Method for producing agglomerated vinyl chloride resin particle and method for producing vinyl chloride resin composition

Abstract

To provide a method for producing agglomerated vinyl chloride resin particles that have strength required for processes such as washing, and which satisfy excellent kneadability; and to provide a method for producing a vinyl chloride resin composition containing the agglomerated vinyl chloride resin particles obtained in the method for producing the vinyl chloride resin composition.SOLUTION: A method for producing agglomerated vinyl chloride resin particles, comprises: subjecting a mixture containing a vinyl chloride resin latex and a coagulant to shear force using a colloid mill to obtain an agglomerated latex containing agglomerated vinyl chloride resin particles; and performing heat treatment on the agglomerated latex within a temperature range of [Tg-10°C] to [Tg+5°C], where Tg is the glass transition temperature of the vinyl chloride resin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing agglomerated vinyl chloride resin particles and a method for producing a vinyl chloride resin composition. [Background technology]

[0002] Because vinyl chloride resins are inexpensive and have excellent processability and durability, they are widely used for coating the inner surfaces of metal cans and as marking films. For example, Patent Document 1 describes the use of a composition containing vinyl chloride resin agglomerated particles having a particle diameter D50 of 0.5 μm to 5.0 μm at a cumulative volume percentage of 50 volume% in a volume particle diameter distribution and a particle diameter D90 of 8.0 μm or less at a cumulative volume percentage of 90 volume% in a volume particle diameter distribution, and a Na concentration of 90 ppm or less, as a coating composition for metal cans or a marking film composition. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2019 / 159896 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0004] Resin compositions used for coating the inner surfaces of metal cans or for marking films require low sol coarse particles (for example, coarse particles of 25 μm or less according to Method A). Therefore, in Patent Document 1, vinyl chloride resin latex particles are aggregated into particles of about 100 μm or more, and the aggregates are washed, dehydrated, and then pulverized to obtain a composition that satisfies the low sol coarse particle requirement. However, there is a problem in that the pulverization load is high. Furthermore, to use the vinyl chloride resin aggregated particles in a composition, they need to be kneaded with compounding agents such as plasticizers, and kneadability is required.

[0005] In order to solve the above-mentioned problems of the related art, the present invention provides a method for producing a vinyl chloride resin composition from which vinyl chloride resin agglomerated particles having the strength required for steps such as washing and good kneadability can be obtained, and a method for producing a vinyl chloride resin composition containing vinyl chloride resin agglomerated particles obtained by the method for producing a vinyl chloride resin composition. [Means for solving the problem]

[0006] The present invention relates to a method for producing vinyl chloride resin agglomerated particles, comprising the steps of: applying shear force to a mixture containing vinyl chloride resin latex and an aggregating agent using a colloid mill to obtain an agglomerated latex containing vinyl chloride resin agglomerated particles; and heat-treating the agglomerated latex in a temperature range of [Tg-10°C] to [Tg+5°C], where Tg is the glass transition temperature of vinyl chloride resin.

[0007] The present invention relates to a method for producing a vinyl chloride resin composition, the vinyl chloride resin composition containing vinyl chloride resin agglomerated particles obtained by the method for producing vinyl chloride resin agglomerated particles and a plasticizer, and the method for producing a vinyl chloride resin composition includes a step of kneading the vinyl chloride resin agglomerated particles and the plasticizer. [Effects of the Invention]

[0008] According to the method for producing vinyl chloride resin agglomerated particles of the present invention, it is possible to obtain vinyl chloride resin agglomerated particles that have the strength required for steps such as washing and that have good kneadability. Furthermore, by kneading the vinyl chloride resin agglomerated particles with a plasticizer, it is possible to obtain a vinyl chloride resin composition having low sol coarse particles and good kneadability. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a schematic diagram illustrating the aggregation of vinyl chloride resin latex particles to form vinyl chloride resin aggregate particles. DETAILED DESCRIPTION OF THE INVENTION

[0010] The inventors of the present invention conducted extensive research to solve the above-mentioned problems. As a result, they surprisingly found that vinyl chloride resin agglomerated particles can be produced by applying shear force to a mixture containing a vinyl chloride resin latex and a flocculant using a colloid mill to agglomerate the vinyl chloride resin latex, followed by heat treatment, and that by setting the heat treatment temperature within a predetermined range, vinyl chloride resin agglomerated particles can be obtained that have the strength required for processes such as washing and have good kneadability. Furthermore, by kneading the vinyl chloride resin agglomerated particles with a plasticizer, a low-sol coarse vinyl chloride resin composition can be obtained with good kneadability. In particular, a vinyl chloride resin composition can be obtained with good kneadability even when the amount of plasticizer mixed relative to the vinyl chloride resin agglomerated particles is low.

[0011] Specifically, a mixture containing a vinyl chloride resin latex and a flocculant is subjected to shear force using a colloid mill to aggregate the vinyl chloride resin latex, resulting in vinyl chloride resin agglomerated particles containing secondary particles formed by aggregation of vinyl chloride resin latex particles (primary particles) and tertiary particles formed by further aggregation of the secondary particles. After the aggregation process, the vinyl chloride resin agglomerated particles are heat-treated at a temperature range of [Tg-10°C] to [Tg+5°C], where Tg is the glass transition temperature of the vinyl chloride resin. It is believed that the bond strength between the primary particles is relatively stronger than the bond strength between the secondary particles, and that the bond strength between the secondary particles is within an appropriate range. Because the bond strength between the primary particles is relatively stronger than the bond strength between the secondary particles, the vinyl chloride resin agglomerated particles will not disintegrate into primary particles even when subjected to external forces during processes such as washing, and will have the strength required for such processes. Furthermore, it is presumed that the vinyl chloride resin agglomerated particles have an appropriate bond strength between secondary particles, which makes it easier for tertiary particles to become secondary particles due to external forces during kneading, thereby improving kneadability. In particular, the kneadability is good even when the blending amount of plasticizer is less than the blending amount of vinyl chloride resin agglomerated particles.

[0012] In this specification, when a numerical range is indicated with "to", the numerical range includes both end values ​​(upper and lower limits). For example, a numerical range of "X to Y" includes both end values ​​X and Y, and is the same range as "X or more and Y or less". Any number within that range and any range included within that range are specifically disclosed. In addition, when multiple numerical ranges are described in this specification, they are intended to include numerical ranges that combine the upper and lower limits of different numerical ranges as appropriate.

[0013] (Method of producing vinyl chloride resin agglomerated particles) In the method for producing vinyl chloride resin agglomerated particles according to one or more embodiments of the present invention, first, a shear force is applied to a mixture containing a vinyl chloride resin latex and an aggregating agent using a colloid mill to obtain an agglomerated latex containing vinyl chloride resin agglomerated particles (hereinafter also simply referred to as the aggregating step).

[0014] The vinyl chloride resin latex is not particularly limited, but can be obtained, for example, by adding a polymerization initiator and an emulsifier to a vinyl chloride monomer or a mixture of a vinyl chloride monomer and a monomer copolymerizable therewith in an aqueous medium such as ion-exchanged water, and then carrying out emulsion polymerization, seed emulsion polymerization, microsuspension polymerization, or seed microsuspension polymerization. In the polymerization, a dispersing aid such as a higher alcohol or a higher fatty acid, and a pH adjuster such as sodium bicarbonate or sodium carbonate may be used as necessary.

[0015] The monomer copolymerizable with vinyl chloride monomer is not particularly limited, and any monomer copolymerizable with vinyl chloride can be used, including, for example, olefins such as ethylene, propylene, and butene; vinyl esters such as vinyl acetate, vinyl propionate, and vinyl stearate; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, octyl vinyl ether, and lauryl vinyl ether; vinylidenes such as vinylidene chloride; unsaturated carboxylic acids and their anhydrides such as acrylic acid, methacrylic acid, fumaric acid, maleic acid, itaconic acid, maleic anhydride, and itaconic anhydride; unsaturated carboxylic acid esters such as methyl acrylate, ethyl acrylate, monomethyl maleate, dimethyl maleate, and butylbenzyl maleate; aromatic vinyl compounds such as styrene, α-methylstyrene, and divinylbenzene; unsaturated nitriles such as acrylonitrile; and crosslinking monomers such as diallyl phthalate. These monomers can be used alone or in combination. The amount of these monomers used is preferably less than 50% by weight in the monomer mixture with vinyl chloride monomer. The content of vinyl chloride monomer in the mixture of vinyl chloride monomer and a monomer copolymerizable with vinyl chloride monomer is more than 50% by weight, and may be 60% by weight or more, 70% by weight or more, 80% by weight or more, or 90% by weight or more.

[0016] The emulsifier is not particularly limited, and for example, an anionic surfactant can be used. Examples of the anionic surfactant include potassium salts, sodium salts, and ammonium salts of fatty acids, alkyl sulfates, alkyl benzene sulfonates, alkyl sulfosuccinates, α-olefin sulfonates, and alkyl ether phosphate esters. From the viewpoint of viscosity stability of a composition containing vinyl chloride resin agglomerated particles, the emulsifier is preferably a fatty acid salt, more preferably one or more selected from the group consisting of potassium salts of fatty acids, sodium salts of fatty acids, and ammonium salts of fatty acids, and even more preferably one or more selected from the group consisting of sodium lauryl sulfate, potassium stearate, potassium myristate, and ammonium myristate.

[0017] The emulsifier can be used in an amount of, for example, about 0.1 to 3.0 parts by weight per 100 parts by weight of the total monomers. From the viewpoint of improving the stability of the resulting vinyl chloride resin latex and the transparency of films such as can inner surface films and marking films, the emulsifier is preferably used in an amount of 0.2 to 1.0 part by weight, more preferably 0.2 to 0.5 part by weight, per 100 parts by weight of the monomers.

[0018] Examples of the polymerization initiator include oil-soluble polymerization initiators and water-soluble polymerization initiators. Examples of the oil-soluble polymerization initiator include organic peroxides and azo initiators. Examples of organic peroxides include hydroperoxides such as t-butyl hydroperoxide; diacyl peroxides such as dilauroyl peroxide and di-3,5,5-trimethylhexanoyl peroxide; peroxydicarbonates such as diisopropyl peroxydicarbonate and di-2-ethylhexyl peroxydicarbonate; and peroxyesters such as t-butyl peroxypivalate and t-butyl peroxyneodecanoate. Examples of azo initiators that can be used include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), and 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile). Examples of the water-soluble polymerization initiator that can be used include ammonium persulfate, potassium persulfate, sodium persulfate, and aqueous hydrogen peroxide. The polymerization initiators can be used alone or in combination of two or more. The polymerization initiators can be used in combination with reducing agents such as sodium sulfite, sodium thiosulfate, sodium hydroxymethanesulfinate dihydrate (also known as Rongalit), ascorbic acid, and sodium ascorbate, as needed. The reducing agents can be used alone or in combination of two or more.

[0019] In the vinyl chloride resin latex, the volume average particle diameter of the vinyl chloride resin latex particles is not particularly limited, but is preferably 0.1 to 2.0 μm from the viewpoint of polymerization stability. When the volume average particle diameter of the vinyl chloride resin latex particles is 0.1 μm or more, mechanical stability during latex transfer is improved, thereby improving productivity. When the volume average particle diameter of the vinyl chloride resin latex particles is 2.0 μm or less, polymerization stability is improved. From the viewpoint of polymerization stability, the volume average particle diameter of the vinyl chloride resin latex particles is more preferably 1.7 μm or less, and even more preferably 1.4 μm or less.

[0020] From the viewpoint of reducing the viscosity of a composition containing vinyl chloride resin aggregate particles and promoting gelation, the vinyl chloride resin latex preferably contains 5 to 95 volume % vinyl chloride resin latex particles F having a volume average particle diameter of 0.5 μm or less and 5 to 95 volume % vinyl chloride resin latex particles R having a volume average particle diameter larger than that of the vinyl chloride resin latex particles F but 1.7 μm or less; more preferably 10 to 90 volume % vinyl chloride resin latex particles F and 10 to 90 volume % vinyl chloride resin latex particles R; even more preferably 15 to 85 volume % vinyl chloride resin latex particles F and 15 to 85 volume % vinyl chloride resin latex particles R; and even more preferably 20 to 50 volume % vinyl chloride resin latex particles F and 50 to 80 volume % vinyl chloride resin latex particles R. From the viewpoint of the stability of vinyl chloride resin polymerization, the volume average particle diameter of the vinyl chloride resin latex particles R is more preferably 1.4 μm or less. From the viewpoint of achieving low viscosity and promoting gelation, the volume average particle diameter of the vinyl chloride resin latex particles F is more preferably 0.4 μm or less.

[0021] The vinyl chloride resin latex preferably has a resin solids concentration of 22% by weight or more, more preferably 25 to 50% by weight, and even more preferably 30 to 45% by weight. When the vinyl chloride resin latex has a resin solids concentration within the above range, the vinyl chloride resin latex has excellent fluidity and can be easily transferred to a colloid mill.

[0022] A water-soluble flocculant can be used as the flocculant. Examples of the water-soluble flocculant include inorganic salts, inorganic acids, organic acids, organic salts, and water-soluble polymers. Examples of the inorganic salt include, but are not limited to, metal sulfates and metal chlorides. Examples of the metal sulfate include sodium sulfate and aluminum sulfate. Examples of the metal chloride include sodium chloride, potassium chloride, calcium chloride, and aluminum chloride. For example, sodium sulfate is suitable as the inorganic salt from the viewpoint of versatility. Examples of the inorganic acid include, but are not limited to, sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid. Examples of the organic acid include, but are not limited to, citric acid, malic acid, tartaric acid, gluconic acid, succinic acid, malonic acid, glutaric acid, maleic acid, fumaric acid, and glutaconic acid. Examples of the organic salt include, but are not limited to, sodium acetate and calcium acetate.

[0023] Examples of the water-soluble polymer that can be used include synthetic polymers, natural polymers, and semi-synthetic polymers. Examples of the synthetic polymers include polymers of acryloyl group-containing monomers, vinyl polymers, polyamidines, polyethylene oxides, and polyethyleneimines. Examples of the natural polymers include polysaccharides and proteins. Examples of the semi-synthetic polymers include cellulose ethers and starch derivatives. From the viewpoint of reducing the moisture absorption rate of the vinyl chloride resin agglomerated particles, the amount of the water-soluble polymer to be blended is preferably 25 wt% or less, and more preferably 10 wt% or less, of the total weight of the flocculant.

[0024] From the viewpoint of reducing the moisture absorption rate of vinyl chloride resin agglomerated particles and stabilizing the viscosity of a composition containing the vinyl chloride resin agglomerated particles during storage, it is preferable to use, as the agglomerating agent, one or more selected from the group consisting of inorganic salts, inorganic acids, organic acids, and organic salts, it is more preferable to use one or more selected from the group consisting of inorganic salts and inorganic acids, and it is even more preferable to use an inorganic salt.

[0025] The flocculant may be added to the vinyl chloride resin latex in the form of either a solid or an aqueous solution, but from the viewpoint of dispersibility, the flocculant is preferably added to the vinyl chloride resin latex in the form of an aqueous solution, and more preferably added to the vinyl chloride resin latex in a fluidized state. The flocculant is also preferably added to the vinyl chloride resin latex after the polymerization of the vinyl chloride resin is completed.

[0026] Specifically, the aggregation of the vinyl chloride resin latex is carried out by feeding an aqueous solution of the vinyl chloride resin latex and an aggregating agent such as an inorganic salt into a colloid mill, mixing the vinyl chloride resin latex and the aggregating agent at the inlet of the colloid mill, and applying shear force to the mixture inside the colloid mill. The conditions for applying the shear force are not particularly limited. For example, to facilitate the formation of secondary particles in which primary particles are strongly bonded and the formation of tertiary particle structures in which the secondary particles are loosely bonded, a frequency of 20 to 60 Hz and a clearance of 40 to 1240 μm may be used. The frequency may also be 40 to 60 Hz. The temperature may also be 20 to 50°C. The residence time may also be 1.5 to 10 seconds. The colloid mill is not particularly limited, but for example, a "Type-K120" manufactured by PUC Corporation may be used as appropriate.

[0027] The amount of the flocculant to be added is not particularly limited as long as it can flocculate the vinyl chloride resin latex, but from the viewpoint of easily obtaining agglomerated vinyl chloride resin particles having the required strength in a process such as washing, the concentration of the flocculant in the mixture containing the vinyl chloride resin latex and the flocculant is preferably 1.5% by weight or more, or may be 1.5 to 50% by weight, 1.5 to 40% by weight, 1.5 to 30% by weight, 2.0 to 20% by weight, 2.0 to 15% by weight, or 2.0 to 10% by weight.

[0028] In the agglomerated latex (slurry containing agglomerated vinyl chloride resin particles) obtained in the agglomeration step, the concentration of resin solids is preferably 22% by weight or more, more preferably 25 to 50% by weight, and even more preferably 30 to 45% by weight. When the concentration of resin solids in the agglomerated latex is within the above-mentioned range, the agglomerated latex has excellent fluidity and is easy to transport. The concentration of the agglomerating agent in the agglomerated latex obtained in the agglomeration step is the same as the concentration of the agglomerating agent in the mixture.

[0029] Next, the agglomerated latex is heat-treated. During the heat treatment, the bonds between the primary particles that form the secondary particles and the bonds between the secondary particles that form the tertiary particles in the vinyl chloride resin agglomerated particles become stronger. The heat treatment temperature is [Tg-10°C] to [Tg+5°C], where Tg is the glass transition temperature of the vinyl chloride resin. This improves the kneadability of the resulting vinyl chloride resin agglomerated particles, and, for example, makes it possible to obtain a vinyl chloride resin composition that contains the vinyl chloride resin agglomerated particles and a plasticizer and satisfies the low sol coarse particle requirement with good kneadability. The heat treatment temperature may be [Tg-10°C] to [Tg] from the viewpoint of further improving the kneadability of the vinyl chloride resin agglomerated particles and the plasticizer. The heat treatment time is not particularly limited, but after reaching a predetermined temperature, it may be maintained for 30 seconds to 300 minutes, 3 to 120 minutes, or 5 to 30 minutes from the viewpoint of industrial implementation.

[0030] In the agglomerated latex (slurry containing vinyl chloride resin agglomerated particles) after the heat treatment, the bond strength between the primary particles forming the secondary particles and the bond strength between the secondary particles forming the tertiary particles are higher than the bond strength between the primary particles forming the secondary particles and the bond strength between the secondary particles forming the tertiary particles in the agglomerated latex before the heat treatment.

[0031] As shown in Figure 1, the vinyl chloride resin agglomerated particles include tertiary particles 3 formed by further agglomeration of secondary particles 2 formed by agglomeration of vinyl chloride resin latex particles (primary particles) 1. The vinyl chloride resin agglomerated particles may include secondary particles in addition to tertiary particles. In the vinyl chloride resin agglomerated particles, the bonding strength between the primary particles is higher than the bonding strength between the secondary particles, and the bonding between the secondary particles is relatively weak.

[0032] In the heat-treated agglomerated latex, the particle size of the vinyl chloride resin agglomerated particles is preferably 2 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more, from the viewpoint of enhancing the strength required for processes such as washing (including centrifugal dehydration after washing), although not particularly limited thereto. Furthermore, in the heat-treated agglomerated latex, the particle size of the vinyl chloride resin agglomerated particles is preferably 500 μm or less, more preferably 300 μm or less, and even more preferably 200 μm or less, from the viewpoint of easily satisfying the low sol coarse particle requirement, although not particularly limited thereto. More specifically, in the heat-treated agglomerated latex, the particle size distribution of the vinyl chloride resin agglomerated particles may be 2 to 500 μm, 5 to 300 μm, or 10 to 200 μm. The particle size distribution of the vinyl chloride resin agglomerated particles can be measured by laser diffraction / scattering, more specifically, as described in the Examples.

[0033] The pH of the heat-treated agglomerated latex may be adjusted, if necessary, to a range of 4 to 11, preferably 5 to 10, and more preferably 6 to 9. When the pH is within the above range, the resulting vinyl chloride resin agglomerated particles have a low moisture absorption rate, and the composition containing the vinyl chloride resin agglomerated particles has good storage stability. The pH can be adjusted using any compound capable of adjusting the pH within the above range, and is not particularly limited. For example, sodium hydroxide can be used.

[0034] The heat-treated agglomerated latex or the pH-adjusted agglomerated latex is dehydrated and dried to obtain vinyl chloride resin agglomerated particles. The dehydration can be performed by filtration, although not limited thereto. The drying temperature is not particularly limited, but the resin temperature can usually be set within a range of 35 to 100°C. From the viewpoint of achieving excellent strength that allows for washing and centrifugal dehydration, the agglomerated particles obtained after dehydration and drying are kneaded by placing 10 g of the agglomerated particles (dry powder) in a mortar and grinding them for 10 seconds at low speed (200 rpm) using a pestle-equipped grinder. The agglomerated particles after kneading preferably have a particle size of 2 μm or more, more preferably 3 μm or more, in terms of the volume-based particle size distribution. Furthermore, from the viewpoint of easily obtaining a composition that satisfies the low sol coarse particle size requirement (25 μm or less, according to Method A), the agglomerated particles after the kneading described above preferably have a particle size of 50 μm or less, more preferably 40 μm or less, and even more preferably 30 μm or less, in terms of the volume-based particle size distribution. More specifically, the particle size distribution of the agglomerated particles after the kneading may be 2 to 50 μm, 3 to 40 μm, or 3 to 30 μm on a volume basis. From the viewpoint of excellent kneadability, the agglomerated particles after the kneading preferably have a volume ratio of particles having a particle size of 10 μm or more of 20% or less, more preferably 15% or less.

[0035] After dehydration and before drying, the agglomerated latex may be washed by adding water (also referred to as water washing). The vinyl chloride resin agglomerated particles have the strength required for processes such as washing, and washing can reduce the metal and salt concentrations of the vinyl chloride resin agglomerated particles. For example, after dehydrating the agglomerated latex, water can be added in an amount from 2 to 100 times the weight of the resin solids obtained after dehydration (dehydrated vinyl chloride resin agglomerated particles) to wash the agglomerated latex, and centrifugal dehydration may be performed after washing.

[0036] The vinyl chloride resin agglomerated particles obtained after drying can be used as is, without pulverization, in vinyl chloride resin compositions such as metal can coating compositions and marking film compositions, and still satisfy the low sol coarse particle size requirement (25 μm or less by Method A). If necessary, the vinyl chloride resin agglomerated particles obtained after drying may be appropriately pulverized and / or classified. However, in the vinyl chloride resin agglomerated particles obtained by the production method according to one or more embodiments of the present invention, the bond strength between primary particles is higher than the bond strength between secondary particles, and the bond between secondary particles is relatively weak, so the burden of pulverization and / or classification is low. For example, a roller mill, a high-speed rotary pulverizer, a ball mill, a jet mill, or the like can be used for the pulverization.

[0037] The vinyl chloride resin composition can be suitably used as a metal can coating composition. From the viewpoints of the processability, retort resistance, and tearability of the coating film, the metal can coating composition preferably contains (A) 20 to 80 parts by weight of the vinyl chloride resin aggregate particles, (B) 1 to 30 parts by weight of one or more resins selected from the group consisting of phenolic resins, epoxy resins, and acrylic resins, (C) 1 to 60 parts by weight of a polyester-based resin, and (D) an organic solvent, with the total amount of (A), (B), and (C) being 100 parts by weight. The metal can coating composition may be a can interior coating composition used on the inner surface of a metal can, or may be a can exterior coating composition used on the outer surface of a metal can. The phenolic resin, epoxy resin, acrylic resin, and polyester-based resin are not particularly limited, and, for example, those typically used in coating films for metal cans can be used as appropriate. The organic solvent (volatile component) used in the metal can coating composition may be any solvent that does not dissolve the vinyl chloride resin aggregate particles but dissolves phenolic resin, epoxy resin, acrylic resin, and polyester resin.

[0038] The composition containing the vinyl chloride resin aggregate particles may be used as a composition for a marking film. From the viewpoint of the transparency, water resistance, and weather resistance of the marking film, the composition for a marking film preferably contains (a) 50 to 90 parts by weight of the vinyl chloride resin aggregate particles, (b) 10 to 50 parts by weight of a plasticizer, and (c) an organic solvent, the total amount of (a) and (b) being 100 parts by weight. As the plasticizer, a conventional plasticizer for vinyl chloride resin can be appropriately used. As the organic solvent (volatile component), one that disperses the vinyl chloride resin aggregate particles but does not dissolve the vinyl chloride resin aggregate particles can be appropriately used.

[0039] (Method of producing vinyl chloride resin composition) A method for producing a vinyl chloride resin composition according to one or more embodiments of the present invention includes a step of kneading the vinyl chloride resin agglomerated particles with a plasticizer. Because the vinyl chloride resin agglomerated particles have good kneadability, they can be kneaded with additives such as a plasticizer to obtain a low-sol coarse-particle vinyl chloride resin composition. For the kneading, a known kneading machine, such as a Hemmel mixer, a roll compaction machine, a gear pelletizer, a Banbury mixer, or an extruder, can be used as appropriate.

[0040] The vinyl chloride resin composition may contain 100 parts by weight or less, less than 100 parts by weight, 90 parts by weight or less, 80 parts by weight or less, or 10 to 80 parts by weight of the plasticizer relative to 100 parts by weight of the vinyl chloride resin agglomerated particles. Because the vinyl chloride resin agglomerated particles have good kneadability, a vinyl chloride resin composition can be obtained with good kneadability even when the blending amount of the plasticizer is small.

[0041] The plasticizer may be any of ordinary plasticizers for vinyl chloride resins, such as phthalate ester plasticizers such as di-2-ethylhexyl phthalate, di-normal octyl phthalate (also called dioctyl phthalate), dibutyl phthalate, diisononyl phthalate, and butyl benzyl phthalate; phosphate ester plasticizers such as tricresyl phosphate and tri-2-ethylhexyl phosphate; adipate ester plasticizers such as di-2-ethylhexyl adipate; sebacate ester plasticizers such as di-2-ethylhexyl sebacate; and azelaate ester plasticizers such as di-2-ethylhexyl azelate. Examples of plasticizers that can be used include trimellitic ester plasticizers such as tri-2-ethylhexyl trimellitate, polyester plasticizers, benzoic ester plasticizers such as di-2-ethylhexyl benzoate, diethylene glycol dibenzoate, and 2,2,4-trimethyl-1,3-pentanediol isobutyrate benzoate, citrate ester plasticizers such as acetyl tributyl citrate, glycolic ester plasticizers, chlorinated paraffin plasticizers, chlorinated fatty acid ester plasticizers, epoxy plasticizers, and texanol isobutyrate. These may be used alone or in combination of two or more.

[0042] The vinyl chloride resin composition may optionally contain a resin other than vinyl chloride resin. Examples of such resins include phenolic resins, epoxy resins, acrylic resins, and polyester resins. The vinyl chloride resin composition may optionally contain various other additives commonly used in vinyl chloride resin compositions, such as organic solvents, stabilizers, antistatic agents, colorants, UV absorbers, lubricants, modifiers, fillers, and diluents. When the vinyl chloride resin composition contains other resins and / or other additives, the vinyl chloride resin agglomerated particles, plasticizers, other resins, and / or other additives may be directly kneaded together. Alternatively, it is preferable to knead the vinyl chloride resin agglomerated particles with solid other resins and / or other additives, and then knead the plasticizers and / or liquid other resins and / or other additives. [Example]

[0043] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0044] (Production Example 1) A 300 L jacketed pressure vessel was charged with 136.4 kg of vinyl chloride monomer, 150 kg of ion-exchanged water, 16.7 g of sodium lauryl sulfate, 127.5 g of sodium hydroxymethanesulfinate dihydrate (Rongalite), and 60 g of sodium bicarbonate. The mixture was heated to 50 °C and polymerization was carried out by continuously adding 3.2 kg of a 0.3 wt% aqueous solution of t-butyl hydroperoxide and 7.9 kg of a 4 wt% aqueous solution of sodium lauryl sulfate while stirring. Polymerization continued until the polymerization pressure dropped to 0.35 MPa from the initial pressure (0.7 MPa). The remaining monomer was then recovered to obtain a vinyl chloride resin latex. The final vinyl chloride resin latex had a polymerization conversion rate of 90% relative to the total amount of vinyl chloride monomer charged. The resulting vinyl chloride resin latex had a volume-average particle diameter of 0.45 μm and an average degree of polymerization of 1480. The concentration of the resin solid content in the vinyl chloride resin latex was 38% by weight.

[0045] (Production Example 2) A 300 L jacketed pressure vessel was charged with 150 kg of vinyl chloride monomer, 150 kg of ion-exchanged water, 14.6 kg of the vinyl chloride resin latex obtained in Production Example 1, 83.3 g of potassium myristate aqueous solution (0.06 parts by weight per 100 parts by weight of the total vinyl chloride monomer charge), 127.5 g of sodium hydroxymethanesulfinate dihydrate (Rongalit), and 15 g of potassium phosphate. The mixture was heated to 48 °C and, while stirring, 5.44 kg of a 0.4 wt% aqueous t-butyl hydroperoxide solution and 6.8 kg of a 10 wt% aqueous potassium myristate solution (0.45 parts by weight per 100 parts by weight of the total vinyl chloride monomer charge) were continuously added to carry out polymerization. Polymerization continued until the polymerization pressure dropped by 0.3 MPa from the initial pressure (0.65 MPa), and the remaining monomer was recovered to obtain a vinyl chloride resin latex. In the finally obtained vinyl chloride resin latex, the polymerization conversion rate of the total amount of vinyl chloride monomer charged was 90%. The obtained vinyl chloride resin latex contained 80 volume % vinyl chloride resin latex particles with a volume average particle diameter of 1.24 μm and 20 volume % vinyl chloride resin latex particles with a volume average particle diameter of 0.45 μm, and the average degree of polymerization of the vinyl chloride resin was 1640. In addition, the concentration of resin solids in the vinyl chloride resin latex was 40 weight %, and the Tg of the vinyl chloride resin was 80°C.

[0046] Example 1 The vinyl chloride resin latex obtained in Production Example 2 was diluted with pure water to a resin solids concentration of 36.5% by weight. The diluted vinyl chloride resin latex and an aqueous solution of sodium sulfate (concentration: 20% by weight) as a coagulant were sent to a colloid mill (PUC, Type-K120). The vinyl chloride resin latex and the aqueous solution of sodium sulfate were mixed at the inlet of the colloid mill. Shear force was applied to the mixture inside the colloid mill at a temperature of 30°C, a frequency of 60 Hz, a clearance of 40 μm, and a residence time of 6 seconds to coagulate the vinyl chloride resin latex. The sodium sulfate concentration in the mixture (total amount of vinyl chloride resin latex and aqueous solution of sodium sulfate) was 4.0% by weight. The obtained coagulated latex was diluted with pure water to a resin solids concentration of 20% by weight, and the diluted coagulated latex was heat-treated by holding it at 85°C for 10 minutes. Thereafter, the mixture was dehydrated by filtration, and the dehydrated resin solid content was dried at 40° C. for 24 hours to obtain vinyl chloride resin agglomerated particles (dry powder).

[0047] (Examples 2 and 3) Agglomerated vinyl chloride resin particles were prepared in the same manner as in Example 1, except that the heat treatment temperature was changed as shown in Table 1 below.

[0048] Example 4 Agglomerated vinyl chloride resin particles were prepared in the same manner as in Example 1, except that the heat treatment temperature and clearance were changed as shown in Table 1 below.

[0049] Example 5 Agglomerated vinyl chloride resin particles were prepared in the same manner as in Example 4, except that the concentration of sodium sulfate was adjusted to 2.0% by weight.

[0050] Example 6 Vinyl chloride resin agglomerated particles were prepared in the same manner as in Example 5, except that the clearance was changed as shown in Table 1 below.

[0051] (Comparative Example 1) Agglomerated vinyl chloride resin particles were prepared in the same manner as in Example 1, except that the heat treatment temperature was changed as shown in Table 1 below.

[0052] (Comparative Example 2) Agglomerated vinyl chloride resin particles were prepared in the same manner as in Example 1, except that the heat treatment temperature and clearance were changed as shown in Table 1 below.

[0053] In Examples 1 to 6 and Comparative Examples 1 and 2, the particle size distribution of the agglomerated particles and the particle size distribution of the agglomerated particles after the disintegration test were evaluated as follows. Furthermore, based on the particle size distribution of the agglomerated particles after the disintegration test, the applicability for washing and centrifugal dehydration, and the kneadability were evaluated as follows. The results are shown in Table 1 below. In Table 1 below, the proportion of particles with a particle size of 2 μm or less and the proportion of particles with a particle size of 10 μm or more are both on a volume basis.

[0054] (Particle size distribution of agglomerated particles) Using the heat-treated agglomerated latex as a sample, the particle size distribution of the vinyl chloride resin agglomerated particles was measured on a volume basis using a laser diffraction / scattering particle size distribution analyzer (Horiba, Ltd., Partica LA-950). The measurement conditions were: temperature 25°C, material information transparent, refractive index 1.51, no spherical particle check, water used as carrier, refractive index 1.33. Also, set zero 10 seconds, measurement 10 seconds, no dry cut calculation.

[0055] (Agglomerate particle disintegration test) 10 g of vinyl chloride resin agglomerated particles (dry powder) was placed in a mortar and kneaded by grinding for 10 seconds at low speed (200 rpm) using a mortar equipped with a pestle. The aqueous dispersion of vinyl chloride resin agglomerated particles after kneading (after the disintegration test) was used as a sample, and the particle size distribution of the vinyl chloride resin agglomerated particles was measured as described above.

[0056] (Washing and centrifugal spin-drying available?) Based on the particle size distribution of the vinyl chloride resin agglomerated particles after the disintegration test, the suitability of washing and centrifugal dehydration of the vinyl chloride resin agglomerated particles was evaluated according to the following criteria. Acceptable: No particles with a particle size of 2 μm or less exist, and the strength required for washing and centrifugal dehydration is sufficient. Unacceptable: Particles with a diameter of 2 μm or less are present and the material does not have the strength required for washing and centrifugal dehydration.

[0057] Based on the particle size distribution of the vinyl chloride resin agglomerated particles after the disintegration test, the kneadability of the vinyl chloride resin agglomerated particles was evaluated according to the following criteria. (Mixability) Good: The percentage of particles with a particle size of 10 μm or more is 20% or less by volume Poor: The percentage of particles with a particle size of 10 μm or more exceeds 20% by volume

[0058] Compositions (sols) containing vinyl chloride resin agglomerated particles of Examples 1 to 6 and Comparative Examples 1 and 2 were prepared, and the viscosity of the compositions, the amount of coarse particles, and the particle size of the vinyl chloride resin agglomerated particles in the compositions were measured and evaluated as described below. The results are shown in Tables 2 and 3 below. In Tables 2 and 3 below, the proportion of particles with a particle size of 10 μm or more is based on the volume.

[0059] (Preparation of vinyl chloride resin composition: Formulation 1) Dioctyl phthalate (also referred to as DOP) was added to 100 parts by weight of vinyl chloride resin agglomerated particles (dry powder) in an amount of 100 parts by weight, and the mixture was kneaded twice for 2 minutes each at 2000 rpm using a dissolver-type kneader (ROBO mix, manufactured by Primix Corporation) to prepare a vinyl chloride resin composition (hereinafter also referred to simply as the composition).

[0060] (Preparation of vinyl chloride resin composition: Formulation 2) A composition was prepared by adding 80 parts by weight of dioctyl phthalate (also referred to as DOP) to 100 parts by weight of vinyl chloride resin agglomerated particles (dry powder), and kneading the mixture twice for 2 minutes each at 2000 rpm using a dissolver-type kneader (ROBO mix, manufactured by Primix Corporation).

[0061] (viscosity) The composition (sol) was used as a sample 2 hours after preparation, and the viscosity of the composition was measured at rotation speeds of 6 rpm and 12 rpm using a Brookfield viscometer (BM-type Viscometer, manufactured by Tokimec Inc.). The temperature of the composition was 25°C.

[0062] (coarse sol particles) For the composition (sol) of Blend 1, the coarse particles remaining in each sol were measured using a grindmeter by Method A. Note that Method A is the particle size at which the amount of coarse particles increases.

[0063] (Particle size distribution of vinyl chloride resin agglomerated particles in the composition) The particle size distribution of the vinyl chloride resin aggregated particles in the composition (sol) was measured using a laser diffraction / scattering particle size distribution measuring device (Partica LA-950, manufactured by Horiba, Ltd.).

[0064] (sol mixability) The sol kneadability with the plasticizer was evaluated according to the following criteria. Acceptable: When the agitator was moving during sol mixing using a dissolver at 2000 rpm for 2 minutes Not possible: If the agitator stops during sol mixing using a dissolver at 2000 rpm for 2 minutes.

[0065] [Table 1]

[0066] [Table 2]

[0067] [Table 3]

[0068] As can be seen from the data in Tables 1 to 3, in the examples, it was possible to obtain agglomerated particles that could be washed (including centrifugal dehydration) and had good kneadability. Furthermore, as can be seen from the data in Table 2, the composition obtained by kneading the agglomerated particles obtained in the examples with a plasticizer had a particle size of 25 μm or less for the coarse sol particles obtained by Method A, satisfying the low sol coarse particle requirement. Furthermore, when the agglomerated particles obtained in the examples were used, sol kneading was possible even when the amount of plasticizer blended was less than the amount of agglomerated particles blended.

[0069] On the other hand, as can be seen from the data in Tables 1 to 3, the agglomerated particles obtained in Comparative Example 1, in which the temperature of the heat treatment step was high, had a ratio of particles with a particle size of 10 μm or more exceeding 20% ​​after the disintegration test, indicating poor kneadability. Specifically, the agglomerated particles obtained in Comparative Example 1, in which the temperature of the heat treatment step was high, could be sol-kneaded when the blending amount of plasticizer was equal to the blending amount of the agglomerated particles, but the ratio of agglomerated particles with a particle size of 10 μm or more in the sol exceeded 20%, indicating poor kneadability. In particular, the agglomerated particles obtained in Comparative Example 1, in which the temperature of the heat treatment step was high, could not be sol-kneaded when the blending amount of plasticizer was less than the blending amount of the agglomerated particles. Furthermore, the aggregated particles obtained in Comparative Example 2, in which the temperature in the heat treatment step was low, could not be washed and centrifuged for dehydration.

[0070] The present invention is not particularly limited, but may include, for example, the following embodiments. [1] A method for producing vinyl chloride resin agglomerated particles, comprising: a step of applying shear force to a mixture containing the vinyl chloride resin latex and the flocculant using a colloid mill to obtain an agglomerated latex containing agglomerated vinyl chloride resin particles; A method for producing agglomerated vinyl chloride resin particles, comprising a step of heat-treating the agglomerated latex in a temperature range of [Tg-10°C] to [Tg+5°C], where Tg is the glass transition temperature of the vinyl chloride resin. [2] The method for producing agglomerated vinyl chloride resin particles according to [1], wherein the clearance of the colloid mill is 40 to 1240 μm. [3] The method for producing vinyl chloride resin aggregated particles according to [1] or [2], wherein the aggregating agent is an inorganic salt. [4] A method for producing a vinyl chloride resin composition, comprising: the vinyl chloride resin composition contains vinyl chloride resin agglomerated particles obtained by the method for producing vinyl chloride resin agglomerated particles according to any one of [1] to [3] and a plasticizer; a step of kneading the vinyl chloride resin agglomerated particles and the plasticizer; [5] The method for producing a vinyl chloride resin composition according to [4], wherein the amount of the plasticizer blended is less than 100 parts by weight per 100 parts by weight of the vinyl chloride resin agglomerated particles. [Explanation of symbols]

[0071] 1. Vinyl chloride resin latex particles 2 Secondary particles (vinyl chloride resin agglomerated particles) 3 Tertiary particles (vinyl chloride resin agglomerated particles)

Claims

1. A method for producing vinyl chloride resin agglomerated particles, comprising: a step of applying shear force to a mixture containing the vinyl chloride resin latex and the flocculant using a colloid mill to obtain an agglomerated latex containing agglomerated vinyl chloride resin particles; a step of heat-treating the agglomerated latex at a temperature ranging from [Tg-10°C] to [Tg+5°C], where Tg is the glass transition temperature of the vinyl chloride resin.

2. 2. The method for producing agglomerated vinyl chloride resin particles according to claim 1, wherein the clearance of the colloid mill is 40 to 1240 μm.

3. The method for producing vinyl chloride resin agglomerated particles according to claim 1 , wherein the aggregating agent is an inorganic salt.

4. A method for producing a vinyl chloride resin composition, comprising: The vinyl chloride resin composition contains vinyl chloride resin agglomerated particles obtained by the production method according to any one of claims 1 to 3 and a plasticizer, a step of kneading the vinyl chloride resin agglomerated particles and the plasticizer;

5. 5. The method for producing a vinyl chloride resin composition according to claim 4, wherein the blending amount of the plasticizer is less than 100 parts by weight per 100 parts by weight of the vinyl chloride resin agglomerated particles.

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