NL7904768A - PROCESS FOR FORMING A THERMOPLASTIC RESIN REINFORCED IN A LAYERED PRODUCT, REINFORCED WITH FIBER GLASS. - Google Patents

Abstract

A method of preparing a fiber glass reinforced resin sheet comprising continuously feeding one or more fiber glass mat(s) 102, 103 to a heating zone 120, introducing resin e.g. in the form of sheets 100, 101 into the zone with the mat(s), applying pressure to the mat(s) and resin e.g. by platens 121, 122 at a temperature sufficient to melt the resin and thoroughly wet the mat(s), cooling the mat(s) in a cooling zone 130 to solidify the resin into a resin-mat sheet while maintaining pressure on the resin and mat(s) during cooling e.g. by platens 131, 132 at least equal to the pressure applied to the resin and mat(s) in the heating zone, and removing from the cooling zone a solid sheet of glass mat reinforced resin. In an alternative procedure, pressure is applied by passing the assembly under tension around pressing rollers. <IMAGE>

Description

PPG Industries, Inc, of Pittsburgh, Pennsylvania, USA, America

Method for molding thermoplastic resin, reinforced with fiber glass, into a layered product.

Fiber glass reinforced thermoplastic plates, which can be heat and pressure pressed in a variety of shapes for automotive use, have been described in the literature. Examples of methods hitherto employed to produce such products are described in U.S. Pat. Nos. 3,666,909, 3,668,659, 3,713,962, and 3,850,723. The glass strands used for making the wet placed in the product are usually treated with an appropriate surface treatment system prior to making the mat. Such a system is described in U.S. Pat. No. 3,891,18,8. The mat used in the thermoplastic sheet products produced is usually pricked, which is described in U.S. Pat. Nos. 3,888,333 and 3,666,909.

The layered products produced by the known methods and according to the invention can be processed by pressing using the methods described in U.S. Pat. Nos. 3,621,092 and 3,626,053.

In the prior art methods described above, layers of a pricked mat and thermoplastic resin, wherein polypropylene is used.

2 ° is useful to form a layered product in a table press for producing the sheet product. In another method, shown in Fig. 2 of the present drawing, the laminating of resins and the mat takes place in a continuous machine for producing layered products.

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In the process using the table press, an acceptable product is produced, however, the manufacturing process itself is slow and expensive, because the mats and thermoplastic plates used to make the layered products are laid by hand, and the method by its nature is a method operating per charge.

In the continuous operating method shown in Fig. 2, insufficient control of the pressure applied to the layered product in the cooling section often results in the production of layered products with an irregular void content.

In accordance with the invention, there is provided a method of continuously producing a layered product of glass fiber reinforced thermoplastic resin, which method overcomes many of the shortcomings of the prior art. The present method 15 involves passing a fiber glass mat and the thermoplastic resin into a layered product forming region, which region has two separate temperature regimes. In the first portion of the layered product forming region, heat and pressure are supplied to the thermoplastic resin and the glass mat to ensure that the resin is maintained in the molten state during its passage through the region. The mat and molten resin are allowed sufficient residence time as they pass through this region to allow the molten resin to flow through the glass mat and thoroughly impregnate it. The mat and molten resin sheet are then passed into a cooling zone, which is kept under pressure to solidify the resin throughout the entire mat, and at the exit end of the cooling zone from the process of producing a layered product, to provide a continuous sheet of fiber glass reinforced thermoplastic resin, which sheet has a controlled void content, and which can be pressed into a finished part using the prior art pressing processes.

Various thermoplastic resins can be used to produce layered products according to the invention, conventional resins suitable for this purpose being homo-polymers and copolymers of resins, such as (1) vinyl resins, formed by the polymerization of vinyl halides or by the copolymerization of vinyl halides with unsaturated polymerisable compounds, for example vinyl esters, alpha, beta-unsaturated acids, alpha, beta-unsaturated esters, alpha, beta-unsaturated ketones, alpha, beta-unsaturated aldehydes and unsaturated hydrocarbons such as butadienes and styrenes, (2) poly-alpha-olefins, such as polyethylene, polynropene, polybutene, polyisoprene and the like, including copolymers of poly-alpha-olefins, (3) phenoxy resins, (¼) polyamides, such as polyhexamethylene adamide, (5) polysulfones, (6) polycarbonates, (7) polyacetals, (8) polyethylene oxide, (9) poly-IQ styrene, including copolymers of styrene with monomeric compounds, such as acrylonitrile and butadien, (10) acrylic resins, such as, for example, the polymers of methyl acrylate, acrylamide, methylolacrylamide, acrylonitrile and copolymers thereof with styrene, vinyl pyridenes, etc., (11) neoprene, (12) polyphenylene oxide resins, (13) ) polymers, such as poly-15-butene terephthalate and polyethylene terephthalate, and (1U) cellulose esters, such as the nitrate, acetate, propionate, etc. esters. This list is not intended to be exhaustive or exhaustive, but only to demonstrate the wide range of polymer materials that can be used in the present invention.

The Ce fiber glass mat used in making the layered products can be advantageously made by the method described in U.S. Pat. No. 3,883,333. In the method described in this patent, the mat is formed by depositing endless strands on a conveyor surface, usually an interlocking chain, to the desired depth. The strands are usually placed on the chain by moving the stretchers transversely, which bring the strands to the conveyor surface along its width in an direction transverse to the conveyor movement. The mat formed in this way is then passed through a lancing device, which usually consists of a conventional felt loom, containing a number of barbed needles, which needles penetrate the mat, thereby entangling the endless strands to thereby intertwine providing dimensional stability to the mat and simultaneously breaking it to arbitrary lengths. The puncture provides a significant amount of short glass fibers in the finished mat due to the action of 790 47 68 hk barbed needles penetrating the depth of the mat, thereby breaking a significant number of endless strands to short lengths staple fibers. "Short fibers" as used in the description means strands or fibers with a length of 2.5 cm or less. The amount of short fibers produced by the piercing is variable depending on the speed of the piercing, from the number and types of needles used In general, the short fibers present in the mat are between 10 and 25%, preferably between 15 and 20% by weight of the mat, the rest of the mat being strands and fibers with lengths of more than 2.5 cm, generally 3.8 to 12.7 cm or longer As also shown in the aforementioned patent, the speed of the piercing device and of the mat-forming surface is synchronized for providing a regular mat density which is recovered at the outlet of the lancing device The needles used may include barbs which point down or up so that when penetrating the top mat surface, they will transfer fibers from that surface to the intrude Draw firm pressures of the mat or fibers from the bottom surface of the mat upward into its interior. In certain instances, barbed needles in both directions are used to provide strand penetration to the interior of both the top and bottom surfaces during a single down and up stroke of the mount carrying the needles. . If desired, the present method can also be used with finely chopped strand mats, used as the glass source. A conventional mat of this kind is described in U.S. Patent 2,790,7-1.

When using the invention, the thermoplastic resin can be introduced into the process of forming a layered product in various ways. In certain cases, the resin is supplied to the layer-forming region in a preformed sheet form of a desired thickness, the number of sheets used being dependent on the desired thickness of the finished product and the mat or mats used. It is also within the scope of the invention to add the thermoplastic resin to the method of manufacturing a layered product as a pre-melted extruded product from an extrusion line with high temperature and pressure. In this system, 7904768 • * 5, the extruded product is passed between the surfaces for producing a layered product in a sheet form, usually from an extrusion die, which is maintained at a temperature and pressure sufficient to be in a liquid maintaining the resin when it is fed to the layer-making region. In a conventional operation, both a molten, extruded product and sheet molding of the used thermoplastic resin are fed to the layered product manufacturing area, as explained in more detail below.

It is also within the scope of the invention to add compatible materials which do not affect the particular soil properties of the product to the layered products produced by the invention. These materials include colorants such as paints and pigments, fillers and similar additives. Additives such as oxidation inhibitors, bacteria killers, static electricity inhibitors, stabilizers and water contaminants are also included. Generally, the amount of additives, if used, is below about 30% by weight of the product, usually from 20 to 20%.

When applying the invention, the method of manufacturing a layered product is carried out under different pressure and temperature conditions. Thus, the first stage of operation involves contacting the reinforcing fiber glass mat with molten resin to ensure proper penetration of the mat structure through the resin system used to produce the finished sheet product. Pressures are applied in the hot phase portion of the laminated fabrication system, and can be between 3b and 827 kPa, preferably in the range of 138 to 13 kPa. The hot phase of the layered product manufacturing process is usually controlled in a temperature range of from 117 ° C to 288 ° C, which temperature is somewhat dependent on the melting temperatures of the resins used. For example, in a polypropylene resin system, the hot phase temperatures of the production of a layered product are usually between 20 ° C and 232 ° C. In the cold phase of the process, pressures of the same size or greater than those used in the hot phase are generally applied, which pressures are generally in the aforementioned ranges for the hot phase.

The invention will be further elucidated with reference to the drawing, in which: Fig. 1 schematically shows a machine for producing the present layered fiber glass-reinforced thermoplastic plates, and Fig. 2 schematically shows a method for the underlayment. Broken manufacture of a layered product, which method is currently used to produce fiber glass reinforced thermoplastic resin sheets suitable for pressing.

As shown in Fig. 2, a two-conveyor laminating machine 12 is used to produce an endless plate 2 consisting of a resin and a fiber glass mat. In the method shown, fiber glass mats 1 and 1 'are fed between two conveyor belts 3 and k forming a layered product. Molten resin 5 is fed between the mats 1 and 11 from an adjustable slot 6, which is along the length of an extrusion die 7. Two resin plates 8 and 9 are fed to the conveyor belts 3 and 1+ forming a layered product. above and below the mats 1 'and 1.

The conveyor belt 3, while running around the roller 11, is preheated by a heater 13 prior to its engagement on the heating press roller 15. Similarly, the conveyor belt 3 is preheated by the heater 16 prior to its engagement on the press roller 15 · The heating press roller is equipped with heaters 18. Pressure is exerted on the layered product 2 by placing tensile force on the conveyor belts 3 and H. The tensile force exerted on the conveyor belts 3 and U results in the application of 30 radial forces on the resin mat composition. The radial forces and the resulting pressures assist in resin saturation of the mats 1 and 1, and melt the plates 8 and 9 in conjunction with the heat supplied when the tensile force is applied. The roller 2k exerts pulling force on the conveyor belt 3, the roller 25 exerting pulling force on the conveyor belt 1 *. The material then becomes like a compressed sheet 790 4768

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7 of resin and fiber glass due to the passage of the materials along the press roller 15, leads to a cooling roller 20 between the conveyor belts 3 and i +, the material being partially cooled, but not solidifying, as it passes over this roller. The roller 20 is equipped with a cooler 21 for lowering the temperature of the conveyor belts and of the resin. After leaving the roller 20 between the conveyor belts 3 and U, the plate is then passed through another elongated cooling area 22 to further reduce the temperature of the conveyor belts 3 and k to further cool and solidify the mats and the resin to the plate 2. The conveyor belt 3 is then deflected over the roller 23 for return to the pulling roller 2kt, the conveyor belt 2k being returned over the roller 25 to the roller 11, and the product 2 is removed at the location where separate the conveyor belts 3 and 4.

Although the described method of manufacturing a layered product is used to produce useful commercial products, it has certain shortcomings which are overcome by the invention. The impregnation pressures are applied to the mat and the resin by the tensile force applied to the conveyor belts 3 and k by the pull rollers 2b and 25. The experience has shown that, for example, when a pressure of 207 kPa is applied in the heating press roller 15, only about 3.5 to 6.9 kPa can be maintained in the cooling area 22. This in many cases gives a larger volume of voids in the product due to the tendency of the glass mat to expand when pressure is released thereto, thus expansion is caused by trapped gases when the resin is not fully solidified. The roller system used and the conveyor belt curves required in this unit also result in irregular conveyor belt speeds because, for example, on the press roller 15 »the conveyor belt 1¾ is on the outside and in the cooling area on the inside. Thus, the conveyor belts 3 and 30, which move at equal rectilinear speeds, move relative to each other on the rollers due to the fact that they run along the rollers under different radii depending on which roll they are running on.

In the method schematically shown in Fig. 1, resin plates 100 and 101, fiber glass mats 102 and 103 and molten resin 10¼ 790 47 68 8 are fed between the conveyor belts 105 and 106 of a machine for continuous production of a layered product. The conveyor belts 105 and 106 are endless conveyor belts which are driven around rollers 107 and 108 and rollers 109 and 110.

.5 The laminating machine is divided into two separate sections 120 and 130, as shown. For convenience, only two sections are shown, since it is obvious to one skilled in the art that each of these sections may consist of one or more more separate units. In the illustrated embodiment, the portion 10 120 is the hot region of the method of manufacturing a layered product, and is equipped with an upper platform 121 and a lower platform 122, which platforms are movable in a direction perpendicular to the path of movement of the conveyor belts 105 and 106. These platforms 121 and 122 are operated under hydraulic pressure, and can exert forces from ^ 5 o to 207 kPa on the material passing through this area to produce a layered product between the conveyor belts 105 and 106.

With modification, the platforms can be operated at an even higher pressure.

Movement of the material made into a layered product through this region is maintained by a plurality of rollers 123 and 12¾, which rollers are located in the upper and lower portions of the layered product region 120. The rollers 123 and 12 are rods extending across the width of the conveyor belts 105 and 106.

They are coupled at their ends by a school chain which in turn runs on the sprockets 125 for the rods 123 and the sprockets 126 for the rods 12. The sprockets 125 and 126 are driven by a suitable motor, not shown. As is clear from the drawing, the pressure to form a layered product exerted on the conveyor belts 105 and 106 on these conveyor belts is transferred by the rollers 123 and 122 when the platforms 121 and 122 are in contact therewith. The rollers 123 and 12¾ move the conveyor belts 105 and 166 through the region 120, the pressures from the platforms 121 and 122 being applied to the conveyor belts 105 and 106 as they pass through this region.

The area 120 is also supplied with heat, which is transferred to the sheet material as it passes through the area 120, E> 7904768 * 9 for keeping it in a molten state and thus ensuring the resin penetrates through the entire glass matrix of the layered product being formed.

The layered product exits from region 120 in region 130, which includes platforms 131 and 132, and rolls 133 and 131 in the upper and lower portions thereof. Similarly to the region 120, the rollers 133 and 13¾ are moved by sprockets 135 and 136, which run on a chain 137, attached to the rollers 133 and 13 ^, the sprockets 135 and 136 being driven by a -] q appropriate motor assembly (not shown). The platforms 132 and 131 apply pressure to the layered product as it passes through region 130, which is supplied with a heat transfer fluid in an indirect heat exchange feed system (not shown), which removes heat from the layered product through the rollers 133 and 13¾ for cooling the layered product and solidifying the resin as a whole. The solid finished product 1H0 is removed from area 130 and can then be subjected to longitudinal cutting, otherwise cutting and packaging, which is not part of the invention.

As is apparent to one skilled in the art, the present process provides considerable versatility in the physical manufacture of layered products of thermoplastic resins reinforced with glass fibers. Thus, pressure can be applied in the hot region 120 by using the tables 121 and 122 to any desired degree within the confines of the machine. Generally, the pressures can be changed from 0 to 207 kPa, usually between 138 and 207 kPa.

Similarly, in the hot region 120, heat can be supplied in a range of values to ensure sufficient flow of the resin throughout the glass fiber matrix when the pressure is applied for a given line speed of the conveyor belts 105 and 106.

Thus, a temperature of lk9 ° C to 360 ° C is usually used in the region 120 to insure the resin temperature in the range of 121 ° C to 288 ° C. It has been found that for a polyolefin, a resin temperature range from 20 ° C to 232 ° C is preferred.

During the operation of the area 130, the application of pressures by the platforms 131 and 132, when the layered product 790 47 68 10ρ 10 from the area 120 enters the area 130, can be used to accurately control the volume of empty cavities of the finished layered product 1, 0 which has hitherto not been possible with processes for the continuous production of a layered product, as shown in FIG. 2. Thus, if pressure in the region 130 is at a If the value is kept larger than in region 120, this results in a product with a low void content or virtually no void content.

For example, in a conventional operation of the system of FIG. 2, it has been found that when manufacturing a polypropylene layered product with glass fiber mats below 208 kPa in the hot region, a pressure of less than 6.9 kPa is achieved in the cooling area 22, the resulting product having an empty void content of 8 to 10%. Using the method of Figure 1, and applying 208 kPa in both the hot region 120 and the cooling region 130, a product with 3 to vol% voids is common. A lower volume void content using greater pressures in the cooling region 130 than used in the heating region can be easily obtained.

The void content can also be controlled to some extent by using only molten resin without resorting to a layered product manufacturing system using sheet products. Thus, by using molten resin 10U alone with mats 102 and 103, and omitting the outer plates 100 and 101, the layered product produced appears to have significantly less void volume than a layered product produced using external resin plates. If the surface appearance is not predominant, this provides a useful system for the continuous production of layered products with a small volume of voids. Coupling this with careful control of the pressure in the cooling region of the process of manufacturing a layered product to maintain it at or greater than the pressure in the heating region of the process produces layered products with constant small volumes of voids .

Generally, the fiber glass mats used in the manufacture of a layered product by the present method are pricked to provide mat cohesion and to deliver broken 790 4768 ie 11jt wires and strands to the mat so that they are inherent after pricking. 10 to 25 sev.% Of the mat has short fibers (that is, fibers in the range up to 2.5 cm or less in length), the rest of the mat being longer strands. The endless stranded mats can be formed by the process of U.S. Pat. No. 3,883,333 of fibers ranging in diameter between a T fiber and a G fiber or less. The fiber strands used to make the cam are usually in bundles of 50 fibers or less, although bundles of 100 or more strands can be used.

The endless strands mat may be made directly from a spinneret, such as in U.S. Pat. No. 3,883,333, or may be formed by drawing strands of preformed moldings with an appropriate stretcher, and laying on a conveyor the strands in a manner similar to that described in U.S. Pat. No. 3,883,333.

In Fig. 2, preformed films of thermoplastic material 100 and 101 are used with a molten extrusion material 10U placed between the glass mats 102 and 103. It is not necessary for the method to be carried out in this manner, although this method represents a preferred method. It is also possible that the present process is carried out using a plurality of extruded layers, from separate extruders or using a single multi-head extruder. In the latter case, the mats or the mat is fed such that extruded material is fed on the outside of the glass mat, as well as on the inside thereof. The advantage of using extruded material instead of the film layers 100 and 101 is that the heating by the extruded material of the molten thermoplastic material does not require the heat load in the hot region 120 required for melting the films 100 and 101, so that the machine is not subjected to the heating loads used when using films. It is also possible for a single mat to be used in conjunction with a preformed thermoplastic film or with only an extruded material. In single-mat constructions, it is preferable to use an extruded material instead of the foil as the 790 47 68

Claims (6)

10 CONCLUSIONS 1. A method of manufacturing a glass fiber reinforced resin sheet, characterized by supplying a fiberglass mat to a heating region, applying resin to the mat in this region, applying pressure to the mat and the resin at a temperature, sufficient to keep the resin melted and wet the mat thoroughly with resin, and subject the mat to cooling at a temperature sufficient to solidify the resin into a resin mat plate at least equal to keeping the pressure exerted on the resin and mat in the heating region from the pressure on the resin and mat during cooling, and removing a solid glass mat reinforced resin sheet from the cooling region. 2. A method of manufacturing a glass fiber reinforced thermoplastic resin sheet, characterized by continuously feeding a pressurized heating zone. a fiber glass mat and a thermoplastic resin, maintaining sufficient pressure and temperature in the heating region to thoroughly impregnate the fiber glass mat with molten resin, cooling the resin saturated mat and the molten resin to a temperature sufficient for solidifying the resin, by keeping at least equal to the pressure applied in the heating region the pressure on the resin and the resin-saturated mat during the cooling, and removing a solid plate of the resin from the cooling region glass fiber reinforced thermoplastic resin. Method according to claim 1, characterized in that the pressure on the resin and mat in the cooling area is kept at a greater value than that on the resin and mat in the heating area. The method according to claim 2, characterized in that the pressure exerted on the resin and the mat in the cooling zone is greater than the pressure exerted on the resin and the mat in the heating zone. 5 5 · A method of manufacturing a glass fiber reinforced thermoplastic resin sheet, characterized by feeding a glass mat and molten thermoplastic resin to a heated area to produce a layered product, applying pressure to the mat and the resin in the area for manufacturing a layered product from 10 138 to 208 kPa while maintaining sufficient temperature for keeping the resin in a molten state, continuously feeding the resin and the mat from the area for manufacturing a layered product in a cooling zone, applying a pressure of 138 to 208 kPa on the resin and mat in the cooling zone, which pressure is however at least as great as the pressure used in the heating zone, and cooling the resin, and the mat in this area to a temperature sufficient for the resin to solidify, and the removal of a solid glass fiber optic site from the cooling area reinforced resin. 6. Method for manufacturing a glass fiber reinforced thermoplastic resin sheet, characterized by supplying two glass mats, molten thermoplastic resin and two plates of thermoplastic film to a heated area for the manufacture of a layered product, said molten thermoplastic resin between the glass mats is introduced, the plates of thermoplastic film being fed to the outside of each of the mats, applying pressure to the mats, the molten thermoplastic resin and the thermoplastic films and supplying heat sufficient to melt the films leading the resulting composite resin-mat product to a cooling region maintained at a pressure at least equal to that of the heated layer-producing region and cooling the composite therein product to a temperature sufficient to solidify it composite product into a solid sheet of fiber glass reinforced thermoplastic resin. 7. A method according to claim 6, characterized in that the area for manufacturing a layered product is under a pressure of 138 to 208 kPa, which pressure also prevails in the cooling area. 8. Method substantially as described in the description and shown in the drawing. 790 4 7 68