Manufacturing method of chloroprene polymer composition, chloroprene polymer composition, dip molded article, and manufacturing method of dip molded article

Abstract

Provided is a method for manufacturing a chloroprene-based polymer composition whereby it is possible to simultaneously obtain a polymerization liquid in which the polymer concentration is sufficiently increased and a target solid content concentration is reached in a short period of time, suppress the occurrence of aggregates during polymerization, and obtain a chloroprene-based polymer composition in which stability after polymerization is high, and aggregates hardly occur. According to the present invention, provided is a method for manufacturing a chloroprene-based polymer composition containing a chloroprene-based polymer, the method including a polymerization step in which chloroprene, or chloroprene and a monomer copolymerizable with chloroprene are polymerized until a polymerization completion conversion ratio is reached. The polymerization step comprises a monomer addition step and an emulsifier addition step. When the amount of all monomers used in the polymerization step is set to be 100%, the initial addition amount of monomers when initiating polymerization is X%. In the monomer addition step, the remaining monomers are added into the polymerization system during the time period from the point in time at which polymerization has advanced to the conversion of Y% of the initially added monomer when the initial addition amount is set to be 100%, until prior to reaching the polymerization completion conversion ratio. In the emulsifier addition step, an emulsifier is added during the time period from the point in time at which polymerization has advanced to the conversion of Z% of the monomers when the amount of all monomers used in the polymerization step is set to be 100%, until prior to reaching the polymerization completion conversion ratio. Furthermore, 1 ≦ XY / 100 ≦ 40, 20 ≦ Z ≦ 75, and -65 ≦ Y – Z ≦ 50.

Description

[Technical field]

[0001] The present invention relates to a method for producing a chloroprene polymer composition, a chloroprene polymer composition, a dip-molded article, and a method for producing a dip-molded article. [Background technology]

[0002] Conventionally, when a chloroprene-based polymer is polymerized, chloroprene and, if necessary, a monomer copolymerizable with chloroprene are charged all at once, and emulsion polymerization or solution polymerization is carried out. The polymerization rate during polymerization of chloroprene polymers is generally controlled by the amount of initiator added. However, if the polymerization rate is too fast, the heat removal from the system cannot be kept up, which makes it difficult to control the polymerization. In the case of emulsion polymerization, the cooling efficiency can be increased by increasing the amount of water in the system, and in the case of solution polymerization, the amount of solvent can be increased. However, increasing the amount of water or solvent decreases the polymer concentration in the polymerization liquid obtained after the completion of polymerization, which increases the time and energy required to remove the water or solvent from the polymerization liquid and decreases the efficiency of recovering the polymer from the polymerization liquid.

[0003] With regard to a method for producing a chloroprene polymer composition, Patent Document 1 discloses a method for producing a polychloroprene polymer, in which, when polymerizing chloroprene or chloroprene and a monomer copolymerizable with chloroprene, polymerization is started with an initial amount of monomer added of 10 to 50% of the total monomers, and, during the period from when polymerization has progressed to a monomer conversion rate of between 1 to 40% of the total monomers until the polymerization termination conversion rate is reached, the remaining monomers cooled to a temperature of -20 to 0°C are continuously added little by little to the polymerization system to polymerize a polychloroprene polymer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4238021 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in conventional methods for producing a chloroprene polymer composition, it has not been possible to simultaneously achieve the following: obtaining a polymerization liquid having a sufficiently high polymer concentration in the resulting polymerization liquid and reaching a target solid content concentration in a short period of time; suppressing the generation of aggregates during polymerization; and obtaining a chloroprene polymer composition after polymerization that is highly stable and less likely to generate aggregates.

[0006] The present invention has been made in view of the above circumstances, and provides a method for producing a chloroprene polymer composition, which can simultaneously achieve the following: obtaining a polymerization liquid that reaches a target solid content concentration in a short time by sufficiently increasing the polymer concentration in the resulting polymerization liquid; suppressing the occurrence of aggregates during polymerization; and obtaining a chloroprene polymer composition that is highly stable after polymerization and is less likely to cause aggregates, all of which have been difficult to achieve with conventional chloroprene polymer compositions. [Means for solving the problem]

[0007] According to the present invention, there is provided a method for producing a chloroprene polymer composition containing a chloroprene polymer, comprising the steps of: The method includes a polymerization step of polymerizing chloroprene, or chloroprene and a monomer copolymerizable with chloroprene, until a polymerization termination conversion is reached, The polymerization step includes a monomer addition step and an emulsifier addition step, When the total amount of monomers used in the polymerization step is 100%, the initial amount of monomer added at the start of polymerization is X%; In the monomer addition step, when the initial amount of added monomer is taken as 100%, the remaining monomer is added to the polymerization system from a point where the polymerization has proceeded until the initially added monomer is converted to Y% until the polymerization termination conversion rate is reached, In the emulsifier addition step, when the total amount of monomers used in the polymerization step is taken as 100%, an emulsifier is added between the point at which the polymerization has progressed to Z% conversion of the monomers and the point before the polymerization termination conversion is reached, 1≦XY / 100≦40 20≦Z≦75 -65≦YZ≦50 The present invention provides a method for producing a chloroprene-based polymer composition,

[0008] The present inventors have conducted extensive research and have found that, in a method for producing a chloroprene polymer composition, by setting the timing and amount of monomer addition during polymerization and the timing and amount of emulsifier addition to specific timing and amounts, it is possible to highly control the particle size, number and degree of aggregation of chloroprene polymer particles in the resulting polymerization liquid and composition, and to simultaneously achieve the following: sufficiently increasing the polymer concentration in the resulting polymerization liquid to obtain a polymerization liquid that reaches a target solids concentration in a short period of time; suppressing the formation of aggregates during polymerization; and obtaining a chloroprene polymer composition that is highly stable after polymerization and is less likely to form aggregates, all of which have been difficult to achieve using conventional methods for producing chloroprene polymer compositions, and have thus completed the present invention.

[0009] Various embodiments of the present invention will be described below. The embodiments described below can be combined with each other. It is Noh. Preferably, The monomer concentration in the reaction solution at the start of polymerization is less than 55.0% by mass, The concentration of the emulsifier in the reaction liquid at the start of polymerization is 0.1 to 5.7% by mass, The concentration of the chloroprene polymer in the polymerization solution at the end of the polymerization is 45.0% by mass or more, The concentration of the emulsifier in the polymerization liquid at the end of the polymerization is 2.4% by mass or more. Preferably, the emulsifier comprises an alkali metal salt of a rosin acid, which contains either dehydroabietic acid or a dehydroabietic acid salt. According to another aspect of the present invention, there is provided a chloroprene polymer composition obtained by the above-described method for producing a chloroprene polymer composition. According to another aspect of the present invention, there is provided a dip-molded article comprising the above-mentioned chloroprene polymer composition. Preferably, the dip molded article is a glove, a balloon, a catheter or a boot. According to another aspect of the present invention, there is provided a method for producing a dip-molded article, comprising the step of dip-molding the chloroprene polymer composition obtained by the above-described method for producing a chloroprene polymer composition. Effect of the Invention

[0010] According to the present invention, there is provided a method for producing a chloroprene polymer composition, which can simultaneously achieve the following: obtaining a polymerization liquid having a sufficiently high polymer concentration in the resulting polymerization liquid, thereby obtaining a polymerization liquid that reaches a target solid content concentration in a short period of time; suppressing the occurrence of aggregates during polymerization; and obtaining a chloroprene polymer composition that is highly stable after polymerization and is less likely to cause aggregates. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention will be described in detail below by illustrating the embodiments of the present invention. The present invention is not limited by these descriptions. The features of the embodiments of the present invention described below can be combined with each other. In addition, each feature can be an invention independently.

[0012] 1. Chloroprene polymers The chloroprene polymer according to the present invention means a polymer containing a monomer unit derived from 2-chloro-1,3-butadiene (hereinafter referred to as chloroprene). The chloroprene polymer according to the present invention is a homopolymer of chloroprene or a copolymer of a chloroprene monomer and another monomer copolymerizable therewith.

[0013] Examples of monomers copolymerizable with chloroprene monomers include 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, butadiene, isoprene, styrene, acrylonitrile, acrylic acid or esters thereof, and methacrylic acid or esters thereof. These may be used alone or in combination of two or more. Although not particularly limited, from the viewpoint of maintaining the properties derived from chloroprene, the chloroprene-based polymer according to one embodiment of the present invention preferably has 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more of monomer units derived from chloroprene monomers when the chloroprene-based polymer is taken as 100% by mass.

[0014] 2. Method for producing chloroprene polymer composition The chloroprene polymer composition according to the present invention contains a chloroprene polymer. The method for producing a chloroprene polymer composition according to the present invention includes a polymerization step of polymerizing chloroprene, or chloroprene and a monomer copolymerizable with chloroprene, until a polymerization termination conversion is reached. The polymerization process according to the present invention includes a monomer addition step and an emulsifier addition step.

[0015] 2.1 Polymerization process In the polymerization step, chloroprene, or chloroprene and a monomer copolymerizable with chloroprene, is polymerized until a polymerization end conversion is reached. Here, the polymerization end conversion refers to the monomer conversion at the end of the polymerization step, that is, the amount of monomer converted by the end of the polymerization when the amount of all monomers used in the polymerization step is taken as 100%. In the polymerization step according to the present invention, chloroprene, or chloroprene and a monomer copolymerizable with chloroprene are polymerized until a predetermined target polymerization end conversion is reached, and at the point in time when the polymerization end conversion is reached, a polymerization terminator is added to terminate the polymerization.

[0016] Although not particularly limited, the polymerization process of the chloroprene polymer can be terminated before the monomer conversion rate reaches 100%. That is, the polymerization termination conversion rate is a value of 100% or less, can be less than 100%, and can be in the range of 60 to 95%. By setting the polymerization termination conversion rate within the above numerical range, it is possible to suppress a decrease in adhesive strength and the formation of gel. The polymerization termination conversion rate can be, for example, 60, 65, 70, 75, 80, 85, 90, or 95%, and may be within a range between any two of the numerical values ​​exemplified here.

[0017] In the polymerization process according to the present invention, when the amount of all monomers used in the polymerization process is taken as 100%, the initial amount of monomer added at the start of polymerization is X%. In the monomer addition step, when the initially added amount of monomer is taken as 100%, the remaining monomer is added to the polymerization system from the point at which the polymerization has proceeded until the initially added monomer is converted to Y% until the polymerization termination conversion rate is reached. In the emulsifier addition step, when the total amount of monomers used in the polymerization step is taken as 100%, an emulsifier is added during the period from when the polymerization has progressed to Z% conversion of the monomers to before the polymerization completion conversion is reached. That is, in the polymerization step according to the present invention, a specific initial amount of monomer is first added to the polymerization system to start polymerization, and then the addition of the remaining monomer is started between a specific timing and the end of polymerization, and an emulsifier is added between the specific timing and the end of polymerization. The timings of starting the addition of the monomer and the emulsifier are specified to have a specific relationship with the degree of progress of polymerization, and the timings of starting the addition of the monomer and the emulsifier are specified to have a specific relationship. According to the present invention, by specifying these, it is possible to simultaneously achieve the following: a polymerization liquid having a sufficiently high polymer concentration in the obtained polymerization liquid, which reaches a target solid content concentration in a short time; the occurrence of aggregates during polymerization is suppressed; and a chloroprene polymer composition having high stability after polymerization and less occurrence of aggregates is obtained.

[0018] 2.2 Initiation of the polymerization process In the polymerization process according to the present invention, a reaction liquid is first prepared by adding a raw material containing a monomer into a polymerization system.

[0019] <Monomer> The monomer includes the above-mentioned chloroprene monomer and a monomer copolymerizable with the chloroprene monomer. Here, when the total amount of monomers used in the polymerization step is taken as 100%, the initial amount of monomers added at the start of polymerization is X%. The initial addition amount X% is preferably 5 to 50%, more preferably 10 to 40%, and even more preferably 10 to 35%. The initial addition amount X% can be, for example, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50%, and may be within a range between any two of the numerical values ​​exemplified here.

[0020] The monomer concentration in the reaction solution at the start of polymerization is preferably less than 55% by mass. The monomer concentration in the polymerization solution at the start of polymerization can be, for example, 20, 25, 30, 35, 40, 45, 50, or 54% by mass, and may be within a range between any two of the numerical values ​​exemplified here. By controlling the amount of monomer in the polymerization liquid at the start of polymerization to be equal to or less than the above upper limit, rapid progress of polymerization in the initial stage of the polymerization reaction can be suppressed, and the generation of aggregates in the polymerization liquid can be suppressed, thereby increasing the chloroprene polymer concentration in the finally obtained polymerization liquid.

[0021] The reaction liquid at the start of polymerization contains the monomers, and may further contain water, an emulsifier, a pH adjuster, a polymerization initiator, a chain transfer agent, and the like.

[0022] <Emulsifier> The reaction liquid at the start of polymerization may contain an emulsifier. The emulsifier is not particularly limited, and any of the known anionic, nonionic and cationic emulsifiers used in the polymerization of chloroprene polymers can be used. Anionic emulsifiers include carboxylic acid type, sulfonic acid type, and sulfate type, and examples thereof include higher fatty acid salts, alkenyl succinate salts, alkali metal salts of rosin acid, alkyl sulfonates having 8 to 20 carbon atoms, alkyl aryl sulfates, and condensates of sodium naphthalenesulfonate and formaldehyde. Examples of nonionic emulsifiers include polyvinyl alcohol or its copolymers (e.g., copolymers with acrylamide), polyvinyl ether or its copolymers (e.g., copolymers with maleic acid), polyvinylpyrrolidone or its copolymers (e.g., copolymers with vinyl acetate), or chemically modified versions of these (co)polymers, or cellulose derivatives (hydroxyethyl cellulose), etc. Cationic emulsifiers include aliphatic amine salts and aliphatic quaternary ammonium salts, such as octadecyltrimethylammonium chloride, dodecyltrimethylammonium chloride, and dilauryldimethylammonium chloride. Among these, the emulsifier preferably contains rosin acid or an alkali metal salt of rosin acid. The rosin acid or the alkali metal salt of rosin acid preferably contains either dehydroabietic acid or a dehydroabietic acid salt. These may be used alone or in combination of two or more.

[0023] The concentration of the emulsifier in the reaction solution at the start of polymerization is preferably 0.1 to 5.7% by mass, and more preferably 1.0 to 5.5% by mass. The concentration of the emulsifier in the reaction solution at the start of polymerization can be, for example, 0.1, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, or 5.7 parts by mass, and may be within a range between any two of the numerical values ​​exemplified here.

[0024] The amount of the total emulsifier used in the polymerization step can be 2.0 to 7.5 parts by mass, more preferably 2.5 to 7.0 parts by mass, based on 100 parts by mass of the total monomers used in the polymerization step. The amount of the total emulsifier used in the polymerization step can be, for example, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5 parts by mass based on 100 parts by mass of the total monomers used in the polymerization step, and may be within the range between any two of the exemplified values.

[0025] The initial addition amount of the emulsifier at the start of polymerization can be 1.0 to 5.5 parts by mass, more preferably 1.5 to 5.0 parts by mass, based on 100 parts by mass of the total monomers used in the polymerization step. The initial addition amount of the emulsifier can be, for example, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5 parts by mass, and may be within the range between any two of the exemplified values.

[0026] The initial addition amount of the emulsifier at the start of polymerization can be 50 to 90% by mass, preferably 60 to 80% by mass, based on 100% by mass of the total emulsifier used in the polymerization step. The initial addition amount of the emulsifier can be, for example, 50, 55, 60, 65, 70, 75, 80, 85, 90% by mass based on 100% by mass of the total emulsifier used in the polymerization step, and may be within the range between any two of the exemplified values.

[0027] By setting the amount of the emulsifier at the start of polymerization to be not less than the above lower limit, the generation of aggregates can be suppressed. Also, by setting the amount of the emulsifier to be not more than the above upper limit, the number of chloroprene-based polymer particles generated initially can be suppressed, and the stability of the chloroprene-based polymer composition can be maintained.

[0028] <pH adjuster> The raw material added to the polymerization system at the start of polymerization may contain a pH adjuster. Examples of pH adjusters include potassium pyrosulfite, potassium sulfite, potassium hydrogen sulfite, potassium phosphate, potassium hydrogen phosphate, sodium pyrosulfite, sodium sulfite, sodium hydrogen sulfite, sodium phosphate, sodium hydrogen phosphate, potassium hydroxide, and sodium hydroxide. The pH adjuster may be used alone or in combination of two or more kinds. Among these pH adjusters, potassium hydroxide and sodium hydroxide are preferred because they are highly effective in increasing the pH value. The amount of the pH adjuster added may be 0.01 to 2.0 parts by mass relative to 100 parts by mass of all the monomers used in the polymerization step.

[0029] <Polymerization initiator> The raw materials added to the polymerization system at the start of polymerization may contain a polymerization initiator, such as potassium persulfate, benzoyl peroxide, ammonium persulfate, and hydrogen peroxide, which are used in normal radical polymerization. The amount of the polymerization initiator added can be 0.001 to 1 part by mass relative to 100 parts by mass of all the monomers used in the polymerization step.

[0030] <Chain transfer agent> The chain transfer agent is not particularly limited as long as it is one that is generally used in the production of chloroprene-based polymers. For example, known chain transfer agents such as long-chain alkyl mercaptans such as n-dodecyl mercaptan, tert-dodecyl mercaptan, and n-octyl mercaptan, dialkyl xanthogen disulfides such as diisopropyl xanthogen disulfide and diethyl xanthogen disulfide, and iodoform can be used. The amount of the chain transfer agent added can be 0.001 to 10 parts by mass relative to 100 parts by mass of all the monomers used in the polymerization step.

[0031] In order to control the molecular weight to a target value, in some cases, it may be easier to control the molecular weight by adding the chain transfer agent, like the monomer described below, to the polymerization system initially at the start of polymerization and then separately at a different timing, for example, during the monomer addition step. Whether the entire amount of the chain transfer agent is added at the start of polymerization or whether it is added in portions at the start of polymerization and then later added can be determined by carrying out a preliminary test.

[0032] <Polymerization temperature> The polymerization temperature is preferably in the range of 0 to 55° C. from the viewpoint of ease of reaction control, etc. In order to carry out the polymerization reaction more smoothly and safely, it is preferable that the lower limit of the polymerization temperature is 10° C. or more and the upper limit is 45° C. or less.

[0033] 2.3 Monomer addition process In the monomer addition step, when the initial amount of monomer added is taken as 100%, the remaining monomer is added to the polymerization system from the point where the polymerization has progressed until the conversion of the initially added monomer reaches Y% until the polymerization completion conversion rate is reached. Y% can be 5 to 95%, preferably 20 to 90%, and more preferably 40 to 85%. Y% can be, for example, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, or 95%, and may be within a range between any two of the values ​​exemplified here.

[0034] Y% and the initial amount of monomer added at the start of polymerization, X%, when the amount of all monomers used in the polymerization step is taken as 100% satisfy the following relationship. 1≦XY / 100≦40

[0035] Here, XY / 100 indicates the monomer conversion rate when the total amount of monomers used in the polymerization step is taken as 100%. That is, in the monomer addition step according to the present invention, when the monomer conversion rate when the total amount of monomers used in the polymerization step is taken as 100% falls within the range specified by the above formula, the addition of the remaining monomer can be started. XY / 100 can be, for example, 1, 5, 10, 15, 20, 25, 30, 35, or 40, and may be within a range between any two of the values ​​exemplified here. By making XY / 100 equal to or more than the above lower limit, it becomes possible to start adding the remaining monomers when the monomers have progressed to an appropriate degree, and it is possible to prevent the polymerization reaction from progressing too rapidly. In addition, when XY / 100 is equal to or less than the upper limit, a stable reaction rate can be maintained, the polymer concentration at the end of the polymerization can be increased, the generation of aggregates during the polymerization can be suppressed, and a highly stable chloroprene polymer composition can be obtained.

[0036] In the monomer addition step, the remaining monomer can be added in one or more portions, or can be added continuously at a constant flow rate. When the remaining monomer is added in portions, it is preferable to add the remaining monomer in two or more portions. In the case of continuous addition, the monomer is preferably added at a rate of 4.0 to 64.0% / hour based on 100% by mass of the monomer used in the polymerization step.

[0037] In the monomer addition step according to one embodiment of the present invention, it is preferable to add the monomer so that the monomer concentration in the reaction solution is always 70% by mass or less, and it is more preferable to add the monomer so that the monomer concentration is 60% by mass or less.

[0038] The monomer added in the monomer addition step is preferably cooled to a temperature lower than the polymerization temperature. By subsequently adding a monomer cooled to a temperature lower than the polymerization temperature, the temperature in the polymerization system can be lowered, and as a result, the polymerization time can be shortened. The temperature of the monomer added in the monomer addition step is preferably lower than the polymerization temperature, and from the viewpoint of the melting point of chloroprene (-130°C) and prevention of polymerization, it is preferable to add the monomer to the polymerization system at -120 to 20°C. From the economic viewpoint, it is more preferably -50 to 20°C, and most preferably -20 to 0°C.

[0039] 2.4 Emulsifier addition process In the emulsifier addition step, when the amount of all monomers used in the polymerization step is taken as 100%, an emulsifier is added between the point where the polymerization has progressed to Z% conversion of the monomers and the point where the polymerization end conversion rate is reached. The emulsifier added in the emulsifier addition step can be the above-mentioned emulsifiers, and preferably contains rosin acid or an alkali metal salt of rosin acid. In addition, it is preferable that the rosin acid or the alkali metal salt of rosin acid contains either dehydroabietic acid or a dehydroabietic acid salt. These may be used alone or in combination of two or more.

[0040] Here, Z satisfies the following formula: 20≦Z≦75 Z % can be, for example, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75%, and may be within a range between any two of the values ​​exemplified herein. By setting Z to the above lower limit or more and adding an emulsifier after a certain amount of monomer has been converted, it is possible to prevent an excessive increase in the number of chloroprene polymer particles in the polymerization system, which would otherwise cause an increase in particles with a high specific surface area and poor stability. By setting Z to the above upper limit or less, it is possible to suppress aggregation of the produced chloroprene polymer particles due to contact with each other, and it is possible to obtain a chloroprene polymer composition that has a high polymer concentration at the end of polymerization, is capable of suppressing the generation of aggregates during polymerization, and is highly stable.

[0041] In addition, when the above-mentioned initial addition amount is taken as 100%, the conversion rate Y% of the initially added monomer at the time when the monomer addition step can be started and the above-mentioned Z% satisfy the following relationship. -65≦YZ≦50 YZ can be, for example, -65, -60, -55, -50, -45, -40, -35, -30, -25, -20, -15, -10, -5, 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, or may be within a range between any two of the values ​​exemplified here. By setting YZ to the lower limit or more, the addition of the emulsifier is not too slow relative to the progress of polymerization of the initially added monomer, and the aggregation of the generated chloroprene polymer particles can be prevented. Also, by setting YZ to the upper limit or less, the addition of the emulsifier is not too fast relative to the progress of polymerization of the initially added monomer, and the number of chloroprene polymer particles is not excessively increased, and the increase of particles with a high specific surface area and poor stability can be prevented.

[0042] In the emulsifier addition step, the remaining emulsifier can be added in one or more portions, or can be added continuously at a constant flow rate. When the remaining emulsifier is added in portions, it can be added in one portion or in two or more portions. In the case of continuous addition, the emulsifier is preferably added at a rate of 0.1 to 45 parts by mass / hour per 100 parts by mass of the total amount of monomers used in the polymerization step.

[0043] 2.5 End of polymerization process In the polymerization step according to the present invention, when the monomer conversion rate reaches a polymerization termination conversion rate, a polymerization terminator is added to terminate the polymerization, thereby obtaining a polymer liquid in which the reaction has been completed.

[0044] <Polymerization terminator> As the polymerization terminator, for example, thiodiphenylamine, 4-tert-butylcatechol, 2,2'-methylenebis-4-methyl-6-tert-butylphenol, etc. can be used.

[0045] <Removal of unreacted monomer> After the completion of the emulsion polymerization, unreacted monomers are removed from the polymerization solution by a conventional method such as steam stripping or reduced pressure heating evaporation, to obtain a chloroprene polymer composition.

[0046] The concentration of the chloroprene polymer in the polymerization solution at the end of the polymerization is preferably 45% by mass or more, more preferably 50% by mass or more. The concentration of the chloroprene polymer in the polymerization solution at the end of the polymerization can be, for example, 45, 50, 55, 60, 65, or 70% by mass, and may be within a range between any two of the values ​​exemplified here.

[0047] After the polymerization is completed, the polymerization liquid is heated at 70°C under reduced pressure to remove unreacted monomer components. If the solid content of the polymerization liquid after the monomer removal step is less than 60%, the polymerization liquid is heated again at 70°C under reduced pressure and concentrated until the target solid content of 60% is reached. At this time, it is preferable that the time required for concentration is within 1 hour.

[0048] The concentration of the emulsifier in the polymerization solution at the end of the polymerization is preferably 2.4% by mass or more. The concentration of the emulsifier in the polymerization solution at the end of the polymerization can be, for example, 2.4, 2.5, 3.0, 3.5, 4.0, or 4.5% by mass, and may be within a range between any two of the values ​​exemplified here.

[0049] The amount of aggregates in the polymerization solution at the end of the polymerization is preferably 0.8% or less, more preferably 0.7% or less, and even more preferably 0.6% or less. The amount of aggregates in the polymerization solution at the end of the polymerization is a comprehensive evaluation of the aggregates generated in the system from the start of the polymerization to the end of the polymerization, and can be evaluated by the method described in the Examples.

[0050] The mechanical stability in the polymerization solution at the end of the polymerization is preferably 1% or less, more preferably 0.9% or less, and even more preferably 0.8% or less. The mechanical stability in the polymerization solution at the end of the polymerization can be evaluated by the method described in the Examples.

[0051] 3. Chloroprene polymer composition The chloroprene polymer composition according to one embodiment of the present invention is obtained by the above-mentioned production method. In the chloroprene polymer composition according to one embodiment of the present invention, the particle size, number and degree of aggregation of the chloroprene polymer particles in the composition are highly controlled by adjusting the timing and amount of monomer addition during polymerization and the timing and amount of emulsifier addition to specific timing and amounts, thereby providing a high level of stability.

[0052] 4.Dip molding A dip-molded article according to one embodiment of the present invention contains the above-mentioned chloroprene polymer composition. The dip-molded article is preferably a glove, a balloon, a catheter, or a boot. The dip-molded article of the present embodiment contains the chloroprene polymer composition, and may further contain a vulcanizing agent and / or a vulcanization accelerator, a filler or a reinforcing agent, a plasticizer, a processing aid or a lubricant, an antiaging agent, a silane coupling agent, etc. These agents can be appropriately selected from known materials depending on the purpose and application.

[0053] 5. Manufacturing method of dip-molded body The method for producing a dip-molded article according to one embodiment of the present invention includes a step of dip-molding the chloroprene polymer composition obtained by the above-described method for producing a chloroprene polymer composition. The method for producing the dip-molded article according to this embodiment includes, for example, a coagulation liquid immersion method, but is not limited thereto, and molding may be performed according to a conventional method. EXAMPLES

[0054] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0055] Example 1 In a polymerization vessel having an internal volume of 50 L, 30 parts by mass of chloroprene monomer, 0.14 parts by mass of n-dodecyl mercaptan, 62.6 parts by mass of pure water, 2.5 parts by mass of disproportionated rosin (manufactured by Arakawa Chemical Industries, Ltd., product name: Longis K-25), 0.47 parts by mass of potassium hydroxide, and 1.5 parts by mass of sodium salt of β-naphthalenesulfonic acid formalin condensate (manufactured by Kao Corporation, product name: Demol N) were added. After adding 0.1 parts by mass of potassium persulfate as a polymerization initiator, polymerization was started under a nitrogen gas flow at a polymerization temperature of 40°C. The conversion rate was estimated by integrating the polymerization heat, and when the conversion rate reached 80% relative to the initial amount of chloroprene monomer added (100%), the addition of the remaining monomer was started. The addition was carried out continuously at a rate of 20% / hour relative to 100% by mass of the monomer used in the polymerization process. The conversion rate was estimated by integrating the heat of polymerization, and when the conversion rate reached 60%, the remaining emulsifier, disproportionated rosin, was added. When the polymerization rate reached 95%, which is the conversion rate at which polymerization was terminated, diethylhydroxylamine, a polymerization terminator, was added to terminate the polymerization. Unreacted monomers were removed under reduced pressure to obtain a chloroprene polymer composition with a solid content of 60%.

[0056] (Examples 2 to 6, Comparative Examples 1 to 8) A chloroprene polymer composition was obtained in the same manner as in Examples, except that the amounts of chloroprene monomer and rosin acid at the start of polymerization, the amounts and start timing of portionwise addition of monomers, and the amount and start timing of portionwise addition of rosin acid were as shown in Table 1. In Comparative Example 5, the amount of pure water added was 317 parts by mass.

[0057] (Mechanical stability of polymerization solution) The mechanical stability of the polymerization solution was measured in accordance with JIS K 6392 using a Maron mechanical stability tester by the following method. Procedure: The sampled polymerization liquid was filtered through a wire mesh to remove impurities, and then the filtered polymerization liquid was adjusted to 20°C, and 50 g was weighed into a test container. The test container was attached to a tester, and a measurement was performed for 10 minutes with a load of 10 kg. The sample in the test container after the measurement was filtered through an 80-mesh wire mesh that had been dried at 125°C for 1 hour and cooled in a desiccator, and the 80-mesh wire mesh and precipitate were dried in a dryer at 125°C for 1 hour, then cooled in a desiccator, and the 80-mesh wire mesh and precipitate were weighed. In addition, the total solid content (unit: %) of the sampled chloroprene polymer composition was calculated in accordance with JIS K 6387. Next, the coagulation rate (unit: mass%) of the polymerization liquid was calculated using the following formula. [(Mass of 80 mesh wire net and precipitate after drying (unit: g)) - (Mass of 80 mesh wire net (unit: g))] / [50 × ((Total solid content of polymerization solution (unit: mass%)) / 100)] × 100 The obtained solidification rate of the polymer solution was regarded as the mechanical stability of the polymer solution.

[0058] (Amount of aggregates in polymerization liquid) The polymerization liquid was filtered through a 200 mesh wire net, and the 200 mesh wire net and precipitate were dried in a dryer at 125°C for 1 hour, then allowed to cool in a desiccator, and the 200 mesh wire net and precipitate were weighed. The total solid content (unit: %) of the sampled polymerization liquid was calculated in accordance with JIS K 6387. Next, the amount of aggregates (unit: mass%) in the polymerization liquid was calculated using the following formula. [(Mass of 200 mesh wire net and precipitate after drying (unit: g)) - (Mass of 200 mesh wire net (unit: g))] / [50 × ((Total solid content of polymerization solution (unit: mass%)) / 100)] × 100

[0059] (Concentration time required to reach target solids content) The obtained polymerization liquid was heated at 70° C. under reduced pressure, and after removing the unreacted monomer, it was heated again at 70° C. and the time required to reach the target solid content of 60% was measured. The polymerization liquid according to the examples did not require additional concentration because it reached the target solid content concentration at the time when the unreacted monomer was removed.

[0060] [Table 1]

Claims

1. A method for producing a chloroprene polymer composition containing a chloroprene polymer, comprising the steps of: The method includes a polymerization step of polymerizing chloroprene, or chloroprene and a monomer copolymerizable with chloroprene, until a polymerization termination conversion is reached, The polymerization step includes a monomer addition step and an emulsifier addition step, When the amount of all monomers used in the polymerization step is 100%, the amount of monomers initially added at the start of polymerization is X%; In the monomer addition step, when the initial amount of added monomer is taken as 100%, the remaining monomer is added to the polymerization system from a point where the polymerization has proceeded until the initially added monomer is converted to Y% until the polymerization termination conversion rate is reached, In the emulsifier addition step, when the amount of the total monomers used in the polymerization step is taken as 100%, an emulsifier is added during a period from when the polymerization has progressed to Z% conversion of the monomers to before the polymerization termination conversion rate is reached, 1≦XY / 100≦40 30≦Z≦75 −65≦Y−Z≦50 Y≦95 The present invention relates to a method for producing a chloroprene polymer composition.

2. The monomer concentration in the reaction solution at the start of polymerization is less than 55.0% by mass, The concentration of the emulsifier in the reaction liquid at the start of polymerization is 0.1 to 5.7% by mass, The concentration of the chloroprene polymer in the polymerization solution at the end of the polymerization is 45.0% by mass or more, The concentration of the emulsifier in the polymerization liquid at the end of the polymerization is 2.4% by mass or more. A method for producing the chloroprene polymer composition according to claim 1.

3. The method for producing a chloroprene polymer composition according to claim 1 or 2, wherein the emulsifier comprises an alkali metal salt of a rosin acid containing either dehydroabietic acid or a dehydroabietic acid salt.

4. A chloroprene polymer composition obtained by the method for producing a chloroprene polymer composition according to any one of claims 1 to 3.

5. A dip-molded article comprising the chloroprene polymer composition according to claim 4.

6. The dip-molded article according to claim 5 , which is a glove, a balloon, a catheter or a boot.

7. A method for producing a dip-molded product, comprising a step of dip-molding a chloroprene polymer composition obtained by the method for producing a chloroprene polymer composition according to any one of claims 1 to 3.

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