JP2000226479A - Colored resin composition of injection molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preventing the formation of striped color shading irrespective of whether or not an inorganic filler is contained. SOLUTION: 0.01 to 3 pts.wt. of silicon oxide having a size of 50 nm or below is compounded in 100 pts.wt. of a polypropylene resin composition containing a finely divided inorganic filler such as a pigment, talc or the like. The polypropylene may be a propylene homopolymer or an ethylene/propylene copolymer. Because the silicon oxide compounded in a small amount acts as a color shading preventive, an injection-molded, colored resin composition becomes a uniform colored, molded product, which is free of striped color shading without lowering mechanical properties.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a colored resin composition for eliminating streak-like color unevenness in a molded product when a resin composition containing polypropylene as a main component is processed by injection molding. The colored resin composition of the present invention can be used for all molded products made of a polypropylene resin composition.

[0002]

2. Description of the Related Art In recent years, polypropylene has been used for a wider range of applications than conventional ones, because its moldability and physical properties have been improved by improving catalysts and polymerization methods, and it is easy to recycle. In particular, as a material for environmentally conscious plastic products, there is an active development of alternatives to products made of polyvinyl chloride (PVC), such as extrusion or calendering into films or sheets, or injection. Processing into a structural member by molding has been widely performed.

[0003] In particular, polypropylene to which an inorganic filler is added has been used as an easily recyclable polypropylene resin composition having excellent impact resistance and rigidity, for use in automobiles, home appliances, distribution materials, miscellaneous goods, and the like. As a typical resin composition, polypropylene homopolymer, polypropylene copolymerized with ethylene and polypropylene, ethylene-propylene rubber such as polypropylene randomly copolymerized ethylene-propylene rubber blend,
A blend obtained by blending ethylene-propylene rubber and ethylene-butene rubber or ethylene-octene rubber with polypropylene, and further incorporating talc is used.

A filler such as talc is usually contained in a polypropylene resin composition in an amount of not more than 40% by weight, and such a resin composition is generally colored with an inorganic or organic pigment for the purpose of design, identification, light shielding and the like. Is done. However, when these colored resin compositions are molded, light-colored or dark-colored streaks (called streak-like color unevenness) sometimes occur on the surface of the molded product. In particular, the phenomenon in injection molding is remarkable. In the case of a large molded product, it occurs at a fixed position with respect to the mold gate.
m or more, significantly reducing the commercial value. The color streaks are uneven distribution or partial absence of the pigment in the resin composition, uneven distribution of the inorganic filler in the resin composition, and the like, in other words, a poor state of uniform dispersion of the pigment and the inorganic filler. For example, in a resin composition into which talc has been kneaded, uneven distribution of talc may be observed.

Conventionally, in order to prevent such streak-like color unevenness, use of a specific pigment, utilization of a modified polyolefin or a fluorine-based compound, or use of an inorganic filler itself has been considered for an inorganic filler composite resin composition mainly composed of talc. Many methods such as surface treatment have been proposed.

That is, a polyolefin composition comprising an ethylene / propylene block copolymer and a multicomponent pigment containing iron black (Japanese Patent Publication No. 62-14576), and similarly a polypropylene coloring composition comprising a black metal oxide as a pigment (Japanese Patent Publication No. 4-76384), a polyolefin composition for injection molding comprising a propylene / α-olefin block copolymer and a modified polyolefin (JP-A-2-43)
No. 243 and JP-A-2-43249), a polypropylene coloring composition comprising an ethylene / propylene block copolymer and a black pigment containing channel carbon black or acidic furnace black (Japanese Patent Publication No. Hei 6-43).
27236 and JP-B-6-76536),
Similarly, a polyolefin composition for injection molding using a specific carbon black as a black pigment (Japanese Patent Laid-Open No. 5-1203), an ethylene block copolymer in which carbon black and titanium oxide are kneaded, and a montanic acid ester wax. Resin coloring composition (JP-A-6-88009), coloring composition comprising polypropylene, modified polyolefin, modified wax, pigment and silane compound (JP-A-8-134278), propylene-α-olefin block copolymer A coloring masterbatch composition and a compound (JP-A-9-227734) comprising a powdered ultrahigh molecular weight polyethylene and a resin composition for coloring comprising a polyolefin, a fluorinated olefin copolymer and a polyalkylene oxide ( JP-A-9-2558
No. 31 and JP-A-9-255975) and a polyolefin composition for injection molding comprising an ethylene / propylene block copolymer and a filler surface-treated with a silane-based compound (JP-A-8-31294). It has been disclosed.

[0007]

Generally, inorganic fillers of 4
In order to color a polypropylene resin composition containing 0% by weight or less, a specific pigment is selected and a pigment dispersant is selectively used or talc is used in order to prevent streak-like color unevenness occurring in injection molding. It is necessary to provide an additive for preventing uneven distribution. However, none of them can be used widely. For example, in Japanese Patent Publication No. 62-14576, a metal oxide represented by iron black is used as a black pigment. However, since coloring of low brightness does not have coloring power of these pigments, they must be used in large amounts. Affects the physical properties of the resin composition. On the other hand, the use of the specific carbon black described in JP-B-6-27236 and the like is advantageous in that respect, but eliminates the streaky color unevenness that occurs in high-brightness coloring that hardly requires a black component. Can not.

On the other hand, the method using a modified polyolefin or a silane-based compound described in JP-A-2-43249 or JP-A-8-134278 does not need to be used depending on the brightness of the color. The substance is difficult to handle, and tends to cause aggregation of the pigment used for coloring or aggregation of the filler itself. As a result, clear or stable coloring cannot be obtained, and the desired physical properties of the resin composition may be impaired.

Furthermore, means for limiting the selection and composition ratio of the constituent components of the polypropylene resin composition itself, controlling the mixing and kneading conditions at the preparation stage appropriately, and controlling and solving the dispersion of the filler are also taken. It can be done. However,
Even in the case of these resin compositions prepared in this way, in injection molding, streaky color unevenness may occur depending on molding conditions, and there is a drawback that the degree of freedom of molding conditions is restricted.

[0010] The present invention solves the problems of the disclosed technology and provides a method for simply preventing the occurrence of streak-like color unevenness irrespective of the presence or absence of an inorganic filler. The purpose is to provide.

[0011]

Under these circumstances, the present inventors have conducted intensive studies on streaky color unevenness on the surface of a molded article produced by molding of a polypropylene resin composition. It has been found that the generation can be prevented by using silicon oxide.

That is, in the present invention, first, in a polypropylene composition containing a finely powdered inorganic filler and a coloring pigment, the filler is added to 100 parts by weight of the resin composition. A colored resin composition for injection molding, comprising 0.01 to 3 parts by weight of different fine particles of silicon oxide having a particle size of 50 nm or less.

According to a second aspect of the present invention, there is provided the colored resin composition according to the first aspect, wherein the polypropylene is a propylene homopolymer or an ethylene / propylene copolymer.

According to a third aspect of the present invention, there is provided the colored resin composition according to the first or second aspect, wherein the inorganic filler is talc.

According to a fourth aspect of the present invention, there is provided the colored resin composition according to any one of the first to third aspects, wherein the colored resin composition is granular.

And so on. Such a composition is usually obtained as a melt-kneaded body and usually takes a granular form as a color compound.

In short, the present invention relates to a conventional polypropylene composition containing a pigment and a finely divided inorganic filler, in the case where a line-like color unevenness occurs on the surface of a molded article molded using the same, the composition is further added to the composition. Particle size 50nm as compounding ingredient
It is disclosed that by blending the following fine particle silicon oxide at a fixed blending ratio, it acts as a color non-uniformity preventing agent, and this color non-uniformity can be effectively avoided.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The typical embodiment and the best state of the embodiment of the present invention are specifically shown in the following examples. This will be described in detail.

The polypropylene used in the present invention is a propylene polymer, an ethylene-polypropylene copolymer or a propylene-α-olefin copolymer, and has a melt fluidity (MFR, 230 ° C.-2.16 kg load) which is colored. It is desirable that the fluidity be higher than that of the polypropylene resin composition. The polymerization type is a product synthesized with a Ziegler-Natta catalyst or single-site catalyst regardless of the liquid phase or gas phase, and the stereoregularity at the synthesis stage is irrespective of whether it is isotactic or syndiotactic. May be random or block. Such polypropylenes include ordinary olefin rubbers, that is, those obtained by copolymerizing ethylene with propylene or butene-1 or octene, or dicyclopentadiene, methyltetrahydroindene, methylenenorbornene, ethylidene nor. One of the constituent components may be a terpolymer obtained by adding any one of non-conjugated dienes such as Bonnene and 1,4 hexadiene as a third component and copolymerizing the same. Similarly, a propylene-butene-1 copolymer may be included.

As the inorganic filler, talc, calcium carbonate, clay, mica, barium sulfate, glass fiber and the like are usually used in order to enhance the physical properties of the polypropylene and to enhance the dimensional stability. It is obtained by pulverizing with an impact-type pulverizer or the like and then finely pulverizing with a jet mill or the like and having a particle size of several μ or less, and contained in the polypropylene resin composition at a ratio of more than 0 to 40% by weight or less. .

The resin composition used for automobile parts generally contains 10 to 30% by weight of talc, and its melt fluidity (MFR: 230 ° C-2.16 kg load) is 10 to 10% by weight.
It is 50 gr / 10 min.

The fine particle silicon oxide used in the present invention has a primary particle of 50 nm or less and is a zeolite-based compound synthesized based on clay, or anhydrous silica obtained by hydrolyzing silicon tetrachloride in a flame of oxygen and hydrogen. It is. It is usually used for thickening, thixotropic, and preventing sedimentation of liquids. It is desirable that the particles are spherical and uniform in particle size, have low cohesiveness and good dispersibility. As a commercial product, Aerosil manufactured by Nippon Aerosil Co., Ltd. can be mentioned as a typical example.

In the present invention, such fine particle silicon oxide may be treated with a silane compound or a silicone compound.

The pigments used in the present invention are known in the field of plastics processing, and include, for example, inorganic pigments such as titanium oxide, zinc oxide, red iron oxide, fired titanium oxide pigments, ultramarine, cobalt aluminate, and carbon black; Organic pigments such as azo, quinacridone, anthraquinone, perylene, isoindolinone, phthalocyanine, quinophthalone, sulene, and diketopyrrolopyrrole, and extenders such as barium sulfate and calcium carbonate.

In the present invention, a dispersant for assisting pigment dispersion, a heat stabilizer for improving suitability for use, a light stabilizer, a flame retardant,
Plasticizers, lubricants or other fillers can be added as needed.

The polypropylene resin composition of the present invention preferably takes the form of a generally-known colored compound. Further, as a granular colorant called a master batch color, a pigment and fine particle silicon oxide are concentrated and blended so as to be reduced to a concentration used in a coloring compound, and a pigment dispersant and an olefin resin as a carrier resin are mixed. In addition, a product obtained by mixing and kneading and a polypropylene resin composition particle containing a fine powdery inorganic filler may be mixed.

When preparing a granular colorant as the precursor, the pigment dispersant to be used may be a usual one such as a fatty acid metal salt, a low molecular weight polyolefin, a fatty acid ester, a fatty acid amide, etc., and the carrier resin is a homopolypropylene, a block copolymer. Olefinic resins such as low-density polyethylene, linear low-density polyethylene, and high-density polyethylene may be used alone or in combination, if necessary, in addition to polypropylene or random copolymerized polypropylene. In addition, these olefin resins other than the propylene resin can be mainly used, but it is extremely effective to mainly use the polypropylene resin.

The essential components of the coloring composition of the present invention are as follows:
In the coloring compound, the pigment is 0.01 to 10% by weight,
The remainder excluding the pigment is finely divided silicon oxide and other finely divided inorganic fillers, for example, talc and an olefin resin mainly composed of polypropylene. In the granular colorant, the pigment is 1 to
At 80% by weight, it contains finely divided silicon oxide and need not contain a finely divided inorganic filler. The reason is that the olefin-based resin mainly composed of polypropylene to be colored may contain a finely powdered inorganic filler.

In the case of a coloring compound, the amount of the fine particle silicon oxide to be used is 1 to 200 parts by weight based on 100 parts by weight of the pigment in the compound, and 3 parts by weight or less based on 100 parts by weight of the coloring compound. desirable. When the polypropylene-based resin composition contains a granular colorant as one component or is produced via the component, in the case of the granular colorant, the mixing ratio of the granular colorant to the polypropylene to be colored is taken into consideration. Then, the concentration of the fine particle silicon oxide determined when obtaining the coloring compound may be concentrated.

The effect of the finely divided silicon oxide in the coloring composition of the present invention is considered as follows. First, in the molding step in which the polypropylene-based resin composition is heated and melt-plasticized, the pigment and the finely divided inorganic filler (hereinafter abbreviated as talc), or the polypropylene and the talc, or the separation of the polypropylene and the pigment are suppressed. I guess it has a function to do. The fine particle silicon oxide in the present invention has a small number of particles, but a large number of particles. Originally, it has a function as a gelling agent for a liquid material, and the effect is exhibited even with a molten resin. Therefore, it has a function of suppressing aggregation of talc and the like, and it is considered that streaky color unevenness which is a state of uneven distribution or lack of pigment or talc does not appear during molding.

Also, since a small amount is added, the physical properties and processability of the polypropylene resin composition are not impaired, and the coloring power of the pigment is not impaired, so that the cost can be reduced, and the effect can be exhibited regardless of the type of the pigment. No need to select
There is an advantage that any hue can be handled.

The particulate colorant is obtained by mixing essential components of the colorant and other components as desired, and melt-kneading them. For example, the pigment is previously mixed with a pigment dispersant with a high-speed mixer,
After kneading with a Banbury mixer or kneader, the pigment is finely ground with a heating two roll or heating three roll, and then the carrier resin and other components are kneaded with a kneading machine such as a single screw or twin screw extruder. It is a product obtained by kneading with the components, or mixing all these components at once, a Banbury mixer, a kneader, a high-speed intensive mixer,
It is obtained by melt-kneading with a twin screw extruder or the like. The shape of the kneaded material may be a granular material obtained by hot cutting or a granular material obtained by cold-cutting a sheet or a strand, depending on how to take out the kneaded product.

The resin to be colored with such a coloring agent is a polypropylene-based resin composition containing a finely divided inorganic filler without a pigment, and the resin 1 to be colored so as to have a desired pigment concentration.
The colorant is usually added in an amount of 10 parts by weight or less based on 00 parts by weight.

[0034]

Next, the present invention will be described specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples but has a wide range of application. All parts and percentages in Examples and Comparative Examples are based on weight.

Examples 1 and 2 and Comparative Example 1 Carbon black (CIPB7), titanium yellow (Sb-Ni-Tioxide, CIPY53) and titanium oxide (rutile type CIPW6) pigments shown in Table 1 were mixed with low molecular weight polyethylene, respectively. The mixture was mixed with a high-speed mixer at the mixing ratio (parts) shown in Table 1 to obtain a powder. Next, the powdery material is heated and melted and kneaded by a pressure kneader, taken out, finely ground by a three-roll mill into a lump, and crusher-pulverized into an irregularly shaped granular material having a good pigment dispersion. did. The talc-kneaded polypropylene shown in Table 1 and only the finely divided silicon oxide A or talc-kneaded polypropylene shown in Table 1 were mixed with the granules in a tumbler at the mixing ratio shown in Table 1. Next, the mixture was melt-kneaded with a twin screw extruder (L / D = 30), extruded into strands, and then, with a rotary blade cutting type pelletizer, a cylindrical gray compound 100 having a length of 2 to 3 mm. Processed into parts. After drying the obtained coloring compound at 100 ° C. for 2 hours, a streaking test (method A) was performed by injection molding.
And subjected to a physical property test. The results are shown in Table 2. The coloring compound of the present invention had no streaks, had a good appearance and good physical properties.

The method for evaluating the occurrence of streaks in injection molding and the method for testing physical properties are as follows. Injection molding streak development evaluation test-A
Method: Coloring compound with full flight screw (L / D = 2
2) Injection molding machine with installed mold clamping pressure of 60 tons and molding temperature of 230
C., Mold temperature 40 ° C., Back pressure 0MPa and molded into a film gate flat plate mold (thickness 2mm × width 80mm × length 150mm).

The evaluation of the streaks is made based on the size of the streaks observed on the flat plate, and the evaluation standard is set to five levels.

Injection molding physical property test: The coloring compound was molded with a full flight screw (L / D = 20) using an injection molding machine with a mold clamping pressure of 60 tons, molding temperature 210 ° C., mold temperature 40 ° C., back pressure 2.0MP.
Form with a physical piece mold in a. Molded pieces are tensile test, bending test, IZOD impact test, heat deformation test (HD
T). Each test condition conforms to ASTM. Tensile test ASTM-D638 Sample shape: Type 1 turntable bending test ASTM-D790 Sample shape: 1/4 "base IZOD impact test ASTM-D256 Sample shape: 1/4" base Room temperature HDT test ASTM-D648 (455 KPa stress) ) Sample shape: 1/4 "pace

Evaluation criteria: 100% of the physical property value of the uncolored resin
The retention rate of the physical properties of the colored resin is indicated based on the following criteria. ：: The retention of physical property values is 95% or more. Δ: The retention of physical property values is 90% or more and less than 95%. X: Retention of physical property value is less than 90%.

The details of the raw materials in Table 1 are as follows. Low molecular weight polyethylene: molecular weight (Mn) = 5000, viscosity (CPS: 140 ° C.) = 3000, softening point = 111 ° C. Fine particle silicon oxide-A: anhydrous silica having a particle diameter ≦ 50 nm and a specific surface area = 200 m ² / gr and particles A 1: 1 mixture with monomethyltrichlorosilane surface-treated silica having a diameter ≦ 50 nm and a specific surface area = 120 m ² / gr. Talc kneaded polypropylene (PP): Ethylene-propylene olefin block copolymer (MFR = 30gr / 10min) 60 parts ethylene-α-olefin rubber (MFR = 8gr / 10min, melting temperature = 95 ° C) and talc (average) A particle obtained by adding several parts of an antioxidant to 20 parts of 20 parts, mixing with a high-speed mixer, and melt-kneading with a twin-screw extruder to form granular pellets.

[0041]

[Table 1]

[0042]

[Table 2]

Examples 3 and 4 and Comparative Example 2 Titanium oxide (CIPW7) and iron oxide (CIPR10
1) A mixture of carbon black (CIPB7) and copper phthalocyanine blue (β-type CIPB15: 3) pigment, magnesium stearate and low molecular weight polyethylene in a mixing ratio (parts) shown in Table 3 with a high-speed mixer, and powdered Things. Next, this mixture was heated and melt-kneaded by a pressure kneader, and then finely ground by three rolls. The obtained kneaded material was further pulverized with a crusher to form irregular shaped particles having good pigment dispersion. The amorphous granules were mixed with finely divided silicon oxide B and isotactic polypropylene or isotactic polypropylene alone at the compounding ratio shown in Table 5, and mixed with a twin screw extruder (L / D = 30).
, And extruded into strands, and processed into 100 parts of a cylindrical black master batch color having a length of 2 to 3 mm using a rotary blade cutting type pelletizer. The obtained masterbatch color is talc kneaded polypropylene 97
3 parts per part was added and subjected to an injection molding streak development test (Method B) and a physical property test. The results are shown in Table 4. The masterbatch color of the composition of the present invention had no streak and good retention of various physical properties.

The method for evaluating the occurrence of streaks in injection molding and the method for testing physical properties are as follows. Injection molding streak development evaluation test -B
Method: A mixture of masterbatch color and talc kneading compound is molded at a molding temperature of 230 ° C, a mold temperature of 40 ° C, and back pressure with an injection molding machine equipped with a dalmage screw (L / D = 22) with a mold clamping pressure of 60 tons. 2.0 MPa, film gate flat mold (2 mm thick x
(Width 80mm x length 150mm).

The evaluation of the streak is made based on the size of the streak observed on the flat plate, and the evaluation standard is set to five levels.

Injection molding property test: same as described in Examples 1 and 2 and Comparative Example 1.

The details of the ingredients in Table 3 are as follows. Low molecular weight polyethylene: the same as described in Table 1. Fine particle silicon oxide-B: particle diameter ≦ 50 nm, specific surface area = 120
m ² / gr, monomethyltrichlorosilane surface-treated silica Magnesium stearate: a mixture of stearate (55%), palmitate, and myristate, melting point (differential calorimetric analysis) = 118 ° C. Isotactic PP-A: Homopolypropylene MFR (load at 230 ° C 2.16 kg) = 350 gr / 10 min Polypropylene (PP) with talc kneading: Same as the one described in Table 4.

[0048]

[Table 3]

[0049]

[Table 4]

[0050]

When the specific polypropylene coloring composition of the present invention is used, the homopolypropylene or the ethylene or α-olefin copolymerized polypropylene of this type can be used in spite of containing the finely powdered inorganic filler, especially talc. Does not generate color streaks that occur when the composition is molded.
Since the obtained colored molded product becomes beautiful and does not deteriorate in physical properties, molding is facilitated and cost can be greatly reduced.

Continued on the front page F term (reference) 4F206 AA04E AA11 AA11E AB11 AB12 AB16 JA07 4J002 BB121 BB151 DJ017 DJ046 FD016 FD017 FD090

Claims (4)

[Claims] 1. A polypropylene composition containing a finely divided inorganic filler and a coloring pigment, wherein the resin composition
0n by weight, different from the filler, particle size 50n
A colored resin composition for injection molding, comprising 0.01 to 3 parts by weight of fine particle silicon oxide having a particle size of m or less. 2. The polypropylene according to claim 1, wherein the polypropylene is a propylene homopolymer or an ethylene / propylene copolymer.
The colored resin composition according to the above. 3. The method according to claim 1, wherein the inorganic filler is talc.
Or the colored resin composition according to 2. 4. The colored resin composition according to claim 1, wherein the colored resin composition is in a granular form.