JP7601281B2 - Method for producing glass fiber reinforced polyester resin composition - Google Patents

Description

The present invention relates to a method for producing a glass fiber-reinforced polyester resin composition, and more specifically, to a method for producing a glass fiber-reinforced polyester resin composition containing a high concentration of glass fibers using a twin-screw extruder, which suppresses strand breakage, enables continuous and stable production, has high productivity, and is produced as pellets that retain a good pellet shape.

Polyester resins, such as polybutylene terephthalate resin and polyethylene terephthalate resin, are widely used in a variety of electrical and electronic components, machine parts, and automotive parts, primarily for injection molding. In particular, glass fiber-reinforced polyester resin compositions that contain a high content of glass fiber have excellent mechanical strength, heat resistance, chemical resistance, and other properties, and are used as parts in the automotive and electrical and electronic equipment fields.

Patent Document 1 describes a resin composition in which 5 to 80% glass fiber is blended with polybutylene terephthalate resin, while Patent Document 2 describes a glass fiber-reinforced polyester resin composition in which 100 parts by mass of polyester resin is blended with 10 to 150 parts by mass of glass fiber.

However, when a polyester resin composition containing glass fibers at a high concentration of 40% by mass or more is extruded from a die in a twin-screw extruder, strand breakage is likely to occur. This reduces productivity, and when the broken strands are fed into a pelletizer, they overlap with each other, disturbing the flow of the strands and making it easy for long pellets to be produced. In addition, the strands are not easily cut, the cross section of the pellets is not sharp, and more chips are produced. This tendency becomes more pronounced as the glass fiber concentration increases. Long pellets and chips are prone to plasticization failure during molding in an injection molding machine, which increases the metering time, stops the injection molding machine, and reduces productivity. Strand-cut pellets are usually cylindrical or elliptical, but if the flattening ratio of the ellipse increases, plasticization may become unstable.

Special Publication No. 51-7702 JP 2006-16577 A

The objective (purpose) of the present invention is to suppress breakage of strands emerging from a die when a glass fiber-reinforced polyester resin composition containing a high content of glass fiber is produced using a twin-screw extruder, thereby enabling continuous and stable production, suppressing the generation of long pellets, and suppressing the generation of chips.

As a result of intensive research by the present inventors to solve the above problems, when a polyester resin composition containing a high content of glass fibers, 40 to 70 mass %, is produced using a twin-screw extruder, the viscosity of the resin composition becomes high. However, by adjusting the shear viscosity to 400 to 2000 Pa·s (265° C., 91/sec) and setting the die pressure during extrusion through a die to a range of 2 to 9 MPa, it is possible to suppress strand breakage, enable continuous and stable production, and significantly suppress the generation of long pellets and chips, thereby completing the present invention.
It was also found that, at that time, it is preferable that the temperature of the die holder is as high as 260 to 340°C, and that the temperature of (B) the second kneading section in which the glass fiber is kneaded after the side feeding is as low as 150 to 220°C, and further, that the strand temperature when cutting the strands with a pelletizer is preferably 100 to 150°C.
The present invention relates to the following production method.

1. A method for producing a glass fiber reinforced polyester resin composition comprising (A) 10 to 60% by mass of polyester resin, (B) 40 to 70% by mass of glass fiber, and (C) 0 to 50% by mass of other polymers or additives (the total of each component is 100% by mass) using a twin-screw extruder, wherein the glass fiber reinforced polyester resin composition has a shear viscosity of 400 to 2000 Pa·s at 265°C and 91/sec,
The present invention has a first step of kneading (A) polyester resin and (C) other polymers or additives in a first kneading section, a second step of adding (B) glass fiber downstream of the first kneading section and kneading the resulting mixture in a second kneading section, a third step of reducing the pressure of a vent downstream of the second kneading section to remove volatile matter and increase the pressure, and extruding the mixture through a die attached to a die holder, and a fourth step of water-cooling the strands discharged from the die and cutting them with a pelletizer,
A method for producing a glass fiber reinforced polyester resin composition, characterized in that in the third step, the pressure is increased at the tip of the screw and the resin is extruded so that the resin pressure in the die when it exits the die is 2 to 9 MPa.
2. The method according to claim 1, wherein the temperature of the die holder in the third step is 260 to 340° C.
3. The method according to the above 1 or 2, wherein the cylinder temperature of the second kneading section in the second step is 150 to 220°C.
4. The method according to the above 1, wherein the strand temperature when cutting the strands with the pelletizer in the fourth step is 100 to 150°C.

According to the manufacturing method of the present invention, a glass fiber reinforced polyester resin composition (pellets) containing a high content of glass fibers can be produced while suppressing strand breakage, enabling continuous and stable production, and significantly suppressing the generation of long pellets and chips.

FIG. 1 is a conceptual diagram showing an example of a process from a twin-screw extruder to a pelletizer used in the present invention. FIG. 2 is a conceptual diagram of a screw configuration of an extruder used in the Examples and Comparative Examples.

The present invention will be described in detail below with reference to embodiments and examples, but the present invention is not limited to the embodiments and examples shown below, and can be modified as desired without departing from the gist of the present invention. In this specification, the symbol "to" is used to mean that the numerical values before and after it are included as the lower and upper limits.

In the manufacturing method of the present invention, a glass fiber-reinforced polyester resin composition consisting of (A) 10 to 60 mass% polyester resin, (B) 40 to 70 mass% glass fiber, and (C) 0 to 50 mass% other polymers or additives is manufactured using a twin-screw extruder.

The extruder used in the present invention is a vented twin-screw extruder, preferably a co-rotating intermeshing twin-screw extruder having two screws rotating in the same direction inside the barrel, and preferably having a kneading section consisting of multiple kneading discs in a mutually intermeshing form midway through the screws.

As shown in FIG. 1, the vented twin-screw extruder has a cylinder equipped with a main raw material hopper 1, an open vent 2, a side feed hopper 3, and a reduced pressure vent 4, and a die holder 8 at the tip via a flange 6. The screw inside the cylinder is driven and rotated by a motor 16 via a screw connection part 14 and a gear box 15. A ring plate or a breaker plate is connected between the flange 6 and the die holder 8 to prevent resin leakage. The resin is spread by this die holder and discharged as a strand from a die (having multiple nozzles). Usually, the resin is spread laterally in the die holder section and discharged as a strand 10 from multiple nozzles arranged laterally, called a flat die.
The flange 6 may also be called a hinge plate. The die holder may also be called a die plate. The flange 6 (or hinge plate) and the die holder 8 (or die plate) are generally collectively called a die head. In order to stably produce a glass fiber reinforced polyester resin composition, that is, to suppress breakage of the strands, the temperature of the die holder is also important.

(A) Polyester resin and (C) other polymers or additives are supplied from a main raw material hopper 1 and kneaded in the first kneading section (first step). (B) Glass fiber is side-fed from a side feed hopper 3 downstream of the first kneading section and kneaded in the second kneading section (second step). Next, in the downstream section of the second kneading section, the vent 4 is depressurized to devolatilize and increase the pressure, and the mixture is extruded from a die attached to a die holder 8 (third step). The strands 10 coming out of the die are then water-cooled and cut by a pelletizer 11 (fourth step), and pellets 12 of the resin composition are obtained.

In the first step, (A) polyester resin and (C) other polymers or additives are fed from the main raw material hopper 1 into the extruder and heated, kneaded, and melted by the screw. A first kneading section consisting of multiple kneading discs is formed in the middle of the screw. The first kneading section is a kneading section in which (A) polyester resin and (C) other polymers or additives are kneaded after being added, and refers to a kneading section before (B) glass fiber is added. The screw configuration is preferably composed of a combination of two or more of R kneading discs, N kneading discs, L kneading discs, L screws, seal rings, mixing screws, or rotor screws, and the length is preferably 5.0 to 9.0D (D is the cylinder diameter). The first kneading section is a kneading section in which (A) polyester resin and (C) other polymers or additives are kneaded after being added, and refers to a kneading section before (B) glass fiber is added.

This first kneading section may be combined into one, or may be divided into several sections. In other words, the first kneading section may also be divided, with a feed screw inserted between them. Even when divided, it is preferable that the total length of the kneading section is in the range of 5.0 to 9.0 D.

The R kneading disc (hereinafter sometimes referred to as R) is a progressive kneading disc element, which usually has two or more blades, and the blade twist angle θ is preferably 10 degrees to 75 degrees. By displacing the blades at a predetermined angle in this way, a pseudo-screw structure is formed, which applies a strong shearing force while sending out the resin in the sending direction, forming a zone where kneading is performed.
The L kneading disc (hereinafter sometimes referred to as L) is a reverse kneading disc element, and usually has two or more blades, and the twist angle θ of the blade is preferably −10 degrees to −75 degrees. The reverse kneading disc element is an element that has a pressure increasing ability to block the resin being fed or to act in the direction of feeding the resin back, and by providing it downstream of the element that promotes kneading, it blocks the resin and exerts a strong kneading effect.
The N kneading disc (hereinafter sometimes referred to as N) is an orthogonal kneading disc element, which usually has two or more blades and a twist angle θ of the blades is 75 degrees to 105 degrees. Since the blades are installed offset by approximately 90 degrees, the resin delivery force is weak but the kneading force is strong.

The L screw is a reverse feed screw, the seal ring restricts the flow upstream by using the gaps in the seal ring section, the mixing screw is a screw element with notches in the screw crest (flight section), and the rotor screw is a screw element with one or more grooves on its outer surface.

Of these, R kneading discs, N kneading discs and L kneading discs are preferred, and a configuration in which multiple of these are combined is preferred.

It is preferable that the screw configuration of the first kneading section in the first step is such that an element that promotes kneading is arranged upstream and an element with pressure-increasing capability is arranged downstream. Therefore, in the first kneading section, it is preferable to arrange two or more types selected from R, N and L in the order R → N → L from the upstream side, and it is also preferable to arrange multiple R, N and L. In particular, a configuration in which R is arranged upstream, followed by multiple N, and then L is arranged.

The screw length of the first kneading section is preferably in the range of 5.0 to 9.0D, where D is the cylinder diameter, and such a screw length ensures sufficient melt plasticization of the (A) polyester resin and can also prevent decomposition of the resin composition. If the screw length of the first kneading section is shorter than 5.0D, insufficient shearing tends to result in insufficient melt plasticization of the resin, and if it exceeds 9.0D, excessive kneading tends to lead to localized decomposition of the resin composition, and the mechanical properties of the composition are likely to deteriorate.

After the polyester resin (A) is kneaded and melted in the first step, it is preferable to vent it through the release vent 2. It is preferable to provide a seal ring downstream of the release vent 2.

In the second step, after the above-mentioned first step, the (B) glass fiber is side-fed from a side feed hopper 3 located downstream of the first kneading section, and the (B) glass fiber and the molten (A) polyester resin are kneaded in the second kneading section.
The second kneading section refers to a kneading section in which (B) glass fiber enters and is opened and kneaded. The screw configuration of the second kneading section is preferably a configuration in which one or more of R kneading disks, N kneading disks, L kneading disks, L screws, seal rings, and mixing screws are combined, and kneading with such a screw configuration tends to result in sufficient opening and dispersion of (B) glass fiber. Among the above, it is preferable to have at least a mixing screw, particularly a forward notched mixing screw and a reverse notched mixing screw.

The screw length of the second kneading section is preferably in the range of 2.5 to 5.0D. This second kneading section may be combined into one, or may be divided into multiple sections. In other words, the second kneading section may be divided and a feed screw may be inserted between them. In either configuration, it is preferable that the total kneading section length is in the range of 2.5 to 5.0D. By setting the screw length of the second kneading section in this way, the opening and dispersion of the (B) glass fibers is improved, and the strength of the resin composition is likely to be improved.

The resin temperature (cylinder temperature) in the second step is generally operated at about 260°C, but in the method of the present invention, it is preferable to set the temperature at 150 to 220°C, which is lower than usual. This second kneading section is a process in which (B) glass fiber enters and is kneaded with (A) polyester resin and (C) other polymers or additives, and the resin temperature is likely to rise. By setting the cylinder temperature in this section to a temperature range of 150 to 220°C, which is lower than usual, it is effective in suppressing breakage of the strand 10 when it leaves the die holder 8. If the temperature is lower than 150°C, the viscosity of the resin is high, the impregnation of (B) glass fiber is not successful, kneading becomes uneven, and the strand is likely to break. On the other hand, if the temperature is higher than 220°C, the resin temperature is likely to become high, pyrolysis gas is likely to be generated, and the strand is likely to break. The resin temperature (cylinder temperature) in the second step is more preferably 160°C or higher and 210°C or lower.

The screw speed of the twin-screw extruder is preferably 250 to 800 rpm, more preferably 300 to 700 rpm. The discharge rate is preferably 200 to 650 kg/h for TEX44αIII, more preferably 250 to 630 kg/h. For extruders of different sizes, the preferred range is a discharge rate proportional to the 2.5th power of the cylinder diameter ratio.

After the second step, in the third step, the pressure is reduced at the vacuum vent 4 downstream of the second kneading section to devolatilize and increase the pressure, and the mixture is extruded through a die attached to the die holder 8. The degree of vacuum during the reduced pressure devolatilization at the vacuum vent 4 is preferably -0.097 MPa to -0.07 MPa. Here, the degree of vacuum means the gauge pressure.

In the third step, the pressure is increased at the tip of the screw and the resin is extruded so that the resin pressure inside the die when it leaves the die is 2 to 9 MPa.
The resin pressure in the die (also called die pressure) is the resin pressure at the position of the tip of the screw. The pressure at this position is the highest. Usually, a flange is located at this position, and a resin pressure gauge 7 is installed, so that the pressure can be measured over time. The resin pressure in this die is set to 2 MPa or more and 9 MPa or less. (B) glass fibers are usually in a bundle shape when fed, and by setting the resin pressure in the die to 2 MPa or more and 9 MPa or less, they are kneaded together with the resin, and by applying an appropriate pressure, the resin is easily impregnated into the (B) glass fiber bundle, making it possible to perform uniform kneading, and the occurrence of strand breakage can be suppressed. If it is less than 2 MPa, the kneading state of the resin and (B) glass fiber is not uniform, and the strand is likely to break when it comes out of the die. A more preferable resin pressure in the die is 2.5 MPa or more, and even more preferably 3 MPa or more. On the other hand, if the resin pressure is too high, the retention area at the tip of the screw becomes long, gas is easily generated by thermal decomposition, and the strand is easily broken by the gas when it comes out of the die. The resin pressure is more preferably 8 MPa or less, and further preferably 7 MPa or less.

The temperature of the die holder 8 is preferably higher than usual, and is preferably 260°C or higher and 340°C or lower. By setting the temperature at such a temperature, it becomes easier to suppress strand breakage. If it is less than 260°C, the temperature of the die is lower than the resin temperature of the resin composition, and the temperature of the strands at both ends of the die is lower than the temperature of the strand in the center. This causes a difference in viscosity between the strands, making them more likely to break. The temperature of the die holder 8 is more preferably 270°C or higher, and even more preferably 280°C or higher. If it exceeds 340°C, gas is more likely to be generated due to heat retention inside the die, and the strands are also more likely to break. The temperature of the die holder 8 is more preferably 330°C or lower, and even more preferably 320°C or lower.

The second kneading section thermocouple 5 and die holder thermocouple 9 are inserted into the cylinder and die holder 8 of the extruder, respectively, making it possible to measure the temperatures of the cylinder and die holder. Furthermore, heaters are built into the cylinder and die holder, making it possible to control the temperature. The temperature of the cylinder and the temperature of the die holder are the temperatures measured by the inserted thermocouples.

In the fourth step, the strand 10 emerging from the die is water-cooled and cut by a pelletizer 11. The strand temperature during strand cutting is preferably 100°C or higher and 150°C or lower. By setting the temperature at such a level, it becomes easier to prevent chipping and pellets of poor shape. If the temperature is lower than 100°C, the strand is hard and chipping is likely to occur when cutting with a pelletizer. This makes it easy for plasticization to become unstable during molding such as injection molding. If the temperature exceeds 150°C, the flattening ratio of the elliptical cylindrical shape of the cut pellets becomes large, which may also result in poor plasticization. The strand temperature during strand cutting is more preferably 110°C or higher and 140°C or lower.

Glass fiber reinforced polyester resin compositions containing a high concentration of glass fiber tend to break after coming out of the die, before cooling and strand cutting. The low resin content weakens the viscoelastic properties, and the strands lose their toughness, becoming brittle and easily broken. In addition, the large amount of glass fiber makes it easy to produce fiber bundles with poor opening properties. Fiber bundles with poor opening properties are likely to become the starting point of breakage when drawn (stretched). Furthermore, if the fiber bundle is filled with little resin, that part may become the starting point of breakage (insufficient resin impregnation of the glass fiber bundle). And because of the high concentration of glass fiber, the viscosity of the resin increases and the resin temperature tends to rise. This generates pyrolysis gas, which causes the strands to break when they come out of the die. In this way, it becomes difficult to cut the strands stably due to the decrease in strand toughness, insufficient opening of the glass fiber bundles, insufficient resin impregnation of the glass fiber bundles, gas generation, etc. If the strand breaks, it is necessary to manually re-feed the strand into the pelletizer. At that time, the flow of the entire strand becomes disturbed, and the strand enters the cutter at an angle, which makes it easy for long pellets to be generated. Furthermore, because the glass fiber is highly concentrated and the strand is hard, the cut surface by the pelletizer is not sharp, but becomes dull, and chips are generated. In order to suppress the generation of chips, it is necessary to raise the strand cut temperature. This makes the cut sharper and reduces the amount of chips. However, if the strand cut temperature is raised too high, the strand becomes soft and is crushed by the pelletizer's take-up roll, and the eccentricity of the elliptical cylindrical pellets increases. The more long pellets and chips there are and the higher the flattening ratio, the more likely it is that poor plasticization will occur when the pellets are used for injection molding, resulting in a decrease in productivity. The number of long pellets (usually more than twice the length of the pellets) is preferably 5 or less per 1 kg. The amount of chips is preferably 300 mass ppm or less of the total mass (pellets + chips). The flattening ratio (long axis/single axis) is preferably 1.30 or less.

There are no particular limitations on the shape of the extrusion die, and any known die may be used. The diameter of the die hole depends on the desired pellet size, but is usually about 2 to 5 mm, and preferably about 3 to 4 mm.

The strand 10 is taken up by a take-up roller, brought into contact with water, and cooled. The contact with water may be carried through water stored in a cooling water tank 13, or water may be poured onto the strand 10 to cool it, or the strand may be pulled by a mesh belt conveyor and water is sprayed onto it with a water-spraying device. It is better for the time between the strand being extruded from the die and being cooled with water or being immersed in water to be short. Usually, it is better for the strand to be immersed in water within one second after being extruded from the die.

The cooled strands are sent to the pelletizer by take-up rollers, cut, and turned into pellets.

In the method of the present invention, the shear viscosity of the glass fiber reinforced polyester resin composition at 265°C and 91/sec is 400 Pa·s or more and 2000 Pa·s or less. By setting the range of 400 to 2000 Pa·s and combining it with each of the above-mentioned steps, strand breakage is suppressed and continuous stable production is possible. If the viscosity is below 400 Pa·s, the elastic properties of the strand are weak and the strand is easily broken. Also, if it exceeds 2000 Pa·s, shear heat generation becomes large, the resin temperature rises, thermal decomposition occurs, and the strand easily breaks. A more preferable range is 500 Pa·s or more and 1700 Pa·s or less, and an even more preferable range is 600 Pa·s or more, preferably 1400 Pa·s or less.

The shear viscosity is measured using a Capillograph (Capillograph 1D2 manufactured by Toyo Seiki Seisakusho Co., Ltd.) with an orifice having a capillary diameter of 1 mm and a capillary length of 3 mm at 265°C and a shear rate of 91/sec in accordance with JIS K7199.

To adjust the shear viscosity to the above range, the amount of (B) glass fiber can be increased to increase the shear viscosity, and the amount of (C) other polymers, such as styrene-based polymers or polycarbonate resins, can be decreased to decrease the shear viscosity. It is also possible to adjust the shear viscosity by changing the viscosity of (A) polyester resin.

Next, the raw material components used in the present invention will be described.

(A) Polyester Resin The (A) polyester resin is a thermoplastic polyester resin, and is a polyester obtained by polycondensation of a dicarboxylic acid compound and a dihydroxy compound, polycondensation of an oxycarboxylic acid compound, or polycondensation of these compounds, and may be either a homopolyester or a copolyester.

As the dicarboxylic acid compound constituting the polyester resin (A), an aromatic dicarboxylic acid or an ester-forming derivative thereof is preferably used.
Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, 1,5-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, biphenyl-2,2'-dicarboxylic acid, biphenyl-3,3'-dicarboxylic acid, biphenyl-4,4'-dicarboxylic acid, diphenylether-4,4'-dicarboxylic acid, diphenylmethane-4,4'-dicarboxylic acid, diphenylsulfone-4,4'-dicarboxylic acid, diphenylisopropylidene-4,4'-dicarboxylic acid, 1,2-bis(phenoxy)ethane-4,4'-dicarboxylic acid, anthracene-2,5-dicarboxylic acid, anthracene-2,6-dicarboxylic acid, p-terphenylene-4,4'-dicarboxylic acid, and pyridine-2,5-dicarboxylic acid. Terephthalic acid is preferably used.

These aromatic dicarboxylic acids may be used in combination of two or more. As is well known, in addition to the free acids, these may be used in the polycondensation reaction as ester-forming derivatives such as dimethyl esters.
In addition, a small amount of aliphatic dicarboxylic acids such as adipic acid, azelaic acid, dodecanedioic acid, and sebacic acid, and alicyclic dicarboxylic acids such as 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid can be mixed and used together with these aromatic dicarboxylic acids.

Examples of the dihydroxy compound constituting the (A) polyester resin include aliphatic diols such as ethylene glycol, propylene glycol, butanediol, hexylene glycol, neopentyl glycol, 2-methylpropane-1,3-diol, diethylene glycol, and triethylene glycol, alicyclic diols such as cyclohexane-1,4-dimethanol, and mixtures thereof.
In addition, if the amount is small, one or more long-chain diols having a molecular weight of 400 to 6,000, such as polyethylene glycol, poly-1,3-propylene glycol, polytetramethylene glycol, etc. may be copolymerized.
Additionally, aromatic diols such as hydroquinone, resorcin, naphthalenediol, dihydroxydiphenyl ether, and 2,2-bis(4-hydroxyphenyl)propane can also be used.

In addition to the bifunctional monomers mentioned above, small amounts of trifunctional monomers such as trimellitic acid, trimesic acid, pyromellitic acid, pentaerythritol, and trimethylolpropane can also be used in combination to introduce a branched structure, or monofunctional compounds such as fatty acids can be used in combination to adjust the molecular weight.

(A) The polyester resin is usually made of a polycondensation product of a dicarboxylic acid and a diol, i.e., 50% by weight or more, preferably 70% by weight or more of the total resin is made of this polycondensation product. As the dicarboxylic acid, an aromatic dicarboxylic acid is preferable, and as the diol, an aliphatic diol is preferable.

Among these, polyalkylene terephthalates in which 95 mol % or more of the acid component is terephthalic acid and 95 mass % or more of the alcohol component is an aliphatic diol are preferred. Representative examples are polybutylene terephthalate resin and polyethylene terephthalate resin. These are preferably close to homopolyesters, that is, 95 mass % or more of the entire resin is composed of terephthalic acid components and 1,4-butanediol or ethylene glycol components.

(A) As the polyester resin, it is preferable that the main component (i.e., 50% by mass or more) is polybutylene terephthalate resin or polyethylene terephthalate resin, and polybutylene terephthalate resin is particularly preferable.

(A) It is preferable to use a polyester resin having an intrinsic viscosity of preferably 0.60 dl/g or more and less than 1.0 dl/g, more preferably 0.60 dl/g or more and less than 0.95 dl/g, and even more preferably 0.65 dl/g or more and less than 0.95 dl/g. If a resin having an intrinsic viscosity lower than 0.60 dl/g is used, the mechanical strength of the resulting resin composition tends to be low, the hydrolysis resistance tends to be poor, and the heat shock resistance tends to be low, and if the intrinsic viscosity is 1.0 dl/g or more, it tends to be difficult to obtain good fluidity.

The intrinsic viscosity of polyester resin is measured at 30°C in a mixed solvent of 1,1,2,2-tetrachloroethane and phenol in a 1:1 (mass ratio).

The amount of terminal carboxyl groups in the (A) polyester resin may be appropriately selected and determined, but is usually 60 eq/ton or less, preferably 50 eq/ton or less, and more preferably 30 eq/ton or less. If it exceeds 60 eq/ton, gas tends to be generated during melt molding of the resin composition. There is no particular lower limit for the amount of terminal carboxyl groups, but it is usually 10 eq/ton, taking into account the productivity of the polyester resin production.

The amount of terminal carboxyl groups in the polyester resin is the value obtained by dissolving 0.5 g of polyalkylene terephthalate resin in 25 mL of benzyl alcohol and measuring by titration using a 0.01 mol/l benzyl alcohol solution of sodium hydroxide. The amount of terminal carboxyl groups can be adjusted by any conventional method, such as adjusting the polymerization conditions such as the raw material charge ratio during polymerization, polymerization temperature, and pressure reduction method, or by reacting a terminal blocking agent.

(B) Glass Fiber As the (B) glass fiber, any known glass fiber can be used as long as it is one that is usually used in polyester resins, regardless of the form of the glass fiber when blended, such as A glass, E glass, alkali-resistant glass composition containing a zirconia component, chopped strand, roving glass, master batch of thermoplastic resin and glass fiber, etc. Among them, as the (B) glass fiber used in the present invention, alkali-free glass (E glass) is preferred for the purpose of improving the thermal stability of the resin composition.

As the (B) glass fiber, it is also preferable to use glass fiber having a longitudinal cross-sectional irregularity ratio in the range of 2.0 to 6.0.
The irregularity ratio of the longitudinal cross section is the ratio of the long axis to the short axis when a rectangle of the minimum area circumscribing a cross section perpendicular to the longitudinal direction of the glass fiber is assumed, and the length of the long side of this rectangle is defined as the long axis and the length of the short side is defined as the short axis.

(B) The cross-sectional area in the longitudinal direction of the glass fiber is preferably more than 90 μm ² and not more than 300 μm ^2. With such a cross-sectional area, the polyester resin is easily made to become a matrix, and as a result, the heat resistance is easily improved. The cross-sectional area is more preferably more than 90 μm ² and not more than 250 μm ² , and even more preferably more than 90 μm ² and not more than 200 μm ² .
The thickness of the (B) glass fiber is not particularly limited, but it is preferable that the minor axis is about 2 to 20 μm and the major axis is about 5 to 50 μm.

(B) The glass fibers may be treated with a bundling agent or a surface treatment agent. In addition, when producing the resin composition of the present invention, a bundling agent or a surface treatment agent may be added separately from the untreated glass fibers to perform surface treatment.

Examples of the sizing agent include resin emulsions such as vinyl acetate resin, ethylene/vinyl acetate copolymer, acrylic resin, epoxy resin, polyurethane resin, and polyester resin.
Examples of the surface treatment agent include aminosilane compounds such as γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, and γ-(2-aminoethyl)aminopropyltrimethoxysilane; chlorosilane compounds such as vinyltrichlorosilane and methylvinyldichlorosilane; alkoxysilane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, and γ-methacryloxypropyltrimethoxysilane; epoxysilane compounds such as β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane; acrylic compounds, isocyanate compounds, titanate compounds, and epoxy compounds.

Two or more of these sizing agents and surface treatment agents may be used in combination, and the amount used (adhesion amount) is usually 10% by mass or less, and preferably 0.05 to 5% by mass, based on the mass of the (B) glass fiber. By keeping the adhesion amount to 10% by mass or less, a necessary and sufficient effect is obtained, and it is economical.

(B) Two or more types of glass fibers may be used in combination depending on the required characteristics.

The content of (B) glass fiber is set to a high content of 40 to 70 mass% relative to 100 mass% of the total of (A) polyester resin, (B) glass fiber, and (C) other polymers or additives. If the content of (B) glass fiber is less than 40 mass%, rigidity is likely to be insufficient, and conversely, if it exceeds 70 mass%, impact resistance and fluidity are likely to be insufficient, and production is likely to be difficult. The content of (B) glass fiber is more preferably 42 mass% or more, more preferably 65 mass% or less, and even more preferably 60 mass% or less.

(C) Other polymers or additives are (A) other polymers other than polybutylene ester resin and/or various other additives.

Other additives include various resin additives, such as (B) fillers other than glass fiber (talc, glass flakes, mica, kaolin, ceramic beads, clay, zeolite, barium sulfate, titanium oxide, silicon oxide, aluminum oxide, magnesium hydroxide, zinc sulfide, etc.), flame retardants, flame retardant assistants, stabilizers, antioxidants, release agents, ultraviolet absorbers, weathering stabilizers, lubricants, colorants such as dyes and pigments, catalyst deactivators, antistatic agents, foaming agents, plasticizers, crystal nucleating agents, crystallization accelerators, etc.

Examples of other polymers include various elastomers; styrene-based polymers described below; polycarbonate resins; polyolefin resins such as polyethylene resins and polypropylene resins; polyamide resins; polyimide resins; polyetherimide resins; polyphenylene ether resins; polyphenylene sulfide resins; polysulfone resins; and polymethacrylate resins.
The other resins may be contained either alone or in any combination and ratio of two or more kinds.

(C) The amount of other polymers or additives is 0 to 50% by mass, based on 100% by mass of the total of (A) to (C), and is preferably 45% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less, and is preferably 1% by mass or more, more preferably 2% by mass or more, of which 3% by mass or more, 4% by mass or more, and particularly preferably 5% by mass or more.

Examples of styrene-based polymers include homopolymers of styrene, graft copolymers obtained by polymerizing styrene in the presence of rubber, copolymers of styrene and (meth)acrylonitrile, copolymers of styrene and (meth)acrylic acid alkyl esters, copolymers of styrene, (meth)acrylonitrile and other copolymerizable monomers, and graft copolymers obtained by graft polymerizing styrene and (meth)acrylonitrile in the presence of rubber. Specific examples of the resin include polystyrene (general purpose polystyrene, GPPS), impact resistant polystyrene (high impact polystyrene, HIPS), acrylonitrile-styrene copolymer (AS resin), acrylonitrile-butadiene-styrene copolymer (ABS resin), styrene-butadiene-styrene copolymer (SBS resin), hydrogenated styrene-butadiene-styrene copolymer (hydrogenated SBS), hydrogenated styrene-isoprene-styrene copolymer (SEPS), styrene-maleic anhydride copolymer (SMA resin), acrylonitrile-styrene-acrylic rubber copolymer (ASA resin), methyl methacrylate-butadiene-styrene copolymer (MBS resin), methyl methacrylate-acrylonitrile-butadiene-styrene copolymer (MABS resin), acrylonitrile-acrylic rubber-styrene copolymer (AAS resin), acrylonitrile-ethylene propylene rubber-styrene copolymer (AES resin) and styrene-IPN type rubber copolymer, or mixtures thereof.

Among these, acrylonitrile-styrene copolymer (AS resin), polystyrene (GPPS), high impact polystyrene (HIPS), and acrylonitrile-butadiene-styrene copolymer (ABS resin) are preferred, and acrylonitrile-styrene copolymer (AS resin), polystyrene (GPPS), high impact polystyrene (HIPS), and acrylonitrile-butadiene-styrene copolymer (ABS resin) are particularly preferred.

As the styrene-based polymer, a styrene-based elastomer can also be used.
As the styrene-based elastomer, a block copolymer comprising a polymer block having a vinyl aromatic compound as a polymerization component and a polymer block having a conjugated diene as a polymerization component, and a hydrogenated product thereof are preferable.

Examples of vinyl aromatic compounds constituting the vinyl aromatic hydrocarbon polymer block include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, p-t-butylstyrene, 1,3-dimethylstyrene, lower alkyl-substituted styrene, vinylnaphthalene, vinylanthracene, and other styrene or derivatives thereof. These can be used alone or in combination of two or more.

Examples of conjugated dienes that make up the conjugated diene blocks include butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, etc.

The styrene-based polymer may be used alone or in combination of two or more kinds.
The amount of the styrene-based polymer is preferably 5 to 45% by mass, based on 100% by mass of the total of (A) to (C).

The polycarbonate resin is preferably an aromatic polycarbonate resin, specifically a thermoplastic aromatic polycarbonate polymer or copolymer obtained by reacting an aromatic dihydroxy compound with phosgene or a diester of carbonic acid.

Examples of aromatic dihydroxy compounds include 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), tetramethylbisphenol A, etc.

Preferred examples of polycarbonate resins include polycarbonate resins containing 2,2-bis(4-hydroxyphenyl)propane as a dihydroxy compound or 2,2-bis(4-hydroxyphenyl)propane in combination with other aromatic dihydroxy compounds.

The polycarbonate resin may be a homopolymer consisting of one type of repeating unit, or a copolymer having two or more types of repeating units. In this case, the copolymer may be of various copolymer forms, such as a random copolymer or a block copolymer.

There are no restrictions on the molecular weight of the polycarbonate resin, but the viscosity average molecular weight (Mv) is usually about 10,000 to 100,000, and preferably about 12,000 to 35,000. By making the viscosity average molecular weight equal to or greater than the lower limit of the above range, the mechanical strength can be further improved, making it more preferable for use in applications requiring high mechanical strength.

The viscosity average molecular weight (Mv) of the polycarbonate resin is a value calculated from the intrinsic viscosity ([η]) obtained by measuring the viscosity of a methylene chloride solution of the polycarbonate resin at 25° C. using an Ubbelohde viscometer, and then using the following Schnell viscosity formula:
[η]=1.23× ^10-4 Mv ^0.83

The method for producing the polycarbonate resin is not particularly limited, and polycarbonate resins produced by either the phosgene method (interfacial polymerization method) or the melting method (ester exchange method) can be used. Also preferred is polycarbonate resin produced by the melting method, which has been subjected to post-treatment to adjust the amount of OH groups at the terminals.

In addition, polycarbonate resin can be made not only from virgin raw materials, but also from aromatic polycarbonate resins recycled from used products, i.e., aromatic polycarbonate resins that have been so-called material recycled. Preferred examples of used products include optical recording media such as optical disks, light guide plates, automobile window glass, automobile headlamp lenses, transparent vehicle components such as windshields, containers such as water bottles, eyeglass lenses, soundproof walls, glass windows, corrugated sheets, and other building components. In addition, crushed products obtained from non-conforming products, sprues, or runners, or pellets obtained by melting these can also be used as recycled polycarbonate resin.

When polycarbonate resin is contained, the amount is preferably 5 to 45% by mass, based on 100% by mass of the total of (A) to (C).

The glass fiber reinforced polyester resin composition produced by the method of the present invention can be used to produce molded products with high strength, fully satisfying the requirements for weight reduction, thinning and strength, and can be widely used in molded products or parts in, for example, the electrical and electronic equipment field, the office automation equipment field such as computers, the precision equipment field, the optical equipment field, the automotive field and various other industrial fields.

The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples, and can be modified as desired without departing from the spirit of the present invention.

The raw materials (A) polyester resin, (B) glass fiber, and (C) other polymers used in the examples and comparative examples are as shown in Table 1 below.

In the following examples and comparative examples, a vented intermeshing co-rotating twin screw extruder ("TEX44αIII" manufactured by Japan Steel Works, Ltd., cylinder diameter D = 47 mm) was used.

The screw configuration is shown in FIG.
C1 was a feed cylinder, C7 and C12 were vent cylinders, C7 was an open vent, C12 was a reduced pressure vent, and C9 was a side feed cylinder. The first kneading section, which melt-kneaded (A) polyester resin and (C) other polymers, was located at C5 to C6, and the screw configuration was RRNNL with 5 paddles at 1D (1D = 44 mm). (B) Glass fiber was side fed from C9. The second kneading section, which kneaded (B) glass fiber, was 1D with 5 paddles R and three 1D back mixing screws (lead 0.25D) arranged as shown in Figure 2.

The kneading section from where (A) polyester resin and (C) other polymers are added until (B) glass fibers are fed is the first kneading section, and the section from C1 to C9 is the first step.
Next, (B) the glass fiber enters the extruder, and the mixing section up to the reduced pressure vent is the second mixing section, and from C10 to C11 is the second process. From C12 to C14, including the die holder, the mixing resin comes out of the die is the third process. Furthermore, the strand coming out of the die is cooled with water, cut by a pelletizer, and pelletized is the fourth process.

In the following Examples 1 to 11 and Comparative Examples 1 and 2, resin compositions were produced using the raw material ratios set forth in Recipe 1 of Table 1 above.

Example 1
57.5 kg/h of polybutylene terephthalate resin (PBT2), 45 kg/h of polyethylene terephthalate resin (PET), and 10 kg/h of elastomer (EL) were fed from the main raw material hopper to the C1 feed barrel of the twin-screw extruder "TEX44αIII", and 137.5 kg/h of glass fiber (GF) was fed from the side feed hopper to the C9 side feed cylinder. The total feed rate of the raw materials was 250 kg/h, and the screw rotation speed was 300 rpm.

The set temperatures of cylinders C2 to C9 and cylinders C12 to C14 were 250°C. The set temperatures of cylinders C10 and C11 in the second kneading section were 170°C. The set temperature of the die holder in the third process was 300°C. The flange temperature was also 300°C, the same as the die holder. In addition, a flat die with a hole diameter of 3.8 mm, a land length of 20 mm, and 10 holes arranged horizontally was used. The resin pressure in the die at this time was 5.2 MPa.
In the following examples and comparative examples, the temperature of the flange was set to be the same as the temperature of the die holder.

The strand coming out of the die was cooled in a water bath and cut into elliptical cylindrical pellets with a length of 3 mm by a pelletizer. The strand take-up speed of the pelletizer was 40 m/min. The water-cooling distance of the strand was adjusted at this time, and the temperature of the strand at the time of cutting was set to 130°C. The temperature of the strand was measured by an infrared thermometer. This extrusion was continued for one hour. No breakage of a single strand occurred during the one hour.
The size of the obtained elliptical cylindrical pellets, calculated as the number average of 20 pellets, was 3.0 mm in length, 3.0 mm in major axis, and 2.4 mm in minor axis (flattening ratio: 1.25).
1 kg of pellets were collected, and the amount of chips was measured using a sieve with 1 mm openings to determine the chip ratio (ppm by mass). The pellets remaining on the sieve (approximately 1 kg) were visually inspected, and the number of long pellets (pellets longer than 6 mm) was counted. These results are shown in the table.
The amount of chips was extremely small, and the number of long pellets was 0. The flattening ratio of the elliptical cylindrical pellets was good at 1.25.

The obtained pellets were dried at 120° C. for 5 hours, and the shear viscosity was measured at a shear rate of 91/sec at a temperature of 265° C. using a “Capilograph 1D2” manufactured by Toyo Seiki Seisakusho Co., Ltd., with an orifice having a capillary diameter of 1 mm and a capillary length of 3 mm. The shear viscosity was 1020 Pa·s.
The results are shown in Table 2.

The strand breakage was evaluated according to the following criteria.
A: Number of strand breaks: 0/hour B: Number of strand breaks: 1-2/hour C: Number of strand breaks: 3-9/hour D: Number of strand breaks: 10 or more/hour The pellet shape was evaluated according to the following criteria.
A: Chips≦300 ppm, flatness≦1.30, and long pellets≦5 pieces/kg
B: Chips > 300 ppm or flatness > 1.30 or long pellets > 5 pieces/kg

Example 2
The same procedure as in Example 1 was repeated except that the die land length was 10 mm. The resin pressure at the die was 2.8 MPa. The results are shown in Table 2.

Example 3
The same procedure as in Example 1 was carried out except that the die land length was set to 30 mm. The resin pressure at the die portion at this time was 7.2 MPa. The results are shown in Table 2.

Example 4
The same procedure as in Example 1 was repeated except that the temperature of the die holder was 270° C. The results are shown in Table 2.

Example 5
The same procedure as in Example 1 was repeated except that the temperature of the die holder was 330° C. The results are shown in Table 2.

Example 6
The same procedure as in Example 1 was repeated except that the temperature of the die holder was 250° C. The results are shown in Table 2.

Example 7
The same procedure as in Example 1 was repeated except that the temperature of the die holder was 350° C. The results are shown in Table 2.

Example 8
The same procedure as in Example 1 was repeated except that the temperature of the second kneading zone was 140° C. The results are shown in Table 2.

Example 9
The same procedure as in Example 1 was carried out except that the temperature of the second kneading section was set to 240° C. The results are shown in Table 2.

Example 10
The same procedure as in Example 1 was repeated except that the strand cut temperature was 95° C. The results are shown in Table 2. The strand cut temperature was low, and a large amount of chips was generated.

Example 11
The same procedure as in Example 1 was repeated except that the strand cutting temperature was 155° C. The results are shown in Table 2. The amount of chips was small, but the flattening ratio of the elliptical cylindrical pellets was large.

Comparative Example 1
The die land length was set to 5 mm, and the experiment was carried out in the same manner as in Example 1. The resin pressure at the die was 1.7 MPa. Strand breakage occurred 16 times during the one-hour experiment. This was not a situation conducive to stable production.

Comparative Example 2
The die land length was set to 40 mm, and the experiment was carried out in the same manner as in Example 1. The resin pressure at the die was 9.4 MPa. Strand breakage occurred 19 times during the one-hour experiment. This was not a situation conducive to stable production.

The above results are shown in Table 2 below.

In the following Examples 12 to 22 and Comparative Examples 3 to 4, resin compositions were produced using the raw material ratios set forth in Recipe 2 of Table 1 above.

Example 12
50.0 kg/h of PBT1, 75 kg/h of PS, and 12.5 kg/h of PC were fed from the main raw material hopper to the C1 feed barrel of the twin-screw extruder "TEX44αIII", and 112.5 kg/h of glass fiber was fed from the side feed hopper to the C9 side feed cylinder. The total feed amount of the raw materials was 250 kg/h. The same procedure as in Example 1 was followed except that the screw rotation speed was 370 rpm.
The results are shown in Table 3 below.
The obtained pellets were dried at 120° C. for 5 hours, and the shear viscosity was measured at a shear rate of 91/sec at a temperature of 265° C. using a “Capilograph 1D2” manufactured by Toyo Seiki Seisakusho Co., Ltd., with an orifice having a capillary diameter of 1 mm and a capillary length of 3 mm. The shear viscosity was 720 Pa·s.

Example 13
The same procedure as in Example 12 was repeated except that the die land length was 10 mm. The resin pressure at the die was 2.6 MPa. The results are shown in Table 3.

Example 14
The same procedure as in Example 12 was repeated except that the die land length was 30 mm. The resin pressure at the die was 7.1 MPa. The results are shown in Table 3.

Example 15
The same procedure as in Example 12 was repeated except that the die holder temperature was 270° C. The results are shown in Table 3.

Example 16
The same procedure as in Example 12 was repeated except that the die holder temperature was 330° C. The results are shown in Table 3.

Example 17
The same procedure as in Example 12 was repeated, except that the temperature of the die holder was 250° C. The results are shown in Table 3.

Example 18
The same procedure as in Example 12 was repeated, except that the temperature of the die holder was 350° C. The results are shown in Table 3.

Example 19
The same procedure as in Example 12 was repeated except that the temperature of the second kneading zone was 140° C. The results are shown in Table 3.

Example 20
The same procedure as in Example 12 was repeated except that the temperature of the second kneading section was 240° C. The results are shown in Table 3.

Example 21
The same procedure as in Example 12 was repeated except that the strand cut temperature was 95° C. The results are shown in Table 3. The strand cut temperature was low, and a large amount of chips was generated.

Example 22
The same procedure as in Example 12 was repeated except that the strand cut temperature was 155° C. The results are shown in Table 3. The amount of cutting chips was small, but the flattening ratio of the elliptical cylindrical pellets was large.

Comparative Example 3
The die land length was set to 5 mm, and the experiment was carried out in the same manner as in Example 12. The resin pressure at the die was 1.6 MPa. Strand breakage occurred 14 times during the one-hour experiment. This was not a situation conducive to stable production.

Comparative Example 4
The die land length was set to 40 mm, and the experiment was carried out in the same manner as in Example 12. The resin pressure at the die was 9.1 MPa. Strand breakage occurred 21 times during the one-hour experiment. This was not a situation conducive to stable production.

According to the manufacturing method of the present invention, it is possible to stably produce high-quality pellets of a glass fiber reinforced polyester resin composition containing a high concentration of glass fibers.

1: Main raw material hopper 2: Open vent 3: Side feed hopper 4: Reduced pressure vent 5: Second kneading section thermocouple 6: Flange 7: Resin pressure gauge 8: Die holder 9: Die holder thermocouple 10: Strand 11: Pelletizer 12: Pellets 13: Cooling water tank 14: Screw connection section 15: Gear box 16: Motor

Claims (4)

A method for producing a glass fiber-reinforced polyester resin composition comprising (A) 10 to 60 mass% of polyester resin, (B) 40 to 70 mass% of glass fiber, and (C) 0 to 50 mass% of other polymers or additives (the total of each component is 100 mass%), using a twin-screw extruder, wherein the glass fiber-reinforced polyester resin composition has a shear viscosity of 400 to 2000 Pa s at 265°C and 91/sec,
The method comprises a first step of kneading (A) polyester resin and (C) other polymers or additives in a first kneading section, a second step of adding (B) glass fiber downstream of the first kneading section and kneading the resulting mixture in a second kneading section, a third step of reducing the pressure of the resin in a vent section downstream of the second kneading section to devolatilize it , and extruding the resin from a die attached to a die holder while increasing the pressure , and a fourth step of water-cooling the strands discharged from the die and cutting them with a pelletizer.
A method for producing a glass fiber reinforced polyester resin composition, characterized in that in the third step, the pressure is increased at the tip of the screw and the resin is extruded so that the resin pressure in the die when it exits the die is 2 to 9 MPa. The manufacturing method according to claim 1, wherein the temperature of the die holder in the third step is 260 to 340°C. The manufacturing method according to claim 1 or 2, wherein the cylinder temperature of the second kneading section in the second step is 150 to 220°C. The manufacturing method according to claim 1, in which the strand temperature when cutting the strands with the pelletizer in the fourth step is 100 to 150°C.

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