JP4726785B2 - Liquid crystal polymer composition - Google Patents

Description

  Liquid crystal polymer (LCP) compositions with improved resistance to degradation from thermal aging at elevated temperatures include LCP and glass fillers with no sizing.

  Because liquid crystal polymers (LCP) are useful in the electrical and electronics industries as molding resins for general purpose applications, and more specifically because of their thermal stability, chemical resistance, and other desirable properties, It has become an important commercial item. For many applications, the molded resins should exhibit good stability not only when they are kept at high temperatures for extended periods of time, but also when heated for a short time.

  When aging at high temperatures, LCP compositions exhibit one or more deleterious properties. Blistering is a phenomenon when gas encapsulation ("bubbles"), particularly when larger encapsulations are formed in the polymer matrix. The result observed is an undesired blister that forms directly under the skin of the part. Thermal oxidative degradation is a phenomenon exhibited by virtually all organic polymers, especially at higher temperatures and / or in the presence of oxygen. The rate of degradation depends on factors such as temperature, the nature of the media in contact with the part, the presence of damaging radiation, and the time the part is exposed to this environment. They often have excellent heat aging resistance compared to other thermoplastic materials, but even LCP sometimes undergoes thermal oxidative degradation, assuming sufficiently severe conditions. Such degradation often leads to gradual weight loss from the polymer parts, leaving behind an inert component such as a filler. Other physical properties such as toughness, tensile strength and elongation at break often fall in parallel with this weight loss, and therefore they are often measurable indicators for thermal oxidative degradation. The rate of thermal oxidative degradation usually becomes progressively higher at higher temperatures and typically follows an exponential Allenium-type correlation with temperature.

  Glass fillers such as fibers are used extensively to modify physical properties. Such glass fillers are manufactured by a variety of methods, the most commonly used of which provide glass fibers in the form of bundles of tens or hundreds of fibers, respectively. The advantage of fiber bundles is that they are easily packaged and transported and easy to be later fed into the compounding equipment used to produce glass reinforced plastics. To form these bundles, the glass fibers receive a very thin coating ("sizing") after they are extruded, this sizing holds the fibers together in these bundles and rubs against each other Protect individual fibers from accidental damage. Under high shear conditions with normal heating, for example during compounding into a thermoplastic resin, the bundles break apart and release individual fibers into the plastic matrix. In addition to these functions, sizing on glass fillers intended for incorporation into thermoplastic resins also includes, for example, epoxides, silanes, etc., binders that improve the adhesion of the glass to the thermoplastic resin. It may be. Glass fillers such as glass fibers (particularly shredded glass fibers) and milled glass (fibers) used as fillers for thermoplastic resins almost always have a sizing on them.

  LCP compositions containing glass fibers without sizing have been documented, see (Patent Literature 1), (Patent Literature 2), (Patent Literature 3), and US Patent Publication (Patent Literature 4). The compositions described in these references contain LCPs with melting points below 350 ° C. and / or contain significant amounts of other types of polymers that are not stable at higher temperatures. All of these documents are directed to compositions having improved physical properties such as tensile strength and elongation.

Japanese Patent Laid-Open No. 08-134334 JP 07-003137 A JP 05-331356 A US Pat. No. 5,646,209 U.S. Pat. No. 4,118,372 International Patent Application No. 02/02717 Pamphlet N-C Lee, "Reflow Soldering Processes and Troubleshooting", Boston, Newnes, 2001. J. et al. S. By Hwang, “Modern Solder Technology for Competitive Electronics Manufacturing”, New York, McGraw Hill, 1996.

The present invention
(A) a glass filler without sizing;
And (b) a composition comprising a thermotropic liquid crystal polymer having a melting point of about 350 ° C. or higher.

The present invention also relates to a method of forming a conductive path in an electrical or electronic device by a solder bath method, the device comprising: (a) a glass filler without sizing;
(B) It contains as an improvement point containing the composition containing the thermotropic liquid crystal polymer which has melting | fusing point about 280 degreeC or more.

This specification also describes
(A) a glass filler without sizing;
Also disclosed is an electrical or electronic device having one or more conductive paths comprising (b) a thermotropic liquid crystal polymer having a melting point of about 280 ° C. or higher.

  “Thermotropic liquid crystal polymer” is used herein to refer to any possible variations thereof, such as those described in the US Patent Publication (US Pat. It means a polymer that is anisotropic when tested. Useful LCPs include polyesters, poly (ester-amides), and poly (ester-imides). One preferred form of the polymer is “totally aromatic”, that is, all of the groups in the polymer backbone are aromatic (except for linking groups such as ester groups), but there are non-aromatic side groups. May be. Preferably, the LCP is at least about 35 weight percent of the composition. Preferably, the melting point of LCP is about 350 ° C. or higher, more preferably about 365 ° C. or higher, particularly preferably about 390 ° C. or higher. Melting points are measured by the American Society for Testing and Materials (ASTM) method D3418. The melting point is taken as the maximum of the melting endotherm and is measured by secondary heating at a heating rate of 10 ° C./min. If more than one melting point is present, the melting point of the polymer is taken as the highest of the melting points.

  “Glass filler” as used herein means any relatively small particulate or fibrous glass material suitable for mixing with a thermoplastic resin. Useful glass materials include so-called “E-glass”, “S-glass”, soda lime glass, and borosilicate glass. The filler may be in any form such as fiber (fiberglass), milled glass (ground glass fiber), glass flake, hollow or solid sphere. Preferred forms of glass are glass fiber and milled glass, with glass fiber being particularly preferred.

  “No sizing” means that the glass (or other material) is not intentionally coated with any organic compound, including polymers, oligomers, monomeric compounds, or polymerizable compounds. Without sizing, any glass filler that has been treated (baked) at a temperature high enough to remove any organic components from its surface is included. The glass filler may be coated with an inorganic compound such as silica or alumina. Typically, the sizing glass filler contains about 0.5 to 2 weight percent sizing.

  All weight percentages herein are based on the total composition containing LCP and glass filler unless otherwise specified.

  Preferably, the amount of LCP in the composition is at least about 35 weight percent, more preferably at least about 45 weight percent. Preferably, the amount of glass filler (which may be considered a reinforcement in some cases) is from 0.1 to about 65 weight percent, more preferably from about 5 to about 50 weight percent.

  Other materials may also be present in the composition, particularly those that are often found in thermoplastic resin compositions or that are made for use in the compositions. These materials should preferably be chemically inert and reasonably thermally stable in the operating environment of the molded part during use and / or during part formation. In particular, other polymers that are not substantially thermally stable in the operating environment of the molded part in use or while it is being processed should preferably be avoided. Stable materials may include one or more fillers, reinforcements, pigments, and nucleating agents. Other polymers may also be present, thus forming a polymer blend. If other polymers (other than LCP) are present, they are preferably less than 25 weight percent of the composition. In another preferred type of composition, the other polymers (other than LCP) are in a small total amount (less than 5 weight percent, more preferably less than 3 weight percent, very preferably 1), such as lubricants and processing aids. It is not present except for less than 0 weight percent (particularly preferably none) of the polymer. In another preferred form, the composition contains from about 1 to about 55 weight percent filler and / or reinforcement (other than glass filler), more preferably from about 5 to about 40 weight percent of these materials. Reinforcing materials and / or fillers include fibrous materials such as aramid fibers, wollastonite, titanium dioxide whiskers and powders (fine particles) such as mica, clay, calcium sulfate, calcium phosphate, barium sulfate, talc. . Some of these materials may serve to improve the strength and / or elastic modulus of the composition and / or may improve flame resistance (eg, incorporated herein by reference). (See Patent Document 6). Preferred filler / reinforcing materials include mica and talc. Preferably, the filler / reinforcing material is not sized or otherwise coated with an organic material.

  Preferred LCPs are made from 4,4'-biphenol / terephthalic acid / isophthalic acid / 4-hydroxybenzoic acid or derivatives thereof (100/95/5/100 mole parts) and have a melting point of about 400 ° C. The molar part of terephthalic acid / isophthalic acid can also range from 90/10 to about 97.5 / 2.5.

  Such compositions for many electrical and electronic applications are preferably flame retardant, i.e. the composition is 0.79 mm thick with a V-1 UL-94 rating, more preferably 0.79 mm thick. It is also preferred to have a UL-94 rating of V-0. The UL-94 test (Underwriter's Laboratories) is a flammability test for plastic materials and the V-0 rating requirement is more stringent than the V-1 rating requirement. The thinner the specimen, the more difficult it is to achieve a better burn resistance rating.

  Preferably, the composition has a heat deflection temperature (HDT) at 1.82 MPa of at least about 240 ° C., more preferably at least about 275 ° C., particularly preferably at least about 340 ° C. HDT is measured by ASTM method D648.

  The compositions described herein may be produced by conventional methods used to mix and mold thermoplastic resin compositions and molded into parts. The composition is made by melt mixing (the LCP and any other low melting ingredients are melted) in a typical mixing device such as a single or twin screw extruder or melt kneader. May be. The part may be formed by typical thermoplastic molding methods such as extrusion, extrusion coating, thermoforming, blow molding, or injection molding.

  These compositions (any LCP with the melting points mentioned above) are particularly useful in electrical and electronic applications, especially up to 260 ° C. or even 300 ° C. during lead-free soldering or other processing steps. Useful if peak temperatures may be reached rapidly, or if continuous temperatures above 260 ° C are encountered during use, and especially for temperatures above 280 ° C. Such applications include lamp sockets, lamp holders, lamp bases, electrical or electronic connectors, circuit boards, terminal blocks, terminal connectors, heater mounts, ignition coils, relay sockets, high voltage connectors, spark plug components, emergency switches; ovens Controllers and switches for household appliances, including cooking utensils and washing machines; electric motor brush holders, rolls, circuit breakers, circuit breaker housings, contactor housings and printed connectors, and electrical and electronic connectors, distributors Office equipment parts exposed to high temperatures such as in copiers and printers; transformer parts such as spacers and supports, switches and microswitches. Further applications include engine turbocharger parts, and engine exhaust parts such as found in gas recycling systems.

  Thus, the composition of the present invention in which the melting point of LCP is about 280 ° C. or higher, more preferably about 300 ° C. or higher, particularly preferably about 350 ° C. or higher is applied to a circuit board or a device such as an electrical or electronic connector ( Heat may be easily applied in the solder bath to form an (electrical) connection. As mentioned above, due to the high thermal stability of these compositions, they are particularly useful when using solder baths that are lead-free. These solder baths tend to operate at higher temperatures.

  “Solder bath method” means a circuit board or electrical circuit that may have one or more components attached to it, such as surface mount and / or through-hole devices, and may have a single layer or multiple layers. By a method such as reflow soldering or wave soldering used to form a conductive path in / on a device such as a connector. Such methods are well known, see for example (Non-Patent Document 1) and (Non-Patent Document 2), both of which are hereby incorporated by reference.

  The use of these solder bath methods typically results in electrical or electronic components having at least one conductive path. At least one of these paths typically includes solder.

  Other applications (when the melting point of the LCP is 350 ° C. or higher, or about 280 ° C. or higher) include cookware and bakeware, allowing for the environment experienced by the cookware and bakeware throughout use . The cookware may be coated with a release coating such as a fluoropolymer or silicone-based coating. It is often necessary to bake on such release coatings to treat the surface of the cookware and / or to use primers and / or to make these release coatings durable. High temperatures are often used when it is desirable to bake on a primer and / or topcoat. The high temperature stability of the LCP compositions of the present invention, in particular, allows the use of high melt temperature fluoropolymer coatings, providing desirable quality superior durability, stain resistance and improved delamination. At these high temperatures, in particular, the stability of the LCP so that the LCP composition does not emit any gas that may become trapped under the release coating or within the LCP, thereby forming bubbles (bulges). Sex is highly desirable. Since the LCP compositions of the present invention have excellent thermal stability, they are particularly useful for producing such coated cookware, or indeed any device that is desired to be coated with such non-stick coatings. is there.

  The paint used in the present invention can be applied to the substrate by conventional methods in a single or multi-coat layer, optionally by pre-grit blasting to the substrate to increase adhesion. Spraying and roller coating to form each layer is the most convenient coating method, depending on the shape of the substrate being coated. Other known coating methods may also be used, including dipping and coil coating.

  Surprisingly, the presence of sizing on the glass makes the LCP itself less thermally stable.

  In the examples, LCP1 is prepared from 4,4′-biphenol / terephthalic acid / isophthalic acid / 4-hydroxybenzoic acid or derivatives thereof (100/95/5/100 mole parts) and has a melting point of about 400 ° C. .

  LCP2 is prepared from hydroquinone / 4,4′-biphenol / terephthalic acid / 2,6-naphthalenedicarboxylic acid / 4-hydroxybenzoic acid (50/50/60/40/320 mole parts) and has a melting point of about 335 ° C. Had.

  In Examples 1-3, the sizing chopped glass fiber (original length of about 5.0 mm before compounding) of the proprietary patent is TP-78, the non-sized coated milled glass is REV-4, both Both were manufactured by Nippon Sheet Glass Co., Ltd., Takachaya, Tsu, Mie, Japan.

(Example 1)
LCP1 is used to feed the raw material to a Werner and Pfleiderer ZSK-40 40mm twin-leaf twin screw extruder, the temperature of the melt leaving the extruder is about 410 ° C. Was set as follows. Square cups (60 mm × 60 mm × 30 mm height, wall thickness 2 mm) were molded on an Angel 1450 injection molding machine with a clamping force of about 145 tons. The melt temperature was about 410 ° C and the mold temperature was about 80 ° C. The composition (weight percentage of total composition) is shown in Table 1 along with measured weight loss over 12 weeks during aging in a 280 ° C. air circulating oven. Note that the weight loss in sizing glass is much higher than the estimated amount of sizing in the composition, and that in this test sizing seems to make the LCP itself less thermally stable. The weight loss percentages in Table 1 are based on the weight of the total composition.

(Examples 2-3)
The composition LCP used contained 60% LCP and 40% glass fiber. The LCP had a composition of 4,4′-biphenol / terephthalic acid / isophthalic acid / 4-hydroxybenzoic acid, 100/95/5/100 mole parts. Two types of plaques were made and used. The first type uses LCP composition pellets that have been heat-treated (from 23 to 250 ° C. for 1 hour, then 2 hours at 250 ° C., then 250 ° C. to 350 ° C. for 7 hours), which is then treated with plaque Injection molded. The second type used heat treatment (from 23 to 200 ° C. at 10 ° C./min, then from 200 to 290 ° C. at 1 ° C./min for 3 hours at 290 ° C.) for the test specimen after injection molding. The heat treatment was used to reduce the bulge as discussed in the technical background of this application. Plaques were formed by injection molding at a barrel temperature of 430 ° C and a melt temperature of 428 ° C.

Some of the plaques were grit blasted to increase adhesion as described. The grit blasting was performed using a pressure of 300 kPa (3 bar) and 80 mesh aluminum oxide particles. Typical surface roughness after grit blasting was 4 ± 0.3 μm _RA . Although not used in these examples, chemical etching may also be used to roughen such surfaces.

The primers and non-stick topcoat used in this study are listed in Table 2. All of these are available from the assignee of the present patent (Delaware, USA, 1999, Wilmington, DE 11989, USA). The resin is abbreviated as follows:
FEP-Teflon (registered trademark) FEP (copolymer of tetrafluoroethylene and hexafluoropropylene)
PFA-Teflon (registered trademark) PFA (copolymer of tetrafluoroethylene and perfluoro (propyl vinyl ether))
PAI-poly (amide-imide)
PES-polyethersulfone

  Adhesion was evaluated by (finger) nail adhesion (NA), post water (finger) nail adhesion (PWNA) and post water adhesion (PWA). In the nail adhesion test, a small scuff was made on the coating using a scalpel. The fingernail was then used to scrape or remove the coating from the scalpel edge of the surgical knife. Report nail mark length in mm. A nail mark length of 0 mm represents excellent adhesion. The PWNA test is performed similarly except that the coated LCP is exposed to boiling water for 15 minutes and cooled before the nail test. The PWA test is a variation of the ASTM-D-3359 (ISO 2409) adhesion test in which the cross-hatched coating is exposed to boiling water for 20 minutes followed by 3M Scotch® brand 898 tape (3M Company, It was subjected to tape pulling using St. Paul, Minnesota (3M Company, St. Paul, MN, USA).

(Example 2)
The LCP plaques were optionally grit blasted to roughen the surface and spray painted with a primer composition as shown in Table 3. After baking at 220 ° C., the plaques were overcoated with the topcoat composition shown in Table 3 and baked at 335 ° C. for 45 minutes. The adhesion of the coating was tested using NA and PWNA test procedures. The results are also shown in Table 3.

(Example 3)
LCP plaques were optionally spray painted with the primer composition of Table 4. After baking at 218 ° C. for 15 minutes, the plaques were overcoated with the topcoat composition of Table 4 and baked at 316 ° C. for 10 minutes. The adhesion of the coating was tested using the PWA adhesion test as described above.

(Example 4 and Comparative Example A)
A composition containing LCP2 was prepared in a twin screw extruder while the glass used was added by a side feeder. Compositions are obtained from 55.8 (wt) percent LCP2, 4% carbon black concentrate, 40% glass, and Clariant, Inc. 28205, North Carolina, USA (Clariant Corp., Charlotte, NC 28205, USA). Possible 0.2% Licowax® PE190 polyethylene wax. For Example 4, the glass used was OCF739 milled glass, but for Comparative Example A, OCF408 fiber glass (Fiberglass) was used. Both are available from Owens Corning Fiberglass, Owens Corning Fiberglass, Toledo, OH, USA. The milled glass was bare (has no sizing), but the fiberglass was sized. Bars of these compositions (1.6 mm thickness, other dimensions according to bars for bending tests according to ASTM method D790) were injection molded. These bars were plunged into molten metal (solder) maintained at approximately 270 ° C. and held in the bath for a specified time. The rod was then removed, allowed to cool and visually inspected. All Comparative Example A bars that were in the metal bath for 1, 3, 6, and 9 minutes were swollen. The bar of Example 4 immersed for the same time did not swell.

Claims (2)

A method of forming a conductive path in an electrical or electronic device by a solder bath method, the device comprising:
(A) a glass filler without sizing;
(B) a composition comprising a thermotropic liquid crystal polymer having a melting point of 300 ° C. or higher ,
An improvement is that when other polymers than one or more thermotropic liquid crystal polymers are present in the composition, the polymer contains a composition comprising less than 25 weight percent of the composition. A method characterized by comprising. (A) a glass filler without sizing;
(B) a thermotropic liquid crystal polymer having a melting point of 300 ° C. or higher ,
A solder bath process that reaches a temperature of 260 ° C. when other polymers other than one or more thermotropic liquid crystal polymers are present in the composition, the polymer comprising less than 25 weight percent of the composition An electrical or electronic device having one or more conductive paths manufactured at least in part.