MXPA00004322A - Reinforced thermoplastic composite systems - Google Patents

Abstract

A process is disclosed for manufacture of reinforced composites. This method provides a process that allows for the direct mixing of discontinuous reinforcement such as wet chopped strands of glass fibers or continuous reinforcement such as glass strands, with an aqueous suspension of a solution polymerized polymer, such as polyvinyl chloride. The process results in a cost-effective means for reinforcing means for reinforcing polymers such as PVC while simultaneously substantially improving properties such as impact strength, stiffness and moldability without the need for a binder.

Description

THERMOPLASTIC COMPOSITE BODY SYSTEMS REINFORCED DESCRIPTION Background and fields of the invention The present invention relates to a process and method for manufacturing reinforced thermoplastic composite bodies. In particular, the present invention provides a process for the manufacture of composites composed of reinforced thermoplastics such as: (1) thermoplastic reinforced with glass fiber blanket (GMT) a molding compound containing chloride resin polyvinyl (PVC); (2) reinforced bulk molding compound (BMC) and sheet molding compound (SMC) containing PVC resin; (3) continuous fiberglass yarns impregnated with PVC resin; and (4) other bodies composed of reinforced thermoplastic polymers according to the invention. In accordance with this process, the reinforcing component such as cut and wet fiberglass strings, fiberglass strings, spheres or glass flakes are directly combined with the contents of a white water tank containing a polymerized polymer slurry. such as PVC. The process can also be carried out by adding the reinforcement to the polymerization chamber in solution while the monomer and / or oligomer is polymerized. This type of process results in cost-effective means to reinforce polymers such as PVC while improving impact resistance, heat distortion and toughness without the need to add chemical binders. The process can also result in the elimination of several manufacturing steps such as centrifugation, filtration, drying and grinding. Usually cut glass fibers are used as reinforcing materials in thermoplastic articles. Generally such fibers are formed by drawing fused glass into filaments through a nozzle or orifice plate, applying a sizing composition containing lubricants, coupling agents and film-forming binder resins in filaments, collecting the filaments into strings, cutting the fiber strings in segments to the desired length and drying the sizing composition. These subsequently cut rope segments are mixed with a polymerized resin and the mixture is fed to a compression or injection molding machine to be formed into glass fiber plastic articles. Typically, the cut ropes are mixed with dry powder of a polymerized thermoplastic resin, and the mixture is fed to an extruder in which the resin is melted, the integrity of the glass fiber ropes is destroyed and the fibers are completely dispersed in the molten resin, and the fiber / resin mixture is formed into pellets. These pellets are then fed to the molding machine and molded articles are formed having a substantially homogeneous dispersion of the glass fibers therethrough. Alternatively, reinforced thermoplastic composite bodies can be formed by compression molding of fibrous blankets loaded with thermoplastic polymer. Methods of manufacturing such fiber-reinforced composite materials are known starting from a thick aqueous suspension of solid polymer and reinforcing material. See published European patent applications 0,148,760 and 0,148,761, Essling et al., United States of America Patent No. 4,426,470 issued January 17, 1984 and Gatward et al., United States of America Patent No. 3,716,449 issued. On February 13, 1973, all of them are incorporated herein by reference only. In general, these reinforced polymer composite bodies have a uniform blend of fiber, polymer and binder, and are prepared from dilute aqueous slurries of a solid, heat-fusible organic polymer, a reinforcing material and optionally a latex binder.

Wessling et al. U.S. Patent No. 4,426,470 issued January 17, 1984 describes in column 4, lines 18-21 that different chemical additives such as antioxidants, UV stabilizers, thickeners, foaming agents, antifoaming agents, bactericides, electromagnetic radiation absorption agents, etc., in composite bodies comprising a hot melt polymer and reinforcing material. Alternatively, sections of a preformed glass blanket, or other shaped glass blanket, for example in the form of a U-channel, or saddle seats, may be impregnated with a thermoplastic resin powder, and then thermoformed under sufficient heat and pressure to melt the thermoplastic polymer and join the glass blanket. For glass blankets impregnated with PVC, PVC is usually dry mixed with a thermal stabilizer and alpha-SAN, and any other additive, to form a homogeneous powder before impregnation of the glass blanket. If the glass mat is impregnated with a modified impact mix, the impact modifier is typically added as a powder and mixed dry with the other ingredients and does not interfere with the formation of single phase PVC and alpha-SAN. After this, the glass blanket is "powdered" or "filled" with the desired amount of the powder mixture, generally so that there is from about 30% to about 60% uniformly spread mixture through the blanket and the Powdered blanket is then molded under pressures of 100-1000 psi and temperatures of 170 ° C-190 ° C (338 ° F-374 ° F), to form the shaped, mixed PVC reinforced fiberglass article. Glass blanket, or other fiberglass shaped materials can also be impregnated with a fusion of the ingredients of the mixture, such as in stretch extrusion. Generally, there is approximately an equal weight of resin and glass fibers in each sheet. Several such sheets can be cut in predetermined configurations stacked in a mold and conventionally molded at a temperature of 160 ° C -200 ° C (320 ° F-392 ° F) and at a pressure of about 1000 psi (about 30,000 lbf) to form an article made of thick walls. Although there are numerous methods for making reinforced molded composites, many of these processes are either too inefficient, or can not be controlled enough to produce a fiber reinforced product that provides the resulting composite article with sufficient properties, such as strength, to meet operating requirements. Thus, even with the current technology of aqueous methods for making reinforced composites, there are numerous drawbacks, including loss of polymer properties as a result of the manufacturing process. Specifically, in the prior art using polymers in solution such as polyvinyl chloride, the vinyl chloride is polymerized and stripped of the free residual monomer, the polymer is then processed by some combination of centrifugation, filtration, and drying. At this point, additives are usually mixed. Typically, the dry polymer is combined with the reinforcement either by extrusion, dry blending, or aqueous methods. However, once compounded, PVC has an important thermal history since before being combined with the reinforcement the PVC has already been heated to dry. Subsequently there is the heating that occurs while combined with the reinforcement. As a result, before the composite becomes molded to some final product, several important properties have already been reduced due to the multiple applications of heat to the polymer. Accordingly, there is a need for a more effective process that controllably provides a fiber reinforced molding compound that provides improved performance characteristics to composite articles molded therewith. Such a process would preferably eliminate the need for the binder and improve the thermal history of the polymer. This need is completely covered by the process of the invention described below.

In addition to the above drawbacks, current injection molding technology does not have the ability to retain the length of the reinforcement material. In particular, the technology present through the combination of reinforcement and polymer produces a compound having the consistency of sand and thus erases the length of the reinforcement. The invention described below has the ability to retain the length of the reinforcement. For example, if a cut glass fiber of 1 inch (3.175 centimeters) is used, the final composite contains reinforcement essentially of that length. The same is true using continuous reinforcement. The present invention provides an efficient aqueous process for making molding compound and reinforced polymer composite materials. The process not only eliminates the need for a binder as well as a variety of process steps, but even more significantly, the process significantly increases the options available in terms of molding and performance, compared to previous methods that use the same content. of reinforcement. Properties such as impact, flexural strength and tensile strength are significantly increased compared to those of conventionally reinforced and molded composite materials (see table 1). The process of the invention provides reinforced molding compounds ranging from granular and sheet to continuous films. The resulting blankets or reinforced molding composites can be used in the manufacture of materials as diverse as siding, sewers, and commercial windows. In general, the invention is mainly oriented to the production of thermoplastic compounds such as: thermoplastic reinforced with glass fiber blanket (GMT for its acronym in English); (2) bulk molding compound (BMC); (3) reinforced polymer films; or (4) continuous impregnated fiberglass ropes, yarns, yarn, or fabric. One mode of the process allows the direct mixing of stabilized polymer by means of heat to be added directly, together with the reinforcing material, to a white water tank. An additional mode uses polymer stabilized by non-drying heat that is placed in a white water tank and then mixed directly with the reinforcement. In another embodiment, the process comprises the use of a suspension of polymerized polymerized solution which can be practically free of residual monomer. The reinforcing material such as cut and wet glass strings is then fully dispersed in the polymer suspension. A GMT or BMC is then prepared as is customary without the need for any binder addition. In another embodiment, the reinforcing material is continuous such as with a continuous glass cord, fiberglass yarns or yarn. The resulting impregnated complex can be used as feed for several secondary processes such as filament winding, weaving, stretch extrusion and compression molding. A further embodiment comprises adding the reinforcing material to the polymerizable polymer in solution before, or simultaneously with, the polymerization process. A particular aspect of the process of the invention comprises the following: vinyl chloride monomer is polymerized in an aqueous medium to form an aqueous suspension of polyvinyl chloride; the excess monomer of free vinyl chloride is removed; Fiberglass strings comprised of a multiplicity of virtually continuous glass fibers are cut into segments of the desired length, the fiberglass strings cut either wet or dry are then dispersed throughout the PVC suspension. A sufficient amount of the aqueous medium is then removed to form a mouldable composition. In another aspect of the invention, a continuous rope of glass, carbon or other reinforcement is drawn from the aqueous suspension of PVC or other polymer. The molded products made in accordance with the invention have comparable or better physical properties compared to molded products made by systems prepared by prior aqueous and non-aqueous methods.

Brief description of the drawings Figure 1 is a schematic representation of one embodiment of the process of the invention. The obvious benefits are simplification of the process by eliminating several steps such as polymer drying and dry mixing. The schematic illustration shows that the process allows raw material such as reinforcement and polymer to be used at the first point to lower the cost of materials. It is also clear from the illustration that the resulting compound contains polymer with little or no thermal history. Figure 2 is a schematic representation of the conventional process currently used in the medium.

Detailed description and preferred modalities The present invention provides a process for the manufacture of reinforced composite bodies. This method allows direct and inexpensive mixing of reinforcements in any form, such as wet cut glass, dry cut glass, continuous glass rope, wet continuous glass rope or glass flakes in a white water tank containing an aqueous suspension of poly-bristled polymers in solution such as polyvinyl chloride. As used herein, "white water system" is an aqueous solution in which the reinforcing fibers are dispersed and which may contain various dispersants, thickeners, softeners, hardeners, or dispersed or emulsified thermoplastic monomers capable of solution polymerization. Typical examples of various white water systems include aqueous solutions having acrylamide monomers alone or with hydroxyethyl cellulose and similar suspension aids to provide a highly viscous aqueous solution at high concentrations of material. Also, white water systems include those having any of the numerous amine oxide surfactants as shown in U.S. Patent No. 4,179,331. In addition to chemical compounds such as acrylamides or amine oxides which are present in the white water system, small amounts of surfactants may also be present such as polyethoxylated derivatives of condensation products of fatty acid amides and polyethylene polyamines as shown in the patent of the United States of America No. 4,265,704. Numerous other chemical agents can also be added to a white water system as is known to those of average skill in the art. Reinforcements useful in the invention include materials that can be dispersed, materials that can not be dispersed and combinations of the two forms. Preferred dispersible reinforcements include materials such as cut and wet glass strings, aramid, carbon, polyvinyl alcohol (PVA), hemp, jute, organic materials, mineral fibers and rayon. Preferred non-dispersible reinforcing materials include dry cut cords and glass fibers designed for processes such as SMC molding, BMC molding and continuous board manufacturing; cut and continuous reinforcements such as aramid, carbon, glass, wollastonite, jute; mica, glass flake, glass and carbon spheres, blankets, organic materials, mineral fibers, and fabrics. Preferred reinforcing materials include organic and inorganic materials such as graphite, metallic fibers, aromatic polyamides, cellulose fibers and polyolefin, but preferably and advantageously comprise glass fibers such as cut and wet glass strings having a length of about 1 / 8 to 2.0 inches (approximately 3.2 to approximately 50.8 mm), ground glass fibers which generally have a length of approximately 1/32 to 1/8 inch (approximately 0.79 to 3.2 mm) and their mixtures. The preferred type of reinforcement is glass fiber in any of its commercially produced compositions. Preferably the fibers are surface treated with chemical primers or coupling agents which are well known in the medium. The sizes are preferably selected so as to assist dispersion without adversely affecting the properties in the dispersed reinforcement systems. Preferred sizes for non-dispersed reinforcement systems are selected to minimize dispersion. Preferred sizes should be compatible with the selected polymer so that these properties are optimized. The most preferred reinforcement of continuous glass rope or cut fiberglass is used wet. A preferred fiber reinforcement is finely moist cut glass obtained from Owens Corning. Similarly, fiber reinforcement can be used in the form of continuous glass rope. For example, glass ropes such as TYPE 30R glass fiber yarns obtained from Owens Corning can be used. Preferably, the glass cord or cut glass fibers are used wet and are added to the polymerized polymer in solution. The typical water content for cut and wet ropes varies from about 10% to about 25%. For continuous fiberglass yarn the content ranges from about 2% to about 15%. The reinforcing material generally comprises from about 10 to about 80 weight percent of a composite body when cut material is used. When continuous reinforcing material is used the weight percentage of reinforcement comprises from about 30 to about 80 weight percent of the composite body. In applications where a rigid molded part is desired, generally the reinforcing material comprises from about 10 to about 80 weight percent of the composite body. Whereas in applications such as films where poor stability of the reinforcing material is generally required, it comprises from about 10 to about 50 percent of the composite body. In a preferred embodiment, it comprises from about 20% to about 40% of a composite body using cut material. When using continuous reinforcement to produce a prepreg, the prepreg will generally contain about 20% to about 60% polymer by weight. In a more preferred embodiment it will contain about 25% to about 45%. When non-continuous reinforcement is used - the composite material will generally contain about 50 to about 90 weight percent of the polymer. In a more preferred embodiment it will contain about 60 to about 80 percent. Aqueous polymer suspensions useful in the invention include suspensions in which the size of the polymer particles ranges from about 10 microns to about 500 microns. In a more preferred embodiment, the average particle size varies from about 30 microns to about 200 microns. The polymer particle size used will typically be larger or in the same order as the filament diameter of the reinforcing material. One of the direct processes of the invention for producing a reinforced polymer composite material or blanket involves forming an aqueous suspension of discontinuous fibers such as cut and wet glass fibers.; and an aqueous suspension of a thermoplastic polymer usually with stirring in a mixing tank. The resulting combined aqueous suspension, usually referred to as slurry or pulp medium, can be processed into a sheet-like material, wetted by machines such as Fourdinier or cylinder machines or other technologically advanced machinery, such as Stevens For machines. er, Roto Former, Inver Former and VertiFormer machines. The aqueous suspension is deposited from a headbox on a moving wire mesh or on the surface of a mobile cylinder covered with wire. The aqueous slurry thickened on the screen or cylinder is processed in the sheet-like and non-woven blanket by removal of water, usually by means of a suction and / or vacuum device. This process is exemplified in U.S. Patent No. 5,393,379. The processes of dehydration and sheeting can be achieved by any conventional papermaking apparatus such as a sheet mold or Fourdrinier or cylinder machines. After the blanket was formed on a dehydrated sheet of paper, it may be desirable to increase its density by compressing it with a flat press or by sending it through calendering rolls. The increase in density after drying the blanket is particularly useful for increasing the tensile strength and tearing of the blanket. The drying of the blanket can be either by drying in the air at room temperature or by drying in an oven. The process of the invention provides direct formation of molding compound containing from about 10% to about 80% reinforcing material. . Preferably, the process provides a molding compound having from about 20% resin to about 90% resin. In the process, a dilute aqueous suspension is prepared which contains the monomer particles to be polymerized. The suspension solution will also contain the necessary initiator. In addition, depending on the polymerizable polymer in solution used, a thermal stabilizer may also be added. For polymers that use a thermal stabilizer, this can be added at the time of polymerization, when reinforcing material is added, or at any other convenient time during the process. The monomer solution is then allowed to polymerize. If desired, after polymerization any excess free monomer is removed or distilled from the polymer solution. This step can be avoided by starting with previously polymerized material that is wet or dry. The preferred polymer of the invention is polymerizable in solution. Polymerizable polymers in solution such as polyvinyl chloride (PVC), acrylonitrile-butadiene-styrene (ABS), and polypropylene (PP) are among the preferred ones. Additionally, suitable polymers include addition and condensation polymers such as, for example, polyolefins, polystyrenes, phenolics, epoxies, butadienes, acrylonitriles, and acrylics.

In addition, the preferred polymer will be "hot melt." By "hot melt" is meant that the polymer particles are capable of deformation under heat to join in a unitary structure. The thermofusible polymers can be either thermoplastic or thermosetting resins. The thermofusible organic polymer component of the present invention is desirably a water insoluble and hydrophobic polymer. Polymers polymerized in solution are generally, and are advantageously, either PVC, ABS or PP. The polymers are generally employed in an amount of about 20 to about 90 weight percent solids (dry weight basis of the combined weight of formulated fibers and resins). A particularly preferred organic polymer is a polyvinyl chloride resin that already contains a thermal stabilizer. Mixtures of polymers can also be used. Regardless of whether a polymer or a mixture is used, the preferred initiator will be selected for the particular monomer or monomer mixture in use. In another process of the invention, a rope of virtually continuous glass fibers is formed by conventional techniques such as drawing of molten glass through a heated nozzle to form a multitude of virtually continuous glass fibers and collecting the fibers on a rope. In the present invention, any known apparatus in the medium can be suitably used to produce such fibers and collect them on a string. Suitable fibers are fibers having a diameter of about 3 to about 90 microns, and convenient cords can contain from about 50 to about 4000 fibers. Preferably, the cords formed in the process of the invention contain from about 200 to about 2000 fibers having a diameter of from about 3 to about 25 microns. After the fibers have been formed, and before they are collected on a rope, the fibers are covered with the size according to the invention. Preferably the sizing composition is selected to aid the dispersion of the reinforcement in the white water solution of polymerized polymer. For example, a preferred size for a continuous fiberglass yarn reinforcement will allow the use of a wet glass fiber yarn, ie, containing about 2 to about 15% by weight of water. The sizes are preferably water-based and comprise one or more silanes, film formers, surfactants, etc. An example of such sizing may be the cut and wet fiber of Owens Corning with a sizing designated 9501. When PVC is used in a mode the preferred sizing contains an amino silane such as A 1126, A 1125, A 1120, A 1102 , and A 1100 affordable carbide union. As is known to a person with average knowledge in the field, the final material may or may not be stabilized for UV depending on the needs and use of the composite material. In addition, the material may contain any number of other additives, such as colorants, necessary to fulfill the functional task of the application.

Example I - Preparation of GMT from cut and wet glass fiber A 1 inch (2.54 cm) PVC / fiberglass sheet was successfully formed, randomly oriented on a wet process blanket line by mixing thermally stabilized PVC powder directly with cut and wet glass strings obtained from Owens Corning in a tank of white water. No additional chemical binder was added or required. For different line speeds, process limits were determined in terms of leaf weight and maximum drying temperatures as is usual in the medium. The PVC powder could be sintered to the glass at 25 ft / min (7.62 m / min) with little, if any, degradation of the resin. The resulting blankets contained 80% PVC resin (by weight) and 20% fully dispersed E-type glass fibers. The blankets were successfully molded into boards. The actual molding of the composite board was carried out by stacking several sheets of the dry blanket in line (no more than 1% water retention), molding in a heated press, and subsequent cooling under pressure. The physical properties obtained from the boards of such blankets can be found in Table 1 shown below. Table 1 compares the properties of molded boards of composite fiberglass blankets made by the inventive process (designated: Direct process) with molded boards made without reinforcement (designated: Without reinforcement) and molded boards made with current technology (designated : Previous technology). The previous technology uses PVC and glass pellets; which were used directly in injection molding. As shown in Table 1, not only are the properties of the molded boards of the glass blankets of the invention comparable to those of the prior art, but in many of them they are far superior.

Table 1 Designated Process Without Direct Technology previous reinforcement Type of polymer PVC PVC PVC Glass shape Strings None Cut strings wet dry cut Fiber length of 25 mm 4 mm feed glass Glass content by 20% 0% 20% weight Example II - Preparation of a composite blanket from cut and wet glass fiber and non-dispersed type E glass As with Example 1, sheets of PVC GMT were formed. Composite glass / PVC blankets were formed with two different proportions in them from dispersed glass (wet cut rope) to undispersed glass (973 SMC glass fiber yarns, obtained from Owens Corning). The proportions were 1: 2 and 2: 1. Both proportions produced successful formation of composite blankets.

Example III - Preparation of a continuous reinforced system The actual production involved making a PVC suspension as in Example 1. The continuous fiberglass yarns were then pulled through the PVC suspension. The continuous fiberglass yarns used were TYPE 30R fiberglass yarns (obtained from Owens Corning) which were not dry ie they contained 14% water by weight and which contained a size designed for use in wet processes.

Claims (19)

1. A process for the preparation of a reinforced composite body characterized in that it comprises: a) preparing an aqueous suspension of polymerizable polymer in solution; b) adding reinforcing material directly to the aqueous polymer suspension during or after the polymerization process; and c) removing a sufficient amount of the aqueous medium from the suspension to form a moldable composition.

2. The process according to claim 1, further characterized in that the aqueous polymer suspension is prepared from the group consisting of dry polymer, wet polymer, or monomer polymerizable in solution.

3. The process according to claim 1, further characterized in that the reinforcing material is added wet.

4. The process according to claim 1, further characterized in that the reinforcing material is added dry.

5. The process according to claim 1, further characterized in that the reinforcing material is continuous.

6. The process according to claim 1, further characterized in that the reinforcement material is discontinuous.

The process according to claim 1, further characterized in that the reinforcing material is selected from the group comprising: that can be dispersed, that can not be dispersed, or combinations of the two forms.

The process according to claim 7, further characterized in that the dispersible reinforcement is selected from the group comprising: wet cut, spider, carbon, polyvinyl alcohol, hemp, jute, organic materials, mineral fibers and rayon. .

The process according to claim 7, further characterized in that the non-dispersible reinforcement is selected from the group comprising: dried used cut glass strings; glass fibers designed for processes such as SMC molding, BMC molding and manufacture of continuous boards; continuous and cut reinforcements such as aramid, carbon, glass, wollastonite, and jute; mica, glass flake, glass and carbon spheres, blankets, mineral fibers, organic materials and fabrics.

10. The process according to claim 8, further characterized in that the cut and wet glass strings have a length of about 3.2 mm to about 50.8 mm.

11. A process for the preparation of a reinforced composite material that practically retains the length of the aggregate reinforcing material characterized in that it comprises: a) preparing an aqueous suspension of polymerizable polymer in solution; b) adding reinforcing material directly to the aqueous polymer suspension during or after the polymerization process; and c) removing a sufficient amount of the aqueous medium from the suspension to form a moldable composition.

12. A process for the preparation of a reinforced composite body that practically improves the thermal history of the polymer in the resulting composite body characterized in that it comprises: a) preparing an aqueous suspension of polymerizable polymer in solution; b) directly adding reinforcing material to the aqueous polymer suspension during or after the polymerization process; and c) removing a sufficient amount of the aqueous medium from the suspension to form a moldable composition.

13. A process for the preparation of glass fiber reinforced polyvinyl chloride composite body characterized in that it comprises: a) preparing an aqueous suspension of polyvinyl chloride; b) dispersing cut and wet glass strings throughout the polyvinyl chloride suspension; and c) removing a sufficient amount of the aqueous medium from the suspension to form a moldable composition.

14. A process for the preparation of glass fiber reinforced polyvinyl chloride composite body characterized in that it comprises: a) forming a woven or non-woven complex of reinforcing fibers; b) preparing an aqueous suspension of polyvinyl chloride; c) impregnating the polyvinyl chloride suspension throughout the reinforced complex; and d) drying the reinforced complex to form a moldable article.

15. A process for the preparation of glass fiber reinforced polyvinyl chloride composite body characterized in that it comprises: a) preparing an aqueous suspension of polyvinyl chloride; b) preparing a fiberglass rope comprised of a multiplicity of practically continuous fibers; c) impregnate the fiber rope with the polyvinyl chloride suspension; and d) removing a sufficient amount of the aqueous medium to form a moldable composition.

16. A process for the preparation of reinforced composite body characterized in that it comprises: a) forming a woven or non-woven complex of reinforcing fibers; b) preparing an aqueous suspension of polymerized polymer in solution; c) impregnating the aqueous suspension completely in the reinforced complex; and d) drying the reinforced complex to form a moldable article.

17. A process for the preparation of reinforced composite body characterized in that it comprises: a) preparing an aqueous suspension of polymerized polymer in solution; b) preparing a fiber cord comprising a multiplicity of practically continuous fibers; c) impregnating the fiber cord with the aqueous suspension; and d) removing a sufficient amount of the aqueous medium to form a moldable composition.

The process according to claim 16, further characterized in that the reinforcing fiber is selected from the group comprising one or more of the following: blanket, web, continuous fibers, woven fibers, finely cut rope blanket, filament blanket continuous, woven blanket or needle punch fabric or fabric.

19. A process for the preparation of a reinforced blanket compound characterized in that it comprises: a) preparing an aqueous suspension of polymerizable polymer in solution; b) adding reinforcing material directly to the aqueous polymer suspension; c) transferring the reinforcement and polymer mixture to a blanket machine; d) drying the reinforced blanket; and e) sintering the organic material on the reinforcement if necessary for the specific polymer used.