, there remains a need for a partial or total replacement for fuming silica in order to impart thixotropy to the resins intended for the production of fiber-reinforced composites which does not have the disadvantages of the latter material, which does not introduce significant different disadvantages by itself and that does not incur a significant cost penalty. This need has now been filled using an organic amide as the agent to produce thixotropic shear thinning. It is already known how to incorporate amides in coating compositions containing an unsaturated polyester resin and a copolymerizable unsaturated monomer such as styrene. In particular, this coating composition is used for gel layer compositions. The gel layers are used as a protective layer, for example in boat hulls made of GRP. According to a current product data sheet from Kusumoto Chemicals Ltd, this amide can be incorporated into gel layer compositions in a predispersed form in a non-polymerizable organic solvent (xylene) in such a way that the total amount of xylene is present at from 2 percent to 3 percent by weight of the composition. However, this level of solvent in a composition for producing fiber reinforced structural compounds will result in a product of very poor quality. In addition, this data sheet does not provide motivation for a person skilled in the art to use amides in the resins to make fiber-reinforced structural composites. Another data sheet from Kusumoto Chemical Ltd suggests incorporating a polyamide dispersed in styrene monomer into the molding compounds (ie resin compositions with crushed glass fibers to make pressure molded parts) as well as gel layers and other coatings . The amount of amide proposed is equivalent to a level of 0.05 percent to 0.3 percent by weight, in the molding composition. The compositions of the present invention especially when not exclusively intended for use in compositions reinforced with fibers of the laminate type, generally those produced by manual placement and application by spraying. There is no simple extrapolation of the molding compounds to the laminated structural applications due to a number of reasons. The crushed fibers in the molding composition result in a different rheology and the molding compositions contain very high levels of filler or filler, typically calcium carbonate. For laminates, dilution of thixotropic shear stress is essential while for molding, only thickening is required (for ease of handling and to prevent separation of resin from filler or filler material and crushed glass). In addition, the maximum amount specified (0.3 percent) in the data sheet mentioned above makes it totally inappropriate for rolling applications. Thus, in accordance with a first aspect of the present invention, there is provided a composition for molding fiber reinforced structural compounds, the composition comprising: (a) unsaturated polyester resin, (b) a co-polymerizable monomer, and (c) from 0.4 percent to 5 percent by weight of the total composition of an organic amide thixotropic agent; the composition comprises less than 2 weight percent of the total composition of the non-polymerizable organic solvent. The operation of the compositions in accordance with the present invention has been found to be stable over extended storage periods.

- - The amount of the thixotropic agent in the compositions according to the present invention is from 0.4 percent to 5 percent by weight of the total composition, but is preferably present at 0.5 percent to 3 percent by weight. Preferably, the amount of the non-polymerizable organic solvent in the compositions according to the present invention is not greater than 1.5 percent, more preferably not more than 1 percent, and still especially preferably not greater than 0.5 percent in weight of the total composition. Especially preferred is each solvent that is almost completely absent. Preferably, the thixotropic agent comprises one or more amide oligomers and / or amide polymers, which oligomers and polymers incorporate a hydroxy-functional acid. Preferably, they have a number average molecular weight of from 250 to 1,500, more preferably from 290 to 1,000. Especially preferred materials include hydroxystearic acid or hydrogenated castor oil fatty acid. Other saturated acids may be included such as decanoic, dodecanoic (lauric) and hexadecanoic (palmic). Preferred diamines are ethylene diamine and examethylene, although other aliphatic diamines are also suitable. The amides are prepared by condensation of an acid melting process and amine values of less than 10 milligrams of KOH per gram. To facilitate subsequent dispersionIt is preferred that the amide solids are micronized so that more than 99 percent of the solid amide particles are of a size less than 45 microns in diameter. It is also preferred to incorporate one or more performance enhancing additives into the compositions according to the present invention. The typical performance enhancing additives are the following, with the amounts stated (by weight of the total composition): inhibitors to impart stability and shelf life (50-500 ppm) - accelerators to promote the cure in the workshop / mold temperatures typically cobalt soaps and amine compounds (0.01 percent - 0.5 percent) leather pigments and cosmetic characteristics (0.5 percent - 10 percent - filler or filler materials to confer rigidity or flame retardant characteristics (5 percent - 60 percent) percent) halogen and phosphorus compounds in a similar manner to impart flame retardancy (2 percent - 15 percent) film-forming compounds to reduce surface tack and styrene emissions from the surface of the laminate (0.05 percent - 2 percent) the compositions according to the present invention, the amount of the unsaturated polyester resin (which option it may be comprised of two or more different resins) is typically from 20 percent to 75 percent, preferably from 25 percent to 65 percent, especially preferably from 30 percent to 60 percent by weight of the total composition . The unsaturated polyester resin is appropriately formed from the polycondensation of polybasic acids and anhydrides with polyhydric alcohols, with dibasic / anhydride acids and dihydric alcohols most commonly employed. Typical acids / anhydrides include maleic anhydride, italic anhydride, isophthalic acid, terephthalic acid and fumaric acid. Typical alcohols include 1,2-ethanediol, 1,3-propanediol, diethylene glycol, and dipropylene glycol. The monofunctional acids or alcohols can also be used as chain terminators. The ethylenically unsaturated groups are essential to serve as crosslinking sites during the curing process. The unsaturated polyester resin can also be formulated to include dicyclopentadiene and / or cyclopentadiene. The polycondensation of the resin is usually carried out as an intermittent or batch process at a temperature between 150 ° C and 220 ° C either through a fusion or azeotropic process. A degree of polymerization is typically achieved which corresponds to an acid value of between 5 and 50 milligrams of KOH per gram and a number average molecular weight of between 500 and 4000. The resin is diluted in the unsaturated monomer and can be stabilized by the addition of an inhibitor such as hydroquinone. The unsaturated polyester resin is typically prepared in a high temperature polycondensation reactor before being placed in the monomeric reactive diluent. The addition of the organic thixotropic agent and the additives that induce the operation is through a dispersion phase of room temperature, or near room temperature or optionally the thixotropic agent can be added through a pre-gelling step. The derived resins exhibit pronounced thixotropic shear thinning performance ideally suited for manual spraying / placement applications. The co-polymerizable monomer will normally be present in an amount of 20 percent to 55 percent, preferably 20 percent to 50 percent, and most preferably 25 percent to 45 percent by weight of the total composition.

The copolymerizable monomer serves both to mobilize the unsaturated polyester resin and to act as a copolymerizable crosslinker in the curing phase. Due to techno-economic reasons, styrene is generally used, but other monomers may be included such as alpha-methylstyrene, vinyl toluene, methyl methacrylate and diallyl phthalate. Although the present invention uses an organic amide thixotropic agent as a substitute for fuming silica due to the disadvantages of the latter, optimal performance in terms of minimum sedimentation together with desired shear thinning behavior is achieved by simultaneous incorporation. of small amounts of fumed silica, for example from 0.1 percent to 2.5 percent, preferably from 0.2 percent to 1.2 percent by weight of the composition. The thixotropic agent can be incorporated into the compositions according to the present invention, in one of several different ways. First it can be incorporated into the unsaturated polyester resin material itself. This process involves the batch or in-line dispersion of the thixotropic agent in the polyester resin by mixing therewith, before the resin is mixed with any of the other ingredients. This has the advantage that it is compatible with the conventional plant and the processing of silica-based polyester resins. A second alternative method for incorporating the thixotropic agent is in the form of a pregel in the copolymerizable monomer. A pregel is a solution of high viscosity or dispersion of the thixotropic agent in another medium. The process typically consists of forming the pregel, followed by batch dispersion of the pregel of the other ingredients. The advantage of this approach is the reduction of dispersion times during the final processing stage. A third possibility for incorporating the thixotropic agent is in the form of a thermally activated pregel in a mixture of the co-polymerizable monomer and an organic solvent. A thermally activated pregel means a pregel that has been heat treated. This incorporation process for example may comprise dispersing the thixotropic agent in an appropriate medium, followed by heat treatment at a temperature of about 50 ° C before dispersion in the resin. This incorporation process has the advantage that lower levels of the thixotropic agent can be used for a given level of operation. The organic solvent preferably contains one or more -OH groups and is typically a lower alcohol such as ethanol or propanol, or a polyol such as ethylene glycols or propylene glycol, or may for example be an industrial methylated alcohol or benzyl alcohol. The weight ratio of the co-polymerizable monomer to the solvent is preferably from 5: 1 to 10: 1, more preferably from 6: 1 to 9: 1. Compositions containing both the organic amide thixotropic agent and the fuming silica can be prepared by the aforementioned method. If the second or third method is used, the silica must be dispersed with the pregel in the resin. The present invention is further extended to a method for producing a fiber reinforced composite such as a glass fiber reinforced composite or a carbon fiber reinforced composite. The method comprises forming the fiber reinforced material with a composition according to the present invention, in a desired configuration and curing the composition. The present invention also includes an article comprising a fiber reinforced composite consisting of a fiber reinforcing material and a cured composite in accordance with the present invention. The invention will now be explained in more detail by the following non-limiting examples.

EXAMPLES A. Unsaturated polyester resin base Maleic anhydride / phthalic anhydride / propylene glycol in the 1.0: 1.0: 2.1 molar ratio were condensed in a melt process to provide an acid-value resin of 30 milligrams KOH per gram and an Mn number average molecular weight of 1400. The resin was dissolved in styrene to provide 65 percent (+ 2 percent) solids and stabilized at 100 parts per million hydroquinone.

B. Organic Thixotropic Agent The fatty acid of hydrogenated castor oil (60 parts) and decanoic acid (28 parts) were heated to 80 ° C. The ethylene diamine (11 parts) was charged and the batch was allowed to exotherm to about 120 ° C with the formation of a salt. The batch was heated to 200 ° C and condensed in an acid and amine values of less than 10 milligrams of KOH per gram, discharged, allowed to solidify and micronized so that 99 percent was less than 45 microns.

C. Performance improving additives The following additives were dispersed in a mixture of 85 parts of base A resin and 15 parts of styrene: pph 0.15 Air release additive (ex BYK Chemie A555) 0.05 Phenyl dietanolamine 0.15 Cobalt octoate 10 percent 0.01 Hydroquinone 0.75 LSE film-forming additive in a carrier medium (ex BYK Chemie S740) Example 1 940. kilograms of the resin base A and 155 kilograms of styrene were loaded into a 1 500 liter capacity mixer equipped with an in-line rotor / stator dispersion apparatus. 13.4 kilograms of the organic thixotropic agent B was loaded into the mixer and the batch was recirculated through the dispersion device until a Hegraan milling of 6. The operating additives C in the same ratio as the resin base A was achieved. dispersed to provide a resin with the following properties: - Solids 58 percent Viscosity of rotation at 25 ° C (ISO 3219) 0.24 Pa.s (2.4 p) RVT Brookfield at 25 ° C (Spindle 2, 5/50 rpm) 2.2 / 0.7 Pa.s (ISO 2555) (22 / 7 p) Gel time at 25 ° C, 2% M50 MEKP (ISO 2535) 16 minutes Example 2 92. 5 parts of styrene were heated to 50 ° C in a mixer equipped with a high speed batch dissolving apparatus. 7.5 parts of the organic thixotropic agent B was charged to the dissolution apparatus at 1500 revolutions per minute. The resulting gel was allowed to cool to 20 ° C. 16.0 parts of this pregel were charged to 84 parts of Resin base A with the dissolution apparatus at 1500 revolutions per minute to provide a resin with the following properties: Solids 55 percent Brokfield RVT at 25 ° C (Spindle 2, 5/50) rpm) 1.6 / 0.5 Pa.s - - Example 3 940 kilograms of resin-based A and 155 kilograms of styrene were charged in a 1500-liter capacity mixer equipped with an in-line rotor / stator dispersion apparatus. 6.6 kilograms of the organic thixotropic agent B and 4.4 kilograms of the fuming silica (Cabot M5) were charged into the mixer and the batch was recirculated through the dispersion apparatus until a Hegman grind of 5 was achieved. The performance C additives in the same ratio as in the resin base they were dispersed to provide a resin with the following properties: Solids 58.5 percent Viscosity of rotation at 25 ° C 0.27 Pa.s (2.7 p) Brookfield RVT at 25 ° C (Spindle 2, 5/50 rpm) 2.0 / 0.7 Pa.s (20/7 p) Gel time at 25 ° C, 2% M50 MEKP 19 minutes Example 4 - - 80 parts of styrene inhibited with 100 parts per million of tertiary butyl catechol were added to 10 parts of ethanol and 10 parts of the organic thixotropic agent C. The dispersion was heated to 50 ° C and maintained at > 50 ° C for 24 hours. To 25 parteds of the Resin base A, 10 parts of the aforementioned pregel were added and dispersed to provide a highly structured gel. An additional 60 parts of the resin base A and 4 parts of styrene were mixed to provide a resin with the following properties: Solids 57 percent Rotation viscosity at 25 ° C 0.27 Pa.s (2.7 p. Brookfield RVT at 25 ° C (Spindle 2, 5/50 rpm) 2.6 / 0.7 Pa.s (26/7 p)

Claims (12)

CLAIMS:

1. A composition for molding fiber reinforced structural composites comprising the composition: (a) unsaturated polyester resin, (b) a co-polymerizable monomer, and (c) from 0.4 percent to 5 percent preferably 0.5 percent to 3 weight percent of the total composition of an organic amide thixotropic agent; the composition comprises less than 2 percent, preferably not more than 1.5 percent and more preferably not more than 1 percent, and still more especially not more than 0.5 percent by weight of the total composition of the organic solvent is not polymerizable.

2. A composition according to claim 1, further comprising fumed silica preferably in an amount of 0.1 percent to 2.5 percent, more preferably 0.2 percent to 1.2 percent by weight of the total composition.

3. A composition according to claim 1 or claim 2, wherein the thixotropic agent comprises one or more amide oligomers and / or polymers that incorporate a hydroxy-functional acid.

4. A composition according to any of the preceding claims, wherein the organic amide has acid and amine values which is not 10 milligrams of KOH per gram.

A composition according to any of the preceding claims, wherein the thixotropic agent is in the form of a particulate solid wherein no more than 99 weight percent of the particles have a diameter less than 45 microns.

6. A composition according to any of the preceding claims, which further comprises one or more performance enhancing additives.

7. A composition according to any of the preceding claims, which further comprises fuming silica.

A method for producing a composition according to any of the preceding claims, wherein the thixotropic agent is mixed with the unsaturated polyester resin, before the resin is mixed with any other ingredient (s).

9. A method for producing a composition according to any of claims 1 to 7, wherein the thixotropic agent is incorporated in the form of a pregel into the copolymerizable monomer.

10. A method for producing a composition according to any of claims 1 to 7, wherein the thixotropic agent is incorporated in the form of a thermally activated pregel in a mixture of the copolymerizable monomer and an organic solvent.

11. A method for producing a fiber reinforced composite, the method comprising forming the fiber reinforcing material together with a composition according to any of claims 1 to 7, in a desired configuration and curing the composition.

12. An article comprising a fiber reinforced composite comprising the fiber reinforcing material and a cured composition according to any of claims 1 to 7.