Processing aids for vinyl chloride resin compositions

Abstract

The processing aid for a vinyl chloride-based resin composition according to one embodiment of the present invention comprises a first polymer and a second polymer. The first polymer has a weight-average molecular weight of 600,000 to 4,000,000 and contains 60 to 100% by weight of alkyl methacrylate. The second polymer has a weight-average molecular weight of 10,000 to 400,000 and contains 30 to 90% by weight of an aromatic vinyl compound. The proportion of the first polymer is 20 to 90% by weight, and the proportion of the second polymer is 10 to 80% by weight. When the processing aid is set to 100% by weight, the proportion of the aromatic vinyl compound is 20% by weight or more.

Description

Technical Field

[0001] This invention relates to a processing aid for vinyl chloride-based resin compositions, vinyl chloride-based resin compositions, and molded articles thereof. Background Technology

[0002] Vinyl chloride (PVC) resins are widely used in various molded products due to their properties, but they suffer from various processing problems, such as processing temperatures close to their thermal decomposition temperatures and a lack of fluidity. To overcome these problems, a method has been proposed that uses copolymers with methyl methacrylate (MDMA) as the main component as processing aids. This method promotes gelation without reducing the properties of the PVC resin, resulting in molded products with excellent transparency and surface gloss. However, it has the following drawbacks: flow marks and shrinkage cavities are generated on the surface of the rolled sheets and films during rolling, reducing the commercial value of the molded products. Furthermore, methyl methacrylate is relatively expensive among commonly used (meth)acrylates, prompting a search for processing aids using inexpensive raw materials.

[0003] On the other hand, Patent Document 1 discloses a method for adding a processing aid comprising a first polymer containing a cyanide-based compound and an aromatic vinyl group, and a second polymer containing an alkyl acrylate and having a low Tg, to a vinyl chloride-based resin composition. In this method, by using styrene, an inexpensive aromatic vinyl group, a shorter gelation time can be achieved while maintaining low cost.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2016 / 195013 Summary of the Invention

[0007] However, the processing aid disclosed in Patent Document 1, which contains inexpensive aromatic vinyl compounds, has low compatibility with vinyl chloride resins, leading to poor mixing and potentially a significant reduction in the gloss of the molded article. Furthermore, while increasing the melt viscosity of the processing aid or increasing its dosage can improve mixing and thus enhance gloss, this may worsen surface properties (flow marks and fish eyes). In other words, there is a trade-off between the surface properties and gloss of the molded article, making it difficult to achieve a balance between these characteristics.

[0008] To address the aforementioned issues, the inventors conducted repeated and in-depth research, discovering that by incorporating processing aids containing a first polymer and a second polymer with specific compositions and weight-average molecular weights, and thereby utilizing aromatic vinyl compounds as inexpensive raw materials in large quantities, it is possible to maintain good transparency and yellowness while appropriately considering the surface properties and gloss of the molded article, thus completing this invention. This invention includes the following methods.

[0009] <1> A processing aid for a vinyl chloride-based resin composition comprises a first polymer and a second polymer; the first polymer has a weight-average molecular weight of 600,000 to 4,000,000, and the first polymer as a whole is 100% by weight, consisting of 60 to 100% by weight alkyl methacrylate and 0 to 40% by weight other vinyl compounds that can copolymerize therewith; the second polymer has a weight-average molecular weight of 10,000 to 400,000, and the second polymer as a whole is 100% by weight, consisting of 30 to 90% by weight aromatic vinyl compounds and 10 to 70% by weight other vinyl compounds that can copolymerize therewith; the total of the first polymer and the second polymer is 100% by weight, the proportion of the first polymer in the processing aid is 20 to 90% by weight, and the proportion of the second polymer is 10 to 80% by weight; the processing aid as a whole is 100% by weight, and the proportion of aromatic vinyl compounds in the processing aid is 20% by weight or more.

[0010] <2> The processing aid for the vinyl chloride resin composition according to <1> further comprises a third polymer as the outermost layer covering the first polymer and / or the second polymer, the third polymer having a Tg of -40 to 60°C, and the third polymer being 100% by weight, consisting of 30 to 90% by weight of alkyl acrylate and 10 to 70% by weight of other vinyl compounds that can copolymerize therewith.

[0011] <3> The processing aid for the vinyl chloride resin composition according to <1> or <2>, wherein the weight average molecular weight of the first polymer is 1,000,000 to 2,000,000, and the first polymer as a whole is 100% by weight, consisting of 80 to 100% by weight of alkyl methacrylate and 0 to 20% by weight of other vinyl compounds that can copolymerize therewith; the weight average molecular weight of the second polymer is 15,000 to 150,000, and the second polymer as a whole is 100% by weight, consisting of 5 to 40% by weight of cyanide-based compound, 60 to 85% by weight of aromatic vinyl compound and 0 to 20% by weight of other vinyl compounds that can copolymerize therewith; the total of the first polymer and the second polymer is 100% by weight, and in the processing aid, the proportion of the first polymer is 40 to 80% by weight, and the proportion of the second polymer is 20 to 60% by weight.

[0012] <4> The processing aid for the vinyl chloride resin composition according to <3>, wherein the first polymer is set to 100% by weight, the first polymer is composed of 90-100% by weight of alkyl methacrylate and 0-10% by weight of other vinyl compounds that can copolymerize therewith; the weight average molecular weight of the second polymer is 20,000-80,000; the total of the first polymer and the second polymer is set to 100% by weight, and in the processing aid, the proportion of the first polymer is 50-70% by weight, and the proportion of the second polymer is 30-50% by weight.

[0013] <5> A vinyl chloride-based resin composition, comprising 100 parts by weight of a vinyl chloride-based resin and 0.1 to 20 parts by weight of the processing aid described in any one of <1> to <4>.

[0014] <6> A molded body is obtained by molding the vinyl chloride-based resin composition described in <5>.

[0015] According to the present invention, a processing aid for vinyl chloride resin compositions can be provided that maintains good transparency and yellowness while taking into account the surface properties (flow marks, pinholes) and gloss of the molded articles of vinyl chloride resin compositions. Detailed Implementation

[0016] The following describes one embodiment of the present invention, but the present invention is not limited thereto. The present invention is not limited to the configurations described below, and various modifications can be made within the scope indicated by the claims. Embodiments and examples obtained by appropriately combining different combinations of the technical means disclosed in the embodiments are also included within the technical scope of the present invention. Furthermore, all academic and patent documents described in this specification are cited as references herein. Additionally, unless otherwise specified in this specification, "A~B" indicating a numerical range refers to "A~B".

[0017] <Processing aids>

[0018] The processing aid (hereinafter also simply referred to as processing aid) for the vinyl chloride-based resin composition of the present invention comprises at least a first polymer having a constituent unit composed of alkyl methacrylate and a second polymer having a constituent unit composed of aromatic vinyl compounds. In this specification, "processing aid for vinyl chloride-based resin compositions" refers to an additive that does not substantially reduce the properties of vinyl chloride-based resins, but promotes gelation during molding of the vinyl chloride-based resin composition or improves the surface properties of the molded article.

[0019] In the processing aid, the total of the first polymer and the second polymer is set at 100% by weight, wherein the proportion of the first polymer is 20-90% by weight and the proportion of the second polymer is 10-80% by weight. Preferably, the proportion of the first polymer is 40-80% by weight and the proportion of the second polymer is 20-60% by weight; more preferably, the proportion of the first polymer is 50-70% by weight and the proportion of the second polymer is 30-50% by weight.

[0020] From the perspective of prioritizing raw material prices and maintaining improved surface properties of the molded body, the processing aid is set to contain 100% by weight of aromatic vinyl compounds, with the proportion being 20% ​​by weight or more. From the above perspective, the proportion of aromatic vinyl compounds is preferably 22-60% by weight, more preferably 23-50% by weight, even more preferably 24-40% by weight, and particularly preferably 25-35% by weight. It should be noted that the aromatic vinyl compounds mentioned in this paragraph refer to the total aromatic vinyl compounds contained in the processing aid. If aromatic vinyl compounds are also contained in the first polymer and / or the third polymer in addition to those contained in the second polymer, then the aromatic vinyl compounds contained in the first polymer and / or the third polymer are also included.

[0021] The inventors have discovered that when using a processing aid consisting only of either the first polymer or the second polymer in a vinyl chloride-based resin composition, it is difficult to adequately balance the gloss and surface properties (flow marks, pinholes) of the resulting molded article. However, if the processing aid contains both the first polymer and the second polymer, and they have specific compositions, ratios, and weight-average molecular weights, it is possible to adequately balance the gloss and surface properties of the resulting molded article.

[0022] In this specification, "flow mark" refers to a portion of the molten resin mass generated by the gap between the rollers during the molding of a vinyl chloride-based resin composition, which remains on the surface of the molded article as a rib-like or striped pattern as it passes through the gap. Additionally, "pinhole" is defined as a spherical or elliptical foreign object formed by the non-dispersion and aggregation of processing aids in a vinyl chloride-based resin, with a maximum length L of 50 μm or more.

[0023] The processing aid is preferably in a granular structure, more preferably comprising a first polymer and a second polymer in one particle, and particularly preferably existing independently in one particle without being chemically bonded to each other. That is, the processing aid preferably does not have a cross-linked structure. Furthermore, the structure of the processing aid in the vinyl chloride-based resin composition is not particularly limited and can be either granular or linear.

[0024] When the processing aid has a granular structure, from the viewpoint of particle stability and polymerization rate (productivity) during manufacturing, the volume average particle size of the processing aid is preferably 0.05 μm to 0.5 μm, more preferably 0.07 μm to 0.3 μm, and even more preferably 0.1 μm to 0.2 μm. The volume average particle size can be measured in powdered processing aids or in processing aids in latex as described later.

[0025] The processing aid may consist solely of the first and second polymers. From the viewpoint of the granulation properties of the processing aid, a third polymer may be further incorporated into the first and second polymers. In this case, the third polymer becomes the outermost layer covering the first and / or second polymers. Furthermore, each polymer can be a single-layer structure or a multi-layer structure. That is, the first polymer, the second polymer, and the third polymer can each be a single-layer structure or a multi-layer structure.

[0026] From the perspective of balancing granulation and cost, in the processing aid, the total amount of the first polymer and the second polymer is set to 100 parts by mass, and the content of the third polymer is preferably 1 to 50 parts by mass, more preferably 5 to 30 parts by mass, and even more preferably 8 to 15 parts by mass.

[0027] <First Polymer>

[0028] The weight-average molecular weight of the first polymer is 600,000 to 4,000,000. From the viewpoint of appropriately balancing processability, gloss of the molded article and surface properties, the weight-average molecular weight of the first polymer is preferably 700,000 to 3,500,000, more preferably 800,000 to 2,500,000, and even more preferably 1,000,000 to 2,000,000.

[0029] The first polymer is set to 100% by weight, comprising 60-100% by weight of alkyl methacrylate and 0-40% by weight of other vinyl compounds that can copolymerize with it (i.e., other vinyl compounds that can copolymerize with alkyl methacrylate). By including alkyl methacrylate, which has high compatibility with vinyl chloride resins, in the first polymer, processability and gloss of the molded article can be improved. From the above viewpoint, setting the first polymer to 100% by weight is preferably 70-100% by weight of alkyl methacrylate and 0-30% by weight of other vinyl compounds that can copolymerize with it, more preferably 80-100% by weight of alkyl methacrylate and 0-20% by weight of other vinyl compounds that can copolymerize with it, and even more preferably 90-100% by weight of alkyl methacrylate and 0-10% by weight of other vinyl compounds that can copolymerize with it.

[0030] Examples of alkyl methacrylates include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, nonyl methacrylate, decyl methacrylate, undecyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, tetradecyl methacrylate, pentadecyl methacrylate, hexadecyl methacrylate, and octadecyl methacrylate, which are straight-chain alkyl methacrylates with 1 to 20 carbon atoms; isopropyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, and isobutyl methacrylate. Branched alkyl methacrylates with 3 to 20 carbon atoms, including pentyl methacrylate, 2-ethylhexyl methacrylate, isooctyl methacrylate, isononyl methacrylate, isodecanyl methacrylate, isoundecyl methacrylate, isododecyl methacrylate, isotridecyl methacrylate, isotetradecyl methacrylate, isopentadecanyl methacrylate, isohexadecyl methacrylate, isoheptadecyl methacrylate, and isooctadecyl methacrylate; and cyclic alkyl methacrylates with 3 to 20 carbon atoms, including cyclopropyl methacrylate, cyclobutyl methacrylate, cyclopentyl methacrylate, cyclohexyl methacrylate, and cyclooctyl methacrylate. These can be used alone or in combination of two or more.

[0031] The alkyl group of the above-mentioned alkyl methacrylate preferably has 1 to 14 carbon atoms, more preferably 1 to 12, even more preferably 1 to 10, even more preferably 1 to 8, and particularly preferably 1 to 6. Among the above compounds, straight-chain alkyl methacrylates are more preferred, and methyl methacrylate and ethyl methacrylate are even more preferred.

[0032] Other vinyl compounds that can copolymerize with alkyl methacrylates include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, nonyl acrylate, decyl acrylate, undecyl acrylate, dodecyl acrylate, tridecyl acrylate, tetradecyl acrylate, pentadecyl acrylate, and hexadecyl acrylate, which are straight-chain alkyl acrylates with 1 to 20 carbon atoms; isopropyl acrylate, isobutyl acrylate, sec-butyl acrylate, and tert-butyl acrylate. Esters, including isoamyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, isononyl acrylate, isodecanyl acrylate, isoundecyl acrylate, isododecyl acrylate, isotridecyl acrylate, isotetradecyl acrylate, isopentadecanyl acrylate, isohexadecyl acrylate, isohexadecanyl acrylate, isoheptadecyl acrylate, isooctadecyl acrylate, and other branched alkyl acrylates with 3 to 20 carbon atoms; cyclopropyl acrylate, cyclobutyl acrylate, cyclopentyl acrylate, cyclohexyl acrylate, cyclooctyl acrylate, and cyclodecyl acrylate, and other branched alkyl acrylates with 3 to 20 carbon atoms. Cyclic alkyl acrylates; phenyl methacrylate, methyl methacrylate, and other aromatic methacrylates; benzyl methacrylate and other aryl methacrylates; maleic anhydride, itaconic anhydride, citraconic anhydride, and other unsaturated acid anhydrides; acrylic acid, methacrylic acid, and other unsaturated acids; maleamide, N-methylmaleamide, N-butylmaleamide, N-(p-methylphenyl)maleamide, N-phenylmaleamide, N-cyclohexylmaleamide, and other α,β-unsaturated dicarboxylic acid imide compounds; glycidyl methacrylates, allyl glycidyl ethers, and other compounds containing... Unsaturated compounds with epoxy groups; unsaturated carboxylic acid amides such as acrylamide and methacrylamide; unsaturated compounds containing amino groups such as acrylate, urethane methacrylate, amino ether methacrylate, aminopropyl methacrylate, and aminostyrene; unsaturated compounds containing hydroxyl groups such as 3-hydroxy-1-propene, 4-hydroxy-1-butene, cis-4-hydroxy-2-butene, trans-4-hydroxy-2-butene, 3-hydroxy-2-methyl-1-propene, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, and hydroxystyrene; vinyl groups. Azoline and other containing Unsaturated compounds of azoline, etc. These compounds can be used alone or in combination of two or more.

[0033] The alkyl group of the above-mentioned alkyl acrylate preferably has 1 to 14 carbon atoms, more preferably 1 to 12, even more preferably 1 to 10, even more preferably 1 to 8, and particularly preferably 1 to 6. Among the above compounds, linear alkyl acrylates are more preferably preferred, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and particularly preferably butyl acrylate.

[0034] <Second Polymer>

[0035] The weight-average molecular weight of the second polymer is 10,000 to 400,000. When a first polymer, acting solely as a high molecular weight component, is added to a vinyl chloride-based resin composition intended for general sheet applications, there is a tendency for the melt viscosity to become excessively high, leading to worsening of flow marks and pinholes. However, by using a second polymer with a lower molecular weight in conjunction with the first polymer, flow marks and pinholes can be improved. From this perspective, the weight-average molecular weight of the second polymer is preferably 15,000 to 150,000, more preferably 15,000 to 120,000, even more preferably 15,000 to 100,000, and particularly preferably 20,000 to 80,000.

[0036] The second polymer is set to 100% by weight, comprising 30-90% by weight of an aromatic vinyl compound and 10-70% by weight of other vinyl compounds that can copolymerize with it (i.e., other vinyl compounds that can copolymerize with the aromatic vinyl compound). By including the aromatic vinyl compound, the second polymer can reduce melt viscosity and decrease flow marks and pinholes compared to processing aids that, for example, contain large amounts of methyl methacrylate. From the above perspective, it is preferable that the second polymer comprises 50-90% by weight of an aromatic vinyl compound and 10-50% by weight of other vinyl compounds that can copolymerize with it, out of a total of 100% by weight.

[0037] Examples of aromatic vinyl compounds include styrene, α-methylstyrene, p-methylstyrene, monobromostyrene, dibromostyrene, tribromostyrene, and chlorostyrene. From the perspective of raw material prices, styrene is preferred. These can be used alone or in combination of two or more.

[0038] Other vinyl compounds capable of copolymerizing with aromatic vinyl compounds include the compounds exemplified in the first polymer described above and vinyl cyanide compounds. Acrylonitrile and methacrylonitrile are preferred vinyl cyanide compounds, and acrylonitrile is more preferred. These compounds can be used alone or in combination of two or more.

[0039] From the viewpoints of processability and the transparency and yellowness of the molded article, the second polymer is set to 100% by weight. The second polymer preferably consists of 5-40% by weight of a cyanide-based compound, 60-85% by weight of an aromatic vinyl compound, and 0-20% by weight of other vinyl compounds that can copolymerize with it (i.e., other vinyl compounds that can copolymerize with the cyanide-based compound and the aromatic vinyl compound). The proportion of the cyanide-based compound is more preferably 10-28% by weight, and even more preferably 15-25% by weight. The proportion of the aromatic vinyl compound is more preferably 65-85% by weight, and even more preferably 70-85% by weight.

[0040] <Third Polymer>

[0041] From the viewpoint of improving the granulation properties of the processing aid, the Tg of the third polymer is preferably in the range of -40°C to 60°C, more preferably -30°C to 40°C, and even more preferably -25°C to 20°C.

[0042] From the viewpoint of reducing the Tg of the processing aid and improving granulation properties, the third polymer is taken as 100% by weight. Preferably, the third polymer consists of 30-90% by weight of alkyl acrylate and 10-70% by weight of other vinyl compounds that can copolymerize with it (i.e., other vinyl compounds that can copolymerize with alkyl acrylate), more preferably consisting of 50-80% by weight of alkyl acrylate and 20-50% by weight of other vinyl compounds that can copolymerize with it. As the alkyl acrylate, the compounds exemplified in the first and second polymers described above can be used in the same way. As other vinyl compounds that can copolymerize with alkyl acrylate, the compounds exemplified in the second polymer and aromatic vinyl compounds described above can be used in the same way.

[0043] <Method for manufacturing processing aids>

[0044] Processing aids, from the viewpoints of ease of recycling, low odor of the polymer, operability, resistance to blockage, and economy, can be obtained through water-based polymerization methods such as emulsion polymerization and suspension polymerization. Among these, emulsion polymerization is more preferred from the viewpoint of dispersibility with vinyl chloride-based resins. Furthermore, emulsion polymerization, soap-free emulsion polymerization, and dropwise suspension polymerization, which yield particulate structures, are particularly preferred polymerization methods for obtaining two or more polymer structures.

[0045] According to one embodiment, monomers, emulsifiers, free radical polymerizers, etc., constituting a first polymer are firstly added to water and polymerized to form a particulate first polymer. Next, monomers, emulsifiers, free radical polymerizers, chain transfer agents, etc., constituting a second polymer are added to the system comprising the particulate first polymer, and further polymerization is carried out to form a second polymer. Furthermore, monomers, emulsifiers, free radical polymerizers, etc., constituting a third polymer are added and further polymerization is carried out to form a third polymer as the outermost layer. Based on the above, a processing aid can be manufactured. The order in which the first polymer and the second polymer are formed is not limited to this; the first polymer can be formed after the second polymer is formed.

[0046] As emulsifiers for emulsion polymerization, conventionally known emulsifiers can be used, including anionic emulsifiers such as fatty acid salts, alkyl sulfate salts, alkylbenzene sulfonates, alkyl phosphate salts, and sulfosuccinate diesters; cationic emulsifiers such as alkylamine salts; and nonionic emulsifiers such as polyoxyethylene alkyl ethers and polyoxyethylene fatty acid esters. From the viewpoint of polymerization stability, anionic emulsifiers are preferred, more preferably fatty acid salts and sulfosuccinate diesters, and even more preferably semi-cured tallow fatty acid potassium and dioctyl sulfosuccinate sodium. These compounds can be used alone or in combination of two or more. Additionally, as co-catalysts for polymerization, disodium ethylenediaminetetraacetate, sodium formaldehyde sulfoxylate, and ferrous sulfate can be used; as viscosity modifiers for latex, sodium sulfate can be used; and as pH adjusters, sodium hydroxide can be used.

[0047] The weight-average molecular weights of the first and second polymers can be adjusted by changing the monomer ratios contained therein. Furthermore, these weight-average molecular weights can also be adjusted by changing the amount of free radical polymerizer and chain transfer agent used as needed, as well as the polymerization temperature and polymerization time.

[0048] As free radical polymerizing agents used in emulsion polymerization, organic hydroperoxides such as tert-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, menthol hydroperoxide, and tert-butyl perlaurate can be used; initiators of redox systems consisting of oxidants composed of the above-mentioned organic hydroperoxides and reducing agents such as sulfites, bisulfites, thiosulfates, first metal salts, and sodium formaldehyde sulfoxylate; persulfates such as potassium persulfate and ammonium persulfate; nitrogen compounds such as azobisisobutyronitrile, dimethyl-2,2'-azobisisobutyronitrile, and 2-carbamoylazaisobutyronitrile; and organic peroxides such as benzoyl peroxide and lauroyl peroxide can be used. Among these, potassium persulfate is preferred as the free radical polymerizing agent.

[0049] The amount of free radical polymerizer used relative to 100 parts by mass of the monomer used is, for example, 0.0001 to 1.0 parts by mass, preferably 0.0005 to 0.5 parts by mass, and more preferably 0.001 to 0.1 parts by mass. If the amount of free radical polymerizer is high, there is a tendency for the weight-average molecular weight to decrease; if the amount of free radical polymerizer is low, there is a tendency for the weight-average molecular weight to increase.

[0050] <Chain transfer agent>

[0051] When performing emulsified polymerization of the second polymer, a chain transfer agent is preferably used. Examples of such chain transfer agents include thiols such as octylthiol, n-dodecylthiol, tert-dodecylthiol, n-hexylthiol, n-hexadecylthiol, n-tetradecylthiol, and tert-tetradecylthiol; hydrocarbon salts such as tetraethylthiuram sulfide, carbon tetrachloride, ethylene bromide, and pentanephenylethane; terpenes; or acrolein, isobutylene aldehyde, allyl alcohol, 2-ethylhexylthiodiol, and α-methylstyrene dimer. Among these, thiols are preferred, and tert-dodecylthiol is more preferred. Two or more of these chain transfer agents can be used individually or in combination.

[0052] The amount of chain transfer agent used is typically 0 to 1 part by weight relative to 100 parts by weight of the monomer component. When using a chain transfer agent, the amount used is determined based on the balance between flow marks and pinholes and gloss, for example, 0.001 to 3 parts by weight, preferably 0.01 to 1 part by weight, and more preferably 0.05 to 0.5 parts by weight.

[0053] <Aggregation Time>

[0054] The polymerization time can be varied depending on the monomers, emulsifiers, free radical polymerizers, chain transfer agents used, and their amounts, for example, from 1 hour to 50 hours or from 5 hours to 24 hours.

[0055] The polymerization temperature can be adjusted according to the monomers, emulsifiers, free radical polymerizers, chain transfer agents used, and their amounts, for example, from 10°C to 90°C, preferably from 30°C to 80°C.

[0056] <Particle size>

[0057] The volume average particle size of the processing aids in latex is, for example, 0.100 μm to 0.500 μm. The volume average particle size can be calculated using a particle size analyzer (manufactured by Nikkiso Corporation, Nanotracwave).

[0058] <Processing>

[0059] Next, the latex containing the obtained processing aid can be powdered, for example, by a coagulation method. When pulverizing the processing aid, methods such as coagulation with salt or acid (contacting an inorganic salt (preferably a divalent inorganic salt, more preferably calcium chloride) or spray drying the latex to obtain powder can be used. After coagulation, heat treatment, dehydration, washing, and drying processes can be performed to prepare the processing aid.

[0060] <Resin Composition>

[0061] The vinyl chloride-based resin composition of the present invention comprises 100 parts by weight of vinyl chloride-based resin and 0.1 to 20 parts by weight of the above-mentioned processing aid. From the viewpoint of obtaining good results through the addition of the processing aid, the amount of the processing aid is preferably 0.1 parts by weight or more, and from the viewpoint of ensuring good dispersibility of the processing aid with the vinyl chloride-based resin, it is preferably 20 parts by weight or less. The amount of the above-mentioned processing aid relative to 100 parts by weight of the vinyl chloride-based resin is preferably 0.2 to 18 parts by weight, more preferably 0.3 to 15 parts by weight, and even more preferably 0.5 to 12 parts by weight.

[0062] Impact modifiers, stabilizers, lubricants, plasticizers, colorants, fillers, foaming agents, etc., can be added to the vinyl chloride resin composition as needed.

[0063] Vinyl chloride resin compositions can be obtained by mixing various components using mixers such as Banbury mixers, kneaders, roller mixers, belt mixers, and Henschel mixers, for example, by mixing at 100–200°C.

[0064] <Molded Body>

[0065] The molded article of the present invention is obtained by molding the above-mentioned vinyl chloride-based resin composition. For example, the molded article of the vinyl chloride-based resin composition can be obtained by molding the compounded vinyl chloride-based resin composition using extrusion molding, blow molding, injection molding, roll forming, vacuum forming, expansion molding, etc. The molded article is, for example, a sheet with a thickness of 0.2 to 1.0 mm or a film with a thickness of 0.01 to 0.2 mm. When the above-mentioned vinyl chloride-based resin composition is applied to roll forming, the generation of flow marks and shrinkage cavities can be suppressed, and a sheet or film with excellent gloss, transparency, and yellowness can be obtained. Furthermore, the above-mentioned vinyl chloride-based resin composition can be used in the manufacture of molded articles of other known vinyl chloride-based resin compositions. For example, it can be applied to building materials such as wall materials, floor materials, window frames, wall coverings, and tile patterns; interior and exterior automotive materials; backings, gaskets, interlayers, pipes, joints, wires, and cables.

[0066] Example

[0067] The following describes embodiments of the present invention, but the present invention is not limited thereto.

[0068] <Abbreviation>

[0069] AN: Acrylonitrile

[0070] St: Styrene

[0071] BA: Butyl acrylate

[0072] MMA: Methyl methacrylate

[0073] t-DM: tert-dodecyl mercaptan

[0074] <Weight-average molecular weight of the first or second polymer>

[0075] The first or second polymer was dissolved in tetrahydrofuran (THF), and the soluble component was subjected to gel permeation chromatography (Tosoh Corporation, HLC-8220GPC) based on polystyrene to determine the weight-average molecular weight (sample solution: 20 mg sample / 10 mL THF, measurement temperature: 25 °C, detector: differential refractive index and UV detector, injection volume: 1 mL).

[0076] <Tg of the third polymer>

[0077] Based on the Tg of homopolymers as recorded in "Polymer Handbook Fourth Edition" by J. Brand, published by Wiley in 1998, the Tg of each monomer was calculated, and based on this, the Tg of the third polymer was calculated.

[0078] <Sheet gloss>

[0079] The sheet gloss of the vinyl chloride-based resin composition was evaluated as an indicator of sheet material properties. 100 parts by weight of vinyl chloride-based resin (Kanevinyl S-1008, trade name, average degree of polymerization 800, manufactured by Kaneka Corporation) were mixed in powder form with 1 part by weight of processing aid from each example or comparative example, 6.0 parts by weight of impact modifier (Kanevinyl B-625, manufactured by Kaneka Corporation), 1.0 part by weight of thiol butyltin stabilizer (TVS#1360, manufactured by Nitto Kasei Corporation), 0.5 parts by weight of internal lubricant (GH4, manufactured by Emery Oleo Chemicals), and 0.4 parts by weight of external lubricant (G70S, manufactured by Emery Oleo Chemicals). The resulting mixture was kneaded for 2 minutes at 17 rpm and 198°C using an 8-inch test roller (manufactured by Kansai Roller Co., Ltd.) to produce a test piece with a thickness of 0.4 mm. The reflectance of light at 60° angles was measured at five locations in the center of the test piece relative to the obtained test piece using a gloss meter manufactured by BYK Gardner, and the average value was calculated.

[0080] <Flow Marks (Sheet Haze)>

[0081] As a surface indicator, the HAZE value at both ends of the roll-formed sheet was measured to evaluate the flow marks in the vinyl chloride-based resin composition. The HAZE value at both ends of the sheet is an indicator of the presence or absence of flow marks; the lower the HAZE value at both ends of the sheet, the easier it is to suppress the formation of flow marks. To 100 parts by weight of vinyl chloride resin (Kanevinyl S-1008, average degree of polymerization 800, manufactured by Kaneka Corporation), 1.6 parts by weight of processing aids from each example or comparative example, 6.0 parts by weight of impact modifier (Kanevinyl B-625, manufactured by Kaneka Corporation), 1.0 part by weight of thiol butyltin stabilizer (TVS#1360, manufactured by Nitto Kasei Corporation), 0.5 parts by weight of internal lubricant (GH4, manufactured by Emery Oleo Chemicals), and 0.4 parts by weight of external lubricant (G70S, manufactured by Emery Oleo Chemicals) were mixed in powder form. The resulting mixture was then kneaded for 2 minutes at 17 rpm and 207°C using an 8-inch test roller (Kansai Roller Co., Ltd.), to produce a test sheet (sheet) with a thickness of 0.5 mm. Based on JIS-K7136, using a haze meter (manufactured by Nippon Denshoku Kogyo Co., Ltd., trade name: NDH4000), the HAZE value was measured at a total of 18 locations at both ends of the sheet, and the average value was calculated.

[0082] <Number of shrinkage holes>

[0083] As a surface indicator, the number of pinholes in the molded body of the vinyl chloride resin composition was determined. In 100 parts by weight of vinyl chloride resin (Kanevinyl S-1008, average degree of polymerization 800, manufactured by Kaneka Corporation), 10 parts by weight of processing aids from each example or comparative example, 50 parts by weight of plasticizer (DOP, manufactured by J-Plus Corporation), 3.0 parts by weight of Ba / Zn stabilizer (AC-186, manufactured by ADEKA Corporation), 0.5 parts by weight of lubricant (H-St, manufactured by Sakai Chemical Co., Ltd.), 0.4 parts by weight of titanium dioxide (R-62N, manufactured by Sakai Chemical Industry Co., Ltd.), and 0.02 parts by weight of carbon black (SEAST 3H, manufactured by Tokai Carbon Co., Ltd.) were mixed in powder form. The resulting mixture was kneaded for 1 minute at 18 rpm and 170°C using an 8-inch test roller (manufactured by Kansai Roller Co., Ltd.) to produce a test piece with a thickness of 0.4 mm. The number of shrinkage cavities in a 3 cm × 3 cm area of ​​the test piece was visually counted.

[0084] <Total light transmittance>

[0085] As an indicator of transparency, the total light transmittance of the vinyl chloride-based resin composition was measured. In 100 parts by weight of vinyl chloride-based resin (Kanevinyl S-1008, average degree of polymerization 800, manufactured by Kaneka Corporation), 3 parts by weight of processing aids from each example or comparative example, 1.0 part by weight of thiol butyltin stabilizer (TVS#1380, manufactured by Nitto Kasei Corporation), 0.5 parts by weight of internal lubricant (GH4, manufactured by Emery Oleo Chemicals), and 0.4 parts by weight of external lubricant (G70S, manufactured by Emery Oleo Chemicals) were mixed in powder form. The resulting mixture was then kneaded for 5 minutes at 17 rpm and 165°C using an 8-inch test roller (Kansai Roller Co., Ltd.), followed by pressing and molding at 180°C for 15 minutes to produce a pressure plate with a thickness of 1.0 mm. A test sample for transparency testing, with a thickness of 5.0 mm, a length of 30 mm, and a width of 40 mm, was made from the pressure plate. Using the obtained test sample, the total light transmittance was measured at 23°C based on JIS K 7375 standard "Plastics - Method for determining total light transmittance and total light reflectance", which served as an indicator of transparency.

[0086] <Yellow Index (YI)>

[0087] The yellowness (reflectance YI) of the vinyl chloride-based resin composition was determined. In 100 parts by weight of vinyl chloride-based resin (Kanevinyl S-1008, average degree of polymerization 800, manufactured by Kaneka Corporation), 3 parts by weight of processing aids from each example or comparative example, 1.0 part by weight of thiol butyltin stabilizer (TVS#1380, manufactured by Nitto Kasei Corporation), 0.5 parts by weight of internal lubricant (GH4, manufactured by Emery Oleo Chemicals), and 0.4 parts by weight of external lubricant (G70S, manufactured by Emery Oleo Chemicals) were mixed in powder form. The resulting mixture was then kneaded for 5 minutes at 17 rpm and 165°C using an 8-inch test roller (Kansai Roller Co., Ltd.), followed by pressing and molding at 180°C for 15 minutes to produce a pressure plate with a thickness of 1.0 mm. A yellowness test sample with a thickness of 5.0 mm, a length of 30 mm, and a width of 40 mm was made from the pressure plate. Using the obtained test sample, the yellowness was measured at 23°C based on JIS K 7373 "Plastics - Method for determining yellowness and yellowing degree".

[0088] <Comparison of weight-average molecular weights of the first polymer>

[0089] (Example 1)

[0090] 1.2 parts (by weight, the same below) of sodium dioctyl succinate and 0.05 parts of sodium sulfate, pre-dissolved in water, were added to a reactor equipped with a stirrer. Water was then added further, bringing the total water volume to 200 parts. Nitrogen replacement was performed inside the reactor to remove oxygen from the space and water. The contents were then heated to 75°C while stirring.

[0091] After adding 0.01 parts of potassium persulfate, 47.5 parts of methyl methacrylate and 2.5 parts of butyl acrylate were added over a period of 2 hours to polymerize the first polymer.

[0092] After the first polymer polymerization is completed, 0.1 parts of sodium dioctyl succinate and 0.02 parts of potassium persulfate are added. After 2 hours, 2.6 parts of butyl acrylate, 28.9 parts of styrene, 8.5 parts of acrylonitrile, and 0.4 parts of tert-dodecyl mercaptan are continuously added to carry out the polymerization of the second polymer.

[0093] After the polymerization of the second polymer was completed, 0.1 parts of sodium dioctyl succinate and 0.02 parts of potassium persulfate were added. Then, after 30 minutes, 7 parts of butyl acrylate and 3 parts of methyl methacrylate were continuously added to polymerize the third polymer. At the end of the addition, 0.02 parts of potassium persulfate were added. The mixture was stirred continuously for 1 hour while maintaining the contents at 75°C. After polymerization was completed and cooled, the latex of the processing aid was obtained.

[0094] The latex containing the processing aid was coagulated by adding it to 4 parts of a calcium chloride aqueous solution diluted to a concentration of 1% by weight at a temperature of 70°C. Then, without heat treatment, dehydration, washing, or drying, a powder of the processing aid was obtained. The obtained powder of the processing aid was used to evaluate the molded article of the above-described vinyl chloride-based resin composition.

[0095] (Examples 2-3 and Comparative Example 1)

[0096] Based on the composition shown in Table 1, the weight-average molecular weight of the first polymer was changed, and the powders of the processing aids of Examples 2-3 and Comparative Example 1 were obtained in the same manner as in Example 1. The obtained powders of processing aids were used to evaluate the molded articles of the above-described vinyl chloride-based resin compositions. It should be noted that the weight-average molecular weight of the first polymer was adjusted by changing the amount of potassium persulfate added during the manufacture of the first polymer.

[0097] [Table 1]

[0098]

[0099] According to the results in Table 1, the higher the weight-average molecular weight of the first polymer, the better the gloss of the sheet. Furthermore, the lower the weight-average molecular weight of the first polymer, the better the flow marks (sheet haze) of the sheet. Specifically, comparing Examples 1-3 with Comparative Example 1, using the processing aids obtained in Examples 1-3 yields sheets that maintain good transparency and yellowness while exhibiting a good balance between gloss and flow marks, and excellent pinhole characteristics. In particular, Example 1 yields sheets with an even better balance between gloss and flow marks. However, when using the processing aids obtained in Comparative Example 1, which increased the weight-average molecular weight of the first polymer to a level beyond the scope of this invention, the balance between gloss and flow marks deteriorates; although the gloss is good, the flow marks worsen.

[0100] <Comparison of the ratios and composition of the first polymer>

[0101] (Examples 4-7)

[0102] Based on the composition shown in Table 2, the ratio and / or composition of the first polymer were changed, and the powders of the processing aids of Examples 4 to 7 were obtained in the same manner as in Example 1. The obtained powders of processing aids were used to evaluate the molded articles of the above-described vinyl chloride resin compositions.

[0103] [Table 2]

[0104]

[0105] As shown in Table 2, the higher the weight ratio of methyl methacrylate in the first polymer, the better the gloss. Specifically, comparing Examples 1, 4, and 5, using the processing aids obtained in Examples 1 and 4 yields sheets that maintain good transparency and yellowness while exhibiting a good balance between gloss and flow marks, as well as excellent pinhole characteristics. Furthermore, the higher the ratio of the first polymer, the higher the gloss. Specifically, comparing Examples 1, 6, and 7, using the processing aids obtained in Examples 1 and 6 yields sheets that maintain good transparency and yellowness while exhibiting a good balance between gloss and flow marks, as well as excellent pinhole characteristics.

[0106] <Comparison of the composition and weight-average molecular weight of the second polymer, and comparison with the equivalent product of Patent Document 1>

[0107] (Examples 8-12, Comparative Examples 2-3)

[0108] Based on the composition shown in Table 3, the composition and / or weight-average molecular weight of the second polymer were changed, except that the powders of the processing aids of Examples 8-12 were obtained in the same manner as in Example 1. The obtained powders of processing aids were used to evaluate the molded articles of the above-described vinyl chloride-based resin compositions. It should be noted that the weight-average molecular weight of the second polymer was adjusted by changing the amount of tert-dodecyl mercaptan added during the manufacture of the second polymer.

[0109] (Comparative Example 4)

[0110] As described below, a processing aid equivalent to that in Patent Document 1 was prepared. 0.5 parts (by weight, hereinafter the same) of sodium dioctyl succinate dissolved in water, 0.0008 parts of ferrous sulfate (FeSO4·7H2O), 0.0032 parts of disodium ethylenediaminetetraacetate, and 0.06 parts of sodium formaldehyde sulfoxylate were first loaded into a reactor equipped with a stirrer, and then water was added to a total volume of 200 parts.

[0111] After nitrogen purging to remove oxygen from the space and water in the reactor, the contents were heated to 60°C while stirring. Simultaneously, a mixture of 18 parts methyl methacrylate, 6 parts butyl acrylate, 43.4 parts styrene, 12.6 parts acrylonitrile, and 0.05 parts tert-butyl hydroperoxide was continuously added over 170 minutes, and polymerization was carried out. At the 60th and 120th minutes of this continuous addition, 0.2 parts sodium dodecylbenzenesulfonate were added respectively.

[0112] A mixture of 14 parts methyl methacrylate, 6 parts butyl acrylate, and 0.05 parts tert-butyl hydroperoxide was continuously added to the mixture for 50 minutes to carry out polymerization. After the addition of the copolymerizing components was completed, the contents were kept at 60°C and stirred continuously for more than 1 hour to terminate the polymerization. After cooling, the latex of the processing aid was obtained.

[0113] Four parts of calcium chloride diluted to 1% at 70°C were added to the obtained processing aid, and the mixture was allowed to solidify without heat treatment, dehydration, washing, or drying, to obtain a powder of the processing aid. The obtained processing aid was then used to evaluate the above-mentioned vinyl chloride-based resin composition.

[0114]

[0115] As shown in Table 3, the more the weight ratio of acrylonitrile in the second polymer is reduced and the more the weight ratio of styrene is increased, the higher the flow mark becomes. Specifically, comparing Examples 1, 8, and 9, the processing aids obtained in Examples 1 and 9 can produce sheets that maintain good transparency and yellowness while having a good balance of gloss, flow marks, and excellent pinhole characteristics.

[0116] Furthermore, the lower the weight-average molecular weight of the second polymer, the better the flow mark and cavitation characteristics. Specifically, comparing Examples 1, 10, and 11, using the processing aids obtained in Examples 1 and 10 yields sheets that maintain good transparency and yellowness while exhibiting a better balance between gloss and flow marks, as well as excellent cavitation characteristics. However, when using the processing aids obtained in Comparative Examples 2 and 3, which significantly increase the weight-average molecular weight of the second polymer beyond the scope of this invention, the cavitation characteristics deteriorate substantially.

[0117] Furthermore, even if the proportion of styrene in the processing aid is within the scope of the present invention, if the processing aid obtained in Comparative Example 4, where the first polymer and the second polymer are outside the scope of the present invention, is used, the gloss and pinhole properties deteriorate.

[0118] Industrial availability

[0119] One aspect of the present invention can be suitably used in the manufacture of vinyl chloride-based resin compositions and their molded articles that maintain good transparency and yellowness while exhibiting excellent surface properties and gloss.

Claims

1. A processing aid for vinyl chloride-based resin compositions, comprising a first polymer, a second polymer, and a third polymer forming the outermost layer covering the first polymer and / or the second polymer, for use in vinyl chloride-based resin compositions. The first polymer has a weight-average molecular weight of 600,000 to 4,000,000. The first polymer as a whole is defined as 100% by weight. The first polymer consists of 60-100% by weight alkyl methacrylate and 0-40% by weight other vinyl compounds that can copolymerize with it. The second polymer has a weight-average molecular weight of 10,000 to 400,000. Taking the entire second polymer as 100% by weight, the second polymer consists of 5 to 40% by weight of cyanide-based compounds, 60 to 85% by weight of aromatic ethylene-based compounds, and 0 to 20% by weight of other ethylene-based compounds that can copolymerize with it. The third polymer has a Tg of -40 to 60°C. The total third polymer is set at 100% by weight. The third polymer is composed of 30 to 90% by weight of alkyl acrylate and 10 to 70% by weight of other vinyl compounds that can copolymerize with it. The total of the first polymer and the second polymer is set at 100% by weight. In the processing aid, the proportion of the first polymer is 20-90% by weight and the proportion of the second polymer is 10-80% by weight. The processing aid is set to 100% by weight, and the proportion of aromatic vinyl compounds in the processing aid is 20% by weight or more.

2. The processing aid for the vinyl chloride-based resin composition according to claim 1, wherein, The first polymer has a weight-average molecular weight of 1,000,000 to 2,000,000. The first polymer as a whole is defined as 100% by weight. The first polymer consists of 80-100% by weight alkyl methacrylate and 0-20% by weight other vinyl compounds that can copolymerize with it. The weight-average molecular weight of the second polymer is 15,000 to 150,000. The total of the first polymer and the second polymer is set at 100% by weight. In the processing aid, the proportion of the first polymer is 40-80% by weight and the proportion of the second polymer is 20-60% by weight.

3. The processing aid for the vinyl chloride-based resin composition according to claim 2, wherein, The first polymer is set at 100% by weight, and it consists of 90-100% by weight of alkyl methacrylate and 0-10% by weight of other vinyl compounds that can copolymerize with it. The weight-average molecular weight of the second polymer is 20,000–80,000. The total of the first polymer and the second polymer is set at 100% by weight. In the processing aid, the proportion of the first polymer is 50-70% by weight and the proportion of the second polymer is 30-50% by weight.

4. A vinyl chloride-based resin composition comprising 100 parts by weight of a vinyl chloride-based resin and 0.1 to 20 parts by weight of the processing aid described in any one of claims 1 to 3.

5. A molded article obtained by molding the vinyl chloride-based resin composition of claim 4.

Images