Aromatic polyester and molded article using the same

An aromatic polyester having the following structural units, (1), (2), (3), (4) and (5), wherein the amount of the structural unit (1) is 30 to 50% based on the total of the all structural units, (2)/(3) is more than 2.78 and smaller than 4, (4)/(5) is more than 1.0 and smaller than 1.5, and {(2)+(3)}/{(4)+(5)} is from 0.9 to 1.1: ##STR1## wherein Ra, Rb, Rc, Rd, Re and Rf each independently represents a lower alkyl group, lower alkoxy group, phenoxy group, phenyl group or halogen atom, and l, m, n, o, p and q each independently represents an integer from 0 to 3, is provided; and the aromatic polyester has excellent molding property and a molded article made from this polyester has excellent soldering temperature resistance and rigidity.

BACKGROUND OF THE INVENTION
 The present invention relates to an aromatic polyester having the following
 structural units (1) to (5) and a molded article using the aromatic
 polyester.
 ##STR2##
 wherein Ra, Rb, Rc, Rd, Re and Rf each independently represents a lower
 alkyl group, lower alkoxy group, phenoxy group, phenyl group or halogen
 atom, and n represents an integer from 0 to 3.
 Conventionally, aromatic polyesters having the above-described structural
 units (1), (2), (3), (4) and (5) have been known. Particularly, aromatic
 polyesters which contain industrially easily available structural unit (2)
 more than diol structural unit (3) are proposed. For example, aromatic
 polyesters have been proposed in which the ratio of (2)/(3) (=molar ratio
 of (2) to (3), that is, ratio of number of unit (2) to number of unit (3)
 in the aromatic polyester. Hereinafter in this specification, each (1),
 (2), (3), (4) and (5) sometimes refer the structural units (1), (2), (3),
 (4) and (5), respectively, and the molar ratio of a unit to another unit
 is indicated by using b "/".) is 1 or more and 12 or smaller, and (4)/(5)
 is 0 or more and 1 and smaller (Hereinafter, this aromatic polyester is
 referred to as "Polyester I".). Specifically, an aromatic polyester in
 which (2)1/(3) is 5.00 and (4)/(5) is 0.31 Is disclosed(JP-A-60-38425).
 Besides this, as aromatic polyesters having more improved molding property
 than Polyester I, those in which the ratio of (4)/(5) is 1.04 or more and
 19 or smaller, and (2)/(3) is 0.1 or more and 2.67 and smaller has been
 proposed (Hereinafter, this aromatic polyester is referred to as
 "Polyester II".). Specifically, an aromatic polyester in which (2)/(3) is
 1.00 and (4)/(5) is 2.33 is disclosed(JP-A-63-57633).
 In recent years, since aromatic polyesters are used for electric and
 electronic components, those which give molded articles having excellent
 solder temperature resistance and rigidity(flexural elastic modulus) are
 demanded. However, there are problems that molded articles made from
 Polyester I exhibit low solder temperature resistance, and Polyester II
 exhibit low rigidity.
 SUMMARY OF THE INVENTION
 Under such circumstances, the present inventors have intensively studied to
 find an aromatic polyester containing unit (2) more than unit (3) and
 giving molded articles having excellent solder temperature resistance and
 rigidity. As the results, they have found that an aromatic polyester
 having a specific composition of (1), (2), (3), (4) and (5) not only has
 good molding property, but also gives a molded articles having remarkably
 excellent solder temperature resistance and rigidity. The present
 invention has thus been completed.
 The present invention provides an aromatic polyester having the following
 structural units, (1), (2), (3), (4) and (5), wherein the amount of the
 structural unit (1) is 30 to 50based on the total of the all structural
 units, (2)/(3) Is more than 2.78 and smaller than 4, (4)/(5) is more than
 1.0 and smaller than 1.5, and {(2)+(3)}/{(4)+(5)} is from 0.9 to 1.1:
 ##STR3##
 wherein Ra, Rb, Rc, Rd, Re and Rf each independently represents a lower
 alkyl group, lower alkoxy group, phenoxy group, phenyl group or halogen
 atom, and l, m, o, p and q each independently represents an integer from 0
 to 3.
 PREFERRED EMBODIMENT OF THE INVENTION
 In the aromatic polyester of the present invention, the structural unit (1)
 is usually derived from p-hydroxybenzoic acids represented by the
 following general formula (6):
 ##STR4##
 wherein, each Ra independently represents a lower alkyl group, lower alkoxy
 group, phenoxy group, phenyl group or halogen atom; 1 represents an
 integer from 0 to 3; R.sup.1 represents a hydrogen atom or lower acyl
 group; and R.sup.2 represents a hydroxyl group, lower alkoxy group,
 phenoxy group or halogen atom.
 Examples of the lower alkyl group include a methyl group, ethyl group and
 propyl group. Examples of the lower alkoxy group include a methoxy group,
 ethoxy group and t-butoxy group. Examples of the halogen atom include
 chlorine and bromine. 1 represents an integer from 0 to 3, and an
 unsubstituted group in which 1 is 0 is preferable
 Examples of the lower acyl group include an acetyl group, propionyl group
 and benzoyl group.
 Typical examples of the p-hydroxybenzoic acids include p-hydroxybenzoic
 acid, methyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, p-acetoxybenzoic
 acid, methyl p-acetoxybenzoate, ethyl p-acetoxybenzoate, propyl
 p-hydroxybenzoate, phenyl p-hydroxybenzoate and benzyl p-hydroxybenzoate.
 Among other, p-hydroxybenzoic acid and p-acetoxybenzoic acrid are
 preferred.
 The structural unit (2) is usually derived from hydroquinones represented
 by the following general formula (7):
 ##STR5##
 wherein each Rb independently represents a lower alkyl group, lower alkoxy
 group, phenoxy group, phenyl group or halogen atom; m represents an
 integer from 0 to 3; and R.sup.3 and R.sup.4 each independently represents
 a hydrogen atom or lower acyl group. Typical examples of the hydroquinones
 include hydroquinone and 1,4-diacetoxybenzene.
 The structural unit (3) is usually derived from 4,4'-dihydroxybiphenyls
 represented by the following general formula (8):
 ##STR6##
 wherein Rc and Rd each independently represents a lower alkyl group, lower
 alkoxy group, phenoxy group, phenyl group or halogen atom: n and
 each:independently represents an integer from 0 to 3: and R.sup.5 and
 R.sup.6 each independently represents a hydrogen atom or lower acyl group.
 Examples of the 4,4'-dihydroxybiphenyls include 4,4'-dihydroxybiphenyl and
 4,4'-diacetoxybiphenyl.
 The structural unit (4) is usually derived from terephthalic acids
 represented by the following general formula (9);
 ##STR7##
 wherein each Re independently represents a lower alkyl group, lower alkoxy
 group, phenoxy group, phenyl group or halogen atom; p represents an
 integer from 0 to 3; and R.sup.7 and R.sup.8 each independently represents
 a hydroxyl group, lower alkoxy group, phenoxy group or halogen atom.
 Typical examples of the terephthalic acids include terephthalic acid and
 dimethyl terephthalate.
 The structural unit (5) is usually derived from isophthalic acids
 represented by the following general formula (10):
 ##STR8##
 wherein, each Rf independently a lower alkyl group, lower alkoxy group,
 phenoxy group, phenyl group or halogen atom; q represents an integer from
 0 to 3; and R.sup.9 and R.sup.10 each is independently represents a
 hydroxyl group, lower alkoxy group, phenoxy group or halogen atom.
 Typical examples of the isophthalic acids include isophthalic acid and
 dimethyl isophthalate.
 In the aromatic polyester of the present invention, the content of the
 structural unit (1) Is usually from about 30 to 50%, preferably from about
 35 to 50% based on the total of the all structural units. In this
 specification, "%" indicating the content of a structural unit is molar
 basils, that is, based on the number of the structural unit, not based on
 the weight of the structural unit, unless otherwise mentioned.
 When the content of the structural unit (1) is less than 30%, molding
 property of the aromatic polyester tends to deteriorate, or rigidity and
 heat resistance of the molded article made from the polyester tends to
 drop. When the content of the structural unit (1) exceeds 50%, molding
 property and solder temperature resistance of the aromatic polyester tends
 to deteriorate.
 In the aromatic polyester of the present invention, (2)/(3) is more than
 2.78 and smaller than 4.
 When (2)/(3) exceeds the upper limit of the above range, solder temperature
 resistance of the molded article made from the aromatic polyester tends to
 drop. When it is not more than 2.78, rigidity of the molded article tends
 to drop.
 In the aromatic polyester of the present invention, (4)/(5) is more than
 1.0 and smaller than 1.5.
 When (4)/(5) is less than 1.0, rigidity of the molded article made from the
 aromatic polyester tends to drop. When it is not smaller than 1.5, molding
 property and solder temperature resistance of the aromatic polyester tends
 to deteriorate.
 In the present invention, {(2)+(3)}/{(4)+(5)} is about 0.9 to 1.1.
 The method for producing the aromatic polyester of the present invention is
 not particularly restricted. As an example of the method, Japanese Patent
 Publication No. 2838119 discloses a method in which a polycondensate of
 compounds represented by the formulae (6), (7), (8), (9) and (10) is taken
 out in a melted condition, then, is subjected to a solid phase
 polymerization. More specifically, a method is exemplified in which a
 compound having a hydroxyl group is acylated with an acylating agent such
 as acetic anhydride and the like, then polycondensed together with a
 carboxylic compound while distilling oft the unreacted acylating agent,
 by-produced acids and the like; and, thereafter, the resulting
 slightly-polycondensed compound is recovered in a melted condition, cooled
 to solidify, pulverized, and then subjected to a solid phase
 polymerization under reduced pressure or in an inert gas atmosphere at
 usually from about 230 to 370.degree. C.
 In the polycondensation of the compounds represented by the formulae (6),
 (7), (8), (9) and (10), (6)/[(6)+(7)+(8)+(9)+(10)] is preferably from
 about 30 to 50%; (7)/(8) is more than 2.78 and smaller than 4; (9)/(10) is
 more than 1.0 and smaller than 1.5; and {(7)+(8)}/{(9)+(10)} is about 0.9
 to 14, wherein (6), (7), (8), (9) and (10) represent molar amounts of the
 compounds of formulae (6), (7), (8), (9) and (10), respectively.
 A catalyst may be used for accelerate the above-described polycondensation
 reaction. As the catalyst, metal oxides and organometal salts are
 exemplified. Specific examples thereof include oxides, acetates and
 oxalates of germanium, tin, titanium, antimony, cobalt and manganese.
 The flow initiation temperature of the aromatic polyester in the present
 invention is usually from about 250 to 400.degree. C., preferably from
 about 270 to 370.degree. C.
 The flow initiation temperature herein referred to is a temperature at
 which the melt viscosity is 48000 poise (4800Pa.multidot.s) using a
 capillary typerheometer equipped with a dice having an internal diameter
 of 1 mm and a length of 10 mm and the aromatic polyester being extruded
 through a nozzle at a temperature raising speed of 4.degree. C./minutes
 under a load of 100 kg/cm.sup.2 (9.807MPa).
 A molded article of the present invention is obtained by compounding the
 above-described aromatic polyester with inorganic fillers and the like, if
 necessary, and molding the mixture.
 Examples of the inorganic fillers include glass fiber such as milled glass
 fiber and chopped glass fiber; inorganic fillers such as a glass bead,
 hollow glass sphere, glass powder, mica, talc, clay, silica, alumina,
 potassium titanate, wollastonite, calcium carbonate including heavy,
 light, colloidal and the like, magnesium carbonate, basic magnesium
 carbonate, sodium sulfate, calcium sulfate, barium sulfate, calcium
 sulfite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide,
 calcium silicate, silica sand, silica stone, quartz, titanium oxide, zinc
 oxide, iron oxide graphite, molybdenum, asbestos, silica alumina fiber,
 alumina fiber, gypsum fiber, carbon fiber, carbon black, white carbon,
 diatomaceous earth, bentonite, cellite, shirasu and graphite; and metal or
 non-metal whiskers such as potassium titanate whisker, alumina whisker,
 aluminum borate whisker, silicon carbide whisker and silicon nitride
 whisker. Among them, glass fiber, glass powder, mica, talc, carbon fiber
 and the like are preferable.
 Two or more kinds of above-described inorganic fillers may be combined and
 compounded into the molded article of the present invention. The amount of
 the inorganic filler to be compounded into the molded article is usually
 from about 0 to 400 parts by weight based on 100 parts by weight of the
 aromatic polyester.
 Inorganic fillers subjected to a surface treatment may also be used.
 Examples of the surface treatment method include a method in which a
 surface treatment agent is adsorbed on the surface of an inorganic filler,
 and a method is in which a surface treatment agent is added in kneading an
 aromatic polyester with an inorganic filler.
 Examples of the surface treatment agent include reactive coupling agents
 such as silane-based coupling agents, titanate-based coupling agents and
 borane-based coupling agents, and lubricants such as higher fatty acids,
 higher fatty esters, higher fatty metal salts and fluorocarbon-based
 surfactants.
 The molded article of the present invention may also contain additives,
 thermoplastic resins and the like. Examples of the additive include
 releasing improving agents such as fluorine resins and metal soaps,
 nucleating agents, antioxidants, stabilizers, plasticizers, lubricants,
 coloring inhibitors, coloring agents, ultraviolet ray absorbers,
 antistatic agents and flame retardants.
 Examples of the thermoplastic resin include polycarbonate resin, polyamide
 resins, polysulfone resins, polyphenylene sulfide resins, polyphenylene
 ether resins, polyether ketone resins and polyether imide resins.
 As the method for producing a molded article, following methods (a), (b),
 (c) and (d) are exemplified.
 (a) Raw materials such as an aromatic polyester, an inorganic filler, an
 additive etc. are put into a kneader such as a single screw extruder, twin
 screw extruder, banbury mixer, roll, brabender, kneaderand the like, then,
 melt-kneaded. The melt-kneaded product is fed into a molding machine such
 as an extrusion molding machine, injection molding machine, compression
 molding machine and blow molding machine to conduct molding.
 (b) Raw materials are pre-mixed using a mortar, henschell mixer, ball mill,
 ribbon blender and the like. Then, melt-kneading and molding are conducted
 as in (a).
 (c) Raw materials are added into a reaction vessel and mixed.
 (d) Raw materials are fed into a molding machine, and molded while mixing
 in melted condition.
 The molded article of the present invention can be molded into various
 forms including fiber, film or the like.
 Due to its excellent molding property, mechanical property, electrical
 property, chemical resistance, heat resistance and oil resistance, it can
 be applied to mechanical parts such as gears, bearings and motor parts,
 electric and electronic parts such as switches, coil bobbins, relays,
 connector and sockets, business and information appliance parts such as
 printers, copying machines, facsimiles, video decks, video cameras, floppy
 disk drives, hard disk drives, CD-ROM drives and photomagnetic disk
 drives, semiconductor production process-related parts such as IC trays
 and wafer carriers, cooking appliances such as microwave cocking pans and
 heat resistant table wares for oven, large scale molder articles and
 molded articles having complicated forms, and the like
 The molded article of the present invention can be molded into films or
 sheets and can be used as parts for displays, electric insulation films,
 films for flexible circuit board, wrapping films, films for recording
 medium, and the like.
 Moreover, the molded articles molded in the form of fibers such as
 continuous fibers, short fibers and pulp can be used as clothes, heat
 resistant insulation material, reinforcing materials for FRP, rubber
 reinforcing materials, ropes, cables, non-woven cloth and the like.

The following examples further illustrate the present invention in more
 detail, but do not limit the scope of the invention. "Parts" in the
 examples and comparative examples is weight basis unless otherwise
 mentioned.
 EXAMPLE 1
 Production of an Aromatic Polyester
 Into a vessel equipped with a reflux condenser, thermometer,
 nitrogen-introducing tube and stirring rod were charged 525 parts (38% by
 mole) of p-hydroxybenzoic acid, 273 parts (24.8% by mole) of hydroquinone.
 116 parts (6.20% by mole) of 4,4'-dihydroxybiphenyl, 281 parts (16.91% by
 mole) of terephthalic acid, 234 parts (14.09% by mole) of isophthalic acid
 and 1123 parts (110% by mole) of acetic anhydride. Then, the mixture was
 heated to about 140.degree. C., and stirred for 3 hours under reflux
 condition. Thereafter, the acetic acid was distilled off while heating up
 to about 320.degree. C., and the mixture was further kept at about
 320.degree. C. for 1 hour to obtain 1246 parts of a prepolymer.
 The resulted prepolymer was cooled, then, ground by a grinder.
 Subsequently, it was put In a hot air circulation type oven, and the gas
 phase temperature in the oven was raised to 250.degree. C. under nitrogen
 atmosphere. Further, the gas phase temperature was raised from 250.degree.
 C. to 280.degree. C. over 5 hours, then, kept at 280.degree. C. for 3
 hours to obtain 1240 parts of a polyester having a flow initiation
 temperature of 315.degree. C.
 Production of Molded Article
 600 Parts of the aromatic polyester obtained above and 400 parts of chopped
 glass fiber (manufactured by Asahi FiberGlass K. K., CS03JAPx-1) were
 mixed by a henshell mixer, and granulated using a twin screw extruder
 (manufactured by Ikegai Corp., type PCM-30) at a cylinder temperature of
 340.degree. C. to obtain pellet.
 The above-described pellet was dried at 120.degree. C. for 3 hours, then,
 injection-molded using an injection molding machine (manufactured by
 Nissei Plastic Industrial Co., Ltd. PS40E5ASE) at a cylinder temperature
 of 340.degree. C. and a mold temperature of 130.degree. C. to obtain a
 test piece of 12.7 mm.times.6.4.times.mm.times.127 mm.
 EXAMPLE 2-4 AND COMATIVE EXAMPLES 1-11
 The same procedure, Production of an aromatic polyester and Production of
 molded article, was conducted as in Example 1 except that the composition
 of (1) to (5) (% by mole), (2)/(3) and (4)/(5) were changed as shown in
 Table 1.
 In Table 1, each compound used is indicated by name is of the structural
 unit, that is, (1), (2), (3), (4) or (5), derived from the compound, as
 shown below.
 (1) p-Hydroxybenzoic acid
 (2) Hydroquinone
 (3) 4,4'dihydroxybiphenyl
 (4) Terephthalic acid
 (5) Isophthalic acid
 Physical properties of the molded articles obtained in Examples 1-4 and
 Comparative examples 1-5 are shown in Table 1.
 Measuring Method
 Physical properties shown in Table 1 were measured according to the
 following methods.
 Plexural Elastic Modulus
 Using the test piece of 12.7 mm.times.6.4 mm.times.127 mm obtained in
 Examples and Comparative examples as above, Flexural elastic modulus was
 measured according to ASTM D790.
 Solder Resistant Temperature
 According to the similar manner to the above method for obtaining a test
 peace in Example or Comparative example, dumbbell shape test pieces were
 obtained (JIS K7113 (1/2)). Each test piece was dipped in a soldering bath
 kept at a temperature of one of every 5.degree. C. from 270.degree. C. to
 300.degree. C. for 60 seconds. Solder resistant temperature is the highest
 temperature at which no distortion of the test piece or blister (swelling
 by the inner generated gas.) was observed.
 TABLE 1
 (1)
 Examples
 1 2 3 4
 Composition
 % by mole
 (1) 38.00 40.00 40.00 40.00
 (2) 25.60 23.08 22.22 23.08
 (3) 6.40 6.92 7.78 6.92
 (4) 16.36 16.36 16.36 17.50
 (5) 13.64 13.64 13.64 12.50
 Ratio
 by mole
 (2)/(3) 4.00 3.34 2.86 3.34
 (4)/(5) 1.20 1.20 1.20 1.40
 Molding property good good good good
 Flexural elastic 16500 15400 14800 16000
 modulus (Mpa)
 Solder resistant 295 295 290 295
 temperature (.degree. C.)
 (2)
 Comparative examples
 1 2 3 4 5
 Composition
 % by mole
 (1) 56.00 45.00 60.00 56.00 56.00
 (2) 15.17 22.90 16.70 11.00 13.00
 (3) 6.83 4.60 3.30 11.00 9.00
 (4) 13.00 13.00 3.30 15.50 12.00
 (5) 9.00 14.50 16.70 6.50 10.00
 Ratio
 by mole
 (2)/(3) 2.22 4.98 5.06 1.00 1.44
 (4)/(5) 1.44 0.90 0.20 2.38 1.20
 Molding property not good good good good
 good
 Flexural elastic -- 12400 18400 13400 12400
 modulus (Mpa)
 Solder resistant -- &lt;230 &lt;230 310 295
 temperature (.degree. C.)
 (3)
 Comparative examples
 6 7 8 9 10 11
 Composition
 % by mole
 (1) 25 55 40 40 40 40
 (2) 28.85 17.31 25 21.43 23.08 23.08
 (3) 8.65 5.19 5 8.57 6.92 6.92
 (4) 20.45 12.27 16.36 16.36 18.5 12.35
 (5) 17.05 10.23 13.64 13.65 11.5 17.65
 Ratio
 % by mole
 (2)/(3) 3.34 3.34 5.00 2.50 3.34 3.34
 (4)/(5) 1.20 1.20 1.20 1.20 1.61 0.70
 Molding property good good good good not good
 modulus (Mpa) good
 Flexural elastic 12200 17600 17300 13500 -- 12800
 modulus (Mpa)
 Solder resistant 290 &lt;230 230 295 -- 270
 temperature (.degree. C.)
 The aromatic polyester of the present invention has excellent molding
 property. Further, a molded article made from this polyester has excellent
 soldering temperature resistance and rigidity. Therefore, it can be
 applied to large scale molded articles, electric and electronic parts,
 precision instruments, and the like.