JP2001002862A - Pellet-like colorant, preparation thereof and molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition effective in reducing the change of hue and color shading by compounding a dispersion composed of carbon black as a pigment and a propylene homopolymer or a propylene/ethylene random copolymer, a pigment and a carrier resin as a pigment dispersant. SOLUTION: A dispersion is composed of 1-50 wt.% of carbon black, as a black pigment, having an average particle size of at least 20 μm and 50-99 wt.% of a propylene homopolymer or a propylene/ethylene copolymer as a pigment dispersant. A pellet-like colorant comprises this dispersion, 1-60 wt.% of a pigment component, 40-99 wt.% of a polypropylene resin as a carrier resin, and if required, a low molecular weight dispersant such as an ethylene wax or the like or a lubricant such as a metal salt of a fatty acid or the like. With 100 pts.wt. of a diluting resin are admixed 1-20 pts.wt. of the pellet-like colorant, and if required, an antistat, an ultraviolet absorber, a light stabilizer and the like, and the resultant mixture is molded to give a product.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a colorant in the form of pellets added at the time of molding a polypropylene resin (C), characterized in that a change in hue, uneven color, and streaks of a molded article due to a difference in molding conditions hardly occur. The present invention relates to a pellet colorant (master batch) for coloring a polypropylene resin, a method for producing the same, and a molded product.

[0002]

2. Description of the Related Art Colorants in the form of pellets are widely used for coloring thermoplastic resins such as polypropylene because of their good handling properties. This pellet-like colorant is prepared by adding various pigments and additives to a thermoplastic resin as a carrier resin in a kneading machine such as a single-screw or twin-screw extruder, an FCM, and a Banbury mixer. Distributed to
After being processed into various pellet shapes, the mixture is melt-kneaded with a diluent resin and is provided for molding.

[0003] However, since the pigment concentration is increased as described above, with a specific organic pigment such as carbon black or the like, the dispersion operation by melt kneading in a single stage as described above requires molding such as a thin film or the like. The product did not have a sufficient pigment dispersion level in terms of product performance.

In order to solve this problem, a pigment and a polyethylene wax as a dispersant for the pigment have been conventionally used.
A dispersion in which a metal salt of stearic acid, bisamide, and the like (hereinafter, referred to as a dispersant) are preliminarily dispersed by a three-roll mill is used. In particular, a diluting resin for a pellet colorant (master batch) is an olefin resin. If it is,
Polyethylene wax has been preferred from the viewpoints of heat resistance, pigment dispersibility, printability, heat sealability, bleed resistance, and price.

[0005] When a plastic molded article is colored in a chromatic and neutral color, carbon black is generally used as a black component pigment. Since carbon black has a number of hydrophilic polar groups, such as a carboxyl group, a carbonyl group, an amino group, and a sulfone group, on its particle surface, it has poor compatibility with an olefin resin having no hydrophilic polar group. In addition, the cohesive force between carbon particles is greater than other pigments, and their dispersion requires advanced technology. The method of dispersing carbon black and polyethylene wax as a dispersant using a three-roll mill or the like is a technique that can relatively easily realize uniform dispersion of carbon black. This is presumed to be because, among the olefin resins, the polyethylene component and the carbon black have relatively good wettability, and uniform dispersion is easily performed.

[0006]

However, the compatibility between the polyethylene wax as the dispersant and the polypropylene resin (C) as the diluting resin is not always sufficient, and the amount of the polyethylene wax added to the colorant increases. The delamination of the molded polypropylene resin is known as one of the phenomena indicating its incomplete compatibility, and this phenomenon is caused by fluctuations in conditions during molding, especially fluctuations in shear stress during melting (for example, T-die). Dispersion of the polyethylene wax and carbon black in the polypropylene resin (C) due to non-uniform dissolution in the polypropylene resin (C) due to the difference in the number of revolutions of the screw of the extruder at the time of extrusion, etc. Problems such as occurrence of white streaks have occurred, and it has been difficult to manufacture products stably. Also, due to the manufacturing process of the plastic product, it may not be possible to manufacture under the same conditions as the previous manufacturing. At this time, even if other physical properties are good, if the coloring state is poor (for example, color reproducibility, hue change, uneven color, white streak, etc.), it is often discarded as a defective product. Was a very serious problem in the processing steps.

To solve these problems, Japanese Patent Application Laid-Open No. 55-31801 discloses that it is effective to use iron black instead of carbon black as a black pigment. Since the coloring power is only 1/5 to 1/10 that of carbon black, it is necessary to compensate for the low coloring power by the added amount, which adversely affects the physical properties and is not economically advantageous.

Japanese Patent Application Laid-Open No. Hei 6-88009 discloses a method for coloring a resin using a montanic acid ester as a dispersant. The montanic acid ester is 5 to 10 times as expensive as polyethylene wax, and is practically usable. Not used, and when the carrier resin is an olefin resin, the compatibility is not as good as polyethylene wax, and when the content in the pellet colorant exceeds approximately 5%, melt kneading with a single screw extruder is not possible. However, this is not always a good idea because the slip of the screw occurs and a steady melt-kneading can be performed.

[0009]

That is, a first invention is a pellet colorant added for coloring the polypropylene resin (C), and carbon black having an average particle diameter of 20 mμ or more as a black pigment; A black pigment dispersant is a pellet colorant for coloring a polypropylene resin containing a dispersion composed of a propylene homopolymer or a propylene-ethylene random copolymer (A), and a pigment and a carrier resin (B).

[0010] The second invention is directed to carbon blacks 1 to 50.
% By weight and 50 to 99% by weight of a propylene homopolymer or propylene-ethylene random copolymer (A)
Is melt-kneaded to form a dispersion, and then the dispersion, the pigment and the polypropylene resin as the carrier resin (B) are melt-kneaded, and the polypropylene resin pellets according to the first aspect of the present invention are characterized in that: This is a method for producing a colorant.

A third invention is a molded article obtained by using the pellet colorant for coloring a polypropylene resin according to any one of the first and second inventions.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The carbon black used as a black pigment in the present invention may be of any kind, but oil furnace black is generally used because of its low price.

The carbon black preferably has a particle diameter of at least 20 μm, particularly preferably 30 to 90 μm.
μ, more preferably 30 to 60 μm. Generally, the specific surface area tends to increase as the particle size of the carbon black decreases, so that the carbon black particles tend to form aggregates, resulting in a difference in the dispersion state of the carbon black in the molded product, A particle size of less than 20 mμ is not preferred because it easily causes a change in hue.

The amount of carbon black in the dispersion depends on the desired color, but is preferably 1 to 50% by weight. If it is less than 1% by weight, sufficient coloring ability cannot be obtained, and if it exceeds 50% by weight, the dispersion of carbon black becomes unfavorable.

The thing used as a black pigment dispersant in the present invention is preferably a homopolymer of propylene or a random copolymer (A) of propylene and ethylene. If one or a combination of two or more of these is used. But any compound or mixture, but block copolymers of propylene and ethylene are not preferred. Block copolymers are produced by adding and reacting a large amount of ethylene to polypropylene.At this time, since the monomer component of polyethylene is slightly free, carbon black is selectively compatible with the polyethylene component. As a result, a dispersion behavior similar to that of a dispersion using polyethylene wax is exhibited, so that high compatibility and uniform dispersibility with the polypropylene resin (C) are reduced.

The homopolymer of propylene or the random copolymer (A) of propylene and ethylene used in the present invention is preferably 50 to 99% by weight based on the dispersion. If it is less than 50% by weight, the effect as a black pigment dispersant is not sufficient, and if it exceeds 99% by weight, the amount of carbon black to be added becomes relatively small, and the coloring power is undesirably reduced.

A method for dispersing carbon black with a homopolymer of polypropylene or a propylene-ethylene random copolymer (A) includes a conventional melt kneading equipment,
For example, it can be relatively easily performed by using a disperser capable of obtaining a high shearing force, such as a Banbury mixer, an FCM, and a twin screw extruder.

In the present invention, the term “resin” refers to a resin having a weight average molecular weight of 10,000 or more and a MI of MI according to JIS K7210.
The term "wax" refers to a substance that can be measured and is generally called "thermoplastic resin", and the term "wax" means that the weight average molecular weight is less than 10,000 and the MI cannot be measured according to JIS K7210. Is shown.

The colorant in the form of pellets of the present invention is a chromatic and intermediate color. Therefore, the pigment of the present invention contains not only carbon black but also other pigments. As the other pigment, any pigment for coloring a synthetic resin can be used. For example, examples of the organic pigment include azo, anthraquinone, phthalocyanine, quinacridone, isoindolinone, dioxazine, and quinophthalone pigments. Examples of inorganic pigments include pigments such as titanium oxide, iron oxide, cobalt blue, ultramarine, and graphite.

The amount of the pigment component added to the pellet colorant for coloring the polypropylene resin is preferably 1% or more and 60% or less, although it depends on the desired color and the material to be molded. If it is less than 1%, the coloring is insufficient, and if it exceeds 60%, the shape of the pellet-shaped colorant cannot be maintained, which is not preferable.

In order to improve the dispersion of the pigment other than carbon black, a low molecular weight dispersant or a lubricant is used as necessary. Examples of the low molecular weight dispersant include ethylene wax, polypropylene wax, and the like, and the same amount as the amount of the pigment component is added to the pellet colorant. Examples of the lubricant include a fatty acid metal salt, ethylene bisamide, a higher fatty acid ester, and the like.

The polypropylene resin which is the carrier resin (B) used in the pellet colorant (master batch) for coloring the polypropylene resin of the present invention is not particularly limited, but the pellet colorant for coloring the polypropylene resin is added. It is more preferable that the resin is the same as the polypropylene resin (C) which is a diluting resin.

The amount of the carrier resin (B) to be added to the pellet colorant for the polypropylene resin is preferably from 40% to less than 99%. If it is less than 40%, the shape as a pellet-like colorant cannot be maintained, and if it exceeds 99%, the coloring power becomes weak, which is not preferable.

That is, the pellet colorant (masterbatch) for polypropylene resin of the present invention is prepared by mixing carbon black with a homopolymer of polypropylene or a propylene-ethylene random copolymer (A) which is a black pigment dispersant in advance. Make a dispersion. The surface free energy value of the carbon black surface is reduced by uniformly wetting the surface of the carbon black with a homopolymer of polypropylene or a propylene-ethylene random copolymer (A). Next, through a two-stage melt-kneading step of kneading the dispersion, another pigment and the carrier resin (B), the mixture is formed into a pellet.

It is not preferable to carry out these steps in one step, because the dispersion state of carbon black becomes poor and the quality of the molded product deteriorates.

In the carbon black that has been subjected to the dispersion treatment with the black pigment dispersant in the first step, a polypropylene resin layer is formed around the carbon black particles. Even when melt-kneaded with polyethylene wax or the like as a molecular weight dispersing agent, they are not compatible with polyethylene wax and are uniformly dispersed in the polypropylene resin as the carrier resin (B).

The pellet colorant for coloring a polypropylene resin in the present invention refers to a colorant in the form of strips, flakes, rounds, beads, or blocks.

[0028] The pellet colorant for polypropylene resin of the present invention may optionally contain an antistatic agent, an ultraviolet absorber,
Various additives such as a light stabilizer and an antioxidant can be added. Known antioxidants can be used. When an antioxidant is added, the content is preferably 2% by weight or less based on the colorant in the form of pellets.

The pellet colorant (masterbatch) for coloring the polypropylene resin of the present invention is a T-die, a deformed die, an inflation, a blow extrusion molding, an injection molding, a calender molding of a polypropylene resin (C) which is an uncolored diluting resin. Sometimes added. The pellet colorant for coloring the polypropylene resin of the present invention is preferably blended in an amount of 1 to 20 parts by weight based on 100 parts by weight of the diluting resin (C). If the amount is less than 1 part by weight, color unevenness and physical properties may be reduced.
If the amount exceeds 20 parts by weight, the degree of coloring is lowered, which is not preferred.

When the pellet colorant for coloring the polypropylene resin of the present invention is added to the diluting resin (B), a lubricant, an antistatic agent, an ultraviolet absorber, a light stabilizer,
Various additives such as antioxidants can be added.

Examples of molded articles produced using the pellet colorant for coloring a polypropylene resin of the present invention include plastics for building materials, especially films, especially films having a film thickness of 200.
Examples include films having a size of not more than μm.

[0032]

EXAMPLES The present invention will be described in detail below with reference to Examples and Comparative Examples, but the present invention is not limited thereto. (Comparative Example 1) Carbon black (average particle size = 24 m
μ, specific surface area 125 m ² / g) 10% by weight, polyethylene wax as a black pigment dispersant (softening point = 108 ° C.,
(Weight average molecular weight = 3500) 90% by weight was preliminarily mixed with a Henschel mixer, and then melt-kneaded with a 4-inch three-roll mill heated to 115 ° C. to perform a dispersion treatment to obtain a dispersion.

Next, 5% by weight of the obtained dispersion, 24% by weight of siloxane-treated titanium oxide treated with siloxane, 27% by weight of titanium yellow, 10% by weight of the above polyethylene wax as a low molecular weight dispersant, and polypropylene resin as a carrier resin (MI = 7, random copolymer) 33.9% by weight and 0.1% by weight of a phenolic antioxidant were mixed with a Henschel mixer, and mixed with a twin screw extruder with L / D = 36.
The mixture was melt-kneaded at 0 ° C. to obtain a pellet (a pellet-like coloring agent for coloring a polypropylene resin).

The obtained pellets were added to a polypropylene resin (C) as a diluting resin during film formation by the following three methods. The first method uses a polypropylene resin (MI = 7, random copolymer) 1 as a diluting resin in a 6-inch two-roll mill heated to 180 ° C.
Add 17 parts by weight of the present pellet-shaped colorant to 00 parts by weight and add 4 parts by weight.
After melt-kneading for one minute, press molding was performed to produce a film having a thickness of 100 μm. The second method is the same as that of the first method, except that a single-screw extruder having a diameter of 30 mm and L / D = 32 is used in a single screw extruder.
A die head was mounted, and the mixture was melt-kneaded by a cylinder, a die temperature of 260 ° C. and a high-speed screw rotation (130 rpm) to produce a film having a thickness of 100 μm.

The third method is the same method as the first method, except that the film is changed to low-speed screw rotation (50 rpm), and the same method as the second method is used to form a film having a thickness of 100 μm. Was prepared.

Colorimeter (AuColo, manufactured by Kurabo Industries, Ltd.)
r7x), using a D65 light source, the L,
The a and b values are measured, and the film obtained by the first method is set to 0 (standard; hereinafter, referred to as STD) to derive the color difference of the sample in the second and third methods. Table 1 shows the results of comparing the color differences (ΔE values) of the films prepared in the above.

Example 1 A black pigment dispersant used in Comparative Example 1 was changed to a polypropylene resin (MI = 7, random copolymer) and kneaded with a BR type Banbury mixer for 5 minutes to obtain a dispersion. Prepared a colorant pellet in the same manner as in Comparative Example 1. The film preparation method and the film evaluation method were performed in the same manner as in Comparative Example 1, and the results are shown in Tables 1 and 2.

Example 2 A pellet colorant was prepared in the same manner as in Example 1 except that the black pigment dispersant used in Example 1 was changed to a polypropylene resin (MI = 22, homopolymer). The method for producing the film and the method for evaluating the film were performed in the same manner as in Comparative Example 1, and the results are shown in Table 1.

Comparative Example 2 A pellet colorant was prepared in the same manner as in Example 1 except that the black pigment dispersant used in Example 1 was a polypropylene resin (MI = 25, block copolymer). The method for producing the film and the method for evaluating the film were performed in the same manner as in Comparative Example 1, and the results are shown in Table 1.

Example 3 The carbon black used in Example 1 had an average particle diameter of 50 μm and a specific surface area of 51 m ² / g.
A pellet-shaped colorant was prepared in the same manner as in Example 1 except that the colorant was changed to that of Example 1. The method for producing the film and the method for evaluating the film were performed in the same manner as in Comparative Example 1, and the results are shown in Table 2.

Example 4 The carbon black used in Example 1 was prepared by using the carbon black having an average particle diameter of 40 mμ and a specific surface area of 56 m ² / g.
A pellet-shaped colorant was prepared in the same manner as in Example 1 except that the colorant was changed to that of Example 1. The method for producing the film and the method for evaluating the film were performed in the same manner as in Comparative Example 1, and the results are shown in Table 2.

Example 5 The carbon black used in Example 1 was average particle size of 30 μm and specific surface area of 85 m ² / g.
A pellet-shaped colorant was prepared in the same manner as in Example 1 except that the colorant was changed to that of Example 1. The method for producing the film and the method for evaluating the film were performed in the same manner as in Comparative Example 1, and the results are shown in Table 2.

Example 6 The carbon black used in Example 1 had an average particle diameter of 22 μm and a specific surface area of 134 m ² /
A pellet-shaped colorant was prepared in the same manner as in Example 1 except that the colorant was changed to g. The method for producing the film and the method for evaluating the film were performed in the same manner as in Comparative Example 1, and the results are shown in Table 2.

(Comparative Example 3) The carbon black used in Example 1 was prepared using an average particle size of 19 mμ and a specific surface area of 140 m ² /
A pellet-shaped colorant was prepared in the same manner as in Example 1 except that the colorant was changed to g. The method for producing the film and the method for evaluating the film were performed in the same manner as in Comparative Example 1, and the results are shown in Table 2.

Comparative Example 4 The carbon black used in Example 1 was prepared using an average particle diameter of 18 μm and a specific surface area of 200 m ² /
A pellet-shaped colorant was prepared in the same manner as in Example 1 except that the colorant was changed to g. The method for producing the film and the method for evaluating the film were performed in the same manner as in Comparative Example 1, and the results are shown in Table 2.

[0046]

[Table 1]

[0047]

[Table 2]

[0048]

EFFECTS OF THE INVENTION By using the pellet colorant for coloring a polypropylene resin of the present invention, it is possible to reduce the hue change and color unevenness of a molded article such as a film which requires a high level of pigment dispersion due to a difference in molding conditions. Can be expected.

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Claims (3)

[Claims] 1. A pellet-shaped colorant added to color the polypropylene resin (C), carbon black having an average particle diameter of 20 μm or more as a black pigment, and propylene homopolymer or propylene as a black pigment dispersant. A pellet colorant for coloring a polypropylene resin, comprising a dispersion composed of an ethylene random copolymer (A), a pigment and a carrier resin (B). 2. A dispersion obtained by melt-kneading 1 to 50% by weight of carbon black and 50 to 99% by weight of a homopolymer of propylene or a propylene-ethylene random copolymer (A), and then dispersing the dispersion, a pigment and a carrier. The method for producing a pellet colorant for coloring a polypropylene resin according to claim 1, wherein the resin (B) is melt-kneaded with a polypropylene resin. 3. A molded article obtained by using the pellet colorant for coloring a polypropylene resin according to claim 1.