JP4092960B2 - Method for producing master batch containing titanium dioxide, master batch containing titanium dioxide and molded article - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thermoplastic resin masterbatch containing a titanium dioxide pigment. In particular, the present invention relates to a method for producing a master batch excellent in high temperature and high speed workability when producing a high white thin film.
[0002]
[Prior art]
In general, in the production of thermoplastic resin molded products containing titanium dioxide, after producing a masterbatch in which titanium dioxide is dispersed in a thermoplastic resin at a high concentration in advance, the same or different type of masterbatch is formed during molding of the molded product. A method of diluting the master batch to a predetermined concentration with resin is adopted.
[0003]
A resin composition in which titanium dioxide is blended with a thermoplastic resin is excellent in weather resistance, mechanical properties, and the like. For this reason, it has been actively used for various applications such as injection molded products, films and sheets. In particular, a laminate in which a white film is coated on one or both sides of a sheet-like substrate such as paper or polyester has excellent water resistance, so it is widely used as a support for printing paper, photographic paper, packaging materials, etc. ing. These supports are generally produced by a melt extrusion lamination method, but a high temperature and high speed melt extrusion process is required to obtain high adhesion and productivity.
[0004]
[Problems to be solved by the invention]
In addition, these supports are required to improve the concealability of the base and improve optical characteristics such as resolving power. This can be obtained by increasing the titanium dioxide concentration in the film. However, when the amount of titanium dioxide added is increased, in the case of a thermoplastic resin composition containing a titanium dioxide pigment, particularly a polyolefin resin composition, it is melt extruded from a slit die. Thus, when forming into a film shape, the occurrence of acicular or icicle-like deposits or dirt (hereinafter simply referred to as die lip dirt) is promoted around the slit die.
[0005]
Die lip stains are organic oxidative degradation products and aggregates of titanium dioxide contained in the resin composition, and are likely to occur when the processing temperature is set to 300 ° C or higher in order to obtain high adhesion to a substrate such as paper. Become.
[0006]
If the production is continued with the die lip stains attached, vertical stripes or stripe-like unevenness may occur on the film surface, or sometimes the die lip stains may adhere to the film and foreign matter may appear. As a result, the surface quality of the film is significantly impaired and the product value is lost. Therefore, it is necessary to temporarily stop the operation of the molding line during the molding operation and remove the die lip dirt manually, and improvement in production efficiency has been demanded. .
[0007]
For the purpose of suppressing photodegradation and discoloration over time of the film, the surface of titanium dioxide is generally coated with a treatment agent such as an inorganic substance such as hydrous aluminum oxide or hydrous silicon oxide. And there exists a tendency for a water | moisture content to adhere easily by the influence of the coat | covered processing agent. For this reason, when film-forming a titanium dioxide-containing masterbatch, if it is passed through a slit die under high temperature and pressure, the moisture on the surface of the titanium dioxide pigment is volatilized and activated, and oxidation of organic substances contained in the masterbatch is promoted, resulting in die lip contamination. It is a factor of.
[0008]
As a method for suppressing the occurrence of die lip stains, it is possible to add a surfactant typified by a metal soap such as zinc stearate, calcium stearate, zinc palmitate when preparing a masterbatch or compound. This is described in Japanese Patent No. 046819. However, the main purpose of adding this metal soap is to improve the peelability between the cooling roll of the melt extruder and the film surface, and the metal composition is added to the resin composition for a thermoplastic resin film containing a titanium dioxide pigment. Even when soap was added, a film satisfying all of the concealability, peelability and die lip stain could not be obtained.
[0009]
By the way, the present inventors show that when a fatty acid metal salt (metal soap) having a decomposition temperature near 300 ° C. comes into contact with titanium dioxide, particularly anatase-type titanium dioxide, a relatively low temperature near the melting point of a thermoplastic resin such as polyethylene. It was also found that free fatty acids are produced due to the progress of decomposition.
[0010]
Usually, commercially available fatty acid metal salts contain about 0.5% of free fatty acids. However, contact with titanium dioxide under heating conditions promotes the production of free fatty acids, and depending on the conditions, the proportion of free fatty acids may exceed 50%.
[0011]
The free fatty acid in the master batch does not contribute to the lubricity between the resin and the metal unlike the fatty acid metal salt, and has no roll peeling effect. In addition, free fatty acids not only induce die lip contamination when forming a film, but also cause generation of oily smoke and cooling roll contamination.
[0012]
[Means for Solving the Problems]
When the present inventors melt-extruded from a slit die of a molding machine using a master batch, particularly a polyolefin resin master batch, and formed into a film shape, the above-described die lip contamination is small, and the peelability between the cooling roll and the film is low. In order to provide a masterbatch for obtaining a titanium dioxide-containing thermoplastic resin film having a good and high hiding property, the content of the fatty acid metal salt before the masterbatch production, the fatty acid metal salt after the production and the free fatty acid content Has been found to be in a specific range, and the present invention has been achieved.
[0013]
In the present invention, a compound comprising at least 30 to 70% by weight of a titanium dioxide pigment, a thermoplastic resin, and 2.5 to 4% by weight of a fatty acid metal salt is melt-kneaded and molded, and the fatty acid metal salt is 1.8 % by weight or more. And it is a manufacturing method of the titanium dioxide containing masterbatch made into the range of 1.5 weight% or less of free fatty acids.
[0014]
Moreover, the titanium dioxide pigment is rutile type titanium dioxide, the resin temperature in the melt kneading step is 180 ° C. or less, and the method for producing a titanium dioxide-containing masterbatch in which the melt kneading step is performed under reduced pressure.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The master batch of the present invention contains a high concentration of titanium dioxide pigment, and the pigment content is diluted to a predetermined concentration with a resin to be colored (uncolored thermoplastic resin) at the time of molding. It refers to a pellet-shaped resin composition for coloring which is melt-extruded from and used for film forming. As the resin to be colored, the same resin as the thermoplastic resin used in the masterbatch production or a compatible resin can be used.
[0017]
Examples of the thermoplastic resin used in the present invention include polyolefin, polystyrene, polyvinyl chloride, polyethylene terephthalate and the like. Of these, polyolefins having good thin film properties, particularly polyethylene, are preferred.
[0018]
Examples of the fatty acid metal salt used in the present invention include zinc stearate, calcium stearate, aluminum stearate, magnesium stearate, lithium stearate, zirconium octylate, sodium palmitate, calcium palmitate, sodium laurate and the like. In the present invention, one or more of these fatty acid metal salts may be added.
[0019]
Next, the amount of fatty acid metal salt added will be described.
The master batch of the present invention is first melt-kneaded with a blend of 30 to 70% by weight of a titanium dioxide pigment, a thermoplastic resin, and 2.5 to 4% by weight of a fatty acid metal salt.
[0020]
When the compounding amount of the fatty acid metal salt exceeds 4% by weight, the occurrence of die lip contamination is reduced when melt-extruding from the slit die together with the resin to be diluted to form a film, but the film concealing property increases with the addition amount. It gradually decreases, and generation of oily smoke and chill roll contamination become prominent. On the other hand, when the blending amount is less than 2.5 % by weight, the dispersibility of the titanium dioxide pigment at the time of melt kneading is poor, and at the time of masterbatch production and film molding, the extrusion is performed due to clogging of the wire mesh attached to the tip of the extruder. The resin pressure rises in the machine, and the productivity is significantly reduced.
[0021]
In the present invention, the content of the fatty acid metal salt contained in the masterbatch is a value measured by a calibration curve method using an infrared absorption spectrum. The calibration curve is an absorption band based on the carboxylate of fatty acid (in the case of zinc stearate) using a fatty acid metal salt, titanium dioxide, and thermoplastic resin kneaded with two rolls at 120 ° C, pressed, and thinned into a standard sample. 1545 cm ^-1 ) as a key band, and the relationship between the absorbance [D ₁₅₄₅ / D ₁₃₆₇ ] of the key band per thermoplastic resin internal standard band ( ₁₃₆₇ cm ^{-1 in} the case of polyethylene) and the reference value [addition amount of fatty acid metal salt] Can plot and create. When measuring the infrared absorption spectrum of the master batch itself, the master batch is kneaded and pressed with two rolls at 120 ° C. to prepare a thinned sample for use in measurement. Shimadzu FTIR-8300 can be used as an infrared absorption spectrum measuring apparatus.
[0022]
Further, the content of free fatty acid in the present invention is measured by a calibration curve method using a gas chromatograph. A calibration curve can be created by plotting the relationship between the [peak area] and the reference value [addition amount of fatty acid] at a retention time specific to fatty acids under specific conditions of gas chromatography using an acetone solution of fatty acid as a standard sample. In the present invention, GC-9A manufactured by Shimadzu Corporation, FES capillary column ULBON HR-54 0.24 mmI. D. Using 160 mm, measurement was performed under the conditions of a hydrogen flame detector (FID), a nitrogen gas flow rate of 50 ml as a carrier gas, a temperature of 100 ° C. to 280 ° C., a temperature of 10 ° C./min, and a sample injection amount of 2 μl. The retention times of palmitic acid and stearic acid under these conditions were 12.6 minutes and 14.5 minutes, respectively.
[0023]
As the titanium dioxide pigment used in the present invention, various titanium dioxide pigments such as a sulfuric acid method, a chlorine method, a rutile type, an anatase type, a surface treatment with a hydrated metal oxide, and a surface treatment with an organic compound can be used.
The particle diameter is desirably an average diameter of 0.1 to 0.3 μm for the purpose of improving the optical characteristics of the thermoplastic resin composition.
[0024]
In order to improve light stability or dispersibility, the surface of the titanium dioxide is preferably subjected to a surface treatment with an inorganic substance such as aluminum oxide, silicon oxide or zirconium oxide, or a hydrate thereof. Among these, in this invention, the hydrate of aluminum oxide is desirable, and also the process is 0.1-0.5 weight part in conversion of aluminum oxide with respect to 100 weight part of titanium dioxide. If the amount is less than 0.1 parts by weight, the catalytic action of titanium dioxide by light is not sufficiently suppressed, and therefore the deterioration of the resin with time tends to easily proceed. On the other hand, if it exceeds 0.5 parts by weight, the moisture accompanying the alumina increases, and as a result, the melt extrusion processability tends to deteriorate significantly.
[0025]
Moreover, it is preferable to use a titanium dioxide pigment whose surface is treated with an organic material for the purpose of preventing aggregation of titanium dioxide and improving dispersibility in the resin to be colored. Specific examples include silane coupling agents, organopolysiloxane compounds, alkanolamine compounds, etc. described or exemplified in JP-B-60-3430 and JP-B-61-26652. It is preferable to use a titanium dioxide pigment surface-treated with 0.05 to 4% by weight. If the surface treatment amount is less than 0.05% by weight, the effect of the organic surface treatment is small, and if it exceeds 4% by weight, it is easy to peel off from the titanium dioxide surface, and the workability of the film may be deteriorated during high temperature processing.
[0026]
From the viewpoint of adjusting the fatty acid metal salt and free fatty acid content contained in the masterbatch of the present invention, rutile type titanium dioxide is preferred. The reason is not clear, but when rutile type titanium dioxide is used, decomposition of the fatty acid metal salt contained in the masterbatch is suppressed as compared with the anatase type, so the fatty acid metal salt and free fatty acid defined in the present invention It becomes easy to obtain the content of.
[0027]
The masterbatch of the present invention includes white pigments such as zinc oxide, talc, and calcium carbonate, aliphatic amides such as stearic acid amide and arachidic acid amide, phenols, and thioethers, as long as the effects of the present invention are not impaired. System, phosphite-based antioxidants, cobalt blue, ultramarine, titanium yellow and other colored pigments, fluorescent whitening agents, and the like.
[0028]
The master batch of the present invention uses titanium dioxide, a thermoplastic resin, a fatty acid metal salt, and the various additives as necessary, using a two-roll, three-roll, kneader, Banbury mixer, twin-screw kneader, etc. It is manufactured by extruding into a pellet after melt-kneading.
[0029]
The resin temperature during the melt kneading is preferably 180 ° C. or lower. When the resin temperature exceeds 180 ° C., the decomposition of the fatty acid metal salt contained in the master batch is promoted, and it is difficult to obtain the range of the content of the fatty acid metal salt and the free fatty acid defined in the present invention. There is.
[0030]
Further, it is preferable to use a vacuum vent during melt-kneading to reduce the content of free fatty acid remaining in the masterbatch by forcibly exhausting the free fatty acid generated by decomposition and reducing the content of free fatty acid.
[0031]
The content of the fatty acid metal salt contained in the melted, kneaded, pellet-molded master batch is 1.8 to 4% by weight, and the content of the free fatty acid produced by the melt-kneading process is 0 to 1.5% by weight. % Range is required.
[0032]
When the content of the fatty acid metal salt is less than 1.8 % by weight, the die lip stain becomes remarkable. On the other hand, when the content of free fatty acid exceeds 1.5% by weight, generation of oily smoke and contamination of the cooling roll become remarkable. This is because, when melt extrusion from a slit die, the fatty acid metal salt contained in the master batch undergoes thermal decomposition and changes to free fatty acid, so that the amount of fatty acid metal salt effective against die lip stains is insufficient and This is because an increase in free fatty acids causing chill roll soiling, and subsequent generation of die lip soiling due to thermal decomposition of free fatty acids occurs.
[0033]
【Example】
Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. The evaluation results of the obtained master batch and molded product are shown in Table 1.
[0034]
[ Reference Example 1]
(Manufacture of coated titanium dioxide)
Anatase-type titanium dioxide having an average particle size of 0.2 μm was mixed with water and adjusted to an aqueous slurry having a weight of titanium dioxide of 300 g / liter using a sand mill.
While maintaining this slurry at 60 ° C., sodium aluminate was added in an amount of 0.5% by weight based on the weight of titanium dioxide in terms of Al ₂ O ₃ while stirring, and then neutralized to pH 5.0 with sulfuric acid. After coating the surface of titanium dioxide with aluminum hydrated oxide, it was filtered and washed with a filter press to obtain a cake.
The cake was dried at 120 ° C. for 10 hours to obtain base titanium dioxide (a).
[0035]
The base titanium dioxide and 0.5% by weight of trimethylolethane with respect to the weight of the titanium dioxide were stirred and mixed with a Henschel mixer and then pulverized with a steam mill to obtain coated titanium dioxide (b).
[0036]
(Manufacture of master batch)
Coated titanium dioxide (b) 60% by weight, low density polyethylene (specific gravity 0.917, MFR 7.0 g / 10 min.) 39% by weight, zinc stearate 1% by weight, and mixed by a super mixer. The dry mixture was heated and extruded at a resin temperature of 160 ° C. while reducing the pressure from the vacuum vent port using a twin-screw kneading extruder equipped with a 200-mesh wire mesh at the tip. The diameter was about 2 mm and the length was about 3 mm. A pellet-shaped masterbatch was obtained.
[0037]
(Fatty acid metal salt content)
Shimadzu FTIR-8300 was used as an infrared absorption spectrum measuring apparatus. The calibration curve is an absorption band based on the carboxylate of fatty acid (in the case of zinc stearate) using a fatty acid metal salt, titanium dioxide, and thermoplastic resin kneaded with two rolls at 120 ° C, pressed, and thinned into a standard sample. 1545 cm ^-1 ) as a key band, and the relationship between the absorbance [D ₁₅₄₅ / D ₁₃₆₇ ] of the key band per thermoplastic resin internal standard band ( ₁₃₆₇ cm ^{-1 in} the case of polyethylene) and the reference value [addition amount of fatty acid metal salt] Plotted and created. When measuring the infrared absorption spectrum of the master batch itself, the master batch was kneaded and pressed with two rolls at 120 ° C. to prepare a thinned sample for measurement.
[0038]
(Free fatty acid content)
As a gas chromatograph measuring apparatus, GC-9A manufactured by Shimadzu Corporation, FES capillary column ULBON HR-54 0.24 mmI. D. Using 160 mm, measurement was performed under the conditions of a hydrogen flame detector (FID), a nitrogen gas flow rate of 50 ml as a carrier gas, a temperature of 100 to 280 ° C., a temperature increase of 10 ° C./min, and a sample injection amount of 2 μl.
The calibration curve was created by plotting the relationship between the [peak area] and the reference value [addition amount of fatty acid] at the retention time peculiar to fatty acid under specific conditions of gas chromatography using an acetone solution of fatty acid as a standard sample. The retention times of palmitic acid and stearic acid under these conditions were 12.6 minutes and 14.5 minutes, respectively.
[0039]
As a result of measuring the amount of fatty acid metal salt and the amount of free fatty acid in the master batch, the content of fatty acid metal salt was 0.5% by weight and the content of free fatty acid was 0.3% by weight.
[0040]
In the twin-screw kneading extruder after master batch production, the clogged state of the wire mesh attached to the tip was observed with an optical microscope, and the dispersibility of titanium dioxide was evaluated according to the criteria shown in Table 2. The dispersibility of titanium dioxide is better when the wire mesh is less clogged.
[0041]
(Film production)
A total of 25 kg of a composition consisting of 20 wt. The film was melt-extruded at 300 ° C. and drawn and stretched with a cooling roll to form a film having a thickness of 30 μm.
[0042]
The oily smoke generated when the resin melt was discharged from the slit die during film formation, the ease of peeling of the film from the cooling roll, and the degree of dirt on the cooling roll after completion of molding were visually evaluated. Further, the total length of the needle-like or icicle-like dirt adhering to the periphery of the slit die after molding (the length of the die lip dirt × number) was measured. The evaluation criteria are shown in Table 2.
[0043]
[Examples 1 and 2, Reference Examples 1-11 , Comparative Examples 1-5]
A master batch and a film were produced under the production conditions shown in Table 1. Particularly detailed description is not conditions performed in the same manner as in Reference Example 1, was evaluated in the same manner as in Reference Example 1.
[0044]
[Table 1]
[0045]
[Table 2]
[0046]
【The invention's effect】
The method for producing a titanium dioxide-containing masterbatch of the present invention melts and kneads and forms a blend of at least 30 to 70% by weight of a titanium dioxide pigment, a thermoplastic resin, and 2.5 to 4% by weight of a fatty acid metal salt. The dispersibility of titanium dioxide is good, and the amount of free fatty acid produced is low.
In addition, the fatty acid metal salt in the titanium dioxide-containing masterbatch is in the range of 1.8 to 4% by weight and the free fatty acid is in the range of 1.5% by weight or less. , Roll contamination, roll peeling and other problems do not occur.
[0047]
Since the titanium dioxide pigment used in the method for producing a titanium dioxide-containing masterbatch of the present invention is rutile titanium dioxide, decomposition of the fatty acid metal salt is suppressed when melt-kneaded with the fatty acid metal salt. Moreover, in the manufacturing method of the titanium dioxide containing masterbatch of this invention, since the resin temperature of a melt-kneading process is 180 degrees C or less, decomposition | disassembly of a fatty-acid metal salt is suppressed. Furthermore, since the manufacturing method of the titanium dioxide containing masterbatch of this invention performs a melt-kneading process under reduced pressure, the generated free fatty acid is forcedly exhausted and the content of the free fatty acid remaining in the masterbatch can be reduced.
[0048]
Since the titanium dioxide-containing masterbatch of the present invention obtained by any one of the above production methods has less free fatty acids, production efficiency is good because there is no die lip contamination, generation of oily smoke, and cooling roll contamination when forming the film of the present invention. In addition, the quality of the obtained film is good, and a high white thin film can be formed. In particular, it is useful as a coating film for a photographic paper support that requires high hiding properties.

Claims (1)

When the total amount of the blend is 100% by weight, a blend of at least 30 to 70% by weight of titanium dioxide pigment, a thermoplastic resin, and 2.5 to 4% by weight of a fatty acid metal salt is melt-kneaded and molded. Is rutile titanium dioxide, and the melt-kneading step is performed under reduced pressure using a vacuum vent at a resin temperature of 180 ° C. or lower, and the fatty acid metal salt is 1.8 wt% or more and free fatty acid 1.5 wt% or less. The manufacturing method of the titanium dioxide containing masterbatch to make into the range.