JP2016003331A - polypropylene - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polypropylene having excellent mechanical characteristics.SOLUTION: A raw material polypropylene is heat-treated at temperatures of equal to or higher than the temperature 15°C lower than the melting point of the raw material polypropylene, measured by a differential scanning calorimetric method (DSC method) based on the method specified in JIS K7122(1987), and lower than the melting point of the raw material polypropylene and irradiated with an ionization radiation. The procedure cross-links the raw material polypropylene and improves the mechanical characteristics, especially the tensile elastic modulus, stably in proportion to the absorption amount of the ionization radiation irradiated.

Description

  The present invention relates to polypropylene.

  Polypropylene is used in a wide range of fields such as automotive parts materials, electrical product parts materials, household goods materials, and packaging materials.

In recent years, it has been studied to improve various physical properties of polypropylene by irradiating with an electron beam. For example, as a raw material for a film having a low thermal shrinkage, a high dielectric breakdown voltage, and excellent stretchability, ( 1) Based on ASTM D1238, the melt flow rate (MFR) measured at 230 ° C. under a 2.16 kg load is in the range of 1 to 10 g / 10 min. (2) Measured using ¹³ C-NMR The pentad isotactic fraction (mmmm fraction) is 94% or more, (3) the amount of ash obtained by complete combustion in air is 30 ppm or less, and (4) ion chromatography. Polypropylene film for film capacitors obtained by irradiating a propylene homopolymer having a chlorine content of 10 ppm or less measured by the above with an absorbed dose of 0.1 to 500 kGy. Pyrene has been proposed (e.g., see Patent Document 1.).

International publication pamphlet WO2010 / 107052A1

  On the other hand, depending on the purpose and application used, further improvement of the mechanical properties of polypropylene is desired.

  An object of the present invention is to provide a polypropylene having excellent mechanical properties.

  The polypropylene of the present invention is made of a raw material polypropylene having a temperature 15 ° C. lower than the melting point of the raw material polypropylene measured by a differential scanning calorimetry method (DSC method) based on the method defined in JIS K 7122 (1987). It is characterized by being obtained by irradiating with ionizing radiation after heat treatment at a temperature lower than the melting point.

  In the polypropylene of the present invention, it is preferable that the absorbed dose of the ionizing radiation is 10 kGy or more and 100 kGy or less.

  The polypropylene of the present invention is a raw material polypropylene whose temperature is 15 ° C. lower than the melting point of the raw material polypropylene measured by the differential scanning calorimetry method (DSC method) based on the method specified in JIS K 7122 (1987) and lower than the melting point of the raw material polypropylene. After the heat treatment with, ionizing radiation is further irradiated.

  Therefore, the raw material polypropylene is cross-linked, and the mechanical properties of polypropylene, in particular, the tensile elastic modulus can be improved.

  In the polypropylene of the present invention, first, the raw material polypropylene is heat-treated.

  Examples of the raw material polypropylene include a propylene homopolymer (homopolypropylene), a copolymer of propylene and a monomer copolymerizable with propylene, and the like.

  In the copolymer, examples of the monomer copolymerizable with propylene include α-olefins (excluding propylene). Specific examples include ethylene, 1-butene, 1-pentene, 1-pentene, and the like. Hexene, 1-octene, 1-decene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, etc. And α-olefins having 2 to 20 carbon atoms.

  These monomers copolymerizable with propylene can be used alone or in combination of two or more.

  When using a copolymer of propylene and a monomer copolymerizable with propylene, the content of the structural unit derived from propylene in the copolymer is, for example, 95 mol% or more and can be copolymerized with propylene. The content of structural units derived from such monomers is, for example, 5 mol% or less.

  As a raw material polypropylene, Preferably, a homo polypropylene is mentioned.

  These raw material polypropylenes can be used alone or in combination of two or more.

  In addition, there are three stereoisomers of raw material polypropylene, atactic polypropylene, isotactic polypropylene and syndiotactic polypropylene, due to the regularity of arrangement of methyl groups in the side chain.

  Of these stereoisomers, isotactic polypropylene is preferable. These stereoisomers can be used alone or in combination of two or more.

  Note that the mmmm pentad fraction of isotactic polypropylene is, for example, 80% or more.

  Polycrystalline polymorphism (crystal structure) of polypropylene, especially isotactic polypropylene, includes α phase (monoclinic structure), β phase (hexagonal crystal structure), and γ phase (orthorhombic crystal structure). And a mesophase (smectic crystal structure) which is an intermediate order state between amorphous and amorphous. The α phase is further divided into an α1 phase and an α2 phase.

  When isotactic polypropylene in a molten state or in solution is crystallized by a usual method such as allowing to cool at room temperature (25 ° C.) and gradually cooling it, the crystal structure is an isotactic polypropylene. Is obtained.

  The isotactic polypropylene having a mesophase crystal structure can be obtained, for example, by a method of rapidly immersing isotactic polypropylene in a molten state or in a solution and quickly immersing it in ice water.

  The crystal structure of the raw material polypropylene can be determined by a known method such as an X-ray diffraction method (XRD method).

  The crystal structure of the raw material polypropylene preferably has a mesophase.

  If the raw material polypropylene has a mesophase, the crystallinity can be increased by heat treatment (described later), and as a result, the mechanical properties of polypropylene, in particular, the tensile modulus can be improved.

  The crystal structure of raw material polypropylene and the crystal structure of polypropylene may be a single phase, or two or more phases may be mixed.

  The proportion of the mesophase in the raw material polypropylene can be measured by a known method such as X-ray diffraction method (XRD method) or differential scanning calorimetry (DSC method). For example, the proportion of mesophase measured by the DSC method is It is 20% or more, preferably 30% or more, and for example, 40% or less.

  If the proportion of the mesophase in the raw material polypropylene is within the above range, the crystallinity can be increased by heat treatment (described later), and as a result, the mechanical properties of polypropylene, in particular, the tensile elastic modulus can be improved. Can do.

  Moreover, the weight average molecular weight of a raw material polypropylene is 10,000 or more, for example, and is 500,000 or less, for example.

  The raw material polypropylene includes other polymers, rust preventives (rust preventive pigments), antioxidants, ultraviolet absorbers, light stabilizers, silane coupling agents, and epoxy as long as the effects of the present invention are not impaired. Resin, catalyst, coatability improver, leveling agent, nucleating agent, lubricant, mold release agent, antifoaming agent, plasticizer, surfactant, pigment, dye, organic or inorganic fine particles, antifungal agent, flame retardant, filling An additive such as an agent can be appropriately blended. In addition, the mixture ratio of an additive is suitably set according to the objective and use.

  The method for molding the raw material polypropylene is not particularly limited, and examples thereof include known molding methods such as melt extrusion molding, injection molding, compression molding, and inflation molding.

  In such a method, molding conditions and the like in melt extrusion molding are appropriately set according to the type of raw material resin used.

  Moreover, it does not restrict | limit especially as a shape of raw material polypropylene, For example, the solid shape according to uses, such as a film form, a sheet form, a pipe form, is mentioned, Preferably, a film form is mentioned.

  The method for heat-treating the raw material polypropylene is not particularly limited. For example, the raw material polypropylene can be heated in a heat treatment furnace and air-cooled to room temperature (25 ° C.) after the heat treatment time has elapsed.

  As a heat treatment condition, the heat treatment temperature is, for example, 15 ° C. lower than the melting point of the raw material polypropylene, preferably 10 ° C. lower than the melting point of the raw material polypropylene, more preferably 8 ° C. lower than the melting point of the raw material polypropylene. Also, for example, it is less than the melting point of the raw material polypropylene, preferably 2 ° C. or lower than the melting point of the raw material polypropylene, more preferably 5 ° C. or lower from the melting point of the raw material polypropylene.

  When the heat treatment temperature is within the above range, the mechanical properties of polypropylene, in particular, the tensile modulus can be improved.

  The melting points of the raw material polypropylene and polypropylene are melting peak temperatures of the raw material polypropylene and polypropylene, respectively, measured by a differential scanning calorimetry method (DSC method) based on a method defined in JIS K 7122 (1987).

  The heat treatment time is, for example, 1 minute or more, preferably 5 minutes or more, more preferably 10 minutes or more, and for example, 40 minutes or less, preferably 30 minutes or less, more preferably 20 minutes or less. is there.

  When the heat treatment time is within the above range, the mechanical properties of polypropylene, in particular, the tensile elastic modulus can be improved.

  The crystallinity of the heat-treated raw material polypropylene can be determined from known methods such as X-ray diffraction, differential scanning calorimetry (DSC method), density measurement by Archimedes method, and is usually 60% or less. For example, it is 38% or more, preferably 40% or more, and more preferably 44% or more.

  If the crystallinity of the heat-treated raw material polypropylene is within the above range, the mechanical properties of polypropylene, in particular, the tensile modulus can be improved.

  Preferably, the raw material polypropylene is preheated before the heat treatment.

  The method for pre-heat treatment of the raw material polypropylene is not particularly limited, and examples thereof include the same method as the method of heat-treating the raw material polypropylene described above.

  As a pre-heat treatment condition, for example, the pre-heat treatment temperature is 60 ° C. lower than the melting point of the raw material polypropylene, preferably 50 ° C. lower than the melting point of the raw material polypropylene, more preferably 45 ° C. lower than the melting point of the raw material polypropylene. More than the temperature, for example, below 20 ° C lower than the melting point of the raw material polypropylene, preferably below 30 ° C lower than the melting point of the raw material polypropylene, more preferably below 35 ° C lower than the melting point of the raw material polypropylene. .

  If the preliminary heat treatment temperature is within the above range, the mechanical properties of polypropylene, in particular, the tensile elastic modulus can be improved.

  The preliminary heat treatment time is, for example, 10 minutes or more, preferably 30 minutes or more, more preferably 60 minutes or more, and for example, 120 minutes or less, preferably 100 minutes or less, more preferably 80 minutes or less. It is.

  When the preliminary heat treatment time is within the above range, the mechanical properties of polypropylene, in particular, the tensile elastic modulus can be improved.

  Subsequently, ionizing radiation is irradiated to the heat-treated raw material polypropylene.

  Examples of ionizing radiation include γ rays and electron beams.

  If gamma rays or electron beams are used as the ionizing radiation, the raw material polypropylene can be ionized and crosslinked.

  Examples of the γ-ray radiation source include cobalt 60, and the electron beam can be generated by accelerating the thermal electrons obtained by heating a tungsten filament, for example.

  The method of irradiating the heat-treated raw material polypropylene with ionizing radiation is not particularly limited. For example, the heat-treated raw material polypropylene is sealed in a glass ampoule in an argon atmosphere, and a predetermined absorbed dose is obtained at room temperature (25 ° C.). As described above, the distance from the ionizing radiation source to the heat-treated raw material polypropylene and the irradiation time are adjusted.

  The irradiation condition of the ionizing radiation is that the absorbed dose is, for example, 10 kGy or more, preferably 30 kGy or more, for example, 100 kGy or less, preferably 60 kGy or less. If it is, about other conditions, it will not specifically limit.

  Regarding the absorbed dose of ionizing radiation, for example, the absorbed dose of γ-rays can be measured with an alanine dosimeter, a PMMA (Polymethylmethacrylate) dosimeter, or the like. The absorbed dose of the electron beam is a value calculated by the product of the acceleration voltage, current, and irradiation time of the electron beam irradiation apparatus.

  The absorbed dose of ionizing radiation is a total amount, and may be irradiated only once or may be irradiated a plurality of times. Further, the ionizing radiation may be irradiated with only one type of line type or may be irradiated with a plurality of types of line types, preferably irradiation with only one type of line type.

  If the absorbed dose of ionizing radiation is within the above range, the mechanical properties of polypropylene, in particular, the tensile elastic modulus can be improved.

  In this way, by irradiating the heat-treated raw material polypropylene with ionizing radiation, the raw material polypropylene is cross-linked, and the mechanical properties of the polypropylene, in particular, the tensile modulus can be improved.

  The polypropylene of the present invention thus obtained is further irradiated with ionizing radiation after heat-treating the raw material polypropylene.

  Therefore, the mechanical properties of polypropylene, in particular, the tensile elastic modulus can be improved.

  Such polypropylene can be suitably used as, for example, an automobile part material, an electrical product part material, a daily miscellaneous goods material, a packaging material, and particularly an automobile part material.

  When the polypropylene of the present invention is used as an automobile part material, examples of the shape of the polypropylene include a sheet shape and a pipe shape.

  Next, although this invention is demonstrated based on an Example and a comparative example, this invention is not limited by the following Example. In the following description, “part” and “%” are based on mass unless otherwise specified. In addition, the numerical value of the Example shown below can be substituted to the corresponding numerical value (namely, upper limit value or lower limit value) described in embodiment.

The melting point described below uses a differential scanning calorimeter (DSC-8500, manufactured by Perkin Elmer) by a differential scanning calorimetry method (DSC method) based on a method defined in JIS K 7122 (1987). And a melting peak temperature measured at a heating rate of 10 ° C./min. The temperature rise rate during the measurement of the melting peak temperature and the heat treatment was determined by ((temperature after temperature increase) − (temperature before temperature increase)) / (time required for temperature change).
(Manufacture of raw material polypropylene)
Production Example 1
Homopolypropylene (trade name: FL0007, MFR: 7.5, melting point 160 ° C., weight average molecular weight: 135000, antiblocking agent and slip agent are not added, manufactured by Nippon Polypro Co., Ltd.) is melted, and a film is formed using a film molding machine. At the same time, it was rapidly cooled to room temperature (25 ° C.) to obtain a raw material polypropylene having a meso phase (melting point: 160 ° C., crystallinity: 37.2%, width: 195 mm, thickness: 0.1 mm). .
(Heat treatment of polypropylene)
Production Example 2
A heat treatment furnace (trade name: VO-230, manufactured by ADVANTEC) was previously placed at 152 ° C. in an air atmosphere, and the raw material polypropylene (size: 150 × 100 × 0.1 mm) obtained in Production Example 1 was used. It was charged and heat-treated for 15 minutes, then taken out and air-cooled to room temperature (25 ° C.) to obtain heat-treated polypropylene (specific gravity 0.95 g / cc).

  Next, by heating the obtained heat-treated raw material polypropylene (5.0 mg) in nitrogen using a differential scanning calorimeter (DSC-8500, manufactured by Perkin Elmer) at a rate of temperature increase of 10 ° C./min. The amount of heat of fusion (ΔH) (J / g) was measured, and the crystallinity (%) was calculated to be 44.1% according to the following formula. In the following formula, the heat of fusion of the complete crystal of polypropylene was 209 J / g. The results are shown in Table 1.

In Table 1, the temperature difference (° C.) of the heat treatment temperature (° C.) to the melting point (° C.) of the raw material polypropylene (temperature difference (° C.) from the melting point) is expressed as melting point (° C.) − Heat treatment temperature (° C.). It shows as a calculation result of.
(Manufacture of polypropylene)
Example 1
The heat-treated raw material polypropylene obtained in Production Example 2 was sealed in a glass ampoule in an argon atmosphere and heat-treated from a γ-ray source so that the absorbed dose of γ-ray was 10 kGy at room temperature (25 ° C.). Using the No. 1 accelerator in the Takasaki Quantum Applied Research Institute Cobalt Building owned by the Japan Atomic Energy Agency, using Cobalt 60 as the radiation source by adjusting the distance to the raw material polypropylene and the irradiation time, Polypropylene was obtained by irradiating the line.

Example 2
Polypropylene was obtained by irradiating γ rays in the same manner as in Example 1 except that the absorbed dose of γ rays was 30 kGy.

Example 3
Polypropylene was obtained by irradiating γ rays in the same manner as in Example 1 except that the absorbed dose of γ rays was 50 kGy.

Example 4
Polypropylene was obtained by irradiating γ rays in the same manner as in Example 1 except that the absorbed dose of γ rays was 100 kGy.

Comparative Example 1
The heat-treated raw material polypropylene obtained in Production Example 2 was used as it was without being irradiated with ionizing radiation.

Comparative Example 2
The raw material polypropylene obtained in Production Example 1 was used as it was without heat treatment and without irradiation with ionizing radiation.

Comparative Example 3
The raw material polypropylene obtained in Production Example 1 was irradiated with γ rays in the same manner as in Example 1 without heat treatment to obtain polypropylene.

Comparative Example 4
Polypropylene was obtained by irradiating γ rays in the same manner as in Comparative Example 3 except that the absorbed dose of γ rays was 30 kGy.

Comparative Example 5
Polypropylene was obtained by irradiating γ rays in the same manner as in Comparative Example 3 except that the absorbed dose of γ rays was 60 kGy.

Comparative Example 6
Polypropylene was obtained by irradiating γ rays in the same manner as in Comparative Example 3, except that the absorbed dose of γ rays was 160 kGy.
(Evaluation)
(Tensile test)
A JIS No. 8 tensile test piece (conforming to JIS K 6251 (2004)) was punched from the polypropylene obtained in each example and each comparative example using a punching jig.

  Thereafter, each tensile test piece was subjected to a tensile test at room temperature (25 ° C.) and at a tensile speed of 10 mm / min using a tensile tester (trade name: AG-50kNG, manufactured by SHIMADZU).

  From the test results, the tensile modulus, the tensile yield point, and the tensile fracture strain of the polypropylene of each Example and each Comparative Example were obtained.

  The results are shown in Table 1.

(Discussion)
As shown in Table 1, in Comparative Example 5 in which γ-rays were irradiated without heat treatment, even when the absorbed dose was 60 kGy, compared with Comparative Example 2 in which neither heat treatment nor γ-ray irradiation was performed, The elastic modulus is improved only by about 500 MPa.

  On the other hand, in Example 3 in which γ-rays were further irradiated after heat treatment, the tensile modulus was 600 MPa as compared with Comparative Example 1 in which γ-rays were not irradiated even though the absorbed dose was 50 kGy. It is estimated that the tensile modulus is further improved when the absorbed dose is 60 kGy.

  In Comparative Examples 3 to 6 where γ rays were irradiated without heat treatment, the tensile elastic modulus was lower in Comparative Examples 3 and 4 than Comparative Example 2 where no γ rays were irradiated. Lack of sex.

  On the other hand, in Examples 1 to 3 in which γ rays are further irradiated after heat treatment, the tensile elastic modulus is improved in proportion to the absorbed dose of γ rays to be irradiated. This is preferable because the absorbed dose of γ rays to be irradiated can be selected.

  In Comparative Example 6 in which γ-rays are irradiated at an absorbed dose of 160 kGy, the tensile elastic modulus is lower than that in Comparative Example 2 in which γ-rays are not irradiated, and the absorbed dose of γ-rays is too large. It can be seen that has been disassembled.

  In Example 4 in which γ rays are irradiated at an absorbed dose of 100 kGy, the tensile modulus is improved as compared with Comparative Example 1 in which γ rays are not irradiated, but γ rays are irradiated at an absorbed dose of 50 kGy. The tensile elastic modulus is lower than in Example 3. Therefore, it can be seen that the absorbed dose of γ rays of 100 kGy is the boundary where polypropylene is decomposed (deteriorated).

  Note that, for example, a material generally used for automobile outer plates in which 35% by mass of talc is combined with polypropylene has a specific gravity of 1.16 g / cc, an elastic modulus of 2850 MPa, and a tensile fracture strain of 27%. On the other hand, in the present invention, the mechanical characteristics are equivalent by appropriately selecting the production conditions, and the specific gravity is as light as 0.95 g / cc.

  Moreover, when manufacturing the outer plate | board for motor vehicles using this invention, in order to suppress a surface quality change and a dimensional change, it can also attach to a restraining jig and can also heat-process and irradiate.

Claims (2)

  After heat-treating the raw material polypropylene at a temperature of 15 ° C. lower than the melting point of the raw material polypropylene measured by a differential scanning calorimetry method (DSC method) based on the method prescribed in JIS K 7122 (1987) at a temperature not lower than the melting point of the raw material polypropylene. Furthermore, polypropylene obtained by irradiating with ionizing radiation.   2. The polypropylene according to claim 1, wherein an absorbed dose of the ionizing radiation is 10 kGy or more and 100 kGy or less.