JP7473263B1 - Surface-treated calcium carbonate filler, and resin composition and molded article using same - Google Patents

Abstract

[Problem] To provide a surface-treated calcium carbonate filler which can improve all of the weather resistance, heat resistance, and strength of a resin composition obtained by kneading with a resin such as a polyolefin-based resin, and a resin composition and a molded article using the same. [Solution] The surface-treated calcium carbonate filler of the present invention satisfies the following formulae (a), (b), and (c): (a) 2.0≦Sw≦20.0 (m2/g), (b) 300≦Pw≦5000 (ppm), and (c) 0.01≦Tw≦0.30 (mass%). Here, Sw is the BET specific surface area (m2/g) of the surface-treated calcium carbonate filler, Pw is the content (ppm) of phosphorus element in the surface-treated calcium carbonate filler measured with an inductively coupled plasma (ICP) optical emission spectrometer, and Tw is a weight loss value (mass%) at 140° C. to 220° C. measured with a differential thermobalance. [Selected Figure] None

Description

The present invention relates to a surface-treated calcium carbonate filler, and a resin composition and a molded article using the same.

Polyolefin resins are characterized by their excellent rigidity, impact resistance, heat resistance, moldability, transparency, chemical resistance, etc., and are widely used in a variety of applications, such as in various industrial materials, automobile-related parts, various containers for medical and cosmetic use, and various films and fibers for daily necessities and industrial use, for example, when combined with calcium carbonate inorganic pigments. They are also known as relatively environmentally friendly resins, and there are hopes for attempts to use polyolefin resins as a base material in green infrastructure applications. On the other hand, there is also a demand for resin compositions containing such polyolefin resins that are melt-kneaded to produce products with further improved weather resistance, heat resistance, and strength.

In addition, efforts have been made to stabilize resin compositions by adding metal soaps such as calcium stearate, phenolic antioxidants, and phosphorus-based antioxidants to the resin to be melt-kneaded. Alternatively, efforts have been made to add calcium carbonate treated with a fatty acid such as stearic acid or stearic acid soap to these resins, thereby combining the function of calcium carbonate with the role of enhancing the stability of the resin (see, for example, Patent Document 1). The resin composition obtained in this way is useful, for example, as a material for porous films that can be used for battery separators (Patent Documents 2 to 4).

On the other hand, methods proposed for obtaining such resin compositions include a method in which the resin and an antioxidant such as a phenolic or phosphorus-based antioxidant are mixed in advance using a mixer such as a super mixer or tumbler mixer and then melt-kneaded, a method in which the resin and additives are separately and simultaneously added and melt-kneaded, and a method in which the resin is side-fed into the middle of the kneader after it has melted.

However, although it is unclear why the antioxidant does not reach every corner of the resulting resin composition, or does not function properly due to thermal degradation of the antioxidant, all of these methods result in the antioxidant not reaching every corner of the resulting resin composition, or the antioxidant does not function properly due to thermal degradation, and the thermal stability of the molded resin composition may be insufficient. For this reason, there is a demand for the development of an additive that can reach every corner of the resin composition, not deteriorate thermally, fully function in terms of sliding properties, and further improve the stability of the resin composition.

JP 2002-363443 A JP 2006-169421 A International Publication No. 2007/088707 JP 2004-196917 A

The present invention aims to solve the above problems, and its object is to provide a surface-treated calcium carbonate filler that can improve the weather resistance, heat resistance, and strength of a resin composition obtained by kneading it with a resin such as a polyolefin resin, and to provide a resin composition and a molded product using the same.

The present invention provides a surface-treated calcium carbonate filler that satisfies the following formulas (a), (b), and (c):
(a) 2.0≦Sw≦20.0 ( ^m2 /g)
(b) 300≦Pw≦5000 (ppm)
(c) 0.01≦Tw≦0.30 (mass%)
(S w is the BET specific surface area (m ² /g) of the surface-treated calcium carbonate filler,
The Pw is the content (ppm) of the phosphorus element in the surface-treated calcium carbonate filler measured with an inductively coupled plasma (ICP) emission spectroscopic analyzer,
The Tw is a weight loss value (mass%) of the surface-treated calcium carbonate filler at 140° C. to 220° C. measured with a differential thermobalance device.

In one embodiment, the surface treated calcium carbonate filler of the present invention further satisfies the following formula (d):
(d) 0.80≦bw≦1.50
The bw is a hue change rate calculated by the following formula using yellowness values (b values) measured by a spectrophotometer before and after continuous heating at 140° C. for 48 hours for a paste in which the surface-treated calcium carbonate filler and dioctyl phthalate (DOP) are mixed in a mass ratio of 3 to 7:
Hue change rate (bw) = (b value of paste after heating / b value of paste before heating)
It is.

In one embodiment, the surface treated calcium carbonate filler of the present invention further satisfies the following formulas (e), (f) and (g):
(e) 0.10≦D50≦2.00 (μm)
(f) 0.9≦(D90−D10)/D50≦2.0
(g) Da≦5.0 (μm)
The D50 is a 50% diameter (μm) accumulated from the small particle side in a volume particle size distribution of the surface-treated calcium carbonate filler measured with a laser diffraction particle size distribution measuring device,
The D90 is a 90% diameter (μm) accumulated from the small particle side in the volume particle size distribution of the surface-treated calcium carbonate filler measured with the laser diffraction particle size distribution measurement device,
The D10 is a 10% diameter (μm) accumulated from the small particle side in the volume particle size distribution of the surface-treated calcium carbonate filler measured with the laser diffraction particle size distribution measurement device,
The Da is the maximum particle size (µm) in the volume particle size distribution of the surface-treated calcium carbonate filler measured with the laser diffraction particle size distribution measurement device.

In one embodiment, the surface-treated calcium carbonate filler of the present invention is used to form a polyolefin-based resin composition.

The present invention also relates to a resin composition comprising a resin and the above-mentioned surface-treated calcium carbonate filler.

In one embodiment, the resin is a polyolefin resin.

The present invention also relates to a molded article made from the above resin composition.

In one embodiment, the molded article of the present invention has the form of a film.

According to the present invention, it is possible to provide a resin composition that is excellent in heat resistance and can be easily mixed with a resin. The surface-treated calcium carbonate filler of the present invention also has good dispersibility in a resin, and can reduce the occurrence of resin burning and agglomerates during melt kneading, clogging of a strainer, and the like, and can provide a resin composition with excellent operational stability. Furthermore, for example, a film obtained by using the surface-treated calcium carbonate filler of the present invention and a polyolefin-based resin has a feature that strength deterioration is unlikely to occur in terms of weather resistance and heat resistance.

1. Surface-treated calcium carbonate filler First, the surface-treated calcium carbonate filler of the present invention will be described.

The surface-treated calcium carbonate filler of the present invention satisfies the following formulas (a), (b), and (c).

(a) BET specific surface area (Sw)
The surface-treated calcium carbonate filler of the present invention has a predetermined BET specific surface area (Sw; m ² /g) measured by a nitrogen adsorption method. In the present invention, the Sw of the surface-treated calcium carbonate filler is 2.0≦Sw≦20.0 (m ² /g), preferably 3.0≦Sw≦15.0 (m ² /g), and more preferably 5.0≦Sw≦12.0 (m ² /g). When the Sw of the surface-treated calcium carbonate filler is less than 2.0 (m ² /g), the primary particles thereof become too large, and when the filler is blended in a resin composition, the strength of the resin composition is reduced. In addition, due to the large primary particles, for example, undesired protrusions are formed on the surface of a resin molded body to be obtained, and the slidability of the resin molded body may be reduced. When the Sw of the surface-treated calcium carbonate filler exceeds 20.0 (m ² /g), the crystallinity of calcium carbonate constituting the surface-treated calcium carbonate filler becomes weak, and a resin composition obtained by mixing the surface-treated calcium carbonate filler with a polyolefin-based resin or the like cannot have sufficient weather resistance or heat resistance. In addition, as the primary particles become smaller, the cohesive force between the particles becomes larger, so that, for example, the primary particles cannot be sufficiently dispersed when kneaded with a resin, and undesired protrusions are formed on the surface of a resin molded body, and the sliding property of the resin molded body may be reduced.

(Method of measuring Sw)
The Sw of the surface-treated calcium carbonate filler can be measured, for example, using Macsorb HM model-1201 manufactured by Mountech Co., Ltd. as follows.

Specifically, about 300 mg of the surface-treated calcium carbonate filler to be measured is placed in the measuring device, and a pretreatment is performed by heating at 200°C for 10 minutes in a mixed gas atmosphere of nitrogen and helium, and then Sw is measured by low-temperature, low-humidity physical adsorption in a liquid nitrogen environment.

Sw can be controlled by varying various conditions when producing the surface-treated calcium carbonate filler of the present invention. Examples of conditions that can control Sw within the above range include the concentration of the milk of lime used in the carbonation reaction, the temperature employed in the carbonation reaction, the concentration of the carbon dioxide gas used, and the type of additive used in the carbonation reaction, as well as combinations of these, as described below. If such conditions are not set sufficiently, it may be difficult to obtain a surface-treated calcium carbonate filler that satisfies the above Sw range.

(b) The content of phosphorus element (Pw) measured by an inductively coupled plasma (ICP) emission spectrometer
The surface-treated calcium carbonate filler of the present invention has a predetermined phosphorus content (Pw; ppm) measured by an ICP optical emission spectrometer. In the present invention, the Pw of the surface-treated calcium carbonate filler is 300≦Pw≦5000 (ppm), preferably 400≦Pw≦3000 (ppm), and more preferably 500≦Pw≦1500 (ppm). When the Pw is lower than 300 (ppm), the filler itself does not have sufficient heat resistance. When the Pw exceeds 5000 (ppm), the obtained surface-treated calcium carbonate filler is likely to aggregate, so that the dispersibility in a resin is reduced, and further, satisfactory thermal stability cannot be obtained in a resin composition.

(Method of measuring Pw)
Pw can be measured, for example, using an ICP optical emission spectrometer SPS3500 manufactured by SII NanoTechnology Inc. as follows.

(1) First, about 1,000 mg of a surface-treated calcium carbonate filler to be measured is placed in a crucible and fired in an electric furnace at 300° C. for 3 hours.
(2) After firing, a small amount (e.g., about 60 mL) of distilled water and 7.5 mL of 1.38 N nitric acid (nitric acid for measuring hazardous metals (1.38), manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) are added to a 200 mL beaker, and the mixture is boiled on an electric stove and slowly cooled.
(3) 100 μL of yttrium standard solution (Y1000 manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) is placed in a 100 mL measuring flask, the mixture after gradual cooling is added, and the mixture is made up to 100 mL with distilled water.
(4) Next, the solution is filtered through No. 5C filter paper, and a sample for ICP measurement is prepared from the obtained filtrate.
(5) After that, the content (ppm) of elemental phosphorus contained in the sample is measured using the ICP atomic emission spectrometer.

(c) Weight loss value (Tw)
The surface-treated calcium carbonate filler of the present invention has a predetermined weight loss value (Tw; mass%) at 140° C. to 220° C. measured by a differential thermobalance apparatus. In the present invention, Tw of the surface-treated calcium carbonate filler is 0.01≦Tw≦0.30 (mass%), preferably 0.01≦Tw≦0.20 (mass%), and more preferably 0.01≦Tw≦0.15 (mass%). When Tw is less than 0.01 (mass%), there is no significant problem in the physical properties of the filler itself, but a large production load is required to increase the crystallinity of calcium carbonate constituting the filler. When Tw exceeds 0.30 (mass%), the obtained surface-treated calcium carbonate filler does not have sufficient heat resistance, and it is difficult to obtain a resin composition excellent in all of weather resistance, heat resistance, and strength.

(Method of measuring Tw)
Tw can be measured using a differential thermobalance (for example, DTG-60A manufactured by Shimadzu Corporation) as follows.

(1) First, about 30 mg of the surface-treated calcium carbonate filler is weighed into a platinum sample pan and set in the measuring machine.
(2) Thereafter, the temperature of the measuring device is increased from room temperature to 550° C. at a temperature increase rate of 30° C./min, and measurement is performed, and a weight loss value (mass%) from 140° C. to 220° C. per 1 g of the surface-treated calcium carbonate filler is calculated.

Moreover, it is more preferable that the surface-treated calcium carbonate filler of the present invention satisfies the following formula (d) in addition to the above formulas (a) to (c).

(d) Hue change rate (bw)
In the surface-treated calcium carbonate filler of the present invention, with respect to a paste (also referred to as "DOP paste") obtained by mixing the surface-treated calcium carbonate filler and dioctyl phthalate (DOP) in a mass ratio of 3:7, it is preferable that the hue change rate (bw) calculated from the yellow value (b value) measured by a spectrophotometer before and after continuous heating at 140° C. for 48 hours with reference to JIS K 7368:1999 (Plastics-Polypropylene and propylene copolymers-Method for measuring thermooxidative stability in air-Oven method) has a predetermined value. Note that the hue change rate (bw) is calculated from the following formula:
Hue change rate (bw) = (b value of paste after heating / b value of paste before heating)

In the present invention, the bw of the surface-treated calcium carbonate filler is preferably 0.80≦bw≦1.50, and more preferably 1.00≦bw≦1.20. When the bw is less than 0.80, there is no significant problem in the physical properties of the filler itself, but a large production load is required to increase the crystallinity of calcium carbonate constituting the filler. When the bw is more than 1.50, the obtained surface-treated calcium carbonate filler does not have sufficient heat resistance, and it is difficult to obtain a resin composition excellent in all of weather resistance, heat resistance, and strength.

(Method of measuring bw)
bw can be measured, for example, as follows.

(1) First, a surface-treated calcium carbonate filler and dioctyl phthalate (DOP) are weighed in a mass ratio of 3:7 and mixed with each other using a degassing mixer (e.g., Mazerustar manufactured by Kurabo Industries, Ltd.) to prepare a DOP paste.
(2) Next, the color difference of this DOP paste is measured using a spectrophotometer (for example, ZE-2000 manufactured by Nippon Denshoku Industries Co., Ltd.) as the "b value of the paste before heating."
(3) The DOP paste is then placed in a glass petri dish and heated continuously for 48 hours in a forced air oven set at 140° C. (i.e., a heat resistance test is performed).
(4) After removing from the oven and allowing to cool, the color difference of the DOP paste is measured as the "b value of the paste after heating" using a spectrophotometer (for example, ZE-2000 manufactured by Nippon Denshoku Industries Co., Ltd.).
(5) From the "b value of the paste before heating" and the "b value of the paste after heating" obtained above, the hue change rate bw before and after heating is calculated (bw = (b value of the paste after heating / b value of the paste before heating)).

Furthermore, the surface-treated calcium carbonate filler of the present invention preferably satisfies one or more of the following formulae (e), (f) and (g) in addition to the above formulae (a) to (c), and more preferably satisfies all of the formulae (e), (f) and (g).

(e) 50% diameter (D50) accumulated from the small particle side in the volume particle size distribution
The surface-treated calcium carbonate filler of the present invention preferably has a 50% diameter (D50; μm) accumulated from the small particle side in a volume particle size distribution measured by a laser diffraction particle size distribution measuring device that satisfies a predetermined range. In the present invention, the D50 of the surface-treated calcium carbonate filler is preferably 0.10≦D50≦2.00 (μm), more preferably 0.30≦D50≦0.80 (μm). Surface-treated calcium carbonate particles having a D50 of less than 0.10 (μm) can be technically obtained, but since more advanced and precise technology is required, there is a risk of an increase in production cost. When the D50 exceeds 2.00 (μm), the cohesive force of secondary particles constituted by aggregates of primary particles becomes large, and the secondary particles cannot be sufficiently dispersed when kneaded with a resin, and clogging of a strainer may easily occur.

(Method of measuring D50)
D50 can be measured, for example, using a laser diffraction particle size distribution measuring device (MT-3300EX II manufactured by Microtrack Bell Co., Ltd.) as follows, together with D10, D90 and Da described below.
(1) First, about 0.3 g of a sample of a surface-treated calcium carbonate filler and 50 mL of a medium are combined and suspended in a 100 mL beaker.
(2) Next, the contents in the beaker are dispersed by irradiating them with ultrasonic waves at 300 μA for 1 minute using a tip-type ultrasonic disperser (for example, US-300T manufactured by Nippon Seiki Seisakusho Co., Ltd.).
(3) After that, the volumetric particle size distribution of the surface-treated calcium carbonate particles in the sample is measured using a laser diffraction particle size distribution measuring device (MT-3300EX II manufactured by Microtrac-Bell, Inc.).

Note that media that can be used in the above measurements include methanol and ethanol, as well as combinations thereof.

D50 can be controlled by varying various conditions when producing the surface-treated calcium carbonate particles that constitute the filler of the present invention. Various methods for dispersing calcium carbonate particles have been known in the past, such as a method of finely crushing the particles to reduce D50 using mechanical techniques such as a ball mill, sand grinder mill, impact mill, homogenizer, and dyno mill. In the wet synthesis carbon dioxide gas synthesis method, it is preferable to use Ostwald ripening, which grows the calcium carbonate particles to a certain particle size and disperses them, as a method for controlling the particle size of the calcium carbonate particles.

(f) Sharpness index of volume particle size distribution ((D90-D10)/D50)
The surface-treated calcium carbonate filler of the present invention preferably has a sharpness index ((D90-D10)/D50) in a volume particle size distribution measured with a laser diffraction particle size distribution measuring device that satisfies a predetermined range. Here, D50 is as described above, D90 is a 90% diameter (μm) accumulated from the small particle side in the volume particle size distribution measured with the laser diffraction particle size distribution measuring device, D10 is a 10% diameter (μm) accumulated from the small particle side in the volume particle size distribution measured with the laser diffraction particle size distribution measuring device, and Da is a maximum particle diameter (μm) in the volume particle size distribution measured with the laser diffraction particle size distribution measuring device.

In the present invention, the sharpness index ((D90-D10)/D50) of the surface-treated calcium carbonate filler is preferably 0.9≦(D90-D10)/D50≦2.0, and more preferably 1.0≦(D90-D10)/D50≦1.5. It is technically possible to obtain a surface-treated calcium carbonate filler having a sharpness index of less than 0.9, but this requires more advanced and precise technology, and therefore there is a risk of increased production costs. If the sharpness index of the surface-treated calcium carbonate filler exceeds 2.0, the variation in size of voids formed in a molded product (e.g., a film) obtained by kneading the obtained surface-treated calcium carbonate filler with a resin increases, and it may become difficult to obtain a porous film having a uniform distribution of voids in the plane.

(Method of measuring sharpness index ((D90-D10)/D50))
D10, D90 and Da constituting the sharpness index can be measured in the same manner as in the measurement of D50 described above, for example, using a laser diffraction particle size distribution measuring device (e.g., MT-3300EX II manufactured by Microtrack Bell Co., Ltd.) described for measuring D50 above.

The sharpness index can be controlled by varying various conditions when producing the surface-treated calcium carbonate filler of the present invention. The sharpness index of calcium carbonate particles can be reduced (for example, by reducing the number of coarse particles and fine particles to sharpen the particle size distribution) by using the above-mentioned mechanical techniques such as a ball mill, a sand grinder mill, an impact mill, a homogenizer, and a dyno mill, or a method for separating fine particles and coarse particles by utilizing the difference in sedimentation velocity in water due to particle size, such as elutriation. However, it is preferable to use Ostwald ripening from the viewpoint of improving the uniformity of the particle size of calcium carbonate particles and thus making it easier to reduce the sharpness index.

(g) Maximum particle diameter in volume particle size distribution (Da)
The surface-treated calcium carbonate filler of the present invention preferably has a maximum particle diameter (Da) that satisfies a predetermined range in a volume particle size distribution measured with a laser diffraction particle size distribution measuring device. In the present invention, Da of the surface-treated calcium carbonate filler is preferably Da≦5.0 (μm) (i.e., 0<Da≦5.0 (μm)), more preferably Da≦3.0 (μm) (i.e., 0<Da≦3.0 (μm)). When Da exceeds 5.0 μm, problems may occur, for example, in which the surface-treated calcium carbonate filler is easily broken and dropped off when a resin composition containing the obtained surface-treated calcium carbonate filler and a resin is stretched for film formation, undesired protrusions are formed on the surface of the obtained resin molded body, and the slidability of the resin molded body is reduced.

(Method of measuring Da)
Da can be measured in the same manner as in the measurement of D50 above, for example, using a laser diffraction particle size distribution measuring device (e.g., MT-3300EX II manufactured by Microtrack Bell Co., Ltd.) described for measuring D50 above.

Da can be controlled by varying various conditions when producing the surface-treated calcium carbonate filler of the present invention. As a method for reducing the maximum particle size (Da) in the volumetric particle size distribution, it is preferable to carry out classification using gravity, centrifugal force, flotation, etc., such as decantation, and removal using a sieve or filter, etc., for the purpose of removing impurities and coarse particles at the stage of the aqueous slurry form, or to carry out classification operations such as air classification at the stage of the powder form to remove aggregates generated by drying.

(Surface-treated calcium carbonate filler that has been surface-treated with a surface treatment agent)
As described above, the surface-treated calcium carbonate filler of the present invention satisfies all of the formulas (a), (b), and (c), and at least one of the formulas (d), (e), (f), and (g) as necessary. Such a surface-treated calcium carbonate filler contains surface-treated calcium carbonate particles that have been surface-treated with a surface treatment agent, and is preferably constituted of the surface-treated calcium carbonate particles as a main component.

Here, the term "surface-treated" as used in this specification is used to mean the "state" of the surface of the surface-treated calcium carbonate filler and/or the surface-treated calcium carbonate particles. On the other hand, the term "surface-treated/has been surface-treated" as used in this specification is used to mean that calcium carbonate particles that have not been subjected to surface treatment (i.e., untreated) have been subjected to a process for modifying (surface treating) their surfaces.

The surface-treated calcium carbonate particles in the present invention are unmodified (before surface treatment) calcium carbonate particles that have been surface-treated with a surface treatment agent.

(Unmodified calcium carbonate particles)
Here, the unmodified calcium carbonate particles are, from the viewpoint of deaeration during kneading with a resin, rather than natural white saccharified limestone (ground calcium carbonate) which contains a large amount of fine particles.
Synthetic calcium carbonate particles (e.g., light/colloidal calcium carbonate) prepared by a synthetic method in which natural gray dense limestone is fired. Synthetic calcium carbonate particles can be controlled uniformly, and hydrochloric acid-insoluble ores that are the source of relatively coarse particles have been removed in advance. Synthetic calcium carbonate crystal forms include three types of crystals: vaterite crystals, which are the most unstable in water systems and thermodynamically, metastable aragonite crystals, and stable calcite crystals. Those containing calcite crystals as the main component are preferred because of their good stability.

Such unmodified calcium carbonate particles can be produced by the well-known carbon dioxide gas method, for example by adding water to quicklime obtained by calcining gray dense limestone to form calcium hydroxide, which is then reacted with the carbon dioxide gas released during calcination. The calcium carbonate slurry reacted by this carbon dioxide gas method can also be adjusted by Ostwald aging until it has the desired BET specific surface area, thereby obtaining the desired calcium carbonate particles.

In addition, for the purpose of further improving the weather resistance and heat resistance of the resin composition when blended with a polyolefin resin, which is the main object of the present invention, it is preferable to use calcium carbonate particles undergoing Ostwald ripening as seed particles and to use a seed chemical method in which a carbonation reaction is carried out on the calcium carbonate particles, rather than a method of preparing the desired calcium carbonate particles by Ostwald ripening, in that this method can produce calcium carbonate particles with higher crystallinity.

In addition, for the purpose of further increasing the uniformity of the synthetic calcium carbonate particles, the calcium carbonate particles may be obtained by separating the water slurry used to obtain the synthetic calcium carbonate particles, or the water slurry containing calcium hydroxide before the synthetic calcium carbonate particles are produced, into a light liquid (fine particle side) and a heavy liquid in an appropriate ratio using a separation device such as a liquid cyclone machine.

(Surface treatment agent)
The surface treatment agent is used for the unmodified calcium carbonate particles for the purpose of improving the flowability of the powder, the alkali resistance and activity resistance of calcium carbonate, and other properties of the calcium carbonate filler. Examples of the surface treatment agent include phosphorus-based compounds. Examples of the phosphorus-based compounds include inorganic phosphoric acids, organic phosphoric acids, and combinations thereof.

Examples of inorganic phosphoric acids include orthophosphoric acid, phosphorous acid, phosphinic acid, pyrophosphoric acid, polyphosphoric acid (e.g., tripolyphosphoric acid), and condensed phosphoric acid, their salts (e.g., alkali metal salts such as sodium salts and potassium salts; alkaline earth metal salts such as magnesium salts; aluminum salts), and combinations thereof. Specific examples of salts of inorganic phosphoric acids include sodium phosphate, potassium phosphate, aluminum phosphate, sodium polyphosphate, sodium pyrophosphate, sodium tripolyphosphate, sodium acid tripolyphosphate, sodium tetrapolyphosphate, sodium pentapolyphosphate, sodium metaphosphate, sodium hexametaphosphate, sodium metaphosphate, and sodium ultraphosphate, and combinations thereof.

Examples of organic phosphoric acids include hydroxyethylidene diphosphonic acid, nitrilotrismethylenephosphonic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, ethylenediamidetetramethylenephosphonic acid, and phenylphosphonic acid; and salts thereof; esters such as trimethyl phosphoric acid ester, triethyl phosphoric acid ester, tripropyl phosphoric acid ester, mono- or dimethyl phosphoric acid ester, dimethyl phenylphosphonic acid ester, diethyl phenylphosphonic acid ester, trimethyl phosphite (methyl phosphorous acid ester), triethyl phosphite (ethyl phosphorous acid ester), and acidic phosphoric acid esters; and combinations thereof.

The above-mentioned surface treatment agents can effectively improve all of the weather resistance, heat resistance, and strength of the resulting resin composition, and therefore, as phosphorus-based compounds, inorganic phosphoric acids such as sodium hexametaphosphate, sodium polyphosphate, sodium pyrophosphate, sodium tripolyphosphate, and sodium ultraphosphate, and organic phosphoric acids such as nitrilotrismethylenephosphonic acid and trimethyl phosphoric acid ester, and combinations thereof can be preferably used.

In the present invention, the surface treatment agent may contain other surface treatment agents in addition to the phosphorus-based compound.

Examples of other surface treatment agents include fatty acid/fatty acid soap-based surface treatment agents, coupling agent-based surface treatment agents, and surfactant-based surface treatment agents, as well as combinations thereof. The other surface treatment agents may be commercially available products.

Examples of fatty acid/fatty acid soap-based surface treatment agents include fatty acids, fatty acid salts, and combinations thereof.

Fatty acids include, for example, saturated fatty acids, unsaturated fatty acids, alicyclic carboxylic acids, and resin acids, as well as combinations thereof.

Examples of saturated fatty acids include capric acid, caproic acid, lauric acid, myristic acid, palmitic acid, stearic acid, and isostearic acid, as well as combinations thereof. Examples of unsaturated fatty acids include oleic acid, linoleic acid, and linolenic acid, as well as combinations thereof. Examples of alicyclic carboxylic acids include naphthenic acid, which has a carboxyl group at the end of a cyclopentane or cyclohexane ring. Examples of resin acids include abietic acid, pimaric acid, and neoabietic acid, as well as combinations thereof.

Fatty acid salts include alkali metal salts (e.g., sodium salts, potassium salts), alkaline earth metal salts (e.g., calcium salts, magnesium salts), ammonium salts, and amine salts of the above fatty acids, as well as combinations thereof. It is preferable to use alkali metal salts of fatty acids because they have high solubility in water and are easy to treat on the calcium carbonate surface.

Examples of fatty acid salts include saturated fatty acid salts such as potassium laurate, potassium myristate, potassium palmitate, sodium palmitate, potassium stearate, sodium stearate, and sodium isostearate, unsaturated fatty acid salts such as potassium oleate and sodium oleate, and alicyclic carboxylates such as sodium naphthenate and lead cyclohexylbutyrate, potassium abietate, and sodium abietate, as well as combinations thereof.

The fatty acid/fatty acid soap-based surface treatment agent may be, for example, a modified or unmodified fatty acid derived from an animal or a plant. For example, it may be a mixed fatty acid such as beef tallow fatty acid, palm oil fatty acid, palm kernel oil fatty acid, soybean oil fatty acid, etc., which are widely used in the technical field; an alkali metal salt thereof; or a so-called hydrogenated mixed fatty acid or an alkali metal salt thereof, which is a mixed fatty acid that has been hydrogenated to reduce the degree of unsaturation.

When fatty acids are used as they are as fatty acids, it is preferable to dissolve the fatty acid in hot water heated to above its melting point in advance, add a known emulsifier such as an anionic surfactant or a nonionic surfactant as appropriate, and emulsify the fatty acid using an emulsifying disperser such as a homomixer or homogenizer before adding it to the unmodified calcium carbonate, in order to enable more uniform surface treatment of the unmodified calcium carbonate particles.

Of the above fatty acids, unsaturated fatty acids not only have high solubility in water, but also have low melting points, making it easier to perform a more uniform surface treatment on the surface of unmodified calcium carbonate particles. However, from the viewpoint of heat resistance, unsaturated fatty acids are characterized by being susceptible to thermal degradation due to the presence of unsaturated double bonds. For this reason, in the present invention, the fatty acids are preferably saturated fatty acids and/or saturated fatty acid salts, since concerns about thermal degradation such as those of the above unsaturated fatty acids are eliminated in advance. Alternatively, the total amount of saturated fatty acids and saturated fatty acid salts is preferably 90% by mass or more, and more preferably 100% by mass, of the total mass of the fatty acids.

Examples of coupling agent-based surface treatments include vinyl silane coupling agents, amino silane coupling agents, phenyl silane coupling agents, epoxy silane coupling agents, styryl silane coupling agents, acrylic silane coupling agents, methacryl silane coupling agents, isocyanurate silane coupling agents, ureido silane coupling agents, mercapto silane coupling agents, and isocyanate silane coupling agents, as well as combinations thereof. Vinyl silane coupling agents are preferred because they can impart good strength to the resulting resin composition, and phenyl silane coupling agents are preferred because they can impart good weather resistance and heat resistance to the resulting resin composition.

Examples of surfactant-based surface treatment agents include aromatic sulfonic acids and/or resin acids and their salts or esters; alcohol-based surfactants; polyhydric alcohols; sorbitan fatty acid esters; amide-based surfactants; amine-based surfactants; polyoxyalkylene alkyl ethers; polyoxyethylene nonylphenyl ether; sodium alpha-olefin sulfonate; long-chain alkyl amino acids; amine oxides; alkylamines; and quaternary ammonium salts; and combinations thereof.

In consideration of good compatibility and dispersibility with a resin when the surface-treated calcium carbonate filler to be obtained is blended with the resin, the other surface treatment agent is preferably a fatty acid/fatty acid soap-based surface treatment agent, more preferably a saturated fatty acid, an unsaturated fatty acid, or a salt thereof, and most preferably a saturated fatty acid salt.

(Surface treatment of unmodified calcium carbonate particles)
The surface treatment of unmodified calcium carbonate particles with the above-mentioned surface treatment agent is carried out, for example, as follows.

For the surface treatment of unmodified calcium carbonate particles, either a general dry treatment or a general wet treatment may be used. Preferably, a method of adding the above-mentioned surface treatment agent to a water slurry containing unmodified calcium carbonate particles may be used. This method is generally called a wet treatment, and is preferable in that it can adequately achieve both the degree of surface treatment of the calcium carbonate particles and production efficiency.

The amount of the surface treatment agent, particularly the amount of the phosphorus-based compound, used varies depending on the BET specific surface area and/or amount of the unmodified calcium carbonate particles, the content of the phosphorus element contained in the phosphoric acid itself, the type of resin to be kneaded in the end, the kneading conditions, etc., so is not particularly limited and can be appropriately selected by a person skilled in the art so as to satisfy the above Pw range.

The order of treatment of unmodified calcium carbonate particles with the above-mentioned surface treatment agents, particularly the phosphorus-based compound and the other surface treatment agent, is not particularly limited. For example, unmodified calcium carbonate particles may be first treated with the other surface treatment agent and then treated with the phosphorus-based compound. Alternatively, unmodified calcium carbonate particles may be first treated with the phosphorus-based compound and then treated with the other surface treatment agent. Alternatively, unmodified calcium carbonate particles may be treated with the phosphorus-based compound and the other surface treatment agent together, i.e., simultaneously.

The temperature employed for the surface treatment is not particularly limited, and an appropriate temperature can be selected by a person skilled in the art.

After the above surface treatment, the resulting particles may be powdered through any operation, such as dehydration, drying, or grinding, according to conventional methods.

The dehydration can be performed by using a filter press or a centrifugal dehydrator to dehydrate the slurry containing the surface-treated calcium carbonate particles. For drying, a hot air dryer such as a micron dryer, which can dry the surface-treated calcium carbonate particles efficiently by directly contacting them with high-temperature hot air, may be used, or a heat transfer dryer such as a CD dryer, which brings the surface-treated calcium carbonate particles into contact with a heating plate and dries them indirectly through the heating plate, may be used.

In this manner, surface-treated calcium carbonate particles that have been surface-treated with a surface treatment agent can be obtained. These surface-treated calcium carbonate particles can be used as they are as a surface-treated calcium carbonate filler that satisfies all of the above formulae (a), (b), and (c), and, if necessary, at least one of formulae (d), (e), (f), and (g).

2. Resin Composition Next, the resin composition of the present invention will be described.

The resin composition of the present invention contains a resin and the above-mentioned surface-treated calcium carbonate filler.

The resin contained in the resin composition is not particularly limited, but examples thereof include polyolefin resins, polystyrene resins, acrylic resins, methacrylic resins, vinyl chloride resins, vinylidene chloride resins, polyamide resins, polyether resins, vinyl acetate resins, and polyvinyl alcohol resins, as well as combinations thereof. Specific examples of polyolefin resins include polyethylene resins such as low-density polyethylene (LDPE), high-density polyethylene (HDPE), linear low-density polyethylene (L-LDPE), and ultra-high molecular weight polyethylene (UHMWPE), polypropylene resins, ethylene-propylene copolymers, and copolymers of ethylene or propylene with other monomers. The resin may be derived from petroleum, plants (e.g., bioplastics), or combinations thereof. In the present invention, the resin is preferably a polyolefin resin, since it has a relatively low molding temperature compared to engineering plastics and has sufficient heat resistance at temperatures at which the surface-treated calcium carbonate particles can exhibit heat resistance.

The content of the surface-treated calcium carbonate filler contained in the resin composition is not necessarily limited because it varies depending on the type of resin used in combination, the application of the obtained resin composition, and desired physical properties, for example, but is, for example, 0.05 parts by mass to 100 parts by mass, preferably 50 parts by mass to 100 parts by mass, and more preferably 70 parts by mass to 100 parts by mass relative to 100 parts by mass of resin. When the content of the surface-treated calcium carbonate filler contained in the resin composition exceeds 100 parts by mass (i.e., exceeds the content of the resin), the kneadability with the resin decreases and the hue (whiteness) decreases due to deterioration of the resin. When the content of the surface-treated calcium carbonate filler contained in the resin composition is less than 0.05 parts by mass, the obtained resin composition may not have sufficient heat resistance.

The resin composition of the present invention may contain other additives such as lubricants, such as fatty acids, fatty acid amides, ethylene bisstearic acid amide, and sorbitan fatty acid esters; plasticizers; stabilizers, such as heat stabilizers and light stabilizers; antioxidants; ultraviolet absorbers; neutralizing agents; antifogging agents; antiblocking agents; antistatic agents; slip agents; and colorants; as well as combinations thereof. The content of the other additives is not particularly limited, and an appropriate amount can be selected by a person skilled in the art within a range that does not inhibit the effects of the surface-treated calcium carbonate filler.

The resin and the surface-treated calcium carbonate filler, as well as other additives that are included as necessary, can be mixed using a known mixer, such as a super mixer, a Henschel mixer, a tumbler mixer, or a ribbon blender. After being mixed in the mixer, the resin composition is heated and kneaded using a single-screw or twin-screw extruder, a kneader mixer, a Banbury mixer, or the like, and once processed into pellets as a master batch, which can be melted and formed into a film using a known molding machine such as a T-die extrusion or inflation molding.

3. Molded Article The molded article of the present invention is formed from the above-mentioned resin composition.

The molded article of the present invention preferably has the form of a film.

For example, the resin composition kneaded as described above can be formed into a sheet shape using a T-die or the like, and then uniaxially or biaxially stretched to obtain a porous film having fine pores on the surface. Alternatively, after the kneading, a film can be formed using a known molding machine such as T-die extrusion or inflation molding, and the film can be treated with acid to dissolve the surface-treated calcium carbonate filler present inside, thereby obtaining a porous film having fine pores on the surface. Furthermore, if necessary, a plurality of T-die extruders in the above process may be stacked, or the film may be laminated after stretching to form a multilayer film. In addition, for the purpose of imparting printability to the film, the film surface may be subjected to a surface treatment such as plasma discharge, and an ink-receiving layer may be coated thereon.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. In the following description, % means % by mass, and parts means parts by mass, unless otherwise specified.

The materials, surface-treated calcium carbonate filler, and pellets described in each of the examples and comparative examples were evaluated as follows.

(1) BET specific surface area of unmodified calcium carbonate About 300 mg of the unmodified calcium carbonate particles used in each of the Examples and Comparative Examples was placed in a measuring device (Macsorb HM model-1201 manufactured by Mountec Co., Ltd.) and subjected to a pretreatment of heating at 200°C for 10 minutes in a mixed gas atmosphere of nitrogen and helium, and then to low-temperature, low-humidity physical adsorption in a liquid nitrogen environment to measure the BET specific surface area (m ² /g) of the unmodified calcium carbonate particles.

(2) BET specific surface area (Sw) of surface-treated calcium carbonate filler
About 300 mg of the surface-treated calcium carbonate filler obtained in each of the Examples and Comparative Examples was placed in a measuring device (Macsorb HM model-1201 manufactured by Mountech Co., Ltd.), and a heat treatment was performed at 200° C. for 10 minutes in a mixed gas atmosphere of nitrogen and helium as a pretreatment, and then a low-temperature, low-humidity physical adsorption was performed in a liquid nitrogen environment, so that the BET specific surface area (m ² /g) of the surface-treated calcium carbonate particles constituting the filler was measured.

(3) Phosphorus content (Pw) of surface-treated calcium carbonate filler measured using an inductively coupled plasma (ICP) emission spectrometer

About 1000 mg of the surface-treated calcium carbonate filler obtained in each Example and Comparative Example was charged into a crucible and fired in an electric furnace at 300 ° C for 3 hours. After firing, a small amount of distilled water and 7.5 mL of 1.38 N nitric acid (nitric acid for measuring harmful metals (1.38), manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added to a 200 mL beaker containing the mixture, and the mixture was boiled on an electric stove and cooled slowly. The mixture after the above-mentioned cooling was added to a 100 mL measuring flask containing 100 μL of yttrium standard solution (Y1000 manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and the mixture was further diluted with distilled water to 100 mL. The mixture was then filtered through 5C filter paper, and a sample for ICP measurement was prepared from the obtained filtrate. The phosphorus content (ppm) of this sample was then measured using an inductively coupled plasma (ICP) optical emission spectrometer (SPS3500 ICP optical emission spectrometer manufactured by SII NanoTechnology Inc.).

(4) Weight loss value (Tw) of surface-treated calcium carbonate filler at 140 ° C. to 220 ° C.
About 30 mg of the surface-treated calcium carbonate filler obtained in each of the Examples and Comparative Examples was weighed out in a platinum sample pan and set in a differential thermobalance device (DTG-60A manufactured by Shimadzu Corporation). Thereafter, measurement was performed by increasing the temperature of the measuring device from room temperature to 550° C. at a temperature increase rate of 30° C./min, and a weight loss value (mass%) from 140° C. to 220° C. per 1 g of the surface-treated calcium carbonate filler was calculated.

(5) Hue Change Rate (bw) of Surface-Treated Calcium Carbonate Filler
The surface-treated calcium carbonate filler obtained in each of the Examples and Comparative Examples and dioctyl phthalate (DOP) were weighed in a mass ratio of 3:7, and mixed with a defoaming mixer (Mazerustar manufactured by Kurabo Industries, Ltd.) to prepare a DOP paste. Next, the color difference of this DOP paste was measured as the "b value of the paste before heating" with a spectrophotometer (ZE-2000 manufactured by Nippon Denshoku Industries Co., Ltd.). Thereafter, the DOP paste was placed in a glass petri dish and heated continuously for 48 hours in a forced-air oven set at 140°C. After being taken out of the oven and allowed to cool, the color difference of the DOP paste was measured as the "b value of the paste after heating" with the above spectrophotometer.

From the obtained "b value of the paste before heating" and "b value of the paste after heating", the hue change rate bw before and after heating was calculated according to the following formula:
bw = (b value of paste after heating/b value of paste before heating).

(6) D50, sharpness index ((D90-D10)/D50) and Da of surface-treated calcium carbonate filler
About 0.3 g of the surface-treated calcium carbonate filler obtained in each of the Examples and Comparative Examples and 50 mL of methanol were added to a 100 mL beaker. Next, the contents in the beaker were irradiated with ultrasonic waves at 300 μA for 60 seconds using, for example, an ultrasonic disperser US-300T manufactured by Nippon Seiki Seisakusho Co., Ltd., to disperse the contents to obtain a sample. Thereafter, the volumetric particle size distribution of the surface-treated calcium carbonate particles in the sample was measured using a laser diffraction particle size distribution measuring device (MT-3300EX II manufactured by Microtrack Bell Co., Ltd.). From the results of the obtained volumetric particle size distribution, the values of D50, D10, D90, and Da, as well as the sharpness index ((D90-D10)/D50) calculated using the same were obtained.

(7) Thermo-oxidative stability of pellets From the pellets obtained in each Example and Comparative Example, a 50 x 50 x 1 mm test piece was prepared using a tabletop hot press G-12 manufactured by Orihara Seisakusho Co., Ltd. adjusted to 200 ° C. This test piece was heated in air at a set temperature of 140 ° C. using a forced draft oven based on Japanese Industrial Standard JIS K7368 (Plastics - Polypropylene and propylene copolymers - Measurement method for thermo-oxidative stability in air - Oven method) to accelerate deterioration, and the number of days required from the start of the test until local cracks, crumbling and / or discoloration could be visually observed was recorded and evaluated according to the following criteria.
◎: No noticeable change even after 10 days.
○: Discoloration was observed after 10 days.
Δ: Discoloration and cracks were observed after 10 days.
×: Discoloration and cracks were already observed after 5 days.

(8) Evaluation of heat resistance of pellets The pellets obtained in each Example and Comparative Example were heated in air for 10 days using a forced draft oven at 140°C to accelerate degradation. The MFR value (g/10 min) of the obtained heat-degraded pellets and the pellets in the initial state (not heat-degraded) was measured at a test temperature of 230°C and a nominal load of 21.6 kg using a MELT INDEXER F-F01 manufactured by Toyo Seiki Seisakusho Co., Ltd., based on Japanese Industrial Standard JIS K7210 (Test method for melt mass flow rate (MFR) and melt volume flow rate (MVR) of plastics-thermoplastics). Furthermore, from the obtained results, the rate of change (%) of MFR was calculated according to the following formula to evaluate the presence or absence of heat resistance.

(7) Evaluation of pellet dispersibility The pellets obtained in each Example and Comparative Example were kneaded and extruded into a twin-screw kneader (2D25W manufactured by Toyo Seiki Co., Ltd.) equipped with a three-plate strainer having openings of 100 μm, 60 μm, and 400 μm at a cylinder set temperature of 170° C., a screw rotation speed of 150 rpm, and a feed rate of 6 kg/hour. The resin pressure after 60 minutes was measured, and the dispersibility was evaluated according to the following criteria.
⊚: The resin pressure after 60 minutes of kneading was less than 4 MPa.
◯: The resin pressure after 60 minutes of kneading was 4 MPa or more and less than 6 MPa.
Δ: The resin pressure after 60 minutes of kneading was 6 MPa or more and less than 8 MPa.
×: The resin pressure after 60 minutes of kneading was 8 MPa or more, or vent-up occurred before 60 minutes had elapsed due to clogging of the strainer.

(8) Tensile Strength Evaluation For the pellets obtained in each Example and Comparative Example, a 200 μm thick film was prepared using a tabletop hot press G-12 manufactured by Orihara Manufacturing Co., Ltd., adjusted to 200 ° C. This film was punched out into 20 dumbbell-shaped test pieces using a punching blade, and the thickness of each test piece was measured, and five test pieces with a thickness within ± 10% of the average thickness of the 20 pieces were selected. The selected test pieces were subjected to a tensile strength evaluation at a test force of 500 N and a test speed of 5 mm / minus using an autograph AG-I manufactured by Shimadzu Corporation based on the Japanese Industrial Standards JIS K7127 (Plastics - Test Method for Tensile Properties - Part 3), and the dispersibility was evaluated according to the following criteria. The tensile strength referred to here indicates the stress measured when the test piece breaks.
⊚: The tensile strength was 33 MPa or more.
Good: The tensile strength was 30 MPa or more and less than 33 MPa.
Δ: The tensile strength was 27 MPa or more and less than 30 MPa.
×: The tensile strength was less than 27 MPa.

(9) Sliding property evaluation: Measurement of static and dynamic friction coefficients For the pellets obtained in each Example and Comparative Example, a test piece of 80 × 200 × 1 mm was prepared using a tabletop hot press G-12 manufactured by Orihara Seisakusho Co., Ltd., adjusted to 200 ° C. Based on the Japanese Industrial Standard JIS K7125 (Plastic-Film and Sheet-Friction Coefficient Test Method), the static and dynamic friction coefficients of the test piece were measured using a friction coefficient measuring instrument AN-S2 manufactured by Toyo Seiki Seisakusho Co., Ltd., at a load of 200 g and a test speed of 100 mm / min, and the sliding property was evaluated according to the following criteria. In addition, a lower value of both the static and dynamic friction coefficients indicates a higher sliding property.
(Evaluation of static friction coefficient)
⊚: The static friction coefficient was less than 0.60.
Good: The static friction coefficient was 0.60 or more and less than 0.70.
Δ: The static friction coefficient was 0.70 or less and less than 0.80.
×: The static friction coefficient was 0.80 or more.
(Evaluation of the dynamic and static friction coefficient)
⊚: The dynamic friction coefficient was less than 0.40.
Good: The dynamic friction coefficient was 0.40 or more and less than 0.50.
Δ: The dynamic friction coefficient was 0.50 or less and less than 0.60.
×: The dynamic friction coefficient was 0.60 or more.
(Overall evaluation of sliding properties)
⊚: The sliding property was extremely good.
◯: The sliding property was good.
Δ: The sliding property was somewhat good.
×: The sliding properties were poor.

(Example 1: Preparation of surface-treated calcium carbonate filler (E1))
Gray dense limestone was fired in a firing furnace using natural gas as a heat source, and the quicklime was dissolved in water to obtain a calcium hydroxide slurry having a specific gravity of 1.050. This calcium hydroxide slurry was reacted with _CO2 gas discharged from the firing furnace to obtain a synthetic calcium carbonate slurry having a concentration of 8.0% by mass.

The obtained synthetic calcium carbonate slurry was subjected to particle growth by Ostwald aging to a BET specific surface area of 10.0 m ² /g. After that, using the obtained calcium carbonate as a seed, calcium hydroxide was added in an amount of 10 mass% based on the calcium carbonate solid, and a seed compound was carried out in which the calcium carbonate was reacted with CO ₂ gas discharged from a calcination furnace, thereby obtaining a calcium carbonate slurry having a BET specific surface area of 8.0 m ² /g.

To this, 0.6% by mass of ultrasodium phosphate (UltraPoline manufactured by Taihei Chemical Industry Co., Ltd.) based on the calcium carbonate solid content and an aqueous solution of a phosphorus compound prepared in warm water to a concentration of 10% by mass were added to the calcium carbonate slurry, stirred at 60°C for 12 hours, dehydrated to a solid content of 65% by mass using a filter press, dried in a hot air dryer (Dry Meister DMR-1 dryer manufactured by Hosokawa Micron Corporation), impact crushed, and the obtained powder was classified using an air classifier to obtain the surface-treated calcium carbonate filler for polyolefin resin (E1) of Example 1. The physical properties of the obtained surface-treated calcium carbonate filler (E1) are shown in Table 1.

(Example 2: Preparation of surface-treated calcium carbonate filler (E2))
A surface-treated calcium carbonate filler (E2) was obtained in the same manner as in Example 1 except that, instead of the aqueous solution of a phosphorus-based compound prepared in Example 1, an aqueous solution of a phosphorus-based compound prepared in warm water to give a concentration of 10 mass% and an aqueous solution of a phosphorus-based compound containing 1.0 mass% aluminum phosphate (50% aluminum phosphate solution manufactured by Taihei Chemical Industry Co., Ltd.) relative to the calcium carbonate solid content were added to the calcium carbonate slurry, and a fatty acid salt obtained by saponifying 1.6 mass% of a saturated fatty acid (NAA-122 (lauric acid: 99%) manufactured by NOF Corporation) with caustic soda and preparing the fatty acid salt in warm water to give a concentration of 10 mass% were added thereto. The physical property values of the obtained surface-treated calcium carbonate filler (E2) are shown in Table 1.

(Example 3: Preparation of surface-treated calcium carbonate filler (E3))
A surface-treated calcium carbonate filler (E3) was obtained in the same manner as in Example 1 except that an aqueous solution of a phosphorus-based compound prepared in Example 1 in which 0.3 mass% of sodium pyrophosphate (sodium pyrophosphate manufactured by Taihei Chemical Industry Co., Ltd.) relative to the calcium carbonate solid content was added to warm water to give a concentration of 10 mass%, and a saturated fatty acid soap (NONSAAL SN-1 (saturated fatty acid rate 100%) manufactured by NOF Corporation) in an amount of 2.2 mass% relative to the calcium carbonate solid content was prepared in warm water to give a concentration of 10 mass% was used instead of the aqueous solution of a phosphorus-based compound prepared in Example 1. The physical property values of the obtained surface-treated calcium carbonate filler (E3) are shown in Table 1.

The NOF Corp. Nonsal SN-1 used above had the following composition (myristic acid 3% by mass, palmitic acid 27% by mass, stearic acid 66% by mass, and others 4% by mass).

(Example 4: Preparation of surface-treated calcium carbonate filler (E4))
A surface-treated calcium carbonate filler (E4) was obtained in the same manner as in Example 3 except that an aqueous solution of a phosphorus compound prepared by adding 1.5% by mass of orthophosphoric acid (75% orthophosphoric acid manufactured by Rasa Kogyo Co., Ltd.) to warm water to give a concentration of 10% by mass relative to the calcium carbonate solid content was used instead of the aqueous solution of a phosphorus compound prepared in Example 3. The physical property values of the obtained surface-treated calcium carbonate (E4) are shown in Table 1.

(Example 5: Preparation of surface-treated calcium carbonate filler (E5))
A surface-treated calcium carbonate filler (E5) was obtained in the same manner as in Example 3 except that an aqueous solution of a phosphorus compound was prepared in warm water to have a concentration of 10 mass% by adding sodium hexametaphosphate (sodium hexametaphosphate manufactured by Taihei Chemical Industry Co., Ltd.) at 0.6 mass% relative to the calcium carbonate solid content, instead of the aqueous solution of a phosphorus compound prepared in Example 3. The physical property values of the obtained surface-treated calcium carbonate filler (E5) are shown in Table 1.

(Example 6: Preparation of surface-treated calcium carbonate filler (E6))
In the same manner as in Example 1, the obtained synthetic calcium carbonate slurry was subjected to Ostwald aging to grow particles of calcium carbonate slurry having a BET specific surface area of 13.0 m ² /g.

A surface-treated calcium carbonate filler (E6) was obtained in the same manner as in Example 2, except that this calcium carbonate slurry was used, and instead of the aqueous solution of the phosphorus compound prepared in Example 1, an aqueous solution of the phosphorus compound was prepared in warm water to a concentration of 10 mass% with 0.3 mass% linitrilotrismethylenephosphonic acid (JPCN-300 manufactured by Johoku Chemical Co., Ltd.) relative to the calcium carbonate solid content, and the solution was dried for 2 hours at a steam pressure of 0.25 MPa using a CD dryer manufactured by Kurimoto Iron Works, Ltd. as a heat transfer dryer. The physical property values of the obtained surface-treated calcium carbonate filler (E6) are shown in Table 1.

(Example 7: Preparation of surface-treated calcium carbonate filler (E7))
In the same manner as in Example 1, the obtained synthetic calcium carbonate slurry was subjected to Ostwald aging to grow particles to a BET specific surface area of 10.0 m ² /g, and then a calcium carbonate slurry in which particles were grown to a BET specific surface area of 8.0 m ² /g by seed compounding was obtained.

An aqueous solution of a phosphorus-based compound was prepared in hot water by adding 0.6% by mass of ultrasodium phosphate (UltraPoline, manufactured by Taihei Chemical Industry Co., Ltd.) based on the calcium carbonate solids content to this calcium carbonate slurry to give a concentration of 10% by mass, and the solution was stirred at 60°C for 12 hours. The solution was then dehydrated to a solid content of 65% by mass using a filter press, dried in a hot air dryer (Dry Meister DMR-1, manufactured by Hosokawa Micron Corporation), and crushed by impact to obtain phosphorus-based compound-treated calcium carbonate powder.

The obtained phosphorus compound-treated calcium carbonate powder was put into a Super Mixer SMV (G)-100 manufactured by Kawata Co., Ltd., and glycerin (refined glycerin manufactured by Miyoshi Oil Co., Ltd.), which is a polyhydric alcohol, was added as a surface treatment agent in an amount of 0.6 mass% based on the calcium carbonate solid content while stirring. Dry treatment was carried out at 110°C for 0.5 hours, followed by impact crushing, and the obtained powder was classified with an air classifier to obtain a surface-treated calcium carbonate filler (E7). The physical property values of the obtained surface-treated calcium carbonate filler (E7) are shown in Table 1.

(Example 8: Preparation of surface-treated calcium carbonate filler (E8))
A surface-treated calcium carbonate filler (E8) was obtained in the same manner as in Example 7 except that a vinyl silane coupling agent (KBM-1003 manufactured by Shin-Etsu Chemical Co., Ltd.) which is a coupling agent was used in an amount of 1.0 mass% relative to the calcium carbonate solid content, instead of the surface treatment agent used in Example 7. The physical property values of the obtained surface-treated calcium carbonate filler (E8) are shown in Table 1.

(Example 9: Preparation of surface-treated calcium carbonate filler (E9))
In the same manner as in Example 1, the obtained synthetic calcium carbonate slurry was subjected to particle growth by Ostwald aging to a BET specific surface area of 4.0 m ² /g. Then, using the obtained calcium carbonate as a seed, 10% by mass of calcium hydroxide was added to the calcium carbonate solid, and a seed compound was carried out in which the calcium carbonate slurry was reacted with the CO ₂ gas discharged from the firing furnace to obtain a calcium carbonate slurry having a BET specific surface area of 2.8 m ² /g. Then, in the same manner as in Example 7, a phosphorus-based compound-treated calcium carbonate powder was obtained.

A surface-treated calcium carbonate filler (E9) was obtained in the same manner as in Example 7, except that 1.0% by mass of saturated fatty acid (Sakura Stearic Acid Beads manufactured by NOF Corporation) was used relative to the calcium carbonate solid content instead of the surface treatment agent used in Example 7. The physical properties of the obtained surface-treated calcium carbonate filler (E9) are shown in Table 1.

The Sakura Stearic Acid Beads manufactured by NOF Corporation used above had the following composition (myristic acid 4% by weight, palmitic acid 30% by weight, stearic acid 65% by weight, and others 1% by weight).

(Example 10: Preparation of surface-treated calcium carbonate filler (E10))
In the same manner as in Example 1, the obtained synthetic calcium carbonate slurry was subjected to particle growth by Ostwald aging to a BET specific surface area of 20.0 m ² /g, and then calcium hydroxide was added in an amount of 10 mass% based on the calcium carbonate solid matter using the obtained calcium carbonate as a seed, and a seed compound was carried out in which the calcium carbonate was reacted with CO ₂ gas discharged from a calcination furnace, thereby obtaining a calcium carbonate slurry having a BET specific surface area of 17.0 m ² /g.

A surface-treated calcium carbonate filler (E10) was obtained in the same manner as in Example 1, except that an aqueous solution of a phosphorus compound was prepared with 3.0% by mass of sodium ultraphosphate (UltraPoline manufactured by Taihei Chemical Industry Co., Ltd.) based on the calcium carbonate solid content in warm water to give a concentration of 10% by mass, and a fatty acid salt obtained by saponifying 2.7% by mass of a saturated fatty acid (NAA-122 manufactured by NOF Corporation (lauric acid: 99%)) with caustic soda based on the calcium carbonate solid content in warm water was added to the calcium carbonate slurry. The physical properties of the obtained surface-treated calcium carbonate filler (E10) are shown in Table 1.

(Example 11: Preparation of surface-treated calcium carbonate filler (E11))
In the same manner as in Example 1, the obtained synthetic calcium carbonate slurry was subjected to particle growth by Ostwald aging to a BET specific surface area of 24.0 m ² /g, and then calcium hydroxide was added in an amount of 10 mass% based on the calcium carbonate solid matter using the obtained calcium carbonate as a seed, and a seed compound was carried out in which the calcium carbonate was reacted with CO ₂ gas discharged from a calcination furnace, thereby obtaining a calcium carbonate slurry having a BET specific surface area of 20.0 m ² /g.

A surface-treated calcium carbonate filler (E11) was obtained in the same manner as in Example 11, except that an aqueous solution of a phosphorus compound was prepared by adding 4.0 mass% of sodium ultraphosphate (UltraPoline manufactured by Taihei Chemical Industry Co., Ltd.) based on the calcium carbonate solid content to warm water to give a concentration of 10 mass%, and a fatty acid salt obtained by saponifying a saturated fatty acid (NAA-122 (lauric acid: 99%) manufactured by NOF Corporation) with caustic soda was added to the calcium carbonate slurry to give a concentration of 10 mass% in warm water to give a concentration of 3.4 mass% based on the calcium carbonate solid content. The physical properties of the obtained surface-treated calcium carbonate filler (E11) are shown in Table 1.

(Comparative Example 1: Preparation of Surface-Treated Calcium Carbonate Filler (C1))
Heavy calcium carbonate having a BET specific surface area of 1.9 m ² /g (Super S manufactured by Maruo Calcium Co., Ltd.) was stirred with a super mixer SMV (G)-100 manufactured by Kawata Co., Ltd., while 0.3 mass% of ultrasodium phosphate (Ultraporin manufactured by Taihei Chemical Industry Co., Ltd.) relative to the calcium carbonate solids content, which was prepared to have a concentration of 10 mass% in warm water, was added thereto, and further 1.0 mass% of saturated fatty acid (beads stearate (sakura stearate rate 100%) manufactured by NOF Corporation) relative to the calcium carbonate solids content was added thereto as a surface treatment agent, and the mixture was stirred at 110° C. for 0.5 hours to obtain a surface-treated calcium carbonate filler (C1). The physical property values of the obtained surface-treated calcium carbonate filler (C1) are shown in Table 2.

(Comparative Example 2: Preparation of Surface-Treated Calcium Carbonate Filler (C2))
The synthetic calcium carbonate slurry obtained in the same manner as in Example 1 was subjected to particle growth by Ostwald aging to a BET specific surface area of 30.0 m ² /g. Then, using the obtained calcium carbonate as a seed, calcium hydroxide was added in an amount of 10 mass% based on the calcium carbonate solid, and a seed compound was carried out in which the calcium carbonate was reacted with CO ₂ gas discharged from a calcination furnace, thereby obtaining a calcium carbonate slurry having a BET specific surface area of 25.0 m ² /g.

A surface-treated calcium carbonate filler (C2) was obtained in the same manner as in Example 1, except that an aqueous solution of a phosphorus compound was prepared with 1.2 mass% ultrasodium phosphate (UltraPoline, manufactured by Taihei Chemical Industry Co., Ltd.) based on the calcium carbonate solid content in warm water to give a concentration of 10 mass%, and a saturated fatty acid soap (NonSal SN-1, manufactured by NOF Corporation (saturated fatty acid rate 100%)) was added to the calcium carbonate slurry in an amount of 4.0 mass% based on the calcium carbonate solid content in warm water to give a concentration of 10 mass%. The physical properties of the obtained surface-treated calcium carbonate filler (C2) are shown in Table 2.

(Comparative Example 3: Preparation of Surface-Treated Calcium Carbonate Filler (C3))
A surface-treated calcium carbonate filler (C3) was obtained in the same manner as in Example 3 except that no phosphorus-based compound was added. The physical property values of the obtained surface-treated calcium carbonate filler (C3) are shown in Table 2.

(Comparative Example 4: Preparation of Surface-Treated Calcium Carbonate Filler (C4))
A surface-treated calcium carbonate filler (C4) was obtained in the same manner as in Example 3 except that an aqueous solution of a phosphorus-based compound prepared by adding 5.0 mass% sodium ultraphosphate (UltraPoline manufactured by Taihei Chemical Industry Co., Ltd.) based on the calcium carbonate solid content to warm water to give a concentration of 10 mass% was used instead of the aqueous solution prepared in Example 3. The physical property values of the obtained surface-treated calcium carbonate filler (C4) are shown in Table 2.

(Comparative Example 5: Preparation of Surface-Treated Calcium Carbonate Filler (C5))
The synthetic calcium carbonate slurry obtained in the same manner as in Example 1 was subjected to particle growth by Ostwald aging to a BET specific surface area of 19.5 m ² /g, thereby obtaining a calcium carbonate slurry.

A surface-treated calcium carbonate filler for resin (C5) was obtained in the same manner as in Example 1 except that an aqueous solution of a phosphorus compound was prepared by adding 1.0 mass% of ultrasodium phosphate (UltraPoline manufactured by Taihei Chemical Industry Co., Ltd.) based on the calcium carbonate solids content to warm water to give a concentration of 10 mass%, and a saturated fatty acid soap (NONSAAL SN-1 manufactured by NOF Corporation) based on the calcium carbonate solids content to warm water to give a concentration of 10 mass% was added to this calcium carbonate slurry. The physical property values of the obtained surface-treated calcium carbonate filler (C5) are shown in Table 2.
The physical properties of the obtained surface-treated calcium carbonate (C4) are shown in Table 2.

(Comparative Example 6: Preparation of Surface-Treated Calcium Carbonate Filler (C6))
The synthetic calcium carbonate slurry obtained in the same manner as in Example 1 was subjected to particle growth by Ostwald aging to a BET specific surface area of 16.0 m ² /g, thereby obtaining a calcium carbonate slurry having a concentration of 10.0 mass %.

A surface-treated calcium carbonate filler (C6) was obtained in the same manner as in Example 1, except that an aqueous solution of a phosphorus compound was prepared by adding 1.67% by mass of sodium hexametaphosphate (sodium hexametaphosphate manufactured by Taihei Chemical Industry Co., Ltd.) based on the calcium carbonate solids content to warm water to give a concentration of 10% by mass, and 4.0% by mass of saturated fatty acid soap (NonSal SN-1 manufactured by NOF Corporation) based on the calcium carbonate solids content to warm water to give a concentration of 10% by mass, and the mixture was stirred at 80°C for 0.5 hours. The physical properties of the obtained surface-treated calcium carbonate filler (C6) are shown in Table 2.

(Examples 12 to 22 and Comparative Examples 7 to 12: Preparation of pellets (PE1) to (PE11) and (PC1) to (PC6))
30 parts by mass of the surface-treated calcium carbonate (E1) to (E11) and (C1) to (C6) produced in Examples 1 to 11 and Comparative Examples 1 to 6, 70 parts by mass of a polypropylene resin (Novatec PP FB3B manufactured by Japan Polypropylene Corporation: MFR 7.5 g/10 min), and 1.0 part by weight of a phenol-based antioxidant (Irganox 1010 manufactured by BASF Japan Ltd.) were mixed to obtain a resin mixture of 10 kg. The mixture was melt-kneaded in a twin-screw kneader TEX25αIII manufactured by Japan Steel Works, Ltd. (JSW) equipped with a strainer having an opening of 100 μm at a cylinder setting temperature of 170° C., a screw rotation speed of 250 rpm, and a feed rate of 8 kg/hour, and then cut with a cold pelletizer manufactured by Inoue Seisakusho Co., Ltd. to produce pellets (PE1) to (PE11) and (PC1) to (PC6). The results of application evaluation of the obtained pellets (PE1) to (PE11) and (PC1) to (PC6) are shown in Tables 3 and 4.

(Comparative Example 13: Preparation of pellets (PC7))
Pellets (PC7) were prepared in the same manner as in Comparative Example 9 except that 1.0 part by weight of a phosphorus-based antioxidant (Irgafos 168 manufactured by BASF Japan Ltd.) was further added when the surface-treated calcium carbonate filler, the polypropylene resin, and the phenol-based antioxidant were mixed. The results of the application evaluation of the obtained pellets (PC7) are shown in Table 4.

As shown in Tables 3 and 4, the pellets (PE1) to (PE11) produced in Examples 12 to 22 all had superior thermal oxidation stability compared to the pellets (PC1) to (PC7) in Comparative Examples 7 to 13, and the MFR change rate was also significantly reduced. There were also significant differences between the two in terms of dispersibility and maximum stress (strength).

From this, it can be seen that the surface-treated calcium carbonate fillers (PE1) to (PE11) prepared in Examples 1 to 11 all have the ability to improve the stability, heat resistance, dispersibility, and strength of the resulting resin composition, compared with the surface-treated calcium carbonate fillers (C1) to (C6) of Comparative Examples 1 to 6.

In this way, the surface-treated calcium carbonate filler of the present invention can reduce resin burning and the generation of aggregates during melt-kneading of a resin composition using the filler, suppress clogging of strainers, and provide excellent operational stability. Furthermore, it is possible to provide a polyolefin resin composition that is less susceptible to strength deterioration, for example.

The present invention is useful, for example, in the fields of resin molding, architecture and housing, paint, and a wide range of related technical fields.

Claims (7)

A surface-treated calcium carbonate filler satisfying the following formulas (a), (b) , (c) , (e), (f) and (g) :
(a) 2.0≦Sw≦20.0 ( ^m2 /g)
(b) 300≦Pw≦5000 (ppm)
(c) 0.01≦Tw≦0.30 (mass%)
(e) 0.10≦D50≦2.00 (μm)
(f) 0.9≦(D90−D10)/D50≦2.0
(g) Da≦5.0 (μm)
Sw is the BET specific surface area (m ² /g) of the surface-treated calcium carbonate filler,
The Pw is the content (ppm) of the phosphorus element in the surface-treated calcium carbonate filler measured with an inductively coupled plasma (ICP) emission spectroscopic analyzer,
The Tw is a weight loss value (% by mass) of the surface-treated calcium carbonate filler at 140° C. to 220° C. measured with a differential thermobalance device,
The D50 is a 50% diameter (μm) accumulated from the small particle side in a volume particle size distribution of the surface-treated calcium carbonate filler measured with a laser diffraction particle size distribution measuring device,
The D90 is a 90% diameter (μm) accumulated from the small particle side in the volume particle size distribution of the surface-treated calcium carbonate filler measured with the laser diffraction particle size distribution measurement device,
The D10 is a 10% diameter (μm) accumulated from the small particle side in the volume particle size distribution of the surface-treated calcium carbonate filler measured with the laser diffraction particle size distribution measurement device,
The Da is the maximum particle size (µm) in the volume particle size distribution of the surface-treated calcium carbonate filler measured with the laser diffraction particle size distribution measurement device . The surface-treated calcium carbonate filler according to claim 1, further satisfying the following formula (d):
(d) 0.80≦bw≦1.50
The bw is a hue change rate calculated by the following formula using yellowness values (b values) measured by a spectrophotometer before and after continuous heating at 140° C. for 48 hours for a paste in which the surface-treated calcium carbonate filler and dioctyl phthalate (DOP) are mixed in a mass ratio of 3 to 7:
Hue change rate (bw) = (b value of paste after heating / b value of paste before heating)
It is. The surface-treated calcium carbonate filler according to claim 1, which is used to constitute a polyolefin-based resin composition. A resin composition comprising a resin and the surface-treated calcium carbonate filler according to claim 1 or 2 . The resin composition according to claim 4 , wherein the resin is a polyolefin resin. A molded article made from the resin composition according to claim 4 . The molded article according to claim 6 , which has the form of a film.