JP3510002B2 - Fiber reinforced resin composition and molded article - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fiber reinforced resin composition, and more particularly to a fiber reinforced resin composition which is excellent in mechanical properties such as rigidity and strength and environmental stress crack resistance, and which is particularly suitable as a material for hollow molded articles.

[0002]

2. Description of the Related Art Polyolefin resins have characteristics such as easy moldability, chemical resistance, etc., and are lightweight and economically inexpensive. Therefore, they are used as packaging materials for cosmetics, pharmaceuticals, toiletries, foods, etc. It has been used extensively. Mechanical properties such as rigidity and strength, environmental stress crack resistance, and the like are required for these packaging materials, particularly containers formed by the blow molding method. In order to improve these physical properties, in recent years, development of high-rigidity and high-strength materials by compounding with glass fiber etc. has been actively carried out, and various inorganic reinforcing materials, reinforcing materials such as inorganic fillers are used as matrix resins. It is widely known that by blending, a resin composition having excellent rigidity, strength, heat resistance, dimensional stability and the like can be obtained. However, the specific gravity of various inorganic reinforcing materials to be compounded is large,
When these are compounded in a matrix resin, the mechanical properties such as rigidity and strength of the resin composition are improved, but the weight is significantly increased, and one of the advantages of the resin material is that it is lighter than metal materials and the like. In addition to the above, the interface strength between the inorganic reinforcing material and the matrix resin is weak, so that environmental stress crack resistance is also impaired.

In order to solve these problems, compounding of carbon fiber, aramid fiber and polyethylene fiber having high elasticity and high strength in place of the inorganic reinforcing material has been studied, and mechanical properties such as rigidity and strength have been studied. It is described in JP-A-6-9802 that it is possible to improve the physical properties of. Further, resin compositions using silane-crosslinked polyethylene fibers as a reinforcing material are described in JP-A-63-296927 and JP-A-64-26783. However, these resin compositions have a drawback that mechanical strength such as rigidity and strength of the resulting resin composition is not sufficiently improved because the adhesive strength between the fiber reinforcement and the matrix interface is weak. When the matrix resin is a resin having a polar group such as an epoxy resin, the bonding strength can be improved by adding a polar group to the fiber reinforcement by low temperature plasma treatment or corona discharge treatment. Is a polyolefin resin having no polar group, when using a silane cross-linked polyolefin fiber as the fiber reinforcement, because it has a polar group in its molecular structure,
The adhesive strength at the interface between the fibers and the matrix resin becomes weak. At present, there is a strong demand for development of a resin composition suitable for a hollow molded container, which is lightweight, has excellent mechanical properties, and has excellent resistance to environmental stress cracking, mainly in the field of toiletry products.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a fiber reinforced resin composition which is capable of solving the problems of the prior art and which is excellent in mechanical properties such as rigidity and strength and environmental stress crack resistance. With the goal.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventor has found that the present invention can be achieved by blending a matrix resin with crosslinked polyolefin fibers having high elasticity and low surface free energy. Reached
That is, the above-mentioned subject is polyolefin resin 50-90.
50% to 10% by weight of crosslinked polyolefin fibers having a tensile elastic modulus of 30 GPa or more and a surface free energy of less than 40 ergs / cm ^{2 with} respect to % by weight are uniformly mixed and dispersed.
Fiber-reinforced resin composition characterized that you have been, polyolefin resin, JIS K7210, the melt flow rate measured according to the condition 4 is 0.01 to 10 g / 10
The fiber-reinforced resin composition described above, wherein the fiber-reinforced resin composition is a polyethylene resin, and the cross-linked polyolefin fiber is a cross-linked polyethylene fiber cross-linked by irradiation, the fiber-reinforced resin composition described above, This can be solved by a molded article characterized by hollow molding of the fiber-reinforced resin composition described above.

The polyolefin resin in the present invention means
Homopolymers or copolymers of olefins, such as polyethylene, polypropylene, copolymers of ethylene and α-olefins, and the like, and the α-olefins include, for example, 1-butene, 1-hexene and the like. Can be mentioned. The polyolefin resin of the present invention may be one type or a combination of two or more types. In the polyolefin resin used in the present invention, various additives used for ordinary polyolefin resins such as stabilizers, antioxidants, ultraviolet absorbers, processability improvers, lubricants, antistatic agents, flame retardants, pigments, dyes and fillers. You may use it in combination with an agent.

The polyolefin resin used in the present invention has a melt flow rate (measured according to JIS K7210, condition 4: hereinafter referred to as MFR) of 0.01 to 10 g / 10.
Min, preferably 0.2 to 3.0 g / 10 min. MFR of less than 0.01 g / 10 minutes and 10
Those exceeding g / 10 minutes are not suitable because the molding processability is significantly reduced.

The crosslinked polyolefin fiber used in the present invention is obtained by subjecting the polyolefin fiber to a crosslinking treatment according to JIS.
The tensile modulus measured according to R7601 is 30 GPa or more, the surface free energy is less than 40 erg / cm ² , the fiber diameter is in the range of 5 to 100 μm, and the fiber length is 0.2.
Those within a range of up to 2 mm are preferable. In the present invention, the surface free energy of the crosslinked polyolefin fiber can be determined from the contact angle measured using water and methylene iodide, and can be determined according to the method disclosed in JP-A-61-241330. . When the tensile elastic modulus of the crosslinked polyolefin fiber is less than 30 GPa, the effect of sufficiently improving the mechanical properties of the resin composition cannot be obtained. In addition, the surface free energy of crosslinked polyolefin fiber is 4
When it is 0 ergs / cm 2 or more, the adhesive strength with the polyolefin resin that serves as the matrix is lowered, and the effect of sufficiently improving the mechanical properties of the resin composition cannot be obtained. further,
If the fiber diameter of the crosslinked polyolefin fiber is less than 5 μm, a sufficient effect of improving the mechanical properties of the resin composition cannot be obtained,
If it exceeds 100 μm, not only the moldability is deteriorated, but also the mechanical properties of the resin composition are not improved. further,
When the fiber length of the crosslinked polyolefin fiber is less than 0.2 mm, the effect of sufficiently improving the mechanical properties and environmental stress crack resistance of the resin composition cannot be obtained, and when it exceeds 2 mm, the crosslinked polyolefin fiber is kneaded or molded. May cause deformation of the resin composition, and may cause clogging or gel generation inside the extruder.

The crosslinked polyolefin fiber in the present invention is obtained by melt spinning a polyolefin resin, stretching and orienting the obtained fiber, and then crosslinking. Examples of the method for crosslinking include a method of crosslinking by irradiation with radiation, a method of simultaneously melt-mixing a crosslinking agent and a crosslinking aid, and the like. Among them, the method using radiation irradiation is preferable because the operation is simple and the crosslinking treatment can be performed in a short time. The type of cross-linked polyolefin resin is not particularly limited, but MFR 0.45 to 1.2 g
Those within the range of / 10 minutes are preferable because they can be easily processed into fibrous form. Examples of the method for melt-spinning a polyolefin resin include a usual method for producing a base yarn for a polyolefin drawn yarn and a method for producing the same drawn yarn. Also,
When the polyolefin fiber is stretched, a fiber having high elasticity and high strength can be obtained. Therefore, it is preferable to stretch the polyolefin fiber to 3 to 15 times its original length.

As the radiation for irradiation used in the present invention, ionizing radiation such as electron beam from electron accelerator, γ ray and X ray is used. The dose rate, the irradiation temperature and the irradiation time must be values within a range such that the irradiated polyolefin fibers form the necessary crosslinks and do not cause deterioration such as discharge breakdown. The preferable dose rate, irradiation temperature and irradiation time are MF of the cross-linked polyolefin resin.
It depends on R, crystallinity, kind of additives, etc., and is determined so as to satisfy the target physical properties of the crosslinked polyolefin fiber. In the present invention, in order to prevent the discharge breakdown of the polyolefin resin by irradiation with radiation, or in order to accelerate the crosslinking of the polyolefin resin by irradiation, the polyolefin fiber to be irradiated is premixed with an antioxidant such as dibrovagyl malate. You may.

The blending ratio of the polyolefin resin and the crosslinked polyolefin fiber can be arbitrarily selected depending on the use of the resin composition, but usually 10 to 50% by weight as the crosslinked polyolefin fiber with respect to the finally obtained resin composition. It is a range. If the content of the crosslinked polyolefin fiber is less than 10% by weight, the effect of sufficiently improving the mechanical properties of the resin composition cannot be obtained. On the other hand, when the amount of the crosslinked polyolefin fiber is more than 50% by weight, the fluidity of the composition in the molten state is lowered, the workability in each step such as extrusion is lowered, and further, uniform mixing and dispersion is performed. Since the state cannot be obtained, the appearance of the molded product made of the resin composition is deteriorated.

In the present invention, the blending ratio of the polyolefin resin is preferably 50 to 90% by weight. If it is less than 50% by weight, the fluidity of the composition in the molten state is lowered, so that the molding processability is lowered and the appearance of the molded article is deteriorated. Further, if it exceeds 90% by weight, the effect of improving the mechanical properties of the resin composition becomes insufficient.

The fiber-reinforced resin composition of the present invention is obtained by dry blending pellets, granules, or powders of a polyolefin resin with crosslinked polyolefin fibers, and then using a polyolefin in an extruder such as a conventional single-screw or twin-screw extruder. Tree
It is obtained by mixing at a temperature at which the fat melts, cooling after extrusion, and cooling.

The fiber-reinforced resin composition of the present invention can be formed into a molded product by various methods. Among them, a molded product obtained by the hollow molding method is preferable because the effect of the invention is great. Examples of the blow molding method include direct blow molding, injection blow molding, stretch blow molding and the like.

[0015]

【Example】

Crosslinked Polyolefin Fibers I to VI Crosslinked polyolefin fibers were manufactured by using a drawing raw yarn (strand) manufacturing apparatus having the following specifications. A full flight type screw having a screw diameter of 20 mmφ, an effective screw length (L / D) of 20, a screw compression ratio of 3.0, a die length of 240 mm, a die outlet inner diameter of 1 mmφ, and a die of L / D = 40. As a resin for crosslinked polyolefin fiber, a high-density polyethylene resin (trade name: SHORELEX S6006M, manufactured by Showa Denko KK) having an MFR of 0.5 g / 10 min was used, and the extruder supply section, the melt compression section, the measurement section, Set the die temperature to 170 ℃, 200 ℃,
Set 220 ℃, 220 ℃, screw rotation speed 30r
Then, the polyethylene fiber having an outer diameter of 250 μmφ was produced by setting pm and taking it off at a speed of 150 m / min with a take-up machine. The polyethylene fiber obtained was subsequently stretched and oriented 11 times in a boiling water bath. Next, this polyethylene fiber was subjected to various crosslinking treatments shown in Table 1. In the case of radiation treatment, an acceleration energy of 1.
Irradiation with 5 MeV and a dose rate of 0.2 Mrad / sec was performed to produce a crosslinked polyolefin fiber. In addition, JP-A-63-296
Silane-crosslinked polyethylene fibers were produced based on the method described in Japanese Patent No. 927. The elastic modulus of the produced crosslinked polyolefin fiber was measured based on JIS R7601. Further, the surface free energy of the crosslinked polyolefin fiber was calculated by measuring the contact angle with water and methylene iodide based on the method described in JP-A-61-241330. The obtained crosslinked polyolefin fibers are shown in Table 1.

(Examples 1 to 5 and Comparative Examples 1 to 8) The crosslinked polyolefin fiber was cut into a length of 1 mm,
Dry blend with the polyolefin resin so that the blending ratio is as shown in Table 2, and melt the polyolefin resin with a single-screw extruder .
After mixing at different temperatures, it was pelletized. As the polyolefin resin, (A) MFR 0.25 g / 10 min high-density polyethylene resin (trade name: SHORELEX S6002F
D, Showa Denko KK), (B) MFR 3.0 g / 10
Minute high-density polyethylene resin (trade name: SHOREEX 5
020, Showa Denko KK), (C) MFR 20g / 1
A 0 minute high-density polyethylene resin (trade name: SHORELEX T7300FL, manufactured by Showa Denko KK) was used. Pellets of the crosslinked polyolefin fiber-reinforced polyolefin resin composition were produced using a single-screw extruder having the following specifications. Screw diameter 50 mmφ, effective screw length (L / D) 2
Full flight type screw with 0 and screw compression ratio of 3.0. The set temperatures of the extruder supply unit, the melt compression unit, the metering unit, and the die unit are 150 ° C, 180 ° C, 200 ° C, and 20 ° C, respectively.
The molten strand was extruded at a screw rotation speed of 40 rpm, set at 0 ° C., solidified in a cooling water tank at 30 ° C., and then cut into pellets by a cutter. The flexural modulus of the produced resin composition pellet was measured according to JIS K7074, and the tensile strength (yield) was measured according to JIS K7073. The results are shown in Table 2. Moreover, the hollow molding container (380 ml flat bottle) was manufactured from the said resin composition pellet using the Sumitomo Heavy Industries Ltd. make BEKUM-SE91 hollow molding machine. The extruder set temperature of the blow molding machine is
The extruder supply unit, the melt compression unit, the metering unit, and the die unit were set at 150 ° C, 170 ° C, 175 ° C, and 180 ° C, respectively,
The parison was extruded at a screw rotation speed of 25 rpm to manufacture a hollow molded container at a mold cooling temperature of 20 ° C. Environmental stress crack resistance (F50) of manufactured hollow molded container is ASTM
It was measured by a method according to D2561. The results are shown in Table 2.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

The fiber-reinforced resin composition of the present invention has rigidity,
It has excellent mechanical properties such as strength, is superior in environmental stress crack resistance to conventional fiber reinforced resin compositions, and is lightweight, so it can be used for hollow molding of toiletry product containers, industrial chemical cans, kerosene cans, etc. It is suitable as a material for containers.

Claims (4)

(57) [Claims] 1. A polyolefin resin in an amount of 50 to 90% by weight .
On the other hand , 50 to 10% by weight of crosslinked polyolefin fibers having a tensile elastic modulus of 30 GPa or more and a surface free energy of less than 40 ergs / cm ² are uniformly mixed and dispersed. Resin composition. 2. The polyolefin resin is JIS K72.
10. The fiber-reinforced resin composition according to claim 1, which is a polyethylene resin having a melt flow rate of 0.01 to 10 g / 10 minutes measured according to the conditions of 10 and 4. 3. The fiber-reinforced resin composition according to claim 1, wherein the crosslinked polyolefin fiber is a crosslinked polyethylene fiber crosslinked by irradiation with radiation. 4. A molded article obtained by blow molding the fiber-reinforced resin composition according to claim 1.