Method of making continuous filament reinforced structural plastic profiles using pultrusion/coextrusion
a technology of continuous filament and structural plastics, applied in the direction of layered products, etc., can solve the problems of pvc fence and rail materials, metal reinforcements used, prone to corrosion attack, and thermoplastics that do not have the strength and rigidity of wood and lumber
Inactive Publication Date: 2014-10-09
SAINT GOBAIN PERFORMANCE PLASTICS CORP
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- Abstract
- Description
- Claims
- Application Information
AI Technical Summary
Benefits of technology
The process results in thermoplastic profiles with improved mechanical strength, durability, and reduced weight, along with increased production rates, overcoming the limitations of conventional methods by achieving superior bonding and efficient manufacturing.
Problems solved by technology
Thermoplastics typically do not have the strength and rigidity of wood and lumber and, therefore, the rail for the fence and railing needs a steel or aluminum reinforcement channel inside the rail.
Metal fence and rail materials, as well as the metal reinforcements used with current PVC fence and rail materials, are prone to corrosion attack, and lose strength in long-term endurance tests.
Additionally, where dark-colored thermoplastics materials are employed, thermal expansion problems can arise due to differences in expansion between opposing sides of the product when the product is exposed to sunlight.
Since the dark color absorbs heat more readily on the sun-facing side of the product, the resultant uneven heat buildup causes the rail to deform.
An additional problem is the lack of long-term stiffness of polymeric products, which has limited the rail span between the posts to lengths less than traditional lumber and metallic rails.
Conventional continuous filament reinforced thermoplastic profile products produced using conventional pultrusion processes still suffer from deficiencies in mechanical properties in the cross direction (e.g., flexural strength, tensile strength, impact strength, and compression strength), due typically to poor bonding between the substrate resin and the filaments.
This poor bonding is primarily due to poor resin wet-out of the filaments by the resin.
Additionally, cracking, splitting and separation of filaments in these profiles can easily occur during transportation, application, and installation.
Both of these approaches may result in a higher than desirable profile weight.
Additionally, conventional pultrusion processes for incorporating long filaments are relatively slow, and thus result in an undesirably low output rate (e.g., frequently on the order of only 2-3 feet per minute).
The slowness of the process is due to the time required for (1) melting of the thermoplastics, and (2) wet-out of the melted thermoplastics around the filaments.
Filament wet-out with thermoplastic resin is typically poor, even at higher temperature and longer residence times, due to the relatively high viscosity of thermoplastic materials.
Further, incompatibility between the thermoplastic resin and the filament material can also lead to poor wet-out.
The additional machines, however, take up additional manufacturing floor space and involve larger amounts of capital investment, thus leading to increased costs.
Alternatively, conventional filament reinforced thermoplastic profile products produced using conventional extrusion processes suffer from deficiencies in mechanical properties in the cross direction because current processes only allow for the incorporation of very short filament lengths.
Such processes can result in filament lengths of about one tenth of their originally added length.
If the filament length is too long (i.e., over ½-inch), the filaments will form a bridge at the introduction hopper, clogging the hopper and inhibiting feeding of the filaments into the extruder.
Such short filament lengths are undesirable for use as reinforcement for thermoplastic products because they do not provide the enhanced strength that is desired.
Additionally, filament loading using such processes is low.
Method used
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[0079]A PVC-Glass fiber / PVC Plastisol-Acrylic cap stock profile extrusion was carried out using a 3.5″ Davis Standard single screw extruder as a main extruder for PVC substrate extrusion, a three stage 0.705″×0.705″ crosshead die, with a square hole in the center, a 1.5″ Polytruder single screw extruder, a vacuum calibration system, a fiber creel, and a plastisol resin bath. The substrate resin (second resin 22) was a rigid PVC material having a composition as shown in the table below.
Parts byMaterialweightSource of materialOxyVinyls 216Polyvinyl100.00OxyVinyls, Dallas, TXchlorideMark 1900Stabilizer1.50Chemtura Corporation,Middlebury, CTKronos 2073Titanium dioxide1.00Kronos, Inc., Cranbury, NJRheolub 250Lubricant0.90Honeywell, Morristown, NJAC 629 ALubricant0.15Honeywell, Morristown, NJLoxiol G60Lubricant0.50Cognis, Ambler, PACa StCalcium stearate0.50Paraloid K 400Flow aid6.50Rohm and Haas, SpringHouse, PAOmyacarb UFTCalcium3.00Omya Inc., Alpharetta,carbonateGeorgiaTOTAL phr114.05
Th...
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Abstract
A system and method are disclosed for producing a continuous filament reinforced thermoplastic profile having consistent cross section. A continuous reinforcing filament is pre-wetted with a first thermoplastic resin and introduced into a die, where it is contacted with a second thermoplastic resin extruded from an extruder at melt state. The temperature of the die is carefully controlled so that the pre-wetted filament and first resin do not cure or solidify until after they have contacted and mixed with the second thermoplastic resin. The mixture temperature is then controlled to make a substantially solidified profile pre-shape. A capping layer comprising a third thermoplastic resin is then co-extruded onto the outer surface of the pre-shape. A multistage die for bringing together the filament and thermoplastic resins and for maintaining appropriate temperatures at each stage of the profile-forming process is also disclosed.
Description
FIELD OF THE INVENTION[0001]The invention relates to reinforced plastic composite materials and methods for their manufacture, and more particularly to improved continuous filament reinforced thermoplastic products and methods for their manufacture.BACKGROUND OF THE INVENTION[0002]Current residential and commercial fence and rail materials are made of traditional lumber, metal or polymers including thermoplastics. Typical thermoplastics used in these applications are PVC (polyvinyl chloride) and polyolefins such as polyethylene and polypropylene. Thermoplastics typically do not have the strength and rigidity of wood and lumber and, therefore, the rail for the fence and railing needs a steel or aluminum reinforcement channel inside the rail. Metal fence and rail materials, as well as the metal reinforcements used with current PVC fence and rail materials, are prone to corrosion attack, and lose strength in long-term endurance tests. Additionally, where dark-colored thermoplastics mat...
Claims
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IPC IPC(8): B29C70/52
CPCB29C70/521B29C70/526B29C70/523
InventorZHOU, XIXIANJACOBS, GREGORY F.WATERS, ERIC S.
OwnerSAINT GOBAIN PERFORMANCE PLASTICS CORP