Cleaning resin composition and method for cleaning resin molding machine

Abstract

Provided is a cleaning resin composition that is used for cleaning a resin composition to be subjected to molding processing in a relatively low temperature range and that has good cleaning performance. This cleaning resin composition comprises: a thermoplastic resin including an olefin-based resin; an inorganic powder that contains calcium carbonate having a mean particle diameter of 0.7-6.0 µm as measured by an air permeation method in accordance with JIS M8511:2014; a sulfate ester-based surfactant; and a hydrogenated petroleum resin. The mass ratio of the thermoplastic resin and the inorganic powder is 50:50 to 10:90, the amount of the sulfate ester-based surfactant is 0.2-5.0 mass%, and the amount of the hydrogenated petroleum resin is 0.5-3.0 mass%.

Description

Resin composition for cleaning, and method for cleaning a resin molding machine.

[0001] The present invention relates to a cleaning resin composition for cleaning a resin molding machine, and a method for cleaning a resin molding machine using the same.

[0002] Conventionally, many products have been manufactured by molding various resin compositions using resin molding machines (hereinafter also simply referred to as "processing machines"). When changing the type of resin composition used for molding, it is necessary to clean the inside of the processing machine. Furthermore, when using a processing machine for a long period of time, it is preferable to perform periodic cleaning even when manufacturing products with the same resin composition. If previously used resin composition remains inside the processing machine, the residual components will turn into carbonized material (burnt residue), which may be mixed into subsequent products. In addition, residual components may cause defects in the appearance or performance of subsequent products. However, it is not efficient to disassemble the processing machine and clean all the parts. Therefore, it is common practice to clean the processing machine by supplying a cleaning resin composition to the machine and allowing it to flow within the machine.

[0003] The above-mentioned cleaning resin composition generally contains a resin and, if necessary, a filler. The type of resin in the cleaning resin composition is appropriately selected according to the processing temperature of the resin composition to be cleaned, the type of resin contained in the composition to be cleaned, etc. Conventionally, many cleaning resin compositions have been developed for cleaning targets that are processed at relatively high temperatures, such as polycarbonates and engineering plastics. In contrast, there have been very few options for cleaning resin compositions for cleaning targets that are processed at relatively low temperatures, such as olefin resins. For example, Patent Document 1 describes a cleaning resin composition for low temperature ranges, and it is stated that the cleaning resin composition contains an olefin resin.

[0004] International Publication No. 2007 / 116920

[0005] However, conventional cleaning resin compositions for low-temperature ranges often lacked sufficient cleaning performance. Therefore, the present invention aims to provide a cleaning resin composition for cleaning resin compositions that are molded in a relatively low-temperature range, which has good cleaning performance, and a method for cleaning a resin molding machine using the same.

[0006] In response to the above-mentioned problems, the present inventors diligently investigated and found that a cleaning resin composition containing a thermoplastic resin including an olefin-based resin and an inorganic powder containing calcium carbonate having a predetermined average particle size in a predetermined ratio, and further containing predetermined amounts of a sulfate ester-based surfactant and a hydrogenated petroleum resin, provides excellent cleaning performance.

[0007] The present invention provides the following cleaning resin compositions: [1] A cleaning resin composition comprising a thermoplastic resin containing an olefin resin, an inorganic powder containing calcium carbonate with an average particle size of 0.7 μm or more and 6.0 μm or less as measured by the air permeation method in accordance with JIS M8511:2014, a sulfate ester surfactant, and a hydrogenated petroleum resin, wherein the mass ratio of the thermoplastic resin to the inorganic powder is 50:50 to 10:90, the amount of the sulfate ester surfactant is 0.2% by mass or more and 5.0% by mass or less, and the amount of the hydrogenated petroleum resin is 0.5% by mass or more and 3.0% by mass or less. [2] The cleaning resin composition according to [1], wherein the olefin resin is linear low-density polyethylene. [3] The cleaning resin composition according to [2], wherein the linear low-density polyethylene has a melt mass flow rate of 0.5 g / 10 min or more and 4.0 g / 10 min or less at 190°C and a 2.16 kg load, as measured in accordance with JIS K7210-1:2014. [4] The cleaning resin composition according to any one of [1] to [3], wherein the calcium carbonate is heavy calcium carbonate. [5] The cleaning resin composition according to any one of [1] to [4], wherein the sulfate ester surfactant is alkyl sulfate. [6] The cleaning resin composition according to any one of [1] to [5], wherein the softening point of the hydrogenated petroleum resin according to JIS K2207:1996 is 80°C or more and 100°C or less. [7] The cleaning resin composition according to any one of [1] to [6], further comprising a metal soap, wherein the amount of the metal soap is 0.5% by mass or more and 5.0% by mass or less. [8] The cleaning resin composition according to [7], wherein the metal soap is magnesium 12-hydroxystearate.

[0008] The present invention provides the following method for cleaning a resin molding machine: [9] A method for cleaning a resin molding machine, comprising the steps of: cleaning the resin molding machine using a cleaning resin composition described in any of [1] to [8] above; recovering the cleaning resin composition from the resin molding machine and crushing it; and cleaning the resin molding machine again using the crushed cleaning resin composition.

[0009] The present invention provides a cleaning resin composition for cleaning resin compositions that are molded in a relatively low temperature range, which has good cleaning performance, and a method for cleaning a resin molding machine using the same.

[0010] One embodiment of the present invention will be described in detail below. However, the present invention is not limited to this embodiment. Furthermore, in this specification, a numerical range represented by "~" means a range that includes the numbers written before and after "~" as the lower limit and upper limit.

[0011] 1. Cleaning Resin Composition A cleaning resin composition according to one embodiment of the present invention (hereinafter also referred to as the "cleaning composition") is mainly used to clean resin compositions that are molded in a relatively low temperature range. The cleaning composition comprises a thermoplastic resin containing an olefin resin, an inorganic powder containing calcium carbonate having a specific average particle size, a sulfate ester surfactant, and a hydrogenated petroleum resin. The mass ratio of the thermoplastic resin to the inorganic powder is 50:50 to 10:90, the amount of the sulfate ester surfactant is 0.2% by mass or more and 5.0% by mass or less, and the amount of hydrogenated petroleum resin is 0.5% by mass or more and 3.0% by mass or less. As described above, the cleaning composition provides very good cleaning performance and makes it possible to clean processing machines efficiently in a short time. The reason for this is not clear, but it is presumed to be as follows.

[0012] The cleaning composition of this embodiment contains a relatively large amount of inorganic powder relative to the thermoplastic resin. Therefore, when the cleaning composition is introduced into the processing machine, the inorganic powder easily scrapes off resin and burnt residue adhering to the inside of the machine. At this time, the hydrogenated petroleum resin acts as a coupling agent that physically binds the thermoplastic resin and the inorganic powder. Thus, it is possible to discharge the residual resin and burnt residue scraped off by the inorganic powder together with the thermoplastic resin (cleaning composition). Furthermore, because the cleaning composition contains a sulfate ester-based surfactant, burnt residue is more easily lifted from the surface of the processing machine (metal), which also results in significantly improved cleaning performance.

[0013] Furthermore, the cleaning composition of this embodiment does not need to contain styrene-derived components (e.g., polystyrene), which have been restricted in recent years. Therefore, it can be an environmentally friendly cleaning composition. Moreover, as will be described later, the cleaning composition of this embodiment does not easily deteriorate in performance even after repeated use. Therefore, it can be used multiple times, and has the advantage of being a cleaning composition that is excellent in terms of cost and environmental considerations. The components of the cleaning composition of this embodiment will be described below.

[0014] 1-1. Thermoplastic Resin The thermoplastic resin in this embodiment may contain an olefin resin, may contain only an olefin resin, or may contain an olefin resin and other resins. However, it is preferable that the thermoplastic resin contains an olefin resin as its main component. More specifically, it is preferable that the amount of olefin resin in the thermoplastic resin be 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. The thermoplastic resin may contain only one type of olefin resin, or may contain two or more types. Furthermore, the olefin resin may be a virgin resin, a recycled resin, or a mixture thereof.

[0015] In this specification, "olefin-based resin" refers to a resin whose main component is olefin-derived structural units. More specifically, it refers to a resin in which the amount of olefin-derived structural units relative to the total structural units of the resin is 50% by mass or more. The olefin-based resin may be a homopolymer of one olefin, a copolymer of two or more olefins, or a copolymer of one or more olefins and one or more other monomers (monomers other than olefins). The amount of olefin-derived structural units in the olefin-based resin is preferably 75% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more.

[0016] Examples of olefins mentioned above include ethylene and α-olefins having 3 to 10 carbon atoms. Specific examples include ethylene, propylene, 1-butene, isobutylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3,4-dimethyl-1-butene, 1-heptene, 4-methylpentene-1, 3-methyl-1-hexene, and 1-octene. Olefin resins may contain only one of these constituent units, or two or more.

[0017] The other monomers mentioned above are not particularly limited as long as they do not impair the purpose and effects of this embodiment. Examples of other monomers include diene monomers such as 1,4-hexadiene, 1,6-octadiene, 5-methyl-1,4-hexadiene, 3,7-dimethyl-1,6-octadiene, dicyclopentadiene (DCPD), ethylidene norbornene (ENB), norbornadiene, and 5-vinyl-2-norbornene; acid (or acid anhydride) modified olefins such as maleic anhydride modified olefins; and (meth)acrylates such as methyl (meth)acrylate. The olefin resin may contain only one of these constituent units, or it may contain two or more.

[0018] The olefin resin is preferably an "ethylene-based resin" in which the amount of ethylene-derived constituent units relative to the total constituent units of the resin is 50% by mass or more. Ethylene-based resins have a lower melting point compared to other olefin resins. Therefore, when a cleaning resin composition contains an ethylene-based resin, the fluidity of the cleaning composition in the processing machine tends to be good. Here, examples of ethylene-based resins include ethylene homopolymers and copolymers of ethylene and other monomers (ethylene copolymers). An example of an ethylene homopolymer is high-density polyethylene (HDPE): 0.942 g / cm³ ３ Polyethylene with the above density, medium-density polyethylene: 0.930 g / cm³ ３ 0.942g / cm or more ３ Polyethylene with a density of less than 0.910 g / cm³, low-density polyethylene (LDPE): 0.910 g / cm³ ３ 0.930g / cm or more ３Polyethylene with a density of less than 0.911 g / cm³, linear low-density polyethylene (hereinafter also referred to as "LLDPE"): 0.911 g / cm³ ３ 0.940g / cm or more ３ Linear polyethylene with a density of less than 0.910 g / cm³, and ultra-low density polyethylene (ULDPE): 0.910 g / cm³ ３ It contains polyethylene having a density of less than 1.5. On the other hand, the ethylene copolymer may be a binary copolymer of ethylene and other monomers, or a polypolymer of ethylene and two or more other monomers. Examples of preferred copolymer components (other monomers) include vinyl acetate and α-olefins having 3 or more carbon atoms.

[0019] Among ethylene-based resins, linear low-density polyethylene (LLDPE) is particularly preferred. Although linear low-density polyethylene (LLDPE) has a low melting point, it remains highly viscous even at high temperatures. Therefore, when the cleaning composition contains LLDPE as a thermoplastic resin, friction between the cleaning composition and the cylinder or screw surface of the processing machine becomes easier. As a result, the cleaning performance of the cleaning composition tends to be further enhanced. Here, the linear low-density polyethylene preferably has a melt mass flow rate (hereinafter also referred to as "MFR") of 0.5 g / 10 min to 4.0 g / 10 min at 190°C and a 2.16 kg load, according to JIS K7210-1:2014, and more preferably 1.0 g / 10 min to 3.0 g / 10 min. When the MFR of linear low-density polyethylene (LLDPE) is within this range, the cleaning performance of the cleaning composition is further enhanced.

[0020] Here, the thermoplastic resin may further contain resins other than olefin-based resins, as described above, and the type of resin other than olefin-based resin is not particularly limited. However, the amount of styrene-based resin containing styrene as a constituent unit is preferably 5% by mass or less relative to the total amount of thermoplastic resin, and from the standpoint of environmental consideration, it is particularly preferable that it is not included at all.

[0021] The amount (total amount) of thermoplastic resin in the resin composition is limited to a range where the mass ratio of thermoplastic resin to the inorganic powder described later is 50:50 to 10:90, and more preferably a range where the mass ratio of thermoplastic resin to the inorganic powder described later is 50:50 to 25:75. More specifically, the amount of thermoplastic resin is preferably 20% to 50% by mass, and more preferably 25% to 45% by mass, relative to the total amount of the resin composition. When the amount of thermoplastic resin is within this range, the fluidity of the cleaning composition tends to fall within an even more favorable range.

[0022] 1-2. Inorganic Powder The inorganic powder may be any powder made of an inorganic substance having a predetermined average particle size and containing calcium carbonate. The inorganic powder may contain only the calcium carbonate, or it may contain the calcium carbonate and other inorganic substances. However, it is preferable that the inorganic powder contains calcium carbonate as its main component. More specifically, it is preferable that the amount of calcium carbonate in the inorganic powder be 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0023] The average particle size of calcium carbonate, measured by the air permeation method in accordance with JIS M8511:2014, should be between 0.7 μm and 6.0 μm, but is more preferably between 1.0 μm and 4.0 μm. The above average particle size is calculated from the specific surface area measurement results obtained by the air permeation method in accordance with JIS M8511:2014. An example of a specific surface area measuring device is the SS-100 specific surface area measuring device manufactured by Shimadzu Corporation. If the average particle size of calcium carbonate is 0.7 μm or larger, it becomes easier to scrape out residual resin and burnt residue inside the processing machine. On the other hand, if the average particle size of calcium carbonate is 6.0 μm or smaller, the calcium carbonate can easily penetrate into the fine details of the processing machine, making it easier to clean those details. Furthermore, if the average particle size of calcium carbonate is within the above range, it is less likely to cause damage to the processing machine during cleaning.

[0024] The shape of calcium carbonate is not particularly limited as long as the above average particle size is satisfied. It may be any of particulate, flaky, granular, fibrous, etc. Also, in the case of particulate, it may be spherical as generally obtained by a synthetic method, or may be irregularly shaped as obtained by pulverizing collected natural minerals.

[0025] Calcium carbonate may be prepared by a synthetic method, so-called light calcium carbonate. On the other hand, it may be so-called heavy calcium carbonate obtained by mechanically pulverizing and classifying natural raw materials mainly composed of CaCO ３ . Furthermore, it may be a combination of light calcium carbonate and heavy calcium carbonate. Among these, heavy calcium carbonate is more preferable. Heavy calcium carbonate is often irregularly shaped, and according to such heavy calcium carbonate, the removability of residual resin and charring tends to be good.

[0026] Here, the above calcium carbonate may be surface-modified or may not be surface-modified. From the viewpoints of the dispersibility of calcium carbonate and the fluidity (retention suppression) in the processing machine, it is preferable that it is surface-modified. Examples of the surface modification method of calcium carbonate include physical modification methods such as plasma treatment, and chemical modification methods using coupling agents, surfactants, etc. Examples of coupling agents that can be used in chemical modification methods include silane coupling agents, titanium coupling agents, etc. As the surfactant, any of anionic, cationic, nonionic, and amphoteric ones can be used, and examples thereof include higher fatty acids, higher fatty acid esters, higher fatty acid amides, higher fatty acid salts, etc.

[0027] On the other hand, examples of inorganic substances other than calcium carbonate include magnesium carbonate, zinc oxide, titanium dioxide, silica, alumina, clay (e.g., talc and 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, zeolite, molybdenum, diatomaceous earth, sericite, shirasu, calcium sulfite, sodium sulfate, potassium titanate, bentonite, wollastonite, dolomite, graphite, etc. These may be synthetic or derived from natural minerals. The inorganic powder may contain only one of these or two or more.

[0028] Furthermore, these shapes are not particularly limited as long as they do not impair the purpose and effects of this embodiment, and may be particulate, flake-shaped, granular, fibrous, etc. In the case of particulate matter, they may be spherical, as is generally the case with synthesis methods, or they may be irregularly shaped, as is the case with pulverized collected natural minerals. These may also be surface-treated. However, it is preferable that the average particle size of these inorganic materials, as measured by the air permeation method in accordance with JIS M8511:2014, is between 0.7 μm and 6.0 μm.

[0029] The amount of inorganic powder in the cleaning composition of this embodiment may be any amount such that the mass ratio of the thermoplastic resin to the inorganic powder is in the range of 50:50 to 10:90. However, the amount of inorganic powder (total amount) is preferably 50% to 80% by mass, and more preferably 55% to 75% by mass, relative to the total amount of the resin composition. When the amount of inorganic powder is within this range, the inorganic substance makes it easier to scrape off residual resin and burnt residue, and the cleaning performance of the cleaning composition tends to improve further.

[0030] 1-3. Sulfate ester surfactants. Sulfate ester surfactants are any surfactants that contain a sulfate ester structure. The cleaning composition may contain only one type of sulfate ester surfactant, or it may contain two or more types.

[0031] Examples of sulfate ester surfactants include higher alcohol sulfate salts; alkyl sulfates (also known as alkyl sulfates); polyoxyethylene alkyl ether sulfates, polyoxyethylene alkylaryl sulfates, polyoxyethylene alkylphenyl ether sulfates, sulfate esters of polyoxyethylene alkylphenyl ether polymers, polyoxyethylene benzylphenyl ether sulfates, polyoxyethylene styrylphenyl ether sulfates, sulfate esters of polyoxyethylene styrylphenyl ether polymers, sulfate esters of polyoxyethylene polyoxypropylene block polymers, sulfated olefins, and salts thereof. Examples of the above salts include metal salts (Na, K, Ca, Mg, Zn, etc.), ammonium salts, alkanolamine salts, and aliphatic amine salts.

[0032] Among these, alkyl sulfates are preferred because they do not have a clear melting point and maintain a relatively high viscosity even at high temperatures. The alkyl group in the alkyl sulfate may be linear or branched. The number of carbon atoms in the alkyl group is preferably 8 to 20, and more preferably 10 to 18. Examples of alkyl sulfates include sodium octyl sulfate, sodium lauryl sulfate, sodium hexadecyl sulfate, and sodium stearyl sulfate.

[0033] The amount (total amount) of sulfate ester surfactant in the cleaning composition of this embodiment may be 0.2% by mass or more and 5.0% by mass or less, and preferably 0.5% by mass or more and 3.0% by mass or less. When the amount of sulfate ester surfactant is within this range, as described above, the burn marks tend to lift off the surface of the processing machine (metal). In addition, the fluidity of the cleaning composition also improves. Furthermore, the antistatic effect of the sulfate ester surfactant can suppress the adsorption of dust and other particles during the manufacturing and storage of the cleaning composition.

[0034] 1-4. Hydrogenated Petroleum Resins In this specification, "hydrogenated petroleum resin" refers to a resin obtained by further hydrogenating a copolymer (petroleum resin) of the liquid fraction (including diolefins, olefins, aromatic olefins, paraffins, etc.) obtained after separating gaseous olefins from fractions obtained by the decomposition or reforming of petroleum. Therefore, the types and amounts of monomer components in hydrogenated petroleum resins vary widely, and it is not possible to specify their composition in general, but they all share the common feature of containing C5 to C9 aliphatic rings. These hydrogenated petroleum resins have a high affinity for olefin-based resins and inorganic powders in the thermoplastic resins mentioned above.

[0035] The hydrogenated petroleum resin may be a commercially available product. Examples of commercially available hydrogenated petroleum resins include the Alcon series from Arakawa Chemical Industries, Ltd., the T-REZ series from ENEOS Corporation, the Easttac series from Eastman Chemical Corporation, and the iMarb series from Idemitsu Corporation.

[0036] The softening point of the hydrogenated petroleum resin is preferably between 80°C and 135°C, and more preferably between 80°C and less than 95°C. When the softening point of the hydrogenated petroleum resin is within this range, it becomes easier to bind the thermoplastic resin and inorganic powder mentioned above.

[0037] The amount of hydrogenated petroleum resin in the cleaning composition of this embodiment may be 0.5% by mass or more and 3.0% by mass or less, and preferably 1.0% by mass or more and 2.5% by mass or less. When the amount of hydrogenated petroleum resin is 0.5% by mass or more, the thermoplastic resin and inorganic powder are sufficiently bound together, and residual resin and burnt residue scraped off by the inorganic powder are further easily discharged together with the cleaning composition. On the other hand, when the amount of hydrogenated petroleum resin is 3.0% by mass or less, the dischargeability of the cleaning composition from the processing machine tends to be even better.

[0038] 1-5. Metallic Soaps As described above, the cleaning composition may further contain metallic soaps as needed. When the cleaning composition contains metallic soaps, the dispersibility of the inorganic powder in the cleaning composition tends to improve further. As a result, the cleaning performance of the cleaning composition tends to improve further.

[0039] In this specification, "metal soap" refers to a salt of a long-chain fatty acid and a metal. The long-chain fatty acid may be a saturated fatty acid, an unsaturated fatty acid, or an aliphatic dicarboxylic acid. From the viewpoint of enhancing the cleaning effect of the cleaning composition, saturated fatty acids with 12 to 30 carbon atoms or unsaturated fatty acids with 12 to 30 carbon atoms are preferred, and saturated fatty acids with 12 to 30 carbon atoms are more preferred. Examples of metals include zinc, calcium, magnesium, aluminum, barium, lithium, sodium, potassium, and manganese.

[0040] Specific examples of the metal soap include lithium salts such as lithium stearate, lithium 12-hydroxystearate, lithium laurate, lithium oleate, lithium 2-ethylhexanoate, lithium behenate, and lithium montanate; sodium salts such as sodium stearate, sodium 12-hydroxystearate, sodium laurate, sodium oleate, sodium 2-ethylhexanoate, sodium behenate, and sodium montanate; potassium salts such as potassium stearate, potassium 12-hydroxystearate, potassium laurate, potassium oleate, potassium 2-ethylhexanoate, potassium behenate, and potassium montanate; magnesium salts such as magnesium stearate, magnesium 12-hydroxystearate, magnesium laurate, magnesium oleate, magnesium 2-ethylhexanoate, magnesium behenate, and magnesium montanate; calcium salts such as calcium stearate, calcium 12-hydroxystearate, calcium laurate, calcium oleate, calcium 2-ethylhexanoate, calcium behenate, and calcium montanate; barium salts such as barium stearate, barium 12-hydroxystearate, barium laurate, barium behenate, and barium montanate; zinc salts such as zinc stearate, zinc 12-hydroxystearate, zinc laurate, zinc oleate, zinc 2-ethylhexanoate, zinc behenate, and zinc montanate; lead salts such as lead stearate, lead 12-hydroxystearate, lead behenate, and lead montanate; aluminum salts such as aluminum stearate, aluminum behenate, and aluminum montanate; manganese oleate; barium ricinoleate; cobalt stearate; etc.

[0041] Among these, magnesium 12-hydroxystearate is particularly preferred from the viewpoint of having a high affinity with the above sulfate surfactant and being likely to improve the dispersibility of the inorganic powder.

[0042] The amount of the metal soap in the cleaning composition of this embodiment is preferably 0.5% by mass or more and 5.0% by mass or less, and more preferably 1.0% by mass or more and 3.0% by mass or less. When the amount of the metal soap is within this range, the dispersibility of the inorganic powder tends to be even better. In addition, the content ratio (mass ratio) of the sulfate surfactant and the metal soap is preferably 6:4 to 4:6, and more preferably 5:4 to 4:5. When the content ratio of the sulfate surfactant and the metal soap is within the above range, the cleaning effect of the cleaning composition tends to be even higher.

[0043] 1-6. Other components The cleaning composition may further contain components other than those described above as long as the objects and effects of this embodiment are not impaired. Examples of components other than those described above include moisture absorbents, antioxidants, flame retardants, and the like.

[0044] The moisture absorbent is not particularly limited as long as it can suppress the moisture absorption of the cleaning composition and is hardly affected by the components in the cleaning composition. Examples of the moisture absorbent include metal oxides such as calcium oxide, magnesium oxide, strontium oxide, and barium oxide, zeolite, silica gel, activated carbon, and the like. When the cleaning composition contains these moisture absorbents, it is possible to suppress the moisture absorption and modification during storage of the cleaning composition. The amount of the moisture absorbent is appropriately selected according to the type of the moisture absorbent, but usually, it is preferably 0.1% by mass or more and 3% by mass or less based on the total mass of the cleaning composition.

[0045] On the other hand, the antioxidant may be any component that can suppress the deterioration of the cleaning composition by oxygen. Examples thereof include phosphorus-based antioxidants, phenol-based antioxidants, and pentaerythritol-based antioxidants. The resin composition may contain these alone or in combination of two or more. Also, the amount thereof is appropriately selected. Among the above, phosphorus-based, more specifically phosphorus-based antioxidant stabilizers such as phosphite esters and phosphate esters are preferably used. Examples of phosphite esters include tri-esters, di-esters, and mono-esters of phosphorous acid such as triphenyl phosphite, trisnonylphenyl phosphite, and tris(2,4-di-t-butylphenyl) phosphite.

[0046] Examples of phosphate esters include trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, triphenyl phosphate, tricresyl phosphate, tris(nonylphenyl) phosphate, and 2-ethylphenyldiphenyl phosphate.

[0047] Examples of phenolic antioxidants include α-tocopherol, butylhydroxytoluene, cinapyl 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.

[0048] The flame retardant is not particularly limited, but for example, halogenated flame retardants or non-phosphorus halogenated flame retardants such as phosphorus-based flame retardants or metal hydrates can be used. The resin composition may contain one of these alone or two or more. The amount of flame retardant is selected as appropriate.

[0049] Examples of halogenated flame retardants include halogenated bisphenol compounds such as halogenated bisphenylalkanes, halogenated bisphenyl ethers, halogenated bisphenyl thioethers, and halogenated bisphenylsulfones, as well as bisphenol-bis(alkyl ether) compounds such as brominated bisphenol A, brominated bisphenol S, chlorinated bisphenol A, and chlorinated bisphenol S. Examples of phosphorus-based flame retardants include aluminum tris(diethylphosphinate), bisphenol A bis(diphenyl phosphate), triarylisopropyl phosphate, cresyldi2,6-xylenyl phosphate, and aromatic condensed phosphate esters. Examples of metal hydrates include aluminum trihydrate, magnesium dihydrate, or combinations thereof.

[0050] Furthermore, the above-mentioned flame retardants may be combined with flame retardant additives. Examples of flame retardant additives include antimony oxides such as antimony trioxide and antimony pentoxide, zinc oxide, iron oxide, aluminum oxide, molybdenum oxide, titanium oxide, calcium oxide, and magnesium oxide.

[0051] 1-7. Shape and Physical Properties of the Resin Composition The shape of the cleaning composition in this embodiment is not particularly limited and can be any shape, such as particulate, pelletized, or lumpy. When the cleaning composition is in pellet form, the shape of the pellet is not particularly limited and can be cylindrical, spherical, ellipsoidal, or any other shape. The size is also not particularly limited and can be appropriately selected according to the shape. For example, in the case of spherical pellets, the diameter may be 1 to 10 mm. In the case of ellipsoidal pellets, the major axis may be about 1 to 10 mm and the aspect ratio may be about 0.1 to 1.0. In the case of cylindrical pellets, the diameter may be about 1 to 10 mm and the height may be about 1 to 10 mm.

[0052] Furthermore, the MFR of the cleaning composition of this embodiment, measured in accordance with JIS K7210-1:2014 at 190°C and a 2.16 kg load, is preferably 0.1 g / 10 min to 3.0 g / 10 min, and more preferably 0.5 g / 10 min to 2.5 g / 10 min. When the MFR of the cleaning composition is within this range, the fluidity within the processing machine and the discharge from the processing machine tend to be further improved.

[0053] 1-8. Method for Manufacturing the Cleaning Composition The method for manufacturing the above cleaning composition is not particularly limited. Any method that allows for the uniform mixing of a thermoplastic resin, inorganic powder, sulfate ester surfactant, hydrogenated petroleum resin, and optionally metal soap and other components is acceptable. These may be mixed simultaneously, or some may be mixed first and the rest later. Examples of mixing methods include melt kneading. The apparatus for performing melt kneading is not particularly limited, and general extruders, kneaders, Banbury mixers, etc., can be used. In particular, from the viewpoint of obtaining a cleaning composition with a uniform composition, kneading with a twin-screw kneader is preferable.

[0054] 2. Cleaning Method for Processing Machines Using the Cleaning Composition The above-described cleaning composition can be used to clean resin molding machines (processing machines). The type of processing machine is not particularly limited, and examples include injection molding machines, inflation molding machines, blow molding machines, extrusion molding machines, etc. Furthermore, the cleaning resin composition can be used to clean the resin flow paths such as cylinders, screws, and molds of these machines.

[0055] Furthermore, the above-mentioned cleaning composition is used when changing the resin composition used in the processing machine or when periodically cleaning the inside of the processing machine. The resin composition to be cleaned is preferably a composition that is molded at a relatively low temperature, as described above. For example, it is preferably a composition that is molded at a temperature of 120°C to 250°C, and more preferably a composition that is molded at a temperature of 130°C to 230°C. Examples of such resin compositions include resin compositions containing olefin resins.

[0056] When cleaning a processing machine using the above-mentioned cleaning composition, the following procedure can be followed. However, the cleaning method is not limited to this method.

[0057] The cleaning composition is supplied to the desired processing machine. The processing machine is then operated so that the cleaning composition flows through its interior. After that, the cleaning composition is discharged from the processing machine. At this time, the temperature of the processing machine is preferably the same as the processing temperature of the material to be cleaned, for example, preferably between 120°C and 250°C.

[0058] The amount of cleaning composition supplied to the processing machine and the cleaning time are appropriately selected according to the type of processing machine and the purpose of cleaning the machine. For example, when cleaning a processing machine for resin replacement (changing the type of resin composition used), it is preferable to continue supplying and discharging the cleaning composition until the previously used resin composition and burnt residue are no longer discharged along with the cleaning composition. In this case, the timing of the end of cleaning may be determined by the color and properties of the discharged cleaning composition. Alternatively, the timing may be determined by disassembling a part of the processing machine and checking whether residual resin or burnt residue is adhering to the inside. On the other hand, for periodic cleaning of the processing machine or cleaning before using the processing machine, cleaning may be completed by supplying and discharging a predetermined amount or a predetermined time of cleaning composition.

[0059] In this embodiment, after performing the cleaning step of the processing machine according to the procedure described above, the cleaning composition discharged from the processing machine may be recovered, crushed, and then the processing machine may be cleaned again using the resin composition. In other words, the used cleaning composition used to clean a particular processing machine may be reused to clean another or the same processing machine. As will be specifically shown in the examples described later, the cleaning resin assembly of this embodiment can maintain about 70% of its initial cleaning power even after being used four times (recycled three times). Therefore, the cleaning method using the cleaning composition of this embodiment can reduce the cost of cleaning and is also excellent from the standpoint of being environmentally friendly.

[0060] The present invention will be described in detail based on examples, but the present invention is not limited to these examples.

[0061] 1. Preparation of Materials The following materials were used in the following examples and comparative examples.

[0062] (Thermoplastic resins) LLDPE: Linear low-density polyethylene (Measured according to JIS K7210-1:2014, MFR at 190°C and 2.16 kg load: 3.0 g / 10 min, melting point 123°C) PP: Polypropylene (Measured according to JIS K7210-1:2014, MFR at 230°C and 2.16 kg load: 2.4 g / 10 min, melting point 160°C)

[0063] (Inorganic powder) ・Heavy calcium carbonate powder (manufactured by Takehara Chemical Co., Ltd., Sunlight SL-1500, average particle size 2.0 μm) The average particle size was calculated from the specific surface area measurement results using the air permeability method in accordance with JIS M8511:2014, using the specific surface area measuring device "SS-100" manufactured by Shimadzu Corporation.

[0064] (Surfactants) ・TB-160: Alkyl sulfate (manufactured by Matsumoto Oil & Fat Co., Ltd.) ・Alkyl ether sulfate / sulfonic acid type surfactant

[0065] (Hydrogenated petroleum resin) Alcon P-90 (manufactured by Arakawa Chemical Co., Ltd., softening point 90±5℃) Alcon P-115 (manufactured by Arakawa Chemical Co., Ltd., softening point 115±5℃)

[0066] (Metal soap) MS6:12-Magnesium hydroxystearate (manufactured by Nitto Chemical Industries, Ltd.) (For comparison, commercially available product) Asaclin UP (manufactured by Asahi Kasei Corporation)

[0067] 2. Preparation of the Cleaning Composition Thermoplastic resin, inorganic powder, surfactant, hydrogenated petroleum resin, and metal soap were fed into a Parker HK-25D co-rotating twin-screw compounding extruder (φ25 mm, L / D = 41) in the mass ratios shown in Tables 1 and 2. After melt-kneading at a cylinder temperature of 230°C, the mixture was extruded into strands. The extruded resin composition was then cooled and cut to obtain pellets of the cleaning composition. In Comparative Example 7, (virgin) polypropylene was used as the cleaning composition, and in Comparative Example 8, Asaclin UP (manufactured by Asahi Kasei Corporation) was used as the cleaning composition.

[0068] 3. Evaluation The cleaning performance of the cleaning composition obtained above for residues inside the processing machine was evaluated using the following method. The results are shown in Tables 1 and 2.

[0069] (1) Cleaning Performance Evaluation 1 A standard PP plate was prepared by introducing 1 kg of polypropylene (MFR (230°C, 2.16 kg load): 0.5 g / 10 min) into a laboplast mill (small extruder) and extruding it at 200°C. Then, 1 kg of a resin composition (to be cleaned) containing 95% by mass of polypropylene (MFR (230°C, 2.16 kg load): 0.5 g / 10 min) and 5% by mass of red pigment was supplied to the laboplast mill and extruding it at 200°C in the same manner. Subsequently, 1 kg each of the cleaning compositions prepared in the example and comparative example were supplied to the laboplast mill and extruded at 200°C for cleaning. Again, 0.5 kg of polypropylene (MFR (230°C, 2.16 kg load): 0.5 g / 10 min) was introduced to the laboplast mill and extruded at 200°C to prepare a PP plate after cleaning. The color difference ΔE between the standard PP plate and the washed PP plate was measured using a spectrophotometer to evaluate the cleaning performance of the cleaning composition. A smaller color difference ΔE indicates higher cleaning performance. The results are shown in Tables 1 and 2.

[0070] (2) Cleaning performance evaluation 2 A standard PP plate was produced by introducing 1 kg of polypropylene (MFR (230°C, 2.16 kg load): 21 g / 10 min) into a 30 t injection molding machine and performing injection molding at 200°C. Subsequently, 1 kg of a resin composition (to be cleaned) containing 95% by mass of polypropylene (MFR (230°C, 2.16 kg load): 21 g / 10 min) and 5% by mass of red pigment was supplied to the 30 t injection molding machine and injection molding was performed in the same manner at 200°C. Subsequently, 0.3 kg each of the cleaning compositions prepared in the example and comparative example were supplied to the 30 t injection molding machine and injected at 200°C to perform cleaning. Again, 0.5 kg of polypropylene (MFR (230°C, 2.16 kg load): 21 g / 10 min) was introduced into the 30t injection molding machine, and injection molding was performed at 200°C to produce a PP plate after washing. The color difference ΔE between the standard PP plate and the washed PP plate was then measured using a spectrophotometer to evaluate the cleaning performance of the cleaning composition. A smaller color difference ΔE indicates higher cleaning performance. The results are shown in Tables 1 and 2.

[0071] (3) Burn Removal Properties 1 kg of a resin composition containing 99% by mass of polypropylene (MFR (230°C, 2.16 kg load): 21 g / 10 min), 0.5% by mass of malic acid, and 0.5% by mass of alkanolamide) was supplied to a 30t injection molding machine, and injection molding was performed at 200°C. This forced burn formation. Subsequently, 0.3 kg each of the cleaning compositions prepared in the example and comparative example were supplied to the 30t injection molding machine, and cleaning was performed by injecting them. After that, 0.2 kg of polypropylene (MFR (230°C, 2.16 kg load): 21 g / 10 min) was introduced into the 30t injection molding machine, and a PP plate was prepared after cleaning. The PP plate was then observed, and the amount of burn contained in the PP plate was visually observed. The injection molding machine was also disassembled, the screw part was wiped with a cloth, and the presence or absence of burn was observed. Furthermore, the presence or absence of burn marks on the nozzle was examined under a microscope. The results are shown in Tables 1 and 2.

[0072] (4) Discharge Performance 1 kg of polyethylene (MFR (190°C, 2.16 kg load): 3.0 g / 10 min) was introduced into a 30 ton injection molding machine, and injection molding was performed at 200°C. Then, 1 kg each of the cleaning compositions prepared in the example and comparative example were supplied to the 30 ton injection molding machine, injected, and cleaning was performed. Then, 2 kg of polyethylene (MFR (190°C, 2.16 kg load): 3.0 g / 10 min) was introduced, and extrusion molding was performed at 200°C to produce a PE plate after cleaning. The PE plate was then observed, and the number of Fish-EYEs was measured. Note that Fish-EYEs are generated by the gelation of the cleaning composition remaining in the molding machine, etc. The fewer the number of Fish-EYEs, the higher the discharge performance of the cleaning composition from the processing machine. The results are shown in Tables 1 and 2.

[0073] 4. result

[0074]

[0075] As shown in Table 1, in Examples 1 to 9, where the mass ratio of LLDPE to calcium carbonate was 50:50 to 10:90, the amount of sulfate ester surfactant was 0.2% to 5.0% by mass, and the amount of hydrogenated petroleum resin was 0.5% to 3.0% by mass, the cleaning performance evaluation was better than that of a commercially available cleaning composition (Comparative Example 8). Furthermore, in the cleaning compositions of Examples 1 to 9, even if burn occurred in the processing machine, it was easy to discharge, and the dischargeability of the cleaning composition itself was also excellent.

[0076] In contrast, when the amount of calcium carbonate was insufficient, or when the amount of sulfate ester-based surfactant or hydrogenated petroleum resin did not meet the above requirements, the cleaning performance deteriorated in all cases (Comparative Examples 1-7).

[0077] 5. Reusability The reusability of the cleaning compositions of the examples was evaluated using the following method.

[0078] (1) Test Method (0th Recycle) 1 kg of a resin composition containing 95% by mass of polypropylene (MFR (230°C, 2.16 kg load): 21 g / 10 min) and 5% by mass of red pigment was supplied to a 30t injection molding machine and extruded at 200°C. Subsequently, the cleaning composition prepared in Example 1 was supplied to the 30t injection molding machine and injection molded. The amount of cleaning composition discharged that was equivalent in color to the original cleaning composition was then determined. After that, the cleaning composition used for cleaning was recovered and crushed.

[0079] (First Recycling) 1 kg of a resin composition containing 95% by mass of polypropylene (MFR (230°C, 2.16 kg load): 21 g / 10 min) and 5% by mass of red pigment was supplied to a 30t injection molding machine and extruded at 200°C. Subsequently, the cleaning composition recovered and crushed above was supplied to the 30t injection molding machine and injection molded. The amount of cleaning composition discharged that was equivalent in color to the color before supply was then determined. After that, the cleaning composition used for cleaning was recovered and crushed.

[0080] (Second Recycling) 1 kg of a resin composition containing 95% by mass of polypropylene (MFR (230°C, 2.16 kg load): 21 g / 10 min) and 5% by mass of red pigment was supplied to a 30t injection molding machine and extruded at 200°C. Subsequently, the cleaning composition recovered and crushed above was supplied to the 30t injection molding machine and injection molded. The amount of cleaning composition discharged that was equivalent in color to the color before supply was then determined. After that, the cleaning composition used for cleaning was recovered and crushed.

[0081] (Third Recycling) 1 kg of a resin composition containing 95% by mass of polypropylene (MFR (230°C, 2.16) kg load: 21 g / 10 min) and 5% by mass of red pigment was supplied to a 30t injection molding machine and extruded at 200°C. Subsequently, the cleaning composition recovered and crushed above was supplied to the 30t injection molding machine and injection molded. The amount of cleaning composition discharged that was equivalent in color to the color before supply was then determined.

[0082] (2) Evaluation results The amount of cleaning composition required for each cleaning and the time required are shown in Table 3 below.

[0083]

[0084] As shown in Table 3 above, although the efficiency decreases with repeated recycling, the cleaning efficiency remained at approximately 70% of the initial level even after three recycling cycles. Therefore, it can be said that the above cleaning composition is reusable.

[0085] This application claims priority under Japanese Patent Application No. 2024-198907, filed on November 14, 2024. All provisions of the said application are incorporated herein by reference.

[0086] The cleaning resin composition of the present invention makes it possible to efficiently clean the inside of a processing machine in a short amount of time. Furthermore, the cleaning resin composition can be used repeatedly. This cleaning resin composition is extremely useful in the field of manufacturing various industrial products.

Claims

1. A cleaning resin composition comprising: a thermoplastic resin containing an olefin-based resin; an inorganic powder containing calcium carbonate with an average particle size of 0.7 μm or more and 6.0 μm or less, as measured by the air permeation method in accordance with JIS M8511:2014; a sulfate ester-based surfactant; and a hydrogenated petroleum resin, wherein the mass ratio of the thermoplastic resin to the inorganic powder is 50:50 to 10:90; the amount of the sulfate ester-based surfactant is 0.2% by mass or more and 5.0% by mass or less; and the amount of the hydrogenated petroleum resin is 0.5% by mass or more and 3.0% by mass or less.

2. The cleaning resin composition according to claim 1, wherein the olefin resin is linear low-density polyethylene.

3. The cleaning resin composition according to claim 2, wherein the linear low-density polyethylene has a melt mass flow rate of 0.5 g / 10 min or more and 4.0 g / 10 min or less at 190°C and a 2.16 kg load, as measured in accordance with JIS K7210-1:2014.

4. The cleaning resin composition according to claim 1, wherein the calcium carbonate is heavy calcium carbonate.

5. The cleaning resin composition according to claim 1, wherein the sulfate ester surfactant is an alkyl sulfate.

6. The cleaning resin composition according to claim 1, wherein the softening point of the hydrogenated petroleum resin according to JIS K2207:1996 is 80°C or higher and 100°C or lower.

7. The cleaning resin composition according to claim 1, further comprising a metal soap, wherein the amount of the metal soap is 0.5% by mass or more and 5.0% by mass or less.

8. The cleaning resin composition according to claim 7, wherein the metal soap is magnesium 12-hydroxystearate.

9. A method for cleaning a resin molding machine, comprising: a step of cleaning the resin molding machine using the cleaning resin composition described in any one of claims 1 to 8; a step of recovering the cleaning resin composition from the resin molding machine and crushing it; and a step of newly cleaning the resin molding machine using the crushed cleaning resin composition.

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