NO337091B1 - Process for producing a thermoplastic material-wrapped composite strand. - Google Patents

Description

The present application is separated from Norwegian patent application no. 19990608 and concerns a method for producing a composite product. More particularly, the application relates to a method for producing a thermoplastic material-sheathed composite string.

Fibers or fibrous materials are often used as reinforcement in composite materials. Glass and other ceramic fibers are usually produced by adding ceramic in molten form to a bushing, pulling fibers from the bushing, carrying out a chemical treatment such as gluing the drawn ceramic fibers and then collecting the glued fibers into a fuse or a string. There are generally three known types of chemical treatment systems, namely solvent-based systems, melt-based systems and radiation-curing-based systems.

In general, the solvent-based chemical treatment systems include organic materials that are aqueous solutions (eg, dissolved, suspended, or otherwise dispersed in water), as well as those dissolved in organic solvents. US 5 055 119, 5 034 276 and 3 473 950 are examples of such chemical treatment. The solvent (ie water, organic solvent or other suitable solvent) is used to reduce the viscosity of the chemical treatment mass to facilitate wetting of the glass fibres. The solvent is essentially non-reactive with the other components in the chemical treatment mass and is driven out of it after wetting the glass fibres. In each process for applying solvent-based chemical treatment compounds, an external heat source or other external source is used to evaporate or otherwise remove water or other solvent from the applied chemical treatment compound, leaving a coating of organic material on the glass fibers. A shortcoming of a solvent-based process is that the added step of removing the solvent increases production costs. In addition, some organic solvents are highly flammable in vapor form and pose a fire risk in themselves. Another problem with solvent-based systems is that it is very difficult, if not completely impossible, to remove all solvent from an applied chemical treatment mass. Therefore, the solvent-based chemical treatments are limited for practical reasons to those systems where any residual solvent left in the coating of organic material left on the fibers has essentially no adverse effect.

With previous, melt-based chemical treatments, organic solids of the thermoplastic type are melted and applied to glass fibres. US 4,567,102, 4,537,610, 3,783,001 and 3,473,950 describe examples of such chemical treatment. A shortcoming of previous melting-based processes is the energy costs in connection with the melting of the chemical treatment masses. The organic solids used with known melt-based systems are melted at relatively high temperatures so that the melted organic solids can be brought onto the glass fibres. The high temperatures are needed because the organic solids that have previously been used have relatively high molecular weights. Such high melting temperatures also present a risk to workers of burns due to the equipment used to melt the plastic material and due to the melted plastic material per se. In addition, specialized equipment is typically required to apply and otherwise process the molten, high-temperature plastic material.

Radiation-curing-based chemical treatment is characteristically carried out using acrylate-based, organic chemicals, either with or without solvent, and which are cured with ultraviolet radiation via a photoinitiator. US 5,171,634 and 5,011,523 describe examples of such chemical treatment. A significant shortcoming of processes that use chemical treatment is that the irradiation used, for example ultraviolet radiation, and the chemical treatment mass used, for example acrylates, are relatively risky and often require special treatment and special safety rules. Some of these processes, such as that described in US 5,171,634, require the radiation curing to be repeated a number of times to achieve maximum benefit. Each additional radiation hardening step increases the risk involved and adds additional costs to the old ones. Furthermore, radiation-curable, thermosetting plastics and the necessary photoinitiators represent a highly specialized area of thermosetting chemistry. As a result, such radiation-cured chemical curing compounds are expensive and generally not compatible with various classes of matrix resins.

EP 0657395 B and EP 0657396 B show methods for the production of composite material consisting of coated glass fibers which, among other things, include the steps of forming a number of glass fibers, applying a chemical treatment mass to the fibers and heating that mass for eventual polymerization/hardening, forming coated fibers.

To produce composite parts, strands of glass fibers are often further treated in an off-line impregnation process with a polymer resin. The resin can be a thermoset, either one- or two-part, or a thermoplastic. In one example, previously formed and bonded continuous glass fibers are impregnated with a thermosetting resin and then drawn through a heated pultruding die to harden the resin and produce the composite article as ladder rails. In such an off-line process, the continuous glass fibers must be separated in some way to allow impregnation of the resin between the fibers, and then brought together. This requirement almost always results in the use of additional material such as spreading rods, impregnation baths and drying or curing ovens. These types of processes have the disadvantage that they add cost and complexity to the process. In addition, additional treatment of the glass fibers can lead to breakage of the individual glass filaments and thereby a breakdown and deterioration of the properties of the composite object. While such off-line processes can therefore be effective, they are time-consuming and inefficient (e.g. requiring additional process steps), and therefore also expensive.

Accordingly, there is a need in this technique for safer, more efficient and more cost-effective processes for applying a chemical treatment compound to glass fibers, where the viscosity of the chemical treatment compound is low enough to sufficiently wet the glass fibers without the need for a solvent, where the chemical treatment does not require radiation curing and the viscosity of the applied chemical treatment compound increases while producing very little, if any, water, volatile organic carbon (VOC) or other solvent vapors, and where the resulting chemically treated fibers are suitable for subsequent processing into a composite object. There is also a need for an in-line process for forming pre-impregnated glass composite strands from a number of continuously formed glass fibers which are chemically treated in this way, where the resulting prepreg strand is suitable for subsequent in-line or off-line processing to a composite object.

The use of composites with fiber-reinforced polymer matrices is widespread. Fiber-reinforced polymeric composite products are manufactured using a number of processes and materials. As mentioned above, such a process involves impregnating one or more of the strands or bundles of reinforcing fibers (for example, glass fibers, synthetic fibers or some other reinforcing fibers) with a thermoplastic material, and using the resulting composite strand to mold a composite article. These composite strands have been used in the form of continuous strands (that is, long strand lengths) and discrete pellets (that is, short strand lengths). The fibers from the composite strands provide the reinforcement and the thermoplastic material forms at least part of the matrix for the composite object.

It is desirable that each fiber strand is fully impregnated with the thermoplastic matrix material, that is to say that the thermoplastic material is essentially evenly distributed over each bundle of fibers and between the fibers. Due to the fact that all fibers start surrounded by the matrix material, the fully impregnated fiber strands can be cast less expensively and more effectively and the corresponding composite objects can show improved properties. However, it is difficult and time-consuming to fully impregnate fiber strands with characteristic thermoplastic matrix materials (for example construction thermoplastics). Fully impregnating strands at high throughput rates is particularly difficult, especially at throughput rates typically present during the manufacture of continuous formed glass reinforcing fibers.

In an attempt to fully impregnate continuously formed fiberglass strands, the number of fibers used to form each strand (that is, the fiber density) has been reduced from a typical density of around 2000 fibers per string to 1200 fibers per strand or less, to reduce the time it takes to impregnate each fiber strand. However, by reducing the number of fibers in each strand being processed at a given time, the production volume and cost efficiency of the process can be adversely affected. In addition, full impregnation even at such a lower strand density is still sufficiently time-consuming to prevent even strands with the lower density from being fully impregnated and processed at the high throughput rates that characteristically occur in the production of continuous reinforcing fibers of glass.

In an attempt to achieve higher throughput, a known process only partially impregnates the fiber strand, uniformly coating the strand with thermoplastic matrix material and leaving a central core of fibers that is not impregnated with thermoplastic. This coating and partial impregnation of the string is accomplished by pulling the string through what has previously been called a "wire coating" device. Wire coating devices as described in US 5,451,355 typically include an extruder for feeding molten thermoplastic matrix material and a die with an inlet opening, an outlet opening and a coating chamber therebetween. The extruder supplies molten thermoplastic material to the coating chamber. The strand is coated and partially impregnated with the thermoplastic matrix material as it passes through the coating chamber and the coating is converted into a uniform layer when the coated strand passes through the outlet in the nozzle. The resulting coated strand is either used in the form of a strand (ie in compression molding applications) or cut into discrete pellets (ie in injection molding applications). Because the strand is only partially impregnated with the thermoplastic matrix material, the strand can be processed at relatively high throughputs.

However, these partially impregnated, wire-coated strands also present a number of problems due to the central core of non-impregnated fibers. When in pellet form, the fibers in the central, non-impregnated core tend to fall out of the thermoplastic coating. When the strand is in the form of a thread, the core fibers are less likely to fall out, but the core of these coated threads must still be impregnated to some extent to optimize the properties of the resulting composite article. Impregnation of the central core of such wire-coated wires during casting can be difficult and time-consuming if not impossible as a practical work. Thus, casting with wire-coated wires may cause a decrease in overall production rates rather than a desired increase.

There is therefore a need to be able to produce fully impregnated fiber strands at even higher throughput rates, even when each strand has a relatively high fiber density, where the resulting composite strands, either in wire or pellet form, are suitable for molding fiber-reinforced thermoplastic objects .

An object of the invention is to provide such a chemical treatment mass for fibres, for example glass fibres, which is essentially free of unreacted solvent. Another object is to obtain a solvent-free chemical treatment composition which is substantially non-photosetting. Another object of the invention is to provide such a chemical treatment mass which has an increased wetting ability. Yet another object is to provide a solvent-free chemical treatment composition which can be cured or have its viscosity reduced by the application of heat energy to the chemical treatment composition deposited on fibers.

Another object of the invention is to provide an advantageous process for applying a chemical treatment mass to fibers so that the coated fibers can be converted into composite strands which can be used in the formation of composite objects. A further object is to provide such a process which provides fibers which are thoroughly impregnated with the chemical treatment mass.

These aims and objectives are achieved by a method for producing a thermoplastic material-sheathed composite string as stated in claim 1.

A method for manufacturing a composite product, such a composite string or a molded article made from such a string product may be described, generally comprising providing a thermoplastic-encased composite string material for placement in a matrix material. The thermoplastic sheathed composite is prepared by steps comprising: applying a chemical treatment compound in an amount sufficient to coat substantially all of a plurality of fibers comprising reinforcing fibers to form prepreg fibers, wherein the chemical treatment compound is compatible with the matrix material; assembling the prepreg fibers into a prepreg strand with the chemical treatment agent disposed between substantially all of the plurality of fibers; and sheathing the prepreg strand by a process including wire coating the prepreg strand with a thermoplastic material to form a thermoplastic coating and forming the thermoplastic coating into a thermoplastic sleeve to thereby form a thermoplastic sheathed composite strand.

In one embodiment, the thermoplastic sheathed composite strand is cut into lengths to form a number of pellets. Alternatively, the thermoplastic sheathed composite string can be wrapped as a wire. In one embodiment, the reinforcing fibers include preformed reinforcing fibers. The number of fibers may also include matrix fibers. The method can also further include steps such as the production of reinforcing fibers by a process which includes the continuous formation of reinforcing fibers from molten glass or the prior formation of matrix fibers from a polymer material. Optionally, the method may comprise the production of reinforcing fibers in-line by a process which includes continuous formation of reinforcing fibers from a molten glass material. The chemical treatment used in such a manner may comprise water and an organic material in an amount which provides the pre-impregnated strand with an organic material content of from about 2 to about 25% by weight, where essentially all water in the chemical treatment agent is evaporated before the collection step. The organic material can be a solid or a liquid dispersed or emulsified in the water. More particularly, the content of organic matter is from about 2 to about 15% by weight, and the evaporation step comprises heating the chemical treatment mass after the application step, and most preferably the method relates to a content of organic matter from about 6 to about 7% by weight, where the heating step provides heat energy to the chemical treatment mass from an external source or from a number of fibres. In one embodiment, the chemical treatment mass is thermo-setting and the production of the thermoplastic-sheathed composite string material further comprises the step of partially curing the chemical treatment mass after the application step. The chemical treatment mass is preferably essentially solvent-free and essentially non-photobinding and the organic material comprises a film former and a coupling agent. In one embodiment, the chemical treatment composition is thermoplastic, the film former includes a low molecular weight thermoplastic polymer and the coupling agent includes a functionalized organic substrate. In a further embodiment, the chemical treatment composition is thermosetting, the film former includes at least one of a multifunctional monomer and a low molecular weight monofunctional monomer and the coupling agent includes a functionalized organic substrate. The method may further comprise combining the thermoplastic-sheathed composite strand with matrix material to form a composite formulation and molding this. Furthermore, the method may comprise forming thermoplastic-sheathed composite string into pellets and molding these pellets combined with a resinous matrix material to form a fiber-reinforced composite article.

In addition, there is described a composite product comprising a number of thermoplastic-encased composite strands which can be used when forming a fibre-reinforced composite object containing a matrix material, where each thermoplastic-encased composite strand comprises a pre-impregnated strand comprising a number of aggregate fibers including reinforcing fibers in the main coated with a thermoplastic or a thermosetting chemical treatment agent compatible with the matrix material. In one embodiment, the composite product comprises pellets cut from the composite strands where the chemical treatment compound holds the number of aggregate fibers together in these pellets. Alternatively, the composite strands can be wrapped in wire form. Preferably, the number of total fibers is within the range of about 1,500 to about 10,000 and most preferably from about 2,000 to about 4,000. The number of total fibers may optionally include matrix fibers made from a thermoplastic material. In one embodiment, the chemical treatment compound comprises an organic material and each pre-impregnated strand has an organic material content of from about 2 to about 25% by weight, preferably from about 2 to about 15% and most preferably from about 6 to about 7% by weight %. The chemical treatment composition may be thermoplastic, substantially solvent-free and substantially non-photosetting, and comprise (i) a film former containing a low molecular weight thermoplastic polymer material and

(ii) a coupling agent containing a functionalized organic substrate.

Alternatively, the chemical treatment composition may be thermo-setting, substantially solvent-free and substantially non-photosetting, and comprise (i) a film former containing at least one of a multifunctional monomer and a low molecular weight monofunctional monomer and

(ii) a coupling agent containing a functionalized organic substrate.

The number of composite strings can be molded with a matrix material.

Furthermore, a method for producing a composite product is described and this method comprises: applying a thermo-setting or thermoplastic chemical treatment compound to a number of fibers including glass or synthetic reinforcing fibers to form fibers coated with applied chemical treatment compound, this essentially is solvent-free and substantially non-photosetting; and heating the applied chemical treatment mass to reduce the viscosity of at least a portion of the applied mass or at least partially cure the applied chemical treatment mass or both, forming coated fibers. The chemical treatment compound can be applied in an amount from about 0.1 to about 1% by weight to glue the number of fibers, or in an amount from about 2% to about 25% by weight to preimpregnate the number of fibers. The fibers can further comprise polymeric matrix fibers. In one embodiment, the reinforcing fibers comprise glass reinforcing fibers and the heating step comprises supplying heat energy to the applied chemical treatment mass from the glass reinforcing fibers where the glass reinforcing fibers have a temperature preferably from about 150°C to about 350°C and preferably from about 200°C to about 300°C, during the application step . The reinforcing fibers may comprise previously formed reinforcing fibers, where the method further comprises a step of preheating the previously formed reinforcing fibers. Furthermore, the reinforcing fibers may comprise glass fibers where the method further comprises the formation of glass fibers from a source of molten glass reinforcing material and where the heating step comprises the supply of heat energy retained in the glass reinforcing fibers from the formation step to the applied chemical treatment mass. The heating step may include supplying the applied chemical treatment mass with heat energy from a source external to the number of fibers. In one embodiment, the chemical treatment compound is thermosetting and the heat step cures at least part of the applied chemical treatment compound. Alternatively, the chemical treatment compound is thermoplastic and the heating step reduces the viscosity of at least part of the applied chemical treatment compound. The method can further include a step of gathering the coated fibers into a composite strand and the heating step can occur after the gathering step. The chemical treatment mass may contain an organic material and the composite string may have an organic material content of from about 2 to about 25% by weight. The method may also include a step of forming the composite strand into a composite article with the number of fibers arranged in a matrix formed at least in part by the applied chemical treatment mass. The number of fibers includes polymeric matrix fibers which constitute at least part of the matrix in the composite article. The formation step can also be carried out in-line with the assembly step. In addition, reinforcing fibers and matrix fibers can be entangled to give the number of fibers. The application step may involve simultaneous coating of the reinforcing fibers and the matrix fibers with the chemical treatment compound.

An apparatus for carrying out the methods described above is also described.

It also describes a chemical treatment mass for application to fibers for processing into a composite strand which can be used for arrangement in a matrix material to form a fiber-reinforced composite article and where the chemical treatment mass comprises: a film former comprising at least one of a multifunctional monomer and a low molecular weight monofunctional monomer; and a coupling agent comprising a functionalized organic substrate. The chemical treatment mass is thermo-settable, at least partially heat-curable, substantially solvent-free and substantially non-photo-settable. Optionally, the treatment mass may include a processing aid, for example an epoxy functional viscosity modifier or butoxyethyl stearate. In one embodiment, the chemical treatment compound is heat curable at a temperature of from about 150°C to about 350°C. The film former may comprise a monomer chosen from polyester alkyd, epoxy resins and compounds containing functional glycidyl ether groups. The film former may also comprise at least one selected from urethanes, vinyl esters, amino acids, reactive Deals Alder species and Cope rearrangement compounds. Preferably, the chemical treatment mass has a viscosity of up to 300 cPs at a temperature in the range of about 93°C to about 110°C.

Furthermore, a chemical treatment mass is described for application to fibers for processing into a composite strand that can be used for arrangement in a matrix material to form a fiber-reinforced composite article where the chemical treatment mass comprises a film former comprising at least a thermoplastic low molecular weight polymer material and a coupling agent comprising a functionalised, organic substrate where the chemical treatment mass is thermoplastic, substantially solvent-free and substantially non-photo-binding. Optionally, the processing aid may comprise a processing aid. The thermoplastic low molecular weight polymer may comprise a cracked polyester or a polyamide where the polyester or polyamide is preferably selected from polyethylene terephthalate, polybutylene terephthalate and nylon. In one embodiment, the treatment composition comprises a processing aid including a monomer equivalent selected from di-n-butyl terephthalate, dibenzoate esters of 1,4-butanediol, diethyl terephthalate, dibenzoate esters of ethylene glycol, caprolactone, adduct of adipoyl chloride and n-aminohexane and adduct of 1,6-hexanediamine and hexanoyl chloride. Preferably, the chemical treatment composition has a viscosity of up to about 300 cPs at a temperature in the range of about 93°C to about 110°C.

Other objects, features and advantages of the various aspects of the method will become apparent from the following detailed description of the method and its preferred embodiments in conjunction with the accompanying illustrative drawings, in which: Figure 1 is a perspective sketch of an embodiment of an apparatus for chemical treatment of fibers which are continuously formed from a molten material and are suitable for making a composite article;

figure 2 is a perspective view of another embodiment of a system for chemical treatment of fibers in which a heater is arranged between a fiber forming mechanism and a chemical treatment applicator;

Figure 3 is a perspective view of a further embodiment of an apparatus for chemically treating fibers continuously formed from a molten material and preformed fibers drawn from fiber bundles;

Figure 4 is a perspective view of an embodiment of an apparatus for manufacturing and then chopping a thermoplastic-sheathed composite strand of pre-impregnated reinforcing fibers into a number of pellets suitable for molding into a thermoplastic fiber-reinforced composite article;

Figure 5 is a plan view of a winding device for winding a thermoplastic sheathed composite strand into a wire package suitable for molding into a fiber-reinforced thermoplastic composite article; and

Figure 6 is a perspective view of a further embodiment of an apparatus for making and then chopping a thermoplastic-sheathed composite strand of pre-impregnated fibers into a number of pellets suitable for molding into a fiber-reinforced thermoplastic composite article.

Solvent-free, chemical treatment compounds.

A general feature of the method concerns essentially solvent-free, chemical treatment masses for application to fibers to be processed into composite objects. One or more chemical treatment compounds can be applied to the fibers, for example with one or more conventional applicators, for example to glue and/or prepreg a sufficient number of reinforcing fibers to achieve the desired composite properties.

More particularly, fibers or filaments are glued and/or pre-impregnated with a chemical treatment compound. This has a low viscosity, is essentially free of non-reacting solvent and does not harden by actinic radiation. The low viscosity can be achieved by choosing components with a relatively low molecular weight for the chemical treatment mass.

Heat energy can be used to reduce the viscosity and improve the wetting ability of the chemical treatment mass after it has been applied to the fibres. In addition or alternatively, heat energy can be used to increase the molecular weight of, or otherwise cure (for example cross-link or otherwise increase the molecular weight of), the applied chemical treatment mass. Alternatively, no heat energy is supplied to the applied chemical treatment mass. Regardless of whether or not heat is used, there is little, if any, generation of water vapor, volatile organic carbon (VOC) vapor, or other solvent vapor.

The resulting chemically treated fibers are suitable for forming a composite string, for example a prepreg or so-called prepreg. The composite strand can then be processed in-line or off-line into a composite object with reinforcing fibers arranged in a polymeric matrix material.

An apparatus suitable for producing one or more composite strands in wire or pellet form suitable for molding into a fiber-reinforced thermoplastic composite article includes a source for reinforcing fibers and, optionally, a source for one or more other fiber types. One such source is a bushing of molten reinforcing material (eg glass) from which continuous reinforcing fibers can be drawn in sufficient numbers to form at least a proportion of, if not the entire strand. It may also be desirable for the source of reinforcing fibers to be one or more coils or other packages of previously formed reinforcing fibers. A source for previously produced reinforcing fibers can be used in combination with a source for continuously formed reinforcing fibers. The fiber source can also include matrix fibers that are produced continuously, for example from a bushing or a spinner and/or preformed and supplied in suitable packages such as spools.

Where glass reinforcing fibers are formed, the fiber forming mechanism forms the fibers from a source of molten glass fiber material, for example a conventional glass fiber manufacturing bushing. The fiber formation operation can be carried out off-line from or in-line with the rest of the apparatus. When the fibers being formed are glass reinforcing fibers, the fiber forming mechanism forms the fibers from a source of molten glass as reinforcing fiber material. In one embodiment, the fiber manufacturing mechanism forms the fibers so that they provide heat energy for a certain time after they are manufactured.

An applicator is used for applying chemical treatment compound to essentially all fibres. The applicator may be of any conventional type or any other construction suitable for the application of the desired type and amount of chemical treatment compound. The applicator may be arranged in-line with the fiber manufacturing mechanism for applying chemical treatment compound to the fibers while forming a number of coated fibers. The applicator applies the chemical treatment compound which is essentially solvent-free and essentially non-photo-binding.

The apparatus according to the description includes an applicator system which applies the chemical treatment compound when the fibers are at a higher temperature than that of the applied chemical treatment compound. When this mass is applied, the fibers are at a sufficiently high temperature to provide enough heat energy to bring the applied mass to a lower viscosity or to at least partial heat curing (if, for example, the chemical treatment mass is a heat-setting type) or both. However, the temperature in the fibers when the chemical mass is applied is not sufficient to cause significant decomposition of the applied mass. The temperature difference between applied chemical mass and the fibers on which the mass is deposited can be achieved by incorporating a heater or "maintainer" as part of the applicator system. This temperature difference can also be achieved by placing the applicator close enough (for example next to) the fiber making mechanism so that the fibers have a sufficiently higher temperature than the chemical mass when this is applied. Such an applicator system may include a heat holder arranged to support maintenance of the temperature in the fibers or to at least reduce the rate of temperature drop during and/or after the chemical mass is applied.

A gathering shoe or any other suitable device is used to gather the coated fibers into at least one strand. The string can then be coated or sheathed with a suitable polymer material, preferably a thermoplastic, and converted into the desired composite object.

The material used to coat or sheath the chemically treated strand may be provided from a source of thermoplastic material, such as an extruder. In order to coat the treated strand and to form sheathed composite strand, the treated strand can be drawn or otherwise passed through a suitable coating device. For example, sheathed composite strands may be formed by drawing or otherwise passing a number of strands through a corresponding number of dies where each die has at least one exit opening sized to form the coating into a thermoplastic sheath of desired thickness (eg to provide a weight ratio thermoplastic: glass in the range of around 30:70 to around 70:30).

Preferably, a wire coating is used to envelop the strings. A wire coater is a device or a group of devices capable of coating one or more strands with plastic material to thereby form an envelope or sleeve of relatively uniform thickness on each strand. Preferably, the wire coater comprises a form of nozzle which shapes the sleeve to the desired, uniform thickness and/or cross-section.

The string is fed or guided through the coating device using suitable equipment. For example, a puller can be used to pull the strand through the wire coater. This puller can be separate or part of the wire coater. A chopper can be adapted to also act as a puller or to support one when pulling the string through the wire coater.

The resulting coated or sheathed composite strand may be cut or otherwise separated into discrete lengths to form a number of sheathed composite pellets, or otherwise wound or packaged to obtain a sheathed composite wire. The chemical treatment compound helps hold the fibers together in each polymer-encased composite pellet or wire.

A composite object can be produced by casting one or more of the sheathed composite strands, for example in pellets, wire or other form. The sheathing for the sheathed composite strings can form at least part of or the entire matrix for the composite object to be shaped. Examples of molding processes that can be used to form the composite article include injection molding, compression molding or other suitable molding techniques.

Figures 1 to 3 show an embodiment of chemically treating a number of fibers 10 which are suitable for the production of a composite article. A typical composite object comprises a number of reinforcing fibers 12 arranged in a matrix of the polymer material.

In addition to reinforcing fibers 12, the fibers 10 can also include other types of fibers that are suitable for the production of composite objects, for example matrix fibers 13. The matrix fibers 13 are preferably produced from a polymeric matrix material and form at least part of the matrix. The reinforcing fibers 12 may be glass that can be continuously drawn from a source of molten glass reinforcing material (for example, a conventional glass fiber manufacturing bushing as shown in Figures 1 and 2). Continuously produced glass reinforcing fibers are particularly advantageous because heat energy remains in the glass fibers from the forming process and can later be used to efficiently provide heat which is passed on to the chemical treatment mass. In addition to or instead of using continuously produced glass fibers, the reinforcing fibers 12 may include pre-produced reinforcing fibers made from glass and/or synthetic reinforcing material.

The expression "pre-formed" refers to fibers that are produced off-line before they are fed to or equipped with chemical treatment mass according to the invention. The term "glass" means an inorganic molten product which solidifies to a solid, non-crystalline state on cooling and is intended to include ordinary silicate glasses as well as glassy mineral materials suitable for the manufacture of reinforcing fibers, such as borosilicate glass, glass wool, rock wool, slag and mineral wool. In contrast, "synthetic" reinforcing materials are non-glass materials such as Kevlar®, carbon or graphite, silicon carbide (SiC), and other non-glass materials that have suitable reinforcing characteristics. When fibers made from different materials are used, it is intended that the same or different chemical treatment compounds can be used for each fiber type.

In one embodiment, the chemical treatment mass is applied according to methods and using apparatus that use heat energy to effect at least one of two changes in the applied chemicals. Heat energy can be used to reduce the viscosity, which improves the wetting ability of a chemical treatment compound applied to the fibers. Alternatively or in addition, heat energy can be used to increase the molecular weight in or otherwise harden the applied chemical treatment mass. Figures 1 and 2 show examples of embodiments of apparatus and methods for applying chemical treatment compounds.

The chemical treatment mass used to coat the fibers 10 has a relatively low molecular weight and viscosity compared to the matrix material and is also essentially free of non-reacting solvent. A "non-reacting solvent" (eg water and certain organic solvents) is a solvent that evaporates from the chemical treatment mass in the presence of heat energy rather than reacting with a component of the chemical mass or matrix material. The chemical treatment mass is essentially "solvent-free", that is to say essentially free of such an essentially non-reactive solvent.

Thus, there may be traces of a non-reacting solvent in the chemical treatment mass, but the amount of such solvent present is not large enough by itself to significantly reduce the viscosity of the chemical treatment mass (that is, affect the ability of the mass to to wet fibers). In addition, the applied chemical treatment compounds are essentially free of all non-exchangeable solvents so that no significant amount of water vapor, VOC vapor or other solvent vapor is generated when the chemical treatment compound is heated, including during casting of the composite object. Being essentially solvent-free, the chemical treatment mass of the invention can have its viscosity reduced and/or heat-cured without significant loss of mass. Thus, most of the chemical treatment compound applied to the fibers remains on them.

The fact that the chemical treatment mass is solvent-free does not, however, prevent the use of one or more additives in the chemical treatment mass which are soluble or compatible with the other components (for example coupling agent). For example, a compatible viscosity modifier such as Heloxy® (functional epoxy modifier), available from Shell Chemical Company, such as a diglycidyl ether of 1,4-butanediol (Heloxy modifier 67) or a polyglycidyl ether of castor oil (Heloxy modifier 505), used in a film making system to interact or react with one or more other ingredients to reduce the viscosity of the chemical treatment mass rather than being driven off as a vapor in the presence of heat energy.

The chemical treatment compound is also not curable due to actinic radiation (that is, not photo-binding) to any significant extent. This means that the chemical treatment mass does not react photochemically to harden or significantly increase its viscosity under the influence of actinic radiation.

The chemical treatment compound, which can be thermosetting or thermoplastic in nature, is used for gluing and/or pre-impregnation of the number of reinforcing fibers 12 that need to achieve the desired composite properties. The chemical treatment can also be used for gluing and/or pre-impregnation of other types of fibres, for example fibers 13 produced from a polymeric matrix material.

The matrix fibers can either be formed continuously in-line or formed in advance and then used to make up part or all of the matrix in the composite object. Where matrix fibers are used, the step of applying the chemical treatment compound may include gluing and/or pre-impregnating the matrix fibers with the same or a different chemical treatment compound applied to the reinforcing fibers.

In most cases, pre-impregnation and also gluing is desirable and therefore it is preferred that the same chemical treatment compound is used both for gluing and for impregnation of the fibers 10. However, possibly one chemical treatment compound can be used to glue the reinforcement and/or matrix fibers and another chemical treatment is used to pre-impregnate the reinforcement and/or matrix fibres. If different types of matrix fibers are used, it may be advantageous that a different chemical treatment compound is applied to each type of matrix fiber.

Bonding of fibers involves applying at least a monolayer of the chemical treatment compound to the surface of each fiber. Glass reinforcing fibers 12 are generally considered bonded when a content of chemical treatment compound in the order of 0.1 to 1.0%, for example around 0.5%, all calculated on the weight of the total weight of the treated fibers, is applied to the fibers 12. Pre-impregnation involves coating or otherwise applying a sufficient amount of the chemical treatment compound to a number of fibers to substantially fill the spaces between the fibers, when the fibers 10 are formed into a bundle or strand 14. A bundle or strand 14 of glass reinforcing fibers 12 is considered usually as prepreg when the strand 14 has a content of chemical treatment compound from about 2 to about 25% by weight.

The fibers can be glued without being pre-impregnated at the same time, for example when the chemical treatment compound is applied in small quantities and/or when it has a sufficiently low viscosity. The viscosity of a chemical treatment compound can be adjusted by adjusting the temperature. For example, the viscosity of the treatment mass can be appropriately adjusted after application using the heat present in the fibers.

Preferably, at least the reinforcing fibers 12 in the strand fibers 10 are coated with chemical treatment compound in an amount of from about 2 to about 15% by weight, as much as from about 5 to about 15% by weight and most preferably about 8% by weight, all calculated on the weight of treated fibers. A conventional loss on fire (LOI) method can be used to determine how much of the applied chemical treatment mass is on the fibers 12 which are preferably made of glass.

A preferred LOI range or value is that which provides the desired composite string properties at the lowest possible cost. At an LOI value of 8%, sample strands 14 are found to be well impregnated but not moist to the touch. LOI values that are too low may cause disruption of the strand 14 (ie breakage of a number of individual glass fibers in the strand) during subsequent in-line or off-line treatment or processing. The more chemical treatment mass that is added, however, the more the final product will cost. Higher LOI values may also drain low-viscosity components from the strand 14. In any case, an LOI value of from about 25 to about 40% by weight is preferred for making a composite article where all the matrix polymer is provided from the composite strand 14.

Thus, the fibers 10 can be chemically treated according to the described method to form a prepreg (pre-impregnated composite strand) 14, or a composite strand 14 containing only bonded fibers 10. One or more of the composite strands 14 can then be processed in-line or off-line to a number of composite objects. For example, the step of forming the composite strand can be carried out in-line with an assembly step. Examples of composite articles into which the strand 14 can be transformed are mats, textiles, sheets, plates, filament wound tubes, pultruded articles or spray-up articles (gun roving). The strings 14 can also be chopped into lengths or pellets which are suitable for use in injection or other molding for the production of composite objects.

In general, a chemical treatment mass according to the description comprises a film former and a coupling agent. The film former forms a layer of polymeric materials around each fiber which is coated with the chemical treatment compound. The coupling agent supports bonding or otherwise connects the film former to at least the reinforcing fiber. The coupling agent, if used, may also be selected to support the film forming reaction or an interaction with the polymeric matrix material.

The applied chemical treatment compound behaves as a thermo-debonder or a thermoplastic. Furthermore, the treatment mass can have both thermo-setting and thermoplastic components, that is to say that the treatment mass can contain an essentially thermoplastic polymer with reactive end groups which can participate in a thermo-setting/hardening reaction. Film formers used in both types of chemical treatment compound can be the same polymeric material used for the composite matrix.

A chemical treatment compound of the thermo-setting type is partially or fully heat-curable and essentially not photo-setting and can be used with a polymeric matrix material which is either thermo-setting or a thermoplastic. If the chemical treatment compound behaves as a thermosetting compound, the applied heat energy can at least partially cure and cause an increase in the viscosity of at least a portion of the applied chemical treatment compound which is cured. A preferred chemical treatment compound is heat curable at temperatures around 350°C and below.

In examples of thermo-setting chemical treatment masses, the film former preferably comprises either one or more relatively low molecular weight monofunctional monomers, one or more relatively low or high molecular weight multifunctional monomers, or a combination thereof. A monofunctional monomer has one reaction site per molecule, while a multifunctional monomer has two or more reaction sites per molecule. The monomer is heat curable without generating any significant amount of water vapor, volatile organic carbon vapor, or other solvent vapor. For example, the film former used in a thermosetting type chemical treatment mass may include at least one functional low molecular weight monomer from the group comprising, for example, a polyester alkyd, an epoxy resin and a combination of functional glycidyl ether groups sufficient to form a film on each fiber without constitute an epoxy resin. Other suitable functional monomers for use as all or part of the film former are urethane, vinyl ester, amino acid, reactive Diels Alder species (such as dienes or dienophiles) and molecules capable of Cope rearrangement. The molecular weight of the functional monomers is suitably low compared to the matrix material in order to obtain a chemical treatment mass with low viscosity.

In examples of thermoplastic type chemical treatment compounds, the film former preferably comprises at least one thermoplastic low molecular weight polymer material which has a relatively low viscosity at elevated temperatures. Thermoplastics usually have relatively high molecular weights and thus high viscosities, compared to typical non-cured thermo-separators. However, such high molecular weight thermoplastics can still be used in the film former in a chemical treatment composition of the thermoplastic type if it is cracked or otherwise processed to a sufficiently low molecular weight. High molecular weight thermoplastics such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT) and other polyesters, and polyamides such as nylon, can be cracked for this purpose.

Such thermoplastics, even when cracked, have an undesirably high viscosity. In such cases, a processing agent or a viscosity modifier can be used in the film forming system. For example, a monomer equivalent of thermoplastic material or a mixture of a monomer equivalent and an oligomer (for example a cracked thermoplastic material), can be used as a processing aid with a high molecular weight thermoplastic. Examples of thermoplastic monomer equivalents are di-n-butyl terephthalate and the dibenzoate ester of 1,4-butanediol for PBTs; diethyl terephthalate and the dibenzoate ester of ethylene glycol for PETs; and caprolactone, the adduct of aidpoyl chloride and n-aminohexane, and the adduct of 1,6-hexanediamine and hexanoyl chloride for the nylon. In these examples, the monomer equivalent molecules can act as processing aids to allow high molecular weight thermoplastics such as PBT, PET, and nylon to form at least a portion of the film former in the chemical treatment composition.

The above-mentioned examples of monomer-equivalent processing aids can be used with other thermoplastics and/or they can be made reactive and used with thermal binders or thermoplastics. Satisfactory results have been obtained using butoxyethyl stearate (BES) as processing aids in BES-containing treatment masses as described in the examples below for thermo-setting matrices. Preferably, such processing aids contain the same types of functional groups as the matrix polymer. There may be myriads of molecules and/or combinations of molecules that may be useful as monomer equivalent processing aids.

If the chemical treatment compound behaves as a thermal debonder, a heating step is preferably used to at least partially cure the applied chemical treatment compound and to increase the viscosity of at least a portion of the applied chemical treatment compound which is cured (that is, the part most directly exposed to heat). The increase in viscosity can be caused by an increase in the molecular weight as chemical treatment compounds of the thermo-separator type are used. The thermosetting type of film formers are heat curable without generating any significant amount of solvent vapor upon heating. Preferably, the functional monomers used for the film former are heat curable at temperatures around 350°C or below because the risk of permanent degradation increases to an undesired degree for many chemical treatment compounds at temperatures above around 350°C.

If the chemical treatment compound behaves as a thermoplastic, the heating may cause a reduction in viscosity for at least a portion of the applied chemical treatment compound most directly exposed to heat (eg near a hot fiber). If the viscosity is reduced during the heating step, there is preferably a sufficient drop in viscosity to desirably improve the ability of the applied thermoplastic type of chemical treatment agent to wet the fibers 10 (to coat the fibers and interact with the fiber surface). The wetting of the applied chemical treatment mass on the fibers 10 will more likely improve when a drop in viscosity occurs for at least the part of the applied chemical treatment mass which is located closest to the fiber surface. To reduce the chance of permanent degradation during heating, it is also preferred that thermoplastic type film formers in particular and for the thermoplastic type of chemical treatment mass as a whole, exhibit a sufficiently low viscosity at temperatures around 350°C and below.

The viscosity of both types of chemical treatment compound is low enough to at least partially, if not fully, wet the fibers 10 when the chemical treatment compound is initially applied. In order to be able to apply chemical treatment compound using conventional equipment (for example with a standard single or double roller applicator 26) without causing the fibers 10, and especially glass fibers, to break significantly in large numbers, the chemical treatment compound preferably has a viscosity of about 1000 cPs or less before application. The lower the viscosity of the chemical treatment compound that is applied, the faster the fibers 10 can be processed without this leading to significant fiber breakage. Preferably, therefore, the chemical treatment mass before application has a viscosity of around 300 cPs or less. In one embodiment of the proposed processing of the fibers, the chemical treatment compound, as applied, has a viscosity of the order of 50 cPs and most preferably around 10 cPs, as measured by a conventional viscometer (eg a Brookfield or ICI viscometer).

Below are specific examples of film formers which are divided into two main categories, liquid and fusible. In the "liquid" category, three examples of maleate-based film formers have been synthesized. In addition, there are 12 epoxy-based film formers that are prepared from commercially available ingredients. There is a further liquid film former (allylpropoxylaurethane) which can be used both in a thermo-setting type or a thermoplastic type of chemical treatment agent. In the "meltable" category there are two film forming systems, each prepared from a commercially available polycaprolactone and one of the liquid film formers. Examples of the polycaprolactone system are a solid polymer at room temperature. These examples of film formers are all processable according to the ideas of the invention.

EXAMPLES 1 - 6: LIQUID FILM FORMERS

Example 1 - Propylene glycol fumarate:

A conventional 38 liter stainless steel reactor was charged with 17.02 kg of propylene glycol (available from Ashland Chemical Company, Columbus, Ohio) and 12.98 kg of fumaric acid (available from Huntsman Specialty Chemical, Salt Lake City, Utah). For stability, 3.62 g (120 ppm) of toluhydroquinone (THQ) (available from Aldrich Chemical Company, Milwaukee, Wisconsin) was added to the reactor. The molar ratio in the charge was 2:1 PG:FA. The mixture was heated under a nitrogen atmosphere to 193°C for 5 hours. The end point of the reaction was determined by the viscosity of the PG-FA product which was 360 to 450 cPs at 49°C, determined using a cone and plate viscometer, for example, as manufactured by ICI, Wilmington, Delaware. The acid value for the reaction end point is characteristically observed to be 10 to 36 Meq. KOH/g alkyd (milliequivalent potassium hydroxide per g alkyd). This material can be used directly as a film former.

Example 2 - Propoxylated bisphenol-A maleate:

A 198 liter stainless steel reactor was charged with 159.68 kg of propoxylated bisphenol-A (available from Milliken Chemical, Inman, South Carolina) and 20.33 kg of maleic anhydride (available from Huntsman Specialty Chemical). For stability, 18 g or 100 ppm of hydroquinone (HQ) (available from Aldrich Chemical Company) was added to the reactor. The mixture was heated under a nitrogen atmosphere to 79°C for 2 hours and then to 135°C for 3 hours. The end point of the reaction was determined by the acid number and the reaction was considered complete when the acid values reached a level of 63.6 Meq. KOH/g alkyd and when no more maleic anhydride was observed by IR spectroscopy. The viscosity of this product ranged from 100 to 130 cPs at 93°C, as measured by an ICI cone and plate viscometer. This material could be used directly as a film former.

Example 3 - Propoxylated allyl alcohol maleate:

A 57 liter volume stainless steel reactor was charged with 15.49 kg of propoxylated allyl alcohol (available from Arco Chemical Company, New Town Square, Pennsylvania) and 9.88 kg of maleic anhydride (available from Huntsman Specialty Chemical). For the sake of stability, 2.53 g corresponding to 100 ppm HQ was added to the reactor. The mixture was heated under a nitrogen atmosphere to 121-149°C for 4 hours. The reaction end point was when the acid number reached a level of 263.4 Meq. KOH/g alkyd and no more maleic anhydride was observed by IR spectroscopy. The viscosity of this product ranged from 100 to 130 cPs at 93°C, as measured by an ICI cone and plate viscometer. This material could be used directly as a film former.

Examples 4A - K - Low Viscosity Epoxy Systems:

A typical epoxy-based film former contains one or more epoxy compounds available from Shell Chemical Company, such as EPON Resin 8121, EPON Resin SU-2.5, EPON Resin 160, HELOXY Modifier 62 (cresyl glycidyl ether), HELOXY Modifier 67 (diglycidyl ether of 1,4-butanediol) and HELOXY Modifier 505 (polyglycidyl ether of castor oil). All of the above-mentioned epoxy-based film forming systems have a viscosity below 50 cPs at room temperature. The specified percentages are by weight (all percentages and ratios in the description are by weight unless otherwise stated).

(A) 100% HELOXY Modifier 67

(B) 98% HELOXY Modifier 67, 2% HELOXY Modifier 62

(C) 90% HELOXY Modifier 67, 10% HELOXY Modifier 62

(D) 98% HELOXY Modifier 67, 2% EPON Resin 160

(E) 90% HELOXY Modifier 67, 10% EPON Resin 160

(F) 98% HELOXY Modifier 67, 2% EPON Resin SU-2.5

(G) 90% HELOXY Modifier 67, 10% EPON Resin SU-2,5

(H) 97% HELOXY Modifier 67, 3% HELOXY Modifier 505

(I) 100% HELOXY Modifier 62

(J) 70% HELOXY Modifier 62, 30% EPON Resin 8121

(K) 65% HELOXY Modifier 62, 30% EPON Resin 8121, 5% EPON Resin SU-2,5

Example 5 - High viscosity epoxy:

In addition to the above epoxy systems, an example of a higher temperature, higher viscosity epoxy film forming system is a 1:1 mixture of DER 337 epoxy resin (available from Dow Chemical) and Araldite GT7031 (available from Ciba-Geigy Corp., Switzerland). This film former has a viscosity of 350-450 cPs at 93°C, as determined using a Brookfield viscometer.

Example 6 - AUylpropoxylaturethane:

A 12-liter 3-neck glass round-bottom flask, equipped with a cooling jacket, a Friedrich condenser, a 1-liter addition funnel, an electric overhead stirrer, and a thermocouple temperature probe was charged with 3.63 kg (21.6 mol) of Desmodur H (hexamethylene diisocyanate, available from Bayer Chemical, Pittsburgh, Pennsylvania). To this was added 0.5 g (50 ppm) dibutyltin dilaurate (available from Aldrich Chemical Company). Next, 6.37 kg (43.6 moles) of ARCAL allyl propoxylate 1375 (propoxylated allyl alcohol, available from Arco Chemical Company) was added via the separatory funnel. The allyl propoxylate was added dropwise and the temperature was maintained at 80°C by varying the rate of addition and the temperature of the heating jacket. After the addition was complete, the temperature of the reactor contents was maintained at 80°C for 3 hours or for a period of time until the 2200 wavenumber peak in the IR spectrum of the reaction mixture, corresponding to the isocyanate groups in Desmodur H, disappeared. This film former can be used directly without further purification or further manipulation.

Examples 7 and 8: Fusible film formers:

Example 7 - Propoxylated bisphenol A maleate/ TONE 0260

The propoxylated bisphenol A maleate from Example 2 was mixed with TONE 0260 (a polycaprolactone polymer available from Union Carbide) in a 1:1 weight ratio. This mixture is solid at room temperature, but has a viscosity of 50-250 cPs at 93-110°C.

Example 8 - Propoxylertallyl alcohol maleate/ TONE 0260

The propoxylated allyl alcohol maleate from Example 3 was mixed with TONE 0260 in a 1:1 weight ratio. This mixture is solid at room temperature, but has a viscosity of 50-250 cPs at a temperature of 93-110°C.

Any constituents

In addition to or instead of other viscosity modifiers such as those mentioned above, n-butylamic acid can also be used as a modifier where it is suitably reactive with either thermoplastic or thermosetting materials to reduce the viscosity of the film former and the overall chemical treatment mass. A preferred reactive amic acid modifier was prepared as follows: A 2-liter 3-neck round-bottom flask, equipped with a heating jacket, Friedrich condenser, a 1-liter addition funnel, electric stirrer, and thermocouple temperature probe, was charged with 150 g (1.53 mol ) maleic anhydride (available from Huntsman Specialty Chemical) and 0.02 g of hydroquinone (available from Aldrich Chemical Co.). These solids were dissolved by adding 350 ml of acetone (high purity grade from Aldrich Chemical). The solution of maleic anhydride and hydroquinone was stirred in the reactor. A solution of lllg(1.51 mol) n-butylamine (available from Aldrich Chemical) in 150 ml of acetone was added to the reactor, the n-butylamine solution was added dropwise and the temperature was maintained at 55°C by varying the rate of addition and the temperature of the heating jacket. After the addition was finished, the temperature of the reactor and its contents was maintained at 60°C for 3 hours. The acetone was then removed under reduced pressure and 60°C by rotary evaporation. The solid n-butyl-amic acid product was removed from the reactor as a liquid at 90°C, which can then be used directly without further purification or manipulation. A small proportion of the n-butylamic acid produced was recrystallized from acetone. The melting point of the recrystallized material was 74.9°C, measured by differential scanning calorimetry (DSC).

Coupling means

For either a thermosetting or thermoplastic chemical treatment mass, the coupling agent comprises a functionalized, organic substrate (that is, at least one functional, organic group bonded to an organic substrate). Exemplary types of functionalized organic substrates are alcohols, amines, esters, ethers, hydrocarbons, siloxanes, silazanes, silanes, lactams, lactones, anhydrides, carbenes, nitrenes, orthoesters, imides, enamines, imines, amides, imides and olefins. The functionalized organic substrate is capable of interaction and/or reaction with the surface of the fibers at an elevated temperature, preferably from about 100°C to about 350°C), to provide sufficient coupling or bonding between the reinforcing fibers and the matrix material to thereby achieve the desired properties. Interaction involves bonding that originates from an attractive force, such as a hydrogen bond or a Van der Waals bond. Metabolism involves chemical bonding which is characteristically covalent bonding. The functionalized, organic substrate can also be interactive or reactive with the matrix material. Examples of coupling agents are silanes such as γ-aminopropyltriethoxysilane (A-I 100), γ-methacryloxypropyltrimethoxysilane (A-I 74) and γ-glycidoxypropyltrimethoxysilane (A-I 87), all available from Witco Chemical Company, Chicago, Illinois. Non-silane coupling agents can also be used. By choosing one or more appropriately functionalized, organic substrates for the coupling agent system, the desired mechanical properties can be achieved between the reinforcing fibers and the matrix material in the composite object.

Without wishing to be bound by any particular theory with regard to the chemical treatment masses, a possible explanation of how the treatment may be carried out is given below. Silane-type coupling agents are characteristically found in water-based, chemical coating compounds. According to the current view, with a conventional silane-type coupling agent, the hydroxysilane portion of the molecule undergoes hydrolysis and becomes a hydroxysilane or a silanol to water-solubilize the coupling agent. The end of the molecule reacts or interacts with the glass surface and the other end of the molecule reacts or interacts with the matrix material. More particularly, coupling agents that have typically been used in the glass industry are organosilanes which have an organic part believed to react or interact with the matrix polymer and a silane part or more particularly a silanol part, which is believed to react or interact with the glass surface. In some cases, it is also generally accepted that the organic part of an organosilane is capable of reaction (for example covalent or ionic bonding) or interaction (for example hydrogen or Van der Waals bonding) with the glass surface. In general, hydrogen bonding and other associations are assumed to be thermodynamic (reversible under mild conditions) processes. In some cases, such as when silanols are bound to a glass surface, the chemical binding is believed to be a thermodynamic process. With previous coupling agent technology, the bonding of a water-based chemical treatment mass to the glass occurs as a thermodynamic process. This is because conventional processes are usually carried out under relatively mild conditions and are usually reversible to some extent. In a conventional process and after the glass fibers are coated with a water-based, chemical treatment compound, the coated fibers are packed and dried in an oven. In the oven, there is the possibility that some of the organic functional groups in the coupling agent react irreversibly with some of the organic functional groups in the film former. This does not happen to a large extent, because the oven temperature that is typically used is around 66-88°C and thus not high enough.

With solvent-free, chemical treatment masses according to the invention, in contrast to this, the binding or coupling process becomes more kinetic in nature. This means that the binding can take place under relatively robust conditions (for example at higher temperatures) and can involve an essentially irreversible reaction. In addition to a coupling agent that binds to the fiber surface, an interphase area can now also be formed between the reinforcing fibers and the matrix material in the composite object. The interphase region is formed at least in part by means of the applied chemical treatment mass. The interphase area can also include, in whole or in part, an area around the fiber where the chemical treatment compound and the matrix material have interacted and/or reacted with each other. The chemical treatment mass can also be completely dispersed or dissolved in the surrounding matrix material.

Although conventional silane coupling agents may be used in the present chemical treatment compositions, it is believed that the mechanism of their interaction or reaction with the glass surface differs from that occurring in previous processes. Because there is essentially no water present during the treatment described here, the alkoxysilanes react directly with the glass surface and produce a siloxane bond and release alcohol. Thus, there is experimental evidence (proton NMR data) which suggests that the alkoxysilanes do not hydrolyze in the present chemical treatment masses under the conditions to which they are exposed, when they are processed according to the invention. It is believed that the alkoxysilane group of the coupling agent used in the present chemical treatment mass reacts or interacts with the glass surface in a kinetic manner, forming a siloxane bond and a released alcohol. Thus, the present process is kinetic rather than thermodynamic as demonstrated by observations that good composite properties are achieved both for thermosetting and thermoplastic composites, when alkoxysilane coupling agents were used with the chemical treatment compounds described according to the invention, while less desirable composite properties are obtained for both thermosetting and thermoplastic composites when Alkoxysilane coupling agents were not present in the chemical treatment masses.

If an alkoxysilane coupling agent in a chemical treatment composition herein reacts or interacts with a newly formed glass or other reinforcing fiber surface via a kinetic process, other types of molecules containing sufficiently reactive functional groups such as those indicated above will also react or interact with the glass or other reinforcing fiber surface via a kinetic process. Furthermore, these same functional groups that react or interact with the glass or the other fiber surface via a kinetic process, can react or interact with the rest of the organic material in the chemical treatment mass and/or matrix material via a kinetic process in the same way. This can then serve to build up an interphase area at or very close to the glass or the other fiber surface and can also serve to increase the average molecular weight of the chemical treatment mass and thereby give the resulting glass strand product desirable physical characteristics. Thus, the advantages of the method according to the description include the flexibility of using a wider variety of coupling agents and building up an interphase area between fiber and matrix.

In order for the composite object to exhibit desirable mechanical properties between the reinforcing fibers and the matrix material, the chemical treatment compound is preferably compatible with the matrix material in the composite object. In general, a chemical treatment compound is considered compatible with the matrix material if it is capable of interacting with and/or reacting with the matrix material. The film former of all types of applied chemical treatment mass may comprise the same polymer material as the matrix material and be provided in an amount sufficient to make up all or part of the matrix in the composite object.

The chemical treatment masses can be mixed in the matrix material, in whole or in part, and/or can perform a separate phase from the matrix material. If it is a separate phase, the chemical treatment mass arranged around each fiber can form a number of separate phase areas that are dispersed in the matrix material and/or a single, separate phase area that surrounds its corresponding fiber.

When it is desirable for the composite object to be produced with one type of chemical treatment compound and another type of matrix material, a thermobond type is preferably used for the chemical treatment compound with a thermoplastic matrix. A low molecular weight chemical treatment mass of the thermosetting type may harden during the thermoplastic processing and/or may react with the chain ends in the thermoplastic matrix material. As a consequence, such types of molecules will not easily soften the thermoplastic matrix material. When choosing a suitable chemical treatment mass, it should be noted that certain low molecular weight thermoplastic materials can soften thermoplastic matrix resins when the chemical structure of the thermoplastic matrix resin and the low molecular weight thermoplastic material are very different. An example of such different thermoplastic materials is dibutyl terephthalate as part of the chemical treatment compound or polypropylene as the matrix material.

Optionally, the chemical treatment mass can further comprise a compatibilizer to improve the interaction and/or reaction between the chemical treatment mass and the matrix material to thereby bring otherwise non-compatible or poorly compatible polymer components or constituents in the treatment mass, more compatible (for example, more miscible) in the matrix material . When a thermosetting or a thermoplastic chemical treatment compound is used with a thermoplastic matrix material, examples of compatibilizers are the PBT monomer equivalents di-n-butyl terephthalate and the dibenzoate ester of 1,4-butanediol; The PET monomer equivalents diethyl terephthalate and the dibenzoate ester of ethylene glycol; and the nylon monomer equivalents caprolactone, the adduct of adipoyl chloride and n-aminohexane and the adduct of 1,5-hexanediamine and hexanoyl chloride.

When these types of chemical treatment mass are used with a thermo-setting matrix material, it is preferred to use a more reactive compatibilizer. For a polyester or vinyl ester thermoset, a suitable compatibilizer is glycidyl methacrylate end-capped diacids and esters of the trimellitic anhydride system. Specific examples of suitable compatibilizers for polyester and vinyl ester thermosets include diallyl phthalate (DAP which is commercially available), glycidyl methacrylate-capped isophthalic acid, trimellitic acid anhyride dodecinate, the bis-allyl alcohol adduct of terephthalic acid, and CH3CH2(OCH2CH2)„(CH2)mC02H, where n is an integer from 3 to 7 and m is 16 (eg, CBA-60, available from Witco Chemical, Chicago, Illinois). For epoxy-based thermal binders, esters based on glycidol can be suitable compatibilizers, such as glycidyl methacrylate per se, diglycidyl ester of adipic acid and triglycidyl isocyanurate

(TGIC).

The chemical treatment composition may also include one or more processing aids to facilitate the use of the chemical treatment composition at points during the manufacturing process and/or to optimize properties of the resulting composite article. For a thermosetting type chemical treatment mass, the processing aid may include, for example, a viscosity reducer to reduce the viscosity of the thermosetting type of chemical treatment agent before it is applied to the fibers. The viscosity reducer is essentially solvent-free and preferably supports curing of a thermosetting film former. The processing aids used in this type of chemical treatment compound can include, for example, styrene and peroxide. Styrene is preferably used to dilute the film former and participate in the thermal debonding reaction. Peroxides preferably act as a catalyst or curing agent.

Optionally, the non-aqueous versions of other types of additives that are typically used to glue glass fibers can also be used as processing aids in the chemical treatment compounds described here. For example, process aids or additives may be used to help control the lubrication of the glass rope or strand, to control the relative amount of static, or to control the handleability of the glass strand or rope product. Lubricity can be modified by adding processing aids or lubricants, such as a polyethylene glycol ester emulsion in mineral oil (eg, Emerlube 7440, available from Henkel Textile Technologies, Charlotte, North Carolina); polyethylene glycols such as PEG-400-MO (polyethylene glycol monooleate) and PEG-400 monoisostearate (available from Henkel Corporation); and butoxyethyl stearate (BES). These lubricants serve to increase the flowability of the glass by acting as lubricants and should have little, if any, adverse effect on the properties of the finished composite article. The formation of static can be controlled by adding processing aids such as polyethylene imines, such as Emery 6760-O and Emery 6760-U (available from Henkel Corporation). Handleability can be improved by processing aids such as polyvinylpyrrolidone (eg, PVP K90, available from GAF Corporation, Wayne, New Jersey), which can provide good strand integrity and cohesiveness, as well as wetting agents or surfactants such as Pluronic L101 and Pluronic Pl05 (both available from BASF Corporation) which can improve the ability of matrix materials to wet fibers. Any ingredient present, however, has a formulation and is added in an amount such that the chemical treatment mass remains solvent-free.

Methods and apparatus for applying the method's chemical treatment compounds must be described in more detail with reference to the figures.

Figure 1 shows an embodiment of an apparatus 20 for applying a chemical treatment mass to fibers 10, used in the manufacture of a composite article, and includes a fiber manufacturing mechanism 22, for example a conventional glass fiber manufacturing bushing 24, which is operatively formed according to well-known practices of continuous production of a number of glass reinforcing fibers 12 from a source of molten glass material in a melter above the bushing 24.1 this example of method, the glass reinforcing fibers 12 emit heat energy a certain time after they have been produced. One or more applicators 26, for example a standard single or double roller type applicator 28 and an associated pan 30, may be used to apply one of the above described examples of chemical treatment compound to the reinforcing fibers 12 to thereby form a number of coated fibers 32. In order for the process to continue to proceed after the chemical treatment mass has been applied, i.e. without any significant amount of the fibers 10 breaking, the viscosity of the chemical treatment mass is created so that it is sufficiently low before application or drops sufficiently after application as discussed above.

Two alternative processes for applying chemical treatment compound to newly manufactured glass fibers are described below. Example process 1 is used when the viscosity of the chemical treatment mass is relatively low at relatively low temperatures (for example viscosities of 150 cPs or less at temperatures of 66°C or less). Example process 2 is used for chemical treatment compounds with a higher viscosity. Chemical treatment compounds that include one of the film formers from Examples 1 to 4(K) and 6 above can be used in Process 1. Chemical treatment compounds that include one of the film formers from Examples 5, 7 and 8 can be used with Process 2. Any chemical treatment mass that is used in process 1 can also be used in process 2. Any treatment mass that can be used in either process 1 or process 2 can also be used in process 3, which is a further example system.

Process 1:

This chemical treatment mass application process utilizes conventional glass-reinforcement fiber manufacturing equipment, modified in the area around the applicator 26 so that the position of the applicator 26 is adjustable in a plane perpendicular to the flow of glass fibers 12 (ie, the flow of fibers 10) as well as the plane which contains the fibers 10. The applicator 26 is attached to a cart with wheels by means of a bracket. The carriage is on rails so that it can be easily positioned along the axis perpendicular to the path of movement of the fibres. The top of the carriage is connected to the main body of the carriage by means of a case check and other suitable equipment. This allows the applicator 26 to be raised or lowered in relation to the bushing 24. The position of the applicator 26 can be adjusted along both axes, while the process is running. The chemical treatment compound is stored in a suitable metal container, for example an approx. 20 liter bucket.

The heating of the chemical treatment mass is possible. To heat the mass, the bucket may be placed on a hot plate and/or enveloped with a suitable heating element, such as a Model 5 available from OHMTEMP Corporation, Garden City, Michigan. The temperature of the chemical treatment mass is maintained at the desired level by means of a variable alternating current thermocouple-based heating control, for example as available from major suppliers such as Fisher Scientific or VWR Scientific. The chemical treatment mass is pumped to and from the applicator pan 30 by means of a peristaltic pump, such as a Masterflex, model #7529-8, equipped with a Masterflex pump control, model #7549-50 and Masterflex tubing part #6402-73, all available from the Barnant Company (a division of Cole-Parmer of Barrington, Illinois). Applicator 26 is of standard construction for a fiberglass manufacturing process and consists of a metal pan 30 which carries a single graphite roller 28 having a diameter of 7.6 cm and which is driven by an electric motor at speeds in the range of 0.9 to 6.1 m per minute. An alternative pump can be used to replace the peristaltic pump, such as a Zenith pump, model #60-20000-0939-4, available from Parker Hannifin Corporation, Zenith Pump Division, Sanford, NC. This alternative pump is a gear type pump equipped with a heated feed and return hose assembly and generally has the following features: Teflon lined, high pressure, 0.564 cm ID x 183 cm length, 83 MPa shock, 21 MPa operating pressure, stainless steel, 7 /16-20 Thread JIC Female Crank Connector, 120 Volt, 300 Watt, 100 Ohm Platinum RTD, 183 cm long wire with Amphenol #3106A-14S-06P Plug, available from The Conrad Company, Inc., Columbus, Ohio (the heated tubing assembly is a difference between the two alternative (peristaltic vs. gear-type) pump systems).

Process 2:

In another example process, a two-roll applicator is used to apply the high-viscosity, high-temperature chemical treatment compound in non-aqueous form. The two-roll applicator is fixed in position relative to the glassmaking apparatus. The position of the two-roll applicator is essentially the same as that found in a standard fiberglass manufacturing process, which is approximately 127 cm from the bushing. The heating system and pump system used for the chemical treatment mass in this process is the same as described for process 1.

The two-roll applicator includes a secondary applicator roll, which is the larger of the two rolls, for transferring and dosing the chemical treatment mass to a smaller, primary application roll. The primary roller is used to directly apply the chemical treatment compound to the fibres. The relatively small diameter of the primary roller reduces the stretch between roller and fibers by reducing the contact area between them. The tensile stress in the fibers is also reduced due to the reduction of the pull. The thickness of the applied chemical treatment compound can be dosed by controlling the gap between the primary and secondary rolls and by providing a doctor blade on the smaller roll. Such a two-roll applicator is described in US 3,817,728 and 3,506,419.

Process 3:

In this embodiment, a two-roll applicator according to process 2 and the positional adjustment option from process 1 are used together in addition to the above-mentioned heating and pumping systems for the chemical treatment mass. The coated fibers 32 are collected into a strand 14 using collection mechanisms 34, for example a conventional collection shoe. A drawing mechanism 36, for example a conventional pair of counter-rotating drawing rollers, is used to continuously draw the fibers 12 from the bushing 24 in a manner known per se. The string 14 can be wound on a package not shown or cut into segments of the desired length and stored for subsequent processing off-line into a composite object. Alternatively, the composite string 14 can be processed directly into a composite object in-line with the assembly step.

In addition to the continuously formed reinforcing fibers 12, the fibers 10 may additionally comprise a number of matrix fibers 13 produced from a suitable matrix material. If matrix fibers 13 are used, the application step for the chemical treatment compound may include gluing and/or pre-impregnation of the matrix fibers 13 with the same or a different chemical treatment compound than that applied to the reinforcing fibers 12. If different types of matrix fibers 13 are used, it may also be advantageous that a different chemical treatment compound is applied to each type of matrix fiber 13. If different types of reinforcing fibers 12 are used, it can likewise be advantageous that a different chemical treatment compound is applied to each type of reinforcing fiber 12. The same techniques and equipment can be used for chemical to treat each type of reinforcing fiber and matrix fiber, regardless of whether these are continuously formed or preformed.

Examples of chemical treatment compound

Below are examples of chemical treatment compounds for application to glass reinforcing fibers and various matrix fibers and suitable for use with PBT, nylon and polypropylene matrix resins. The different matrix fibers are made from the same material as the corresponding matrix resin. The designations "HEAT" or "NON-HEAT" indicate that the listed chemical treatment compounds are heated to a significant degree or not after they are applied to their respective fibers. The chemical treatment compounds below for reinforcing fibers with "NO HEAT" can also be used on matrix fibers made from the corresponding matrix resin. When the continuously produced glass fibers reach the applicator at a conventional location (for example, the applicator is at a significant distance from the source of molten glass), the glass fibers will still emit some residual heat. At this distance from the bushing, however, it may happen that the amount of heat from the fibers is not sufficient to have any significant effect on any of the applied chemical treatment compounds. The designation "NO HEAT" therefore covers such a situation.

Example A

Composite matrix resin: PBT

Formulation for reinforcing fibers:

(1) For HEAT: 83% HELOXY Modifier 67, 10% EPON SU-2.5, 5% Maleic Anhydride and 2% A-I 100; (2) For NON-V ARME: 95% HELOXY Modifier 67, 3% HELOXY Modifier 505 and 2% A-1100.

Formulation for matrix fibers:

(1) For WARM: 83% HELOXY Modifier 67, 10% EPON 160 and 7% DICY; (2) For NON-V ARME: 83% HELOXY Modifier 67, 10% HELOXY Modifier 62 and 7% TGIC.

Example B

Composite matrix resin: nylon

Formulation for reinforcing fibers:

(1) For HEAT: 44.5% PG fumarate with hydroxy end groups, 44.5% TONE 0260, 5% DESMODUR N-100, 5% BES and 1% A-1100;

(2) For NON-V ARMS:

(a) 47% propoxylated bis-A-maleate, 47% TONE 0260, 5% BES and 1% A-1100;

or

(b) 99% allylpropoxylaurethane and 1% A-I 100.

Formulation for matrix fibers:

(1) For HEAT:

(a) 90% allylpropoxylaturethane and 10% amic acid; or

(b) 90% allylpropoxylaturethane, 5% PG fumarate (hydroxy-terminated) and 5%

DESMODUR N-l 00;

(2) For NON-HEAT: 47.5% propoxylated bis-A-maleate, 47.5% TONE 0260 and 5%

BES.

Example C

Composite matrix resin: polypropylene

Formulation for reinforcing fibers:

(1) For HEAT:

(a) 68% PG fumarate, 20% propoxylated allyl alcohol, 5% maleic anhydride, 5%

TBPB and 2% A-I 100 or A-I74; or

(b) 83% PG fumarate (hydroxy terminated), 5% DESMODUR N-100, 5% maleic anhydride, 5% TBPB and 2% A-I 100 or A-174;

(2) For NON-V ARMS:

(a) 88% allylpropoxylaturethane, 10% EPON 8121 and 2% A-I 100; or (b) 90% allylpropoxylaturethane, 5% diallyl phthalate, 2% maleic anhydride, 2% BPO

and 1% A-I 100.

Formulation for matrix fibers:

(1) For HEAT: 91% allylpropoxylaturethane, 5% diallyl phthalate, 2% maleic anhydride and 2% TBPB;

(2) For NON-V ARMS:

(a) 90% allylpropoxylaturethane and 10% EPON 8121; or (b) 91% allylpropoxylaturethane, 5% diallyl phthalate, 2% maleic anhydride and 2%

BPO.

The abbreviation DICY stands for dicyandiimide which is a high temperature, amine-based curing agent for epoxy resins. Both the DICY curing agent and the reactive modifier diallyl phthalate (to reduce viscosity) are available from Aldrich Chemical Company. DESMODUR N-100 is a polyisocyanate available from Witco Chemical Company. PG fumarate, propoxylated bis-A-maleate, propoxylated bisphenol-A-maleate), allyl propoxylaturethane, propoxylated allyl alcohol and amic acid (ie n-butyl amic acid) can all be prepared as described above. BES means butoxyethyl stearate, which in the above-mentioned chemical treatment compounds can be completely or partially replaced by compounds such as the adduct of adipoyl chloride and n-aminohexane or the adduct of 1,6-diaminohexane and hexanoyl chloride, caprolactone (available from Aldrich Chemical Co.) and amic acids such as n- butyl-amic acid, and these alternative compounds may fulfill other functions in addition to those provided by BES. TPBP and BPO are the peroxides t-butyl peroxybenzoate and benzoyl peroxide, respectively, and are available from Akzo-Nobel Chemical Company, Chicago, Illinois. EPON 8121 is a bisphenol-A type epoxy resin available from Shell Chemical Company.

The chemical treatment compound of 99% allylpropoxylaurethane and 1% A-I 100 was applied to glass fibers, the coated glass fibers were converted into a composite strand, this was wire coated or sheathed with a sleeve of thermoplastic nylon matrix material and the sheathed composite strand was chopped into pellets, after which these were injection molded for composite test pieces. The sheathed composite pellets were formed using the wire processing process of the invention as described in more detail below. The glass fibers in these composite test pieces were not completely dispersed in the matrix material. This lack of complete dispersion of the glass fibers from the individual strands in the finished composite articles suggests that at least a portion of the chemical treatment compound reacted sufficiently, at some point during the manufacturing process, to prevent the fibers from separating from each other and becoming dispersed in the melted the matrix material into the mold of the composite article (that is, to maintain strand cohesion). In order to reduce the activity (that is, to reduce the fiber cohesion in each composite strand during the composite object casting process) and thereby achieve more dispersion of the reinforcing fibers in the matrix material, the allylpropoxylethane can be diluted with another film former, for example for a nylon system, for a nylon system TONE can be used for example 0260 (a polycaprolactone, available from Union Carbide Corp.).

Below are further examples of thermo-bonding types and thermoplastic types of chemical treatment compounds according to the method.

Nylon-based chemical treatment compound:

A particularly preferred nylon-based chemical treatment compound of the thermoplastic type was prepared by depositing approx. 9 kg of polycaprolactone and particularly TONE 0260 (available from Union Carbide Corporation) and about 9 kg of a polyester alkyd, particularly propoxylated bisphenol-A maleate, in separate 19-gallon metal cans. After complete melting or liquefaction of these two materials, they were combined in a heated 19 liter jug and stirred until the mixture became homogeneous. The temperature was maintained at or above 93°C with constant stirring until complete mixing was achieved, after approx. 30 minutes. The heating was then discontinued and the mixture allowed to cool to 88°C. While the temperature was maintained at 88°C, approx. 360 g of aminosilane coupling agent A-I 100 (γ-aminopropyltriethoxysilane) was added to the mixture with constant stirring. The resulting chemical treatment mass contained on a weight basis 49-49.5% TONE 0260, 49-49.5% propoxylated bisphenol-A maleate and 1-2% A-I 100. This chemical treatment mass was solid at approx. 25°C and had a viscosity of 6600 cPs at 75°C, 260 cPs at 100°C, 120 cPs at 125°C and 60 cPs at 150°C.

The chemical treatment mass was then transferred with its container to a bucket heater as described in process 2 above and pumped to a suitable applicator. Glass fibers 12 were drawn and allowed to contact the applicator roll 28. The chemical treatment compound was then, at a temperature of about 115°C, transferred onto the glass fibers 12. The fibers 12 were collected in a conventional shoe 34 and wound on a collector to produce a square package and allowed cooling.

The resulting package is stable and transportable and the fuse runs out without problems. The resulting composite strand 14 can be wire coated and chopped into pellets for possible use in injection molding applications.

PBT-based chemical treatment compound:

A particularly preferred thermoplastic-type PBT-based chemical treatment compound was prepared by placing 17.28 kg of diglycidyl ether of 1,4-butanediol (HELOXY 67) in a 19 liter metal can. To this was added 540 g of polyglycidyl ether of castor oil (HELOXY 505). To this mixture was added 180 g of A-1100 (γ-aminopropyltriethoxysilane) as coupling agent. The resulting chemical treatment composition contained by weight 96% HELOXY 67, 3% HELOXY 505 and 1% A-I 100. This mixture was stirred until homogeneous. It was then transferred with its container to a bucket heater as described in process 1 (although it is not necessary to heat this chemical treatment mass to process it). To apply this chemical treatment compound, the applicator 26 was raised to within 20.32 to 25.4 cm of the bushing 24.

Polyester or vinyl ester-based chemical treatment compound:

A particularly preferred polyester or vinyl ester based chemical curing compound of the thermosetting type was prepared by placing 6.75 kg of DER 337 epoxy (a bisphenol-A epoxy resin, available from Dow Chemical Company) in a 19 liter metal can. This material was heated to 104°C and stirred until all the solids were completely liquid. To this liquid was added 6.75 kg of Aradite GT7013 epoxy (a bisphenol-A epoxy resin, available from Ciba-Geigy Corporation). The araldite was added slowly with vigorous agitation over 2 hours. After complete dissolution of the aradite-epoxy compound, the mixture was allowed to cool in air to 93°C and 0.76 kg of Pluronic L101 (an ethylene oxide/propylene oxide copolymer surfactant, available from BASF) and 2.21 kg of Pluronic Pl05 (an ethylene oxide/propylene oxide copolymer surfactant , also available from BASF) is added. At this point, 1 kg of PEG 400 MO (polyethylene glycol monooleate, available from Henkel Corporation) and 0.5 kg of butoxyethyl stearate (BES) (available from Stepan Company, Northfield, Illinois) are also added. The mixture is allowed to further cool with continuous stirring to 61-77°C, at which time 2 kg of A-174 (γ-methacryloxypropyltrimethoxysilane, available from Witco Chemical Corporation) is added. Finally, 20 g of Uvitex OB (a fluorescent brightener, available from Ciba-Geigy, Hawthorne, New York) is added to the mixture with stirring to facilitate good dispersion. The resulting chemical treatment compound contains, by weight, 33.78% DER 337 epoxy, 33.78% Aradite GT7013 epoxy, 3.79% Pluronic L101, 11.05% Pluronic P105, 5% PEG 400 MO, 2.5% BES, 0.10% Uvitex OB and 10% A-174. This chemical treatment mass is then transferred with its container to a bucket heater as described under process 2.

Epoxy-based chemical treatment compound:

The formulation in this example of a thermoset type chemical treatment compound is as described above for polyester and vinyl ester based thermoset type chemical treatment compounds, except that A-187 (γ-glycidoxypropyltrimethoxysilane, available from Witco Chemical Company) is used instead of A-174.

Two-silane, polyester or vinyl ester-based chemical treatment compound: The formulation for this example of a treatment compound of the thermo-setting type and which has multi-compatibility (compatibility with polyester, vinyl ester or epoxy) is as described for the above-described polyester or vinyl ester-based, thermosetting type chemical treatment compounds, except that the silane coupling system consists of 1.25 kg (5 wt%) A-187 and 1.25 kg (5 wt%) A-174, instead of A -174 alone.

In the embodiment shown in Figure 3, matrix fibers 13 are prepared in advance and then mixed with the reinforcing fibers 12 before being assembled into a composite strand 14. Alternatively, the matrix fibers 13 can be formed continuously in-line with the reinforcing fibers 12. The matrix fibers 13 ultimately form part of or all matrix in a resulting composite object. The fibers 10 can comprise both continuously produced and previously formed reinforcing fibers 12 or only previously formed reinforcing fibers. If preformed reinforcing fibers 12 are used, these can be processed directly into a strand 14 containing only the preformed reinforcing fibers 12. Such preformed reinforcing fibers 12 can also be mixed with any other type of fibers in the same or a different way than the preformed matrix fibers 13 as shown in Figure 3. While only two spools or bundles of preformed fibers are shown, it should be understood that any number of bundles of preformed fibers may be fed in the manner shown or in another suitable way.

The same applicator 26 can be used to chemically treat both the preformed fibers (for example, preformed matrix fibers as indicated by the dashed lines 13') and continuously formed fibers (for example, the continuously formed reinforcing fibers 12) before the fibers are collected into a strand 14. Alternatively, a separate applicator 26' may be used to chemically treat the preformed fibers (eg the preformed matrix fibers 13). If a separate applicator 26' is used, the collection mechanism 34 may include a rod or roller 39 to assist in intermingling the fibers 12 and 13 before they are collected into a strand 14. Preformed fibers and continuously formed fibers may be chemically treated either together in use by the same applicator or separately using different applicators, for example as described in US-SN 08/527 601, to which reference is made for details. Alternatively, some of the fibers 10, for example the matrix fibers 13, can be collected together with the coated fibers 32 without chemical treatment compound being applied first.

The applied chemical treatment mass can be heated before, during and/or after the gathering step for the fibers. If it behaves as thermosetting, the applied chemical curing compound may be heat cured in whole or in part at any time during the formation of the composite strand 14. How much and when such applied thermosetting chemical curing compound is heat cured, depends on the type of composite object one wishes to produce from the strand 14. For example, a composite strand 14 with full, partial or no heat curing of the applied chemical treatment mass, can be chopped into a number of short, discrete lengths, mixed in a casting mixture and injection molded into a composite object .

For chopped lengths of strand 14, an applied chemical treatment compound is cured sufficiently, if at all, to ensure that the short lengths of composite strand 14 remain cohesive (ie, the fibers 10 stay together) during subsequent processing. Where it behaves as a thermobinder or is otherwise heat curable, the applied chemical treatment compound on the coated fibers is preferably only partially cured during the formation of the composite strand 14. Curing of the applied chemical treatment compound is preferably completed in a subsequent in-line or off-line processing (eg, pultruding, filament winding, transfer injection molding, compression molding, and so on) of the composite strand 14 into a composite article. A chemical treatment mass of the thermosetting type preferably remains only partially cured until the formation of the composite article because if the molecular weight in the chemical treatment mass approaches infinity (that is, is maximized) during the formation of the composite strand 14, it may be found that the strand 14 can no longer be processed downstream -composite manufacturing facilities. Such partial curing can be accomplished by selecting components that do not fully react with each other under the conditions present during the manufacturing process for the composite strand. It can also be achieved by choosing the relative amounts of the reactive components of the chemical treatment mass so that at least one of the thermosetting components in the chemical mass (for example a resin) remains only partially reacted or hardened until the formation of the composite article (for example by control the stoichiometry in the chemical treatment mass). An example of a chemical treatment composition having at least one reactive component that may remain only partially reacted or cured during the strand making process comprises about 85 wt% PG fumarate, about 10 wt% styrene and about 5 wt% t-butyl peroxybenzoate.

In the chemical treatment compositions listed in Examples A-C above, different reactive species are represented. While in most cases it is preferred that some unreacted chemical species remain on the strand 14 at the end of the strand making process, in some cases it may be advantageous, for example in the above-mentioned chemical treatment compositions containing isocyanates or amic acids, that the chemical species are fully converted when they are in string form. If, in the case of the isocyanates, a diol is present and in sufficient quantity (for example, about 20 times the number of isocyanate groups) and if the chemical treatment compound is applied at a sufficiently high fiber surface temperature, the isocyanate groups will be fully reacted in the composite strand 14. If in the same way the reaction conditions are right (for example high temperature and relatively low concentration), the amic acid in the chemical treatment mass will in the same way be completely converted to imide.

A chemical treatment composition can be prepared comprising about 45% by weight PG fumarate, about 50% by weight styrene and about 5% by weight t-butyl peroxybenzoate. This represents a polyester resin formulation which can be applied to glass fibers using an applicator device as described above in processes 1 to 3, and which can harden to a hard mass on a glass fiber strand 14 after the addition of heat originating from the newly produced glass fibers. By removing approx. 90% of styrene, this chemical polyester resin treatment compound can be made only partially curable when placed on the fibers. An additional chemical treatment composition may be prepared comprising 35% by weight of epoxy resin Epon 828, available from Shell Chemical Company, about 35% by weight of the reactive epoxy modifier HELOXY 505, about 28% by weight of maleic anhydride and about 2% by weight of A-I 100. This epoxy resin formulation can be applied to the glass fibers using any of the applicator equipment described above, and cures to a hard mass on a glass fiber strand 14 by the heat emanating from the newly formed glass fibers. By removing about 90% and up to all of the maleic anhydride, this chemical epoxy resin curing compound can be made only partially curable when applied to the fibers.

By elevating the applicator 26 to a position closer to the heat emanating from the molten glass (eg bushing 24), it has been observed that the viscosity of a chemical thermoplastic type treatment compound on the surface of the applicator rollers 28 (ie, where the roller 28 contacts the glass fibers 10 ) has decreased, as well as that on the surface of the glass fibers 12. A thermosetting type chemical treatment compound that behaves as a thermoplastic at this process step will also undergo such a viscosity reduction. Gradients in the viscosity of the chemical treatment compound are observed along the surface of the applicator roll 28. The viscosity is found to be lowest behind the fan of glass fibers 10 and appears to increase towards each end of the roll 28.

For the Figure 1 embodiment of the apparatus 20, the applicator 26 is positioned next to or sufficiently close to the bushing 24 that the chemical treatment compound is applied when the fibers 12 are at a sufficiently high temperature (that is, when the fibers 12 emit sufficient heat energy) to cause the desired viscosity drop and/or the desired degree of heat curing by cross-linking or otherwise increasing the molecular weight of the applied chemical treatment mass. At the same time, the applicator 26 is preferably positioned sufficiently far away from the bushing 24 so that the chemical treatment compound is applied while the fibers 12 are at a temperature that will not cause significant damage to the chemical treatment compound (for example decomposition of organic chemicals or compounds present). In this way, a resulting string 14 can be provided with the properties that are desired for the subsequent processing into a composite object.

Examples of fiber temperatures for laying on the chemical treatment compounds are temperatures up to around 350°C, as it is possible to apply some treatment compound even at higher temperatures without it being damaged or degraded to a significant extent. Fiber temperatures as low as 150°C or even lower can be used. In order to protect the applied chemical treatment mass and to provide at least one of the two above-mentioned desired changes in the mass, the fibers 12 are preferably at a temperature of around 200°C to around 300°C. Satisfactory results have been obtained when the viscosity of the chemical treatment compound of any type drops to from about 200 cPs to about 400 cPs at a temperature of from about 200°C to about 300°C.

For glass reinforcing fibers drawn from a conventional bushing 24 with a normal passage, the applicator 28 is preferably arranged so that the chemical treatment compound is placed on the glass fibers 12 at least 7.62 cm and as much as 15.24 cm or more from the bushing 24 (that is, from there the fibers 12 emerge from the bushing). The chemical treatment compound can be placed on the glass reinforcing fibers 12 at a distance of about 20.32 to 25.4 cm from the bushing 24. The exact location of the applicator 26 relative to the bushing 24 depends, for example, on the type of bushing used (the number of fibers pulled from the bushing ), the temperature in the molten glass material, the type of chemical treatment compound used, the desired properties of the interphase region around the reinforcing fibers 12 as well as the properties desired for the resulting strand 14 and later from the composite article.

With reference to the embodiment in Figure 2, an apparatus 38 includes the components of the previously described apparatus 20 and a heat container 40.1 accordingly, components of the apparatus 38 with the same or similar functions to components of the apparatus 20 are given the same reference numbers. The heat container 40 is arranged in whole or in part at least around the fibers 12 and is adapted for use by conventional techniques to retain the heat energy originating from the surface of the fibers 12 for a longer period of time and at a longer distance from the fiber making mechanism 22. Satisfactory results have been obtained with a fiber bushing 24 with low glass penetration using a heat container 40 made of sheet metal formed into an open-ended rectangular box about 38.1 cm long, about 7.6 cm wide, and about 40.64 cm high. A low throughput fiberglass bushing 24 typically forms reinforcing fiberglass at a rate less than about 13.6 to 18.2 kg/hour. The box-shaped heating container 40 is arranged between the fiber forming mechanism 22 and the applicator 26 so that at least the fibers 12 are drawn through the open ends 42 and 44. Preferably, the heating container 40 is sufficiently insulating to maintain the surface of each fiber 12 at a temperature from about 150°C to about 350°C at which time the applicator 26 applies the chemical treatment compound to the fibers 12.

The use of such a heating container 40 is particularly advantageous when a bushing is used for the production of continuous glass fibers with a low throughput. The amount of heat energy that is stored by the fibers 12 when using such a bushing 24 is less than what is stored by the fibers 12 when using a bushing at normal or high throughput. Thus, the heater 40 allows fibers 12 formed using low-flow bushing to be kept at the temperature necessary to provide the desired reaction (viscosity loss and/or at least partial heat hardening) in the applied chemical treatment compounds. The heat container 40 can be modified to be arranged up to or even further downstream past the applicator 26 to maintain the fibers 12 at a desired, elevated surface temperature at a point up to or downstream from the applicator 26. For example, a further heat treater with a similar construction to the container 40 can is arranged partially or completely around the coated fibers 32 and between the applicator 26 and the collection mechanism 34. The use of such an additional heating container may be desirable when further hardening of the chemical treatment mass is necessary before the strand 14 is collected, for example on a spool, or processed in a different way afterwards. An example of agents that can be used as such heat containers according to the invention and especially after the chemical treatment mass has been applied to the fibers, is described in US 5 055 119.

The energy used in heating the applied chemical treatment mass can be at least partially, if not completely, provided by the heat energy originating from the coated fibers 32. For example, residual heat from or remaining in the continuously formed glass fibers can provide a significant amount of the heat energy. Residual heat from continuously formed polymer matrix fibers 13 can likewise be used to effect desired changes in applied chemical treatment mass.

If residual heat from the fiber manufacturing process is not available or if this is insufficient, such as when the fibers 10 are pre-manufactured, have cooled or are otherwise not at the desired temperature, the fibers 10 can be preheated to provide the heat energy desired in connection with the application of the chemical treatment compound. Such preheating can be carried out using a conventional heating system. With reference to Figure 2, a conventional, open-ended, not shown oven can for example be used instead of the heating container 40 to preheat at least the fibers 12 to the desired temperature before the chemical treatment compound is applied.

By using heat energy from the fibers 32 to provide at least part of the necessary heat energy, the applied chemical treatment mass has a reduced viscosity and/or it is at least partially heat-cured from the surface of the coated fibers 32 outwards through into the at least a part of the prescribed treatment mass. Heat from the fiber surface outwards is particularly preferred and an effective way of heating the applied treatment mass and supporting an optimization of the bond between the chemical treatment mass and the surface of the coated fibers 32.1 additionally allows heating from the surface of the coated fibers 32 outwards, a greater versatility with a view to providing an interphase area formed by the applied, chemical treatment mass, between each of the coated fibers 32, and the matrix material in the composite object.

Heating an applied chemical treatment compound of the thermoplastic type from the inside outwards supports that the viscosity at the surface of the fibers will be low enough to achieve sufficient wetting of the fiber surface. Heating an applied heat-curable chemical treatment compound in this manner additionally allows the compound to be fully cured only at the interface with the fiber surface, thereby retaining an outer area of only partially cured or uncured chemical treatment compound which can then be fully cured when and where is desired during the subsequent processing. For example, it may be desirable for this outer area that it is only partially cured or not cured at all to facilitate bonding between chemical treatment compound and subsequently applied matrix material or between layers in contact of applied treatment compound on neighboring fibers.

Preferably, the heat from the fibers 12 is used to heat the applied chemical treatment mass. Optionally, the energy used to heat the applied treatment mass can be partially, substantially or completely provided by heat energy from a source external to the coated fibres. After the chemical treatment compound is applied, for example, the coated fibers may be passed through a conventional, open-ended, not shown oven either before, during, or after the coated fibers 32 are assembled into the strand 14. The applied treatment compound may also be heated externally while forming the strand 14 into a composite article. With external heating, the viscosity of the applied treatment mass is reduced and/or it is at least partially heat-set from the outer surface into the applied, chemical mass towards the surface of the coated fibers 32. Thus, it is aimed that the energy used to heat the applied treatment compound can be provided by a combination of heat from the coated fibers 32 and one or more external heat sources arranged so that at least the reinforcing fibers 12 are heated before and/or after the chemical treatment compound is applied.

The chemical treatment compound can be kept chilled before it is applied to the fibers to allow the use of highly reactive ingredients and to reduce the risk of heat-induced degradation of the chemical treatment compound. The temperature in the chemical treatment mass before it is applied can be kept below or equal to room temperature for the same reasons. The chemical treatment mass can be kept at the desired temperature in any way. For example, a cooling coil not shown can be immersed in the chemical treatment mass. When continuously produced glass fibers are formed, the apparatus can also be adapted so that the glass fibers 12 are surrounded by an inert atmosphere before the chemical treatment compound is applied. The inert atmosphere will help prevent moisture from accumulating on the surface of the fibers 12 and will thereby inhibit moisture-induced cracking and moisture-induced passivation of potential reactive species on the glass fiber surface. An inert atmosphere may be undesirable when a bushing with a high outlet quantity is used or at any time the temperature in the glass fibers is sufficiently high. The glass fibers 12 can be surrounded with an inert atmosphere by using heating containers (see Figure 2) or a similar structure to surround the glass fibers where the inert atmosphere is led into the heating container 40 as the fibers 12 pass through. Suitable inert atmospheres are, for example, a combination of nitrogen and argon.

An advantage of the chemical treatment compounds according to the description is that they can be carried out using known equipment for the production of fibres, strings and composite objects. In one embodiment, the solvent-free, chemical treatment agents are preferably used in a wire coating system as described below.

MANUFACTURE OF COVERED STRINGS

A general aspect of the invention relates to a method for producing one or more plastic-encased composite strands which can be molded into a composite object with a polymer or resin matrix reinforced with fibers produced from a suitable reinforcing material, for example a glass material, a synthetic or polymer material, or any preferably other suitable non-glass material. The sheathed composite strings can be in wire form (that is, long lengths) or pellet form (that is, short lengths).

More particularly, each sheathed composite strand has a number of fibers including at least reinforcing fibers and possibly fibers produced from the thermoplastic matrix material to be used in the composite article. The fibers are processed into strands or bundles where each strand preferably contains about 1,500 to about 10,000 fibers, fully about 2,000 to about 4,000 fibers. The string is pre-impregnated with a chemical treatment compound before the string is formed.

The pre-impregnated composite string is encased in a sleeve of thermoplastic material. When the sheathed composite strand is to be converted into pellets, the chemical treatment compound is applied in sufficient quantity and between a sufficient number of the fibers to ensure that the fibers do not fall out of the pellet. When the sheathed composite strand is to be converted into thread, the chemical treatment compound is arranged between essentially all fibers.

In a preferred embodiment, the chemical treatment compound is a polymer material of the thermoplastic type. Alternatively, the chemical treatment compound that impregnates the composite string can be a polymer material of the thermosetting type which is fully, partially or not cured. The strand of fibers may optionally be fully impregnated with a manufacturing thermoplastic matrix material such as that used to wrap or coat the composite strand. Although some thermoplastic manufacturing materials have relatively high melting points and high viscosities, which can make it very difficult or impractical to apply this thermoplastic to the fibers using conventional applicators, the person skilled in the art will easily be able to modify such plasters for use as chemical treatment mass according to the invention.

Preferably, the sleeve that envelops the composite string is made from the same thermoplastic material that is used to form the matrix in the composite article. The thermoplastic sleeve material can form part or all of the matrix in the composite article, depending on the thickness of the sleeve. Preferably, the chemical treatment compound will sufficiently bind or otherwise support that the sleeve holds the fibers together in a pre-impregnated state, at least until the composite article is formed. In addition, the chemical treatment compound is at least compatible with the thermoplastic matrix material in the composite article.

According to a preferred process for manufacturing one or more of the thermoplastic sheathed composite strands, a wire coating or extrusion coating process is used. The process comprises the steps of: providing a number of fibers comprising at least reinforcing fibers; applying a chemical treatment compound to coat substantially all fibers thereby forming prepregs; gathering or otherwise combining the coated fibers into at least one pre-impregnated strand by the chemical treatment mass disposed between substantially all fibers forming the pre-impregnated strand; coating at least the exterior of the pre-impregnated strand with a thermoplastic material to form at least one coated strand; and converting the coated strand into at least one wire-coated or otherwise sheathed composite strand.

The fibers can be provided using an in-line process that includes the continuous production of reinforcing fibers from a source of molten reinforcing material such as glass. In addition to continuously produced reinforcing fibers, the fibers provided may include preformed reinforcing fibers, preformed matrix fibers, continuously produced matrix fibers, or combinations thereof. In an aqueous system, the chemical treatment compound on the fibers is heated to evaporate a significant amount of the moisture before the coated fibers are assembled into a pre-impregnated strand. When it is of the thermosetting type, the chemical treatment compound is applied to the fibers either in an uncured or partially cured state. The uncured or partially cured chemical treatment mass that ends up impregnating the sheathed composite strand may be further processed (eg, by heating) to induce further partial or full cure, depending on the desired condition of the sheathed composite strand during casting of the composite article. In a preferred embodiment, a solvent-free, chemical treatment mass as described above is used. Alternatively, a non-aqueous, two-component chemical treatment mass can be used as described in US-SN 08/487 948.

Examples of systems for forming polymer-sheathed strands are shown in the drawings and particularly in Figures 4 to 6. Figure 4 shows an embodiment of an apparatus 110 including a source 112 for fibers 113 which in this embodiment consists of reinforcing fibers 114. An example of a source 112 is a conventional bushing 115 for molten reinforcing material (eg glass) from which the continuous reinforcing fibers 114 are drawn.

An applicator 116 applies a chemical treatment compound to substantially all fibers 114. In one example embodiment, the chemical treatment compound applied is aqueous and the applicator 116 is a conventional type suitable for applying water-based chemical treatment compounds. The applicator example 116 includes a rear facing applicator roller 118 which applies chemical treatment compound to the reinforcing fibers 114 thereby forming prepreg or coated fibers 120. The chemical treatment compound is applied when the fibers 114 contact the roller 118 as they pass over it. A trough 122 containing the chemical treatment mass is located below the roller 118. The roller 118 runs down into the trough 122 and transfers treatment mass from the trough 122 to the fibers 114 where the roller 118 is turned by a conventional device, for example a motor not shown. Other suitable devices or techniques for applying glue or other chemical treatment compounds can be used instead of the applicator roller unit 116 to apply the chemical treatment compound to the reinforcing fibers 114.

The water-based chemical treatment compound applied to the prepreg or coated fibers 120 is heated to evaporate a substantial amount of the moisture and then the coated fibers 120 are assembled into a prepreg composite strand 124. The moisture can be driven out of the applied water-based , chemical treatment compound using any suitable heating device 125. For example, the coated fibers 120 may be passed over and brought into contact with a heating device 125 substantially similar to one of the heating plates described in US-SN 08/291 801 and 08/311 817.

A conventional collection shoe or any other form of collection device 127 can be used to collect the dried fibers 120 into at least one prepreg strand 124. This prepreg strand 124 is coated or sheathed with a layer of polymer material and thereby converted into a sheathed composite strand 126 by drawing or otherwise passing the prepreg strand 124 through a thread coater 128. A thread coater is a device or devices capable of, or means for coating one or more prepreg fiber strands with a polymer material to thereby form a polymer sleeve on each prepreg strand 124. Preferably, each strand contains from about 1,500 to about 10,000 fibers and more preferably from about 2,000 to about 4,000 fibers.

The fibers 113 used in forming a sheathed composite strand 126 can be produced using an in-line process such as that shown in Figure 4, where reinforcing fibers 114 are continuously drawn from a bushing 115 from a molten reinforcing material such as glass. In addition to or instead of continuously formed reinforcing fibers 114, the fibers 113 may comprise prefabricated reinforcing fibers. Furthermore, the fibers 113 may include pre-produced matrix fibers and also continuously produced matrix fibers, or combinations thereof. An example of a system for applying an aqueous chemical treatment composition to continuous and preformed fibers to form a prepreg strand is described in US-SN 08/311,817, supra.

The matrix fibers ultimately form part or all of the matrix in the resulting composite article or product, for example pellets 132. Examples of suitable polymer materials for the matrix fibers are polyesters, polyamides, polypropylenes and polyphenylene sulphides. The continuous and prefabricated reinforcing fibers can be of glass fibers, synthetic fibers and/or any suitable reinforcing fibers, for example fibers of traditional silicate glass, rock wool, beaten gold, carbon, and so on. When different fibers made from different materials are used, the same or different chemical treatment compounds can be used for each type of fiber.

Preferably, the wire coater 128 includes a source of molten polymer material, such as a conventional extruder, to provide the material used to coat the prepreg strand 124. The wire coater preferably also includes a nozzle or other suitable means with at least one outlet or outlet opening to shape the sleeve to the desired thickness and/or cross-section, preferably to a thickness and a cross-section which is maintained relatively uniformly along the length. Exemplary wire coaters 128 are manufactured by Killion of Cedar Grove, New Jersey and include a KN200 5 cm extruder equipped with a crosshead coating die. One or more sheathed composite strands 126 may be formed by drawing or otherwise passing one or more of the coated strands 124 through one or more such dies. The sleeve material is preferably thermoplastic and can form part or all of the matrix in the composite object, for example depending on the thickness of the sleeve. In a preferred embodiment, the sleeve that envelops the composite string 124 is made from the same thermoplastic material that is used to make the matrix in the composite article.

When it is desired that the sheathed composite strand 126 be supplied in short lengths, the apparatus 110 may include means such as a chopper 130 to cut or otherwise separate the sheathed composite strand 126 into a number of sheathed composite pellets

132. An example of a chopper 132 is the Model 204T Chopper, manufactured by Conair-Jettro, Bay City, Michigan. When pellets 132 are formed, during the chemical treatment mass to hold the fibers 114 together in each sheathed pellet 132 (helps to keep a significant number of fibers 114 from falling out of a pellet 132).

The coated composite pellets preferably have lengths from about 0.476 cm to about 3.8 cm, although they may be longer or shorter as desired. In an example embodiment, these pellets have a length of about 1.27 cm. Of course, the length of each pellet can vary from one application to another. Furthermore, the shape of the sheathed composite strand may vary as a result of the particular application.

The fibers 114 can be pulled through the apparatus 110 using a puller 134 which, for example, causes the reinforcement fibers 114 to be pulled from the bushing 115 and to pull the pre-impregnated strand through the wire coater 128. An example of a wire coater 134 that has been successfully used in-line with the Killion wire coater 128 described above is a 4/24 High Speed Puller, also manufactured by Killion. Alternatively, the wire coater 128 and/or the chopper 130 may be adapted to fulfill the function of pulling or supporting the puller in pulling the prepreg strand through the wire coater 128.

When it is desired that the sheathed composite strand product is in wire form, the cutter 130 can be replaced with a winding device 136 for pulling the reinforcing fibers 114 from the bushing 115, drawing the prepreg strand 124 through the wire coater 128 and winding the sheathed composite strand 126 on a spool or a second bundle 128 of sheathed composite wire 140. When in wire form, strand 124 is at least substantially, if not completely, impregnated with the applied chemical treatment compound. That is to say that the strand 24 is sufficiently impregnated to provide satisfactory properties for the composite object thus formed.

Optionally, the winding device 136 may include a puller that supports fibers 114 and/or pulls the strand 124. The example of winding device 136 shown in Figure 5 comprises a rotatable part or a spindle 142 on which a large diameter removable coil 144 is arranged . The winder 136 also includes a traversing mechanism 146 for distributing the continuous composite strand 126 along the length of the coil 144 to form a bundle 138. An air supply device, not shown, may be provided to feed streams of air impinging on the strand 126 for cooling. the one before winding.

Examples of winding devices 136 that can be used in connection with an off-line wire coating operation combine a Hall Capstan machine No. 634 (a puller) and a Hall Winder machine No. 633, both manufactured by Hall Industries, Branford, Connecticut. In such an off-line wire coating operation, the prepreg strand 124 is first formed and wrapped, then the wrapped strand 124 is unwound off-line and pulled through the wire coater 128 and the resulting sheathed composite strand 126 is rewound into a package. If appropriate, the aforementioned Hall wire winder may be adapted using techniques known in the wire and cable handling industry to handle the high processing speeds associated with an in-line wire coating process. For example, the coil 144 on which the sheathed composite wire 140 is wound can be formed with a larger diameter.

An example of a procedural setup for the apparatus 110 and generally for a wire coater 128 includes threading or otherwise passing the free end of the prepreg strand 124 through the wire coater 128 and pulling sufficient strand 124 through to allow the process to continue on its own (that is, allowing the string to be pulled automatically). Such an arrangement may include temporarily drawing the free end of a pre-impregnated strand 124 (indicated by the dashed line 124'), for example by means of a pair of conventional drawing wheels 137 arranged adjacent to the wire coater 128, until a sufficient length of the prepreg strand 124 is available for feeding through the wire coater 128. This length of the prepreg strand 124 is passed through the wire coater 128 and drawn through it by means of the puller 134, the cutter 130, the winder 136 or a combination thereof. With the wire coater 128 described above, a feed line is preferably used to pull the free end of the pre-impregnated string 124 through the wire coating die. Such a feeding cord has one end capable of being attached to the free end of the string 128. For example, a length of wire with a hook at one end can be used as a feeding cord. The feed line can be pre-positioned through the wire coater die and the free end of the string 124 is doubled over, hooked up by the feed line and then pulled through the wire coater 128. It is preferred to implement such a setup procedure at the beginning of the process and in case of breakage (that is, string - or fiber breakage).

Preferably, the die used in the wire coater 128 has an openable configuration that allows the pre-impregnated strand 124 to be inserted into the die from one end to the other instead of using a longitudinal thread through the die. Such a nozzle that can be opened can eliminate the need for the feed line described above. An example of such an openable nozzle comprises two nozzle halves that fit together using guide rods or pins through matching holes provided on opposite surfaces of the nozzle halves. Alternatively, the two nozzle halves may be hinged along abutting edges and adapted to be fastened together along the opposite edges when the halves are hinged against each other. The faces of each nozzle half define one half of the nozzle cavity through which the prepreg strand is drawn. When the nozzle halves are fitted together, the nozzle cavity has an inlet opening and an outlet opening. It is preferred that the inlet opening is oversized to minimize fiber wear and that the outlet is sized to define the desired end diameter, and sleeve thickness, for the sheathed composite strand 126.

When the nozzle halves are separated from each other, the string 124 can be quickly arranged between the nozzle halves and the string 124 caught between these in the nozzle cavity by closing the nozzle half. A high-temperature gasket can be arranged between the surfaces lying above each other of the two nozzle halves along the length of the cavity. Each die half has one or more ports (ie, through-holes) through which one or more streams of molten thermoplastic sheath material, for example from the extruder, are delivered to the cavity to sheath the pre-impregnated strand 124 as it is drawn through. Each nozzle half can be adapted to receive a number of tailor-made inserts with different nozzle cavities to vary the cross-sectional profile (eg, round, rectangular, oval, irregular, and so on) of the sheathed strand 126. With such replaceable inserts, the same nozzle can handle a variety of fiber diameters with less non-productive time caused by the need to replace the entire die.

Preferably, the chemical treatment compound is selected to bind or otherwise support that the sleeve holds the fibers 113 together in the sheathed composite strand 126 and at least until casting of the composite article. To ensure that the composite object exhibits optimal mechanical properties between the reinforcing fibers and the matrix, the chemical treatment compound should be compatible with the thermoplastic matrix material in the composite object. A chemical treatment mass is considered compatible with the matrix material if it does not cause important properties such as tensile strength, tensile modulus, flexural strength or flexural modulus, for the resulting composite material, to be inadequate. Such compatibility can be achieved by formulating the chemical treatment mass to be capable of interaction with and/or reaction with the thermoplastic matrix material. The interaction and/or reaction between the chemical treatment mass (for example of the thermoplastic or thermosetting type) and the matrix material can take place during the production of the sheathed composite string and during the casting of the composite object, or during both processes.

The chemical treatment masses can be mixed with the matrix material, in whole or in part, or can form a separate phase from the matrix material. Where a separate phase is formed, the chemical treatment mass arranged around each fiber can form a number of separate phase areas dispersed in the matrix material and/or a single separate phase area surrounding its corresponding fibers. A chemical treatment compound such as one of those described below may be selected to improve the properties of the composite article.

Aqueous, chemical treatment compounds

The aqueous, chemical treatment mass that is applied, for example when using the apparatus 110, may comprise one or more polymer film formers in the form of a solid powder or other particles that are dispersed in an aqueous medium. The particulate film former may be a polymer of the thermoplastic type, of the thermosetting type or a combination. Solid, low and/or high molecular weight polymers of the thermoplastic or thermosetting type can be used to form a special film former. The aqueous chemical treatment mass may also include one or more binders arranged in the aqueous medium together with the particulate film former. The binder may include a thermoplastic and/or thermosetting liquid, low melting point thermoplastic particles, or a combination thereof.

Preferably, the binder prevents the solid particles in the film former from falling out of the sheathed composite strand and prevents the fibers from falling out of the composite strand, even when the strand is in the form of a pellet. To achieve this, the thermoplastic binder particles are at least partially melted or fusible due to the heat energy used to evaporate the water out of the chemical treatment mass. In addition, the liquid binder has the necessary degree of stickiness or adhesiveness to sufficiently maintain the cohesiveness of the film-forming particles and fibers. Preferably, a thermoplastic film former powder with a higher melting point is modified or combined with a thermoplastic binder powder with a lower melting point, for example particles of polyvinyl acetate (PVAc), aqueous urethane, and so on.

The aqueous chemical treatment mass may also contain a liquid film former which is dispersed in the aqueous medium (for example as an emulsion). The liquid film former may comprise one or more low molecular weight thermoplastic polymers, one or more thermosetting polymers and/or a combination thereof. With an aqueous, chemical treatment compound emulsion, the film former preferably also acts as a binder. The aqueous chemical treatment mass can also be a combination of a liquid-solid dispersion and a liquid-liquid emulsion.

Film formers and binders of the thermo-setting type used in the aqueous, chemical treatment mass are preferably applied to the fibers in an uncured state, although they can also be applied in a partially cured state. The amount of debonding or hardening of a chemical treatment mass of thermo-debonding type can be controlled by choosing a thermo-debonding material with a suitable curing temperature, which will harden to the desired degree at the temperatures seen during the processing according to the invention. The uncured or partially cured thermosetting type chemical treatment compound impregnating the sheathed composite strand may be processed (eg, by heating) to induce further or full cure, depending on the desired condition of the sheathed composite strand during the cutting operation, folding, or molding. of the composite object. The degree to which an applied chemical treatment compound of the thermosetting type cures, regardless of whether it is aqueous or not, can be controlled by the use of a heating device (for example, a heater 125).

Therefore, the thermosetting type chemical curing compound can be tailored to allow only sufficient curing, if any, to maintain the cohesiveness and/or degree of impregnation for the sheathed composite strand until the casting of the composite article. The individual fibers that make up the strand do not need to be separated in the thermoplastic matrix material to form a desired composite article. The thermo-setting, chemical treatment compound can then be adapted for full curing so that the fibers essentially remain permanently together, or also during casting of the composite object.

The treatment mass in the form of an aqueous solution contains an amount of one or more chemical treatment polymers or other organic compounds or materials (for example film formers, binders) to sufficiently pre-impregnat the fibres. For example, the aqueous chemical treatment stock contains enough film formers and, if present, binder polymers to impregnate the fibers to the desired degree. It is preferred that the aqueous chemical treatment composition contains one or more film formers, binder polymers and/or other organic materials in sufficient concentrations to provide the prepreg with an organic material content of up to about 25% by weight, preferably up to about 15% by weight -% and most preferably around 6-7% by weight, calculated on the total weight of the chemical treatment mass plus fibres, after the desired amount of moisture has been removed from the applied chemical treatment mass. This degree of replenishment of organic material can also be used for non-aqueous, chemical treatment masses as discussed here. The method of determining the value of loss on burning (LOI) can be used to determine the amount of applied chemical treatment compound that has been applied to the fibres. Satisfactory results have been achieved with a chemical treatment solution with an organic material content of around 30% by weight. Such a concentration of organic material gives strands which are pre-impregnated with 5-15% by weight of organic compounds present in the chemical treatment mass.

A suitable concentration of organic material in the aqueous chemical treatment mass can generally be chosen regardless of the form of the chemical treatment mass (ie dispersion, emulsion or the like). In addition, the concentration of organic materials in the pre-impregnated strand can vary for a given concentration, depending on a number of factors such as how fast the fibers move, the temperature of the heating device, the temperature of the chemical treatment mass when it is applied, the tendency of this mass to to remain impregnated on the fibers (for example the viscosity), the speed (rpm) of the applicator roll and whether a prepad water spray is used.

The invention shall be further illustrated by examples of aqueous, chemical treatment masses which can be applied, for example using the apparatus 110, to pre-impregnate fibres.

Example I

6000 g of chemical treatment mass was obtained by the following procedure. 15 g (0.25% by weight as received) of amine silane coupling agent A-I 100 was added to 2345 g of deionized water.

This was stirred for several minutes. Next, 1875 g (31.25%) film former Covinax 201 and 1500 g (25.0%) film former Covinax 225 were combined in a 7.6 L container. The silane solution was then mixed with the mixture of film formers with moderate stirring. Next, 480 g (8.0%) of Maldene 286 was added to the mixture of silane and film formers. Finally, 200 g (3.3%) of BES homogenate (the fatty acid ester KESSCO BES which is emulsified in a homogenate) was added with continuous stirring. The concentration of organic compound in the resulting treatment solution was 30% by weight. The resulting mass is suitable for application to polyamide fibers as well as glass fibers.

Example II

6000 g of chemical treatment pulp was obtained as follows. 15 g (0.25%) of A-I 100 silane was added to 1870 g of deionized water. This was stirred for several minutes. Next, 3450 g (57.5%) film former Synthemul 97903-00 was poured into a 7.6 L container. The silane solution was then mixed with the film former under moderate stirring. Next, 480 g (8.0%) of Maldene 286 was added to the mixture of silane and film former. Finally, 200 g (3.3%) of BES-

homogenate added with continuous stirring. The organic compound concentration of the resulting treatment solution was 30%. This solution was suitable for application to polyamide fibers as well as glass fibers.

Example III

6000 g of chemical treatment mass was formed by the following procedure. 15 g (0.25%) of A-I 100 was added to 2325 g of deionized water. This was stirred for several minutes. Next, 1875 g (31.25%) Covinax 201 and 1500 g (25.0%) Covinax 225 were combined in a 7.6 L container. The silane solution was then mixed with the mixture of Covinax film formers with moderate agitation. A terephthalic acid solution was prepared by dissolving 30 g (0.5%) of terephthalic acid in 30 ml of concentrated ammonium hydroxide. The terephthalic acid solution was added to the mixture of silane and film formers. Then 300 g (5.0%) Polyemulsion 43N40 was added to the mixture. Finally, 200 g (3.3%) BES homogenate was added with continuous stirring. The concentration of organic compound in the resulting treatment solution of 30%. The resulting mass is suitable for application to polypropylene fibers as well as glass fibers.

Example IV

6000 g of chemical treatment mass was obtained in the following way. 15 g (0.25%) of A-1100 (silane) was added to 2020 g of deionized water. This was stirred for several minutes. Next, 3450 g (57.5%) of Synthemul 97903-00 (film former) was poured into a 7.6 L container. The silane solution was then mixed with the film former using moderate agitation. A terephthalic acid solution was prepared by dissolving 30 g (0.5%) of terephthalic acid in 30 ml of concentrated ammonium hydroxide. The terephthalic acid solution was added to the mixture of silane and film former. Then 300 g (5.0%) Polyemulsion 43N40 was added to the mixture. Finally, 200 g (3.3%) BES homogenate was added with continuous stirring. The concentration of organic compound in the resulting treatment solution was 30%. The resulting chemical treatment solution could be applied to polypropylene fibers as well as glass fibers.

Example V

6000 g of chemical treatment mass was obtained in the following way. 15 g (0.25%) of A-1100 was added to 1870 g of deionized water. This was stirred for several minutes. Next, 3450 g (57.5%) Synthemul 97903-00 was poured into a 7.6 L container. The silane solution was then mixed with the film former with moderate stirring. Finally, 200 g (3.3%) BES homogenate was added with continuous stirring. The concentration of organic compound in the resulting chemical solution was 30%. The resulting resolution could

applied to fibers made from a wide range of materials including polyphenylene sulphide and inorganic fibres.

Example VI

6000 g of chemical treatment mass was prepared in the following way. 15 g (0.25%) of A-I 100 was added to 2345 g of deionized water. This was stirred for several minutes. Next, 1875 g (31.25) of Covinax 201 and 1500 g (25.0%) of Covinax 225 were combined in a 7.6 L container. The silane solution was then mixed with the mixture of film formers with moderate agitation. Finally, 200 g (3.3%) BES homogenate was added with continuous stirring. The concentration of organic compound in the resulting treatment solution was 30%. The resulting treatment solution could be applied to fibers made from a wide range of materials including polyphenylene sulfide and inorganic fibers.

Referring to Examples I-VI above, Covinax 201 and Covinax 225 are thermoplastic vinyl acrylic compounds that act as film formers and are commercially available from Franklin International, Columbus, Ohio. Synthemul 97903-00 is a thermoplastic urethane film former and is commercially available from Reichold Chemicals Inc., Research Triangle Park, North Carolina. Epoxies, polyvinyl acetates and polyesters can also be used as film formers. A-I 100 is a silane-based coupling agent commercially available from Witco Chemical Company, Chicago, Illinois. KESSCO BES is a fatty acid ester that acts as a lubricant and is commercially available from Stepan Co., Northfield, Illinois. Other lubricants that can be used are a mixture of stearic acid and acetic acid, commercially available from Owens Corning under the product designation Kl 2. Polyemulsion 43N40 is a maleic anhydride-modified polypropylene wax that is dispersed in water and is commercially available from Chemical Corporation of America , East Rutherford, New Jersey. Polyemulsion 43N40 acts as an interphase modifier to improve the interphase area (adhesion) between glass fibers and a polypropylene matrix material by chemical reaction with the coupling agent. The terephthalic acid is commercially available from Aldrich Chemical Company, Milwaukee, Wisconsin, and also acts as an interphase modifier to improve the adhesion between the glass and the polypropylene matrix material by inducing the polypropylene to crystallize near the glass surface. Maldene 286 is a partial ammonium salt of butadiene-maleic acid copolymer commercially available from Lindau Chemical Inc., Columbia, South Carolina. The templates 286 act as an interphase modifier to improve adhesion between glass fibers and nylon matrix material.

Solvent-free, chemical treatment compounds

Solvent-free chemical treatment compounds such as those described above can also be used to produce sheathed strands. The use of such chemical treatment compounds has advantages, for example, there are no significant amounts of water vapor, volatile organic carbon or other solvent vapors generated during processing (eg heating) according to the above-described wire-coating method, even during casting of the composite article. By being essentially solvent free, the chemical treatment mass can be viscosity reduced and/or heat cured without experiencing any significant mass loss thereby allowing most of the chemical mass brought onto the fibers to remain on the fibers. Such chemical treatment masses are preferably also substantially non-photo-binding.

Figure 6 shows an embodiment of an apparatus 150 capable of producing one or more polymer-encased composite strands 126 using solvent-free, chemical treatment compounds. The resulting sheathed composite strands 126 which can be converted into pellets or threads are also suitable for molding into fiber-reinforced composite articles. Construction elements and components of the apparatus 150 which are identical or similar to what has been described previously in the apparatus 110 are indicated with the same reference numbers as above. The apparatus 150 comprises an applicator 116 with a forward-facing applicator roller 118 which places chemical treatment compound on the reinforcing fibers 114 and thereby forms coated fibers 120. A conventional two-roll applicator can also be used instead of the individual roller 118.

When it is desired that the applied chemical treatment compound on the fibers is heated before gathering the fibers 113, the device example 150 has an applicator 116 arranged close to the side of the bushing 115. The applicator 116 is positioned so that the chemical treatment compound is applied, while the fibers 114 are located at a sufficiently high temperature (for example, sufficient heat energy given off to the fibers 114) to cause the desired drop in viscosity and/or the desired degree of heat curing (cross-linking or other increase in molecular weight) of the applied chemical treatment mass depending on the type applied. At the same time, the applicator 116 is positioned far enough away from the bushing 115 for the chemical treatment mass to be applied, while the fibers 114 are at a temperature that does not cause significant damage to the mass (for example decomposition of any chemicals or compounds present). In this way, the resulting strand 126 can be provided with the desired properties for subsequent processing into a composite article.

For glass reinforcing fibers 114 pulled from a conventional bushing 115 at normal production speed, the applicator 116 is preferably arranged so that the chemical treatment compound is placed on the glass fibers 114 at least 7.62 cm and preferably about 15.24 cm from the bushing 115 (from the point where the fibers penetrate out of the bushing). Satisfactory results can be obtained when the chemical treatment compound is applied to the glass reinforcing fibers 114 in the range from about 20.32 cm to 25.4 cm from the bushing 115. The optimal location of the applicator 116 in relation to the bushing 115 depends, for example, on the type of bushing used ( for example, the number of fibers pulled from the bushing 115), the temperature of the molten glass material, the type of chemical treatment compound applied, the desired proportions of the interphase region around at least the reinforcing fibers 14, and the properties desired for the resulting strand 124 and the final composite object.

It may be desirable for the chemical treatment mass to be kept cooled before it is applied to the fibers 14 to allow highly reactive components to be used in the mass and to reduce the risk of heat-induced degradation of the chemical treatment mass. It may also be desirable that the temperature in the chemical treatment mass, before it is applied, is kept equal to less than around room temperature, for the same reason. The chemical treatment mass can be kept at the desired temperature in a suitable manner. For example, a cooling coil can be immersed in the chemical treatment mass. When continuous glass fibers are formed, it may also be desirable for the apparatus to be adapted so that the glass fibers 114 are surrounded by an inert atmosphere before the chemical mass is applied. The inert atmosphere will help prevent moisture from accumulating on the surface of the fibers 114 and thereby inhibit moisture-induced cracking and moisture-induced passivation of potentially reactive species on the fiber surfaces as discussed above. However, an inert atmosphere is preferably not used when a high production rate from the bushing is desired or at any time when the temperature in the glass fibers is sufficiently high.

In the same way as with the water-based system shown in Figure 4, the fibers 113 which are coated with solvent-free, chemical treatment mass may include fibers other than the continuous drawn reinforcing fibers 114. Thus, the fibers 113 may comprise pre-manufactured reinforcing and/or or matrix fibers 152. As shown in Figure 6, the pre-manufactured fibers 152 are pulled off from coils or other packages and then mixed into the continuously manufactured reinforcing fibers 114 before all fibers 113 are collected into a composite strand 124. Prior to entanglement, the pre-manufactured fibers 152 coated with the same or a different chemical treatment compound than that which was used on the reinforcing fibres

114. Depending on the type of fibers 152, it is not necessary to apply a chemical treatment compound to the fibers 152 before the fibers 113 are tangled. The same techniques and equipment can be used to chemically treat each type of reinforcing fiber and matrix fiber regardless of whether they are continuously formed or pre-fabricated.

The same applicator 116 can be used to chemically treat both the preformed fibers 152 and the continuously produced fibers 114 before the fibers 113 are collected into a strand 124. Alternatively, a separate applicator 116' can be used to chemically treat the preformed fibers 152 (as indicated in dashed lines 152'). If a separate applicator 116' is used, the collection mechanism 127 may include a rod or roller 154 to assist in entangling the fibers 114 and 152 before they are collected into the strand 124. US-SN 08/527 601 supra, describes other methods and apparatus for chemical treatment of pre-manufactured fibers and continuously manufactured fibers together using the same applicator or separately using different applicators. Alternatively, some of the fibers 113, for example the matrix fibers 152, can be assembled with the coated fibers 120 without any chemical treatment compound being applied first.

One can then produce a composite object using conventional techniques, for example by casting one or more sheathed composite strings 116, in the form of pellets 132, threads 140 or both. The resulting composite article can be obtained using injection molding, compression molding, transfer molding, or any other molding technique. The sheathed composite threads 140 can be converted into a textile, for example by a weaving or knitting process, and then compression or transfer molded into the desired composite object. An example of such a textile production method and apparatus is described in US-SN 08/527 601.

Upon consideration of the above description and implementation of the invention, modifications will be obvious to the person skilled in the art and the scope of the invention shall therefore not be limited by the detailed description above or the allusion to preferred embodiments, but shall be defined by the claims and their equivalents.

Claims (21)

1. Method for manufacturing a thermoplastic material-sheathed composite strand (126), characterized in that it comprises supplying to a plurality of individual reinforcing fibers (114) a polymer composition comprising a first polymer, the first polymer comprising a thermoplastic resin in an amount sufficient to cover substantially all of the fibers (114), thereby forming prepregs ( 120); assembling the prepreg fibers (120) into a strand (124) having the polymer composition interposed between substantially all of the fibers; and wrapping the strand (124) of prepreg fibers with a second polymer comprising a thermoplastic resin to form a thermoplastic material-encased composite strand (126). 2. Method according to claim 1, wherein it further comprises cutting said thermoplastic material-enclosed composite strand (126) into lengths. 3. Method according to claim 1, wherein the polymeric composition further comprises water, and said preparation of the thermoplastic material-enclosed composite strand (126) further comprises the step of evaporating substantially all the water in the chemical treatment prior to the assembly step. 4. Method according to claim 3, where the polymeric composition is in solid or liquid form dispersed or emulsified in water. 5. Method according to claim 1, where the coating on the fibers is from approx. 2% to about 15%, expressed by weight, and the method further comprises an evaporation step which comprises heating the polymeric composition after said application step. 6. Method according to claim 5, where the coating on the fibers is from approx. 6% to approx. 7%, expressed by weight, and the heating comprises supplying heat energy to the polymeric composition from an external source or from said fibres. 7. Method according to claim 1, where the polymeric composition comprises a thermosetting material, and the enclosing step further comprises the step of at least partially curing the polymer after said application step. 8. Method according to claim 1, wherein the polymeric composition is substantially solvent-free and substantially non-photocuring, and comprises a film former and a coupling agent. 9. Method according to claim 8, where said film former is thermoplastic and said coupling agent comprises a functionalized organic substrate. 10. Method according to claim 8, where said film former is thermosetting, and the coupling agent comprises a functionalized organic substrate. 11. Method according to claim 1, wherein it further comprises combining said thermoplastic material-enclosed composite strand with a matrix material to form a composite formulation and molding said composite formulation. 12. The method of claim 1, further comprising forming the thermoplastic material-enclosed composite strand (126) into pellets (132), combining said pellets with a resinous material to form a castable composition, and molding the composition to form a fiber-reinforced composite object. 13. Method according to claim 1, where the reinforcing fibers (114) comprise glass fibers. 14. Method according to claim 1, where the reinforcing fibers (114) are continuously formed from a molten glass material and receive said polymeric composition before said fibers are cooled to room temperature. 15. Method according to claim 1, where the fibers additionally include matrix fibers (152) which are entangled with said reinforcing fibers (114) before they receive the coating of said polymer material. 16. Method according to claim 1, where the fibers additionally include matrix fibers (152), and said matrix fibers (152) receive a coating of a polymer composition that is different from that applied to the reinforcing fibers (114), and are entangled with said reinforcing fibers (114) before the collection of said fibers into a strand (124). 17. A method according to claim 16, wherein the polymer composition is applied to the fibers in an amount sufficient to provide the resulting prepreg strand with a coating content of from about 2% to approx. 25%, expressed by weight. 18. Method according to claim 16, where the polymer composition is at least partially cured by heating to a temperature below approx. 350°C. 19. Method according to claim 16, where the polymer composition has a viscosity of less than 1000 eps at a temperature of below approx. 350°C. 20. Method according to claim 1, where the thermoplastic material-wrapped strings are placed in said matrix material, thereby forming a composite object. 21. Method according to claim 1, where said thermoplastic material-wrapped strand comprises fibers which are able to form at least part of a matrix material of a composite object.