JP2009108195A - Chloroprene polymer latex composition for producing vulcanized rubber and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chloroprene polymer latex composition capable of manufacturing vulcanized rubber equipped with excellent rubber physical properties by enhancing bridges of chloroprene rubber stably. <P>SOLUTION: The chloroprene polymer latex composition for manufacturing the vulcanized rubber is characterized by that it contains 2-20 pts.wt. of hydrotalcite based on 100 pts.wt. of chloroprene polymer. The manufacturing method of the composition is also provided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a latex composition containing a chloroprene polymer as a main component and a method for producing the same. Specifically, the present invention relates to a chloroprene polymer latex composition for obtaining a vulcanized rubber product and a method for producing the same.

  Chloroprene rubber is used in a wide range of applications because it has a good balance of physical properties among various synthetic rubbers. Among them, they are often used not as chip-like raw rubber but as polymer latex for water-based adhesive applications, asphalt modifiers, and immersion molding applications. In particular, in dip molding applications, chloroprene polymer latex is positioned as one of the main raw materials for gloves for household use, industrial use, and surgical use.

  In general, when manufacturing vulcanized rubber products from chloroprene rubber, a compound containing rubber, filler, reinforcing agent, anti-aging agent, lubricant, plasticizer, acid acceptor, zinc oxide, vulcanization accelerator, sulfur, etc. is prepared. Then, a vulcanized rubber is obtained by causing a vulcanization reaction by heating with a press molding machine or the like.

  On the other hand, in order to produce vulcanized rubber products by immersion molding using chloroprene polymer latex, filler, reinforcing agent, anti-aging agent, plasticizer, zinc oxide, vulcanization accelerator, sulfur, etc. are added to chloroprene polymer latex. A latex composition in which a suspension in which water is dispersed and, if necessary, an emulsifier, a viscosity adjuster and a pH adjuster are added, a rubber film is formed by immersing a mold impregnated with a flocculant therein. A general method is to form, heat as it is in an oven, and dry and vulcanize.

  The vulcanization reaction of chloroprene is accompanied by elimination of chlorine atoms of 1,2-bond units contained in the polymer structure, thereby generating hydrochloric acid. There are many vulcanization accelerators in which the vulcanization rate decreases when the pH in the system decreases, so it is necessary to contain an acid acceptor in the composition to suppress the pH decrease and maintain the vulcanization reaction rate. As an acid acceptor to be added to a compound when producing a vulcanized rubber product from chloroprene rubber chips, magnesium oxide is the most excellent in terms of acid acceptability and cost, and is widely used in general. However, in the process of preparing a dispersion for addition to a latex composition for immersion applications, magnesium oxide reacts with water and changes to magnesium hydroxide, so a stable dispersion cannot be created, resulting in a latex composition. Cannot be blended into products. Therefore, the formulation for immersion applications generally does not contain a highly active acid acceptor such as magnesium oxide, and a method of adding a large amount of zinc oxide that acts as a weak acid acceptor simultaneously with the vulcanizing agent (for example, Non-Patent Document 1).

  However, in order to stably improve the crosslinking efficiency of the chloroprene rubber, it is necessary to add a highly active acid acceptor, and an acid acceptor dispersion that can be added to the chloroprene polymer latex composition is desired.

Emulsion Latex Handbook Editorial Committee, “Emulsion Latex Handbook”, first edition, Taiseisha Co., Ltd., March 1975, p. 541-p. 542

  The present invention has been made in view of the above-mentioned problems, and the object thereof is a chloroprene polymer latex composition for obtaining a vulcanized rubber product, and in order to stably improve the crosslinking efficiency, It is an object of the present invention to provide a chloroprene polymer latex composition for producing a vulcanized rubber containing an acid acceptor capable of efficiently supplementing generated hydrochloric acid.

  As a result of intensive studies in order to solve the above-mentioned problems, the present inventors have added a suspension of hydrotalcite as an acid acceptor to the chloroprene polymer latex, which occurs during the vulcanization reaction. It has been found that hydrochloric acid can be efficiently supplemented, thereby improving the crosslinking efficiency. That is, the present invention is a chloroprene polymer latex composition for producing vulcanized rubber, which contains 2 to 20 parts by weight of hydrotalcite with respect to 100 parts by weight of chloroprene polymer, and a method for producing the same.

  The present invention is described in detail below.

  The chloroprene polymer latex composition for vulcanized rubber production of the present invention contains 2 to 20 parts by weight of hydrotalcite with respect to 100 parts by weight of chloroprene polymer. This hydrotalcite functions as an acid acceptor.

  The hydrotalcite contained in the chloroprene polymer latex composition of the present invention is generally a compound represented by the following structural formula (1), and has a layered and scaly crystal structure.

Mg ₆ Al ₂ (OH) ₁₆ CO ₃ .4H ₂ O (1)
The content of hydrotalcite is required to be 2 to 20 parts by weight with 100 parts by weight of the chloroprene polymer. When the hydrotalcite is less than 2 parts by weight, the ability as an acid acceptor is insufficient, and when it exceeds 20 parts by weight, the viscosity of the latex composition is greatly increased, and molding by dipping becomes difficult. 4 to 10 parts by weight is preferred.

  Crystallized water of hydrotalcite can be eliminated by calcination and is generally sold as a baked product. However, in the chloroprene polymer latex composition of the present invention, hydrotalcite is used to maintain latex stability. It is necessary to be stable in a dispersion state suspended in water, and it is preferable to use uncalcined hydrotalcite.

  The method for producing a chloroprene polymer latex composition for producing a vulcanized rubber according to the present invention is to directly apply hydrotalcite to a chloroprene polymer latex as a powder in order to maintain the stability of the latex and prevent the formation of aggregates. It is preferable to prepare a suspension containing hydrotalcite in advance by adding it to water together with an emulsifier and stirring it, and adding it to the chloroprene polymer latex rather than adding it.

  The concentration of hydrotalcite in the suspension containing hydrotalcite is not particularly limited, but it prevents the decrease in total solids, improves the productivity of vulcanized rubber, and moderately adjusts the concentration of the suspension. In order to maintain and improve the workability | operativity at the time of composition production, 30 to 80 weight% is preferable.

  The emulsifier used in the suspension containing hydrotalcite is not particularly limited as long as it is a commonly used surfactant, and includes an anionic emulsifier such as a carboxylate type, a sulfonate type, and a sulfate type, and Nonionic emulsifiers and the like are used. Specifically, alkali metal salt of disproportionated rosin acid, alkali metal salt of rosin acid, alkali metal salt or ammonium salt of higher fatty acid, ammonium salt of casein, alkyl sulfonate, alkyl Aryl sulfonate, alkyl sulfate, alkyl aryl sulfate, condensate of sodium naphthalene sulfonate and formaldehyde, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, sorbitan fatty acid ester, polyoxyethylene acyl ester, etc. Single or two It can be used in combination of the above. Although the optimum range of the amount of the emulsifier varies depending on the type, 0.01 to 15 parts by weight with respect to 100 parts by weight of hydrotalcite is preferable as the range in which the stability of the suspension containing hydrotalcite can be maintained. .05 to 10 parts by weight is particularly preferred.

  The chloroprene polymer latex in the chloroprene polymer latex for producing a vulcanized rubber of the present invention is a monomer mixture composed of 2-chloro-1,3-butadiene and a chain transfer agent, or 2-chloro-1,3-butadiene, 2- It is a polymer latex obtained by emulsion polymerization of a monomer mixture comprising at least one comonomer copolymerizable with chloro-1,3-butadiene and a chain transfer agent.

  The chain transfer agent is not particularly limited as long as it is a compound used for general radical polymerization. For example, alkyl mercaptans such as n-dodecyl mercaptan, t-dodecyl mercaptan, octyl mercaptan, diethyl xanthogen disulfide, dibutyl Examples thereof include xanthogen sulfides such as xanthogen disulfide and diisopropylxanthogen disulfide, benzyl iodide, iodoform, and the like, which are used alone or in combination of two or more. The amount of the chain transfer agent is not particularly limited as long as it is an amount used in general radical polymerization for adjusting the molecular weight, but other than the chain transfer agent in order to achieve the desired molecular weight of the polymer obtained. The amount is preferably 0.01 to 1 part by weight, more preferably 0.1 to 0.5 part by weight, based on 100 parts by weight of the monomer mixture.

  The at least one comonomer copolymerizable with 2-chloro-1,3-butadiene is not particularly limited as long as it is a monomer capable of radical polymerization. For example, acrylonitrile, methacrylonitrile, vinylidene chloride, etc. Monovinyl compounds, aromatic vinyl compounds such as styrene and α-methylstyrene, unsaturated group-containing carboxylic acids such as acrylic acid and methacrylic acid, unsaturated group-containing carboxylic esters such as acrylic acid esters and methacrylic acid esters, isoprene , 1,3-butadiene, 1-chloro-1,3-butadiene, conjugated diene compounds such as 2,3-dichloro-1,3-butadiene and the like can be used, and these can be used alone or in combination of two or more. . Of these, 1-chloro-1,3-butadiene and 2,3-dichloro-1,3-butadiene are easily copolymerized with 2-chloro-1,3-butadiene, and the resulting chloroprene rubber is improved. This is particularly preferable because of its high quality effect. In a monomer mixture comprising 2-chloro-1,3-butadiene, at least one comonomer copolymerizable with 2-chloro-1,3-butadiene, and a chain transfer agent, 2-chloro-1,3-butadiene is used. The ratio of butadiene and at least one comonomer copolymerizable with 2-chloro-1,3-butadiene is not particularly limited as long as it is a copolymerizable amount ratio, but the characteristics as chloroprene are maintained. Therefore, the weight ratio is preferably 25/75 to 99/1, and more preferably 80/20 to 99/1 in order to exert the characteristics of chloroprene strongly.

  The emulsifier for obtaining the chloroprene polymer latex is not particularly limited as long as it is a surfactant generally used in emulsion polymerization, and includes an anionic emulsifier such as a carboxylate type, a sulfonate type, and a sulfate type. Nonionic emulsifiers and the like are used. Specifically, alkali metal salt of disproportionated rosin acid, alkali metal salt of rosin acid, alkali metal salt of higher fatty acid, alkyl sulfonate, alkyl aryl sulfonate, alkyl sulfate , Alkyl aryl sulfates, condensates of sodium naphthalene sulfonate and formaldehyde, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, sorbitan fatty acid esters, polyoxyethylene acyl esters, etc., alone or in combination of two or more Can be used together. Although the optimum range of the amount of each emulsifying dispersant added varies depending on the type, 0.1 to 15 parts by weight per 100 parts by weight of the monomer mixture other than the chain transfer agent can be used as a range in which emulsion polymerization can be carried out stably. Preferably, 0.1 to 10 parts by weight is particularly preferable.

  The polymerization initiator for obtaining the chloroprene polymer latex is not particularly limited as long as it is a free radical generating substance, and examples thereof include persulfate oxides such as potassium persulfate and ammonium persulfate, hydrogen peroxide, paramentane hydroper Inorganic or organic peroxides such as oxide, t-butyl hydroperoxide, cumene hydroperoxide, etc. are mentioned. These alone or the above compounds and ferrous sulfate, hydrosulfite sodium, sodium formaldehyde sulfoxylate, thiosulfuric acid A redox system using a reducing substance such as a salt, thiosulfite, or organic amine is used.

  The polymerization conversion rate for stopping the polymerization for obtaining the chloroprene polymer latex is not particularly limited as long as the chloroprene polymer is within the range in which the chloroprene polymer latex is obtained. 100% is preferable, and 85 to 99% is particularly preferable. Here, it is also possible to add a polymerization terminator as necessary when terminating the polymerization, and the polymerization terminator is not particularly limited as long as it is a compound that traps radicals. For example, phenothiazine, 2,2′-methylenebis- (4-methyl-6-tert-butylphenol), 2,2′-methylenebis- (4-ethyl-6-tert-butylphenol), 2,6-di-tert-butyl-4- Examples thereof include radical inhibitors such as methylphenol, hydroquinone, 4-methoxyhydroquinone and N, N-diethylhydroxylamine, and one or two or more of them can be used. The optimum range of the addition amount of each polymerization terminator varies depending on the type, but as a range in which the polymerization can be stopped reliably and the stability of the obtained chloroprene polymer can be ensured, the monomer mixture other than the chain transfer agent is 100 wt. 0.01 to 5 parts by weight is preferable with respect to parts, and 0.02 to 2 parts by weight is particularly preferable.

  The polymerization temperature in the polymerization for obtaining the chloroprene polymer latex can be performed in the range of 0 to 60 ° C, and preferably in the range of 5 to 50 ° C.

  The method for removing the unreacted monomer carried out after the completion of the polymerization in order to obtain the chloroprene polymer latex is not particularly limited, and examples thereof include steam stripping under reduced pressure.

  The chloroprene polymer latex composition for producing vulcanized rubber according to the present invention contains a metal oxide such as zinc oxide and a vulcanization accelerator acting as a vulcanizing agent in addition to the above chloroprene polymer latex and hydrotalcite suspension. Further, sulfur, fillers, reinforcing agents, plasticizers, lubricants, anti-aging agents, colorants, wetting agents, antifoaming agents, emulsifiers, pH stabilizers, anti-adhesive agents, viscosity modifiers, etc. It is also possible to contain.

  The chloroprene polymer latex composition for vulcanized rubber production of the present invention can efficiently supplement hydrochloric acid generated during vulcanization by the hydrotalcite contained therein. Therefore, according to the same method as that of normal immersion molding, a rubber film can be formed by applying or impregnating a coagulant to a mold of a target vulcanized rubber molding and immersing it in a latex composition. It is possible to obtain a vulcanizate by immersing a rubber film in water together with a mold, washing away excess emulsifier and the like, and then drying by heating together with the mold.

  Since the chloroprene polymer latex composition for producing vulcanized rubber of the present invention contains suspended hydrotalcite, the chloroprene polymer latex composition can efficiently supplement hydrochloric acid generated in the vulcanization reaction. Compared with latex, a vulcanized product having a high vulcanization density, high breaking strength and high modulus can be produced.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited by these Examples.

  The solid content of the chloroprene polymer latex composition in the examples was evaluated from the weight before and after drying when about 2 g of the latex composition was dried in a hot air dryer at 105 ° C. for 2 hours. The viscosity of the latex composition was 25 ° C. using a bismetholone rotational viscometer (manufactured by Shibaura System). 2 or No. The measurement was performed under conditions of 3 rotors and 60 rpm.

  The vulcanizate properties were evaluated according to JIS K6251 (1993 version) using dumbbell-shaped No. 4 type test pieces under the conditions of a tensile speed of 500 mm / min and 23 ° C.

Example 1
100 parts by weight of 2-chloro-1,3-butadiene and 0.300 parts by weight of n-dodecyl mercaptan were charged into a 10 L autoclave equipped with a stirrer, and 5 parts by weight of potassium rosinate and formaldehyde condensate of sodium naphthalenesulfonate 0.7 An emulsified liquid consisting of parts by weight, 0.6 part by weight of sodium hydroxide and 90 parts by weight of distilled water was added thereto, and after sufficiently purging with nitrogen, the mixture was emulsified by stirring. A 3% by weight aqueous sodium hydrosulfite solution was added, and polymerization was started by continuous dropwise addition of a 0.2% by weight aqueous potassium persulfate solution while controlling the jacket temperature so that the inside of the polymerization vessel was kept constant at 40 ° C.

  When the conversion rate with respect to the monomer reached 99%, 0.03 part by weight of phenothiazine was dissolved in toluene and emulsified with an aqueous sodium dodecylbenzenesulfonate solution as a polymerization terminator to complete the polymerization. The remaining unreacted monomer was removed by a vacuum steam stripping method to obtain a polymer latex of a chloroprene homopolymer.

  On the other hand, hydrotalcite (DHT-6 (unfired product) manufactured by Kyowa Chemical Industry Co., Ltd.), zinc oxide, sulfur, vulcanization accelerator CA (N, N'-diphenylthiourea), vulcanization accelerator ZnEDC (diethyldithiocarbamine) Each zinc oxide) was mixed with 100 parts by weight, 3 parts by weight of ammonium casein, 3 parts by weight of formalin condensate of sodium naphthalenesulfonate, and 100 parts by weight of distilled water, and stirred for 1 day in a ball mill. A stable suspension of the agent was made.

  A suspension of each compounding agent was added to the chloroprene polymer latex so as to have the composition shown in Table 1, and the mixture was stirred for 1 hour to prepare a chloroprene polymer latex composition. The solid content and viscosity of the latex composition are shown in Table 1.

  A rubber plate was agglomerated and formed on the flat plate by dipping the flat plate mold dipped in a 25% calcium nitrate aqueous solution and dried in the chloroprene polymer latex composition. Immerse it in 30 ° C warm water together with the mold to elute water-soluble impurities, heat it in a hot air dryer at 120 ° C for 30 and 50 minutes, dry and vulcanize it, and vulcanized rubber with a thickness of about 0.25mm A sheet was obtained. The normal physical properties of the vulcanizate were measured. The vulcanizate properties are shown in Table 1.

加硫密度が高く、破断強度およびモジュラスが高い優れたゴム物性を有する加硫物が得られた。

A vulcanized product having a high vulcanization density and excellent rubber properties with high breaking strength and modulus was obtained.

Example 2
A chloroprene homopolymer polymer latex prepared in the same manner as in Example 1 and the suspension of each compounding agent were blended so as to have the composition shown in Table 1 to prepare a chloroprene polymer latex composition. The solid content and viscosity of the latex composition are shown in Table 1.

  Further, a vulcanized rubber sheet was prepared in the same manner as in Example 1, and the normal physical properties of the vulcanized product were measured. The vulcanizate properties are shown in Table 1.

  A vulcanized product having a high vulcanization density and excellent rubber properties with high breaking strength and modulus was obtained.

Example 3
Except for 95 parts by weight of 2-chloro-1,3-butadiene, 5 parts by weight of 2,3-dichloro-1,3-butadiene, 0.320 parts by weight of n-dodecyl mercaptan, and a polymerization termination conversion rate of 96%. A chloroprene polymer latex was prepared in the same manner as in Example 1. A suspension of each compounding agent prepared in the same manner as in Example 1 was compounded so as to have the composition described in Table 1 to prepare a chloroprene polymer latex composition. The solid content and viscosity of the latex composition are shown in Table 1.

  Further, a vulcanized rubber sheet was prepared in the same manner as in Example 1, and the normal physical properties of the vulcanized product were measured. The vulcanizate properties are shown in Table 1.

  A vulcanized product having a high vulcanization density and excellent rubber properties with high breaking strength and modulus was obtained.

Example 4
A chloroprene polymer latex prepared in the same manner as in Example 3 and a suspension of each compounding agent prepared in the same manner as in Example 1 were blended so as to have the composition shown in Table 1 to prepare a chloroprene polymer latex composition. The solid content and viscosity of the latex composition are shown in Table 1.

  Further, a vulcanized rubber sheet was prepared in the same manner as in Example 1, and the normal physical properties of the vulcanized product were measured. The vulcanizate properties are shown in Table 1.

  A vulcanized product having a high vulcanization density and excellent rubber properties with high breaking strength and modulus was obtained.

Example 5
A polymer latex of a chloroprene homopolymer was prepared in the same manner as in Example 1 except that 0.250 parts by weight of n-dodecyl mercaptan was used, the polymerization temperature was 35 ° C., and the polymerization termination conversion was 90%. A suspension of each compounding agent prepared in the same manner as in Example 1 was compounded so as to have the composition described in Table 1 to prepare a chloroprene polymer latex composition. The solid content and viscosity of the latex composition are shown in Table 1.

  Further, a vulcanized rubber sheet was prepared in the same manner as in Example 1, and the normal physical properties of the vulcanized product were measured. The vulcanizate properties are shown in Table 1.

  A vulcanized product having a high vulcanization density and excellent rubber properties with high breaking strength and modulus was obtained.

Example 6
A chloroprene homopolymer polymer latex was prepared in the same manner as in Example 5. A suspension of each compounding agent prepared in the same manner as in Example 1 was compounded so as to have the composition described in Table 1 to prepare a chloroprene polymer latex composition. The solid content and viscosity of the latex composition are shown in Table 1.

  Further, a vulcanized rubber sheet was prepared in the same manner as in Example 1, and the normal physical properties of the vulcanized product were measured. The vulcanizate properties are shown in Table 1.

  A vulcanized product having a high vulcanization density and excellent rubber properties with high breaking strength and modulus was obtained.

Comparative Example 1
A chloroprene homopolymer latex prepared in the same manner as in Example 1 and a suspension of each compounding agent were blended so as to have the composition shown in Table 2 to prepare a chloroprene polymer latex composition. Table 2 shows the solid content and viscosity of the latex composition.

  Further, a vulcanized rubber sheet was prepared in the same manner as in Example 1, and the normal physical properties of the vulcanized product were measured. The vulcanizate properties are shown in Table 2.

実施例ではハイドロタルサイトが担っていた高活性の受酸剤として機能する化合物が存在しないため、加硫密度が低く、破断強度およびモジュラスの低い加硫物となってしまった。

In the examples, since there was no compound functioning as a highly active acid acceptor carried by hydrotalcite, the vulcanization density was low, and the vulcanizate had a low breaking strength and a low modulus.

Comparative Example 2
A chloroprene homopolymer latex prepared in the same manner as in Example 1 and a suspension of each compounding agent were blended so as to have the composition shown in Table 2 to prepare a chloroprene polymer latex composition. Table 2 shows the solid content and viscosity of the latex composition.

  Further, a vulcanized rubber sheet was prepared in the same manner as in Example 1, and the normal physical properties of the vulcanized product were measured. The vulcanizate properties are shown in Table 2.

  In the examples, there is no compound that functions as a highly active acid acceptor that hydrotalcite was responsible for, so even if the vulcanization accelerator is increased, the vulcanization density is low, the breaking strength and modulus are low, and the elongation at break is further increased. Became a low vulcanizate.

Comparative Example 3
A chloroprene homopolymer latex prepared in the same manner as in Example 1 and a suspension of each compounding agent were blended so as to have the composition shown in Table 2 to prepare a chloroprene polymer latex composition. Table 2 shows the solid content and viscosity of the latex composition.

  Further, a vulcanized rubber sheet was prepared in the same manner as in Example 1, and the normal physical properties of the vulcanized product were measured. The vulcanizate properties are shown in Table 2.

  Since the hydrotalcite content was lower than in the examples, the function as an acid acceptor was insufficient, the vulcanization density was low, the breaking strength and modulus were low, and the rupture elongation was low.

Comparative Example 4
A chloroprene homopolymer latex prepared in the same manner as in Example 1 and a suspension of each compounding agent were blended so as to have the composition shown in Table 2 to prepare a chloroprene polymer latex composition. Table 2 shows the solid content and viscosity of the latex composition.

  Since a large amount of hydrotalcite was contained, the viscosity of the latex composition became very high, and a uniform rubber film could not be formed by immersion molding, and physical properties of vulcanized rubber could not be measured.

Comparative Example 5
A chloroprene polymer latex prepared in the same manner as in Example 3 and a suspension of each compounding agent prepared in the same manner as in Example 1 were blended so as to have the composition shown in Table 2 to prepare a chloroprene polymer latex composition. Table 2 shows the solid content and viscosity of the latex composition.

  Further, a vulcanized rubber sheet was prepared in the same manner as in Example 1, and the normal physical properties of the vulcanized product were measured. The vulcanizate properties are shown in Table 2.

  In the examples, there is no compound that functions as a highly active acid acceptor that hydrotalcite was responsible for, so even if the amount of zinc oxide and vulcanization accelerator is increased, the vulcanization density is low, the breaking strength and modulus are low, Furthermore, it became a vulcanizate having low elongation at break.

Claims (3)

A chloroprene polymer latex composition for producing vulcanized rubber, comprising 2 to 20 parts by weight of hydrotalcite with respect to 100 parts by weight of chloroprene polymer. The method for producing a chloroprene polymer latex composition for vulcanized rubber production according to claim 1, wherein a suspension containing hydrotalcite is added to the chloroprene polymer latex. The chloroprene polymer latex composition for producing vulcanized rubber according to claim 1, wherein the vulcanized rubber is produced by immersion molding.