Manufacturing method for blow-molded containers

Abstract

To provide a producing method of a blow molding container made of an olefin resin, having suppressed generation of carbon dioxide during incineration, having a smooth inner surface and being excellent in cleanliness.SOLUTION: The present invention provides the producing method of the blow molding container, in which olefin resin particles with a diameter of 1 to 10 mm are produced by melt-extruding, crushing or cutting a resin composition comprising an olefin-based resin of 100 pts.wt., and liposome of 1 to 10 pts.wt. formed by a supercritical reverse phase evaporation method from an additive composition consisting of 93 to 97% wt.% of phospholipid and 7 to 3 wt.% of an additive consisting of approximately the same amount of a carbon dioxide absorber and a crystal nucleating agent of the olefin resin, and subsequently, a carbon dioxide emission reducing resin composition consisting of 100 pts.wt. of the olefin-based resin and 1 to 10 pts.wt. of the obtained olefin-based resin particle are melt-kneaded and then subjected to blow-molding.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a blow container that has a small amount of carbon dioxide emissions even when incinerated.

Background Art

[0002] Conventionally, olefin-based resins have characteristics such as being lightweight, having excellent corrosion resistance, water resistance, hygiene, gas barrier properties, transparency, etc., having high mechanical strength and being easy to manufacture, and are used in a wide range of applications. However, due to their large-scale use, many problems have occurred during disposal. In particular, when burned for disposal, a large amount of carbon dioxide is emitted, contributing to global warming.

[0003] As a method for suppressing the generation of carbon dioxide during incineration, it has been proposed to add calcium carbonate, aluminosilicate, calcium hydroxide, zeolite, coconut mesocarp fiber, etc. to an olefin-based resin molded body (see, for example, Patent Documents 1, 2 or 3).

[0004] However, even when these additives are added to an olefin-based resin molded body, the effect of suppressing the generation of carbon dioxide is small. When added in a large amount to improve the suppression effect, there are drawbacks such as a decrease in moldability and a decrease in the surface properties of the molded body (see, for example, Patent Document 1).

[0005] To overcome the above drawbacks, suppress carbon dioxide generation during incineration, and provide a resin composition with excellent moldability, for example, a method for producing a carbon dioxide emission-reducing resin composition has been proposed, characterized by adding liposomes formed by a supercritical reverse-phase evaporation method to a polyolefin resin so as to contain a carbon dioxide absorbent and a polyolefin resin nucleating agent, wherein the liposomes are formed by the supercritical reverse-phase evaporation method with a total additive nucleating agent consisting of the carbon dioxide absorbent and the polyolefin resin nucleating agent in equal weights relative to the phospholipid, at an amount of 3 to 7%, and the supercritical reverse-phase evaporation method is characterized by a process in which a mixture of the carbon dioxide absorbent, the nucleating agent and ion-exchanged water is stirred and mixed with carbon dioxide in a supercritical state at a critical temperature of 30.98°C or higher and a critical pressure of 7.3773 MPa or higher, thereby containing the carbon dioxide absorbent and the nucleating agent within the liposomes. (See, for example, Patent Document 4.)

[0006] Although the dispersibility of liposomes in the above resin composition is superior to that of additives described in Patent Documents 1, 2, or 3, it was insufficient for manufacturing containers, particularly those with smooth inner surfaces and excellent cleanliness, which are produced by blow molding. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2008-106171 [Patent Document 2] Japanese Unexamined Patent Publication No. 7-188487 [Patent Document 3] Japanese Patent Publication No. 2006-77058 [Patent Document 4] Patent No. 6060451 [Overview of the project] [Problems that the invention aims to solve]

[0008] In view of the above problems, the object of the present invention is to provide a method for manufacturing a blow-molded container made of an olefin resin, which suppresses the generation of carbon dioxide during incineration, has a smooth inner surface, and is excellent in cleanliness. [Means for solving the problem]

[0009] In other words, the present invention is [1] A method for manufacturing a blow-molded container, characterized by melt-extruding, crushing or cutting a resin composition comprising 100 parts by weight of an olefin resin, 7 to 3 parts by weight of an additive composition comprising 93 to 97% by weight of phospholipid and approximately the same weight of a carbon dioxide absorbent and a crystal nucleating agent for the olefin resin, using a supercritical reverse-phase evaporation method to form liposomes of 1 to 10 parts by weight, and then melt-kneading a carbon dioxide emission reduction resin composition comprising 100 parts by weight of the olefin resin and 1 to 10 parts by weight of the obtained olefin resin particles, followed by blow molding, and [2] A method for manufacturing a blow-molded multilayer container having at least an inner layer and an outer layer, characterized in that the inner layer is an olefin resin, and the outer layer is a resin composition comprising 100 parts by weight of an olefin resin, 100 parts by weight of an olefin resin, and 1 to 10 parts by weight of liposomes formed by supercritical reverse-phase evaporation of an additive composition comprising 93 to 97% by weight of phospholipid and approximately the same weight of a carbon dioxide absorbent and an additive comprising a crystal nucleating agent for the olefin resin, melt-extruded, crushed or cut to obtain a carbon dioxide emission reduction resin composition comprising 1 to 10 parts by weight of olefin resin particles with a diameter of 1 to 10 mm, then co-extruded and blow-molded. Regarding. [Effects of the Invention]

[0010] The method for manufacturing the blown container of the present invention is as described above, is easy to manufacture, and the resulting blown container is made of an olefin resin, suppresses the generation of carbon dioxide during incineration, has a smooth inner surface, and is excellent in cleanliness. [Modes for carrying out the invention]

[0011] The present invention provides a method for manufacturing a blow-molded container, characterized by melt-extruding, crushing, or cutting a resin composition comprising 100 parts by weight of an olefin resin and 1 to 10 parts by weight of liposomes formed by supercritical reverse-phase evaporation of an additive composition comprising 93 to 97% by weight of phospholipid, approximately the same weight of a carbon dioxide absorbent, and an additive comprising a crystal nucleating agent for the olefin resin; producing olefin resin particles with a diameter of 1 to 10 mm; and then melt-kneading a carbon dioxide emission reduction resin composition comprising 100 parts by weight of the olefin resin and 1 to 10 parts by weight of the obtained olefin resin particles, followed by blow molding.

[0012] Examples of the olefin resins mentioned above include high-density polyethylene resin, medium-density polyethylene resin, low-density polyethylene resin, linear low-density polyethylene resin, polypropylene resin, ethylene-propylene copolymer, ethylene-1-butene copolymer, ethylene-1-pentene copolymer, ethylene-1-hexene copolymer, and ethylene-vinyl acetate copolymer. Depending on the desired physical properties, two or more types may be blended. Low-density polyethylene resin and linear low-density polyethylene resin are preferred when obtaining a highly flexible container, and high-density polyethylene resin and polypropylene resin are preferred when obtaining a container with high mechanical strength.

[0013] Furthermore, the above-mentioned olefin resin may contain, as needed, additives that have been commonly used in the molding of olefin resins, such as heat stabilizers, heat resistance improvers, light stabilizers, ultraviolet absorbers, antioxidants, impact modifiers, anti-fogging agents, antistatic agents, flame retardants, colorants, and pigments.

[0014] The above liposomes are formed by supercritical reverse-phase evaporation, consisting of an additive composition comprising 93-97% by weight of phospholipids and 7-3% by weight of an additive comprising approximately the same weight of a carbon dioxide absorbent and a crystal nucleating agent of the olefin resin.

[0015] The above-mentioned phospholipids are capsule membrane components in liposomes and can encapsulate carbon dioxide absorbents and olefin resin crystal nucleating agents. However, when mixed with olefin resin powder or pellets and heated and stirred, they disintegrate and act as dispersants. Examples include glycerophospholipids such as phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidic acid, phosphatidylglycerol, phosphatidylinositol, cardiopine, egg yolk lecithin, hydrogenated egg yolk lecithin, soy lecithin, and hydrogenated soy lecithin, as well as sphingophospholipids such as sphingomyelin, ceramide phosphorylethanolamine, and ceramide phosphorylglycerol.

[0016] The carbon dioxide absorbent described above can be any substance that chemically or physically adsorbs carbon dioxide, and examples include metal hydroxides such as lithium hydroxide, sodium hydroxide, magnesium hydroxide, calcium hydroxide, and barium hydroxide; metal oxides such as magnesium oxide, calcium oxide, and zinc oxide; amorphous aluminosilicates, natural zeolites, synthetic zeolites, and other aluminosilicates; titanate compounds such as barium titanate and barium orthotitanate; lithium silicate, silica gel, alumina, and activated carbon.

[0017] Crystallization nucleating agents for olefin resins are substances dispersed in the olefin resin that form nuclei for the crystals of the olefin resin, or substances that crystallize at or above the crystallization temperature or melting point of the olefin resin, and whose crystals form nuclei for the crystals of the olefin resin. Examples include phosphate ester metal salts such as sodium 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate, aluminum hydroxybis[2,2-methylenebis(4,6-di-t-butylphenyl) phosphate], and sodium bis(4-t-butylphenyl) phosphate; sorbitol-based substances such as dibenzylidene sorbitol, bis(4-methylbenzylidene) sorbitol, and bis(3,4-dimethylbenzylidene) sorbitol; and aluminum benzoate-based substances such as hydroxydi-t-butylbenzoate aluminum.

[0018] The liposome is composed of an additive composition comprising a phospholipid, a carbon dioxide absorbent, and a crystal nucleating agent for the olefin resin, and is formed by the supercritical reverse phase evaporation method. The supercritical reverse phase evaporation method may be the conventionally known supercritical reverse phase evaporation method. For example, a mixture of the carbon dioxide absorbent, the crystal nucleating agent, and ion-exchanged water is stirred and mixed with carbon dioxide in a supercritical state where the temperature is 30.98 °C or higher and the pressure is 7.3773 MPa or higher, and the carbon dioxide absorbent and the crystal nucleating agent are encapsulated in the phospholipid which is a capsule membrane component, thereby forming a liposome.

[0019] Incidentally, the supercritical reverse phase evaporation method is disclosed in Reissue Patent Publication No. 02 / 032564, JP-A-2003-119120, JP-A-2005-298407, JP-A-2008-063284, etc.

[0020] When the addition amounts of the carbon dioxide absorbent and the crystal nucleating agent for the olefin resin are reduced, the dispersion effect disappears. When they are increased, the particle size of the liposome becomes large and the dispersion effect decreases. Also, the ratio of the addition amounts of the carbon dioxide absorbent and the crystal nucleating agent for the olefin resin is most effective when they are the same, and the effect decreases when one ratio increases. Therefore, the liposome is formed by the supercritical reverse phase evaporation method from an additive composition comprising 93 to 97% by weight of phospholipid and 7 to 3% by weight of an additive comprising a carbon dioxide absorbent and a crystal nucleating agent for the olefin resin having substantially the same weight.

[0021] Incidentally, since the particle size of the liposome is preferably uniformly dispersed in the olefin resin, it is preferably small. However, since it is formed by the supercritical reverse phase evaporation method, generally, it is 100 to 300 nm.

[0022] The method for manufacturing the blow container of the present invention first melt-extrudes a resin composition comprising 100 parts by weight of an olefin resin and 1 to 10 parts by weight of a liposome, and pulverizes or cuts it to produce olefin resin particles having a diameter of 1 to 10 mm.

[0023] By melt-extruding a resin composition consisting of an olefin resin and liposomes, the olefin resin is melted and stirred to uniformly disperse the liposomes within the olefin resin. This stirring ensures that the liposomes are uniformly dispersed within the olefin resin. Subsequently, the phospholipids that form the capsule membrane of the liposomes break down, exposing and dispersing the encapsulated carbon dioxide absorbent and the crystal nucleating agent of the olefin resin. This prevents the poorly compatible carbon dioxide absorbent and the crystal nucleating agent of the polyolefin resin from agglomerating, resulting in uniform dispersion within the olefin resin particles.

[0024] If the amount of liposomes added to the olefin resin particles is too small, the amount of liposomes contained in the blow-molded container when it is manufactured will be small, reducing its effectiveness in suppressing carbon dioxide generation during incineration. Conversely, if the amount is too large, the carbon dioxide absorbent and the crystal nucleating agent of the olefin resin will be exposed on the surface of the manufactured blow-molded container, reducing its smoothness and cleanliness. Therefore, 1 to 10 parts by weight of liposomes are added per 100 parts by weight of olefin resin.

[0025] Since the above olefin resin particles will be blow-molded in the next step, after melt-extrusion they are crushed or cut to process them into olefin resin particles with a diameter of 1 to 10 mm that are suitable for blow molding.

[0026] The present invention provides a method for manufacturing a blow-molded container, which involves first producing a carbon dioxide emission reduction resin composition consisting of 100 parts by weight of an olefin resin and 1 to 10 parts by weight of the obtained olefin resin particles, then melt-kneading the obtained carbon dioxide emission reduction resin composition, and finally blow-molding it to produce a blow-molded container.

[0027] If the amount of olefin resin particles added is too small, the amount of liposomes contained in the blow-molded container will decrease when the container is manufactured, reducing its effect in suppressing carbon dioxide generation during incineration. Conversely, if the amount is too large, the carbon dioxide absorbent and the crystalline nucleating agent of the olefin resin will bleed onto the surface of the manufactured blow-molded container, reducing its smoothness and cleanliness. Therefore, 1 to 10 parts by weight of olefin resin are added per 100 parts by weight, preferably 2 to 5 parts by weight.

[0028] Since the above carbon dioxide emission reduction resin composition is blow-molded to manufacture the blow-molded container, it is preferable that the olefin resin constituting the carbon dioxide emission reduction resin composition and the olefin resin constituting the olefin resin particles are made of the same type of olefin resin.

[0029] Furthermore, when producing olefin resin particles by melt-extruding a resin composition consisting of olefin resin and liposomes, the liposomes are uniformly dispersed within the olefin resin constituting the olefin resin particles. Subsequently, the phospholipids, which are the capsule membrane components of the liposomes, break down, exposing and dispersing the encapsulated carbon dioxide absorbent and the nucleating agent of the olefin resin. As a result, the poorly compatible carbon dioxide absorbent and the nucleating agent of the polyolefin resin do not aggregate and are uniformly dispersed within the olefin resin constituting the olefin resin particles. Moreover, when this carbon dioxide emission reduction resin composition consisting of olefin resin particles and olefin resin is melt-kneaded and blow-molded, the carbon dioxide absorbent and the nucleating agent of the olefin resin dispersed within the olefin resin particles are again dispersed within the olefin resin constituting the blow-molded container. Therefore, in the manufactured blow-molded container, the carbon dioxide absorbent and the nucleating agent of the olefin resin are more uniformly dispersed within the olefin resin constituting the blow-molded container, suppressing the generation of carbon dioxide during incineration, and exhibiting excellent surface smoothness and mechanical strength.

[0030] Therefore, in order to further improve the dispersibility of the carbon dioxide absorbent and the nucleating agent of the olefin resin, it is preferable that the melt flow rate (MFR) of the olefin resin constituting the olefin resin particles is greater than the melt flow rate (MFR) of the olefin resin constituting the carbon dioxide emission reduction resin composition.

[0031] Blow molding may employ conventionally known blow molding methods, such as supplying a carbon dioxide emission reduction resin composition consisting of an olefin resin and olefin resin particles to an extruder, melting it, extruding it, and then lowering a parison made of the molten carbon dioxide emission reduction resin composition. The parison is then pressurized in a molding die while gas is injected into it to form the parison.

[0032] If the melt viscosity of the parison is low, or if the parison is large and heavy, the parison will break under its own weight, making blow molding impossible. Therefore, when molding large blow-molded containers, a low MFR of the olefin resin is preferable, preferably between 0.01 and 4.0 (g / 10 min). MFR is an index representing the melt viscosity of thermoplastic resins as defined in JIS K 7210.

[0033] By molding using the blow molding method, blow-molded containers have excellent mechanical strength and can be easily manufactured in various capacities, from small quantities to large capacities of over 200 liters. Furthermore, not only single-layer but also multi-layer molded products with two or more layers can be easily manufactured.

[0034] The present invention relates to a method for manufacturing a multilayer blow-molded container having at least an inner layer and an outer layer, characterized in that the inner layer is an olefin resin, and the outer layer is a resin composition consisting of 100 parts by weight of an olefin resin, 100 parts by weight of an olefin resin, and 1 to 10 parts by weight of liposomes formed by supercritical reverse-phase evaporation of an additive composition consisting of 93 to 97% by weight of phospholipid and approximately the same weight of a carbon dioxide absorbent and an additive of the olefin resin, melt-extruded, crushed or cut to obtain a carbon dioxide emission reduction resin composition consisting of 1 to 10 parts by weight of olefin resin particles with a diameter of 1 to 10 mm, which is then melt-kneaded, co-extruded, and blow-molded.

[0035] The above-described method for manufacturing a multilayer blow-molded container is a method for manufacturing a multilayer blow-molded container having at least an inner layer and an outer layer. A multilayer blow-molded container is a two-layer blow-molded container having an inner layer and an outer layer, and a blow-molded container having at least an inner layer and an outer layer with one or more intermediate layers made of olefin resin in between.

[0036] The inner layer described above is made of an olefin resin, but in order to further improve cleanliness, it is preferable that it does not contain components that can be eluted from the olefin resin or additives that can be separated or detached, and is preferable that it is made only of the olefin resin.

[0037] The outer layer described above is the same as that of the blow-molded container in the manufacturing method of the blow-molded container. Specifically, a multilayer blow-molded container is manufactured by melt-kneading a resin composition consisting of an olefin resin as the inner layer, and 1 to 10 parts by weight of olefin resin particles with a diameter of 1 to 10 mm obtained by melt-extruding, crushing, or cutting an additive composition consisting of 100 parts by weight of olefin resin, 100 parts by weight of olefin resin, and 7 to 3 parts by weight of an additive composition consisting of 93 to 97% by weight of phospholipid and approximately the same weight of carbon dioxide absorbent and a crystal nucleating agent for the olefin resin, as the outer layer, followed by co-extrusion and blow molding.

[0038] Next, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

[0039] Liposome Manufacturing 0.125 parts by weight of sodium aluminosilicate powder with an average particle size of 10-50 nm, 0.125 parts by weight of sodium 2,2'-methylene-bis-(4,6-di-t-butylphenyl) phosphate powder with an average particle size of 10-50 nm, and 5 parts by weight of phosphatidylcholine, a phospholipid, were placed together with 100 parts by weight of deionized water in a high-pressure stainless steel container maintained at 60°C and sealed. Carbon dioxide was injected to bring the pressure to 20 MPa to a supercritical state, and after stirring and mixing for 15 minutes while maintaining the temperature and pressure, the carbon dioxide was released and the pressure was returned to atmospheric pressure to perform supercritical treatment, obtaining an aqueous dispersion containing liposomes in which sodium aluminosilicate and sodium 2,2'-methylene-bis-(4,6-di-t-butylphenyl) phosphate are encapsulated in the phospholipid.

[0040] Furthermore, supercritical carbon dioxide refers to carbon dioxide in a supercritical state above the critical temperature (30.98°C) and critical pressure (7.3773±0.0030 MPa), while carbon dioxide under temperature or pressure conditions above the critical point refers to carbon dioxide under conditions where only the critical temperature or only the critical pressure exceeds the critical condition (provided that the other condition does not exceed the critical condition).

[0041] The obtained liposomes were obtained by removing deionized water from the aqueous dispersion containing the obtained liposomes. The average particle size of the obtained liposomes was measured using a particle size analyzer (NICOMP 380ZLS, Particle Sizing Systems Co.) and was found to be approximately 200 nm.

[0042] Manufacturing of olefin-based resin particles High-density polyethylene resin (blow grade, MFR=0.30, density=0.949g / cm³) 3A composition consisting of 95 parts by weight of the obtained liposome and 5 parts by weight of the obtained liposome was supplied to a uni-screw compounding extruder with a screw diameter of 70 mm and melt-mixed and extruded at 210°C to produce a 3 mm diameter filament, which was then cut into 5 mm lengths to obtain olefin resin particles with a thickness of 3 mm and a length of 5 mm.

[0043] (Examples 1 and 2, Comparative Example 1) High-density polyethylene resin (blow grade, MFR=0.03, density=0.954g / cm³) 3 A carbon dioxide emission reduction resin composition consisting of 100 parts by weight of ), 2.5 parts by weight of inorganic pigment, and 2 parts by weight (Example 1), 4 parts by weight (Example 2), and 0 parts by weight (Comparative Example 1) of the obtained olefin resin particles was supplied to a single-screw compounding extruder with a screw diameter of 70 mm, and a parison was formed by melt-mixing and extrusion at 210°C. Next, the parison was blow-molded in a mold to obtain a bottomed cylindrical container with a capacity of 20 liters, which had no bumps on the surface and was smooth both inside and out.

[0044] The carbon dioxide emissions from the obtained bottomed cylindrical containers were measured, and the carbon dioxide emission reduction rate was calculated to be 40.3% in Example 1 and 70.0% in Example 2. Furthermore, the measurement of the carbon dioxide emission reduction rate is as follows:

[0045] Measuring the rate of reduction in carbon dioxide emissions The side walls of the obtained bottomed cylindrical containers were cut to a size of 1.5 cm x 5 cm and supplied to an annular furnace combustion measuring instrument (Shimadzu Corporation, CGT7100) according to JIS K7127 (annular furnace combustion method). Combustion was performed at 400°C and the amount of carbon dioxide emissions was measured. The carbon dioxide emission reduction rate is shown as a percentage, with the carbon dioxide emissions of Comparative Example 1 set to 100%.

[0046] (Examples 3 and 4, Comparative Example 2) As the resin composition for the inner layer, high-density polyethylene resin (blow grade, MFR=0.0 3, density=0.954g / cm 3), as the outer layer resin composition, high-density polyethylene resin (blow grade, MFR=0.03, density=0.954g / cm³) 3 A carbon dioxide emission reduction resin composition consisting of 100 parts by weight of the obtained olefin resin particles and 2 parts by weight (Example 3), 4 parts by weight (Example 4), and 0 parts by weight (Comparative Example 2) was supplied to a single-screw compounding extruder with a screw diameter of 110 mm, melt-kneaded at 210°C, and co-extruded to form a parison. Next, the parison was blow-molded in a mold to obtain a bottomed cylindrical container with a capacity of 200 liters, which had no bumps on the surface and was smooth both inside and out.

[0047] The carbon dioxide emissions from the obtained bottomed cylindrical containers were measured in the same manner as in Example 1, and the carbon dioxide emission reduction rate was calculated. If the carbon dioxide emissions of Comparative Example 2 are set to 100%, then the reduction rate in Example 3 was 20%, and in Example 4 it was 35%. [Industrial applicability]

[0048] The blow-molded containers of the present invention are easy to manufacture and can be produced in large capacities. Furthermore, since the blow-molded containers are made of olefin resin, carbon dioxide generation is suppressed during incineration, resulting in a low environmental impact. In addition, the surface of the blow-molded containers is smooth and has excellent cleanliness, and in particular, the inner surface of multi-layered blow-molded containers is smooth, resulting in less foreign matter that leaches out or peels off from the blow-molded container and thus excellent cleanliness. Therefore, the blow-molded containers of the present invention are suitable for use as containers that are incinerated after use. They are also suitable for use as containers where it is required that foreign matter such as chemicals and photoresists not be mixed in or leached out, and as photomask containers for storing and transporting photomask substrates.

Claims

[Claim 1] A method for manufacturing a blow-molded multilayer container having at least an inner layer and an outer layer, wherein the inner layer consists only of an olefin resin, and the outer layer consists of a resin composition comprising 100 parts by weight of olefin resin A, 100 parts by weight of olefin resin B, and 1 to 5 parts by weight of liposomes formed by supercritical reverse-phase evaporation of an additive composition comprising 93 to 97% by weight of phospholipid and approximately the same weight of a carbon dioxide absorbent and a crystal nucleating agent for the olefin resin, the carbon dioxide emission reduction resin composition comprising 2 to 4 parts by weight of olefin resin particles with a diameter of 1 to 10 mm obtained by melt-extrusion, pulverization, or cutting, and then co-extrude and blow-molding, wherein the melt flow rate (MFR) of olefin resin B is greater than the melt flow rate (MFR) of olefin resin A.