JP2745685B2 - Thermoplastic resin pellet mixture and molded article using the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a thermoplastic resin pellet which provides a molded article having excellent moldability and excellent mechanical properties.

(Prior art) Fiber-reinforced thermoplastic resin pellets are produced by kneading a thermoplastic resin chip, reinforcing fibers having a length of 3 to 6 mm, and an inorganic filler depending on the application in an extruder, and then pelletizing. It had been. However, since the reinforcing fibers break during the kneading process in the extruder,
There was a drawback that the mechanical properties, particularly impact resistance, of the molded product obtained using the pellets were low.

In order to avoid such a drawback, a method has been studied in which a long fiber bundle is taken out while providing a thermoplastic resin from an extruder into a mold into which a long fiber bundle for reinforcement has been guided, and then pelletized. However, since the pellets have poor wettability of the thermoplastic resin to the reinforcing fibers, there is a disadvantage that the bending strength of a molded product obtained by using the pellets is not so large as expected.

In order to avoid such a drawback, a method has been studied in which a mixed fiber comprising a reinforcing fiber and a thermoplastic resin fiber is heated and pressed, and then pelletized. When the pellets are used, a molded article having excellent impact resistance, bending properties and tensile properties can be obtained.

However, molding processability (for example, mold releasability during injection molding, low molding shrinkage) has not yet been satisfied as fiber-reinforced thermoplastic resin pellets.

(Problems to be Solved by the Invention) The present invention has been made in view of the above circumstances, and an object of the present invention is to obtain a molded article having excellent impact resistance, bending properties, and tensile properties. An object of the present invention is to provide a fiber-reinforced thermoplastic resin pellet having a good moldability.

(Means for Solving the Problems) That is, the present invention relates to the following fiber obtained by cutting a fiber-reinforced thermoplastic resin rod processed from a mixed fiber obtained from a reinforcing fiber and a thermoplastic resin fiber. The reinforced thermoplastic resin pellet (A) and the thermoplastic resin pellet (B) having a lower melting temperature or softening temperature than the fiber reinforced thermoplastic resin pellet (A), or a higher melting index than the fiber reinforced thermoplastic resin pellet (A). ) Is mixed with a thermoplastic resin pellet mixture.

Fiber reinforced thermoplastic resin pellet (A): (i) Reinforced fiber content 30 to 80% by weight, (ii) Mixed dispersion ratio 20% or more, and molded using resin pellets (A) and (B) It is a molded article.

Fiber-reinforced thermoplastic resin pellet (A) in the present invention
Are polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polyamide resins such as nylon 6, nylon 66 and nylon 610, polyphenylene sulfide resins, polyether ketone resins, and polyolefins such as polyethylene and polypropylene. It is a resin capable of forming fibers, such as a base resin.

The thermoplastic resin pellet (B) in the present invention is a resin pellet having a lower melting temperature or softening temperature than the fiber-reinforced thermoplastic resin pellet (A) of the present invention, or a higher melting index (melt index) than the pellet. The thermoplastic resin constituting the pellets may be a compound which gives the thermoplastic resin constituting the fiber-reinforced thermoplastic resin pellets (A) a crystallization promoting effect to the resin, or an oligomer or polymer thereof, a release agent, or a plastic. Compounds or oligomers and polymers that give the agent effect, blended, such as an inorganic filler, modified by adding, modified thermoplastic resin, such as a thermoplastic resin compatible with the thermoplastic resin, What is necessary is just to improve the moldability of the thermoplastic resin.

Next, a typical method for producing the fiber-reinforced thermoplastic resin pellets of the present invention will be described.

That is, the reinforcing fiber and the thermoplastic resin fiber are mixed by a known method to obtain a mixed fiber. For example, a method in which both long fibers are aligned and electrostatically opened, and both single fibers are entangled with each other, or both long fibers are aligned and passed through jet turbulent air to spread and entangle. A mixed fiber is obtained by a method or the like. Here, the reason why the mixed fiber is used is that the content of the reinforcing fiber can be increased. Next, after heating the mixed fiber at a temperature equal to or higher than the melting point of the thermoplastic resin, a fiber reinforced thermoplastic resin rod is obtained by roller compression.

Next, the fiber-reinforced thermoplastic resin rod is cut into a length of 2 to 60 mm by a known method, for example, a pelletizer to obtain a fiber-reinforced thermoplastic resin composition pellet (A).

On the other hand, a thermoplastic resin and, if necessary, a crystallization accelerator, a release agent, an inorganic filler and the like are kneaded with an extruder to obtain a thermoplastic resin rod. The thermoplastic resin rod is cut into a length of 2 to 60 mm by a known method, for example, a pelletizer to obtain a fiber-reinforced thermoplastic resin composition pellet (B).

Next, the fiber-reinforced thermoplastic resin pellets (A) and the thermoplastic resin composition pellets (B) are mixed by a known method, for example, a V-blender (fiber-reinforced) to obtain a thermoplastic resin pellet mixture. The mixing ratio of the pellet (A) and the pellet (B) is 95/5 to 30/70 (weight ratio), preferably 90/10 to 50/50 (weight ratio).

In the fiber-reinforced thermoplastic resin pellet (A) of the present invention,
Since the reinforcing fiber has a length of 2 to 60 mm, preferably 6 to 20 mm, it has good biteability from the hopper to the screw during injection molding or extrusion molding, and the obtained molded article has tensile properties and bending properties. Good properties and impact resistance. Conversely, when the length of the reinforcing fiber exceeds 60 mm, the biting property deteriorates, and when the length of the reinforcing fiber is less than 2 mm, the tensile properties, bending properties, and impact resistance of the molded product decrease.

In the fiber-reinforced thermoplastic resin pellet (A) of the present invention,
Reinforced fiber content of fiber reinforced thermoplastic resin pellets is 30 ~
Since the content is 80% by weight, the wettability of the thermoplastic resin with respect to the reinforcing fibers is good, and the resulting molded article has good tensile properties, bending properties and impact resistance. Conversely, if the reinforcing fiber content of the fiber-reinforced thermoplastic resin composition exceeds 80% by weight, the wettability of the thermoplastic resin with respect to the reinforcing fibers becomes poor, and the tensile properties, bending properties,
Impact resistance is reduced. When the fiber content is less than 30% by weight, the tensile properties, bending properties, and impact resistance of the obtained molded product are low because the amount of reinforcing fibers is small.

The content of reinforcing fibers in the total weight of the (fiber reinforced) thermoplastic resin pellet mixture of the present invention is preferably 20/70% by weight, and the obtained molded product has good tensile properties, bending properties and impact resistance. And the effect of adding a crystallization accelerator, a mold release agent, an inorganic filler, etc. (for example, mold release properties, surface smoothness,
Low molding shrinkage).

When the fiber content in the fiber reinforced thermoplastic resin pellet mixture is adjusted to less than 20% by weight, the obtained molded product has low tensile properties, bending properties and impact resistance. On the other hand, when the reinforcing fiber content of the fiber-reinforced thermoplastic resin pellet mixture exceeds 70% by weight, the effect of adding a crystallization accelerator, a release agent, an inorganic filler, and the like is reduced.

In the (fiber-reinforced) thermoplastic resin pellet mixture of the present invention, the mixed dispersion ratio of the fiber-reinforced thermoplastic resin pellet (A) is 20% or more, the microvoid density index is 5 or more, and the macrovoid density index is 80 or less. Preferably, there is.

However, the mixed dispersion ratio referred to in the present invention refers to the number (N) of the total reinforcing fibers observed in a visual field at a magnification of 200 times when the cross section of the fiber-reinforced thermoplastic resin composition is observed with an optical microscope. When the number (n) of reinforcing fibers in contact with each other, Xi =
Calculate n / N × 100 and average Xi of 5 fields of view Is defined by

Further, the microvoid density index referred to in the present invention is to observe the cross section of the fiber reinforced thermoplastic resin composition with an optical microscope, magnification
The total value in 10 visual fields, where ni is the number of voids with a maximum length of 5μ or less per visual field unit area among the voids observed in a 200 times visual field Is defined by

Further, the macro void density index referred to in the present invention, by observing the cross section of the fiber-reinforced thermoplastic resin composition with an optical microscope, in a visual field of 20 times magnification, the maximum length of the observed voids of the void of 100μ or more. The total value for 10 visual fields, where ni is the number per visual field unit area Is defined by

In the (fiber-reinforced thermoplastic resin pellet mixture) of the present invention, since the mixing and dispersing ratio of the fiber-reinforced thermoplastic resin pellet (A) is 20% or more, there is little floating of the fiber on the surface of the molded product, and the surface smoothness is low. On the other hand, when the mixing and dispersing ratio is less than 20%, the fiber is often raised on the surface of the molded product, and the surface smoothness is deteriorated.

The fiber-reinforced thermoplastic resin pellet (A) has a microvoid density index of 5 or more and a macrovoid density index of 80 or more.
It is preferable that, in this case, the breakage of the reinforcing fibers during molding is reduced, and further, the void generation rate in the molded product is reduced, so that the tensile properties, bending characteristics,
Good impact resistance. Conversely, the macrovoid density index
If it exceeds 80, the void generation rate of the molded article rapidly increases, and this becomes a source of destruction, so that the tensile properties and bending properties deteriorate. When the microvoid density index is less than 5,
Due to a decrease in the bending elastic modulus in the longitudinal direction of the fiber-reinforced thermoplastic resin composition in the pellet, the fiber-reinforced thermoplastic resin composition pellet in an unmelted state in a compression section from a screw supply section of an injection molding machine or an extrusion molding machine. Since the breakage of the reinforcing fibers in the inside increases, the tensile properties, bending properties, and impact resistance of the molded product decrease.

Further, the thermoplastic resin pellet (B) in the present invention
Is that the melting temperature or softening temperature is lower or the melting index is higher than that of the resin pellet (A) containing the reinforcing fiber, so that the pellet (B) is broken in the injection molding machine of the reinforcing fiber in the pellet (A). Can be suppressed, and the fiber length distribution of the reinforcing fibers does not spread, and the reinforcing fibers can be kept long, so that high mechanical properties can be exhibited. Further, the pellet (B) has an effect of suppressing the floating of the reinforcing fiber and improving the appearance such as surface smoothness and gloss of the molded product.

In addition, the fiber-reinforced thermoplastic resin pellet of the present invention (A)
Examples of the thermoplastic resin fibers used in the production of polyester fiber include polyester fibers such as polyethylene terephthalate and polybutylene terephthalate.
6, polyamide fibers such as nylon 610 and nylon 612, polyolefin fibers such as polyethylene and polypropylene,
Polyphenylene sulfide fiber, polyether ketone fiber, polyether ether ketone fiber and the like can be used.

Inorganic fibers such as glass fibers and carbon fibers can be used as the reinforcing fibers.

Examples of the thermoplastic resin constituting the thermoplastic resin pellet (B) include polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polyamide resins such as nylon 6, nylon 66, nylon 610, and nylon 612, and polyethylene and polypropylene. Polyolene fin resin, polyphenylene sulfide resin, polyether ketone resin, polyether ether ketone resin and the like can be used.

Further, it is preferable that the thermoplastic resin constituting the fiber-reinforced thermoplastic resin composition and the thermoplastic resin constituting the thermoplastic resin composition are of the same kind, but the injection molding and the compatibility at the time of extrusion molding are sufficiently good. If so, the thermoplastic resin fibers and the thermoplastic resin may be different types.

Also, a release agent as a constituent of the thermoplastic resin composition pellet (B), and inorganic fillers such as lower alcohol esters of higher fatty acids, polyhydric alcohol esters of fatty acids, liquid paraffin, etc.
Barium sulfate, shirasu, asbestos, aluminum hydroxide, antimony oxide and the like can be used. Improve the quality and functionality of other components depending on the application, such as dispersants, organic polymer type dispersants, flame retardants, antistatic agents, antioxidants, ultraviolet absorbers, colorants, crystallization accelerators, etc. Substances can be incorporated. Here, examples of the crystallization accelerator include an alkylene glycol derivative, a polyalkylene glycol derivative, an ionomer, titanium dioxide, talc, and mica.

(Example) Example 1 A mixed fiber for obtaining a fiber-reinforced thermoplastic resin composition was constructed using E glass fiber and polyethylene terephthalate fiber having the following characteristics.

E glass fiber: Total fineness 67.5 tex (JIS R3420) Number of filaments 400 (JIS R3420) Polyethylene terephthalate fiber: Total fineness 150 denier (JIS L1013) Number of filaments 30 (JIS L1013) That is, 8 polyethylene terephthalate fibers are E glass + 0.3% overfeed for 4 fibers, Taslan method (Air pressure: 5kg / cm ² G, Processing speed: 100m
at a rate of / min continuously in heated air to 230 ° C,
Continue to add N ₂ gas to the heating zone where the far infrared heater is installed.
After raising the temperature of the mixed fiber to 300 ° C. while flowing 5 Nm ³ / h to melt the polyethylene terephthalate fiber, 6 pairs of male and female meshing rollers (roller temperature: 40 to 55 ° C., forming groove width: 3 mm, roller Pressure (linear pressure): 2kg / cm) 3mm wide and 1mm thick
Into a rod, and cut the rod into a length of 10 mm to produce fiber-reinforced thermoplastic resin composition pellets (glass fiber content 6%).
6.7% by weight).

The melting start temperature of the fiber-reinforced thermoplastic resin composition pellet is 250 ° C., and the result of observing the cross section of the pellet is as follows:
The mixed dispersion ratio was 70%, the microvoid density index was 12, and the macrovoid density index was 6.

On the other hand, polyethylene terephthalate (intrinsic viscosity 0.63dl
/ g) 87% by weight, polyethylene glycol (molecular weight 600)
8% by weight of diglycidyl ether (about 440 epoxies)
After premixing 5% by weight of talc (average particle size 10μ),
A strand obtained by melt-kneading at 250 to 275 ° C. using a 40 mm-2 vent extruder was cut into a length of 10 mm to obtain a thermoplastic resin mixture pellet. The melting start temperature of this pellet is 245
° C.

Next, the fiber-reinforced thermoplastic resin composition pellets and the thermoplastic resin composition pellets were adjusted to a weight ratio of 75/25 and mixed by a V-type blender, and a (fiber-reinforced) thermoplastic resin pellet mixture (glass fiber Content 50% by weight).

The (fiber reinforced) thermoplastic resin pellets were dried under reduced pressure at 120 ° C for 17 hours, and then cylinder temperature was 300 ° C-290 ° C-280 ° C.
A test piece was molded by an injection molding machine (mold clamping force: 160 ton, screw: φ50 mm, compression ratio (depth ratio) 2.09, with check valve) adjusted to 300 ° C, nozzle temperature 300 ° C, and mold temperature 95 ° C. Table 1 shows the properties of the molded products.

 However, each characteristic was evaluated based on the method shown below.

(1) Releasability: The mold release and the sprue coming off when forming the test piece were visually evaluated.

(2) Tensile properties: ASTM D638 (3) Bending properties: ASTM D790 (4) Akzot impact strength: ASTM D256 (5) Melting onset temperature: Rise of melting peak obtained by differential calorimeter (PerkinElmer) temperature. (Heating rate 20 ° C / min).

Comparative Example 1 Polyethylene terephthalate fiber described in Example 1
Twelve fibers are supplied in an overfeed state of + 0.3% to three E glass fibers, and the Taslan method (air pressure: 5 kg / cm ² G,
(Processing speed: 100 m / min) to obtain a mixed fiber.

Next, a fiber-reinforced thermoplastic resin composition pellet was obtained in the same manner as in Example 1 (mixing dispersion ratio: 74%, microvoid density index: 12, macrovoid density index: 7, glass fiber content: 50% by weight). .

Test pieces were molded and evaluated from the fiber-reinforced thermoplastic resin composition pellets in the same manner as in Example 1. Table 1 shows the properties of the molded products.

Comparative Example 2 40 E glass fibers described in Example 1 were passed through a 300 ° C. die (exit cross section: width 3 mm, thickness 1 mm) installed at the tip of a φ40 mm-2 vent extruder, and then carried out. A mixture consisting of 95% by weight of polyethylene terephthalate, 3.75% by weight of polyethylene glycol diglycidyl ether, and 1.25% by weight of talc described in Example 1 was fed from an extruder, and was subjected to 250
While being melted and kneaded at 275275 ° C. and extruded into a heating die, the E glass fiber fused with the polyethylene terephthalate resin was pulled out at 10 m / min. Next, the drawn material was cooled and solidified by running in a water tank, and then cut to a length of 10 mm to obtain fiber-reinforced thermoplastic resin pellets (glass fiber content: 50% by weight).

The fiber-reinforced thermoplastic resin pellets were molded and evaluated by the method described in Example 1. Table 1 shows the properties of the molded products.

Example 2 The fiber-reinforced thermoplastic resin composition pellets and the thermoplastic resin composition pellets described in Example 1 were adjusted to a weight ratio of 5/5 and mixed by a V-type blender to obtain a fiber-reinforced thermoplastic resin pellet ( The glass fiber content was 33% by weight.

The fiber-reinforced thermoplastic resin pellets were molded and evaluated by the method described in Example 1. Table 1 shows the properties of the molded products.

Comparative Example 3 Polyethylene terephthalate fiber described in Example 1
16 fibers are supplied in an overfeed state of + 0.3% to two E glass fibers, and the Taslan method (air pressure: 5 kg / cm ² G,
(Processing speed: 100 m / min) to obtain a mixed fiber.

Next, pellets of the fiber-reinforced thermoplastic resin composition were obtained in the same manner as in Example 1. (Mix dispersion ratio: 73%, microvoid density index: 13, macrovoid density index: 5, glass fiber content: 33% by weight) The test piece was prepared from the fiber-reinforced thermoplastic resin composition pellets in the same manner as in Example 1. Molded and evaluated. Table 1 shows the properties of the molded products.

It is clear from Example 1 and Comparative Example 1 and Example 2 and Comparative Example 3 that the effect of improving the moldability of the product of the present invention is remarkable.
From Example 1 and Comparative Example 2, it is clear that a molded article obtained from the pellet mixture of the present invention is suitable for securing high mechanical properties.

(Effect of the Invention) The use of the (fiber-reinforced) thermoplastic resin pellet mixture of the present invention has excellent moldability and high mechanical properties which could not be achieved by the conventional kneading method of resin and reinforcing fibers. ,
In addition, a molded article excellent in appearance can be obtained.

Claims (2)

(57) [Claims] 1. A fiber-reinforced thermoplastic resin pellet (A) obtained by cutting a fiber-reinforced thermoplastic resin rod processed from a mixed fiber obtained from a reinforcing fiber and a thermoplastic resin fiber, It is characterized by being mixed with a thermoplastic resin pellet (B) having a lower melting temperature or softening temperature than that of the fiber-reinforced thermoplastic resin pellet (A), or a higher melting index than that of the fiber-reinforced thermoplastic resin pellet (A). Thermoplastic resin pellet mixture. Fiber reinforced thermoplastic resin pellets (A): (i) Reinforced fiber content 30 to 80% by weight, (ii) Mixed dispersion ratio 20% or more 2. A molded article formed using the fiber-reinforced thermoplastic resin pellet (A) and the thermoplastic resin pellet (B) according to claim 1.