Calcium carbonate filler for biodegradable resin, and biodegradable resin composition and resin molded article using the same

Abstract

To provide a calcium carbonate filler for biodegradable resin, which can enhance the biodegradability efficiency of the biodegradable resin used in combination therewith, as well as a biodegradable resin composition and a resin molded article using the same.SOLUTION: A biodegradable resin calcium carbonate filler of the present invention comprises surface-treated calcium carbonate particles surface-treated with a surface treatment agent comprising a polyphosphoric acid-based surface treatment agent component, the polyphosphoric acid-based surface treatment agent component including at least one polyphosphoric acid, wherein an amount calculated as phosphorus pentoxide (P2O5) contained in the polyphosphoric acid is 75 mass% or more and less than 100 mass% based on the mass of the polyphosphoric acid, the surface-treated calcium carbonate particles satisfying the following formula: 0.8≤A≤3.0 (μm), 13,000≤B≤30,000 (cm2 / g), C≤100 (ppm), 4.0≤D≤8.5, 800≤E≤5000 (ppm), 0.1≤Tw≤0.8 (mass%). Here, A represents an average particle diameter of 50% particles of the surface-treated calcium carbonate particles, B represents a specific surface area by an air permeability method, C represents a 45 μm sieve residue in accordance with JIS standard sieve, D represents a pH when made into a 10 mass% aqueous suspension, E represents a phosphorus element content measured by an inductively coupled plasma emission spectrophotometer, and Tw represents a thermal weight loss at 200-500°C measured by a differential thermogravimetric apparatus.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a calcium carbonate filler for biodegradable resins, and a biodegradable resin composition and a resin molded product using the same.

Background Art

[0002] Biodegradable resins represented by polylactic acid (PLA) can be decomposed into substances originally present in nature through hydrolysis and microbial metabolism in the environment. For this reason, biodegradable resins have attracted attention and are widely used as environmentally friendly resins, and further expansion of applications is expected in the future.

[0003] PLA has mechanical strength comparable to that of general-purpose plastics. However, it has poor heat resistance compared to petrochemical polyesters such as polyethylene terephthalate and polybutylene terephthalate. PLA also has relatively good hardness, but lacks flexibility and processability, and has a high specific gravity and poor lightness. In addition, in recent years, due to the increasing demand, it has become difficult to obtain PLA itself, and there are concerns about cost increases.

[0004] In a film composed of PLA, the rate-determining hydrolysis reaction is relatively slow near room temperature, and it takes a considerable amount of time until it can be assimilated by microorganisms. Especially in the application of agricultural films (mulch films), decomposition progresses from the film surface by the action of enzymes by microorganisms in the soil. For this reason, depending on the conditions, it takes a remarkably long time until the biodegradable resin constituting the film is completely decomposed, and there is concern that it will remain in the soil for a long time after being dug in. That is, the characteristics of biodegradability are not fully utilized, and further improvement is desired.

[0005] Also, generally, polylactic acid (PLA) is known to have a slow biodegradation rate, which impairs its essential characteristics in terms of biodegradability.

[0006] The biodegradation rate of polylactic acid is known to vary depending on the environment inside or around the resin. For example, Non-Patent Document 1 tested the biodegradability of polylactic acid at various pH values under the condition of 37°C, and reported that the degradation of the resin proceeds relatively rapidly under acidic or alkaline conditions, but the biodegradation rate is very slow under neutral conditions.

[0007] In order to improve the biodegradation rate of polylactic acid, a method has been proposed in which the inside of the resin is exposed to acidic conditions to promote the hydrolysis of the resin by adding an acidic substance or a substance that generates an acidic substance by a reaction such as decomposition. However, when producing a resin composition using polylactic acid and an inorganic substance powder, if the inorganic substance powder (for example, calcium carbonate) is contained, it is considered that the inside of the polylactic acid resin composition is neutralized by the alkaline calcium carbonate, and the biodegradability of polylactic acid is inhibited.

[0008] In addition, when a biodegradable resin such as polylactic acid contains an inorganic substance powder such as calcium carbonate, the biodegradation rate may be faster than when it does not contain the inorganic substance powder. However, the biodegradation rate is not dramatically improved.

[0009] The problem of controlling the biodegradation rate of these biodegradable resins can exist in many biodegradable resins such as polylactic acid, as well as polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), and the like.

[0010] In addition, since the form of use of an additive for promoting and controlling the biodegradation rate of a biodegradable resin varies depending on the type of additive used, problems may occur in the handling property during addition and the processability of the resin.

[0011] Furthermore, although the biodegradation rate is improved by including such additives in the resin composition, there may be problems in terms of a decrease in the mechanical properties of the resulting resin composition and resin molded articles containing the same, as well as cost issues.

[0012] Thus, there are still numerous problems remaining in the popularization of products using biodegradable resins.

[0013] Also, Patent Document 1 discloses a white resin composition containing surface-treated calcium carbonate in which the surface of synthetic calcium carbonate is surface-treated with condensed phosphoric acid and organo-modified silicone oil.

[0014] However, since the surface-treated calcium carbonate described in Patent Document 1 is synthetic calcium carbonate, it is disadvantageous in that the production cost increases as compared with heavy calcium carbonate, which can be obtained at a lower cost.

[0015] Moreover, in the case of the average particle diameter of the obtained surface-treated calcium carbonate (especially less than 0.8 μm), since the particles are too small, it is difficult to sufficiently disperse them in the resin at the stage of compounding by melt-kneading with the resin using the capabilities of a commonly used kneading extruder. Therefore, there is a possibility of causing screen mesh clogging during kneading extrusion or a decrease in the mechanical properties of the molded article, and it is difficult to say that it is suitable as a filler for resin molded articles.

Prior Art Documents

Patent Documents

[0016]

Patent Document 1

Non-Patent Documents

[0017]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0018] The present invention aims to solve the above problems, and its object is to provide a calcium carbonate filler for biodegradable resins, a biodegradable resin composition using the same, and a resin molded article, which can enhance the biodegradability efficiency of the biodegradable resin to be used in combination.

Means for Solving the Problems

[0019] The present invention relates to a surface treatment agent containing a polyphosphoric acid-based surface treatment agent component, wherein the polyphosphoric acid surface treatment agent component contains at least one kind of polyphosphoric acid, and the equivalent amount of metaphosphoric acid (P2O5) contained in the polyphosphoric acid is 75% by mass or more and less than 100% by mass based on the mass of the polyphosphoric acid. The calcium carbonate filler for biodegradable resins contains surface-treated calcium carbonate particles that are surface-treated with the surface treatment agent and satisfy the following formulas (1) to (6): (1) 0.8 ≤ A ≤ 3.0 (μm) (2) 13,000 ≤ B ≤ 30,000 (cm 2 / g) (3) C ≤ 100 (ppm) (4) 4.0 ≤ D ≤ 8.5 (5) 800 ≤ E ≤ 5000 (ppm) (6) 0.1 ≤ Tw ≤ 0.8 (mass%) A is the average particle diameter (d50) of 50% of the surface-treated calcium carbonate particles measured by a Microtrac MT3300 laser particle size distribution analyzer. B is the specific surface area by the air permeability method. C is the residue on a 45 μm sieve of a JIS standard sieve. D is the pH when made into a 10% by mass aqueous suspension. E is the content of phosphorus element measured by an inductively coupled plasma (ICP) optical emission spectrometer. Tw is the thermal weight loss at 200 to 500 °C measured by a differential thermal balance device.

[0020] In one embodiment, the polyphosphoric acid-based surface treatment agent component contains polyphosphoric acid, which is an oxo acid of a polymer composed of tetrahedral phosphate structural units, and at least one selected from the group consisting of salts of the polyphosphoric acid and esters of the polyphosphoric acid.

[0021] The present invention is also a biodegradable resin composition containing a biodegradable resin and the calcium carbonate filler for the biodegradable resin.

[0022] In one embodiment, the mass ratio of the biodegradable resin to the calcium carbonate filler for the biodegradable resin is from 97:3 to 60:40.

[0023] In one embodiment, the biodegradable resin is at least one resin selected from the group consisting of polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH).

[0024] The present invention is also a resin molded article containing the biodegradable resin composition.

[0025] In one embodiment, the resin molded article of the present invention has the form of a film.

[0026] In one embodiment, the resin molded article of the present invention has any one of the forms of an agricultural mulch film, a seedling raising pot, a sheet for preventing damage by wild animals and pests, a packaging film, or a tape for fixing seedlings, branches, and fruits.

Advantages of the Invention

[0027] According to the present invention, it is possible to provide a biodegradable resin composition and a resin molded article that enhance the efficiency of biodegradability of the biodegradable resin to be used in combination, can be molded by a general-purpose plastic molding method, have good moldability and handleability, and have sufficient mechanical strength. Further, the calcium carbonate filler for the biodegradable resin of the present invention has low toxicity to animals, plants, particularly the human body, and can be used for various applications.

Brief Description of the Drawings

[0028]

Figure 1

Embodiments for Carrying Out the Invention

[0029] Hereinafter, the present invention will be described in detail. [[ID=IS]]

[0030] 1. Calcium carbonate filler for biodegradable resin The calcium carbonate filler for the biodegradable resin of the present invention contains surface-treated calcium carbonate particles that satisfy the following formulas (1) to (6).

[0031] (Surface-treated calcium carbonate particles) In one embodiment, in the present invention, the surface-treated calcium carbonate particles satisfy the following formula (1): (1) 0.8 ≦ A ≦ 3.0 (μm)

[0032] Here, A is the average particle diameter (d50) (μm) of 50% of the surface-treated calcium carbonate particles measured by a Microtrac MT3300 laser particle size distribution analyzer. When A is less than 0.8 μm, the calcium carbonate particles themselves become too fine, resulting in an increase in their surface area, deterioration of handleability, and, for example, a significant increase in the viscosity of the composition when kneaded with the above biodegradable resin, making it difficult to manufacture a film. When A exceeds 3.0 μm, for example, when a biodegradable film is molded, the calcium carbonate particles may protrude from the film surface, leading to the occurrence of detachment and impairment of surface properties and mechanical strength. In the present invention, it is preferable that the surface-treated calcium carbonate particles do not contain particles with a 50% particle diameter (d50) (A) exceeding 3.0 μm because the strength of the obtained molded product is significantly reduced.

[0033] On the other hand, in the present invention, A in the surface-treated calcium carbonate particles is preferably 1.0 to 2.8 μm, more preferably 1.3 to \(2.5\) μm, and particularly preferably 1.6 to \(2.2\) μm.

[0034] The average particle diameter A can be controlled by varying various conditions during the production of the surface-treated calcium carbonate particles in the present invention. Conditions that can control the average particle diameter A within the above range include, for example, using calcium carbonate with an average particle diameter that satisfies the above range of A before the surface treatment (i.e., unmodified); adjusting the type and / or amount of the surface treatment agent used; and combinations thereof. If the setting of such conditions is insufficient, it may be difficult to obtain surface-treated calcium carbonate particles that satisfy the above range of the average particle diameter A.

[0035] For the measurement of the 50% particle diameter (d50) of the surface-treated calcium carbonate particles, for example, methanol can be used as the medium. Further, during the measurement, an ultrasonic disperser (Ultra Sonic Generator US-300T manufactured by Nippon Seiki Co., Ltd.) can be used as a pre-dispersant in the methanol slurry used for the measurement.

[0036] In one embodiment, the surface-treated calcium carbonate particles in the present invention satisfy the following formula (2): (2) 13,000 ≦ B ≦ 30,000 (cm 2 / g)

[0037] Here, B is the specific surface area (cm 2 / g) by the air permeability method. Further, the B is preferably 15,000 to 25,000 cm 2 / g, and more preferably 18,000 to 23,000 cm 2 / g. When the specific surface area B is within this range, the physical properties of the obtained molded product are improved, and there are many interfaces between the resin and the filler that serve as the starting point of the biodegradation reaction, so that the biodegradability in the natural environment can be promoted well. On the other hand, it is also possible to suppress the decrease in the processability of the resin composition by blending calcium carbonate particles.

[0038] The specific surface area B can be controlled by varying various conditions when producing the surface-treated calcium carbonate particles in the present invention. Conditions that can control the specific surface area B within the above range include, for example, using calcium carbonate (i.e., unmodified) whose specific surface area before the surface treatment described later satisfies the above range of B; adjusting the type and / or amount of the surface treatment agent used; and combinations thereof. If the setting of such conditions is insufficient, it may be difficult to obtain surface-treated calcium carbonate particles that satisfy the above range of the specific surface area B.

[0039] Note that the specific surface area by the air permeability method of the above surface-treated calcium carbonate particles can be measured under the following measurement conditions, for example, using a constant pressure powder specific surface area apparatus (manufactured by Shimadzu Corporation: SS-100). Specific gravity of calcium carbonate: 2.7 g / ml Sample: 2.7 g Amount of water to pass through: 5 ml Thickness of the sample layer: 10,000 cm as an estimated value 2When measuring the specific surface area less than / g, it is adjusted to 8 - 9 mm, and as an expected value, 10,000 cm 2 / g or more and 20,000 cm 2 / g or less, when measuring the specific surface area, it is adjusted to 9 - 12 mm, and as an expected value, 20,000 cm 2 / g, when measuring the specific surface area exceeding / g, it is adjusted between 12 - 13 mm.

[0040] In one embodiment, the surface - treated calcium carbonate particles in the present invention satisfy the following formula (3): (3) C ≤ 100 (ppm)

[0041] Here, C is the residue on a 45 - μm sieve of the JIS standard sieve. Further, the C is preferably 10 ppm or less, more preferably 5 ppm or less. When the sieve residue C exceeds 100 ppm, when preparing a biodegradable resin composition using the obtained calcium carbonate filler for biodegradable resin and forming it into a film, the strength of the obtained molded product may be significantly reduced. Also, when the sieve residue C is 10 ppm or less, when preparing a biodegradable resin composition using the obtained calcium carbonate filler for biodegradable resin and forming it into a film, the strength of the film can be further improved.

[0042] The sieve residue C can be controlled by varying various conditions in the production of the surface - treated calcium carbonate particles in the present invention. Conditions that can control the sieve residue C within the above range include, for example, using calcium carbonate (i.e., unmodified) whose sieve residue before the surface treatment described later satisfies the above range of C; adjusting the type and / or amount of the surface treatment agent used; adjusting the temperature employed in the surface treatment step described later; adjusting the conditions of dehydration, drying, and / or pulverization after the surface treatment step; and combinations thereof. If the setting of such conditions is insufficient, it may be difficult to obtain surface - treated calcium carbonate particles that satisfy the above range of the sieve residue C.

[0043] The sieve test method for measuring the sieve residue C is performed as follows.

[0044] First, 500 g of the sample is weighed into a 2 L stainless steel beaker, and 1000 g of industrial methanol is added to prepare a slurry. Next, while pouring this slurry onto a JIS standard sieve with an inner diameter of 200 mm and a mesh opening of 45 μm, the sample is passed through by gently mixing with a brush. The solids attached to the brush are also washed off with water, and the sieve is gently swept with the brush until the sieve passing liquid becomes completely transparent. Next, the residue is transferred to a JIS standard sieve with an inner diameter of 75 mm and a mesh opening of 45 μm, and left in a dryer (105 °C) for 30 minutes or more. Then, after cooling in a desiccator for 15 minutes, the residue is taken on a medicine wrapping paper and the sieve residue is calculated.

[0045] In addition, coarse particles that affect the above sieve residue C can be removed, for example, by passing through a sieve such as a vibrating sieve in a classification step using a sieve in addition to air classification. The removal of coarse particles can be carried out as necessary before or after the surface treatment step.

[0046] In one embodiment, the surface-treated calcium carbonate particles in the present invention satisfy the following formula (4): (4) 4.0 ≤ D ≤ 8.5

[0047] Here, D is the pH when the surface-treated calcium carbonate particles are made into a 10% by mass aqueous suspension. Further, the D is preferably 5.0 to 8.0, and more preferably 6.5 to 7.8.

[0048] Generally, unmodified calcium carbonate particles, which are mainly composed of calcium carbonate, often exhibit a pH value that is mainly greater than 8.5 and less than or equal to 10.0 due to the alkalinity of the aqueous solution derived from calcium carbonate. Also, even for surface-treated calcium carbonate particles obtained by surface-treating calcium carbonate particles using a commonly used surface treatment agent such as a fatty acid-based surface treatment agent by a known method, the pH mainly exceeds 8.5. However, the surface-treated calcium carbonate particles in the present invention are surface-treated with a polyphosphoric acid-based surface treatment agent component on the surface of the calcium carbonate particles (for example, so as to partially or completely cover them), so it is possible to achieve a pH of 8.5 or less in a 10% by mass aqueous suspension. Therefore, when the pH exceeds 8.5 in a 10% by mass aqueous suspension, it is considered that the effect of the polyphosphoric acid-based surface treatment agent component is not sufficiently obtained. Also, when the pH value D in a 10% by mass aqueous suspension is less than 4.0, when a biodegradable resin composition is prepared using the obtained calcium carbonate filler for biodegradable resin, the degradation of the biodegradable resin in the composition may progress rapidly, and the mechanical properties such as the strength and elongation of the resin molded product using it may decrease.

[0049] The D (that is, the pH in a 10% by weight aqueous suspension) can be controlled by varying various conditions during the production of the surface-treated calcium carbonate particles in the present invention. Conditions that can control the D within the above range include, for example, using at least one polyphosphoric acid-based surface treatment agent component as the surface treatment agent; adjusting the type and / or amount of the polyphosphoric acid-based surface treatment agent component; adjusting the type and / or amount of other surface treatment agent components used in combination; adjusting the temperature employed in the surface treatment step described later; adjusting the conditions of dehydration, drying, and / or pulverization after the surface treatment step; and combinations thereof. If the setting of such conditions is insufficient, it may be difficult to obtain surface-treated calcium carbonate particles that satisfy the above range of D.

[0050] In one embodiment, the surface-treated calcium carbonate particles in the present invention satisfy the following formula (5): (5) 800 ≦ E ≦ 5000 (ppm)

[0051] Here, E is the content of phosphorus element measured by an inductively coupled plasma (ICP) optical emission spectrometer. Further, the E is preferably 900 to 4000 ppm, more preferably 1000 ppm to 3500 ppm. When the phosphorus content E is less than 800 ppm, the surface-treated calcium carbonate filler containing the surface-treated calcium carbonate particles may reduce the biodegradation efficiency of the biodegradable resin in the biodegradable resin composition. When the phosphorus content E exceeds 5000 ppm, the effect of the filler cannot be further improved. Rather, the surface of the filler becomes calcium phosphate, which may cause poor dispersion and cause mesh clogging and molding defects when producing the biodegradable resin composition and resin molded products.

[0052] The phosphorus content E can be controlled by varying various conditions in the production of the surface-treated calcium carbonate particles in the present invention. Conditions that can control the phosphorus content E within the above range include, for example, using at least one polyphosphoric acid-based surface treatment agent component as the surface treatment agent; adjusting the type and / or amount of the polyphosphoric acid-based surface treatment agent component; adjusting the type and / or amount of other surface treatment agent components used in combination; adjusting the temperature employed in the surface treatment step described later; adjusting the dehydration, drying, and / or pulverization conditions after the surface treatment step; and combinations thereof. If the setting of such conditions is insufficient, it may be difficult to obtain surface-treated calcium carbonate particles that satisfy the above range of the phosphorus content E.

[0053] Note that the phosphorus content E can be measured as follows, for example, using an ICP optical emission spectrometer SPS3500 manufactured by SII NanoTechnology Inc.: First, 1.0 g of the surface-treated calcium carbonate particles to be measured is charged into a crucible and calcined in an electric furnace at 300 °C for 3 hours; Next, about 60 mL of distilled water and 7.5 mL of nitric acid of normality 1.38 (nitric acid for measurement of harmful metals (1.38), manufactured by Fujifilm Wako Pure Chemical Corporation) are put into the beaker after firing, and this mixture is boiled on an electric stove and gradually cooled; Then, the mixture after the above-mentioned gradual cooling is added to a 100 mL volumetric flask containing 100 μg of yttrium, and it is further made up to 100 mL with distilled water; It is filtered with a No. 5C filter paper, and a sample for ICP measurement is prepared from the obtained filtrate; Then, using this sample, the content (ppm) of phosphorus element contained in the sample is measured by the above-mentioned ICP emission spectroscopic analyzer.

[0054] In one embodiment, the surface-treated calcium carbonate particles in the present invention satisfy the following formula (6): (6) 0.1 ≦ Tw ≦ 0.8 (mass%)

[0055] Here, Tw is the thermal weight loss at 200 to 500 °C measured by a differential thermal balance device. Further, the Tw is preferably 0.1 to 0.5 mass%, and more preferably 0.15 to 0.4 mass%.

[0056] In general, for calcium carbonate used as an inorganic substance powder in a resin composition, if the thermal weight loss is too high, when kneading calcium carbonate and resin or when forming a kneaded product into a film, the volatile substances such as moisture of calcium carbonate react with the resin, causing yellowing deterioration, or the particles themselves fall off due to the formation of voids, and the mechanical properties of the molded product may be reduced due to the formation of aggregates of surface-treated calcium carbonates. Therefore, if Tw exceeds 0.8 mass%, the above problems may occur. When Tw is less than 0.1 mass%, there are no particular problems in terms of the physical properties of the obtained resin composition and molded product, but for the calcium carbonate particles, the effects such as maintaining the mechanical properties of the biodegradable resin composition and molded product and improving (controlling) the efficiency of biodegradability given by coating with a surface treatment agent containing at least a polyphosphoric acid-based treatment agent component may not be fully confirmed.

[0057] The heat loss Tw can be controlled by varying various conditions during the production of the surface-treated calcium carbonate particles in the present invention. Conditions under which the heat loss Tw can be controlled within the above range include, for example, using at least one polyphosphoric acid-based surface treatment agent component as the surface treatment agent; adjusting the type and / or amount of the polyphosphoric acid-based surface treatment agent component; adjusting the type and / or amount of other surface treatment agent components used in combination; adjusting the temperature employed in the surface treatment step described below; adjusting the conditions of dehydration, drying, and / or pulverization after the surface treatment step; and combinations thereof. If the setting of such conditions is insufficient, it may be difficult to obtain surface-treated calcium carbonate particles that satisfy the above range of the heat loss Tw.

[0058] Regarding the heat loss Tw, for example, using a DTG-60A manufactured by Shimadzu Corporation as a differential thermal balance device, first, 30 mg of the sample is weighed into a platinum pan with a diameter of 5 mm, this is set in the differential thermal balance device, and the temperature is raised at a rate of 30 °C / min, and the heat loss at 200 to 500 °C can be measured.

[0059] In addition, the surface-treated calcium carbonate particles constituting the calcium carbonate filler for the biodegradable resin of the present invention contain calcium carbonate as the main component, and the calcium carbonate has the form of calcium carbonate particles. The content ratio of calcium carbonate in the surface-treated calcium carbonate particles is preferably 95% by mass or more, more preferably 97% by mass or more, and even more preferably 99% by mass or more. By the content ratio of calcium carbonate in the surface-treated calcium carbonate particles being 95% by mass or more, that is, by containing calcium carbonate particles with high purity, the obtained surface-treated calcium carbonate particles can suppress undesirable effects on the human body and the environment, and can reduce the friction of the machine when molding the resin composition using the obtained calcium carbonate filler for biodegradable resin.

[0060] Note that the purity of the above calcium carbonate can be measured by a method according to JIS K8617 calcium carbonate.

[0061] In the calcium carbonate filler for biodegradable resin of the present invention, the surface-treated calcium carbonate particles satisfying the above formulas (1) to (6) are particles in which (unmodified) calcium carbonate particles are surface-treated with a surface treatment agent containing a polyphosphoric acid-based surface treatment agent component.

[0062] (Calcium carbonate) The calcium carbonate that can be used to obtain the above surface-treated calcium carbonate particles may be, for example, so-called heavy calcium carbonate obtained by mechanically pulverizing limestone, or any of the precipitated calcium carbonate obtained by the carbonation method. From the viewpoint of workability and cost, it is preferable that the calcium carbonate is heavy calcium carbonate. High-purity limestone, which is a raw material for calcium carbonate, is abundantly produced in Japan and can be obtained very economically. In the present invention, the calcium carbonate may be obtained from one type of raw material or a combination of those obtained from two or more types of raw materials.

[0063] Such calcium carbonate is preferably unmodified (before surface treatment) calcium carbonate particles. If they are already modified (after surface treatment) calcium carbonate particles, when they are surface-treated with a surface treatment agent containing at least a polyphosphoric acid-based surface treatment agent component, the components derived from the polyphosphoric acid-based treatment agent component may not be able to sufficiently bond to the surface of the calcium carbonate particles, and it may be difficult to obtain the desired surface-treated calcium carbonate particles.

[0064] (Surface treatment agent) (a) Polyphosphoric acid-based surface treatment agent component As used herein, the term "surface treatment agent containing a polyphosphoric acid-based surface treatment agent component" refers to a surface treatment agent containing at least the above "polyphosphoric acid-based surface treatment agent component", and includes both those composed of the "polyphosphoric acid-based surface treatment agent component" alone and those in which the "polyphosphoric acid-based surface treatment agent component" and a surface treatment agent component other than the polyphosphoric acid-based surface treatment agent component (sometimes referred to as "other surface treatment agent components") are used in combination.

[0065] Here, the "polyphosphoric acid-based surface treatment agent component" in the present invention includes, for example, polyphosphoric acid which is an oxo acid of a polymer composed of tetrahedral phosphoric acid structural units, and analogs of the polyphosphoric acid. Examples of the analogs of polyphosphoric acid include salts of the polyphosphoric acid, esters of the polyphosphoric acid, and combinations thereof. That is, the polyphosphoric acid-based surface treatment agent component in the present invention contains at least one kind of polyphosphoric acid.

[0066] As an example of the above polyphosphoric acid, there is a polymer of orthophosphoric acid (H3PO4) of the general formula (H n+2 P n O 3n+1 ), where n is a positive integer (for example, an integer from 1 to 15).

[0067] Polyphosphoric acid is composed of a mixture of orthophosphoric acid and pyrophosphoric acid, tripolyphosphoric acid, and higher-order acids, and is often characterized based on the calculated H3PO4 content or the equivalent amount of anhydrous phosphoric acid (P2O5). Also, metaphosphoric acid and ultraphosphoric acid are similar mixtures with different H3PO4 contents and are included as examples of the above polyphosphoric acid in the present invention.

[0068] In the present invention, in the polyphosphoric acid contained in the above polyphosphoric acid surface treatment agent component, the lower limit value of the equivalent amount of anhydrous phosphoric acid (P2O5) contained in the polyphosphoric acid is 75% by mass or more, preferably 78% by mass or more, more preferably 80% by mass or more, and even more preferably 82% by mass or more, based on the mass of the polyphosphoric acid. Also, the upper limit value of the equivalent amount of anhydrous phosphoric acid (P2O5) contained in the polyphosphoric acid is less than 100% by mass, preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less.

[0069] In one embodiment, the polyphosphoric acid may be anhydrous in structure (i.e., an anhydride). Further, the amount of H3PO4 in terms of the polyphosphoric acid is preferably 100 to 120% by mass, more preferably 103 to 118% by mass, and even more preferably 104 to 117% by mass, based on the mass of the polyphosphoric acid. Alternatively, the amount of H3PO4 in terms of the polyphosphoric acid is, for example, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, or 116% by mass based on the mass of the polyphosphoric acid.

[0070] In one embodiment, examples of the polyphosphoric acid-based surface treatment agent component include condensed phosphoric acids such as pyrophosphoric acid, tripolyphosphoric acid, and tetrapolyphosphoric acid; mixtures of these condensed phosphoric acids or ultraphosphoric acid or superphosphoric acid containing water; chain oligophosphate salts such as orthophosphate, pyrophosphate, tripolyphosphate, and tetrapolyphosphate; chain oligophosphate esters such as orthophosphate ester, pyrophosphate ester, tripolyphosphate ester, and tetrapolyphosphate ester; and combinations thereof.

[0071] In one embodiment, superphosphoric acid, which is an example of the polyphosphoric acid-based surface treatment agent component, can be easily prepared, for example, by heating and dehydrating commercially available orthophosphoric acid or by adding an appropriate amount of water to phosphorus pentoxide and heating and dissolving it.

[0072] (b) Surface treatment agent components other than the polyphosphoric acid-based surface treatment agent component (other surface treatment agent components) The "surface treatment agent component other than the polyphosphoric acid-based surface treatment agent component (other surface treatment agent components)" is a surface treatment agent (component) composed of components other than the above polyphosphoric acid-based surface treatment agent component. The types and amounts of the other surface treatment agent components are not particularly limited as long as they do not impair the effect of the calcium carbonate filler for biodegradable resins of the present invention.

[0073] Examples of other surface treatment agent components include fatty acids, fatty acid salts, phosphoric acids, aromatic sulfonic acids and their salts or esters; resin acids and their salts or esters; alcohol-based surfactants, sorbitan fatty acid esters, amide-based surfactants, amine-based surfactants, polyoxyalkylene alkyl ethers, polyoxyethylene nonylphenyl ethers, sodium alpha olefin sulfonate, long-chain alkyl amino acids, amine oxides, alkyl amines, quaternary ammonium salts and other surfactants; and silane coupling agents, titanium coupling agents and other coupling agents; and combinations thereof.

[0074] Fatty acids include fatty acids, fatty acid salts, and combinations thereof.

[0075] Examples of fatty acids include saturated fatty acids, unsaturated fatty acids, and alicyclic carboxylic acids, and combinations thereof.

[0076] Examples of saturated fatty acids include capric acid, lauric acid, myristic acid, palmitic acid, and stearic acid, and combinations thereof. Examples of unsaturated fatty acids include oleic acid, linoleic acid, and linolenic acid, and combinations thereof. Examples of alicyclic carboxylic acids include naphthenic acids having a carboxyl group at the end of a cyclopentane ring or cyclohexane ring.

[0077] Fatty acid salts include alkali metal salts of the above fatty acids (e.g., sodium salts, potassium salts), alkaline earth metal salts (e.g., calcium salts, magnesium salts), ammonium salts, and amine salts, and combinations thereof.

[0078] Examples of fatty acid salts include saturated fatty acid salts such as potassium laurate, potassium myristate, potassium palmitate, sodium palmitate, potassium stearate, and sodium stearate; unsaturated fatty acid salts such as potassium oleate and sodium oleate; alicyclic carboxylates such as lead naphthenate and lead cyclohexylbutyrate; and combinations thereof.

[0079] The above fatty acids may be, for example, modified or unmodified fatty acids derived from animals or plants. For example, mixed fatty acids such as beef tallow fatty acid, palm oil fatty acid, palm kernel oil fatty acid, and soybean oil fatty acid, which are commonly used in the art; their alkali metal salts; or so-called hydrogenated mixed fatty acids obtained by adding hydrogen to reduce the degree of unsaturation of these mixed fatty acids and their alkali metal salts may also be used.

[0080] Examples of phosphoric acids include inorganic phosphoric acids, organic phosphoric acids, and combinations thereof.

[0081] The content of the above other surface treatment agent components that may be included in the surface treatment agent can be selected by those skilled in the art in an amount appropriate within a range that does not inhibit the effects of the surface-treated calcium carbonate filler for biodegradable resins of the present invention.

[0082] In the present invention, the surface treatment agent is preferably prepared such that the total content of orthophosphoric acid and pyrophosphoric acid as its constituent components is 98% by mass or less (that is, 0% by mass or more and 98% by mass or less based on the total mass of the surface treatment agent), more preferably 75% by mass or less, still more preferably 35% by mass or less, and even more preferably 25% by mass or less. Alternatively, the surface treatment agent is prepared such that the total content of orthophosphoric acid and pyrophosphoric acid as its constituent components is 0% by mass or more and 98% by mass or less based on the total mass of the surface treatment agent, for example, 0.0001% by mass or more and 75% by mass or less, 0.001% by mass or more and 35% by mass or less, or 0.01% by mass or more and 25% by mass or less.

[0083] When orthophosphoric acid and / or pyrophosphoric acid were contained in the surface treatment agent at a ratio exceeding 98% by mass in total, the surface-treated calcium carbonate particles obtained using the surface treatment agent might aggregate due to poor dispersion when added to the biodegradable resin composition as a calcium carbonate filler, and it might be impossible to perform appropriate kneading on the resin composition, and finally it might become difficult to form a film in the form of a film.

[0084] (Surface treatment method) The surface-treated calcium carbonate particles constituting the calcium carbonate filler for biodegradable resin of the present invention are obtained by surface-treating the above calcium carbonate with a surface treatment agent containing a polyphosphoric acid-based surface treatment agent component.

[0085] Examples of the method for surface-treating calcium carbonate with a surface treatment agent containing a polyphosphoric acid-based surface treatment agent component include a dry treatment method and a wet treatment method.

[0086] The dry treatment method is a method in which a surface treatment agent containing a polyphosphoric acid-based surface treatment agent component is added to and mixed with calcium carbonate powder, and then dried. The polyphosphoric acid-based surface treatment agent component or the surface treatment agent containing the polyphosphoric acid-based surface treatment agent component can be added in a liquid form.

[0087] The wet treatment method is a method in which a surface treatment agent containing a polyphosphoric acid-based surface treatment agent component is added to and mixed with an aqueous suspension containing calcium carbonate, and then the aqueous suspension is filtered and dried. In this method, an alkali metal salt of polyphosphoric acid or the like may be used as the polyphosphoric acid-based treatment agent component. However, in order to reduce the content of alkali metal contained in the obtained calcium carbonate filler for biodegradable resin, it is preferably used in the form of an acid.

[0088] The addition amount of the surface treatment agent containing the polyphosphoric acid-based surface treatment agent component needs to be added so that the surface treatment amount Tw of the obtained calcium carbonate filler for biodegradable resin satisfies the above range (that is, 0.1 ≦ Tw ≦ 0.8 (mass%)).

[0089] In one embodiment, when surface treatment is performed on calcium carbonate using only a polyphosphoric acid-based surface treatment agent component as the surface treatment agent, the addition amount of the polyphosphoric acid-based surface treatment agent component is preferably 0.1 part by mass or more and 3 parts by mass or less, more preferably 0.5 part by mass or more and 2 parts by mass or less, and even more preferably 0.8 part by mass or more and 1.5 parts by mass or less with respect to 100 parts by mass of the calcium carbonate particles to be surface-treated. When the addition amount of the polyphosphoric acid-based surface treatment agent component exceeds 3 parts by mass, the thermal weight loss Tw in the formula (6) of the calcium carbonate filler for biodegradable resin obtained will exceed the range, and formation of aggregates due to excessive surface treatment or a decrease in the mechanical properties of the resulting biodegradable resin may be caused. When the addition amount of the polyphosphoric acid-based surface treatment agent component is less than 0.1 part by mass, the thermal weight loss Tw in the formula (6) of the calcium carbonate filler for biodegradable resin obtained does not satisfy the range, the polyphosphoric acid-based surface treatment agent does not sufficiently act on the calcium carbonate particles, and the effect as the calcium carbonate filler for biodegradable resin of the present invention may not be obtained.

[0090] The addition amount of the surface treatment agent containing the polyphosphoric acid-based surface treatment agent component can be varied according to the specific surface area of the so-called unmodified calcium carbonate particles before being subjected to surface treatment, within the range where the surface treatment amount Tw of the calcium carbonate filler for biodegradable resin obtained satisfies the range of 0.1 ≦ Tw ≦ 0.8 (mass%). For example, the larger the specific surface area of the unmodified calcium carbonate particles, the more desirable it is to increase the addition amount.

[0091] In one embodiment, when surface treatment is performed using a combination of a polyphosphoric acid-based surface treatment agent component and another surface treatment agent component as the surface treatment agent, from the viewpoint that the surface state of the obtained surface-treated calcium carbonate particles can be made more uniform and the dispersibility can be improved, it is also possible to simultaneously add the polyphosphoric acid-based surface treatment agent component and another surface treatment agent component to the unmodified calcium carbonate particles for treatment.

[0092] In one embodiment, when performing surface treatment by a dry treatment method, a solvent such as water may be added in order to make the polyphosphate-based surface treatment agent component more likely to act on calcium carbonate particles. Since some of the polyphosphate-based surface treatment agent components have viscosity, the addition of the solvent improves the fluidity of the calcium carbonate particles and the polyphosphate-based surface treatment agent component, enabling more uniform surface treatment to be performed.

[0093] Regarding the surface treatment temperature when performing surface treatment by a dry treatment method, it is preferable to perform surface treatment at a temperature equal to or higher than the melting point of the component used as the surface treatment agent. If the surface treatment temperature is lower than the melting point of the component used as the surface treatment agent, the surface treatment of the calcium carbonate particles may become non-uniform. On the other hand, when the surface treatment temperature exceeds the melting point of the component used as the surface treatment agent, the uniformity of the surface treatment improves, and it becomes possible to perform surface treatment in a short time.

[0094] In one embodiment, this surface treatment temperature may be equal to or higher than the melting point of the surface treatment agent and equal to or lower than the temperature at which the surface treatment agent does not deteriorate. For example, with respect to the temperature of the melting point of the surface treatment agent used, it is preferably the temperature obtained by adding 0°C to 70°C, more preferably the temperature obtained by adding 10°C to 60°C, and even more preferably the temperature obtained by adding 20°C to 50°C.

[0095] In one embodiment, this surface treatment temperature is preferably 20°C to 150°C, more preferably 40°C to 125°C.

[0096] After the above surface treatment, the obtained particles may be pulverized through any operations such as dehydration, drying, and pulverization.

[0097] In particular, the particles obtained immediately after surface treatment may contain aggregates such as coarse particles. In that case, in addition to air classification, it is possible to remove coarse particles and aggregates by performing a classification step using a sieve, for example, a step of passing through a sieve such as a vibrating sieve. This classification step is not limited to after the surface treatment and may also be performed before the surface treatment step as necessary.

[0098] In this way, surface-treated calcium carbonate particles can be obtained.

[0099] The obtained surface-treated calcium carbonate particles can be directly used as the particles constituting the calcium carbonate filler for the biodegradable resin of the present invention.

[0100] 2. Biodegradable resin composition The biodegradable resin composition of the present invention contains a biodegradable resin and the above-mentioned calcium carbonate filler for biodegradable resin.

[0101] (a) Biodegradable resin Examples of the biodegradable resin include polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), and combinations thereof.

[0102] Polylactic acid (PLA) is a copolyester having lactic acid as a monomer component. Lactic acid, which is the monomer component, has one asymmetric carbon, and there are two types, the L-form and the D-form. PLA is commercially available as a biodegradable plastic. It is known that the biodegradability of PLA is slower compared to other biodegradable resins. On the other hand, among biodegradable plastics, PLA is the resin in which research and practical application have progressed the most.

[0103] Polybutylene adipate terephthalate (PBAT) is a biodegradable random copolymer, specifically a copolyester having adipic acid, 1,4-butanediol, and terephthalic acid as monomer components. PBAT has high biodegradability among known biodegradable resins and is commercially available. PBAT is also known to have excellent balanced physical properties such as strength and heat resistance, and physical properties similar to those of general-purpose polyethylene. For this reason, it can be easily molded using general-purpose plastic molding methods.

[0104] Polybutylene succinate (PBS) is a copolyester having succinic acid and 1,4-butanediol as monomer components, and is commercially available as a plant-derived biodegradable plastic. PBS is also known to be excellent in heat sealability, compatibility, heat resistance, and flexibility.

[0105] Polybutylene succinate adipate (PBSA) is a copolyester having adipic acid, 1,4-butanediol, and succinic acid as monomer components, and is commercially available as a plant-derived biodegradable plastic. PBSA is also known to be excellent in moldability by itself.

[0106] Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) and poly-3-hydroxybutyric acid (PHB) are copolyesters having 3-hydroxybutyric acid and 3-hydroxyhexanoic acid as monomer components, respectively, and are homopolymers of hydroxybutyric acid, and both are a type of polyhydroxyalkanoate (PHA). They are commercially available as biodegradable plastics due to the establishment of a synthesis method by microorganisms. PHBH is also known to be excellent in terms of marine biodegradability.

[0107] In the present invention, the biodegradable resin may contain a resin having biodegradability other than the above (other biodegradable resins). Examples of other biodegradable resins include polyhydroxyalkanoate (PHA), starch polyester resin, cellulose acetate (diacetate), polyvinyl alcohol (PVA), polyglycolic acid (PGA), and polyethylene terephthalate succinate (PETS), and combinations thereof. The appropriate content of other biodegradable resins can be selected by those skilled in the art within a range that does not inhibit the effects of the present invention by the calcium carbonate filler for biodegradable resins.

[0108] In addition, the melt flow rate (MFR) of the above biodegradable resin is a value measured at 190°C under a load of 2.16 kg based on JIS K7210 (1999), and is preferably 0.1 g / 10 min or more and 10 g / 10 min or less. From the viewpoints of moldability and mechanical strength, the MFR of the biodegradable resin is more preferably 8 g / 10 min or less, and particularly preferably 6 g / 10 min or less. This is because if the MFR is higher than 10 g / 10 min, it becomes difficult to perform molding processing using a film forming machine. The MFR of the biodegradable resin can be adjusted by the molecular weight.

[0109] Depending on the type of biodegradable resin, physical properties such as melting point, crystallization temperature, melt viscosity, and melt flow rate (MFR) are different. Therefore, although not particularly limited, in the biodegradable resin composition of the present invention, when forming a polymer alloy composed of two or more biodegradable resins, it is preferable to determine the composition in consideration of the differences in these physical properties.

[0110] When the biodegradable resin composition in the present invention is particularly molded into the form of a film as a resin molded product, it is preferable to contain polybutylene adipate terephthalate (PBAT) as the biodegradable resin. Polybutylene adipate terephthalate (PBAT) has high biodegradability among various biodegradable resins and is mass-produced, so it is easily available. It is also excellent in the balance with physical properties such as strength and heat resistance, and because its physical properties are close to those of general-purpose polyethylene, it can be molded by a general-purpose plastic molding method. Therefore, it is also easy to modify it into a resin having preferable physical properties according to the use of the biodegradable resin composition and the like. Furthermore, the high biodegradability of polybutylene adipate terephthalate (PBAT) and the calcium carbonate filler for the biodegradable resin can further improve the biodegradability of the PBAT.

[0111] (b) Content ratio of biodegradable resin and biodegradable calcium carbonate filler In the biodegradable resin composition of the present invention, the ratio (mass ratio) of the content of the biodegradable resin to the calcium carbonate filler for biodegradable resin is preferably from 97:3 to 60:40, more preferably from 90:10 to 70:30, and even more preferably from 85:15 to 75:25. In the mass ratio of the biodegradable resin to the calcium carbonate filler for biodegradable resin, when the proportion of the content of the calcium carbonate filler for biodegradable resin is less than 3, the releasability of the film obtained from such a resin composition deteriorates and the processability is inferior, and furthermore, the effects of the biodegradable physical properties may not be sufficiently confirmed. On the other hand, when the proportion of the content of the calcium carbonate filler for biodegradable resin exceeds 40, the mechanical strength of the film obtained from such a resin composition may decrease.

[0112] In the biodegradable resin composition of the present invention, the calcium carbonate filler for biodegradable resin can function as an inorganic filler, for example.

[0113] (c) Inorganic substance powder The biodegradable resin composition of the present invention may also contain an inorganic substance powder as another inorganic filler as long as it does not inhibit the effects of the present invention by the calcium carbonate filler for biodegradable resin.

[0114] Examples of the inorganic substance powder include calcium carbonate, talc, anhydrous silica, mica, muscovite, clay, titanium oxide, diatomaceous earth, allophane, bentonite, potassium titanate, zeolite, sepiolite, smectite, kaolin, kaolinite, glass, limestone, carbon, wollastonite, fired perlite, calcium silicate, silicates such as sodium silicate, quicklime, aluminum oxide, magnesium carbonate, hydroxides such as calcium hydroxide, ferric carbonate, zinc oxide, iron oxide, aluminum phosphate, and barium sulfate, and combinations thereof.

[0115] Particularly when using calcium carbonate as the inorganic substance powder, in order to enhance the dispersibility or reactivity of calcium carbonate, the surface of the particles constituting calcium carbonate may be surface-modified. Examples of methods for performing surface modification include physical methods such as plasma treatment, and chemical surface treatment methods using a surface treatment agent. However, the surface treatment agent here refers to a surface treatment agent amount other than the polyphosphate-based surface treatment agent amount shown above (other surface treatment agent amounts), and it must be used within a range that does not inhibit the effects of the present invention. On the other hand, the surface of calcium carbonate particles may not be surface-modified, and unmodified calcium carbonate may be rather preferable in that it can reduce the risk of odor generation due to thermal decomposition of the surface treatment agent during molding.

[0116] (d) Other components In the biodegradable resin composition of the present invention, within a range that does not inhibit the effects of the present invention, in addition to the above components, any other components may be further included.

[0117] Examples of other components that can be included in the biodegradable resin composition of the present invention include plasticizers, fillers other than calcium carbonate, colorants, lubricants, coupling agents, fluidity improvers, dispersants, antioxidants, ultraviolet absorbers, flame retardants, stabilizers, antistatic agents, foaming agents, etc. These may be used alone or in combination of two or more. Also, these may be blended in the kneading step described later, or may be premixed before the kneading step.

[0118] Examples of plasticizers include acetyl tributyl citrate, triethyl citrate, triethyl citrate, acetyl triethyl citrate, dibutyl phthalate, diaryl phthalate, dimethyl phthalate, diethyl phthalate, di-2-methoxyethyl phthalate, dibutyl tartrate, o-benzoylbenzoic acid ester, diacetin, and epoxidized soybean oil, and combinations thereof.

[0119] The filler is made of inorganic materials other than the above calcium carbonate, and examples thereof include carbonates (excluding calcium carbonate) such as calcium, magnesium, aluminum, titanium, iron, and zinc, sulfates, silicates, phosphates, borates, oxides, and hydrates thereof. Specific examples of the filler include talc, zeolite, mica, clay, calcium oxide, calcium hydroxide, feldspar, quartz, magnesium carbonate, zinc oxide, titanium oxide, silica, alumina, kaolin, aluminum hydroxide, magnesium hydroxide, aluminum silicate, magnesium silicate, calcium silicate, aluminum sulfate, magnesium sulfate, calcium sulfate, magnesium phosphate, barium sulfate, silica sand, carbon black, molybdenum, diatomaceous earth, sericite, shirasu, calcium sulfite, sodium sulfate, potassium titanate, bentonite, wollastonite, and graphite, as well as combinations thereof. The filler may be synthetic or derived from natural minerals.

[0120] The colorant and the coloring agent may be any known organic pigment, inorganic pigment, or dye. Specific examples of the colorant include organic pigments such as azo-based, anthraquinone-based, phthalocyanine-based, quinacridone-based, isoindolinone-based, dioxazine-based, perinone-based, quinophthalone-based, and perylene-based pigments; inorganic pigments such as ultramarine, titanium oxide, titanium yellow, iron oxide (red iron oxide), chromium oxide, zinc white, and carbon black; and combinations thereof.

[0121] As the antioxidant, a single one or any combination of phosphorus-based antioxidants, phenol-based antioxidants, pentaerythritol-based antioxidants, etc. can be used. Specific examples of the phosphorus-based antioxidants include phosphorus-based antioxidant stabilizers such as phosphite esters and phosphate esters.

[0122] Here, examples of the phosphite ester include triesters, diesters, monoesters, etc. of phosphorous acid such as triphenyl phosphite, trisnonylphenyl phosphite, tris(2,4-di-t-butylphenyl) phosphite, etc., and combinations thereof.

[0123] Examples of phosphate esters include trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, triphenyl phosphate, tricresyl phosphate, tris(nonylphenyl) phosphate, and 2-ethylphenyldiphenyl phosphate, and combinations thereof.

[0124] Examples of phenolic antioxidants include α-tocopherol, butylhydroxytoluene, sinapyl alcohol, vitamin E, n-octadecyl 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2-t-butyl-6-(3'-t-butyl-5'-methyl-2'-hydroxybenzyl)-4-methylphenyl acrylate, 2,6-di-t-butyl-4-(N,N-dimethylaminomethyl)phenol, 3,5-di-t-butyl-4-hydroxybenzylphosphonate diethyl ester, and tetrakis[3-(3-5-di-t-butyl-4-hydroxyphenyl)propionyloxymethyl]methane, and combinations thereof.

[0125] Examples of the flame retardant include one or more combinations of non-phosphorus non-halogen flame retardants such as halogen-based flame retardants, phosphorus-based flame retardants, and metal hydrates. Examples of the halogen-based flame retardants include halogenated bisphenol compounds such as halogenated bisphenyl alkane, halogenated bisphenyl hartel, halogenated bisphenyl thioether, and halogenated bisphenyl sulfone, bisphenol-rubis (alkyl ether) compounds such as brominated bisphenol A, brominated bisphenol S, chlorinated bisphenol A, and chlorinated bisphenol S. Examples of the phosphorus-based flame retardants include aluminum tris (diethylphosphonic acid), bisphenol A bis (diphenyl phosphate), triaryl isopropyl phosphate, cresyl di-2,6-xylyl phosphate, and aromatic condensed phosphate esters. Examples of the metal hydrates include aluminum trihydrate and magnesium dihydroxide. In addition to such flame retardants, antimony oxides such as antimony trioxide and antimony pentoxide, zinc oxide, iron oxide, aluminum oxide, molybdenum oxide, titanium oxide, calcium oxide, magnesium oxide, etc. may be used in combination as flame retardant aids if necessary.

[0126] The foaming agent is mixed or injected into the biodegradable resin composition of the raw materials in a molten state in a melt kneader, and is a substance that undergoes a phase change from solid to gas or from liquid to gas, or is a gas itself, and is mainly used to control the foaming ratio (foaming density) of the foamed sheet. The foaming agent dissolved in the biodegradable resin composition of the present invention changes from a liquid at room temperature to a gas by the resin temperature and dissolves in the molten resin, and the gas at room temperature dissolves in the molten resin without undergoing a phase change. The foaming agent dispersed and dissolved in the molten resin expands inside the sheet when the molten resin is extruded into a sheet shape from the extrusion die because the pressure is released, and a large number of fine independent bubbles are formed in the sheet to provide a foamed sheet. The foaming agent secondarily acts as a plasticizer that lowers the melt viscosity of the biodegradable resin composition of the present invention, and can lower the temperature for plasticizing the biodegradable resin composition, so it can be added as necessary.

[0127] Examples of the foaming agent include aliphatic hydrocarbons such as propane, butane, pentane, hexane, and heptane; alicyclic hydrocarbons such as cyclobutane, cyclopentane, and cyclohexane; halogenated hydrocarbons such as chlorodifluoromethane, difluoromethane, trifluoromethane, trichlorofluoromethane, dichloromethane, dichlorofluoromethane, dichlorodifluoromethane, chloromethane, chloroethane, dichlorotrifluoroethane, dichloropentafluoroethane, tetrafluoroethane, difluoroethane, pentafluoroethane, trifluoroethane, dichlorotetrafluoroethane, trichlorotrifluoroethane, tetrachlorodifluoroethane, and perfluorocyclobutane; inorganic gases such as carbon dioxide, nitrogen, and air; and water.

[0128] In the biodegradable resin composition of the present invention, the content of other components can be selected by those skilled in the art as long as the effects of the present invention due to the blending of the above-described biodegradable resin and the calcium carbonate filler for biodegradable resin are not inhibited. For example, with respect to the total mass of the biodegradable resin composition, the individual content of each component constituting the other components is preferably 0 to 5% by mass, and the total content of the other components is preferably 10% by mass or less.

[0129] 3. Preparation of the biodegradable resin composition The biodegradable resin composition of the present invention can be prepared using the above components based on, for example, a method conventionally known as a method for producing a resin composition. That is, the biodegradable resin composition of the present invention can be obtained, for example, through mixing and melt-kneading of the components.

[0130] The timing of mixing and melt-kneading can be appropriately set according to the molding method to be adopted (such as extrusion molding, injection molding, vacuum molding, etc.). For example, the biodegradable resin and the calcium carbonate filler for biodegradable resin can be kneaded and melted before being fed into the molding machine from the hopper, and then fed into the molding machine. Alternatively, the biodegradable resin and the calcium carbonate filler for biodegradable resin can be kneaded and melted simultaneously with molding integrally with the molding machine. It is preferable that the kneading and melting uniformly disperse the calcium carbonate filler for biodegradable resin in the biodegradable resin while applying a high shear stress for kneading. For example, it is more preferable to knead using a twin-screw kneader.

[0131] A screen mesh may be provided near the outlet of the extrusion in the kneader used for mixing and melt-kneading. By providing a screen mesh and passing the biodegradable resin composition through the screen mesh, it tends to be possible to remove the inclusion of foreign substances into the obtained biodegradable resin composition.

[0132] Examples of the screen mesh include SUS (stainless steel) mesh and copper mesh. The mesh size of the screen mesh is preferably 20 to 500 μm, more preferably 25 to 300 μm. By setting the mesh size of the screen mesh to 20 μm or more, an excessive increase in resin pressure is not caused, and thus productivity tends to be improved. Further, by setting the mesh size of the screen mesh to 500 μm or less, finer foreign substances can be removed.

[0133] In the present invention, the biodegradable resin composition may be passed through the screen mesh only once or may be passed through two or more times. When passing through two or more times, it is preferable to pass in order from the one with the largest mesh size.

[0134] In the present invention, the form of the resulting biodegradable resin composition is not particularly limited, and for example, it may have the form of pellets. When the biodegradable resin composition of the present invention has the form of pellets, its shape is not particularly limited, and for example, it may be cylindrical, spherical, ellipsoidal, etc. The granulation process for obtaining the pellets can be carried out by procedures or apparatuses commonly used by those skilled in the art. For example, while melting the above biodegradable resin using a twin-screw extruder or the like, a calcium carbonate filler for biodegradable resin and, if necessary, the above other components are added and melt-kneaded, extruded into a strand shape and cooled, and then processed into the form of pellets by a pelletizer. After the obtained pellets are sufficiently dried to remove moisture, a desired film can be obtained by molding.

[0135] In the present invention, the size of the pellets is not particularly limited. For example, when having the form of spherical pellets, its diameter may be 1 mm to 10 mm. When having the form of elliptical pellets, for example, the aspect ratio may be 0.1 to 1.0, and the longitudinal and transverse lengths may be 1 mm to 10 mm. When having the form of cylindrical pellets, for example, the diameter may be 1 mm to 10 mm and the length may be 1 mm to 10 mm.

[0136] After drying the resin composition of the present invention as necessary, the following resin molded articles can be obtained by molding.

[0137] 4. Resin Molded Articles (a) Resin Molded Articles The resin molded article according to the present invention is molded using the above biodegradable resin composition.

[0138] The form of the resin molded article according to the present invention is not particularly limited and may have various forms. Examples of resin molded articles include various molded articles in the fields of films, sheets, food containers and other container bodies, packaging products, daily necessities, automotive parts, electrical and electronic parts, building materials, agricultural materials, etc.

[0139] The thickness of the resin molded article according to the present invention is not particularly limited, and may have various thicknesses from a thin film to a thick film depending on the form of the molded article. The thickness of the moldable resin molded article is, for example, 5 μm to 5000 μm. If the thickness is within this range, it is possible to form a resin molded article excellent in biodegradability without problems in moldability and processability as a resin molded article made of a biodegradable resin composition containing a calcium carbonate filler for biodegradable resins.

[0140] In one embodiment, when the resin molded article has the form of a film, in order to function as a biodegradable film, it preferably has a thickness of 5 μm to 2000 μm, more preferably 10 μm to 500 μm. A film having a thickness within such a range can be suitably used as a biodegradable film for any application such as agriculture, forestry, printing, and packaging.

[0141] In one embodiment, when the resin molded article has the form of a biodegradable film and is used as an agricultural mulch film, the thickness of the biodegradable film is preferably 5 μm to 30 μm, more preferably 10 μm to 25 μm. When the thickness of the biodegradable film is less than 5 μm, it may not be possible to maintain the mechanical strength required for use as a mulch film. When the thickness of the biodegradable film exceeds 30 μm, the biodegradability as an agricultural mulch film becomes insufficient, and it may be difficult to embed it in the soil with a shovel or the like after use.

[0142] In one embodiment, when the resin molded article has the form of a seedling raising pot, the thickness of the biodegradable film used in manufacturing the seedling raising pot is preferably 100 μm to 2000 μm. If the thickness of the biodegradable film is less than 100 μm, the mechanical strength may be insufficient, and the function as a seedling raising pot may not be obtained. If the thickness of the biodegradable film exceeds 2000 μm, the moldability and workability during molding as a seedling raising pot may decrease, and the biodegradability may be impaired.

[0143] In one embodiment, when the resin molded article has the form of a sheet for preventing damage by animals or pests, the thickness of the sheet is not particularly limited, but is preferably 50 μm to 5000 μm from the viewpoints of the durability and strength retention of the sheet for preventing damage by animals or pests, handleability, and biodegradability.

[0144] In one embodiment, when the resin molded article of the present invention has the form of a packaging film, the thickness of the packaging film is not particularly limited, but is preferably 5 μm to 300 μm from the viewpoints of the durability and strength retention of the packaging film, handleability, and biodegradability.

[0145] (b) Method for molding a resin molded article As the method for molding the resin molded article of the present invention, a method known in the art can be used. Examples thereof include an injection molding method, a foam injection molding method, an injection compression molding method, an extrusion molding method, a blow molding method, a rotary blow molding method, a press molding method, a calender molding method, a vacuum molding method, and the like.

[0146] Furthermore, when molding the resin molded article, within a range that does not significantly inhibit its biodegradability and mechanical strength, resin additives such as a colorant, an ultraviolet absorber, an antioxidant, or the like, or other polymers may be added to the biodegradable resin composition.

[0147] In one embodiment, for film formation, a film forming machine used in a known inflation method or T-die method can be used. Particularly for forming a biodegradable film into a multilayer film, it is necessary to have a good balance of tensile strength. For this reason, it is preferable to perform film formation by the inflation method.

[0148] The film obtained as described above may be stretched in a uniaxial, biaxial, or multi-axial direction during or after molding.

[0149] Specific molding conditions for obtaining the above resin molded article can be appropriately set by those skilled in the art according to the composition of the biodegradable resin composition used, the type of the resin molded article, and the like.

[0150] Thus, the resin molded article of the present invention can be used as a biodegradable film in various applications such as agricultural applications (e.g., mulch film, seedling raising pots), measures against animal and food damage, and packaging applications.

[0151] According to the present invention, by using a biodegradable resin composition containing a biodegradable resin and a calcium carbonate filler for biodegradable resin, it can be molded by a general-purpose plastic molding method, has excellent moldability and handleability, and ensures sufficient mechanical strength. Moreover, a resin molded article with greatly improved biodegradability in the environment can be obtained.

[0152] Furthermore, the calcium carbonate filler for biodegradable resin of the present invention that enables the molding of such a resin molded article has a main component composed of calcium carbonate. Therefore, the interface formed between the biodegradable resin and the calcium carbonate filler for biodegradable resin in the obtained film can be increased. Additionally, when the biodegradable resin composition of the present invention decomposes in soil, it is considered that the components derived from polyphosphoric acid contained in the calcium carbonate filler for biodegradable resin activate the enzyme reaction of microorganisms in the soil. As a result, it is expected to further increase the biodegradation rate of the biodegradable resin as a constituent component.

[0153] Also, when the calcium carbonate filler for biodegradable resin of the present invention is made into a 10% by weight aqueous suspension, its pH is mainly in the neutral region or a region near it. Thus, it can be widely used regardless of the components in the biodegradable resin composition. For example, in order to promote the degradability by hydrolysis of the biodegradable resin, a substance that releases an acidic substance may be added as a component. However, when calcium carbonate particles commonly used for them are added, due to the alkalinity derived from the calcium carbonate particles, the acidic substance added inside the biodegradable resin composition may be neutralized to become neutral, and the degradability may be inhibited. In contrast to this case, by adding the calcium carbonate filler for biodegradable resin of the present invention instead of ordinary calcium carbonate particles, while maintaining the mechanical properties, the biodegradability can be promoted without inhibiting the hydrolysis promoting effect by adding an acidic substance.

[0154] Furthermore, since the enzymes of microorganisms in soil and the ocean are generally activated in the neutral region, the calcium carbonate filler for biodegradable resin of the present invention, whose pH is in the neutral region or a region near it when made into a 10% by weight aqueous suspension, is expected to proceed with biodegradation as designed without inhibiting the decomposition by the enzymes of microorganisms when added to the biodegradable resin.

[0155] Also, since polyphosphoric acid consists of a high-energy phosphate bond similar to ATP, which is the energy of organisms, it is known to be consumed as food or an energy source of organisms in nature. Therefore, when a biodegradable resin composition containing the calcium carbonate filler for biodegradable resin of the present invention, which contains a polyphosphoric acid-based surface treatment agent component, is brought into contact with soil containing microorganisms, activation of the microorganisms by the polyphosphoric acid component is caused, and biodegradation promotion derived from the enzymes of the microorganisms is expected.

[0156] That is, the calcium carbonate filler for biodegradable resin of the present invention, which contains a polyphosphoric acid-based surface treatment agent component, can be expected to maintain the mechanical properties of the biodegradable resin composition containing them, not inhibit the decomposition by hydrolysis of the biodegradable resin composition, and promote the biodegradation derived from the enzymes of microorganisms.

[0157] Furthermore, the polyphosphoric acid-based surface treatment agent component used in the calcium carbonate filler for the biodegradable resin of the present invention can stably exist in the natural environment and has low toxicity to animals, plants, especially the human body, so it can be used in various applications.

Examples

[0158] Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. In the following description, unless otherwise specified, % means mass %, and part means mass part.

[0159] (Evaluation method) The physical property values in the following Examples 1 to 18 and Comparative Examples 1 to 21 were evaluated by the following methods, respectively.

[0160] (Average particle size (d50)) The average particle size (d50) (μm) of 50% of the surface-treated calcium carbonate particles constituting the obtained calcium carbonate filler for biodegradable resin was measured as described above.

[0161] (Specific surface area) The specific surface area (cm 2 / g) of the surface-treated calcium carbonate particles constituting the obtained calcium carbonate filler for biodegradable resin was measured as described above. [[ID=�2]]

[0162] (Residue on 45 μm sieve of JIS standard sieve) The residue on a 45 μm sieve of the JIS standard sieve (ppm) of the surface-treated calcium carbonate particles constituting the obtained calcium carbonate filler for biodegradable resin was measured as described above.

[0163] [[ID=ģ9]] (pH in 10% by mass aqueous suspension) The pH of the aqueous suspension when a 10% by mass aqueous suspension was prepared using the surface-treated calcium carbonate particles constituting the obtained calcium carbonate filler for biodegradable resin was measured as described above.

[0164] (Content of phosphorus element measured by inductively coupled plasma optical emission spectrometer) The content of phosphorus element measured by an inductively coupled plasma (ICP) optical emission spectrometer in the surface-treated calcium carbonate particles constituting the obtained calcium carbonate filler for biodegradable resin was measured as described above.

[0165] (Thermogravimetric loss at 200 - 500 °C) The thermogravimetric loss (mass %) at 200 - 500 °C measured by a differential thermal balance in the surface-treated calcium carbonate particles constituting the obtained calcium carbonate filler for biodegradable resin was measured as described above.

[0166] (Measurement of melt flow rate (MFR) of resin) The melt flow rate (MFR) of the resin was measured at 190 °C and a load of 2.16 kg using a melt indexer based on JIS K7210 (1999). The unit was g / 10 min.

[0167] (Compounding) First, for the examples and comparative examples, the raw materials with the compounding ratios shown in the table were kneaded at 170 °C, a screw rotation speed of 250 rpm, and an extrusion rate of 22 kg / h using a co-rotating twin-screw kneading extruder (D = 32 mmφ, L / D = 60, manufactured by Plastic Engineering Laboratory Co., Ltd.) equipped with a screen mesh (aperture: approximately 150 μm) near the exit of the extrusion, extruded into strands in water, cooled, and cut to produce pellets. The unit of the numerical values of the composition in the table is "mass %".

[0168] From the obtained pellets, a non-stretched multi-film with a thickness of 15 μm was obtained by extrusion from a T-die at 170 °C using a film extruder (Laboplastmill 2D30W2 type: manufactured by Toyo Seiki Co., Ltd.). A strength test was conducted using test pieces prepared from the obtained multi-film. The results obtained are shown in Table 1.

[0169] (Evaluation of biodegradable film) The obtained biodegradable film was evaluated for (1) tensile strength and elongation (TD direction: transverse direction, MD direction: extrusion direction), (2) biodegradability, and (3) film-forming properties by the following methods to evaluate whether it is suitable for use as an agricultural film. The results are shown in Table 1.

[0170] (1) Tensile strength and elongation in the TD direction and MD direction In accordance with JIS K6781, a tensile test of a test piece prepared with a film extruder was carried out at a temperature of 23 °C using a precision universal testing machine manufactured by Shimadzu Corporation. The stretching speed was 50 mm / min. From the obtained stress-strain curve, the tensile strength (unit: MPa) and elongation at break (unit: %) in the TD direction and MD direction were measured respectively.

[0171] Note that the higher the values of tensile strength and elongation at break, the better the tensile strength and elongation at break. Also, the evaluation criteria for tensile strength and elongation at break are as follows respectively.

[0172] (Evaluation criteria for tensile strength) A: The tensile strength was over 30 MPa. B: The tensile strength was 25 MPa or more and less than 30 MPa. C: The tensile strength was 20 MPa or more and less than 25 MPa. D: The tensile strength was less than 20 MPa.

[0173] (Evaluation criteria for elongation at break) A: The elongation at break was over 300%. B: The elongation at break was 250% or more and less than 300%. C: The elongation at break was 200% or more and less than 250%. D: The elongation at break was less than 200%.

[0174] (2) Biodegradability The biodegradability under compost conditions was measured by the following method.

[0175] First, a multi-film to be measured (size: 100 mm × 100 mm) was buried in soil (cultivated soil: leaf mold = 1:1) and left standing in accordance with the temperature and humidity conditions of JIS K6953. After a certain period of time had passed, the multi-film was taken out, and the area of the multi-film after decomposition for a certain period was calculated by performing image analysis. From these results, the film decomposition rate (%) was derived from the following formula.

[0176] Film decomposition rate (%) after decomposition for a certain period = { (area of the multi-film before the start of the test) - (area of the multi-film after decomposition for a certain period)} / (area of the multi-film before the start of the test) × 100

[0177] The obtained film decomposition rate was evaluated according to the following criteria. A: At the 2-month point after the start of the test, the film decomposition rate was 40% or more. B: At the 2-month point after the start of the test, the film decomposition rate was 30% or more and less than 40%. C: At the 2-month point after the start of the test, the film decomposition rate was 20% or more and less than 30%. D: At the 2-month point after the start of the test, the film decomposition rate was less than 20%.

[0178] (3) Film-forming property It was evaluated according to the following criteria. ○: It was possible to continuously form a film without problems. △: A film could be formed, but stability was difficult. ×: A film could not be formed.

[0179] (Material) The components used in the following Examples 1 to 20 and Comparative Examples 1 to 25 were as follows, respectively.

[0180] (Biodegradable resin) P1: Polybutylene adipate terephthalate TH801T manufactured by Miyako Chemical Co., Ltd., MFR: 5.0 g / 10 min, melting point: 120°C P2: Polybutylene succinate BioPBS FZ91 manufactured by PTTMCC Biochem, MFR: 5.0 g / 10 min, melting point: 115 °C P3: Luminy LX175 manufactured by Total Cabion, MFR: 3.0 g / 10 min, melting point: 155 °C P4: Polybutylene succinate adipate BioPBS FD92 manufactured by PTTMCC Biochem, MFR: 4.0 g / 10 min, melting point: 84 °C P5: 3-Hydroxybutyric acid-3-hydroxyhexanoic acid polycondensate PHBH BP330-05 manufactured by Choris Bluepha, MFR: 18.0 g / 10 min, melting point: 148 °C

[0181] (Calcium carbonate) Calcium carbonate 1: Super #2000 manufactured by Maruo Calcium Co., Ltd. (average particle size: 1.7 μm, specific surface area: 20,000 cm 2 / g, 45-μm sieve residue: 1 ppm or less, no surface treatment) Calcium carbonate 2: Super #2300 manufactured by Maruo Calcium Co., Ltd. (average particle size: 1.4 μm, specific surface area: 23,000 cm 2 / g, 45-μm sieve residue: 1 ppm or less, no surface treatment) Calcium carbonate 3: Caltex 5 manufactured by Maruo Calcium Co., Ltd. (average particle size: 1.0 μm, specific surface area: 32,000 cm 2 / g, 45-μm sieve residue: 1 ppm or less, no surface treatment) Calcium carbonate 4: Super S manufactured by Maruo Calcium Co., Ltd. (average particle size: 6.3 μm, specific surface area: 8,000 cm 2 / g, 45-μm sieve residue: 80 ppm, no surface treatment) Calcium carbonate 5: Super SSS manufactured by Maruo Calcium Co., Ltd. (average particle size: 4.0 μm, specific surface area: 13,000 cm 2 / g, 45-μm sieve residue: 10 ppm, no surface treatment) Calcium carbonate 6: Super 4S manufactured by Maruo Calcium Co., Ltd. (average particle size: 3.0 μm, specific surface area: 14,000 cm 2 / g, 45-μm sieve residue: 10 ppm, no surface treatment) Calcium carbonate 7: Super #1500 manufactured by Maruo Calcium Co., Ltd. (average particle size: 2.2 μm, specific surface area: 15,000 cm 2 / g, 45 μm sieve residue; 5 ppm, with surface treatment) Calcium carbonate 8: Calfine YM-23 manufactured by Maruo Calcium Co., Ltd. (average particle size: 0.6 μm, specific surface area 40,000 cm 2 / g, 45 μm sieve residue; 1 ppm or less, with surface treatment).

[0182] (Polyphosphate-based surface treatment agent) Polyphosphoric acid (Strong phosphoric acid manufactured by Rasa Industries Co., Ltd., chemical formula H (n+2) P n O (3n+1) , polyphosphoric acid, 116% in terms of phosphoric acid H3PO4, content as anhydrous phosphoric acid 84.2%)

[0183] (Other surface treatment agents) Orthophosphoric acid (75% phosphoric acid manufactured by Rasa Industries Co., Ltd.) Pyrophosphoric acid (Diphosphoric acid (phosphoric acid-containing) manufactured by Fujifilm Wako Pure Chemical Corporation; conversion amount as anhydrous phosphoric acid (P2O5) was 74.3% based on the total mass) Triethyl phosphate (Triethyl phosphate manufactured by Daihachi Chemical Industry Co., Ltd.) Fatty acid (Stearic acid-based fatty acid manufactured by Estochem Co., Ltd.) Silicone oil (Silicone oil manufactured by Dow Corning Toray Co., Ltd.)

[0184] (Compound products) M1: Biodegradable compound (Ecovio M2351 manufactured by BASF)

[0185] (Preparation of calcium carbonate filler for biodegradable resin) Example 1: Preparation of calcium carbonate filler (E1) for biodegradable resin Calcium carbonate 1 was used as the calcium carbonate particles. 1.0 part by mass of polyphosphoric acid and 0.5 part by mass of water were charged per 100 parts by mass of the calcium carbonate particles, and while mixing with a super mixer, the temperature was raised to 125 °C for surface treatment to produce a calcium carbonate filler (E1) for biodegradable resin. The physical property values of the obtained calcium carbonate filler (E1) for biodegradable resin are shown in Table 1.

[0186] Example 2: Preparation of Calcium Carbonate Filler (E2) for Biodegradable Resin Except for changing to use a mixture of calcium carbonate 1 and calcium carbonate 2 at a ratio of 1:1 (mass ratio) as the calcium carbonate particles with respect to the components for the preparation of the calcium carbonate filler (E1) for biodegradable resin, the calcium carbonate filler (E2) for biodegradable resin was prepared in the same manner as the preparation of the calcium carbonate filler (E1) for biodegradable resin. The physical property values of the obtained calcium carbonate filler (E2) for biodegradable resin are shown in Table 1.

[0187] Example 3: Preparation of Calcium Carbonate Filler (E3) for Biodegradable Resin Except for adding 0.2 part by mass of triethyl phosphate per 100 parts by mass of the calcium carbonate particles with respect to the components for the preparation of the calcium carbonate filler (E2) for biodegradable resin, the calcium carbonate filler (E3) for biodegradable resin was prepared in the same manner as the preparation of the calcium carbonate filler (E1) for biodegradable resin. The physical property values of the obtained calcium carbonate filler (E3) for biodegradable resin are shown in Table 1.

[0188] Example 4: Preparation of Calcium Carbonate Filler (E4) for Biodegradable Resin Except for adding 0.2 part by mass of fatty acid as a surface treatment agent per 100 parts by mass of the calcium carbonate particles and changing the addition amount of the solvent to 0.5 part by mass of water with respect to the components for the preparation of the calcium carbonate filler (E1) for biodegradable resin, the calcium carbonate filler (E4) for biodegradable resin was prepared in the same manner as the preparation of the calcium carbonate filler (E1) for biodegradable resin. The physical property values of the obtained calcium carbonate filler (E4) for biodegradable resin are shown in Table 1.

[0189] Example 5: Preparation of Calcium Carbonate Filler (E5) for Biodegradable Resin Calcium carbonate filler (E5) for biodegradable resin was prepared in the same manner as the preparation of calcium carbonate filler (E1) for biodegradable resin, except that 0.5 part by mass of silicone oil was further added as a surface treatment agent to 100 parts by mass of calcium carbonate particles. The physical property values of the obtained calcium carbonate filler (E5) for biodegradable resin are shown in Table 1.

[0190] Example 6: Preparation of Calcium Carbonate Filler (E6) for Biodegradable Resin Calcium carbonate filler (E6) for biodegradable resin was prepared in the same manner as the preparation of calcium carbonate filler (E1) for biodegradable resin, except that the calcium carbonate particles were changed to calcium carbonate 3. The physical property values of the obtained calcium carbonate filler (E6) for biodegradable resin are shown in Table 1.

[0191] Example 7: Preparation of Calcium Carbonate Filler (E7) for Biodegradable Resin Calcium carbonate filler (E7) for biodegradable resin was prepared in the same manner as the preparation of calcium carbonate filler (E1) for biodegradable resin, except that calcium carbonate 1 was used as the calcium carbonate particles and 2.0 parts by mass of polyphosphoric acid and 0.5 part by mass of water were charged as surface treatment agents to 100 parts by mass of the calcium carbonate particles. The physical property values of the obtained calcium carbonate filler (E7) for biodegradable resin are shown in Table 1.

[0192] Example 8: Preparation of Calcium Carbonate Filler (E8) for Biodegradable Resin For the components in the preparation of the calcium carbonate filler (E1) for biodegradable resin, calcium carbonate 1 was used as the calcium carbonate particles. Except that the amounts were changed to 1.0 part by mass of polyphosphoric acid, 0.3 part by mass of orthophosphoric acid, and 0.5 part by mass of water as the surface treatment agent per 100 parts by mass of the calcium carbonate particles, calcium carbonate (E8) for biodegradable resin was produced in the same manner as the preparation of the calcium carbonate filler (E1) for biodegradable resin. The physical property values of the obtained calcium carbonate filler (E8) for biodegradable resin are shown in Table 1.

[0193]

Table 1

[0194] (Preparation of surface-treated calcium carbonate) Comparative Example 1: Preparation of surface-treated calcium carbonate (C1) Calcium carbonate 5 was used as the calcium carbonate particles. Per 100 parts by mass of the calcium carbonate particles, 1.0 part by mass of polyphosphoric acid and 0.5 part by mass of water were charged as the surface treatment agent, and while mixing with a super mixer, the temperature was raised to 125 °C for surface treatment to produce surface-treated calcium carbonate (C1). The physical property values of the obtained surface-treated calcium carbonate (C1) are shown in Table 2.

[0195] Comparative Examples 2 to 9: Preparation of surface-treated calcium carbonates (C2) to (C9) As shown in Table 2, surface-treated calcium carbonates (C2) to (C9) were produced in the same manner as the preparation of surface-treated calcium carbonate (C1), except that the types and addition amounts of the calcium carbonate particles and the surface treatment agent were changed. The physical property values of the obtained surface-treated calcium carbonates (C2) to (C9) are shown in Table 2.

[0196]

Table 2

[0197] Example 9: Preparation and evaluation of biodegradable film The biodegradable resins P1 and P2 were used as resin components, and the calcium carbonate filler (1) for biodegradable resin was used as the inorganic substance powder. A biodegradable film with a thickness of 15 μm was produced through the above method at the compounding ratios shown in Table 3. Using test pieces obtained from the produced biodegradable film, evaluations were carried out on (1) tensile strength and elongation (TD direction and MD direction), (2) biodegradability, and (3) film-forming property. The obtained results are shown in Table 3. Note that the numerical values of each component in Table 3 are values in parts by mass.

[0198] Examples 10 to 20 and Comparative Examples 10 to 25: Production and Evaluation of Biodegradable Films Except that the types and amounts of each component in the biodegradable resin composition were changed as shown in Table 3, biodegradable films with a thickness of 15 μm were produced in the same manner as in Example 9, and evaluations were carried out on (1) tensile strength and elongation (TD direction and MD direction), (2) biodegradability, and (3) film-forming property. The obtained results are shown in Tables 3 and 4.

[0199] [Table 3]

[0200] [Table 4]

[0201] In addition, Fig. 1 shows the appearance of the films produced in Example 9 and Comparative Example 19 at the time when two months had passed since the start of the test.

[0202] As is clear from Tables 3 and 4, it can be seen that the biodegradable films produced in Examples 9 to 20 were superior in both moldability and biodegradability compared to the biodegradable films produced in Comparative Examples 10, 12, 13, 16 to 17, and 19 to 25.

[0203] Further, as shown in Fig. 1, when comparing the film of Example 9 prepared using the calcium carbonate filler (E1) for biodegradable resin added in Example 1 with the film of Comparative Example 19 added with unmodified calcium carbonate, the biodegradation of the film of Example 9 had progressed more. This tendency could also be confirmed from the biodegradability evaluation results in other Examples and Comparative Examples.

[0204] On the other hand, in the film of Comparative Example 10 blended with surface-treated calcium carbonate (C1) having a large average particle size (d50), film formation was unstable, and both the strength and elongation of the film decreased. Also, the biodegradability was insufficient.

[0205] In the film of Comparative Example 11 blended with surface-treated calcium carbonate (C2) having a small average particle size (d50), due to the small average particle size (d50), aggregates due to poor dispersion occurred, clogging of the screen mesh of the kneader occurred, and film formation could not be carried out.

[0206] In the film of Comparative Example 12 blended with surface-treated calcium carbonate (C3) having a small specific surface area, the strength and elongation of the film decreased, and the biodegradability was insufficient.

[0207] In the film of Comparative Example 13 blended with surface-treated calcium carbonate (C4) having a large 45 μm sieve residue, film formation was unstable and the strength and elongation of the film decreased, and the biodegradability was insufficient.

[0208] In the films of Comparative Examples 14 and 15 blended with surface-treated calcium carbonates (C5) and (C6) treated with orthophosphoric acid instead of polyphosphoric acid, respectively, aggregates due to poor dispersion occurred, clogging of the screen mesh of the kneader occurred, and film formation could not be carried out.

[0209] In the film of Comparative Example 16 blended with surface-treated calcium carbonate (C7) treated with polyphosphoric acid but having a low phosphorus content, the elongation in the MD direction of the film decreased, and the biodegradability was insufficient.

[0210] In the film of Comparative Example 17 containing surface-treated calcium carbonate (C8) treated with a fatty acid instead of polyphosphoric acid, the biodegradability was insufficient.

[0211] In the film of Comparative Example 18 containing surface-treated calcium carbonate (C9) treated with pyrophosphoric acid instead of polyphosphoric acid, aggregates due to poor dispersion occurred, clogging of the screen mesh of the kneader occurred, and film formation could not be performed.

[0212] In the films of Comparative Examples 19 and 20 containing unmodified calcium carbonate in the inorganic substance powder, either the strength or the elongation of the film decreased, and the biodegradability was insufficient.

[0213] In the films of Examples 17 and 18 containing PLA as the biodegradable resin, since PLA itself has a slower biodegradability than PBAT and PBS, the biodegradability evaluation was lower than that of the films of Examples 9 to 16. However, when compared with the films of Comparative Examples 21 and 22 using unmodified calcium carbonate 1 as calcium carbonate without changing the component ratio of the biodegradable resin, it can be seen that Examples 17 and 18 containing the calcium carbonate filler for biodegradable resin had better biodegradability.

[0214] In the film of Comparative Example 23 using a commercially available biodegradable compound product (M1), the elongation in the MD direction decreased, and the biodegradability was insufficient.

[0215] In the films of Examples 19 and 20 containing PBSA and PHBH as the biodegradable resin, the biodegradability was better than that of the films of Comparative Examples 24 and 25 containing unmodified calcium carbonate 1.

Industrial Applicability

[0216] According to the present invention, for example, it is useful in the fields of resin molding, construction and housing, paints, and a wide range of technical fields related thereto.

Claims

1. A surface treatment agent containing a polyphosphoric acid-based surface treatment agent component, wherein the polyphosphoric acid surface treatment agent component contains at least one polyphosphoric acid, and the equivalent amount of metaphosphoric acid (P ２ O ５ ), based on the mass of the polyphosphoric acid, is 75% by mass or more and less than 100% by mass, and is surface-treated with the surface treatment agent, and contains surface-treated calcium carbonate particles that satisfy the following formulas (1) to (6): Calcium carbonate filler for biodegradable resin (1) 0.8 ≤ A ≤ 3.0 (μm) (2) 13,000 ≤ B ≤ 30,000 (cm ２ / g) (3) C ≤ 100 (ppm) (4) 4.0 ≤ D ≤ 8.5 (5) 800 ≤ E ≤ 5000 (ppm) (6) 0.1 ≤ Tw ≤ 0.8 (mass%) A is the average particle diameter (d50) of 50% of the surface-treated calcium carbonate particles measured by a Microtrac MT3300 laser particle size distribution analyzer, B is the specific surface area by the air permeability method, C is the residue on a 45 μm sieve of a JIS standard sieve, D is the pH when made into a 10 mass% water suspension, E is the phosphorus element content measured by an inductively coupled plasma (ICP) optical emission spectrometer, Tw is the thermal weight loss from 200 to 500 °C measured by a differential thermal balance device.

2. The calcium carbonate filler for biodegradable resin according to claim 1, wherein the polyphosphoric acid-based surface treatment agent component contains at least one selected from the group consisting of polyphosphoric acid, which is an oxo acid of a polymer composed of tetrahedral phosphoric acid structural units, a salt of the polyphosphoric acid, and an ester of the polyphosphoric acid.

3. A biodegradable resin composition containing a biodegradable resin and the calcium carbonate filler for biodegradable resin according to claims 1 to 2.

4. The biodegradable resin composition according to claim 3, wherein the mass ratio of the biodegradable resin to the calcium carbonate filler for biodegradable resin is from 97:3 to 60:

40.

5. The biodegradable resin composition according to claim 3, wherein the biodegradable resin is at least one resin selected from the group consisting of polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH).

6. A resin molded article containing the biodegradable resin composition according to any one of claims 3 to 5.

7. The resin molded article according to claim 6, having the form of a film.

8. The resin molded article according to claim 6, having any one of the forms of an agricultural multifilm, a seedling raising pot, a sheet for preventing damage by animals or pests, a packaging film, or a tape for fixing seedlings, branches, or fruits.

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