JP4127534B2 - Masterbatch and manufacturing method thereof - Google Patents

Description

  The present invention relates to a masterbatch used for coloring various plastic molded products such as injection molded products, molded products, films and fibers, and a method for producing the same.

  When coloring various plastic molded products such as injection molded products, molded products, films, fibers, etc., the method of using a master batch as a colorant can reduce the contamination of the production line compared to the stock solution coloring method. In addition, it is economically advantageous compared to the method using a color compound for processing the whole amount, and further, it is evaluated for the fact that there is less color unevenness in the molded product than the dry blend method in which the pigment is directly mixed with the plastic. It has been used a lot. However, it is inferior in terms of color unevenness occurring in the molded product as compared with the stock solution coloring method and the color compound method.

  Conventionally, when manufacturing a masterbatch in which a high content of inorganic particles is blended with a polyolefin such as polyethylene as a matrix resin, the matrix resin is generally blended with a wax as a dispersant for the purpose of reducing uneven mixing of the inorganic particles. A method for improving the fluidity at the time of melting is adopted. However, if the amount of wax used is too large, the blades and screws of the mixing device will slip too much during kneading of the master batch components, resulting in large mixing unevenness in the resulting master batch, for example, impact strength and tensile strength of injection molded products. The mechanical strength such as the thickness is reduced, or the flow mark such as uneven color, fading and streaks is generated on the surface of the molded product, the gloss is also lowered, and the commercial value of the molded product is lowered.

  Patent Document 1 proposes to improve the above-mentioned drawbacks by blending a sorbitol compound and / or a benzoic acid compound with waxes. However, in this proposal, although the color unevenness in the molded product is improved, there is no description about the decrease in the mechanical strength of the molded product, and the deterioration of the physical properties of the molded product due to the use of low molecular weight wax is inevitable. Patent Document 2 proposes to improve the impact strength of a molded product using polypropylene, polyolefin rubber and a small amount of wax. However, in this proposal, although the mechanical properties of the molded product are improved, there is no description about prevention of uneven color of the molded product, and no consideration is given.

As described above, the conventional proposal has not proposed a master batch that can satisfy both the mechanical properties of the molded product and the prevention of uneven color.
JP-A-5-339442 Japanese Patent Laid-Open No. 2002-3667

  An object of the present invention is to provide a masterbatch capable of producing a colored molded article satisfying both mechanical properties and color unevenness prevention, and a production method thereof.

  The above object is achieved by the present invention described below. That is, the present invention provides a master batch characterized in that it contains 0.5 to 2% by mass of carbon dioxide gas as closed cells and is composed of a pigment and / or a filler, a dispersant, and a polyolefin or polystyrene resin. In the present invention, the polyolefin resin preferably contains a polyolefin rubber.

  The present invention also provides the method for producing a masterbatch, wherein carbon dioxide is injected in a supercritical or subcritical state when the pigment, filler and dispersant are kneaded.

  The masterbatch of the present invention is a masterbatch that gives a colored molded product that satisfies both mechanical properties and color unevenness prevention. When mixed with a resin, the masterbatch is enclosed in closed cells in the molten masterbatch. The carbon dioxide gas expands the master batch and increases the volume, thereby improving the mixing effect with the resin to be colored (diluted resin) and contributing to the prevention of uneven color without reducing the mechanical strength of the molded product. can do.

Next, the present invention will be described in more detail with reference to preferred embodiments.
The master batch of the present invention is characterized in that it contains 0.5 to 2% by mass of carbon dioxide gas mixed at the time of producing the master batch as closed cells. The content of carbon dioxide is assumed to be that the supplied carbon dioxide remains in the closed cells of the master batch. This assumption was that the error was less than 10% when the masterbatch was dissolved in a phase-separated liquid of water and xylene and the carbon dioxide dissolved in water was quantified by titration. If the content of carbon dioxide is too small, the contribution to the mixing effect of the master batch and diluted resin in the supercritical or subcritical state of carbon dioxide is insufficient. If there is too much carbon dioxide gas, the expansion of the pellet master batch due to insufficient cooling at the time of master batch production will be large, and it will be necessary to increase the cutting speed in order to maintain the pellet size. Absent.

  The supercritical condition of carbon dioxide gas is generally said that the temperature is about 30 ° C. or higher and the pressure is about 7 MPa or higher, and the subcritical condition is generally said that either the temperature or the pressure is outside the above range. The master batch production conditions of the present invention are preferably a maximum temperature of 150 ° C. or higher and a maximum pressure of 2 MPa or higher. More preferably, it is 180 degreeC or more, More preferably, it is 220 degreeC or more.

  Examples of the polyolefin resin that is the main raw material (matrix resin) of the masterbatch used in the present invention include, for example, low density polyethylene, linear low density polyethylene, high density polyethylene, polypropylene, polyethylene / polypropylene block copolymer, polyethylene / polypropylene. Examples include olefin homopolymers and copolymers such as random copolymers. Among them, polyethylene / polypropylene block copolymers and polyethylene / polypropylene random copolymers are also called polyolefin rubbers because of their physical properties.

  Polystyrene resins include polystyrene, acrylonitrile / styrene copolymer, acrylonitrile / butadiene / styrene copolymer, and the like. As the matrix resin which is the main raw material of the master batch, it is preferable to select the same material as the resin to be colored in order not to lower the mechanical properties of the final molded product.

  Examples of the natural inorganic pigment used in the present invention include yellow ocher, tail belt, low senna, kassel earth, gypsum, and the like, and examples of the fired earth pigment include burnt senna, burnt amber, and the like. Examples of mineral pigments include lapis lazuli, azurite, malachite, opiment, and cinnabar, and examples of other pigments include powder and pepper powder. Examples of the synthetic inorganic pigment include oxide pigments such as cobalt blue, cerulean blue, cobalt violet, cobalt green, zinc white, titanium white, light red, chrome oxide green, and mars black. Examples include viridan, yellow ocher, and alumina white. Examples of the sulfide pigment include cadmium yellow, cadmium red, vermilion, and lithopone. Examples of the silicate pigment include ultramarine, talc, Examples of the phosphate pigment include mineral violet and rose cobalt violet. Examples of the carbonate pigment include silver white and calcium carbonate. Examples of metal powder pigments include gold powder, bronze powder, and aluminum powder. Examples of other pigments include ivory black, peach black, lamp black, carbon black, Prussian blue, Examples include aureolin and mica.

  Organic pigments include dyed lake pigments (alizarin lake, rhodamine lake, etc.), azo pigments (first yellow, disazo yellow, naphthol red, chromophthal yellow, chromophthal red, nickel azo yellow, benzimidazolone yellow, etc.), phthalocyanine pigments (Phthalocyanine blue, phthalocyanine green, etc.), condensed polycyclic pigments (thioindigo, perylene red, dioxazine violet, quinacridone red, perinone, isoindolinone, azothymene, etc.) and fluorescent pigments.

  Examples of the filler include inorganic materials such as glass fiber, talc, clay, wollastonite, calcium carbonate, diatomaceous earth, barium sulfate, bentonite, stone powder and silica, pulp powder, wood powder, kenaf powder, starch, bone powder, shellfish Organic materials such as powder and chitin powder are listed.

  Examples of the dispersant include higher fatty acids such as stearic acid and 12-hydroxystearic acid, higher fatty acid metal salts such as calcium stearate and magnesium stearate, natural waxes, polyhydric alcohol partial esters, paraffin wax, and low molecular weight polyethylene. And hydrocarbons such as stearyl alcohol and polyethylene glycol, silicone compounds, polyolefins modified with unsaturated carboxylic acids, fatty acid amides or derivatives thereof, and the like.

  Among them, lauric acid amide, stearic acid amide, oleic acid amide, behenic acid amide, erucic acid amide, ethylene bis stearic acid amide, methylene bis stearic acid amide, ethylene bis oleic acid amide, N-stearyl erucamide, hexamethylene bis Stearic acid amide is preferable, and monoamides such as lauric acid amide, stearic acid amide, oleic acid amide, behenic acid amide, and erucic acid amide are more preferable.

  The blending amount of the pigment and / or filler is about 80% by volume of the entire master batch, and when it exceeds that, the pigment or filler is mixed with the colored resin (diluted resin) to form a colored molded product. The agent becomes poorly dispersed in the resin to be colored, which easily leads to uneven color of the molded product and deterioration of mechanical properties. Further, it is preferable that the blending amount of the dispersing agent is as small as possible, since there is little decrease in mechanical properties of the obtained molded product. Since the pigment, filler, or dispersant is mixed in a supercritical or subcritical state of carbon dioxide gas, the apparent viscosity of the matrix resin is reduced by about 30%, and the dispersant is added even if the blending amount of the pigment and / or filler is the same. In the invention, it can be reduced. Therefore, the deterioration of mechanical properties of the obtained molded product can be reduced.

  When the masterbatch of the present invention is produced, in order to mix resins, pigments, fillers, dispersants, and the like having different particle sizes, the above ingredients are pre-stirred and kneaded with a high-speed rotary mixer such as a Henschel mixer, and then It is preferable to further mix by an extruder in a supercritical or subcritical state to form the master batch into pellets.

  In the present invention, the extruder for mixing and extruding carbon dioxide gas in a supercritical or subcritical state preferably has a raw material supply unit, a carbon dioxide gas injection unit, a compression kneading unit, a decompression unit, a metering unit, and a die. The mixture (cord) extruded from the die in a string shape is extruded into water and cut with an underwater cutter or cooled with a cooling tank and then cut with a cutter. The set temperature of the extruder varies depending on the matrix resin, but in the case of a polyolefin resin, the die temperature is generally 180 ° C to 250 ° C.

  The degree of expansion of the string-like mixture (cord) extruded from the die varies depending on its diameter, temperature, cooling tank temperature, discharge amount, carbon dioxide content, raw material viscosity, and carbon dioxide diffusion rate. Factors that are easy to control during operation are the die temperature, the discharge rate, and the cooling bath temperature. By adjusting these, the expansion rate of the string-like material, that is, the pellet can be adjusted. This expansion coefficient is particularly important when a large amount of a high density inorganic filler is blended in the matrix resin.

  Since the expansion rate of the pellet master batch can be adjusted as described above, the apparent density of the pellet master batch can be adjusted. In order to make the pre-mixing of the pellet-shaped master batch and the diluted pellet (colored resin) uniform, the diameter and length of the pellet-shaped master batch and the specific gravity of the pellet-shaped colored resin as long as possible It is important that the shape of the master batch of the present invention is adjusted.

  The master batch of the present invention is used as a coloring raw material for various molded articles such as an inflation film. The dilution ratio of the master batch (mixing ratio with the resin to be colored) is about 10 to 50 times. For example, in forming an inflation film, a master batch and a diluted resin (colored resin) are mixed from a supply hopper of the apparatus and supplied to the forming apparatus. For example, an extruder for an inflation film has many full flat screws and kneading efficiency is not so good. However, the master batch of the present invention expands in the compression section of the apparatus, and the kneading effect between the master batch and the diluted resin is improved. Most of the carbon dioxide gas is removed at the time of kneading, and the remainder is released to the outside as soon as it comes out of the die of the extruder, so that no holes or voids are formed in a molded product such as a film to be molded.

  Even in the injection molding, since the injection mold has a vent hole and the enthalpy of carbon dioxide gas is small, defects such as flash due to residual moisture do not occur due to the residual carbon dioxide gas.

Next, the present invention will be described more specifically with reference to examples.
[Example 1]
40 parts by mass of high-density polyethylene with MFR (load 2.16 kg, orifice diameter 2 mm, orifice length 10 mm, temperature 190 ° C., measurement time 10 minutes) 20 parts by mass, talc 80 parts by mass, wax 20 parts by mass, dispersion 2 parts by mass of an agent (erucamide) and 10 parts by mass of carbon black were pre-kneaded and mixed at 130 ° C. with a Henschel mixer, and then a screw diameter of 50 mm, a raw material supply unit, a carbon dioxide injection unit, a compression kneading unit, a decompression unit, a metering unit, and It was fed to an extruder consisting of a die.

  Carbon dioxide gas is fed into the extruder so as to be 1% by mass with respect to the total mass of the master batch, and the maximum temperature of the compression kneading part is brought to a supercritical state of carbon dioxide gas of 250 ° C. and 7 MPa, and the pressure is reduced to 2 MPa in the decompression part. Then, a string-like extrudate is extruded through a 100-mesh filter through a nozzle diameter of 0.5 mm into cooling bath water at 4 ° C., and the string-like extrudate is taken out and cut into a length of 2 mm by a cutter. Batch pellet A was produced. The diameter of the pellet A was 0.7 mm. When the cross section in the machine direction of the pellet A was observed with a scanning electron microscope, a layered stripe pattern was observed. In the cross section perpendicular to the machine direction of pellet A, small closed cells were observed. The apparent specific gravity of pellet A was 1.31. When heated at 100 ° C. for 3 minutes, the heated pellet A changed to 3.2 mm in diameter and 1.5 mm in length, and the volume expanded 15.7 times.

  In the said manufacturing method, the masterbatch pellet B was manufactured like the above except raising only the water temperature conditions of a cooling tank to 50 degreeC. The obtained pellet B had a diameter as large as 0.85 mm and an apparent specific gravity of 0.98, which was substantially the same as the specific gravity of 0.95 of high-density polyethylene. In the cross section perpendicular to the machine direction of pellet B, closed cells larger than pellet A were observed, but the number of closed cells per unit mass was not significantly different between pellets A and B.

As a reference example, a pellet C was produced in the same manner as above except that carbon dioxide gas was not supplied in the method for producing the pellet A.
A colored molded product was molded using the above pellets A to C, and a test was performed to compare color unevenness generated in each colored molded product. In this test, the dilution ratio was increased so that the difference in color unevenness generated could be easily judged, and pellets A, B and C and high-density polyethylene for dilution were each used at a mass ratio of 1: 100 using a rotating drum mixer. Mixed for minutes. The mixed pellet was sequentially taken out and divided into 100, and a sample plate was formed with an injection molding machine every 10 divisions. The degree of color unevenness was compared by visual observation of each plate.

  In the sample plate molded using the pellet A, no color unevenness or color streak was observed, but a difference in color density was observed due to the division. This is due to uneven mixing due to the specific gravity difference between the pellet A and the pellet of the diluted resin. In the sample plate formed using the pellet B, no color unevenness, color streaking, or color density difference due to division was observed. On the other hand, color unevenness, color streaking, and color density difference due to division were observed in the sample plate formed using the pellet C of the reference example.

[Example 2]
40 parts by mass of high-density polyethylene with MFR (load 2.16 kg, orifice diameter 2 mm, orifice length 10 mm, temperature 190 ° C., measurement time 10 minutes) 20 parts by mass, talc 80 parts by mass, wax 2 parts by mass, dispersion 1 part by weight of an agent (erucamide) and 10 parts by weight of carbon black were pre-kneaded and mixed at 130 ° C. with a Henschel mixer, and then a screw diameter of 50 mm, a raw material supply part, a carbon dioxide injection part, a compression kneading part, a decompression part, a weighing part, and It was fed to an extruder consisting of a die.

  Carbon dioxide gas is supplied to the extruder so as to be 1% by mass with respect to the total mass of the master batch, the maximum temperature of the compression kneading part of the apparatus is set to 250 ° C. and 7 MPa of carbon dioxide gas supercritical state, and the decompression part to 2 MPa. Reduce the pressure, pass through a 100 mesh filter, extrude the cable from the nozzle diameter of 0.5mm into the cooling bath water at 4 ° C, pull the cable and cut it to 2mm in length with the cutter, master batch pellet D of the present invention Manufactured. The diameter of the pellet D was 0.7 mm. When the cross section in the machine direction of the pellet D was observed with a scanning electron microscope, a layered stripe pattern was observed. In the cross section perpendicular to the machine direction of pellet D, small closed cells were observed. The apparent specific gravity of pellet D was 1.43.

  In the above production method, master batch pellets E were produced in the same manner as above except that only the water temperature condition of the cooling bath was raised to 60 ° C. The diameter of the obtained pellet E was as thick as 0.90 mm, and the apparent specific gravity was 0.95, which was almost the same as the specific gravity of high density polyethylene of 0.95. In the cross section perpendicular to the machine direction of pellet E, closed cells larger than pellet D were observed, but the number of closed cells per unit mass was not significantly different between pellets D and E.

  For reference, in the above example, when master batch pellets were produced with a carbon dioxide gas supply amount of 0.2% by mass, uneven color was observed in the pellets at the time of the master batch pellets. Further, when the master batch pellets were manufactured by increasing the supply amount of carbon dioxide gas to 5% by mass in the above examples, the pellet diameter exceeded 4 mm at a water temperature of 50 ° C., which was greatly different from the pellet size of the diluted resin. What mixed dilution resin pellets was worried about the bite in a general extruder. Further, when a plate was molded by injection molding using the above mixture, bubbles remained in the injection molded plate, although they were slight.

The masterbatch of the present invention is a masterbatch that gives a colored molded product that satisfies both mechanical properties and color unevenness prevention. When mixed with a resin, the masterbatch is enclosed in closed cells in the molten masterbatch. The carbon dioxide gas expands the master batch and increases the volume, thereby improving the mixing effect with the resin to be colored (diluted resin) and contributing to the prevention of uneven color without reducing the mechanical strength of the molded product. can do.

Claims (3)

  A masterbatch comprising carbon dioxide in an amount of 0.5 to 2% by mass as a closed cell and comprising a pigment and / or a filler, a dispersant, and a polyolefin or a polystyrene resin.   The masterbatch according to claim 1, wherein the polyolefin resin contains a polyolefin rubber. The method for producing a masterbatch according to claim 1 or 2, wherein carbon dioxide is injected in a supercritical or subcritical state when the pigment, filler and dispersant are kneaded.