JP7616910B2 - Resin molded body and method for producing the same - Google Patents

Description

The present invention relates to a resin molded body and a method for manufacturing the resin molded body, and in particular to a resin molded body used as a wire coating material for insulated wires used in automotive wire harnesses, electronic devices, etc., and a method for manufacturing the resin molded body.

In recent years, the signal band of information and communication devices and the CPU clock time of computers have become increasingly high-frequency, reaching the gigahertz (GHz) band, and it is known that the higher the frequency of the signal used, the greater the dielectric loss. Since the increase in dielectric loss attenuates the electrical signal and impairs the reliability of the signal, it is necessary to select a material with excellent dielectric properties for the insulator in order to suppress the dielectric loss.
For example, in automobiles, the on-board information and communication devices are becoming increasingly electronic, and in order to suppress dielectric loss in the information and communication devices, it is necessary to select materials with excellent dielectric properties for the coating materials used to coat the electric wires used in the information and communication devices.

In addition, with the progress of electronicization of information and communication devices, the number of electric and electronic wiring circuits in the information and communication devices has increased significantly, forming a complex wiring circuit structure. For the covering material for covering the electric wires used in the complex wiring circuit structure, it is necessary to select a material that is soft and has excellent formability so that it can follow the complex wiring circuit structure. Therefore, soft polyvinyl chloride is sometimes used as a material with excellent dielectric properties and formability. In order to reduce the dielectric properties of soft polyvinyl chloride, it has been proposed to use it by foaming (see, for example, Patent Document 1). However, the plasticizer contained in soft polyvinyl chloride tends to bleed out with long-term use. The dielectric properties tend to deteriorate due to the influence of the bleed-out plasticizer.
In order to prevent the deterioration of the dielectric properties of soft vinyl chloride, a polyolefin resin is sometimes added to the vinyl chloride resin (see, for example, Patent Document 2). However, in the case of such a mixed resin, molding is difficult due to the difference in molding temperature of the mixed resins.

JP 2018-9117 A JP 2020-198240 A

In view of the above circumstances, the present invention aims to provide a resin molded body having excellent dielectric properties and moldability, and a method for manufacturing the resin molded body.

As a result of intensive research conducted by the inventors to achieve the above object, they discovered that it is possible to obtain a resin molded article with excellent dielectric properties and moldability by molding a mixed resin of vinyl chloride resin and polypropylene resin while maintaining the granular shape of the polypropylene resin. Based on this knowledge, the inventors conducted further research and completed the present invention.

The present invention has been made to solve the above problems, and the gist of the present invention is as follows.
[1] A resin molding comprising a resin composition for moldings having 10 to 70 parts by mass of polypropylene resin per 100 parts by mass of vinyl chloride resin, wherein the average size of granular agglomerates of the polypropylene resin per unit area of 1 ^cm2 in the resin molding is 1 to 25 μm.
[2] The resin molded body according to [1], wherein the vinyl chloride resin has a softening point (Ta) of 50 to 80° C.
[3] The resin molded body according to [1] or [2], wherein the vinyl chloride resin is a vinyl chloride copolymer.
[4] The resin molded body according to any one of [1] to [3], wherein the polypropylene resin has a softening point (Tb) of 110 to 150°C.
[5] The resin molded body according to any one of [1] to [4], wherein the difference (Tb-Ta) between the softening point (Tb) of the polypropylene resin and the softening point (Ta) of the vinyl chloride resin is 60 to 100°C.
[6] The resin molded article according to any one of [1] to [5], which is a wire coating material.
[7] A method for producing a resin molded product, comprising: a preparation step of preparing a resin composition for molded products having 10 to 70 parts by mass of a polypropylene resin per 100 parts by mass of a vinyl chloride resin; and a molding step of molding the resin composition for molded products at a molding temperature that is equal to or higher than the softening point (Ta) of the vinyl chloride resin and equal to or lower than the softening point (Tb) of the polypropylene resin.
[8] The method for producing a resin molded body according to [7], wherein the molding temperature is 70 to 150° C.

The present invention provides a resin molded body with excellent dielectric properties and moldability, and a method for manufacturing the resin molded body.

1 is a TEM image of a resin molded body according to Example 1. 13 is a TEM image of a resin molded body according to Comparative Example 3. 1 is an image of a resin molded body according to Example 1 taken by a laser microscope. 13 is an image of a resin molded body according to Comparative Example 3 taken by a laser microscope.

[Resin molded body]
The resin molded body according to the embodiment of the present invention is made of a resin composition for molding having 10 to 70 parts by mass of polypropylene resin relative to 100 parts by mass of vinyl chloride resin. If the blending ratio of polypropylene resin in the resin composition for molding forming the resin molded body is less than 10 parts by mass relative to 100 parts by mass of vinyl chloride resin, the dielectric constant after molding cannot be sufficiently reduced, and a molded body having excellent dielectric properties cannot be obtained. If the blending ratio of polypropylene resin in the resin composition for molding forming the resin molded body is more than 70 parts by mass relative to 100 parts by mass of vinyl chloride resin, molding at or below the softening point of the polypropylene resin becomes difficult.
From the above viewpoints, the blending ratio of the polypropylene-based resin in the resin composition for molding is preferably 20 to 60 parts by mass, more preferably 25 to 55 parts by mass, and even more preferably 30 to 50 parts by mass, per 100 parts by mass of the vinyl chloride-based resin.

In the resin molded body according to the embodiment of the present invention, the average size of the polypropylene resin granular agglomerates per 1 ^cm2 unit area is 1 to 25 μm. If the average size of the polypropylene resin granular agglomerates per 1 ^cm2 unit area in the resin molded body is less than 1 μm, the dispersibility of the polypropylene resin granular agglomerates will be poor, and the granular agglomerates will aggregate, resulting in poor moldability. If the average size of the polypropylene resin granular agglomerates per 1 ^cm2 unit area in the resin molded body exceeds 25 μm, it will be difficult to mold well when using the resin composition for molded bodies.
From the above viewpoints, the average size of the polypropylene resin granular mass per 1 ^cm2 unit area in the resin molded body is preferably 1 to 25 μm, more preferably 1 to 20 μm, and even more preferably 1 to 15 μm.
<Method for measuring the average size of granular mass>
Three 1 ^cm2 locations are arbitrarily selected from the cross section of the resin molded body, and the maximum diameter of each granular mass within that range is measured using a transmission electron microscope (TEM). The maximum diameter of each granular mass of polypropylene resin present at each location is measured, and the average of the measured maximum diameters is calculated to be the average size of the granular mass of polypropylene resin per 1 ^cm2 unit area in the resin molded body. At this time, the maximum diameter is not measured for those where only a portion of the granular mass of polypropylene resin is photographed.

The resin molded article according to the embodiment of the present invention has excellent dielectric properties and moldability, and can therefore be suitably used as a wire coating material for insulated wires used in automotive wire harnesses, electronic devices, etc.

<Vinyl chloride resin>
The vinyl chloride resin is not particularly limited, and examples thereof include homopolymers of vinyl chloride monomers, (1) copolymers of vinyl chloride monomers and polymerizable monomers other than vinyl chloride monomers, and (2) graft copolymers in which vinyl chloride monomers or vinyl chloride resins are grafted onto polymers other than vinyl chloride resins. Furthermore, examples thereof include chlorinated vinyl chloride resins in which these vinyl chloride resins are chlorinated. These vinyl chloride resins may be used alone or in combination of two or more.

(1) The polymerizable monomer in the copolymer of vinyl chloride monomer and a polymerizable monomer other than vinyl chloride monomer is not particularly limited, but may be α-olefins having 2 to 16 carbon atoms (e.g., ethylene, propylene, and butylene); vinyl esters of aliphatic carboxylic acids having 2 to 16 carbon atoms (e.g., vinyl acetate and vinyl propionate); alkyl vinyl ethers having 2 to 16 carbon atoms (e.g., butyl vinyl ether and cetyl vinyl ether); alkyl (meth)acrylates having 1 to 16 carbon atoms (e.g., methyl (meth)acrylate, ethyl (meth)acrylate, and butyl acrylate); aryl (meth)acrylates (e.g., phenyl methacrylate); aromatic vinyls (e.g., styrene and α-substituted styrenes (e.g., α-methylstyrene)); vinyl halides (e.g., vinylidene chloride and vinylidene fluoride); and N-substituted maleimides (N-phenylmaleimide and N-cyclohexylmaleimide).

(2) Polymers that give graft copolymers together with vinyl chloride monomer or vinyl chloride resin include any polymers that can be graft-polymerized to vinyl chloride monomer, regardless of whether they are homopolymers or copolymers. Examples include copolymers of α-olefins and vinyl esters (e.g., ethylene-vinyl acetate copolymers); copolymers of α-olefins, vinyl esters, and carbon monoxide (e.g., ethylene-vinyl acetate-carbon monoxide copolymers); copolymers of α-olefins and alkyl (meth)acrylates (e.g., ethylene-methyl methacrylate copolymers and ethylene-ethyl acrylate copolymers); copolymers of α-olefins, alkyl (meth)acrylates, and carbon monoxide (e.g., ethylene-butyl acrylate-carbon monoxide copolymers); copolymers of two or more different α-olefins (e.g., ethylene-propylene copolymers); copolymers of unsaturated nitriles and dienes (e.g., acrylonitrile-butadiene copolymers); polyurethanes; and chlorinated polyolefins (e.g., chlorinated polyethylene and chlorinated polypropylene).

The average polymerization degree of the vinyl chloride resin is not particularly limited, but a smaller average polymerization degree leads to a decrease in the physical properties of the resin molded product, whereas a larger average polymerization degree leads to an increase in melt viscosity, making molding difficult. Therefore, the average polymerization degree is preferably 400 to 1,600, more preferably 500 to 1,500, and even more preferably 600 to 1,400.
The average degree of polymerization mentioned above means an average degree of polymerization measured in accordance with JIS K 6720-2:1999 "Plastics-Vinyl chloride homopolymer and copolymer (PVC)-Part 2: Preparation of test pieces and determination of properties" using a resin obtained by dissolving a vinyl chloride resin in tetrahydrofuran (THF), removing insoluble components by filtration, and then drying and removing the THF in the filtrate.

The polymerization method for the vinyl chloride resin is not particularly limited, and any conventionally known polymerization method can be used, such as bulk polymerization, solution polymerization, emulsion polymerization, and suspension polymerization.

The method for chlorinating the vinyl chloride resin is not particularly limited, and any conventionally known chlorination method can be used, such as thermal chlorination and photochlorination.

The softening point (Ta) of the vinyl chloride resin used in the present invention is preferably 50 to 80° C., more preferably 53 to 75° C., and even more preferably 55 to 70° C. When the softening point of the vinyl chloride resin is within this range, even when the resin is molded at a temperature equal to or lower than the softening point (Tb) of the polypropylene resin shown below, the resin can be sufficiently gelled, resulting in good moldability.
In the present invention, the term "softening point" refers to the temperature at which a substance such as a resin softens and begins to deform due to an increase in temperature. Usually, the temperature at which a substance becomes completely liquid when the temperature of the substance is increased is called the melting point. However, substances such as resins do not show a clear melting point, but gradually soften to a molten state, and it is difficult to identify a clear change in state, so they are sometimes called softening points to distinguish them from melting points. The softening point referred to here can be expressed by the Vicat softening temperature measured in accordance with Method A of JIS K7206:2016 "Plastics-Thermoplastics-Determination of Vicat Softening Temperature (VST)".

<Polypropylene resin>
The polypropylene resin is not particularly limited, and examples thereof include homopolypropylene, ethylene-propylene random copolymers mainly composed of propylene, and ethylene-propylene block copolymers mainly composed of propylene. These polypropylene resins may be used alone or in combination of two or more. Among them, it is preferable to contain an ethylene-propylene random copolymer mainly composed of propylene. From the viewpoint of reducing the dielectric constant, an ethylene-propylene block copolymer mainly composed of propylene may be contained. Incidentally, "mainly composed" here means that the propylene content in the copolymer is 50% by mass or more.

The softening point (Tb) of the polypropylene-based resin used in the present invention is preferably 110 to 150° C., more preferably 115 to 148° C., and even more preferably 120 to 145° C. When the softening point (Tb) of the polypropylene-based resin is within this range, when a resin molding is formed using the resin composition for molding obtained by mixing the polypropylene-based resin with the vinyl chloride resin, the molding temperature can be set lower than the softening point (Tb) of the polypropylene-based resin, thereby making it possible to improve moldability.
The softening point can be represented by the Vicat softening temperature measured in accordance with Method A of JIS K7206:2016 “Plastics-Thermoplastics-Determination of Vicat Softening Temperature (VST)”.

The difference (Tb-Ta) between the softening point (Tb) of the polypropylene resin used in the present invention and the softening point (Ta) of the vinyl chloride resin is preferably 60 to 100°C, more preferably 65 to 95°C, and even more preferably 70 to 90°C. When the difference (Tb-Ta) between the softening point (Tb) of the polypropylene resin and the softening point (Ta) of the vinyl chloride resin is within this range, it becomes easier to set the temperature during molding when molding a resin molded product using the resin composition for molding, and the moldability becomes good.

(Additives)
In addition, additives may be added to the resin molded product of the present invention within the scope of not impairing the object of the present invention. Examples of various additives that may be added to the resin molded product include heat stabilizers, lubricants, processing aids, impact modifiers, heat resistance improvers, antioxidants, ultraviolet absorbers, antistatic agents, light stabilizers, pigments, flame retardants, inorganic fillers, and plasticizers. Only one type of additive may be used, or two or more types may be used in combination.

The heat stabilizer is not particularly limited, and examples thereof include a heat stabilizer and a heat stabilization assistant, etc. The heat stabilizer is not particularly limited, and examples thereof include an organotin-based stabilizer, a lead-based stabilizer, a calcium-zinc-based stabilizer, a barium-zinc-based stabilizer, and a barium-cadmium-based stabilizer, etc.
Examples of the organic tin stabilizer include dibutyltin mercapto, dioctyltin mercapto, dimethyltin mercapto, dibutyltin mercapto, dibutyltin maleate, dibutyltin maleate polymer, dioctyltin maleate, dioctyltin maleate polymer, dibutyltin laurate, and dibutyltin laurate polymer, etc. The above stabilizers may be used alone or in combination of two or more kinds.
The heat stabilization aid is not particularly limited, and examples thereof include epoxidized soybean oil, phosphoric acid ester, polyol, hydrotalcite, zeolite, etc. The heat stabilization aid may be used alone or in combination of two or more kinds.

The lubricant may be an internal lubricant or an external lubricant. The internal lubricant is used to reduce the flow viscosity of the molten resin during molding and to prevent heat generation due to friction.
The internal lubricant is not particularly limited, and examples thereof include butyl stearate, lauryl alcohol, stearyl alcohol, epoxy soybean oil, glycerin monostearate, stearic acid, bisamide, etc. The above lubricants may be used alone or in combination of two or more kinds.
The external lubricant is used for the purpose of increasing the sliding effect between the molten resin and the metal surface during molding. The external lubricant is not particularly limited, and examples thereof include wax-based lubricants such as paraffin wax, polyolefin wax, ester wax, and montanic acid wax. The above lubricants may be used alone or in combination of two or more.

A wide variety of known processing aids can be used, and there are no particular limitations. Examples of processing aids include acrylic processing aids such as alkyl acrylate-alkyl methacrylate copolymers having a weight average molecular weight of 100,000 to 2,000,000. The acrylic processing aids are not particularly limited, and examples include n-butyl acrylate-methyl methacrylate copolymers, 2-ethylhexyl acrylate-methyl methacrylate-butyl methacrylate copolymers, and the like. These may be used alone, or two or more of them may be used in combination.

A wide variety of known impact modifiers can be used, and there are no particular limitations. As the impact modifier, for example, one or more selected from the group consisting of methyl methacrylate-butadiene-styrene copolymer (MBS), chlorinated polyethylene, acrylic rubber, etc. can be used.

A wide variety of known heat resistance improvers can be used, and there are no particular limitations. Examples of heat resistance improvers that can be used include α-methylstyrene-based and N-phenylmaleimide-based resins.

The antioxidant is not particularly limited, and a wide variety of known antioxidants can be used. Examples of antioxidants include phenol-based antioxidants.

The ultraviolet absorbing agent is not particularly limited, and a wide variety of known agents can be used. Examples of ultraviolet absorbing agents include salicylic acid ester-based, benzophenone-based, benzotriazole-based, and cyanoacrylate-based ultraviolet absorbing agents. These may be used alone or in combination of two or more types.

The antistatic agent is not particularly limited, and conventionally known antistatic agents can be used, and anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants, etc. can be used. Examples of anionic surfactants include fatty acid salts, higher alcohol sulfate ester salts, liquid fatty oil sulfate ester salts, fatty amines, sulfate salts of amides, sulfonic acid salts of dibasic fatty acid esters, fatty acid amide sulfonates, alkylaryl sulfonates, formalin condensation naphthalene sulfonates, and mixtures thereof. Examples of cationic surfactants include fatty amine salts, quaternary ammonium salts, alkylpyridinium salts, and mixtures thereof. Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol esters, polyoxyethylene alkyl esters, sorbitan alkyl esters, polyoxyethylene sorbitan alkyl esters, and mixtures thereof. A mixture of a nonionic surfactant and an anionic surfactant or a cationic surfactant may also be used. Examples of amphoteric surfactants include imidazoline type, higher alkylamino type (betaine type), sulfate ester, phosphate ester type, sulfonic acid type, etc. Antistatic agents may be used alone or in combination of two or more types.

The light stabilizer is not particularly limited, and a wide variety of known light stabilizers can be used. Examples of light stabilizers include hindered amine light stabilizers.

The pigment is not particularly limited, and a wide variety of known pigments can be used. Examples of pigments include organic pigments such as azo, phthalocyanine, threne, and dye lake pigments; and inorganic pigments such as oxide, molybdenum chromate, sulfide/selenide, and ferrocyanide pigments. These may be used alone or in combination of two or more.

The flame retardant is not particularly limited, and a wide variety of known flame retardants can be used. Examples of flame retardants include red phosphorus, phosphate esters, phosphate-containing flame retardants, bromine-containing flame retardants, boric acid-containing flame retardants, antimony-containing flame retardants, and metal hydroxides. These may be used alone or in combination of two or more.

The inorganic filler is not particularly limited, and examples thereof include inorganic fillers such as carbonates such as talc, heavy calcium carbonate, precipitated calcium carbonate, and colloidal calcium carbonate, aluminum hydroxide, magnesium hydroxide, titanium oxide, clay, mica, wollastonite, zeolite, silica, zinc oxide, magnesium oxide, carbon black, graphite, glass beads, glass fibers, carbon fibers, and metal fibers, as well as polyamides. The above fillers may be used alone or in combination of two or more.

The plasticizer is not particularly limited, and a wide variety of known plasticizers can be used. For example, the plasticizer may be one or more selected from the group consisting of dibutyl phthalate, di-2-ethylhexyl phthalate, and di-2-ethylhexyl adipate.

[Method of manufacturing resin molded body]
The method for producing a resin molded product in the present invention includes a preparation step of preparing a resin composition for molding having 10 to 70 parts by mass of a polypropylene-based resin relative to 100 parts by mass of a vinyl chloride-based resin, and a molding step of molding the resin composition for molding at a temperature not lower than the softening point (Ta) of the vinyl chloride-based resin and not higher than the softening point (Tb) of the polypropylene-based resin.

In the preparation step, the vinyl chloride resin, polypropylene resin, and optional components can be mixed using known devices such as a bead mill, a Banbury mixer, a kneader mixer, a kneading roll, a Raikai mixer, and a planetary mixer to obtain a resin composition for molding. In addition, when the resin composition for molding that forms the resin molding of the present invention is diluted with a solvent, the diluted solution of the resin composition for molding can be obtained by further adding a solvent to these and mixing them using the above-mentioned mixing device.

In the molding process, the resin composition for molded bodies is heated to a temperature equal to or higher than the softening point (Ta) of the vinyl chloride resin and equal to or lower than the softening point (Tb) of the polypropylene resin by a molding means such as extrusion molding, injection molding, or press molding, and molded to obtain a resin molded body.
The molding method is preferably extrusion molding, and molding can be performed using a single screw extruder, a twin screw extruder, an injection molding machine, or the like.
The resin molded product obtained by the method for producing a resin molded product of the present invention can be used as a wire covering material having a desired thickness by rolling it with a rolling machine or the like.

If the molding temperature in the molding process is lower than the softening point (Ta) of the vinyl chloride resin, the vinyl chloride resin will gel too much or too little during molding, resulting in poor moldability. If the molding temperature in the molding process exceeds the softening point (Tb) of the polypropylene resin, the polypropylene resin will melt entirely and will no longer remain in the resin molded body as granular lumps, making it difficult to maintain the dielectric constant of the polypropylene resin. From the above perspective, the molding temperature in the molding process is preferably 70 to 150°C, more preferably 75 to 145°C, and even more preferably 80 to 140°C.

According to the method for producing a resin molded body of the present invention, a resin molded body is produced from a resin composition for molding having 10 to 70 parts by mass of polypropylene-based resin per 100 parts by mass of vinyl chloride-based resin, whereby a resin molded body having excellent dielectric properties and moldability can be obtained.
Furthermore, according to the method for producing a resin molded body of the present invention, by heating and molding the resin composition for molding to a temperature equal to or lower than the softening point (Tb) of the polypropylene resin, the polypropylene resin does not melt entirely and remains in the resin molded body as granular lumps, so that it is possible to maintain the dielectric constant of the polypropylene resin. Also, according to the method for producing a resin molded body of the present invention, by heating and molding the resin composition for molding to a temperature equal to or higher than the softening point (Ta) of the vinyl chloride resin, it is possible to eliminate problems such as excess or deficiency of gel of the vinyl chloride resin during molding.

The above describes the embodiments of the present invention, but the present invention is not limited to these examples, and can of course be embodied in various forms without departing from the spirit of the present invention.

The following provides a more detailed explanation of the present invention based on examples, but the present invention is not limited to these.

<Preparation of resin molded body>
[Example 1, Comparative Examples 1 and 3]
100 parts by mass of vinyl chloride resin (Tokuyama Sekisui Co., Ltd., product number SL-P40) was mixed with 2 parts by mass of organotin stabilizer (Nitto Kasei Co., Ltd., product number ONZ-7F), 0.5 parts by mass of wax lubricant (Clariant Japan Co., Ltd., product number Wax OP), and further with polypropylene resin (Seishin Co., Ltd., product number PPW-5J) in the ratios shown in Table 1, and then stirred and mixed in a Henschel mixer (Kawata Co., Ltd.) with an internal volume of 200 liters to obtain a resin composition for molding. The obtained resin composition for molding was kneaded with rolls heated to the temperature shown in Table 1, and a molded article was produced with a press machine heated to 100°C, to obtain a resin molded body.

[Examples 2 to 3, Comparative Examples 2 and 4]
100 parts by mass of vinyl chloride resin (Tokuyama Sekisui Co., Ltd., product number TG40) was mixed with 2 parts by mass of organotin stabilizer (Nitto Kasei Co., Ltd., product number ONZ-7F), 0.5 parts by mass of wax lubricant (Clariant Japan Co., Ltd., product number Wax OP), and polypropylene resin (Seishin Co., Ltd., product number PPW-5J) in the ratios shown in Table 1, and then stirred and mixed in a Henschel mixer (Kawata Co., Ltd.) with an internal volume of 200 liters to obtain a resin composition for molding. The obtained resin composition for molding was kneaded with rolls heated to the temperature shown in Table 1, and a molded product was produced with a press machine heated to 100°C, to obtain a resin molded body.

<Softening point (Vicat softening temperature) measurement>
The softening points of the vinyl chloride resin and polypropylene resin used were measured in accordance with Method A of JIS K7206:2016 "Plastics - Thermoplastics - Determination of Vicat softening temperature (VST)". The resin was dried at 100°C for 3 hours and then heat-pressed at a melting point (Tm) + 30°C to prepare a test piece of 10 mm x 10 mm x 5 mm thick. The measurement was carried out three times under the condition of a test load of 10 N at 100° C., and the average value of these was taken as the Vicat softening temperature. Ta) is shown in Table 1.

<Dielectric property evaluation>
The dielectric constant of the obtained resin molded product was measured in accordance with IEC 62631-2-1 "Automatic Balance Bridge Method". A Precision LCR Meter E4980A (manufactured by Agilent Technologies, Inc.) was used as the measuring device, and the product was set between parallel electrodes of conductive silver paint with a diameter of 36 mm, and the dielectric constant was obtained under the conditions of room temperature (23°C) and a frequency of 1 MHz. The obtained dielectric constant was judged according to the following criteria.
"Judgment criteria"
A (pass): Dielectric constant is 3.1 (F/m) or less B (fail): Dielectric constant is more than 3.1 (F/m)

<Moldability evaluation>
When kneaded in a heated open roll mixer, the resin molded sheet was wrapped around the front roll within 5 minutes, and the appearance of the resin molded sheet was observed 3 minutes later and rated according to the following criteria.
"Judgment criteria"
A (pass): Appearance is smooth and the sheet is not loose. B (fail): Sheet molding is impossible due to melting of the resin, but a molded product can be made by collecting the kneaded pieces and pressing them. C (fail): Sheet molding is impossible due to melting of the resin.

<Confirmation of granular mass>
From the produced resin molded body, 1 ^cm2 pieces were cut out from three random locations as samples for TEM, the maximum diameter of the polypropylene resin granular agglomerates in the samples was measured by TEM, and the average of the measured maximum diameters was calculated to obtain the average size of the polypropylene resin granular agglomerates per 1 ^cm2 unit area in the resin molded body. The results are shown in Table 1.

*Because it was difficult to measure the average size of the granular masses using a TEM, it was measured using a laser microscope (see Figure 4).

<Experimental Results>
As shown in Examples 1 to 3, in order to obtain a resin molded product having excellent dielectric properties and moldability, it is necessary to mix 100 parts by mass of vinyl chloride resin with 10 to 70 parts by mass of polypropylene resin and mold the resin at a temperature below the softening point of the polypropylene resin.
As shown in Comparative Example 1, when no polypropylene resin is added, molding at or below the softening point of the polypropylene resin passes, but the dielectric constant becomes high and the product fails.
As shown in Comparative Example 2, when the blending amount of polypropylene-based resin is large, even if the molding temperature is below the softening point of the polypropylene-based resin, the sheet cannot be formed because the sheet does not wind around the front roll, and the moldability is unacceptable.
As shown in Comparative Examples 3 and 4, even if the blending amount of polypropylene-based resin was within the range of 10 to 70 parts by mass, the molding temperature exceeded the softening point of the polypropylene-based resin, so the sheet did not wrap around the front roll, making it impossible to mold into a sheet, and the moldability was unacceptable.
As examples, a TEM image of the resin molded product in Example 1 is shown in Figure 1, and a TEM image of the resin molded product in Comparative Example 3 is shown in Figure 2. Furthermore, as an overall distribution map of the polyolefin-based resin, a laser microscope image of the resin molded product in Example 1 is shown in Figure 3, and a laser microscope image of the resin molded product 3 in Comparative Example is shown in Figure 4. As shown in Figures 1 to 4, the average size of the granular agglomerates can be set to 1 to 25 μm by setting the molding temperature to be equal to or lower than the softening point of the polypropylene-based resin.

Claims (7)

A resin molding comprising a resin composition for molding having 100 parts by mass of a vinyl chloride resin and 10 to 70 parts by mass of a polypropylene resin,
the average size of the granular agglomerates of the polypropylene resin per unit area of 1 ^cm2 in the resin molded body is 1 to 25 μm,
The resin molded product has a difference (Tb-Ta) between the softening point (Tb) of the polypropylene resin and the softening point (Ta) of the vinyl chloride resin of 60 to 100°C . The resin molded body according to claim 1, wherein the vinyl chloride resin has a softening point (Ta) of 50 to 80°C. The resin molded body according to claim 1 or 2, wherein the vinyl chloride resin is a vinyl chloride copolymer. The resin molded body according to any one of claims 1 to 3, wherein the polypropylene resin has a softening point (Tb) of 110 to 150°C. The resin molded article according to any one of claims 1 to 4 , which is a wire coating material. a preparation step of preparing a resin composition for molding having 10 to 70 parts by mass of a polypropylene resin relative to 100 parts by mass of a vinyl chloride resin;
and a molding step of molding the resin composition for molding at a molding temperature that is equal to or higher than the softening point (Ta) of the vinyl chloride resin and equal to or lower than the softening point (Tb) of the polypropylene resin,
a difference (Tb-Ta) between the softening point (Tb) of the polypropylene resin and the softening point (Ta) of the vinyl chloride resin is 60 to 100°C . The method for producing a resin molded article according to claim 6 , wherein the molding temperature is 70 to 150°C.