JP2003034732A - Polybutylene terephthalate resin foamed molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foamed molded article having a fine and uniform foamed state without impairing the inherent characteristics of a polybutylene terephthalate resin. SOLUTION: The foamed molded article is obtained by introducing and injection-molding the polybutylene terephthalate resin and a supercritical fluid in an injection molding machine wherein the relative viscosity ηr and the concentration of the terminal carboxy group [COOH] of the polybutylene terephthalate resin satisfy the formula: 0.30<ηr/([COOH]×10<5> )<2.50...(A).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polybutylene terephthalate resin foam-molded article having a fine and uniform foaming state without impairing the original properties of the polybutylene terephthalate resin.

[0002]

2. Description of the Related Art Polybutylene terephthalate resin has been widely used for automobiles, electric / electronics, etc. by utilizing its excellent moldability, mechanical properties, durability, chemical resistance, abrasion resistance and the like. There is.

However, since the polybutylene terephthalate resin has a smaller specific gravity than a metal, it is often used as a metal substitute for the purpose of weight reduction, and there is a strong demand for further weight reduction. A method for producing a uniform and fine foam molded article using a polybutylene terephthalate resin has not been known yet.

Generally, as a method for obtaining a foamed molded product, for example, foaming with an organic or inorganic thermally decomposable foaming agent, foaming with a volatile foaming agent, etc. are known. , Industrial Research Council, 1997, pp. 398-400. However, these methods have a problem that it is difficult to foam the polybutylene terephthalate resin finely and uniformly, and as a result, the original characteristics of the polybutylene terephthalate resin cannot be exhibited.

On the other hand, in recent years, research and development of foam molding technology using a supercritical fluid has been actively conducted, and a foam molded article is produced by introducing nitrogen gas or carbon dioxide gas in a supercritical state together with resin into an injection molding machine. Has been developed for injection molding.

For example, a foam obtained by continuously introducing a supercritical fluid into a resin material to foam the material (US Pat. No. 4,473,665, US Pat. No. 5,158,986, US Pat. No. 5,334,356, Japanese patent No. 2625576). ,
And a method for obtaining a foam-molded article by introducing a supercritical fluid during injection molding of a resin composition consisting of 50 to 99 parts by weight of a styrene resin and 1 to 50 parts by weight of a polypropylene resin (JP-A-10-24436). ) Is known.

However, the above-mentioned "Practical Plastic Molding Encyclopedia", Industrial Research Committee, 1997, 398-
The method described on page 400 has a problem that it is difficult to form a fine and uniform foamed state of the polybutylene terephthalate resin, and as a result, the original characteristics of the polybutylene terephthalate resin cannot be exhibited.

Further, the above-mentioned US Pat. No. 4,473,665,
US Pat. No. 5,158,986, US Pat. No. 5,334,356
Japanese Patent No. 2625576 and Japanese Patent Laid-Open No. 10-
Japanese Patent No. 24436 describes a foam injection molding method using a supercritical fluid, but none of them mentions foaming of a polybutylene terephthalate resin.

Incidentally, in the above-mentioned US Pat. No. 4,473,665, page 3, lines 21 to 23 and claim 23, polyester is mentioned as one of the resin materials to which the technique can be applied. No mention is made of structural polyesters being suitable.

Also, page 6 lines 4 to 15 of the above-mentioned US Pat. No. 5,334,356 and the above-mentioned US Pat. No. 5,158,98.
It is described on page 6, lines 4 to 15 of No. 6 that modified PET (PETG) in which glycol is modified as a copolymerization component can be used, but use of other polyester resins is completely described. Not not.

Further, on page 11, lines 26 to 35 of the above-mentioned Japanese Patent No. 2625576, glycol-modified PET is contained.
Although it is described that (PETG) can be used, there is no description regarding foaming of polybutylene terephthalate resin.

As described above, a method for obtaining an injection-foamed molded article having a fine and uniform foaming state without impairing its characteristics by using the polybutylene terephthalate resin is described.
The reality is that it has not been discovered so far.

[0013]

SUMMARY OF THE INVENTION The present invention has been achieved as a result of studying the solution of the above-mentioned problems of the prior art.

Therefore, an object of the present invention is to provide a polybutylene terephthalate resin foam-molded article having a fine and uniform foaming state without impairing the original properties of the polybutylene terephthalate resin.

[0015]

As a result of studies to solve the above problems, the present inventors have used a polybutylene terephthalate resin having a ratio of relative viscosity and terminal carboxyl group concentration within a specific range, The inventors have found that a polybutylene terephthalate resin foam-molded product obtained by introducing this and a supercritical fluid into an injection molding machine and performing injection molding meets the above-mentioned object, and arrived at the present invention.

That is, the polybutylene terephthalate resin foam-molded product of the present invention is a polybutylene terephthalate resin foam-molded product obtained by introducing a polybutylene terephthalate resin and a supercritical fluid into an injection molding machine and performing injection molding. The polybutylene terephthalate resin satisfies the following formula (A).

0.30 <ηr / ([COOH] × 10 ⁵ ) <2.50 ... (A) (where ηr is the relative viscosity of the polybutylene terephthalate resin, and [COOH] is the polybutylene terephthalate resin. The respective terminal carboxyl group concentrations (unit: mol / g) are shown.) In the polybutylene terephthalate resin foam-molded article of the present invention, the polybutylene terephthalate resin contains an inorganic filler, and the inorganic filler is Glass fiber and / or carbon fiber,
Both are mentioned as preferable conditions.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. In the present invention, “weight” means “mass”.

The polybutylene terephthalate resin used in the present invention is a polymer obtained by a polycondensation reaction containing terephthalic acid or an ester-forming derivative thereof and 1,4-butanediol or an ester-forming derivative as a main component. And satisfies the following general formula (A).

0.30 <ηr / ([COOH] × 10 ⁵ ) <2.50 (A) where ηr is the relative viscosity of the polybutylene terephthalate resin, and more specifically, polybutylene terephthalate 0.125 g of resin is dissolved in 25 mL of o-chlorophenol, and the relative viscosity is measured at 25 ° C. using an Ubbelohde viscometer.

[COOH] is the terminal carboxyl group concentration of the polybutylene terephthalate resin. More specifically, 1.00 g of the polybutylene terephthalate resin is added to 50 mL of a mixed solvent of o-cresol / chloroform = 2/1 volume ratio. After dissolution, thymol blue is added and the terminal carboxyl group concentration is measured when titrated with an ethanol solution of 1 / 25N potassium hydroxide. The unit is m
ol / g.

If the ratio of the relative viscosity ηr of the polybutylene terephthalate resin to the terminal carboxyl group concentration [COOH] does not fall within the range of the above formula (A), a fine and uniform foaming state cannot be formed. The reason has not been completely clarified, but the viscosity ratio between the polybutylene terephthalate resin and the supercritical fluid and the affinity between the polybutylene terephthalate resin and the supercritical fluid have a great influence on the dispersibility of the supercritical fluid. It is considered that this is due to fine dispersion when the ratio of the relative viscosity and the terminal carboxyl group concentration, which is a parameter corresponding to these two factors, reaches a specific region.

Generally, when the relative viscosity ηr is low, the terminal carboxyl group concentration [COOH] is high, and when the relative viscosity ηr is high, the terminal carboxyl group concentration [COO].
By lowering [H], a polybutylene terephthalate resin suitable for the purpose can be obtained. If the relative viscosity is simply low, the injected supercritical fluid tends to foam in the mold, and bubbles tend to be connected to form a nonuniform and coarse foaming state, but the terminal carboxyl group concentration [COOH] It is presumed that when the value is high, the affinity with the supercritical fluid is increased, so that the foaming in the mold is suppressed to some extent, and as a result, uniform and fine foaming is formed. Further, when the relative viscosity is simply high, the injected supercritical fluid is less likely to foam in the mold, and there is a tendency that a fine foamed state with a sufficient density is not formed, but the terminal carboxyl group concentration [C
It is presumed that when the content of [OOH] is low, the affinity with the supercritical fluid is suppressed, so that foaming in the mold is promoted to some extent, and as a result, uniform and fine foaming is formed.

As long as the above formula (A) is satisfied,
The value of the relative viscosity ηr is not limited, but is usually 1.00 to
The range is 3.00, preferably 1.20 to 2.5
The range is 0, more preferably 1.30 to 2.20.

The value of the terminal carboxyl group concentration [COOH] is not particularly limited as long as the above formula (A) is satisfied, but it is usually 0.2 × 10 ^-5 to 15 × 10 ^-5 mo.
The range is l / g, preferably 0.4 × 10 ⁻⁵ to 10 ×
10 ⁻⁵ mol / g, more preferably 0.5 × 10 ⁻⁵ to 8 × 1
It is in the range of 0 ^-5 mol / g.

Ηr / ([COO in the above equation (A)
H] × 10 ⁵ ) is appropriately controlled depending on the reaction temperature during polymerization, reaction time, presence or absence of solidity, selection of polymerization monomer (dicarboxylic acid or its ester), type of antioxidant during polymerization, and addition amount. can do.

The polybutylene terephthalate resin used in the present invention is, for example, terephthalic acid or its ester-forming component or 1, to the extent that the characteristics are not impaired.
4-butanediol or one of its ester-forming components
You may replace 0 mol% or less with other copolymerization components.

Preferred examples of these polybutylene terephthalate polymers or copolymers are polybutylene terephthalate, polybutylene (terephthalate / isophthalate), polybutylene (terephthalate / adipate), polybutylene (terephthalate / sebacate), polybutylene (terephthalate). / Dodecanoate), polybutylene (terephthalate / 2,6-naphthalate), polybutylene (terephthalate / 2,7-naphthalate), and polybutylene (terephthalate /
1,4-naphthalate) and the like, and these may be used alone or in combination of two or more kinds. Among these, polybutylene terephthalate and polybutylene (terephthalate / dodecanoate) are particularly preferably used from the viewpoint of moldability and mechanical properties. Further, the polybutylene terephthalate resin in the present invention contains an inorganic or organic filler. May be.

As the filler used in the present invention, glass fibers generally used in a reinforced polybutylene terephthalate resin are preferable, but by using various other fibrous or non-fibrous reinforcing materials, the surface of a molded product can be further improved. It is also possible to improve the sex. The fiber diameter and fiber length of the glass fiber are not particularly limited.

Examples of other inorganic fillers include carbon fibers, potassium titanate whiskers, zinc oxide whiskers, aluminum borate whiskers, aramid fibers, alumina fibers, silicon carbide fibers, ceramic fibers, asbestos fibers,
Gypsum fiber, fibrous filler such as metal fiber, wollastonite, zeolite, sericite, kaolin, mica, clay, pyrophyllite, bentonite, asbestos,
Silicates such as talc and alumina silicate, alumina,
Metal oxides such as silicon oxide, magnesium oxide, zirconium oxide, titanium oxide and iron oxide, carbonates such as calcium carbonate, magnesium carbonate and dolomite, sulfates such as calcium sulfate and barium sulfate, magnesium hydroxide and calcium hydroxide, Examples include hydroxides such as aluminum hydroxide, glass flakes, glass beads, ceramic beads, non-fibrous fillers such as boron nitride, silicon carbide and silica, which may be hollow.
It is also possible to use plural kinds of these fillers together.

Further, these fibrous / non-fibrous inorganic fillers are simultaneously or preliminarily used with a coupling agent such as an isocyanate compound, an organic silane compound, an organic titanate compound, an organic borane compound and an epoxy compound. It is preferable to use after treating in terms of obtaining better mechanical properties and appearance of the molded product.

The amount of the filler added is not particularly limited, but is usually 50 to 400 parts by weight, preferably 25 to 300 parts by weight, based on 100 parts by weight of the polybutylene terephthalate resin. Is the range.

Further, in the polybutylene terephthalate resin, other polyester resins and other polymers, additives, crystal nucleating agents, heat-resistant agents and ultraviolet rays may be added according to the required characteristics within the range not impairing the object of the present invention. Stabilizers such as absorbents,
It is also possible to add flame retardants, antistatic agents, plasticizers, lubricants, colorants, coupling agents and the like.

The supercritical fluid used in the present invention includes:
There is no particular limitation as long as it is used in a supercritical state during injection molding. It may be a single substance or a mixture. Generally, an inert gas such as carbon dioxide, nitrogen, argon and helium is used, and carbon dioxide and nitrogen are preferably used. Particularly preferred is carbon dioxide.

The amount of the supercritical fluid injected at the time of injection molding is not particularly limited, but is usually 0.01 to 100 parts by weight, preferably 0.05 to 50 parts by weight with respect to 100 parts by weight of the polybutylene terephthalate resin. And more preferably 0.1 to 30 parts by weight.

The method of injecting the supercritical fluid into the molten polybutylene terephthalate resin during injection molding is not particularly limited, but for example, a method of directly injecting an inert gas in a gaseous state, a method of injecting under pressure, and a reduced pressure And a method of injecting an inert gas in a liquid state or a supercritical fluid state with a plunger pump or the like.

Next, one example of the method for producing the foam-molded article of the present invention will be described below with reference to the schematic configuration diagram of FIG.

First, the polybutylene terephthalate resin pellet A is supplied from the hopper B and heated and melted. An inert gas such as nitrogen or carbon dioxide serving as a supercritical fluid is supplied from a gas cylinder K, pressurized by a booster pump J, and then supplied to a molten polybutylene terephthalate resin. At this time, the inside of the cylinder D is kept at a critical temperature or higher and a critical pressure or higher so that the supplied inert gas maintains a supercritical state and is dissolved and diffused in the molten polybutylene terephthalate resin in a short time. ing.

For example, in the case of nitrogen, the critical temperature is -12.
At 7 ° C, the critical pressure is 3.5 MPa. In the case of carbon dioxide, the critical temperature is 31 ° C and the critical pressure is 7.4 MPa.

In the cylinder, the molten polybutylene terephthalate resin and the inert gas are kneaded by the screw C, and the static mixer E and the diffusion chamber F form a completely compatible state of the molten polybutylene terephthalate resin and the inert gas. Then, it is injected into the cavity H of the mold I through the nozzle G, and the pressure is released to form a fine foam molded article. Here, it is also possible to control the foaming diameter by loading counter pressure into the mold, and an inert gas may be supplied from the counter pressure gas cylinder L as necessary. The pressure at that time is not particularly limited, but is preferably in the range of 0.5 to 15 MPa.

As a method of rapidly lowering the pressure in the mold to promote foaming, after injecting the molten polybutylene terephthalate resin into the cavity H of the mold I, part or all of the core of the mold is injected. It is also possible to retreat to rapidly increase the internal volume of the mold.

The polybutylene terephthalate resin foam-molded article of the present invention can be applied to all the applications to which the polybutylene terephthalate resin can be applied in general. For example,
Cylinder head cover, timing belt cover, balance shaft gear, oil braking valve, oil level gauge, oil cleaner case, radiator tank, water pump impeller, thermostat housing, cooling fan, intercooler tank, air duct,
Air control valve, air regulator, air flow meter housing, air duct intake, silencer, resonator, exhaust gas pump side seal, exhaust gas valve, carburetor, gasoline injection nozzle, piston valve, carburetor valve, surge tank, fuel filter housing, fuel strainer, fuel Segmental case, canister, EGI tube, solenoid valve, gasoline float, gasoline chamber, fuel check valve, fuel injector, fuel injector connector, fuel injector nozzle cover, fuel filler cap, master cylinder piston, clutch oil reservoir, thrust washer, shift Arm coat Ingu, shift lever knob,
Transmission case, Turkish thrust washer, transmission bush, power steering tank, steering column cover, steering horn pad, steering ball joint, wheel full cap, wheel cap center, wheel center hub cap, brake oil reservoir, brake oil float, brake reservoir cap , Side brake wire protector, radiator grill, front end bumper, rear end bumper, bumper molding, front fender, side mirror stay, side mirror housing, emblem, retractable headlamp cover, electric mirror base, fuel lid, bonnet hood looper, extract grill. , Door, rhino Louvers, door latch covers, door side moldings, outer door handles, pillar louvers, trunk lower back finishers, trunk rear aprons, hatchback slide brackets, license plates, license plate pockets, fuel lids, sunroof frames, side moldings, window pivots, window glass. Slider, window molding, air spoiler, instrument panel core, lid outer, center cluster, switch, upper garnish, lid cluster, meter hood, meter panel, glove box, change lever cover, glove box lid, glove box knob, glove Door outer, ash tray lamp housing, ash tray panel Sun visor bracket, sun visor shaft, sun visor holder, pillar garnish, room mirror stay, regulator handle, door trim, the inside door lock knob, inner lock knob, window regulator handle, window regulator handle knob,
Roof side rail garnish, armrest insert, armrest base, armrest guide, rear shelf side, headrest guide, seat belt tongue plate, seat belt retractor gear, seat belt buckle, seat belt through anchor, lid cluster, safety belt mechanism parts, cooler Sirocco fan, cooler vacuum pump, air conditioner magnet clutch bobbin, air conditioner actuator, compressor valve, air ventilation fin, air conditioner control knob, heater core tank, heater valve,
Generator coil bobbin, generator cover,
Generator bush, circuit board, brush holder, condenser case, regulator case,
Starter lever, starter coil bobbin, starter interval gear, distributor point bush, ignition coil case, ignition coil bobbin, distributor insulating terminal, distributor cap, sleeve bearing, helical gear, vacuum controller, junction box, wire harness connector, relay terminal base Case coil bobbin, fuse box, switch base, relay case, various switch boards, lamp sockets, lamp reflectors, back horn housing, silent gear, power window switch board case, wiper lever, washer motor housing, wiper motor insulator, wiper arm head cover Washer nozzle, wiper arm head, speedometer driven gear, speedometer control meter connector, the rotation sensor, speed sensor, power seat gear housing,
Brush holders, commutators, motor gears, bonnet clips, molding clips, interior clips, bumper clips, band clips for electrical wiring, antenna inner tubes, fenders, spoilers, roof rails, tailgates, bumpers and the like.

In addition, as other uses, casings of personal computers, liquid crystal projectors, mobile devices, mobile phones, etc.,
Examples include mechanical parts such as internal combustion engine applications and electric tool housings, various electric / electronic parts, medical equipment, food containers, household / office supplies, building material-related parts, and furniture parts. The evaluation of various characteristics was performed by the methods described below.

[0044]

EXAMPLES The present invention will be described more concretely with reference to the following examples. The present invention is not limited to the description of these examples. In addition, in the compounding ratios shown in the examples and comparative examples, all "%", unless otherwise noted, means% by weight. [Relative viscosity of polybutylene terephthalate resin (η
r)] Polybutylene terephthalate resin 0.125 g was accurately weighed, dissolved in 25 mL of o-chlorophenol, and measured at 25 ° C. using an Ubbelohde viscometer. [Terminal carboxyl group concentration of polybutylene terephthalate resin] 1.00 g of polybutylene terephthalate resin was accurately weighed and dissolved in 50 mL of o-cresol / chloroform = 2/1 volume ratio mixed solvent, and then thymol blue was added. And titrated with 1 / 25N potassium hydroxide in ethanol. [Injection molding machine] -Maximum mold clamping force 2000 kN-Screw diameter 42 mm (L / D = 28) [Specific gravity] The obtained molded product was used and measured according to ASTM D792. [Mechanical Properties] Tensile Properties: Measured according to ASTM D638. Bending property: Measured according to ASTM D790. [Sledding, sinking] -The obtained molded article was visually evaluated for warping and sinking.

[Reference Example 1] Production of polybutylene terephthalate resin (A-1) 75.5 parts of terephthalic acid, 1,4-butanediol 6
1.4 parts, tetrabutyl titanate 0.05 parts, and monobutyl tin oxide 0.05 parts were charged into a reaction can equipped with a rectification column and a stirrer, and the temperature was gradually raised to 150 ° C to 230 ° C under normal pressure. While carrying out the esterification reaction. Water and tetrahydrofuran generated during the reaction were distilled off through a rectification column to complete the reaction. The obtained esterification reaction product contained 0.05 part toterabutyl titanate, 0.02 part phosphoric acid as an anti-coloring agent, and N, N-hexamethylene bis (3,5-di-t-butyl-) as an antioxidant. 4-hydrocinnamamide) 0.01 part is added, and atmospheric pressure is 0.5 mm.
Reduce the pressure to Hg or less over 50 minutes, then 245 ° C
The temperature was raised to 150 ° C. and the reaction was carried out for 150 minutes to obtain a polybutylene terephthalate resin. The polybutylene terephthalate resin was taken out in a strand form from the lower part of the polymerization vessel and cut into pellets. Relative viscosity ηr of the polybutylene terephthalate resin (A-1) obtained was 1.4.
5, terminal carboxyl group concentration [COOH] = 4.6 × 1
0 ⁻⁵ mol / g, ηr / ([COOH] × 10 ⁵ ) =
It was 0.315.

[Reference Example 2] Production of polybutylene terephthalate resin (A-2) 75.5 parts of terephthalic acid, 1,4-butanediol 6
1.4 parts, tetrabutyl titanate 0.05 parts, and monobutyl tin oxide 0.05 parts were charged into a reaction can equipped with a rectification column and a stirrer, and the temperature was gradually raised to 150 ° C to 230 ° C under normal pressure. While carrying out the esterification reaction. Water and tetrahydrofuran generated during the reaction were distilled off through a rectification column to complete the reaction. The obtained esterification reaction product contained 0.05 part of toterabutyl titanate, 16.4 parts of 1,4-butanediol, and 0.02 phosphoric acid as a coloring inhibitor.
Part, 0.12 parts of N, N-hexamethylene bis (3,5-di-t-butyl-4-hydrocinnamamide) as an antioxidant are added, and the pressure from normal pressure to 0.5 mmHg or less is 50. The pressure was reduced over a period of time, the temperature was further raised to 245 ° C., and the reaction was performed for 150 minutes to obtain a polybutylene terephthalate resin. The polybutylene terephthalate resin was taken out in a strand form from the lower part of the polymerization vessel and cut into pellets. The obtained polybutylene terephthalate resin (A-2) has a relative viscosity ηr = 1.45 and a terminal carboxyl group concentration [COOH] = 2.1 × 10 ⁻⁵ mol.
/ G, ηr / ([COOH] × 10 ⁵ ) = 0.690.

[Reference Example 3] Production of polybutylene terephthalate resin (A-3) 88.2 parts of dimethyl terephthalate, 51.1 parts of 1,4-butanediol, tetraisopropyl titanate 0.0
Charge 6 parts into a reaction can equipped with a rectification column and a stirrer,
The esterification reaction was carried out while gradually raising the temperature from 140 ° C. to 230 ° C. under normal pressure, and the produced methanol was distilled off through the rectification column to complete the reaction. The obtained esterification reaction product contained 12.3 parts of 1,4-butanediol and N, N-hexamethylenebis (3,5-di-t) as an antioxidant.
-Butyl-4-hydrocinnamamide) was added, the pressure was reduced from atmospheric pressure to 0.5 mmHg or less over 60 minutes, the temperature was further raised to 245 ° C., and the reaction was performed for 120 minutes. A butylene terephthalate resin was obtained. The polybutylene terephthalate resin was taken out in a strand form from the lower part of the polymerization vessel and cut into pellets. The obtained pellets were heated at 195 ° C. under a nitrogen gas stream for 7 hours.
Solid-state polymerization was carried out for a period of time. The obtained polybutylene terephthalate resin (A-3) has a relative viscosity ηr = 1.55 and a terminal carboxyl group concentration [COOH] = 0.7 × 10 ⁻⁵ mol /
g, ηr / ([COOH] × 10 ⁵ ) = 2.21.

[Reference Example 4] Production of polybutylene terephthalate resin (A-4) 75.5 parts of terephthalic acid, 1,4-butanediol 6
1.4 parts, tetrabutyl titanate 0.05 parts, and monobutyl tin oxide 0.05 parts were charged into a reaction can equipped with a rectification column and a stirrer, and the temperature was gradually raised to 150 ° C to 230 ° C under normal pressure. While carrying out the esterification reaction. Water and tetrahydrofuran generated during the reaction were distilled off through a rectification column to complete the reaction. To the obtained esterification reaction product, 0.05 part of toterabutyl titanate was added, the pressure was reduced from atmospheric pressure to 0.5 mmHg or less over 50 minutes, the temperature was further raised to 260 ° C., and the reaction was performed for 80 minutes. , Polybutylene terephthalate resin was obtained. The polybutylene terephthalate resin was taken out in a strand form from the lower part of the polymerization vessel and cut into pellets. Relative viscosity ηr of the obtained polybutylene terephthalate resin (A-4) =
1.34, terminal carboxyl group concentration [COOH] = 4.
8 × 10 ⁻⁵ mol / g, ηr / ([COOH] × 1
0 ⁵ ) = 0.28.

[Reference Example 5] Production of polybutylene terephthalate resin (A-5) 88.2 parts of dimethyl terephthalate, 51.1 parts of 1,4-butanediol, tetraisopropyl titanate 0.0
Charge 6 parts into a reaction can equipped with a rectification column and a stirrer,
The esterification reaction was carried out while gradually raising the temperature from 140 ° C. to 230 ° C. under normal pressure, and the produced methanol was distilled off through the rectification column to complete the reaction. The obtained esterification reaction product contained 12.3 parts of 1,4-butanediol and N, N-hexamethylenebis (3,5-di-t) as an antioxidant.
-Butyl-4-hydrocinnamamide) was added, the pressure was reduced from atmospheric pressure to 0.5 mmHg or less over 60 minutes, the temperature was further raised to 245 ° C., and the reaction was performed for 120 minutes. A butylene terephthalate resin was obtained. The polybutylene terephthalate resin was taken out in a strand form from the lower part of the polymerization vessel and cut into pellets. The obtained pellets were subjected to 1 at 195 ° C. under a nitrogen gas stream.
Solid-state polymerization was carried out for 4 hours. The obtained polybutylene terephthalate resin (A-5) has a relative viscosity ηr = 1.65 and a terminal carboxyl group concentration [COOH] = 0.5 × 10 ⁻⁵ mol.
/ G, ηr / ([COOH] × 10 ⁵ ) = 3.30. In all of the following examples, an injection molding machine whose configuration is schematically shown in FIG. 1 was used. The cylinder temperature was set as follows from the hopper side to the nozzle side. -Polybutylene terephthalate resin 225 ° C / 235 ° C / 245 ° C / 240 ° C-Reinforced polybutylene terephthalate resin 245 ° C / 250 ° C / 255 ° C / 250 ° C Also, the molded product is ASTM No. 1 tensile test piece and 50 mm
2 x 50 mm x 30 mm size and 1.5 mm thick box
The seed was molded, the former was used to measure specific gravity, tensile properties and bending properties, and the latter was used to evaluate warpage and sink marks. Regarding the bubble diameter, the center of the tensile test piece was observed with an optical microscope and
The average value of 00 bubbles was taken as the bubble diameter. The mold temperature was 30 ° C. in all cases. Nitrogen or carbon dioxide was used as the supercritical fluid, and the injection amount was 1 g per 100 g of the polybutylene terephthalate resin or the polybutylene terephthalate resin composition.

[Examples 1 to 3] Using the polybutylene terephthalate resins produced in Reference Examples 1 to 3, supercritical foam injection molding was performed using nitrogen gas as the supercritical fluid.
Table 1 shows the evaluation results of the physical properties and appearance of the obtained molded product.

[Examples 4 to 6] Using the polybutylene terephthalate resins produced in Reference Examples 1 to 3, supercritical foam injection molding was performed using carbon dioxide as a supercritical fluid.
Table 1 shows the evaluation results of the physical properties and appearance of the obtained molded product.

[Examples 7 to 9] 30% by weight of glass fiber (fiber diameter 10 µm, 3 mm chopped strand, manufactured by Nippon Electric Glass Co., Ltd.) was melt-kneaded with the polybutylene terephthalate resin produced in Reference Examples 1 to 3. Was used to perform supercritical foam injection molding using nitrogen gas as the supercritical fluid. Table 1 shows the evaluation results of the physical properties and appearance of the obtained molded product.

[Examples 10 to 12] 30% by weight of glass fiber (fiber diameter 10 µm, 3 mm chopped strand, manufactured by Nippon Electric Glass Co., Ltd.) was melt-kneaded with the polybutylene terephthalate resin produced in Reference Examples 1 to 3. Was used to perform supercritical foam injection molding using carbon dioxide as a supercritical fluid. Table 1 shows the evaluation results of the physical properties and appearance of the obtained molded product.

[Examples 13 to 14] A material obtained by melt-kneading 30% by weight of PAN-based carbon fiber (fiber diameter 7 μm, 6 mm chopped strand, manufactured by Toray) with the polybutylene terephthalate resin produced in Reference Example 2 was used. , Supercritical fluid injection molding was performed using nitrogen gas or carbon dioxide gas as the supercritical fluid. Table 1 shows the evaluation results of the physical properties and appearance of the obtained molded product.

[0055]

[Table 1] [Reference Examples 6 to 8] Except that no supercritical fluid was injected,
Injection molding was performed in the same manner as in Examples 1 to 3. That is, it is a normal injection molding. Table 2 shows the evaluation results of the physical properties and appearance of the obtained molded product.

[Reference Examples 9 to 11] Injection molding was performed in the same manner as in Examples 7 to 9 except that the supercritical fluid was not injected. That is, it is a normal injection molding. Table 2 shows the evaluation results of the physical properties and appearance of the obtained molded product.

[Reference Example 12] Injection molding was performed in the same manner as in Example 13 except that the supercritical fluid was not injected.
That is, it is a normal injection molding. Table 2 shows the evaluation results of the physical properties and appearance of the obtained molded product.

[0058]

[Table 2] [Comparative Examples 1 and 2] Supercritical foam injection molding was performed in the same manner as in Example 1 except that the polybutylene terephthalate resin produced in Reference Examples 4 to 5 was used. Table 3 shows the evaluation results of the physical properties and appearance of the obtained molded product.

[Comparative Examples 3 to 4] Supercritical foam injection molding was performed in the same manner as in Example 4 except that the polybutylene terephthalate resin produced in Reference Examples 4 to 5 was used. Table 2 shows the evaluation results of the physical properties and appearance of the obtained molded products.
Shown in.

[Comparative Examples 5 to 6] Supercritical foam injection molding was carried out in the same manner as in Example 7 except that the polybutylene terephthalate resin produced in Reference Examples 4 to 5 was used. Table 3 shows the evaluation results of the physical properties and appearance of the obtained molded products.
Shown in.

[Comparative Examples 7 to 8] Supercritical foam injection molding was carried out in the same manner as in Example 10 except that the polybutylene terephthalate resin produced in Reference Examples 4 to 5 was used.
Table 3 shows the evaluation results of the physical properties and appearance of the obtained molded product.

[Comparative Examples 9 to 10] Supercritical foam injection molding was performed in the same manner as in Examples 13 to 14 except that the polybutylene terephthalate resin produced in Reference Examples 4 to 5 was used. Table 3 shows the evaluation results of the physical properties and appearance of the obtained molded product.

[Comparative Example 11] 100 parts by weight of the polybutylene terephthalate resin produced in Reference Example 2 was dried with 0.5 part by weight of 5-phenyltetrazole ("Cell Tetra" PT5, Eiwa Chemical Industry Co., Ltd.) as a thermally decomposable blowing agent. Other than using the blended material and not the supercritical fluid,
Injection molding was performed in the same manner as in Example 2. Table 3 shows the evaluation results of the physical properties and appearance of the obtained molded product.

Comparative Example 12 Pellets obtained by melt-kneading 70 parts by weight of the polybutylene terephthalate resin prepared in Reference Example 2 with 30 parts by weight of glass fiber (fiber diameter 10 μm, 3 mm chopped strand, manufactured by Nippon Electric Glass Co., Ltd.) In the same manner as in Example 8 except that a material obtained by dry blending 0.5 part by weight of 5-phenyltetrazole (Ewawa Kasei "Certetra" PT5) as a thermally decomposable foaming agent was used and no supercritical fluid was used. And injection molding was performed. Table 3 shows the evaluation results of the physical properties and appearance of the obtained molded products.
Shown in.

[0065]

[Table 3] From the results of Examples 1 to 3, the ratio of the relative viscosity ηr and the terminal carboxyl group concentration [COOH] was 0.30 <ηr /.
([COOH] × 10 ⁵ ) <2.50 Polybutylene terephthalate resin is supercritically foamed by injection molding to obtain a molded product with fine and uniform foam, lightweight and excellent physical properties. I understand. Further, it can be seen that a box-shaped molded product having no warp or sink is obtained.

It can be seen from Examples 4 to 6 that even if the supercritical fluid is changed from nitrogen to carbon dioxide, the same effect as in Examples 1 to 3 using nitrogen can be obtained.

From the results of Examples 7 to 9, the ratio of the relative viscosity ηr and the terminal carboxyl group concentration [COOH] was 0.30 <
By supercritical foam injection molding of a composition in which glass fiber is mixed with a polybutylene terephthalate resin falling within the range of ηr / ([COOH] × 10 ⁵ ) <2.50,
It can be seen that the foamed product is fine and uniform, and a molded product that is lightweight and has excellent physical properties can be obtained. Further, it can be seen that a box-shaped molded product having no warp or sink is obtained.

From the results of Examples 10 to 12, Example 7 using nitrogen even if the supercritical fluid was changed from nitrogen to carbon dioxide gas
It can be seen that the same effect as that of ~ 9 can be obtained.

From the results of Example 13, the ratio of the relative viscosity ηr and the terminal carboxyl group concentration [COOH] was 0.30 <
By supercritical foam injection molding of a composition in which carbon fiber is mixed with a polybutylene terephthalate resin falling within the range of ηr / ([COOH] × 10 ⁵ ) <2.50, the foaming is fine and uniform, lightweight and It can be seen that a molded product having excellent physical properties can be obtained. Further, it can be seen that a box-shaped molded product having no warp or sink is obtained.

From the results of Example 14, it can be seen that even if the supercritical fluid is changed from nitrogen to carbon dioxide, the same effects as in Example 13 using nitrogen can be obtained.

From the results of Comparative Examples 1 to 4, the ratio of the relative viscosity ηr and the terminal carboxyl group concentration [COOH] was 0.30 <
When a polybutylene terephthalate resin that does not fall within the range of ηr / ([COOH] × 10 ⁵ ) <2.50 is subjected to supercritical foam injection molding, a molded product without warpage and sink marks is obtained, but specific gravity and bubble diameter Is large and the physical properties are low.

From the results of Comparative Examples 5 to 8, the ratio of the relative viscosity ηr and the terminal carboxyl group concentration [COOH] was 0.30 <
When a composition in which glass fiber is mixed with polybutylene terephthalate resin that does not fall within the range of ηr / ([COOH] × 10 ⁵ ) <2.50 is subjected to supercritical foam injection molding, a molded product without warpage and sink marks is obtained. Although obtained, specific gravity,
It can be seen that the bubble diameter is large and the physical properties are low.

From the results of Comparative Examples 9 to 10, the relative viscosity ηr
The ratio of the terminal carboxyl group concentration [COOH] is 0.30
<Ηr / ([COOH] × 10 ⁵ ) <2.50 When a composition in which carbon fiber is mixed with a polybutylene terephthalate resin that does not fall within the range is subjected to supercritical foam injection molding, a molded product free from warpage and sink marks Specific gravity,
It can be seen that the bubble diameter is large and the physical properties are low.

From the results of Comparative Example 13, the ratio of the relative viscosity ηr and the terminal carboxyl group concentration [COOH] was 0.30 <
Even if a polybutylene terephthalate resin in the range of ηr / ([COOH] × 10 ⁵ ) <2.50 is used, a molded product free from warpage and sink marks can be obtained when foam injection molding is performed using a chemical foaming agent. , Specific gravity and bubble diameter are large,
It can be seen that the physical properties are low.

From the results of Comparative Example 14, the ratio of the relative viscosity ηr and the terminal carboxyl group concentration [COOH] was 0.30 <
Even if a composition obtained by compounding glass fibers into a polybutylene terephthalate resin falling within the range of ηr / ([COOH] × 10 ⁵ ) <2.50 is used, when foam injection molding is performed using a chemical foaming agent, warpage and sink marks are generated. It can be seen that, although a molded product free from cracks is obtained, the specific gravity and bubble diameter are large and the physical properties are low.

[0076]

As described above, the polybutylene terephthalate resin foam-molded product of the present invention has a fine and uniform foaming state without impairing the original characteristics of the polybutylene terephthalate resin, and has a sink mark or a warp. Few.

Therefore, according to the present invention, it is possible to reduce the weight of various molded products made of polybutylene terephthalate resin and improve the appearance and dimensional accuracy.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of an injection molding machine used in the present invention.

[Explanation of symbols]

A ... Polybutylene terephthalate resin pellets B: Hopper C ... screw D ... Cylinder E: Static mixer F ... Diffusion chamber G: Nozzle H: Cavity (molded product) I ... Mold J ... Booster pump K ... Gas cylinder L: Counter pressure gas cylinder

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B29K 105: 04 B29K 105: 04

Claims (3)

[Claims] 1. A polybutylene terephthalate resin foam-molded article obtained by introducing a polybutylene terephthalate resin and a supercritical fluid into an injection molding machine and performing injection molding,
A polybutylene terephthalate resin foam-molded article, characterized in that the polybutylene terephthalate resin satisfies the following formula (A). 0.30 <ηr / ([COOH] × 10 ⁵ ) <2.50 ... (A) (where, ηr is the relative viscosity of the polybutylene terephthalate resin, and [COOH] is the terminal carboxyl of the polybutylene terephthalate resin. Group concentration (unit: mol / g) is shown.) 2. The polybutylene terephthalate resin foam-molded article according to claim 1, wherein the polybutylene terephthalate resin contains an inorganic filler. 3. The inorganic filler is glass fiber and / or
Alternatively, the polybutylene terephthalate resin foam-molded article according to claim 2, which is carbon fiber.