Preparation method for vinyl chloride-series copolymer, and vinyl chloride-series copolymer latex, paste resin, liquid composition and solid composition

Abstract

The present invention relates to a preparation method for a vinyl chloride-series copolymer, and a vinyl chloride-series copolymer latex, paste resin, liquid composition and solid composition. The preparation method for the vinyl chloride-series copolymer comprises: in an aqueous medium which does not contain a surfactant, performing emulsion polymerization on vinyl chloride A, a copolymerization monomer B and a functional monomer C in the presence of a polymerization initiator under stirring, wherein per molecule of the functional monomer C contains one free radical polymerizable group and two functional groups which are selected from an amide group, a carboxyl group and a carboxylate group and which are not an amide group or a carboxyl group at the same time, and the mass ratio of the copolymerization monomer B to the functional monomer C is 1 / 12-12 / 1. The vinyl chloride-series copolymer latex of the present invention does not contain a surfactant; and the vinyl chloride-series copolymer constituting the latex has a vinyl chloride A-based unit, a copolymerization monomer B-based unit and a functional monomer C-based unit.

Description

Process for preparing vinyl chloride copolymer and vinyl chloride copolymer latex, paste resin, liquid composition, and solid composition Technical Field The present invention relates to a process for preparing a vinyl chloride copolymer and a vinyl chloride copolymer latex, paste resin, liquid composition, and solid composition. Background Art Vinyl chloride is a byproduct of the chlor-alkali industry and is inexpensive, making it an important raw material for the plastics and chemical industries. The solid product of polyvinyl chloride prepared by emulsion polymerization is called "paste resin", which is one of the important varieties of polyvinyl chloride resins. It has good pasting properties and dispersibility and is mainly used in soft material products such as artificial leather, floor plastics, wallpapers, impregnated coatings, adhesives, and coatings. In addition to polyvinyl chloride homopolymer products, polyvinyl chloride paste resins can also be copolymerized with other monomers to obtain paste resin products of vinyl chloride copolymers. However, since emulsifiers are usually required in the emulsion polymerization involving vinyl chloride and drying processes such as direct spray drying in the post-treatment of paste resin, usually, small molecule emulsifiers remain in the paste resin, and this residue has an adverse effect on the water resistance, solvent resistance, adhesiveness, transparency, etc. of the paste resin product. In addition, although it is possible to try to wash the small molecule emulsifiers during post-treatment, since the emulsifier is sometimes wrapped on the surface of the latex particles during polymerization, simply washing is difficult to fundamentally solve the problem of emulsifier residue. Therefore, in this field, attention has been paid to how to reduce or not use small molecule emulsifiers. Usually, the strategies adopted are to use macromolecular emulsifiers or to carry out soap-free emulsion polymerization, etc. Among them, soap-free emulsion polymerization includes soap-free emulsion polymerization with an emulsifier concentration lower than the CMC value and soap-free emulsion polymerization based on reactive emulsifiers. Among them, the former often requires a very low monomer concentration in the emulsion polymerization system, which is disadvantageous for industrial production. The latter is difficult to implement in the polymerization involving vinyl chloride because vinyl chloride itself has a large molecular polarity and a strong electron-withdrawing effect. When copolymerizing with other monomers, it tends to homopolymerize itself, and there are few monomers that can polymerize with it (even fewer hydrophilic monomers that may act as reactive emulsifiers). Moreover, vinyl chloride monomer is in a gaseous state, so the latex is prone to agglomeration during the polymerization process, resulting in unstable soap-free emulsion and being unfavorable for industrial production. In addition, this also leads to that even if soap-free emulsion is tried, the emulsion polymerization involving vinyl chloride often cannot do without the use of emulsifiers. For example, Patent Document 1 discloses a method for reacting vinyl chloride, vinyl acetate, a hyperbranched monomer, an initiator, an emulsifier, and a neutralizing agent in water to prepare a hyperbranched aqueous vinyl chloride copolymer emulsion, wherein the hyperbranched monomer is prepared by reacting pentaerythritol with maleic anhydride or fumaric anhydride. The emulsion prepared by this method can be used for modifying polyurethane adhesives and has good adhesiveness, but still cannot do without using an emulsifier. For example, Non-Patent Document 1 discloses a method for emulsion copolymerization of vinyl chloride, vinyl acetate, and maleic anhydride. In this method, a combination of SDS and a reactive emulsifier HS-10 is used as the emulsifier. In addition, for the purpose of expanding the application range of the paste resin of vinyl chloride-based copolymers, there are times when it is desired that the paste resin has more abundant functional groups. However, for the paste resin of vinyl chloride-based copolymers obtained by soap-free emulsion polymerization, there is sometimes a competitive relationship between increasing the content of functional groups and retaining as much as possible the properties achieved based on vinyl chloride monomers (i.e., the so-called "original properties of polyvinyl chloride paste resin"). Prior Art Documents Patent Documents Patent Document 1: CN201911282721.9 Non-Patent Documents Non-Patent Document 1: Conversion Rate and Latex Characteristics of Emulsion Copolymerization of Vinyl Chloride-Vinyl Acetate-Maleic Anhydride, Xiang Hongwen et al., Chemical Reaction Engineering and Technology, Vol. 30, No. 6, December 2014, pp. 522-527. Summary of the Invention Problems to be Solved by the Invention In view of the above problems in the prior art, an object of the present invention is to provide a method for preparing a vinyl chloride-based copolymer, in which emulsion polymerization is simply achieved without using an emulsifier (whether it is a macromolecular emulsifier or a small-molecular emulsifier), the operation is simple, suitable for industrial production, and the obtained vinyl chloride-based copolymer can have more functional groups while ensuring the properties based on vinyl chloride monomers (for example, based on vinyl chloride units can reach more than 70% by mass relative to 100% by mass of all structural units), and the obtained latex has excellent stability. Another object of the present invention is to provide a vinyl chloride-based copolymer latex and a liquid composition based on the latex, the latex can be free of surfactants, is easy to obtain and has excellent stability, and the contained vinyl chloride-based copolymer can have more functional groups while ensuring the properties based on vinyl chloride monomers. Another object of the present invention is to provide a paste resin of a vinyl chloride-based copolymer and a solid composition based on the paste resin, the paste resin is free of surfactants and is easy to obtain, and can have more functional groups while ensuring the properties based on vinyl chloride monomers. Solutions for Solving the Problems According to the intensive research of the inventors of the present invention, it is found that by implementing the following technical solutions, the above technical problems can be solved: [1]. A method for preparing a vinyl chloride-based copolymer, wherein the method comprises: Vinyl chloride A, comonomer B, and functional monomer C are subjected to emulsion polymerization in a surfactant-free aqueous medium with stirring in the presence of a polymerization initiator. The functional monomer C has one radically polymerizable group and two functional groups selected from amide groups, carboxyl groups, and carboxylate groups, and they are not amide groups or carboxyl groups simultaneously in one molecule. The mass ratio of the comonomer B to the functional monomer C, comonomer B / functional monomer C, is 1 / 12 to 12 / 1. [2]. The preparation method according to [1], wherein the comonomer B is at least one selected from monofunctional (meth)acrylate monomers, monofunctional (meth)acrylamide monomers, monofunctional vinyl ester monomers, monofunctional vinyl ether monomers, vinyl pyrrolidone monomers, vinyl pyridine monomers, and vinyl lactam monomers. [3]. The preparation method according to [1] or [2], wherein the functional monomer C is a monomer obtained by reacting an acid anhydride monomer and / or a dicarboxylic acid monomer with a basic compound. [4]. The preparation method according to [3], wherein the basic compound is at least one selected from ammonia gas, aqueous ammonia, sodium hydroxide, and potassium hydroxide, the acid anhydride monomer is at least one selected from maleic anhydride, itaconic anhydride, citraconic anhydride, dimethyl maleic anhydride, aconitic anhydride, and phenyl maleic anhydride, and the dicarboxylic acid monomer is at least one selected from C2-C20 olefin dicarboxylic acids. [5]. The preparation method according to any one of [1] to [4], wherein, based on the total mass of 100% by mass of vinyl chloride A, comonomer B, and functional monomer C, the amount of vinyl chloride A is 70% by mass or more and 95% by mass or less, the amount of comonomer B is greater than 0% by mass and less than 30% by mass, and the amount of functional monomer C is greater than 0% by mass and 20% by mass or less. [6]. The preparation method according to any one of [1] to [5], wherein a pH regulator is further added to the aqueous medium so that the initial pH value of the polymerization system before the start of the emulsion polymerization is greater than 7 and 11 or less. [7]. The preparation method according to any one of [1] to [6], wherein, in the emulsion polymerization, the polymerization temperature is 30-65°C and the polymerization time is 1-72 hours. [8]. A vinyl chloride copolymer latex, wherein the vinyl chloride copolymer latex does not contain a surfactant. The vinyl chloride copolymer constituting the latex has units based on vinyl chloride A, units based on comonomer B, and units based on functional monomer C. The functional monomer C has a radically polymerizable group and two functional groups selected from an amide group, a carboxyl group, and a carboxylate group, and not both of them are amide groups, in one molecule. [9]. The vinyl chloride copolymer latex according to [8], wherein the average particle diameter of the vinyl chloride copolymer particles in the latex is 100 to 350 nm; in the vinyl chloride copolymer, the mass ratio of the unit based on the comonomer B to the unit based on the functional monomer C, the unit based on the comonomer B / the unit based on the functional monomer C, is 1 / 20 to 40 / 1.

[0010] . A vinyl chloride copolymer liquid composition, wherein the composition contains a vinyl chloride copolymer latex obtained by the production method according to any one of [1] to [7], or the vinyl chloride copolymer latex according to [8] or [9].

[0011] . A paste resin of a vinyl chloride copolymer, wherein the paste resin is obtained by using the vinyl chloride copolymer latex obtained by the production method according to any one of [1] to [7], or using the vinyl chloride copolymer latex according to [8] or [9].

[0012] . A solid composition of a vinyl chloride copolymer, wherein the composition contains the paste resin according to

[0010] . Effects of the Invention The present invention provides a method for producing a vinyl chloride copolymer. In this method, the comonomer B ensures good copolymerizability among the three monomers, and the functional monomer C having a specific structure plays a role in stabilizing emulsion polymerization. Therefore, by allowing the comonomer B and the functional monomer C to participate in the polymerization in a specific ratio, emulsion polymerization involving vinyl chloride can be achieved without using an emulsifier. In addition, the introduction of the functional monomer C also enables the obtained vinyl chloride copolymer to have more functional groups while ensuring the properties based on the vinyl chloride monomer. Moreover, the production method of the present invention is easy to operate, has a low raw material cost, is suitable for industrial production, and the obtained latex has excellent stability. The present invention provides a vinyl chloride copolymer latex and a liquid composition based on the latex. The latex does not contain a surfactant, thus avoiding problems caused by the residue of the emulsifier, and can be easily obtained and has excellent stability. In addition, the vinyl chloride copolymer in the latex has more functional groups while ensuring the properties based on the vinyl chloride monomer. Furthermore, the latex of the present invention can be directly used in applications such as coatings and adhesives, or can be used to prepare a paste resin. The present invention provides a paste resin of a vinyl chloride-based copolymer and a solid composition based on the paste resin. The paste resin does not contain a surfactant, thus avoiding problems caused by the residue of the emulsifier and can be easily obtained. In addition, while ensuring the properties based on vinyl chloride monomers, the paste resin also has more functional groups. Detailed Description Various exemplary embodiments, features and aspects of the present invention will be described in detail below. The special word "exemplary" used here means "serving as an example, embodiment or illustration". Any embodiment described as "exemplary" here does not have to be construed as superior to or better than other embodiments. In addition, for a better illustration of the present invention, numerous specific details are given in the following detailed description. Those skilled in the art should understand that the present invention can also be implemented without some specific details. In other instances, methods, means, equipment and steps well-known to those skilled in the art are not described in detail in order to highlight the gist of the present invention. Unless otherwise stated, the units used in this specification are all international standard units, and the numerical values and numerical ranges appearing in the present invention should be understood to include the systematic errors inevitable in industrial production. In this specification, the numerical range represented by "numerical value A to numerical value B" means a range including the end point numerical values A and B. In this specification, the numerical ranges represented by "above" and "below" mean ranges including the end point numerical values. In this specification, the numerical ranges represented by "greater than" and "less than" mean ranges not including the end point numerical values. In this specification, unless otherwise specified, "%" all represents weight percentage. In this specification, the meaning represented by "can" includes both meanings of performing a certain treatment and not performing a certain treatment, or includes both meanings of having a certain component and not having a certain component. In this specification, "optional" or "optionally" means that the event or situation described next may or may not occur, and this description includes the situation where the event occurs and the situation where the event does not occur. In this specification, "alkyl" or "alkylene" means an unsubstituted "alkyl" or "alkylene" that is linear, branched or cyclic, and "aryl" or "arylene" means an "aryl" or "arylene" in which there are no other substituents on the aromatic ring (such as benzene ring, naphthalene ring, etc.) except alkyl. In this specification, the "unit" in a polymer refers to a polymerization unit derived from the monomer formed by monomer polymerization and a polymerization unit formed by converting a part of the polymerization unit into other structures by treating the polymer. In this specification, when "normal temperature" or "room temperature" is used, the temperature can be 10 to 40 °C. In this specification, "some specific / preferred embodiments", "other specific / preferred embodiments", "embodiments", etc. refer to the specific elements related to the described embodiment (e.g., features, structures, properties, and / or characteristics) included in at least one of the embodiments described herein, and may or may not exist in other embodiments. Additionally, it should be understood that the elements can be combined in various embodiments in any suitable manner. <Method for Preparing Vinyl Chloride Copolymer> The method for preparing the vinyl chloride copolymer of the present invention includes: subjecting vinyl chloride A, comonomer B, and functional monomer C to emulsion polymerization in a surfactant-free aqueous medium under stirring in the presence of a polymerization initiator. The functional monomer C has one free-radical polymerizable group and two functional groups selected from amide groups, carboxyl groups, and carboxylate groups, and not both amide groups or carboxyl groups in one molecule. The mass ratio of the comonomer B to the functional monomer C is 1 / 15 to 15 / 1. In some preferred embodiments, from the perspective of better obtaining the desired technical effects of the present invention, the mass ratio of the comonomer B to the functional monomer C is preferably 1 / 10 to 10 / 1, more preferably 1 / 6 to 6 / 1, and further preferably 1 / 2 to 4 / 1. In the present invention, the term "not both amide groups or carboxyl groups" means that the two functional groups are not both amide groups and not both carboxyl groups. In the present invention, the term "carboxylate group" is a group containing a carboxylic acid anion and a counter cation. There is no particular limitation on the type of the counter cation. For example, it can be In the present invention, the term "surfactant" refers to a substance that can dissolve in water to lower the surface tension of water, and encompasses not only those substances commonly referred to as emulsifiers (such as small molecule emulsifiers and macromolecule (polymer) emulsifiers) in the art, but also those substances commonly referred to as stabilizers in the art. Examples of surfactants include anionic surfactants such as sodium dodecyl sulfate, sodium salts of styrene / maleic anhydride copolymers, and sodium salts of acrylic copolymers; nonionic surfactants such as sorbitan esters and polyethylene oxide ethers; cationic surfactants such as dodecyltrimethylammonium chloride; and amphoteric surfactants such as dodecyldimethylamine oxide. In the present invention, there is no particular limitation on the amount of vinyl chloride used. From the viewpoints of better ensuring the properties based on vinyl chloride and better ensuring the progress of soap-free emulsion polymerization, the amount of vinyl chloride A is preferably 70% by mass or more and 95% by mass or less, more preferably 72% by mass or more and 93% by mass or less, and still more preferably 75% by mass or more and 90% by mass or less, based on 100% by mass of the total mass of vinyl chloride A, comonomer B, and functional monomer C. Since vinyl chloride is more difficult to enter water and more prone to homopolymerization compared with other monomers, and the functional monomer C described later cannot homopolymerize due to its specific structure (steric hindrance, polarity, etc.), vinyl chloride and functional monomer C cannot effectively form amphiphilic oligomers at the initial stage of polymerization. However, the present inventors have found that by using comonomer B in combination with functional monomer C in a specific ratio, the copolymerizability between vinyl chloride and functional monomer C can be improved without negatively affecting the role of functional monomer C in stable emulsion polymerization, thereby enabling the soap-free emulsion polymerization to proceed smoothly. In the present invention, there is no particular limitation on the specific structure of comonomer B, as long as it can copolymerize with both vinyl chloride and the functional monomer C described later and has no negative impact on the stability of emulsion polymerization. In some preferred embodiments, from the viewpoints of more favorably ensuring the stable progress of emulsion polymerization and being able to participate in copolymerization in a wide range of ratios, comonomer B is preferably at least one selected from monofunctional (meth)acrylate monomers, monofunctional (meth)acrylamide monomers, monofunctional vinyl ester monomers, monofunctional vinyl ether monomers, vinyl pyrrolidone monomers, vinyl pyridine monomers, and vinyl lactam monomers. There is no particular limitation on the monofunctional (meth)acrylate monomers, and examples thereof include, but are not limited to: (meth)acrylic acid alkyl esters (preferably, (meth)acrylic acid alkyl esters having an alkyl group with 1 to 8 carbon atoms), such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, octadecyl (meth)acrylate, etc.; (meth)acrylic acid hydroxyalkyl esters (preferably, (meth)acrylic acid hydroxyalkyl esters having an alkyl group with 1 to 8 carbon atoms), such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate; glycidyl (meth)acrylate, etc. These monofunctional (meth)acrylate monomers can be used alone or in combination of any two or more. There is no particular limitation on the monofunctional (meth)acrylamide-based monomer, and examples thereof include, but are not limited to: (meth)acrylamide and the like. These monofunctional (meth)acrylamide-based monomers can be used alone or in combination of any two or more. There is no particular limitation on the monofunctional vinyl ester-based monomer, and examples thereof include, but are not limited to: vinyl acetate, vinyl propionate, vinyl butyrate, allyl acetate, and the like. These monofunctional vinyl ester-based monomers can be used alone or in combination of any two or more. There is no particular limitation on the monofunctional vinyl ether-based monomer, and examples thereof include, but are not limited to: methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, isobutyl vinyl ether, n-butyl vinyl ether, pentyl vinyl ether, hexyl vinyl ether, and the like. These monofunctional vinyl ether-based monomers can be used alone or in combination of any two or more. There is no particular limitation on the vinylpyrrolidone-based monomer, and examples thereof include, but are not limited to: N-vinylpyrrolidone and the like. These vinylpyrrolidone-based monomers can be used alone or in combination of any two or more. There is no particular limitation on the vinylpyridine-based monomer, and examples thereof include, but are not limited to: 2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine, and the like. These vinylpyridine-based monomers can be used alone or in combination of any two or more. There is no particular limitation on the vinylcaprolactam-based monomer, and examples thereof include, but are not limited to: vinylcaprolactam, vinylheptanolactam, vinylhexadecanamide, and the like. These vinylcaprolactam-based monomers can be used alone or in combination of any two or more. In some preferred embodiments, from the perspective of further achieving the above-mentioned effects desired by the present invention, especially better copolymerizability with vinyl chloride A and functional monomer C, the comonomer B is more preferably at least one selected from monofunctional (meth)acrylate-based monomers, monofunctional (meth)acrylamide-based monomers, monofunctional vinyl ester-based monomers, and monofunctional vinyl ether-based monomers, and particularly preferably a monofunctional vinyl ester-based monomer, for example, vinyl acetate and / or vinyl propionate. In the present invention, there is no particular limitation on the amount of the comonomer B. From the perspective of better ensuring the progress of soap-free emulsion polymerization, relative to the total mass of 100% by mass of vinyl chloride A, comonomer B, and functional monomer C, the amount of the comonomer B is preferably greater than 0% by mass and less than 30% by mass, more preferably 2% by mass or more and 25% by mass or less, and further preferably 2.5% by mass or more and 20% by mass or less. In the present invention, as long as the functional monomer C has a radical polymerizable group and two functional groups selected from amide groups, carboxyl groups, and carboxylate groups, and they are not both amide groups or carboxyl groups in one molecule, there is no particular limitation on the specific structure of the functional monomer C. In the present invention, the functional monomer C can be used alone or in any combination of two or more. Here, the radical polymerizable group is not particularly limited. For example, it can be an alkynyl group (carbon-carbon triple bond C≡C) or an alkenyl group (carbon-carbon double bond C=C). In some preferred embodiments, from the perspective of better realizing emulsion polymerization without using an emulsifier and more easily obtaining the functional monomer C, the radical polymerizable group is preferably an alkenyl group. In some preferred embodiments, the structure of the functional monomer C is shown in the following formula (1): In formula (1), A is Or Wherein, R3, R6, R7, R8 each independently represent a direct bond or a C1-C20 substituted or unsubstituted alkylene group, and R4, R5, R9, R 10 Each independently represents hydrogen or a C1-C20 substituted or unsubstituted alkyl group. Here, the substituents on the alkylene group or alkyl group can include hydroxyl groups, amino groups, halogen atoms (for example, fluorine, chlorine, bromine, iodine, etc.), and the like. In formula (1), R1, R2 each independently represent -NR 11 R 12 (R 11 , R 12 Each independently represents hydrogen or a C1-C8 alkyl group), -OH, -OM (M represents an alkali metal or ammonium), but they are not both -NR 11 R 12 Or -OH. In addition, in the present invention, there is no particular limitation on the source of obtaining the functional monomer C. It can be commercially available or self-made. As a self-made method, there is also no particular limitation, and various known chemical means in the art can be adopted. In some preferred embodiments, from the perspective of more easily obtaining the functional monomer C, the functional monomer C is preferably a monomer obtained by reacting an acid anhydride monomer and / or a dicarboxylic acid monomer with a basic compound. In other words, the preparation method of the present invention includes the following preparation step of the functional monomer C: reacting an acid anhydride monomer and / or a dicarboxylic acid monomer with a basic compound to obtain the functional monomer C. In the present invention, there is no limitation on the timing of the reaction between the acid anhydride-based monomer and / or the dicarboxylic acid-based monomer and the basic compound. For example, in some specific embodiments, the reaction between the acid anhydride-based monomer and / or the dicarboxylic acid-based monomer and the basic compound can be carried out in advance, and then the obtained functional monomer C is added to the polymerization system. For example, in some other specific embodiments, the acid anhydride-based monomer and / or the dicarboxylic acid-based monomer and the basic compound can be directly added to the polymerization system, and the reaction occurs before polymerization or in situ during polymerization to obtain the functional monomer C. In this case, there is no particular limitation on the charging order of the acid anhydride-based monomer and / or the dicarboxylic acid-based monomer and the basic compound. In addition, although there is no particular limitation, further preferably, from the viewpoint of obtaining the above functional monomer C at a lower cost and being more conducive to exerting the function of the functional monomer C, in some specific embodiments, the acid anhydride-based monomer is preferably at least one selected from maleic anhydride, itaconic anhydride, citraconic anhydride, dimethyl maleic anhydride, aconitic anhydride, phenyl maleic anhydride, and more preferably at least one selected from maleic anhydride, itaconic anhydride, citraconic anhydride. Although there is no particular limitation, further preferably, from the same viewpoint, the dicarboxylic acid-based monomer is at least one selected from C2-C20 olefin dicarboxylic acids, and more preferably C4-C8 olefin dicarboxylic acids. Here, C2-C20 olefin dicarboxylic acids refer to compounds in which two carboxyl groups are connected at any position of an olefin having 2 to 20 carbon atoms, such as ethylenedicarboxylic acid, propylenedicarboxylic acid, isopropylenedicarboxylic acid, maleic acid, itaconic acid, citraconic acid, n-hexenedicarboxylic acid, etc. Although there is no particular limitation, further preferably, from the viewpoint of obtaining the above functional monomer C at a lower cost, in some specific embodiments, the basic compound is at least one selected from ammonia gas, ammonia water, sodium hydroxide, and potassium hydroxide. There is no particular limitation on the amount of the basic compound used. In order to better obtain the functional monomer C, it is preferably used in an over-equivalent manner. Here, the so-called "over-equivalent" means an amount exceeding the chemical equivalent required to complete the reaction for forming the target structure. Preferably, the upper limit is 4 equivalent times. Here, in the case of using two or more basic compounds, the amount of the basic compound used is the total amount of all the basic compounds. In the present invention, there is no particular limitation on the amount of the functional monomer C used. From the viewpoint of better ensuring the progress of the soap-free emulsion polymerization, relative to the total mass of 100% by mass of vinyl chloride A, comonomer B, and functional monomer C, the amount of the functional monomer C used is preferably more than 0% by mass and 20% by mass or less, and more preferably 2% by mass or more and 18% by mass or less. In addition, within the scope that does not damage the technical effects of the present invention, other monomers except vinyl chloride A, comonomer B, and functional monomer C, such as various monomers copolymerized only with vinyl chloride A or functional monomer C, can also participate in the emulsion polymerization. In the present invention, the aqueous medium refers to a medium in which the above various monomers can be dispersed. Specific examples thereof include: water, a combination of water and one or more organic solvents as cosolvents, etc. Here, there is no particular limitation on the type of cosolvent, and those commonly used in the art can be used, for example, alcohols such as methanol, ethanol, ethylene glycol, diethylene glycol, etc., and ketones such as acetone, methyl ethyl ketone, butanone, cyclohexanone, etc. The amount of the cosolvent can be, for example, 0 to 30% by mass, for example, 1 to 25% by mass, and more preferably 2 to 22% by mass relative to the total mass of 100% by mass of water and the cosolvent. In the present invention, relative to the total mass of 100% by mass of the aqueous medium, the total mass of the monomers used (when there are no other monomers, it is only vinyl chloride A, comonomer B, and functional monomer C) can be 5 to 100% by mass, preferably 10 to 80% by mass. In the present invention, there is no particular limitation on the method of introducing each monomer into the aqueous medium. It can be all introduced into the aqueous medium before polymerization and then polymerized, or a part or all of a certain monomer or multiple monomers can be added in portions or continuously to the aqueous medium during the polymerization process. In the present invention, there is no particular limitation on the specific type of the polymerization initiator. Specific examples may include, but are not limited to: azo initiators such as azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptonitrile, azobis(isobutylamidine) hydrochloride, azobis(isobutylimidazoline) hydrochloride, etc.; organic peroxide initiators such as tert-butyl peroxyneoheptanoate, tert-butyl peroxyneodecanoate, di-sec-butyl peroxydicarbonate, bis(4-tert-butylcyclohexyl) peroxydicarbonate, di(hexadecyl) peroxydicarbonate, tert-amyl peroxyneodecanoate, di-tert-butyl peroxide, cyclohexylsulfonylacetyl peroxide, benzoyl peroxide, diisobutyryl peroxide, lauroyl peroxide, 1,1,3,3-tetramethylbutyl peroxyneodecanoate, di-3-methoxybutyl peroxydicarbonate, 1,1,3,3-tetramethylbutyl peroxypivalate, etc.; persulfate initiators such as potassium persulfate, ammonium persulfate, etc.; redox initiators, where the oxidizing agent can be potassium persulfate, ammonium persulfate, etc., and the reducing agent can be sodium bisulfite, sodium thiosulfate, etc. These initiators can be used alone or in combination of two or more. From the viewpoint of suppressing the chain transfer of vinyl chloride, redox initiators are preferably used. The amount of the initiator relative to the total mass of the monomers can be, for example, 0.001 to 4% by mass, preferably 0.005 to 3% by mass, and more preferably 0.01 to 2% by mass. In addition, if necessary, the polymerization system may further contain various additives well-known in the art, such as, for example, chain transfer agents, buffering agents, etc. In the present invention, there is no restriction on the initial pH value of the polymerization system before the start of emulsion polymerization, and it can be acidic, neutral or alkaline, and is usually appropriately adjusted according to the specific structures of the polymerization initiator and the functional monomer C used. In some preferred embodiments, from the viewpoint of facilitating industrial operation, a pH regulator is preferably further added to the aqueous medium so that the initial pH value of the polymerization system before the start of emulsion polymerization is preferably greater than 7 and 11 or less, more preferably greater than 7.5 and 10.5 or less, and further preferably 8 to 10. There is no restriction on the specific type of the pH regulator, as long as it can achieve the above initial pH value and has no negative impact on the polymerization reaction. Specific examples may include, but are not limited to: ammonia water, ammonium bicarbonate, sodium bicarbonate, sodium hydroxide, disodium hydrogen phosphate, etc. There is no particular restriction on the method for adjusting the initial pH value of the polymerization system before the start of emulsion polymerization. For example, the pH regulator can be added to the polymerization system alone, or the reaction solution remaining with alkaline substances directly obtained after pre-preparing the functional monomer C with an alkaline compound can be added to the polymerization system. In the present invention, there is no particular restriction on the polymerization conditions, and they can be appropriately adjusted according to the composition of the polymerization system, etc. In some specific embodiments, without limitation, the polymerization temperature can be 30 to 65 °C, for example, 35 to 60 °C. In some specific embodiments, without limitation, the polymerization time can be 1 to 72 hours, for example, 5 to 36 hours or 5 to 20 hours. In the present invention, there is no particular restriction on the stirring conditions, as long as the stable progress of emulsion polymerization can be maintained. In addition, stirring can be applied by various devices well-known in the art. In addition, in the present invention, without limitation, the average particle diameter of the vinyl chloride-based copolymer particles obtained by emulsion polymerization can be 80 to 350 nm, such as 170 nm, 200 nm, 250 nm, etc. In the present invention, the average particle diameter can be measured by a laser particle size analyzer according to known methods. In addition, the preparation method of the present invention optionally further includes various solid-liquid separation steps, washing steps, drying steps, pulverizing steps, sieving steps, etc. known in the art. <Vinyl chloride-based copolymer latex> The vinyl chloride-based copolymer latex of the present invention does not contain a surfactant. Here, the definition of the surfactant is as described in the above <Preparation method of vinyl chloride-based copolymer>. The vinyl chloride copolymer constituting the latex has units based on vinyl chloride A, units based on comonomer B, and units based on functional monomer C, and the functional monomer C has one free-radical polymerizable group and two functional groups selected from an amide group, a carboxyl group, and a carboxylate group, and not both amide groups, in one molecule. In addition, the vinyl chloride copolymer may optionally contain units based on other monomers. Details of vinyl chloride A, comonomer B, functional monomer C, and other monomers are as described in the above <Preparation Method of Vinyl Chloride Copolymer> and will not be elaborated here. In the present invention, in some preferred embodiments, the average particle diameter of the vinyl chloride copolymer particles in the latex can be 120 to 300 nm, for example, 150 to 260 nm. In the present invention, the average particle diameter can be measured by a laser particle size analyzer according to known methods. In the present invention, there is no particular limitation on the method for preparing the vinyl chloride copolymer latex, and it can be obtained by various methods. For example, an initial latex is obtained by emulsion polymerization using a surfactant and then subjected to post-treatment such as removing the surfactant, or emulsion polymerization is carried out using a pre-prepared copolymer having an initiating end and having units based on vinyl chloride A and / or comonomer B and units based on the structure of functional monomer C as a macromolecular emulsifier, or the method described in the above <Preparation Method of Vinyl Chloride Copolymer>. In some preferred embodiments, from the viewpoint of more easily obtaining the vinyl chloride copolymer latex of the present invention, the method described in the above <Preparation Method of Vinyl Chloride Copolymer> is preferably adopted. In addition, the vinyl chloride copolymer latex of the present invention can be an initial latex directly obtained after emulsion polymerization, or a latex obtained by concentrating or diluting the initial latex. In the present invention, there is no particular limitation on the proportion of each constituent unit, and it can be appropriately adjusted by adjusting the preparation method according to actual needs. In particular, when the method described in the above <Preparation Method of Vinyl Chloride Copolymer> of the present invention is adopted, the proportion of each constituent unit can be adjusted by adjusting the feed ratio, the pH of the system before polymerization, the type of initiator, the temperature, etc. In some preferred embodiments, the mass ratio of the units based on comonomer B to the units based on functional monomer C, units based on comonomer B / units based on functional monomer C, is preferably 1 / 20 to 40 / 1, more preferably 1 / 15 to 35 / 1, and further preferably 1 / 5 to 30 / 1. In other preferred embodiments, based on 100% by mass of the total mass of the units based on vinyl chloride A, the units based on comonomer B, and the units based on functional monomer C, the content of vinyl chloride A is preferably 70% by mass or more and 95% by mass or less, more preferably 72% by mass or more and 93% by mass or less, and still more preferably 75% by mass or more and 90% by mass or less. In other preferred embodiments, based on 100% by mass of the total mass of the units based on vinyl chloride A, the units based on comonomer B, and the units based on functional monomer C, the content of the units based on comonomer B is preferably more than 0% by mass and less than 30% by mass, more preferably 2% by mass or more and 25% by mass or less, and still more preferably 3% by mass or more and 20% by mass or less. In other preferred embodiments, based on 100% by mass of the total mass of the units based on vinyl chloride A, the units based on comonomer B, and the units based on functional monomer C, the content of the units based on functional monomer C is preferably more than 0% by mass and 18% by mass or less, more preferably 0.5% by mass or more and 10% by mass or less, and still more preferably 1% by mass or more and 5.5% by mass or less. <Vinyl chloride copolymer liquid composition> The vinyl chloride copolymer liquid composition of the present invention contains a vinyl chloride copolymer latex obtained by the above-described production method of the present invention, or the above-described vinyl chloride copolymer latex according to the present invention. In the vinyl chloride copolymer latex of the present invention, various additives, various resin latexes, and / or rubber latexes can be further blended as needed to form a vinyl chloride copolymer composition, which can then be used for various purposes. Examples of the additives include pigments, dyes, tackifiers, metal oxides, thickeners, fillers, film-forming aids, ultraviolet absorbers, antioxidants, plasticizers, vulcanizing agents, vulcanization accelerators, defoamers, silane compounds, surfactants, and the like. <Paste resin of vinyl chloride copolymer> The paste resin of the vinyl chloride copolymer of the present invention is obtained by using the vinyl chloride copolymer latex obtained by the above-described production method of the present invention, or by using the above-described vinyl chloride copolymer latex of the present invention. In the present invention, the method for obtaining the paste resin from the above latexes is not particularly limited, and any method can be used. For example, methods such as spray drying and fluidized bed drying can be used. In addition, the dried crude product can also be subjected to conventional processes such as pulverization and screening. <Vinyl chloride copolymer solid composition> The vinyl chloride copolymer solid composition of the present invention contains the paste resin of the vinyl chloride copolymer according to the present invention. In the paste resin of the vinyl chloride-based copolymer of the present invention, various additives can be further compounded as needed to form a vinyl chloride-based copolymer composition, which can then be used for various purposes. Examples of additives include, for example, other resins, rubbers, pigments, dyes, tackifiers, metal oxides, fillers, film-forming aids, ultraviolet absorbers, antioxidants, plasticizers, vulcanizing agents, vulcanization accelerators, defoaming agents, silane compounds, and the like. Examples The embodiments of the present invention will be described in detail below in conjunction with examples. However, those skilled in the art will understand that the following examples are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention. For those not specified in the examples, they are carried out under conventional conditions or conditions recommended by the manufacturer. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase. <Evaluation method> For each of the examples and comparative examples, the solid content of the vinyl chloride-based polymer latex, the stability of the vinyl chloride-based polymer latex (storage stability, calcium ion stability, mechanical stability, freeze-thaw stability), the redispersibility of the paste resin, and the water resistance of the paste resin film (water absorption of the film) are determined by the following methods. (Copolymer composition) The copolymer composition is determined by a Bruker AV400 nuclear magnetic resonance spectrometer (using THF-d8 as the solvent). (Solid content) The solid content of the latex is measured by the weighing method. Weigh m1 grams of the latex, and then place the latex in an oven at 105 °C and dry it to a constant weight. The mass of the resulting dry product is denoted as m2 grams. Then, (m2 / m1) × 100% is the solid content of the latex. (Storage stability) The latex is stored at room temperature of 25 °C for 3 months, and the state of the latex system is observed. If it is slightly layered, it is shaken and mixed, and the state of the latex liquid after shaking is observed. The evaluation criteria are as follows. In this evaluation and each of the following stability evaluations, the phenomenon of the appearance of polymer flocs or precipitates, etc. is regarded as a sign of demulsification. The term "demulsification" refers to the complete destruction of the state of the emulsion (latex). ○: The latex after storage is not layered, and no flocs or precipitates or other demulsification situations appear after shaking. △: The latex after storage is slightly layered, but no flocs or precipitates or other demulsification situations appear after shaking. ×: Flocs and / or precipitates appear in the latex after storage. Here, the so-called "slight delamination" means that a water layer that can be visually distinguished appears on the surface part of the latex system after storage, but there are no flocculants or precipitates of the polymer in the overall latex system. When the evaluation is "○" or "△", the storage stability is considered acceptable, while when the evaluation is "×", the storage stability is considered unacceptable. (Calcium ion stability) Prepare an aqueous CaCl2 solution with a concentration of 5 g / L, mix it with the latex in a mass ratio of 5:1, let it stand for 24 h, and observe the state of the latex system after standing. The evaluation criteria are as follows. ○: No demulsification such as flocculants or precipitates appears in the latex after standing. ×: Demulsification such as flocculants or precipitates appears in the latex after standing. When the evaluation is "○", the calcium ion stability is considered acceptable, while when the evaluation is "×", the calcium ion stability is considered unacceptable. (Mechanical stability) Pour 20 ml of the latex into a centrifuge tube and centrifuge it for 30 minutes using a high-speed centrifuge with a rotation speed set at 3000 r / min. Observe the state of the latex system after centrifugation. The evaluation criteria are as follows. ○: No demulsification occurs in the latex after centrifugation. ×: Demulsification occurs in the latex after centrifugation. When the evaluation is "○", the mechanical stability is considered acceptable, while when the evaluation is "×", the mechanical stability is considered unacceptable. (Freeze-thaw stability) Place 20 ml of the latex in an environment at -20 °C and freeze it for 16 h, then thaw it at room temperature of 25 °C for 8 h, and repeat this 5 times. Observe the state of the obtained latex system. The evaluation criteria are as follows. ○: No demulsification such as flocculants or precipitates appears in the obtained latex. ×: Demulsification such as flocculants or precipitates appears in the obtained latex. When the evaluation is "○", the freeze-thaw stability is considered acceptable, while when the evaluation is "×", the freeze-thaw stability is considered unacceptable. (Redispersibility) Demulsify the latex with an aqueous CaCl2 solution, wash the obtained precipitate with water and dry it to a constant weight. Take 1.0 g of the sample powder, add deionized water with a mass conversion of twice, and observe the state of the obtained mixture after ultrasonic treatment for 15 min. The evaluation criteria are as follows. ○: The mixture is a stable latex (emulsion), and there are no undispersed solid components. △: The mixture is a stable latex (emulsion), but there are a small number of undispersed solid components. ×: The mixture cannot form a stable emulsion, or although a partially stable emulsion is formed, there are a large number of solid components that cannot be dispersed. When the evaluation is "○" or "△", the redispersibility is considered acceptable, while when the evaluation is "×", the redispersibility is considered unacceptable. (Water absorption rate) The paste resin obtained by drying the latex is mixed evenly according to the paste resin (100 phr), plasticizer (DOP, 20 phr), and heat stabilizer (Ca-Zn, 2 phr), hot-pressed into a film at 150 °C, and cut into a 20 mm × 20 mm film to measure the water absorption rate. Record the mass of the resin film as m3 grams. Then, place the resin film in deionized water at 25 °C room temperature for 24 h. After taking it out, blot the surface moisture with filter paper. At this time, record the mass of the resin film as m4 grams. Then, [(m4 - m3) / m3] × 100% is the water absorption rate of the resin film. <Example 1> Add 5.0 g of deionized water to 5.0 g of maleic acid, and add 8.8 g of ammonia water as an alkaline compound to carry out ring-opening to obtain functional monomer C1 (the two functional groups are ammonium carboxylate and ammonium carboxylate respectively). Then, add the remaining 288.4 g of deionized water, and use ammonia water to control the pH to 9.4. Subsequently, in a polymerization reactor, add the above-mentioned alkaline mixture containing the functional monomer, and add a redox initiator (2.0 g of potassium persulfate and 1.2 g of sodium bisulfite). Add 15 g of vinyl propionate as a comonomer (the mass ratio of vinyl propionate / functional monomer C1 is 3 / 1). After removing the air in the polymerization reactor by the inert gas nitrogen replacement method, add 80.0 g of vinyl chloride (at this time, the pH of the system before polymerization is about 9.6). Pre-emulsify for half an hour, then raise the temperature to 45 °C, and carry out the reaction under mechanical stirring at 400 rpm. The initial reaction pressure is 0.56 MPa. React for 10 h until the pressure in the kettle drops to 0.20 MPa, and it is considered that the reaction end point is reached, and the reaction is stopped. After the reaction is completed, obtain the latex of vinyl chloride copolymer E1 from the reaction kettle. Obtain a latex of vinyl chloride copolymer with a solid content of 21.5%. The composition of this vinyl chloride copolymer is as follows: in terms of mass conversion, the unit based on vinyl chloride: the unit based on vinyl propionate: the unit based on functional monomer C1 = 82.2:15.6:2.2, where the unit based on vinyl propionate / the unit based on functional monomer C1 is 7.1 / 1. Furthermore, conduct a stability evaluation on the latex. In addition, dry the above latex to constant weight to remove water, wash the dried product with water, and repeat three times. After washing, dry it to constant weight again, and obtain the paste resin of vinyl chloride copolymer after pulverization. Table 1 shows the physical properties and stability evaluation results of the latex and the paste resin respectively. <Example 2> Except that the pH in Example 1 was controlled to 7.0 (so that the pH of the system before polymerization was about 7.2) to obtain functional monomer C1 (the two functional groups were ammonium carboxylate and ammonium carboxylate) respectively, a latex of a vinyl chloride copolymer with a solid content of 13.4% was obtained in a method similar to that in Example 1. The composition of this vinyl chloride copolymer was as follows: in terms of mass conversion, the unit based on vinyl chloride: the unit based on vinyl propionate: the unit based on functional monomer C1 = 84.9:13.8:1.3, and the unit based on vinyl propionate / the unit based on functional monomer C1 was 10.6 / 1. In addition, a paste resin of a vinyl chloride copolymer was obtained in a method similar to that in Example 1. Table 1 shows the physical properties and stability evaluation results of the latex and the paste resin respectively. <Example 3> Except that the pH in Example 1 was controlled to 10.5 (so that the pH of the system before polymerization was about 10.8) to obtain functional monomer C1 (the two functional groups were ammonium carboxylate and ammonium carboxylate) respectively, a latex of a vinyl chloride copolymer with a solid content of 17.9% was obtained in a method similar to that in Example 1. The composition of this vinyl chloride copolymer was as follows: in terms of mass conversion, the unit based on vinyl chloride: the unit based on vinyl propionate: the unit based on functional monomer C1 = 87.7:11.3:1.0, and the unit based on vinyl propionate / the unit based on functional monomer C1 was 11.3 / 1. In addition, a paste resin of a vinyl chloride copolymer was obtained in a method similar to that in Example 1. Table 1 shows the physical properties and stability evaluation results of the latex and the paste resin respectively. <Example 4> Except that the amounts of functional monomer C1 and vinyl propionate in Example 1 were changed (the mass ratio of vinyl propionate / functional monomer C1 was 1 / 1), a latex of a vinyl chloride copolymer with a solid content of 22.1% was obtained in a method similar to that in Example 1. The composition of this vinyl chloride copolymer was as follows: in terms of mass conversion, the unit based on vinyl chloride: the unit based on vinyl propionate: the unit based on functional monomer C1 = 86.4:10.1:3.5, and the unit based on vinyl propionate / the unit based on functional monomer C1 was 2.9 / 1. In addition, a paste resin of a vinyl chloride copolymer was obtained in a method similar to that in Example 1. Table 1 shows the physical properties and stability evaluation results of the latex and the paste resin respectively. <Example 5> Except that 17.6 g of ammonia water in Example 4 was replaced with 3.5 g of sodium hydroxide, and the total amount of deionized water was 300.0 g to obtain functional monomer C2 (the two functional groups were carboxylate and carboxylate respectively), and the reaction was carried out in a mass ratio of acrylyl vinyl ester / functional monomer C2 of 1 / 1, a latex of a vinyl chloride copolymer with a solid content of 20.8% was obtained by a method similar to that in Example 4. The composition of the vinyl chloride copolymer was as follows: in terms of mass conversion, units based on vinyl chloride: units based on vinyl propionate: units based on functional monomer C2 = 89.2:9.6:1.2, and the ratio of units based on vinyl propionate to units based on functional monomer C2 was 8 / 1. In addition, a paste resin of a vinyl chloride copolymer was obtained by a method similar to that in Example 1. Table 1 shows the physical properties and stability evaluation results of the latex and the paste resin respectively. <Example 6> Except that comonomer B in Example 4 was replaced with vinyl acetate, and the reaction was carried out in a mass ratio of vinyl acetate / functional monomer C1 of 1 / 1, a latex of a vinyl chloride copolymer with a solid content of 22.3% was obtained by a method similar to that in Example 4. The composition of the vinyl chloride copolymer was as follows: in terms of mass conversion, units based on vinyl chloride: units based on vinyl acetate: units based on functional monomer C1 = 86.6:10.4:3.0, and the ratio of units based on vinyl acetate to units based on functional monomer C1 was 3.5 / 1. In addition, a paste resin of a vinyl chloride copolymer was obtained by a method similar to that in Example 1. Table 1 shows the physical properties and stability evaluation results of the latex and the paste resin respectively. <Example 7> Except that the reaction temperature in Example 4 was raised to 48 °C, a latex of a vinyl chloride copolymer with a solid content of 21.5% was obtained by a method similar to that in Example 4. The composition of the vinyl chloride copolymer was as follows: in terms of mass conversion, units based on vinyl chloride: units based on vinyl propionate: units based on functional monomer C1 = 85.3:10.9:3.8, and the ratio of units based on vinyl propionate to units based on functional monomer C1 was 2.9 / 1. In addition, a paste resin of a vinyl chloride copolymer was obtained by a method similar to that in Example 1. Table 1 shows the physical properties and stability evaluation results of the latex and the paste resin respectively. <Example 8> Except that the maleic acid monomer in Example 6 was replaced with maleic anhydride to obtain functional unit C3 (the two functional groups are amide group and ammonium carboxylate), and the reaction was carried out in such a way that the mass ratio of vinyl acetate / functional monomer C3 was 1 / 1, a latex of a vinyl chloride copolymer with a solid content of 22.6% was obtained in a similar manner to Example 6. The composition of this vinyl chloride copolymer is as follows: in terms of mass conversion, units based on vinyl chloride: units based on vinyl acetate: units based on functional monomer C3 = 87.2:10.0:2.8, and the ratio of units based on vinyl acetate to units based on functional monomer C3 is 3.6 / 1. In addition, a paste resin of a vinyl chloride copolymer was obtained in a similar manner to Example 1. Table 1 shows the physical properties and stability evaluation results of the latex and the paste resin, respectively. <Example 9> Except that the initiator in Example 4 was replaced with azodiisobutylamidine hydrochloride and the reaction temperature was 56 °C, a latex of a vinyl chloride copolymer with a solid content of 22.4% was obtained in a similar manner to Example 4. The composition of this vinyl chloride copolymer is as follows: in terms of mass conversion, units based on vinyl chloride: units based on vinyl propionate: units based on functional monomer C1 = 84.6:10.4:5.0, and the ratio of units based on vinyl propionate to units based on functional monomer C1 is 2.1 / 1. In addition, a paste resin of a vinyl chloride copolymer was obtained in a similar manner to Example 1. Table 1 shows the physical properties and stability evaluation results of the latex and the paste resin, respectively. <Example 10> Except that the pH in Example 4 was controlled to 6.2 (so that the pH of the system before polymerization was about 6.5) to obtain functional monomer C4 (the two functional groups are carboxyl group and ammonium carboxylate), and the initiator in Example 4 was replaced with azodiisobutylamidine hydrochloride and the reaction temperature was 56 °C, a latex of a vinyl chloride copolymer with a solid content of 18.6% was obtained in a similar manner to Example 4. The composition of this vinyl chloride copolymer is as follows: in terms of mass conversion, units based on vinyl chloride: units based on vinyl propionate: units based on functional monomer C4 = 85.6:10.3:4.1, and the ratio of units based on vinyl propionate to units based on functional monomer C4 is 2.5 / 1. In addition, a paste resin of a vinyl chloride copolymer was obtained in a similar manner to Example 1. Table 1 shows the physical properties and stability evaluation results of the latex and the paste resin, respectively. <Example 11> Except for changing the amounts of the functional monomer C1 and vinyl propionate in Example 1 (the mass ratio of vinyl propionate / functional monomer C1 is 10 / 1), a latex of a vinyl chloride copolymer having a solid content of 13.6% was obtained in a similar manner to Example 1. The composition of this vinyl chloride copolymer is as follows: in terms of mass conversion, units based on vinyl chloride: units based on vinyl propionate: units based on functional monomer C1 = 91.3:8.4:0.3, and the units based on vinyl propionate / units based on functional monomer C1 is 28.0 / 1. In addition, a paste resin of a vinyl chloride copolymer was obtained in a similar manner to Example 1. Table 2 shows the physical properties and stability evaluation results of the latex and the paste resin, respectively. <Example 12> Except for changing the amounts of the functional monomer C1 and vinyl propionate in Example 1 (the mass ratio of vinyl propionate / functional monomer C1 is 5 / 1), a latex of a vinyl chloride copolymer having a solid content of 15.5% was obtained in a similar manner to Example 1. The composition of this vinyl chloride copolymer is as follows: in terms of mass conversion, units based on vinyl chloride: units based on vinyl propionate: units based on functional monomer C1 = 89.8:9.5:0.7, and the units based on vinyl propionate / units based on functional monomer C1 is 14.7 / 1. In addition, a paste resin of a vinyl chloride copolymer was obtained in a similar manner to Example 1. Table 2 shows the physical properties and stability evaluation results of the latex and the paste resin, respectively. <Example 13> Except for changing the amounts of the functional monomer C1 and vinyl propionate in Example 1 (the mass ratio of vinyl propionate / functional monomer C1 is 1 / 5), a latex of a vinyl chloride copolymer having a solid content of 14.6% was obtained in a similar manner to Example 1. The composition of this vinyl chloride copolymer is as follows: in terms of mass conversion, units based on vinyl chloride: units based on vinyl propionate: units based on functional monomer C1 = 94.9:2.0:3.1, and the units based on vinyl propionate / units based on functional monomer C1 is 1 / 1.6. In addition, a paste resin of a vinyl chloride copolymer was obtained in a similar manner to Example 1. Table 2 shows the physical properties and stability evaluation results of the latex and the paste resin, respectively. <Example 14> Except for changing the amounts of the functional monomer C1 and vinyl propionate in Example 1 (the mass ratio of vinyl propionate / functional monomer C1 is 1 / 10), a latex of a vinyl chloride copolymer with a solid content of 9.6% was obtained in a similar manner to Example 1. The composition of this vinyl chloride copolymer is as follows: in terms of mass conversion, the unit based on vinyl chloride: the unit based on vinyl propionate: the unit based on functional monomer C1 = 92.7:1.3:6.0, and the unit based on vinyl propionate / the unit based on functional monomer C1 is 1 / 4.6. In addition, a paste resin of a vinyl chloride copolymer was obtained in a similar manner to Example 1. Table 2 shows the evaluation results of the physical properties and stability of the latex and the paste resin respectively. <Comparative Example 1> Except for using only vinyl chloride as the monomer and adding sodium dodecyl sulfate with a dosage of 1% by mass, the polymerization was carried out in a similar manner to Example 1. The initial reaction pressure was 0.56 MPa, and after reacting for 10 h, the pressure in the reactor dropped to 0.12 MPa, and the reaction was stopped. A latex of homopolyvinyl chloride with a solid content of 24.6% was obtained. The above latex was dried to a constant weight to remove water, and the dried product was washed with water and repeated three times. After washing, it was dried again to a post-constant weight, and after pulverization, a paste resin of homopolyvinyl chloride was obtained. Table 2 shows the evaluation results of the physical properties and stability of the latex and the paste resin respectively. <Comparative Example 2> Except for replacing maleic acid in Example 1 with acrylic acid to obtain a functional monomer CC1 (with only one functional group in the molecule), the polymerization was carried out in a similar manner to Example 1. The initial reaction pressure was 0.56 MPa, and after reacting for 10 h, the pressure in the reactor dropped to 0.15 MPa, and the reaction was stopped. No latex was obtained, and the product agglomerated and demulsified. <Comparative Example 3> Except for directly using maleic acid as the functional monomer CC2 (both functional groups of the functional monomer are carboxyl groups) in Example 4, the polymerization was carried out in a similar manner to Example 4. The pressure in the reactor did not drop after reacting for 10 h, and the reaction was stopped. No latex was obtained, and there were a small amount of white insoluble substances in the solution. <Comparative Example 4> Except for changing the amounts of vinyl propionate and functional monomer C1 in Example 1 (the mass ratio of vinyl propionate / functional monomer C1 is 15 / 1), the polymerization was carried out in a similar manner to Example 1. The pressure in the reactor did not drop after reacting for 10 h, and the reaction was stopped. No latex was obtained, and there were extremely small amounts of white insoluble substances in the solution. <Comparative Example 5> Except for changing the amounts of the functional monomer C1 and vinyl propionate in Example 1 (the mass ratio of vinyl propionate / functional monomer C1 is 1 / 15), polymerization was carried out in a similar manner to that in Example 1. After reacting for 10 h, the pressure in the reactor did not decrease, and the reaction was stopped. No latex was obtained, and there was a very small amount of white insoluble matter in the solution. <Comparative Example 6> Except for not using vinyl propionate, polymerization was carried out in a similar manner to that in Example 1. After reacting for 10 h, the pressure in the reactor did not decrease, and the reaction was stopped. No latex was obtained, and the solution was slightly yellow and unreacted. In Comparative Example 1, from the evaluation result of high water absorption rate, it can be seen that even after washing three times, there is still a surfactant in the paste resin that is difficult to remove. In Comparative Examples 2 to 6, stable latex was not obtained during polymerization (even though polymerization products were obtained in Comparative Examples 2 and 3), so the evaluation of stability, redispersibility, and water absorption was not carried out. In addition, in Table 2, for the sake of convenient description, the component C and its amount listed for Comparative Example 2 are all descriptions of the functional monomer CC1, and the component C and its amount listed for Comparative Example 3 are all descriptions of the functional monomer CC2. It should be noted that although the technical solutions of the present invention have been introduced by specific examples, those skilled in the art can understand that the present invention should not be limited thereto. The embodiments of the present invention have been described above. The above description is exemplary and not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations are obvious to those of ordinary skill in the art in the technical field without departing from the scope and spirit of the described embodiments. The choice of terms used herein is intended to best explain the principles of the embodiments, practical applications, or improvements to the technology in the market, or to enable other ordinary skilled persons in the technical field to understand the disclosed embodiments.

Claims

1. A method for preparing a vinyl chloride copolymer, characterized in that, The method includes: Emulsion polymerizing vinyl chloride A, comonomer B, and functional monomer C in an aqueous medium without a surfactant under stirring in the presence of a polymerization initiator. The functional monomer C has one radically polymerizable group and two functional groups selected from amide groups, carboxyl groups, and carboxylate groups, and not both an amide group or a carboxyl group in one molecule. The mass ratio of the comonomer B to the functional monomer C, comonomer B / functional monomer C, is 1 / 12 to 12 / 1.

2. The preparation method according to claim 1, characterized in that, The comonomer B is at least one selected from monofunctional (meth)acrylate monomers, monofunctional (meth)acrylamide monomers, monofunctional vinyl ester monomers, monofunctional vinyl ether monomers, vinyl pyrrolidone monomers, vinyl pyridine monomers, and vinyl lactam monomers.

3. The preparation method according to claim 1 or 2, characterized in that, The functional monomer C is a monomer obtained by reacting an acid anhydride monomer and / or a dicarboxylic acid monomer with a basic compound.

4. The preparation method according to claim 3, characterized in that, The basic compound is at least one selected from ammonia gas, aqueous ammonia, sodium hydroxide, and potassium hydroxide. The acid anhydride monomer is at least one selected from maleic anhydride, itaconic anhydride, citraconic anhydride, dimethyl maleic anhydride, aconitic anhydride, and phenyl maleic anhydride. The dicarboxylic acid monomer is at least one selected from C2-C20 olefin dicarboxylic acids.

5. The preparation method according to any one of claims 1 to 4, characterized in that Relative to the total mass of 100% by mass of the vinyl chloride A, the comonomer B, and the functional monomer C, the amount of the vinyl chloride A is 70% by mass or more and 95% by mass or less, the amount of the comonomer B is greater than 0% by mass and less than 30% by mass, and the amount of the functional monomer C is greater than 0% by mass and 20% by mass or less.

6. The preparation method according to any one of claims 1 to 5, characterized in that, A pH regulator is further added to the aqueous medium so that the initial pH value of the polymerization system before the start of the emulsion polymerization is greater than 7 and 11 or less.

7. The preparation method according to any one of claims 1 to 6, characterized in that, In the emulsion polymerization, the polymerization temperature is 30-65°C and the polymerization time is 1-72 hours.

8. A vinyl chloride copolymer latex, characterized in that, The vinyl chloride copolymer latex does not contain a surfactant. The vinyl chloride copolymer constituting the latex has units based on vinyl chloride A, units based on comonomer B, and units based on functional monomer C. The functional monomer C has one radically polymerizable group and two functional groups selected from amide groups, carboxyl groups, and carboxylate groups, and not both an amide group in one molecule.

9. The vinyl chloride copolymer latex according to claim 8, wherein, The average particle diameter of the vinyl chloride copolymer particles in the latex is 100-350 nm; in the vinyl chloride copolymer, the mass ratio of the units based on the comonomer B to the units based on the functional monomer C, units based on comonomer B / units based on functional monomer C, is 1 / 20 to 40 / 1.

10. A vinyl chloride-based copolymer liquid composition, characterized by The composition contains a vinyl chloride copolymer latex obtained by the production method according to any one of claims 1-7, or the vinyl chloride copolymer latex according to claim 8 or 9.

11. A paste resin of a vinyl chloride copolymer, characterized in that, The paste resin is obtained by using the vinyl chloride copolymer latex obtained by the production method according to any one of claims 1-7, or by using the vinyl chloride copolymer latex according to claim 8 or 9.

12. A solid composition of a vinyl chloride copolymer, characterized in that, The composition comprises the paste resin according to claim 10.

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