Method for producing vinyl chloride-based polymer

Abstract

To provide a vinyl chloride-based polymer that has, when dissolved in a solvent, excellent filterability.SOLUTION: A method for producing a vinyl chloride-based polymer comprises a polymerization step of suspension-polymerizing a monomer mixture comprising vinyl chloride monomer and a monomer copolymerizable with vinyl chloride monomer in the presence of an aldehyde, wherein the added amount of the aldehyde is 0.1 wt.% to 4.0 wt.% relative to the weight of the monomer mixture, the whole charged amount of the monomer copolymerizable with vinyl chloride monomer relative to the whole charged amount of vinyl chloride monomer and the monomer copolymerizable with vinyl chloride monomer is 16.0 wt.% to 22.0 wt.%, and the amount of initial charge of vinyl chloride monomer relative to the whole charged amount of vinyl chloride monomer is 28.0 wt.% to 38.0 wt.%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a vinyl chloride polymer. [Background technology]

[0002] Vinyl chloride resins are used in a variety of applications due to their excellent chemical resistance, water resistance, weather resistance, flame retardancy, processability, and colorability, and are therefore used as coating binders for paints, inks, and the like.

[0003] Vinyl chloride polymers used as such binders are required to be soluble in solvents and to be filterable when dissolved in a solvent. Furthermore, in recent years, along with the trend toward high-speed inkjet printing, there has been a demand for solutions with lower viscosity. To meet the demand for lower solution viscosity, a technique is known in which a chain transfer agent is used to reduce the degree of polymerization of a vinyl chloride copolymer, thereby achieving a lower solution viscosity. However, the use of a chain transfer agent in the polymerization of vinyl chloride polymers has been problematic in that the conversion rate decreases. The present inventors have reported that the use of an aldehyde as a chain transfer agent can reduce the decrease in conversion rate (e.g., Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2023-137813 Summary of the Invention [Problem to be solved by the invention]

[0005] However, although the above-mentioned conventional techniques are excellent, when an aldehyde is used as a chain transfer agent, the filterability of the resulting solution when the vinyl chloride polymer is dissolved in a solvent may deteriorate, and there is room for improvement.

[0006] An object of one aspect of the present invention is to provide a method for producing a vinyl chloride polymer, which, when dissolved in a solvent, provides a solution having excellent filterability. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, one embodiment of the present invention includes the following configuration.

[0008] [1] A polymerization process comprising a polymerization step of suspension polymerizing a monomer mixture containing vinyl chloride monomer and a monomer copolymerizable with vinyl chloride monomer in the presence of an aldehyde represented by the following general formula (I), the amount of the aldehyde added is 0.1% by weight to 4.0% by weight based on the weight of the monomer mixture; the total amount of the vinyl chloride monomer copolymerizable with the vinyl chloride monomer charged is 16.0% by weight to 22.0% by weight based on the total amount of the vinyl chloride monomer charged and the total amount of the vinyl chloride monomer copolymerizable with the vinyl chloride monomer charged; A method for producing a vinyl chloride polymer, wherein the initial amount of vinyl chloride monomer charged is 28.0% by weight to 38.0% by weight based on the total amount of vinyl chloride monomer charged.

[0009] [ka]

[0010] (In formula (I), R represents an alkyl group having 2 to 4 carbon atoms.) [2] The production method according to [1], wherein the initial amount of the vinyl chloride monomer is 53.0% by weight to 65.0% by weight based on the total amount of the vinyl chloride monomer and the initial amount of the monomer copolymerizable with the vinyl chloride monomer.

[0011] [3] The production method according to [1] or [2], wherein the polymerization step includes a step of adding the aldehyde in portions.

[0012] [4] The method according to any one of [1] to [3], wherein the monomer copolymerizable with the vinyl chloride monomer is a vinyl ester monomer.

[0013] [5] The method according to [4], wherein the vinyl ester monomer is vinyl acetate.

[0014] [6] The production method according to any one of [1] to [5], wherein the aldehyde represented by the general formula (I) is an aldehyde represented by the following formula (II) or (III):

[0015] [ka]

[0016] [ka]

[0017] [7] The method according to any one of [1] to [6], wherein the polymerization temperature in the polymerization step is 65°C to 85°C. [Effects of the Invention]

[0018] According to one aspect of the present invention, it is possible to provide a vinyl chloride polymer that, when dissolved in a solvent, provides a solution having excellent filterability. DETAILED DESCRIPTION OF THE INVENTION

[0019] One embodiment of the present invention will be described below, but the present invention is not limited thereto. The present invention is not limited to the respective configurations described below, and various modifications are possible within the scope of the claims. Furthermore, embodiments or examples obtained by combining the technical means disclosed in different embodiments or examples are also included in the technical scope of the present invention. All academic literature and patent documents described in this specification are incorporated herein by reference. Furthermore, unless otherwise specified in this specification, "A to B" representing a numerical range means "A or more (including A and greater than A) and B or less (including B and less than B)."

[0020] For example, in the case of inkjet ink, a process of filtering the ink beforehand in the inkjet printer is required to prevent clogging of the machine (head) for ejecting the ink by machine. Therefore, for example, a solution containing a vinyl chloride polymer used in inkjet printing is required to have excellent filterability, i.e., a short filtration time and a filtration rate that does not change over time.

[0021] In the polymerization of vinyl chloride polymers, the use of a chain transfer agent has been associated with a problem of reduced conversion, but the present inventors have reported that the use of an aldehyde as a chain transfer agent can reduce the reduction in conversion. However, the present inventors have newly discovered that the use of an aldehyde can sometimes result in a deterioration in the filterability of a solution containing a vinyl chloride polymer.

[0022] Therefore, the present inventors investigated the factors that cause the filterability of solutions containing vinyl chloride polymers to deteriorate when an aldehyde is used. In the study, they analyzed the molecular weight distribution of vinyl chloride polymers obtained by polymerizing vinyl chloride monomer and a monomer copolymerizable with the vinyl chloride monomer, and the content of the copolymerizable monomer in vinyl chloride polymers of various molecular weights. They found that the content of the copolymerizable monomer is more molecular weight-dependent when an aldehyde is used than when an aldehyde is not used. For example, when vinyl acetate is used as the copolymerizable monomer, the vinyl acetate monomer content ranged from 19% to 21% by weight regardless of molecular weight when an aldehyde is not used. However, when an aldehyde is used, the vinyl acetate monomer content was as low as 16% by weight in low-molecular-weight vinyl chloride polymers and as high as 24% by weight in high-molecular-weight vinyl chloride polymers, indicating a strong molecular weight dependency.

[0023]

[0009] Based on these findings, the present inventors have hypothesized that when an aldehyde is used, a vinyl chloride polymer with a low content of vinyl acetate monomer is produced in the low molecular weight region, and that this polymer may be the cause of adverse effects on filterability. They then discovered that, in a copolymerization reaction of vinyl chloride monomer and a monomer copolymerizable with vinyl chloride monomer, the ratio of the total amount of vinyl chloride monomer copolymerizable with vinyl chloride monomer to the total amount of vinyl chloride monomer and the total amount of vinyl chloride monomer copolymerizable with vinyl chloride monomer is set within a predetermined range, and the ratio of the initial amount of vinyl chloride monomer to the total amount of vinyl chloride monomer is set within a predetermined range, whereby the filterability of the solution obtained when the vinyl chloride polymer is dissolved in a solvent can be ensured, thereby completing the present invention.

[0024] In this specification, "initial charging" refers to adding raw materials to a polymerization vessel before "the point at which heating is started to adjust the internal temperature of the polymerization vessel to the polymerization temperature," which is certainly before the start of polymerization. "Initial charging amount" refers to the amount of raw materials added to the polymerization vessel before the start of heating, in other words, the amount of raw materials present in the polymerization vessel at the start of heating. "Additional charging" refers to additionally adding raw materials to a polymerization vessel after the start of polymerization, and "additional charging amount" refers to the amount of raw materials additionally added to the polymerization vessel after the start of polymerization. "Total charging amount" refers to the sum of the "initial charging amount" and the "additional charging amount." "Start of polymerization" refers to "the point at which the internal temperature of the polymerization vessel reaches the polymerization temperature."

[0025] 1. Method for producing vinyl chloride polymers A method for producing a vinyl chloride polymer according to one embodiment of the present invention comprises a polymerization step of suspension polymerizing a monomer mixture containing a vinyl chloride monomer and a monomer copolymerizable with the vinyl chloride monomer in the presence of an aldehyde represented by the following general formula (I), wherein the amount of the aldehyde added is 0.1 to 4.0% by weight based on the weight of the monomer mixture, the total amount of the monomer copolymerizable with the vinyl chloride monomer charged is 16.0 to 22.0% by weight based on the total amount of the vinyl chloride monomer charged and the total amount of the monomer copolymerizable with the vinyl chloride monomer charged, and the initial amount of the vinyl chloride monomer charged is 28.0 to 38.0% by weight based on the total amount of the vinyl chloride monomer charged.

[0026] [ka]

[0027] (In formula (I), R represents an alkyl group having 2 to 4 carbon atoms.) The production method according to one embodiment of the present invention, as configured above, can produce a vinyl chloride polymer from a solution containing the vinyl chloride polymer that has excellent filterability. Furthermore, by carrying out polymerization in the presence of the aldehyde, there are advantages in that the degree of polymerization is low, the viscosity of the solution when dissolved in a solvent is low, and a decrease in conversion can be minimized.

[0028] [1.1] Polymerization process In one embodiment of the present invention, the polymerization step is a step of suspension polymerizing a monomer mixture containing vinyl chloride monomer and a monomer copolymerizable with vinyl chloride monomer in the presence of an aldehyde represented by the above general formula (I).

[0029] <Monomers copolymerizable with vinyl chloride monomer> The monomer copolymerizable with the vinyl chloride monomer is not particularly limited, and examples thereof include vinyl esters such as vinyl acetate, vinyl propionate, and vinyl stearate; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, octyl vinyl ether, lauryl vinyl ether, and isobutyl vinyl ether; alkyl acrylates (methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and the like); hydroxyalkyl acrylates ((meth)acrylate, 2-ethylhexyl (meth)acrylate, and the like); The copolymer may be at least one selected from the group consisting of unsaturated carboxylic acid esters such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and maleic acid esters (e.g., monomethyl maleate, dimethyl maleate, and butyl benzyl maleate); unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, maleic anhydride, and itaconic anhydride; salts of the unsaturated carboxylic acids (e.g., alkali metal salts such as sodium and potassium salts of the unsaturated carboxylic acids); and crosslinkable monomers (e.g., diallyl phthalate). From the viewpoint of reducing the solution viscosity when dissolved in a solvent, among these monomers copolymerizable with vinyl chloride monomers, vinyl esters (vinyl ester monomers) are more preferred, and at least one selected from the group consisting of vinyl acetate, vinyl propionate, and vinyl stearate is even more preferred.

[0030] <Monomer mixture> In this specification, the term "monomer mixture" means a mixture of monomers containing vinyl chloride monomer and a monomer copolymerizable with vinyl chloride monomer, and does not include components other than the monomers, such as solvents and "other additives" described below.

[0031] When the weight of the monomer mixture is taken as 100 parts by weight, the content of the vinyl chloride monomer is preferably 78 parts by weight to 84 parts by weight. In this specification, the terms "weight of the monomer mixture," "content of the vinyl chloride monomer," and "content of the monomer copolymerizable with the vinyl chloride monomer" refer to the total amount charged and the content throughout the polymerization process. That is, the total amount of vinyl chloride monomer charged relative to the total amount of vinyl chloride monomer charged and the total amount of monomer copolymerizable with the vinyl chloride monomer charged is preferably 78% by weight to 84% by weight. Setting the content of the vinyl chloride monomer in the monomer mixture within this range has the advantage of reducing the solution viscosity of the resulting vinyl chloride polymer when dissolved in a solvent.

[0032] Furthermore, when the weight of the monomer mixture is taken as 100 parts by weight, the content of the monomer copolymerizable with vinyl chloride monomer is preferably 16.0 parts by weight to 22.0 parts by weight. In other words, the total amount of the monomer copolymerizable with vinyl chloride monomer charged relative to the total amount of the vinyl chloride monomer charged and the total amount of the monomer copolymerizable with vinyl chloride monomer charged is preferably 16.0% by weight to 22.0% by weight. By setting the content of the monomer copolymerizable with vinyl chloride monomer in the monomer mixture within this range, there is an advantage in that the solution viscosity of the resulting vinyl chloride polymer when dissolved in a solvent is reduced.

[0033] <Aldehyde represented by general formula (I)> The polymerization step is a step of suspension polymerizing the monomer mixture in the presence of the aldehyde represented by the general formula (I).

[0034] In the general formula (I), R is an alkyl group having 2 to 4 carbon atoms. The alkyl group may be linear or branched. Examples of R include an ethyl group, a 1-methylethyl group, a propyl group, a 1-methylpropyl group, a 2-methylpropyl group, and a butyl group.

[0035] By carrying out suspension polymerization of the monomer mixture in the presence of the aldehyde, a vinyl chloride polymer with a low degree of polymerization can be produced with little decrease in conversion.

[0036] The aldehyde is more preferably butyraldehyde (NBD) represented by the following formula (II) or propionaldehyde represented by the following formula (III): By using these aldehydes, a vinyl chloride polymer can be produced with even less decrease in conversion rate in the polymerization of a vinyl chloride polymer with a low degree of polymerization.

[0037] [ka]

[0038] [ka]

[0039] In one embodiment of the present invention, the aldehyde is preferably used as a chain transfer agent, which enables the production of a vinyl chloride polymer with a low degree of polymerization with little decrease in conversion.

[0040] <Solvents and other additives> In one embodiment of the present invention, the suspension polymerization of the monomer mixture may be carried out in a liquid in which the monomer mixture is dispersed. The liquid may contain, for example, a solvent and other additives such as a dispersant, an antioxidant, and a polymerization initiator.

[0041] (solvent) Examples of the solvent used in one embodiment of the present invention include aqueous solvents and mixtures of water and a water-insoluble organic solvent.

[0042] The aqueous solvent is not limited to water, but may be, for example, a mixture of water and an organic solvent that is miscible with water, such as methyl alcohol or ethyl alcohol.

[0043] Examples of water-insoluble organic solvents include chloroform, halogenated hydrocarbons, aromatic hydrocarbons, and ketones. Examples of halogenated hydrocarbons include carbon tetrachloride. Examples of aromatic hydrocarbons include benzene and toluene. Examples of ketones include methyl ethyl ketone and methyl isobutyl ketone.

[0044] (dispersant) The dispersant used in one embodiment of the present invention is not limited, and examples thereof include methyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, partially saponified polyvinyl alcohol, polyethylene oxide, etc. These may be used alone, or two or more types of dispersants may be used in combination.

[0045] (antioxidant) Examples of antioxidants used in one embodiment of the present invention include hindered phenol-based, thiodipropionic acid ester-based, aliphatic sulfide-based and disulfide-based antioxidants, etc. These may be used alone, or two or more types of dispersants may be used in combination.

[0046] (Polymerization initiator) Examples of the polymerization initiator used in one embodiment of the present invention include an oil-soluble polymerization initiator and a water-soluble polymerization initiator. From the viewpoints of increasing the reaction efficiency and reducing scaling to improve productivity, it is more preferable to use an oil-soluble polymerization initiator as the polymerization initiator.

[0047] Examples of oil-soluble polymerization initiators include (3,5,5, trimethylhexanoyl) peroxide; diacyl peroxides such as dilauroyl peroxide and di-3,5,5, trimethylhexanoyl peroxide; peroxydicarbonates such as diisopropyl peroxydicarbonate and di-2-ethylhexyl peroxydicarbonate; organic peroxide initiators such as benzoyl peroxide, t-butyl peroxypivalate, t-butyl peroxyneodecanoate, and peroxyesters; and azo initiators such as 2,2'-azobisisobutyronitrile and 2,2'-azobis(2,4-dimethylvaleronitrile). These may be used alone or in combination with two or more dispersants. From the viewpoint of suppressing polymerization delay and improving reaction efficiency, the oil-soluble polymerization initiator is preferably (3,5,5, trimethylhexanoyl) peroxide or benzoyl peroxide.

[0048] Examples of water-soluble polymerization initiators include ammonium persulfate, potassium persulfate, sodium persulfate, and aqueous hydrogen peroxide. When a water-soluble polymerization initiator is used, a reducing agent (e.g., sodium sulfite, sodium thiosulfate, formaldehyde sodium sulfoxylate dihydrate, ascorbic acid, and sodium ascorbate) may be used in combination, if necessary.

[0049] It is preferable to select a polymerization initiator that exhibits an appropriate half-life temperature relative to the polymerization temperature.

[0050] <Suspension polymerization of a monomer mixture in the presence of an aldehyde represented by general formula (I)> The polymerization step is a step of suspension polymerizing (e.g., suspension polymerization, microsuspension polymerization, seed microsuspension polymerization) a monomer mixture containing vinyl chloride monomer and a monomer copolymerizable with vinyl chloride monomer in the presence of an aldehyde represented by the general formula (I). More specifically, the polymerization step is a step of suspension polymerizing a monomer mixture containing vinyl chloride monomer and a monomer copolymerizable with vinyl chloride monomer in a polymerization vessel in the presence of the aldehyde. Suspension polymerization has the following advantages: (1) vinyl chloride polymer particles having a specific average particle size (e.g., 50 μm to 400 μm) can be easily produced, and (2) vinyl chloride polymers can be produced more productively and at lower cost than emulsion polymerization.

[0051] In one embodiment of the present invention, in the polymerization step, a portion of the vinyl chloride monomer is initially charged, and the remainder is additionally charged. The initial charge amount of the vinyl chloride monomer relative to the total amount of vinyl chloride monomer charged is preferably 28.0 wt% to 38.0 wt%, more preferably 28.5 wt% to 37.5 wt%, and even more preferably 29.0 wt% to 37.0 wt%. This configuration can reduce the production of vinyl chloride polymers with low molecular weights and low contents of monomers copolymerizable with vinyl chloride monomer. This has the advantage of improving the filterability of the resulting solution containing the vinyl chloride polymer.

[0052] In one embodiment of the present invention, the timing of additionally charging a portion of the vinyl chloride monomer is not particularly limited. For example, the additional charging can be carried out after the polymerization temperature has been reached. The additional charging may be carried out all at once or in portions.

[0053] Furthermore, the initial charge amount of the vinyl chloride monomer relative to the total of the initial charge amount of the vinyl chloride monomer and the initial charge amount of the monomer copolymerizable with the vinyl chloride monomer is preferably 53.0 wt% to 65.0 wt%, more preferably 53.5 wt% to 64.5 wt%, and even more preferably 54.0 wt% to 64.0 wt%. This configuration can reduce the production of vinyl chloride polymers with low contents of monomers copolymerizable with the vinyl chloride monomer in the low molecular weight region. This has the advantage of improving the filterability of the resulting solution containing the vinyl chloride polymer.

[0054] Furthermore, the initial charge amount of the monomer copolymerizable with the vinyl chloride monomer relative to the total of the initial charge amount of the vinyl chloride monomer and the initial charge amount of the monomer copolymerizable with the vinyl chloride monomer is preferably 35.0 wt% to 47.0 wt%, more preferably 35.5 wt% to 46.5 wt%, and even more preferably 36.0 wt% to 46.0 wt%. This configuration can reduce the production of vinyl chloride polymers with low contents of monomers copolymerizable with the vinyl chloride monomer in the low molecular weight range. This has the advantage of improving the filterability of the resulting solution containing the vinyl chloride polymer.

[0055] In one embodiment of the present invention, in the polymerization step, it is preferable that the monomer copolymerizable with vinyl chloride monomer is initially charged all at once into the polymerization vessel. This configuration makes it possible to reduce the production of vinyl chloride polymers with a low content of monomers copolymerizable with vinyl chloride monomer in the low molecular weight region. However, the method of adding the monomer copolymerizable with vinyl chloride monomer is not limited to initial all-at-once charging, and additional charging may be carried out to the extent that it does not adversely affect the effects of the present invention.

[0056] The polymerization temperature in the polymerization step is preferably 65°C to 85°C. By keeping the polymerization temperature within this range, it is possible to reduce a decrease in conversion rate. Since this makes it possible to particularly reduce a decrease in conversion rate, the polymerization temperature is more preferably 68°C to 85°C, and even more preferably 70°C to 80°C.

[0057] In the polymerization step, the amount of the aldehyde added is preferably 0.1 to 4.0% by weight, more preferably 0.5 to 2.0% by weight, and even more preferably 0.7 to 1.5% by weight, based on the weight of the monomer mixture. By adding such an amount, it is possible to reduce a decrease in conversion rate in the polymerization of vinyl chloride polymers with a low degree of polymerization.

[0058] In the polymerization step, the aldehyde may be added in portions. More specifically, for example, the aldehyde may be added all at once before the start of polymerization (initial charging), or a portion of the aldehyde may be added before the start of polymerization (initial charging) and the remainder may be added after the start of polymerization (additional charging). Among these, it is more preferable to add the aldehyde in portions in the polymerization step. This configuration has the advantage of further improving the filterability of the resulting vinyl chloride polymer-containing solution.

[0059] Although the reason why the filterability of the solution is further improved by adding the aldehyde in portions is not clear, it is thought that when the concentration of the aldehyde is high at the beginning of polymerization, a large amount of polymers with low degrees of polymerization and small molecular weights are produced.Since in the low molecular weight region, vinyl chloride polymers with a low content of monomers copolymerizable with vinyl chloride monomers tend to be produced, it is speculated that by adding the aldehyde in portions, the concentration of the aldehyde at the beginning of polymerization is reduced, thereby reducing the production of vinyl chloride polymers with a low content of monomers copolymerizable with vinyl chloride monomers, which have an adverse effect on filterability.

[0060] In one embodiment of the present invention, the timing of additionally adding a portion of the aldehyde is not particularly limited. For example, additional addition can be performed when the polymerization conversion reaches a predetermined conversion. The additional addition can be performed all at once or in separate portions. For example, when the aldehyde is added in n separate portions, (i) the final conversion X is divided by the number n of separate additions to calculate the conversion X / n, (ii) a portion is added (initial addition) before the start of polymerization, (iii) a second addition of the aldehyde is performed when the conversion reaches approximately X / n, (iv) a third addition of the aldehyde is performed when the conversion reaches approximately twice X / n, and (v) the aldehyde is added in the same manner until the conversion reaches (n-1) times X / n.

[0061] For example, when the final conversion rate of the vinyl chloride polymer is 85% to 100%, the following methods can be employed: (i) a method in which a portion of the aldehyde is initially charged, and the remaining aldehyde is added when the conversion rate is 30% to 60% or 40% to 50%; or (ii) a method in which a portion of the aldehyde is initially charged, and the first additional addition of the aldehyde is made when the conversion rate is 15% to 45% or 20% to 40%, and the second additional addition of the aldehyde is made when the conversion rate is 45% to 75% or 50% to 70%.

[0062] In order to determine the timing of additionally charging a portion of the aldehyde, the aldehyde may be divided into portions while monitoring the conversion rate of the polymerization reaction. Here, the conversion rate of the polymerization reaction can be monitored by calculating it from the amount of the monomer mixture charged into the polymerization vessel and the solids concentration of a sampled slurry.

[0063] When the aldehyde is added in portions, the ratio between the initial charge amount and each additional charge amount is not particularly limited, and the initial charge amount and each additional charge amount may be the same weight or different weights. For example, when the aldehyde is added in n portions, the weight obtained by dividing the total charge amount of the aldehyde by n may be added at each charge.

[0064] The polymerization time in the polymerization step (specifically, the time from when the polymerization temperature is reached to when the polymerization is terminated) is not limited and can be set depending on the heat removal capacity. The polymerization time in the polymerization step is preferably 240 to 480 minutes.

[0065] The polymerization vessel used in the polymerization step is not limited, and a synthetic vessel commonly used in the production of vinyl chloride polymers may be used. The lower limit of the volume of the polymerization vessel is not limited, and may be, for example, 1 L or more, 10 L or more, 100 L or more, or 1000 L or more. The upper limit of the volume of the polymerization vessel is not limited, and may be, for example, 1.0 × 10 5 It can be L.

[0066] [1.2] Other processes The production method according to one embodiment of the present invention may include a step other than the polymerization step.

[0067] (Raw material supply process) The raw material supply step is a step of supplying each raw material into a polymerization vessel, and is a step of adding a monomer mixture into a polymerization vessel that has been deoxygenated by adding, for example, the aldehyde, solvent, dispersant, polymerization initiator, etc., before the polymerization step. The monomer mixture may be added, for example, in the form of a slurry. The order of adding the raw materials is not particularly limited.

[0068] (Dehydration process) The dehydration step is a step of removing the solvent from the slurry of the vinyl chloride polymer obtained in the polymerization step when the polymer is in a slurry state, and is carried out after the polymerization step. For example, the vinyl chloride polymer slurry is separated into the vinyl chloride polymer and the filtrate by suction filtration to obtain a dehydrated vinyl chloride polymer.

[0069] (drying process) The drying step is a step in which, after the dehydration step, the vinyl chloride polymer is removed from the polymerization vessel, dehydrated as necessary in the dehydration step, and then dried in a dryer.

[0070] The drying temperature is, for example, preferably 40°C or higher and 100°C or lower, more preferably 40°C or higher and 80°C or lower, and even more preferably 40°C or higher and 60°C or lower.

[0071] The drying time is, for example, preferably 1 hour or more and 16 hours or less, and more preferably 1 hour or more and 10 hours or less.

[0072] (Isolation process) The production method according to one embodiment of the present invention may include an isolation step of isolating vinyl chloride polymer particles having an average particle size of 50 μm to 400 μm after the polymerization step, the dehydration step, or the drying step.

[0073] [2. Physical properties of vinyl chloride polymers] (Degree of polymerization) The K value is used as an index of the degree of polymerization. The K value can be calculated by the method described in the Examples.

[0074] Although there are no limitations on the K value, vinyl chloride polymers used in inks, paints, and the like usually have a K value of 30 to 50, and preferably 35 to 45. By adjusting the K value of the vinyl chloride polymer to fall within this range, the vinyl chloride polymer can have a low degree of polymerization, and as a result, when dissolved in a solvent, the viscosity of the solution can be reduced.

[0075] (conversion rate) The conversion rate can be calculated by the following method. A vinyl chloride polymer slurry produced by a production method according to one embodiment of the present invention is dried, and the vinyl chloride polymer from which unreacted vinyl chloride monomer and unreacted monomers including monomers copolymerizable with the unreacted vinyl chloride monomer are removed is weighed. The conversion rate is calculated by dividing the weight of the vinyl chloride polymer by the total amount of charged vinyl chloride monomer and monomers including monomers copolymerizable with the vinyl chloride monomer.

[0076] The conversion rate is not limited, but is preferably 60 to 100%, more preferably 70 to 100%, more preferably 80 to 100%, and most preferably 85 to 100%. By setting the conversion rate of the vinyl chloride polymer within this range, a vinyl chloride copolymer with a stable particle shape can be obtained, making it possible to achieve a polymerization method with excellent productivity.

[0077] (viscosity) The viscosity of a vinyl chloride polymer produced by a production method according to one embodiment of the present invention can be evaluated by measuring the viscosity at 25°C of a solution obtained by dissolving the vinyl chloride polymer in a solvent consisting of methyl ethyl ketone (MEK), toluene (TOL), and butyl acetate (BAC), a solvent consisting of ethyl acetate (EAC), or a solvent consisting of ethylene glycol monobutyl ether acetate (BGA) using a Brookfield viscometer. The lower this viscosity, the higher the solubility in the solvent, and therefore the lower the viscosity of the solution can be.

[0078] The viscosity of the solution is not limited, but when dissolved in MEK / TOL / BAC solvent at a solids content of 25%, it is preferably 60 mPa·S to 120 mPa·S, and more preferably 70 mPa·S to 100 mPa·S. When dissolved in EAC solvent at a solids content of 20%, it is preferably 20 mPa·S to 60 mPa·S, and more preferably 30 mPa·S to 50 mPa·S. When dissolved in BGA solvent at a solids content of 15%, it is preferably 40 mPa·S to 80 mPa·S, and more preferably 50 mPa·S to 70 mPa·S. When the viscosity of the solution is within this range, the vinyl chloride polymer produced by the production method of one embodiment of the present invention can be suitably used as an ink resin or a paint resin. [Example]

[0079] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0080] [Measurement method] The measurement methods for the K value, conversion rate, vinyl acetate monomer content of the vinyl chloride-based polymers produced in the examples and comparative examples, the viscosity of the vinyl chloride-based resin solution dissolved in each solvent, and the filterability of the vinyl chloride-based resin solution are as follows.

[0081] <K value> 0.25 g of the obtained vinyl chloride-based polymer was dissolved in 50 mL of cyclohexanone, and the flow-down time was measured with a capillary viscometer in an atmosphere of 25°C for the obtained solution. Further, based on the conversion table of JIS K7367-2-1999, the K value corresponding to the viscosity ratio (the ratio of the flow-down time of the solution to cyclohexanone: the flow-down time of the solution / the flow-down time of cyclohexane) was calculated.

[0082] <Conversion rate> The weight of the obtained vinyl chloride-based polymer was weighed. The conversion rate was calculated by dividing the weight of the vinyl chloride-based polymer by the total weight of the total charged amount of vinyl chloride monomer and the total charged amount of vinyl acetate monomer.

[0083] <Vinyl acetate monomer content in the vinyl chloride-based polymer> The content of vinyl acetate monomer in the vinyl chloride-based polymer was calculated by FT-IR (FT / IR4700 manufactured by JASCO Corporation). Using a 5% tetrahydrofuran (THF) solution, a cast film was prepared on a KBr plate, and after drying the cast film at 120°C, FT-IR was measured. Based on the absorption ratio of C-H and C=O, the content of vinyl acetate monomer in the vinyl chloride-based polymer was calculated.

[0084] <Viscosity of the vinyl chloride-based resin solution dissolved in each solvent> The obtained vinyl chloride-based polymer was dissolved in the following three types of solvents to prepare a vinyl chloride-based resin solution, and the viscosity of the obtained solution was measured.

[0085] (MEK / TOL / BAC solvent) 50 parts by weight of a vinyl chloride polymer was dissolved in 30 parts by weight of methyl ethyl ketone (MEK), 30 parts by weight of toluene (TOL), and 90 parts by weight of butyl acetate (BAC) by stirring at 2000 rpm for 20 minutes at 30° C. The viscosity of the resulting solution at 25° C. was measured using a Brookfield viscometer.

[0086] (EAC solvent) 20 parts by weight of a vinyl chloride polymer was dissolved in 80 parts by weight of ethyl acetate (EAC) by stirring at 2000 rpm for 20 minutes at 30° C. The viscosity of the resulting solution at 25° C. was measured using a Brookfield viscometer.

[0087] (BGA solvent) 15 parts by weight of a vinyl chloride polymer was dissolved in 85 parts by weight of ethylene glycol monobutyl ether acetate (BGA (CAS number: 112-07-2)) by stirring at 2000 rpm for 120 minutes at 50° C. The viscosity of the resulting solution at 25° C. was measured using a B-type viscometer.

[0088] <Filterability> 15 parts by weight of the resulting vinyl chloride polymer was dissolved in 85 parts by weight of ethylene glycol monobutyl ether acetate (BGA) by stirring at 2000 rpm for 120 minutes at 50°C, and then diluted 3-fold with ethylene glycol monobutyl ether acetate to prepare a 5% vinyl chloride polymer solution. 300 mL of the resulting 5% vinyl chloride polymer solution was placed in a suction filtration apparatus (Advantec KG47) equipped with an APFB 1 μm filter (Merck APFB04700 (trade name), 1 μm pore size, 47 mm diameter) and a container with a sealable lid. The pressure in the suction bottle (AS ONE, 1000 mL) was reduced to 0.090 MPa, and the solution was subjected to suction filtration. The time from the start of pressure reduction until 50 mL of the solution passed through the filter, the time from the start of pressure reduction until 150 mL of the solution passed through the filter, the time from the start of pressure reduction until 200 mL of the solution passed through the filter, and the time from the start of pressure reduction until 300 mL of the solution passed through the filter were measured using a stopwatch.

[0089] The "time until 50 mL of the solution passes through the filter" was defined as T1 (0-50 mL filtration time), the "time until 150 mL of the solution passes through the filter - T1" was defined as T2 (50 mL-150 mL filtration time), the "time until 200 mL of the solution passes through the filter - T2" was defined as T3 (150 mL-200 mL filtration time), and the "time until all of the solution passes through the filter - T3" was defined as T4 (200 mL-300 mL filtration time).

[0090] From T1 to T4, the following indexes were calculated as indices of filterability.

[0091] (Clogging index: T1 / T3) As an index of clogging, T1 (0-50 mL filtration time) / T3 (150 mL-200 mL filtration time) was calculated. T1 / T3 is the ratio of the initial filtration rate to the later filtration rate, and the closer it is to 100%, the smaller the clogging and the smaller the decrease in filtration rate over time.

[0092] (Filtration rate index: T1+T2+T3+T4) As an index of the filtration rate, T1 + T2 + T3 + T4 was calculated. T1 + T2 + T3 + T4 is the filtration time until all of 300 mL of a 5% vinyl chloride polymer solution has passed through, and a smaller value indicates a faster filtration rate.

[0093] Example 1 A stainless steel polymerization vessel equipped with a stirring blade and an external jacket was charged with 130.0 parts by weight of ion-exchanged water as a solvent; 0.1 part by weight of polyethylene oxide (manufactured by Sumitomo Seika Chemicals Co., Ltd.) as a dispersant; and 0.0243 part by weight of benzoyl peroxide (manufactured by NOF Corporation) and 0.0922 part by weight of (3,5,5-trimethylhexanoyl) peroxide (manufactured by NOF Corporation) as polymerization initiators, and then the polymerization vessel was sealed.

[0094] Subsequently, the inside of the polymerization vessel was degassed with a vacuum pump, and then stirring was started, and the polymerization vessel was charged with 17.0 parts by weight of vinyl acetate monomer, 30.0 parts by weight of vinyl chloride monomer, and 0.725 parts by weight of butyraldehyde (NBD) (manufactured by Tokyo Chemical Industry Co., Ltd., CAS number: 123-72-8, molecular weight 72.1) as a chain transfer agent (initial charging).

[0095] The temperature of the solution inside the polymerization vessel was then increased using the external jacket. The point at which the temperature inside the polymerization vessel reached 75°C was designated as the start of polymerization, and the remaining 53.0 parts by weight of vinyl chloride monomer was continuously charged (additional charging). The temperature inside the polymerization vessel was maintained at 76°C, and the polymerization was terminated 7 hours after the start of polymerization (polymerization temperature: 76°C). The resulting slurry was stirred at 80°C for 1 hour to remove unreacted vinyl acetate monomer, vinyl chloride monomer, and butylaldehyde, and then the resulting slurry was dried to obtain a vinyl chloride polymer.

[0096] Example 2 The same solvent, dispersant, polymerization initiator and other raw materials as in Example 1 were charged into a stainless steel polymerization vessel equipped with a stirring blade and an external jacket, and the vessel was then sealed.

[0097] Subsequently, the inside of the polymerization vessel was degassed with a vacuum pump, and then stirring was started, and 20.0 parts by weight of vinyl acetate monomer, 24.5 parts by weight of vinyl chloride monomer, and 0.447 parts by weight of butyraldehyde (NBD) as a chain transfer agent were charged into the polymerization vessel (initial charging).

[0098] The temperature of the solution inside the polymerization vessel was then raised using the external jacket. The point at which the temperature inside the polymerization vessel reached 72°C was designated the start of polymerization, and the remaining 55.5 parts by weight of vinyl chloride monomer was continuously charged (additional charging). The temperature inside the polymerization vessel was maintained at 73°C, and 0.447 parts by weight of butyraldehyde was added 80 minutes after the start of polymerization and 190 minutes after the start of polymerization, respectively. The polymerization was terminated 7 hours after the start of polymerization (polymerization temperature: 73°C). The same procedures as in Example 1 were performed to remove unreacted vinyl acetate monomer, vinyl chloride monomer, and butyraldehyde, and the resulting slurry was dried to obtain a vinyl chloride polymer. The conversion rate was 30% 80 minutes after the start of polymerization, and 90% 190 minutes after the start of polymerization.

[0099] Comparative Example 1 A vinyl chloride polymer was obtained by the same procedure as in Example 1, except that the initial amount of vinyl chloride monomer was changed from 30.0 parts by weight to 37.5 parts by weight, the additional amount was changed from 53.0 parts by weight to 45.5 parts by weight, and the amount of epoxy soybean oil was changed to 0.15 parts by weight.

[0100] Comparative Example 2 A vinyl chloride polymer was obtained by the same procedure as in Example 1, except that the initial amount of vinyl chloride monomer was changed from 30.0 parts by weight to 33.75 parts by weight and the additional amount was changed from 53.0 parts by weight to 49.25 parts by weight.

[0101] [Reference example 1] A vinyl chloride polymer was obtained by the same procedure as in Comparative Example 1, except that the initial amount of vinyl chloride monomer charged was changed from 37.5 parts by weight to 35.0 parts by weight, the initial amount of vinyl acetate charged was changed from 17.0 parts by weight to 19.5 parts by weight, and butyraldehyde (NBD) was not added.

[0102] The amounts of each raw material used in the Examples, Comparative Examples, and Reference Examples are shown in Table 1. Table 2 also shows the results of measuring the K value, conversion rate, vinyl acetate monomer content, viscosity of the vinyl chloride resin solution obtained by dissolving the vinyl chloride polymers in each solvent, and filterability of the vinyl chloride resin solution, for the vinyl chloride polymers produced in the Examples, Comparative Examples, and Reference Examples.

[0103] [Table 1]

[0104] [Table 2]

[0105] 〔summary〕 Comparison of Examples 1 and 2 and Comparative Examples 1 and 2 with Reference Example 1 reveals that the vinyl chloride polymers obtained in Examples 1 and 2 and Comparative Examples 1 and 2, in which aldehyde was added, have smaller K values, i.e., smaller degrees of polymerization, and lower viscosities of vinyl chloride resin solutions, compared to the vinyl chloride resin of Reference Example 1, in which no aldehyde was added.

[0106] Furthermore, the resin solutions containing vinyl chloride polymers of Examples 1 and 2, in which the initial amounts of vinyl chloride monomer charged relative to the total amount of vinyl chloride monomer charged were 36.1 wt % and 30.6 wt %, respectively, showed shorter filtration times and less change in filtration rate over time than the resin solutions containing vinyl chloride polymers of Comparative Examples 1 and 2, in which the initial amounts of vinyl chloride monomer charged were 45.2 wt % and 40.7 wt %, respectively. [Industrial Applicability]

[0107] According to the method for producing a vinyl chloride polymer according to one embodiment of the present invention, it is possible to provide a vinyl chloride polymer which, when dissolved in a solvent, has excellent filterability as a solution, and is therefore highly useful and suitable for use in applications such as paints and inks.

Claims

1. The method includes a polymerization step of suspension polymerizing a monomer mixture containing vinyl chloride monomer and a monomer copolymerizable with vinyl chloride monomer in the presence of an aldehyde represented by the following general formula (I): the amount of the aldehyde added is 0.1% by weight to 4.0% by weight based on the weight of the monomer mixture; the total amount of the vinyl chloride monomer copolymerizable with the vinyl chloride monomer charged is 16.0% by weight to 22.0% by weight based on the total amount of the vinyl chloride monomer charged and the total amount of the vinyl chloride monomer copolymerizable with the vinyl chloride monomer charged; A method for producing a vinyl chloride polymer, wherein the initial amount of vinyl chloride monomer charged is 28.0% by weight to 38.0% by weight based on the total amount of vinyl chloride monomer charged. 【Chemical 1】 (In formula (I), R represents an alkyl group having 2 to 4 carbon atoms.)

2. 2. The production method according to claim 1, wherein the initial charge amount of the vinyl chloride monomer is 53.0% by weight to 65.0% by weight based on the total of the initial charge amount of the vinyl chloride monomer and the initial charge amount of the monomer copolymerizable with the vinyl chloride monomer.

3. The method according to claim 1 , wherein the polymerization step includes a step of adding the aldehyde in portions.

4. 2. The method according to claim 1, wherein the monomer copolymerizable with the vinyl chloride monomer is a vinyl ester monomer.

5. The process of claim 4, wherein the vinyl ester monomer is vinyl acetate.

6. The method according to claim 1, wherein the aldehyde represented by the general formula (I) is an aldehyde represented by the following formula (II) or (III): 【Chemistry 2】 【Chemistry 3】

7. The method according to claim 1, wherein the polymerization temperature in the polymerization step is 65°C to 85°C.

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