JP2023151470A - Crosslinked polyethylene for cleaning agents for resin processing machines, resin composition for cleaning agents for resin processing machines, and method for cleaning resin processing machines - Google Patents

Abstract

To provide a crosslinked polyethylene for cleaning agents for resin processing machines that is superior in cleaning efficacy and ease of replacement.SOLUTION: A crosslinked polyethylene for cleaning agents for resin processing machines has a gel fraction (in accordance with JIS K6796) of 10-34% and a melt mass flow rate (220°C, load 10 kg) of 0.01-0.50 g/10 min.SELECTED DRAWING: None

Description

The present invention relates to a crosslinked polyethylene for a cleaning agent for resin processing machines, a resin composition for a cleaning agent for resin processing machines, and a method for cleaning resin processing machines.

In general, resin processing machines such as extrusion molding machines and injection molding machines are used for operations such as coloring, mixing, and molding of resins. In addition to additives such as dyes and pigments contained in resins and molding materials, degraded products (thermal decomposition products, burnt products, carbonized products, etc.) generated from resins may remain in resin processing machines. If this residue is left unattended, it will be mixed into the molded product during the subsequent resin molding process, and may cause poor product appearance. In particular, when molding transparent resin, even minute carbides are easily visible, resulting in poor appearance of the molded product and increasing the incidence of molded product defects. Therefore, it is desired to completely remove the residue from inside the resin processing machine.

Conventionally, in order to remove the residue from inside the resin processing machine, there were two methods: (1) manually disassembling and cleaning the resin processing machine, and (2) using the molding material for the next molding without stopping the resin processing machine. Methods include filling a resin processing machine with the resin and gradually discharging the residue, and (3) using a cleaning agent.
The method (1) above is inefficient because it requires stopping the resin processing machine, and the resin processing machine is easily damaged because the removal work is physically performed manually. Method (2) above often requires a large amount of molding material to remove the residue, takes time to complete the work, and also has the problem of generating a large amount of waste. . Therefore, in recent years, the method (3) using a cleaning agent has been preferred because it has excellent cleaning power to remove residues from resin processing machines.
In order to increase the effectiveness of cleaning agents, various methods have been proposed for increasing the cleaning power of cleaning agents. For example, Patent Documents 1 and 2 describe a method of increasing detergency by blending a crosslinked olefin resin.

Japanese Patent Application Publication No. 54-29351 Japanese Patent Application Publication No. 3-99822

The cleaning agent is required to have high cleaning power for the molding material used in the previous molding and to be easily replaceable by the molding material used in the next molding.
Since the cleaning agents of Patent Documents 1 and 2 use crosslinked resins, they are effective in removing residues, but there is a need to improve the ease with which they can be replaced by molding materials after cleaning. .

Therefore, an object of the present invention is to provide a crosslinked polyethylene for use as a cleaning agent for resin processing machines, which has excellent cleaning performance and easy replaceability.

As a result of intensive studies to solve the above problems, the present inventors have found that cross-linked polyethylene having a specific gel fraction and a specific melt mass flow rate (220°C, load 10 kg) does not remain in the resin processing machine. They discovered that it can be easily replaced and developed the present invention.

That is, the present invention is as follows.
[1]
Cleaning for resin processing machines characterized by having a gel fraction (according to JIS K6796) of 10 to 34% and a melt mass flow rate (220°C, load 10 kg) of 0.01 to 0.50 g/10 minutes. Cross-linked polyethylene for agents.
[2]
The crosslinked polyethylene for a cleaning agent for a resin processing machine according to [1], which is crosslinked polyethylene crosslinked by peroxide or electron beam crosslinking.
[3]
The crosslinked polyethylene for a cleaning agent for a resin processing machine according to [1] or [2], which is crosslinked polyethylene obtained by recycling or volume reduction.
[4]
A resin composition for a resin processing machine cleaner, comprising the crosslinked polyethylene (A) for a resin processing machine cleaner according to any one of [1] to [3] and a polyolefin resin (B). .
[5]
The resin composition for a cleaning agent for resin processing machines according to [4], wherein the component (B) is at least one selected from the group consisting of polyethylene resins and polypropylene resins.
[6]
[4] or [5] containing 10 to 90 parts by mass of the component (A) and 90 to 10 parts by mass of the component (B), based on a total of 100 parts by mass of the component (A) and the component (B). ] The resin composition for a cleaning agent for resin processing machines.
[7]
The resin composition for a cleaning agent for resin processing machines according to any one of [4] to [6], wherein the component (B) has a melt mass flow rate of 0.10 to 1.0 g/10 minutes.
[8]
Pellets containing 10 to 1000 parts by mass of (B) polyolefin resin based on 100 parts by mass of the crosslinked polyethylene for cleaning agent for resin processing machines according to any one of [1] to [3].
[9]
Using the crosslinked polyethylene for cleaning agents for resin processing machines according to any one of [1] to [3] or the resin composition for cleaning agents for resin processing machines according to any one of [4] to [7] A method for cleaning resin processing machines, characterized by:
[10]
Clean the resin processing machine by dry blending 10 to 1000 parts by mass of (B) polyolefin resin to 100 parts by mass of the crosslinked polyethylene for cleaning agent for resin processing machines according to any one of [1] to [3]. A method for cleaning a resin processing machine, characterized by:

According to the present invention, it is possible to provide crosslinked polyethylene for cleaning agents, which has excellent cleaning performance and easy replacement.

Hereinafter, a mode for carrying out the present invention (hereinafter referred to as "this embodiment") will be described in detail. The present embodiment below is an illustration for explaining the present invention, and the present invention is not limited to the following content. The present invention can be implemented with various changes within the scope of its gist.

[Crosslinked polyethylene for cleaning agent for resin processing machines]
The crosslinked polyethylene for cleaning agent for resin processing machines of this embodiment has a gel fraction (according to JIS K6796) of 10 to 34% and a melt mass flow rate (220°C, load 10 kg) of 0.01 to 0.50 g. /10 minutes.

Examples of the crosslinked polyethylene for cleaning agents for resin processing machines include high-density polyethylene, linear low-density polyethylene, branched low-density polyethylene, ethylene-vinyl acetate copolymer (EVA), chlorinated polyethylene, and ethylene-ethyl acrylate. Examples include crosslinked polymers such as polyethylene, and these are used alone or in combination of two or more. The mass proportion of repeating units derived from ethylene in the polyethylene is preferably more than 50% by mass, more preferably 70% by mass or more, and still more preferably 90% by mass or more.

There are no particular restrictions on the method for crosslinking the polyethylene, and peroxide crosslinking, electron beam crosslinking, and water crosslinking (also called silane crosslinking) in which a silane compound is grafted and then crosslinked by contacting with water are used. From the viewpoint of controlling MFR, peroxide crosslinking and electron beam crosslinking are preferred.

The gel fraction (according to JIS K6796) of the crosslinked polyethylene is preferably 10 to 34% by mass, more preferably 15 to 33% by mass.
The MFR (220° C., load 10 kg) of the crosslinked polyethylene is preferably 0.01 to 0.50 g/10 minutes, more preferably 0.03 to 0.40 g/10 minutes.
By setting the gel fraction and MFR within the above ranges, a cleaning agent with excellent balance between cleaning performance and load reduction on a melt-kneading machine and a molding machine can be obtained.

The above-mentioned cross-linked polyethylene includes cross-linked polyethylene resin molded products such as used electric wire covering materials, pipe materials for floor heating, films, various foams, volume-reduced products thereof, and cross-linked polyethylene resin products generated during the manufacturing stage of these products. It may be a pulverized product of waste, etc., and is preferably a crosslinked polyethylene obtained by recycling or volume reduction, and more preferably a recycled product or a volume reduced product obtained by a method including a plasticization step using an extruder. .

The crosslinked polyethylene of the present embodiment (preferably recycled or volume-reduced crosslinked polyethylene) is crosslinked polyethylene in which carbon-carbon bonds and the like in the crosslinked portion of crosslinked polyethylene are cut to improve the fluidity of the resin. Examples of the method of cutting the bonds of the crosslinked portion and improving the fluidity of the resin include a method of regenerating and reducing the volume of the crosslinked polyethylene resin, and a method of regenerating and reducing the volume at a high temperature is more preferable.
The temperature for regeneration and volume reduction is preferably 230 to 400°C, more preferably 230 to 380°C, and particularly preferably 250 to 350°C. When the regeneration and volume reduction temperature is lower than 230°C, plasticization becomes difficult and the crosslinked polyethylene becomes difficult to be recycled and volume reduced. On the other hand, if the regeneration or volume reduction temperature exceeds 400° C., molecular cleavage of crosslinked polyethylene will proceed excessively, and the properties of the resulting crosslinked polyethylene resin will deteriorate.

Normally, crosslinked polyethylene has a three-dimensional network structure, so it does not melt even at temperatures above its melting point, making it impossible to measure MFR. The crosslinked polyethylene of this embodiment is crosslinked polyethylene in which at least part of the crosslinked structure within the molecule has been cut. Therefore, the MFR can be measured under the conditions of a temperature of 220° C. and a load of 10 kg.
In addition, since cross-linked polyethylene (preferably recycled or volume-reduced cross-linked polyethylene) partially contains a plasticizing component, it improves compatibility with other polyethylene resins described below and/or facilitates substitution. It is presumed that this improves (however, the effects of this embodiment are not limited to this).

The crosslinked polyethylene of this embodiment has excellent compatibility and easy substitution, and therefore can be suitably used as a cleaning agent for resin processing machines. Examples of the resin processing machine include an injection molding machine, an extrusion molding machine, and the like.

[Resin composition for cleaning agent for resin processing machines]
The resin composition for a cleaning agent for resin processing machines of the present embodiment (in this specification, may be simply referred to as "cleaning agent") is the crosslinked polyethylene for cleaning agents for resin processing machines (in this specification, (sometimes referred to as "component (A)"). It is preferable that the cleaning agent of the present embodiment further contains a polyolefin resin (B) (herein sometimes referred to as "component (B)"). The cleaning agent of this embodiment may be a cleaning agent consisting only of the above-mentioned (A) component, or may be a cleaning agent consisting only of the above-mentioned (A) component and the above-mentioned (B) component.

(Polyolefin resin (B))
The polyolefin resin may be a thermoplastic resin, such as high density polyethylene, low density polyethylene, linear low density polyethylene, polyethylene resin such as a copolymer of ethylene and α-olefin, polypropylene, Examples include polypropylene resins such as propylene-ethylene copolymers and copolymers of propylene and α-olefin, polybutene, and the like. Among these, from the viewpoint of compatibility with component (A), at least one selected from the group consisting of polyethylene resins and polypropylene resins is preferable, and high density polyethylene, low density polyethylene, and linear low density polyethylene are preferred. , polypropylene is preferred because of its excellent cleaning performance and easy displacement, and high-density polyethylene, low-density polyethylene, and linear low-density polyethylene are more preferred from the viewpoint of compatibility with component (A). The above polyolefin resins can be used alone or in combination of two or more.
Note that polyethylene resin refers to a resin in which the mass proportion of repeating units derived from ethylene in the resin is more than 50 mass% (preferably 70 mass% or more, more preferably 90 mass% or more), and polypropylene resin refers to a resin in which the mass proportion of repeating units derived from propylene in the resin is more than 50% by mass (preferably 70% by mass or more, more preferably 90% by mass or more).

When the polyolefin resin is a polyethylene resin, the MFR (190°C, load 2.16 kg) is 0.01 g/10 from the viewpoint of excellent cleaning power and easy replacement with the molding material used after cleaning. It is preferably at least 20 g/10 minutes, more preferably at most 20 g/10 minutes, and even more preferably from 0.1 to 1.0 g/10 minutes, from the viewpoint of the cleaning effect. When using a plurality of polyethylene thermoplastic resins, it is preferable to mix those within the above melt flow range or those outside the above melt flow rate range to adjust the melt flow rate within the above range.

When the polyolefin thermoplastic resin is a polypropylene resin, the MFR (230°C, load 2.16 kg) is 0.01 g/ The washing time is preferably 10 minutes or more, more preferably 20 g/10 minutes or less, and even more preferably 0.1 to 1.0 g/10 minutes from the viewpoint of cleaning effect. When using a plurality of polypropylene thermoplastic resins, it is preferable to adjust the melt flow rate within the above range by mixing those within the above melt flow range or those outside the above melt flow rate range.

From the viewpoint of detergency and manufacturing stability, the cleaning agent of this embodiment is designed to contain 10 to 90 parts by mass of component (A) and 10 to 90 parts by mass of component (B), based on a total of 100 parts by mass of component (A) and component (B). ) is preferably 90 to 10 parts by weight, more preferably 20 to 80 parts by weight of component (A), 80 to 20 parts by weight of component (B), even more preferably 20 to 70 parts by weight of component (A), ( 30 to 80 parts by weight of component B), particularly preferably 30 to 70 parts by weight of component (A) and 30 to 70 parts by weight of component (B).

(other ingredients)
The cleaning agent of this embodiment may further contain other components.
The above-mentioned other components are components other than the above-mentioned (A) component and the above-mentioned (B) component, such as thermoplastic resins other than the (A) component and (B) component, lubricants, surfactants, antioxidants, Inorganic fillers, inorganic foaming agents, ultra-high molecular weight resins, light stabilizers, stabilizers such as ultraviolet absorbers, antiblocking agents, antistatic agents, antifogging agents, nucleating agents, crosslinking accelerators, crosslinking inhibitors, colorants, etc. can be mentioned.

-Aliphatic hydrocarbon compounds-
The cleaning agent of this embodiment may contain an aliphatic hydrocarbon compound as another component.
The aliphatic hydrocarbon compound is not particularly limited as long as it has a weight average molecular weight of 200 to 20,000, and examples include mineral oil, paraffin wax, and olefin wax.

The above-mentioned mineral oil is an oil obtained by refining petroleum, and is a saturated hydrocarbon oil containing naphthenes, isoparaffins, etc., also called mineral oil, lubricating oil, liquid paraffin, etc. Mineral oils with a wide viscosity range can be used. For example, in the case of liquid paraffin, those with a kinematic viscosity of 50 to 500 mm ² /s measured according to JIS K2283, the Redwood method (Japan Oil Chemists Association standard oil and fat analysis test method) 2.2.10.4-1996) with a viscosity in the range of 30 to 2000 (seconds) may be used. The above-mentioned paraffin wax is a paraffin compound obtained by refining petroleum and is solid at room temperature, and those having a melting point of 40 to 80°C are often used.

Examples of the olefin wax include low-molecular polyolefins, and are not particularly limited, but general low-density or high-density polyethylene, polypropylene, etc. are used. Those with a weight average molecular weight of about 800 to 20,000 and a dropping point of 80 to 180°C are most effective.

The content of the aliphatic hydrocarbon compound is preferably 0.01 parts by mass or more and 20 parts by mass or less, more preferably 0.05 to 15 parts by mass, and even more preferably 0.01 to 20 parts by mass, based on 100 parts by mass of the cleaning agent. .1 to 10 parts by mass. When the content of the aliphatic hydrocarbon compound is within the above range, the ease of substitution can be improved while maintaining the washability. Furthermore, by adding an aliphatic hydrocarbon compound, the motor load (torque) of a kneader such as a twin-screw extruder is reduced during kneading of the detergent, making it easier to manufacture the detergent.

-Lubricant-
Examples of the lubricant include organic acids, organic acid metal salts, organic acid amides, organic acid derivatives such as organic acid esters, various ester waxes, fluorine resins, etc., but are not particularly limited thereto. Note that the above-mentioned lubricant does not contain the above-mentioned aliphatic hydrocarbon compound. The lubricants may be used alone or in combination of two or more.

The organic acid is preferably a saturated fatty acid having 9 to 28 carbon atoms, an unsaturated fatty acid having 9 to 28 carbon atoms, or benzoic acid. A portion of the chain may have a hydroxyl group. In particular, from the viewpoint of availability and heat resistance, stearic acid, 12-hydroxystearic acid, palmitic acid, myristic acid, and lauric acid are more preferred. Further, mixed fatty acids having different alkyl chains may be used. When the number of carbon atoms is within the above range, it is preferable because there is no problem of gas generation or odor, it is easily available, and its properties as a lubricant at the interface function well.

The metal in the organic acid metal salt is not particularly limited, but includes sodium, potassium, lithium, cesium, magnesium, calcium, aluminum, zinc, iron, cobalt, barium, and the like. Among these, lithium, calcium, barium, zinc, and aluminum are preferred because they are most effective as lubricants. Among these, aluminum and zinc are more preferable because they have low polarity and tend to exhibit external slipperiness due to bleed-out from the thermoplastic resin. Particularly preferred is zinc.

The hydrocarbon moiety in the above-mentioned organic acid metal salt is preferably a saturated fatty acid having 9 to 28 carbon atoms, an unsaturated fatty acid having 9 to 28 carbon atoms, or benzoic acid, as is the case with the above-mentioned organic acids, and these are easy to obtain and have good heat resistance. From this viewpoint, stearic acid, 12-hydroxystearic acid, palmitic acid, myristic acid, and lauric acid are more preferred.

Examples of the organic acid amide include saturated fatty acid amide, unsaturated fatty acid amide, saturated fatty acid bisamide, and unsaturated fatty acid bisamide having 9 to 28 carbon atoms. Among them, fatty acids with 12 to 18 carbon atoms such as lauric acid, myristic acid, palmitic acid, and stearic acid, amides of unsaturated fatty acids such as erucic acid, and saturated fatty acid bisamides such as ethylene bisstearic acid amide are easily available. , from the viewpoint of effectiveness as a lubricant, and more preferably saturated fatty acid bisamide such as ethylene bisstearamide.

Examples of the organic acid esters and ester waxes include polyol esters having 9 to 28 carbon atoms, such as saturated fatty acid esters, unsaturated fatty acid esters, medium-chain fatty acid triglycerides, and hydrogenated oils. In terms of availability and effectiveness as a lubricant, stearic acid stearate, glycerin fatty acid ester monoglyceride, and the like are preferred.

Examples of the fluororesin include PTFE, PFA, PVDF, PVDF copolymer, ETFE, PFE, etc., and can be expected to have the effect of suppressing resin adhesion to metal surfaces. Various shapes can be used, such as pellets and powders, but powders are particularly preferred in order to ensure uniform dispersion during processing. The average particle size is not particularly limited, but is preferably 1,000 μm or less.

From the viewpoint of cleaning performance, the lubricant preferably has a surface tension of 32 mN/m or less. For example, the surface tension of zinc stearate is 24 mN/m, and the surface tension of aluminum stearate is 25 mN/m. Further, the melting point or softening point of the lubricant is preferably 70°C or higher, more preferably 80°C or higher, and even more preferably 90°C or higher.

The content of the lubricant is preferably 0.1 to 10 parts by weight, more preferably 0.2 to 10 parts by weight, and even more preferably 0.5 to 8 parts by weight based on 100 parts by weight of the cleaning agent. . When the content of the lubricant is within the above range, easy replacement can be improved while maintaining cleanability.

-Surfactant-
Examples of the surfactant include anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants, and the like. Examples of the anionic activator include higher fatty acid alkali salts (alpha sulfo fatty acid methyl ester sodium, etc.), alkyl sulfates, alkyl sulfonates, alkylaryl sulfonates, sulfosuccinate ester salts, and the like. Examples of the cationic activator include higher amine halide salts, alkylpyridinium halides, and quaternary ammonium salts. Examples of the nonionic activator include polyethylene glycol alkyl ether, polyethylene glycol fatty acid ester, sorbitan fatty acid ester, pentaerythritol fatty acid ester (pentaerythritol tetrastearate, etc.), fatty acid monoglyceride, and the like. Examples of amphoteric surfactants include amino acids. The surfactants may be used alone or in combination of two or more.
The content of the surfactant is preferably 0.1 to 10 parts by weight, more preferably 0.2 to 10 parts by weight, and even more preferably 0.5 to 8 parts by weight based on 100 parts by weight of the cleaning agent. It is. When the content of the surfactant is within the above range, easy replacement can be improved while maintaining cleanability.

-Antioxidant-
Examples of the antioxidant include phosphorus antioxidants, phenolic antioxidants, etc., but are not particularly limited to these. Specific examples of phosphorous antioxidants include tris(2,4-di-t-butylphenyl) phosphite, bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, and 2,2' -methylenebis(4,6-di-t-butyl-1-phenyloxy)(2-ethylhexyloxy)phosphite and the like. Specific examples of phenolic antioxidants include pentaerythritol tetrakis [3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t-butyl) -4-hydroxyphenyl)propionate, 4,4'-butylidenebis(6-t-butyl-m-cresol), and the like. The antioxidants may be used alone or in combination of two or more.
The content of the antioxidant is preferably 0.01 to 5 parts by weight, more preferably 0.05 to 3 parts by weight, and even more preferably 0.1 to 2 parts by weight based on 100 parts by weight of the cleaning agent. It is. When the content of the antioxidant is within the above range, deterioration of the resin can be suppressed, and the decomposition products of the antioxidant themselves do not have an inhibitory effect on other additives (such as lubricants). It is preferable because it is less.

-Inorganic filler-
The above-mentioned inorganic filler refers to an inorganic compound other than the inorganic blowing agent described below, and includes both natural products and artificial compounds. Specific examples of inorganic compounds include talc, mica, wollastonite, xonotlite, kaolin clay, montmorillonite, bentonite, sepiolite, imogolite, sericite, lawsonite, smectite, calcium sulfate fiber, calcium carbonate, magnesium carbonate, titanium oxide, and water. Examples include aluminum oxide, magnesium hydroxide, zeolite, diatomaceous earth, glass powder, glass bulbs, glass fibers, and shirasu balloons.

-Inorganic foaming agent-
The above-mentioned inorganic foaming agent refers to an inorganic compound that decomposes upon heating and foams, that is, generates gas. Specific examples of inorganic blowing agents include inorganic physical blowing agents such as water, hydrogen carbonates such as sodium hydrogen carbonate and ammonium hydrogen carbonate, carbonates such as sodium carbonate and ammonium carbonate, nitrites such as ammonium nitrite, and borohydrides. Known compounds such as hydrides such as sodium, azide compounds such as calcium azide, light metals such as magnesium and aluminum, combinations of sodium bicarbonate and acids, combinations of hydrogen peroxide and yeast, and combinations of aluminum powder and acids, etc. Inorganic chemical blowing agents may be mentioned.

-Ultra high molecular weight resin-
The ultra-high molecular weight resin is a polymer having a viscosity average molecular weight of 1 million or more, and includes, for example, an ethylene-based ultra-polymer, a styrene-acrylonitrile-based ultra-polymer, a methyl methacrylate-based ultra-polymer, and the like. Among these, ethylene-based superpolymers are preferred. The upper limit of the molecular weight is not particularly limited, but is generally preferably 10 million or less for practical purposes.

Further, the ultra-high molecular weight resin may be a homopolymer or a copolymer, and in the case of a copolymer, the content of the main component (for example, ethylene, styrene-acrylonitrile copolymer, methyl methacrylate, etc.) must be 50% by mass or more. .

From the viewpoint of cleaning power and easy replacement, the content of the ultra-high molecular weight resin is preferably 0.1 parts by mass or more and 10 parts by mass or less, and 0.2 parts by mass or more, based on 100 parts by mass of the cleaning agent. It is more preferably 7 parts by mass or less, and even more preferably 0.3 parts by mass or more and 5 parts by mass or less.

In the cleaning agent of the present embodiment, the content of the additives having a scrubbing effect such as the inorganic filler, inorganic foaming agent, ultra-high molecular weight resin, etc. is preferably 10 parts by mass or less, for easy replacement. It is more preferably 5 parts by mass, and even more preferably 5 parts by mass.

Although the effect of additives with a scrubbing effect on substitutability is not necessarily clear, additives with a scrubbing effect such as inorganic fillers, inorganic blowing agents, and ultra-high molecular weight resins improve detergency while extrusion molding and If the flow path inside a mold or die for injection molding is complex, it tends to accumulate inside the resin processing machine, making it difficult to discharge and impeding replacement performance (however, the effect is not limited to this). .

[Cleaning agent manufacturing method]
The method for producing the cleaning agent of this embodiment is not particularly limited, and any known kneading machine can be used, such as a single-screw extruder, a multi-screw extruder including a twin-screw extruder, a roll, a kneader, a Brabender, etc. Examples include heating melt kneading machines such as Plastograph and Banbury mixer. Among the above, a melt-kneading method using a twin-screw extruder is preferred. Specifically, the ZSK series manufactured by Coperion, the TEM series manufactured by Shibaura Machinery Co., Ltd., the TEX series manufactured by Japan Steel Works, Ltd., etc. can be used.

[pellet]
It is preferable that the pellets of this embodiment contain the above-described crosslinked polyethylene for cleaning agent for resin processing machines of this embodiment, and further contain (B) polyolefin resin. The pellets preferably contain 10 to 1000 parts by mass of the (B) polyolefin resin based on 100 parts by mass of the crosslinked polyethylene for cleaning agent for resin processing machines.
It is preferable that the pellets contain the above-mentioned resin composition for a cleaning agent for resin processing machines.
The above-mentioned pellets can be manufactured by pelletizing the above-mentioned resin composition for a cleaning agent for resin processing machines. Examples of the pelletizing method include melt kneading, dry blending, and the like.
The above pellets can be used, for example, for cleaning resin processing machines.

[How to clean resin processing machine]
The crosslinked polyethylene for cleaning agent for resin processing machines and the cleaning agent of this embodiment can be used for any resin processing machines without any particular restrictions.
Specific examples of resin processing machines include injection molding machines, extrusion molding machines, and the like.

The cleaning method for a resin processing machine of this embodiment uses the above-described crosslinked polyethylene for resin processing machine cleaning agent of this embodiment or the cleaning agent of this embodiment. The cleaning method for a resin processing machine of this embodiment may include a step of retaining the above-described crosslinked polyethylene for resin processing machine cleaning agent of this embodiment or the cleaning agent of this embodiment in the resin processing machine. Specific examples of resin processing machines include those mentioned above.

The cleaning method of this embodiment not only allows the molded material to be efficiently discharged before cleaning, but also fills the resin processing machine with crosslinked polyethylene for cleaning agent or cleaning agent when the molding machine is stopped after cleaning. By allowing the resin to remain in this state, even if material molded before cleaning remains in the resin processing machine due to insufficient cleaning, there is an advantage that thermal deterioration of the remaining material can be prevented.

The method for cleaning the resin processing machine of this embodiment is a method of dry blending 10 to 1000 parts by mass of component (B) with 100 parts by mass of component (A). This method greatly simplifies the process.

The crosslinked polyethylene for cleaning agent for resin processing machines of this embodiment is particularly excellent in cleaning performance and replaceability of resin processing machines after using polyethylene. In addition, for cleaning and replacement after using polyethylene and other polyolefin resins in a resin processing machine, the above-mentioned crosslinked polyethylene for cleaning agent for resin processing machines and component (B) (preferably other than the above used in the resin processing machine) are used. It is preferable to use a cleaning agent containing a polyolefin resin (same as the polyolefin resin).

Hereinafter, the present embodiment will be specifically described with reference to Examples and Comparative Examples, but the present embodiment is not limited to the Examples and Comparative Examples described below unless the gist thereof is exceeded.
Various measuring methods for the cleaning agents and the like of Examples and Comparative Examples and the raw material components of the cleaning agents and the like used in the Examples and Comparative Examples are shown below.

Measurements of each material were performed as follows.
[MFR]
The MFR of each raw material was measured under the following conditions.
Cross-linked polyethylene: 220℃, load 10kg
Polyethylene: 190℃, load 2.16kg
Polypropylene: 230℃, load 2.16kg

[Gel fraction]
The gel fraction of crosslinked polyethylene was measured according to JIS K6796.

In the Examples and Comparative Examples, the following raw materials were used.
[raw materials]
(A) Cross-linked polyethylene (A-1) Foamed cross-linked polyethylene obtained by adding peroxide dicumyl peroxide to branched low-density polyethylene (MFR: 2.3 g/10 minutes) is processed into a barrel using a 95 mmφ single-screw extruder. Cross-linked polyethylene resin whose volume was reduced at a temperature of 300°C, gel fraction 30%, MFR 0.20 g/10 minutes (A-2) Linear low density polyethylene (MFR: 3.0 g/10 minutes) with an electron beam Offcuts of recycled crosslinked polyethylene film obtained by crosslinking: Gel fraction 20%, MFR 0.04g/10min (A-3) Low density polyethylene (MFR: 2.8g/10min) mixed with peroxide Crosslinked polyethylene obtained by adding milperoxide, gel fraction 35%, MFR measurement not possible

(B) Polyolefin resin (B-1) High density polyethylene MFR: 0.3 g/10 minutes (B-2) High density polyethylene MFR: 1.4 g/10 minutes (B-3) Propylene block copolymer MFR: 0. 8g/10 minutes

[Examples 1, 2, 5-7, Comparative Examples 1-3]
Each component was blended in the proportions shown in Table 1, and evaluated by the following method. The measurement and evaluation results are shown in Table 1. In Examples 5 to 7, the evaluation was performed after dry blending each raw material.

[Examples 3 and 4]
Each component was blended in the proportions shown in Table 1, and a cleaning agent was produced using a twin-screw extruder (TEM-26SX manufactured by Shibaura Kikai Co., Ltd.). The kneading conditions were a barrel temperature of 210 to 240°C, a discharge rate of 15 kg/hour, and a screw rotation speed of 150 rpm. The melt-kneaded product thus obtained was extruded into a strand, cooled with water, and then cut with a strand cutter to obtain a pellet-like cleaning agent. Using the obtained pellets, evaluation was performed by the following method. The measurement and evaluation results are shown in Table 1.

[Comparative example 4]
Detergent pellets were obtained in the same manner as above, except that the barrel temperature of the twin-screw extruder was changed to 300°C. The gel fraction was 1% and the MFR was 0.71 g/10 minutes.

The cleaning agents obtained in Examples and Comparative Examples were evaluated by the following method.

(1) Plasticization stability 1 kg of the pellets produced in the examples or comparative examples were put into a small extruder (Plasticorder manufactured by Brabender), and polyethylene was used only as the component (A) and as the component (B). In this case, the cylinder temperature is 200°C and the die temperature is 200°C, and when polypropylene is used as component (B), the resin is discharged from the die by rotating the screw at a cylinder temperature of 240°C and a die temperature of 240°C. Evaluated using evaluation criteria.
(Evaluation criteria)
+++: Torque fluctuation range is 0% or more and less than 5% ++: Torque fluctuation range is 5% or more +: The load on the small extruder was large and could not be evaluated.

(2) Burn removal Pour 100g of polyethylene resin into a small extruder (Plasticorder manufactured by Brabender), rotate the screw at a cylinder temperature of 310°C, discharge the resin from the nozzle, and deposit the resin inside the small extruder. Ta. Thereafter, the mixture was allowed to remain at the same temperature for 2 hours, and the remaining polyethylene resin adhered to the inside of the extruder was burnt. Thereafter, the cylinder temperature was raised to 200° C., and 100 g of the cleaning agents obtained in Examples and Comparative Examples were charged into the extruder to clean the inside.
Thereafter, the screw was removed, the amount of burn remaining on the screw surface was measured, and the cleaning performance (burn removal performance) was evaluated using the following evaluation criteria. Note that "-" in Example 7 and Comparative Example 3 indicates that no evaluation was performed.
(Evaluation criteria)
+++: The remaining area of the burn is less than 20% of the total surface area of the screw ++: The remaining area of the burn is less than 30% of the total surface area of the screw +: The remaining area of the burn is 30% of the total surface area of the screw % or more

(3-1) Cleanability (color change performance) (when the cleaning agent consists of component (A) only or component (A) and component (B) which is polyethylene)
Mix 10% by mass of a blue colored masterbatch and 90% by mass of high-density polyethylene, put 0.5 kg into a small extruder (Plasticorder manufactured by Brabender), and rotate the screw to expel the resin mixture from the die. It was discharged to cause false dirt to adhere to the inside of the extruder.
Thereafter, 1 kg of the cleaning agent obtained in the Examples and Comparative Examples was put into the extruder, and cleaning was performed by rotating the screw at a cylinder temperature of 200°C and a die temperature of 200°C. While visually observing the color tone of the purge waste discharged from the die, the purge waste was discharged until cleaning was completed. The amount (g) of discharged purge waste was measured using a balance, and the cleaning performance (color change performance) was evaluated using the following evaluation criteria.
Note that cleaning was completed when the color tone of the purge waste discharged from the die during cleaning was cooled to room temperature and solidified, changing from blue to the color of the cleaning agent.
(Evaluation criteria)
+++: The amount of purge waste discharged is less than 230 g.++: The amount of purge waste discharged is 230 g or more and less than 280 g. +: The amount of purge waste discharged is 280 g or more.

(3-2) Cleanability (color change performance) (when component (B) is polypropylene)
3% by mass of a black colored masterbatch and 97% by mass of polypropylene were mixed, 0.5 kg was put into a small extruder (Plasticorder manufactured by Brabender), and the resin mixture was discharged from the die by rotating a screw. This caused pseudo dirt to adhere to the inside of the extruder.
Thereafter, 1.5 kg of the cleaning agents obtained in the Examples and Comparative Examples were put into the extruder, and the cleaning agent was washed by rotating the screw at a cylinder temperature of 240°C and a die temperature of 240°C. While visually observing the color tone of the purge waste discharged from the die, the purge waste was discharged until cleaning was completed. The amount (g) of discharged purge waste was measured using a balance, and the cleaning performance (color change performance) was evaluated using the following evaluation criteria.
Note that cleaning was completed when the color tone of the purge waste discharged from the die during cleaning was cooled to room temperature and solidified, changing from black to the color of the cleaning agent.
(Evaluation criteria)
+++: The amount of purge waste discharged is less than 650 g ++: The amount of purge waste discharged is 650 g or more and less than 750 g. +: The amount of purge waste discharged is 750 g or more.

(4-1) Substitution property (when the cleaning agent consists of component (A) only or component (A) and component (B) which is polyethylene)
After the above "(3-1) Cleanability", 1 kg of high-density polyethylene was put into a small extruder (Plasticorder manufactured by Brabender) and replaced by screw rotation at a cylinder temperature of 200°C and a die temperature of 200°C. Then, while visually observing the external color tone of the molten resin discharged from the die, purge waste was discharged until replacement was completed. The amount (g) of discharged purge waste was measured using a balance, and the replacement performance was evaluated using the following evaluation criteria.
The replacement was completed when the external color of the molten purge waste discharged from the die during replacement changed from the color of the cleaning agent to colorless and transparent.
(Evaluation criteria)
+++: The amount of purge waste discharged is less than 50 g ++: The amount of purge waste discharged is 50 g or more and less than 100 g. +: The amount of purge waste discharged is 100 g or more.

(4-2) Substitution property (when component (B) is polypropylene)
After the above "(3-2) Cleanability", 1 kg of polypropylene resin was put into a small extruder (Plasticorder manufactured by Brabender) and replaced by screw rotation at a cylinder temperature of 240°C and a die temperature of 240°C. Then, while visually observing the external color tone of the molten resin discharged from the die, purge waste was discharged until replacement was completed. The amount (g) of discharged purge waste was measured using a balance, and the replacement performance was evaluated using the following evaluation criteria.
The replacement was completed when the external color of the molten purge waste discharged from the die during replacement changed from the color of the cleaning agent to colorless and transparent.
(Evaluation criteria)
+++: The amount of purge waste discharged is less than 50 g ++: The amount of purge waste discharged is 50 g or more and less than 100 g. +: The amount of purge waste discharged is 100 g or more.

From the above results, it can be seen that the cleaning agents obtained in Examples 1 to 7 have good cleaning properties and easy replacement properties. In addition, in Comparative Example 1, the load on the small extruder was large and could not be measured.

The crosslinked polyethylene for cleaning agents for resin processing machines and the resin composition for cleaning agents for resin processing machines of the present invention not only exhibit excellent cleaning performance, but also have excellent easy displacement and plasticization stability. It is useful as a cleaning agent for resin processing machines for injection molding and extrusion molding of thermoplastic resins.

Claims (10)

Cleaning for resin processing machines characterized by having a gel fraction (according to JIS K6796) of 10 to 34% and a melt mass flow rate (220°C, load 10 kg) of 0.01 to 0.50 g/10 minutes. Cross-linked polyethylene for agents. The crosslinked polyethylene for a cleaning agent for a resin processing machine according to claim 1, which is crosslinked polyethylene crosslinked by peroxide or electron beam crosslinking. The crosslinked polyethylene for a cleaning agent for a resin processing machine according to claim 1 or 2, which is crosslinked polyethylene obtained by recycling or volume reduction. A resin composition for a cleaning agent for a resin processing machine, comprising the crosslinked polyethylene (A) for a cleaning agent for a resin processing machine according to any one of claims 1 to 3 and a polyolefin resin (B). . The resin composition for a cleaning agent for resin processing machines according to claim 4, wherein the component (B) is at least one selected from the group consisting of polyethylene resins and polypropylene resins. According to claim 4 or 5, the method comprises 10 to 90 parts by mass of the component (A) and 90 to 10 parts by mass of the component (B), based on a total of 100 parts by mass of the component (A) and the component (B). The resin composition for a cleaning agent for resin processing machines as described above. The resin composition for a cleaning agent for a resin processing machine according to any one of claims 4 to 6, wherein the melt mass flow rate of the component (B) is 0.10 to 1.0 g/10 minutes. Pellets containing 10 to 1000 parts by mass of (B) polyolefin resin based on 100 parts by mass of the crosslinked polyethylene for cleaning agents for resin processing machines according to any one of claims 1 to 3. Use of the crosslinked polyethylene for cleaning agents for resin processing machines according to any one of claims 1 to 3, or the resin composition for cleaning agents for resin processing machines according to any one of claims 4 to 7. A cleaning method for a resin processing machine, characterized by: Cleaning a resin processing machine by dry blending 10 to 1000 parts by mass of (B) polyolefin resin to 100 parts by mass of the crosslinked polyethylene for cleaning agent for resin processing machines according to any one of claims 1 to 3. A method for cleaning a resin processing machine, characterized by: