阅读说明：本技术 氯丁二烯共聚物胶乳组合物和其成型物 (Chloroprene copolymer latex composition and molded article thereof ) 是由 村田智映 尾川展子 上条正直 于 2018-09-26 设计创作，主要内容包括：本发明提供即使是在比以往温和的条件下进行硫化成型,也可以得到具有优异的机械特性和柔软性的成型物的氯丁二烯共聚物胶乳组合物。一种氯丁二烯共聚物胶乳组合物,含有氯丁二烯共聚物胶乳(A)、金属氧化物(B)、硫化促进剂(C)和抗氧化剂(D),所述氯丁二烯共聚物胶乳(A)含有氯丁二烯共聚物的粒子,所述氯丁二烯共聚物是氯丁二烯(A-1)、2,3-二氯-1,3-丁二烯(A-2)和硫(A-3)的共聚物,所述氯丁二烯共聚物中的所述硫(A-3)的含量,在将所述氯丁二烯(A-1)和所述2,3-二氯-1,3-丁二烯(A-2)的合计量设为100质量份时是0.1质量份以上且1.0质量份以下。(The invention provides a chloroprene copolymer latex composition which can obtain a molded product with excellent mechanical properties and flexibility even if vulcanization molding is carried out under milder conditions than the conventional conditions. A chloroprene copolymer latex composition comprising a chloroprene copolymer latex (A) comprising particles of a chloroprene copolymer, wherein the chloroprene copolymer is a copolymer of chloroprene (A-1), 2, 3-dichloro-1, 3-butadiene (A-2) and sulfur (A-3), a metal oxide (B), a vulcanization accelerator (C), and an antioxidant (D), and wherein the content of the sulfur (A-3) in the chloroprene copolymer is 0.1 to 1.0 parts by mass, based on 100 parts by mass of the total amount of the chloroprene (A-1) and the 2, 3-dichloro-1, 3-butadiene (A-2).)

1. A chloroprene copolymer latex composition comprising a chloroprene copolymer latex (A), a metal oxide (B), a vulcanization accelerator (C) and an antioxidant (D),

the chloroprene copolymer latex (A) contains particles of a chloroprene copolymer which is a copolymer of chloroprene (A-1), 2, 3-dichloro-1, 3-butadiene (A-2) and sulfur (A-3),

the content of the sulfur (A-3) in the chloroprene copolymer is 0.1 to 1.0 part by mass, based on 100 parts by mass of the total amount of the chloroprene (A-1) and the 2, 3-dichloro-1, 3-butadiene (A-2).

2. The chloroprene copolymer latex composition according to claim 1, wherein the copolymerization ratio of chloroprene (A-1) and 2, 3-dichloro-1, 3-butadiene (A-2) in the chloroprene copolymer is 76 mass% or more and 93 mass% or less of chloroprene (A-1) and 24 mass% or less and 7 mass% or more of 2, 3-dichloro-1, 3-butadiene (A-2) when the total amount of chloroprene (A-1) and 2, 3-dichloro-1, 3-butadiene (A-2) is 100 mass%.

3. The chloroprene copolymer latex composition according to claim 1 or 2, wherein the amount of the metal oxide (B) is 1 part by mass or more and 10 parts by mass or less, the amount of the vulcanization accelerator (C) is 0.1 part by mass or more and 5 parts by mass or less, and the amount of the antioxidant (D) is 0.1 part by mass or more and 5 parts by mass or less, based on 100 parts by mass of the solid content in the chloroprene copolymer latex (a).

4. A molded article comprising the chloroprene copolymer latex composition according to any one of claims 1 to 3, wherein the 300% modulus of elasticity is 0.5MPa or more and 1.6MPa or less, the tensile strength is 18MPa or more, and the tensile elongation at break is 800% or more.

5. A shaped article according to claim 4, which is an impregnated article.

6. A shaped article according to claim 5, which is a glove.

7. The shaped article according to claim 5, which is a disposable glove for medical use.

Technical Field

The present invention relates to a chloroprene copolymer latex composition and a molded article thereof.

Background

Chloroprene rubber, which has flexibility and mechanical properties close to those of natural rubber and is relatively economical, has been used as a material for medical disposable gloves, particularly surgical gloves. However, conventional chloroprene rubbers and polymers have insufficient structure, and therefore, high-temperature or long-time vulcanization is required to obtain a vulcanized rubber having a desired strength. Therefore, when a dipped product such as a glove is produced by a dipping process using a chloroprene rubber latex, the production efficiency is low and the energy cost required for the production is large.

It is known that sulfur-modified chloroprene rubber obtained by copolymerizing chloroprene rubber with sulfur has a high vulcanization rate, but if a dipped product is produced using a sulfur-modified chloroprene rubber latex, there is a problem that it is difficult to obtain flexibility required for surgical gloves. Further, the sulfur-modified chloroprene rubber latex has a problem that it is difficult to use industrially because it has insufficient storage stability.

For example, patent document 1 discloses a technique for improving the storage stability of a chloroprene rubber latex, and patent documents 2 and 3 disclose a technique for improving the mechanical properties and flexibility of a chloroprene rubber, but the reduction of the temperature conditions and the treatment time conditions in the vulcanization step (crosslinking step) is not sufficient, and a high temperature or a long time is required in the vulcanization step.

Documents of the prior art

Patent document

Patent document 1 Japanese patent application laid-open No. 04238686

Patent document 2 Japanese patent laid-open publication No. 218225 of 2015

Patent document 3 Japanese patent laid-open publication No. 106994 No. 2007

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made to solve the problems of the prior art described above, and an object of the present invention is to provide a chloroprene copolymer latex composition which can give a molded article having excellent mechanical properties and flexibility even when molded by vulcanization under milder conditions than those of the prior art. Further, the present invention has an object to provide a molded article having excellent mechanical properties and flexibility, which is molded from the chloroprene copolymer latex composition.

Means for solving the problems

To solve the above problems, the present invention has the following aspects [1] to [7].

[1] A chloroprene copolymer latex composition comprising a chloroprene copolymer latex (A), a metal oxide (B), a vulcanization accelerator (C) and an antioxidant (D),

the chloroprene copolymer latex (A) contains particles of a chloroprene copolymer which is a copolymer of chloroprene (A-1), 2, 3-dichloro-1, 3-butadiene (A-2) and sulfur (A-3),

the content of the sulfur (A-3) in the chloroprene copolymer is 0.1 to 1.0 part by mass, based on 100 parts by mass of the total amount of the chloroprene (A-1) and the 2, 3-dichloro-1, 3-butadiene (A-2).

[2] The chloroprene copolymer latex composition according to [1], wherein the copolymerization ratio of the chloroprene (A-1) and the 2, 3-dichloro-1, 3-butadiene (A-2) in the chloroprene copolymer is 76 mass% or more and 93 mass% or less of the chloroprene (A-1) and 24 mass% or less and 7 mass% or more of the 2, 3-dichloro-1, 3-butadiene (A-2) when the total amount of the chloroprene (A-1) and the 2, 3-dichloro-1, 3-butadiene (A-2) is 100 mass%.

[3] The chloroprene copolymer latex composition according to [1] or [2], wherein the amount of the metal oxide (B) is 1 part by mass or more and 10 parts by mass or less, the amount of the vulcanization accelerator (C) is 0.1 part by mass or more and 5 parts by mass or less, and the amount of the antioxidant (D) is 0.1 part by mass or more and 5 parts by mass or less, assuming that the amount of solid components in the chloroprene copolymer latex (a) is 100 parts by mass.

[4] A molded article of the chloroprene copolymer latex composition according to any one of [1] to [3], which has a 300% modulus of elasticity of 0.5MPa or more and 1.6MPa or less, a tensile strength of 18MPa or more, and a tensile elongation at break of 800% or more.

[5] The shaped article according to [4], which is an impregnated article.

[6] The shaped article according to [5], which is a glove.

[7] The shaped article according to [5], which is a disposable glove for medical use.

Effects of the invention

The chloroprene copolymer latex composition of the present invention can give a molded article having excellent mechanical properties and flexibility even when vulcanization molding is carried out under milder conditions than in the conventional cases. In addition, the molded article of the present invention has excellent mechanical properties and flexibility.

Detailed Description

An embodiment of the present invention will be described below. The chloroprene copolymer latex composition of the present embodiment contains a chloroprene copolymer latex (a), a metal oxide (B), a vulcanization accelerator (C), and an antioxidant (D). The chloroprene copolymer latex (A) contains particles of a chloroprene copolymer which is a copolymer of chloroprene (A-1), 2, 3-dichloro-1, 3-butadiene (A-2) and sulfur (A-3).

The content of sulfur (A-3) in the chloroprene copolymer is 0.1 to 1.0 part by mass, based on 100 parts by mass of the total amount of the chloroprene (A-1) and the 2, 3-dichloro-1, 3-butadiene (A-2). When the content of sulfur (A-3) is 0.1 parts by mass or more, the chloroprene copolymer latex composition is excellent in crosslinking reactivity, and therefore, a molded article having excellent mechanical properties and flexibility can be obtained even when vulcanization molding is performed under milder conditions than in the past (for example, at a lower temperature and/or for a shorter processing time than in the past). Further, if the content of sulfur (A-3) is 1.0 part by mass or less, the polymerization conversion can be improved without inhibiting the polymerization reaction among chloroprene (A-1), 2, 3-dichloro-1, 3-butadiene (A-2), and sulfur (A-3). In order to further enhance such effects, the content of sulfur (a-3) in the chloroprene copolymer is more preferably 0.2 parts by mass or more and 0.4 parts by mass or less, assuming that the total amount of chloroprene (a-1) and 2, 3-dichloro-1, 3-butadiene (a-2) is 100 parts by mass.

The content of the tetrahydrofuran-insoluble matter in the chloroprene copolymer may be 50 mass% or more and 85 mass% or less.

Further, when the amount of solid components in the chloroprene copolymer latex (a) is 100 parts by mass, the amount of the metal oxide (B) in the chloroprene copolymer latex composition of the present embodiment may be 1 part by mass or more and 10 parts by mass or less, the amount of the vulcanization accelerator (C) may be 0.1 part by mass or more and 5 parts by mass or less, and the amount of the antioxidant (D) may be 0.1 part by mass or more and 5 parts by mass or less.

In the chloroprene copolymer latex composition of the present embodiment, if the content of the tetrahydrofuran insoluble content in the chloroprene copolymer is controlled as described above, the following effects can be enhanced: even when the chloroprene copolymer latex composition of the present embodiment is subjected to vulcanization molding under milder conditions than in the past (for example, at a lower temperature and/or for a shorter processing time than in the past), a molded article having excellent mechanical properties and flexibility can be obtained.

When the chloroprene copolymer latex composition of the present embodiment is used, the heat energy required for vulcanization can be reduced, and therefore a molded product of a chloroprene copolymer can be economically produced with high productivity.

Further, the chloroprene copolymer latex composition of the present embodiment can give a molded article having excellent flexibility because 2, 3-dichloro-1, 3-butadiene is blended as a copolymerization component of the chloroprene copolymer.

When the chloroprene copolymer latex composition of the present embodiment is molded, a molded article having a 300% elastic modulus (elastic modulus at 300% elongation) of 0.5MPa or more and 1.6MPa or less, a tensile strength of 18MPa or more, and a tensile elongation at break of 800% or more can be obtained.

In addition, a dipped product can be obtained by molding the chloroprene copolymer latex composition of the present embodiment by a dipping process. Examples of the molded article obtained by the dipping process include gloves, balloons, sphygmomanometer cuffs, and rubber threads. An example of the glove is a medical disposable glove.

The chloroprene copolymer latex composition of the present embodiment and a molded article thereof will be described in more detail below. The present embodiment is merely an example of the present invention, and the present invention is not limited to the present embodiment. Various changes and modifications may be made to the present embodiment, and the modified or modified form is also within the scope of the present invention.

[1] chloroprene (A-1)

Chloroprene, which is a main raw material monomer of the chloroprene copolymer and is one of the components of the chloroprene copolymer latex composition of the present embodiment, is a compound called 2-chloro-1, 3-butadiene or 2-chloroprene.

[2] chloroprene copolymer and chloroprene copolymer latex (A)

The chloroprene copolymer which is one of the components of the chloroprene copolymer latex composition of the present embodiment is a copolymer of chloroprene (a-1), 2, 3-dichloro-1, 3-butadiene (a-2), and sulfur (a-3). The copolymerization properties of 2, 3-dichloro-1, 3-butadiene (A-2) and chloroprene (A-1) are good, and the properties such as the resistance to crystallization and, in turn, the flexibility of the chloroprene copolymer can be easily adjusted by changing the copolymerization ratio.

The copolymerization ratio of chloroprene (a-1) and 2, 3-dichloro-1, 3-butadiene (a-2) in the chloroprene copolymer is not particularly limited, and when the total amount of chloroprene (a-1) and 2, 3-dichloro-1, 3-butadiene (a-2) is 100 mass%, chloroprene (a-1) may be 76 mass% or more and 93 mass% or less, and 2, 3-dichloro-1, 3-butadiene (a-2) may be 24 mass% or less and 7 mass% or more.

If the ratio of 2, 3-dichloro-1, 3-butadiene (a-2) is 7 mass% or more, the stability of the chloroprene copolymer with time becomes good, and if it is 24 mass% or less, the crystallization of the chloroprene copolymer can be suppressed and the flexibility becomes good. In order to further enhance such an effect, the ratio of 2, 3-dichloro-1, 3-butadiene (a-2) is more preferably 15 mass% or less and 10 mass% or more.

The chloroprene copolymer may be copolymerized with "another monomer (A-4)" other than chlorobutadiene (A-1), 2, 3-dichloro-1, 3-butadiene (A-2) and sulfur (A-3) within a range not to impair the object of the present invention. Examples of the other monomer (A-4) include 1-chloro-1, 3-butadiene, isobutylene, styrene, acrylonitrile, acrylic acid and ester compounds thereof, and methacrylic acid and ester compounds thereof. As the other monomer (A-4), 1 kind may be used alone, or 2 or more kinds may be used in combination.

The amount of the other monomer (A-4) used is not particularly limited, and may be in the range of 0.1 to 10 parts by mass based on 100 parts by mass of the total of chloroprene (A-1) and 2, 3-dichloro-1, 3-butadiene (A-2). When the amount is 10 parts by mass or less, not only the tensile strength and tensile elongation at break of the chloroprene copolymer are improved, but also the stability with time of flexibility can be maintained well.

The polymerization method of the chloroprene copolymer is not particularly limited, and emulsion polymerization can be employed, and aqueous emulsion polymerization is industrially preferred. Chloroprene copolymer latex (a) in which particles of a chloroprene copolymer are dispersed in water can be obtained by emulsion polymerization of chloroprene (a-1), 2, 3-dichloro-1, 3-butadiene (a-2), and sulfur (a-3). The chloroprene copolymer latex (a) obtained contains an emulsifier. As the emulsifier for emulsion polymerization, a common rosin acid soap is used in view of easiness of the coagulation operation. In particular, sodium salt and/or potassium salt of disproportionated rosin acid is preferable from the viewpoint of coloring stability.

The amount of the emulsifier containing rosin acid soap used in the chloroprene copolymer latex (a) is preferably 3 to 8 parts by mass, assuming that the total amount of all monomers such as chloroprene (a-1), 2, 3-dichloro-1, 3-butadiene (a-2), sulfur (a-3), and other monomer (a-4) is 100 parts by mass. If the amount is 3 parts by mass or more, not only emulsification failure is unlikely to occur, but also heat generation due to polymerization can be suppressed, and problems such as generation of aggregates and poor product appearance are unlikely to occur. On the other hand, if the amount is 8 parts by mass or less, an emulsifier such as rosin acid is less likely to remain in the chloroprene copolymer, and thus the adhesion to the chloroprene copolymer is less likely to occur. Therefore, deterioration in processability and workability due to adhesion of the chloroprene copolymer latex composition to a mold (former) at the time of molding, adhesion at the time of use of a molded article, and the like is less likely to occur, and deterioration in color tone of the molded article is less likely to occur.

As the polymerization initiator, a general radical polymerization initiator can be used. For example, in the case of emulsion polymerization, organic or inorganic peroxides such as benzoyl peroxide, potassium persulfate, ammonium persulfate, cumyl hydroperoxide and t-butyl hydroperoxide, and azo compounds such as azobisisobutyronitrile are used. The polymerization initiator may be used alone in 1 kind or in combination of 2 or more kinds.

In the polymerization of the chloroprene copolymer, a co-catalyst may be used as needed together with a polymerization initiator. The cocatalyst which can be used together with the polymerization initiator is not particularly limited, and a usual cocatalyst can be used. For example anthraquinone sulfonates, potassium sulfite, sodium metabisulfite, sodium sulfite, tetraethylenepentamine, N-dimethyl-p-toluidine. The cocatalyst may be used alone in 1 kind or in combination of 2 or more kinds.

In general, in the production of a chloroprene polymer, a polymerization inhibitor is added to stop a polymerization reaction when a predetermined polymerization rate is reached in order to obtain a polymer having a desired molecular weight and molecular weight distribution. In this embodiment, a polymerization inhibitor may also be used. The type of the polymerization inhibitor is not particularly limited, and commonly used polymerization inhibitors such as phenothiazine, p-tert-butylcatechol, hydroquinone monomethyl ether, and diethylhydroxylamine can be used. The polymerization inhibitor may be used alone in 1 kind or in combination of 2 or more kinds.

In addition, chloroprene polymers are generally susceptible to degradation by oxygen. Therefore, a stabilizer such as an oxygen acceptor or an antioxidant may be added to the chloroprene copolymer latex (a) within a range not to impair the object of the present invention.

The polymerization conversion rate in the polymerization of the chloroprene copolymer is not particularly limited, but is preferably 95% or more, and more preferably 98% or more. If the polymerization conversion is 95% or more, the unreacted sulfur (A-3) is small, and thus the physical properties of the molded article are not likely to change. Further, if the amount of unreacted sulfur (a-3) is small, the storage stability of the chloroprene copolymer latex (a) becomes excellent, and as a result, the storage stability of the chloroprene copolymer latex composition becomes excellent.

[3] the content of tetrahydrofuran-insoluble matter in the chloroprene copolymer

The content of the tetrahydrofuran-insoluble matter in the chloroprene copolymer is 50 to 85 mass%. The content of tetrahydrofuran-insoluble matter is controlled by the content of sulfur (A-3) and the polymerization conversion. When the content of the tetrahydrofuran insoluble matter is 50% by mass or more, the tensile strength of a molded product of the chloroprene copolymer latex composition becomes high, and the chloroprene copolymer latex composition is less likely to cause adhesion of the chloroprene copolymer to a mold during molding and is likely to be peeled off.

On the other hand, if the content of the tetrahydrofuran insoluble matter in the chloroprene copolymer is 85 mass% or less, the chloroprene copolymer becomes strong and tough, and the molded article is excellent in flexibility, tensile strength, and tensile elongation at break.

In order to further enhance the effect, the content of the tetrahydrofuran insoluble matter in the chloroprene copolymer is preferably 60 mass% or more and 85 mass% or less.

[4] A chloroprene copolymer latex composition

The chloroprene copolymer latex composition of the present embodiment contains at least a chloroprene copolymer latex (a), a metal oxide (B), a vulcanization accelerator (C), and an antioxidant (D). The chloroprene copolymer latex composition containing the metal oxide (B), the vulcanization accelerator (C) and the antioxidant (D) can form a molded article having sufficient tensile strength and flexibility. The component insoluble in water among the metal oxide (B), the vulcanization accelerator (C) and the antioxidant (D), or the component for destabilizing the colloidal state of the chloroprene copolymer latex (a) may be dispersed in water in advance to prepare a dispersion, and the dispersion may be mixed with the chloroprene copolymer latex (a).

The amounts of the metal oxide (B), the vulcanization accelerator (C), and the antioxidant (D) contained in the chloroprene copolymer latex composition of the present embodiment are as follows. That is, the amount of the metal oxide (B) contained in the chloroprene copolymer latex composition of the present embodiment is 1 to 10 parts by mass, the amount of the vulcanization accelerator (C) is 0.1 to 5 parts by mass, and the amount of the antioxidant (D) is 0.1 to 5 parts by mass, assuming that the amount of solid components in the chloroprene copolymer latex (a) is 100 parts by mass.

The kind of the metal oxide (B) is not particularly limited, and for example, zinc oxide, lead oxide, and lead tetraoxide can be used, and zinc oxide is particularly preferable. The metal oxide (B) may be used alone in 1 kind or in combination of 2 or more kinds.

The amount of the metal oxide (B) contained in the chloroprene copolymer latex composition of the present embodiment is 1 to 10 parts by mass based on 100 parts by mass of the solid content in the chloroprene copolymer latex (a), and if the amount of the metal oxide (B) is within this range, an appropriate crosslinking rate can be obtained, and insufficient crosslinking or scorching is unlikely to occur. Further, since the chloroprene copolymer latex composition is stabilized in a colloidal state, problems such as precipitation are less likely to occur.

The type of the vulcanization accelerator (C) is not particularly limited, and those generally used for vulcanization of chloroprene type polymer latex can be used. Examples thereof include thiuram-based, dithiourethane-based, thiourea-based, and guanidine-based vulcanization accelerators.

Examples of the thiuram-based vulcanization accelerator include tetraethylthiuram disulfide and tetrabutylthiuram disulfide. Examples of the dithiocarbamate vulcanization accelerator include sodium dibutyldithiocarbamate, zinc diethyldithiocarbamate, and the like. Examples of the thiourea-based vulcanization accelerator include ethylene thiourea, diethyl thiourea, trimethyl thiourea, and N, N' -diphenyl thiourea (DPTU). Examples of the guanidine-based vulcanization accelerator include Diphenylguanidine (DPG), di-o-tolylguanidine, and the like. The vulcanization accelerator (C) may be used alone in 1 kind or in combination of 2 or more kinds.

The amount of the vulcanization accelerator (C) contained in the chloroprene copolymer latex composition of the present embodiment is 0.1 to 5 parts by mass based on 100 parts by mass of the solid content in the chloroprene copolymer latex (a), and if the amount of the vulcanization accelerator (C) is within this range, an appropriate crosslinking rate can be obtained, and insufficient crosslinking or scorching is unlikely to occur. In addition, since the chloroprene copolymer latex composition of the present embodiment has a suitable crosslink density in a molded product, it is possible to impart suitable flexibility to the molded product. In order to further enhance such effects, the amount of the vulcanization accelerator (C) is more preferably 0.5 to 1.5 parts by mass.

The type of the antioxidant (D) is not particularly limited, and when high heat resistance is required, it is preferable to use an antioxidant for preventing heat aging and an antioxidant for preventing ozone aging in combination.

Examples of the antioxidant for preventing thermal aging include diphenylamine-based antioxidants such as octylated diphenylamine, p- (p-toluene-sulfonamide) diphenylamine and 4, 4' -bis (. alpha.,. alpha. -dimethylbenzyl) diphenylamine. Such an antioxidant can impart not only heat resistance but also stain resistance (discoloration inhibition and the like).

Examples of the antioxidant for preventing ozone-induced aging include N, N '-diphenyl-p-phenylenediamine (DPPD) and N-isopropyl-N' -phenyl-p-phenylenediamine (IPPD).

However, when the molded product of the chloroprene copolymer latex composition of the present embodiment is used as, for example, a medical glove, it is preferable to use a hindered phenol-based antioxidant as the antioxidant (D) because the appearance (particularly color tone) and hygienic properties of the molded product are important.

The amount of the antioxidant (D) contained in the chloroprene copolymer latex composition of the present embodiment is 0.1 part by mass or more and 5 parts by mass or less based on 100 parts by mass of the solid content in the chloroprene copolymer latex (a), and if the amount of the antioxidant (D) is within this range, a sufficient oxidation preventing effect can be obtained, and inhibition of crosslinking and deterioration of color tone are less likely to occur.

In the chloroprene copolymer latex composition of the present embodiment, additives may be added as necessary in addition to the chloroprene copolymer latex (a), the metal oxide (B), the vulcanization accelerator (C), and the antioxidant (D) within a range not to impair the object of the present invention. Examples of additives that can be blended include pH adjusters, fillers, pigments, colorants, antifoaming agents, and thickeners.

[5] A method for producing a molded article of a chloroprene copolymer latex composition

The chloroprene copolymer latex composition of the present embodiment can be molded to obtain a molded article, and for example, a dipped product can be obtained by molding by a dipping method. For example, a mold is dipped in the chloroprene copolymer latex composition of the present embodiment, the chloroprene copolymer is coagulated on the mold surface, and then the steps of leaching (removal of water-soluble impurities), drying, and vulcanization (crosslinking) are sequentially performed to obtain a film-shaped molded product.

The vulcanization temperature (crosslinking temperature) in the vulcanization step (crosslinking step) is required to be higher than that of the natural rubber (120 to 140 ℃) in comparison with the conventional chloroprene type polymer latex, but the chloroprene copolymer latex composition of the present embodiment may be lower than the conventional one. Therefore, the molded product can be produced at a lower energy cost than in the past.

For example, the vulcanization temperature (crosslinking temperature) in the vulcanization step (crosslinking step) may be set to 100 ℃ to 110 ℃. The vulcanization time (crosslinking time) at the vulcanization temperature (crosslinking temperature) may be set to, for example, 20 minutes or more and 60 minutes or less, but is preferably sufficiently performed within a range in which the tensile strength and the tensile elongation at break of the molded product are not deteriorated. In order to avoid problems in appearance of the molded article, such as generation of blisters and pinholes, the molded article may be preliminarily dried at a relatively low temperature of 70 ℃ to 100 ℃ before the vulcanization step (crosslinking step).

As described above, a molded article having a 300% modulus of elasticity of 0.5MPa or more and 1.6MPa or less, a tensile strength of 18MPa or more (more preferably 20MPa or more), and a tensile elongation at break of 800% or more can be obtained. The 300% elastic modulus is an index of flexibility, and a smaller value indicates a higher flexibility. The molded article obtained by molding the chloroprene copolymer latex composition of the present embodiment has excellent flexibility.

Examples

The present invention will be described in more detail below by way of examples and comparative examples.

[ example 1]

(1) Preparation of chloroprene copolymer latex (A)

Chloroprene 1355g, 2, 3-dichloro-1, 3-butadiene 145g, sulfur 3.8g, purified water 1290g, abietic acid (rosin HTR available from seikagawa chemical corporation) 36g, potassium hydroxide 57.8g, sodium hydroxide 29.7g, sodium salt of β -naphthalenesulfonic acid-formaldehyde condensate 15g, and copper sulfate 11.7mg were put into a reactor having an internal volume of 5L, and emulsified to convert abietic acid into rosin soap.

Chloroprene, 2, 3-dichloro-1, 3-butadiene, and sulfur were added as raw material monomers, and pure water was added as a dispersion medium for emulsion polymerization. In addition, abietic acid, potassium hydroxide and sodium hydroxide are used as raw materials of an emulsifier, sodium salt of a beta-naphthalenesulfonic acid-formaldehyde condensate is used as the emulsifier, and copper sulfate is used as a cocatalyst for emulsion polymerization.

To the emulsion was added 4g of potassium persulfate as a polymerization initiator, and emulsion polymerization was carried out at 40 ℃ for 5 hours in a nitrogen atmosphere. The temperature was then raised to 45 ℃ to continue the polymerization for 1 hour. And the polymerization was stopped after 6 hours in total from the start of the polymerization. Subsequently, unreacted chloroprene and 2, 3-dichloro-1, 3-butadiene were distilled off with steam to obtain a chloroprene copolymer latex (a).

The polymerization conversion was calculated as follows. The polymerized emulsion was collected and dried at 141 ℃ for 30 minutes to obtain a dry solid. The polymerization conversion rate was calculated by substituting the following equation with the value obtained by subtracting the mass of the solid other than the polymer from the mass of the dried solid, which was taken as the "amount of the chloroprene copolymer produced". The mass of solid components other than the polymer was calculated by determining the components which did not volatilize at 141 ℃ among the various components used in the emulsion polymerization. The calculated polymerization conversion is shown in Table 1.

Polymerization conversion [% ] [ (amount of produced chloroprene copolymer)/(total feed mass of all monomers) ] × 100

The solid content concentration of the chloroprene copolymer latex (a) was calculated as follows. The chloroprene copolymer latex (A) was dried at 100 ℃ for 2 hours to obtain a dry solid. Then, the mass of the dried solid was measured, and the solid content concentration was calculated from the ratio of the measured mass to the mass of the chloroprene copolymer latex (a) before drying (see the following formula).

Solid content concentration [% by mass ] - [ (mass after drying)/(mass before drying) ] × 100

Further, the respective contents of a chloroprene-derived site, a 2, 3-dichloro-1, 3-butadiene-derived site, and sulfur in the resulting chloroprene copolymer were calculated from the polymerization conversion. The calculation method is explained below, and table 1 shows the calculation results.

2, 3-dichloro-1, 3-butadiene (A-2) is substantially consumed at the initial stage of polymerization to polymerize the same. Further, sulfur (A-3) does not volatilize and remains in the polymer even if it is unreacted. Therefore, since the unreacted monomer contributing to the polymerization conversion rate is only chloroprene (a-1), the content of each component in the chloroprene copolymer can be approximated by the following formula.

[ content (parts by mass) of a site derived from 2, 3-dichloro-1, 3-butadiene (a-2) ] which is the total amount of the site derived from chloroprene (a-1) and the site derived from 2, 3-dichloro-1, 3-butadiene (a-2) in the chloroprene copolymer is taken as 100 parts by mass ] - [ feed amount (parts by mass) of 2, 3-dichloro-1, 3-butadiene (a-2) ]/[ polymerization conversion (%) ] x 100 [ ]

The physical properties of the resulting chloroprene copolymer latex (a) were evaluated, assuming that the total amount of the chloroprene copolymer-derived site (a-1) and the 2, 3-dichloro-1, 3-butadiene-derived site (a-2) was 100 parts by mass, as the content (parts by mass) of sulfur (a-3) — (the amount of sulfur (a-3) fed (parts by mass))/[ polymerization conversion ] × 100.

The content of tetrahydrofuran-insoluble matter in the chloroprene copolymer was measured as follows. That is, 1g of the chloroprene copolymer latex (A) was dropped into 100mL of tetrahydrofuran, shaken overnight, and then centrifuged with a centrifuge to obtain a clear dissolved phase. The resulting dissolved phase was heated to 100 ℃ for 1 hour to evaporate tetrahydrofuran and dry it, and the mass of the dry solid was measured. The mass of the dissolved component dissolved in the dissolved phase in the chloroprene copolymer is obtained in this way.

Then, the mass of the chloroprene copolymer in 1g of the chloroprene copolymer latex (a) and the mass of the above-mentioned dissolved component were substituted into the following formula to calculate the content of a tetrahydrofuran insoluble component insoluble in tetrahydrofuran in the chloroprene copolymer. Table 1 shows the measured tetrahydrofuran insoluble content.

The tetrahydrofuran insoluble content (%) {1- [ (mass of dissolved component)/(mass of chloroprene copolymer in 1g of chloroprene copolymer latex (a)) } × 100

The storage stability of the chloroprene copolymer latex (a) was evaluated as follows. The chloroprene copolymer latex (a) charged into a closed vessel was heated in an oven at 70 ℃ for 168 hours, and then the amount of residual alkali in the chloroprene copolymer latex (a) was measured. The amount of residual base was determined by neutralization titration using hydrochloric acid having a concentration of 1/3 mol/L. Then, the storage stability was judged to be excellent when the reduction rate of the residual alkali amount was low as compared with that before heating. The evaluation results of the storage stability are shown in table 1. When the reduction rate of the residual alkali amount was 60% or less, the storage stability was judged to be excellent, and indicated by the symbol "o" in table 1, and when the reduction rate of the residual alkali amount was more than 60%, the storage stability was judged to be insufficient, and indicated by the symbol "x" in table 1.

(2) Preparation of chloroprene copolymer latex composition

The chloroprene copolymer latex (A) obtained in the above (1), zinc oxide AZ-SW manufactured by Kawasaki industries, vulcanization accelerator ノクセラー C (diphenylthiourea) manufactured by Kawasaki industries, vulcanization accelerator ノクセラー D (diphenylguanidine) manufactured by Kawasaki industries, and phenolic antioxidant セロゾール L-306-40 manufactured by Mikyo grease Co., Ltd were put in a vessel equipped with a stirrer. Then, the mixture was stirred for 5 minutes and mixed uniformly, thereby obtaining a chloroprene copolymer latex composition. The chloroprene copolymer latex composition after completion of the stirring was left to stand at room temperature (20 ℃ C.) for 24 hours to age it.

The amounts of zinc oxide AZ-SW, vulcanization accelerator ノクセラー C, vulcanization accelerator ノクセラー D, and phenol antioxidant セロゾール L-306-40 added were 5 parts by mass, vulcanization accelerator ノクセラー C2 parts by mass, vulcanization accelerator ノクセラー D1 part by mass, and phenol antioxidant セロゾール L-306-40 2 parts by mass, respectively, based on 100 parts by mass of the solid content in the chloroprene copolymer latex (a) added.

Wherein the zinc oxide AZ-SW and the phenolic antioxidant セロゾール L-306-40 are in the form of a dispersion in which the effective components zinc oxide and antioxidant are dispersed in a liquid medium, and the amount of the zinc oxide AZ-SW and the phenolic antioxidant セロゾール L-306-40 added is only the amount of the effective components in the zinc oxide AZ-SW and the phenolic antioxidant セロゾール L-306-40 added.

(3) Manufacture of membranes

Using the chloroprene copolymer latex composition obtained in the above (2), a film of a chloroprene copolymer was formed by a dip processing method. As a mold for molding a film of a chloroprene copolymer, a ceramic plate having a height of 200mm, a width of 100mm and a thickness of 4mm was prepared. The mold was immersed in a 30 mass% calcium nitrate aqueous solution, then pulled out, and dried in an oven at 40 ℃ for 5 minutes to attach the setting agent calcium nitrate to the surface of the mold.

Further, the dried mold was immersed in the chloroprene copolymer latex composition obtained in the above (2), and a film was formed on the surface of the mold. The mold was pulled from the chloroprene copolymer latex composition and dried in an oven at 70 ℃ for 30 minutes.

Next, the mold having the film formed on the surface was heated in an oven at 110 ℃ for 30 minutes to be vulcanized (crosslinking reaction), and cured. After cooling by leaving in the air, the film was peeled from the surface of the mold to obtain a film of a crosslinked chloroprene copolymer.

The crosslinked film was cut into a dumbbell No. 6 test piece prescribed in JIS K6251. The thickness of the test piece is 0.15 to 0.25 mm. The test piece was then heat-treated in air at 110 ℃ for 16 hours, thereby being subjected to heat aging treatment. Tensile tests were conducted at room temperature on the test pieces before and after the heat aging treatment in accordance with the method in JIS K6301, and the tensile strength, the tensile elongation at break and the modulus of elasticity at 300% elongation (300% modulus of elasticity) were measured. Table 1 also shows various physical properties of the film measured as described above.

[ example 2]

A chloroprene copolymer latex (a), a chloroprene copolymer latex composition, a film and a test piece were prepared in exactly the same manner as in example 1 except that the chloroprene copolymer latex (a) was prepared by changing the amount of 2, 3-dichloro-1, 3-butadiene used as shown in table 1, and various evaluations were carried out in the same manner as in example 1. The results are shown in table 1.

[ example 3]

A chloroprene copolymer latex (a), a chloroprene copolymer latex composition, a film, and a test piece were prepared in exactly the same manner as in example 1 except that the chloroprene copolymer latex (a) was prepared by changing the amount of 2, 3-dichloro-1, 3-butadiene used as shown in table 1 and a chloroprene copolymer latex composition was prepared by changing the amount of the vulcanization accelerator ノクセラー C as shown in table 1, and various evaluations were performed in the same manner as in example 1. The results are shown in Table 1.

[ examples 4 and 5]

A chloroprene copolymer latex (a), a chloroprene copolymer latex composition, a film, and a test piece were prepared in exactly the same manner as in example 1 except that the chloroprene copolymer latex (a) was prepared by changing the usage amount of rosin acid in table 1 and the chloroprene copolymer latex composition was prepared by changing the type and usage amount of the vulcanization accelerator and the usage amount of the antioxidant in table 1, and various evaluations were performed in the same manner as in example 1. The results are shown in Table 1. The vulcanization accelerator (C) ノクセラー BZ in table 1 is a vulcanization accelerator ノクセラー BZ (zinc dibutylcarbamate) manufactured by shichenjian chemical industries co.

[ comparative examples 1 to 3]

A chloroprene copolymer latex (a), a chloroprene copolymer latex composition, a film and a test piece were prepared in exactly the same manner as in example 1 except that the chloroprene copolymer latex (a) was prepared by changing the respective amounts of 2, 3-dichloro-1, 3-butadiene, sulfur and abietic acid used as shown in table 1, and various evaluations were carried out in the same manner as in example 1. The results are shown in Table 1.

[ comparative example 4]

Except that the conditions for vulcanization of the film were 120 ℃ and 45 minutes (conventional vulcanization conditions), a chloroprene copolymer latex (a), a chloroprene copolymer latex composition, a film, and a test piece were produced in exactly the same manner as in comparative example 1, and various evaluations were carried out in the same manner as in example 1. The results are shown in Table 1.

[ comparative example 5]

Except that the chloroprene copolymer latex composition was prepared by changing the type and amount of the vulcanization accelerator and the amount of the antioxidant as shown in table 1, the chloroprene copolymer latex (a), the chloroprene copolymer latex composition, the film and the test piece were prepared in exactly the same manner as in comparative example 1, and various evaluations were carried out in the same manner as in example 1. The results are shown in Table 1.

[ comparative example 6]

Except that the conditions for vulcanization of the film were 130 ℃ for 30 minutes, the chloroprene copolymer latex (a), the chloroprene copolymer latex composition, the film, and the test piece were produced in the same manner as in comparative example 5, and various evaluations were carried out in the same manner as in example 1. The results are shown in Table 1.

In examples 1 to 3, since sulfur was added during preparation of the chloroprene copolymer latex (a), a film having high mechanical strength could be obtained even when vulcanization was carried out under a lower temperature condition than in comparative example 1 in which no sulfur was added. Further, it is understood from a comparison of examples 4 and 5 that the film of the crosslinked chloroprene copolymer having a large amount of sulfur used has a high tensile strength.

In comparative example 3, the content of the tetrahydrofuran-insoluble matter was small because of the large amount of sulfur blended, and the flexibility of the film was improved, but the storage stability of the chloroprene copolymer latex (a) was low.

Further, it is understood from a comparison of examples 1 to 3 with comparative example 2 that the flexibility of the film is improved when 2, 3-dichloro-1, 3-butadiene is used. Further, it is understood from a comparison of comparative examples 5 and 6 that, when sulfur is not used, differences occur in the tensile strength, tensile elongation at break, and 300% elastic modulus of the film of the crosslinked chloroprene copolymer depending on the difference in the vulcanization temperature.