JP2657242B2 - Orientation sheet - Google Patents

Description

BACKGROUND OF THE INVENTION Extruded sheets of liquid crystal polymer and multiaxially oriented laminates therefrom are described in US Pat. No. 4,384,016.
The patent points out that extruding a polymer exhibiting anisotropy in the melt phase through a slit die and stretching in the melt phase results in a sheet that exhibits high process direction properties but poor poor transverse properties. ing. Biaxially oriented films of liquid crystal polymers are described in U.S. Pat. No. 4,333,907.

It is also known that heat treatment of fibers from liquid crystal polymers increases the fiber's tensile strength, as well as increasing the melting point and molecular weight of the assembly.

Finally, strong nonwoven sheets of liquid crystal polymer fibers self-bonded at intersections are described in US Pat. No. 4,362,777.

SUMMARY OF THE INVENTION The present invention provides a transparent sheet formed from a hot-pressed warp of a polymeric filament capable of forming an optically anisotropic melt. The present invention relates to laminates of such sheets, prepared with or without binders, and sheets prepared by drawing a heat-strengthened sheet in a direction perpendicular to the warp yarns, and the manufacture of these products. Also encompasses the method.

DETAILED DESCRIPTION OF THE INVENTION The uniaxial sheet of the present invention has properties superior to conventional extruded sheets. It is known that liquid crystal polymers can be melt extruded into highly oriented filaments. These filaments differ from polyesters such as, for example, polyethylene terephthalate, in that they are oriented as spun and are strengthened by heating rather than by drawing. See U.S. Pat. No. 4,183,895. The present invention utilizes the high degree of orientation formed in the as-spun liquid crystal polymer fibers.

New uniaxial sheets, which can be in the form of narrow tapes, if desired, are produced by forming as-spun liquid crystal polymer warps, i.e., sheets of essentially parallel filaments. I do. Warp yarns can be made by preferably drawing untwisted yarn from a number of bobbins and arranging the yarns side by side to form a sheet. It can also be produced by winding the yarn at a very small winding angle with respect to one plane. Regardless of the manner of its preparation, it is desirable that the filaments in the sheet be arranged substantially in one direction.

The filaments useful in the present invention are melt spun from liquid crystal polymers. Liquid crystal polymers are known and many are described in U.S. Pat. No. 4,362,777 and the patents cited therein. Fibers from liquid crystalline aromatic polyesters are preferred.

As mentioned above, the filaments as spun from the liquid crystal polymer melt are highly oriented. The method of the present invention takes full advantage of that orientation to maintain a substantial portion of the orientation in the hot pressed and heat strengthened sheet. The filaments are essentially unidirectionally aligned, the filament crystals are highly oriented in the filament direction, and the hot press fuses adjacent filaments together without significant deorientation of the crystals. That is why the hot pressed sheet is transparent. Heat strengthening following hot pressing does not significantly deorient the crystals. Thus, the heat-strengthened uniaxially oriented sheet of the present invention is transparent and has substantially better tensile properties than extruded sheets, which tend to lose orientation during extrusion.

After preparing the as-spun liquid crystal polymer filament warp, it is hot pressed, for example, between heated hot plates, for a time sufficient to form a coalesced transparent sheet. The uniaxial orientation of the crystalline polymer is responsible for the transparency. In forming a coalesced transparent sheet by hot pressing selected filaments, there is a certain temperature-pressure relationship. Relatively low temperatures require relatively high pressures, while relatively high temperatures allow the use of relatively low pressures. To avoid crystal deorientation, it is not desirable to maintain higher temperature and pressure conditions than required to obtain a transparent sheet.
That is, the temperature and pressure used must be sufficient to form a coalesced transparent sheet, but preferably not higher. The hot press preferably has a temperature of 20 ° C. below the temperature of the melting endotherm as measured using a differential operating calorimeter (DSC) and preferably has a pressure of at least 100 pounds per square inch, and more preferably a pressure of 100 to 350 psi. preferable.

The hot-pressed sheet is subjected to a time sufficient to increase the tensile strength in the warp direction to a level of at least 180 kpsi after the pressure is removed, in an inert purge gas atmosphere such as nitrogen, argon, or under vacuum. By heating at a temperature below the melting point, the heating is strengthened. At least 100 ° C, preferably 200-400 ° C
A temperature of is useful.

Uniaxial sheets can be prepared at any desired thickness. However, a sheet thickness not exceeding about 30 mils (0.076 cm) is preferred for best heat treatment response within a reasonable time range.

If desired, the uniaxially heat-strengthened sheet can be preheated and stretched transversely to achieve biaxial orientation and reduce tensile strength anisotropy.
These stretched sheets are no longer transparent because they have lost their uniaxial orientation. In contrast, such sheets are reasonably strong in two directions, unlike uniaxial sheets, which are relatively weak in the transverse direction.

The uniaxial sheet of the present invention can be laminated uniaxially or in a quasi-isotropic structure. Uniaxial laminates consist of multiple layers of uniaxial sheets at a temperature within about 30 ° C of the onset of DSC melting endotherm.
It can be made by hot pressing at a nominal pressure of 0 to 50 psi or, alternatively, by the use of thermoplastic hot melt adhesives or conventional epoxy resins.

Examples of thermoplastic adhesives are thin extruded films of precursor polymers (or other anisotropic melt-forming polymers having lower melting points than uniaxial sheets), and polyoxyethylene terephthalate (PETG) commercial films (Eastman)
Is included. Examples of epoxy resins are, for example, Epon 1139
(Chiver Geigy) and ECN 1299 (Chiver Geigy)
And phenol-formaldehyde resins. Such addition of an adhesive is desirable in the case of a quasi-isotropic laminate.

The materials of the present invention include automotive hoods and leaf springs, belts for radial tires, structural members, pressure vessels, rigid cladding, optical cables, flexible tubing, and other metal replacement applications expected in common advanced composite materials. And is useful in many reinforcement applications. Significant cost savings in manufacturing compared to conventional high-grade composites can be expected as a result of the absence of the resin matrix. Moreover, the outstanding transparency of the uniaxial sheet of the present invention allows its use in polarizing prisms and information storage devices.

The following examples are illustrative of the present invention and are not intended to limit the invention in any way.

Example 1 This example demonstrates copoly (chloro-p-phenylene / 4,4 '
-Bisphenylene / terephthalate / isophthalate)
This illustrates the production of a uniaxially oriented sheet from (40/10/40/10 mole percent) yarn, but a substantial portion of the fiber orientation can be maintained during conversion to the sheet. The polymer is prepared by the method described in U.S. Pat. No. 4,412,058. 45 ° C in pentafluorophenol
The polymer having a 2.5 η inh is melted in a twin-screw melt spinning machine having a melting zone temperature of 330 ° C., and a perimeter is fed through a 34-hole spinneret having a diameter of 0.023 cm and a length of 0.061 cm. Spin in the surrounding air and wind at 1200 mpm, spinning draw ratio = 83. The 219 denier / 34 filament yarn has an orientation angle of 14 °, a tensile strength of 143 kpsi (1000 pounds per square inch) and a tensile modulus of 8.7 Mpsi (one million pounds per square inch). It has a differential scanning calorimetry (DSC) melting endotherm starting at 300 ° C.

The yarn is rewound through a 1% by weight aqueous solution of potassium iodide and then coated on a heat-resistant film (Kapton Polyimide Film, I. D. Du Pont de Nimores & Co.) and crossed over a card winder. Wrap continuously on a fixed, 17.8 cm square x 0.64 cm thick flat aluminum plate with 0.1 gpd tension and 11.8 turns / cm (wrap angle ~ 0.3 °). A standard release agent is sprayed on the film surface. Twenty-seven layers of 5.08 cm wide yarn are wound in parallel on both sides of the board. It is then placed in a vacuum oven at 130 ° C. for 60 minutes for drying. The dried sample is transferred to a press (Pasadena Hydro-Rich Bench Press) equipped with a 30.5 cm square hot plate heated to 285 ° C. A pressure of 300 psi (lbs / square inch) is first applied and then reduced to 190 psi during the 10 minutes required for the sample to reach the hotplate temperature (measured by a thermocouple in an aluminum plate). The pressure is then released and the sample is removed from the press and cooled to room temperature. 8.2cm in width, 15.7c in length
Collect a transparent amber plastic sheet, m, 0.038 cm thick.

The sheet sample was placed on a woven glass fiber mat in a nitrogen purged oven and stepped at 240 ° C for 2 hours at 270 ° C.
After heating at 2 ° C. for 2 hours and 305 ° C. for 16 hours, the oven is cooled to room temperature (RT), and the heat-treated sample is taken out. The heat treated sample retains its transparency and has significantly increased toughness.

The tensile properties in the fiber axis direction of the molded and heat-treated sample are measured with an Instron tensile tester. The specimen is cut into a dampel shape having a length of 12.7 cm and outer and inner widths of 1.3 cm and 0.64 cm, respectively. Using standard thermosetting epoxy resin tape as the adhesive, attach rectangular aluminum hangs 1.3 cm wide and 3.9 cm long to both ends of the sample. The as-molded (unheat-treated) sample had a tensile strength of 82.0 kpsi, a tensile modulus of 6.5 Mpsi and a light distribution angle of 14 ° (18.8 °), while the heat-treated sample had a tensile strength of 217.5 kpsi, It has a tensile modulus of 6.8 Mpsi and an orientation angle of 13 ° (17.7 °). The precursor yarn coated with potassium iodide and heat-treated under the same conditions is 35
It exhibits a tensile strength of 4.5 kpsi, a tensile modulus of 8.9 Mpsi and an orientation angle of 16 ° (19.1 °).

Example 2 This example illustrates the production of a uniaxially oriented sheet and the evaluation of the tensile properties in the oriented (0 °) and transverse (90 °) directions. A polymer of the composition of Example 1 was prepared by the same procedure and spinning 100 holes with a hole of 0.013 cm diameter and 0.061 cm length using the same spinning machine with a melting zone temperature of 335 ° C. Spin through a die at 331 ° C. into the surrounding air and wind up at 500 mpm (m / min), spin draw = 33. The 500 denier / 100 filament yarn has essentially the same tensile properties and
Figure 2 shows a DSC melting endotherm starting at 301 ° C.

The yarn was rewound through a 1% by weight aqueous solution of potassium iodide containing a dispersant, then covered with a film of "Kapton" polyimide and fixed on a traversing card winder, width 25.4 cm x length 27.3 cm x thickness Wound continuously on a 0.64cm flat aluminum plate at 0.1gpd tension and 1.18 turns / cm. Wrap four layers of yarn 15.2 cm wide on both sides of the board. The sample is then dried in a vacuum oven at 130 ° C. for 60 minutes and then transferred to the same press as in Example 1 with a hot plate heated to 290 ° C. Allow the sample to reach hotplate temperature (approx.
Heat at contact pressure, then apply 111 psi pressure and hold at 290 ° C. for 10 minutes. The pressure is then released and the sample is removed from the press and cooled to room temperature. 15.2cm in width, length
Collect two clear plastic sheets 22.9 cm thick and 0.023 cm thick. The sheets were placed on woven glass fiber mats in a nitrogen purged oven and stepped 2
After heating to 200 ° C. over time, from 200 ° C. to 306 ° C. over 7.3 hours, and then at 306 ° C. for 7.5 hours, the oven is cooled to room temperature and the heat-treated sample is taken out.

The tensile properties in the fiber axis direction are measured on the test specimen prepared as in Example 1. This sample exhibits a tensile strength (0 °) = 259.4 kpsi, a maximum elongation (0 °) = 6.0% and a tensile modulus (0 °) = 69 Mpsi. Lateral (90
The tensile properties in ゜) are measured by cutting a 1.27 cm wide transverse specimen. Example 1
With a sag similar to that described above, measurement is performed with an Instron tensile tester at a cage width of 2.5 cm. This sample has a tensile strength (90 °) = 5.2 kpsi, maximum elongation (90 °) = 3.5%,
Indicates a tensile modulus = 0.5 Mpsi.

Example 3 This example demonstrates the preparation of a thermochromic copolyester copoly (chloro-p-phenylene / 4,4'-, biphenylene / terephthalate / isophthalate) (40/10/47/3, mol% basis) from fibers. 2 illustrates the production of a uniaxially oriented sheet. The polymer is prepared by the method described in U.S. Pat. No. 4,412,058 and has an .eta.inh of 2.97 at 45 DEG C. in pentafluorophenol. This polymer is
The melt is melted in a twin-screw spinning machine having a melt zone temperature of 40 ° C. and spun into the surrounding air through a 34-hole spinneret having a hole of 0.018 cm in diameter and 0.23 cm in length, and
Wind at mpm and spinning draw ratio = 58. 190 denier / 3
4 filament yarn has a tensile strength of 77.9 kpsi (4.2 gpd), 11.
Start at 2Mpsi tensile modulus (605gpd) and 317 ° C
3 shows DSC endotherm.

A reinforcement containing 32 layers of yarn is prepared as in Example 1 and pressed under the same conditions as in Example 1, except that the hot plate temperature is maintained at 300 ° C. Two transparent,
Collect the amber plastic sheet of thickness 0.047cm.

The sheet sample is heat treated as in Example 1. The heat-treated sample almost fibrous in its transparency and shows a marked increase in toughness. The results of measuring the tensile strength (TS) and tensile modulus (TM) in the orientation (0 °) direction of the as molded and heat treated sheet according to the procedure of Example 1 are as follows: TS (kpsi) TM ( Mpsi) As molded 70.3 7.6 After heat treatment 212.8 8.8 Example 4 This example relates to a thermochromic copolyester, copoly (chloro-p-phenylene / terephthalate / naphthalate).
1 illustrates the preparation of uniaxially oriented sheets from (50/35/15, mol% basis) fibers. The polymer is prepared using the method described in U.S. Pat. No. 4,118,372 and is insoluble in pentafluorophenol at 45.degree.
The polymer is melted in a twin-screw melt spinning machine with a melting zone temperature of 325 ° C and the air surrounding at 330 ° C through a 100-hole spinneret with a 0.013 cm diameter and 0.030 cm long hole. It is spun in and wound up at 878 mpm (spinning draw ratio = 49).

384 denier / 100 filament yarn is 102kpsi (5.5gpd)
Tensile strength, 9.5Mpsi (513gpd) tensile modulus and 2
Has a DSC melting endotherm starting at 97 ° C.

The yarn is twisted twice, and a reinforcing material containing 4 layers of 2-ply yarn having a width of 40.6 cm is prepared in the same manner as in Example 1, and a hot plate temperature of 290 ° C is pressed. Apply 250 psi pressure to the sample at 290
After holding at 10 ° C. for 10 minutes and then releasing the pressure, the sample is removed from the press and cooled to room temperature. 40.6cm width, 15.2
Collect two clear, amber plastic sheets, cm long and 0.028 cm thick.

A sample of this sheet is heat-treated as in Example 2. The heat treated sample retains most of its transparency and shows a significant increase in toughness. When tested according to the procedures of Examples 1 and 2, the TS and TM in the orientation (0 °) and transverse (90 °) directions of the heat-treated sample are as follows: TS (kpsi) TM (Mpsi) 0゜ direction 254.3 7.3 90 ゜ direction 3.0 0.25 The corresponding heat treated yarn has a tensile strength of 451 kpsi and a modulus of 9.1 Mpsi.

Example 5 This example demonstrates improved tensile strength balance obtained by transverse stretching of a uniaxially oriented sheet prepared from the yarn of the thermochromic copolyester composition of Example 1. 2 illustrates the preparation of an axial film. The polymer is prepared by the method of Example 1 and spun as in Example 2. The 560 denier / 100 filament yarn exhibits essentially the same tensile properties as in Example 1. thickness
A pair of uniaxially oriented sheets of 0.033 cm, wrapped 6.35 c wide
Prepared under essentially the same conditions as in Example 1 except that it consists of 10 layers of m yarns. This sheet is thermally strengthened in the same manner as in Example 2. A 6.0 cm square specimen is then cut from one sheet and clamped in a conventional film stretcher preheated to 200 ° C. The sample is clamped (fixed) in the orientation, that is, in the vertical (0 °) direction, heated at 200 ° C. for 10 minutes, and then stretched 400% in the horizontal (90 °) direction. Next, a rectangular test piece having a width of 1.27 cm and a thickness of 0.009 cm is cut from the opaque stretched sheet in the vertical (0 °) and horizontal (90 °) directions. The test specimen was sagged as in Example 1 and gauged 1.27 cm (0 ° specimen) and 2.54 cm (90 ° specimen) with an Instron tensile tester.
Measure the tensile strength with.

The 0 ° and 90 ° tensile strengths of the unstretched heat-strengthened sheet are also measured by the method described in Example 2. The tensile strength (TS) in the longitudinal (0 °) and transverse (90 °) directions of the unstretched and stretched heat-treated sheet reflects the balance of enhanced tensile strength due to stretching, as summarized in the table below.

TS (0 °), kpsi TS (90 °) psi, k unstretched 275 4.5 Extended 36.4 20.6 Example 6 This example illustrates the production of a uniaxially oriented laminate without added adhesive. A polymer of the composition of Example 1 is prepared by a similar procedure and spun as described in Example 2. A uniaxial sheet was prepared from the 490 denier yarn as described in Example 1 and 12 layers of 15.2 cm wide yarn were wound onto a 22.9 cm square, 0.64 cm thick flat aluminum plate, and the sample was prepared. At 352 ° C. for 5 minutes at 285 ° C. The dimensions of the plastic sheet pair thus obtained are
It is 16.5cm x 22.9cm x 0.053cm (thickness). One sheet is heat strengthened according to the procedure of Example 2. The heat treated sheet has a DSC melting endotherm beginning at 329 ° C. 1.27cm wide x
Six test pieces of 15.24 cm in length (length corresponds to the orientation (0 °) direction of the sheet) are cut and placed in a metal Univer mold. Transfer the mold to a press heated to 325 ° C and allow the sample to
(Minimum contact pressure) at 325 ° C. for 7 minutes. The thicknesses of the samples before and after pressing are 0.32 cm and 0.30 cm, respectively.
The flexural strength and modulus measured using a standard Instron bend tester are 42.9 kpsi and 5.1 Mpsi, respectively, at a span / thickness ratio of 32/1. A short beam strength of 5.4 kpsi is obtained at a span / thickness ratio of 4.2 / 1.

Example 7 This example illustrates the production of uniaxial and cross-ply laminates from high strength uniaxial sheets using a thin extruded film of the precursor polymer as the thermoplastic adhesive. A polymer of the composition of Example 1 is prepared by analogous means and spun as fibers in the same manner as described in Example 2. This yarn is the same as that used in Example 6. 2 with dimensions of 10.2cm wide x 15.2cm long x 0.036cm thick
A set of uniaxial sheets is laid on a flat aluminum plate of 17.8 cm square x 0.64 cm thick with 10 layers of 560 denier yarn 6.35 cm wide.
Prepared by winding at 11.8 turns / cm. A sample is formed in the same manner as in Example 1 at a press temperature of 285 ° C. and a pressure of 300 psi. The sheet thus obtained is heat-treated in the same manner as in Example 2. Cut the sheet into 6.35cm square elements,
It is used to prepare 4-ply uniaxial (0 ° / 0 ° / 0 ° / 0 °) and cross-ply (0 ° / 90 ° / 90 ° / 0 °) laminates.
A 0.002 cm thick film of the same polymer composition prepared by standard film extrusion methods is also cut into 6.35 cm square elements and placed between the three successive sheet layers making up each laminate. The extruded film has a DSC melting endotherm at 304 ° C. The laminates are transferred to a press heated to 315 ° C. and squeezed between aluminum plates coated with “Kapton” film at about 50 psi (close to the minimum contact pressure). It is then removed from the press and allowed to cool to room temperature. The laminate is observed to have a smooth glossy surface. Their thickness is 0.14cm (0 ゜ / 0 ゜ / 0 ゜ / 0
゜) and 0.15 cm (0 ゜ / 90 ゜ / 90 ゜ / 0 ゜). Then width
A 1.27 cm specimen (0 ° / 0 ° / 0 ° / 0 ° / 0 ° / 0 ° laminate) is cut and flexural strength (FS), flexural modulus (FM) is measured using a standard Instron bending tester. ) And short beam shear (SBS) strength. The results obtained for each laminate are summarized below: 0 ゜ / 0 ゜ / 0 ゜ / 0 ゜ FS (span / thickness = 16/1) = 66.6 kpsi FM (span / thickness = 32/1) ) = 7.6Mpsi SBS (span / thickness = 7/1) = 4.9kpsi 0 ゜ / 90 ゜ / 90 ゜ / 0 ゜ FS (span / thickness = 16/1) = 44.0kpsi FM (span / thickness = 32/1) = 4.6Mpsi SBS (span / thickness = 7/1) = 4.2kpsi Example 8 This example illustrates the production of uniaxial and cross-ply laminates from uniaxial sheets using epoxy thermoset adhesive. Is what you do. A set of heat treated uniaxial sheets of 0.064 cm thickness is prepared under the same conditions as described in Example 7.
Eight layers of 860 denier / 200 filament yarn are used and pressing conditions are 293 ° C., 111 psi for 5 minutes. After heat treatment, from the sheet, in both orientation directions of 0 ° and 90 °, 1.
A 27 cm wide and 12.7 cm long long strip was cut and used to make a 4-ply shaft (0/0/0/0) and a cross ply (0/90 /). 90 ゜ / 0 ゜) Prepare a laminate. Standard phenol novolak resin in methylene chloride (EPN 1
139, Ciba Geigy) is prepared. The strip is coated with an epoxy solution, air-dried for 5 minutes, and then coated and dried again. The 4-ply uniaxial and cross-ply bar laminates are then assembled, press heated at 300 ° C. between aluminum plates coated with “Kapton” film and pressed at 50 psi (close to the minimum contact pressure). Then, it is taken out of the press and allowed to cool to room temperature. Then, in the same manner as in Example 7, the bending strength (FS) and the bending modulus (FS)
Is measured.

0 ゜ / 0 ゜ / 0 ゜ / 0 ゜ thickness = 0.28cm FS (span / thickness = 16/1) = 67.4kpsi FM (span / thickness = 44/1) = 6.6Mpsi 0 ゜ / 90 ゜ / 90 ゜ / 0 ゜ thickness = 0.24cm FS (span / thickness = 16/1) = 21.0kpsi FM (span / thickness = 50/1) = 5.4Mpsi The main features and aspects of the present invention are as follows. It is as follows.

1. Hot-pressing a filament warp yarn melt-extruded from a polymer capable of forming an optically anisotropic melt at a temperature and pressure sufficient to form an agglomerated transparent sheet. A method for producing a uniaxially oriented sheet.

2. Heat strengthening the hot pressed sheet by heating it in a purge inert atmosphere at a temperature below its melting point for a time sufficient to increase the tensile strength in the warp direction. The described method.

3. The process of claim 1 wherein the temperature used is within 20 ° C. below the temperature of the melting endotherm and the pressure used is at least 100 pounds per square inch.

Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location B29L 7:00

Claims (1)

(57) [Claims] 1. A method comprising hot pressing filament warp yarns melt extruded from a polymer capable of forming an optically anisotropic melt at a temperature and pressure sufficient to form a coalesced transparent sheet. A method for producing a uniaxially oriented sheet.