AU647320B1 - Process for pultruding fiber reinforced furan composites - Google Patents

Description

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AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT u

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Applicant(s) NATIONAL SCIENCE COUNCIL Invention Title: PROCESS FOR PULTRUDING FIBER REINFORCED FURAN COMPOSITES r r The following statement is a full description of this invention, including the best method of performing it known to me/us: PROCESS FOR PULTRUDING FIBER REINFORCED FURAN COMPOSITES TECHNICAL FIELD OF THE INVENTION The present invention relates to a pultrusion process for producing fiber reinforced furan composites.

BACKGROUND OF THE INVENTION In a paper given at the 26th Annual Technical Conference 1971, Reinforced Plastics/Composites Division, The Society of the Plastics Industry, Inc., entitled "Fiberglass Reinforced Furan Composites An Unique Combination of Properties", 1971, K. B. Bozer, et al. disclosed fiberglass reinforced furan laminates made by modified furan resins and a series of new catalysts. These resin-catalyst systems offer improved processing characteristics. The 15 laminates prepared with these systems were reported to have physical properties comparable to polyesters while exhibiting outstanding chemical resistance, good heat distortion and flame resistance, and low smoke emission.

K. B. Bozer and L. H. Brown, in an article entitled "High Temperature and Combustion Properties of Furan Composites" given at the 27th Annual Technical Conference 1972, Reinforced Plastics/Composites Institute, The Society of the Plastics Industry, Inc., reported the performance of furan resins and chemically resistant furan-fiberglass composites at elevated temperatures, in particular the flame resistance of these materials. The furan-fiberglass composites used in this article are laminates ;fabricated by conventional hand lay-up technique.

J. E. Selley, in his article entitled "Furfuryl Alcohol Resins with Low Flame-Spread Low Smoke" given at the 29th Annual Technical Conference 1972, Reinforced Plastics/Composites Institute, The Society of the Plastics Industry, Inc., disclosed new catalysts suitable to be used in furan resins, which allow improved processing and fire performance. In this article, fiber reinforced furan resin composites are fabricated by lamination.

K. B. Bozer and D. D. Watson, in their article entitled "Furfuryl Alcohol Resin Systems for Hand Lay-Up and Spray-Up Fabrication" given at the 30th Annual Technical Conference 1975, 2 Reinforced Plastics/Composites Institute, The Society of the Plastics Industry, Inc., disclosed a new furfuryl alcohol-based resin and catalyst system with improved handling and laminate prformance properties for hand lay-up or spray-up fabrication of fiberglass/furan resin composite.

W. A. Szymanski and D. W. Kloda, in their article entitled "Polyester and Furfuryl Alcohol Resins for Corrosion Control", Chemical Engineering Progress, Vol. 70 No. 1 pp. 51-54 (1974), described processes for preparing fiberglass reinforced plastics by using polyester and furfuryl alcohol resins, which include a spray winder technique, a molding process and a laminating process. The spray winder technique integrally combines filament winding with chopped glass strand and resin spray-up.

.In an article entitled "Glass fibre Reinforced furan 15 Resins", The Chemical Engineer, April 1978, P. A. Downing discussed the characteristics of glass fibre reinforced furan resin composite and illustrates the advantages thereof in corrosion control, in which the composites are fabricated by hand lay-up and filament winding techniques.

The He.

tn f te- c-inventor of present invention, Chen-Chi Martin Ma, and his co-worker in U.S. patent 4,873,128, disclosed a process for pultruding fiber reinforced phenolic resin products, in which a liquid phenolic resin for impregnating filaments is heated to a temperature of 45-65°C during the impregnating step so that the 25 phenolic resin has a suitable impregnating viscosity.

It can be seen from the above-mentioned articles that the fiber reinforced furan resin composites have relatively strong physical strength, outstanding chemical resistance at elevated temperature and good flame resistance. However, there is no one who attemps to produce fiber reinforced furan resin composites by pultrusion process prior to the present 4nqntion.

The main object of present invention is to provide a process for pultruding fiber reinforced furan resin composites.

SUMMARY OF THE INVENTION The present invention is a process for pultruding fiber *US E reinforced furan resin composites comprising the steps of drawing a F I

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i r* l- Of 3plurality of continuous filaments through an impregnating bath of liquid furan resin to wet-out the filaments with said resin and a squeeze orifice for removal of excess resin and air, and continuously pulling the resin-impregnated filaments through a pultrusion die to heat and cure said resin, in which the liquid furan resin is maintained at a temperature of 15-35°C and has a viscosity ranging from 500-3000 cps during the impregnating step.

Advantageously, the pultrusion die used in the present process is designed to have multiple different heating temperatures along the pultrusion directions, e. g. three heating zones, in which the first heating zone, i.e. near the entrance of the pultrusion die, is kept at a temperature of 150-180°C, the second heating zone is kept at a temperature of 180-225°C, and the third heating zone is kept at a temperature of 170-220 0 Q, and the second heating zone is kept at a 15 temperature higher than those of the first and the third heating zones.

The liquid furan resin used in the present process is a composition containing a furfuryl alcohol prepolymer and an acid catalyst. Suitable acid catalysts can be, for example, p-toluene 20 sulfonic acid, maleic anhydride and phosphoric acid. Among these three catalysts, p-toluene sulfonic acid has the highest catalytic activity.

The amount of p-toluene sulfonic acid catalyst used is 0.05-2.5 wt% based on the weight of the prepolymer, preferably 0.5-1.5 wt%. As to the maleic anhydride and phosporic acid catalysts, a higher amount is 25 required to have the same degree of catalytic activity. The fresh liquid furan resin will have a pot life of about 8 hours at the impregnating temperatures and will be sufficiently cured when the go resin-impregnated filaments are pulled through the pultrusin die at a pulling rate up to 150 cm/min.

In addition, a postcuring treatment may be optionally employed to the fiber reinforced furan resin composites for improving their physical and mechanical properties, which comprises heating the pultruded composites at a temperature of 100-220°C for a period of 1-18 hours.

DETAILED DESCRIPTION OF THE INVENTION The liquid furan resin used in the present process can be prepared by 4 polymerizing furfuryl alcohol mo iomers with an addition of an acid catalyst to form a furfuryl a'.cohol prepolymer and mixing the resulting prepolymer mixture with a suitable amount of acid catalyst.

Preferably, the liquid furan resin is prepared just before the commencement of the impregnating step. A typical process for preparing the liquid furan resin comprises polymerizing 100 parts by weight of furfuryl alcohol monomers with an addition of 0.05-2.5, preferably 0.3-1.5, parts by weight of p-toluene sulfonic acid catalyst at a temperature of 35-70°C until the reaction mixture has a viscosity of about 300-400 cps, cooling the reaction mixture until the temperature of the reaction mixture reaches the impregnating temperature such that the viscosity thereof is increased to 500-800 cps, and then adding and mixing 0.05-2.5, preferably 0.5-1.5, parts by weight of p-toluene sulfonic acid catalyst into the reaction mixture. The term "viscosity" 15 used in the present invention means the viscosity measured by the method according to ASTM D2393 with a Brookfield type viscometer unless otherwise indicated. In addition to p-toluene sulfonic acid, maleic anhydride and phosphoric acid also can be used as the catalyst.

However, the amount of maleic anhydride or phosphoric acid used is relative higher than that of p-toluene sulfonic acid due to their catalytic activities being slightly lower than that of p-tulene sulfoninc acid.

The liquid furan resin is maintained at a temperature of 0 .15-35°C and has a viscosity of 500-3000 cps during the impregnating 25 step, preferably the liquid furan resin is maintained at room temperature 25°C and has a viscosity of 500-2000 cps, preferably 800-1200 cps. As it is well known to those skilled in the art, in general, the viscosity of a liquid resin will increase during the course of impregnation. In one of the preferred embodiments, the initial viscosity of the liquid furan resin containing 1.5 wt% of p-toluene sulfonic acid based on the weight of furfuryl alcohol prepolymer is 880 cps at 25°C, and it increases to 1400 cps after a period of 2 hours, and about 2000 cps after a period of 4 hours; if the liquid furan resin contains 1.0 wt% of p-toluene sulfonic acid based on the weight of the furfuryl alcohol prepolymer, the viscosity will increase from the initial 620 cps to 750 cps for a period of 4 hours and to 980 cps for a period of 8 hours. This embodiment shows 5 the liquid furan resin contained in the impregnating bath has a long pot life.

The continuous filaments may be employed in various forms such as strand, roving, woven roving, cloth, and mat. Various filamentary materials may be used in producing the composites of the invention such as glass, carbon, aromatic polyamides, ceramic, metal and hybrid thereof.

The pultrusion die which functions to form and cure the fiber reinforced composite is well known in the art, as described in U.S. patent 3,244,784, the disclosure of which is incorporated herein by reference. Normally, the temperature of the pultrusion die is higher than fiber reinforce composita by about 10 to 20°C because of the short residence time of the composite in the die. The dimension and profile of the pultruded composites also affect the heating 15 temperature of the pultrusion die. In one of the preferred embodiments of the present invention, the heating temperature profile of a 82-cm long, 1.27-cm wide and 0.219-cm thick curing die is controlled to have •three different heating temperatures along the pultrusion direction.

Among the three heating temperatures, the second heating temperature is the highest, which ranges from 180-225°C, preferably 190-215°C, the first heating temperature, i.e. near the entrance of the pultrusion die, ranges from 150-180°C, preferably 160-170"C, and the third heating temperature ranges from 170-220°C, preferably 180-215°C.

Because the furfuryl alcohol prepolymer/catalyst system used to S. 25 prepare the liquid furan resin has a high reactivity and the furfuryl alcohol prepolymer has been polymerized to a certain extent in advance, the fiber reinforced composite is able to be produced at a pulling rate of about 150 cm/min under the above-described heating temperature profile and still sufficiently cured. In addition, said first heating temperature can be kept at a temperature higher than 100 0 C in order to expel the water contained in the furan resin, and said third heating temperature is also able to be kept at a temperature lower than the second heating temperature to prevent from the water vaporising and expanding inside the pultruded composites at the exit of the pultrusion die.

The pultruded composites may be optionally subjected to a postcuring treatment to improve their physical and mechanical 6 properties. The postcuring treatment is carried out by heating the pultruded composites at a temperature of 100-220°C for a period of 2-18 hours. The postcuring temperature is generally in inverse proportion to the postcuring time, i.e. a higher postcuring temperature will require a shorter postcuring period. Preferably, the postcuring treatment is carried out by heating the pultruded composites at 200°C for 6 hours.

As it is well known in the art, mineral fillers such as talc, silica, and clay, etc. may be added into the liquid furan resin in order to improve the mechnical properties of the pultruded composites. The amount of said mineral fillers added is 1-15 wt% based on the weight of the liquid furan resin.

The apparatus suitable for practising the present process is .disclosed in U.S. patent 3,244,784, the disclosure of which is incorporated herein by reference.

The invention will be further illustrated by the following examples in which parts and percentages are by weight unless otherwise indicated. The following examples are only meant to illustrate the invention, but not to limit it.

k** Example 1: I) Preparation of the impregnating furan resin: The impregnating furan resin is prepared according to the formula listed in the following Table 1, in which the constituents 2 25 (5 g) and 3 (10 g) were well mixed and then added into the constituent 1 with stirring, the resulting mixture was kept at 50°C for polymerizing 3.5 hours, and then the resulting reaction mixture was immediately cooled in an ice bath for about one hour to a temperature of 25°C, in which the viscosity of the reaction mixture prior to the cooling was determined and found 300 cps. 9 g of the constituent 2 and 18 g of the constituent 3 were well mixed and then added into the cooled prepolymer reaction mixture, and the resulting mixture was stirred to form a homogenous impregnating resin which has a temperature of 25C and a viscosity of 400-600 cps.

Table 1 Constituent Weight (gram) 1) Furfuryl alcohol monomer 1000 2) p-Toluene sulfonic acid, monohydrate 15.0 3) Ethanol 30.0 1) Furfuryl alcohol monomer is a commercial product with a solid content of 80%, a specific gravity of 1.15 1.17 and a viscosity of 30-70 cps which is sold under a code of CF-7452 from Chang Chun Plastics Co., Ltd., Taiwan.

2) p-Toluene sulfonic acid monohydrate is a reagent grade compound with a molecular weight of 190.21 and a melting point of 104-107°C, which is available from Japan Pure 15 Chemicals Industrial Co. (Japan).

3) Ethanol used is reagent grade with a purity higher than 99.5 vol% (Taiwan Tobacco and Alcohol Bureau, Taiwan).

II) Pultrusion 16 rovings of 764-NT-218 glass fiber (PPG Co.) were drawn into a bath of the impregnating furan resin prepared above which was maintained at 25 0 C. They were passed through a squeeze orifice to remove excess resin and air and through a 82-cm long, 1.27-cm wide and 0.219-cm thick curing die. Three sets of individually controlled electricl plate heaters were installed on both top and bottom of the die, where the first and the third set of plate heaters have a length of 15 cm, and the second set of plate heaters has a length of 40 cm, III) Test specimens of the pultruded composites: The glass fiber content in the final pultruded composite is about 57.5 vol%. The glass fiber reinforced furan resin composites pultruded according to the above-described process by different pulling rates and different curing teperatura profiles were tested in accordance with the method of ASTM D790 to obtain their f.exural strength and the flexural modulus. The results are shown in Table 2.

Die temperature, C (1st, 2nd, 3rd zone) 165, 215, 210 170, 200, 195 175, 190, 185 8 Table 2 Flexural Strength and Flexural Modulus Pulling rate (cm/min) 40 70 103 130 150 a) 636 692 481 282 197 b) 52.3 52.4 49.2 44.5 40.3 a) 554 442 333 b) 39.6 38.1 35.1 a) 305 258 137 b) 39.0 36.5 25.6 4 0 a) Flexural strength: MPa b) Flexural modulus: GPa IV) Postcuring treatment: The composites pultruded by a curing temperature profile of 165-215-210°C and a pulling rate of 130 cm/min were further subjected to postcuring treatments at different postcuring temperatures and for different postcuring periods as listed in Table 3. The flexural strength and the tensile strength of the postcured composites are also shown in Table 3. The tensile strength was determined in accordance with the method of ASTM D3039.

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Postcuring temperature, °C Table 3 Flexural Strength and Tensile Strength Postcuring time (hours) 0 6 12 18 24 a) 662 728 739 756 769 b) 282 904 968 1045 1080 a) 662 772 797 807 824 b) 282 1016 1071 1073 1118 a) 662 898 960 906 837 b) 282 1198 1185 1180 1165 a) Flexural strength: MPa b) Tensile strength: MPa 9 It can be clearly seen from Table 3 that the postcuring treatment is carried out under 200°C for Furthermore, the data of Table 3 show that the postcuring composites will have improved mechnical properties.

preferred 6 hours.

pultruded Example 2: The present example illustrates the preparation of carbon fiber reinforced furan resin composites. The procedures of the above Example 1 were repeated except that 22, 24, 25 and 27 rovings of HTA-12000 carbon fiber (Toho co., Japan) were usec 'nstead of 16 rovings of glass fiber, in which the curing temperature profile of the pultrusion die was 165-215-210°C, and the pulling rate was 70 cm/min.

The fiber contents of the pultruded composites are listed in Table 4 together with their tensile strength and flexural strength.

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Table 4 Numbers of 22 45.7 869 400 Fiber content, vol% Tensile strength, MPa Flexural strength, MPa roving 24 49.5 948 560 of carbon fiber 25 27 51.5 56.1 1070 1360 671 790

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Example 3: 25 The purpose of this exaaple is to show the effect of mineral filler on the mechnical properties of the pultruded composites. 0.0 g, 50 g and 100 g of talc having a specific gravity of 2.71 and an average particle size of 2.121m were added in 1000 g the furan resin, respectively in three different runs. The procedures of the above Example 1 were repeated in each run except that said amount of talc was added into the impregnating furan resin, wherein rovings of 764-NT-218 glass fiber were used, the curing temperature profile was 165-215-210°C, and the pulling rate was 100 cm/min. The tensile strength and flexural strength of the pultruded composites are shown in Table 10 Table Amount of talc used (gram) 0.0 50 100 Tensile strength, MPa 741 758 588 Flexural strength, MPa 480 525 364 Data of Table 5 show that the mechnical strength of the pultruded composite will be improved when 50 g of talc is added into the impregnating resin; however, the mechnical strength of the pultruded composite will be adversely affected when 100 g of talc is added into the impregnating resin, It is believed that the poor mechnical strength of the composite using 100 g talc results from the catalytic activity of the acid catalyst used in the resin system being decreased, owing to the acidity of the resin system decreasing 15 after 100 g of talc is added. A higher amount of p-toluene sulfonic acid catalyst or a more severe curing condition should be employed in order to obtained high mechnical strength pultruded composites, when an impregnating furan resin containing a high content of mineral fillers is used in the present process.

Claims (10)

1. A process for pultruding fiber reinforced furan resin composites which comprises drawing a plurality of continuous filaments through an impregnating bath of liquid furan resin to saturate the filamens with said resin and a squeeze orifice for removal of excess resin and air, and continuously pulling the resin-impregnated filaments through a pultrusion die to heat and cure said resin, characterized in that the liquid furan resin comprises a furfuryl alcohol prepolymer and 0.05-2.5 wt% of an acid catalyst based on the weight of the prepolymer, and the liquid furan resin is maintained at a temperature of 0 C and has a viscosity ranging from 500-3000 cps during the impregnating step, wherein the pultrusion die has at least three heating zones therein and the last zone has a temperature below the temperature of a preceding zone.

2. A process in accordance with claim 1 wherein said liquid furan resin has a viscosity of 500-800 cps at the beginning of the impregnating step. 20

3. A process in accordance with claim 1 wherein said furfuryl alcohol prepolymer is prepared by polymerizing 100 parts by weight of furfuryl alcohol monomers with an addition of 0.05-2.5 parts by weight of an acid catalyst at a temperature of 35-70 0 C until the resulting polymerization 25 mixture has a viscosity of 300-400 cps.

4. A process in accordance with claim 1 wherein said acid catalyst is selected from the group consisting of p- toluene sulfonic acid, maleic anhydride and phosphoric acid. 3U

5. A process in accordance with claim 3 wherein said acid catalyst is selected from the group consisting of p- toluene sulfonic acid, maleic anhydride and phosphoric acid. A 'CE 12

6. A process in accordance with claim 1 wherein said pultrusion die has three different heating temperatures ranging from 150-225 0 C along the pultrusion direction, and among the three heating temperatures the second heating temperature is the highest.

7. A process in accordance with claim 6 wherein the first heating temperature, which is near the entrance of the pultrusion die, ranges from 150 to 180 0 C, the second heating temperature ranges from 180 to 225 0 C, and the third heating temperature ranges from 170 to 220 0 C.

8. A process in accordance with claim 1 wherein said process further comprises a postcuring treatment for the pultruded composites, said postcuring treatment comprising heating the pultruded composites at a temperature of 100- 220 0 C for a period of 1-18 hours.

9. A process in accordance with claim 1 wherein said continuous filaments is made of a material selected from the group consisting of glass fiber, carbon fiber, aromatic polyamide fiber, ceramic fiber, metal fiber and hybrid S 20 fiber thereof.

10. A process in accordance with claim 1 wherein said liquid furan resin contains 1-15 wt% of a mineral filler based on the weight of the liquid furan resin. :'DATED THIS 24TH DAY OF DECEMBER 1993 25 NATIONAL SCIENCE COUNCIL By its Patent Attorneys: GRIFFITH HACK CO rellows Institute of Patent Attorneys of Australia. ABSTRACT The present invention relates to a pultrusion process for preparing fiber reinforced furan resin composites by drawing a plurality of continuous filaments through an impregnating bath of liquid furan to wet-out the filaments with the resin and a squeeze orifice for removal of excess resin and air, and continuously pulling the resin-impregnated filament through a pultruion die to heat and cure the resin. The liquid furan resin contains a furfuryl alcohol prepolymer and a minor portion of an acid catalyst, and is maintained at a temperature of 15-35°C and has a viscosity of 500-3000 cps during the impregnating step. A postcuring treatment may be optionally employed to the pultruded fiber reinforced furan resin composites for improving their mechnical properties, which includes heating the pultruded composites at a temperature of 100-220 0 C for a period of 1-18 hours. Adding 1-15 wt% of mineral fillers may also improve the mechanical properties of the pultruded composites.